Gear transmission system is a typical elastic mechanical transmission system, which produces dynamic response under the influence of internal and external dynamic excitation. The external excitation is the excitation from the outside of the system to the system, mainly including the active torque exerted by the motor and the resistance and resistance moment of the load; the internal excitation is the excitation existing in the gear system during the meshing process of the gear pair, mainly including stiffness excitation, error excitation and meshing impact excitation.
Stiffness excitation is the main excitation form of gear system meshing internal excitation. It is the primary task to determine the elastic deformation and calculate the meshing stiffness in the process of gear meshing. Stiffness excitation refers to the dynamic excitation caused by the time-varying of meshing stiffness during gear meshing. There are four commonly used methods to calculate time-varying meshing stiffness: square wave method, energy method, finite element method and experimental method.
For a continuously running healthy gear, the meshing stiffness is a periodic function. In this paper, the meshing stiffness of gears is approximately estimated by using the square wave method, where the period of the square wave is equal to the period of a tooth meshing. The meshing stiffness of gears calculated by square wave method is easy to be applied. It can reflect the meshing period of gears and the number of tooth pairs involved in gear meshing. However, it ignores the difference of meshing stiffness caused by different elastic deformation of gear teeth in different meshing positions.