| With the rapid development of China’s space industry, thehigher requirements areproposed in service life and reliabilityand other technical indicators of spacetransmission mechanism. The use-pattern of kinds of spacecraft is changing from “testapplied” to “business service-oriented”. The way change requires that the orbitingspacecraft hasa longer service life and higher reliability.As a kind of important transmission mechanism, harmonic driver is widely used inkinds of spatial mechanism with excellent transmission performance，but dynamicservice behavior and failure mechanism of harmonic driver have not been furtherstudiedand analyzed under complex space environment. What’s more, the scientific andreasonable life test method and the life reliability evaluation system have not beenestablished, which greatly restrictharmonic driver using in the subsequent spacecraftmechanism.Aiming at these problems, this research subject uses harmonic driver as theresearch object. Some accelerated degradation tests are carried out, which imitate theservice state in space environment. The failure mechanism of the space environment isstudied to establishperformance degradation and reliability life distribution model.The main research contentsare as follows:(1) The failure mechanism of space harmonic driveris analyzed. Firstly, thespecial requirements are analyzed in the space environment, as well as lubrication formsand failure reasons of the main friction pairs.Secondly, disassembleda harmonic driverand observedthe internal wear, and combined with the research achievements of theteam. Finally, the failure mechanism of harmonic driver is got.(2) Some imitating space environment accelerated degradation tests of harmonicdriver performance are carried out. Based on the failure mechanism, using the spaceenvironment lubrication form,choosing reasonableaccelerated stress and accelerationfactor, multiple sets of transmission degradation accelerated testsare implemented underdifferent working conditions to obtain performance degradation and life distributionparameters.(3)Performance degradation failure models of a space harmonic driver areestablished. Through the analysis of typical model of the accelerated degradation andthe influence factors about transmission performance, performance degradation modelis established which is based on the random degradation Brown motion and parametersstatistical analysis methodof the model is given. Physical failure degradation wearmodelis built as well.Analysis of the wear rate under mixed lubrication, thereby lifeacceleration equation is built.(4)Reliabilitylife distribution model of space harmonic driver is established. Onthe basis of the failure mechanism of space harmonic driver, reliability life distributionmodel of space harmonic driver based on Weibull is established.The model is validatedfrom two aspects in failure life distribution and failure acceleration equation. Throughfailure life distribution hypothesis test and distribution parameter equal hypothesis test,the accuracy of failure life distribution is verified. Through fitting acceleration equation,chart analysis and statistical test of acceleration equation and residual analysis, theaccuracy of failure acceleration equation is verified. Finally, estimating the reliabilityindex of space harmonic driver, the average life, acceleration coefficient andextrapolation service life are obtained under different stress. |
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