Tuning a Pneumatic System

When tuning a pneumatic cylinder, use the basic instructions in the Tuning a Position Axis topic, but use the order of the gains below.

Tuning Order

When using high-order gains, increasing the highest order will allow you to increase lower order gains. However, you need to first set the lower gains to some value before you can set the higher ones. Then, you can go back and increase the lower order gains.

The Output Filter can significantly improve control of pneumatics. Without the Output Filter, the Differential Gain can cause the Control Output to oscillate, causing oscillation of the axis. By using the output filter, the differential gain can be increased significantly to help the Actual Velocity track the Target Velocity.

Suggested Tuning Order:

Proportional Gain
Output Filter
Differential Gain
Double Differential Gain
Triple Differential Gain
Double Differential Gain
Differential Gain
Proportional Gain
Integral Gain
Repeat several times.

Feed Forwards are not useful on poor systems. They may be more significant on low-friction cylinders. If your application requires Feed Forwards, set them before setting the Integral Gain.

The P, D, DD and TD gains typically differ from each other by an order of magnitude. For example, the ratio of the gains to each other may be as shown below. Keep in mind that the actual value of gains required on your system may differ significantly.

P: 10

I: 10

D: 0.1 or smaller

DD: 0.01 or smaller

TD: 0.001 or smaller

Other tips:

Use the Output Filter, setting it to a low value, comparable to the natural frequency of the system.
Deadband may be required on systems with high static friction.
The Velocity and Acceleration may need to be filtered, or using the model may help.