Anti-windup design for uncertain nonlinear systems subject to actuator saturation and external disturbance

A novel anti-windup design method is provided for a class of uncertain nonlinear systems subject to actuator saturation and external disturbance. The controller considered incorporates both an active disturbance rejection controller as well as an anti-windup compensator. The dynamical uncertainties and external disturbance are treated as an extended state of the plant, and then estimate it using an extended state observer and compensate for it in the control action, in real time. The anti-windup compensator produces a signal based on the difference between the controller output and the saturated actuator output, and then augment the signal to the control to deal with the windup phenomenon caused by actuator saturation. We first show that, with the application of the proposed controller, the considered nonlinear system is asymptotically stable in a region including the origin. Then, in the case that the controller in linear form, we establish a linear matrix inequality-based framework to compute the extended state observer gain and the anti-windup compensation gain that maximize the estimate of the domain of attraction of the resulting closed-loop system. The effectiveness of the proposed method is illustrated by a numerical example. Copyright (c) 2016 John Wiley & Sons, Ltd.