A model matching approach for designing decentralized MIMO controllers

A frequency-domain methodology for the design of decentralized control systems for multiple-input–multiple-output (MIMO) plants is presented. The method allows the designer to directly specify the disturbance response of the individual loops. The desired responses are incorporated through appropriately chosen reference models. A streamlined reference specification procedure is developed, which allows the designer to visualize the tradeoff between robustness and response speed. This makes it easy to pick a meaningful reference model, and significantly reduces the trial and error iterations necessary to meet the design requirements. The method is applicable to stable, non-minimum phase, irrational, and to a certain class of unstable plant models. The frequency-domain controller synthesis technique produces low order, easily implementable controllers, making the method attractive to the industry. The design examples demonstrate that achieving good disturbance rejection in each individual loop in most cases guarantees satisfactory set-point response, and good decoupling.