Adaptive Control - a Novel Approach to Control System Design

Although modern control theory has promised a great deal, its actual impact on the design of practical control systems has been disappointing. Most designers have found classical methods to be more reliable than the so-called modern methods. One reason for this has been the fact that modern control theory relies upon sophisticated linear models of the process and these are, either not available or, worse still, ill-defined because the model changes with operating point. Adaptive control offers a fresh new approach to control system design which overcomes many of the disadvantages of other modern methods. An integral part of any adaptive control scheme is an on-line parameter estimator which is capable of initially tuning the controller and of retuning it should the model subsequently change. Also, adaptive controllers are downwards compatible in the sense that they revert to conventional PID controllers if the adaptation mechanism is switched off. This paper will give a brief survey of some recent results in adaptive control with emphasis on the practical utility of these design methods.