A Higher-Order Sliding Mode Three-Axis Solar Pressure Satellite Attitude Control System

This paper presents the design of a higher-order sliding-mode control system for the three-axis attitude control of spacecraft using solar-radiation pressure in a finite time. The spacecraft, equipped with four solar plates, is assumed to be orbiting in an elliptic orbit. The nonlinear spacecraft model includes uncertain parameters and external-disturbance moments. The objective is to control the roll-, pitch-, and yaw-angle trajectories of the spacecraft along prescribed reference trajectories using the solar plates. A higher-order sliding-mode control system is designed which consists of (1) a nominal nonlinear finite-time-stabilizing control law designed based on the notion of geometric homogeneity, and (2) a discontinuous sliding-mode control law to attenuate the effect of uncertainties in the model. For the synthesis of this control system, the attitude-angle errors and their first two derivatives are used. It is shown that in the closed-loop system, the attitude error as well as its first and second derivatives converge to the origin in a finite time. Then a high-gain observer is designed to estimate the first and second derivatives of the attitude-tracking error for synthesis, using only attitude-angle measurement. The closed-loop system including the observer achieves a fast recovery of the performance of the state-feedback higher-order sliding-mode control system. Simulation results are presented which show precise attitude control of the satellite, despite uncertainties in the model, using state variable as well as output feedback. (C) 2015 American Society of Civil Engineers.