Attitude

This article investigates the spacecraft attitude reorientation control problem in the presence of attitude constraint, actuator saturation, parametric uncertainty, and external disturbance. First, a nonlinear tracking law based on a strictly convex potential function is proposed to generate the virtual control angular velocity which has only one global minimum. Then, utilizing the auxiliary system governed by the difference between the upper bound of actuator torque and the untreated command torque, a novel backstepping controller is presented, which is able to satisfy the constraint of actuator saturation and guarantee the stability of control system. In addition, an extended state observer with the uniformly ultimately bounded estimation error and finite-time stability is put forward to realize the real-time compensation of the compound disturbance consisting of parametric uncertainty and external disturbance. Therefore, it enhances the robustness and improves the accuracy of the extended state observer–based backstepping controller. Finally, simulation results validate the effectiveness and reliability of the proposed schemes