Rockwell Automation 8510 AC Spindle Drive System Programming Manual - Manual (Page 37)

Drive Tuning
Chapter 3
3-34
Spindle/Servo Mode Tuning The following steps describe the tuning process for spindle or servo mode.
ATTENTION: If an oscilloscope is used during start-up, tuning
or troubleshooting, it must be properly grounded. The
oscilloscope chassis may be at a potentially fatal voltage if not
properly grounded. Always connect the oscilloscope chassis to
earth ground.
When using an oscilloscope it is recommended that the test
probe ground be connected to the test point labeled “GND.”
!
o 1. Program the following parameters (for the mode you are using) as
follows (refer to Chapter 2 as necessary) :
P Gain (Servo or Spindl) – set to the default value (5.0)
I Gain (Servo or Spindl) – set to zero
o 2. Program ANALOG OUTPUT – Output #1 for “
±
MOTOR RPM” and
ANALOG OUTPUT – Output #2 for “% TORQUE.” While observing
the motor rpm and per cent torque via the analog outputs or test
points, adjust P Gain to achieve the desired speed of response with no
more than one overshoot.
Ideally, P Gain should be adjusted with minimum load inertia. Tuning
with maximum load inertia could result in instability with a smaller
load inertia. Lost motion between the motor and load may
intermittently decouple the load inertia from the motor. This situation
could also lead to instability if the drive were tuned for maximum
inertia.
Lowering P Gain slows response, reduces overshoot, improves
stability, and reduces torque ripple. P Gain should not be increased
beyond the required amount for acceptable system response. Too high
of a P Gain setting will amplify digital and analog system noise and
increase velocity and torque ripple. High torque ripple can overheat
the motor and deteriorate surface finish. If P Gain is increased to
extremes, the system will become unstable, oscillate at a high
frequency, and produce significant audible noise.
It will not be possible to achieve high bandwidth on high inertia
systems. The high P Gain required will cause very high torque ripple
due to digital noise amplification.
o 3. Increase I Gain to achieve the required stiffness. Ideally, I Gain
should be adjusted with maximum load inertia. Tuning with minimum
load inertia could result in an underdamped response or instability
when larger load inertia is applied.