Reference Manual

PMAC 2 Software Reference
98 PMAC I-Variable Specifiation
See Also
I-variables Ix30, Ix65
Closing The Servo Loop
Ix65 Motor x Deadband Size
Range
0 .. 32,767
Units
1/16 count
Default
16 (=1 count)
Remarks
Ix65 defines the size of the position error band, measured from zero error, within which
there will be changed or no control effort, for the PMAC feature known as deadband
compensation. Ix64 controls the effective gain relative to Ix30 within the deadband.
Note:
The units of this parameter are 1/16 of a count, so the value should
be 16 times the number of counts in the deadband. For example, if
modified gain is desired in the range of +/-5 counts of following
error, Ix65 should be set to 80.
See Also
Deadband (Closing the Servo Loop)
I-variables Ix30, Ix64
Ix66 Motor x PWM Scale Factor {PMAC2 only}
Range
0 .. 32,767
Units
PWM_CLK cycles
Default
0
Remarks
Ix66 multiplies the output of the digital current loops for Motor x (which are values
between -1.0 and 1.0) before they are written to the PWM output registers. As such, it
determines the maximum value that can be written to the PWM output register. Ix66 is
only used if Ix82>0 to activate digital current loop execution.
The PWM output value for each phase is compared digitally to the PWM up-down
counter, which increments or decrements once per PWM_CLK cycle to determine whether
the outputs are on or off. The limits of the up-down counter are I900+1 and -I900-2 for
channels 1 to 4; I906+1 and -I906-2 for channels 5 to 8.
Generally, Ix66 is set to about 10% above I900 (or I906) for motors commutated by
PMAC2. This permits a full-on command of the phase for a substantial fraction of the
commutation cycle, providing maximum possible utilization of the power devices at
maximum command. If Ix66 is set to a smaller value than I900 or I906, it serves as a
voltage limit for the motor (Vmax = I900/Ix66*VDC). Ix69 serves as the current limit.
Ix67 Motor x Linear Position Error Limit
Range
0 .. 8,388,607
Units
1/16 count
Default
4,194,304 (=262,144 counts)
Remarks
Ix67 defines the biggest position error that will be allowed into the servo filter. This is
intended to keep extreme conditions from upsetting the stability of the filter. However, if
it is set too low, it can limit the response of the system to legitimate commands (this
situation can particularly be noticed on very fine resolution systems).
This parameter is not to be confused with Ix11 or Ix12, the following error limits. Those
parameters take action outside the servo loop based on the real (before limiting) following
error.