Rockwell Automation 1398-DDM-xxx ULTRA 100 Series Drives Installation Manual - Manual (Page 169)

Publication 1398-5.2 – PDF 1997
Tuning 9-3
Backlash
Backlash between the motor and load effectively unloads the motor
over a small angle. Within this small angle, the increased gain can
result in oscillations. Some backlash may be unavoidable, especially
with gear reduction. If backlash is present, the inertia match between
the load and motor must be properly sized for good servo performance
(load inertia should roughly equal motor inertia). Gearing reduces the
inertia reflected to the motor by the square of the gear reduction from
motor to load. Therefore, the gear ratio must provide the required
match.
Auto Tune Mode
The Auto Tune mode uses a “self-tuning” algorithm that automatically
adjusts the drive’s position and velocity loop gain parameters.
Adjustments do not require special equipment. This mode will tune a
drive for constant response across different applications. The results
often provide acceptable response, but in general should be considered
a starting point.
Tuning parameters adjustments are set to achieve a reasonable
bandwidth and servo response based on the system inertia and friction.
Auto tune may be used when a significant amount of compliance or
backlash exists (for example, belt systems) in the mechanical load, but
precise tuning requires the load be fully coupled to the motor.
Instability problems occur when the load is not fully coupled to the
motor.
Auto Tuning
A PC running ULTRA Master or the TouchPad is required to perform
tuning on the drive.
Before auto tuning is invoked, three autotuning parameters must be
set:
Figure 9.2 Torque Current Conditioning Structure
PEAK DETECT
PEAK DETECT
CURRENT
AVERAGE
LIMIT
CURRENT
CURRENT
LIMIT
LP ENABLE
LOW PASS
FILTER
TORQUE
CURRENT
COMMAND
INPUT
TORQUE CURRENT
COMMAND OUTPUT
AVERAGE CURRENT
CURRENT LIMIT
POSITIVE
CURRENT PEAK
NEGATIVE
CURRENT PEAK
EXCESSIVE CURRENT
Note: The autotune algorithm will not provide satisfactory results in
systems with significant gravitational effects.