Sliding-Mode-Based Attitude Tracking Control of Spacecraft Under Reaction Wheel Uncertainties

The attitude tracking operations of an on-orbit spacecraft with degraded performance exhibited by potential actuator uncertainties(including failures and misalignments) can be extraordinarily challenging. Thus, the control law development for the attitude tracking task of spacecraft subject to actuator(namely reaction wheel) uncertainties is addressed in this paper. More specially, the attitude dynamics model of the spacecraft is firstly established under actuator failures and misalignment(without a small angle approximation operation). Then, a new non-singular sliding manifold with fixed time convergence and anti-unwinding properties is proposed, and an adaptive sliding mode control(SMC) strategy is introduced to handle actuator uncertainties, model uncertainties and external disturbances simultaneously. Among this, an explicit misalignment angles range that could be treated herein is offered. Lyapunov-based stability analyses are employed to verify that the reaching phase of the sliding manifold is completed in finite time, and the attitude tracking errors are ensured to converge to a small region of the closest equilibrium point in fixed time once the sliding manifold enters the reaching phase. Finally, the beneficial features of the designed controller are manifested via detailed numerical simulation tests.

Coordinated attitude control for flexible spacecraft formation with actuator configuration misalignment

This paper investigates the coordinated attitude control problem for flexible spacecraft formation with the consideration of actuator configuration misalignment.First,an integral-type sliding mode adaptive control law is designed to compensate the effects of flexible mode,environmental disturbance and actuator installation deviation.The basic idea of the Integral-type Sliding Mode Control(ISMC)is to design a proper sliding manifold so that the sliding mode starts from the initial time instant,and thus the robustness of the system can be guaranteed from the beginning of the process and the reaching phase is eliminated.Then,considering the nominal system of spacecraft formation based on directed topology,an attitude cooperative control strategy is developed for the nominal system with or without communication delay.The proposed control law can guarantee that for each spacecraft in the spacecraft formation,the desired attitude objective can be achieved and the attitude synchronization can be maintained with other spacecraft in the formation.Finally,simulation results are given to show the effectiveness of the proposed control algorithm.