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.

本文解决了具有外部干扰、模型不确定性和执行器故障的刚性航天器的容错最优姿态控制问题。首先，采用增量非线性控制技术，将姿态控制系统简化为具有综合不确定性/故障项的增量标称模型，该模型由非奇异终端滑模扰动观测器估计。其次，考虑二次性能指标，将原容错最优控制问题转化为标称模型的保证性能最优问题。得益于增量模型的简单性，这种修改后的最优控制问题通过修改后的策略迭代自适应动态规划在线求解，无需任何初始稳定策略假设。最后，使用李雅普诺夫方法，理论上证明了闭环系统的姿态角最终一致地有界于期望状态。仿真结果验证了所提出的容错最优姿态控制策略的有效性。