移动机械臂平台位置优化及运动规划

Optimization of platform placement and motion planning for mobile manipulators

针对移动机械臂执行任务时移动机械臂的平台位置对机械臂能否完成任务有较大的影响这个问题,研究了平台位置的优化。首先对机械臂的工作空间进行了分析,指出冗余度机械臂对同一个末端点的关节位形不唯一,从而无法度量机械臂的最优运动性能。然后利用机械臂关节自运动,采用可操作度指标向关节梯度方向进行投影,使机械臂的操作能力最大化,从而得到某个末端点的最大操作能力。进而根据得到的工作空间中操作能力分布,定义了相对可操作度指标,并绘制了全局操作能力图,得到了平台相对于目标对象的最佳平台位置。最后利用相对可操作度指标来启发快速搜索随机树(RRT)搜索,使机械臂在完成任务的过程中不断提高操作能力,在达到目标对象时处于最佳位形。对上述方法进行了数值仿真,结果验证了该方法的有效性。

In view of the issue that the placement of the platform of a mobile manipulator has a great influence on whether the manipulator can perform a given task, the optimization of the platform placement was studied. Firstly, the workspace of a redundant manipulator was investigated, and the manipulation capability of the redundant manipulator was maximized based on the manipulability index through the joint self-motion of the redundant manipulator. Secondly, the maximum manipulation capability at the specified work point was determined. Thirdly, the relative manipulability index （RMI） was defined by analyzing the manipulation capability of the manipulator in its workspace, and the global manipulability map （GMM） was presented based on the above analysis. Moreover, the optimal platform placement related to the given task was determined, and motion planning was implemented by an improved rapidly-exploring random trees （RRT） algorithm, which can enhance the manipulation capability from the initial point to the target point. The feasibility of the proposed algorithm was illustrated with numerical simulations on the mobile manipulator.