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793 Tuning and Calibration

1. Note The Function Generator is very useful for quickly setting up a tuning program If you use the same tuning program on a regular basis you may wish to create and save your tuning procedure using Basic TestWare or by using the optional MultiPurpose TestWare application Initial tuning is best done with a waveform that has abrupt changes This excites the system at frequencies likely to be unstable with excessive gain Square and ramp waveforms are preferred Final tuning can be done with the actual program command for the test Note Always monitor the sensor feedback or error signal to evaluate the control accuracy See Monitoring Waveforms While Tuning on page 40 A typical tuning program is a low amplitude 5 to 10 of full scale low frequency 1 Hz to 2 Hz square waveform The amplitude frequency and waveform type of a tuning program can be selected to reflect the capabilities of the testing system or the testing requirements MTS 793 Tuning and Calibration Introduction 33 About Tuning Square and Tapered A square waveform requires the servovalve to open rapidly to a large Square waveform opening It is the most demanding waveform because it requires the maximum response from the servoloop system It also places a large acceleration on the test system and specimen Tapered square waves taper from 0 to 100 amplitude at the beginning of execution and from 100 to 0 at the end of execution e A squa
2. Remove the shunt Standalone FlexTest SE Controllers Set the Shunt State control to Off Automated Controllers In the Shunt tab click the button with one white bar to remove the shunt The bar in the button will turn red 123 Displacement Sensor Calibration Displacement Sensor Calibration Prerequisites Initial calibration Recalibration Considerations for full range conditioners 124 A displacement sensor also called an LVDT is calibrated with a dial indicator or some other displacement measuring device The indicator is mounted between the actuator rod and a stationary point A typical LVDT has a positive and a negative output This is usually considered tension and compression Displacement is usually calibrated such that the maximum extension and retraction represent 100 of the full scale capacity of the LVDT with mid displacement set at zero Be sure the items described in Pre Calibration Considerations on page 117 are true An LVDT requires AC excitation which requires either a dedicated AC conditioner or a digital universal conditioner DUC configured in the AC mode You must know which conditioner is connected to the LVDT Note Ifyou are recalibrating a sensor use the existing calibration values as a Starting point If you are calibrating a sensor for the first time you may find it necessary to e Perform an initial tuning of the sensor channel before calibration e Perf
3. e Perform the procedure twice If you are recalibrating a sensor use the existing calibration values as a starting point Full range conditioners allow you to choose Gain Delta K or Gain Linearization for calibrating force conditioners The mV V Pos Tension and mV V Pos Comp calibration types are typically not used for controllers equipped with full range conditioners e During calibration Manual Offset should always be set to zero e During calibration ensure that Electrical Zero Lock is checked on the Offset Zero tab of the Inputs panel e After calibration do not change the electrical zero adjustment Readjustment of electrical zero after calibration will change the point at which linearization takes place disturbing other calibration settings especially Delta K MTS 793 Tuning and Calibration Range support What you will need Force Sensor Calibration Full range conditioners e g Model 493 25 DUCs do not require individual ranges Ranged conditioners e g Model 493 21 21B DUCs and Model 497 22 DC Conditioners support up to four ranges for force sensor calibration Force can be calibrated to any range within the full scale capacity of the sensor Also ranges do not have to be centered on Zero You will need the following items to calibrate a a force sensor e A load standard can be a calibrated force sensor with its own electronics or it can be a calibrated set of dead weights e A DVM to monitor th
4. eee ee ee ee ee aqbap asey4 Frequency Hz 111 Tuning Procedures MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques Lead Lag 2 Lead Lag 2 Pole 2 Zero P1 5Hz P2 20Hz 71 S0Hz 72 100Hz b Gain d Phase degree Frequency Hz How to Enable a Tuning Filter 1 Select an access level of Tuning Standalone FlexTest SE Controllers Select Setup gt Tuning Automated Controllers In the Station Manager window s toolbar select an access level of Tuning 2 Display the Filter tab for the control mode being tuned Standalone FlexTest SE Controllers Select Setup gt desired control mode gt Tuning gt Filter Type Automated Controllers A In the Station Manager window s Display menu select Station Setup B In the Station Setup window s navigation pane locate and select the control mode being filtered C In the Station Setup window click 4 D In the Tuning panel click the Filter tab 112 Tuning Procedures MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques 3 To select a Forward Loop filter select and set up the desired filter type of None Low Pass Band Stop Break Recover Lead Lag For Low Pass filters set the Frequency For Band Stop filters set the Notch frequency and Bandwidth For Break Recover filters set the Break and Recovery frequencies For Lead Lag filters select the number of pol
5. Apply a tensile force command that is 80 of the full scale range Standalone FlexTest SE Controllers A Using the Dial adjust the Setpoint for a tensile force command that is 80 of the full scale range B Verify that your force transducer feedback signal is 80 of the full scale range Automated Controllers A Open the Manual Command window and then click on the Enable Manual Command B Adjust the Manual Cmd slider on the Manual Command window for 80 of the full scale range C Use the Station Signals panel to verify that your force transducer signal equals 80 of the full scale range During the initial calibration and tuning of your system it may require repeated adjustment for the tensile force command and feedback values to match Note Ifthe actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this contro mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the reset integration value I Gain to help the feedback match the command MTS 793 Tuning and Calibration Calibrate compression MTS 793 Tuning and Calibration Force Sensor Calibration At this point unless the conditioner is already in calibration the tensile force applied to the force transducer will not equal your commanded value You will adjust gain in the next step so that the actual tensile force as measured
6. Automated Controllers A m o oO g In the Station Manager window click a to open the Auto Tuning control panel For Control Channel select the channel to be auto tuned For Control Mode select a displacement control mode For Mode to Tune select the displacement mode For Auto Tuning Type select Basic Advanced or Advanced Only Basic provides an adequate level of tuning for most control modes Advanced automatically performs Basic auto tuning followed by a sweep function that provides a higher level of tuning based on Tracking values Advanced Only performs only the sweep function using the Tracking values For Actuator Type select Normal or Hydrostatic For most cases select Normal If you receive a Feedback is not responding to drive signal message during tuning select Hydrostatic This setting allows more and faster valve movements which results in more actuator movement For Upper Limit and Lower Limit set the upper and lower limits for actuator travel during auto tuning Basic auto tuning exercises within 80 of these limits Advanced and Advanced Only auto tuning functions exercise the actuator within 20 of these limits If the limits are exceeded the auto tuner will quit and trip an interlock For Advanced and Advanced Only auto tuning Set the Tracking value The 50 default setting is appropriate for most systems For Advanced and Advanced Only auto tuning Set the Sweep
7. For a description of specific tuning and calibration controls as displayed in the MTS 793 control software user interface for FlexTest IIm automated FlexTest SE FlexTest GT and TestStar IIm Controllers see the MTS 793 Control Software manual For a description of the specific tuning and calibration controls displayed on the front panel of standalone FlexTest SE Controllers see the FlexTest SE Users manual About Tuning 16 How the Tuning Controls Work 17 Proportional P Gain 19 Derivative D Gain 23 Feed Forward F or F2 Gain 26 Stabilization Gain S Gain 28 Delta P Stabilization 28 Acceleration Stabilization 29 Forward Loop Filter FL Filter 30 Tuning Characteristics of Control Modes 31 Creating a Tuning Program 33 About Auto Tuning 36 Other Tuning Considerations 38 Monitoring Waveforms While Tuning 40 Introduction 15 About Tuning About Tuning Control loop elements 16 Summing junction Introduction About Calibration 42 system Calibration 42 Sensor Calibration 43 Tuning is adjusting your test system so that its servo loop responds accurately to its command signal When you tune you are setting the response and stability of the servo control loop Proper tuning improves the performance of your test system just like setting the timing on an automobile improves its performance It is not necessary for you to always have every control mode of every control channel perfectly tuned Tune whenever necessar
8. MTS 793 Tuning and Calibration Introduction 21 About Tuning More about Integral Integral gain introduces an integral of the error signal that gradually gain I over time boosts the low frequency response of the servovalve command Integral gain increases system response during static or low frequency Operation and maintains the mean level at high frequency operation It can offset a DC or steady state error such as that caused by valve imbalance Overshoot Huntin Droop K ra i Reset Too Low Mean Level Stability Reset Too High Excessive Reset A ramp and hold waveform illustrate different levels of reset The I Gain adjustment determines how much time it takes to improve the mean level accuracy Integral gain e Improves mean level response during dynamic operation e Corrects feedback droop caused by the spring characteristic of the servovalve in static and very low frequency test programs e Minimizes the amount of time the system needs to recover from transitions or transients Keep in mind e Higher integral gain settings increase system response e Too much integral gain can cause a slow oscillation hunting e You may want to use the max min display to monitor the mean level reset the display and check it again Integrator limit The Integrator Limit control allows you to set the maximum integrator value as a percentage of full scale output 22 Introduction MTS 793 Tuning and Calibration Derivative
9. on page 130 for a detailed procedure Set the zero position The zero position can be set anywhere within the full scale range of the device Standalone FlexTest SE Controllers A Using the front panel Dial adjust the Setpoint to move the actuator to the position you want to assign as zero B Select any control mode that does not use the encoder Select Status gt Control Mode Note Ifthe actuator should move after making the change in control modes you will need to reposition the actuator then change to a more stable contro mode MTS 793 Tuning and Calibration Task 6 C Encoder and Temposonics Calibration With the actuator in the desired zero position click lt lt Auto Zero gt gt button on the Offset Zero submenu Select Setup gt Disp gt Offset Zero gt lt lt Auto Zero gt gt Automated Controllers A Note Note Adjust the Manual Cmd slider on the Manual Command window to move the actuator to the position you want to assign as Zero Use Control Mode on the Change control modes on the Control Panel Select any control mode that does not use the encoder or Temposonics sensor If the actuator should move after making the change in control modes you will need to reposition the actuator then change to a more stable contro mode With the actuator in the desired zero position click the Auto Zero button on the Offset Zero tab Unputs panel When you change the device resolutio
10. perform the following 1 On the Tools menu select Sensor File Editor 2 Open the sensor file for the sensor you have just calibrated 3 Click Add under Range Definition 4 Select the units for the range and then enter the absolute value of the range 5 Save the new range to the calibration file 6 Calibrate the added range Note Ranges can also be added on the Sensor tab and calibrated on the Calibration tab MTS 793 Tuning and Calibration 149 Force Sensor Calibration Force Sensor Calibration 150 Prerequisites Initial calibration Recalibration Considerations for full range conditioners A force sensor also called a load cell is calibrated with a load standard A load standard can be a special calibrated force sensor with its own electronics or a set of calibrated dead weights A force sensor is calibrated such that the maximum compression and tension represent 100 of the full scale capacity of the sensor with zero force set at midcapacity Be sure the items described in Pre Calibration Considerations on page 117 are true A force sensor requires DC excitation which requires either a dedicated DC conditioner or a digital universal conditioner DUC configured in the DC mode You must know which conditioner is connected to the force sensor If you are calibrating a sensor for the first time you may find it necessary to e Perform an initial tuning of the sensor channel before calibration
11. 20 mm Before beginning ensure the following are true The Fine Zero adjustment is set to 0 Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Fine Zero Automated Controllers Adjust Fine Zero on the Calibration tab MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Displacement Sensor Calibration The Manual Offset is set to 0 Standalone FlexTest SE Controllers Select Setup gt Disp gt Offset Zero gt Manual Offset Automated Controllers Adjust Manual Offset on the Offset Zero tab The Electrical Zero adjustment is set to 0 Standalone FlexTest SE Controllers Select Setup gt Disp gt Offset Zero gt Electrical Zero Automated Controllers Adjust Electrical Zero on the Offset Zero tab Mount the displacement measuring device Mount the measuring device to measure the distance between the end of the actuator s piston rod and a stationary point such as the actuator s upper endcap There are a variety of ways to measure actuator displacement e Dial Indicator e Tape Measure Ruler e Optical Detector e Encoder e You may need to place the dial indicator on a block to measure the mid displacement position e Be sure to zero the dial indicator after you position it properly 133 Displacement Sensor Calibration 134 2 Ensure that displacement control mode is selected Standalone FlexTest SE Controllers Select Status gt Control
12. 6 8 10 20 40 70 and 100 percent of full scale Record dial indicator and conditioner feedback readings at predetermined extension command points Standalone FlexTest SE Controllers A Use the front panel Dial to adjust the Setpoint for a 2 extension command Record the dial indicator value and conditioner feedback at the 2 row of your record sheet 147 Displacement Sensor Calibration 148 12 13 14 15 C Repeat steps A and B for other extension commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A Adjust the Manual Cmd slider for a 2 extension command Record the dial indicator value and conditioner feedback at the 2 row of your record sheet Repeat steps A and B for other extension commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Turn off system hydraulics On the Linearization Data window enter the dial indicator and conditioner feedback readings for all command points previously recorded on a separate sheet Turn on system hydraulics Verify linearization data Standalone FlexTest SE Controllers A Using the front panel Dial adjust the Setpoint for each retraction and extension command point on the Linearization Data window At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditione
13. D Gain About Tuning Derivative gain is an adjustment you may or may not need Another name for derivative gain is Rate gain Get back into the car and back on the race track Only now you re going really fast and the curves are electrifying But it s a race so you are actually accelerating while in the short straightaways In your attempt to accelerate you press the gas pedal all the way to the floor and hold it there But now you re going too fast to safely round a curve so you slam on the brakes just as you enter the curve then release them The brakes stabilize the trip by restraining the driving action at the time that the car is changing direction Consider this you barely need brakes if going slowly down a wide level street Brakes become more essential the faster you go and the quicker you change direction Derivative gain is the same concept It stabilizes the system by reducing the error signal when its rate of change is the greatest This reduces overshoot and ringing at high proportional gain settings Feedback Command 4 Error Derivative gain looks at the feedback side of the summing junction It is the derivative of that signal indicating how fast the feedback is changing Here is a signal with a high degree The same high gain signal after of proportional gain Derivative derivative gain has been applied gain has not been applied yet The derivative gain tends to damp Notice how noisy the sign
14. For Advanced auto tuning you should change the sweep frequency to create a phase shift greater than 90 for 0 tracking or 135 for 100 tracking between the command and compensated command You can monitor the advanced tuner command and compensated command on the scope Introduction 37 About Tuning Other Tuning Considerations Tuning with a dummy Specimens can be very expensive A dummy specimen is an specimen inexpensive material that has similar characteristics to the specimen selected for testing The most important specimen characteristic is its spring rate The advantage of a dummy specimen is that it can simulate how your testing system reacts to real specimen You can establish a more precise level of tuning with a dummy specimen Tuning with a real If you do not have a dummy specimen or if a dummy specimen is not specimen practical review the following recommendations if you must use a real specimen e Start your PIDF controls at minimum settings e Do not use a square waveform for a massive specimen or a specimen prone to vibrations e Adjust rate to minimize any oscillation overshoot or ringing in the waveform e Bevery conservative by beginning with a ramp waveform to establish initial control Then use a waveform that resembles the test waveform to provide a precise level of control Tuning without any A specimen is required to tune force and strain control modes Initial specimen force tuning m
15. When tuning AIC compensator configurations it is necessary to generate random functions to properly simulate typical test conditions Random functions employ a pre emphasis filter to make the convergence rate constant over all frequencies The random function options include e Random 1 F e Random 1 F e Random Flat none e Random F e Random F A low frequency waveform is adequate for most testing Tests at higher frequencies cause a frequency shift that cannot be completely corrected with the PIDF adjustments e Do your initial tuning at a low frequency and then fine tune at the highest frequency in your test program Common values are 1 2 Hz e Servo adjustments that do not improve performance at high frequencies generally indicate that the servovalve is running at 100 capacity or the HPU is running at 100 capacity This characteristic can easily be seen when tuning with a sine waveform The feedback waveform appears to be more like a ramp waveform when running at 100 capacity A system tuned at a low amplitude may become unstable at high amplitudes Tuning should be accomplished under conditions similar to the anticipated usage e Use a moderate amplitude 5 to 10 full scale for initial tuning e Be sure the maximum velocity of the tuning command is 10 to 50 of the maximum velocity of the system e Increase the amplitude for fine tuning e You may find it helpful to check tuning over a v
16. When you set out to tune your system it is best to run auto tuning first Auto tuning establishes reasonable tuning levels that will be adequate for most control modes See How to Auto Tune on page 83 for more information If the results from auto tuning are not satisfactory you should create a tuning function and then manually tune each control mode Tuning for the First Time What if you adjust something wrong If you are unfamiliar with the tuning controls review the following guidelines Before you start tuning you should e Define upper and lower limits for the displacement and force sensor before you start tuning e Tune the displacement control mode first since no specimen is needed e Note the value of the tuning control before adjusting it so you can return it to that value if necessary e Make small initial tuning adjustments If the waveform does not appear to change increase the adjustments If you make an inappropriate adjustment the system will go unstable or shut down An unstable system produces a humming or screeching sound A system shutdown will display an error message If an adjustment causes the system to go unstable quickly readjust the control until the noise stops If you cannot eliminate the sound shut down the system by pressing the Station Stop or Emergency Stop switch Important In multi station configurations pressing Emergency Stop will shut down the HPU and all stations in the inter
17. compensation mode is selected in the navigation pane The Integrator Gain control becomes available by selecting in the Station Builder application the Edit Dual Compensation Modes window s Mean and Amplitude Control About compensation When reading this section assume that the Station Builder application gain settings has defined a Force Displacement dual compensation control mode and that e The force signal is the less stable secondary feedback signal used for command compensation Command programs produced by the Function Generator and other applications use this signal s dimension e The displacement signal is the more stable primary feedback signal used by the PIDF controller to maintain closed loop control Conversion Gain Conversion Gain applies the gain that converts the force command to a displacement command for a PIDF or external controller The force signal provided by the compensator is multiplied by the following equation to create the displacement signal used to program the PIDF or external controller Full Scale Displacement Conversion Gain Value x a Full Scale Force The Conversion Gain setting depends on the specimen stiffness See Calculating conversion gain on page 106 Integrator Gain The Integrator Gain improves the static accuracy when the command is paused or stopped Gain For best performance set I Gain as low as possible when using compensation methods that provide mean correction The
18. this could also mean the specimen is failing Use this checklist when you tune a system You need to determine the following What type of control mode do you wish to tune Read Tuning Characteristics of Control Modes on page 31 What controls should you use Read How the Tuning Controls Work on page 17 What kind of a tuning program should you use Read Creating a Tuning Program on page 33 Do you have a dummy specimen Read Other Tuning Considerations on page 38 Where do you connect the oscilloscope and what signal do you monitor Read Monitoring Waveforms While Tuning on page 40 Tuning Procedures 47 When to Tune What to do before you 48 tune Tuning controls review Tuning Procedures The following are tasks that should be completed before you tune It is not necessary to perform every task each time you tune The condition of your system dictates which of the following tasks you must perform For example a new system or a system under complete recalibration requires all of the following to be completed If you are performing periodic or fine tuning review the following and determine which tasks you need to complete Connect an oscilloscope to your system or use the controller scope You need to monitor the sensor signal or error signal for the control mode you intend to tune Go to Monitoring Waveforms While Tuning on page 40 for help Balance the servovalve T
19. 2 compressive force command B Record the standard s readout signal and corresponding conditioner feedback reading in the 2 row of your record sheet C Repeat steps A and B for other compressive force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Turn off system hydraulics On the Linearization Data window enter the force standard values and corresponding conditioner feedback readings for all command points previously recorded on a separate sheet Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab to open the Linearization Data window MTS 793 Tuning and Calibration Force Sensor Calibration Force transducer If the force transducer has been previously calibrated use the recalibration following procedure 1 Zs MTS 793 Tuning and Calibration Locate the calibration data sheet for the appropriate conditioner Turn off system hydraulics Click Linearization Data to open the Linearization Data window Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab of the Inputs panel Transfer Standard and Conditioner data from the conditioner s calibration dat
20. C Enter the compression sensitivity value mV V in the Neg Compression entry box D Enter the calibration excitation value Vdc in the Excitation entry box MTS 793 Tuning and Calibration mV V Positive Compression Calibration MTS 793 Tuning and Calibration Force Sensor Calibration Automated Controllers A On the Inputs panel enter the full scale force values in the Fullscale Min Max entry boxes Adjust Pos Tension for the required tension sensitivity value mV V Adjust Neg Compression for the required compression sensitivity value mV V Adjust Excitation for the required calibration excitation value Vdo Use the following procedure if your force transducer is set up so that a positive output represents actuator extension compression 1 Select mV V Pos Comp for your calibration type Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt mV V Pos Comp Automated Controllers Select mV V Pos Compression for Cal Type on the Calibration tab of the Inputs panel 2 From the Calibration Data sheet for your force transducer enter the following values on the Calibration submenu or tab Standalone FlexTest SE Controllers A D Enter the full scale force values in the Minimum and Maximum entry boxes Enter the tension sensitivity value mV V in the Neg Tension entry box Enter the compression sensitivity value mV V in the Pos Compression entry
21. DVM to monitor strain feedback from a BNC connector located on the FlexTest SE Controller front panel FlexTest SE Controllers or Analog Out panel all other controllers You can also use the Meters window to monitor strain feedback For Automated Controllers you can also use the Station Signals panel to monitor strain feedback On the Station Manager Display menu select Station Setup In the navigation pane select Station Signals to display the Station Signals panel to monitor current values for user defined signals For more information on using the Station Signals panel refer to About the Station Signals Panel in the MTS 795 Control Software manual Mount the extensometer to the calibrator A Review the extensometer product manual for mounting information and calibrator requirements B Ensure that the extensometer is cabled to an appropriate conditioner Turn on electrical power to your system and allow thirty minutes for warm up Note _ f you already have a sensor calibration file skip Task 2 Note Tasks 2 and 3 do not apply to Standalone FlexTest SE Controllers MTS 793 Tuning and Calibration Extensometer Calibration Task 2 Create a sensor calibration file This task creates a sensor calibration file and sets up any ranges you may want If you already have a sensor calibration file skip this task The following steps provide an overview of sensor file creation For a more detailed description
22. F2 Gain is applied after the forward loop filter When your forward loop filters are set to low frequencies it tends to limit the effectiveness of F Gain F2 Gain may work better in this situation You would tend to use F Gain when there are frequencies you do not wish to excite Using F Gain allows the forward loop filter to filter out these frequencies Original Command Feed Forward Command Original Feedback e Does not compensate for normal changes during testing such as temperature changes servovalve droop and so forth e May be used to minimize phase lag e Should be used like derivative gain However F Gain applies to the test command signal while derivative gain applies to the feedback signal e Feed forward gain helps the servo control loop react quickly to an abrupt change in the command e Is needed when testing a soft specimen in force control Introduction 27 About Tuning Stabilization Gain S Gain Delta P Stabilization 28 Introduction Stabilization gain allows a second signal to be integrated into the composite command signal as a stabilizing factor It enhances stability for systems that move large masses at high speeds The second signal is generated by a special transducer such as AP differential pressure or accelerometer Stabilization controls will be available only if a stabilization resource was added to the control channel Delta P makes use of a differential pressure sen
23. Force Control Mode 71 Tuning the Strain Control Mode 77 How to Perform Advanced Tuning Techniques 83 How to Auto Tune 83 How to Manually Tune Three Stage Servovalves 88 Zero the Spool Position Signal 95 How to Monitor Inner Loop Signals 96 How to Use Error to Tune I Gain 98 About the Cascaded PIDF Control Mode 99 How to Tune a Cascaded PIDF Control Mode 99 About Channel Limited Channel CLC Control Modes 101 How to Tune a CLC Control Mode 101 About Dual Compensation Control Modes 104 How to Tune a Dual Compensation Control Mode 106 About Tuning Filters 109 How to Enable a Tuning Filter 112 MTS 793 Tuning and Calibration Contents 5 Chapter 3 Calibration Procedures 115 Pre Calibration Considerations 117 About TEDS Sensors 118 Shunt Calibration 120 Displacement Sensor Calibration 124 Displacement Sensor Calibration Abbreviated Procedure 126 Displacement Sensor Calibration Detailed Procedure 127 Force Sensor Calibration 150 Force Sensor Calibration Abbreviated Procedure 151 Force Sensor Calibration Detailed Procedure 152 How to Install a Shunt Calibration Resistor on an I O Carrier Board 183 Encoder and Temposonics Calibration 185 Encoder Calibration Abbreviated Procedure 186 Encoder Calibration Detailed Procedure 186 Extensometer Calibration 190 Extensometer Calibration Abbreviated Procedure 191 Extensometer Calibration Detailed Procedure 191 Index 209 6 Contents MTS 793 Tuning and Calibration Technical Support How t
24. Freq Tuning Procedures 85 How to Perform Advanced Tuning Techniques The Sweep Freq sets the upper frequency limit of the sine sweep The 20 Hz default setting is a good starting point Pressing the Run button will put the actuator in motion A moving actuator can injure anyone in its path Always clear the actuator area before pressing the Run button Note While auto tuning Is in process you cannot changes channels or contro modes Also the active and auto tuning signal s tuning parameters will be disabled 5 Press Run to start auto tuning and if desired accept tuning values While auto tuning is in progress the controller displays Auto Tuning in Progress To terminate auto tuning before completion press lt Stop gt When auto tuning is complete the controller displays Auto Tuning for this mode has completed successfully Also when auto tuning is complete the results are displayed showing Current tuning values and Reference values Press Accept to apply the Reference values 6 Save the auto tuning values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters to save the New Values You may save auto tuning values to an existing parameter set or to a new parameter set 86 Tuning Procedures MTS 793 Tuning and Calibration Auto tuning th
25. Gain Linearization Calibration procedure that follows applies only to controllers equipped with full range conditioners e g Model 493 25 DUC module Task 5 Gain Linearization Calibration If you are using Gain Linearization for your calibration type complete the following procedure If not complete Task 4 Gain Delta K Calibration on page 195 Important Using linearization data requires specific conditioner zeroing practices Ensure that Electrical Zero Lock on the Offset Zero menu is set to Locked Adjusting electrical zero after calibration may invalidate linearization data Calibration setup 1 Ensure that the extensometer is properly attached to the calibrator frame using the associated installation drawings and calibrator fixtures 2 Set an initial transducer excitation voltage Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Cal Type gt Gain Linearization gt Excitation peak Set the Excitation peak voltage value typically 5 8 volts 198 MTS 793 Tuning and Calibration Initial extensometer calibration MTS 793 Tuning and Calibration Extensometer Calibration Automated Controllers A In the Station Setup window s navigation pane locate and select the Channels resource providing the strain feedback signal B In the Station Setup window click a C Inthe Inputs panel click the Calibration tab D Set Type to Gain Linearization E Set Excitation peak vo
