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mount control system - control system design description

1. Figure 3 34 Location Of Monitoring Subsystem Nodes 3 7 3 1 Node Box Specification Each node box will have the following specification 3 7 3 1 1 Node Inputs PAGE 60 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Each node shall have 16 multiplexed differential analogue inputs capable of accepting a voltage signal in the range 10Vp p Each node shall have 16 opto isolated binary inputs Each node shall have two opto isolated 8 bit binary word inputs e The node shall receive and act on commands sent from the MCS via CANbus Note that it is the responsibility of the sensor to produce an output in a compatible format 3 7 3 1 2 Node Outputs The node shall make data available over the CANbus representing the values of the individual inputs as required by the Monitoring subsystem The node shall not act as a power supply for external sensors or equipment 3 7 3 1 3 Node Power Supply Power for the Monitoring and Metrology node will be derived from an internal linear DC power supply capable of supplying 12V It is estimated that each node should consume less than 5W in normal operation hence a supply rated at least 12 5W should be used to account for the required de rating The node connects to an external 120VAC single phase supply In addition an external 12V DC power supply may be u
2. 0 00 1 7 00 14 3 1 MAIN SERVOS 8 7 5 5 14 Ded T dIntroduction 3 ue m d ERR 14 9UE 2 C PUFDOSO S Rh ete tele ete ilu de pe pere 14 SU ROM FUNCTION mE 14 Implementation 5 5 8 house pho BHO HOA UO ROMERO EE 14 3 1 3 2 Sery Specificato nan nup ege nee fot nC OB PRIN UIS 15 3 1 3 3 Interfacing 3 1 3 4 Further Servo Development 3 2 ENCODER SUBSYSTEM entree ERU PERI TE I ee 25 38 2 L Inntroducti nzs si eet eto trate vata iex Sve Se 25 222525 PULP OSE 5s SUR ISI EORR NERIS EE oa ento NER IU IRR rS 25 3 213 FU CHOR m tse teme aD ee BR SUA toe 27 3 23 T Implementation epe eie d eR D IO DU panda hae SIME DIS 27 3 2 32 Interfacing 3 2 3 3 Operation aO 3 3 INTERLOCK INTERFACE SUBSYSTEM eese enne 43 3 3 T SOInIEOUCUOR stet 43 ANIMI EO oh Sea ein aR shah GA sede a EN ood ae 43 3 9 9 FWRCHOTLS wanes Bes as bas Bee as 44 3 3 3 1 Electrical Interface 5 cr
3. Echo Mode These bits mirror the virtual encoder mode back to EPICS This ensures that EPICS receives confirmation of the current mode from the virtual encoder Echo Algorithm These bits mirror the virtual encoder algorithm back to EPICS This ensures that EPICS receives confirmation of the current algorithm being used to calculate position Fiducial Passed The Fiducial Passed bit indicates to EPICS that a fiducial has been passed It is set by the virtual encoder and can be read and cleared by EPICS VE OUT WORD This is the 48 bit output of the virtual encoder and is present in PMAC memory at D 1302 One bit of this word represents 5 milli arcseconds on axis VIRTUAL ENCODER OPERATION FLOWCHART The operation of the virtual encoder is summarised in the flowchart in Figure 3 18 This code is executed by PMAC exactly once per servo cycle and is not interruptable by other code PLC programs etc running on the card Figure 3 18 Main virtual encoder flowchart ISSUE 3 14 January 1997 PAGE 39 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION VIRTUAL ENCODER ALGORITHMS The flowcharts shown in Figure 3 19 Figure 3 20 and Figure 3 21 are for algorithms that take the various encoder values and calculate the absolute position to be placed i
4. Velocity Command Algorithm Combining E Circuit Power Encoder Amplifiers ies Devices Tape 8 4 Heads amp FDE Averaged Tac Signal 8 4 Tacho Averaging Circuit Individual Tacho Signals 8 4 Encoder Subsystem Figure 3 2 Main Axis Servo Loops The required set up for the PMAC card is described in reference 11 The definition of the connections and cable types for the main drive systems i e power amplifiers and motors etc is not a formal part of the scope of the MCS work package However in the absence of any other formal definition the MCS Drive system interface from the point of view of the MCS is described below Note that these settings and connections have been based upon experiments on the friction drive test rig HARDWARE CONFIGURATION Figure 3 3 and Figure 3 4 show the overall wiring scheme for the elevation and azimuth axes respectively Note that all tacho signals and the tacho average signal are monitored by the MCS to avoid confusion this is not shown in the diagrams TAV is the Tacho AVeraging circuit This is an op amp circuit that takes the individual tacho signals and produces an averaged tacho signal fanned out eight times four for elevation VCC is the Velocity Command Combining circuit This is an op amp circuit sums the MCS velocity demand and the GIS velocity
5. 2 2 2 4 00 00000000000000000000000000000000000000 30 RE 3 12 RELATIVE POSITION OF USER WRITTEN DSP CODE seen 31 RE 3 13 AZIMUTH USER WRITTEN DSP 32 RE 3 14 ELEVATION USER WRITTEN DSP 2 2 1 111100000000000000000 32 RE 3 15 FLOWCHART FOR INTERPOLATION AND COMPENSATION ALGORITHMS eee 34 RE 3 16 FLOWCHART FOR ARCTANGENT FUNCTION cc cccccccecsessssecececeesesseaeceeececsensaaseeeceeeeenseaees 35 3 17 AZIMUTH HEAD 1 2 41 212 200000000 00010000000000000000000 00 38 RE 3 18 MAIN VIRTUAL ENCODER FLOWCHART c cccccccecssssssesecececeesesaececececeeseaaeceeececeeseaeeeseceeeenes 39 RE 3 19 COMBINING ALGORITHMS COMMON TO BOTH 5 2 2 200 0 0 001 1 41 RE 3 20 AZ FULL AVERAGE FOUR HEADS AZIMUTH AXIS 42 RE 3 21 ELEVATION COMBINING 8 2124400 0 0110010000000000000000000000000 43 RE 3 22 GIS INTERCONNECTION OF A SINGLE AXIS esses 45 RE 3 23 POSITION OF LIMIT SWITCHES ccccceesessececececeesssaececececsessauececececseseneceeececeesenssaeeeeseeenes 46 RE 3 24 POSITION OF MCS PRE LIMIT SWITCH SO cccs cccccccecsesscecceececsesssaeeecececsenseaeeeeeceeeensaaees 47 3 25 SCALE DRAWING SHOWING THE POSITION OF THE VARI
6. 11 Heads OVE 508 1 CMP B A JSEQ Run the TAPE N code OVE 610 1 CMP B A JSEO TAPE MN Run the TAPE M amp N code OVE 518 1 CMP B A JSEQ ALL HEADS Run the ALL HEADS code If no match default to the FDE algorithm JMP FDE ONLY Check if axis has passed a fiducial FIDU CHECK OVE X HMFL1 A1 Mask all but bit 20 of HMFL1 OVE HMFL1_MASK RO and store the value of the bit OVE AND X0 A OVE Al1 X FIDU FLAG OVE X LAST HMFL1 B1 Ditto for the previous HMFL1 value OVE HMFL1_MASK RO OVE RO AND X0 B CMP B A JEQ FIDU_NOT_PASSED If the bits are equal a fiducial has not been passed FIDU PASSED MOVE L VE OUT A10 Store VE OUT in LAST FIDU POS MOVE A10 L LAST FIDU POS MOVE Y FIDU JOPT A1 MOVE JOPT_MASK RO ISSUE 3 14 January 1997 PAGE 77 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION MOVE 0 0 AND X0 A Mask off all but bits 0 7 of FIDU JOPT MOVE A1 X LAST FIDU ID Store ID of this fiducial BSET 20 X SETUP Set the FIDUCIAL PASSED bit in STATUS FIDU NOT PASSED MOVE X HMFL1 A1 MOVE A1 X LAST HMFL1 r Clean up and exit Last one out please turn off the lights EXIT MOVE X SAVE RO RO Restore the RO register JMP 23 PMAC takes over from here Special Mode routines follow so far Diagnostic is the only one Diagnostic mode routines DIAG MODE Set Echo mode bits for EPI
7. Listed below is a partial code implementation of the Motorola 56000 DSP code to perform the interpolation and compensation required for the Heidenhain tape encoding system Note that currently the code only services one head When compiled this code occupies 144 locations of P memory 432 bytes KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK JOHN WILKES HEIDCOMP ASM 25 OCTOBER 1996 2 E HEIDENHAIN TAPE ENCODER INTERPOLATION AND COMPENSATION 1 This file contains the 56000 assembler code to implement interpolation and compensation of the signals from Heidenhain read heads The code is designed to run on PMAC card as a user written servo routine Because of this the code below protects all registers except A B X and Y and only one level of the stack is used The routine is terminated with a jump to location P 23 The data memory used is the free memory between 1 57 0 57 and X and Y memory within the P variable memory space memory map that shows this memory usage in detail along with flowcharts explaining the code can be found in separate documentation i t d There are three values derived from each Heidenhain head There are two quadrature Sine and Cosine values that can be used to interpolate or determine absolute position within a pitch There is also a pitch count value that in
8. Special cases exist for the azimuth axis so we divide the problem into two areas 1 Functionality Common to both Axes 2 Azimuth Axis Special Functionality These are considered in the sections below ISSUE 3 14 January 1997 PAGE 45 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION In the following sections the r le of the GIS from the point of view of the MCS is defined It is not the responsibility of the MCS to implement this functionality 3 3 3 3 1 Main Axis Common Functionality The two main axes azimuth and elevation are very similar in operation but the azimuth axis has a greater functionality Functions common to both axes are dealt with in this section We define three limits positioned as shown in Figure 3 23 1 MCS Limit 2 Interlock System Limit 3 Damper or Physical Limit To MCS To Interlock Physical Only System Only Stop Figure 3 23 Position Of Limit Switches MCS LIMIT The MCS limit is triggered by s1 When this happens the MCS will e Ramp down the demand to the drives at maximum deceleration When the axis reaches zero velocity the drive enable signal is dis asserted e An appropriate error is reported to whichever client issued the original movement command While the axis is still in this limit the MCS will allow movement only in the direction out of the limit If a movement command that contradicts this rule is received then the axis is not moved and an erro
9. 14 January 1997 PAGE 75 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION SETUP EQU 1300 24 bit SETUP word RESULT EQU 1301 Lower 24 bits of the VE output VE OUT EQU 1302 Full 48 bit output position FDE EQU 723 Encoder table FDE value TH1 EQU 1201 Unextended compensated TH1 value TH2 EQU 1202 Unextended compensated TH2 value TH3 EQU 1203 Unextended compensated TH3 value Az TH4 EQU 1204 Unextended compensated TH4 value Az FDE EQU 1303 Position according to FDE VE EQU 1304 Extended compensated TH1 value VE TH2 EQU 1305 E TH2 value VE TH3 EQU 1306 p TH3 value VE_TH4 EQU 1307 H x TH4 value VE TRNS1 EQU 1308 El translation sensor 1 VE TRNS2 EQU 1309 El translation sensor 2 VE TRNS3 EQU 130A El translation sensor 3 VE TRNS4 EQU 130B El translation sensor 4 VE ELITR EQU 130C El corrected position head 1 VE EL2TR EQU 130D El corrected position head 2 LAST FIDU POS EQU 130E VE o p at last fiducial pass LAST FIDU ID EQU 130F ID byte of last passed fiducial FIDU FLAG EQU 1310 Status of HMFL1 after fiducial pass LAST HMFL1 EQU 1311 Value of HMFL1 500us ago imul fro ues m Te d UAI DID I e ur Define PMAC variable locations HMFL1 EQU 5 000 Motor 1 Home Flag locn Bit 20 FIDU_JOPT EQU SFFC2 JOPT J5 inputs Y bits 0 7 me a E HQ SETUP bit masks MODE MASK EQU 07 Mask for BO
10. 1 Datum Inc Bancomm time Provides a highly stable time 1 BC635 VME card IRIG B I O reference 2 Xycom Analogue A D Input General purpose analogue input 1 XVME 566 module capability Table 2 1 Hardware Requirements See reference 7 for details of VME slot allocation ISSUE 3 14 January 1997 PAGE 13 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 3 DETAIL DESCRIPTION 3 1 MAIN SERVOS SUBSYSTEM 3 1 1 Introduction There are two servo systems needed to point and track the telescope line of sight elevation and azimuth A third axis the Cassegrain rotator is needed to maintain field orientation and is the subject of a separate work package under the control of the Instrument Group The mechanics of the drive power amplifiers motors tachos encoders etc have been defined by the TBEG Both the azimuth and elevation axes employ friction type drive systems to supply the required torque for all telescope slewing tracking and offsetting operations To simplify design and manufacture the two drive systems use identical motor housings and motors i e identical rollers bearings motors and housing design Each unit is hydraulically pre loaded against the drive track The azimuth drive consists of four drive units and the elevation drive consists of two drive units one either side of the tube Each drive unit consists of two motors A fuller description of the drive configuration is giv
11. 65 TABLE 3 15 CONTROL MESSAGES sssscccsececessssececececsensaaececccecseseaeeesececseneuaaeceecceesesaaeeeeeeeesessaeaeeess 65 TABLE 3 16 INPUT RESPONSE MESSAGES FROM NODE TO MCS essen 66 TABLE 3 17 OUTPUT COMMAND MESSAGES FROM MCS TO 66 TABLE 3 18 CONFIGURATION BYTE c c cccccscsssssccecececsessaeeecececsensnaececececsensaaececececsesenaeaecececsensnsnaeeecees 66 TABLE 3 19 DATA RATES 1 HZ 1 1 2 424 440000200000000000000000000000000 67 TABLE 3 20 DATA RATES 25 HZ 5 2 22 2 0 00000000000000000000000000000000 67 TABLE 4 1 THE MCS SOFTWARE INTERFACE TO THE GIS 70 TABLE 4 2 THE MCS SOFTWARE INTERFACE TO THE MOUNT MAIN SERVOS 70 TABLE 4 3 THE MCS SOFTWARE INTERFACE TO THE ENCODER 004000001 71 TABLE 4 4 THE MCS SOFTWARE INTERFACE TO THE COUNTERWEIGHT HARDWARE ccce 71 TABLE 4 5 THE MCS SOFTWARE INTERFACE TO THE SERVICE WRAP 71 TABLE 4 6 THE MCS SOFTWARE INTERFACE TO THE MONITORING HARDWARE eee 71 TABLE 4 7 THE MCS SOFTWARE INTERFACE TO THE GEMINI TIME SYSTEM eee 71 ISSUE 3 14 January 1997 PAGE 5 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION INTRODUCTION 1 1 PURPOSE This document is a deliverable of the cr
12. Description 1 Brushless motor with integral fail safe brake MBA105 2005 Elitec Ltd Absolute encoder 5 9 series Elitec Ltd 1 Linear slide system 2EB 24 FTBJL64 Thomson IBL Ltd 1 Power amplifier HPD5 Elitec Ltd 2 Limit switch Unspecified Unspecified Table 3 9 Counterweight Hardware Components Toothed drive belt Brushless motor er MBA 105 2005 with Upper limit switch integral brake Absolute encoder Steel mass Thomson linear slide system 2EB 24 FTBJL64 Lower limit switch Figure 3 29 Counterweight Hardware ISSUE 3 14 January 1997 PAGE 53 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION A dynamic model of a single counterweight has been created using Simulink in Matlab This can be downloaded to the hardware simulator and run in real time to help develop a suitable controller on the counterweight PMAC card The Simulink model is shown in Figure 3 30 the input is a voltage corresponding to a torque demand the output is load mass position Demand Demand Elitec Motor coeff Torque Torque Force voltage limit amp const Amps to torque deadzone relation ls Upper travel Upper limit Upper limit Pint switch Mass Position Mass position limit Lower limit Lower limit Lower travel switch limit Motor constant
13. GIS Interconnection of a Single Axis ENABLING AN AXIS FROM THE MCS While an axis is STOPped the velocity demand from the MCS is zero and its drive enable signal is not asserted This means that the axis drive is disabled as described above This in turn means that the associated drive condition signal is also not asserted Imagine now that the MCS wants to move the axis it must e Assert the drive enable signal e Wait for a pre determined length of time This will depend upon how long it takes the GIS to enable the axis drive as described above e Check the drive condition signal If this is now asserted it means that the brakes have been removed and the power amplifiers are enabled so the required velocity demand can be applied If the drive condition signal is still not asserted it means that there is something interlocking the axis and so the MCS must report an error If the axis is moving when the drive condition signal is dis asserted then it means that the brakes have been applied and power has been removed from the power amplifiers The MCS must immediately reduce the demand signal to the power amplifiers to zero dis assert the drive enable signal and report an error 3 3 3 3 Limit Definitions What happens at limit positions must be considered carefully in order to avoid the possibility of attaining an irreversible interlock condition This condition could for want of a better expression be called Interlock dead lock
14. Service Wrap Hardware Components A dynamic model of the service wrap hardware has been created This can be downloaded to the hardware simulator and run in real time to help develop a suitable controller on the service wrap PMAC card The model is shown in Figure 3 32 and the model parameters are defined in Table 3 12 Note that not all the parameters have been defined by the IGPO so suitable estimates have been made 1 N Gear gt 1 1 gt Ka Km wl Jm s vFm gt P 2 AS ewe St Volts Motor ics Gear Load in PowerAmp Motor Coeff Static MotorMechanics Gear Chain Static Load Amps to Torque Friction SFm Stiffness Friction SFI Mechanics A E 4 Satdratiori Encoder Main Axis Constant Velocity Figure 3 32 Service Wrap Drive Hardware Simulator Model Parameter Value Units Description 100 Gear ratio K 57 3 Nm rad Gearbox stiffness Km 0 3728 Nm A Motor constant Jm 6 849e 4 Kg m Motor and gearbox shaft inertia VEm 6 1e 4 Nm rad s Motor viscous friction SFm 0 078 Nm Motor static Coulomb friction SFI 7 8 Nm Load static Coulomb friction VFI 6 1e 2 Load viscous friction Jl 6 85 Kg m Load inertia 167 V Encoder consta
15. e g wheel spinning is now not expected it would still be useful to look at the mechanism of wheel slippage to see if it can be detected and even eliminated Tests should be conducted with various drive wheel materials hardnesses and pre loads The following variables should be logged e Motor currents Pre load Forces Tacho signals Velocity demand Commutation encoders e Main position encoder These data can then be analysed to see if slippage of the drive wheels can predicted The data can also be compared with data from the slippage model to verify and refine this model Drive roller wear for different roller materials and pre loads can be compared Effective Gear Ratio Mismatch The altitude axis of the telescope consists of two drive discs with a drive unit on each disc Tolerances in manufacture may mean that there could be an effective gear ratio mismatch between the two discs and drive units This is not thought to be a problem because of the single averaged tacho configuration and electrical differences in the tacho loops do not cause problems However it would be easy to make a couple of drive rollers with different diameters to test this theory 3 1 3 4 3 Factory tests The factory pre assembly of the first telescope is expected to be complete by mid February 1997 The assembly will remain intact for one month when tests on the elevation drive can be carried out PAGE 24 of 79 14 January 1997 ISSUE 3 MOUNT CONTR
