Fault-Tolerant Optimal Spacecraft Attitude Maneuver: An Incremental Model Approach

Abstract

This paper addresses the fault-tolerant optimal attitude control problem for a rigid spacecraft with external disturbance, model uncertainties, and actuator faults. Firstly, the incremental nonlinear control technology is used to simplify the attitude control system into an incremental nominal model with a synthetic uncertainty/fault term that is estimated by a nonsingular terminal sliding mode disturbance observer. Secondly, considering a quadratic performance index, the original fault-tolerant optimal control problem is transformed into a guaranteed performance optimal problem of the nominal model. Benefiting from the simplicity of the incremental model, such a modified optimal control problem is solved online by the modified policy iteration adaptive dynamic programming without any initial stable policy assumption. Finally, the attitude angles of the closed-loop system are proved theoretically to be uniformly ultimately bounded at the desired state by using the Lyapunov methods. Simulation results are given to verify the effectiveness of the proposed fault-tolerant optimal attitude control strategy.