Tuning
9-1
Installation Manual for Models ODM-005, ODM-005i, ODM-010, ODM-010i, ODM-020 and ODM-020i
C
HAPTER
9:
Tuning
OMNIDRIVE are tuned quickly and easily for a wide variety of applications. Two tuning modes are
available through the software:
•
Auto Tune
•
Manual Tune
Tuning Guidelines
The following tuning guidelines briefly describe the tuning adjustments. These guidelines provide you
with a basic reference point should the application require additional adjustments.
General Tuning Rules
1. Tune the velocity loop first and then, if the drive uses following or step/direction commands,
tune the position loop.
2. To widen the velocity loop bandwidth, increase the P-gain setting, decrease the I-gain setting or
increase the low-pass filter bandwidth. This provides a faster rise time and increases drive
response.
3. To increase stiffness, increase the I-gain setting. It rejects load disturbance and compensates for
system friction.
4. To reduce velocity loop overshoot, increase P-gain or D-gain, or decrease I-gain.
5. To reduce mechanical resonance, use a stiffer mechanical coupling or select a nega-tive (-) D-
gain value. Alternatively, decrease the low-pass filter value and the velocity loop update rate.
6. If the motor oscillates, decrease either individually or together the:
•
P-gain
•
I-gain
•
low-pass filter bandwidth.
High Inertia Loads
Proper compensation of load inertia may not be simply a matter of increasing the P-gain and I-gain settings.
Problems are often encountered when tuning systems with a high load to motor inertia ratio.
Mechanical Resonance
Mechanical resonance between the motor and the load occurs when the motor and load are oscillating
with the same frequency but opposite phase: when the motor is moving clockwise the load is moving
counter clockwise. The amplitude of the motor and load oscillations is such that the total momentum of
the oscillating system is zero. In the case of a high load to motor inertia ratio this means that the motor
may be moving quite a lot while the load is not moving nearly as much. Mechanical resonance occurs as
a result of compliance (springiness) between the motor inertia and load inertia. It may result from belts,
flexible couplings or the finite torsional stiffness of shafts. In general, the stiffer the couplings, the higher
the resonant frequency and lower the amplitude. If the motor shaft is directly coupled to the load, a
mechanically resonating system usually emits a buzz or squeal at the motor.
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