Abstract: To improve the accuracy of the dynamic model of the six-degree-of-freedom parallel robot in space,taking the 6-RSS parallel robot (R:rotating joint,S:spherical joint) as the research object,a dynamic modeling method combining the elastic deformation of the branch chain and the random change of the joint clearance was proposed.According to the geometric structure and initial state of the parallel robot,the kinematics analysis was carried out under ideal conditions.The mathematical statistics principle and symbolic function were used to establish the kinematic model of the revolute joint with clearance and spherical joint with clearance.The bar virtual length and the collision contact force at each joint were calculated.Combining the bar virtual length,the collision contact force and the elastic dynamics model,the elastic dynamics model of the 6-RSS parallel robot with joint clearance was established.Finally,the reasons for the errors of the elastic deformation of the branch chain and the joint clearance under different conditions and the reasons for the combined errors of the two were analyzed.The results showed that the improved dynamic modeling method fully considered the coupling and instantaneity of the elastic deformation of the branch chain and the joint clearance,and was more accurate than other dynamic modeling methods.

Key words: parallel robot, joint clearance, generalized collision force, elastic dynamics, bar virtual length

摘要： 为了提高空间六自由度并联机器人动力学模型的精度,以6-RSS并联机器人(R:转动副,S:球面副)为研究对象,提出一种将支链弹性变形和运动副间隙随机变化相结合的动力学建模方法。首先,根据几何结构与初始状态,开展理想条件下的运动学分析。利用数理统计原理和符号函数建立含间隙的转动副与球面副运动学模型,进而计算杆件虚长度和各个运动副处的碰撞接触力。然后,将相关参数结合到弹性动力学模型中,建立含运动副间隙的6-RSS并联机器人弹性动力学模型。最后,分析不同状态下支链弹性变形和运动副间隙各自产生误差的原因以及两者综合产生误差的原因。结果表明:改进后的动力学建模方法充分考虑了支链弹性变形和运动副间隙的耦合性与瞬时性,较其他动力学建模方法更加精确。

关键词: 并联机器人, 运动副间隙, 广义碰撞力, 弹性动力学, 杆件虚长度