Open loop control tuning?


Thread Starter


I wonder if it is possible to adjust the open loop controller for better performance for a single high frequency case? Also, can the open loop controller be optimized for both high and low frequency case? If I want the response with a variety of system speeds, which one should I choose? Open loop or closed loop controller?

Any input is appreciated. Thanks alot.

Ken Emmons Jr.

What are you trying to drive? An inverter with induction motor?
Permanent magnet 3 phase servo, brush motor, etc??


William Sturm

You have not provided enough detail of your system. What are you trying to control? What do you currently have? Is this a homework assignment or a working system?

Bill Sturm
Sorry for my inadequate information. It is actually a school lab that I have done on testing the performance of open-loop and close loop controllers as well as high order controller when they are used to control a robot arm. I observed the changes in performance from square wave to sine wave by varying the frequency for open loop and closed loop controllers. Tachnometer and incremental encoder are both used to measure the motion but I guess the tachnometer is a better choice?

So I'm thinking of modelling the gain as a function of frequency or amplitude and add a controller that will automatically adjust. For open loop control, can it be done by just changing the frequency or the gain or both possibly? higher frequency leads the system to be less responsive to sharp and straight disturbances as duration decreases so I must do away with it.

William Sturm

A tachometer only provides velocity information. An encoder typically provides position information, but you may be able to derive velocity from it. You will need to use the encoder if you are controlling position. For velocity control only, the tach is probably easier.

You are not likely to get detailed answers here, but you may get some general advice.

Bill Sturm