26. May yield unstable response is P gain is set too high MTS 793 Tuning and Calibration Introduction 31 About Tuning 32 Strain control Command sources CLC control mode Introduction Strain control uses an extensometer or strain gage bonded to the specimen as the controlling feedback source The strain control mode typically e Requires tuning between tests whenever a specimen is changed and whenever changes are made to the force train e Requires a specimen to be installed you may choose to use a broken specimen e Uses a ramp waveform for the initial tuning Note Do not use a square waveform for tuning A square wave can cause the extensometer to move or fall off the specimen which can cause the system to go unstable e May yield sluggish response if P gain is set too low e May yield unstable response is P gain is set too high The program command source can come from an internal source such as the Function Generator or the MultiPurpose TestWare application or from an external device such as an external profiler or function generator Channel limited channel CLC control modes are used for specimen installation and removal Channel limited channels require two feedback signals MTS 793 Tuning and Calibration About Tuning Creating a Tuning Program Command waveforms The purpose of a tuning program is to produce a command that reflects the most demanding system response expected from a test
27. Mode gt Disp Automated Controllers In the Manual Command window perform the following A B a Select the appropriate Channel associated with the LVDT signal you are calibrating For the Control Mode select Displacement Click Enable Manual Command 3 Evaluate the mid displacement position for the actuator Standalone FlexTest SE Controllers A B D Enable the front panel Dial Use the Dial to increase the Setpoint adjustment for a positive command Select Status gt Setpoint Adjust the Setpoint to fully extend the actuator and note the displacement signal value Adjust the Setpoint to fully retract the actuator and note the displacement signal value Automated Controllers A Move the Manual Cmd slider to apply a positive command extend the actuator Adjust the Manual Cmd slider to fully extend the actuator and note the displacement signal value in the Station Signals panel Adjust the Manual Cmd slider to fully retract the actuator and note the displacement signal value in the Station Signals panel The noted displacement signal values should be within 1 of each other If these displacement signals are not within 1 you can evaluate the following procedures to establish the zero reference MTS 793 Tuning and Calibration Note Displacement Sensor Calibration Use the Fine Zero adjustment to shift the sensor conditioner s zero reference position Standalone FlexTe
28. Phase lag of the filter can be reduced at higher frequencies by limiting the filter attenuation at frequencies above the Zero 1 and Zero 2 frequencies Tuning Procedures 109 How to Perform Advanced Tuning Techniques Refer to the following forward loop filter response curve examples when selecting a filter type for a desired system response Forward loop filter responses Low pass SHz Low Pass k TATL enna L L ee ee eee See eee ee T T a ee eo L l ees a a a Dai i i a a aaa aalhap aseyg Frequency Hz 20Hz 50Hz Bandwidth Band stop Motch Stop Band aalfap aseyd Frequency Hz MTS 793 Tuning and Calibration 110 Tuning Procedures How to Perform Advanced Tuning Techniques 5Hz Recover S0Hz Break Recover Break Break Recover j L LeLIdd TT TPT PTT awa wA AEE a METETA TTT Le F R4dd4 4 I I I I I I I 4 l I ENEE EEEE P STS I O E E e TAREE tee E enn a iW 100 fagJBap aseyd Frequency Hz SHz 1 50Hz Lead Lag 1 Pole 1 era P1 Lead Lag 1 etd dd Lee L a I I I 1 L I I I 4 1 a I L aba dd dbo l ele eee eee ee eee le Ld lll ammm eee d l d WwelJJJLo 0 0 e0 GE Te o EE Ee i 444 wal F I 1 1 1 I I 7 T I 1 1 I 1 1 4 1 T a T a T L I 1 i i t hR 4 H kr
29. Remove all dead weights and then click Auto Offset on the Offset Zero tab Unputs panel Task 5 Gain Delta K Calibration If you using Gain Delta K for your calibration type complete the following procedure If not complete Gain Linearization Calibration on page 164 or Millivolt Volt Calibration on page 175 Calibrate tension Force sensors can be calibrated so that a positive output represents actuator compression and a negative output represents actuator tension and vice versa 156 MTS 793 Tuning and Calibration Gain controls MTS 793 Tuning and Calibration Force Sensor Calibration You calibrate the negative side of the output with gain and Indicated output ai iti the positive side of the output with Delta K AK 1 AK lt 1 Delta K compensates for differences in symmetry between positive and negative outputs mechanical input Calibrate compression at 80 full scale for each range Note This procedure assumes a positive command extends the actuator and a negative command retracts the actuator If not use the opposite polarity for any values given Pre Amp gain is a selectable gain amplifier with predefined values Since changes in Pre Amp gain can cause spikes in the feedback signal Pre Amp gain can only be adjusted when hydraulics are off Post Amp gain is a finer operator defined gain control that can be adjusted when hydraulics are on The Total gain value is calculated by
30. Zero gt Manual Offset Automated Controllers Click the Conditioner tab on the Drive panel then check the Offset setting 3 Apply hydraulic pressure WARNING Do not remove the LVDT adjustment locknut or assembly when adjusting the servovalve LVDT spool position If it is removed hydraulic fluid will soray from the servovalve at full pressure You should refer to the servovalve product manual to identify the main stage LVDT spool adjustment 4 Loosen but do not remove the LVDT locknut MTS 793 Tuning and Calibration Tuning Procedures 95 How to Perform Advanced Tuning Techniques 5 Adjust the LVDT in or out of the servovalve to provide a zero spool position signal 6 Tighten the locknut while holding the LVDT in position How to Monitor Inner Loop Signals Note The following procedure does not apply to FlexTest Ilm Controllers see page 97 1 Connect a service calibration cable package MTS part number 100 026 213 to connector J3 Service on the I O carrier module 2 Connect a DVM or oscilloscope to the appropriate BNC Output Channel on the service cable depending on which slot the valve driver occupies in the I O Carrier module 3 In Station Setup click the Channel Drive icon to display the Drive panel and then click the Conditioner tab 4 From the Service Port Output select one of signals described in the following Service Port Output Signals list Note The Spool Position signal is available to the di
31. accelerometer may be used in place of a delta P signal for stabilization Acceleration Stabilization MTS 793 Tuning and Calibration Test systems with specimens affected by acceleration resonances can use a mass accelerometer signal for stabilization Acceleration stabilization dampens the resonances vibrations affecting the specimen Typical systems that benefit from acceleration stabilization include e Load units that operate at high frequencies with massive grips e Test systems that employ swivels linkages and test tables Sensor feedback is provided by an accelerometer attached to or near the specimen The controller converts this feedback into a stabilization signal which is combined with the composite command signal post PIDF correction The stabilized command signal is then sent to the valve driver Introduction 29 About Tuning Forward Loop Filter FL Filter FL filter adjustments compensate for noise in the servoloop which usually comes from sensor feedback FL filter adjustments establish a frequency bandwidth for the servo loop command signal Noisy Feedback D Gain Amplifies Noise Not All Noise is Removed Keep in mind e By default the FL filter is set to one half the system rate e The minimum FL filter frequency setting is 0 01 e Be sure the forward loop filter frequency is higher than any frequency in the test program Most testing occurs below 50 Hz e Systems with moving
32. auto tuning however advanced auto tuning may be used to optimize the results obtained through basic auto tuning When you run Advanced auto tuning the auto tuner first does basic auto tuning It then runs a sine sweep to exercise the actuator to 20 of the auto tuning limits with frequencies between 0 5 Hz and a user set maximum of 100 Hz Note The advanced auto tuner will reduce the sweep amplitude if it detects a valve opening that is more than 50 of full scale When you run Advanced Only auto tuning the auto tuner skips basic auto tuning and runs a sine sweep described earlier MTS 793 Tuning and Calibration Advanced and Advanced Only controls Tracking Sweep Freq MTS 793 Tuning and Calibration About Tuning Selecting an Auto Tuning Type of Advanced or Advanced Only displays Tracking and Sweep Freg controls in the Auto Tuning applications control panel Tracking specifies how closely the advanced tuner attempts to track the command Tracking values should be appropriate for the test to be performed Too high Tracking values may produce tuning values that are unstable for some systems and can cause auto tuning to fail The 50 default setting is usually a good starting point If auto tuning fails with this default setting lower the Tracking value Sweep Freq specifies the upper frequency limit of the sine sweep used by the Advanced auto tuner The 20 Hz default setting is usually a good starting point
33. calibration file Setting device resolution MTS 793 Tuning and Calibration This task creates a sensor calibration file Note Encoder and lemposonics sensors do not require ranges their resolution is constant See How to Create a Sensor File in the MTS 793 Control Software manual In the Resolution box enter the resolution supplied in the device s documentation Note Ifyou want to use units different than those supplied in the sensor documentation enter the full scale and resolution in the supplied units first and then switch to the desired full scale units The units conversion will be calculated automatically 187 Encoder and Temposonics Calibration Task 3 Task 4 Task 5 188 Assign a calibration file This task links a sensor calibration file to a hardware resource The purpose for this is to select one of the sensor ranges for the input signal definition See How to Assign a Sensor File in the MTS 793 Control Software manual Turn on hydraulic pressure This task sets up the Control Panel so you can turn on the hydraulic pressure Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Stay clear of the actuators when applying hydraulic pressure See Turn on hydraulic pressure
34. calibration value taken before a test should be compared to the shunt calibration reference value recorded when the sensor was last calibrated If the reference value and the current value differ too greatly the sensor conditioner pair should be recalibrated to establish a new shunt reference value Significant variations between current and reference values may occur if the excitation voltage has drifted or the sensor has been damaged or has changed if some other way It is possible to adjust excitation to compensate for small to moderate changes in the shunt calibration value You should perform a shunt calibration check when e You start a new test e You move a sensor to a different DC conditioner e You swap a DC conditioner module e You recalibrate a DC sensor e You change the sensor cable resistance may differ Note Shunt calibration can not be used to compensate for different length cables Note You cannot check shunt calibration of a sensor being used with the active control mode when hydraulic pressure is on Note Shunt calibration does not compensate for changes in the sensor sensitivity over time MTS 793 Tuning and Calibration Shunt Calibration How to perform a shunt Shunt calibration is a feature available for DC conditioners It checks calibration the integrity of the conditioner sensor combination It works by shunting a precision resistor across one arm of the sensor s Wheatstone bridge The res
35. control loops The output of the outer or secondary control loop is used as the input to the inner or primary control loop as if it were the final control element Load Cell Actuator Function Secondary Loop Primary Loop Generator PID Controller PID Controller Control Feedback Displacement Control Feedback Force Cascaded PIDF Control Mode How to Tune a Cascaded PIDF Control Mode Tune the control modes that will supply the primary and secondary feedback signals 1 Select an access level of Tuning Standalone FlexTest SE Controllers Select Tuning gt P Gain Automated Controllers In the Station Manager window s toolbar select an access level of Tuning 2 Display the controls for the control mode to be tuned Standalone FlexTest SE Controllers Select Setup gt desired Cascaded PIDF control mode gt Tuning MTS 793 Tuning and Calibration Tuning Procedures 99 How to Perform Advanced Tuning Techniques Automated Controllers A In the Station Manager window s Display menu select Station Setup B In the Station Setup window navigation pane s Channels locate and select the Cascaded PIDF control mode you are tuning C In the Station Setup window click V D In the Tuning panel click the Adjustments tab 3 Adjust the PIDF controls for the control mode asscciated with the outer control loop 4 Save the outer loop tuning values Standalone FlexTest SE Controllers Sel
36. driver replacement Once the phase is correctly set readjustment is not necessary during routine calibration D Readjust Conditioner gt Gain until the Meter reads 10 V DC E Return Conditioner gt Polarity to its original setting Automated Controllers In the Drive panel Conditioner tab A Reverse the Polarity setting to drive the inner loop spool into MTS 793 Tuning and Calibration one of the end caps Adjust Gain until the meter reads approximately 8 V DC Adjust Phase until the meter displays maximum voltage The phase adjustment matches the phase of the inner loop LVDT feedback with the 10 kHz demodulator reference signal This adjustment provides a maximum output for the maximum LVDT spool position offset Tuning Procedures 91 How to Perform Advanced Tuning Techniques 92 Tuning Procedures Note This adjustment must be set for the initial calibration servovalve replacement cable replacement or valve driver replacement Once the phase is correctly set readjustment is not necessary during routine calibration D Readjust Gain until the meter reads 10 V DC E Return Polarity to its original setting 8 Produce a Spool Position output signal of 10 V DC with the spool driven into the opposite end cap Standalone FlexTest SE Controllers A Reverse the Conditioner gt Polarity setting to drive the inner C loop spool into the other end cap Check the Meter It shoul
37. extensometer is properly attached to the calibrator frame using the associated installation drawings and calibrator fixtures 2 Set an initial transducer excitation voltage Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Cal Type gt Gain Delta K gt Excitation peak Set the Excitation peak voltage value typically 5 8 volts Automated Controllers A In the Station Setup window s navigation pane locate and select the Channels resource providing the strain feedback signal B In the Station Setup window click 2al C In the Inputs panel click the Calibration tab D Set Type to Gain Delta K E Set Excitation peak voltage value typically 5 8 volts 3 If the extensometer uses a zero pin remove the zero pin now 4 Monitor the extensometer s amplified output strain Note Before clicking Auto Zero ensure that any offsets due to Auto Offset and Manual Offset actions are eliminated MTS 793 Tuning and Calibration 195 Extensometer Calibration Calibrate the negative 196 output tension 5 Use Auto Zero to zero transducer output Standalone FlexTest SE Controllers Select Setup gt Strain gt Offset Zero gt lt lt Auto Zero gt gt Automated Controllers Click Auto Zero on the Calibration tab to set transducer s amplified output to 0 000 V DC This task calibrates the extensometer negative output using the calibration Gain controls Since the Gain settin
38. for the current station and you are creating a new parameter set for a specific test save the parameters with a different name e Different tests and or specimens may require different parameter sets Tuning the Force Control Mode To complete this task you will make sure the force tuning values established in your station parameter set are appropriate for the test you are about to run To do this you will e Create and apply a simple tuning program e Evaluate the current force tuning values by comparing command and feedback signals MTS 793 Tuning and Calibration Tuning Procedures 71 How to Manually Tune the Control Loop Once established displacement tuning values are unlikely to require adjustment in contrast optimal force tuning values are a function of your specimen s compliance and often change over time or even from test to test You should also tune force whenever you make any change to the force train such as changing fixtures Prerequisites Be sure the following conditions are present before you begin tuning the force control mode Standalone Controller and Automated Controllers e Hydraulic pressure is off e The specimen is not installed Automated Controllers only e You have created a station configuration file e You have created a station parameter set Procedure The following is a step by step tuning procedure for a force control mode It is a basic procedure that should work for most applica
39. for a compressive force command that is 80 of the full scale range B Use the Station Signals panel to verify that the compressive force signal is approximately equal to 80 of the full scale range Record conditioner feedback readings at predetermined tensile force command points 171 Force Sensor Calibration Note After shutting down system hydraulics you will enter these recorded readings on the Linearization Data window Standalone FlexTest SE Controllers A B Use the Dial to adjust the Setpoint for a 0 command Record the force standard s readout value and corresponding conditioner feedback reading in the 0 row of your record sheet Use the Dial to adjust the Setpoint for a 2 tensile force command Record the force standard s readout signal and corresponding conditioner feedback reading in the 2 row of your record sheet Repeat steps C and D for other tensile force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A B 172 Adjust the Manual Cmd slider for a 0 command Record the force standard readout signal and corresponding conditioner feedback reading at the 0 command line of your record sheet Adjust the Manual Cmd slider for a 2 tensile force command Record the force standard readout signal and corresponding conditioner feedback reading at the 2 command line of your record sheet Repeat steps C and
40. gain can cause the system to become unstable while too little proportional gain can cause the system to become sluggish e Gain settings for different control modes may vary greatly For example the gain for force may be as low as 1 while the gain for strain may be as high as 10 000 20 Introduction MTS 793 Tuning and Calibration About Tuning Integral I Gain Integral gain generates increased gain over longer time spans including steady state Integral gain is sometimes called Reset gain To return to the car analogy The race is over You ve won and the trip home is an easy one You re driving on a straight highway so you are not being as attentive as when you were racing The car drifts off of its desired path The problem is that this happens so slowly that you don t realize it You need something to boost your attention That s what integral gain is or why it is sometimes called Reset Integration It is the integral of the error signal that is it is essentially the error signal multiplied by time This means that even a small error signal eventually will become conspicuous Feedback Command x Error 9 Intergral Reset gain looks at the error side of the summing junction It is the integral of the error indicating the size of the error over time Naa M too much integral gain dc stability An error signal made An error signal that is unstable by too much stabilized by correct gain integral gain
41. it equals your retraction command Adjust Post Amp Gain until your dial indicator or other readout device shows that the actuator s physical retraction equals your retraction command Note This procedure assumes a positive command extends the actuator and a negative command retracts the actuator If not use the opposite polarity for any values given 4 If applicable repeat steps 1 3 for all ranges Example Suppose you have an actuator with a full scale capacity of 10 cm and ranges of 10 cm 5 cm 2 cm and 1 cm In this case you would repeat this process and calibrate retraction at 80 of each range 8 cm 4 cm 1 6 cm and 0 8 cm Note Some systems do not provide or require multiple ranges such as those using full range conditioners e g Model 493 25 DUC module In this case only one range is used typically 100 MTS 793 Tuning and Calibration 137 Displacement Sensor Calibration Calibrate actuator Note This procedure assumes a positive command extends the actuator extension and a negative command retracts the actuator If not use the opposite polarity for any values given 5 Apply an extension command that is 80 of the full scale range Standalone FlexTest SE Controllers A Enable the front panel Dial B Use the Dial to adjust the Setpoint for 80 of the full scale range C Verify that your LVDT displacement signal equals 80 of the full scale range Automated Controllers A Open the Manua
42. multiplying the Pre Amp and Post Amp gain values If the total desired gain amount is known from a calibration sheet you can enter the amount in the Total gain box and the software will calculate the Pre Amp and Post Amp gain values automatically When you are calibrating a DC conditioner use the Post Amp gain control to increase gain If more gain is needed you must disable hydraulics and increase the Pre Amp gain You can then turn on hydraulics and continue to adjust the Post Amp gain 1 Select Gain Delta K for Cal Type Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Delta K Automated Controllers Select Gain Delta K for Cal Type on the Calibration tab of the Inputs panel 157 Force Sensor Calibration 158 2 Exercise the force standard Standalone FlexTest SE Controllers After enabling the front panel Dial adjust the Setpoint to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Select Status gt Setpoint Automated Controllers Use the Manual Cmd slider on the Manual Command window to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Example When calibrating a 10 KN range exercise the actuator between 0 and 10 volts To calibrate the same force sensor for a different range such as 5 kN exercise the load standard between 0 and 5 volts
43. play a role in controlling the actuator and determining how signals are displayed This procedure assumes the servovalve polarity is set to Normal on the Station Setup Drive panel Valve tab 1 Check the sensor connection Be sure the force sensor is properly connected to the controller 2 Apply a load to the force sensor Push on the force sensor with your hand and note the signal value on the DVM front panel meter Standalone or Station Signals automated If the signal value is positive for actuator compression the conditioner polarity is correct If desired you can change the conditioner polarity to make the signal value negative for actuator compression Note The polarity setting should be the same when calibrating additional ranges for the same sensor MTS 793 Tuning and Calibration 155 Force Sensor Calibration Task 4 Set the zero and offset This task records the load standard readout as the zero reference Using a load standard Standalone FlexTest SE Controllers Adjust the Setpoint for 0 KN Then zero the load standard readout Select Status gt Setpoint Automated Controllers Adjust the Manual Cmd slider on the Manual Command window for 0 KN Then zero the load standard readout Using dead weights Standalone FlexTest SE Controllers Remove all dead weights and then click Auto Offset on the Offset Zero menu Select Setup gt Force gt Offset Zero gt lt lt Auto Offset gt gt Automated Controllers
44. point on the Linearization Data window MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Displacement Sensor Calibration B At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditioner with the corresponding values on the Calibration Data sheet Automated Controllers A Adjust the Manual Cmd slider for each retraction and extension command point on the Linearization Data window B At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditioner with the corresponding values on the Calibration Data sheet If the data is valid Stop this procedure If the data is not valid Proceed to the next step Reset Linearization Data window to default values Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization gt lt lt Reset gt gt Automated Controllers Click Reset on the Linearization Data window Apply a retraction command that is 80 of the full scale range Standalone FlexTest SE Controllers A Use the front panel Dial to adjust the Setpoint for 80 of the full scale range Select Status gt Setpoint B Verify that your LVDT displacement signal equals 80 of the full scale range Automated Controllers A Adjust the Manual Cmd slider on the Manual Command window for 80 of the full scale ran
45. replace the current values with the last set that worked properly Note The Reference settings are saved with the parameter set Tuning Procedures 69 How to Manually Tune the Control Loop Overshoot Oyvershoot Ringing The middle waveform is a optimum waveform In some cases the optimum wavetorm will have no overshoot or ringing and the waveform will look more like a square wavetorm with rounded corners Unstable sounds Rule of thumb 70 Tuning Procedures 8 Adjust the P Gain and D Gain tuning controls A Start the tuning function generator B Select Continuous Sweep on the internal or external scope C Increase the P Gain adjustment until you see a little overshoot and a little ringing D Increase the D Gain adjustment to reduce the overshoot and ringing E Repeat C and D until you achieve a optimum waveform Rate D Wo p Voo Low Gain P High For actual testing if your system goes unstable it will sound unstable that is it will emit an annoying high pitched sound that is quite different from the usual tuning sound ka chunk ka chunk If your system begins to go unstable quickly readjust the control that caused the instability to return the control to its previous setting Adjust the P Gain and D Gain controls as high as possible without going unstable Adjust the I Gain tuning control Set up a peak valley meter to monitor the peaks and valleys of the s
46. test systems are configured to extend the actuator in response to a positive command while other test systems are configured to retract the actuator in response to a positive command Conditioner polarity determines feedback polarity You must know how your test system is configured so you can determine the appropriate polarity for the values used in this chapter The valve polarity is established first see How to Set Servovalve Polarity on page 52 Full range All MTS 793 Controllers except FlexTest IIm CTC Controllers may be conditioners equipped with full range conditioners e g Model 493 25 DUCs Consider the following when calibrating sensors that use full range conditioners e Full range conditioners allow a gain linearization calibration option which require you to set up a linearized data table during sensor calibration MTS 793 Tuning and Calibration 117 Pre Calibration Considerations Default sensor file locations Sensor calibration files in Projects About TEDS Sensors 118 e When using linearized data you must retain copies of the initial calibration report containing non linearized data and the calibration report after applying linearization e When calibrating sensors that use a full range conditioner Electrical Zero Lock on the Offset Zero menu must be set to Lock Readjustment of electrical zero after calibration will change the point at which linearization takes place disturbing other calibratio
47. that the primary and secondary signals are offset 11 Save the tuning values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters 108 Tuning Procedures MTS 793 Tuning and Calibration About Tuning Filters Forward loop filters MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques The response of the mechanical system valve actuator test specimen limits the amount of controller gain you can use before the system becomes unstable A filter in the forward path of the controller may be used to shape the system response This may make it possible to increase the controller gain improving command and feedback tracking while maintaining stability Forward loop filters are available for all control modes and include A Low Pass filter that attenuates signals above a specified frequency A Band Stop filter that attenuates signals in a specified band around a specified frequency A Break Recover filter that attenuates signals above the Break frequency Phase lag of the filter is reduced at higher frequencies by limiting the filter attenuation at frequencies above the Recover frequency A Lead Lag filter that applies a lead lag compensator with a maximum of 2 poles lag and 2 zeros lead Signals will be attenuated above the Pole 1 and Pole 2 frequencies
48. the existing calibration values as a Starting point If you are calibrating a sensor for the first time you may find it necessary to e Perform an initial tuning of the sensor channel before calibration e Perform the procedure twice If you are recalibrating a sensor use the existing calibration values as a starting point Full range conditioners allow you to choose Gain Delta K or Gain Linearization for calibrating extensometers The mV V Pos Tension and mV V Pos Comp calibration types are typically not used for controllers equipped with full range conditioners e During calibration Manual Offset should always be set to zero e During calibration ensure that Electrical Zero Lock is checked on the Offset Zero tab of the Inputs panel e After calibration do not change the electrical zero adjustment Readjustment of electrical zero after calibration will change the point at which linearization takes place disturbing other calibration settings especially Delta K MTS 793 Tuning and Calibration What you will need Range Support Extensometer Calibration To calibrate an extensometer you will need e An extensometer calibrator such as an MTS Model 650 03 01 Extensometer Calibrator e A digital voltmeter DVM Extensometers are typically calibrated such that the maximum strain represents 100 of the full scale capacity of the extensometer Extensometer Calibration Abbreviated Procedure Task 1 Get thin
49. the list Special terms Illustrations Electronic manual conventions Hypertext links Conventions The first occurrence of special terms is shown in italics Illustrations appear in this manual to clarify text It is important for you to be aware that these illustrations are examples only and do not necessarily represent your actual system configuration test application or software This manual is available as an electronic document in the Portable Document File PDF format It can be viewed on any computer that has Adobe Acrobat Reader installed The electronic document has many hypertext links displayed in a blue font All blue words in the body text along with all contents entries and index page numbers are hypertext links When you click a hypertext link the application jumps to the corresponding topic Preface 13 Conventions 14 Preface Chapter 1 Introduction Where to find control descriptions for specific controller models Contents MTS 793 Tuning and Calibration This manual describes how to perform servovalve adjustments tune and calibrate all MTS 793 Controllers Note TestStar Ils TestStar II AP and FlexTest II CTM Controllers are not equipped with this manual The equivalent information is located in the associated service manual PDF on the 793 Installation CD This chapter describes how individual tuning and calibration controls work in general that is their principals of operation
50. up a simple test program using the Function Generator FG A For Control Mode select the dual compensation control mode to be tuned B For Command Type select Cyclic C Create a command with an amplitude and frequency appropriate for the specimen D For Wave Shape select Sine Select a Compensator method Configure the Scope window to monitor command and secondary force feedback signals Tuning Procedures 107 How to Perform Advanced Tuning Techniques Standalone FlexTest SE Controllers See Scope in the FlexTest SE Users manual for more information Automated Controllers See About the Scope in the MTS 793 Control Software manual for more information WARNING Pressing the Station Controls panel s Run button will put actuators in motion A moving actuator can injure anyone in its path Always clear the actuator area before pressing the gt button 9 Start the test program A Apply station hydraulic power B Click or press gt to start the tuning program 10 Adjust the Conversion Gain and Integrator Gain A For Adaptation State select Hold and Reset or Reset All B Gradually increase the Conversion Gain until the scope shows that the secondary force feedback is approximately 80 of its commanded value During normal operation the compensator will increase the feedback amplitude until it matches the command amplitude C Increase the Integrator Gain if the scope shows
51. your data depends on the manufacturer of your sensor Your sensor should include a calibration data sheet that shows the data point tolerance Sensors from MTS include a sensor calibration data sheet that shows the data points as it was calibrated 1 Record the data points for compression Standalone FlexTest SE Controllers A Adjust the Setpoint to achieve a load standard readout of Zero B Adjust the Setpoint between zero and full compression three times This exercises the force sensor to remove hysteresis C Establish the zero reference Using a load standard e Adjust Setpoint for 0 kN Then zero the load standard readout Using dead weights e Remove all dead weights e Adjust the Manual Offset for a signal value of 0 KN on the DVM or other monitoring device Select Setup gt Force gt Offset Zero gt Manual Offset D Adjust the Setpoint to achieve a load standard reading of 20 compression and record the meter reading Repeat this step for 40 60 80 and 100 compression Automated Controllers MTS 793 Tuning and Calibration 161 Force Sensor Calibration A Adjust the Manual Cmd slider on the Manual Command window to achieve a load standard readout of zero B Adjust the Manual Cmd slider between zero and full compression three times This exercises the force sensor to remove hysteresis C Establish the zero reference Using a load standard e Adjust Manual Cmd slider for 0 KN Then zero the l
