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利用拉格朗日方程建立了理想并联机构的动力学方程,并利用连续接触模型得到了含间隙S副6-SPS并联机构的动力学方程,该机构动平台上6个运动副全部含有间隙.把动平台S副间隙简化为一个无质量连杆,其长度用随机函数表示,并在机构间隙的变化速度与机构运动速度之间建立函数关系,用机构运动速度表示机构间隙的变化速度.把动平台上6个运动副简化为一个推力轴承,研究摩擦对机构的影响,分析机构所受到的摩擦力矩.通过求解机构的动力学方程,得到机构的动力学特性曲线.结果表明:机构间隙和运动副摩擦对动力学特性都有影响,计算油膜黏性摩擦力矩时引入随机函数,使运动副球体的运动更接近真实状态.
The dynamic equations of an ideal parallel mechanism are established by using Lagrange’s equation. The kinetic equations of 6-SPS parallel mechanism with gap S are obtained by continuous contact model. The six moving pairs on the moving platform all contain gaps. The vice clearance of moving platform S is reduced to a massless link whose length is represented by a random function and a function is established between the variation speed of the mechanism gap and the movement speed of the mechanism and the variation speed of the mechanism gap is expressed by the movement speed of the mechanism. The kinematic pair on the moving platform is simplified as a thrust bearing to study the influence of friction on the mechanism and to analyze the friction moment suffered by the mechanism. The dynamic characteristics of the mechanism are obtained by solving the dynamic equations of the mechanism. The results show that: The kinematic pair friction has an impact on the dynamic characteristics. When calculating the viscous friction moment of the oil film, a random function is introduced to make the motion of the sub-sphere move closer to the true state.