一种新型并联机构的运动分岔特性及运动学分析

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A novel parallel mechanism with bifurcated motion is introduced by integrating a discontinuously movable mechanism in the limb design. The mechanism has instantaneously six degrees of freedom at a singularity point. With the discontinuously movable mechanism moving to different motion branches, the parallel mechanism has the ability to evolve into four configurations with different motion characteristics, including 3T motion configuration, 3R motion configuration, 2T1R motion configuration and 2R1T motion configuration. By rigidizing the input joints, the rationality of input scheme for this mechanism is identified based on screw theory. Six motors nearly mounted to the base can sufficiently drive the parallel mechanism to switch between different motion configurations and perform different motions. The forward and inverse kinematics of the mechanism in different configurations are given. The translational motions axe independent with each other and decoupled with the rotational motions. Kinematics simulation is performed for the parallel mechanism and the results show that theoretical analyses are correct. The workspace of the parallel mechanism in a general configuration is given.将一种四杆运动限定机构引入并联机构支链的设计中,得到一种具有运动分岔特性的并联机构。当机构处于运动分岔点时,动平台具有瞬时的6自由度。通过驱动运动限定机构执行不同的运动,机构可以演变成具有不同自由度特性的构型,包括三移动构型,三转动构型,两移动一转动构型和两转动一移动构型。基于螺旋理论,采用刚化驱动的方法,分析驱动选取的合理性,机构在各个构型下的运动以及构型间的切换可以通过六个固定在基座处的电动机实现。分析并联机构在不同构型时的运动学正反解,结果显示该机构三个方向上的移动彼此独立,且移动运动和转动运动是解耦的。对模型进行运动仿真,仿真结果验证了理论分析的正确性。给出机构在一种一般构型下的工作空间。