52. 249 k 10 499 k 350 Q 1 mV V 100 100 k 50 200 k 20 499 k 10 1000 k 700 Q 2 mV V 100 100 k 50 200 k 20 499 k 10 1000 k 700 Q 1 mV V 100 200 k 50 402 k 20 1000 k 10 2000 k 3 FlexTest SE LE FlexTest GT TestStar IIm Controllers only If you do not have transducer ID modules on your sensor cables install the shunt calibration resistor as follows A m 0 O W Select the appropriate shunt calibration resistor Bend the resistor leads 90 for a 0 3 inch separation Cut the resistor leads 0 12 inch from the bend Insert the resistor into the connector solder cups and solder Complete and attach a shunt calibration label as specified on the 493 40 41 Carrier I O Shunt Calibration Kit MTS PN 100 028 185 Install the shunt cal resistor connector assembly into the appropriate slot of the SHUNT CAL connector on the front panel of the appropriate I O Carrier Module 205 Extensometer Calibration 206 SHUNT CAL I O Option Slot 1 Shunt Cal Resistor Location I O Option Slot 2 Shunt Cal Resistor Location I O Option Slot 3 Shunt Cal Resistor Location I O Option Slot 4 Shunt Cal Resistor Location 4 FlexTest IIm CTC Controllers only Install the shunt calibration resistor into the R Cal jacks in the appropriate DC conditioner You must know which DC O conditioner is associated with the strain sensor You also need to know which of the two DC conditioners on the module is used by your extens
53. 793 Tuning and Calibration 100 147 134 C Copyright information Trademark information Software verification and validation Publication information 2008 MTS Systems Corporation All rights reserved MTS Temposonics and TestWare are registered trademarks of MTS Systems Corporation FlexTest MPT Station Builder Station Manager and TestStar are trademarks of MTS Systems Corporation Adobe is a registered trademark of Adobe Systems Inc Acrobat is a trademark of Adobe Systems Inc PowerPC is a registered trademark of International Business Machines Corporation Microsoft and Windows are registered trademarks of Microsoft Corporation MTS software is developed using established quality practices in accordance with the requirements detailed in the ISO 9001 standards Because MTS authored software is delivered in binary format it is not user accessible This software will not change over time Many releases are written to be backwards compatible creating another form of verification The status and validity of MTS operating software is also checked during system verification and routine calibration of MTS hardware These controlled calibration processes compare the final test results after statistical analysis against the predicted response of the calibration standards With these established methods MTS assures its customers that MTS products meet MTS exacting quality standards when initially installed and will c
54. 793 Tuning and Calibration 1 Get things ready A B a Note If necessary select the tuning access level Remove any specimen Determine which servovalve of the dual valve pair you want to balance first then mount a blocking plate on the port of the other servovalve When installing the blocking plate ensure that its holes are aligned with the servovalve port holes and a gasket is used Tuning Procedures 59 How to Balance the Servovalve D Apply hydraulic pressure A WARNING Selecting the Enable Manual Command allows you to manually position actuators A moving actuator can injure anyone in its path Always clear the actuator area before selecting Enable Manual Command 2 Position the actuator at midstroke Standalone FlexTest SE Controllers A Enable the front panel Dial B Press the Status button twice to display the Status menu and select Setpoint While observing the actuator use the Dial to position the actuator at or near its midstroke position Automated Controllers A In the Station Controls panel s toolbar click a B Inthe Manual Command window select the Channel with the dual valves that need balancing For the Control Mode select a displacement control mode D Select Enable Manual Command Use the Manual Cmd to position the actuator at or near its midstroke position 3 Record and zero displacement I Gain Standalone FlexTest SE Controllers A Select Tuning gt Manua
55. 793 Tuning and Calibration About saving elements of a parameter set How to Manually Tune the Control Loop It is important that you save your parameter set as you complete the various parts that make up a parameter set Throughout this manual you will be performing discrete procedures while building a single parameter set e If you have already established your default parameter set for the current station and you are creating a new parameter set for a specific test save the parameters with a different name e Different tests and or specimens may require different parameter sets Tuning the Strain Control Mode Guidelines When to tune MTS 793 Tuning and Calibration A strain control mode typically uses the feedback signal from an extensometer You need a specimen installed to tune a strain control mode Use a triangle waveform for the initial tuning Do not use a square waveform for tuning A square wave can cause the extensometer to move or fall off the specimen which can cause the system to go unstable If gain is too low the system may be sluggish or unresponsive with large static offsets or it may be uncontrollable If you observe a noisy extensometer feedback signal use the FL Filter setting to help suppress any unwanted mechanical resonance A strain control mode usually only needs to be tuned once However you may want to retune a strain control mode if The type of specimen has changed Any changes
56. 93 Controllers include FlexTest IIm CTC FlexTest SE FlexTest GT and TestStar IIm Controllers For each task instructions are provided for standalone FlexTest SE Controllers and Automated Controllers Standalone FlexTest SE Controllers refer FlexTest SE Controllers configured to operate in the standalone mode not equipped with a PG Automated Controllers refer to controllers equipped with MTS Model 793 Software This includes FlexTest IIm CTC automated FlexTest SE FlexTest GT and TestStar IIm Controllers Note Automated Flexlest SE Controllers are equipped with a PC in which Exclusive Control is assigned to Station Manager For more information about Exclusive Control see the FlexTest SE Users manual Note Because of hardware variations and optional features some of the steps in the procedures may not apply to your specific controller model Steps that apply only to specific models and options are qualified For a description of the specific calibration controls displayed on the front panel of standalone FlexTest SE Controllers see the FlexTest SE Users manual For a description of the specific calibration controls displayed in MTS control software included with Automated Controllers see the MTS 793 Control Software manual This pertains to FlexTest IIm automated FlexTest SE FlexTest GT and TestStar IIm Controllers 115 Contents Pre Calibration Considerations 117 Shunt Calibration 120 Displacement Sensor Calibratio
57. Controllers In the Station Manager window s toolbar select an access level of Tuning 7 Observe actuator response If necessary correct P Gain during warm up If the actuator responds in a sluggish manner increase the P Gain setting If you hear an unusual or unexpected sound decrease the P Gain Standalone FlexTest SE Controllers Select Tuning gt Manual gt P Gain Automated Controllers A On the Station Manager window s Display menu select Station Setup B Click the Channel Tuning icon to open the Tuning panel the click the Adjustments tab to display the P Gain control 8 After 30 minutes click Stop 9 Remove hydraulic pressure from the station How to Set Servovalve Polarity Servovalve polarity refers to the direction the servovalve moves the actuator in response to a positive command It can be set to normal or invert Typically a servovalve with a normal polarity extends the actuator in response to a positive command Conversely a servovalve with an inverted polarity retracts the actuator in response to a positive actuator command Before you can set servovalve polarity you must determine if the current servovalve polarity follows the normal convention The procedures that follow determines servovalve polarity by having you observe actuator movement while applying a positive Setpoint command to the actuator Procedures for both Standalone and Automated Controllers are described 52 Tun
58. D for other tensile force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale MTS 793 Tuning and Calibration Force Sensor Calibration 13 Record conditioner feedback readings at predetermined compressive force command points Standalone FlexTest SE Controllers A Use the Dial to adjust the Setpoint for a 2 compressive force command B Record the force standard s readout value and corresponding conditioner feedback reading in the 2 row of your record sheet C Repeat steps A and B for other compressive force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A Adjust the Manual Cmd slider for a 2 compressive force command B Record the force standard readout signal and corresponding conditioner feedback reading at the 2 command line of your record sheet C Repeat steps A and B for other compressive force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale 14 Turn off system hydraulics 15 On the Linearization Data window enter the force standard values and corresponding conditioner feedback readings for all command points previously recorded on a separate sheet 16 Turn on system hydraulics MTS 793 Tuning and Calibration 173 Force Sensor Calibration 174 17 Verify linearization data Standalone FlexTest SE Controllers A Using the Dial adjust the Se
59. Displacement Sensor Calibration Task 5 132 Standalone FlexTest SE Controllers Using the front panel Dial adjust the Setpoint to fully retract the actuator Select Status gt Setpoint Automated Controllers Adjust the Manual Cmd slider control on the Manual Command window to fully retract the actuator Remove hydraulic pressure Adjust phase for the maximum conditioner output Monitor the appropriate AC conditioner feedback signal Adjust Phase to achieve a maximum value Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Phase Automated Controllers Adjust the Phase control on the Calibration tab to achieve a maximum value Use the Station Signals panel to monitor the appropriate AC conditioner feedback signal Note When adjusting phase the LVDT feedback may exceed 10 volts You may need to lower conditioner gain before continuing phase adjustment Set the zero and offset Establishing zero requires the actuator to be set at mid displacement when you calibrate the LVDT for equal amounts of actuator extension and retraction Suppose you have an actuator with 10 cm displacement which actually has a 20 cm displacement Setting zero at mid displacement produces a displacement of 10 cm this is the most common approach However you can set zero anywhere within the full scale of the sensor such as with the actuator fully extended or retracted to produce a displacement range of 0 mm
60. FlexTest SE Controllers or Enable Manual Command automated controllers allows you to manually position actuators A moving actuator can injure anyone in its path Always clear the actuator area before manually adjusting actuator position 2 Position the actuator at or near its midstroke position Standalone FlexTest SE Controllers A Select Status gt Control Mode gt displacement B Select Status gt Setpoint C Enable the Dial D Use the Dial to adjust the Setpoint to position the actuator Automated Controllers A In the Station Controls panel s toolbar click a In the Manual Command window B Select the Channel whose valve balance needs checking MTS 793 Tuning and Calibration Tuning Procedures 57 How to Balance the Servovalve For the Control Mode select a displacement control mode D Select Enable Manual Command Use the Manual Cmd to position the actuator at or near its midstroke position 3 Record and zero displacement I Gain Standalone FlexTest SE Controllers A Select Tuning gt Manual gt I Gain B Write down the current displacement I Gain C Zero the I Gain Automated Controllers A In the Station Setup window click VV B In the Tuning panel click the Adjustments tab In this tab C Write down the current I Gain D Zero the I Gain 4 Setup a meter to view displacement error Standalone FlexTest SE Controllers A Select Meters B Select an existing meter such as Met
61. How to Perform Advanced Tuning Techniques 83 How to Auto Tune 83 How to Manually Tune Three Stage Servovalves 88 How to Use Error to Tune Gain 98 About Channel Limited Channel CLC Control Modes 101 How to Tune a CLC Control Mode 101 About Dual Compensation Control Modes 104 How to Tune a Dual Compensation Control Mode 106 About Tuning Filters 109 How to Enable a Tuning Filter 112 46 Tuning Procedures MTS 793 Tuning and Calibration When to Tune Checklist MTS 793 Tuning and Calibration When to Tune Tuning is needed whenever any of the following events occurs A gross change in the compliance or size of the test specimen For example you were testing steel and change to rubber The servohydraulic configuration has changed For example a servovalve is replaced or changed to a different capacity The system is sluggish slow to react or not reaching the desired peaks However this is not always a tuning problem it could be insufficient velocity capability such as a low capacity servovalve If a control channel or sensor is recalibrated The system is unstable indicated by a humming or screeching sound When you observe poorly controlled accuracy When you create a new control mode or if the sensor for a control mode is changed The end levels or frequencies are significantly different from those observed earlier in the test For example you notice that the specimen characteristics change during the test
62. Select the control mode to which shunt calibration applies Standalone FlexTest SE Controllers Select Setup gt force or strain gt Calibration Automated Controllers A In the Station Manager window s Display menu select Station Setup B In the Station Setup window s navigation pane Channels locate and select the control mode needing a shunt calibration e g force or strain C In the Station Setup window click 2al Apply the shunt calibration Standalone FlexTest SE Controllers A Locate the shunt calibration controls toward the bottom of the calibration menu B Apply the shunt by setting the Shunt State control to On Automated Controllers A Inthe Inputs panel click the Shunt tab B If desired change units for the Shunt Reference Value C To apply the shunt click the button with three white bars While the shunt is applied the bars will turn green Note To apply a shunt calibration to an auxiliary input select Auxiliary Inputs in the navigation pane and click the input signal needing shunt calibration MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Shunt Calibration 7 Compare the Current Shunt Value to the Shunt Reference Value Consider recalibrating the sensor conditioner pair if the values differ by more than 0 2 For example if the Shunt Reference Value is displayed in Volts consider recalibrating if the Current Shunt Value differs more than 20 mV
63. Test SE Controllers Setup gt Output gt Inner Loop Automated Controllers In the Station Setup window s Drive panel click the Inner Loop tab For optimal system response tune the inner loop to be relatively less responsive and more stable than a typical outer loop A For Rate Input Selection select Spool Position B Increase Inner Loop Gain until you see a little overshoot on the oscilloscope Overshoot Oyvershoot aA FINN Ringing MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques C Slightly increase the Inner Loop Rate to eliminate this overshoot When properly tuned the waveform should be a square wave with rounded corners having no overshoot i N Too Low Correct Too High Zero the Spool Position Signal This task matches the electronic null of the spool position signal with the mechanical null position of the servovalve pilot spool During inner loop tuning it may be necessary to complete this procedure if the spool position signal voltage is not approximately equal though opposite polarity at opposite endcaps of a servovalve 1 Set the Valve Balance to zero Standalone FlexTest SE Controllers Select Setup gt Output 3 stage gt Valve Balance Automated Controllers On the Drive panel click the Valve tab then set the Valve Balance to zero 2 Ensure that the Offset control is set to zero Standalone FlexTest SE Controllers Select Setup gt Disp gt Offset
64. a sheet to corresponding data entries on the Linearization Data window Turn on system hydraulics Verify linearization data Standalone FlexTest SE Controllers A Using the Dial adjust the Setpoint for each tensile and compressive force command point on the Linearization Data window B At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditioner by comparing them with the corresponding values on the Calibration Data sheet Automated Controllers A Adjust the Manual Cmd slider for each tensile and compressive force command point on the Linearization Data window B At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditioner by comparing them with the corresponding values on the Calibration Data sheet If the data is valid Stop this procedure If the data is not valid Proceed to the next step 169 Force Sensor Calibration 170 7 Reset Linearization Data window to default values Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization gt lt lt Reset gt gt Automated Controllers Click Reset on the Linearization Data window to return to default values Exercise the force standard Standalone FlexTest SE Controllers Enable the front panel Dial then adjust the Setpoint to cycle the load standard readou
65. ain settings PID for the control mode are appropriate If the control mode has not been tuned yet use some default values Then recalibrate the sensor after the initial tuning MTS 793 Tuning and Calibration Force Sensor Calibration On the File menu select Open Station to open the appropriate configuration file on the Open Station window Select the Calibration access level Standalone FlexTest SE Controllers Select Config gt Access Level gt Calibration Automated Controllers In the Station Manager window toolbar select Calibration Set up a signal monitor Refer to page 128 for more information Mount the force standard LE a lo Z S t o eee Force Transducer lt lt Load Standard If you are using Gain Delta K or Gain Linearization for calibration set initial conditioner calibration values on the Calibration submenu A typical complement of ranges could be 100 50 20 and 10 of full scale You can create ranges for any percentage of full scale This creates a sensor calibration file and sets up any ranges you may want Example Suppose you have an actuator with a full scale capacity of 10 kN You might create ranges for 10 KN 5 KN 2 0 kN and 1 0 kN 153 Force Sensor Calibration Note Some systems do not provide or require multiple ranges such as those using full range conditioners e g Model 493 25 DUC module In this case only one range is us
66. al is out the ringing MTS 793 Tuning and Calibration Introduction 23 About Tuning Do you need derivative gain More about Derivative gain So derivative gain indicates the change in acceleration in the error signal Or in an equation Derivative Gain Gain x Command Feedback The symbol in the equation above means first derivative There s a good chance you do not It is used primarily in systems performing dynamic tests Consider this scenario You have a specimen that is quite springy such as fiberglass The test is calling for rapid changes in direction say for example more than 5 times a second and high velocities Proportional gain needs to be set quite high to get this kind of response Because things are changing so rapidly the system is electrically noisy If the system is making a rumbling sound you could use some derivative gain On the other hand it is unlikely for you to need derivative gain for soft materials such as elastomers Another quick and incomplete rule of thumb is to write down the ratings of your actuator and servovalve in kips and gallons per minute If kip gpm gt 1 then derivative gain probably has little effect on the loop Derivative gain is used with dynamic test programs It introduces a derivative of the feedback signal This means it anticipates the rate of change of the feedback and slows the system response at high rates of change Overshoot 24 Int
67. alibration Displacement Sensor Calibration Record the dial indicator value and conditioner feedback at the 2 row of your record sheet Repeat steps D and E for other retraction commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers Adjust the Manual Cmd slider for a 0 command Record the dial indicator value for the 0 command Enter the corresponding conditioner feedback reading in the Conditioner column at the appropriate row in the window Adjust the Manual Cmd slider for a 2 retraction command Record dial indicator value and conditioner feedback at the 2 row of your record sheet Repeat steps D and E for other retraction commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Record dial indicator and conditioner feedback readings at predetermined extension command points Standalone FlexTest SE Controllers A Use the Dial to adjust the Setpoint for a 2 extension command Record the dial indicator and conditioner feedback values at the 2 row of your record sheet Repeat steps A and B for other extension commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A Adjust the Manual Cmd slider for a 2 extension command Record the dial indicator value and conditioner feedback at the 2 row of your record sheet 143 Displacement Sensor Cal
68. ance due to specimen size forces from test components cable length and so forth The zero position can be set anywhere within the full scale range of the strain sensor Note The arms of the extensometer must be in the zero reference position Depending on the extensometer this can be accomplished using the zero pin stop block or a special fixture Standalone FlexTest SE Controllers 1 Monitor the current strain output to ensure that it is zero 2 If it is not zero click Auto Offset Select Setup gt Strain gt Offset Zero gt lt lt Auto Offset gt gt Automated Controllers 1 Click Auto Offset icon on the Station Controls panel to display the Signal Auto Offset window 2 If the current strain output is not zero click the Auto Offset icon next to the signal value to offset it automatically Note You can also click the Auto Zero button on the Calibration tab of the Station Setup panel to automatically offset the current strain output Note For calibration purposes it is desirable to use Auto Zero However you must ensure that any other offsets such as those occurring through the use of the Auto Offset are eliminated first MTS 793 Tuning and Calibration Extensometer Calibration Task 4 Gain Delta K Calibration If you are using Gain Delta K for your calibration type complete the following procedure If not complete Task 5 Gain Linearization Calibration on page 198 Calibration setup 1 Ensure that the
69. are made in the force train Any time hydraulic system potential has changed such as after servovalve hose or pump replacement You want to fine tune the control mode You deem it necessary as a result of scheduled system calibration or you feel system response should be improved or reduced Tuning Procedures 77 How to Manually Tune the Control Loop Prerequisites Be sure the following items are completed before you begin tuning the strain control mode e The specimen is installed you may choose to use a broken specimen e You have created a station configuration file e You have created a station parameter set Tuning procedure This basic strain tuning procedure should work for most applications consider it a guideline You should be familiar with the background information presented in this chapter so you can modify the following procedure for your specific system 1 Select an access level of Tuning 2 Define the strain command This step defines the tuning command using the function generator Standalone FlexTest SE Controllers Tuning gt Manual gt FG Automated Controllers Click i on Station Manager CONTROL SETTING Wave Shape Ramp Frequency 1 Hz Target Setpoint 0 mm Amplitude Set an initial amplitude of zero After verifying system control increase the amplitude to a reasonable level typical 0 001 mm mm 3 Set up the Scope Note You can use an oscilloscope instead of the software
70. ariety of amplitudes by creating a test that cycles once at each of the target amplitudes If you have the optional MultiPurpose TestWare application run the test to acquire timed data so you can evaluate the results for each amplitude Introduction 35 About Tuning About Auto Tuning Basic auto tuning Advanced and Advanced Only auto tuning 36 Introduction The auto tuning feature tunes any PIDF control mode to a moderate level It exercises the actuator with a sweep function while monitoring the feedback of the control mode being tuned Then it calculates the control mode s PIDF tuning parameters Note Standalone FlexTest SE Controllers are not equipped with Advanced or Advanced Only auto tuning modes Your controller includes three auto tuning modes Basic Advanced and Advanced Only The Advanced auto tuning mode automatically performs Basic auto tuning before progressing to Advanced auto tuning The Advanced Only mode omits Basic auto tuning and performs only Advanced auto tuning When you run Basic auto tuning the auto tuner disregards your current PIDF gain settings It applies the minimum required drive signal to ramp the feedback to 80 of the auto tuning limits It then measures the relationship between the feedback velocity and the valve opening signal and then derives the minimum PIDF gains required to track the command The majority of tests will run adequately with the settings calculated through basic
71. arm Up Station Hydraulics Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Stay clear of the actuators when applying hydraulic pressure 2 If necessary turn on hydraulic pressure Note The HPU can be configured for first on If this is the case start the appropriate HSM A Inthe power selection box click Low and then High for the HPU If an HPU is not listed start the HPU at the pump B If an HSM is present click Low and then High for the appropriate HSM 3 Check system interlocks If the Hydraulic Interlock or Program Interlock indicator is lit determine the cause correct it and then click Reset If either interlock indicator lights again you will need to determine the cause of the interlock and correct it before proceeding 4 Press Run to start the function generator 5 Open the Tuning submenu or panel Standalone FlexTest SE Controllers Select Tuning gt Manual Automated Controllers A Click A to display the Tuning panel B In the Tuning panel click the Adjustments tab 6 If necessary select an access level of Tuning Standalone FlexTest SE Controllers Config gt Access Level gt Tuning Tuning Procedures 51 How to Set Servovalve Polarity Automated
72. as been connected to analog input Ch 1 Force e J Transducer Identification MTS Systems Corp 661 20F 03 112233 Please confirm the new sensor assignment for this analog input H Change sensor assignment from sParameter Set to Cancel The sensor file list in this window only lists sensor files that match the basic TEDS information conditioner type and dimension The sensor assignment window contains the same sensor assignment list found in the Station Setup window TEDS devices Available TEDS devices include e MTS sensors that include basic TEDS information saved in an integral TEDS chip that is built into the sensor e MTS TEDS Transducer ID modules that include a chip that stores basic TEDS information for a specific sensor The TEDS module connects to the sensor MTS 793 Tuning and Calibration 119 Shunt Calibration Shunt Calibration 120 When to use shunt calibration You can verify the calibration accuracy of a DC sensor conditioner pair through shunt calibration Shunt calibration works by shunting a precision resistor across one arm of the sensor s Wheatstone bridge The resulting imbalance provides a reference value that is recorded on the calibration data sheet that accompanies the sensor Note With systems that use Series 494 hardware you can use the HWI Editor application to select the arm of the bridge where the shunt calibration resistor willl be applied A current shunt
73. ay be accomplished with the actuator up against the force sensor The actuator acts as a specimen reacting against the force sensor Review the following recommendations if you must tune without a specimen e If you are using a load frame adjust the load unit crosshead so the actuator can reach the force sensor e Carefully adjust the actuator using a tuned length control mode so it contacts the force sensor e Switch to force control before you proceed with initial tuning 38 Introduction MTS 793 Tuning and Calibration Compensating for specimen changes Changing the range of tuning controls MTS 793 Tuning and Calibration About Tuning Optimal system operation may require a level of detuning to compensate for specimen changes during a test e lt A highly tuned system provides the greatest level of response but this places the system near the point of oscillation or instability e As a specimen changes characteristics during testing the response of the system also changes This can cause unstable operation e You may need to retune the system response when the characteristics of the specimen change during a test e For the greatest control accuracy use a compensator It is possible that the amount of adjustment for a tuning control is too coarse or inadequate Click the adjustment button such as P Gain and use the Range Select window to change the range of the adjustment Reducing the range produces smaller ste
74. box Enter the calibration excitation value Vdc in the Excitation entry box Automated Controllers A B Enter the full scale force values in the Fullscale Min Max entry boxes Adjust Neg Tension for the required tension sensitivity value mV V 177 Force Sensor Calibration C Adjust Pos Compression for the required compression sensitivity value mV V D Adjust Excitation for the required calibration excitation value DC Task 8 Establish the shunt calibration reference Each resistive bridge type transducer DC sensor uses a shunt resistor to check the calibration accuracy of the sensor conditioner combination Each DC conditioner supports a shunt resistor 1 2 178 Turn off hydraulic power Remove the load standard Turn on hydraulic power Zero the force sensor output Standalone FlexTest SE Controllers Adjust the Setpoint for a 0 kN output The sensor output must be 0 000 kN for a proper shunt calibration If not return to Set the zero and offset on page 156 Automated Controllers Adjust the Manual Cmd slider on the Manual Command window for a 0 kN output The sensor output must be 0 000 kN for a proper shunt calibration If not return to Set the zero and offset on page 156 Change the control mode to displacement Standalone FlexTest SE Controllers Select Status gt Control Mode gt Disp Automated Controllers On the Manual Command window change Control M
75. bration user level on the Access Level list Type the required password By default the password is Calibration however it can be changed during the software installation procedure 127 Displacement Sensor Calibration 4 Set up a signal monitor You will be monitoring sensor output when making adjustments throughout this procedure You can monitor the sensor output in the same units that you are using for the calibration Standalone FlexTest SE Controllers Use an external DVM to monitor sensor output from a BNC connector located on the front panel or use the Meters panel Automated Controllers e Use an external DVM to monitor encoder output from a BNC connector on the Analog Out panel located on your controller chassis e Use the Meters window to monitor sensor output e Use the Station Signals panel to monitor sensor output On the Station Manager Display menu select Station Setup In the navigation pane select Station Signals to display the Station Signals panel to monitor current values for user defined signals For more information on using the Station Signals panel refer to About the Station Signals Panel in Chapter 2 Station Manager of the MTS 793 Control Software manual 5 Select the desired calibration type Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type Automated Controllers On the Station Setup Inputs panel Calibration tab use Cal Type for your selec
76. by the load standard and your commanded tensile force match Example Suppose your actuator has a 100 tensile force rating of 10 KN In this step you would apply 8 kN of command and even though the station signals would read 8 kN of feedback the force standard may only read 4 kN This shows the conditioner sensor pair are out of calibration 4 Adjust Post amp Gain on the Calibration submenu or tab to increase the tensile force reading on the load standard until it equals your tensile force command If applicable repeat steps 2 through 4 for all ranges Example Suppose you have an actuator with a full scale capacity of 10 kN and ranges of 10 kN 5 kN 2 kN and 1 KN In this case you would repeat this process and calibrate tension at 80 of each range 8 kN 4 kN 1 6 kN and 0 8 kN Note Some systems do not provide or require multiple ranges such as those using full range conditioners e g Model 493 25 DUC module In this case only one range is used typically 100 Note This procedure assumes a positive command extends the actuator and a negative command retracts the actuator If not use the opposite polarity for any values given 1 Exercise the force sensor Standalone FlexTest SE Controllers After enabling the front panel Dial adjust the Setpoint to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Select Status gt Setpoint Aut
77. ctuator sticking before moving continue on to the next step to adjust the dither amplitude 64 Tuning Procedures MTS 793 Tuning and Calibration How to Adjust Dither Note Ifyou hear an unusual sound coming from the servovalve the dither amplitude is set too high 8 Increase Dither Amplitude until the feedback is smooth Standalone FlexTest SE Controllers Select Setup gt Output gt Dither Amplitude Automated Controllers A In the Station Manager window s Display menu select Station Setup B In the Station Setup window navigation pane s Channels locate and select the channel whose servovalve dither you want to adjust C In the Station Setup window click zi Three stage valves In the Drive panel click the Valve tab Method 2 1 Select an access level of Tuning 2 Remove any specimen 3 Apply hydraulic pressure to the station 4 Increase Dither Amplitude until you can hear the dither and then decrease Dither Amplitude until the noise goes away Dither Frequency In addition to Dither Amplitude your Controller is equipped with a Adjustment Dither Frequency control The default dither frequency is 528 Hz which is effective for most applications and should not require adjustment However if the dither frequency begins to resonate with test frequencies adjustment may be necessary MTS 793 Tuning and Calibration Tuning Procedures 65 How to Manually Tune the Control Loop How to Manuall
