Robust optimal sliding mode control for spacecraft position and attitude maneuvers

In this paper, we propose new robust optimal control strategies for spacecraft position and attitude tracking maneuvers in the presence of external disturbances. First, two optimal position and attitude controllers are developed to achieve asymptotic convergence to the desired position and attitude. The first optimal control law is designed based on the inverse optimal control concept using Sontag-type formula and a control Lyapunov function. For the second control law, the optimal Lyapunov approach is used to design an optimal position and attitude controller. Then robust optimal position and attitude controllers are designed by using an integral sliding mode control method to combine a second order sliding mode controller with the derived inverse optimal controller or optimal Lyapunov controller. Both developed robust optimal controllers can minimize a performance index and ensure the stability of the closed-loop system and attenuation of external disturbance. An example of position and attitude tracking maneuvers is presented and simulation results are included to show the performance of the proposed controllers.