Abstract: To grasp the dynamic characteristics of 4-UPS-RPU spatial parallel mechanism with clearance,the dynamic model of parallel mechanism with spherical clearance was built and dynamic analysis was realized.By assuming that there was a clearance between driving branches of parallel mechanism and spherical elements attached to the moving platform,the kinematic model of spherical joint with clearance was established based on “Contact-Separation” of two-state model,and the contact deformation and relative contact velocity were presented on account of above research.Based on Lankarani-Nikravesh contact force model and improved Coulomb friction model,the rigid-body dynamic model of 4-UPS-RPU parallel mechanism with spherical clearance was established by Lagrange equation.The dynamic model was solved by numerical calculation,and the dynamic characteristics of parallel mechanism with spherical clearance were analyzed.The result showed that the spherical clearance had a great influence on centroid acceleration and collision force.This research provided theoretical basis for grasping the actual dynamic behavior of parallel mechanism with clearance and gap compensation control.

Key words: parallel mechanism, pair clearance, Lagrange equation, dynamic model

摘要： 为了掌握含间隙4-UPS-RPU并联机构的动力学特性,建立了含球面副间隙空间并联机构的刚体动力学模型,实现了机构的动力学分析。首先假定并联机构的驱动支链与动平台相连的球面副元素之间存在间隙,基于“接触—分离”二状态模型,建立了球面副间隙的运动学模型;然后基于Lankarani-Nikravesh接触力模型和修正的库伦摩擦力模型,利用拉格朗日方程建立了考虑球面副间隙的4-UPS-RPU并联机构的刚体动力学模型;利用数值仿真方法分析了考虑球面副间隙并联机构的动力学特性。研究结果表明,球面副间隙对机构动平台质心点的加速度和碰撞力有较大影响,而且球面副间隙值越大,对机构动态特性的影响越明显。本研究为预测球面副对机构动力学行为的影响,掌握含间隙并联机构的实际动力学行为以及间隙补偿控制提供了理论依据。

关键词: 并联机构, 运动副间隙, 拉格朗日方程, 动力学模型