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

摘要： 针对间隙和柔性构件对多连杆机构动力学响应的影响,研究了一种适用于多连杆机械式压力机的平面六杆机构。建立了转动副间隙矢量模型,通过Lankarani-Nikravesh法向接触力模型和改进的库伦摩擦力模型建立了转动副间隙处的碰撞力模型。基于绝对节点坐标法建立了柔性梁单元模型,通过拉格朗日乘子法建立了含间隙机构的刚柔耦合动力学方程,并通过Adams虚拟仿真软件验证了动力学模型和理论分析的正确性。研究间隙值和摩擦系数对机构动力学响应的影响,利用相图、Poincare映射图和分岔图对机构的非线性特性进行分析,结果表明,随着间隙值的增大和摩擦系数的减小,机构受到的影响越大,产生的响应峰值越高,同时转动副间隙处的混沌现象有所增强。

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