Fault tolerant satellite attitude control using solar radiation pressure based on nonlinear adaptive sliding mode

An adaptive fault tolerant nonlinear control design based on the theory of sliding mode is proposed to control the attitude of a satellite using solar radiation pressure. The system comprises of a satellite with two-oppositely placed solar flaps. The nonlinear model describing the system is used to derive an adaptive fault tolerant control law, based on Lyapunov stability theorem, in the presence of unknown, slow-varying satellite mass distribution and solar parameter. Using this control law the solar flaps are suitably rotated to achieve desired satellite attitude performance. The detailed numerical simulation of the governing nonlinear system equation of motion including the effects of various system parameters on the controller performance, establishes the feasibility of the proposed adaptive control strategy in comparison with the sliding mode control without adaptation. This paper also examines several scenarios including sudden failure of one of the solar flaps, occurrence of an abrupt blockage of one of the rotating solar flaps, and occurrence of a periodic actuator fault. The numerical results show the robustness of the proposed adaptive control scheme in controlling the satellite attitude in the presence of external disturbances as well as in the event of failure of one of the solar flaps.