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PID with constraints

Posted Nov 7, 2013, 9:37 a.m. EST Low-Frequency Electromagnetics, Heat Transfer & Phase Change, Parameters, Variables, & Functions Version 4.0 2 Replies

Alex Sposito
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Hi All,

I have implemented a PID temperature controller in my model that controls the voltage applied to a resistive heater to achieve a set temperature. However the PID algorithm achieves this setpoint by applying voltages outside of whats practical for my system to achieve the shortest rise time.

I want to know how to constrain my voltage applied so that it only solves for and applies voltages within practical limits say V_ctrl<20. I tried using a global constraint in the ODE interface but it does not constrain the voltage.

Thanks in advance for your help.
Alex
2 Replies Last Post Nov 7, 2013, 2:06 p.m. EST
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Nov 7, 2013, 1:21 p.m. EST
Alex,

difficult to give an advice without knowing anything about your implementation. In a PID controller the control variable depends on the P, I and D parameters. But as you implemented the thing I am sure you know that. Are you using the I and D parameters? Particularly D can be tricky.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Alex, difficult to give an advice without knowing anything about your implementation. In a PID controller the control variable depends on the P, I and D parameters. But as you implemented the thing I am sure you know that. Are you using the I and D parameters? Particularly D can be tricky. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Alex Sposito
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Posted: 1 decade ago Nov 7, 2013, 2:06 p.m. EST
Thanks for the reply Edgar.

Yes I just needed to do some more tuning to get my control variable where it needed to be.

Thanks for the reply Edgar. Yes I just needed to do some more tuning to get my control variable where it needed to be.

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