Design of Multivariable Feedback Systems Using Progressive Decoupling

A general procedure for the design of multivariable feedback systems is presented. The system is first rendered weakly coupled by a suitable choice of some controller ratios and then designed by conventional single-loop techniques. One major characteristic of the method is that various degree of coupling of the system can be obtained, dependent on the complexity of the controller ratios chosen. Furthermore, a criterion is given to decide when the system can be regarded as weakly coupled, such that single-loop design techniques can be applied. The method gives the designer more freedom in the design and provides him with many more choices for a suitable controller. The effectiveness of the method is demonstrated by an application to a 4 x 4 boiler furnace example.