Anti-windup techniques for multiple PID Controller feeding the same actuator

Hello,

I am developing a simulink model where I have 1 PI controller and 1 PID controller that sum their outputs and feed the same actuator (I didnt't use the PID build-in blocks of simulink library, I have recreated them from scratch). Now, I would like to implement also an anti-windup method in case of actuator saturation.

The problem, also stated here (https://it.mathworks.com/help/simulink/slref/anti-windup-control-using-a-pid-controller.html), is that both clamping and back-calculation, don't work in this case. Can you suggest me some anti-windup methods or provide me some material (e.g. in simulink) where I can understand how to fix this problem?

Thank you in advance.

Francesco

Answer 1

[Oguz Kaan Hancioglu]

I don't understand why you are using both PI and PID for controlling the actuator. You can implement it using a single PID block by changing gain accordingly. Are you trying to build a cascade controller structure? This is the structure of anti-windup. Each uses the actuator output to reset its intergrator values. How do you define the reset sequence when you connect two controllers to the same actuator? For detail information, you can look this book.

[1] Åström, Karl J., and Tore Hägglund. Advanced PID Control. Triangle Park, NC: International Society of Automation, 2006.

[Francesco Paolo De Simone]

Hello,

Thank you for your answer. I need 2 controllers because they minimize different errors (PI controller is used for the Stability Augmentation System of the helicopter while PID is used for Attitude hold system).

Best regards,

Francesco Paolo De Simone

[Oguz Kaan Hancioglu]

Hi,

You are using cascade control strucure. İn your design inner loop is the sas and the outer loop is the hold. Therfore you need to adjust the sas untiwindup for actuar and to adjust the hold untiwindup for the sas controller. Bests

Answer 2

[Sam Chak]

Hi @Francesco Paolo De Simone

The PID Controller block can be located in the Continuous block library.

Check this out:

https://www.mathworks.com/help/simulink/continuous.html

There is also an anti-windup mechanism built in the PID block that prevents output saturation. Look up the link to study how to apply and enable it in your Helicopter model.

https://www.mathworks.com/help/simulink/slref/pidcontroller.html#mw_4df66f45-b8b4-48f0-a8df-60066e30dd2f

Can you post the image of your designed PI–PID controller? It helps to understand how their configurations are connected to provide both Stability Augmentation and Attitude hold system at the same time.

[Francesco Paolo De Simone]

Hello @Sam Chak,

This is the image of the longitudinal axis of the AFCS of the helicopter. After the sum block I will add an actuator, hence the necessity to build an anti windup strategy for the PI(SAS) and PID(ATT).

Best regards,

Francesco

[Sam Chak]

Hi @Francesco Paolo De Simone

I don't see how you hook up the PI and PID together in the image. But I guess that the input signal to both PI and PID blocks is deltaCLong signal.

Can you sketch the PI and PID blocks on the exisiting image?