Velocity-free saturated PD controller for asymptotic stabilization of spacecraft

This paper addresses the asymptotic stabilization of rigid spacecraft with actuator constraints and without velocity measurement. Two simple saturated proportional-derivative (SPD) controllers are proposed. Lyapunovʹs stability theory is employed to show asymptotic stabilization. Advantages of the proposed approaches include the absence of the modeling information in the control law formulation and the ability to ensure that actuator constraints are not violated. This is accomplished by selecting control gains a priori, removing the possibility of actuator failure due to excessive torque input levels. The effectiveness of the proposed approach is illustrated via simulations.