PID tuning for loop decoupling of multivariable systems with uncertainty

The loop decoupling reduction of multivariable systems that present plant uncertainty is not a simple problem. In this paper the role of the non-diagonal controller elements will be analysed in order to state a multivariable PID quantitative tuning. Thus, the definition of a new coupling matrix and a new quality function of the non-diagonal PID elements come in useful to quantify the amount of loop interaction and to tune the controllers respectively. This yields a criterion that makes possible to propose a sequential design methodology of the fully populated PID matrix controller, in the QFT (Quantitative Feedback Theory) robust control frame. Finally, a numerical example is included to show the practical use of this technique. Copyright (C) 2000 IFAC.