Efficient disturbance rejection for dead-time processes using internal model control

Abstract

Dead-time processes are quite frequent in industrial applications. Because of its simple tuning procedure and good set-point tracking capabilities, Internal Model Control (IMC) has established good results for these processes. However, disturbance rejection is an important issue in process control, especially in delayed systems. The basic tuning rules for IMC exhibits rather sluggish disturbance rejection performance, especially for delay dominant processes (i.e. the relative delay to the process time constant). In this paper we propose a special tuning for effective disturbance rejection with IMC. The proposed disturbance filter compensates nicely for the dead-time, when stochastic disturbance signals have their main spectral energy in a limited frequency interval. The tuning method is using the Diophantine equations to determine the disturbance filter coefficients. Simulation results demonstrate the effectiveness of the proposed approach, as well as its intrinsic robustness when compared to the basic IMC tuning.