AHRS M2, M2-M User`s Manual
Contents
1. 118 7 1127 l gt E toe Ai SE INNALABS AHRS Ps N 3 126 5 3 holes Fig 4 2 The AHRS outline drawing all dimensions are in millimeters When mounting AHRS on your system please pay attention to orientation of input axes X Y Z Fig 2 1 respective marking is engraved on the cover of the AHRS During the ordinary operation on the carrier object the AHRS is set on the surface A with the axis Y directed on the nose of the object To obtain accurate attitude and heading please remember that mounting is very important and mounting error can cause attitude and heading errors When AHRS mounting please align it on two base surfaces relative your system axes A SENSOR SYSTEMS S R L PEMS g gt PIATTAFORME INERZIALI There are two variants of the AHRS mounting on your system 1 Use 4 threaded holes M2x5 mm on the bottom of AHRS see Fig 4 1 positions 1 4 2 Use 3 holes 2 5 mm on 3 lugs see Fig 4 1 positions 5 7 Note For the AHRS with aluminum case it is not recommended to use threaded holes see Fig 4 2 positions 1 4 for mounting the AHRS because of possible damage of these threads Requirements to the mounting surface of the carrier object flatness tolerance is 0 03 mm undulation is Ra 1 25 4 4 Variants of the AHRS mounting relative to the object axes Since firmware version 3 3 9 the AHRS can be mounted on the object in any known position2. te PIATTAFORME INERZIALI Attitude and Heading Reference System AHRS M2 M2 M User s Manual March 2009 Revision 3 0 _ SENSOR SYSTEMS S R L Sten gt PIATTAFORME INERZIALI Revision histo n 14 Jun 07 1 1 to 2 6 Skipped 3 0 20 Mar 09 ON For AHRS firmware since v 4 1 7 Updated output data formats see item 6 3 Realized AHRS initial alignment at slow rocking object for marine applications option gt SENSOR SYSTEMS S R L PSTN Fg e ane ee iene mew INS 12 4 1 Where to install the AHRS for teSts ccccccecceceeeeeceeeeseerereceseessrtsess 12 D Electrical ca ee ek cota 18 5 1 Cable and COMMS CUS ood ccciscadssesutencnssinasisnciebetursinpreesesessnessecresubensuts 18 5 2 Quick Electrical Connections for the AHRS Evaluation 21 6 Software ENEE E A E E R OE E me ee AA 22 Figure 1 1 TS PAR Scie deci ccccsisisdas dea teenddvcesndeensetasounsatectbiddanedcsiiuesedeaevanadanatdans 5 Figure 1 2 Data Cables Set cccccccccsesseceeeseeeseeceeeeeeeceeeeeseeaeeeeeeseeeenseeens 6 Figure 1 3 Protective TUG paaiicccescetcnutenceorrnteceu ya hascdeuanstenadeceueiecOiemietes 7 Figure 1 4 AC DC adapter with interchangeable plug cccssseeeeeeeeeeeeeees 7 Figure 2 1 AHRS with body fixed coordinate system ccceceseeeeeeeeeeeeeeees 7 Figure 2 2 Operational Diagram of the AHRS cccccceeeeeeeeeeeeeeeeeaeeeeees 9 Figure
3. AHRS M2 M is special modification of the AHRS for marine vehicles which allows initial alignment of AHRS at slow rocking vehicle For such modification initial alignment consists from two stages After start the AHRS the short 1 second initial alignment takes place during which initial orientation angles are determined as initial conditions for integration of gyros outputs Next 90 seconds are need for gyros bias estimation using Kalman filter even at rocking vehicle During this period don t accelerate the AHRS only slow rocking is admissible If the AHRS will be moved with acceleration during these initial 90 seconds then gyros bias estimation may be corrupted and large errors may be occurred in orientation angles determination After these 90 seconds will over no limitations are to the AHRS motion AATTAFORME INERZIALI 11 AHRS M2 M SPECIFICATIONS Table 3 1 AHRS M2 M typical specifications Update rate 100 user settable Full accuracy data warm up time sec 90 O Measurement range full in 3D deg pien O Static accuracy at normal conditions pitch and roll lt 0 1 Static accuracy in operating temperature range pitch and roll lt 0 3 Dynamic accuracy e pitch and roll 0 4 i 0 03 heading Noise standard deviation at 100 Hz output Se RMS 0 02 _0 02ptch and ro_ andi roll Sensors bandwidth gt O OE Operating temperature range ren 70 109 x 31 x 29 case Di
4. of single mas byte array 0 49 of byte datflt single flt record bfO byte bfl byte bf2 byte bf3 byte end absolute datflt ii word Begin if not GetData mas_ byte 50 then Break for ii 0 to 11 do begin flt bf0 mas byte ii 4 0 flit bfl mas byte ii 4 1 flt bf2 mas_ byte ii 4 2 flit bf3 mas byte ii 4 3 Mas _sng ii datflt end End Next example shows how to get 17 numbers in smallint format 2 bytes signed integer This is need to get the AHRS output data in the endless loop at the AHRS command see sections 6 2 according to any from four output data formats described in section 6 3 Size of this data block is Cntbyte 36 bytes 17 2 34 2 bytes of the check sum var mas small array 0 16 of smallint mas_byte array 0 35 of byte ii datwrd word wrdW record LO byte HI byte end absolute datwrd Begin if not GetData mas_ byte 36 then Break for ii 0 to 16 do begin wrdW Lo mas byte 11 2 0 wrdW Hi mas byte 11 2 1 mas small ii datwrd end End In this example the array mas_small contains current orientation angles calculated in the AHRS Heading word mas_small 0 100 Pitch mas_small 1 100 Roll mas_small 2 100 Note it is important that Heading must be word 2 bytes unsigned E SENSOR SYSTEMS S R L se gt PIATTAFORME INERZIALI 7 AHRS DEMO PROGRAM provides a AHRS_Demo Dem
