Wavelet based backstepping sliding mode control for spacecraft attitude regulation under control input constraint

In this paper, a wavelet based backstepping sliding mode controller for rotational maneuver is proposed for an orbiting three-axis stabilized spacecraft, taking the actuator saturation into account. Wavelet networks, which have superior learning capability in comparison to conventional neural network, are used for approximation of unknown system dynamics. This proposed controller comprises of a wavelet based saturation compensator and a robust backstepping sliding mode controller, and the latter one is designed to achieve the desired performance by attenuating the effect of approximation error caused by wavelet identifier. Lyapunov stability analysis shows that the resulting closed-loop system is globally asymptotically stable. To study the effectiveness of the corresponding control scheme, traditional methods are also developed for the control system. Both analytical and numerical results are presented to show the theoretical and practical merit of this approach.