Performance Analysis And Dimensional Optimization Of 4-RUP_aR Parallel Mechanism

The parallel mechanism has the advantages of good dynamic response,high bearing capacity,compact space structure,and small cumulative error.Therefore,it has attracted widespread attention from academic and industrial circles at home and abroad.The parallel mechanism body is widely used in fast and accurate sorting devices,industrial robots,new machine tools,rehabilitation training devices,etc.This article takes 4-RUP_aR parallel mechanism as the research object,and studies its performance indicators,singular position,dimensional optimization and prototype design.The main content can be summarized into the following four aspects:(1)The motion/force transmission index and motion/force constraint index model of the 4-RUP_aR parallel mechanism are established by using the screw theory.Based on two performance indicators,an effective transfer position space(ETPW)model and an effective constraint position space(ECPW)model for a 4-RUP_aR parallel mechanism with a fixed attitude are proposed.The independent influence of four structural parameters on ETPW is analyzed by using the control variable method.The boundary curve of X_PY_P section of ETPW and ECPW space with fixed attitude angleαor fixed Z_P value are visualized by using fast polar search method and dichotomy method.The numerical examples of performance index analysis are given,which shows that the working space of the mechanism is relatively large,and the motion/force transmission performance and motion/force constraint performance are will.(2)Based on the velocity Jacobian matrix and the motion/force transfer-constraint index,the forward/reverse kinematic singularity and input/output singularity of the mechanism are obtained,respectively.Two types of simple models of typical singularity positions are given.After analysis and comparison,the forward kinematic singularity of the mechanism is consistent with the input singularity,and the inverse singularity of the mechanism is consistent with the output singularity.The singularity of4-RUP_aR parallel mechanism is that the input singularity position is more than the output singularity position,so trajectory planning should avoid more input singularity situations.(3)The difference mutation operator is added to improve the Teaching-Learning-Based-Optimization(TLBO)algorithm into the Accelerate-Teaching-Learning-Based-Optimization(ATLBO)algorithm with better performance.Function optimization examples and mechanical optimization examples are used to verify that the performance of the ATLBO algorithm is better than the TLBO algorithm.The effectiveness of models and algorithms based on the motion/force transmission index is verified by using the effective transfer workspace(ETW)optimization models of the planar 5R parallel mechanism,spherical 5R parallel mechanism and Z3 parallel mechanism.The ATLBO algorithm is used to solve the maximum of the ETPW model of 4-RUP_aR parallel mechanism,and the optimal structural parameters are obtained.The performance of the optimized mechanism is improved by optimizing the effective transfer position space(ETPW)and regular effective transfer working section(RETW)of the front and rear mechanisms.(4)The 3D"door"character frame track route is designed,and the 9 key pose points are taken.The corresponding driving angle parameter values are obtained by using the inverse kinematics model.The unknown coefficients in the fitted driving angle polynomial are solved by using the ATLBO algorithm,and the corresponding fitted kinematics curves are obtained.Based on the theoretical data of the mechanism,3D models of the mechanism’s moving/fixing platform,active arm and driven arm are established by using Solidwork,and specify the corresponding materials are given.After the mechanism motion mode,three-dimensional assembly model,moment of inertia,and output motion parameters are determined,the appropriate servo motor,reducer,and coupling are selected.The motion curve is basically consistent with the theoretical kinematics curve by using Adams software to simulate the actual trajectory of the mechanism.The research content of this article can improve the basic theory of the parallel mechanism and guide the development of new parallel mechanism equipment.It has important theoretical research value and engineering application value.