Study On The Stability Analysis Of Mode Switching Force And Redundant Drive Optimization Of Multimode Mechanism

The traditional parallel mechanism has fixed topological structure and degree of freedom,so it is difficult to meet the needs of the function and performance of the mechanism in the changing environment,working conditions and tasks.As a kind of variable degree of freedom mechanism which can switch between different operating modes without reassembly,multi-mode mechanism provides the possibility to solve the disadvantages of traditional mechanism theoretically.However,the relevant researches and theories are not perfect at present."How to realize mechanism mode switching smoothly" is one of the key problems.In order to solve this problem,this thesis proposed an evaluation index of the stability of the mode switching force of the multi-mode mechanism,and established the stability analysis process of the multi-mode mechanism according to the index.The force stability analysis was carried out by taking the planar four-link mechanism and parallel mechanism SNU 3-UPU as an example.Finally,the scheme of redundant drive arrangement of SNU 3-UPU mechanism was optimized and the stability of mode switching force was evaluated.The main research contents of this thesis are as follows:Firstly,the instability phenomenon of the multi-mode mechanism was analyzed.Through the simulation and analysis of multiple mechanisms,the force stability problem caused by the binding mutation of the output joint of the mechanism during mode switching was obtained.In order to characterize the Force Stability of the mechanism,a Force Stability Index(FSI)was proposed,and the force stability analysis process of the multi-mode mechanism was developed based on the index.The redundant drive combination optimization method of the multi-mode mechanism was continued by the process.Secondly,the planar equal-length four-link mechanism was selected as an example to analyze its three different operating modes and switching configurations.Through dynamic analysis,it was proved that the binding force mutation of the output joint existed in the mechanism.ADAMS simulation was used to solve the binding force of the output joint and the force stability index value.Then,SNU 3-UPU,a parallel mechanism with typical multi-mode characteristics,was selected as an example to solve and analyze its operation mode and the switching process between different modes.Newton-Euler method was used to analyze the dynamics of the example mechanism to solve the binding force of the output joint,and the mechanical results were verified by ADAMS simulation software.The Total motion/force Constraint Index was used to define the range of mode switching instability and solve the force constraint index.Finally,the mode switching process of parallel mechanism SNU 3-UPU with redundant drivers was selected as the research object,and the optimal redundant drive combination with the optimal force stability was selected by using indicators,so as to achieve the mode switching stability optimization of mechanism.