A self-tuning robust controller

The self-tuning robust controller described in this paper has an error-driven, “robust” structure (Francis and Wonham, J. Appl. Math. Opt., 2, 170–194, 1975; Davison, IEEE Trans. Aut. Control, AC-21, 25–34, 1976) which guarantees asymptotic regulation and tracking in the presence of finite parameter perturbations. The controller utilizes unity feedback and also incorporates an internal model of the external disturbances and set points. The adaptive mechanism tunes the controller parameters such that a quadratic performance index with control weighting is minimized. The adaptive algorithm includes a dead zone and ensures global stability of the system in the presence of bounded noise and disturbances. In its simpler and natural form it can also be formulated to be structurally equivalent to a conventional, discrete PID controller. Experimental evaluation of the proposed controller on a pilot-scale evaporator illustrates its practicality.