Which data set should I trust more?

[kostoglotov]

Homework Statement

Control systems subject. Have a DC motor setup on a difference op-amp, then with gain, and the axel moves a wiper on a pot used for feedback.

I understand the concepts reasonably well enough to complete the assignment.

I'm using MATLAB scripts to approximate parameters for the motors transfer function. As well as required gain to achieve certain percentages of overshoot.

The question I would really love an answer to is this: I get very different motor parameter values depending on whether I'm using closed or open loop responses. Obviously, for an open loop I'm using an open loop model, and for a closed loop I'm using a closed loop model...but I was thinking, wouldn't closed loop responses be less sensitive to variations in the motors parameters, wouldn't closed loop response data be give less accurate approximations of the motors transfer function parameters? Or, everything else being equal, is my closed loop response data better for approximating the motors transfer function?

Homework Equations

The Attempt at a Solution

 

[FactChecker]

I agree with your intuition that closing the loop can mitigate the behavior of the motor. I am not sure that it would make the parameters impossible to determine, but they certainly may be less obvious.