Rockwell Automation 1398-DDM-xxx USE MNL/ULTRA 200 DIG.SERVO.DR - Manual (Page 176)

Publication 1398-5.0 – October 1998
9-6 Tuning
Manual Tune Mode
Manual tuning may be used to adjust the gain settings and filter
frequency of the velocity regulator. The following sections briefly
explain these settings. An understanding of the function for each type
of gain and filtering will allow you to effectively tune the system.
Two types of manual tuning are available:
●
Velocity tuning
●
Position tuning.
Before manual tuning is invoked, the Velocity, Distance and Motor
Direction parameters must be set. Refer to “Auto Tune Mode” on
page 9-4 for information on setting these parameters.
The velocity loop should always be tuned before the position loop, as
velocity loop tuning affects the position loop response.
Gain settings and signal filtering are the primary methods to
electrically tune a system. A understanding of the types of gain and
their purposes, as well as a general understanding of filtering, are
essential background knowledge to properly tune a servo system.
Gains
Table 9.1: Velocity Loop Gains
Parameter Description
P-gain Proportional gain of the velocity regulator.
P-gain controls the bandwidth of the velocity regulator by adjusting the control
response proportional to the error.
The P term of the velocity regulator commands an acceleration current that is propor-
tional to the velocity error.
I-gain Integral gain of the velocity regulator.
Integration in the velocity regulator forces the motor velocity to precisely follow the
commanded velocity. This assumes operation under steady state conditions (velocity
command or load does
not change).
I-gain controls:
The stiffness or the ability to reject load torque disturbance.
The amount of velocity overshoot, which may cause the system to become unstable
or oscillate.
The I term of the velocity regulator commands an acceleration current proportional to
the integral of the velocity error.
D-gain Differential gain of the velocity regulator.
Positive D-gain decreases the amount of overshoot caused by the I-gain.
Negative D-gain decreases the torsional resonance between the motor and the load.