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一种3(Ra)PS变胞并联机构构型与运动学分析

Configuration and Kinematics Analysis of a 3(Ra)PS Metamorphic Parallel Mechanism

  • 摘要: 研究一种基于变胞铰链Ra (Reconfigurable axis)的新型3(Ra)PS变胞并联机构的可重构特性和统一运动学分析方法。根据约束螺旋系统表明,在一个构态下,(Ra)PS支链对平台没有约束,而在另一个构态下,通过改变可重构铰链Ra铰内轴线的位置,可以提供一个约束力。支链的两个构态使3(Ra)PS变胞并联机构具有4种构型,其中包括2R1T(2个旋转1个平移)、3R1T(3个旋转1个平移)、3R2T(3个旋转2个平移)和6 DOF(Degree of freedom)构型。根据支链两构态的差异,提出以一个支链构态作为另一个支链构态特例的统一运动学建模方法。在此基础上,建立3(Ra)PS变胞并联机构的驱动选择方案和可以包含4种构型的统一运动学模型。对逆运动学和正运动学进行求解,数值算例验证了理论结果的正确性。这种特殊类型的并联机构为特殊变胞机构的工作空间、路径规划和控制奠定了基础。

     

    Abstract: The reconfigurability and unified analytical kinematics analysis of a type of 3(Ra)PS metamorphic parallel mechanism were studied. According to the constraint screw system, in one configuration, the(Ra)PS chain had no constraint on the platform, while in another configuration, it can provide a constraint by changing the position of the inner axis of the Ra joint. The two configurations of the limb made the 3(Ra)PS metamorphic parallel mechanism have four kinds of topological structures, which had the ability to move between 2 R1 T(two rotations and one translation), 3 R1 T(three rotations and one translation), 3 R2 T and 6 DOF. The basic principles of metamorphic of such reconfigurable axis joint were revealed by investigating the correlation of the corresponding screw systems consisted of line vectors. A limb that can be used to construct a type of parallel mechanism was proposed. The sub-phases of the limb that accompanied the phase change of a specific reconfigurable axis joint were enumerated and the constraints corresponding to each phase were analyzed based on the reciprocity of the screw. Based on the analysis of the driving scheme, a unified kinematic modelling method with one configuration as a special case of the other was proposed through the difference between the two configurations of the limb. Four kinds of driving schemes and four kinds of unified kinematic models covering 3(Ra)PS metamorphic parallel mechanism were established. The drive selection scheme of 3(Ra)PS metamorphic parallel mechanism and the unified kinematic model covering four configurations were established. The inverse kinematics and forward kinematics were solved analytically, and the theoretical results were verified by numerical examples. The proposed metamorphic parallel mechanism laid a foundation for the workspace, path planning and control of the metamorphic mechanism.

     

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