PERFORMANCE ASSESSMENT OF MULTIVARIABLE FEEDBACK CONTROLLERS

Procedures are developed for assessing the performance of multi-input multi-output (MIMO) linear feedback control system. The predicted perf ormance of the MIMO minimum variance controller is used as a lower bou nd against which current performance is assessed. To use the procedure s, one needs only a set of representative data on the controlled varia bles collected under the current feedback control scheme, and an estim ate of the process interactor matrix characterizing the dead-time stru cture of the process. A non-parametric correlation test allows for a q uick check on the closeness of the performance of the current feedback control system to the theoretical lower bound. A quantitative analysi s then provides an estimate of the theoretical lower bound on the vari ance-covariance matrix of the controlled variables, and on the quadrat ic performance objective of the minimum-variance controller. A measure of controller performance based on the ratio of the current value of the quadratic objective to this thoeretical lower limit can then be mo nitored on-line. The purpose of these methods is to allow engineers to assess the current performance of the existing control systems, to mo nitor how this performance changes over time, to see which variables a re well controlled and which are not, and to help in deciding whether or not there is sufficient incentive to reidentify the process model a nd/or redesign the controller. Copyright (C) 1996 Elsevier Science Ltd .