Dynamic Modeling and Analysis of 5‑PSS/UPU Parallel Mechanism with Elastically Active Branched Chains

To study the characteristics of the 5-prismatic–spherical–spherical(PSS)/universal–prismatic–universal(UPU)parallel mechanism with elastically active branched chains,the dynamics modeling and solutions of the parallel mechanism were investigated.First,the active branched chains and screw sliders were considered as spatial beam elements and plane beam element models,respectively,and the dynamic equations of each element model were derived using the Lagrange method.Second,the equations of the 5-PSS/UPU parallel mechanism were obtained according to the kinematic coupling relationship between the active branched chains and moving platform.Finally,based on the parallel mechanism dynamic equations,the natural frequency distribution of the 5-PSS/UPU parallel mechanism in the working space and elastic displacement of the moving platform were obtained.The results show that the natural frequency of the 5-PSS/UPU parallel mechanism under a given motion situation is greater than its operating frequency.The maximum position error is -0.096 mm in direction Y,and the maximum orientation error is -0.29°around the X-axis.The study provides important information for analyzing the dynamic performance,dynamic optimization design,and dynamic control of the 5-PSS/UPU parallel mechanism with elastically active branched chains.

基于螺旋理论的5-UPS/UPU并联机床自由度分析

并联机床被认为是本世纪最具有革命性的机床设计突破,代表了21世纪机床发展的方向,目前国内外研究的并联机床大都集中在三自由度和六自由度的机型上,而对机床来说要加工复杂的零件最多需要五个自由度就可以完成。燕山大学研究了五自由度的并联机床,但其机构构型(5-UPS/PRPU)的约束支链采用了移动副连接方式,这将影响机床的性能。本文提出采用五自由度并联机构(5-UPS/UPU)应用于并联机床的构型,并分析其自由度数量与性质,证明了本机构适合应用于并联机床。

考虑关节摩擦的5-PSS/UPU并联机构动力学建模及耦合特性分析

为了将并联机构应用于航天器的海面回收平台等领域,提出一种可以实现三移动二转动的新型五自由度并联机构—5-PSS/UPU并联机构作为柔性自适应动态平衡装置,并对该并联机构进行了耦合特性分析。首先,利用矢量法得到了机构运动学的正反解。其次,在考虑关节摩擦效应的情况下,采用牛顿-欧拉法建立了5-PSS/UPU并联机构的动力学模型,并对机构的动力学模型进行了数值仿真验证,结果表明考虑关节摩擦和未考虑关节摩擦时,各移动副的驱动力最大误差分别为:1.62%、0.48%、3.85%、1.21%、5.13%。然后,基于动力学模型,进行动力学耦合特性分析,并给出了惯量耦合特性评价指标。最后,在该并联机构的工作空间内,研究了耦合评价指标随机构运动状况的变化规律。研究结果表明,通过合理规划运动轨迹可以在一定程度上减少动力学耦合特性对并联机构动态性能所产生的影响。