PID Tuning tells me the system has closed loop stability even though it doesn't

Question

Manuel 2015-4-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/212677-pid-tuning-tells-me-the-system-has-closed-loop-stability-even-though-it-doesn-t

回答： Arkadiy Turevskiy 2015-4-24

Hello everyone,

I am using the PID Tuning App to design a PID controler for my plant. It works pretty good, the systems reaction is pretty solid and the PID Tuning tells me that I have closed loop stability.

The problem is, when I check the root locus, it has some poles with positive real values, indicating my system is unstable. There is even a branch that is not reaching into the negative pane, so it would seem impossible to stabilize the system.

Also, if I design the controler with the "sisotool", I get the same result.

Is there something I might be missing?

Thank you in advance for any help!

Is it sometimes acceptable to work with a system even though it is not stable?