16. B2 Mode ALGO MASK EQU 38 Mask for B3 B5 Algorithm MASK EQU 1C0 Mask for 6 8 N_MASK EQU E00 Mask for 9 11 N HMFL1 bit mask HMFL1 MASK EQU 100000 JOPT MASK EQU SFF Location to store volatile PMAC register s SAVE RO EQU 57 0 Save locn for RO Define start of VE code in PMAC Program memory Program code area is from P B800 to P SBBFF May be moved up to allow for Compensation code ORG 5 800 Save register s before the code starts MOVE RO X SAVE RO Clear the registers and accumulators used by PMAC At the start of each servo cycle PMAC sets A Accumulator desired velocity 48 bits B Accumulator desired position 48 bits X Register actual position 48 bits Yl Register Ix08 value Mot X Pos Scale Factor CLR A CLR B Position extend 24 5248 bits all encoder values PAGE 76 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Extract Mode bits MOVE X SETUP A1 MOVE MODE_MASK RO MOVE RO AND X0 A Jump to Diagnostic mode MOVE 501 1 CMP B A JEQ DIAG MODE If Bit 1 set then enter DIAG MODE If no match default to normal mode Set Echo mode bits for EPICS Normal Mode 000 BCLR 21 X SETUP BCLR 22 X SETUP BCLR 23 X SETUP Extract Algorithm bits MOVE X SETUP A1 MOVE ALGO_MASK RO MOVE AND X0 A Jump to FDE Tape N Tape
17. Calculate offset Check to see whether offset overflows If so add 1 if offset is and minus one if offset is ve Add offset to interpolation Shift result 14 bits to the right to scale correctly Shift pitch count 4 bits to the left to scale correctly Combine pitch count and interp Multiply by relevant factor in order to leave result in 5 milliarcsec resolution Store Result VIRTUAL ENCODER CODE COULD BE INCLUDED HERE MOVE X STORE RO RO Restore contents of RO MOVE X STORE_R1 R1 Restore contents of R1 MOVE X STORE R2 R2 Restore contents of R2 MOVE X STORE R3 R3 Restore contents of R3 JMP 23 Return to PMAC Code ISSUE 3 14 January 1997 PAGE 73 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION ip RAR SKK KAR BRK ko ee ke Kok Kok KR ek koe ec OK KA KU UK A IKK KR ICT SKK SKK CK E KO KC SKK SKK oe en END OF MAIN CODE j FEFEFE K K K F Fe ko kk ko kk ko kCk ko kk ko kk ko kk ko kk ko kk ko kk ko kk ko kk ko kk ke Kok ke Kok ke Kok ke Kok A IE ke IE ke IE ke IE ke Kok ee y OCCISUS CRUS SUN GR KO USUS GR ATR RA NON UR OR RUNG RR RIA QUIC AR RUE UNUS NEU SUBROUTINE TO PERFORM ARCTANGENT FUNCTION This subroutine cosine of which memory location Cosine argument fraction completion the The routine uses one of two series expansions of the arcta
18. FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU FIGU LIST OF FIGURES RE 2 1 RELATIVE POSITION OF MOUNT CONTROL 5 8 2 01 11 022 0000000000000000002 11 RE 2 2 MCS INTERNAL 2 2 010 14 240440400000000000000000000000000000000000 12 RE 3 1 ON AXIS ERRORS FOR THE RANGE OF ZENITH DISTANCE cernere 15 RE 3 2 MAIN AXIS SERVO LOOPG ccssssccececeesessececececsesessnaececececsensaaececececsesaaececceeesensaaeaeeeeeeeenss 17 RE 3 3 OVERALL WIRING SCHEME FOR ELEVATION AXIS ccce 18 RE 3 4 OVERALL WIRING SCHEME FOR AZIMUTH AXIS sescenti en enn 19 3 5 DETAILED WIRING OF FST 2 20 3 6 HWILS CONFIGURATION cs ene onae rr rens Ee eE AREE EEEN OA EEEE AREE AEE oT ER 22 RE 3 7 recede tes ruere E Rho dee 23 RE 3 8 DRIVE ROLLER DAMAGE scsscccsccecsesessscecececeesesecececececseeaeceeeceeseaaeceeeceesensaaeeeeceseneneaaees 24 RE 3 9 THE FIDUCIAL ENCODING SYSTEM FOR ONE AXIS 28 RE 3 10 AZIMUTH ENCODER INTERFACE 2 01 20000000 00000000000000000000000000 0 29 RE 3 11 ELEVATION ENCODER INTERFACE
19. Figure 3 10 azimuth and Figure 3 11 elevation Full details of encoder connection and encoder table definition can be found in reference 11 Encoder Counter Table pass H pees Counter nterface xs ENC3 Head X 728 Interface Counter X 729 ENC4 1 X 72A Ds 8 Interface XS72D X 72D Head X 72E Interface X 72F Figure 3 10 Azimuth Encoder Interface ISSUE 3 14 January 1997 PAGE 29 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Head ENC3 Head Interface Counter ENC4 2 Figure 3 11 Elevation Encoder Interface NOTES 1 Head Interface Block In order to derive a position value from each Heidenhain encoder head we need to count pitches every 40 um and interpolate between these pitches using the two quadrature sinusoids The blocks marked Head Interface represent an electronic circuit that will amplify the head signals sine and cosine to the correct level for input to the ACC28 The circuit also provides a quadrature square wave output in phase with the head signals for input to a PMAC counter This circuit will be housed in a box along with the ACC28 boards 2 Encoder Table Units Counter Channels Output of each encoder table entry is counts x32 so each bit represents 3 of a count For the FDE channel each bit represents the resoluti
20. Interface Design Document IGPO International Gemini Project Office IOC Input Output Controller 1 1 Implementation Phase 1 IP2 Implementation Phase 2 IP3 Implementation Phase 3 IRIG B Inter Range Instrument Group format B ISS Instrument Support Structure ITB Inner Topple Bracket kHz One thousand hertz kN One thousand Newtons LAN Local Area Network LSB Least Significant Bit LVDT Linear Variable Differential Transformer MI Primary Mirror M2 Secondary Mirror MCS Mount Control System MEC Mount Engineering Console MHz One million hertz ms millisecond One thousandth of a second MSB Most Significant Bit NCB Node Control Board NCU Node Control Unit O P Output OCS Observatory Control System OPI OPerator Interface OSS Optical Support Structure OTB Outer Topple Bracket PA Power Amplifier PC Personal Computer PCB Printed Circuit Board PCS Primary Mirror Control System PDR Preliminary Design Review PLC Programmable Logic Controller PLD Programmable Logic Device ISSUE 3 14 January 1997 PAGE 7 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION PMAC Programmable Multi Axis Controller PRS Package Requirements Specification PSU Power Supply Unit PTP Package Test Procedure This consists of a Test Design Specification and a Test Case Specification as defined in IEEE 829 1983 PVT Position Velocity Time a PMAC mode of operation see reference 4 page 3 125 rad radian Angular unit of measurement RAM Ra
21. LIST OF TABLES 122159 CPI Ina nmi 6 TABLE 2 1 HARDWARE REQUIREMENTS ccessessssecececeessaececececsensaececececsenssececececeesensaeeececeesenteaeeeeees 13 TABLE 3 1 SUMMARY OF ERROR PREDICTIONS 15 TABLE 3 2 FST 2 PROGRAMMABLE 8 22 11 2 4440 0 0000000000000000000000 21 TABLE 3 3 AZIMUTH RANGES isse 26 TABLE 3 4 VIRTUAL ENCODER MODE 38 TABLE 3 5 VIRTUAL ENCODER ALGORITHM 38 TABLE 3 6 INTERLOCK SYSTEM COMMUNICATION LOGIC TABLE eese nennen nennen 43 TABLEE3 7 MAIN AXIS LIMITS rrr tte oorr Pr er 48 TABLE 3 8 LIMIT POSITION SUMMARY 2 2 2 4 enne N eerta rana nennen 48 TABLE 3 9 COUNTERWEIGHT HARDWARE COMPONENTS 53 TABLE 3 10 COUNTERWEIGHT MODEL PARAMETERS eere enhn ennt eet annis 54 TABLE 3 11 SERVICE WRAP HARDWARE 56 TABLE 3 12 SERVICE WRAP MODEL 8 222 222 00000 01 0000000 56 TABLE 3 13 SERVICE WRAPS INTERLOCK CONDITION TABLE eene eee nennen enne 58 TABLE 3 14 NODE iret re reir o ere N TE E EA EE
22. Sine Cosine TGT A B If Sine gt Cosine then TGT X0 A Swap arguments to keep OVE B X0 Quotient less than one OVEC SR Save SR for later AND SFE CCR Perform one quadrant REP 518 division See 56000 DIV X0 A Manual under DIV instruction OVE 0 Transfer result into OVE COEFF_0 RO Set RO to point to the coeffs for exp about 0 series CMP YO A ONE YO If x lt 0 5 then jump to JLT POLY series calculation OVE COEFF_1 R0 Else prepare for exp about SUB YO A 1 series POLY OVE 0 sux kes aX OVE X RO A ove constant to result OVE X RO YO Move linear coeff to YO AC 0 0 X0 X1 Calc linear term then add to result Make x Note that PMAC s stack restrictions do not allow the following to be written as a DO loop PY X1 X0 B X RO YO Put x 2 into X1 and Get OVE B X1 the x 2 coeff in YO AC X1 Y0 A Add term to result PY X1 X0 B X RO YO Put x 3 into X1 and Get OVE B X1 the x 3 coeff in Y0 AC X1 Y0 A 1 ASN 1 2 X0 Add term to result POLY_END OVE Scale Result so to pi PY X0 X1 A maps to 1 OVEC Y1 SR Restore SR from before JLT QUAD OK If Sine Cosine then EG A 0 5 0 A pi 2 A ADD YO A QUAD OK OVE ARG X Get Sine and Cosine values PY 0 1 1 0 0 Multiply to find sign JPL HALF OK If sign is negative then EG A ONE YO invert result Set up correct offset in YO PAGE 74 of 79
23. Torque deadzone Torque deadzone 3 Torque force constant of linear system 1 Load force 3777N axial 1472N cross axial 3777 Axial 1472 Cross axial Nm rad s Viscous friction of load System 1 Nm Coulomb friction of load System 3 Scaling for mass position m to mm 1 indicates an estimated parameter Table 3 10 Counterweight Model Parameters 3 6 SERVICE WRAP UPS SUBSYSTEM 3 6 1 Introduction In order to provide power data services networking cryogenics and other services to the Cassegrain focus it is necessary to provide a means of passing the services through the azimuth elevation and Cassegrain bearings The Cassegrain cable wrap is a separate work package and is under the control of the Gemini Instrument Group In order to minimise the disturbance torque introduced into the motions of the different axes it is advisable to drive the service separately from the telescope axis It is intended to separately servo the service wrap ups and to drive them as a follower to the axis they are connected to PAGE 54 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION There is one azimuth cable wrap and two elevation cable wraps For a description of the configuration of these see references 24 amp 25 3 6 2 Purpose The service wrap ups subsystem shall receive an input at a suitable servo rate from a differen
24. UC E GC REE REAR Tn OR O O O O O O O G P B800 VE RO X STORE RO VE R1 X STORE VE R2 X STORE R2 VE R3 X STORE R3 HEIDENHAIN INTERPOLATION AND COMPENSATION VE ENC_TABLE R1 VE TH_OUT R2 VE COMP_PARA R3 Some kind of loop for all heads OVE X R1 X1 OVE X R1 X0 OVE 0 B JSET 23 X0 INTERP OVE X1 A OVE BLANKING YO CMPM 0 0 A JLT CALC_RESULT INTERP OVE X L ATAN_ARG JSR ATAN2 JCLR 0 Y R2 CALC RESULT COMP JSR APPLY COMP MOVE A L SAVE A MOVE X L ATAN ARG JSR ATAN2 MOVE A B MOVE L SAVE_A A SUB A B 0 5 Y0 CMPM 0 JLT CALC RESULT OVE 1 0 Y0 JCLR 23 B CORRECT OFFSET OVE fONE YO CORRECT OFFSET ADD 0 RESULT ADD B A X R1 B REP 14 ASR A REP 4 ASL B ADD B A RES X0 MOVE A X1 MPY X0 X1 A MOVE A X R2 End Loop Locate Code Save contents Save contents Save contents Save contents of RO of R1 of R2 of R3 encoder table output table compensation R1 pointer R2 pointer R3 pointer to parameters Get sine analogue channel Get cosine analogue channel Clear offset B Interpolate if cosine is ve And sine is NOT in the blanking region Save arguments and perform Arctangent Skip compensation if turned off Apply compensation to signals Save uncomped interp value Save compensated arguments and perform Arctangent Compensated interp value to B Restore Uncomped interp value
25. assembled The test rig is an adaptation of the friction driven encoder test rig built by the IGPO This consists of a two metre diameter steel wheel mounted vertically in a frame The rig was modified to include two brushless motors with tachometers and commutation encoders mounted so that they friction drive against the outer diameter of the wheel Figure 3 7 shows schematically how the test rig drive system is connected The proposed configuration of the telescope drive components as detailed in Section 3 1 3 3 2 is based upon this scheme PAGE 22 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION E ENCODER M MOTOR T TACHO AUXILIARY INPUT Figure 3 7 Test Rig Connection Some measurements of motor torque and drive wheel slippage have been made using the test rig These tests are in no way comprehensive and are not complete however the following observations have been made mis match in tacho loop parameters leads to corresponding imbalance in motor torques However the torque sum remains the same indicating that the although one motor may be doing more work both motors continue to work together rather than against each other e The drive wheels do slip even if the theoretical friction torque is NOT exceeded This slip seems to occur when the wheel changes direction and is more or less repeatab
26. by the Gemini Interlock System GIS It is a requirement of the Mount Control System MCS to provide velocity signals to the GIS 3 4 2 Purpose The MCS shall provide signals to the interlock system indicating that the velocity of each axis is either above or below some safe limit These signals shall be derived from good quality tacho generators There is no longer a requirement of the MCS to provide binary signals indicating whether or not an axis is near to one of its limits These requirements are obsolete since there is no longer a need for a zone of reduced maximum velocity around the limits see Section 3 3 3 3 1 3 4 3 Function The transducer used to measure velocity is a tacho generator There will be one of these per axis and they will be mounted on one of the encoder brackets The tachos are supplied by Bowmar Instruments Ltd and are type Servotek PN7453B 1 20 8V These units output 20 8 V per 1000 RPM or with a 30 mm diameter wheel mounted on the shaft about 1V per sec of the axis This means that the output at maximum velocity will be about 2 V Located close to the tacho generators will be a small electronic circuit which will perform a comparison between the voltage from the tachos and a reference voltage that represents the safe velocity limit for each axis The output shall be in the standard interlock complimentary TTL format See Section 3 3 2 Figure 3 27 shows a functional block diagram of the connection betwe
27. compensated tape head 4 value VE 4 Calculate VE_TH1 VE_TH2 VE_TH3 VE_TH4 Store result in VE_OUT Store lower 24 bits of VE_OUT in RESULT Stop Figure 3 20 AZ_FULL Average Four Heads Azimuth Axis Only PAGE 42 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION N One elevation tape head and appropriate EL FULL translation sensors 7 Star Start y y sate cho Read associated t Algorithm translation value TH2 to SETUP sensors A amp B y Read ate Y ta va al Read translation Store in ead U 5 Read SETUP word YE TENSI R Y y Read translation sen 1422 Store in VE TRNS3 amp 4 y Extract n value f 2208 n to 1 or 2 Eus oan Store in count amp 2 App n Y y a tion Y Store in head zs t VE ELnTR Store in V V Hn VELTEDDTR VE EL2TR y y Store in VE ELITR Stor e in VE OUT E Store lower 4 bits of VE OUT in RESULT Y Stop 1 Figure 3 21 Elevation Combining Algorithms 3 3 INTERLOCK INTERFACE SUBSYSTEM 3 3 1 Introduction The Interlock System or GIS is part of another work
28. demand and fans the result out eight times four for elevation This allows the GIS to move the telescope Full circuit diagrams of TAV and VCC are given in reference 20 DAx is Drive Assembly No x including motor tacho and encoder ADC is one of the MCS XYCOM 566 VME cards PSU is a 15 supply FST 2 is one of the Power Amplifiers ISSUE 3 14 January 1997 PAGE 17 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Cabinet 1 Figure 3 3 Overall Wiring Scheme For Elevation Axis PAGE 18 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Cabinet 1 Figure 3 4 Overall Wiring Scheme For Azimuth Axis Figure 3 5 shows how each FST 2 amplifier should be connected The following abbreviations are used in this diagram 530 Screened 3 phase motor current cable SMx Multi core cable with x conductors and an overall screen SxTP Multi core cable with x twisted pairs and an overall screen STP Screened twisted pair W Single earth wire Mx Motor associated with drive assembly x Hx Hall sensors associated with the motor of drive assembly x Ex Encoder associated with drive assembly x TEMPx Temperature sensor associated with the motor of drive assembly x Note that where a STP is specified it does not rule out the possibility of combining of many STPs into one SxTP This decision is ultimately up to the engineer responsible for overall telescope cabl
29. encoder subsystem shall have a calibration mode in which the systematic corrections for each encoder input can be derived It shall be possible to up down load the look up tables that implement the systematic corrections These tables shall be in a readable form In order to avoid position ambiguity and to allow zero setting to occur at any position the virtual encoder shall have a resolution of at least 30 bits A 32 bit resolution is preferred NOTE For the Gemini telescope azimuth axis the required resolution is 0 005 arcsecs over 3270 range which is to one part in 388 800 000 or 29 bits To allow an encoder zero set to occur anywhere the effective range of the encoder becomes 540 hence the need for an extra bit It shall be possible to directly connect a computer to the encoder subsystem in order to run diagnostics and tests The encoder subsystem shall provide a virtual encoder output 2 kHz 32 bit parallel word to each axis of the MCS servo subsystem NOTE Given a maximum velocity of 2 s an encoder resolution of 0 005 arcsecs and a sampling frequency of 1 kHz the maximum number of encoder pulses in one sample period will be 720 This can be covered by 10 bits but to resolve any direction ambiguity an extra bit is added hence the interface between the VE and the servo system need only be 11 bits wide An interface shall be provided so that the following outputs for each axis can be monitored by the MCS software a
