Dynamics Analysis And Simulation Of A Planar Four-bar Linkage With Clearanc

The linkage mechanism is an important part of mechanical transmission,which is composed of kinematic pairs and components.Linkage mechanisms are widely used in engineering fields such as engine,industrial machine tool,textile machinery,and aerospace.On the one hand,the existence of the kinematic pair clearance makes the components produce relative movement to transmit power,and on the other hand,it also affects the operation accuracy of the mechanism.The effect of the clearance on the mechanism cannot be ignored.In traditional dynamic analysis,the mechanism is regarded as an ideal mechanism without clearance.However,due to design and assembly errors,the clearance of the kinematic pair is inevitable.This dissertation takes the plane four-bar linkage mechanism as the research object,and studies the effect of clearance on the dynamic response of the mechanism.The research results have important guiding significance for the design of the mechanism with clearance and the prediction of dynamic response.The main research contents are as follows:(1)Three methods of clearance modeling are described,and the advantages and disadvantages of various models are described in detail.A two-state mathematical model of "contact-separation" with clearance rotating pair is established.The composition of the force of the rotating pair with clearance and the relationship between the contact force and the deformation of the contact point are analyzed.The applicable conditions,operating accuracy and operating efficiency of Hertz contact force,H-C contact force,L-N contact force and Bai contact force are analyzed,which lays a necessary foundation for the research of the mechanism with clearance.(2)Taking the planar four-linkage mechanism as the research object,the dynamic equation of the mechanism with clearance is established by using the "contactseparation" two-state model and Newton-Euler equation.The transition conditions between contact state and free state are given,and the correctness of the dynamic equation is verified by ADAMS simulation software.The instability of the system in the early stage is studied,the effects of the clearance value,crank speed,and friction coefficient on the dynamic response of the mechanism are analyzed,and the operating state of the shaft in the bearing is analyzed,which lays an important foundation for the study of the mechanism of clearance.(3)Based on ADAMS software,the dynamic simulation analysis of the plane fourlinkage mechanism with multi clearance is carried out.The clearance model is established in the ADAMS software and embedded into the planar four-linkage threedimensional model.The effect of the position and number of the kinematic pair clearance on the mechanism displacement,velocity,acceleration,relative motion trajectory of axis and puncture depth of the clearance joint is analyzed,and the influence of the clearance on the operation accuracy of the mechanism is analyzed.The mean square deviation of follower acceleration is used as the quantitative analysis index to quantitative analyze all conditions of the clearance.It provides an important theoretical basis for the design of mechanism with clearance.