Abstract: In order to improve the control precision of the robot joint of the harmonic reducer(HD)and adapt to its use under complex working conditions， the friction torque characteristics of HD are studied. By introducing the models of elastohydrodynamic lubrication relationship， the nonlinear stiffness relationship and equivalent dissipation relationship of flexspline elastic deformation， a friction torque model of HD coupled with parameters such as speed， load torque and temperature is established. The genetic algorithm is used to process the test data of the SHF-20-80-2UJ harmonic reducer， the identification results of the parameters to be identified are obtained， and the accuracy of the model is verified. The maximum and average deviations between the simulated and experimental values of friction torque are 8.05% and 4.26% respectively; with full load and input speed being 2000r/min， the maximum deviation between the simulated value and the experimental value of the friction torque at different temperatures is 1.12%. The model effectively reflects the nonlinear relationship between the friction torque of the harmonic reducer with respect to the rotating speed， load torque and temperature changes. The measured elastic deformation energy loss accounts for about 20% and 50% of the total energy loss at no-load and full-load respectively.

Key words: mechanical friction; harmonic reducer; friction model; multi-parameter coupling; elastohydrodynamic lubrication relationship; elastic deformation and dissipation