Kinematic Characteristics Analysis of Gear Teeth in Harmonic Drive

This paper presents a kinematic model of harmonic drive to characterize the rigid-flexible compound motion of gear teeth of circular spline and flexspline. The model reveals the instantaneous inequality between the output angle and flexspline tooth rotation angle. Firstly, the kinematic model is established with consideration of the flexspline cup deformation. Then, the instant rotation center and centrode of the flexspline tooth are systematically analyzed corresponding to different deformed neutral curves. Subsequently, the instantaneous pitch point of the conjugate tooth profile is identified by converting the relative motion of gear teeth into the meshing between a pair of gears with time-varying center distance. On this basis, the conjugate meshing process between the circular spline and flexspline teeth can be abstracted as the pure rolling between two moving centrodes, and the moving centrodes of the circular spline and flexspline teeth are investigated. The outcomes of this paper can provide significant guidance for the kinematic characteristics analysis of gear teeth in harmonic drive.