Spatial Profile Design And Analysis Of Harmonic Drive By Rack Approximation Theory

Harmonic drive is an important core component of robot joint,which accounts for about 36% of robot costs,and its performance has an direct influence on the whole work performance of robot.The gap between China and foreign countries in the high-precision harmonic drive is particularly prominent,which is seriously restricting the maturity of the domestic industrial robot industry and the formation of international competitiveness.In order to solve the common and key problems of industrial robots in our country with high reliability,high precision,high rigidity,long life and high power density,which are urgently needed to solve,this paper study the theory of tooth profile design of harmonic drive and the following work is carried out.Based on the basic assumption,establish the elastic accurate deformation model of harmonic drive,study on the method of rack approximation theory and tooth profile relieving,considering the influence of coning of the flexible tooth,design rack approximation tooth profile which satisfy the spatial engagement and analyze the engagement property of different spatial tooth profile,compare the engagement property of tooth profile of harmonic drive based on different engagement theory,analyze the spatial tooth profile of harmonic drive under no-load and load conditions based on finite element method.Firstly,the basic principle and assumption of harmonic gear drive are described in detail,the geometric relation model of each component is deduced,which includes the radial deformation coefficient of different sections,the neutral curve equation of the new cosine cam based on integral geometry and the traditional neutral curve model,the angle relationship of harmonic drive is obtained,which lay the foundation for derivation of the engagement theory of harmonic drive.Secondly,in consideration of the coning,the spatial tooth profile of harmonic drive is designed.The design method of spatial tooth profile without interference and the design method of spatial tooth profile without slope are presented.The first method adjusts the thickness of the tooth root of other section based on the conjugate tooth profile of the main section;the second method is based on the rack approximate movement trail with different sections,the curve which compose of the envelope of the locus of each section and the trail of the end section of flexspline tooth is taken as the research object,the tooth profile design of rack approximation and tooth profile modification based on the composite curve is carried out.Then,the spatial tooth profile of harmonic drive designed by the method of rack approximation is taken as object of study and the engagement property is analyzed.The assembly state of each tooth profile in different section for different spatial tooth profile is analyzed by MATLAB programming simulation.The movement trail for different spatial tooth profile is simulated to obtain the engagement state of spatial tooth profile and analyze its meshing backlash.At last,design the double-circular-arc tooth profile by the envelope theory,compare the movement trail and meshing backlash of different tooth profile by different engagement theory based on the plane meshing.Finally,the assembly simulation analysis of harmonic drive is carried out by the general analysis module ABAQUS/Standard to obtain the deformation law of the neutral curve and the stress of the flexspline under no-load,and compared with the theoretical analysis.The simulation of load state of harmonic drive is taken out by the explicit analysis module ABAQUS/Explicit to analyze the deformation law of the neutral curve and the stress of the flexspline for different plane tooth profile and different spatial tooth profile under load state.