3-PUU并联机构运动副间隙耦合误差特性分析

Characterization of Gap Coupling Error of Motion Pair of 3-PUU Parallel Mechanism

并联机构运动副间隙直接影响机构的运动精度,导致末端输出特性产生差异。为了探究并联机构运动副耦合特性对末端输出精度的影响,以3-PUU并联机构为研究对象,设置运动副间隙误差为0.05、0.1、0.15、0.2 mm,利用单开链-局部指数积公式法对其进行耦合误差建模,从理论上推导运动副耦合特性与末端输出精度之间的关系,采用MATLAB对运动副耦合误差进行仿真分析,并制作样机进行试验。结果表明:当并联机构不同支链运动副存在误差时,机构末端沿x轴位置偏差随机构运动时间和关节间隙误差的增大呈现波动且伴随拐点和曲线分离;y轴位置偏差波动较大,在运动中轨迹拐点、折点和分离点相继出现,运动不平稳且超出运动空间,当并联机构双支链运动副误差为0.2 mm时,超工作空间达到-5.31 mm;机构末端沿z轴的位置偏差随着运动时间和关节间隙的增大呈现轨迹相互交错,与仿真分析一致。

The gap between the motion pair of a parallel mechanism directly affects the accuracy of its motion and results in differences in the output characteristics at the end effector.In order to investigate the influence of the coupling characteristics of the parallel mechanism motion pairs on the output accuracy of the end effector,taking a 3-PUU parallel mechanism as the research object and setting the gaps of the motion pairs as 0.05 mm,0.1 mm,0.15 mm,and 0.2 mm,the coupling errors were modeled using the single open-chain-local index product formula method,and the relationship between the coupling characteristics of the motion pairs and the output accuracy of the end effector was theoretically derived.The MATLAB was used for simulation analysis of the coupling error of the motion pairs,and a prototype was fabricated for experimental verification.The results show that when there are errors in the motion pairs of different branches in the parallel mechanism,the deviation of the end effector along the x-axis position fluctuates with the increase of the mechanism motion time and joint gap,and accompanying inflection points and curve separations.The y-axis position deviation fluctuates greatly,and inflection points,turning points and separation points appear successively in the motion,indicating unstable motion and exceeding the motion space.When the error of the motion pairs in the parallel mechanism with dual branches is 0.2 mm,the exceeding workspace reaches-5.31 mm.The position deviation of the end effector along the z-axis show trajectories intersect with each other as the mechanism motion time and joint clearance increase,which is consistent with the simulation analysis.