Research On The Dynamic Characteristics Of Beveloid Differential Planetary Gear System

The differential planetary gear system can resolve motion and power,as a special gear mechanism.Because of the great speed controlling performance and stable operation,the differential planetary gear system is applied to the marine transmission system.However,there are the internal and external meshing,the complex structure and the coupling of internal and external excitation.Therefore,it is necessary to do the further research on the dynamic characteristics,such as inherent characteristics,load sharing characteristics and vibration characteristics.And the research could provide the theoretical support and guidance for the optimization design of the marine power transmission system.The thesis focuses on the beveloid differential planetary gear system,which innovatively substitutes the beveloid gears for the helical gears.Based on the lumped parameter method,a three-dimensional model is established considering the impacts of time-varying meshing stiffness,backlash and transmission error.Each component has three degrees of freedom,including one radial DOF,one axial DOF and one rotational DOF,which can be used to characterize the vibration in the three-dimensional space.Based on the force analysis and Newton's second law,the nonlinear dynamic differential equations are established.The dynamic characteristics which include inherent characteristics,load sharing characteristics and vibration characteristics are researched.By solving the eigenvalues problem,the inherent frequencies and vibration modes are obtained.The modal characteristics and the impact of time-varying meshing stiffness on the inherent frequencies are analyzed to determine vibration characteristics and avoid resonance.The load sharing coefficients of the transmission system are calculated.And the impacts of the eccentricity error and beveloid gears on the load sharing characteristics are analyzed to realize the uniform distribution of load and improve the bearing capacity.The dynamic excitation is the main source of vibration and noise,including the external excitation caused by external dynamic load,and the internal excitation caused by time-varying meshing stiffness,backlash and transmission error.The time-displacement response curves with the external excitation and internal excitation are obtained,through the Runge-Kutta numerical integration method based on MATLAB.The impacts of the meshing stiffness variation and beveloid gears on the vibration characteristics are analyzed.And the numerical solutions are compared with the vibration signals through the experiment to reduce the transmission of dynamic excitation and realize vibration and noise reduction.Finally,the dynamic differential equations are solved through the harmonic balance method.The analytical solutions obtained through the harmonic balance method are shown to be accurate through a comparison with the numerical solutions.The thesis can provide a theoretical foundation for the following research and application of dynamic characteristics.