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具有固定转动轴线和变转动轴线3T1R并联机构构型综合

Type Synthesis of 3T1R Parallel Machine with Fixed Rotation Axis and Variable Rotation Axis

  • 摘要: 使用位移流形理论对具有固定转动轴线和变转动轴线两种运动模式的3T1R并联机构进行了构型综合。分析空间球面4R机构的一般运动学方程,通过求极限计算了一种特殊空间球面4R机构连杆在奇异位形的两个瞬时连续转动轴线。根据具有固定转动轴线和变转动轴线两种运动模式的球面机构,得到其连杆位移流形的表达式,从而设计了具有两种运动模式的3T1R并联机构。通过旋量理论,验证该3T1R机构在运动模式变换过程中的自由度和驱动副选取的正确性。结果表明,该3T1R并联机构具有固定转动轴线和变转动轴线两种3T1R运动模式,4条支链的4个驱动副能实现上述两种模式下机构的控制,当机构处于两种运动模式的变换位形时,需要增加一个辅助驱动副,才能实现该机构两种运动模式的变换。

     

    Abstract: Based on the displacement manifold theory, the configuration synthesis of 3 T1 R parallel mechanism with fixed rotation axis and variable rotation axis was carried out. According to the general kinematics equation of spatial 4 R spherical mechanism, the characteristics of rotation axis of spherical 4 R mechanism with two fixed axes were analyzed. The characteristics of rotation axis of spherical 4 R mechanism with fixed axis rotation and variable axis rotation were analyzed. Through limit calculation, the two instantaneous continuous rotation axes of the connecting rod of the spherical 4 R mechanism with fixed rotation axis and variable rotation axis in the motion mode transformation configuration were analyzed. The results showed that the two instantaneous continuous rotation axes of this kind of mechanism did not coincide under the motion mode transformation configuration. According to the spherical mechanism with two motion modes of fixed rotation axis and variable rotation axis, the expression of connecting rod displacement manifold was established. The frame of the spherical mechanism was connected with three moving pairs, and a new 3 T1 R motion mode generator was obtained. Based on its displacement manifold, a 3 T1 R parallel mechanism with two motion modes was designed. Through the screw theory, the correctness of the degree of freedom and the selection of driving pair of the mechanism in the transformation of 3 T1 R motion mode with variable axis rotation and 3 T1 R motion mode with fixed axis rotation were verified. The results showed that the 3 T1 R parallel mechanism had two 3 T1 R motion modes: fixed rotation axis and variable rotation axis. Four drive pairs of four branch chains can realize the control of the mechanism under the above two modes. When the mechanism was in the transformation configuration of the two motion modes, an auxiliary drive pair needed to be added to realize the transformation of the two motion modes of the mechanism.

     

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