From the point of view of vibration theory, gear transmission system is more complex than ordinary mechanical system, and the influence factors of system dynamic response are divided into internal factors and external factors, which determine the dynamic characteristics of the system. As the root cause of the vibration of gear transmission system, the internal and external excitation factors should be considered when studying the dynamic characteristics of the system.
External excitation mainly refers to the fluctuation of system input and load torque or speed during operation, which also includes the excitation generated by the basic characteristics of other components in the system. Internal excitation refers to the inevitable excitation effect in the process of operation due to the particularity of gear structure. Internal excitation is also the main factor to distinguish gear transmission system from general mechanical system.
For the gear transmission system, even if there is no external excitation, the gear system will generate vibration due to the internal excitation factors such as time-varying meshing stiffness, backlash, tooth transmission error, etc., and the internal excitation factor is the main factor in the gear system dynamics research. Therefore, this section analyzes the internal nonlinear excitation factors in the above gear system.