FAQ: Isn't the sensitivity function the same as the function used for steady state error? How are they related?
Posted by Asa Hopkins, 22 November 2002
Yes, the sensitivity function is the transfer function from the reference to the error, which we evaluate at s=0 to determine the steady-state error. More generally, this function tells us about tracking error at whatever frequency -- the steady state error is just the tracking error at zero frequency.