Anisochronic internal model control of time-delay systems

Abstract

This paper is concerned with the robust control of time-delay systems with both state and control delays. The Smith predictor is not a suitable control scheme for this class of systems and special approaches developed hitherto are not practically applicable due to their poor robustness and complicated design and structure. However, a suitable controller design method that is both robust and practicably applicable can be based on the extension of the internal model control scheme. This paper describes the design of internal model controllers for this class of time-delay systems in both one degree-of-freedom and two degrees-of-freedom arrangement. A common feature of the proposed controllers is the application of both delayors and integrators in their final implementation, resulting in a better compensation of infinite order process dynamics. The practical applicability of this approach is demonstrated on a small scale heating plant with several internal delays and nonlinear steady state behaviour.