5. 2 The diagram of electric connection of the AHRS to host computer Fig 5 3 shows the diagram of the interface cable 1 for the AHRS connections to the COM port of host computer and to the DC power source Fig 5 4 shows pinouts of the interface cable 1 connectors SENSOR SYSTEMS S R L PEMS g ye x X2 X3 COM Female c onnector DB 9F i n the case DCD X1 Female connector Binder 719 09 9790 71 05 TX DTR SG DSR RTS CTR Oo ioo NIDIA Ww bd RI X2 Power En e Vop Fig 5 3 The diagram of the interface cable 1 for the AHRS connections to the COM port of host computer and to the AC DC adapter Xl x2 LJ 05 15 Vdd Ot 3 e GND Fig 5 4 The view of plug connectors of the interface cable 1 z SENSOR SYSTEMS S R L PIATTAFORME INERZIALI 5 2 Quick Electrical Connections for the AHRS Evaluation To test the AHRS provide the working place as it is shown in Fig 5 2 Connect cable 1 to the AHRS and to a PC COM port Connection of the cable 1 to the AHRS is done through the Binder 719 09 9789 71 05 Male connector on the AHRS case Connect cable 1 to the AC DC network adapter Apply power to the AHRS for this connect the network adapter to the mains Start up time for the device is not more than 2 seconds Red light of the indicator lamp near the connector see Fig 5 5 will signify readiness of the AHRS Fig 5 5
6. 4 1 The AHRS mounting surfaces A B and mounting holes 1 7 14 Figure 4 2 The AHRS outline drawing ccccsseeeeeeeeeeeeeeeeeeeeeeeeeeeeaeeeeeees 15 Figure 4 3 Examples of the AHRS mounting on the object ce 17 Figure 5 1 5 Pin connector male pinout cccccesesseeeceeeeesesseeseeeenseeees 18 Figure 5 2 The diagram of electric connection of the AHRS to host COMPUSI cerere a a ec mee MURR nr cer emnn een ie Serer rere reer Grey conte 19 Figure 5 3 The diagram of the interface cable 1 for the AHRS connections to the COM port of host computer and to the AC DC adapter 0008 20 Figure 5 4 The view of plug connectors of the interface cable 1 20 Figure 5 5 AHRS light indicator s 2cscseieteesecowectivaeedtecinrecectssdudatasterderneteecce 21 Figure 8 1 Location of the seals on the AHRG cccccceeeeeeeeeeeeeeeeeeesaeees 34 LIST OF TABLES Table 3 1 AHRS M2 typical specifications ccccccceeeceeeeeeeeeeeeeeeeeaaeeeees 11 Table 5 1 Pin diagram of the AHRS COnneCtol ccccceeeeeeeeeeeeeeeeeeeeeeeees 18 Table 5 2 Electrical Specification ccccccccsseesseeeeceeeceeeeeeeseeeeeeeeeseenanaeeeees 18 Table 6 1 COM port parameters ccccccccccesssesseeeeeeeceeeseeeseeeseeeeeessaeeeeees 22 Table 6 2 Structure of the parameter block for loading to the AHRS by LoadBlockPar COMMANG sivccsisceetsdssssccras svavsenssauntsasneless
7. AHRS light indicator red light the AHRS is powered no programs run green light one of the AHRS programs is running Start the demo program see AHRS Demo Program User s Manual When any program in the AHRS is running the light indicator changes its color from red to green __ SENSOR SYSTEMS S R L FSM gt PIATTAFORME INERZIALI 6 SOFTWARE INTERFACE The AHRS provides heading pitch and roll angles outputs as 2 bytes integers signed or unsigned words see below for details After power connection the primary initialization of the AHRS microcomputer takes place and the main program starts working The time of the device pretreatment is not more 1 seconds The program works in the waiting mode of the commands The commands are transmitted through the serial port according to the protocol RS232 Table 6 1 COM port parameters COM port parameters 115200 Data bits Stop bits 1 6 1 Operational Modes of the AHRS and Data Formats The AHRS can operate in the two modes 1 Idle mode All sensors and electronics are powered The AHRS microprocessor waits any command from the host computer to start operate in one of the next modes In idle mode the AHRS indicator lamp lights red see Fig 5 5 2 Operating mode At this the AHRS operates in the endless loop providing the continuous output of calculated orientation angles and some other signals
8. footing 50 bytes including 48 bytes of data and 2 bytes of check sum and goes in the operating mode In the operating mode set by any of these commands the program in the AHRS microprocessor operates in the endless loop providing the process of data reading from ADC and orientation angles calculating Data blocks are transmitted according to chosen variant of output data In all variants data block has 36 bytes 34 bytes of data and 2 bytes of check sum Data structure depends on chosen variant of output data see item 6 3 Output Data Format of the AHRS in the Operating Modes The update rate of data blocks is set by the user in range 1 100 Hz Default update rate is 100 Hz e At the command Stop command code OxFE the program stops operating mode working and goes into the idle mode At that the light indicator changes its color to red see Fig 5 5 Important Note Before using all other commands please send Stop command to the AHRS to switch device into the idle mode Be sure that the AHRS light indicator is red before sending of any other commands E SENSOR SYSTEMS S R L ESNS N y PIATTAFORME INERZIALI e The command LoadBlockPar command code 0x10 is used to load block of the AHRS parameters which available for changing by user into the AHRS nonvolatile memory Below is structure of this block of parameters Table 6 2 Structure of the parameter block for loading to the AHRS by LoadBlockPar command B