78. current calibration values on the Calibration Sensor and Shunt tabs to the sensor calibration file Note Systems equipped with full range conditioners e g Model 493 25 DUCs do not require or support multiple ranges They use one range that is typically set to 100 Task 10 Calibrate additional ranges This task describes how to calibrate additional ranges Each sensor calibration file can have calibration data for four ranges If you have a need for additional ranges simply create another sensor calibration range e Use the calibration values from the previous range as a starting point as 182 MTS 793 Tuning and Calibration Force Sensor Calibration For a starting point set additional range values using the following guideline Fora 50 range multiply the 100 full scale value by 2 Fora 20 range multiply the 100 full scale value by 5 Fora 10 range multiply the 100 full scale value by 10 If you adjust the zero reference it may affect the other ranges Adding a range Ifthe sensor calibration file must have additional ranges defined perform the following 1 2 3 6 On the Tools menu select Sensor File Editor Open the sensor file for the sensor you just calibrated Click Add under Range Definition By default Range 2 is entered Highlight the name Range 2 and change it to something meaningful Example Suppose you are setting up a calibration file for a 5 kN range You ma
79. d Error and select a Trace Time of 5 seconds Also ensure Auto Scale is on it is on by default Note To improve your view of the waveform click the Rescale button to maximize the waveform on the display Apply the tuning program with a square wave and monitor the amplitude of the settled portion of the error signal The settled portion of the error signal should be the same level for both segments if not adjust I Gain as required a oe x Adjust Gain e Ideal Waveform Apply the tuning program with a ramp and monitor the amplitude of the settled portion of the error signal The settled portion of the error signal should be balanced if not adjust I Gain as required M i Balance difference Zero _ Y around zero Monitor the error signal then disrupt the system by changing the command by adjusting the Setpoint control with the Dial When you do this the error should return to zero within 5 10 seconds If not increase the reset I Gain setting and repeat the procedure until the error zeros itself within a reasonable time period MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques About the Cascaded PIDF Control Mode Note Cascaded PIDF control mode is a keyed option It is available when you purchase Model 793 21 Cascade Control The Cascaded PIDF control mode is typically used for testing that requires a high degree of stability under dynamic conditions This control mode uses two
80. d read 10 V DC 40 5 V DO If the voltage is correct proceed to the next step in this procedure If the voltage is off by more than 0 5 V you may need to mechanically center the pilot spool Complete this procedure then recheck spool position voltages at each endcap before you resume inner loop tuning Return Conditioner gt Polarity to its original setting Automated Controllers In the Drive panel click the Valve tab In the Valve tab produce a Spool Position output signal of 10 V DC with the spool driven into the opposite end cap A Reverse the Polarity setting to drive the inner loop spool into the other end cap Check the meter It should read 10 V DC 40 5 V DC If the voltage is correct proceed to the next step in this procedure If the voltage is off by more than 0 5 V you may need to mechanically center the pilot spool Complete this procedure then recheck spool position voltages at each endcap before you resume inner loop tuning Return Polarity to its original setting MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques 9 Monitor the spool position signal with a scope Standalone FlexTest SE Controllers Press Scope to monitor the spool position signal Note _ f your Flexlest SE Controller is not equipped with the optional Scope use an external oscilloscope Automated Controllers A In the Station Manager window s toolbar click m once to display a sin
81. djust Post Amp Gain until your dial indicator or other readout device shows that the actuator s physical retraction equals your retraction command Record dial indicator and conditioner feedback readings at predetermined retraction command points Note After shutting down system hydraulics you will enter these 146 recorded readings on the Linearization Data window MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration 11 Displacement Sensor Calibration Standalone FlexTest SE Controllers A Use the front panel Dial to adjust the Setpoint for a 0 command Record the dial indicator value at 0 command Record the corresponding conditioner feedback reading on your record sheet Use the Dial to adjust the Setpoint for a 2 retraction command Record the dial indicator value and conditioner feedback at the 2 row of your sheet Repeat steps D and E for other retraction commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A B Adjust the Manual Cmd slider for a 0 command Record the dial indicator value at 0 command Record the corresponding conditioner feedback reading at the 0 row of your record sheet Adjust the Manual Cmd slider for a 2 retraction command Record the dial indicator and conditioner feedback values at the 2 row of your record sheet Repeat steps D and E for other retraction commands typically at 4
82. e 1 Select Gain Linearization for Cal Type Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization Automated Controllers Select Gain Linearization for Cal Type on the Calibration tab of the Inputs panel 2 Apply a retraction command that is 80 of the full scale range Standalone FlexTest SE Controllers A B Enable the front panel Dial Use the Dial to adjust the Setpoint for 80 of the full scale range Verify that your LVDT displacement signal equals 80 of the full scale range Automated Controllers A Open the Manual Command window and then click on the Enable Manual Command Adjust the Manual Cmd slider on the Manual Command window for 80 of the full scale range Use the Station Signals panel to verify that your LVDT displacement signal equals 80 of the full scale range During the initial calibration and tuning of your system it may take repeated adjustment for the two values to match 141 Displacement Sensor Calibration Note Ifthe actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this control mode Increase the proportional gain P Gain on the Calibration submenu or tab to correct sluggish actuator movement Increase the reset integration value I Gain to help the feedback match the command At this point unless the conditioner is already in calibration t
83. e an adequate P Gain setting for the displacement control mode skip this step Note For three stage servovalves the initial maximum P Gain setting is 0 8 so enter an initial value 0 5 MTS 793 Tuning and Calibration Tuning Procedures 53 How to Set Servovalve Polarity 54 Tuning Procedures Standalone FlexTest SE Controllers A Select Tuning gt Manual gt P Gain B In P Gain enter 1 Automated Controllers A On the Station Manager Display menu select Station Setup B Ensure that the correct displacement control channel is selected in the navigation panel C Click the Channel Tuning icon to open the Tuning panel D Inthe P Gain box enter 1 Set the polarity of the servovalve Standalone FlexTest SE Controllers Select Setup gt Output gt Polarity Normal Automated Controllers A Ensure that the correct displacement control channel is selected in the navigation panel B Click the Channel Drive icon to open the Channel Drive panel and then click the Valve tab C Select Normal default If necessary clear hydraulic interlocks If the Hydraulic Interlock indicator is lit determine the cause correct it and then press reset If an interlock indicator lights again you will need to determine the cause and correct it before proceeding 5 Apply hydraulic pressure to the station MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How to Set Servovalve Polarity 6 Mov
84. e force control mode MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques 1 Install a dummy specimen 2 Set and enable the force feedback signal s limits typically just outside the signal s full scale range Select Setup gt Force gt Limits 3 Set up auto tuning parameters A Select Tuning gt Auto Tuning B For Control Mode select displacement C For Mode to Tune select force Pressing the Run button will put the actuator in motion A moving actuator can injure anyone in its path Always clear the actuator area before pressing the Run button Note While auto tuning is in process you cannot changes channels or contro modes Also the active and auto tuning signal s tuning parameters will be disabled 4 Press Run to start auto tuning The controller displays the following or a similar message The Mode to Tune CForce is not the control mode which will be active during auto tuning Ensure that the active Control Mode is tuned prior to proceeding If the selected Mode to Tune requires feedback from a specimen ex Force Torque Strain ensure that a specimen is mounted Select Yes or Press lt lt OK gt gt if you have tuned the channel s displacement mode and installed a specimen When the Controller starts auto tuning the following is displayed Auto Tuning in Progress To terminate auto tuning before completion press lt Stop gt Wh
85. e output of the load standard Note All calibration tools should be calibrated to an industry standard Note This calibration procedure calibrates the DC conditioner for a force sensor of 10 KN You will need to adjust the procedure to accommodate your force sensor Force Sensor Calibration Abbreviated Procedure MTS 793 Tuning and Calibration The following abbreviated procedure outlines a force sensor Coad cell calibration process More detailed calibration information is available on the pages listed Task 1 Get things ready on page 152 Task 2 Turn on hydraulic pressure on page 155 Task 3 Verify the conditioner polarity on page 155 Task 4 Set the zero and offset on page 156 Task 5 Gain Delta K Calibration on page 156 Note The Gain Linearization Calibration procedure applies only to controllers equipped with full range conditioners e g Model 493 25 DUC module Task 6 Gain Linearization Calibration on page 164 Task 7 Millivolt Volt Calibration on page 175 151 Force Sensor Calibration Task 8 Establish the shunt calibration reference on page 178 Task 9 Save the calibration on page 182 Note Controllers equipped with full range conditioners e g Model 493 25 DUC module do not provide or require multiple ranges Task 10 Calibrate additional ranges on page 182 Force Sensor Calibration Detailed Procedure Task 1 152 Get thi
86. e proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the integration value I Gain to help the feedback match the command At this point unless the conditioner is already in calibration the tensile force applied to the force transducer will not equal your commanded value You will adjust gain in the next step so that the actual tensile force and your commanded tensile force match Example Suppose your actuator has a 100 tensile force rating of 10 KN In this step you would apply 8 kN of command and even though the station signals would read 8 kN of feedback the force standard may only read 4 kN This shows the conditioner sensor pair are out of calibration Adjust the Post amp Gain control to increase the tensile force reading on the load standard until it equals your tensile force command Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization gt Post Amp Gain Automated Controllers Adjust the Post amp Gain control on the Calibration tab of the Inputs panel Apply a compressive force command that is 80 of the full scale range Standalone FlexTest SE Controllers A Using the Dial adjust the Setpoint for a compressive force command that is 80 of the full scale range B Verify that your force transducer feedback signal is 80 of the full scale range Automated Controllers A Adjust the Manual Command slider
87. e tensile force reading on the load standard until it equals your tensile force command Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization lt Post Amp Gain Automated Controllers Adjust the Post amp Gain control on the Calibration tab of the Inputs panel Apply a compressive force command that is 80 of the full scale range Standalone FlexTest SE Controllers A Using the front panel Dial adjust the Setpoint for a compressive force command that is 80 of the full scale range B Verify that your force transducer feedback signal is 80 of the full scale range MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Force Sensor Calibration Automated Controllers A Adjust the Manual Command slider for a compressive force command that is 80 of the full scale range Use the Station Signals panel to verify that the compressive force signal is approximately equal to 80 of the full scale range 6 Record force standard and conditioner feedback readings at predetermined tensile force command points Note After shutting down system hydraulics you will enter these recorded readings on the Linearization Data window Standalone FlexTest SE Controllers A B Use the Dial to adjust the Setpoint for a 0 command Record the force standard s readout value in the 0 row of your record sheet Enter the corresponding conditioner
88. e the actuator Note The following conditions assume you want a positive command to retract the actuator Standalone FlexTest SE Controllers A B Enable the front panel Dial Press the Status button twice to display the Status menu and select Setpoint While observing the actuator use the Dial to slowly apply a positive Setpoint command to the actuator Automated Controllers A Click the Manual Command button to open the Manual Command window In the Channel selection box select the desired control channel In the Control Mode selection box ensure that displacement control mode is selected Click on the Enable Manual Command check box to enable manual command On the Station Controls panel ensure that the Master Span is set for 100 On the Manual Command window increase the Manual Cmd adjustment to apply a positive command to the actuator 7 Interpret the actuator movement If the actuator extends when a positive command is applied the servovalve polarity is correct If the actuator retracts when a positive command is applied and the polarity setting is Normal some electrical element that affects the servovalve such as conditioner polarity or cable orientation has been reversed and should be remedied If the actuator begins in full retraction and applying a positive command does not extend it zero the command remove hydraulic pressure and change the servovalve polarity Then ret
89. e want the system to react quickly and positively One sign of a system with insufficient proportional gain is that it is sluggish There is only one problem with having proportional gain higher than necessary it is very difficult to keep the car on the road It flies off we overcontrol trying to correct it and the cycle continues A servo loop can do that too it is said to be ringing It is unstable There s nothing subtle about an unstable loop you ll hear it If the test fixture is large enough you ll feel it too So as a general rule the gain should be as high as possible without causing the loop to go unstable General principles to remember are e With a given error signal increasing the gain increases the input to the servovalve e Increasing the input to the servovalve opens it more e Opening the servovalve more moves the oil faster into the actuator e Moving oil faster makes the loop respond quicker reducing the error faster More about Proportional gain is used for all tuning situations It introduces a Proportional gain control factor that is proportional to the error signal Proportional gain increases system response by boosting the effect of the error signal on the servovalve Keep in mind e As proportional gain increases the error decreases and the feedback signal tracks the command signal more closely e Higher gain settings increase the speed of the system response e Too much proportional
90. ect Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters 5 Note the base control mode in the Tuning window 6 Adjust the PIDF controls for the control mode associated with the inner control loop 7 Save the inner loop tuning values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters 100 Tuning Procedures MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques About Channel Limited Channel CLC Control Modes Use a channel limited channels CLC control mode for specimen installation and removal Before CLC control modes can be tuned they must first be defined in the Station Builder application A CLC control mode requires an active and a limiting feedback signal e The active feedback signal controls the actuator s movement It is normally the channel s displacement feedback signal e The limiting feedback signal limits the actuator s force It is normally the channel s force feedback signal When CLC is used as the control mode the controller will not allow the actuator to exceed limits set for either the active or limiting feedback signals e Interlocks can trip if the actuator s active displacement feedback signal exceeds limits set for it in
91. ed typically 100 Note Sensor calibration and range information can be edited on the Sensor tab located on the Station Setup window Inputs panel See How to Create a Sensor File in Chapter 2 Station Manager of the MTS 793 Control Software manual Conditioner For force sensor calibration set the following initial conditioner calibration values calibration values Control Polarity Pre amp Gain Post amp Gain Total Gain Excitation Fine Zero Zero Balance Delta K Gain Delta K calibration only 154 Setting Normal 250 480 for Model 493 25 conditioner 2 1 for Model 493 25 conditioner 500 10 volts 0 0 MTS 793 Tuning and Calibration Force Sensor Calibration Task 2 Turn on hydraulic pressure AA WARNING Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Stay clear of the actuators when applying hydraulic pressure See Turn on hydraulic pressure on page 130 for a detailed procedure Task 3 Verify the conditioner polarity This task checks the polarity of the conditioner Different types of test systems are configured with different conditioner polarities The polarity of the conditioner the polarity of the valve driver and the connection positions of system cabling all
92. en auto tuning is complete the controller displays Auto Tuning for this mode has completed successfully Also when auto tuning is complete the results are displayed showing Current tuning values and Reference values Tuning Procedures 87 How to Perform Advanced Tuning Techniques Press Accept to apply the Reference values 5 Save the auto tuning values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters to save the New Values You may save auto tuning values to an existing parameter set or to a new parameter set How to improve auto You can attempt to further improve tuning using the following techniques tuning results e Use the auto tuning settings as a starting point when manually tuning each control mode e If your feedback signal is noisy use a tuning filter see About Tuning Filters on page 109 How to Manually Tune Three Stage Servovalves Note For Flexlest SE Controllers this procedure requires the optional Scope or an external oscilloscope Note This section applies only to systems using three stage servovalves such as the Model 49715 or 493 15 Servovalve About the inner loop Systems equipped three stage servovalves have an inner control loop inside the test system s primary or outer control loop The inner loop like the outer loop has gai
93. ensor calibration values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers Click Update File on the Calibration tab This saves the current calibration values to your current sensor calibration file 207 Extensometer Calibration 208 MTS 793 Tuning and Calibration Index A AC conditioners calibration 124 polarity 131 155 acceleration stabilizing with 29 actuator determine natural frequency 28 auto tuning 36 auto tuning how to 83 auto tuning the displacement control mode 84 auto tuning the force control mode 87 C Calibration extensometer 44 force 44 shunt 44 system 42 calibration AC conditioners displacement 124 DC conditioners force 124 150 190 encoders 185 gain controls 157 hydraulics turn on 130 155 188 LVDT 124 phase adjustment 131 shunt performing 121 Temposonics sensors 185 using full range conditioner 117 calibration file resource assignment 188 Cascaded Control Mode 99 Channel Limited Channel CLC control modes about 101 tuning 101 channel limited channel control mode 101 command sources 32 conditioner polarity 53 connections encoders 185 control modes displacement 31 force 31 strain 32 D d gain see derivative gain DC conditioners calibration 124 150 190 checking polarity 155 DC sensor calibration shunt calibration 121 default location of sensor calibration files 118 delta P sensors stabi
94. ensor signal The peaks and valleys should be balanced Before adjusting reset I Gain be sure the feedback signal is repeatable that is the same peaks and valleys are achieved MTS 793 Tuning and Calibration How to Manually Tune the Control Loop For example assume the test command is centered on zero and the meter displays 3 mm and 5 mm You want to adjust the reset I Gain control to achieve 4 mm If the command is not centered on zero monitor the difference between peaks and valleys of the sensor feedback to the upper and lower levels of the test command Any difference should be the same Note You can also use the Scope optional for FlexTest SE or an external oscilloscope to adjust Gain by monitoring the Error signal For more information see How to Use Error to Tune Gain on page 98 10 Save your tuning settings Standalone FlexTest SE Controllers Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers On the Station Manger File menu select Save Parameters As You can either select an existing parameter set or enter the name of a new parameter set to save About saving elements It is important that you save your parameter set as you complete of a parameter set the various parts that make up a parameter set Throughout this manual you will be performing discrete procedures while building a single parameter set e If you have already established your default parameter set
95. ent Sensor Calibration 2 Record the data points for LVDT retraction Standalone FlexTest SE Controllers A Adjust the Setpoint to achieve zero command B Adjust the dial indicator for a zero reference C Adjust the Setpoint to 20 retraction and record the dial indicator reading Repeat this step for 40 60 80 and 100 actuator retraction Automated Controllers A Adjust the Manual Cmd slider to achieve zero command B Adjust the dial indicator for a zero reference C Adjust the Manual Cmd slider to 20 retraction and record the dial indicator reading Repeat this step for 40 60 80 and 100 actuator retraction Note The Gain Linearization Calibration procedure that follows applies only to controllers equipped with full range conditioners e g Model 493 25 DUC module 140 MTS 793 Tuning and Calibration Displacement Sensor Calibration Task 7 Gain Linearization Calibration Initial LVDT calibration MTS 793 Tuning and Calibration If you are using Gain Linearization for your calibration type complete the following procedure If not complete Task 6 Gain Delta K Calibration on page 135 Important Using linearization data requires specific conditioner zeroing practices Ensure that Electrical Zero is set to zero and the Electrical Zero Lock box is set enabled Adjusting electrical zero after calibration may invalidate linearization data For initial calibration of an LVDT complete the following procedur
96. er 1 or select lt lt Add Meters gt gt to create a new meter and select it C For Meter Type select Timed D For Signal select Ch Error Automated Controllers A Select the meters icon on the Station Manager tool bar B Select the Meter 1 Setup button C For Meter Type select Timed D In Signal Selection select the channel whose valve balance needs checking For Signal select Displacement Abs Error 58 Tuning Procedures MTS 793 Tuning and Calibration How to Balance Dual Valves How to Balance the Servovalve 5 Zero displacement error with the Valve Balance control Standalone FlexTest SE Controllers A B G Select Setup gt Output gt Valve Balance Enable the Dial While observing Ch Error on the Meters panel adjust the Valve Balance control by rotating the Dial until Ch Error is Zero Automated Controllers A In the Station Setup window click a Three stage valves In the Drive panel click the Valve tab While observing Displacement Abs Error on the Meters panel adjust the Valve Balance control until Displacement Abs Error is zero 6 Return displacement I Gain to its original setting Standalone FlexTest SE Controllers Select Tuning gt Manual gt I Gain Automated Controllers I A B In the Station Setup window click V In the Tuning panel click the Adjustments tab Use the following procedure if you need to balance dual servovalves MTS
97. es and zeros then specify their frequencies 4 Save filter values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters Stabilization filters Stabilization filters are available for control modes equipped with stabilization resources and include e A1HzHigh pass filter that attenuates signals below 1 Hz e lt A Band pass filter that attenuates signals outside of a user definable band To select a Stabilization filter select and set up the desired filter type of 1 Hz High pass or Band pass For Band pass filters set the frequency band with the Frequency Limits control Note Some systems with a higher actuator frequency may benefit by selecting the following Frequency Limits a low cut off frequency that is approximately the actuator frequency and a high cut off frequency approximately 5 10 times the actuator frequency MTS 793 Tuning and Calibration Tuning Procedures 113 How to Perform Advanced Tuning Techniques 114 Tuning Procedures MTS 793 Tuning and Calibration Chapter 3 Calibration Procedures About calibration procedures for specific controller models Where to find control descriptions for specific controller models MTS 793 Tuning and Calibration This chapter contains step by step calibration instructions for MTS 793 Controllers In this manual MTS 7
98. es in Pre Amp gain can cause spikes in the feedback signal Pre Amp gain can only be adjusted when hydraulics are off Post Amp gain is a finer operator defined gain control that can be adjusted when hydraulics are on The Total Gain value is calculated by multiplying the Pre Amp and Post Amp gain values If the total desired gain amount is known from a calibration sheet you can enter the amount in the Total Gain box and the software will calculate the Pre Amp and Post Amp gain values automatically When you are calibrating an AC conditioner use the Post Amp gain control to increase gain If more gain is needed you must disable hydraulics and increase the Pre Amp gain You can then turn on hydraulics and continue to adjust the Post Amp gain Note This procedure assumes a positive command extends the actuator and a negative command retracts the actuator If not use the opposite polarity for any values given 1 Select Gain Delta K for Cal Type Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Delta K Automated Controllers Select Gain Delta K for Cal Type on the Calibration tab of the Inputs panel 2 Apply a retraction command that is 80 of the full scale range Standalone FlexTest SE Controllers Standalone FlexTest SE Controllers A Enable the front panel Dial B Use the Dial to adjust the Setpoint for 80 of the full scale range C Verify that your LVDT displace
99. eter 1 A For Meter Type select Timed B For Signal select Spool Position C For Display Mode and Display Units select Volts D Set a Display Resolution Automated Controllers A On the Station Manager window s toolbar select Create Meters on the Meters icon pull down menu B Select Create Meters again to display a second Meters window C Inthe Meters window click the Meter Setup button Use the Meter Setup window to define the meter D For Meter Type select Timed For Signal Selection select the desired Channel name and Spool Position for Signal type MTS 793 Tuning and Calibration F G How to Perform Advanced Tuning Techniques For Display Mode select Volts Set a Display Resolution 7 Produce a Spool Position output signal of 10 V DC with the spool driven into the end cap Standalone FlexTest SE Controllers A Reverse the Conditioner gt Polarity setting to drive the inner Note loop spool into one of the end caps Adjust Conditioner gt Gain until the Meter reads approximately 8 V DC Adjust Conditioner gt Phase until the Meter displays maximum voltage The phase adjustment matches the phase of the inner loop LVDT feedback with the 10 kHz demodulator reference signal This adjustment provides a maximum output for the maximum LVDT spool position offset This adjustment must be set for the initial calibration servovalve replacement cable replacement or valve
100. f hard drive fragmentation e Connection status to a corporate network For software application problems have the following information available e The software application s name version number build number and if available software patch number This information is displayed briefly when you launch the application and can typically be found in the About selection in the Help menu e It is also helpful if the names of other non MTS applications that are running on your computer such as anti virus software screen savers keyboard enhancers print spoolers and so forth are known and available If You Contact MTS by Phone Identify system type Your call will be registered by a Call Center agent if you are calling within the United States or Canada Before connecting you with a technical support specialist the agent will ask you for your site number name company company address and the phone number where you can normally be reached If you are calling about an issue that has already been assigned a notification number please provide that number You will be assigned a unique notification number about any new issue To assist the Call Center agent with connecting you to the most qualified technical support specialist available identify your system as one of the following types e Electromechanical materials test system e Hydromechanical materials test system e Vehicle test system e Vehicle component tes
101. feedback reading Use the Dial to adjust the Setpoint for a 2 tensile force command Record the force standard s readout value and its corresponding conditioner feedback reading in the 2 row of your record sheet Repeat steps D and E for other tensile force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers Adjust the Manual Cmd slider for a 0 command Record the force standard s readout value and corresponding conditioner feedback reading at 0 command Adjust the Manual Cmd slider for a 2 tensile force command Record the force standard s readout value and its corresponding conditioner feedback reading in the 2 row of your record sheet 167 Force Sensor Calibration 168 E Repeat steps E G for other tensile force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale 7 Record conditioner feedback readings at predetermined compressive force command points Standalone FlexTest SE Controllers A Use the Dial to adjust the Setpoint for a 2 compressive force command B Record the force standard s readout value in the 2 row of your record sheet Enter the corresponding conditioner feedback reading D Repeat steps A C for other compressive force commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Automated Controllers A Adjust the Manual Cmd slider for a
102. for longer displacements a measuring device such as a long ruler laser or optical detector to calibrate an LVDT Note All calibration tools should be calibrated to an industry standard Note This calibration procedure calibrates the conditioner for an actuator displacement of 10 cm You will need to adjust the procedure to accommodate your actuator displacement 125 Displacement Sensor Calibration Displacement Sensor Calibration Abbreviated Procedure 126 The following abbreviated procedure outlines a displacement sensor LVDT calibration process More detailed calibration information is available on the pages listed Task 1 Task 2 Task 3 Task 4 Task 5 Task 6 Note Task 7 Task 8 Note Task 9 Get things ready on page 127 Turn on hydraulic pressure on page 130 Verify the conditioner polarity on page 131 Set the phase on page 131 Set the zero and offset on page 132 Gain Delta K Calibration on page 135 The Gain Linearization Calibration procedure applies only to controllers equipped with full range conditioners e g Model 493 25 DUCs Gain Linearization Calibration on page 141 Save the calibration on page 149 Controllers equipped with full range conditioners e g Model 493 25 DUCs do not require multiple ranges Calibrate additional ranges on page 149 MTS 793 Tuning and Calibration Displacement Sensor Calibration Disp
103. fset Automated Controllers Click Auto Offset on the Offset Zero tab Inputs panel to zero the force output Perform shunt calibration Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Select Cal Type A Select required Shunt Display units B Ensure that Shunt State is set to On Polarity is always positive Note the Shunt Ref value it should be 60 90 80 is ideal of the calibrated range of the sensor C Click Update to copy the current shunt reference value into the Shunt Reference box D Set Shunt State to Off 181 Force Sensor Calibration Automated Controllers A In Station Setup select the appropriate force channel on the navigation panel click the Channel Input Signals icon and then click the Shunt tab B Select the shunt type Use polarity if you are not sure what to select C Inthe Current Shunt Value box click the On button Note the Current Shunt Value it should be 60 90 80 is ideal of the calibrated range of the sensor D Click Update to copy the Current Shunt Value into the Shunt Reference Value box and then click Off Task 9 Save the calibration It is important that you save your sensor calibration values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers On the Station Setup window Inputs panel click the Calibration tab and then Save This saves
