空间机器人组装超大型结构的动力学分析北大核心CSCD

超大型航天结构具有超大柔性、超低固有频率的特点,空间机器人在轨组装时应尽可能避免激起超大型结构的柔性振动.空间机器人组装超大型结构模块的过程分成抓捕阶段、位姿调整与稳定阶段、安装阶段和爬行阶段.通过对安装阶段的动力学与控制研究,提出共线安装的轨迹规划方法,有效避免了柔性结构振动.首先,采用自然坐标法和绝对节点坐标法建立主结构-空间机器人-待组装结构的在轨组装系统动力学模型.然后,将共线安装的要求转化为空间机器人的轨迹规划约束,要求空间机器人质心到主结构/待组装结构的距离保持不变,实现共线安装的轨迹规划.数值仿真表明:提出的组装方法在组装过程中可有效避免超大型结构的横向运动,降低夹持力矩.最后,分析了系统参数对组装过程动力学响应的影响,为超大型航天器的在轨组装提供了参考.

Dynamic Analyses of the Assembling Process of Ultra-Large Structures With Space Robots

Structural vibrations of ultra-large structures during on-orbit assembly should be prevented to the maximum extent, given the extreme structural flexibility and low natural frequencies. The assembling process was divided into 4 stages: the grasping stage, the position-attitude adjusting and stabilizing stage, the mounting stage and the crawling stage. For the mounting stage, the dynamics and control were addressed, and a collinear assembly trajectory planning method was proposed to prevent structural vibrations. First, a dynamic model for the on-orbit assembly system including the main structure, the space robot and the assembling structure, was established based on natural coordinate formulation and absolute node coordinate formulation. Second, the requirements of collinear assembly were transformed into a trajectory planning problem of the space robot. The distance from the space robot mass center to the main structure should remain fixed, which is the main idea of the proposed collinear assembly method. Numerical simulation results show that, the proposed assembly method can effectively prevent the transverse motions of the ultra-large structure and reduce the required grasping moment. Finally, the influences of the system parameters on the dynamic responses during the assembly process were studied. The work provides a theoretical basis for the on-orbit assembly of ultra-large spacecraft.