Adaptive Robust Actuator Fault Accommodation for a Class of Uncertain Nonlinear Systems with Unknown Control Gains

Yuefei Wu,Zhenxing Mu,Fan Yang,Jianyong Yao,Guigao Le,Dawei Ma

doi:10.1155/2014/217501

Abstract

An adaptive robust fault tolerant control approach is proposed for a class of uncertain nonlinear systems with unknown signs of high-frequency gain and unmeasured states. In the recursive design, neural networks are employed to approximate the unknown nonlinear functions, K-filters are designed to estimate the unmeasured states, and a dynamical signal and Nussbaum gain functions are introduced to handle the unknown sign of the virtual control direction. By incorporating the switching functionσalgorithm, the adaptive backstepping scheme developed in this paper does not require the real value of the actuator failure. It is mathematically proved that the proposed adaptive robust fault tolerant control approach can guarantee that all the signals of the closed-loop system are bounded, and the output converges to a small neighborhood of the origin. The effectiveness of the proposed approach is illustrated by the simulation examples.

Highlights

In complex systems like chemical plants, nuclear reactors, and flight control systems, reliability is as important as performance
We propose an adaptive robust approach for actuator fault-tolerant control (ARFTC) of a class of uncertain nonlinear systems
We have guaranteed transient response. This result of transient response of the system is a direct consequence of the underlying robust filter structure of the ARFTC controller

Summary

Introduction

In complex systems like chemical plants, nuclear reactors, and flight control systems, reliability is as important as performance. A robust adaptive state feedback failure compensation method considering modeling uncertainties was proposed in [12, 24, 25] Such techniques were not well suited to suppress the undesirable transients when facing a sudden change in system parameters due to unknown actuator faults. The Nussbaum-type function was originally proposed by [28] for dealing with unknown sign of high frequency gain This method was generalized to higher order linear systems by [29]. For a class of time-varying parameter high-order uncertain nonlinear systems, a robust adaptive output-feedback control method was proposed in [30,31,32,33] for the unknown control gain direction and unpredictable state. In order to show the superior performance of the proposed scheme, comparative studies are performed using simulation examples

Problem Formulation and Preliminaries

Output-Feedback Based ARFTC

Application Example

Conclusions