Life Prediction Methods For The Typical Missile Servo System Based On The Enhancement Test

The missile servo system is a single-use product with long storage periods in its lifecycle.It has the characteristics of high-reliability demands and few samples in development phase.The traditional methods based on lifetime data or failure data are unable to predict its lifetime and reliability scientifically.Reliability enhancement test belongs to a sort of development testing,also referred to as accelerated stress testing,which is conducted in system development phase under step stress and cyclic stress conditions to defect design and manufacturing deficiencies.Additionally,it can obtain the lifetime-relevant information using few quantities of samples in a very short test time.In order to solve the lifetime prediction problems of the missile servo system,this thesis studies the probabilistic physics method to predict the lifetime of servo system based on reliability enhancement test data.The main contents include:(1)The relevant analyses of the failure mechanism of servo systemBy the stress analysis,FMEA,FTA and failure mechanism analysis of servo system,this thesis determines the preliminary degradation characteristics of each component.(2)The design and analysis of reliability enhancement test schemeFor two samples,we design five kinds of enhancement tests scheme,for example cold-step,hot-step,rapid cyclic-temperature,step-vibration and combined stresses.By analyzing the performance data from the above enhancement tests,this thesis determines the final degradation characteristic of servo system.(3)The method to check the consistency of enhancement test dataThe thesis preprocesses cold-step and rapid cyclic-temperature test data to establish the accelerated degradation models regarding temperature change rate that is assumed to be the main applied stress of the servo system during natural storage.Based on the accelerated degradation models and natural storage profile of the servo system,we provide and demonstrate a procedure to check the consistency of two mechanisms by checking the correlation and difference of two sets of degradation data.(4)The method to predict the working lifetime of servo system based on step-vibration test dataThis thesis uses step-vibration test data to establish accelerated degradation model of z-axis antenna shift parameter which is the critical degradation characteristic under vibration stress,and provides the methods to predict the working lifetime of servo system based on B-S cumulative damage model.(5)The method to predict the storage lifetime of servo system based on temperate enhancement test dataThis thesis uses the cold-step test data to establish accelerated degradation equation regarding temperature.Based on this equation,this thesis eliminates the degradation in temperature keeping phases from the rapid cyclic-temperature test data to develop the accelerated degradation equation regarding temperature change rate.Finally,this thesis derives the distribution model of the storage lifetime and reliability model of servo system based on B-S cumulative damage model,and provides the methods to calculate point estimation and interval estimation based on bootstrap.