High-gain Observers in Nonlinear Feedback Control

Abstract

High-gain observers play an important role in the design of feedback control for nonlinear systems. This lectures overviews the essentials of this technique. After a brief historical background, a motivating example is used to illustrate the main features of high-gain observers, with emphasis on the peaking phenomenon and the role of control saturation in dealing with it. The use of the observer in feedback control is discussed and a nonlinear separation principle is presented. The use of an extended high-gain observer as a disturbance estimator is covered. Challenges in implementing high-gain observers are discussed, with the effect of measurement noise as the most serious one. Techniques to cope with measurement noise are presented. The lecture ends by listing the speaker's experience with experimental testing of high-gain observers.