104. g will affect your Delta K setting you should always calibrate the negative side first AK 1 AK lt 1 Indicated output mechanical input To calibrate the negative extensometer output 1 Set an initial nominal Gain setting of 500 2 Adjust the calibrator between zero and 100 of the extensometer s full scale range three times This exercises the extensometer to remove any hysteresis 3 Use Auto Zero to zero transducer output Standalone FlexTest SE Controllers Select Setup gt Strain gt Offset Zero gt lt lt Auto Zero gt gt Automated Controllers Click Auto Zero on the Calibration tab to set transducer s amplified output to 0 000 V DC MTS 793 Tuning and Calibration Extensometer Calibration 4 Set the calibrator micrometer head for 80 of the negative full scale value 5 Note the monitored strain signal value 6 If the signal value does not match the set value adjust the transducer excitation voltage to achieve an 80 value 8 V DC Record your final strain signal value for the 80 output Note After determining an approximate excitation value round it to convenient value e g 8 00 V DC Use Post amp Gain to make fine adjustments of calibration Calibrate the positive To calibrate the positive extensometer output output compression 1 Adjust the calibrator between zero and 100 of the extensometer s full scale range three times This exercises the extensometer to re
105. gain 20 selecting amplitude 35 selecting frequency 35 specimens changing 39 tuning with 38 tuning without 38 three stage valves 88 valve balance 56 when to tune 47 tuning filters forward loop 109 U Upset recovery method 98 using error to tune I Gain 98 V valve balance adjusting 56 Valve clamping and servovalve balance 56 valves polarity check 56 212 Index W warm up procedure 50 120 waveforms 40 areas of interest 40 error signal 41 monitoring 40 Z zero setting displacement sensor 194 encoders 186 188 force sensor 156 LVDT 132
106. ge B Use the Station Signals panel to verify that your LVDT displacement signal equals 80 of the full scale range During the initial calibration and tuning of your system it may take repeated adjustment for the two values to match 145 Displacement Sensor Calibration Note Ifthe actuator response is sluggish and or the signal value does not 10 match the command you will need to adjust the tuning of this contro mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the reset integration value I Gain to help the feedback match the command At this point unless the conditioner is already in calibration the actuator s physical retraction will not equal your commanded value You will adjust gain in the next step so that the actuator s physical retraction and your commanded retraction match Example Suppose your actuator has a 100 retraction of 10 cm In this step you would apply a 8 cm command and even though the station signals would read 8 cm of feedback the actuator may retract only 4 cm This shows the conditioner sensor pair are out of calibration Adjust gain to retract the actuator until it equals your retraction command Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization gt Post Amp Gain Automated Controllers Adjust the Post Amp Gain slider control on the Calibration tab A
107. gital meters or software scope Service Port Output Signals part 1 of 2 SIGNAL DESCRIPTION Valve Current The final output to the servovalve The voltage represents the current output 10 V DC 50 mA standard Demod Filter Output The analog output of the demodulator prior to gain Innerloop Command The input signal to the 3 Stage Valve Driver the test program command Spool Position The Conditioner Out signal summed with the Spool Zero signal Spool Offset Signal that is summed with spool position to remove any DC offset 10 V represents 4 V of zero summing Preamp Output The raw AC input from the spool LVDT 96 Tuning Procedures MTS 793 Tuning and Calibration Monitoring inner loop Signals on FlexTest Ilm Controllers MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques Service Port Output Signals part 2 of 2 SIGNAL DESCRIPTION Conditioner Out The conditioned feedback signal from the servovalve LVDT Voltage Reference 5V Internal board reference test only Inner loop signals can be monitored with external meters via the tip jacks on the Model 497 15 3 Stage Valve Driver module You must specify which signal is available from the tip jacks with the Monitor Mux Output list Note These signals are not available to the built in meters or scope SIGNAL Valve Current Valve Balance Inner loop Cmd Inner loop Err Spool Position Spool Zero Conditi
108. gle Scope window B Inthe Scope window s toolbar click to open the Setup for Scope window 10 Create a program with the function generator application Standalone FlexTest SE Controllers Select FG and select the following settings to set up a tuning program Automated Controllers In the Station Manager window s navigation pane click CONTROL SETTING Type Cyclic Wave Shape Square Control Mode displacement Target Setpoint O mm Amplitude 50 of full scale Frequency 1 Hz Compensator None MTS 793 Tuning and Calibration Tuning Procedures 93 How to Perform Advanced Tuning Techniques 94 Tuning Procedures 11 12 I Start the function generator Standalone FlexTest SE Controllers Press Run to start the displacement command Automated Controllers In the Station Controls panel click to start the Function Generator Observe the spool position signal on the Scope If the Spool Position signal is too small to be properly displayed on the Scope window during tuning increase the Function Generator panel s Amplitude If the Amplitude setting does not amplify the spool signal as expected increase the P Gain Standalone FlexTest SE Controllers Tuning gt P Gain Automated Controllers A In Station Setup window s navigation pane click VV B In the Inputs panel click the Adjustment tab C In the Adjustment tab increase the P Gain Tune the inner loop Standalone Flex
109. gnals have only dynamic characteristics making them unsuitable for use in a control mode Select a dual compensation control mode for a channel when the feedback for the desired control mode is unsuitable for maintaining closed loop control A dual compensation mode requires a primary and a secondary feedback signal e The more stable primary feedback signal is used by the PIDF controller to maintain closed loop control e The less stable secondary feedback signal is used for command compensation in command programs provided by the Function Generator and other applications Conversion Gain Disp Full Scale Compensator amp se E E OT gt PIDF Force Full Scale A Compensated Command Displacement C evar Integrator Gain Primary Feedback to PIDF Displacement Dual compensation control modes compensate based on a secondary feedback signal and maintain closed loop control with a primary feedback signal secondary Feedback to l Compensator Force In this Force Displacement dual compensation control mode 104 Tuning Procedures programming and compensation use the secondary force feedback signal The PIDF controller maintains closed loop control using the primary displacement feedback signal MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques Dual compensation Dual Compensation controls display at the bottom of the Station controls Setup window s Compensators panel tabs when a dual
110. grated shunt calibration resistor 1 7 Card Slot 1 4 sant uses RJ 50 connectors 5 J1A and J1B 6 T A 8 TA DA Card Slot 2 e uses RJ 50 connectors A J2A and J2B Connector speak Card Slot 3 Numbering _ font uses RJ 50 connectors N a J3A and J3B Card Slot 4 Shunt calibration iD uses RJ 50 connectors Plug Assembly n j J4A and J4B 184 MTS 793 Tuning and Calibration Encoder and Temposonics Calibration Encoder and Temposonics Calibration Encoders Linear encoders measure the position change of the actuator s piston rod by digitizing sensing and resolving actuator movement Temposonics MTS Temposonics linear displacement sensors measure the position transducers change of the actuator s piston rod by sensing the position an attached permanent magnet The calibration procedure for both types of devices are similar Daughter board For FlexTest SE LE FlexTest GT and TestStar IIm encoders and support Temposonics sensors require a Model 493 47 Encoder Interface daughter board to be installed in a Model 493 40 Carrier I O board The Carrier I O connector J4 J7 used depends on the installed location of the daughter board on the Carrier I O module For FlexTest IIm CTC encoders and Temposonics sensors require an optional daughter board installed in the 498 ADDA plug in module Determine installed For Automated Controllers determine the installed location of the loca
111. gs ready on page 191 Task 2 Create a sensor calibration file on page 193 Task 3 Adjust offset on page 194 Task 4 Gain Delta K Calibration on page 195 Note The Gain Linearization Calibration procedure applies only to controllers equipped with full range conditioners e g Model 493 25 DUC module Task 5 Gain Linearization Calibration on page 198 Task 6 Establish the shunt calibration reference on page 204 Task 7 Save the calibration settings on page 207 Extensometer Calibration Detailed Procedure Task 1 Get things ready MTS 793 Tuning and Calibration 1 Review Pre Calibration Considerations on page 117 2 Locate all relevant documentation including information about the extensometer such as the serial number model number etc 3 For Automated Controllers open a station configuration file You need a station configuration file that has a defined input signal such as an auxiliary input 191 Extensometer Calibration 192 On the File menu click Open Station to open the appropriate configuration file Select Calibration for Access Level Select Config gt Access Level gt Calibration Set up to monitor strain feedback You will be monitoring strain feedback when making adjustments throughout this procedure You should monitor strain feedback in the same units that you are using for the calibration Alternatively you can use an external
112. hat the actual strain and your calibrator strain setting match Set an initial gain of 500 Adjust Excitation so that the strain signal approaches the target value As the target value is approached determine an appropriate integer or half integer value e g 6 5 V Then make finer adjustments to the sensor output using Post amp Gain Set the calibrator micrometer to a value that is 80 of the positive full scale range Note Since you are using a Model 493 25 conditioner with no Delta K adjustment you can only adjust Post amp Gain at one point either the 80 point or 80 point The other point 80 or 80 simply becomes a data point value for the linearization table 7 Verify that your extensometer feedback signal is 80 of the full scale range Record conditioner feedback readings at predetermined negative strain settings A Set the calibrator micrometer to a value that is 0 of the extensometer s full scale range B Record the calibrator s readout value and the corresponding conditioner feedback reading in the 0 row of your record sheet C Set the calibrator micrometer to a value that is 2 of the extensometer s full scale range D Record the calibrator s readout value and corresponding conditioner feedback reading in the 2 row of your record sheet E Repeat steps C and D for other negative strain settings typically at 4 6 8 10 20 40 70 and 100 percent of full
113. he actuator s physical retraction will not equal your commanded value You will adjust gain in the next step so that the actuator s physical retraction and your commanded retraction match Example Suppose your actuator has a 100 retraction of 10 cm In this step you would apply a 8 cm command and even though the station signals would read 8 cm of feedback the actuator may retract only 4 cm This shows the conditioner sensor pair are out of calibration Adjust gain to retract the actuator until it equals your retraction command Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization gt Post Amp Gain Automated Controllers Adjust Post Amp Gain on the Calibration submenu or tab until your dial indicator or other readout device shows that the actuator s physical retraction equals your retraction command Record dial indicator and conditioner feedback readings at predetermined retraction command points Note After shutting down system hydraulics you will enter these 142 recorded readings on the Linearization Data window Standalone FlexTest SE Controllers Use the Dial to adjust the Setpoint for a 0 command B Record the dial indicator value for the 0 command C Enter the corresponding conditioner feedback reading D Use the Dial to adjust the Setpoint for a 2 retraction command MTS 793 Tuning and Calibration MTS 793 Tuning and C
114. he Linearization Data window to return to default values Adjust the calibrator between zero and 100 of the extensometer s full scale range three times This exercises the extensometer to remove any hysteresis Apply a negative strain command that is 80 of the negative full scale range A Set the calibrator micrometer to a negative strain value that is 80 of the full scale range B Verify that your extensometer feedback signal is 80 of the full scale range At this point unless the conditioner is still in calibration the negative strain applied to the extensometer will not equal your calibrator setting You will adjust gain in the next step so that the actual strain and the strain set on the calibrator match MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Extensometer Calibration 8 Adjust gain until the actual strain equals your strain command Standalone FlexTest SE Controllers Adjust the Post amp Gain control on the Calibration submenu to increase the negative strain reading on the calibrator until it equals your negative strain command Select Setup gt Strain gt Calibration gt Cal Type gt Gain Linearization gt Post Amp Gain Automated Controllers Adjust the Post amp Gain control on the Calibration tab to increase the negative strain reading on the calibrator until it equals your negative strain command Apply a positive strain command that is 80 of the posi
115. he electrical valve balance adjustment compensates for minor mechanical imbalance it is an intermediate adjustment Go to How to Balance the Servovalve on page 56 for help Calibrate each sensor used for a control mode or data acquisition Perform the appropriate calibration procedure If your sensor calibration schedule does not require calibration at this time perform a shunt calibration check to determine if your DC sensor DC conditioner is within tolerance Go to Shunt Calibration on page 120 for help If you have a three stage Series 256 or 257 servovalve tune the inner loop gain and rate before tuning the outer loop The rules for inner loop tuning are similar to those of the outer loop Go to How to Manually Tune Three Stage Servovalves on page 88 for help The following is a brief review of the most prominent tuning controls Proportional gain P Gain increases system response Integral gain I Gain increases system accuracy during static or low frequency operation and maintains the mean level at high frequency operation Derivative gain D Gain improves the dynamic stability when high proportional gain is applied Feed forward gain F Gain increases system accuracy during high frequency operation MTS 793 Tuning and Calibration Getting started Tuning for the First Time e Forward loop filter FL Filter adjustments establish a frequency bandwidth for the servoloop command signal
116. ibration 144 6 ie 8 C Repeat steps A and B for other extension commands typically at 4 6 8 10 20 40 70 and 100 percent of full scale Turn off system hydraulics On the Linearization Data window enter the dial indicator and conditioner feedback readings for all command points previously recorded Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab to open the Linearization Data window Turn on system hydraulics LVDT recalibration If the LVDT has been previously calibrated use the following procedure 1 Locate the calibration data sheet for the appropriate conditioner 2 Ensure that system hydraulics is off 3 Open the Linearization Data window Standalone FlexTest SE Controllers Select Setup gt Disp gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab to open the Linearization Data window 4 Transfer Standard and Conditioner data from the conditioner s calibration data sheet to corresponding data entries on the Linearization Data window 5 Turn on system hydraulics 6 Verify the linearization data Standalone FlexTest SE Controllers A Using the front panel Dial adjust the Setpoint for each retraction and extension command
117. ifferent types of test systems are configured with different conditioner polarities The polarity of the conditioner the polarity of the valve driver and the orientation of system cabling all play a role in controlling the actuator and determining how signals are displayed This procedure assumes the servovalve polarity is set to Normal on the Station Setup Drive panel Valve tab 1 Check the sensor connection Be sure the displacement sensor is properly connected 2 Apply a positive actuator command Standalone FlexTest SE Controllers Enable the front panel Dial and then use the Dial to increase the Setpoint adjustment for a positive command Automated Controllers Open the Manual Command window and then click on the Enable Manual Command check box to enable manual command Increase the Manual Cmd adjustment for a positive command 3 Monitor the displacement feedback If the signal value is positive for actuator extension the conditioner polarity is correct If desired you can change the conditioner polarity to make the signal value negative for actuator extension Note The polarity setting should be the same when calibrating additional ranges for the same sensor Task 4 Set the phase This task determines the proper phase adjustment The phase adjustment matches the phase of the AC feedback signal to the 10 kHz demodulation excitation signal 1 Fully retract the actuator MTS 793 Tuning and Calibration 131
118. ifying e Part of the system e Against a standard or known value e To ensure that measured variables precisely represent the actual physical properties involved All sensors require calibration to ensure that their outputs accurately represent the physical condition they sense e g force or displacement When you calibrate a sensor you are ensuring the test system properly interprets the sensor signal Sensors included with your test system are usually factory calibrated and the corresponding sensor calibration files are included with your system software If you change a sensor or add a new sensor to your system you must calibrate the new sensor conditioner pair against a standard to ensure the sensor s accuracy You must calibrate all sensors before they can be used to support control modes or auxiliary data channels System calibration is performed by a program that calibrates the analog to digital A D converters and the digital to analog D A converters of the digital controller You input a precision 10 volt reference voltage and monitor the output of each converter with a precision voltmeter Any difference between the reference voltage and a converter output becomes a calibration factor The calibration factor for each converter is recorded in a data file MTS 793 Tuning and Calibration Sensor Calibration About Calibration Sensors convert a measured mechanical value such as force displacement or press
119. il Ch Error is Zero Automated Controllers A In the Station Setup window click ai Tuning Procedures 61 How to Balance the Servovalve B While observing Displacement Abs Error on the Meters panel adjust the valve balance control for the non blocked servovalve Valve Balance 1 or Valve Balance 2 until Displacement Abs Error is zero 6 Balance the other servovalve of the dual valve pair A Remove the blocking plate from the port of the other servovalve B Reinstall the servovalve C While observing Displacement Abs Error on the Meters panel adjust the valve balance control for the other servovalve Valve Balance 1 or Valve Balance 2 until Displacement Abs Error is zero 7 Return displacement I Gain to its original setting Standalone FlexTest SE Controllers Select Tuning gt Manual gt I Gain Automated Controllers A In the Station Setup window click VV B In the Tuning panel click the Adjustments tab 62 Tuning Procedures MTS 793 Tuning and Calibration How to Adjust Dither How to Adjust Dither Dither is a small high frequency sine wave applied to a servovalve s spool to improve the valve s response to low amplitude signals by reducing sticking Dither oe exaggerated Y s x Test Waveform The following are signs of an improper dither adjustment e Dither amplitude is too low While running a sinusoidal test on a properly tuned system you notice that the
120. ing Procedures MTS 793 Tuning and Calibration How to Set Servovalve Polarity Please note the following e The polarity of the servovalve must be checked before sensor calibration begins and before hydraulic pressure is applied for the first time e The polarity of any servovalve is generally set when the valve is installed Important The combination of the conditioner polarity and the servovalve polarity affects the final output signal The conditioner polarities should be set before the servovalve polarity because they do not need hydraulics to be turned on In general you will set the conditioner and servovalve polarity the same 1 Get things ready Standalone FlexTest SE Controllers A Ensure the actuator can be fully extended without contacting anything You may need to remove any obstructions B Press the Status button twice to display the Status menu and for Control Mode select displacement C For Access Level select Tuning Automated Controllers A Ensure that the actuator can be fully extended without contacting anything You may need to remove any obstructions B You need displacement control mode If you have not created this type of a control mode create it now C On the Station Manager Toolbar select Tuning in the access level box 2 If necessary enter an initial tuning value for P Gain first time only The actuator cannot move unless an adequate P Gain value is applied If you already hav
121. ing levels that will be adequate for most control modes If the results from auto tuning are not satisfactory you should manually tune each control mode Refer to How to Perform Advanced Tuning Techniques on page 83 66 Tuning Procedures MTS 793 Tuning and Calibration How to Manually Tune the Control Loop Tuning the Displacement Control Mode A displacement control mode uses the feedback signal from an LVDT linear variable differential transformer You do not need a specimen to tune a displacement control mode When to tune A displacement control mode typically needs to be tuned only when recalibrated However you may want to retune the displacement control mode if The fixtures attached to the actuator have changed such as grips The main tuning factor is a change in the mass attached to the actuator Any time hydraulic system potential has changed such as after servovalve hose or pump replacement You want to fine tune the control mode The sensor range has changed You feel system response should be improved or reduced Prerequisites Be sure the following conditions are present before you begin tuning the displacement control mode Hydraulic pressure is off The specimen is not installed Procedure This basic displacement tuning procedure should work for most applications consider it a guideline You should be familiar with the background information presented in this chapter so you can modify the f
122. ion We want our servo loop to work just like the skilled driver that is to turn the steering wheel just the right amount Let s change the road into the square wave shown in the diagram which is one type of test waveform We want our test the car to follow the desired command the road in all respects That means the test system should exert the precise force or displacement or strain that we want on the specimen The only problem is that different types of materials from the softest to the hardest exhibit different reactions to the force or displacement or strain Just as we would tune a car differently for racing than we would for a weekly drive to the store the tuning differs too A system properly tuned for a soft specimen will go unstable if you install a very hard specimen Get the error signal to be a small as possible at all times without compensators because e The error signal tells the servovalve to open e The larger the error signal the more the servovalve opens e Therefore if the error is zero the servovalve is closed This means the servo loop is satisfied and all is well Remember If the error is as close to zero as possible actually maintaining zero is impossible it indicates that the system is closely following the command e Start with the command e Add the feedback it lags the command e Adjust to get the error and phase shift as low as possible Time Lag Error
123. ions are provided for standalone FlexTest SE Controllers and Automated Controllers Standalone FlexTest SE Controllers refer to FlexTest SE Controllers configured to operate in the standalone mode not equipped with a PG Automated Controllers refer to controllers equipped with MTS Model 793 Software This includes FlexTest IIm CTC automated FlexTest SE equipped with a PC in which Exclusive Control is assigned to Station Manager FlexTest GT and TestStar Im Controllers Note Automated Flexlest SE Controllers are equipped with a PC in which Exclusive Control is assigned to Station Manager For more information about Exclusive Control see the FlexTest SE Users manual For a description of the specific tuning controls displayed on the front panel of standalone FlexTest SE Controllers see the FlexTest SE Users manual For a description of the specific tuning controls displayed in the Model 793 Software included with Automated Controllers see the Model 793 Control Software manual This pertains to FlexTest IIm automated FlexTest SE FlexTest GT and TestStar IIm Controllers Tuning Procedures 45 Contents When to Tune 47 Tuning for the First Time 49 How To Warm Up Station Hydraulics 50 How to Set Servovalve Polarity 52 How to Balance the Servovalve 56 How to Adjust Dither 63 How to Manually Tune the Control Loop 66 Tuning the Displacement Control Mode 67 Tuning the Force Control Mode 71 Tuning the Strain Control Mode 77
124. is like Derivative mode except that it anticipates changes rather than reacts to them Feed forward watches the command side of the summing junction and provides a derivative of the command Remember that a derivative is proportional to the rate of change of a signal therefore the faster the command is changing ike during the leading trailing edges of a squarewave the greater the signal is Command Feed forward gain looks at the command side of the summing junction The output is the derivative of that signal indicating how fast the command is changing Inadequate feed forward MTS 793 Tuning and Calibration More about Feed Forward Gain F Gain vs F2 Gain Adjusting F Gain or F2 Gain causes the command signal to start sooner This causes the feedback signal to track the original command signal more closely F F2 Gain MTS 793 Tuning and Calibration About Tuning So look at feed forward as a form of a predictor of where the actuator should be going The signal gives the servovalve an early indicator to tell it that it needs to open faster than would be expected from the existing error signal Feed forward F F2 Gain introduces a derivative of the command signal It anticipates how large a valve opening is needed to reach the required response and adds that to the valve command like compensating for phase lag F Gain is applied to the current control mode before the forward loop filter
125. l gt I Gain B Write down the current displacement I Gain C Zero the I Gain Automated Controllers A Inthe Station Manager window s Display menu select Station Setup 60 Tuning Procedures MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration D E How to Balance the Servovalve In the Station Setup window navigation pane s Channels select the channel with the dual valves that need balancing In the Station Setup window click V i In the Tuning panel click the Adjustments tab In this tab Write down the current I Gain Zero the I Gain Setup a meter to view displacement error Standalone FlexTest SE Controllers A B G D Select Meters Select an existing meter such as Meter 1 or select lt lt Add Meters gt gt to create a new meter and select it For Meter Type select Timed For Signal select Ch Error Automated Controllers A B C D Select the meters icon on the Station Manager tool bar Select the Meter 1 Setup button For Meter Type select Timed In Signal Selection select the channel whose valve balance needs checking For Signal select Displacement Abs Error Zero displacement error with the Valve Balance control Standalone FlexTest SE Controllers A B C Select Setup gt Output gt Valve Balance Enable the Dial While observing Ch Error on the Meters panel adjust the Valve Balance control by rotating the Dial unt
126. l Command window and then click on the Enable Manual Command B Adjust the Manual Cmd slider on the Manual Command window for 80 of the full scale range C Use the Station Signals panel to verify that your LVDT displacement signal equals 80 of the full scale range During the initial calibration and tuning of your system it may take a while for the two values to match Note _ f the actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this control mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the reset integration value I Gain to help the feedback match the command At this point unless the conditioner is already calibrated the actuator s physical extension will not equal your commanded value You will adjust Delta K in the next step so that the actuator s physical extension and your commanded extension match Example Suppose your actuator has a 100 extension of 10 cm In this step you would apply a 8 cm command and even though the station signals would read 8 cm of feedback the actuator may extend only 4 cm This shows the conditioner sensor pair are out of calibration 138 MTS 793 Tuning and Calibration Displacement Sensor Calibration 6 Adjust Delta K to extend the actuator until it equals your extension command Adjust Delta K until the dial indicator or other readout device
127. lacement Sensor Calibration Detailed Procedure Task 1 Get things ready MTS 793 Tuning and Calibration Perform the following before you start sensor calibration 1 Locate relevant documentation e You need information about the sensor such as the serial number model number excitation voltage displacement etc This information can be found on the appropriate Calibration Data sheet included with your system or the Final Inspection card included with all MTS sensors e You need calibration identification numbers for any calibration tools that will be used for this calibration procedure e g the dial indicator used for LVDT calibration The calibration information is usually on a sticker attached to the equipment e You need the appropriate DUC Conditioner serial number 2 Open a station configuration file You need a station configuration file that includes a control channel with a control mode that uses the sensor you intend to calibrate Also to monitor the sensor output signal with an external DVM ensure that you have allocated an analog output resource readout channel in the Station Builder program On the File menu select Open Station and then open the appropriate configuration file on the Open Station window Select the Calibration access level Standalone FlexTest SE Controllers Select Config gt Access Level gt Calibration Automated Controllers On the Station Manager toolbar select the Cali
128. lizing with 28 Derivative 23 derivative gain 24 displacement calibrate actuator retraction 135 control modes 31 mounting dial indicator 133 sensor calibration 124 displacement tuning prerequisites 67 78 procedure 67 78 when to tune 67 77 dither about 63 Dual Compensation mode about 104 gain settings about 105 tuning 106 dual valve tuning 59 E encoder calibration calibration file 187 connections 185 setting resolution 187 setting zero 186 188 signal monitoring 187 error signal 41 Extensometer 190 calibration 44 Index 209 extensometer calibration adjust offset 194 calibrate compression 197 calibrate tension 196 calibration file creating 193 gain delta K 195 gain linearization 198 recalibration 201 record data 198 shunt calibration reference 204 F Feed Forward gain 27 Feed forward gain 26 filter responses forward loop 110 filters enabling 109 forward loop 109 stabilization 113 tuning 109 Force calibration 44 force sensor calibration about 124 150 190 additional ranges 182 check conditioner polarity 155 compression calibration 159 gain delta K 156 gain linearization 164 initial values 153 154 millivolt volt 175 prerequisites 150 recording data 161 setting offset 156 setting zero 156 shunt cal reference 178 shunt calibration 181 206 shunt resistor table 179 tension calibration 156 what you need 151 force tuning prerequisites 72 procedure 72 forward loop filter 30 forward loo
129. llers A Open the Manual Command window and then click on the Enable Manual Command B Adjust the Manual Cmd slider on the Manual Command window for a tensile force command that is 80 of the full scale range 165 Force Sensor Calibration 166 C Use the Station Signals panel to verify that your force transducer signal equals 80 of the full scale range During the initial calibration and tuning of your system it may require repeated adjustment for the tensile force command and feedback values to match Note Ifthe actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this control mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the integration value I Gain to help the feedback match the command At this point unless the conditioner is already in calibration the tensile force applied to the force transducer will not equal your commanded value You will adjust gain in the next step so that the actual tensile force and your commanded tensile force match Example Suppose your actuator has a 100 tensile force rating of 10 KN In this step you would apply 8 KN of command and even though the station signals would read 8 kN of feedback the force standard may only read 4 kN This shows the conditioner sensor pair are out of calibration Adjust the Post amp Gain control to increase th
