Finite-time Attitude Tracking for Spacecraft With Unknown Boundary Disturbance and Angular Velocity

This paper investigates a velocity-free finite-time attitude control scheme for rigid spacecrafts with unknown boundary external disturbance. By using the quadratic Lyapunov function (QLF) method, a finite-time observer is designed to estimate unknown angular velocity and boundary of external disturbance. Combining adaptive control technique with adding a power integrator (AAPI), a finite-time controller is proposed. Rigorous Lyapunov-based analysis shows that both the observation errors and tracking errors can converge to the equilibrium point in finite time under the designed control law. Numerical simulation results illustrate the performance of the proposed control scheme.