Research On Mechanical Characteristics And Transmission Accuracy Of Harmonic Drive

In this thesis,the mechanical characteristics and transmission accuracy of harmonic drive are studied to realize the localization of the core components of robot.An analytical model for calculating meshing force based on backlash and meshing stiffness and an analytical model for harmonic reducer transmission accuracy considering error characteristics are established in this thesis.The main content of the thesis go as follows.(1)The kinematics of the harmonic reducer is analyzed.Based on the envelope theory,the numerical solution of the rigid gear tooth profile and the conjugate region are solved according to the tooth profile equation of the flexspline and the deformation of the neutral layer.Use the least square method to fit the tooth profile of the rigid wheel to obtain the parameters of the tooth profile of the rigid wheel.The tooth profile parameters of the rigid gear are obtained by fitting numerical solution of the rigid gear tooth profile in least-square method.The meshing characteristics of the double-arc tooth profile are analyzed,and the tooth profile interference test is carried out.(2)The stress and deformation of the flexspline under free load condition are theoretically deduced.According to Mohr’s theorem,the circumferential displacement of each meshing point under unit meshing force is obtained,and then the meshing stiffness matrix is obtained.An analytical model of meshing force based on backlash and meshing stiffness matrix is established,and an algorithm is constructed to solve the meshing force distribution under different load conditions.According to the meshing force analytical model,the influence of main structural parameters and tooth profile parameters on the meshing force distribution is analyzed.A finite element simulation model is established to verify the accuracy of the meshing force analytical model in ABAQUS.(3)The source of the transmission error of the harmonic drive is analyzed.An analytical model of transmission accuracy including eccentricity error and tooth profile error is established.The transmission error of the ideal model is calculated.The changes of transmission error and meshing force under different load conditions are analyzed.The transmission error of the harmonic drive under the action of a specific error combination is calculated.According to the spectrogram,the influence of each error source on the transmission accuracy is analyzed.A finite element dynamics simulation model is established in ANSYS/LS-DYNA to verify the accuracy of the analytical model without original errors and the influence of load and speed on the transmission error is analyzed.(4)A model machine of double-arc harmonic drive designed based on the envelope method was made.A test platform is built to test the transmission accuracy and torsional stiffness of the model machine.The comparison with similar product A with the same structural parameters but different tooth profile parameters proves the rationality of designing the arc tooth profile by envelope theory.