130. load cells or heavy grips can produce a noisy force signal e If you observe a noisy sensor feedback signal reduce the FL filter setting to about 100 providing your test does not reach 100 Hz If additional adjustment is needed reduce the setting by 5 10 Hz at a time 30 Introduction MTS 793 Tuning and Calibration About Tuning Tuning Characteristics of Control Modes Each control mode has different tuning characteristics Displacement control The displacement control mode also called stroke control uses an LVDT sensor in the actuator as the controlling feedback source The displacement control mode typically e Requires tuning only when first set up e Does not require a specimen for tuning e Uses a square wave when tuning an LVDT but not when tuning a displacement gage e May not yield actuator movement if P gain is set too low e May yield rapid noisy and unstable actuator movement if P gain is set too high Force control Force control uses a force sensor also called a load cell as the controlling feedback source The force control mode typically e Requires tuning between tests whenever a specimen is changed and whenever changes are made to the force train e Requires a specimen to be installed e Uses a ramp waveform for initial tuning However if the desired results cannot be achieved with a ramp waveform a squarewave is used for tuning e May yield sluggish response if P gain is set too low e
131. lock chain If your system is equipped with a Remote Station Controller pressing Station Stop shuts down the HSM for the specific station only MTS 793 Tuning and Calibration Tuning Procedures 49 How To Warm Up Station Hydraulics Saving the tuning parameters If an adjustment causes the system to shut down readjust the control to the level where the system was last stable Then reset the system and continue tuning The tuning values are saved as part of the controller parameter set The parameter set can save one set of tuning values for each control mode How To Warm Up Station Hydraulics 50 Tuning Procedures It is good practice to warm up station hydraulics before tuning or testing by exercising the actuator without a specimen Remove any specimen and run the system in displacement control for at least 30 minutes using a 80 full scale length command at about 0 1 Hz 1 Select the following settings in the function generator Standalone FlexTest SE Controllers Select Tuning gt Manual gt FG Automated Controllers Click i on Station Manager CONTROL SETTING Control Channel The control channel associated with the Automated Controllers valve you are adjusting only Control Mode Displacement Adaptive None Compensator Target Setpoint 0 Amplitude 80 of the full scale actuator displacement Frequency 0 1 Hz Wave Shape Sine MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How To W
132. ltage value typically 5 8 volts 3 If the extensometer uses a zero pin remove the zero pin now 4 Monitor the extensometer s amplified output strain Note Before using Auto Zero ensure that any offsets due to Auto Offset and Manual Offset actions are eliminated 5 Use Auto Zero to zero transducer output Standalone FlexTest SE Controllers Select Setup gt Strain gt Offset Zero gt lt lt Auto Zero gt gt Automated Controllers Click Auto Zero on the Calibration tab to set transducer s amplified output to 0 000 V DC If you have previously calibrated this extensometer refer to Extensometer recalibration on page 201 If this is a first time calibration use the following procedure 1 Adjust the calibrator between zero and 100 of the extensometer s full scale range three times This exercises the extensometer to remove any hysteresis Set the calibrator micrometer to a value that is 80 of the negative full scale range Verify that your extensometer feedback signal is 80 of the full scale range During the initial calibration of your system it may require repeated adjustment for the negative strain calibrator setting and feedback values to match 199 Extensometer Calibration 200 At this point unless the conditioner is already in calibration the negative strain reading will not equal the value set on your calibrator micrometer You will adjust gain in the next step so t
133. lue I Gain to help the feedback match the command At this point unless the conditioner is already in calibration the compressive force applied to the force transducer will not equal your commanded value You will adjust Delta K in the next step so that the actual compressive force and your commanded compressive force match Example Suppose your actuator has a 100 compressive force rating of 10 KN In this step you would apply 8 kN of command and even though the station signals would read 8 KN of feedback the force standard may only read 4 kN This shows the conditioner sensor pair are out of calibration 3 Adjust Delta K until the actual compressive force equals your compressive force command MTS 793 Tuning and Calibration Force Sensor Calibration Adjust Delta K on the Calibration submenu or tab to increase the compressive force reading on the load standard until it equals your compressive force command 4 Repeat steps 2 and 3 for all ranges Example Suppose you have an actuator with a full scale capacity of 10 kN and ranges of 10 kN 5 kN 2 kN and 1 KN In this case you would repeat this process and calibrate compression at 80 of each range 8 kN 4 kN 1 6 kN and 0 8 kN Note Some systems do not provide or require multiple ranges such as those using full range conditioners e g Model 493 25 DUC module In this case only one range is used typically 100 Record data points The accuracy tolerance of
134. mbalances When the valve balance adjustment is complete there will be no or minimal hydraulic fluid flow when the servovalve s output signal is at null The electrical valve balance procedure is detailed in the following pages for both Standalone and automated Controllers If the servovalve cannot be balanced with the Valve Balance control it may be an indication of a major imbalance that requires a mechanical adjustment before further electrical adjustments are made Valve clamping and Some systems use valve clamping as a means to control actuator servovalve balance behavior when an interlock occurs However to clamp properly the servovalve must be balanced before the interlock occurs 56 Tuning Procedures MTS 793 Tuning and Calibration How to Balance the Servovalve Unexpected actuator movement is possible when the servovalve is clamped Unexpected actuator movement can cause injury and equipment damage Your controller s hardware interface file hwi includes options to clamp the servovalve when a hydraulic interlock occurs these options cause the actuator to stop fully extend or fully retract However if the servovalve is imbalanced it may move unexpectedly when clamped Ensure the servovalve is balanced before using your test system 1 Get things ready A Select the Calibration access level B Remove any specimen C Apply hydraulic pressure A WARNING Enabling the front panel Dial Standalone
135. meet the required accuracy Typically 1 of a reading is the normal accuracy specification If they do not you must go back to recalibrate the extensometer negative and positive outputs Extensometer Ifthe extensometer has been previously calibrated use the following recalibration procedure 1 MTS 793 Tuning and Calibration Locate the calibration data sheet for the appropriate Model 493 25 conditioner 201 Extensometer Calibration 202 Click Linearization Data to open the Linearization Data window Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab Verify linearization data Verify linearization data A Adjust the calibrator micrometer for each strain setting on the Linearization Data window B At each micrometer setting verify both the calibrator readout value Standard and its corresponding conditioner feedback value Conditioner by comparing them with the corresponding values on the Calibration Data sheet If the data is valid Stop this procedure If the data is not valid Proceed to the next step Reset Linearization Data window to default values Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Cal Type gt Gain Linearization gt lt lt Reset gt gt Automated Controllers Click Reset on t
136. ment signal equals 80 of the full scale range Automated Controllers A Open the Manual Command window and then click on the Enable Manual Command MTS 793 Tuning and Calibration Displacement Sensor Calibration B Adjust the Manual Cmd slider on the Manual Command window for 80 of the full scale range C Use the Station Signals panel to verify that your LVDT displacement signal equals 80 of the full scale range During the initial calibration and tuning of your system it may take repeated adjustment for the two values to match Note Ifthe actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this control mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the integration value I Gain to help the feedback match the command At this point unless the conditioner is already in calibration the actuator s physical retraction will not equal your commanded value You will adjust gain in the next step so that the actuator s physical retraction and your commanded retraction match Example Suppose your actuator has a 100 retraction of 10 cm In this step you would apply a 8 cm command and even though the station signals would read 8 cm of feedback the actuator may retract only 4 cm This shows the conditioner sensor pair are out of calibration 3 Adjust gain to retract the actuator until
137. move any hysteresis Note Before clicking Auto Zero ensure that any offsets due to Auto Offset and Manual Offset actions are eliminated 2 Use Auto Zero to zero transducer output Standalone FlexTest SE Controllers Select Setup gt Strain gt Offset Zero gt lt lt Auto Zero gt gt Automated Controllers Click Auto Zero on the Calibration tab to set transducer s amplified output to 0 000 V DC 3 Set the calibrator micrometer to 80 of the positive full scale value 4 Note the monitored strain signal value 5 Adjust Delta K to achieve an 80 value 8 V DC Note The Delta K value can be adjusted above or below 1 000 This means it will correct for an error above or below 8 volts MTS 793 Tuning and Calibration 197 Extensometer Calibration Compare recorded Your sensor should include a calibration data sheet that shows the data data points to point tolerance calibration sheet 1 Record the negative and positive outputs values at the 20 40 60 and 100 data points 2 Compare your recorded output values to the calibration data sheet that accompanied your sensor 3 Make sure your current values fall within the permissible variation Note Itis up to the user to establish whether the recorded data points meet the required accuracy Typically 1 of a reading is the normal accuracy specification If they do not you must go back to recalibrate the extensometer negative and positive outputs Note The
138. n 124 Displacement Sensor Calibration Abbreviated Procedure 126 Displacement Sensor Calibration Detailed Procedure 127 Force Sensor Calibration 150 Force Sensor Calibration Abbreviated Procedure 151 Force Sensor Calibration Detailed Procedure 152 Encoder and Temposonics Calibration 185 Encoder Calibration Abbreviated Procedure 186 Encoder Calibration Detailed Procedure 186 Extensometer Calibration 190 Extensometer Calibration Abbreviated Procedure 191 Extensometer Calibration Detailed Procedure 191 116 MTS 793 Tuning and Calibration Pre Calibration Considerations Pre Calibration Considerations Before you start sensor calibration be sure the following are true e The sensors are properly connected to the controller e A configuration file has been created that includes the hardware resources associated with the sensors you want to calibrate e You have completed an initial nominal tuning of the sensor channel you are calibrating This is especially important if you have not calibrated the sensor before e The hydraulics are warmed up see System warm up below e Conditioner Gain is set to 1 e You know your signal polarity see below System warm up Be sure that both the hydraulic fluid and the servovalve are at operating temperature before calibration Remove any specimen and run the system in displacement control for at least 30 minutes using a 80 full scale length command at about 0 1 Hz Signal polarity Some
139. n and rate controls that can be adjusted to optimize performance The inner loop is tuned at system installation and requires periodic fine tuning when the outer loop becomes sluggish The inner loop is similar to a displacement control mode for the outer loop Three Stage Valve Driver modules include the electronics necessary to support the inner control loop Important Always tune the inner loop without the hydraulics applied to the actuator Perform the inner loop gain adjustments with hydraulic pressure removed from the main spool while maintaining pressure at the pilot stage This prevents interaction between the inner and outer loops 88 Tuning Procedures MTS 793 Tuning and Calibration The innerloop proportional gain and rate derivative adjustments are the same types of adjustments as the proportional and derivative gain adjustments of the outerloop tuning controls Prerequisites Procedure MTS 793 Tuning and Calibration Program Command How to Perform Advanced Tuning Techniques Feedback Outer Loop Hydraulic Power Supply 493 15 Valve Driver The hydraulic fluid and the servovalve should be at operating temperature See When to Tune on page 47 Command compensators should be turned off The specimen should be removed Remove hydraulic pressure from the main spool Disconnect the hydraulic service manifold HSM control cable from the controller Tes
140. n existing parameter set or enter the name of a new parameter set to save About saving elements It is important that you save your parameter set as you complete of a parameter set the various parts that make up a parameter set Throughout this manual you will be performing discrete procedures while building a single parameter set e If you have already established your default parameter set for the current station and you are creating a new parameter set for a specific test save the parameters with a different name e Different tests and or specimens may require different parameter sets How to Perform Advanced Tuning Techniques The following techniques require product features that may be optional for your controller How to Auto Tune When you run auto tuning the controller disregards your current PIDF gain settings and applies the minimum required drive signal to ramp the feedback to 80 of the auto tuning limits It then measures the relationship between the feedback velocity and the valve opening signal and then derives the minimum PIDF gains required to track the command It s good practice to auto tune the displacement control mode first then install a dummy specimen and auto tune the force control mode MTS 793 Tuning and Calibration Tuning Procedures 83 How to Perform Advanced Tuning Techniques Auto tuning the displacement control mode 84 Tuning Procedures 1 Select an access level of Tuning Standal
141. n on the Calibration tab it immediately changes the resolution of signal values displayed on the Station Signals Meters and Scope windows Save the calibration It is important that you save your sensor calibration values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers On the Station Setup window Inputs panel click the Calibration tab and then Save This saves current calibration values on the Calibration Sensor and Shunt tabs to the sensor calibration file MTS 793 Tuning and Calibration 189 Extensometer Calibration Extensometer Calibration 190 Prerequisites Initial calibration Recalibration Considerations for full range conditioners An extensometer is a sensor attached to a specimen that measures a dimensional change gage length or strain that occurs in the specimen during testing It works by means of precision resistance type strain gages bonded to a metallic element to form a Wheatstone bridge circuit Extensometers require special test fixtures to aid in calibration Be sure the items described in Pre Calibration Considerations on page 117 are true An extensometer requires DC excitation which requires either a dedicated DC conditioner or a digital universal conditioner DUC configured in the DC mode You must know which conditioner is connected to the extensometer Note Ifyou are recalibrating a sensor use
142. n settings In MTS 793 software version 3 5x or earlier the default location of sensor calibration files is C MTS software product name for example FTGT calib In MTS 793 software version 4 0 or later the default location of sensor calibration files is C MTS 793 Calibration Files A Project is a folder that contains or references files that are used and generated by MTS 793 applications When you start Station Manager you select a Project By default Projects do not contain sensor calibration files directly but reference their location in the Calibration Files subdirectory on disk You can use the Project Manager application to edit the Project Settings file to change the location of sensor calibration files For more information about the Project Manager and Projects see the MTS Control Software manual PN 100 147 130 and the MTS 793 Controller Overview manual PN 100 162 928 Note Only controllers that use Series 494 hardware support the use of MTS TEDS transducer electronic data sheet sensors TEDS sensors have built in memory chips that store basic TEDS information manufacturer model number and serial number When you connect an intialized TEDS device to a conditioner the Station Manager application reads the basic TEDS information from the device and a sensor assignment window appears MTS 793 Tuning and Calibration Pre Calibration Considerations Station Manager j 4 different sensor h
143. nctions 35 S save station parameter set 71 77 83 tuning parameters 50 sensor output 43 signals 117 sensor calibration shunt calibration 121 sensor calibration files default location 118 servovalve polarity check 56 setting polarity 52 servovalve balance 56 Shunt calibration 44 shunt calibration 178 procedure 121 shunt resistor installation 179 shunt resistor installation Series 494 183 when to use 120 signal polarity 117 specimens 38 changing 39 tuning with 38 tuning without 38 spool position zeroing zero spool position 95 square wave shape 34 stabilization filters 113 stabilizing with acceleration feedback 29 with delta P feedback 28 strain control modes 32 System calibration 42 system hydraulics warm up 50 120 system warm up 117 T TEDS sensor 118 Temposonics sensor calibration connections 185 Temposonics sensors 185 Tuning analogy 17 feed forward gain 26 goal 18 overview 16 proportional gain 19 waveform 18 Index 211 tuning about 16 auto tuning 83 Channel Limited Channel CLC control modes 101 checklist 47 compensation 39 control range adjust 39 controls 16 creating a program 33 displacement 67 dither about 63 Dual Compensation mode about 104 gain 105 tuning 106 dual valve 59 Feed Forward gain about 27 filters about 109 enabling 109 force control modes 71 guidelines 47 inner loop 88 monitoring waveforms 40 pre calibration LVDT 126 prerequisites 48 66 proportional
144. nd C ka chunk ka chunk If your system begins to go unstable quickly readjust the control that caused the instability MTS 793 Tuning and Calibration Tuning Procedures 75 How to Manually Tune the Control Loop The middle waveform is the optimum waveform In some cases the waveform will have 76 no overshoot or ringing Tuning Procedures 10 11 High BN Rate D N SN N Low Gain P High Adjust the I Gain tuning control Standalone and Automated Controllers Set up a peak valley meter to monitor the peaks and valleys of the sensor signal The peaks and valleys should be balanced Before adjusting reset I Gain be sure the feedback signal is repeatable that is the same peaks and valleys are achieved If the command is not centered on zero monitor the difference between peaks and valleys of the sensor feedback to the upper and lower levels of the test command Any difference should be the same Note You can also use the optional Scope or an external oscilloscope to adjust Gain by monitoring the Error signal For more information see How to Use Error to Tune Gain on page 98 Save your tuning settings Standalone FlexTest SE Controllers Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers On the Station Manager File menu select Save Parameters As You can either select an existing parameter set or enter the name of a new parameter set to save MTS
145. nderstand how tuning works let s use the analogy of taking a car on the highway The dashed line down the middle of the road is where the driver wants to be so this is the command This is an automated system that tells the driver if the car is following the command and if not how far it s off and in what direction As the car moves the road begins to curve The driver does not respond immediately so the command the desired path and the feedback the actual path are starting to differ This difference command minus feedback is error It s indicated by the shaded triangle Note that error increases the longer the driver waits to correct it that is the larger the difference between the desired path and the actual path The driver turns the steering wheel to adjust the car s path But there s a problem Note Assume the error detector is set to a value that represents the width of the road If the response is too slow or too quick the error detector can stop the program before you go off the road If you turn the steering wheel too little and the car responds too slowly If you turn the steering wheel too much the car overresponds So the objective for a good driver is to turn the wheels just right If so the car accurately follows the line the passengers have a smooth ride MTS 793 Tuning and Calibration Introduction 17 About Tuning 18 The Test Waveform The Ultimate Goal Getting There Introduct
146. ngs ready Perform the following before you start sensor calibration l Locate relevant documentation You need information about the force sensor such as the serial number model number excitation voltage capacity etc The information can be found on the Force Transducer Calibration Data sheet included with a calibrated force sensor or the Final Inspection card included with all MTS sensors You need calibration identification numbers for the force standard or any other calibration equipment that will be used for this calibration procedure The calibration information is usually on a sticker attached to the equipment You need the serial number of the Digital Universal Conditioner You will need shunt calibration resistors Set up to monitor load standard output Typically you should monitor the load standard output signal with a digital volt meter DVM when you calibrate a force sensor Open a station configuration file You need a station configuration file that includes a control channel with a control mode that uses the sensor you intend to calibrate Also to monitor the force sensor signal with an external DVM ensure that you have allocated an analog output resource readout channel in the Station Builder program MTS 793 Tuning and Calibration The illustration shows a load standard in line with the force train coupled with the force sensor The load standard reacts like a stiff soecimen Be sure the g
147. nstable and the end levels are repeatable simply increase the command to achieve the desired end levels 40 Introduction MTS 793 Tuning and Calibration Monitoring the error signal The error signal from a square wave should show the feedback ringing centered on the zero reference A static accuracy difference in the error signal can be corrected with reset The square wave shape of the error signal represents the phase lag of the feedback signal The error signal from a sine should be a small amplitude sine waveform that looks like a rounded square waveform MTS 793 Tuning and Calibration About Tuning The error signal shows similar characteristics as a feedback signal The error signal represents the difference between the command and sensor feedback The following diagrams show the error signal characteristics for each type of waveform A square waveform is best suited to view the overshoot and ringing characteristics that occur when tuning a system Review the following waveforms to determine the kind of characteristics that can be found in an error signal Command Feedback B Static Zero Ma Accuracy JA Difference Error Signal Command Feedback Following Error Zero Difference Command Zero Introduction 41 About Calibration About Calibration System Calibration 42 Introduction Calibration is the act of cert
148. o Get Technical Support Start with your manuals Technical support methods MTS web site www mts com E mail Telephone Fax The manuals supplied by MTS provide most of the information you need to use and maintain your equipment If your equipment includes MTS software look for online help and README files that contain additional product information If you cannot find answers to your technical questions from these sources you can use the internet e mail telephone or fax to contact MTS for assistance MTS provides a full range of support services after your system is installed If you have any questions about a system or product contact MTS in one of the following ways The MTS web site gives you access to our technical support staff by means of a Technical Support link www mts com gt Contact Us gt Service amp Technical Support techsupport mts com MTS Call Center 800 328 2255 Weekdays 7 00 A M to 5 00 P M Central Time 952 937 4515 Please include Technical Support in the subject line Technical Support 7 Before You Contact MTS Know your site number and system number Know information from prior technical assistance Identify the problem Know relevant computer information 8 Technical Support MTS can help you more efficiently if you have the following information available when you contact us for support The site number contains your company number and identifies your eq
149. oad standard readout Using dead weights e Remove all dead weights On the Inputs panel click on the Offset Zero tab and then adjust Manual Offset for a signal value of 0 KN on the DVM or Station Signals panel D Adjust the Manual Cmd slider to achieve a load standard reading of 20 compression and record the meter reading Repeat this step for 40 60 80 and 100 compression 162 MTS 793 Tuning and Calibration Using a load standard Using dead weights MTS 793 Tuning and Calibration Force Sensor Calibration 2 Record the data points for the tension Standalone FlexTest SE Controllers A Adjust the Setpoint to achieve a load standard readout of Zero Adjust the Setpoint between zero and full tension three times This exercises the force sensor to remove hysteresis Establish the zero reference e Adjust the Setpoint for 0 kN Then zero the load standard readout e Remove all dead weights e Adjust Manual Offset for a signal value of 0 kN on the DVM or other monitoring device Select Setup gt Force gt Offset Zero gt Manual Offset Adjust the Setpoint to achieve a force standard reading of 20 tension and record the meter reading Repeat this step for 40 60 80 and 100 compression Automated Controllers A Adjust the Manual Cmd slider to achieve a load standard readout of zero Adjust the Manual Cmd slider between zero and full tension three times This exercises the fo
150. ode to Displacement Shunt calibration cannot be performed on a sensor when it is in control of the servo loop MTS 793 Tuning and Calibration Force Sensor Calibration 6 Determine the shunt calibration resistor from the following table BRIDGE SENSITIVITY RANGE RESISTOR RESISTANCE FULL SCALE VALUE 350 Q 2 mV V 100 49 9 k 50 100 k 20 249 k 10 499 k 350 Q 1mV V 100 100 k 50 200 k 20 499 k 10 1000 k 700 2 mV V 100 100 k 50 200 k 20 499 k 10 1000 k 700 1mV V 100 200 k 50 402 k 20 1000 k 10 2000 k Note Ifyou are calibrating a FlexTest Il m CTC Controller skip to step 9 7 If you have sensor cables with optional transducer ID modules complete the following procedure If not proceed to Step 8 Install the shunt calibration resistor into the R9 location of the sensor ID module The sensor identification cartridge is molded into the sensor cable Solder the shunt cal resistor here MTS 793 Tuning and Calibration 179 Force Sensor Calibration 8 FlexTest SE LE FlexTest GT TestStar IIm Controllers only If you do not have transducer ID modules on your sensor cables install the shunt calibration resistor as follows Select the appropriate shunt calibration resistor Bend the resistor leads 90 for a 0 3 inch separation Cut the resistor leads 0 12 inch from the bend Insert the resistor into the connector solder cups and solder m 0 O g Complete and attach a shunt calibration label a
151. of an acceptable response time We guarantee a timely response your feedback is important to us The Problem Submittal Form can be accessed e Inthe back of many MTS manuals postage paid form to be mailed to MTS e www mts com gt Contact Us gt Problem Submittal Form electronic form to be e mailed to MTS Preface Before You Begin Safety first Other MTS manuals Before you attempt to use your MTS product or system read and understand the Safety manual and any other safety information provided with your system Improper installation operation or maintenance of MTS equipment in your test facility can result in hazardous conditions that can cause severe personal injury or death and damage to your equipment and specimen Again read and understand the safety information provided with your system before you continue It is very important that you remain aware of hazards that apply to your system In addition to this manual you may receive additional MTS manuals in paper or electronic form If you have purchased a test system it may include an MTS System Documentation CD This CD contains an electronic copy of the MTS manuals that pertain to your test system including hydraulic and mechanical component manuals assembly drawings and parts lists and operation and preventive maintenance manuals Controller and application software manuals are typically included on the software CD distribution disc s Preface 11 C
152. of this procedure refer to How to Create a Sensor File in the MTS 793 Control Software manual 1 2 On Station Manager Tools menu select Sensor File Editor On the Sensor File Editor toolbar click the Open button and then New From the Conditioner Type list select the type Model of conditioner that is connected to the extensometer you are calibrating Note Until you select conditioner type all conditioner entries are disabled 4 Enter a sensor name or model number and then the serial number Specify either Strain or Length for the signal Dimension Enter any additional information Under Range Definition define a range including the Name of the range Set the sensor fullscale min max and unit Set the units and enter the full scale minimum and maximum for the range The system software supports non symmetrical full scales Note Ifyou want to use units different than those supplied in the sensor J documentation enter the full scale in the supplied units first and then switch to the desired full scale units The units conversion will be calculated automatically Enter initial calibration values Note Do not use default values Enter actual calibration values 10 MTS 793 Tuning and Calibration Save your sensor file and close the Sensor File Editor 193 Extensometer Calibration Task 3 Adjust offset 194 This task verifies the sensor s zero position and offsets any imbal
153. ollowing procedure for your specific system MTS 793 Tuning and Calibration 1 Select the Tuning access level 2 Select the following settings in the function generator Standalone FlexTest SE Controllers Tuning gt Manual gt FG Tuning Procedures 67 How to Manually Tune the Control Loop Automated Controllers Click i on Station Manager CONTROL SETTING Wave Shape Square Frequency 1 Hz Target Setpoint 0 mm Amplitude 10 of full scale 3 Set up the Scope Note You can use an oscilloscope instead of the software scope if you want To do that you must define a Readout channel to connect the oscilloscope Standalone FlexTest SE Controllers Select Scope and set up scope parameters to display the displacement feedback signal Note If your FlexlTest SE Controller is not equipped with the optional Scope use an external oscilloscope Automated Controllers On the Display menu select Scope B Select the displacement signal for display C Set the Trace Time to 5 seconds D Ensure Auto Scale is on the default position is ON Note To improve your view of the waveform click the Rescale button to maximize the waveform on the display WARNING Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Sta
154. omated Controllers Use the Manual Cmd slider on the Manual Command window to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Example When calibrating a 10 kN range exercise the load standard between 0 and 10 KN Apply a compressive force command that is 80 of the range s full scale 159 Force Sensor Calibration 160 Standalone FlexTest SE Controllers A Enable the front panel Dial B Using the Dial adjust the Setpoint for a compressive force command that is 80 of the full scale range C Verify that your force transducer feedback signal is 80 of the full scale range Automated Controllers A Open the Manual Command window and then click on the Enable Manual Command B Adjust the Manual Cmd slider on the Manual Command window for a compressive force command that is 80 of the full scale range C Use the Station Signals panel to verify that your force transducer signal equals 80 of the full scale range During the initial calibration and tuning of your system it may require repeated adjustment for the compressive force command and feedback values to match Note Ifthe actuator response is sluggish and or the signal value does not match the command you will need to adjust the tuning of this control mode Increase the proportional gain P Gain on the Tuning menu to correct sluggish actuator movement Increase the reset integration va