30. manuals The Gemini Standard Controller Hardware Documentation Andrew Johnson TC C G0022 Gemini Non linear Servo Simulation Mike Burns and John Wilkes MCSCJCOS Revision 1 1 MCS VME Crate Wiring Schedule Chris Carter TN C G0040 MCSJDW10 Issue 3 Prediction Of Servo Error Using Simulink Model John Wilkes TN C G0041 MCSJDW11 Issue 4 Encoder Tests John Wilkes MCSJDW 12 Issue 2 Tape Encoding System Requirements Specification John Wilkes MCSJDW 14 Issue 1 Main Axis PMAC Set Up John Wilkes MCSJDW 16 Issue 1 Counterweights And Service Wraps PMAC Set Up John Wilkes PAGE 8 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 13 Determination and correction of quadrature fringe measurement errors in interferometers Peter L M Heydemann APPLIED OPTICS Vol 20 No 19 1 October 1981 14 Optical fringe subdivision with nanometric accuracy K P Birch PRECISION ENGINEERING Vol 12 No 4 October 1990 15 PCSPMO1 Primary Mirror Control System Node Box Software Design Description Paul Martin 16 PCSJFM04 PCS IOC NCU CAN Protocol John Maclean 17 IEEE Std 1016 1987 IEEE Recommended Practice for Software Design Descriptions 18 MCSJDWO9 MCS Preliminary Design Review Report John Wilkes 19 Mount Control System Control System Design Description Issue 1 John Wilkes and Chris Carter 20 Subsystem Circuit Diagrams A col
31. method will effectively reduce the value of d1 to zero since s0 and s1 will no longer exist or The decision on to which method is to be used will be dependant upon which is the easier to implement in software NOTE ON LIMIT SWITCHES Since 50 and s1 operate soft limits within the MCS they need not be physical micro switches even though they are depicted as such in the figures above The limits can be triggered by the MCS encoder value INTERLOCK SYSTEM LIMIT Under normal operation s2 will never be activated However in the event of an MCS failure or when the telescope is under the control of the Interlock system s2 will trigger the Interlock System Limit When this happens the Interlock system will e Disable the amplifiers using Enable lines and maybe removing power e Apply the brakes This will of course dis assert the relevant drive condition signal and there is no way that the MCS can drive the axis out of an Interlock System limit The axis must be retrieved under the control of the Interlock System This time the desire is to fix distance d2 such that even if the axis is moving with full velocity the brakes can decelerate to zero velocity before reaching the physical stop For the given values of braking deceleration it can be shown that the d2 distances are quite small so there is no need to provide an area of reduced maximum velocity around each limit ISSUE 3 14 January 1997 PAGE 47 of 79 MOUN
32. package within the Controls Group It has ultimate control over the power to the brakes and drive power amplifiers The MCS must be capable of generating interlock requests in order to instruct the GIS to enable disable the telescope drives 3 3 2 Purpose Each input and output from the Interlock System will be comprised of two TTL signals one being the complement of the other These shall be interpreted based on the logic table shown in Table 3 6 0 Set Reset Reset I se sa Table 3 6 Interlock System Communication Logic Table Signals shall be organised so that the Set state is the fail safe state The Interlock Interface subsystem shall receive drive condition signals from the GIS for each of the main drives The drive condition signal is an Interlock Demand from the GIS ISSUE 3 14 January 1997 PAGE 43 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The Interlock Interface subsystem shall provide drive enable signals to the GIS for the main drives The drive enable signal is an Interlock Event to the GIS There is no longer any requirement to interface drive enable and drive condition signals concerning the service wrap drives and the counterweight drives These drives are considered non safety critical and so do not require to be ultimately controlled by the GIS The limit switches of these drives will be handled by the MCS within the relevant subsystem 3 3 3 Function Because the Interlock System and
33. while wrap will stall against fixed before the main MCS mode axis should already the GIS wrap drive runaway drag plate which axis can be re enabled and GIS is not be disabled limitis cleared fault exists has become a Damage to motor and moving the before the main hard stop since amplifiers is possible axis axis is allowed to main axis is unless suitable current re enable disabled limits are enforced within the amplifier Wrap is dragged Wrap will continue to by main axis be dragged by main GIS wrap limit reached Defined by the GIS Recommend MCS Powered down or Wrap No recovery necessary while GIS is nothing since servo not movement axis moving the dragging of the initialised axis wrap must be permitted in this mode Cables will be Main axis drive will stretched by slip or stall or cables movement of will be ripped out main axis Cable jam Table 3 13 Service Wraps Interlock Condition Table 3 7 MONITORING SUBSYSTEM 3 7 1 Introduction Itis the responsibility of the MCS to provide a generic means of monitoring the many physical quantities that have been identified This shall be implemented with a field bus system based upon CANbus as used by the PCS There will be a number of bus PAGE 58 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION stations at strategic points around the telescope and enclosure Signa
34. word Elevation VE output 24 bits 48 bits Raw tape head outputs FDE incremental encoder readout 48 bits The last elevation fiducial passed Position of elevation tilt switch Output of elevation LVDT Position of elevation striker bracket Records MultiBit In MultiBit In Binary In Binary In MultiBit In MultiBit In Binary In Binary In EPICS MultiBit Out 4 MultiBit Ins MultiBit In MultiBit Out 4 MultiBit Ins MultiBit In Analogue In Records dan Records Board Axial Demand Positions Axial CW Demand 0 970mm lt 50 Hz 2 String Outs PMAC3 Cross Axial Demand Pos Cross Axial Demand 0 970mm lt 50 Hz 2 String Outs PMAC 3 CW Motor Status Motor servo status bits 24 bits lt 50 Hz 4 Status PMAC 3 CW CS Status Co ordinate System status bits 24 bits lt 50 Hz 4 Status PMAC 3 Axial CW Positions Current positions of Axial CWs 0 970mm lt 50 Hz 2 Analogue PMAC 3 Ins Cross Axial CW Positions Current positions of Cross Axial 0 970mm lt 50 Hz 2 Analogue PMAC 3 CWs Ins Table 4 4 The MCS Software Interface to the counterweight hardware Function SW CS Status SW Positions SW Drive Currents SW Motor Status Description Motor servo status bits lt 50 Hz 3 Status PMAC3 Co ordinate System status bits lt 50 Hz 3 Status PMAC3 Different
35. 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION HALF OK JCLR 23 X0 FULL OK ADD 0 FULL ASR A ONE YO JPL ATAN2_STOP ADD 0 0 2 5 RTS Test sign of Cosine value If ve then A A offset Convert range to 0 2 pi maps toa get Clear B offset KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKKKKKKKKKK kk o SUBROUTINE TO APPLY HEYDEMANN COMPENSATION This routine is used to calculate Heydemann compensated Sine and Cosine signals Before execution and Cosine in X0 the X register should contain the uncompensated signals and the compensation parameters should be stored in a table 2 Sine in X memory pointed to by R3 The values should be stored in standard 56000 fractional notation and in the following order 8 0 8 6 8 sin A and p 1 8 cos A Note that all except sin a have a divide by 8 scaling factor to keep the calculations easy and allow multipliers greater than one Note also that the reciprocal of the cos A parameter is used to avoid the need to do division Upon completion and Cosine in X0 The operations performed are Sine Comp Sine P Cosine Comp Sine Comp Sin A The B are used G Cosine Q the compensated signals are stored in the X register Sine in X1 cos A X YO and R3 regis
36. 3 35 Elements of the monitoring node The monitoring node box is designed to interface to both analogue and digital sensors Its core is a node control board or NCB based around the Siemens C167 micro controller This unit is the same as used in the PCS system and handles all the node functionality reading ports converting data CAN interfacing etc The rest of the node circuitry is devoted to interfacing external signals to this unit multiplexing data sampling signals etc In normal operation the NCB will receive commands destined for its particular node box from the MCS over CANbus It will interpret them read various combinations of its inputs process the sampled data and transmit it back to the MCS 3 7 3 3 Node Hardware Nearly all the circuitry in the Monitoring and Metrology node is surface mount to keep size to a minimum There are two main PCBs the NCB containing the node micro controller memory and CAN interface and the motherboard which holds the interfacing and ancillary circuitry 3 7 3 3 1 Node Control Board The NCB was originally designed for the PCS by the RGO and Coefficient Design Ltd Only a brief description of directly relevant features is given here for further details see reference 23 MICRO CONTROLLER The NCB is based around a Siemens SAB C167CR LM micro controller referred to here are the C167 Key features include integral serial ports and extensive port based I O and integrated C
37. 7 3 4 3 Sample Decimation The C167 will be capable of decimating the data that has been sampled at the fixed frequency of 25Hz Decimation is a procedure that takes data originally sampled at a high frequency and re samples it at a lower frequency In essence it involves re filtering the sampled data and then re sampling It is not the same as taking every nth sample that procedure can introduce aliasing errors The decimation scheme will be continuous as samples are taken 25 Hz samples will be passed to through a digital filter implemented in the C167 and re sampled Decimated samples will then be available for transmission over CANbus PAGE 64 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION NE 25Hz sampled Digital filter Decimation Decimated data sampling samples Figure 3 37 The decimation process 3 7 3 4 4 Binary Input Sampling The binary input channels are intended for recording the status of switches parallel digital encoder outputs etc As such the main requirement is that they should be able to reject moderate levels of switch noise contact bounce and so on This is easily handled in software When commanded to read a binary input the node will repeatedly read the associated port pin s a fixed number of times and determine the input state by a majority decision This is effectively an averaging f
38. 73 Storage address for R3 BLANKING EQU 4800 Analogue range around crossover point that is blanked to avoid the one pitch error RES EQU 0 671434916 0 078125 R where R is the required resolution of the result in microns RES 0 671434916 for Azimuth based on 9 6 m RES 0 805721899 for Elevation based on 8 m ENC TABLE EQU 724 Encoder table pointer For all head signals TH OUT EQU 1201 Pointer to output table COMP PARA EQU 1211 Pointer to compensation parameters SAVE A EQU 577 Temporary storage for A register ARG EQU STIE ARCTANGENT FUNCTION ARGUMENTS ORG X 1280 COEFFICIENTS OF ARCTANGENT SERIES COEFF 0 DC 0 0 1 0 3 1 DC 8 1 0 5 0 25 0 125 NOTE SYMBOL DEFINITIONS FOR VIRTUAL ENCODER COULD BE INCLUDED HERE PAGE 72 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION RRA UE KK KC SK SK kk SKK Kk SKK RRR EAR RR KAKA EE RAK ke OK eo oo e ok o e ke ok e Ke IR UR SK OK eK RUE EK KER SARI ICR KR ee CODE FOR INTERPOLATION AND COMPENSATION H Currently simple loop cod e as indicated this code works for one head only However it can be easily expanded to 2 or 4 heads by inclusion of some Note the loop can not be implemented using the DO command since PMAC s restrictions on Stack usage wil l not allow it RAK CROCO UK ERA REAR LEER E EU AEE AK ERA RRR RAR AK ERA KAR ERR e
39. 8mm These signals are to be interfaced to the encoder subsystem via the azimuth and elevation PMAC cards Due to the large number of fiducials the switch signals are encoded into a more compact binary form before transmission to the PMAC cards Because the fiducial encoders are relatively remote from the MCS crate signal transmission is performed using a differential twisted pair scheme An additional circuit at the crate converts these differential signals back into conventional TTL compatible form The physical arrangement is shown in Figure 3 9 Fiducial 1 Differential twisted pair To EPICS Fiducial2 Fiducial encoder Differential line PMAC card circuitry n inputs to m outputs receiver via JOPT input Fiducial n Figure 3 9 The fiducial encoding system for one axis FIDUCIAL ENCODING SYSTEM The individual fiducial signals are converted into a straight binary code plus even parity This coding scheme results in an 8 bit azimuth code 7 bits to uniquely identify the fiducial 1 bit for parity and a 6 bit elevation code 5 bits to uniquely identify the fiducial 1 bit for parity All incoming fiducial signals are opto isolated before being passed to the encoding circuit This is convenient as it handles the conversion of a 12V signal to a logic level signal in addition to providing isolation Further should the type of fiducial swit
40. AGE 25 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Tape encoder head outputs four for azimuth and two for elevation up to 5 kHz pulse stream plus interpolation sinusoids Translation sensors for elevation analogue signals One FDE output per axis up to 2 MHz pulse stream Up to 72 azimuth and 22 elevation fiducials one signal from each fiducial An elevation tilt switch The signal from this will indicate which half of the elevation range the axis is in at MCS IOC power up A signal indicating the position of the elevation limit striker bracket This bracket can be rotated to provide a different set of lower end mechanical elevation limits Two azimuth topple brackets The position of these brackets shall be used to resolve the azimuth position ambiguity at MCS IOC power up The valid topple bracket states are summarised in Table 3 3 AZIMUTH ANGLE OUTER BRACKET INNER BRACKET 270 AZ 90 Not Toppled 90 AZ 90 Not Toppled Not Toppled 90 AZ 270 Toppled Not Toppled Table 3 3 Azimuth Ranges There is no longer a requirement for the MCS to read the azimuth absolute encoder This encoder is intended to back up the topple bracket signals for safety purposes and as such is read by the GIS only It shall be possible to easily extend the number and type of encoders read by the encoder subsystem Note that the encoder subsystem shall accept input in one of the f
41. AN support PAGE 62 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION MEMORY The C167 has 2Kbytes of on chip RAM plus 2Kbytes of internal extension XRAM Additionally the NCB holds 32Kbytes of RAM and 128Kbytes of Flash memory This will more than meet the requirements of the node software I O PORTS The node uses the micro controller I O ports 3 5 and 7 to read the 32 binary inputs once they have been opto isolated CAN INTERFACE The CAN interface is electrically isolated from the rest of the node circuitry 3 7 3 3 2 Analogue Interface Each node has 16 analogue input channels consisting of a differential voltage amplifier followed by a second order anti aliasing filter The circuit diagram of an input channel is given in the supplementary documentation THE ANTI ALIASING FILTER The anti aliasing filter is an operational amplifier circuit that implements a second order Butterworth response The circuit is shown in Figure 3 36 sf 4 Figure 3 36 Second order low pass filter second order low pass filter with a cut off frequency Fc of 10Hz can be realised with R1 R2 470KQ C1 47nF and C2 22nF nearest preferred values The channel outputs are multiplexed and passed to the 14 bit ADC A 16 bit word representing the sampled value is then available 3 7 3 3 3 Binary Interfaces The node reads bi
42. CS Diag Mode 001 BSET 21 X SETUP BCLR 22 X SETUP BCLR 23 X SETUP Diagnostic routines here Could include mirroring PMAC status bits VE or Comp code flags and or variables to EPICS JMP EXIT FDE ONLY BCLR 20 X SETUP Echo Algorithm bits in SETUP 000 BCLR 19 X SETUP BCLR 18 X SETUP MOVE L VE FDE A10 Loads VE FDE into lower 48 bits of A MOVE A10 L VE OUT Loads lower 48 bits of A into VE OUT JSR UPDATE LOW JMP FIDU CHECK Note Elevation version includes translation sensors BCLR 20 X SETUP Echo Algorithm bits in SETUP 001 BCLR 19 X SETUP BSET 18 X SETUP OVE X SETUP A1 OVE N_MASK RO OVE RO AND X0 A Check which head to read OVE 501 1 CMP B A JSEQ READ_VE_TH1 OVE 502 1 CMP B A JSEQ READ_VE_TH2 OVE 503 1 PAGE 78 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION CMP B A JSEQ READ_VE_TH3 MOVE 04 B1 CMP B A JSEQ READ_VE_TH4 Routines to read appropriate tape head READ_VE_TH1 MOVE L VE TH1 A10 JMP TAPE N EXIT READ VE TH2 MOVE L VE TH2 A10 JMP TAPE N EXIT READ VE TH3 MOVE L VE TH3 A10 JMP TAPE N EXIT READ VE 4 MOVE L VE 4 10 JMP TAPE N EXIT Save the head value in VE OUT TAPE N EXIT MOVE A10 L VE OUT JSR UPDATE LOW JMP FIDU CHECK TAPE MN BCLR 20 X SETUP Echo Algorithm bits in SETUP BSET 19 X SETUP BCLR 18 X SETUP Tape MN rout
43. D 3 7 1 2 Electrical Systems Interface 952 PUTO SC si Ue RR RE RR e ER RI A UI RI HERBES FE Ie HEROS 55 05 MI FUNCTION REESE E PAGE 2 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 3 7 3 1 Node Box Specification Je ete HAT RR EIER Ce RD HER D eee Here Noe ugs 3 7 3 2 Functional Description 3 7 3 3 Node Ha rdware eene tentent eene 3 7 3 4 Node Software amp CANbus Issues 3 7 3 5 Enclosure amp Connect O18 sissien teneret ene te eda Eo Eee EE ERU e Een NINE Ek ee Ex n e dese eene reae nara 4 INTERFACE DESCRIPTION eese tn atta neta senten sesto sess suse ta sone 70 4 T INTERNA INTERPFACBS nere PR FREE REDE e A R 70 42 EXTERNALINTERFACE Sa rnt tee UI deer Ui erede ete erigere nee 70 4 2 1 Hardware Interfaces cree de e i e e Bree Rea Eb edes 70 42 2 Software Interfaces 3 o eee e eite eer aie de e e deer eee 70 SPR A E INID LOA Uc ETA 72 5 1 APPENDIX A PMAC USER WRITTEN DSP CODE sees eee een ene 72 5 1 1 Heidenhain Interpolation And Compensation Code eene 72 2 Virtual Encoder Codes i dS RR Ue t et eher ep i ERR RE eet erg 75 ISSUE 3 14 January 1997 PAGE 3 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION FIGU FIGU FIGU FIGU FIGU FIGU
