A Unified Approach for H∞ Complementary Sensitivity Design of PID Controllers Applied to a DC Motor With Communication Delay
In this paper a graphical technique is introduced for finding all continuous-time and discrete-time proportional integral derivative (PID) controllers that satisfy the discrete-time H∞ complementary sensitivity constraint of an arbitrary order transfer function with time delay. These problems can be solved by finding all achievable PID controllers that simultaneously stabilize the closed-loop characteristic polynomial and satisfy constraints defined by a set of related complex polynomials. The key advantage of this procedure is that this method depends only on the frequency response of the system. If the plant transfer function is given, the procedure is still appropriate. The delta operator is used to describe the discrete-time controllers because it not only possesses numerical properties superior to the discrete-time shift operator, but also converges to the continuous-time controller as the sampling period approaches zero. A unified approach allows us to use the same procedure for discrete-time and continuous-time complementary sensitivity design of PID controllers. The method is demonstrated by using the experimental frequency response of a DC motor with communication delay for H∞ complementary sensitivity design of PID controllers.