Dynamic Analysis Of Parallel Mechanism With Joint Clearance And Flexible Links

The parallel mechanism has the characteristics of small accumulative error,strong carrying capacity and high accuracy and so on,which is widely applied in many fields.At present,the parallel mechanism is developing towards light weight,high speed and high precision.But,the elastic deformation of flexible component and the collision produced by clearance joint have influences on dynamic characteristics of mechanism.Therefore,it has important theoretical significance to study the performance of the parallel mechanism with joint clearance and flexible links.In this paper,the dynamic model of 4-UPS/RPS spatial parallel mechanism with clearance joint and flexible links was established,and its dynamic response and nonlinear characteristic are both systematically analyzed.The main contents of this paper are as follows:Firstly,the spatial spherical clearance model was established,and then the rigid body dynamic model of parallel mechanism with spherical joint clearance was derived by the L-N continuous contact force model and the modified Coulomb friction force model.Based on Lagrange equation,the elastodynamic model of parallel mechanism was established.The clearance model was embedded into the elastodynamic model,and the dynamic model of the spatial parallel mechanism with clearance joint and flexible links was built.Secondly,based on the dynamic model,the dynamic equations of space parallel mechanism with clearances joint and flexible links were solved by using the Runge Kutta and Newmark integral method.The influences of different trajectories,different clearance values,different friction coefficients and the flexible links on the displacement,velocity,acceleration of the moving platform and contact force were both analyzed.And the dynamic stress of telescopic rod was also analyzed.Finally,according to the nonlinear dynamics theory,based on the numerical solution of the dynamic equation,the chaotic characteristics of the spatial parallel mechanism with clearance joint and flexible links were analyzed by phase diagram,Poincare mapping,power spectrum and the largest Lyapunov exponent.The influence of clearance size on the nonlinear characteristics of spatial parallel mechanism was analyzed by bifurcation diagram.