Research On The Modulation Law Of Planetary Gear Sets Vibration Based On Manufacturing Error And Fluctuating Load

The planetary gearbox is characterized by its compact structure,large reduction ratio and power density.Due to the complex design,the floating sun gear involved is difficult to balance,which makes the vibration analysis and control of the system unreliable.Furthermore,the gear set performs functionally to transfer power and motion,and thus its vibration is not only affected by the internal excitation,but also closely related to external excitation.However few studies can be found so far..In this dissertation,the transmission shaft of a two-stage NGW type planetary gear set is focused on,and the influence of external fluctuating load on its vibration response is explored.The following work is included.Firstly,the kinematic differential equations are deduced for the shaft of a planetary gear set to establish a dynamic model with the coupling effects of bending and torsion considered.Upon the identified bearing stiffness,the vibration modes are built with or without the shaft effect involved within the system.Then,based on the energy method,the excitation of meshing stiffness and meshing error are calculated.The amplitude and frequency modulations due to the external fluctuating load and manufacturing errors of the sun gear and the inner ring gear are discussed.A modulation sidebands function is defined to evaluate the effect of the external fluctuating load.The influence of modulation parameters on the integrated meshing excitation and the corresponding spectral characteristics are analyzed.It is found that the meshing error and the fluctuating load are also modulated with each other,and thus new modulation frequencies are derived.Following the analysis,a test bench is designed to investigate the vibration characteristics of the gear shaft under the condition of no load,constant load and fluctuating load and the vibration modulation of the planetary gearbox is analyzed emphatically.The influence of the load on the vibration modulation phenomenon is studied upon alteration of the constant torque.Finally,the function expression of the modulation sidebands caused by the external fluctuating load is established and a simulation program is compiled.The results show that the spectral characteristics are in good agreement with the experimental results,which proves that the model is reasonable.