Smooth adaptive finite time attitude tracking control of rigid spacecraft

This paper investigates two chattering-free finite-time controllers for the rigid spacecraft attitude tracking control problem considering modeling uncertainty and external disturbance. First, the basic controller is designed utilizing integral terminal sliding mode surface (ITSMS) with prior knowledge of the total system uncertainty consisting of modeling uncertainty and external disturbance. Second, an adaptive controller is proposed to deal with unknown system uncertainty through on line approximating upper bound information of the first derivative of the total system uncertainty. Compared with the existing literature, advantages of the proposed control laws include not only finite-time convergence rate for the closed-loop system robustness against uncertainty, but also chattering-free control signal since the derivative of the control input signal is designed directly and then the switch functions are hidden behind the integration operation. At last, rigorous stability proof is given via Lyapunov stability theory and digital simulations are undertaken to verify the effectiveness of the proposed controllers.