航天器近距离交会的固定时间终端滑模控制

Fixed-Time Terminal Sliding Mode Control for Close-Range Rendezvous

针对航天器近距离交会段的位置姿态耦合控制问题,假设航天器受外界干扰且目标航天器存在空间自由翻滚情形时,基于固定时间概念设计了一种六自由度位姿终端滑模自适应控制器,通过引入显含正弦函数的切换项来避免奇异问题。此外所设计的控制器含双幂次项,不仅能全局提高姿态和位置的跟踪速度及精度,还能估计系统稳定所需的时间上界,且该上界与状态初始值无关。基于Lyapunov方法分析了闭环系统的固定时间稳定性。仿真结果表明,该控制器能快速实现对航天器近距离交会时相对位置和姿态的控制,具有较高的精度和良好的干扰抑制能力。

The problem of the relative position and attitude coupled control for rendezvous and docking is investigated in this paper, which takes the external disturbances into consideration and assumes that the target spacecraft is freely tumbling. An adaptive 6-DOF control scheme is proposed based on the concept of the fixed-time stabilization. Besides, the singularity problem is solved through a switch function which not only makes the settling time estimable, but also the estimated value is independent of the initial values of states. Then the stability proof is accomplished by the development of a Lyapunov function. The numerical results show that this method achieves good performance and robustness.