Virtual Motor with Synthesized Encoder
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1. so directly because parallel feedback does not support this feature We create a virtual Motor 4 using the fourth channel of an Acc 24E2A analog axis board setting this channel up for pulse and direction output with this output wrapped back internally to the channel s encoder counter as if we were driving an open loop stepper motor The counter is used both for simulated feedback and to create position compare outputs This virtual motor is slaved to the actual position of Motor 1 using Turbo PMAC s automatic position following feature Note that it will often be possible to use the pulse and direction output and encoder counter of the same channel as used for the amplifier output if analog and the flags limits etc because these features of the channel are not used for the actual servo function If this approach were taken in this example we would use Servo IC 2 Channel 1 instead of Servo IC 2 Channel 4 as we do below This example assumes that all clock frequencies servo phase PFM are at their factory default values Explanations for the virtual motor setup can be found in the Pulse and Direction section of the Basic Motor Setup chapter of the Turbo PMAC User Manual Encoder Conversion Table Setup T8000 SF78C00 Read Acc 14E Port A I8001 313000 Filtered 3 19 bits 13 from bit 0 T8002 256 Max legit change 256 LSBs per cycle Pacis 18003 8 for Motor 2 amp 3 feedback I8009 SC78218 Servo IC 2 En2. Application Note Nov 2004 Virtual Motor with Synthesized Encoder Sometimes a user will desire to create a virtual motor on Turbo PMAC with a pulse and direction output a synthesized encoder value or both This is easy to do with a PMAC2 style Servo IC in a Turbo PMAC system as is found on any UMAC axis board in QMAC or on any board level Turbo PMAC2 There are several reasons that a user may want to do this In one case the high speed position capture and compare circuits for PMAC2 encoder counters are not available with other types of feedback A user with for example high resolution parallel format feedback from an interferometer on a real motor can create a virtual motor encoder that uses Turbo PMAC s position following feature to track the position of the real motor create pulse and direction signals that feed the Servo IC channel s hardware encoder counter and use the values of the counter to generate highly accurate position compare outputs Alternately we may want to generate position compare pulses based on a virtual vector path In this case the position of this virtual motor can be derived from the vector path of the real axes as in the example Virtual Vector Master Position In this example we have a UMAC system with 19 bit parallel feedback for Motor 1 coming in on Port A of an Acc 14E board with base address 078C00 We want to generate position compare outputs based on the actual position of Motor 1 but cannot do
3. c 4 no extension Setup for C2 Chan 4 for PFM Output Wrapped into Counter 17203 2258 Default clock freq s for IC 2 17246 3 IC2 Chan 4 PFM and analog outputs 17240 8 Tie IC2 Ch4 PFM to encoder counter Setup for Virtual Motor 4 using IC 2 Chan 4 I1400 1 Activate Motor 4 calculations I1401 0 No commutation I1402 7821C IC2 Chan 4 Pulse Freq output 1403 18009 Use IC 2 Enc 4 counter for pos feedback T404 1I8009 Use IC 2 Enc 4 counter for vel feedback T405 I8002 Use ACC 14E Port A pos as master T406 1 Enable position following 1407 96 1407 1408 is gear ratio I1408 96 1 1 gear ratio Virtual Motor with Synthesized Encoder 1 Nov 2004 Application Note T430 700 Simulated loop Kp for 25Hz nat freq 1431 0 No derivative gain needed T432 15050 Vel FF gain for no tracking error T433 10000 Int gain to assure no steady state error T434 0 Int gain on while moving 1435 0 No accel FF gain T469 16384 Set max freq output The virtual Motor 4 can always be active and following Motor 1 s position feedback We can then use the encoder counter that provides Motor 4 s simulated feedback to generate position compare outputs In this next section we set up the virtual motor s compare output for a 5 count width every 20 counts Substitutions and Definitions define SIC2Ch4EncPos M401 SIC2Ch4EncPos gt Y 078219 0 24 8S define SIC2Ch4CompPosA m408 STC2Ch4CompPosA gt Y 07821F 0 24 S defi
4. ne SIC2Ch4CompPosB m409 STC2Ch4CompPosB gt X 07821E 0 24 S define SIC2Ch4CompiIncr M410 STC2Ch4CompIncr gt Y 07821F 0 24 S define SIC2Ch4CompInitSta M411 SIC2Ch4CompInitSta gt Y 07821D 11 define SIC2Ch4CompInitEna M412 SIC2Ch4CompInitSta gt Y 07821D 12 A t i A A T Raw encoder counter position Compare A reg Compare B reg Compare auto increment reg Compare initial state Compare initialize enable Program Code Section to Set up Compare Circuitry This can be in a motion or PLC program SIC2Ch4CompPosA SIC2Ch4EncPos 10 SIC2Ch4CompPosB SIC2Ch4EncPos 5 SIC2Ch4CompIncr 20 SIC2Ch4CompInitSta 0 SIC2Ch4CompInitEna 1 T 10 counts from present 5 counts from present 20 count auto increment Initialize to 0 Enable initialization Virtual Motor with Synthesized Encoder
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