Study On Multi-Body Dynamics Of Revolute Joint Mechanism With Clearance

Some mechanical structures in the industrial and aerospace fields,such as industrial robot arms,spacecraft with sailboards,etc.,could be simplified as mechanisms which connected by revolute joints.In general,the revolute joint is considered to be ideal,however,in the actual mechanical structure,there are generally revolute joint with clearance,it will transforms the continuous dynamic process into a discontinuous process due to the continuous contact and impact between the elements in the revolute joint with clearance during the process of motion,and the system dynamics equations are differential algebraic equations with high dimension,strong nonlinearity and discontinuous coupling,which not only makes the numerical solution of dynamic equation difficult,but also the existence of revolute joint with clearance will inevitably lead to the sudden change of the movement and stress state of each component in the mechanical system,and then the dynamic behavior of the mechanism is changed,resulting in severe vibration,impact and noise.Therefore,it is crucial to carry out the dynamic analysis of the revolute joint mechanism with clearance,researching its dynamic behavior in the clearance state,and to improve its dynamic performance in order to meet the requirements of movement accuracy and reliability of the mechanism.This paper based on the theory of multi-body system dynamics,the main research object is the revolute joint mechanism with clearance,and the crank-slider mechanism is taken as an example.Through the combination of theoretical research and simulation analysis,the theoretical model and simulation analysis model of crank-slider mechanism with clearance are established,the dynamic model of the mechanism is solved by numerical calculation and simulation method in turn,after that the influence of dynamic characteristics under different mechanism parameters,contact impact force model of revolute joint,the number of revolute joint,flexible deformation of members and other key factors is considered on this basis.The main work of this paper is as follows:(1)Based on the multi-body dynamics modeling theory,the first and the second Lagrange equation modeling methods are used to establish the dynamic theoretical models of two typical planar mechanisms,double pendulum mechanism and crankslider mechanism with ideal revolute joint.The Runge-Kutta,Newmark and HHT numerical algorithms are programmed by MATLAB and used to solve the dynamic equations respectively,and the characteristics of different modeling methods and numerical algorithms of multi-body system dynamics are compared and analyzed,which provides an important theoretical basis for the establishment of dynamic theoretical model and the solution of differential equations of the revolute joint mechanism with clearance.(2)Combined with the generalized coordinates and Lagrange multiplier method,the differential algebraic equations(DAE)of multi-body dynamics of crank-slider mechanism considering the clearance and effect of contact-impact in the revolute joint is established.The Newmark numerical algorithm is compiled by MATLAB to solve the dynamic equations with high dimension,strong nonlinearity and discontinuous coupling.The effects of key factors such as crank speed,clearance size,friction coefficient and coefficient of restitution on the system dynamic characteristics of the revolute joint mechanism with clearance are compared and analyzed.Two kinds of contact-impact force models of the revolute joint with clearance are established,which are embedded into the multi-body dynamic equation of the mechanism respectively.The dynamic response is calculated,and the influence of different contact-impact force models on the dynamic analysis of the revolute joint mechanism with clearance is further studied.(3)In order to explore the complex influence of multiple revolute joints with clearance,different position of revolute joint with clearance and flexible deformation of connecting-rod,a multi-body dynamic simulation model of the revolute joint mechanism with clearance was established by ADAMS.The dynamic characteristics of the crankslider mechanism with clearance were simulated and analyzed,and compared with the theoretical numerical results.Then,the effects of the number of revolute joints with clearance,different positions and the flexible deformation of the connecting-rod on the dynamic characteristics of the mechanism are further studied.