9. next compensation Therefore don t move the AHRS during initial alignment process If this requirement is not met then large errors may be occurred in orientation angles determination As the AHRS uses magnetic sensors for heading reference then it directly determines just magnetic heading The AHRS can also provide true North heading when the current magnetic declination is given Declination also called magnetic variation is the difference between true and magnetic North relative to a point on the Earth Declination angles vary throughout the world and change very slowly over time Declination angle can be entered directly in the AHRS memory using special command see Table 6 2 in item 6 2 For this the declination angle should be known or calculated using AHRS software see AHRS Demo Program User s Manual section 4 Options menu By additional information about latitude longitude altitude and date the AHRS Demo software calculates the declination using the World Magnetic Model produced by the U S National Geophysical Data Center and the British Geological Survey http www ngdc noaa gov geomag WMM DoDWMM shtml The World Magnetic Model is the standard model of the US Department of Defense the UK Ministry of Defense the North Atlantic Treaty Organization NATO and the World Hydrographic Office WHO navigation and attitude heading referencing systems SENSOR SYSTEMS S R L Systems AATTAFORME INERZIAL
10. 5 Full Output Data format AHRS1 command 0x80 Byte CY Ugyro Parameter Heading Pitch Gyrox GyroY GyroZ Uacc ee Utermo Check sum Umag 9x 2 byte 2 byte 2 byte 2 byte 2 byte 2 byte 2 byte 2 byte Length sword sword sword ARR word sword 2byte Raw senso Average angular rates Deet in Note Orientation angles deg 100 incremental angles divided by time x meters step deg s 100 The following data are recorded in the field Combined Data sequentially the AHRS input voltage stabilized voltage supplied to the AHRS sensors the low byte of the Unit Status Word USW see section 6 4 for details the high byte of the USW In the Utermo field ADC codes are recorded sequentially from 7 temperature sensors inside gyros accelerometers and magnetometers The low byte is transmitted by first Check sum is the arithmetical sum of bytes 0 33 The Full Output Data format is used by AHRS developers for full control of calculations in the AHRS microprocessor Table 6 6 Orientation Incremental Sensor Data format AHRS2 command code 0x81 number GyroX AccX MagX aoe Heading Pitch GyroY AccY MagY Reser ved USW Vdd Utermo pee GyroZ AccZ MagZ 3x 3x 3x 2 byte 2 byte 2 byte 2 byte y 2 byte 2 byte Length word sword sword 2 byte 2 byte 2 byte 4 byte word word sword 2 byte sword sword sword Average Average Average Note Orientation angles deg 100 p oe magnetic Temperat rates rations fields VDC 100 Jure C 10
11. AHRS in heading and to correct for gyro drift in the heading angle determination o 2 253022a00D gt go a aE Initial 9 p _ _ Orientati Heading Pith orientation estimati i equations on nol on of gt correctigp signals gt Kalman filter gt based algorthar Fig 2 2 Operational Diagram of the AHRS The AHRS has the sensor fusion algorithm where measurements of gravity accelerometers and magnetic North magnetometers compensate for otherwise unlimited increasing errors from the integration of rate of turn data Thus advantage of the AHRS over other non gyroscopic compasses is using of gyros that allows to determine orientation angles with high accuracy not only in static conditions but in dynamic environment Moreover the AHRS supplies a high output speed of attitude data up to 100 Hz The base of the AHRS algorithm is adaptive Kalman filter which is used for estimation of the bias drift of gyros and calculation of stabilized heading pitch BE SENSOR SYSTEMS S R L RIME g ATTAFORME INERZIALI and roll angles The Kalman filter automatically adjusts for changing dynamic conditions without any external user input After start the AHRS it requires about 60 seconds for initial alignment process At this initial orientation angles are determined as initial conditions for integration of gyros outputs Also gyros drift is estimated using Kalman filter for
12. I 3 AHRS SPECIFICATIONS Table 3 1 AHRS M2 typical specifications Parameter Unit AHRS M2 Update Rate 1 100 user settable Full accuracy data warm up time sec eg Beata Measurement range full in 3D 0 360 heading 90 ee 180 roll Maximum angular rate 30 OS Static accuracy at normal conditions e heading e pitch and lt By a 0 roll Static accuracy in operating temperature range e heading e pitch and lt 0 5 roll lt oa 3 Dynamic accuracy Ey heading pitch and roll Ey por js Noise standard deviation at 100 Hz deg Sensors bandwidth Operating temperature range 40 to 70 Dimencins ae 109 x 31 x 29 case 127 x 31 x 29 0 19 0 16 Power supply 5 5 to 6 5 Supply current including time of initial alignment it may be decreased on request in homogeneous magnetic environment for latitude up to 65 deg root mean square error 1 sigma may depend on type of motion 3 dB level depends on material of the AHRS case AHRS may be powered by AC voltage 100 to 240 V 50 60 Hz from an AC DC adapter which comes with the device SENSOR SYSTEMS S R L SYSTEMS g ATTAFORME INERZIALI 4 INSTALLATION This section describes how to mount the AHRS into your system and make electrical connections To install the AHRS into your system follow these steps choose a mounting location e mechanically mount the AHRS make electrical conn
13. according to chosen output data format see below Data rate is set by user from 1 Hz to 100 Hz The next output data formats are available in the operating mode e Full Output Data e Orientation Incremental Sensor Data SENSOR SYSTEMS S R L Syste AATTAFORME INERZIALI e Quaternion of Orientation e Orientation Sensor Outputs Usually Full Output Data format is used by the AHRS developers for full control of calculations in the AHRS microprocessor Also this format can be used by user at any troubles to get full data from the AHRS for next sending them to developers Orientation Incremental Sensor Data format provides the AHRS output in the form of 3 orientation angles heading pitch and roll and integrated angular rate linear acceleration specific force magnetic field increments In the AHRS output these increments are divided by time step of data output so they may be interpreted as average angular rates linear acceleration and magnetic field for cycle of data output On the other hand incremental sensor data are more fit for the AHRS using as IMU inertial measurement unit Quaternion of Orientation format gives quaternion presentation of an object orientation in addition to 3 orientation angles Orientation Sensor Outputs format adds to orientation angles the calibrated outputs of 9 sensors gyros accelerometers magnetometers that give information about current angular r
