Redesign Parameter Identification Of Harmonic Gear Base On Performance Degradation

Redesign is a continuous improvement process based on the previous testing or operation of product.Redesign is the most important and timeconsuming work for aerospace product development.As an important part of the solar wing drive mechanism,harmonic gear needs to improve its performance and reliability through redesign.Identify the weakness and related design parameter of product is the first step of redesign.Since performance degradation is the main problem for harmonic gears,it is necessary to analyze the performance degradation process to find the weakness that lead to the degradation of harmonic gears,then identify design parameters that needs to be redesign.However,there are two difficulties in redesign parameter identification of harmonic gear based on performance degradation.On the one hand,harmonic gear is high reliability product with low failure rate,resulting in the lack of failure data for degradation process analysis.On the other hand,the existing method for design parameter identification depends on the knowledge and experience of designer,it usually leads to subjectivity bias.Aimed at solving these problem,a redesign parameter identification method for harmonic gears based on performance degradation is proposed.Firstly,an improved RPN method is used to evaluate the performance degradation of harmonic gears based on the degradation data.In order to evaluate the risk of degradation mods objectively,the risk factors are evaluated by using the degradation data,and the specific meaning of the severity of degradation mode is clarified.Aiming at solving the problem that the occurrence rate is difficult to estimate accurately because of the lack of failure data,the Gamma degradation model is established based on the degraded data to estimate the pattern of the degradation modes.And the failure probability of the degradation modes is calculated according to the Gamma model to estimate the occurrence frequency.Then,using reliability sensitivity analysis method,the design parameter – degradation mode correlation matrix is established to evaluate the redesign necessity of harmonic gear’s design parameter.Based on the study of harmonic gear’s performance mechanism,the limit state equation and reliability model of degradation modes are established;By using important sampling based reliability sensitivity analysis method,the correlation strength between design parameter and degradation mode was evaluated;According to the correlation matrix and RPN value of degradation modes,the redesign necessary index was calculated to identify the redesign parameter of harmonic gear.Finally,the results of harmonic gear analysis show that the flex spine fatigue and tooth wear are main reasons for the performance degradation of harmonic gear.The length of flex spine,tooth width and elastic modulus are the design parameters that need to redesign mostly.The results is approved by the experts,the effectiveness and practicality of proposed identification method is proved.