Dynamics Modeling And Analysis Of Multi-link M Echanical Press Mechanism With Clearance

Forging technology has the characteristics of fast forming,better processing stability and lower cost,which occupy an important position in modern industrial production.In different kinds of mechanical press,multi-link mechanical press has lower working speed in working stroke,which can prevent cracking,reduce vibration and noise,and has controllable output curve and high flexibility.Due to these reasons,the multi-link mechanical press is widely applied to automobile,transportation,military industries,electrical,hardware and other fields.Regarding 2 DOF nine bars mechanical press as the research object in the paper,kinematics,rigid-body dynamics,dynamic response and nonlinear with clearance of the mechanism were systematically studied.The main contents are as follows:Firstly,kinematics analysis of multi-link mechanical press was worked out.The structural characteristics of nine bars mechanical press mechanism were introduced.In terms of complex vector method,the kinematic model of the mechanism was established.The kinematics model is calculated by using Matlab,and the displacement,velocity and acceleration curves of the slider of the press are obtained.According to compare with the simulation results of Adams virtual prototype,the correctness of the kinematics model was verified.Taking the quick return characteristic of press and the acceleration of slider working section as design objective,the optimization model of the mechanism was obtained,and dimension optimization based on genetic algorithm was presented.Secondly,rigid-body dynamics analysis of the multi-link mechanical press were carried out.Choosing crank angular displacement as the generalized coordinate,the expressions of kinetic energy and potential energy of the mechanism were listed.The generalized force equation was calculated by using Lagrange,and the rigid body dynamics model of the mechanism is established.Using Matlab software to calculate dynamics model and applying Adams software to simulate this press mechanism,the driving torque of the crank in the case of no-load and load were acquired.The correctness of rigid-body dynamic model was verified by comparing the results of numerical calculation and simulation analysis.Then,rigid-body dynamics of the multi-link mechanical press with single clearance were analyzed.The revolute clearance was regarded as a virtual massless link,the angular displacement of double crank and clearance bar is selected as generalized coordinates,and the expression of generalized force is listed by using Lagrange equation.The Runge-Kutta method is used to solve the dynamic equations of the mechanism,and rigid-body dynamics model of the multi-link mechanical press with single clearance was built.The dynamic response contrast curves under different position clearance,different clearance value and driving speed were drawn out.The nonlinear dynamics characteristics of multi-linkage mechanism with single clearance was researched by analysing phase diagrams,Poincare portraits and bifurcation maps.Finally,rigid-body dynamics analysis of the multi-link mechanical press with multi-clearance were carried out.On the basis of single clearance mechanism,the Lagrange equation with four generalized coordinates is listed.The Runge-Kutta method was used to solve the equation,and rigid-body dynamics model of the multi-link mechanical press with multi-clearance was built.The dynamic response contrast curves under different clearance value and driving speed were drawn out.The chaotic characteristics of mechanism are qualitatively analyzed by phase diagrams and Poincare portraits,and the changing law of chaos are analyzed by using Poincare portraits and bifurcation maps.