14. anges are in warning capture in the main window Fig 5 1 or Fig 5 3 after the AHRS start At short first stage 1 second of the initial alignment the message Initial alignment Please wait is displayed and during large second stage 90 seconds this message changes to Don t move AHRS while its parameters being adjusted Only slow rocking of the AHRS is admissible during the second stage of the initial alignment SENSOR SYSTEMS S R L Syste
15. ates linear acceleration of the AHRS and components of outer magnetic field This is default data format This format represents instant values of 9 sensors output In contrast to Orientation Incremental Sensor Data which provides average output data from 9 sensors 6 2 Executive Instructions for the AHRS After power connection the working program is in the idle mode Red light of the indicator lamp near the connector see Fig 5 5 signifies readiness of the AHRS to receive commands from the host computer When the AHRS switches to operation mode the light indicator changes its color from red to green There are next commands are used for control the AHRS e AHRS1 AHRS2 AHRS3 AHRS4 e Stop e LoadBlockPar O SENSOR SYSTEMS S R L RME g ATTAFORME INERZIALI e ReadBlockPar e GetVerFirmware e The commands AHRS1 AHRS2 AHRS3 AHRS4 command codes 0x80 0x81 0x82 0x83 are used to start the AHRS in the operating mode with one of four variants of output data AHRS1 command code 0x80 Full Output Data format AHRS2 command code 0x81 Orientation Incremental Sensor Data format AHRS3 command code 0x82 Quaternion Of Orientation format AHRS4 command code 0x83 Orientation Sensor Outputs format After receiving of any from these commands the AHRS starts process of initial alignment see item 2 2 Principles of the AHRS Operation After that the AHRS gives out the block of the report
16. deg s 100 g 10000 nT 4 Average angular rates linear accelerations and magnetic fields are in AHRS axes X is lateral axis Y is longitudinal axis Z is vertical axis Average data are integrated sensor output increments divided by time step of data output USW is unit status word see section 6 4 for details Vdd is input voltage of the AHRS SENSOR SYSTEMS S R L AATTAFORME INERZIALI Utermo is averaged temperature in 3 accelerometers The low byte is transmitted by first Check sum is the arithmetical sum of bytes 0 33 Table 6 7 Quaternion of Orientation format AHRS3 command code 0x82 Byte Param Heading Pitch Reser USW Utermo peat eter ved 2 aed byte 2 byte 2 byte 2 byte 2 byte 2 byte 2 byte 2 byte Length sword sword sword 14 byte word word sword 2 byte M f Supply Tempera Note Orientation angles deg 100 Quaternion of orientation 10000 voltage VDC 100 USW is unit status word see section 6 4 for details Vdd is input voltage of the AHRS Utermo is averaged temperature in 3 accelerometers The low byte is transmitted by first Check sum is the arithmetical sum of bytes 0 33 Table 6 8 Orientation Sensor Outputs format AHRS4 command code 0x83 Byte r are GyroX AccX MagX usw Check ater Heading Pitch GyroY AccY MagY Reser ved Vdd Utermo sim Gyo Ace vagz Length 2 gt t 2 byte sword 2 gt te 2 x te 2 te 2 e 4byte wou 2byte 2bvte a
17. e AHRS to the end user During this period warrants the AHRS performance in accordance with the AHRS certificate The warranty makes no provision for periodic maintenance installation and configuration of the device at consumer s site Operating environment of the AHRS shall meet the requirements specified in item 3 1 Consumer has the right to assert claims to in accordance with the warranty regulations All consumer claims shall be asserted in written form with the situation in which problems arose described reserves the right to dismiss a warranty claim of a consumer in the following cases 6 1 If the seals on the AHRS case are broken external view of the seals and their placement location on the AHRS is shown in Fig 8 1 Seals i Seal Fig 8 1 Location of the seals on the AHRS 6 2 If the AHRS has damages resulting from an attempt to unseal the device 6 3 If the AHRS has external damages on basic parts and eternal connector of various origins mechanical chemical If the warranty terms specified in items 3 6 are violated warranty liabilities of specified in item 1 to the consumer are cancelled PIATTAFORME INERZIALI 9 DESCRIPTION OF AHRS M2 M Here are description of additional features of the marine modification of the AHRS and also some differences in operations of such AHRS in comparison with usual AHRS The AHRS Attitude and Heading Reference System is designed for measuring Euler orientat
