PID system critical gain determining

Thread Starter

zazas321

Joined Nov 29, 2015
637
Hey guys, i have a couple questions about my control system.

Question 1.
I have a control system that i need to control using PID controller. How can I determine critical gain if my system is not reaching the oscilation. Many articles that i have read say that in order to find critical gain value you need to increase the gain till your system is oscilatting. But the system that I am working on does not have any poles that would cause the system to get into the oscilation.

Question 2. If i manage to determine Critical gain (Kp) and Oscilation period values I can determine Kp Ti and Td. I am not quite understanding the point of having Ti and Td. I would rather have then in form of gain? Becuase in order to tune the system we know that increasing the gains of the system will:

Kp-decreases the rise time
Kd-reduces overshoot and settling time
Ki- eliminates steady state error
The problem is that I do not know what is Kd and Ki because i have I and D in terms of Time.

 

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