Switching from Constant value to PID controller

Question

Giuseppe 2015-2-8

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https://ww2.mathworks.cn/matlabcentral/answers/176415-switching-from-constant-value-to-pid-controller

回答： mkmat 2015-11-19

Hello!

thanks for your time! i need your help to solve this problem:

i have a system that works with a constant flow rate when the current is zero and, when current is higher than zero, the inlet flow rate must be controlled by a PID controller.

Now i tried to use a Switch block: - the first input is the pid controller; - the second one is linked to current (the control variable) - the last one is the constant block.

the problem encountered are: - i can't automatically tune the PID block ("Pid Tuner could not find an initial stabilizing controller using plant "Plant")

and so the program does not work..

any other solution/ Approach?

thanks to everyone!

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Answer 1

Giuseppe 2015-2-9

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https://ww2.mathworks.cn/matlabcentral/answers/176415-switching-from-constant-value-to-pid-controller#answer_167487

Nobody can solve this problem? :(

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Answer 2

Arkadiy Turevskiy 2015-2-11

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Can you attach the model? Had to troubleshoot otherwise. One thing that could be happening is that PID Tuner works by linearizing a Simulink model "around" the PID Controller. If your switch is set to select not the PID output, but the other switch input, then the plant PID Tuner will see won't make any sense. So you can try to temporarily remove the switch, wire the PID Controller output to plant input directly and tune then.