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.