Reference Manual

PMAC 2 Software Reference
88 PMAC I-Variable Specifiation
Ix32 Motor x PID Velocity Feedforward Gain
Range
0 .. 8,388,607
Units
(Ix30*Ix08)/2
26
DAC bits/(counts/cycle)
Default
1280
Remarks
Ix32 adds an amount to the control output proportional to the desired velocity of Motor x.
It is intended to reduce tracking error due to the damping introduced by Ix31, analog
tachometer feedback, or physical damping effects.
If the motor is driving a current-loop (torque) amplifier, Ix32 will usually be equal to (or
slightly greater than) Ix31 to minimize tracking error. If the motor is driving a tachometer-
loop (velocity) amplifier, Ix32 will typically be substantially greater than Ix31 to minimize
tracking error.
If the servo update time is changed, Ix32 must be changed proportionately in the opposite
direction to keep the same effect. For instance, if the servo update time is cut in half, from
440 µsec to 220 µsec, Ix32 must be doubled to keep the same effect.
This parameter is usually set initially using the Tuning utility in the PMAC Executive
Program. It may be changed on the fly at any time to create types of adaptive control.
See Also
PID Servo Filter (Closing the Servo Loop)
I-variables Ix30-Ix31, Ix32-Ix39
Tuning Instructions (PMAC Executive Program manual)
Ix33 Motor x PID Integral Gain
Range
0 .. 8,388,607
Units
(Ix30*Ix08)/2
42
DAC bits/(counts*cycles)
Default
0
Remarks
Ix33 adds an amount to the control output proportional to the time integral of the position
error for Motor x. The magnitude of this integrated error is limited by Ix63. With Ix63 at
a value of zero, the contribution of the integrator to the output is zero, regardless of the
value of Ix33.
No further errors are added to the integrator if the output saturates (if output equals Ix69),
and, if Ix34=1, when a move is being commanded (when desired velocity is not zero). In
both of these cases, the contribution of the integrator to the output remains constant.
If the servo update time is changed, Ix33 must be changed proportionately in the same
direction to keep the same effect. For instance, if the servo update time is cut in half, from
440 µsec to 220 µsec, Ix33 must be cut in half to keep the same effect.
This parameter is usually set initially using the Tuning utility in the PMAC Executive
Program. It may be changed on the fly at any time to create types of adaptive control.
See Also
PID Servo Filter (Closing the Servo Loop)
I-variables Ix30-Ix32, Ix34-Ix39, Ix63, Ix69
Tuning Instructions (PMAC Executive Program manual)