关键词: 多连杆机构, 绝对节点坐标法, 间隙, 刚柔耦合动力学, 非线性特性

Abstract: In the actual mechanical system,due to the existence of manufacturing accuracy and friction and other factors,there is inevitable clearance in the motion pair.At the same time,the flexible components will lead to the decline of the motion accuracy and stability of the mechanism.To study the effect of clearance and flexible components on the dynamic response of multi-link mechanism,a planar six bar mechanism suitable for multi-link mechanical press was studied.The vector model of the clearance was established,and the collision force model at the clearance of the rotating pair was built through the Lankarani and Nikravesh (L-N)normal contact force model and the improved Coulomb friction model.Based on the absolute node coordinate formulation method,the model of flexible beam element was established,and the rigid-flexible coupling dynamic equation of the mechanism with clearance was set up by Lagrange multiplier method.The correctness of the dynamic model was verified by Adams virtual simulation software.The effects of clearance value and friction coefficient on the dynamic response of the mechanism were studied.The nonlinear characteristics of the mechanism were analyzed by drawing phase diagram,Poincare map and bifurcation diagram.The results showed that with the increase of clearance value and the decrease of friction coefficient,the greater the impact on the mechanism,the higher the response peak could be produced and the chaos phenomenon at the clearance of the rotating pair was enhanced.

Key words: multi-link mechanism, absolute node coordinate formulation method, clearance, rigid-flexible coupling dynamics, nonlinear characteristic