对失控航天器在轨服务的自适应滑模控制器设计

Adaptive sliding mode controller design for on-orbit servicing to uncontrollable spacecraft

为实现对自由翻滚的失控目标航天器进行在轨服务,基于二阶滑模控制算法设计了相对位置与姿态耦合的自适应控制器。考虑相对转动对相对平动的耦合作用,建立了两航天器对接端口间相对位置与姿态耦合的动力学模型,并在此基础上设计了自适应Super twisting控制器,以减弱已知界限的有界干扰所产生的震颤效应,使闭环系统在有限时间内收敛到平衡点。利用李雅普诺夫方法证明了有界干扰下的闭环系统稳定性,并对收敛时间的上界进行了估计。仿真结果表明,与Super twisting算法相比,所设计的自适应二阶滑模控制器对参数不确定性及线性增长有界干扰具有较强的鲁棒性,且控制精度满足在轨服务的任务需求。

A relative position and attitude coupled adaptive controller is designed on the basis of second-order sliding mode control algorithm. It is proposed for on-orbit servicing on the free tumbling uncontrollable target spacecraft. Considering the coupled effect of relative rotation on relative translation, a relative position and attitude coupled dynamic model is derived for two docking ports on different spacecraft. Based on this coupled relative motion model, an adaptive super twisting controller is proposed to attenuate the chattering phenomenon caused by bounded perturbation with known upper bound. It makes the closed-loop system converge to the equilibrium point in finite time. Under the condition of limited disturbances, the closed- loop system is proved to be steady by Lyapunov method and the supremum of convergence time is estimated. By comparison with the super twisting method, numerical simulations are performed to validate strong robustness of the designed adaptive second-order sliding mode controller for parameter uncertainty and linearly growing bounded disturbances. The control accu- racy is high enough for the requirement of on-orbit servicing mission.