Observer-based fault diagnosis incorporating adaptive sliding mode control for spacecraft attitude stabilization

This paper addresses the problem of active fault tolerant control of spacecraft attitude stabilization in the presence of actuator failures, actuator saturation, and external disturbances simultaneously. As a stepping stone, an observer-based fault diagnosis mechanism is presented to reconstruct/estimate the actuator faults through iterative leaning method. Then, with the reconstructed information, an adaptive robust sliding mode fault tolerant control law is developed to ensure the closed-loop attitude control system will reach the real sliding mode surface in finite time, while the singularity and chattering problems have been avoided/restrained via a saturation function and a modified gain adjusting law. The associated stability proof is constructive and accomplished by the development of a novel Lyapunov function candidate. The key feature of the proposed strategies is that the closed-loop system can be guaranteed bounded stable even in the face of actuators' constraints and failures within finite time theoretically. Numerical simulation results are presented to illustrate the performance of the proposed schemes.