| The flexible transmission system composed of universal joint,transmission shafts,gear pairs,and rolling bearings can meet the requirements of smooth transmission of power and fluctuation of torque output point in the short or long distance,thus widely used in the field of engineering.To establish a precise coupling vibration model of the system,to seek the modal identification method of the non-linear system and control the vibration actively are very important for the NVH performance of automotive transmission system.(1)Based on the analysis of coupling vibration mechanism of the automotive power transmission system,the universal joint is regarded as a contact model,and the gear pair can be regarded as a collision model.The mathematical expressions of their general model are formulated based on the lumped parameter method.As for the shaft with regular structures,the overall stiffness and mass matrixes can be obtained based on the finite element method,thus establishing the theoretical and methodological basis of the hybrid dynamic model.(2)The nonlinear torsional vibration model of the system is established by combining system dynamics with structural dynamics.The system dynamics model is established for the connecting parts like universal joints and hypoid gears,while the model of transmission shaft,gear shaft,and half-shaft are modeled based on structural dynamics,thus the torsional vibration model integrated multiple factors of the transmission shaft-rear axle system is established.The modal frequencies of the system are obtained by dynamic frequency-sweeping analysis and computational modal analysis,one of the torsional vibration natural frequencies is about 53 Hz.(3)Considering the influence of tapered roller bearings stiffness,axial and radial deformation of gear shaft,a more accurate torsional-bending coupling vibration model of gear-bearing-rotating shaft is established.The natural frequency of torsional vibration of the system is 53.96 Hz by frequency-sweeping analysis,and the influence of meshing stiffness of gear pairs on the dynamic characteristics of the system is proved.The angular acceleration amplitude at the end of half-axle wheel can be reduced by properly increasing the meshing stiffness of gear pair.(4)Based on the dynamic analysis software ADAMS,considering the structure of intermediate support,the dynamic simulation model of the transmission shaft-rear axle system is established.The second-order(angular)acceleration amplitude curves of the intermediate support,the input position of the rear axle and the end of the half axle at different input speeds are obtained,and the peak location of the second-order(angular)acceleration curve is found.(5)In order to verify the result of calculation model and simulation analysis,further research was carried out to verify the modal frequency of the transmission shaftrear axle system.The experimental results prove the rationality of the nonlinear hybrid model and ADAMS simulation model,and one of the torsional vibration natural frequencies of the system is 57 Hz. |
