Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual - Manual (Page 353)

Publication 1784-UM003A-EN-P – June 2003
Motion Object Attributes 345
Tuning Torque The Tuning Torque attribute value determines the maximum torque of the
MRAT (Motion Run Axis Tune) initiated tuning motion profile. This attribute
should be set to the desired maximum safe torque level prior to running the
MRAT instruction. The default value is 100%, which yields the most accurate
measure of the acceleration and deceleration capabilities of the system. In
some cases a lower tuning torque limit value may be desirable to limit the stress
on the mechanics during the tuning procedure. In this case the acceleration
and deceleration capabilities of the system are extrapolated based on the ratio
of the tuning torque to the maximum torque output of the system. Note that
the extrapolation error increases as the Tuning Torque value decreases.
Damping Factor The Damping Factor attribute value is used in calculating the maximum
Position Servo Bandwidth (see below) during execution of the MRAT (Motion
Run Axis Tune) instruction. In general the Damping Factor attribute controls
the dynamic response of the servo axis. When gains are tuned using a small
damping factor (like 0.7), a step response test performed on the axis would
demonstrate under-damped behavior with velocity overshoot. A gain set
generated using a larger damping factor, like 1.0, would produce a system step
response that have no overshoot but have a significantly lower servo
bandwidth. The default value for the Damping Factor of 0.8 should work fine
for most applications.
Drive Model Time Constant The value for the Drive Model Time Constant represents lumped model time
constant for the drives current loop used by the MRAT instruction to calculate
the Maximum Velocity and Position Servo Bandwidth values. The Drive
Model Time Constant is the sum of the drive’s current loop time constant, the
feedback sample period, and the time constant associated with the velocity
feedback filter. This value is set to a default value when the axis is configured
based on the specific servo module selection. This value is only used by MRAT
when the axis is configured for an External Torque Servo Drive.
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Tuning Torque REAL
%
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Damping Factor REAL
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Drive Model Time Constant REAL Sec