Investigation of the friction behavior of harmonic drive gears at low speed operation

Abstract

The friction behavior of the harmonic drive (HD) at low speed is investigated in this paper. First, a dedicated experimental setup that integrates a pair of torque sensors is developed, and the friction torque of the HD is measured based on a torque transmission model. The results show that the friction torque of the HD has Stribeck effect at low speed. Further, a Coulomb-viscous-Stribeck friction model is established to replicate the friction behavior of the HD at low speed, and an exact match between the simulation and experimental results proves the validity of the model. Last, a parametric analysis is performed to investigate the dependence of the friction behavior of the HD on different model parameters. It is indicated that the Coulomb friction torque, the maximum static friction torque and the viscous friction coefficient affect the whole, ultra-low and high speed regions of the friction torque-rotating speed curve of the HD, respectively. Our research suggests that the friction loss of the HD can be reduced by applying surface coating and improving lubrication condition in teeth meshing and flexible bearing regions, and it also promotes further studies on friction mechanisms in these regions of the HD.