Velocity-free sliding mode control for spacecraft with input saturation

This paper investigates the robust control for spacecraft without angular velocity measurement subject to the external disturbances and input saturation constraints. A novel integral sliding mode surface that is suitable to solve the problem of input saturation constraints is established based on the hyperbolic tangent function. Both controllers can deal with the actuator saturation and external disturbances simultaneously by using the sliding mode surface. The first controller is full state feedback, while the second one just contains attitude information, where the angular velocity is unnecessary due to the existence of a finite-time observer. Finally, Lyapunov theory and simulation results are provided to illustrate the effectiveness of the controllers.