Robust PI control of a laboratory time-delay process

Abstract

The chapter presents robust control of a laboratory process with a transport delay using the industrial control system SIMATIC. The controlled process is identified in the form of a transfer function of a higher order with a transport delay at first and then the transport delay is approximated by the first order Taylor series expansion of the numerator or the denominator. Because the transport delay can vary, the controlled laboratory process is modelled in the form of a transfer function with interval parametric uncertainty. Robust PI controllers are designed for the laboratory process. The method for synthesis of robust controllers is based on plotting the stability boundary locus in the (kp, ki) - plane and the subsequent choice of a stabilizing PI controller using the pole-placement method so that the prescribed behavior of the closed-loop is achieved.