Spacecraft attitude stabilization using optimal sliding mode control

The attitude stabilization problem for a spacecraft is addressed through the combination of optimal control and sliding mode variable structure control method. We first determine an optimal sliding manifold for the kinematical subsystem of the spacecraft. Then a variable structure controller, which is based on equivalent control and the optimal sliding surface, is designed for the whole dynamical and kinematical system. An important feature of the methodology is that when the sliding manifold is reached, the attitude variables will be stabilized to the origin in the sense of optimality with respect to a quadratic cost functional. The proposed controller is also robust to external disturbances. Simulations are performed to demonstrate the effectiveness of the proposed optimal sliding mode controller.