Research On Reliability Analysis Of Harmonic Reducer Based On Physics Of Failure

This subject comes from Civil Aerospace Key Technology Advance Research Program “XXX Experimental Research on High-reliability and Long-life Environment”. With the rapid development of China’s space technology, the demand of in-orbit working life and reliability of spacecraft become increasingly higher than ever. Space driving mechanism as an important part of the spacecraft, its reliability and working performance have a significant impact on in-orbit life of spacecraft. As a typical part of space driving mechanism, Harmonic reducer’s working performance is affected by temperature, load, speed and other factors. These factors coupled with each other, affecting the reliability harmonic reducer together.Focusing on harmonic reducer, this project established a multi-parameter coupling dynamic accuracy degradation model through the analysis of failure mechanisms with the method of physics of failure and the effect of speed, load and temperature on lubrication performance on the base of lubrication theory, then using total mechanical hysteresis as the representative variable of transmission accuracy researched the influence of speed, temperature and load on reliability through Monte Carlo method and AFOSM method. The main contents are as follows:(1) The failure mechanism of space lubrication harmonic reducer is analyzed. From the working principle, transmission characteristics, failure modes, work environment and other aspects of harmonic reducer, the failure mechanisms of space lubrication harmonic reducer is analyzed. Then the theoretical analysis was verified by observing the wear morphology of each contact region of harmonic reducer after reliability life test.(2) Using film thickness ratio, contact load ratio and contact area ratio as the representative variable of mixed lubrication, a mixed lubrication model of contact region between the inner wall of flexspline and the outer wall of wave generator bearing was established. By analyzing the effect of speed, load and temperature on lubrication performance, this paper got the relationship between film thickness ratio and speed, temperature and load, the relationship between film thickness and contact load ratio.(3) Using contact load ratio as the representative variable, an adhesive wear model of mixed lubrication was derived based on the Greenwood-Williamson model and Archard model.(4) A multi-parameter coupling accuracy degradation model was established. Through the analysis of meshing characteristic of harmonic reducer and the simulation of MATLAB, this paper got the relationship between wear loss and mating tooth number, meshing depth and mesh stiffness. Then this paper got the relationship between wear loss and backlash. Using total mechanical hysteresis as the representative variable, a multi-parameter coupling accuracy degradation model was established finally.(5) A reliability analysis model of harmonic reducer’s transmission accuracy was established. Based on the reliability analysis model, this paper analyzed the effect of working time on reliability under rated conditions. Besides, the effect of speed, temperature and load on reliability of harmonic reducer whose working time was 5000 h was researched.