| In this paper,a new type of 5-DOF hybrid mechanism RPU-SPR-SPU+ R + P is proposed based on the less DOF parallel mechanism and the exon mechanism by using the method of branch chain variation.Compared with the exon mechanism,the new mechanism has the advantages of simple assembly and large working space,but it also has some shortcomings,such as its stiffness is worse than that of the exon mechanism.Therefore,in this paper,a series of performance of the new mechanism is studied,so as to evaluate the characteristics of the mechanism(1)The three-dimensional structure of the new mechanism is designed,and the mechanism model is simplified.The screw theory and formula are used to solve the degree of freedom of the mechanism.The closed-loop vector method is used to solve the forward and inverse position solutions of the parallel part,the D-H method is used to solve the forward and inverse position solutions of the series part,and the forward and inverse position solutions of the whole hybrid mechanism are obtained According to the positive and negative position solutions,the vector method is used to solve the velocity and acceleration of the mechanism,and the Jacobian matrix is obtained.(2)The boundary limit search method is used to solve the overall workspace of the hybrid mechanism under the condition of meeting the constraint conditions of the mechanism,analyze the parameters that affect the size of the workspace,find out the influence trend,and optimize the workspace;the singularity of the mechanism is analyzed,and the singular configuration of the mechanism is obtained;the workspace size of the mechanism is roughly calculated based on the calculus method Solution.(3)The static stiffness theoretical model of the parallel part rpu-spr-spu of the new mechanism is established by using the virtual joint method,and then the static stiffness theoretical model of the series part is established to obtain the static stiffness theoretical model of the whole hybrid mechanism The static stiffness finite element simulation is carried out in workbench,and the two methods verify each other to analyze the stiffness performance of the mechanism in all directions under various working conditions;the modal analysis and harmonic response analysis are carried out to understand the vibration resistance of the mechanism;the multi-objective response surface optimization is carried out for the weak links of the mechanism.(4)Based on the principle of virtual work,the dynamic analysis of the mechanism is carried out,and the theoretical model of dynamics is established;the virtual prototype simulation of the mechanism is carried out in ADAMS software,including the kinematic simulation and dynamic simulation of the mechanism,and the driving force on the branch bar is calculated;according to the kinematic and dynamic theoretical model of the mechanism,the program is compiled in MATLAB to verify the simulation results. |
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