18. ections to the AHRS evaluate the AHRS using the included AHRS_Demo Program 4 1 Where to install the AHRS for tests The AHRS has magnetometers with wide dynamic range and its sophisticated calibration algorithms allow it to operate in many environments For optimal performance however you should mount the AHRS with the following considerations in mind e Locate the AHRS away from local sources of magnetic fields The place for testing must not have ferromagnetic magneto susceptible materials and the lab room itself must have the level of intrinsic magnetic and electro magnetic fields suitable for the magnetic heading system testing inside and near the lab room there must be no powerful source of magnetic electrical and electro magnetic fields The magnetic field intensity must not be different from the Earth magnetic field intensity at the test site more than 0 01 small ferromagnetic objects must be as far as 3 meters from the test table Large size ferromagnetic objects such as cars and trucks must be as far as 15 m from the table it is necessary to conduct a regular check up of the magnetic field uniformity inside the lab room It is highly recommended to degauss AHRS before heading test to remove permanent magnetization of some components in the AHRS if you accidentally expose the unit to a large magnetic field You can use a hand held demagnetizer tape eraser to demagnetize the AHRS Most audio and video degau
19. es are 0 90 180 degrees To check correctness of the alignment angles please run the AHRS using the AHRS Demo Program PIATTAFORME INERZIALI 5 ELECTRICAL CONNECTIONS 5 1 Cable and Connectors The AHRS has 5 Pin connector Binder 719 09 9789 71 05 Male for electrical connection to host system Fig 5 1 shows the AHRS connector pinout Fig 5 1 5 Pin Connector Male Pinout view from the AHRS connector Table 5 1 Pin diagram of the AHRS connector Pin Signal Table 5 2 Electrical specifications Parameter __ Conditions Min _ Typical Max Units Input Supply D T Volts DC O mM C Curent V 6v no Power Voo 6V 66o mw For the AHRS power supply the outer AC DC adapter also can be used which receives the power from the 100 240V 50 60Hz AC power source AC DC power adapter is included in the delivery set j SENSOR SYSTEMS S R L Systems A PIATTAFORME INERZIALI The set of components for the AHRS electrical connection includes AHRS interface cable 1 for the AHRS connection to the COM port of IBM PC or another device with branch wires for the AHRS DC powering AC DC adapter Fig 5 2 shows diagram of electric connection of the AHRS to host computer IBM PC The AHRS exchanges the information with host computer through the COM port msan FS Power Block 100 240V co 50 60Hz cH 100 240V 6V AC DC Adapter Host Computer Fig 5
20. f a body which it is mounted to at a rate of up to 100 samples second Data transmissions are made over a bi directional serial port using either RS 232 or USB via COM to USB converter Sampling rate is selected by user from 1 Hz to 100 Hz default setting Fig 1 1 The AHRS SENSOR SYSTEMS S R L VSEM PIATTAFORME INERZIALI 1 2 Package Contents In addition to your AHRS product you should have e 1 Data Cables Set It consists of see Fig 1 2 cable 1 provides electrical connection between the AHRS and an external receiving device through a COM port and power supply COM to USB converter FTDI FT232BM provides connection with an external receiving device via a USB port e 1 Protective Tube optional This tube See Fig 1 3 can be screwed on the AHRS connector to protect it from the external mechanical damage e 1 interchangeable AC DC Adapter The two AC plugs are possible USA and EUR The adapter is used for the AHRS powering from 110 240V 50 60Hz AC power source see Fig 1 4 e 1 miniCD with AHRS Software This software allows you immediately to view the outputs of the AHRS on a PC running Microsoft Windows and save measured data on a PC hard disk e 1 User s Manual It contains useful information about mounting and connecting of the AHRS and usage of enclosed demo software for viewing and saving of the AHRS output data e 1 Demo Program AHRS DEMO User s Manual It contains useful infor
21. h If the projection of Y axis on a horizontal plane is oriented East then heading angle is equal to 90 Thus heading is positive for clockwise rotation around the vertical axis Measured angles are the standard Euler angles to rotate from the earth level frame East North Up to the body frame heading first then pitch and then roll Orientation angles measured by the AHRS are not limited and are within common ranges e Heading 0 360 e Pitch 90 e Roll 180 2 2 Principles of the AHRS Operation The AHRS is designed for measuring Euler orientation angles heading pitch and roll of an object in static and dynamic environment The AHRS is a measurement system that consists of three gyroscopes three accelerometers and three magnetometers All sensor axes are aligned with the AHRS axes Using 3 axis gyro accelerometer and magnetometer units allows making a complete measurement of an object orientation angles The operational diagram of the AHRS is shown in Fig 2 2 The AHRS uses gyros to measure absolute angular rate of the carrier then its orientation angles heading pitch and roll are obtained by using special integration of gyros outputs SENSOR SYSTEMS S R L Syste AATTAFORME INERZIALI Accelerometers are used to determine initial attitude of the AHRS and to correct for gyros drift in the tilt angles pitch roll determination Magnetometers are used to determine initial alignment of the
22. ion angles heading pitch and roll in static and dynamic environment It consists of three gyros three accelerometers three magnetometers and embedded microcomputer Original algorithm is used for above sensors signal processing to achieve high accuracy of attitude and heading determination Fig 1 1 The AHRS AHRS M2 M especially designed for marine applications It has waterproof case Its software allows start and initial alignment of the AHRS at vehicle rocking AHRS M2 M can be used also in other traditional applications Fig 1 2 shows the AHRS own coordinate system Ox y Z This coordinate system is a body fixed and defined as the calibrated sensors coordinate system Non orthogonality between the axes of the body fixed coordinate system Ox YoZo is less then 0 01 PIATTAFORME INERZIALI Zo UP Heading y Yo Forward Roll 7 Pitch Xo Lateral Fig 1 2 AHRS with body fixed coordinate system Measured angles are the standard Euler angles to rotate from the earth level frame East North Up to the body frame heading first then pitch and then roll The heading angle of the AHRS is referenced to the magnetic North 10 PECULIARITY OF THE MARINE AHRS OPERATION After start the AHRS it requires some time for initial alignment process At this initial orientation angles are determined as initial conditions for integration of gyros outputs Also gyros biases are estimated for their compensation in run
