×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Limiting PID Output

Limiting PID Output

Limiting PID Output

(OP)
I am asked if it is possible to limit the output of a PID controller by putting a software restriction on the output signal to the actuator. In this case it is a temperature controller on a fired heater and is regulating heat input into the system and controlling output temperature.

The assumption here is that a reasonable performance will be achieved with this output restriction in steady state. I am concerned that integrating action may make any control response very poor.

Has anybody had any experience with these "hard limits" on controller output and are there any tests that can be performed to get an idea of how the controller might cope under these conditions?

Is there anything else that might need to be considered before we implement this change?

RE: Limiting PID Output

This limiting is a common, even standard, feature of PID controllers.

The phenomenon you are (correctly) worried about is known as "integrator windup". So "anti-windup" is also a standard feature of PID controllers.

The simplest technique for anti-windup protection is simply to disable additions to the integrator when the output is saturated on the limit. It is usually good enough.

Curt Wilson
Omron Delta TAu

RE: Limiting PID Output

Anti Reset Windup is another term used, as Curt says a standard feature of most controllers to be implemented by an interlock action, it could clamp the output at any point.
Not the same as an output limit which would fix it at some max or min value.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close