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

Dynamic Modeling with Joint Friction and Research on the Inertia Coupling Property of a 5-PSS/UPU Parallel Manipulator

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。

In order to apply the parallel mechanism to the sea level recovery platform of spacecraft,a new five-degree-of-freedom parallel mechanism called 5-PSS/UPU parallel mechanism,which can realize three-shift and two-rotation,is proposed as a flexible adaptive dynamic balancing device.Due to the multi-close-loop structure of parallel mechanism,there is a serious inertia coupling between the driving branches,which will cause difficulties in the control of the parallel mechanism and affect the dynamic performance of the mechanism.Thus it is significant to study and evaluate the inertia coupling property of the parallel mechanism.Firstly,the positive and negative solutions of the mechanism are deducted by vector motion.Secondly,The dynamics model of5-PSS/UPU parallel mechanism is established by Newton-Euler method under the condition of joints friction effect.The numerical simulation of the mechanism dynamic model was carried out,which shows that the max errors of each driving forces were 1.62%,0.48%,3.85%,1.21%,5.13%.Then,based on dynamic model,analysis coupling characteristic and obtain the inertia coupling evaluation index in the different poses of this parallel mechanism workspace.The result shows that,to some extent,optimization the reasonable motion trajectory can reduce the influence of dynamic coupling characteristics on the dynamics performance of the parallel mechanism.