3T1R并联机构运动学分析与优化设计

提出了一种可实现三维移动和一维转动的四自由度并联机构,它的2条相同支链通过被动转动副连接到动平台上,每条支链有2个相同分支,通过安装在基座上的移动副驱动。首先,阐述4PPa-2PaR并联机构的构型,通过螺旋理论验证机构的运动性质,基于机构自身特点研究机构的运动学特性;其次,利用数值法确定机构的工作空间,分析各设计参数对工作空间的影响,基于解析法研究机构工作空间的形状及满足的几何约束条件;最后,以工作空间占机构自身的比重为目标函数,设置影响工作空间的约束条件(如边界约束、不干涉性约束、避奇异约束和工作空间形状约束),并选择遗传算法对机构的尺寸参数进行优化设计。分析结果表明,优化后工作空间占机构自身的比重增大,工作空间体积也明显增大,优化结果可为后续样机研制提供参考依据。

Kinematics Analysis and Design Optimization of Novel 3T1R Parallel Manipulator

A new four-degree-of-freedom (4-DOF) parallel manipulator that can produce 3-DOF translations and 1-DOF rotation was proposed. It had two identical limbs connected to the moving platform through passive revolute joints, and each limb had two identical branches driven by a pair of base mounted collinear prismatic joints. Due to such a simple and symmtrical kinematic structure, the 4-DOF parallel manipulator had the advantages of simple kinematics, large workspace, high speed, high positioning accuracy and easy processing. These advantages made it an appropriate candidate for high-speed and high-precision sorting, pick-and-place, palletizing and assembling operations. Compared with similar parallel manipulator, it showed a unique advantage in long-distance high-speed operations. Firstly, the configuration of 4PPa-2PaR parallel manipulator was introduced, the simplified mathematical model of the mechanism was established, the number and nature of mobility were verified with screw theory and the modified Grübler-Kutzbach criterion, and the kinematic characteristics was studied. Secondly, the workspace was determined by a numerical method, the influence of each design parameter on the workspace was analyzed, and the workspace shape and geometric constraint condition were discussed by analytic method in detail. Finally, the ratio of workspace to parallel mechanism itself was determined as the objective function, the design constraints, such as boundary constraints, non-interference constraints, singularity avoidance constraints and workspace shape constrains, were established and genetic algorithm was selected to optimize the size parameters. The results showed that the ratio of workspace to parallel mechanism itself and workspace volume after optimization were significantly increased, and the optimization results provided important guidance for the subsequent prototype development.