Chapter 4 - Observer-based fault tolerant delayed control

Abstract

This chapter addresses the observer-based fault tolerant attitude control problem for spacecraft in the presence of model parameter uncertainty, external disturbances, time-varying input delay, actuator faults, and actuator saturation. The observer with a new variable introduced is proposed to estimate the attitude angle and angular velocity. It ensures ultimately bounded estimation errors, and the time-varying input delay is explicitly reflected using the estimation of time-varying state delay. To achieve fault tolerant control performance, the estimation of fault signal is also applied to the controller. The observer and controller design account for both model parameter uncertainty and time-varying delay. The Lyapunov stability analysis shows that the observer-based controller can make the spacecraft attitude angle and angular velocity uniformly ultimately bounded. Sufficient conditions for the existence of observer-based controller are given based on LMIs. Solving LMIs can obtain the controller gain matrix and observer gain matrix exactly. Furthermore, numerical simulations are performed to demonstrate the effectiveness of the proposed control method.