Analysis On Kinematics And Dynamics Performance Of A Novel 3-PUU Parallel Mechanism

The modules of parallel tool heads with 2R1 T degrees of freedom(DOFs), i.e., two rotational DOFs and one translational DOF, have become so important in the field of machine tools that corresponding research has attracted extensive attention from both academia and industry. A 3-PUU parallel mechanism with 2R1 T DOFs is first proposed in this paper, and a detailed discussion about its kinematics analysis, the rigid body dynamics analysis and workspace analysis are presented. The above analyses illustrate that the 3-PUU parallel mechanism owns good dexterity and orientation capability, which validate the feasibility of applying this mechanism as a tool head module. On the basis of this, the flexible body dynamics analysis is carried out on the mechanism, and the influence of vibration on the precision of the end effector is studied, then the size optimization analysis is carried out. The following is the main contents of the research:1. By using the screw theory, the DOFs of the 3-PUU mechanism is analyzed, and the existence of associated motion can be learned from the information of the DOFs. From the view of the DOFs, the 3-PUU mechanism can be used as mechanical spindle head. According to the special geometric constraint mechanism, the associated equations of motion are derived, and then solving the inverse kinematics problem, Jacobian matrix, the forward kinematics problem.2. Based on the analysis of the dexterity and singularity of the mechanism, the constraint conditions of the working space are established. Different from 3-PRS, through the analysis of the reachable workspace, the 3-PUU workspace volume is much larger than 3-PRS. Through the analysis of flexible working space, the 3-PUU is better in directional function, because there is no cone angle constraint of S pairs. From the view of the working space, the 3-PUU mechanism can be used as mechanical spindle head.3. All of the mechanism is considered as a rigid component, and the rigid body dynamics modeling is carried out. The flexible body dynamics modeling is carried out by considering only the branch rod in the mechanism as a flexible member. This is the theoretical basis for the dynamic simulation.4. In the analysis of rigid body dynamics simulation, the same 3-PUU mechanism and 3-PRS mechanism with the same structure parameters have the same track, in terms of energy consumption, the two are basically the same. From the view of the dynamics, the 3-PUU mechanism can be used as mechanical spindle head.5. In the flexible body dynamics simulation analysis, it can be seen that the dynamic platform is affected by the vibration of the chain elastic deformation in the direction of the Z axis. With the natural frequency of flexible chain as the optimization objective, the thickness and width ratio coefficient is introduced, and the optimal cross section parameters of the component are analyzed again. By comparison, it is found that the optimal error is less than before optimization, which proves the feasibility of the optimization design method of the component size with the inherent frequency of the mechanism.