The task says: The final value of y(t) i.e. after transient has died out, should equal k% of the disturbance magnitude d0. My lecture notes state that for this system and in case of a unit step change d = 1: lim sY(s) = -1/(A+Kc). However when I try to calculate Kc, i become a negative number that later on gives me a complex number for the time derivative of the PD-controller. I doubt this is correct. I get Kc = (-1/k%)-A. I expect some -sign screwing me somewhere but don't know where.
Thank you in advance