44. D SCREENS SYSTEM System ENGINEERING Telescope Control SCREENS System EPICS CHANNEL ACCESS Other Control Systems Cassegrain Primary Control Mount Control Secondary Control Rotator Control System EPICS System EPICS System EPICS System EPICS MI Support Mount Hardware M2 Hardware Cassegrain Rotator Hardware Hardware Figure 2 1 Relative Position Of Mount Control System 2 2 DEPENDENCIES Figure 2 2 shows how the MCS is broken up into subsystems and the relationships between those subsystems The shaded blocks indicate the MCS functions which will be implemented with a mixture of hardware and software The software indicated by the circles in Figure 2 2 is to written using VxWorks C and EPICS and run on a Motorola VME 68000 based computer The design of this software is the subject of a separate document reference 2 The remainder of this document presents the proposed design of the MCS hardware indicated by squares in Figure 2 2 ISSUE 3 14 January 1997 PAGE 11 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Channel Access Service 3 Encoder Transducers System Mount Hardware Over Velocity Protection H W Figure 2 2 MCS Internal Dependencies 2 3 GENERAL CONSTRAINTS The MCS will be implemented in a dedicated VME crate located near the mount base e The VME crate control CPU MVME 167 M68040 will run the VxWorks operating system The MCS software will b
45. ESSAGES Message Description Data Byte 3 Reserved Reserved Node Status Reset Flag Checksum Flag App Error Flags App Error Flags Bus Status Tx Error Count Rx Error Count Table 3 15 Control Messages ISSUE 3 14 January 1997 PAGE 65 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Message Description Data Byte Binary inputs read Binary word Binary word Binary inputs 1 i p 1 i p 2 to 16 Group 1 analogue Analogue i p 1 14 bit value Analogue i p 3 14 Analogue i p 4 14 i ps read 14 bit value bit value bit value i ps read 14 bit value bit value bit value i ps read 10 14 bit value 14 bit value 14 bit value Group 4 analogue Analogue i p 13 14 bit Analogue i p Analogue i p 15 Analogue i p 16 i ps read value 14 14 bit value 14 bit value 14 bit value Table 3 16 Input Response Messages From Node to MCS Data Set up analogue Configuration byte Analogue Sample interval _i p read channelstoread units of 1 25 sec 10 Set up binary i p Configuration byte Binary channels to Read interval units read read of 1 25 sec Table 3 17 Output Command Messages From MCS to Node The configuration byte has the format 7 MSB 6514131 2 Read Binary 2 Read Binary Word 1 Poll Auto send Table 3 18 Configuration Byte LSB set means the node will Auto send i e send the sampled values
46. For Move Completion Open Loop This will disable the relevant PA WN While disabled no power is supplied to the counterweight hardware and the weights will remain in their last commanded position This is assured by a fail safe electrically operated brake integral to the drive motor If a limit switch is triggered while the corresponding counterweight is moving then the counterweights subsystem shall stop the drive and report an error to the EPICS software While the axis is still in this limit movement will be allowed only in the direction out of the limit If a command that contradicts this rule is received then the axis is not moved and an error is reported The actual hardware design of the counterweight system has been carried out by the TBEG Details are included here for reference only Figure 3 28 shows a block PAGE 52 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION diagram of the proposed system Table 3 9 details the actual components to be used and Figure 3 29 shows the layout of the hardware Mass position imit switches Open cct Limit reached Short cct Not at limit 10V torque velocity demand 7 Thomson linear EPICS WRAPS system m x Drive Enable 12 bit parallel word Figure 3 28 The counterweight drive system
47. MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION John Wilkes and Chris Carter Madingley Road ISSUE 3 Cambridge CB3 OEZ MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 1 6 Gh Bike 6 1 2 SCOPE is skits see et ie clie teet DOR 6 1 3 DEFINITIONS ACRONYMS AND 5 6 1 4 REFERENCES 8 15 OVERVIEW ounces eme enne Eee eH eui 9 1 5 1 Philosophy Of Critical Design essent eene eene nenne tnnt 9 1 5 2 Format Of An Control System Design Description eese 9 2 DECOMPOSITION DESCRIPTION ceres eese stet than thats tasses suse ta sonata sens tasses suse tatus eta an 11 2 1 SYSTEM PERSPECTIVE heb nee Dee DRE e DF EPOD ER ER Tee RPG 11 PAPAA B SAA BINI B EDLG LEA rer e E ord re EU tee dben codecs unessistupsuseesss 11 2 3 GENERAL CONSTRAINTS itt tiet HER Ir E E birth IEEE e OE 12 2 4 HARDWARE REQUIREMENTS 12 3
48. OL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 3 2 DRIVE CABINETS Before then a prototype of one of the drive cabinets will be built and shipped to France along with as much of the interconnecting cabling that can be realistically made in advance There are two drive cabinets for each telescope and these house the FST 2 amplifiers and associated hardware Each cabinet will contain 6 amplifiers four for azimuth and two for elevation Since only four amplifiers are needed for the elevation axis a single prototype cabinet containing four amplifiers is sufficient for the factory tests All electrical components other than wires and cables will be procured by the IGPO and delivered to the RGO where the prototype cabinet will be wired according to a wiring schedule supplied by IGPO The cabinet shall be delivered to Telas in time for the elevation tests After the elevation tests are finished final designs for the finished telescope drive cabinets will be produced OTHER HARDWARE In addition to the drive cabinet the following hardware shall be shipped to Telas in time for the elevation tests e VME enclosure with at least one PMAC card and relevant accessories e Prototypes of the VCC and TAV circuits e AP C with PMAC Executive software e Relevant test equipment e g power supplies frequency response analyser etc e Miscellaneous tools e g soldering iron screwdrivers etc Miscellaneous electronic supplies e g compo
49. OUS AZIMUTH LIMITS 48 RE 3 26 SCALE DRAWING SHOWING THE POSITION OF THE V ARIOUS ELEVATION LIMITS 49 RE 3 27 TACHO GENERATOR TO GIS 51 3 28 THE COUNTERWEIGHT DRIVE 5 8 00 0000000000010100000000 53 RE 3 29 COUNTERWEIGHT HARDWARE ccce 53 RE 3 30 DYNAMIC MODEL OF THE COUNTERWEIGHT SYSTEM seen 54 RE 3 31 CONFIGURATION OF A SERVICE WRAP 55 RE 3 32 SERVICE WRAP DRIVE HARDWARE SIMULATOR MODEL eee nennen 56 RE 3 33 POSITION OF CABLE WRAP LIMITS 41 1 0 001 101000100 000000000000 57 RE 3 34 LOCATION OF MONITORING SUBSYSTEM NODES cessere ener 60 RE 3 35 ELEMENTS OF THE MONITORING 62 RE 3 36 SECOND ORDER LOW PASS 0 enne enhn 63 RE 3 37 THE DECIMATION PROCESS cssssssccececsesssaeceeececcesseaececececcessaaecesececeessaeaecececsesensaeseeseeenes 65 RE 3 38 THE MONITORING CANBUS SYSTEM 2 1 2 1 42 00200000000000000000000000000000 66 RE 3 39 CONNECTING SENSORS VIA A BREAKOUT BOX ccsessssssececeessssececececsesenseaeeeeeceesenseaeeeeseeenes 68 PAGE 4 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION
50. RTTETS Without rip Tit With Tip Tilt Azimuth 55 23 Elevation Table 3 1 Summary Of Error Predictions Errors Without Tip Tilt Error Budget Errors With Tip Tilt AB o c o o o o 2 6 2 20 40 60 80 100 Zenith Distance Degrees Figure 3 1 On Axis Errors For The Range Of Zenith Distance 3 1 3 3 Interfacing 3 1 3 3 1 Interface With MCS Software The MCS shall receive position demands at 20 Hz from the TCS or a one off position demand from the TCS or MEC The MCS software will cause the telescope to track these positions with a combination of jog commands and a calculated trajectory based upon interpolation See reference 2 for more details ISSUE 3 14 January 1997 PAGE 15 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION HOW TO PASS THE DEMANDS TO PMAC Forty locations shall be defined within PMAC s dual ported RAM twenty for position demands and twenty for associated velocity demands This shall be known as the move argument buffer Every 50 ms the EPICS software will receive a demand from the TCS and calculate the next ten position and velocity demands These are then downloaded to PMAC card using half of the defined block of memory i e 20 locations ten for positions and ten for velocities The PMAC card will run a motion program in PVT mode See reference 4 page 3 125 with the time interval set to 5 ms This program will consist of an i
51. T CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION DAMPER OR PHYSICAL LIMIT The telescope cannot be moved without an active Interlock System so the theory is that the Damper Limit should never be reached However in the event of Interlock System or brake failure these dampers have been designed to stop the telescope at maximum velocity ACTUAL VALUES Table 3 7 contains the data required for the calculation of limit positions Item Azimuth Elevation Max Velocity Vm 2 9 sec 0 75 sec Max Acceleration Am 0 1 9 sec Min Braking Deceleration Ab 2 Damper Positions DP 275 amp 275 Observing Limits OL 270 amp 270 Table 3 7 Main Axis Limits The distance d2 is calculated first using the following equation 2 2 2x Ab Distance 41 is then given by dl DP OL a2 Vsafe can then be calculated from Vsafe 42x Amxdl Then 40 is given by _ 2Vm Vsafe Vm Vsafe Vm 2Am dO All this gives rise to Table 3 8 axis d2 di do azimuth re 0995 1e elevation 0 35 0 15 012 55 Table 3 8 Limit Position Summary Figure 3 25 amp Figure 3 26 show the various limit positions for the azimuth and elevation axes 185e 1849 182 362 364 365 367 67 Dynamic Initial Contact Veloci Velocity Limit Initial Contact With Damper amp PMAC Limit amp PMAC Limit With Damper Fi
52. across CAN at intervals specified by the sampling interval LSB cleared Poll means the node will only send the values of the channel samples when polled by the MCS using Remote Transmit Request Bits 1 and 2 are only relevant to the binary word input channels When set the node will read the appropriate binary input word Channel Select bytes These 16 bits specify which channels are to be read A set bit indicates a channel is to be read either automatically or when polled LSB corresponds to analogue channel 1 and binary input 1 MSB corresponds to analogue channel 16 and binary input 16 Sample Interval byte Specifies the sampling interval in units of 1 25 second Valid values are from 1 sampling interval is 0 04 sec to 255 sampling interval is 10 2 sec Samples required less frequently can be polled for 3 7 3 4 7 CANbus Capacity It is possible to estimate the data transmission capability of the CANbus system as shown below Node Node Node Node Node Node A B D E F MCS crate CANbus Less than 100m Figure 3 38 The Monitoring CANbus system For this configuration a maximum bit rate of 500kbit second is possible Doubling the bus length to 200m would result in a halving of the bit rate to 250kbit sec this is an option if nodes have to be widely separated Work carried out by the PCS group suggests that for greatest reliability and low sensitivi
53. be implemented as a subroutine A flowchart for this is shown in Figure 3 16 ISSUE 3 14 January 1997 PAGE 33 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION READ AND NORMALISE ANALOGUE INPUTS S amp C SIGNAL NEAR CALCULATE UNCOMPENSATED INTERPOLATION I ATAN2 S C COMPEN SATION NULL OFFSET SWITCHED ON 2 OS 0 APPLY HEYDEMANN COMPENSATION TOS amp C CALCULATE COMPENSATED INTERPOLATION CI ATAN2 CS CC CALCULATE OFFSET OS ENSURE OFFSET IN THE RANGE 180 CALCULATE POSITION P PC 1 5 360 40 PC PITCH COUNTS Figure 3 15 Flowchart For Interpolation And Compensation Algorithms PAGE 34 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION START x ABS SIN COS x ABS COS SIN YES 0 OFFSET STOP Figure 3 16 Flowchart For Arctangent Function OUTPUT SCALING Calculating position last block of flowchart in Figure 3 15 must be done carefully so that the result is scaled correctly The required output scaling is 5 milli arcseconds per bit for each axis this means a linear scaling of Azimuth 0 116355283 um for 9 6 m diameter Elevation 0 096962736 um for 8 m diameter ISSUE 3 14 January 1997 PAGE 35 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The pitch count is a 24 bit number the highest significant 19 bits is the current count of 40 um pitche
54. ch be changed in the future any change in input signal level can be simply accommodated The encoding of the fiducial signal is carried out by an EPROM and a diode matrix Although not the simplest scheme it is flexible in that changing the fiducial coding simply requires a reprogrammed device The encoded outputs are then converted into differential signals before being transmitted over twisted pair to a receiver circuit at the PMAC card At the crate end a differential line receiver converts the signals back to TTL levels before passing them to the PMAC input The circuit diagram of the generic fiducial encoder for both azimuth and elevation axes can be found in the supplementary documentation FIDUCIAL INTERFACE The fiducial encoding system now no longer requires an Accessory 14 card in order to interface to PMAC instead the data is read through the JOPT J5 connector on PMAC once it has been received by the differential line receiver circuit This receiver circuit also generates a fiducial passed signal that is used to trigger PMAC PAGE 28 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION to record the fiducial value This is derived from a logical OR of the received fiducial data lines and is sent to the HMFL1 input on PMAC 3 2 3 2 2 Encoder Interface The various devices required to provide the encoding system shall be interfaced to the relevant PMAC card as shown in
55. ches mounted on the inside of the cable wrap so that they are actuated by the wrap bridge rather than the topple brackets This is unfortunately not possible due to the mechanical design of the wrap The current solution is to compare the topple bracket position with the coarse absolute encoder that is to be mounted on the azimuth axis if these two don t agree then an interlocked condition occurs This is a function of the GIS since the MCS does not read this absolute encoder This is not entirely desirable since the absolute encoder output cannot be made satisfactorily fail safe and there would still be no physical stop if the topple brackets were tampered with MOVEMENT IN THE 0 15 ACCESS POSITION For top end ring changes and mirror cleaning it is required to lower the OSS into the 0 15 range normal elevation limit is 15 While in this range azimuth movement must be limited to a small range or damage to the OSS or surrounding structure is possible To allow the elevation axis to move below the 15 damper limit the striker bracket is designed to rotate to provide a new Interlock System limit and damper limit at 0 There are micro switches on the rotating bracket that are read by the MCS and the GIS so both can determine its position While in the 0 15 mode the MCS will e Use modified values for the MCS limit and the MCS pre limit on the elevation axis in order to allow computer controlled movement below 15 e Use modified va
56. ction Response CDR Critical Design Review CPU Central Processing Unit CRCS Cassegrain Rotator Control System CSDD Control System Design Description CSS Control System Simulator CW CounterWeights DAC Digital to Analogue Converter DC Direct Current DHS Data Handling System DPRAM Dual Ported Random Access Memory DRAM Dynamic Random Access Memory DSP Digital Signal Processor dSPACE digital Signal Processing And Control Engineering German company supplying the HWILS system DXF Drawing eXchange Format File format used by AutoCAD ORCAD etc e g for example PAGE 6 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION ECC Error Checking and Correction ECS Enclosure Control System EMI Electro Magnetic Interference EPICS Experimental Physics and Industrial Control System EPLD Erasable Programmable Logic Device etc et cetera and the rest and so on FCS Functional Control System FDE Friction Driven Encoder FEA Finite Element Analysis FST 2 A two board FAST amplifier by Kollmorgen Inland Motor FAST Flexible Amplifier Servo Technology GIS Gemini Interlock System formerly ISS Interlock Safety System GPO Gemini Project Office GPS Global Positioning System GUI Graphical User Interface H W Hardware HWILS Hardware In the Loop Simulation Hz Hertz Le that is I F Interface IO Input Output IP Input ICD Interface Control Document ICS Instrument Control System IDD
57. depend upon a number of things e The total length of the tape should be divided into a number of equal regions and each region should use its own local compensation parameters This allows compensation for local patches of dirt and scratches For each region a lower limit on the number of samples per compensation run is arbitrarily set at 20 e The number of regions depends upon how much data we are prepared to store on the host and the amount of time allowed to do a compensation run Each region will require the storage of five 24 bit fixed point values A space of 200 Kbytes will allow about 13650 regions A reasonable limit for compensation time is one hour per axis e The samples must be equally spaced across the 0 360 sub pitch range Calculations and experiments see reference 9 indicate that with these constraints compensation will be effective The Heydemann parameters are calculated off line by solving sets of over defined simultaneous equations using a least squares fitting technique see references 9 13 amp 14 3 2 3 3 3 Virtual Encoder The virtual encoder for each of the axes is required to generate a discrete value corresponding to the axis absolute position as summarised in Section 3 2 2 In order to do this the virtual encoder implements a series of algorithms taking as inputs the encoder counts from axis tape encoders the primary encoding system friction driven encoders and in the case of the eleva