23. lure detected 0 No failure 1 Failure detected 0 No failure 1 Failure detected 0 No failure 1 Failure detected 0 No failure 1 Failure detected T Re na ee ee Incorrect Power Supply Detect 14 Environmental Temperature Angular Rate Exceeding Detect 0 Supply voltage is not less than minimum level 1 Low supply voltage detected 0 Supply voltage is not higher than maximum level 1 High supply voltage detected 0 X angular rate within the normal range 1 X angular rate is outrange 0 Y angular rate within the normal range 1 Y angular rate is outrange 0 Z angular rate within the normal range 1 Z angular rate is outrange 0 Total magnetic field within the normal range 1 Total magnetic field limit is exceeded 0 Temperature within the operating range 1 Temperature is out of the operating range 15 Reserved O j SENSOR SYSTEMS S R L Systems A PIATTAFORME INERZIALI 6 5 Examples of Data Reading from the AHRS The following Pascal program is a sample program that can help user to get data easily from the AHRS Below is function GetData for the block data reading This function uses next variables and function which should be described in outer program e Cntbyte size of block to read e masOut array of accepted data from the AHRS e ReadByte the function of accepting of 1 byte from COM port F
24. mation about installing and usage of enclosed demo software for visualization of the AHRS orientation angles and saving of the AHRS output data Cable 1 COM to USB converter Fig 1 2 Data Cables Set Fig 1 3 Protective tube Fig 1 4 AC DC adapter with interchangeable plug 2 AHRS OPERATION PRINCIPLES 2 1 Description of the AHRS orientation angles Fig 2 1 shows the AHRS own coordinate system Ox y Z This coordinate system is a body fixed and defined as the calibrated sensors coordinate system Non orthogonality between the axes of the body fixed coordinate system Ox YoZo is less then 0 01 Zo Up Heading y Yo Forward Roll 7 Pitch 8 Xo Lateral Fig 2 1 AHRS with body fixed coordinate system The roll angle of the AHRS is zero when the X axis is oriented horizontally and Z axis is in upper half sphere If X axis is horizontal and Z axis is in lower half sphere then roll angle is equal to 180 If Z axis is oriented horizontally gt PIATTAFORME INERZIALI and X axis is in lower half sphere then roll angle is equal to 90 The pitch angle of the AHRS is defined as 0 when the Z axis is pointed up or down If Y axis is pointed up then pitch angle is equal to 90 If Y axis is pointed down then pitch angle is equal to 90 The heading angle of the AHRS is referenced to magnetic North and is zero when the projection of the AHRS Y axis on a horizontal plane is oriented Nort
25. mensions 127 x 31 x 29 with mounting lugs and 0 19 0 16 Power supply 5 5 to 6 5 Supply current including time of initial alignment it may be decreased on request jin homogeneous magnetic environment for latitude up to 65 deg root mean square error 1 sigma may depend on type of motion 3 dB level depends on material of the AHRS case AHRS may be powered by AC voltage 100 to 240 V 50 60 Hz from an AC DC adapter which comes with the device gt PIATTAFORME INERZIALI 12 AHRS DEMO PROGRAM provides a AHRS Demo Program for users who want to test the AHRS and to apply this product to a system simply This program can visualize the AHRS orientation angles and save data as well See User s Manual on the AHRS Demo Program for description of the AHRS software operation This document describes only specific of the Demo Program using for the marine modification of the AHRS M2 M Fist you can not change Initial alignment time in the window Device option from the Options menu see Fig 4 2 in the Users Manual on the AHRS Demo Program For the marine modification of the AHRS M2 M the initial alignment consists of two stages For first stage initial alignment time is set to 1 sec this value appears in window on Fig 4 2 and can t be changed Second stage of the initial alignment takes 90 sec According to two stages of the AHRS M2 M initial alignment some ch
26. ndegrees in meters sd 16 19 Altitude _ float_ 4 in meters 20 23 Date Year Month float_ 4 24 27 Alignment angle A1 float 4 _ Angles of the AHRS 28 31 Alignment angle A2 float__ 4 mounting on the object 32 35 Alignment angle A3 float_ 4 _ degrees see section 4 4 36 43 DeviceID char 8 only read 44 49 Reserved J de J S 50 51 Checksum ss word 2 gt S O As in previous LoadBlockPar command the check sum is the arithmetical sum of bytes 0 49 The low byte is transmitted by first e The command GetVerFirmware command code 0x1F is used to read firmware version of AHRS 52 bytes from AHRS nonvolatile memory Table 6 4 Structure of the parameter block read by GetVerFirmware command Byte Parameter Format Length Note 0 49 Firmware version _ char__ 50 o O 50 51 Checksum ___ word_ 2 As in previous ReadBlockPar command the check sum is the arithmetical sum of bytes 0 49 The low byte is transmitted by first 6 3 Output Data Format of the AHRS in the operating modes As it was mentioned above user can select one from 4 variants of output data full output data orientation incremental sensor data quaternion of orientation orientation sensor outputs The last variant is default E SENSOR SYSTEMS S R L SYSTEMS Format of these data is listed below where is denoted word unsigned 2 byte integer sword signed 2 byte integer Table 6
