Flexible spacecraft's active fault-tolerant and anti-unwinding attitude control with vibration suppression

Abstract

Reliable spacecraft's attitude control is one of the core research areas of the space industry due to the need for sustainable space exploration and advancements in space technology. In this paper, an active fault-tolerant control scheme is designed for a flexible spacecraft's attitude control experiencing multiple actuator faults, inertial uncertainties, external disturbances, and fault estimation errors while suppressing the flexible appendages' vibrations. First, a nonlinear flexible spacecraft's relative attitude model with multiple actuator faults is outlined. A sliding mode-based flexible vibration observer is proposed to estimate the flexible appendage-related vibrations. The designed active fault-tolerant control scheme comprises an adaptive time-varying fault-detection strategy for quickly detecting actuator faults and avoiding false alarm rates caused by uncertainties and disturbances. An extended state observer then estimates the lumped faults effects, including the multiple actuator faults and uncertainties. The driving control is switched from nominal to fault-tolerant once the faults are successfully identified with acceptable accuracy. Besides, based on the information from the fault identification and flexible vibration observer, a novel, unwinding-free, and adaptive fault-tolerant attitude controller is designed to effectively acclimatize the detected faults, despite errors in lumped faults and flexible modes' estimations. With multiple actuator faults and uncertainties, the remunerative and precise attitude tracking control with vibration suppression is realized without using smart vibration-suppression materials. Finally, the efficacy of the propounded scheme is illustrated via comparative simulation outcomes with the existing results.