2
$\begingroup$

I am having a hard time grasping the concept of a DC motor with load being unstable, and stable due to a controller

My confusions appears as I am trying to design a controller for one using Z-N method, and the transfer function i've identified using matlab tells me that my DC-motor always will be stable.

Which makes sense, since feeding it constant voltages, will lead to a constant veloicty.

But to use the z-n approach the system has be able to become unstable, and since this isn't possible i am getting confused if a motor are able to become motor for which i am to design a controller for.

The question in simplicity, how come can a controller make a motor, (if the motor itself cannot (due to pole zero plot)) unstable.

$\endgroup$
2
$\begingroup$

2 comments ...

First, as many people said in answer to your other question, you need to understand that your transfer function is not the real transfer function of the motor. Real motors have nonlinear, and other, unmodelled effects that can cause problems in certain cases.

Second, you need to consider the entire system, not just a single subsystem. Stability is a property of the combination of motor+controller, so a poorly designed/tuned controller connected to a stable motor can easily make the whole system unstable.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.