155. ometer R Cal jack for the sensor connected to Jx01 The shunt resistors for the R Cal jack for the sensor Model 497 22 DC connected to Jx02 Conditioner are packaged in a thumb nail sized module It makes it easier to install and remove the shunt calibration resistor Perform shunt calibration Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Select Cal Type gt A Select required Shunt Display units B Ensure that Shunt State is set to On Polarity is always positive Note the Shunt Reference value it should be 60 90 80 is ideal of the calibrated range of the sensor C Click Update to copy the current shunt reference value into the Shunt Reference box D Set Shunt State to Off MTS 793 Tuning and Calibration Extensometer Calibration Automated Controllers A In Station Setup select the appropriate strain channel on the navigation panel click the Channel Input Signals icon and then click the Shunt tab B Select the shunt type Use polarity if you are not sure what to select C Inthe Current Shunt Value box click the On button Note the Current Shunt Value it should be 60 90 80 is ideal of the calibrated range of the sensor D Click Update to copy the Current Shunt Value into the Shunt Reference Value box and then click Off Task 7 Save the calibration settings MTS 793 Tuning and Calibration It is important that you save your s
156. one FlexTest SE Controllers Status gt Access Level gt Tuning Automated Controllers In the Station Manager window s toolbar select an access level of Tuning If necessary remove the specimen Set and enable the displacement feedback signal s limits typically just outside the signal s full scale range Standalone FlexTest SE Controllers Setup gt displacement gt Limits Automated Controllers In the Station Setup window s navigation pane click Detectors and then Limits See How to Set Limit Detectors in the MTS 793 Control Software manual for more about setting limit detectors Set up auto tuning parameters Standalone FlexTest SE Controllers A Select Tuning gt Auto Tuning B For Control Mode select displacement C For Mode to Tune select displacement D For Actuator Type select the type you have The actuator is typically equipped with a label that identifies whether or not it is hydrostatic Note Ifyou receive a Feedback is not responding to drive signal message during tuning select Hydrostatic his setting allows more and faster valve movements which results in more actuator movement E For Upper Limit and Lower Limit set the upper and lower limits for actuator travel during auto tuning Auto tuning exercises the actuator within 80 of these limits MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques
157. oner Out Ground Inner Loop Signals DESCRIPTION The final output to the servovalve The voltage represents the current output 10 V DC 50 mA standard The amount of valve balance introduced by the Valve Balance control on the Valve tab of the Drive page The input signal to the 3 Stage Valve Driver the test program command The difference between the Inner loop Command and the Spool Position signal The Conditioner Out signal summed with the Spool Zero signal The amount of offset introduced by the Offset control on the Valve tab of the Drive page The conditioned feedback signal from the servovalve LVDT The signal common Tuning Procedures 97 How to Perform Advanced Tuning Techniques How to Use Error to Tune Gain setting up the Scope Using a square wave Using a ramp Upset recovery method 98 Tuning Procedures Note This procedure requires the optional Scope or an external oscilloscope This procedure pertains to manually tuning the I Gain control using the Error signal To perform this procedure for the displacement control mode follow the procedure beginning on page 67 then use it as an alternate method to Adjust the I Gain tuning control on page 70 To perform this procedure for the force control mode follow the procedure beginning on page 71 then use it as an alternate method to Adjust the I Gain tuning control on page 76 Set up the Scope to view Command an
158. ontinue to perform as intended over time Manual Part Number Publication Date MTS 793 Software Release 100 147 134 A June 2006 Version 4 0A or higher 100 147 134 B October 2006 Version 4 0B or higher 100 147 134 C January 2008 Version 5 0B or higher Contents Technical Support 7 How to Get Technical Support 7 Before You Contact MTS 8 If You Contact MTS by Phone 9 Problem Submittal Form in MTS Manuals 10 Preface 11 Before You Begin 11 Conventions 12 Documentation Conventions 12 MTS 793 Tuning and Calibration Contents 3 Chapter 1 Introduction 15 4 About Tuning 16 How the Tuning Controls Work 17 Proportional P Gain 19 Integral A Gain 21 Derivative D Gain 23 Feed Forward F or F2 Gain 26 Stabilization Gain S Gain 28 Delta P Stabilization 28 Acceleration Stabilization 29 Forward Loop Filter FL Filter 30 Tuning Characteristics of Control Modes 31 Creating a Tuning Program 33 About Auto Tuning 36 Other Tuning Considerations 38 Monitoring Waveforms While Tuning 40 About Calibration 42 System Calibration 42 Sensor Calibration 43 Contents MTS 793 Tuning and Calibration Chapter 2 Tuning Procedures 45 When to Tune 47 Tuning for the First Time 49 How To Warm Up Station Hydraulics 50 How to Set Servovalve Polarity 52 How to Balance the Servovalve 56 How to Balance Dual Valves 59 How to Adjust Dither 63 How to Manually Tune the Control Loop 66 Tuning the Displacement Control Mode 67 Tuning the
159. ontrollers In the Station Manager window s toolbar select an access level of Tuning 3 Display the compensation controls of the dual compensation control mode Standalone FlexTest SE Controllers Select Setup gt desired Dual Compensation control mode gt desired compensation method Automated Controllers A Inthe Station Manager window s Display menu select Station Setup MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques B In the Station Setup window s navigation pane locate and select the dual compensation control mode being tuned C In the Station Setup window click ad D In the Compensators panel click the tab for the compensation method being used In the selected Compensation tab set the Conversion Gain and Integrator Gain A Set Conversion Gain to either The calculated conversion gain value See Calculating conversion gain on page 106 for the calculation formula A value between 0 8 and 1 0 The stiffer the specimen the smaller the value B Set Integrator Gain to 0 Install a dummy specimen Set Limits to protect you your equipment and your specimen Standalone FlexTest SE Controllers See About Limit Detectors in the FlexTest SE Users manual for more information Automated Controllers See About Limit Detectors in the M7S 793 Control Software manual for more information Set
160. onventions Conventions Documentation Conventions 12 Hazard conventions Preface Notes The following paragraphs describe some of the conventions that are used in your MTS manuals As necessary hazard notices may be embedded in this manual These notices contain safety information that is specific to the task to be performed Hazard notices immediately precede the step or procedure that may lead to an associated hazard Read all hazard notices carefully and follow the directions that are given Three different levels of hazard notices may appear in your manuals Following are examples of all three levels Note For general safety information see the safety information provided with your system Danger notices indicate the presence of a hazard with a high level of risk which if ignored will result in death severe personal injury or substantial property damage Warning notices indicate the presence of a hazard with a medium level of risk which if ignored can result in death severe personal injury or substantial property damage Caution notices indicate the presence of a hazard with a low level of risk which if ignored could cause moderate or minor personal injury equipment damage or endanger test integrity Notes provide additional information about operating your system or highlight easily overlooked items For example Note Resources that are put back on the hardware lists show up at the end of
161. orm the procedure twice If you are recalibrating a sensor use the existing calibration values as a starting point Full range conditioners allow you to choose Gain Delta K or Gain Linearization for calibrating LVDTs The mV V Pos Tension and mV V Pos Comp calibration types are typically not used for controllers equipped with full range conditioners MTS 793 Tuning and Calibration Considerations for Gain Linearization calibrations Range support What you will need MTS 793 Tuning and Calibration Displacement Sensor Calibration Gain Linearization calibrations requires specific conditioner zeroing practices as follows e Before and during calibration ensure the Manual Offset and Electrical Zero controls on the Offset Zero tab of the Inputs panel are set to zero Also ensure the Electrical Zero Lock box is set e After calibration do not change the electrical zero adjustment Readjustment of electrical zero after calibration will change the point at which linearization takes place which will disturb other calibration settings Full range conditioners e g Model 493 25 DUCs do not require individual ranges Ranged conditioners e g Model 493 21 21B DUCs and Model 497 14 AC Conditioners support up to four ranges for LVDT calibration Displacement can be calibrated to any range within the full scale capacity of the sensor Also ranges do not have to be centered on Zero You will need a dial indicator gage or
162. ows Compression mV V Delta K G HE To A A Tension mV V Where Compression is specified using the Neg Compression or Pos Compressive entry box on the Calibration submenu or tab Tension is specified using the Neg Tension or Pos Tension entry box on the Calibration submenu or tab MTS 793 Tuning and Calibration 175 Force Sensor Calibration m V V Positive Tension Calibration 176 Gain See Excitation Voltage x Compression mV V Where Conditioner Output Voltage is typically 10 Vdc Excitation Voltage is specified using the Excitation entry box on the Calibration submenu or tab Compression is specified using the Negative Compression or Positive Compressive entry box on the Calibration submenu or tab Use the following procedure if your force transducer is set up so that a positive Output represents actuator retraction tension 1 Select mV V Pos Tension for your calibration type Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt mV V Pos Tension Automated Controllers Select mV V Pos Tension for Cal Type on the Calibration tab of the Inputs panel From the Calibration Data sheet for your force transducer enter the following values on the Calibration submenu or tab Standalone FlexTest SE Controllers A Enter the full scale force values in the Minimum and Maximum entry boxes B Enter the tension sensitivity value mV V in the Pos Tension entry box
163. p filter responses 110 forward loop filters 109 function generator random 35 210 Index G gain derivative d gain 24 Dual Compensation mode 105 Feed Forward 27 forward loop filter FL filter 30 integral I gain 22 proportional P gain 20 stabilization S gain 28 gain linearization calibration 117 H how to auto tune 83 how to manually tune three stage servovalves 88 how to perform advanced tuning techniques 83 how to use error to tune I Gain 98 how to warm up station hydraulics 50 hydraulics warm up 50 120 I gain See integral gain inner loop tuning three stage valves 88 innerloop signals 97 Integral 21 integral gain 22 L LVDT 44 LVDT calibration about 124 actuator retraction 135 additional ranges 149 calibration types 124 125 150 190 check conditioner polarity 131 gain delta K 135 gain linearization 141 initial values 129 mounting dial indicator 133 pre calibration tuning 126 prerequisites 124 190 setting offset 132 setting zero 132 signal monitoring 128 153 what you need 125 manually tuning three stage servovalves 88 monitor innerloop signals 97 monitoring waveforms 40 areas of interest 40 error signal 41 0 offset setting displacement sensor 194 force sensor 156 LVDT 132 D polarity conditioner 53 displacement sensors 131 155 force sensors 155 servovalve 53 Project definition 118 Project Manager application 118 Proportional gain 19 proportional gain 20 random fu
164. phase shift Program Command Feedback higher Proportional gain Feedback lower Proportional gain MTS 793 Tuning and Calibration Proportional P Gain The shaded square wave represents the test command The solid wavetorm shows an idealized feedback signal MTS 793 Tuning and Calibration About Tuning Proportional gain is the primary and coarsest control of the system It is similar to a radio s volume control in that it amplifies the error signal by an appropriate amount to control the system In its most generic sense the term proportional gain means that the change in power output is proportional to the error Remember that for our car the amount of steering amplitude is proportional to how much we want to correct and how fast This is proportional gain Our formula is now Error Gain x Command Feedback Feedback Proportional gain looks at the Error side of the summing junction A Fh This waveform shows a This waveform shows an sluggish low gain unstable high gain feedback signal feedback signal Note Proportional gain is not speed how far your push down on the gas pedal it s how fast you turn the steering wheel So proportional gain in the servo loop is acceleration The speed of the system Is controlled by the size of the hydraulic components Introduction 19 About Tuning AM At first it may seem desirable to make proportional gain as large as possible After all w
165. ps between values higher resolution while increasing the range produces larger steps between values Example Suppose the default range for the Proportional Gain adjustment is 50 Assume you are adjusting the gain and you reach the maximum adjustment 50 Clicking the P Gain slider label displays the P Gain range window where you can change the range of the adjustment Change the range by typing a new value in the maximum entry field Introduction 39 About Tuning Monitoring Wavetorms While Tuning When you tune the servoloop you need to monitor the results of your adjustments There are two ways to monitor a waveform during tuning e An oscilloscope is preferred e The controller scope is adequate if you do not have an oscilloscope Note Setup your scope to monitor the area of the waveform that shows characteristics useful for tuning You can monitor the sensor feedback or the error signal of the control mode What to monitor The accuracy of the waveform represents how well it reaches the amplitude of the command or how repeatable the end levels are The peaks and valleys of triangle and sine waveforms should be consistent Use the area of the square wave after the ringing settles to monitor the end levels These are the areas of interest on these You do not need to monitor waveforms the entire waveform y ao Instead zoom in on the area of interest If the amplitude of the feedback cannot be achieved without going u
166. r Check validity before entering each pair of values on a new Calibration Data Sheet Automated Controllers A Adjust the Manual Cmd slider for each retraction and extension command point on the Linearization Data window At each command point verify both the dial indicator value Standard and its corresponding conditioner feedback value Conditioner Check validity before entering each pair of values on a new Calibration Data Sheet MTS 793 Tuning and Calibration Displacement Sensor Calibration Task 8 Save the calibration It is important that you save your sensor calibration values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers Click Save on the Calibration tab to save the current calibration values to the sensor calibration file Note Systems equipped with full range conditioners e g Model 493 25 DUC module do not require or support multiple ranges They use one range that is typically set to 100 Task 9 Calibrate additional ranges Adding a range Each sensor calibration file can have calibration data for four ranges If you have a need for additional ranges simply create another sensor calibration range e Use the calibration values from the previous range as a starting point e If you adjust the zero reference it may affect the other ranges If the sensor calibration file must have additional ranges defined
167. r with its own electronics or a set of calibrated dead weights Extensometers require special test fixtures to aid in calibration LVDTs are calibrated with a dial indicator or ruler The indicator is mounted between the actuator rod and a stationary point such as the load unit s platen A typical LVDT has a positive and a negative output This is usually considered as tension and compression but it s actually a motion each way from its centerpoint One output is calibrated with gain typically compression and the other output is calibrated with delta K typically tension Shunt calibration is a feature available for dc conditioners It checks the integrity of the conditioner sensor combination When a sensor range is calibrated a shunt calibration resistor is selected The system gives you the capability of verifying calibration accuracy by shunting a precision resistor across one arm of the sensor s Wheatstone bridge The resulting imbalance provides a reference value for later use MTS 793 Tuning and Calibration Chapter 2 Tuning Procedures About tuning procedures for specific controller models Where to find control descriptions for specific controller models MTS 793 Tuning and Calibration This chapter contains step by step tuning instructions for MTS 793 Controllers In this manual MTS 793 Controllers include FlexTest IIm CTC FlexTest SE FlexTest GT and TestStar IIm Controllers For each task instruct
168. rce sensor to remove hysteresis 163 Force Sensor Calibration C Establish the zero reference Using a load standard 6 Using dead weights s Adjust the Manual Cmd slider for 0 kN Then zero the load standard readout Remove all dead weights Then adjust the Offset control for a Signal Value of 0 kN on the Input Signals window D Adjust the Manual Cmd slider to achieve a force standard reading of 20 tension and record the meter reading Repeat this step for 40 60 80 and 100 compression Note The Gain Linearization Calibration procedure that follows applies only to controllers equipped with full range conditioners e g Model 493 25 DUC module Task 6 Gain Linearization Calibration If you are using Gain Linearization for your calibration type complete the following procedure If not complete Task 5 Gain Delta K Calibration on page 156 or Task 7 Millivolt Volt Calibration on page 175 Important Important 164 Using linearization data requires specific conditioner zeroing practices Ensure that Electrical Zero Lock on the Offset Zero menu is set to Locked Adjusting electrical zero after calibration may invalidate linearization data Changing conditioner polarity after calibration may invalidate linearization data If you need to change conditioner polarity for example when moving a sensor to a different test system the sensor may need to be recalibrated MTS 793 Tuning and Calibration Ini
169. re waveform is most useful for tuning displacement e A square waveform has an infinite velocity command e Do not use a square waveform when tuning a control mode that uses an extensometer The large accelerations can cause the extensometer to move or fall off the specimen which can cause the system to go unstable e Monitor the feedback or error signal to evaluate the system stability Ramp and lapered Ramp A ramp waveform also called a triangle waveform requires the waveform actuator to move at a constant rate This requires the servovalve to move quickly between two discrete openings Cycling a ramp waveform produces a triangle waveform Tapered ramp waves taper from 0 to 100 amplitude at the beginning of execution and from 100 to 0 at the end of execution e Aramp waveform is useful for all levels of tuning e Use a ramp waveform if a square waveform creates excessive velocities or acceleration for the type of specimen being tested e Monitor the feedback or error signal to evaluate the system stability Sine and Tapered Sine A sine waveform also called sinusoidal or haversine requires the waveform servovalve to move at a variety of rates Tapered sine waves taper from 0 to 100 amplitude at the beginning of execution and from 100 to 0 at the end of execution 34 Introduction MTS 793 Tuning and Calibration Random function generator Frequency Amplitude MTS 793 Tuning and Calibration About Tuning
170. rm B Increase the D Gain to achieve an optimum waveform Instability For actual testing if your system goes unstable it will emit an annoying high pitched sound If your system begins to go unstable quickly readjust the control that caused the instability to return the control to its previous setting Rule of thumb Adjust the P Gain and D Gain controls as high as possible without going unstable If instability is present a P Gain or D Gain value approximately 1 2 the current value is appropriate 13 Adjust the I Gain tuning control A Set an initial I Gain that is 10 50 of your current P Gain setting B Monitor the dc error using a scope or meter C Change the command to disrupt the system by setting Valve Balance to a different value Standalone FlexTest SE Controllers Select Setup gt Output gt Valve Balance 82 Tuning Procedures MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques Automated Controllers Adjust the Valve Balance control on the Drive panel The error should return to zero within 5 10 seconds If not increase the reset I Gain setting and repeat the procedure until the error zeros itself within a reasonable time period 14 Save your tuning settings Standalone FlexTest SE Controllers Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers On the Station Manager File menu select Save Parameters As You can either select a
171. ro position on page 188 Task 6 Save the calibration on page 189 Encoder Calibration Detailed Procedure Task 1 Get things ready Perform the following before you start the calibration 1 Locate relevant documentation When calibrating an encoder or Temposonics sensor you will need information about the device such as the serial number model number and a specification called measuring step resolution 2 Open a station configuration file 186 MTS 793 Tuning and Calibration Encoder and Temposonics Calibration You need a station configuration file that includes a control channel and a control mode that uses the sensor you intend to calibrate Standalone FlexTest SE Controllers Select Config gt Edit Config gt Configuration File Automated Controllers On the File menu select Open Station to open the appropriate configuration file 3 Select the Calibration access level You must select the Calibration user access level before you can perform any of the calibration procedures You may need to enter a password Standalone FlexTest SE Controllers Select Config gt Access Level gt Calibration Automated Controllers In the Station Manager window toolbar select Calibration 4 Set up a signal monitor Refer to page 128 for more information Note Ifyou already have a sensor calibration file skip Task 2 Note Tasks 2 and 3 do not apply to Standalone FlexTest SE Controllers Task 2 Create a
172. roduction Needs Rate Optimum Rate More than Excessive Rate Optimal Rate MTS 793 Tuning and Calibration About Tuning Derivative gain e Reduces ringing e Provides stability and reduces noise at higher proportional gain settings e Tends to amplify noise from sensors e Tends to decrease system response when set too high Keep in mind e Too much derivative gain can create instability at high frequencies and too much proportional gain may cause a ringing or screeching sound e Too little derivative gain can make a rumbling sound The correct amount of derivative gain results in the system running quietly Note Series 256 and 257 Servovalves may require derivative gain applied to both the inner contro loop and outer control loop Note Excessive negative D Gain can cause your system to become unstable MTS 793 Tuning and Calibration Introduction 25 About Tuning Feed Forward F or F2 Gain Correct feed forward 26 Introduction Feed Forward is a gain adjustment not needed for many systems It is more likely needed on systems where you need to move a lot of oil fast to get the actuator moving So it s more likely to be found on systems with large actuators massive grips or moving load cells For our car example and if you remember how carburetors work feed forward is equivalent to the accelerator pump that s the gizmo that gives a quick slug of gas when you suddenly floor the gas pedal This mode
173. ry this test If it still does not move return to Step 2 and increase the gain setting Tuning Procedures 55 How to Balance the Servovalve e If the actuator begins in full extension and applying a negative command does not retract it zero the command remove hydraulic pressure and change the servovalve polarity Then retry this test If it still does not move return to Step 2 and increase the gain setting e If the actuator does not move at all return to Step 2 and increase the gain setting 8 Set servovalve polarity to achieve desired actuator movement How to Balance the Servovalve Balancing the servovalve involves a mechanical procedure performed on the servovalve itself to achieve gross mechanical balance and an electrical adjustment performed with the controller s Valve Balance control to fine tune the mechanical adjustment The mechanical procedure must be done before the electrical adjustment and is typically performed at system installation when a new servovalve is installed in an existing system and when performance warrants it The mechanical procedure is detailed in the servovalve product manual typically included in the system documentation set The electrical adjustment is typically performed much more frequently than the mechanical adjustment The electrical adjustment is performed with the Valve Balance control which adjusts the electrical input to the servovalve to compensate for minor mechanical i
174. s specified on the 493 40 41 Carrier I O Shunt Calibration Kit MTS PN 100 028 185 F Install the shunt cal resistor connector assembly into the appropriate slot of the SHUNT CAL connector on the front panel of the appropriate I O Carrier Module SHUNT CAL I O Option Slot 1 Shunt Cal Resistor Location I O Option Slot 2 Shunt Cal Resistor Location I O Option Slot 3 Shunt Cal Resistor Location I O Option Slot 4 Shunt Cal Resistor Location 9 FlexTest IIm CTC Controllers only Install the shunt calibration resistor into the R Cal jacks in the appropriate DC conditioner 180 MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration 10 11 Force Sensor Calibration You must know which DC O conditioner is associated with the force sensor You also need to know which of the two DC conditioners on the module is used by your load cell R Cal jack for the sensor connected to Jx01 The shunt resistors for the R Cal jack for the sensor _ Model 497 22 DC connected to Jx02 Conditioner are packaged in a thumb nail sized module It makes it easier to install and remove the shunt calibration resistor Verify that force is still zero While it is unlikely it is possible for the force signal to change when the control mode changes If it does Standalone FlexTest SE Controllers Click Auto Offset on the Offset Zero submenu to zero the force output Select Setup gt Force gt Offset Zero gt Auto Of
175. scale F Reset the calibrator micrometer to a value that is 0 of the extensometer s full scale range Ensure that the conditioner feedback reading is zero If necessary use Auto Zero to achieve this zero reading MTS 793 Tuning and Calibration 2 10 li 12 1S 14 Extensometer Calibration Record conditioner feedback readings at predetermined positive strain settings A Set the calibrator micrometer to a value that is 2 of the extensometer s full scale range B Record the calibrator s readout value and corresponding conditioner feedback reading in the 2 row of your record sheet C Repeat steps A and B for other positive strain settings typically at 4 6 8 10 20 40 70 and 100 percent of full scale On the Linearization Data window enter the calibrator readout values and corresponding conditioner feedback readings for all command points previously recorded on a separate sheet Standalone FlexTest SE Controllers Select Setup gt Strain gt Calibration gt Cal Type gt Gain Linearization gt Linearization Data Automated Controllers Click Linearization Data on the Calibration tab Save the sensor file Reassign the sensor file to ensure that the new sensor settings take effect Repeat steps 8 and 9 Verify Linearization Data Make sure your current values fall within the permissible variation Note Itis up to the user to establish whether the recorded data points
176. scope if you want To do that you must define a Readout channel to connect the oscilloscope 78 Tuning Procedures MTS 793 Tuning and Calibration How to Manually Tune the Control Loop Standalone FlexTest SE Controllers Select Scope and set up scope parameters to display the strain feedback and strain command signals Set Trace Time to 2 seconds and ensure that Auto Scale is on Automated Controllers A ma 0 oO W Note On the Display menu select Scope Select the strain command signal for Channel A Select the strain feedback signal for Channel B Set the Trace Time to 2 seconds Ensure Auto Scale is on the default position is ON To improve your view of the waveform click the Rescale button to maximize the waveform on the display WARNING Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Stay clear of the actuators when applying hydraulic pressure 4 Turn on hydraulic pressure see page 51 5 Select the force control mode Standalone FlexTest SE Controllers Select Tuning gt Manual gt Control Mode gt Force Automated Controllers A Inthe Station Controls panel toolbar click to display MTS 793 Tuning and Calibration the Manual Command window In the Manual Command windo
177. se methods include peak valley phase PVP peak valley compensation PVC and arbitrary end level compensation ALC Note When using PVC setting Gain too high may result in system instability MTS 793 Tuning and Calibration Tuning Procedures 105 How to Perform Advanced Tuning Techniques Calculating conversion gain Use this method to calculate the proper Conversion Gain setting Assume a Force Displacement dual compensation control mode 1 Set limits as appropriate and install the specimen 2 Using the Station Manager window s Function Generator excite the specimen in displacement control using a small amplitude sine wave 3 Configure two Peak Valley meters to measure force feedback and displacement feedback signals 4 Calculate the specimen stiffness K _ Force Peak Force Valley Displacement Peak Displacement Valley 5 Calculate the Conversion Gain value 1 Full Scale Force a iat Scale Displacement C G 2 oho a Full Scale Displacemen Note For a more conservative estimate use 80 of the calculated Conversion Gain value When using asymmetrical Fullscale values enter the difference between the values How to Tune a Dual Compensation Control Mode 106 Tuning Procedures 1 Tune the control mode that supplies the primary feedback signal base control mode 2 Select an access level of Tuning Standalone FlexTest SE Controllers Select Setup gt Tuning Automated C
178. shows that the actuator s physical extension equals your extension command 7 If applicable repeat steps 5 and 6 for all ranges Example Suppose you have an actuator with a full scale capacity of 10 cm and ranges of 10 cm 5 cm 2 cm and 1 cm In this case you would repeat this process and calibrate extension at 80 of each range 8 cm 4 cm 1 6 cm and 0 8 cm Some systems use full range conditioners e g Model 493 25 DUC module In this case only one range is used typically 100 Record data points The accuracy tolerance of your data depends on the manufacturer of your sensor Your sensor should include a calibration data sheet that shows the data point tolerance Sensors from MTS include a sensor calibration data sheet that shows the data points as it was calibrated 1 Record the data points for LVDT extension Standalone FlexTest SE Controllers A Adjust the Setpoint to achieve zero command B Adjust the dial indicator for a zero reference C Adjust the Setpoint to 20 extension and record the dial indicator reading Repeat this step for 40 60 80 and 100 actuator extension Automated Controllers A Adjust the Manual Cmd slider to achieve zero command B Adjust the dial indicator for a zero reference C Adjust the Manual Cmd slider to 20 extension and record the dial indicator reading Repeat this step for 40 60 80 and 100 actuator extension MTS 793 Tuning and Calibration 139 Displacem
179. sor that measures the difference in pressure at each end of the actuator It compensates for hydraulic compliance compressed hydraulic fluid acts like a spring Delta P improves displacement control of heavy mass loaded systems Delta P is typically used on systems with large hydraulic fluid flow rates This adjustment is usually needed when the natural frequency of the actuator is less than the 90 phase lag frequency of the servovalve The servovalve 90 phase lag frequency can be found in the servovalve product literature The natural frequency can be approximated with the following formula Actuator Frequency we Where C constant for English 2500 or metric units 1060 A actuator piston area expressed as in2 cm2 W any directly coupled mass including the actuator piston mass expressed in Ibs kg V hydraulic fluid volume contained inside the actuator and manifold expressed as in cm MTS 793 Tuning and Calibration About Tuning e If the system response deteriorates when adding delta P then change the polarity of the signal If changing polarity does not improve system response try adjusting the stabilization filter e Check all amplitudes for overshoot Do not allow more than 10 overshoot preferably none at any amplitude of a square wave response e Delta P will not compensate for additional compliance from swivels linkages test tables and so forth In this case a mass accelerometer signal from an
180. st SE Controllers Select Setup gt Disp gt Calibration gt Fine Zero Automated Controllers Adjust Fine Zero on the Calibration tab Some conditioners have two zero adjustments coarse and fine Try to calibrate zero using only the Fine Zero contro whenever possible Using the Coarse Zero control affects the signal before the post amp stage of the conditioner and may require additional Gain adjustments In some cases a mechanical adjustment may be necessary to center the LVDT for instructions see the actuator product manual Task 6 Gain Delta K Calibration Calibrate actuator retraction If you using Gain Delta K for your calibration type complete the following procedure If not complete Task 7 Gain Linearization Calibration on page 141 LVDTs can be calibrated so that a positive output Indicated output AY represents actuator extension and a negative output represents actuator retraction or vice versa You calibrate the negative side of the output with gain and the positive side of the output with Delta K AK 1 AK lt 1 mechanical input Delta K compensates for differences in symmetry between the positive and negative outputs You should calibrate actuator extension at 80 of the full scale range MTS 793 Tuning and Calibration 135 Displacement Sensor Calibration 136 Gain controls Procedure Pre Amp gain is a selectable gain amplifier with predefined values Since chang
