In the machining of complex parts with free-formed surfaces, robots are widely employed due to their advantages of a large operating space and high flexibility. The industrial robot with 6 degrees-of-freedom (DOF) has an extra redundant degree of freedom around the tool axis, which does not affect the tool pose related to the workpieces but influences the robot's joint configuration. The motion performance and machining efficiency can be improved by optimizing the redundant angle. Based on this, an analytical path smoothing algorithm for 6-DOF robots with the consideration of redundant kinematics is proposed to improve the robot's dynamic performance. The tool tip position and orientation are fit with the analytical 5th degree Pythagorean-Hodograph (PH) spline to satisfy continuity, respectively. Therefore, the 5th degree polynomial spline with minimum acceleration is adopted to fit the redundant rotation angle and the tool tip position arc length. Then the tool path position spline, tool orientation spline, and redundant rotary angle spline are all synchronized to the tool position displacement, which makes it convenient to do interpolation along the tool path. The minimum time feed planning method considering the joint dynamic constraints is adopted to interpolate motion commands. Experimental results show that the motion efficiency of the robot in the same test path increases by 33.97 % compared with the regular spline without considering acceleration of the redundant angle spline. Meanwhile, the proposed tool path smoothing method effectively mitigates the joint vibration with a maximum reduction of 65.05 %, without sacrificing motion accuracy.

中文翻译：

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考虑冗余运动学的机器人加工分析刀具路径平滑算法


在自由曲面复杂零件的加工中，机器人因其操作空间大、灵活性高等优点而得到广泛应用。 6自由度工业机器人在工具轴周围具有额外的冗余自由度，这不会影响与工件相关的工具位姿，但会影响机器人的关节配置。通过优化冗余角度可以提高运动性能和加工效率。在此基础上，提出一种考虑冗余运动学的六自由度机器人解析路径平滑算法，以提高机器人的动态性能。刀尖位置和方向分别与分析的 5 度勾股图 (PH) 样条拟合以满足连续性。因此，采用最小加速度的5次多项式样条来拟合冗余旋转角度和刀尖位置弧长。然后刀具路径位置样条、刀具定向样条、多余旋转角度样条均与刀具位置位移同步，方便沿刀具路径进行插补。采用考虑关节动态约束的最小时间进给规划方法来插补运动指令。实验结果表明，在不考虑冗余角度样条加速度的情况下，机器人在相同测试路径上的运动效率比规则样条提高了33.97%。同时，所提出的刀具路径平滑方法有效地减轻了关节振动，最大减少了65.05%，且不牺牲运动精度。