Synthesis And Optimization Of Geared Five-bar Linkage Based On Mobility Characteristics

With the development of production and the improvement of mechanization and automation,the combination linkages has attracted more and more attention from researchers.The geared five-bar linkage is a new type of combination linkage which is developing day by day and has a wide range of uses.It can achieve a variety of complex trajectory.In this paper,the geared five-bar linkage is taken as the study object.Firstly,the trajectory curve and the design parameters are studied.Secondly,the mobility of the geared five-bar linkage is studied,including the branch,the branch point and the full rotatability,to analyze the kinematic characteristics and motion defects of the linkages.It is proposed to correct the branch and to design the branch.Based on this theory,a computer-aided design software is designed.Finally,based on the above theoretical analysis,a new type of turtle-like propulsion linkage based on geared five-bar linkage is designed.(1)Study on the trajectory curve of geared five-bar linkageThe mathematical model of the geared five-bar linkage is established.Using Matlab software,the change rule of the trajectory curve of the geared five-bar linkage is analyzed firstly when the parameters of the member and the geared chain change,then the change rule of the trajectory curve of the linkage when the two parameters of the geared chain change at the same time is analyzed and compared.Finally,the change period and the expression of the track curve are obtained.(2)Study on the mobility of geared five-bar linkageThe mathematical model of five-bar chain and geared chain is established.Combined with an example,the identification process of branch point,branch,sub branch and complete rotation of geared five-bar linkage is analyzed by using discriminant method.(3)Application of the mobility of geared five-bar linkageAccording to the concept of full rotatability,a theoretical method is put forward to avoid the motion defect by taking the non-branch-point as the constraint condition in the process of linkage design and trajectory synthesis.At the same time,this paper puts forward the methods to correct the branch by changing the transmission ratio and the initial phase angle,and to design the branch by changing the length relationship and arrangement of the five-bar chain,so as to avoid the motion defects.(4)CAD software of geared five-bar linkageBased on the theoretical analysis of the mobility of the geared five-bar linkage,a computer-aided software is designed to automatically identify the branches and branch points of the geared five-bar linkage with known parameters under the standard position and obtain the branch diagram of the linkage.For the geared five-bar linkage without full rotatability,the branch correction can be assisted for the geared five-bar linkage without complete rotation.(5)Synthesis optimization example of geared five-bar linkageThrough the study on the flapping wing motion law and propulsion linkage of turtle,a new type of sea turtle like propulsion linkage based on geared five-bar linkage is designed.The transmission ratio parameters are obtained by multi-objective constraint optimization algorithm combined with the motion trajectory research in Chapter 2.The constraint conditions are obtained by combining the complete rotation constraint and branch design theory in Chapter 3,and the trajectory is optimized In the end,we use CAD software to verify the mobility identification.