| Harmonic gear drive is an indispensable component of light industrial robots,but high-end products still rely heavily on imports.In order to help our country get rid of the difficult situation of the key core technology and form the independent innovation ability of harmonic gear reducer,this paper conducts a study on the flexspline stress,fatigue life,reliability and engagement stiffness of harmonic gear drive.The main completed achievements and innovations are as follows:(1)By taking the CSF25 type harmonic gear reducer as the prototype,the tooth profile of the Circular Spline is obtained on the basis of the envelope theory,establishing the modified calculation formula of the flexspline stress theory.By using the successive approximation method,the finite element calculation of six progressive models of flexspline is completed.According to the results,when the radial deformation is equal to the modulus,the longaxle region is the most advantageous meshing area;the stress value of the tooth root near the bottom of the flexspline cup is the largest;with the approximation of the model to the actual structure,the stress in each direction increases gradually,and the increase of the circumferential stress is larger.Based on the analysis results,the tooth profile of double circular arc flexspline is designed.(2)The orthogonal design method is used to combine the main structural parameters,including the length of flexspline,the thickness of ring gear,the thickness of flexspline wall,the width of tooth and the transition fillet of tooth root,analyzing the fatigue life of flexspline.And it is extracted that the fitting curves of the maximum equivalent stress and the number of fatigue cycles under each structural parameter.The effects law of structural parameters on stress and fatigue life are obtained by range analysis and variance analysis.The results show that the length and width of the flexspline have a great influence on the stress and fatigue life of the flexspline,with some certain monotony.In the range of selected parameters,the effect sequences of each parameter for the fatigue life of the flexible wheel are as follows: length,width,transition fillet of the tooth root,ring thickness and wall thickness of the flexspline.(3)The Monte Carlo simulation method is used to conduct the reliability analysis of the flexspline of the harmonic gear drive,overcoming the difficulty in obtaining large sample data in the calculation of the reliability of the flexspline.With the simulation,the reliability of the flexural fatigue of the flexspline is 88.64%,which has the difference of 0.11% with the numerical integration method.So it is verified that the Monte Carlo method is the correct way to calculate the reliability of the flexspline.(4)It is established that the single tooth engagement stiffness formula and engagement stiffness analysis model of the harmonic gear drive.Based on the contact analysis principle of finite element loading,the analysis of one contact and two loading is conducted,calculating the engagement stiffness and comprehensive engagement stiffness of the teeth in the meshing area of flexspline.Studying on the influence of engagement stiffness on the torsional stiffness of flexspline,the contact variation law between flexspline and circular spline is obtained.(5)The prototype of harmonic gear reducer is tested by using the test platform of comprehensive performance of precision robot,which includes no-load,starting torque,transmission error,torsional stiffness,lost motion and transmission efficiency.The related performance indexes such as transmission error,torsional stiffness and transmission efficiency all meet the design requirements,verifying the feasibility and correctness of analyzing flexspline characteristics and optimizing structural parameters.The above research results enrich the design technology and theory of the harmonic gear drive,initiate a new idea of the Monte Carlo method for the analysis of t he fatigue performance of the harmonic gear drive,and provide technical support for the design and manufacture of the precision harmonic gear drive. |
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