Multivariable PI control of unstable systems

Decentralized and centralized multivariable PI controllers are designed for unstable systems described by a transfer function matrix. Decentralized PI controllers are designed by using a constant detuning factor and centralized PI controllers are designed by the Tanttu and Lieslehto method [J.T. Tanttu, J. Lieslehto, A comparative study of some multivariable PI controller tuning methods, in: R. Devanathan (Ed.), Intelligent Tuning and Adaptive Control Methods, Pergamon, 1991, pp. 357-362]. For systems with one-way unstable interaction, both the decentralized and centralized PI controllers stabilize the systems. For systems with two-way unstable interactions, decentralized controllers do not stabilize the systems, whereas the centralized PI controllers do stabilize the systems. The Tanntu and Lieslehto method is extended for designing centralized PID controllers also. (C) 1997 Elsevier Science B.V.