CORRELATION OF THE CONTROLLER GAIN FOR LINEAR-QUADRATIC CONTROL

One of the barriers to acceptance of Linear quadracic (LQ) control in industry, is the lack of convenient tuning ''knobs'' that allow the op erators to quickly adjust the controller gain to desensitize a control ler during, say, an extreme disturbance that was not specifically desi gned for. The controller gain, K-c, is a familiar and very useful onli ne adjustment that is used during commissioning of PID control loops a nd also as a convenient safety ''knob''. The LQ controller has no such intuitive gain that can be quickly adjusted online and this discourag es its use in critical situations where the operator would like some d ecision. This paper describes the development of such a overall contro ller gain for LQ controllers and shows that simple least squares corre lations with a constraint parameter can be obtained, for not only SISO controllers, but also for MIMO controllers. Simulations are used to s how the accuracy of the correlations and example Matlab programs are p rovided to show the detailed calculations. (C) 1998 Elsevier Science L td. All rights reserved.