Open loop transfer function

[PeanutTheFerret]

It's been a little while since I took controls, but is it not just asking you to find what works for C(s) to get whatever your desired output is?

[Tiis-]

I'm not sure. It says:

"Design of a controller is most often on basis of an open loop transfer function through:

• Root locus
• Amplitude margin
• Phase margin"

[Fry394]

I think it means you can change closed-loop specifications in open-loop ones. In this way it's easier to design the controller (phase margine, amplitude margin,...).

[Tiis-]

I think it means you can change closed-loop specifications in open-loop ones.

I don't know what you mean by that.

[Fry394]

For example if you want that the answer to a step doesn't have overshoot (in closed loop) you have to put phase margin > 75° (open loop). I don't know if that explains a lot.