Ali Kasiri - Ph.D. Student of Space Engineering Aerospace Department, AMIRKABIR University of Technology, Tehran, Iran
Farhad Fani Saberi - Assistant Professor Space Sciences and Technology Institute, AMIRKABIR University of Technology, Tehran, Iran

This paper studies an output feedback second-order sliding mode control problem of spacecraft attitude control in the presence of the inertia tensor uncertainty and external disturbance. Mathematical modeling is presented based on spacecraft nonlinear equations of motion and quaternion parameters. Firstly, a new sliding surface based on only attitude error is selected, then the standard second-order sliding mode control approach is followed. Finally, controller stability and tracking problem are guaranteed by choosing suitable auxiliary control input. The stability is proven by using concepts of a strong Lyapunov function and Lyapunov stability theory. Numerical simulations of attitude control of spacecraft equipped with 6 PWPF thrusters are given to demonstrate the performance of the proposed controller.

attitude control-second order sliding mode-finite time convergence-attitude tracking