2-(CRR)_2R结构降耦并联机构及其运动学分析

提出一种能实现三移动一转动(3T1R)的新型完全对称4-CRU并联机构,其4条支链结构完全相同。基于单开链理论及结构降耦原理,对4-CRU并联机构进行结构降耦设计,得到耦合度κ=1的低耦合度2-(CRR)_2R并联机构。其优点在于动平台由两条混合支链并联构成,且支链完全对称,机构姿态转角相对较大。2-(CRR)_2R并联机构耦合度降为1,极大地降低了机构位置正解的难度,有利于机构运动学分析。根据该机构的几何关系与运动约束,建立位置正解的一维搜索模型,再应用黄金分割法求出全部高精度位置正解。推导出机构位置逆解方程,应用数值实例验证了位置正、逆解的正确性。采用矢量法对机构动平台速度及加速度进行分析,得出速度及加速度正、逆解,并利用MATLAB软件编程进行数值计算。同时,应用Adams进行运动学仿真分析,验证了自由度分析的正确性;其运动学分析曲线与MATLAB计算结果一致,表明文中建立的解析模型和分析方法是正确、可行的。

2-(CRR)_2R Parallel Mechanism with Decoupling-reducing Structure and Its Kinematics Analysis

A new kind of parallel mechanism is proposed,which can realize three mobile one rotation(3T1R),and it’s a perfectly symmetrical parallel mechanism of the 4-CRU branch,and then its four branched chains are identical in structure. Based on the theory of SOC and the principle for the structure coupling-reducing,structural decoupling design of 4-CRU parallel mechanism is carried out,and a new 2-(CRR)2R type parallel mechanism with lower coupling degree of κ=1 is proposed. And the advantage of it is that the dynamic platform is composed of two chains in parallel,the angle of the mechanism is relatively large. The coupling degree of 2-(CRR)2R parallel mechanism is reduced to 1,which greatly reduced the difficulty of the positive solution of mechanism position and is conducive to the kinematics analysis. Based on the geometry and motion constraints,the one-dimensional search model of the position positive solution is established,then all the high precision position positive solutions are obtained by the golden section method. The inverse solution equation of the mechanism position is derived,and the correctness of the positive and negative solutions is verified by numerical examples. The velocity and acceleration of the moving platform are analyzed by vector method,the velocity and acceleration of the mechanism are obtained,and the numerical calculation is carried out by MATLAB. At the same time,simulation verification is carried out in Adams,the correctness of the degree of freedom analysis is verified. The kinematics analysis curve is consistent with the MATLAB calculation results,indicating that the analytical model and analysis method established in this paper is correct and feasible.