| In the gear transmission system, fixed axis gear box and planetary gear box are the most common form of gear transmission. As an important part of the transmission system, gear box works in relatively poor environment, which has higher probability of failure. The health condition of the gear box directly affects the working efficiency and stability of entire transmission system. Thus, it will make a lot of sense to model the gear box system and analyze the characteristics of vibration response for gear system under normal state and different fault state in order to achieve real-time online monitoring and fault diagnosis of gear box under working condition.Using lumped parameter method to respectively establish the dynamic analysis model of fixed axis gear transmission system and planetary gear transmission system. The flexibility of shaft, bearing, gear teeth and meshing error and eccentricity of rotating shaft are considered in the fixed axis gear transmission system. While the torsional stiffness, bracing rigidity, time-varying mesh stiffness and meshing error of components are considered in planetary gear transmission. The dynamic differential equations of fixed axis gear transmission system and planetary gear transmission system are expressed in matrix form. Some parameters like the mass, damping, bracing rigidity of gear transmission system are calculated. The external and internal time-varying meshing stiffness are deduced in detail when profile modified gear exists in planetary gear train.For the fixed axis gear transmission system, the frequency characteristics under normal state and different faults(steady-type fault, impact-type fault, compound-type fault) are obtained by the theoretical analysis and simulation. There are only meshing frequency and its harmonics components when gear is normal. In addition to the meshing frequency and its harmonics under the normal state, there are the rotation frequency of the fault shaft and its harmonics modulation sidebands beside the meshing frequency and its harmonics under the steady-type fault, while there are sidebands of the impact frequency beside some natural frequencies of the system under the impact-type fault. The frequency characteristics of the two faults can be detected at the same time in the system under compound-type fault. Through constant speed and variable speed tests, the validities of the theoretical analysis and numerical simulation are verifies.Planetary gear transmission system dynamics model is solved for vibration frequency characteristics under normal state and steady-type fault. When planetary gear system is normal and sensor is fixed at a certain point, near the meshing frequency and the higher harmonics which can be divided exactly by the number of planets, regarding it as a center frequency there exist a number of planets round multiplied by the planet carrier rotation frequency and its higher harmonics modulation sidebands. Under steady-type fault circumstance, in addition to the above frequency components, there are relative rotation frequency and doubling rotation frequency modulation between sun gear and planet carrier when sun gear has fault. There are modulation frequency sidebands of relative rotation frequency and doubling rotation frequency components between inner gear ring and planet carrier when inner gear ring has fault. The results of the simulation analysis are verified by the vibration test of the single stage planetary gear box. |
PDF Full Text Request