A sub-optimal feedback controller for on-line computer applications†

This paper discusses a method of obtaining feedback control for dynamic processes described by non-linear differential equations. Because an optimal feedback control law cannot generally be derived for non-linear processes, the technique described herein is sub-optimal, but the degree of sub-optimality is a design parameter of the technique. The feedback control law is formulated for a model of the non-linear process linearized about the operating state. The optimal control law is developed for the linear model, and is applied to the physical process. Disturbances and model inaccuracies are compensated by the feedback control. An example problem is worked illustrating the application of the technique, and numerical results are presented.