具有2T1R与2R1T运动模式3自由度并联机构型综合

使用位移流形理论综合了具有2T1R与2R1T两种运动模式的并联机构。选取一种具有此类运动模式变换的机构,分析了其自由度变换时的位形特征,使用螺旋理论分析了其在不同运动模式下的自由度特征,分析了支链驱动副选取的可行性。结果表明,该并联机构具有2T1R与2R1T两种运动模式。在两种运动模式的一般位形下,使用3个驱动副可以实现对机构的控制;在两种运动模式的变换位形下,支链2连接动平台和定平台的2个转轴共线,机构自由度为4。在支链1中增加辅助驱动副,此驱动副只在机构运动模式变换时工作,可以实现并联机构在2T1R与2R1T两种运动模式之间变换。

Type Synthesis of 3-DOF Parallel Mechanism with 2T1R and 2R1T Motion Mode

The parallel mechanisms have both 2T1R and 2R1T motion mode were synthesized by using the theory of displacement manifold. The characteristic of a typical variable freedom kinematic chain was analyzed. The structure of the mechanism was constituted with three legs. Two of them were kinematic chain with four and six degrees freedom, respectively. And the other one leg was a variable freedom kinematic chain. A mechanism had both 2T1R and 2R1T motion mode was given for an example. The freedom of the mechanism in different motion mode was verified. The transform configuration of the mechanism between different motion modes was verified feasible by using screw theory. The results showed that the new parallel mechanism had two modes: 2T1R and 2R1T. At the general configuration of the two motion modes of the mechanism, the new type of mechanism can be controlled by using three active joints. At the transformation configuration of two modes of motion of the mechanism, two revolute joints of leg 2 that were connected with moving platform and fix ground respectively were collinear, the degree of freedom of the mechanism was 4 at that configuration. The auxiliary active joint was added in the branch 1, which was only applied when the mechanism motion mode was transformed, and then the motion mode of the parallel mechanism can be transformed between 2T1R and 2R1T.