58. dicates the z incremental number of tape pitches All three of these values are available as H outputs from PMAC s encoder table This routine takes these three values for each head and produces a single 24 bit integer which is the incremental position of the tape head The resolution of this output is 5 milliarcseconds which means the H resolution is slightly different for each axis azimuth elevation To be precise the resolution is 0 116355283 microns for azimuth and 0 096962736 microns for elevation based upon nominal 9 6 m and 8 m diameters for Az and El respectively Note that these values for resolution will allow roll over of the 24 bit word but this will be dealt with by the virtual encoder code Documented spaces have been included in the code below to allow the virtual z encoder code to be added to this file F KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKKKKKKKKKKS KR UK e oes e e KK KK KR e UK KR So OK e kk eK gk sk GE KK Kk EK Ke eK eoe sk e eR Sk Re e OR KK IIE e RO AER TE TREK AACR SYMBOL DEFINITIONS FOR INTERPOLATION AND COMPENSATION KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKKKKKKKKKKS ONE EQU S7FFFFF STORE RO EQU 710 Storage address for RO STORE R1 EQU 771 Storage address for R1 STORE R2 EQU 772 Storage address for R2 STORE R3 EQU 57
59. ducer connections via two 37 way D type connectors The sensors and transducers are not connected directly to the node box itself but are routed via a breakout box as shown in Figure 3 39 This enables a node box to be easily removed without having to break a large number of connections Monitoring amp Metrology Node box 2 x 37 way D type connectors Connector breakout box Figure 3 39 Connecting sensors via a breakout box PAGE 68 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The breakout box will accept two 37 way D type connectors and make analogue and digital sensor connections available via PCB mounted 45 entry screw terminals ISSUE 3 14 January 1997 PAGE 69 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 4 INTERFACE DESCRIPTION 4 1 INTERNAL INTERFACES The internal wiring of the VME enclosure is detailed in reference 7 4 2 EXTERNAL INTERFACES 4 2 1 Hardware Interfaces All of the external hardware interfaces are made through a series of D type and BNC connectors mounted on the back panel of the VME enclosure These are specified in detail in reference 7 4 2 2 Software Interfaces The following tables describe the EPICS process variables that will form the interface between t
60. e implemented using the EPICS database system e There will be a two headed Sun Workstation not provided by the MCS work package permanently connected to the mount control VME crate via ethernet in order to control the system from the enclosure floor A light tight cover will be provided for this console so as not to impact the required enclosure darkness during observing e The serial port of the VME CPU will be monitored in order to provide diagnostics during system initialisation This will be done with a dedicated VT100 type serial terminal or more likely with a terminal emulator running on the sun workstation e The MCS WP is only responsible for specifying the cabling to from the MCS IOC along with the specific connectors to be used It is not a requirement of the MCS WP to provide length and routing information this is the responsibility of the Gemini Systems Group e No signal conditioning or transducers are to be provided by the MCS WP The Monitoring subsystem is simply an ADC function e The power amplifiers drives and encoders for the service wrap ups are to be provided by a separate WP e The hardware used shall be based on the work products of the Standard Instrument Controller by Andrew Johnson RGO see reference 5 e There shall be an additional two spare slots within the VME card frame for the possible addition of a high speed reflective memory bus 2 4 HARDWARE REQUIREMENTS The Gemini Mount Control System is based aro
61. ed Elevation X0759sec 20 200Hz 20 Analogue Outs PMAC 2 velocities El Current Position Current Elevation position 0 4 92 73 so Hz Analogue In PMAC 2 El Current Velocity Current Elevation velocity t 0 75 sec lt 50 Hz Analogue In PMAC 2 El Position Error Elevation position error 90 90 02 lt 50 Hz Analogue In PMAC 2 El Motor Status Motor servo status bits 24 bits lt 50 Hz Status PMAC 2 El CS Status Co ordinate System status 24 bits lt 50 Hz Status PMAC 2 bits El Motor Currents Elevation motor currents 0 50 Amps lt 50 Hz 4 Analogue Ins XYCOM 566 1 El Tachos Elevation tachogenerator o p 1009 sec lt 50Hz 4 Analogue Ins XYCOM 566 2 Table 4 2 The MCS Software Interface to the Mount Main Servos PAGE 70 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Az VE Set Up Az VE Output Az Tape Encoders Az FDE Az Last Fiducial El VE Set Up El VE Output Tape Encoders El FDE El Last Fiducial El Tilt Switch El Translation El Striker Bracket Function Az Inner Topple Bracket Az Outer Topple Bracket Description Azimuth VE Set Up word Azimuth VE output Raw tape head outputs 48 bits 48 bits FDE incremental encoder readout The last azimuth fiducial passed Position of inner topple bracket Position of outer topple bracket Elevation VE Set Up
62. en in reference 3 3 1 2 Purpose The following requirements shall be met by the MCS hardware The elevation and azimuth servo systems shall accept position information from the encoder subsystem at the servo rate It shall be the responsibility of the hardware to close the servo loops The hardware of the servo subsystem shall be implemented using a digital signal processor programmed with suitable servo algorithms The sampling frequency of the servos the servo rate shall be sufficient to allow the servo algorithms to be effective This is expected to be at least 1 kHz The servo subsystem shall implement a scheme to reduce the available torque demand to the motors in the event or possibility of drive slippage The servo subsystem shall provide a demand signal proportional to the required velocity to each of the drive amplifiers at the servo rate The drive amplifiers are Inland FST 2 there is one per motor and each implements a velocity loop using feedback from the tacho generators An interface shall be provided so that the drive current of each motor can be monitored by the software at some rate up to 50 Hz An interface shall be provided so that the information from each tacho generator can be monitored by the MCS software at some rate up to 50 Hz There is no longer a requirement to monitor at the servo rate since the tacho loops are to be closed in the power amplifiers 3 1 3 Function 3 1 3 1 Implem
63. en the tacho generators and the GIS Vr should be set so that an interlock condition is indicated to the GIS when the axis velocity is just outside the designed maximum Nominal values for Vr are 3V 3 s for azimuth and 1V 1 s for elevation The precise value of Vr will be adjustable its setting will depend upon the exact diameter of the drive wheel A circuit diagram showing the implementation of this interface is show in reference 20 A 15V power supply will be required Ideally this should be supplied by the GIS however this may not be possible so the supply for the MCS velocity combining circuit and tacho averaging circuit can be used Tacho Processing Electronics Figure 3 27 Tacho Generator to GIS Connection COUNTERWEIGHTS SUBSYSTEM 3 5 1 Introduction Although the telescope is designed to be well balanced in any of the upper end and instrument cluster configurations it is anticipated that small trim weights will be ISSUE 3 14 January 1997 PAGE 51 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION required to balance the telescope These weights are remotely controlled and remotely monitored The system is comprised of two axial and two cross axial balance devices mounted to the outside face of the centre section assembly Axial is defined here as along the axis of the OSS and cross axial is perpendicular to the OSS axis and to the elevation rotation axis The counterweight u
64. ence of any other formal definition the operation of the GIS from the point of view of the MCS is described in this section Figure 3 22 shows the inputs and outputs of to and from the GIS For each axis the GIS implements a logical AND function When all the inputs are in the safe condition then the axis drives are enabled by the following sequence Power to FST 2 amplifiers is switched on FST 2 lines are pulled low Power to brakes is switched on This removes the brakes e Assert the drive condition signal If one or more of the inputs change to the unsafe or interlocked condition then the axis drives are disabled by the following sequence Dis assert drive condition signal Power to brakes is switched off This applies the brakes FST 2 Enable lines are pulled high Power to FST 2 amplifiers is switched off Note that it is not absolutely necessary to switch the power to the FST 2 amplifiers on and off since the power stages are adequately isolated by pulling the Enable lines high PAGE 44 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Other Interlocking Limit Emergency Locking Pin Devices Switches Stops Switches INPUTS Amp Lines Drive Condition OUTPUTS Enable Lines FST 2 POWER AMPLIFIERS Figure 3 22
65. entation The hardware chosen to implement the position loop controller is the PMAC VME card provided by Delta Tau One of these cards will be used for each axis and it will PAGE 14 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION implement the encoder see Section 3 2 and servo algorithms The set up of these cards is quite complex and is described in detail in reference 11 Note that the default setting for the servo rate in PMAC is approximately 2 kHz Unless a reduction in servo rate is required by another system e g the encoders and the reduction is proved by simulation to have no effect upon servo performance the sampling frequency will be not be changed from the default value 3 1 3 2 Servo Specification The error budget after tip tilt correction agreed with the IGPO is 20 milli arcseconds RMS on axis at zenith This increases with zenith distance Z according to the following equation E 002 x 1 2 Where is the permitted error on axis arcseconds The on axis error is calculated from individual axis errors by using the following equation E il E xsin Z Where Eris total on axis error E is total azimuth error Eg is total elevation error Reference 8 uses the non linear model to estimate the performance of the servos with and without tip tilt correction The results are summarised in Table 3 1 and Figure 3 1 BSYEUTE
66. eto o sa vant 44 3 3 32 GIS Functionality EH RODEO I OD 44 e E eH D aea 45 3 4 PROTECTION HARDWARBE eren Eoee IAS RE rE EEE TIN aE raia 50 3 4 T Introducti nz EAN AE E EEE A 50 QuE2 PUT OSE Ss A sd eie E AE 51 3 4 3 EWRCIOW o SNR tovs isis as ce bs eso cise 51 3 5 COUNTERWEIGHTS SUBSYSTEM 51 3 5 1 Introduction EE E 51 2 292 PULP OSC a n ette Ie eerie tote iit eee EE 52 309 3 FUN CELON Is 52 3 6 SERVICE WRAP UPS SUBSY STEM 0 020200000 04 00000 nnns esent tanus see 54 IBIFOdUGlOn i ib t ht tot c trea i vtr esten de IAS 3 0 2 PUT DOSE e dS ERE ER Re e UR e ed RR teeny 3 073 EUR CIO o ee te Bs e tite ivt toten esed ce iso TE oce 3 6 3 1 Interface To Hardware uses oar estare 3 6 3 2 Famts RH e i EH RE 3 7 MONITORING SUBSYSTEM etre rette ertet ve tror 3 V A Introduction caue nadie atendiendo cde 3 7 1 1 Monitoring and Metrol gy hee er c a Hee eer eH eh eR D PR RR HIRE
67. ffect on tracking performance Development of suitable engineering tests logging and calibration procedures e After integration on site system identification using part of HWIL hardware and subsequent analysis can adjust and improve model Controller development can be undertaken without access to telescope The hardware simulator consists of the following products ISSUE 3 14 January 1997 PAGE 21 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION HARDWARE 1x DS1003 192 5320 40 Processor Board dSPACE 1x DS2002 32 Channel ADC dSPACE 1 x DS4001 Digital I O and Timer Board dSPACE 1 x P C DELL GXMT 5120 SOFTWARE Matlab MATHWORKS Simulink MATHWORKS The Real Time Workshop MATHWORKS Real Time Interface to Simulink C Code Generator dSPACE TRACE Data Acquisition Software dSPACE COCKPIT Graphical Instrument Panel dSPACE Texas Instruments C Compiler for C40 TI The hardware simulator models the main axis hardware from power amp input to virtual encoder output In order to interface the HWILS to PMAC digital word interfaces to PMAC will be required PMAC 14 Figure 3 6 shows how the hardware simulator connects to the MCS for servo development Hardware In The Loop Simulator DS4001 DS2002 ADC DS1003 DSP DIGITAL I O Figure 3 6 HWILS Configuration 3 1 3 4 2 Test Rig As part of the MCS design a friction drive test rig has been
68. gure 3 25 Scale Drawing Showing The Position Of The Various Azimuth Limits PAGE 48 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION EN Fully Compressed 90 4 Initial Contact With Damper 90 05 IS Limit 90 02 Dynamic Velocity Limit amp PMAC Limit 90 bservation Limit 15 bservation Limit 14 9 Dynamic Velocity Limit amp PMAC Limit 14 85 IS Limit 14 5 Initial Contact With Damper 12 Fully Compressed Dynamic Velocity Limit amp PMAC Limit IS Limit Initial Contact With Damper Fully Compressed Figure 3 26 Scale Drawing Showing The Position Of The Various Elevation Limits 3 3 3 3 2 Azimuth Axis Special Functionality There are two reasons why the interlocking of the azimuth axis may depart from the common functionality as described in Section 3 3 3 3 1 1 Someone tampers with the Azimuth Topple Brackets ISSUE 3 14 January 1997 PAGE 49 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 2 Movement in the 0 15 access position TAMPERING WITH THE AZIMUTH TOPPLE BRACKETS It is the azimuth topple brackets that actuate the Interlock System limit micro switches and the damper limits If the brackets are illegally moved into the incorrect position then the azimuth axis is left without any hardware protection electrical or mechanical To partially solve this problem it was originally planned to have additional micro swit
69. hardware shall be completely defined by circuit diagrams wiring schedules layouts and packaging There is some exception to this with regard to the tape encoder interface electronics since this was a late addition to the MCS work package the actual circuit diagrams of the head interfaces have not yet been defined 1 5 2 Format Of An Control System Design Description The format of this document is based loosely upon reference 17 modified to take into account that this document is mainly concerned with the description of hardware rather than software ISSUE 3 14 January 1997 PAGE 9 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The design of the control system is broken up into a number of subsystems and each has a set of attributes The values given to these attributes form the design of the control system The following attributes have been identified as relevant to a control system design e Name e Purpose Or Requirements e Subordinates Can the subsystem be broken down into still smaller subsystems Internal Dependencies Relationships with other subsystems e Internal Interfaces How the subsystem communicates with other subsystems External Dependencies Or Resources External systems that are required by the subsystem e External Interfaces e Function Or Design Detail What the system does and how it does it Each subsequent section of this document presents a design view of the MCS cont
70. he hardware and the software of the MCS Description Frequency EPICS Records VME Board Interlocks Azimuth Axis 2 Binary Outs TIL Status of Azimuth Axis 0 1 2 Binary Ins TIL Function Azimuth Drive Enable Azimuth Drive Condition Elevation Drive Enable Interlocks Elevation Axis 0 1 2 Binary Outs TIL Elevation Drive Condition Status of Elevation Axis 2 Binary Ins TIL Table 4 1 The MCS Software Interface to the GIS Function Description Range Frequency EPICS Records VME Board Az Demand Positions Demanded Azimuth positions 182 20 Analogue Outs PMAC 1 362 Az Demand Demanded Azimuth 2 0 sec 20 200 Hz 20 Analogue Outs PMAC 1 Velocities velocities Az Current Position Current Azimuth position 188 25 Analogue In PMAC 1 367 67 Az Current Velocity Current Azimuth velocity 2 0 Analogue In PMAC 1 Az Position Error Azimuth position error 549 67 Analogue In PMAC 1 550 25 Az Motor Status Motor servo status bits 24 bits PMAC 1 Az CS Status Co ordinate System status 24 bits Status PMAC 1 bits Az Motor Currents Azimuth motor currents 0 50 Amps 8 Analogue Ins XYCOM 566 1 Az Tachos Azimuth tachogenerator o p 100 sec 8 Analogue Ins XYCOM 566 2 El Demand Positions Demanded Elevation 2 739 20 200Hz 20 Analogue Outs PMAC2 positions 90 02 El Demand Velocities Demand
71. his message rate could be handled easily even over a very much slower longer bus CASE 2 Six nodes on a 500kbit sec bus Data required to be transmitted is considered to be made up of 25Hz 25Hz Total Readings sec on bus Table 3 20 Data Rates 25 Hz Sampling With the same assumptions as in Case 1 bj 2850x107 304950 Assuming a transmission rate T across the bus of 500kbit sec allows the bus loading L to be calculated as Quantity O P Rate Readings sec 16 6 96 25Hz ISSUE 3 14 January 1997 PAGE 67 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION porq 299999 166 T 500 x 10 L 61 This is within limits for CANbus which can theoretically operate at close to 100 bus load If polling for each message is added the bus load rises to L 105 This clearly exceeds bus capacity and therefore it is not possible to run six nodes on a 500kbit sec bus at a constant 25Hz message rate Five nodes could be run at this rate however 3 7 3 5 Enclosure amp Connections 3 7 3 5 1 Housing Each node will be housed in an ABS box of a similar type to that used by the Axial Support nodes It will have a conductive coating applied internally to reduce EMI 3 7 3 5 2 Physical Connections The following physical connections are made to the node CANbus screened twisted pair 120VAC single phase mains power 12V external DC in if required Sensor and trans
