平面5R并联机器人约束误差影响分析

Analysis on the Effects of Constraint Errors on Planar 5R Parallel Robot

少自由度并联机器人中的过约束构型,具有结构简单、刚度大的优点,但其依赖运动副轴线间的特殊几何约束关系,如平行、垂直、汇交于一点等,来实现预期的动平台自由度。此类机构有对几何约束条件敏感的缺点,约束误差的存在将对机构产生一系列不良影响。基于此,以平面5R并联机器人为对象,在分析其过约束特性基础上,研究运动副轴线几何约束误差导致的回路封闭变形协调条件。应用矩阵力法计算强制装配引起的机构附加内力以及连杆的变形,从而分析动平台的寄生运动以及机构的应变能波动。对一种具体的5R并联机器人进行仿真分析,计算结果揭示了过约束机构对运动副轴线几何约束误差的敏感性以及约束误差与过约束共同作用下对并联机器人性能的影响机理。

Overconstrained structures of lower-mobility parallel robot are considered more advantageous in simple structure and big rigidity. However certain special geometric constraints, such as joint axes parallel or perpendicular to each other or intersecting at one point, are necessary in realizing the end-effecter motion. Such mechanisms have the essential drawback of sensitivity with respect to the geometrical conditions, and therefore constraint errors can produce a series of bad effects on the mechanisms. Due to this fact, based on overconstraints analysis, the deformation compatibility conditions of planar 5R parallel robot, considering geometric constraint errors of joint axes, are studied. The additional internal force of mechanism and deformation of link are calculated by using the matrix force method, and then parasitic motions of moving platform are analyzed. Moreover, the strain energy fluctuations are investigated. For a specific planar 5R parallel robot, simulation is performed. The results reveal the sensitivity with respect to the constraint errors of overconstrained mechanism, and provide an insight into the effects of constraint errors and overconstraints on the performance of parallel robot mechanisms.