Extended state observer-based third-order sliding mode finite-time attitude tracking controller for rigid spacecraft

In this paper, the attitude tracking control problem for a rigid spacecraft in the presence of system parameter uncertainties and external disturbances is addressed. First, a new nonsingular finite-time sliding surface is introduced and third-order sliding mode finite-time attitude control law is designed to achieve precise accurate tracking responses and robustness against inertia uncertainties and external disturbances.The stability of the closed-loop system is rigorously proved using the Lyapunov stability theory. Then, a new finite-time extended state observer is established to estimate total disturbances of the system. The extended stated observer-based sliding mode control technique yields improved disturbance rejection and high-precision attitude tracking. Moreover, this control law can avoid the unwinding phenomenon and overcome the input saturation constraint by introducing an auxiliary variable to compensate for the overshooting. A Lyapunov based analysis is provided to guarantee sufficiently small observation error and stabilization of the closed-loop system in finite time. Numerical simulations are conducted to verify the effectiveness of the proposed control method.