72. ial positions wrt associated TBD mm lt 50 Hz 3 Analogue Ins PMAC 3 axis Service wrap motor drive currents lt 50 Hz 4 Analogue Ins XYCOM 566 1 Table 4 5 The MCS Software Interface to the service wrap hardware os d Records Analogue Monitors Sensors connected via the Monitoring 10 V 1 Hz 16 Analogue CAN subsystem s analogue inputs Insper Node VIPC 610 Binary Monitors Sensors connected via the Monitoring 0 1 1 Hz 16 Binary Ins CAN subsystem s binary inputs per Node VIPC 610 Word Monitors Sensors connected via the Monitoring 8 bits 1 Hz 2 MultiBit Ins CAN subsystem s digital word inputs per Node VIPC 610 Table 4 6 The MCS Software Interface to the monitoring hardware Function Description Frequency EPICS VME Board Records Time Health Holds the health of the time system 0 2 1 Hz Bancomm 635 7 Time Simulation Is time real or simulated Variable Binary Out Bancomm 635 7 Access to Time Library Subroutine Calls to timeLib N A Variable genSub Bancomm 635 7 Time Log Logged messages about time N A Variable DHS History Bancomm 635 7 system Table 4 7 The MCS Software Interface to the Gemini Time System ISSUE 3 14 January 1997 PAGE 71 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 5 APPENDICES 5 1 APPENDIX A PMAC User Written DSP Code 5 1 1 Heidenhain Interpolation And Compensation Code
73. ilter operation 3 7 3 4 5 Node Commands Table 3 14 shows a list of the main functions that should be controllable via CANbus messages Most of these would be minor modifications of existing PCS Axial Node commands c Poneto Duro lom ipesonp g nrw x Read analogue input s Control the reading of analogue input channels Includes setting sampling frequency which channels to read etc Control the reading of binary input channels Includes setting the read interval which inputs to read etc Read binary word input s Control the reading of binary word input channels Includes setting the read interval Reset Reset the node to a known state Engineering functions Various engineering level status and test functions Table 3 14 Node Commands Read binary inputs s 3 7 3 4 6 CANbus Message Data Format CANbus communications shall follow the protocols established by the PCS See reference 16 for more details In summary e The 11 bit CANbus message identifier will be split into 6 bits to specify the node address and 5 bits to specify individual messages This means that 63 node addresses are available and 32 message types per address e The 32 messages will be divided into Operational and Engineering groups with Operational messages having the highest priority Sampled data will be transferred in the data bytes associated with these messages OPERATIONAL GROUP M
74. ine here JMP FIDU CHECK E ALL_HEADS Differs for Azimuth amp Elevation BCLR 20 X SETUP Echo Algorithm bits in SETUP BSET 19 X SETUP BSET 18 X SETUP ALL_HEADS routine here JMP FIDU_CHECK Iransfer lower 24 bits UPDATE LOW Differs for Azimuth amp Elevation of VE OUT in A10 into RESULT MOVE A0 X RESULT RTS 010 011 ISSUE 3 14 January 1997 PAGE 79 of 79
75. inear velocity of 2 mm s The direction is determined by the value read in 1 Enable axis Issue a HOME command to PMAC Wait for a home complete status bit to become true Read fiducial code from M19 Disable axis Add absolute fiducial position to actual motor position register D 67 UA dace After initialisation the fiducial signals shall be continuously monitored by the virtual encoder code Every time a fiducial mark is passed the virtual encoder output and the fiducial number will be stored by the virtual encoder and a flag set to inform the MCS software For more details see section 3 2 3 3 3 and the relevant parts of reference 2 3 2 3 3 2 Interpolation And Compensation BASIC ALGORITHM To provide a position value from each tape encoder head we need to interpolate between pitches using the analogue sine and cosine signals The following algorithm will do this Normalise the sinusoidal signals so that they lie between 1 and 1 e Take the arc tangent of the sinusoidal amplitude using both the sine and cosine values to obtain an unambiguous angle A in the range 0 360 e Calculate Position using Position PrchCoun 46 x 40um PitchCounts is taken from the counter that counts tape pitches The flowchart in Figure 3 15 shows how the interpolation and compensation algorithm can be implemented Because the arctangent function is not available in Motorola 56000 assembly language it must
76. ing ISSUE 3 14 January 1997 PAGE 19 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION MOTOR x CHASIS Note that in addition the cable types defined in this diagram e The cables between tachos and the tacho averaging circuit shall be STPs shield grounded at the circuit end e The cable between PMAC and the velocity command combining circuit shall be a STP shield grounded at circuit end Motor Phase A B C FST 2 No x Command Hall A B C 5V 0V Encoder Prog Monitor 0V A B C 5V OV Motor Over Temp Motor Over Temp Ret Tacho Tacho Ret Enable Amp OK Amp Enabled OV Connector on cabinet interface panel Auto Config 0V Single Phase 120Vac Via lockout switches activated by GIS All cable screens should be connected to OV Details of the interface with the GIS should be defined by the GIS documentation This connector will not normally be mated It is for engineering purposes only Figure 3 5 Detailed Wiring Of FST 2 Amplifiers FST 2 PROGRAMMABLE PARAMETERS Table 3 2 lists the required values of the FST 2 programmable parameters After these parameters have been programmed via a RS232 link a SAVO command should be issued to save the parameters to non volatile memory For more details on each parameter see reference 22 LOP Parameter Value Purpose ANL 0 Analogue input enabled CCP 32422 Current Com
77. itical design phase of the Gemini mount control system work package Its purpose is to formally describe the proposed design of the hardware and software that implement the mount control system functions The audience of this document is The CDR reviewing panel Individuals working on subsequent phases of the project Individuals working on connected Gemini work packages ISSUE For Review 25 October 1995 15 December 1995 2 For Review 25 November 1996 14 January 1997 Table 1 1 Issue Record 1 2 SCOPE The mount control system provides the basic ability to slew and track the telescope It also interfaces to a number of secondary systems that are required to provide services The MCS is intended as an engineering interface to the mount and its subsystems it is intended that the telescope could be run from here for initial set up and engineering work It is not intended as an interface where the telescope would meet specification 1 3 DEFINITIONS ACRONYMS AND ABBREVIATIONS The following is a list of abbreviations used in this document and related MCS documents A amp G Acquisition and Guiding ABS Polyacrylonitrile butadiene styrene ADC Analogue to Digital Converter ADR Assembly Design Review ATP Acceptance Test Plan This consists of a Test Procedure Specification as defined in IEEE Std 829 1983 BNC British Naval Connector CAD Command Action Directive CAN Controller Area Network CAR Command A
78. le Note that this low level of slippage does not warrant a removal of torque The reduction of torque requirement is meant to apply when the drive wheels are slipping uncontrollably wheel spinning due to some fault situation and this will be achieved by monitoring tacho and encoder signals in the software e Over the test period 3 months the drive rollers have worn quite badly This wear occurred mainly on one side of the roller see Figure 3 8 It is expected that this is due to an imbalance of the loads on the motor shaft non uniformity of the line contact and misalignment of the roller wheel interface Also the ratio of hardness between the aluminium roller and the steel wheel is quite large 98 and 150 Brinell respectively Note that the equivalent hardnesses on the telescope are 42 45 and 48 5 55 5 Rockwell C for roller and track respectively Despite this it is still a worry that the roller can get damaged so quickly ISSUE 3 14 January 1997 PAGE 23 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Area Of Damage More Load Exists On This Side Drive Roller Figure 3 8 Drive Roller Damage FURTHER TESTS Command Passing And Data Logging The test rig will play an important r le in the development of the MCS software interface The move argument buffer and data logging ideas will be tested out on the test rig drive system Comprehensive Slippage Tests Although extensive slipping
79. lection of DXF files containing miscellaneous MCS circuits including e FIDUCIAL DXF OVP_CCT DXF EL_TAV DXF AZ_TAV DXF EL_VCC DXF AZ_VCC DXF 21 Monitoring and Metrology Subsystem Circuit Diagrams MM_ DXF a collection of DXF files containing the monitoring system circuits 22 Kollmorgen Inland Motor FAST Drive Flexible Amplifier Servo Technology User s Manual MN 223 REV Preliminary 2 3 95 23 PCSJFM10 C167 Node Control Board Hardware Manual John Maclean 24 87 GP 1002 0000 Altitude Cable Wrap Drawing Set 25 87 GP 1001 0000 Azimuth Cable Wrap Drawing Set 1 5 OVERVIEW 1 5 1 Philosophy Of Critical Design In its truest form a critical design of a given product should be sufficient information to allow the product to be built and operated to fulfil all given requirements In the case of the software components of a product this information normally is the finished product It is therefore sensible to split a product into two parts hardware and software and treat each differently for the purposes of a critical design This has been done in the MCS SOFTWARE This includes the EPICS software see reference 2 and the lower level software items such as the PMAC user written DSP code and programmable set up The critical design of the software components shall include completed algorithms of how the software shall be implemented and a subset of the actual code HARDWARE All elements of
80. ls can be brought to these bus stations to be interfaced to the Monitoring system The following sections show the sort of input that is to be monitored 3 7 1 1 Monitoring and Metrology In addition to the standard encoders used to determine the current position of the telescope networks of various different types of sensors may be distributed along the mount structure Examples are Temperature sensors Strain gauges Load cells Accelerometers Tilt meters Displacement sensors Note that the translation sensors used to provide corrections to the main elevation encoder are read directly by PMAC not through the monitoring subsystem 3 7 1 2 Electrical Systems Interface In order to meet the 2 down time requirement it is necessary to monitor the status of critical electrical systems The intent is to prevent problems by a system of periodic monitoring and preventative maintenance In this system critical electrical systems could be monitored for voltage level high frequency content and for AC systems conformance with frequency stability specifications In order to be effective such a system must establish a standard means of interfacing to any electrical system This standard could be used by fabricators in order to make their systems compatible 3 7 2 Purpose The Monitoring subsystem shall be capable of accepting analogue signals in the range 10 V The Monitoring subsystem shall be capable of accepting binary signals i
81. lues for the MCS limit and the MCS pre limit on the azimuth axis in order to allow computer controlled movement only between the safe ranges Note that this safe range may map to two different ranges within the total 540 of azimuth movement depending upon its position relative to the cable wrap e Use a lower value for maximum velocity for both azimuth and elevation axes In order that the Interlock System provides adequate protection while in the 0 15 access position there should be an additional pair of limit switches at a suitable distance outside the azimuth safe range MCS limits These switches should be activated by fixed striker brackets rather than topple brackets While in the 0 15 mode the Interlock System will use the output from these micro switches for a modified Interlock System limit The MCS limit the MCS pre limit and the Interlock System limit though triggered at different positions will have the same effect as described above 3 4 PROTECTION HARDWARE 3 4 1 Introduction A number of subsystems require active protection in order to guarantee safety One of the most important of these is the over velocity protection system for the telescope PAGE 50 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The system must actively check that the velocities of the different axes are within safe limits and take appropriate action if they are not The logic of this is to be implemented
82. n OUT They are selected via the MODE bits in SETUP Note that 2 FULL and EL FULL are for the azimuth and elevation axes respectively also that the TH values referred to are the compensated encoder values generated by the interpolation and compensation routine PAGE 40 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Start Read SETUP word Extract m value Start Start Echo Echo Algorithm Algorithm to SETUP to SETUP Read FDE Read SETUP word value VE FDE Y Read compensated tape head m value VE THm Extract n value Y Extract n value Store in VE OUT Read compensated tape head n value VE THn Store lower 24 bits of VE OUT in RESULT Read compensated tape head n value VE THn Store VE THn in VE OUT Stop Figure 3 19 Combining Algorithms Common To Both Axes Store lower 24 bits of VE OUT in RESULT Stop ISSUE 3 14 January 1997 PAGE 41 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Start Echo Algorithm to SETUP Read compensated tape head 1 value VE 1 Add compensated tape head 2 value VE TH2 Add compensated tape head 3 value VE TH3 Add
83. n TTL format The Monitoring subsystem shall be capable of accepting digital words of a generic format and handshaking method It is the responsibility of the individual sensors to produce outputs in one of the standard formats The ADCs contained in the Monitoring subsystem shall have a resolution at least 12 bits An interface shall be provided so that EPICS software can monitor all the measured quantities at a maximum rate of 1 Hz 3 7 3 Function The Monitoring subsystem is based on a system of node boxes nodes that can be placed around the telescope structure linked to each other and the MCS by a CANbus network Each node can read sensors and transducers connected to it convert them into a discrete form and interface them to the MCS crate via CANbus At the MCS a VIPC610 CANbus to VME interface card enables the received data to be passed to EPICS ISSUE 3 14 January 1997 PAGE 59 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Initially the subsystem will consist of six node boxes per telescope five of which will be placed on the structure as shown in Figure 3 34 More nodes may be added to the system at a later date if required Note that no nodes have been placed above the level of the mirror to assist with the requirement of keeping heat sources away from the optical path Any sensors on the top end of the OSS will have to interface to the nearest node sited below mirror level
84. nary inputs in two ways as 8 bit parallel data words and as 16 individual binary bits A node has two 8 bit parallel inputs and 16 individual bit inputs all are opto isolated before being read into the C167 via the I O ports The opto isolators are best driven by a current source capable of supplying at least 5mA 3 7 3 3 4 Ancillary Circuitry ADC VOLTAGE REFERENCE A stable voltage reference for the ADC is provided by a REF 02CP It will be possible to adjust the reference voltage by suitably choosing two fixed high stability resistors POWER SUPPLY CIRCUITRY The node is powered from 120VAC single phase mains by a single linear power supply module that supplies 12V It is also possible to power the node externally ISSUE 3 14 January 1997 PAGE 63 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION from a 12V DC supply via a three pin connector a diode array ensures the internal PSU is not damaged when this is connected Linear regulators on the motherboard supply 5V where required 3 7 3 4 Node Software amp CANbus Issues The software for the Monitoring and Metrology nodes is simply a subset of that already developed and reviewed for the PCS Axial Node box Commands required are essentially those needed to control reading inputs transferring data and housekeeping tasks For details on the PCS software see reference 15 3 7 3 4 1 System Sampling Specification The following is a workable
85. ndom Access Memory RGO Royal Greenwich Observatory RMS Root Mean Square RPM Revolutions Per Minute RTD Resistance Temperature Detector Rx Receive S W Software SAD Status and Alarms Database SDD Software Design Description SDR System Design Review SIC Standard Instrument Controller WP that described generic Gemini hardware See reference 5 SIR Status Information Record SISO Single Input Single Output SMCS Secondary Mirror Control System SRS Software Requirements Specification STP Screened Twisted Pair SW Service Wraps TAI International Atomic Time In French TAV Tacho AVeraging circuit TBD To Be Determined TBEG Telescope Building and Enclosure Group TCS Telescope Control System TF Transfer Function TI Texas Instruments TTL Transistor Transistor Logic Tx Transmit VAT Value Added Tax VCC Velocity Command Combining circuit VE Virtual Encoder VME Versa Module Eurocard The meaning is obsolete WP Work Package WPD Work Product Document wrt with respect to 1 4 REFERENCES 1 2 nm 1 ON tA ccc Nr oO REV C G0036 Mount Control System Design Review Report Mount Control System Software Design Description Andy Foster t 9414257 GEM00067 Telescope Requirements Document Delta Tau Data Systems PMAC User s Manual amp Software Reference Version 1 13 PLUS addendum Versions V1 14 and V1 15 and relevant accessory
86. nents wires connectors etc TEST OBJECTIVES The following objectives have been set for the month of elevation tests e Get drive correctly wired up e Create a makeshift GIS interface Unfortunately the GIS is still in a very early stage of design and will not be available for the factory tests The GIS functionality will be implemented manually e Get velocity loop working each amplifier has to be set up correctly e Get Position loop working e Perform frequency response tests Results can be used to optimise velocity and position loops e Perform tracking error tests ENCODER SUBSYSTEM 3 2 1 Introduction The encoders for the elevation and azimuth axes are a combination of mechanical switches magnetic position sensors tape and friction driven incremental encoders The intent of the encoder subsystem is to hide the details of the physical encoding scheme and provide a device independent virtual encoder to higher level systems The MCS will contain two virtual encoders one each for the azimuth and elevation axes It is also a requirement of the MCS work package to procure the tape encoders Two systems were considered and a decision was made using a series of the tests and a tender exercise The chosen system is to be supplied by Heidenhain for more details see references 9 amp 10 3 2 2 Purpose The encoder subsystem shall receive the following inputs from the mount hardware ISSUE 3 14 January 1997 P
