基于主任务零空间的空间机械臂重复运动规划

针对空间机械臂执行封闭在轨操作任务时，终止时刻机械臂关节角与基座位姿发生漂移的问题，提出一种基于主任务零空间的空间机械臂重复运动规划方法。结合在轨操作任务特点，分析了空间机械臂重复运动要求，将重复运动问题转化为关节构型、末端姿态与基座姿态复位优化问题并设计了空间机械臂重复运动优化算子；在此基础上，引入任务优先级概念，将重复运动优化算子引入主任务的零空间，保证主任务完成的同时机械臂重复运动得以优化；进而为增强重复运动优化能力，空间机械臂基座姿态保持算子也被引入。仿真结果表明，新算法能够减小关节角与基座位姿的漂移，实现空间机械臂重复运动规划，可以应用于实际的控制系统中。

Repetitive Motion Planning for Space Manipulator Based on Null Space of Primary Task

When space manipulator accomplishes a closed trajectory task in Cartesian space, its joint angles and base pose exist drift at the end time. To solve these problems, a repetitive motion planning scheme for space manipulators is presented in this paper. Considering the characteristics of on orbit tasks, the requirements of repetitive motion are analyzed, and then the repetitive motion problem is transformed to the optimization problem of joint configuration reset, end effector attitude reset and base attitude reset. Meanwhile, the repetitive motion optimization operator is designed. On this basis, an order of priority for given tasks is introduced, and the repetitive motion optimization operator is substituted into the null space of the primary task, thus ensuring the repetitive motion optimization in the premise of accomplishing the primary task. Thereafter, in order to enhance the optimization capability, the base attitude maintenance operator is also introduced. Simulation results prove that the new method can be used to reduce drifts of joint angles and base pose and to achieve the repetitive motion of space manipulators, and can be applied to actual control systems.