XtraDrive User Manual Chapter 6: Servo Adjustment
6-20
6.3.10. Tuning Procedure for Position Control Parameters
îš„ System Requirements
Use any command input to the XtraDrive, and watch the performance
of control (see analog output).
It is recommended to use commands that include a constant speed
section (plateau of trapeze for example). Potential vibrations of the
system may not be observed during the tuning procedure if no constant
speed section is used.
Tuning is done while checking the items of the control quality required
for the specific application. These items can vary, depending on the
application.
Typically, items of control quality are:
• Smoothness: Can be estimated by the behavior of the position error
with time. If the position error changes sign rapidly and/or with
great amplitude, then smoothness is poor.
• Settling time: Can be measured as the time it takes to reach a zero
position error after the command speed reaches zero.
• Stiffness: Can be measured by monitoring the position error
amplitude resulting from a perturbation.
This perturbation can be an abrupt change in command acceleration,
for example by using a triangle shape for the speed profile of a
command, or a physical impact applied on shaft or load.
• Overshoot: Can be measured by the sign of position error after
movement stops.
îš„ The Tuning Steps
During each tuning step, the quality of control is monitored with the
user-required movements according to the user’s criteria.
1. Use Fast Tuning in order to load a starting set of parameters for the
given load.
2. Tune the following parameters:
a) Set the Torque Filter (Pn1A4) to zero.
b) Raise K
d
(Pn1AC) to the maximum possible value for a smooth
movement, then decrease that value by about 20%.
c) Increase the torque filter and repeat Step b. Continue increasing
the torque filter until the maximum value of Kd is obtained.
d) Raise K
p
(Pn1AA) to the maximum value that gives a smooth
movement, then decrease that value by about 20%.
e) Raise K
is
(Pn1A9) till there is no overshoot.
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