87. nfinite loop of twenty move commands each one taking its position and velocity arguments from the move argument buffer The buffer needs to be twice as big as each download i e enough for twenty move commands so that EPICS can be writing to one half while PMAC is reading from the other A suitable PMAC motion program is shown in reference 11 Note that at present it is not clear whether both position and velocity demands are required or whether the interpolated rate of 200 Hz is necessary However the method proposed provides the capability to update both position and velocity demands at a rate of 200 Hz Changing the interpolation rate will affect the size of the move argument buffer and the PVT time interval HOW TO SYNCHRONISE PMAC TO TAI The motion program within PMAC can be started from an external hardware signal The software shall set up the time card so that a suitable signal occurs exactly at the desired start time Tests have shown that PMAC motion programs can be started in this way with a time error of less than 1 ms PMAC will remain in sync by using a reference signal also from the time card as a time base see reference 4 pages 3 42 amp 3 171 HOW TO PROVIDE A DATA LOGGING FUNCTION To help with problem diagnosis and system analysis it is extremely useful to be able to log values of important parameters e g servo error raw encoder values etc at a specified frequency for later inspection It is proposed t
88. ngent function Sine Cosine les For Sine Cosine is used Use of finds the unambiguous angle between 0 360 degrees the sine and are given as arguments pointed to by ATAN ARG in Y ATAN ARG Upon completion B accumulator is cleared S than one result 45 degrees greater than one the two expansions The Arguments should be stored at the The Sine argument in X ATAN ARG and the the result is stored in the A p accumulator in standard 56000 fractional notation The result is a positive zero represents 0 degrees and 1 represents 360 degrees Upon H For the expansion about 0 is used result 45 degrees allows greater accuracy from the expansion about one quite low order series Third order series are used Even so the accuracy is H not brilliant and the error can be almost 0 5 degrees in places This is quite sufficient for the present application A Higher order series could be P implemented by adding the extra code a loop could easily be formed to allow cbhiss d The A B X Y and RO registers will be modified by this routine No stack levels are used qu NEARB ER RARE ERE A BARA BB RR EA RB BK A RR RR NUR BA BEA BR BA a RA RA RR KR RA RR RK BB RRR Riss ATAN2 MOVE Y ATAN_ARG B Get Absolute data into the ABS B X ATAN_ARG A accumulators Sine gt A and ABS A B XO Cosine gt B CMP B A 0 5 Y0
89. nits are located on the same side of the OSS as the elevation disks For a fuller description of the OSS counter balance assembly see reference 3 3 5 2 Purpose The counterweights subsystem shall receive a Move command containing the desired position for each of the balance devices from the MCS software The counterweights subsystem shall receive a position signal at a suitable servo rate for each of the balance devices from the counterweight hardware The counterweight subsystem shall provide a demand signal proportional to the required torque or velocity to each of the drive amplifiers at a suitable servo rate Since the failure of a counterweight drive is not a safety issue there is no requirement to interface with the GIS Instead the counterweights subsystem shall read the hardware limit switches and act on them accordingly An interface shall be provided so that the following quantities can be monitored by the MCS software at some fixed rate up to a maximum of 50 Hz The demand signal as sent to the power amplifiers Actual Position 3 5 3 Function The counterweight drives shall be implemented using a PMAC card One PMAC will cope with both counterweight drives and service wrap drives The detailed set up of this card is described in reference 12 In order to move a counterweight the software will have to issue the following commands Close Loop This enables the relevant PA Issue Move Command Wait
90. nt Ka 1 5 A V Amplifier gain l Estimated Values Table 3 12 Service Wrap Model Parameters PAGE 56 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 3 6 3 2 Limits Figure 3 33 shows schematically the interface between the main axis and an associated wrap Three levels of limit can be identified 1 MCS Wrap Limit Triggered from the LVDT reading within the MCS 2 Interlock System Wrap Limit Triggered by micro switches read by the Interlock System 3 Drag Plates Physical plates that provide a mechanical link between the axis and wrap so that the wrap can be dragged around Drag Plates s WRAP Int rlock Interlock System System Limit MCS Limit Limit Figure 3 33 Position Of Cable Wrap Limits The distance d3 between the two drag plates is limited by the span of the LVDT and the amount of give in the cables The MCS shall disable both the service wrap drive and the associated main drive upon reaching a MCS wrap limit The effect of hitting an Interlock System limit will be defined by the GIS Table 3 13 shows the various limit conditions with required actions suggested recovery methods and possible causes The safety of the outcome and the effects of the fault persisting are also shown ISSUE 3 14 January 1997 PAGE 57 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION C
91. o make use of PMAC s data gather function and dual ported RAM in order to provide the data logging function see reference 4 page 3 220 This is capable of logging up to 24 parameters at any frequency up to the servo rate However for real time data logging the performance will depend upon e The amount of DPRAM and processor time taken up by the servo and virtual encoder functions How fast the VME processor can read and store contents of the DPRAM In order to make efficient use of memory resources the parameters to be logged and the logging frequency will be user definable 3 1 3 3 2 Drive Configuration Although multiple motors are used to drive the telescope eight for azimuth and four for elevation each axis is controlled using a single position loop and single velocity loop The single position loop is closed on the relevant PMAC card Each power amplifier closes a velocity loop with the feedback coming from the average of all the tacho signals as long as all the velocity controllers are the same this is effectively a single velocity loop A block diagram of this scheme is shown in Figure 3 2 A reduced version of this scheme two motors only has been successfully employed on the friction driven test rig PAGE 16 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Velocity Command From GIS 1 Velocity Individual Velocity Individual Motor Commands 8 4 Signals 8 4
92. ollowing forms e Incremental Pulses Quadrature or Up Down e Digital word e Analogue voltage 10 V Incremental pulses input are preferred since the other two methods require extra hardware and extra slots in the VME card frame There is no longer a requirement to receive an input from the FDE load cell This is now a function of the Monitoring amp Metrology subsystem The encoder subsystem shall receive a configuration command from the MCS software The encoder subsystem shall implement one of a variety of algorithms in order to produce an output These algorithms shall include but not be limited to e The average of the outputs of all four azimuth tape encoder heads e The average of the outputs of any two azimuth tape encoder heads e The average of the outputs of both elevation tape encoder heads with correction made for axis translation e the output of any one elevation head with correction made for axis translation e The output of any one of the tape encoder heads e The output of the FDE It shall be possible to easily change and extend the algorithms to include new encoders PAGE 26 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION There may also be systematic corrections to apply to certain encoder inputs probably only the tape encoders since friction driven encoder errors will not in general be repeatable The encoder subsystem shall apply these in real time The
93. on of the FDE divided by 32 For the tape pitch counting channels each bit represents 1 25 um on tape or 65 milli arcseconds on elevation and 54 milli arcseconds on azimuth ADC Channels Output of the encoder table is a signed 21 bit integer sign extended to 24 bits representing 5V input to the ACC28 3 2 3 2 3 Software Interface To PMAC It is necessary for the PMAC card to interface with the EPICS database running on the VME processor card in the MCS crate PMAC commands and data can be passed using the VME mailbox registers In essence the operation will be similar to controlling the PMAC card from a PC using the PMAC Executive program Fast data transfer will be carried out using the dual ported RAM interface Data logging will be implemented using PMAC s data gather function as described in Section 3 1 3 3 1 PAGE 30 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 3 2 3 3 Operation The recent choice of the Heidenhain optical tape as the primary encoding system for the Gemini telescope has clarified the role of the virtual encoder Each PMAC axis card will now contain two distinct sections of user written code the first being tape head interpolation program the second the virtual encoder as described in previous documents When the virtual encoder reads its compensated tape head values it is doing so from the output of this compensation code The two sec
94. ondition Action Recover Possible Cause Outcome Persists MCS wrap MCS will disable Successfully re Loss of wrap Safe Initialisation fails with limit reached wrap drive AND initialise the drive or cable Fatal Error limit main drive wrap servo jam before main servo is enabled Wrap drive Safe Initialisation fails with runaway Fatal Error limit Possibility Of hitting GIS wrap Defined by the GIS Defined by the Loss of wrap Safe GIS wrap limit will not limit reached Recommend that GIS drive or cable clear The fault must be while in MCS main axis is Recommend that jam and MCS fixed before the main mode disabled the GIS wrap not reading axis can be re enabled software limit correctly limitis cleared before the main axis is allowed to re enable Wrap drive Wrap servo still GIS wrap limit will not runaway and enabled motor clear The fault must be MCS not will stall against fixed before the main reading drag plate which axis can be re enabled software limit has become a Damage to motor and correctly hard stop since amplifiers is possible main axis is unless suitable current disabled limits are enforced within the amplifier GIS wrap Defined by the GIS Defined by the Repeated re Wrap servo still GIS wrap limit will not limit reached Recommend GIS initialisation enabled motor clear The fault must be while not in nothing since main Recommend that
95. p q a and G are the Heydemann parameters and Sa and Ca represent sin a and cos a respectively The 1 2 and ch2c values are scaled as signed 21 bit integer sign extended to 24 bits representing 5V input to the ACC28 This can also be thought of as 24 bit fraction notation with the binary point after the fourth most significant bit and a range of 8 In this case the 5V input range is represented by a number in the range 1 If Heydemann parameters p q and c are stored in this same format and Sa is stored in standard 56000 fractional notation then the compensation can be applied with the following algorithm 1 Move into accumulator Subtract p from accumulator Move accumulator into chic Move ch2 into accumulator Subtract q from accumulator Multiply accumulator by G Shift accumulator left three times Multiply Sa and and add to accumulator SONAR PAGE 36 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 9 Multiply accumulator by 10 Shift accumulator left three times 11 Move accumulator into ch2c CALIBRATION MODE In order to calculate the relevant Heydemann compensation parameters a set of quadrature i e sine and cosine values need to be acquired This is done by moving the axis at a constant velocity and logging the relevant ADC channels at the correct rate The actual velocity and logging rate will
96. pensation 2 20 65 0 Communications mode CPL 6638 6776 Current loop pole CPN 20001 32767 Current loop gain DGT 0 Digital command 1 Enable H W enable signal 170 24576t Encoder Scaling 2048 pulses rev with 4x interpolation HLL 0 Hall Code Phasing ILM 100 Current Limit IND 0 Index Location Not used Loop rate 1 for tachometer velocity mode PAGE 20 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION MOD 3 Loop Mode Tachometer velocity mode 0 Monitor select Current monitor 10000 Motor temperature fault 0 Position loop compensation Not used 0 Position loop damping gain Not used 0 Phase advance Not used 0 Phase offset 12 30 Auto phasing Parameters 1 2 A for 7 5 s 0 Position integral gain Not used 0 Reset position feedback Not used 0 0 Position loop pole Not used 0 Position loop proportional gain Not used SIN TOF DD Vj do VV VV vz z U SIIII IIJIO 0 Disable auto retry mode 100 100 20 27 RMS current limiting 6390 12780 Absolute current limit 10 4 A 20 8 A for az el 0 Commutation mode Trapezoidal on start up switching to sinusoidal after first hall code transition 0 Torque offset Ot Velocity loop compensation OT Velocity loop in
97. r is reported The desire is to fix distance d1 such that even if the axis is moving with full velocity the MCS can decelerate to zero velocity before reaching s2 It can be shown using the data given below that d1 for azimuth is 20 and 41 for elevation is 5 625 These values are obviously too large so an area of reduced maximum velocity is required around each limit This is achieved by adding the MCS pre limit switch as shown in Figure 3 24 PAGE 46 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Moving Actuator To MCS ToMCS Interlock Physical Only Only System Only Stop Figure 3 24 Position Of MCS Pre Limit Switch s0 The MCS pre limit is triggered by s0 While in this limit the MCS will continue to operate normally except that the velocity limit is reduced to some value Vsafe If the axis velocity exceeds Vsafe upon entering the limit then the MCS will ramp down the demand to the drives at maximum deceleration until the velocity has reached Vsafe The value of Vsafe and dO will depend upon the desired value chosen for 41 An alternative way to reduce the value of d1 is to implement a dynamic velocity limit around the end of the ranges At any time the velocity limit for an axis is given by Limit Vm Limit 42Amx S Whichever is the smallest Vm is the axis velocity limit Am is the axis acceleration limit and S is the distance from the nearest limit This
98. red via one of the MCS ADC boards Figure 3 31 shows a schematic of how the MCS fits in with the service wrap hardware Figure 3 31 Configuration Of A Service Wrap Drive Note that the azimuth wrap may consist of two motors in order to provide the correct amount of torque ISSUE 3 14 January 1997 PAGE 55 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The actual hardware required to implement the service wraps is the responsibility of the TBEG Table 3 11 details the actual components to be used this is included for reference only The following interfaces between this hardware and the MCS are defined INPUTS to hardware e 10 signal for each wrap that represents the torque OR velocity required from the motor OUTPUTS from hardware e 5 signal from each wrap indicating the absolute relative position between the wrap and the axis that it is tracking e 10 signal from each wrap indicating the current flowing in the drive motor e Two sets signals from each wrap drive indicating end of travel position These shall be read and acted upon by the GIS so the format of these signals is dependant upon GIS requirements Description Supplier _Indurex brushed gear motor with integral 100 1 gearbox and brake KR16M4CH BRK KR16 100 Kollmorgen Servo amplifier 48VDC bus 10V control input 360 W KXA 48 Kollmorgen LVDT 5 V DC output Unspecified Unspecified Table 3 11
99. rol system Each design view defines of a subset of the subsystem attributes Section 2 presents the Decomposition Description design view This outlines how the MCS is organised internally and how it fits in with the rest of the Gemini Control System The Name Subordinates and Internal External Dependency attributes are defined in the Decomposition Description Section 3 presents the Detail Description design view For each subsystem the requirements as specified in the MCS PRS see reference 1 are restated The detail of how these requirements are to be met is then explained Section 4 presents the Interface Description design view This presents the hardware and software Internal and External Interfaces PAGE 10 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION 2 DECOMPOSITION DESCRIPTION This section describes the role of the MCS within the Gemini control system and the dependencies upon external systems Also described is the partition of the MCS into a number of functional subsystems 2 1 SYSTEM PERSPECTIVE The MCS is part of the Gemini Telescopes Project It is responsible for the interface between the telescope computer system and the mount hardware It exists alongside a number of other control systems that carry out a similar task in other areas of the telescope Figure 2 1 shows in block diagram form how the MCS fits into the overall Gemini control system OCS GUI AN
