Delta Tau Geo Brick, User Manual

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Geo Brick Drive User Manual
Appendix D 294
Maximum “Commanded” Closed-Loop Velocity
In closed-loop mode, the commanded (desired) velocity register is limited to:
In terms of motor counts per millisecond, the maximum commanded velocity will be the same with or
without shifting but since the number of counts per revolution “unshifted” is 32 times less, then the
maximum programmable velocity is 32 times greater.
Example: Take a 37-bit absolute serial rotary encoder (25-bit Singleturn, 12-bit Multiturn) and its
equivalent linear scale (e.g.10 nm resolution). The maximum ‘commanded” closed-loop velocity (Ixx16,
Ixx22) setting programmable in Turbo PMAC is:
786,432 [counts/msec] with Ixx08=1
8,192 [counts/msec] with Ixx08=96
With Ixx08=1
Rotary [rpm] Linear [mm/sec]
=MaxCmdVel*60000/SF =MaxCmdVel*1000/SF
Technique 1/3 (5-bit Shift) 1,406 7,864
Technique 2 (no Shift) 45,000 251,658
With Ixx08=96
Rotary [rpm] Linear [mm/sec]
=MaxCmdVel*60000/SF =MaxCmdVel*1000/SF
Technique 1/3 (5-bit Shift) 14.645 81.916
Technique 2 (no Shift) 468.667 2621.334
Note
Notice the lower programmable closed-loop velocity settings with
techniques 1 and 3 (5-bit shift), associated with the default position
scale factor Ixx08 of 96.
Maximum Motor Travel
In Jog mode, the rollover is handled gracefully by PMAC and jogging can be virtually performed forever.
However, this can be problematic when running a motion program indefinitely in incremental mode
where the 48-bit fixed motor register can roll over much sooner than the 48-bit floating axis register.
Note
Absolute Serial Encoders with limited multi-turn range normally do
roll over way before the motor position register in Turbo PMAC does
(i.e. 12-bit multi-turn is 2048 revolutions in each direction)
Example: Take a 37-bit absolute serial rotary encoder (25-bit single turn, 12-bit multi-turn) and its
equivalent linear scale (e.g.10 nm resolution):
Total Travel Span In each direction = Span/2 Units
Technique 1/3 (5-bit shift)
Rotary 2
47-25
= 4,194,304 2,097,152 revolutions
Linear
2
47
/SF 1,407,374,883
mm
Technique 2 (no shift)
Rotary 2
47-20
= 134,217,728 67,108,864 revolutions
Linear 2
47
/SF 45,035,996,274 mm