Question

Derivative of a control system provides _________

(a) Low steady state error

(b) Gain proportional to error

(c) Reduced overshoot

(d) Infinite gain

This question was addressed to me during an online interview.

Origin of the question is Control Laws in FBW in chapter Fly by Wire Flight Control of Avionics

Answer 1

Right answer is (c) Reduced overshoot

To explain I would say: Derivative of error control provides a phase advance characteristic to

compensate for the lags in the system, for instance, actuator response, and hence improve the loop stability. This increases the damping of the aircraft response and reduces the overshoot to a minimum when responding to an input or disturbance.