100. rs with units of one bit equals 5 milli arcseconds both axes 3 RESULT is the lower 24 bits of VE OUT 3 2 3 3 1 Initialisation When the Mount Control System is rebooted the telescope will have to move to locate a fiducial in order to set the Encoder subsystem to the correct absolute position Upon reboot the azimuth axis assumes an absolute position of zero and the elevation axis assumes an absolute position of 45 PAGE 32 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Note that the encoding system does not automatically initialise following a reboot it will always wait until it receives an initialisation command from the TCS or the MEC Further the MCS software will not allow a TCS move command until an initialisation has been performed The fiducial signals enter the MCS through the PMAC card as described in Section 3 2 3 2 1 PMAC s standard software homing routine is utilised to reference the encoder system to absolute position The MCS software EPICS would have to implement the following as part of the encoder initialisation procedure 1 Read range switch this is the topple brackets absolute encoder for azimuth and a tilt switch for elevation The status of the range switch indicates which way the axis must move so as not to hit a limit switch 2 Set the velocity of the homing move in I variable 1223 This is 17 2 for azimuth and 20 8 for elevation i e a l
101. s The lower 5 bits are always zero due to the x32 carried out by the encoder table PigPi7Pi6Pis PigPi3Pi2Pi1 PioPoPsP7 PePsP4P3 1 00 0000 The interpolation and offset values are unsigned 23 bit numbers representing 0 40 um i e all zeros represents zero um and all ones represent 40 um 0122121120 Tiolislizlie 11511411311 111110151 17161514 131 111 If the pitch count value is shifted left four times the interpolation value shifted right 14 times then the two can be added together to leave a 24 bit integer with one bit representing 0 078125 um i e 40 2 Thus the combined result is PyaPi3P12P11 PioPoPgP7 PePsPaP3 P2P1Pol22 12112011911 IijIiclisli All that remains is to multiply by one of the following factors to give the required output scaling Azimuth x 0 078125 0 116 0 671434916 Elevation x 0 078125 0 097 0 805721899 So to calculate final position 1 Add interpolation and offset to get a corrected interpolation 2 Shift corrected interpolation 14 bits right 3 Shift pitch count 4 bits left 4 Add shifted pitch count to shifted corrected interpolation 5 Multiply the result by relevant axis scaling factor APPLYING COMPENSATION PARAMETERS If chl and ch2 denote the uncompensated quadrature signals then the compensated signals chic and ch2c are given by the following equations see references 13 amp 14 chlc chl p chlcx Sa G ch2 ch2c Where
102. sed to supply the node via a 3 pin connector This is provided against a situation where a node may be required to be mounted where mains power is unavailable It is not intended that this should be the primary method of powering the nodes 3 7 3 2 Functional Description The Monitoring node design is based on that of the PCS Axial Support node the Monitoring nodes having considerably less functionality The main differences are in the type of peripheral circuitry the nodes described here have analogue and binary inputs only and no outputs The software required is a subset of that already developed for the Axial nodes Full circuit diagrams of the Monitoring and Metrology node are available in reference 21 A block diagram of the Monitoring node is shown in Figure 3 35 ISSUE 3 14 January 1997 PAGE 61 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Low pass filter H of 16 gt N CAN In Differential i p amp 16 channel MUX A D converter Siemens C167 microcontroller based CAN Out Node Control Board Opto isolated binary inputs ADC voltage reference 1 of 16 A l id Single bit i p 3 E 8 bit parallel word i p Microcontroller Ports E E 8 bit parallel word i p e Linear power supply 4 12V 5V 120VAC External DC power 4 12V Figure
103. specification defining how the node is to sample its inputs The node will for each analogue input channel band limit the analogue input signals to 10Hz sample the resulting signal at 25Hz process the sampled data by decimation averaging of the sample sequences store this data internally output this data over CANbus either automatically or when requested by the MCS Note that the node will sample all the analogue input channels at 25Hz and decimate them all to the same sampling interval It will not be possible to automatically sample individual channels at different frequencies 3 7 3 4 2 Analogue Channel Sampling Each of the sixteen analogue inputs is passed through a second order anti aliasing analogue filter that attenuates signal frequencies above 2 by 40dB decade where is the sampling frequency The A D converter then samples the resulting signal at least in this case Fs is 25Hz This process produces a stream of samples at intervals of 1 seconds To allow maximum flexibility these samples can be decimated i e the sample sequence may be filtered and re sampled at a lower sampling frequency than originally used Averaging of the sampled data will also be supported in this case the node will average a specified number of samples and store the result This method could be used when the analogue input is known to be either changing extremely slowly or is constant and is a simple type of sample decimation 3
104. t some fixed rate up to a maximum of 50 Hz Slow virtual encoder output 32 bit parallel word 4x tape head output 32 bit parallel words FDE output 32 bit parallel word An indication of fiducial position Position of the Azimuth Topple brackets Elevation displacement transducer readings For the requirements of the Heidenhain encoding system itself see reference 10 3 2 3 Function 3 2 3 1 Implementation The computation required by each encoding system azimuth and elevation will be implemented in the relevant PMAC card as user written DSP code running in motor 1 For more details on the set up of these cards see reference 11 The relevant parameters required by these computational routines will be supplied by the EPICS database see reference 2 ISSUE 3 14 January 1997 PAGE 27 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION The interface circuitry required by the different systems will be produced on printed circuit boards and housed in boxes mounted in or around the VME enclosure 3 2 3 2 Interfacing Precise details of how the encoder hardware interfaces to the PMAC cards is shown in reference 11 3 2 3 2 1 Fiducial Interface The encoder subsystem has to receive individual binary signals from a total of 94 separate electromagnetic fiducial switches 72 on the azimuth axis and 22 on the elevation axis Each switch provides a 12V output pulse at a maximum activating distance of
105. tegral gain 0 Velocity offset 32767 01 Velocity loop pole lt lt lt lt lt lt v U U 812121012 100 Velocity loop proportional gain 4200 16384 256 Velocity scaling Table 3 2 FST 2 Programmable Parameters NOTES Default values T To be tuned Suggested starting values are given t Exact values calculated by auto configure process Expected values given 3 1 3 4 Further Servo Development 3 1 3 4 1 Hardware Simulator The actual telescope will obviously not be available during controller development A hardware in the loop simulation system will be used to imitate the telescope hardware A HWILS system takes a mathematical model of the system plant and simulates it in real time This simulation is then interfaced to the controller enabling development away from the real physical plant The hardware for the MCS HWILS system is based upon the products of the German company dSPACE and a reduced version of the Gemini non linear servo model by Mike Burns see reference 6 The hardware has been installed and the model has been successfully downloaded The system will be used for the following tasks e Testing and developing correct operation of controller during start up slewing pointing and tracking modes e Optimisation of sampling rates e Identification of failure modes and the development of correct recovery behaviour e Simulation of encoder non linearities and e
106. ters will be modified by this routine No stack levels H KKK KKK KKK ck ckckckckckckckckckckckckckckckockckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckckck o APPLY COMP OVE X1 B OVE X R3 YO SUB YO B OVE B X1 OVE X0 B SUB YO B OVE B XO PY YO X0 B REP 3 ASL B AC Y0 X1 B OVE B XO PY YO X0 B REP 3 ASL B OVE B XO APPLY_COMP_STOP RTS END Xr R3 T YO X 3 Xi t YO X 3 5 1 2 Virtual Encoder Code The following is the current partial code implementation for the Gemini virtual encoder It is written in Motorola DSP56000 assembly language When compiled this code occupies 163 locations of P memory 489 bytes VE MAIN ASM Current development code for the Gemini telescope Mount Control System Virtual Encoder 56000 DSP running on Written by C Carter Last modified 7th November 1996 Royal Greenwich Observatory UK Variable Definitions Move Sine to B Get P parameter Calculate Sine Comp and get q parameter Move cosine to B Calculate intermediate result and get G parameter te intermediate result Sa parameter Then the result by shifting Calcula and get correct te intermediate result 1 Ca parameter Calcula and get Calculate final result for Cosine Comp and correct by shifting Store Cosine Comp in X0 ISSUE 3
107. the MCS of the Gemini Telescopes are the subjects of different work packages the interaction between the two systems must be well defined This section attempts such a definition and is divided into two parts The first part deals with the electrical interface between the two systems The second part describes the desired by the MCS action of the Interlock System in the event of limit condition occurring in one of the axes controlled by the MCS 3 3 3 1 Electrical Interface Each MCS axis azimuth and elevation has an interface to the Interlock System This consists of two dual TTL signals DRIVE ENABLE MCS gt Interlock System an Interlock Event The Interlock System treats this as a lock out signal just as it would a signal from a limit switch or locking pin micro switch This gives the MCS the capability of controlling the power to the brakes and power amplifiers DRIVE CONDITION Interlock System gt MCS an Interlock Demand This signal indicates to the MCS whether the associated drive is interlocked out The MCS will have no knowledge of what is causing the interlock the reason should be available via the Channel Access interface to the Interlock System NOTE These signals shall interface to the GIS via the standard Gemini TTL I O board the XYCOM XVME 240 Digital Input Output Module 3 3 3 2 GIS Functionality It is not the responsibility of the MCS work package to define the operation of the GIS However in the abs
108. tial encoder from each drive azimuth wrap and two elevation wraps indicating the position relative to the associated main axis The service wrap ups subsystem shall provide a demand signal at a suitable servo rate proportional to the required torque or velocity to each of the drive amplifiers azimuth wrap and two elevation wraps Since the failure of a service wrap is not a safety issue there is no requirement for the MCS to interface with the GIS Instead the service wrap ups subsystem shall have internal software limits and act on them accordingly Note that the hardware should contain limit switches which should be read exclusively by the GIS to enable suitable operation during hand paddle mode An interface shall be provided so that the following quantities can be monitored by the software at some fixed rate up to a maximum of 50 Hz The demand signal as sent to the power amplifiers The differential encoder read back Motor drive current 3 6 3 Function The service wrap drives shall be implemented using a PMAC card One PMAC will cope with both service wrap and counterweight drives The detailed set up of this card is described in reference 12 3 6 3 1 Interface To Hardware Each service wrap will utilise one PMAC channel which will be permanently enabled and run as a regulator system with a constant position demand of zero Motor feedback will be via an LVDT and PMAC Accessory 28 The motor current shall be monito
109. tion axis linear translation sensors The tape encoder values are not used directly by the virtual encoder they have interpolation and compensation applied to them beforehand see Section 3 2 3 3 2 In normal operation the virtual encoder is continuously generating a 48 bit output word corresponding to absolute axis position The virtual encoder will also have a diagnostics mode the details of which are to be determined The most likely scenario would involve EPICS commanding the virtual encoder to write diagnostic data to an array of memory locations in the PMAC address space which could then be monitored Data written in this way may include e PMAC status bits e flags used by the virtual encoder or compensation routine e virtual encoder or compensation routine internal variables SET UP WORD The SETUP word is a 24 bit word in PMAC memory space at X 1300 EPICS can cause the virtual encoder to enter certain modes and determine its status by reading and writing to this location ISSUE 3 14 January 1997 PAGE 37 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Echo Mode Echo Algorithm Fiducial Init Done Passed Bit 23 Bit 22 Bit 21 Bit 20 Bit 19 Bit 18 Bit 17 Bit 16 Undefined Bit 15 Bit 14 Biti3 Bit12 Bitii Bitio Bito Bit 8 _ Algorithm Mode Bit 7 Bit 6 Bt5 Bit4 Bt2 Biti Bit 0 How the virtual encoder interprets the vario
110. tions of code have been developed independently the tape interpolation code as a result of encoder evaluation work Sections 3 2 3 3 2 and 3 2 3 3 3 describe the operation of the tape interpolation and compensation algorithm and the virtual encoder respectively The actual DSP assembly language is shown in APPENDIX A The variable space used by these algorithms is part of PMAC s memory normally reserved for P variables and is defined fully in reference 11 Figure 3 12 helps to clarify the situation Figure 3 13 and Figure 3 14 go into more detail for each axis Tape head Tape Heads electronics PMAC Encoder E Tape compensation table algorithm input hardware Other encoders Axis absolute position PMAC card available to EPICS Figure 3 12 Relative Position Of User Written DSP Code ISSUE 3 14 January 1997 PAGE 31 of 79 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION puc Scale amp VE FDE X 1201 Extend I D 1304 M THI VE_THI gerry TH VE THI loup deer HE TD VE Figure 3 14 Elevation User Written DSP Code NOTES 1 Outputs of Interpolation and Compensation routines TH1 TH4 are 24 bit integers with units of one bit equals 5 milli arcseconds both axes 2 Outputs of Virtual Encoder VE are 48 bit intege
111. ty to improper bus termination PAGE 66 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION bus rates of either 250kbit s or 125kbit s be used However dropping to lower rates will prevent data transmission at the fastest sampling rates Fortunately changing bus rate does not impact on the node hardware design The following cases illustrate typical data transmission situations across CANbus CASE 1 Six nodes on a 500kbit sec bus Data required to be transmitted is considered to be made up of Source Quantit O P Rate Readings sec 1Hz 96 channels per node 16 analogue input 16 6 96 inputs per node One 16 bit binary word per node 1 6 6 6 Two 8 bit binary word 2 6 12 1Hz 12 Total Readings sec on bus 114 Source channels per node inputs per node node Table 3 19 Data Rates 1 Hz Sampling To calculate the number of bits that these readings represent we assume the worst case that each message i e each reading has the maximum length a CAN message is allowed 107 bits Then the no of bits to be transmitted is b 114x107 12198 Assuming a transmission rate T across the bus of 500kbit sec allows the bus loading L to be calculated as L 2m x100 12195 x 100 T 500 x 10 L 24 If the MCS has to poll each node for its reading this figure rises by 71 giving L 41 These bus loads are extremely low T
112. und one 21 slot VME crate that will be installed at the telescope mount base two crates are being prepared for the Hawaiian and Chilean telescopes known as Gemini North and Gemini South respectively The table below details the VME cards required to populate one crate PAGE 12 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Description Motorola processor card Xycom TTL I O card Delta Tau PMAC VME card Delta Tau A D Converter Accessory Board Delta Tau I O Expansion board Option 3 Port A Port B 24 latched high true TTL inputs CANbus Industry pack Runs the VxWorks operating system and hosts the EPICS environment Provides digital I O capability Implements servo control of the telescope axes and other subsystems 1 azimuth 1 elevation 1 counterweights amp service wraps per telescope Provides 4 channels of A D conversion Used with the Heidenhain tape system and the LVDTs Provides digital I O capabilities Used for fiducial and absolute encoder interfaces 1 per PMAC card Provides a CANbus interface for Width Slots Occupied per card Part Number MVME167 33B 33MHz MC68040 with 16MB ECC XVME 240 PMAC VME 8 axis 60MHz dual ported RAM ACC14V Option 3 VIPC 610 plus TIP carrier card plus one TIP the Monitoring subsystem 810 810 Industry pack
113. us bit patterns is shown below Mode 220000000 4 14 4 4 NEC CREE e ONE CT 17 0 Normal operation 5 0 1 Diagnostic mode Table 3 4 Virtual Encoder Mode Bits s LL Al Jorithm Bit Bits FDEoly only Tape N only Azimuth only Tape heads 1 Tape M amp N only 4 All heads ojojo a 2 o n 1 Elevation only Tape heads 1 2 plus translation sensors 1 4 1 0 0 sensors 1 2 or 3 4 Elevation only Tape head N plus associated translation Table 3 5 Virtual Encoder Algorithm Bits Head n These are binary values representing the number of the tape head s to be used in the virtual encoder algorithm For azimuth m and n may be 1 2 3 or 4 For elevation they may be 1 or 2 Figure 3 17 shows which tape heads correspond to which head numbers for the azimuth axes In the elevation case tape head 1 is on the left side of the elevation mounting and tape head 2 is on the right when viewed from a position facing the access stairway It may help to refer to Figure 3 34 on page 60 Azimuth axis plan view Tape Head 1 Tape Head 2 Tape Head 4 Figure 3 17 Azimuth tape head numbering PAGE 38 of 79 14 January 1997 ISSUE 3 MOUNT CONTROL SYSTEM CONTROL SYSTEM DESIGN DESCRIPTION Start

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