181. t between zero and full tension three times This removes sensor hysteresis Select Status gt Setpoint Automated Controllers Use the Manual Cmd slider on the Manual Command window to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Example When calibrating a 10 kN range exercise the actuator between 0 and 10 volts To calibrate the same force sensor for a different range such as 5 kN exercise the load standard between 0 and 5 volts Apply a tensile force command that is 80 of the range s full scale Standalone FlexTest SE Controllers A Using the Dial adjust the Setpoint for a tensile force command that is 80 of the full scale range B Verify that your force transducer feedback signal is 80 of the full scale range Automated Controllers A Adjust the Manual Cmd slider for a tensile force command that is 80 of the full scale range B Verify that your force transducer feedback signal is 80 of the full scale range During the initial calibration and tuning of your system it may require repeated adjustment for the tensile force command and feedback values to match MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Force Sensor Calibration Note Ifthe actuator response is sluggish and or the signal value does not 10 11 T2 match the command you will need to adjust the tuning of this control mode Increase th
182. t system e Aero test system Technical Support 9 Write down relevant Be prepared to troubleshoot information After you call Prepare yourself for troubleshooting while on the phone e Call from a telephone when you are close to the system so that you can try implementing suggestions made over the phone e Have the original operating and application software media available e If you are not familiar with all aspects of the equipment operation have an experienced user nearby to assist you Prepare yourself in case we need to call you back e Remember to ask for the notification number e Record the name of the person who helped you e Write down any specific instructions to be followed such as data recording or performance monitoring MTS logs and tracks all calls to ensure that you receive assistance and that action is taken regarding your problem or request If you have questions about the status of your problem or have additional information to report please contact MTS again and provide your original notification number Problem Submittal Form in MTS Manuals 10 Technical Support Use the Problem Submittal Form to communicate problems you are experiencing with your MTS software hardware manuals or service which have not been resolved to your satisfaction through the technical support process This form includes check boxes that allow you to indicate the urgency of your problem and your expectation
183. tStar IIm FlexTest GT and FlexTest SE Controllers At the back of the controller chassis disconnect the cable from connector J28 FlexTest IIm CTC Controllers At the 497 05 Hydraulic Control module s rear panel disconnect the cable from connector J28 Disconnecting this cable disables pressure to the main spool but leaves pressure applied to the pilot stage of the servovalve On systems with multiple HSMs be sure to disconnect the correct cables Note Onsystems with no HSM remove the outer loop LVDT cable from the actuator to disable the outer loop Apply hydraulic pressure Select an access level of Tuning Standalone FlexTest SE Controllers Config gt Access Level gt Tuning Tuning Procedures 89 How to Perform Advanced Tuning Techniques 90 Tuning Procedures Automated Controllers In the Station Manager window s toolbar select an access level of Tuning Set the following valve drive conditioner parameters Standalone FlexTest SE Controllers Setup gt Output gt Conditioner Automated Controllers In the Station Setup window click ul e e aa to display the Drive panel In the Drive panel click the Conditioner tab A Set Excitation to 10V Set Phase to between 10 and 30 deg Set Offset to 0 V Set the Gain to 10 w o o g Set the Polarity to Normal Configure a Meter to monitor the spool position signal Standalone FlexTest SE Controllers Select Meters gt M
184. the extensometer s full scale range Record the calibrator s readout value and corresponding conditioner feedback reading in the 2 row of your record sheet Repeat steps A and B for other positive strain settings typically at 4 6 8 10 20 40 70 and 100 percent of full scale 12 On the Linearization Data window enter the calibrator values Standard and its corresponding conditioner feedback readings Conditioner for all command points previously recorded on a separate sheet 13 Verify linearization data A Set the calibrator micrometer for each strain setting on the Linearization Data window B At each setting verify both the calibrator readout value Standard and its corresponding conditioner feedback value Conditioner C Check validity before entering each pair of values on a new Calibration Data sheet Task 6 Establish the shunt calibration reference 204 Each DC conditioner supports a shunt resistor To establish the shunt reference value perform the following tasks 1 Depending on your extensometer type install a zero pin gage block or special fixturing to mechanically hold the extensometer at its zero position MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration Extensometer Calibration 2 Determine the shunt calibration resistor from the following table BRIDGE RANGE RESISTOR RESISTANCE SENSITIVITY FULL SCALE VALUE 350 Q 2 mV V 100 49 9 k 50 100 k 20
185. the Interlock indicator is lit click Reset If the indicator lights again you must determine the cause and correct it before proceeding 10 Set up the Tuning panel Standalone FlexTest SE Controllers Select Tuning gt Manual Automated Controllers A Note In the Station Setup window navigation pane select the channel that uses the strain signal you intend to tune Click VV to display the Tuning panel In the Tuning panel click the Adjustments tab Select the Show References check box Notice the Reference column on the right side of the window This column shows the current set of tuning parameters Use the buttons to update reference settings with new values or replace the current values with the last set that worked properly The Reference settings are saved with the parameter set 11 Adjust the P Gain Standalone and Automated Controllers A B Set an initial P Gain of at least 1000 Start the function generator After system control is verified slowly increase Amplitude on the function generator Select Continuous Sweep on the Scope Use the scope to monitor the strain command and strain feedback signals Adjust the P Gain achieve the following optimum waveforms that show strain feedback closely tracking strain command Tuning Procedures 81 How to Manually Tune the Control Loop Strain Command Strain Feedback 12 Adjust the D Gain A On the scope monitor the DC error wavefo
186. the Station Setup window s Limits tab e The actuator s limiting force feedback signal cannot exceed limits set for it in the Station Setup window s Adjustment tab How to Tune a CLC Control Mode Tune the control modes that will supply the active and limiting feedback signals MTS 793 Tuning and Calibration Tuning Procedures 101 How to Perform Advanced Tuning Techniques If force feedback gt upper limit And displacement error is positive Then use upper limit error Limit P Gain f 4 Feedback If force feedback lt lower limit And displacement error is negative Then use lower limit Error error Lower Lower Limit Displacement Otherwise use displacement error Command Displacement E E E 1 Acie P Gain f Servovalve Feedback Command Proportional Gain The CLC control mode uses one of three error signals The Limiting P Gain adjustment acts as a conversion factor to scale the limit feedback to similar units as the active P feedback 1 Select an access level of Tuning Standalone FlexTest SE Controllers Select Tuning gt P Gain Automated Controllers In the Station Manager window s toolbar select an access level of Tuning 2 Display the CLC controls for the control mode to be tuned Standalone FlexTest SE Controllers Select Setup gt desired CLC control mode gt Tuning Automated Controllers A In the Sta
187. tial force sensor calibration MTS 793 Tuning and Calibration Force Sensor Calibration For initial calibration of a force sensor complete the following procedure 1 Select Gain Linearization for Cal Type Standalone FlexTest SE Controllers Select Setup gt Force gt Calibration gt Cal Type gt Gain Linearization Automated Controllers Select Gain Linearization for Cal Type on the Calibration tab of the Inputs panel Exercise the force standard Standalone FlexTest SE Controllers Enable the front panel Dial then adjust the Setpoint to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Select Status gt Setpoint Automated Controllers Use the Manual Cmd slider on the Manual Command window to cycle the load standard readout between zero and full tension three times This removes sensor hysteresis Example When calibrating a 10 kN range exercise the actuator between 0 and 10 volts To calibrate the same force sensor for a different range such as 5 kN exercise the load standard between 0 and 5 volts Apply a tensile force command that is 80 of the range s full scale Standalone FlexTest SE Controllers A Enable the front panel Dial B Using the Dial adjust the Setpoint for a tensile force command that is 80 of the full scale range C Verify that your force transducer feedback signal is 80 of the full scale range Automated Contro
188. tion 128 MTS 793 Tuning and Calibration Conditioner calibration values MTS 793 Tuning and Calibration Displacement Sensor Calibration 6 On the Calibration submenu or tab set the initial conditioner calibration values This creates a sensor calibration file and sets up your ranges A typical complement of ranges could be 100 50 20 and 10 of full scale You may create ranges for any percentage of full scale Note Some systems do not provide or require multiple ranges such as those using full range conditioners e g Model 493 25 DUC module In this case only one range is used typically 100 See How to Create a Sensor File in the MTS 793 Control Software manual For LVDT calibration set the following initial conditioner calibration values on the Calibration submenu or tab CONTROL SETTING Polarity Normal Pre Amp Gain 1 0 Post Amp Gain 1 5 Excitation 10 volts Phase 45 Delta K 1 Gain Delta K calibration only Fine Zero O 129 Displacement Sensor Calibration Task 2 Turn on hydraulic pressure This task activates the hydraulic pressure A WARNING Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydraulic pressure to your system Stay clear of the actuators when applying hydraulic pressure SSS I l
189. tion Manager window s Display menu select Station Setup B In the Station Setup window navigation pane s Channels locate and select the CLC control mode you are tuning C In the Station Setup window click VV 102 Tuning Procedures MTS 793 Tuning and Calibration How to Perform Advanced Tuning Techniques D Inthe Tuning panel click the Adjustments tab 3 Set the gain for the active and limiting feedback signals A For Active P Gain enter the value used for the displacement control mode s P Gain B For Limiting P Gain enter the value used for the force control mode s P Gain 4 Select the CLC control mode to test system response Adjust the Active P Gain if the actuator s displacement response is sluggish Adjust the Limiting P Gain if the actuator s force response is sluggish 5 Save the tuning values Standalone FlexTest SE Controllers Select Setup gt Open Save Parameters gt lt lt Save gt gt Automated Controllers In the Station Manager window s File menu select Save Parameters MTS 793 Tuning and Calibration Tuning Procedures 103 How to Perform Advanced Tuning Techniques About Dual Compensation Control Modes Command Force Before dual compensation modes can be tuned they must first be defined in the Station Builder application Sometimes force feedback signals may be too noisy or otherwise unsuitable for use in control modes For example accelerometer feedback si
190. tion sensor s daughter board by using the Hardware tab on the Station Signals window Access Station Signals on the Station Setup window navigation pane For Standalone FlexTest SE Controllers use the Edit gt Config menu to do the same For encoders feedback resources labeled Encoder Input or Heidenhain 417 425 Input indicate that the controller is equipped with an optional encoder interface daughter board For Temposonics sensors feedback resources labeled Temposonics Input or Temposonics III Input indicate that the controller is equipped with an optional Temposonics interface daughter board MTS 793 Tuning and Calibration 185 Encoder and Temposonics Calibration Zeroing For Automated Controllers the sensor signal is defined in the Station Setup Inputs panel For Standalone FlexTest SE Controllers the encoder signal is defined in the Edit gt Config menu Note You cannot zero an encoder or Temposonics sensor if it is selected for the active contro mode Range support Encoder and Temposonics sensors do not support multiple ranges Encoder Calibration Abbreviated Procedure The following abbreviated procedure outlines an encoder calibration process More detailed calibration information is available on the pages listed Task 1 Get things ready on page 186 Task 2 Create a calibration file on page 187 Task 4 Turn on hydraulic pressure on page 188 Task 5 Set the ze
191. tions However you should consider it a guideline The background information presented in this chapter should help you modify the following procedure for your specific system 1 Select the following settings in the tuning function generator Standalone FlexTest SE Controllers Tuning gt Manual gt FG Automated Controllers Click i on Station Manager CONTROL SETTING Wave Shape Ramp 2 Set up the Scope Note You can use an oscilloscope instead of the software scope if you want To do that you must define a Readout channel to connect the oscilloscope 72 Tuning Procedures MTS 793 Tuning and Calibration How to Manually Tune the Control Loop Standalone FlexTest SE Controllers Select Scope and set up scope parameters to display the force feedback signal Note _ f your Flexlest SE Controller is not equipped with the optional Scope use an external oscilloscope Automated Controllers On the Display menu select Scope B Select the Force Abs Error signal for display C Set the Trace Time to 2 seconds D Ensure Auto Scale is on the default position is ON Note To improve your view of the waveform click the Rescale button to maximize the waveform on the display WARNING Do not place any part of your body in the path of a moving actuator A crush zone exists between the actuator and any equipment in the path of its movement Immediate and unexpected actuator response is possible when you apply hydra
192. tive full scale range Note Since you are using a Model 493 25 conditioner with no Delta K adjustment you can only adjust Post amp Gain at one point either the 80 point or 80 point The other point 80 or 80 simply becomes a data point value for the linearization table A Adjust the Setpoint Standalone or Manual Cmd slider Automated for a positive strain command that is 80 of the full scale range B Verify that your extensometer feedback signal is 80 of the full scale range 10 Record conditioner feedback readings at predetermined negative strain settings Note You will enter these recorded readings on the Linearization Data window A Set the calibrator micrometer to a value that is 0 of the extensometer s full scale range B Record the calibrator s readout value and the corresponding conditioner feedback reading in the 0 row of your record sheet C Set the calibrator micrometer to a value that is 2 of the extensometer s full scale range 203 Extensometer Calibration Record the calibrator s readout value and corresponding conditioner feedback reading in the 2 row of your record sheet Repeat steps C and D for other negative strain settings typically at 4 6 8 10 20 40 70 and 100 percent of full scale 11 Record conditioner feedback readings at predetermined positive strain calibrator settings A Set the calibrator micrometer to a value that is 2 of
193. tpoint for each tensile and compressive force command point on the Linearization Data window At each command point verify both the force standard value Standard and its corresponding conditioner feedback value Conditioner Check validity before entering each pair of values on a new Calibration Data Sheet Automated Controllers A Adjust the Manual Cmd slider for each retraction and extension command point on the Linearization Data window At each command point verify both the force standard value Standard and its corresponding conditioner feedback value Conditioner Check validity before entering each pair of values on a new Calibration Data Sheet MTS 793 Tuning and Calibration Force Sensor Calibration Task 7 Millivolt Volt Calibration If you are using mV V Calibration for your calibration type complete the following procedure If not complete Task 5 Gain Delta K Calibration on page 156 or Task 6 Gain Linearization Calibration on page 164 Millivolt volt calibration is used for transducers that have two different slopes positive and negative Positive Tension Slope mv V Negative Compression Slope mV V In this calibration process system software calculates conditioner Delta K Gain and Gain values from previously measured mV V values under both tension and compression The slope and gain values are derived from and are relative to the output of the load cell transducer as foll
194. uipment type material testing simulation and so forth The number is usually written on a label on your MTS equipment before the system leaves MTS If you do not have or do not know your MTS site number contact your MTS sales engineer Example site number 571167 When you have more than one MTS system the system job number identifies which system you are calling about You can find your job number in the papers sent to you when you ordered your system Example system number US1 42460 If you have contacted MTS about this problem before we can recall your file You will need to tell us the e MTS notification number e Name of the person who helped you Describe the problem you are experiencing and know the answers to the following questions e How long and how often has the problem been occurring e Can you reproduce the problem e Were any hardware or software changes made to the system before the problem started e What are the model numbers of the suspect equipment e What model controller are you using Gif applicable e What test configuration are you using If you are experiencing a computer problem have the following information available e Manufacturer s name and model number e Operating software type and service patch information Know relevant software information e Amount of system memory e Amount of free space on the hard drive in which the application resides e Current status o
195. ulic pressure to your system Stay clear of the actuators when applying hydraulic pressure 3 Turn on hydraulic pressure see page 51 4 Ensure that the displacement control mode is selected Standalone FlexTest SE Controllers Press the Back button or select Tuning gt Manual gt Control Mode Automated Controllers On the Manual Command window ensure that displacement is selected for Control Mode 5 Install a dummy specimen Standalone FlexTest SE Controllers A Enable the Dial B Adjust the Dial to position the actuator during specimen installation MTS 793 Tuning and Calibration Tuning Procedures 73 How to Manually Tune the Control Loop Automated Controllers A On the Manual Command window Click Enable Manual Command B Adjust the Manual Command window slider to position the actuator during specimen installation 6 Switch to the force control mode Note For Automated Controllers ensure the Master Span contro on the Station Controls panel is set to100 7 Check system interlocks Standalone FlexTest SE Controllers If the Hydraulic Interlock or Program Interlock indicator is lit determine the cause correct it and then click Reset If either interlock indicator lights again you will need to determine the cause of the interlock and correct it before proceeding Automated Controllers If the Interlock indicator is lit click Reset If the indicator lights again you must determine the ca
196. ulting imbalance provides a reference value for later use Shunt calibration also lets you replace DC conditioners without affecting the sensor calibration accuracy Note The following procedure requires that a valid shunt reference value has already been established Establishing a shunt reference value involves selecting and installing precision shunt resistors and Is a part of detailed calibration instructions included in this manual For information about establishing shunt reference for force sensors see page 178 and for strain sensors see page 204 1 Turn on hydraulic power 2 Zero the DC sensor output Standalone FlexTest SE Controllers Use the Manual Offset control Setup gt Force gt Offset Zero gt Manual Offset to achieve a 0 KN output Automated Controllers Adjust the Manual Cmd slider on the Manual Command window to achieve a 0 kN output 3 If necessary change the control mode Shunt calibration cannot be performed on a sensor when it is in control of the servo loop Standalone FlexTest SE Controllers Select Status gt Control Mode gt displacement Automated Controllers Change Control mode on the Manual Command window to a Displacement control mode Note Ifyou only want to view the current shunt value without changing the shunt reference value the operator access level is adequate 4 Select an access level of Calibration MTS 793 Tuning and Calibration 121 Shunt Calibration 122 5
197. ure into a corresponding electrical signal Each sensor requires conditioning such as AC or DC excitation in order to output a feedback signal that can be used by your servo controller Excitation Conditioner Feedback Module Signal Sensor output Sensor calibration data base MTS 793 Tuning and Calibration Sensor Conditioner Signal Diagram Each sensor conditioner pair must be calibrated to output a voltage that is proportional to the measured output which may be displacement force or some other dimension For example a 10 cm LVDT AC conditioner pair connected to a 10 cm actuator is typically calibrated to output e 0 volts at the piston midstroke position 0 cm e 10 volts at maximum piston retraction 5 cm e 10 volts at maximum piston extension 5 cm The calibration procedure creates a calibration data base for each range of a sensor The data base that is created includes e Calibration data points e Sensor information model type serial number calibration date e Equipment information identifies the equipment used in the calibration e Conditioner information serial number model number excitation voltage circuit parameters Introduction 43 About Calibration Force Sensor Calibration 44 Extensometer Calibration LVDT Calibration Shunt Calibration Introduction Calibrating a force sensor requires a load standard A load standard can be a special calibrated force senso
198. use and correct it before proceeding 74 Tuning Procedures MTS 793 Tuning and Calibration How to Manually Tune the Control Loop 8 Open the Tuning submenu or panel Standalone FlexTest SE Controllers Tuning gt Manual Automated Controllers A Click A to display the Tuning panel B In the Tuning panel click the Adjustments tab C Select the Show References check box Notice the Reference column on the right side of the window This column shows the current set of tuning parameters Use the buttons to update reference settings with new values or replace the current values with the last set that worked properly Note The Reference settings are saved with the parameter set 9 Adjust the P Gain and D Gain tuning controls Standalone and Automated Controllers A Start the function generator B On the Scope menu select Continuous for Sweep Mode Overshoot C On the Manual Tuning submenu increase the P Gain adjustment until you see a little overshoot and a little ringing D Slowly increase the D Gain adjustment to reduce the overshoot and ringing Small adjustments of D can have large effects on the system Ringing E Repeat C and D until you achieve a optimum waveform Unstable sounds For actual testing if your system goes unstable it will sound unstable that is it will emit an annoying high pitched sound accompanied by high frequency actuator movement that is quite different from the usual tuning sou
199. uuuuuuuuuuuuuuuuuuaeesaai 1 Ensure that displacement control mode is selected Standalone FlexTest SE Controllers Select Status gt Control Mode gt Disp Automated Controllers Check Control Mode on the Station Manager Function Generator panel Ensure that the Span is set for 100 Standalone FlexTest SE Controllers Select Status gt Span Automated Controllers Check the Master Span setting on the Station Controls panel Check hydraulic and program interlock indicators Standalone FlexTest SE Controllers If the Hydraulic Interlock or Program Interlock indicator is lit on the front panel determine the cause correct it and then click Reset Automated Controllers If the Interlock or Program indicator is lit on the Station Controls panel determine the cause correct it and then click Reset or Reset Override If either interlock indicator lights again you will need to determine the cause of the interlock and correct it before proceeding In the power selection box click the Low button and then High for the HPU If an HPU is not listed start the HPU at the pump Note he HPU can be configured for first on If this is the case start the 130 appropriate HSM MTS 793 Tuning and Calibration Displacement Sensor Calibration 5 If an HSM is present click the Low button and then High for the HSM Task 3 Verify the conditioner polarity This task checks the polarity of the conditioner D
200. w select the appropriate Channel associated with the strain sensor signal you are tuning For the Control Mode select Force Tuning Procedures 79 How to Manually Tune the Control Loop 80 Tuning Procedures Install a dummy or broken specimen Standalone FlexTest SE Controllers A Enable the Dial B Adjust the Dial to position the actuator during specimen installation Automated Controllers A On the Manual Command window Click Enable Manual Command B Adjust the Manual Command window slider to position the actuator during specimen installation Select strain for control mode Standalone FlexTest SE Controllers Select Tuning gt Manual gt Control Mode gt Strain Automated Controllers In the Manual Command window select Strain for Control Mode Ensure that Span has been set to 100 Standalone FlexTest SE Controllers Select Status gt Span Automated Controllers On the Station Controls panel ensure the Master Span is set for 100 Check system interlocks Standalone FlexTest SE Controllers If the Hydraulic Interlock or Program Interlock indicator is lit determine the cause correct it and then click Reset If either interlock indicator lights again you will need to determine the cause of the interlock and correct it before proceeding MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How to Manually Tune the Control Loop Automated Controllers If
201. waveform distorts at its maximum and minimum points This will normally be more apparent during a test that has either a low frequency or a low amplitude test waveform e Dither amplitude is too high You hear unusual sounds such as hammering squealing or pounding coming from the test system There are two methods for checking and adjusting dither Method 1 uses the controller s scope Method 2 uses your hearing Method 1 1 Select an access level of Tuning 2 Remove any specimen MTS 793 Tuning and Calibration Tuning Procedures 63 How to Adjust Dither 3 Create a program with the function generator as follows CONTROL SETTING Channel automated Select the channel whose dither needs checking Type Cyclic Wave Shape Ramp Control Mode displacement Target Setpoint 0 mm Amplitude 5 mm Frequency 0 001 Hz Compensator None 4 Select the scope and set up scope parameters to display the channel s command and feedback signals WARNING Applying station hydraulic pressure can put actuators in motion A moving actuator can injure anyone in its path Always clear the actuator area before applying hydraulic pressure 5 Apply station hydraulic pressure 6 Press Run to start the displacement command 7 Use the scope to observe the feedback signal If the feedback signal shows a smooth ramp you do not need to adjust the dither amplitude If the feedback signal shows a jagged ramp caused by the a
202. y Tune the Control Loop Tasks related The following are tasks that should be completed before you tune It is to manual tuning not necessary to perform every task each time you tune The condition of your system dictates which of the following tasks you must perform For example a new system or a system freshly recalibrated requires all of the following to be completed If you are performing periodic or fine tuning review the following and determine which tasks you need to complete e Balance the servovalve The electrical valve balance adjustment compensates for minor mechanical imbalance it is an intermediate adjustment Refer to How to Balance the Servovalve on page 56 e Calibrate each sensor used for a control mode or data acquisition Perform the appropriate calibration procedure e If your sensor calibration schedule does not require calibration at this time perform a shunt calibration check to determine if your DC sensor DC conditioner is within tolerance Refer to Shunt Calibration on page 120 e If you have a three stage Series 256 or 257 servovalve tune the inner loop gain and rate before tuning the outer loop The rules for inner loop tuning are similar to those of the outer loop Refer to How to Manually Tune Three Stage Servovalves on page 88 e If your Controller is equipped with the optional auto tuning feature it is best to run auto tuning first Auto tuning establishes reasonable tun
203. y clear of the actuators when applying hydraulic pressure 68 Tuning Procedures MTS 793 Tuning and Calibration MTS 793 Tuning and Calibration How to Manually Tune the Control Loop 4 If necessary turn on hydraulic pressure see page 51 5 Ensure that the displacement control mode is selected Standalone FlexTest SE Controllers Press the Back button or select Tuning gt Manual gt Control Mode Automated Controllers On the Manual Command window ensure that displacement is selected for Control Mode Check system interlocks Standalone FlexTest SE Controllers If the Hydraulic Interlock or Program Interlock indicator is lit determine the cause correct it and then click Reset If either interlock indicator lights again you will need to determine the cause of the interlock and correct it before proceeding Automated Controllers If the Interlock indicator is lit click Reset If the indicator lights again you must determine the cause and correct it before proceeding Open the Tuning submenu or panel Standalone FlexTest SE Controllers Select Tuning gt Manual Automated Controllers A Click A to display the Tuning panel B In the Tuning panel click the Adjustments tab C Select the Show References check box Notice the Reference column on the right side of the window This column shows the current set of tuning parameters Use the buttons to update reference settings with new values or
204. y to whatever extent needed to have your test system behave the way you want it to The controller system software includes several tuning controls You do not need to use all of the controls to properly tune your system In fact most testing can be accomplished with just the proportional gain adjustment The other adjustments introduce a signal to the command to compensate for specific situations Note Throughout this chapter the terms gain rate and reset reoresent proportional gain rate derivative and reset integration respectively The control loop of your test system basically has three elements e The command which is really demanding I want you do this e The feedback which is responding Tm actually doing this at the present time e The error which is complaining You two are out of agreement by this much This means that Error Command Feedback This is the summing junction You want to get the summing junction to drive the error to zero and to do it smoothly and efficiently MTS 793 Tuning and Calibration Consequences of a large degree of error About Tuning While precise tuning is not usually necessary inaccurate tuning increases the error and phase lag between the command and the feedback If the error is large it can reduce control accuracy and repeatability and prevent the full program command from being applied to the specimen How the Tuning Controls Work To u
205. y want to name the full scale range 5 kN Select the units for the range and then enter the absolute value of the range Save the new range to the calibration file Note Ranges can also be added on the Sensor tab and calibrated on the 7 Calibration tab Repeat as necessary for calibrating additional ranges How to Install a Shunt Calibration Resistor on an 1 0 Carrier Board The Model 494 40 I O Carrier board has a front panel socket where you can insert shunt calibration plug assembly for use with DUC cards Each socket is associated with one of the eight RJ 50 connectors on the front panel 1 Determine the RJ 50 connector s used by the transducer s Note Each mezzanine card slot on the I O Carrier board connects to two MTS 793 Tuning and Calibration RJ 50 connectors on the front of the I O Carrier board 183 Force Sensor Calibration 2 Solder the shunt calibration resistors to an MTS shunt calibration plug assembly MTS 11 433 826 Note The shunt calibration plug assembly includes plug assemblies for eight shunt resistors Each resistor should be labeled with its resistance value and transducer serial number 3 Insert the shunt calibration plug assemblies into the front panel sockets Note Ifyou use MTS TEDS modules or MTS transducers with integrated shunt calibration resistors you must insert a jumper plug MTS 100 188 097 into the socket for each transducer input where you will use the inte

793 Tuning and Calibration

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