×
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

Gain and integral

Gain and integral

Gain and integral

(OP)
Basically what a gain of 0.3 and an integral of 1 minute mean in a PID controller.

Bob

RE: Gain and integral

A gain of .3 means that the output moves 0.3 p.u. when a 1 p.u. step difference between setpoint and actual is applied to the input. AKA 3.33 proportional band.

A 1 minute integral means that it takes 1 minute for the output to change linearly with 1 p.u. when same step is applied to input.

These definitions do not take saturation into account. If controller saturates, then work with smaller signals, 0.1 input for instance, and do not forget to scale down expected outputs.

Gunnar Englund
www.gke.org

RE: Gain and integral

(OP)
Thanks Skogsgurra. Besides, what`s the derivative and when can it be useful ?

Thanks

Bob

RE: Gain and integral

Maypot
A simple search of Eng-tips may get you a better explanation.
In a PID controller
P = Proportional gain. This is the factor by which the error is multiplied in the loop algorithm to produce the error correction term.
Increasing this value increases your transient speed response meaning "how fast do you want the response to a disturbance?" If u take it too far the drive will become unstable.

I = Integral gain This factor sums all of the small errors that can accumulate over time. This insures actually reaching zero during steady state load conditions. With out the integral the controller may reach a point where it is happy but still not quite at SP. Increasing this value results in a faster recovery from a disturbance while exactly reaching SP, but if taken too high, can cause oscillatory conditions.

D = derivative. The derivative term will take into account the rate of change of the error signal. So if there is a large change in error, you will see a large change in output. As the PV gets close to the setpoint, the error will get smaller and the output will start to anticipate reaching SP and start cutting back earlier than it would have using only PI control. This will help reduce any overshoot of your controlled output.

Hope this helped

Life is what happens while we're making other plans.

Wally

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!


Resources