Rockwell Automation 1771-QB Linear Pos. - Manual (Page 130)

Initializing and Tuning the Axes
Chapter 8
8Ć12
2. Initialize the loop gains as follows:
Proportional gain: K
P
= 0.0050 ips/mil
Integral gain: K
I
= 0
Derivative gain: K
D
= 0
Feedforward gain K
F
= 20.0%
3. Initiate a move using setpoint or jog commands. Increase the feedforward
gain until the axis begins to overshoot, i.e., to exceed the desired end
position.
4. Decrease the feedforward gain by 10%. This reduced value will result in a
more stable performance of the axis.
PID Loop Gains
The next step in tuning the system is to find the appropriate PID gains. The
following procedure requires that you increase the proportional gain until the
axis oscillates. Do not use this procedure if your equipment cannot tolerate
oscillation.
First, determine the proportional gain:
1. Initialize the loop parameters to the following defaults:
K
P
= 0.0200 ips/ml
K
I
= 0
K
D
= 0
The gain break speed and gain factor should be zero.
2. Initiate a jog or setpoint move with the highest acceleration and
deceleration that you plan to use.
3. Increase the proportional gain using increments of 0.0100 and repeat step
2 until continuous oscillations result.
4. Decrease the proportional gain by 30%. This will result in stable
performance of the axis. In most cases, a proportional gain between 0.0300
and 0.1500 ips/mil will give optimal performance.
K
P(unstable)
= lowest proportional gain at which continuous
oscillations occur
KP = 0.7 x K
P(unstable)
Next determine the integral and derivative gains. The following procedure will
produce near-optimal results for most systems.