Finite-time fault tolerant attitude control for over-activated spacecraft subject to actuator misalignment and faults

A finite-time attitude compensation control scheme is developed for an over-activated rigid spacecraft subject to actuator faults, misalignment, external disturbances and uncertain inertia parameters. The controller is synthesised based on the sliding mode control theory, and guarantees the finite-time reachability of the system states. A sufficient condition for the controller to accommodate misalignment and faults of actuator is presented. An optimised control allocation algorithm based on the Karush-Kuhn-Tucker condition is then applied to distribute the commanded control to each actuator, and optimise the consumption of energy. Numerical simulation results are presented that highlight the performance benefits of the control law.