27. nyi 9 word sword yle ye ye y word word sword y sword sword sword Angular Accele Magnetic Supply Note Orientation angles deg 100 rates rations fields voltage Temperat deg s 100 g 10000 nt 4 VDC 100 ure C 10 Angular rates linear accelerations and magnetic fields are in AHRS axes X is lateral axis Y is longitudinal axis Z is vertical axis USW is unit status word see section 6 4 for details Vdd is input voltage of the AHRS Utermo is averaged temperature in 3 accelerometers The low byte is transmitted by first Check sum is the arithmetical sum of bytes 0 33 6 4 The Unit Status Word definition The Unit Status Word USW provides the AHRS state information The low byte 0 7 of USW indicates failure of the AHRS If this byte is 0 the AHRS operates correctly if it is not 0 see the table 6 9 for type of failure or contact the developers directly The high byte 8 15 contains a warning or is informative for the user Status of each bit of the USW warning byte is specified in the table 6 9 SENSOR SYSTEMS S R L RME g Low failure byte High warning byte Bit Parameter Performance Initial Alignment AHRS Parameters Gyroscope Unit Accelerometer Unit EA Software 7 0 Successful initial alignment 1 Unsuccessful initial alignment due to AHRS moving ing of outer magnetic field 0 Parameters are correct 1 Parameters are incorrect 0 No failure 1 Fai
28. o Program for users who want to test the AHRS and to apply this product to a system simply This program can visualize the AHRS orientation angles and save data as well To run the program set the OS Windows XP on your PC To install the program AHRS_Demo copy the program folder just files AHRS_Demo exe AHRS_Demo ini AHRS_Demo bmp AHRS_Demo dat AHRS_Demo glm and AHRS_Demo lng on the HDD in any handy place for the user The recommended requirements for the PC configuration to ensure the effective operation of the Demo Program AHRS_Demo In order to ensure the effective operation of the program AHRS_Demo you should fill the base unit with the following equipment Table 7 1 The recommended requirements for the PC configuration e Processor Pentium 4 2 2GHz e RAM 256 Mb e Video GeForce Ti 4400 the analog of this card or the card of better model e HDD gt 500 Mb the length needed for data recording Notation To display the all graphic information correctly you need to have the monitor with resolution power more than 1024x768 pixels the color reproduction of 32 bits and font scale factor of 32 pix inch setting in the Windows See User s Manual on the AHRS Demo Program for description of the AHRS software operation SENSOR SYSTEMS S R L PENSE N PIATTAFORME INERZIALI 8 WARRANTY Warranty coverage 1 AHRS is warranted for 12 twelve months from the date of delivery of th
29. rrounding the AHRS is changed If this field is changed due to displacement of ferromagnetic masses of the object or magnetic field sources the AHRS should be re calibrated Field calibration procedure is described in User s Manual on the HRS Demo Program Field calibration procedure is developed by after type of the object on which the AHRS will be used is agreed on with a customer e It is preferable to locate the AHRS as close to the centre of mass of the object as possible E SENSOR SYSTEMS S R L SYSTEMS PIATTAFORME INERZIALI With such location effects of linear accelerations during oscillations on the AHRS accelerometers are reduced and therefore orientation angle determination errors are also reduced 4 3 Mechanically mounting the AHRS The AHRS housing has two base surfaces A and B see fig 4 1 fig 4 2 designed for AHRS mounting during its run and testing A Fig 4 1 The AHRS mounting surfaces A B and mounting holes 1 7 Salient bottom base surface A has threaded holes designed for mounting of the AHRS Lateral base surface B is designed for the AHRS alignment during mounting The AHRS is factory calibrated with respect to the base surfaces A and B thus it must be aligned within the host system with respect to these mounting surface not the device edges A PIATTAFORME INERZIALI 272 Base mounting surface Connector 108 7 Base surface naicator
30. satatieeincssisaccaconmusnce 25 Table 6 3 Structure of the parameter block read by ReadBlockPar CONTAIN stented E emncedddeaiaieinincantaed nines ae cde AE E E 26 Table 6 4 Structure of the parameter block read by GetVerFirmware command periran ear EE Eee E a E AE AET AEAEE AEE 26 Table 6 5 Full Output Data format at AHRS1 command cceeeeeeees 27 Table 6 6 Orientation Incremental Sensor Data format at AHRS2 command reren E E 27 Table 6 7 Quaternion of Orientation format at AHRS3 command 28 Table 6 8 Orientation Sensor Outputs format at AHRS4 command orrien e aii EEE Ea ete 28 Table 6 9 The Unit Status Word description ss00nnsnsnaneennnennsnrnnssnrrennnne 29 Table 7 1 The recommended requirements for the PC configuration 33 E SENSOR SYSTEMS S R L SPENNE PIATTAFORME INERZIALI 1 INTRODUCTION 1 1 Description of the System The AHRS Attitude and Heading Reference System is designed for measuring Euler orientation angles heading pitch and roll in static and dynamic environment It consists of three gyros three accelerometers three magnetometers with internal power regulations and embedded microcomputer Original algorithm is used for above sensors signal processing to achieve high accuracy of attitude and heading determination The AHRS is a high speed digital output orientation measuring system It can transmit the orientation angles heading pitch and roll o
