Novel terminal sliding mode based fault tolerant attitude control for spacecraft under actuator faults

An exponent nonsingular fast terminal sliding mode (ENFTSM) control law is investigated in this paper for a rigid spacecraft with redundant thrusters in which thruster faults, and control input saturation as well as external disturbances have to be explicitly considered simultaneously. More specifically, in this proposed control scheme, fast convergence of spacecraft attitude tracking is achieved and faster reaching time can be guaranteed in comparison with the terminal sliding mode. When thruster fault occurs, the control parameters are adjusted dynamically in such a fashion that no fault detection and isolation mechanism is required in advance, and only the remaining active thrusters are assumed to be able to produce a combined force sufficient to allow the spacecraft to perform the given operations within the saturation magnitude. Lyapunov stability analysis shows that the resulting closed-loop system is stable it can withstand the effect of external disturbances, control input saturation and even faults by appropriately choosing the design parameters. The attitude tracking performance using the controller is evaluated through a numerical example.