Domestic scholars have also carried out a lot of research on the compound fault of gear transmission system. Li Ming et al. Reviewed the development history of gear rotor bearing system dynamics research, and reviewed nearly 20 The research status of coupled bending torsional vibration and nonlinear dynamics of gear rotor bearing system in recent years is reviewed. Some theoretical and applied researches and the development of related disciplines are prospected. Yang Yang et al. Studied the characteristics of the support stiffness of the gear bearing rotor system, obtained the support stiffness by using different bearing stiffness calculation methods, and on this basis, analyzed the influence of the system support stiffness on the vibration response of the system.
Wang Xin et al. Established a two-stage fixedtransmission system with fixed shaft crack fault and planetary gear broken tooth fault, compared and studied the frequency spectrum of normal and coupling fault state, and analyzed the fault frequency characteristics caused by coupling fault. Ping Sitao studied the coupling mechanism of multiple faults of gear failure and shaft crack fault at the same time, established the translational torsional coupling vibration analysis model of train, and analyzed the system dynamic characteristics under the coupling effect of gear fault and shaft crack fault.
To sum up, many scholars have studied the dynamic model of gear pair, root crack and rolling bearing fault, and achieved a lot of research results. Although the related research on the fault of gear transmission system has been carried out, it is only limited to gear fault and rotor fault, and the rolling bearing fault and component composite fault as the key supporting component are less considered. However, during the running process of gear transmission system, the components interact with each other, and the fault characteristics of the components will also transfer to each other, which makes the fault characteristic signal of the gear transmission system very complex.
Therefore, in order to accurately identify the fault characteristics of auxiliary gear transmission system, it is necessary to conduct in-depth study on the influence of component fault on the vibration characteristics of gear transmission system.