A Decoupling Pole Placement Self-Tuning Controller for a Class of Multivariable Processes

Abstract

This paper describes a new multivariable self-tuning controller that specifically handles di fferent time delays between each of the input-output pairs (multiple delays), and deals with unknown or varying time delay (variable dead time compensation) without requiring an explicit estimate of each delay. The new algorithm can control unstable and/or nonminimum phase processes; it eliminates both set-point and load offsets without having to maintain integral action continuously; it decouples the loops, both dynamically and at steady state. The effective decoupling algorithm not only minimizes significant interactions among the control loops, it permits the use of a very simple design criterion, namely the approximate assignment of the primary closed-loop poles to prespecified locations.The controller is demonstrated using a simulated paper machine head box having an unusually large amount of (off-diagonal) interaction and a highly interacting unstable and nonminimum phase system.