31. ssing units can be used Follow the instructions for your demagnetizer E SENSOR SYSTEMS S R L ESNS N y PIATTAFORME INERZIALI e The AHRS should be mounted in a physically stable location Choose a location that is isolated from excessive shock oscillation and vibration Special rotary table must be used for the AHRS accuracy testing that mounted on a special testing basement which is free from the laboratory oscillations and vibrations Tests on vibrations and shocks are fulfilled separately from the main accuracy tests 4 2 Where to install the AHRS on the object It is necessary to follow the recommendations listed in it 4 1 whenever it is possible when installing the AHRS on an object e AHRS should be installed on an object as far as possible from large ferromagnetic masses of the object and powerful sources of magnetic electrical and electro magnetic fields If the residual effects of ferromagnetic masses of the object distort the Earth magnetic field to no more than 20 AHRS software allows compensation of influence of the carrier object soft and hard iron on the heading angle determination accuracy For this purpose field calibration of the AHRS magnetometers is provided This calibration does not require any additional equipment but it requires turns of the carrier object on which the AHRS is mounted Note that the above field calibration remains active until the residual magnetic field of the object su
32. unction GetData var masOut Cntbyte boolean Function for reading the block data with size Cntbyte var Bufdata array 0 SFFF of byte nn ll datwrd sum word wrdW record LO byte HI byte end absolute datwrd label gwl Begin GetData False 11 index in the array for accepted byte 11 0 Read block with size Cntbyte gwl for nn l1l to Cntbyte 1 do if not ReadByte Bufdata nn then Break Search sum of the first Cntbyte 2 bytes sum 0 for nn 0 to Cntbyte 3 do sum sum Bufdata nn Last two bytes are check sum The low byte is first wrdW Lo Bufdata Cntbyte 2 wrdW Hi Bufdata Cntbyte 1 if sum of accepted bytes is not equal to the check sum if datwrd lt gt sum then begin Shift array to 1 byte left for nn 0 to Cntbyte 2 do Bufdata nn Bufdata nn l Read 1 byte to the end of the array 1l1l Cntbyte 1 goto gwl end for nn 0 to Cntbyte 1 do masOut nn Bufdata nn Data block is accepted GetData True End Below is example for using of GetData function to read 12 numbers of 4 bytes float This is need for reading the block of 50 bytes including 48 bytes of data d SENSOR SYSTEMS S R L se PIATTAFORME INERZIALI and 2 bytes of check sum after initial alignment of the AHRS see description of the AHRS commands in above section 6 2 Size of this block is Cntbyte 50 bytes 12 4 48 2 bytes of the check sum var Mas sng array 0 11
33. up to upside down upright etc relative to the object axes Such mounting doesn t change right determination of the object orientation if angles of the AHRS mounting are correctly stored in the AHRS nonvolatile memory To store angles of mounting in the AHRS please use the AHRS Demo Program item Device option from the Options menu or send LoadBlockPar command to the AHRS directly see structure of the LoadBlockPar command in the Table 6 2 below Angles of the AHRS position alignment angles are set in next order like heading pitch and roll setting first alignment angle sets position of the AHRS longitudinal axis Y relative to longitudinal axes of the object measured in the horizontal plane of the object Clockwise rotation is positive second alignment angle is equal to angle of inclination of the AHRS longitudinal axis Y relative to the horizontal plane of the object Positive direction is up SENSOR SYSTEMS S R L SNM third alignment angle is equal to inclination angle of the AHRS lateral axis X measured around AHRS s longitudinal axis Positive rotation is X axis moving down All angles are set in degrees Some examples of the AHRS mounting relative the object are shown on Fig 4 3 Fig 4 3 Examples of the AHRS mounting on the object a alignment angles are 0 0 0 degrees b alignment angles are 0 0 180 degrees c alignment angles are 90 0 0 degrees d alignment angl
34. yte Parameter __ 0 1 Updaterate p paner time Format ey Tie e declination 8 41 Latitude float 12 15 Longitude float 16 19 Altitude float _ 20 23 Date Year Month float _ O 24 27 Alignment angle A1 float _ Angles of the AHRS 28 31 Alignment angle A2 float _ mounting on the object 32 35 Alignment angle A3 float degrees see section 4 4 36 49 Reserved 50 51 Checksum word The AHRS calculates the check sum of accepted parameters and return it for a checking The format of the check sum transmitting 2 bytes low byte high byte The low byte is transmitted by first The check sum is the arithmetical sum of bytes 0 49 check sum byte0 byte1 byte49 Note Before using LoadBlockPar command it is highly recommended to use ReadBlockPar command see below to read parameters from the AHRS at first After that user can change some parameters listed in the Table 6 2 and to send back all block of parameters to the AHRS E SENSOR SYSTEMS S R L RME g PIATTAFORME INERZIALI e The command ReadBlockPar command code 0x11 is used to read block of AHRS parameters 52 bytes from AHRS nonvolatile memory PIATTAFORME INERZIALI Table 6 3 Structure of the parameter block read by ReadBlockPar command heal inns ll ol a Update rate 2 finHz S alls lc time Ti ee pe declination 8 11 Latitude float 4 _ indegrees 12 15 Longitude float 4 _ i
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