Nonlinear dynamic analysis and experimental study of multi-link press with dry friction clearances of revolute joints

In mechanical system, the clearance between revolute joints is ineluctable, which will influence the motion precision and constancy of the system. Currently, studies of simple mechanisms with single clearance are relatively mature, but in-depth studies of sophisticated mechanisms with several clearances are not enough. For the purpose of investigating non-linear dynamic properties of multiple clearances and multi-degree of freedom complex mechanisms, a nonlinear dynamic analysis framework of multi-link mechanism with dry friction clearances was proposed, the rigid body dynamic model of planar 7-bar mechanism containing dry friction clearances was built and analyzed in this paper. To analyze effects of clearances on dynamic response of the mechanism, taking a seven-bar press with mixed driven as an illustration, a dynamic modeling and analytical technique of press mechanism containing dry friction clearances was proposed. Firstly, the clearance model was established according to relevant geometrical relations, then contact force model and friction model were established. Furthermore, Lagrange multiplier method was adopted to set up the rigid body dynamics equation which would be solved by Runge–Kutta method. Secondly, influences of different factors on dynamic response were studied, and correctness of model was verified by emulation contrast with ADAMS. Thirdly, non-linear properties of mechanism were analyzed by related images. Finally, the experimental platform of seven-bar mechanism was built to check the validity of outcomes. The researches provided a foundation for prediction of dynamic trajectory of press mechanism in theory, and settled a solid basis for excogitation and fabrication of high-accuracy press mechanism.