Reserch On Reliability Life Test And Evaluation Method Of Aerospace Electromagnetic Relay

As one of the key components in aerospace system,the accurate reliability evaluation of aerospace electromagnetic relay is very important to improve the safety and stability of the whole system.In general,strict quality screening and reliability evaluation process will be implemented before the electromagnetic relay is delivered.However,due to the limitation of test cost and test equipment,the traditional reliability evaluation is only carried out for a small amount of sample data under the rated load type and rated load level,which is prone to the problems of large bias of reliability evaluation results and narrow application range,and it is difficult to accurately evaluate the application reliability under the actual working conditions.In order to obtain more comprehensive and accurate reliability evaluation results of aerospace electromagnetic relay,a reliability evaluation method based on small sample expansion is proposed in this paper.Based on the development of the life test platform with combined load circuit,the life approximate model,fast calculation model of dynamic characteristics and reliability evaluation method of aerospace electromagnetic relay are deeply studied.Firstly,the life test platform of aerospace electromagnetic relay is designed and implemented.In order to make up for the shortcomings of traditional test platform such as single load type and fixed load level,a combined load circuit with resistive,inductive and capacitive load types and adjustable current range of(0A ～80A)/ 28 V is designed.The signal conditioning circuit is designed by using the scaling and isolation functions of current sensor,operational amplifier and other devices,and the NI board is used as the signal acquisition module.According to the definition of dynamic characteristic parameters,the corresponding extraction algorithms are designed.The centralized control mode is adopted in the test platform,and the upper computer is used to set the test parameters,control the test process and monitor the degradation data.And the three position synchronous test is realized,which greatly improves the efficiency of life test.Secondly,the approximate model of aerospace electromagnetic relay’s life is established.The wavelet transform method is used to preprocess the main dynamic characteristic parameters in the process of relay life test,and the high-frequency interference signal is removed.Based on the processed data and principal component analysis,the key dynamic characteristic parameters of the target relay are determined as the input parameters of the life approximate model.The maximin distance method is used to design the life test under different load levels under the capacity conditions,and the approximate model is trained by the test results.By comparing the accuracy of different approximate modeling methods,the best approximate model is selected as the final result.Then,the fast calculation model of dynamic characteristics of aerospace electromagnetic relay is established.The main design parameters of the target relay are collected through the follow-up investigation to guide the establishment of the simulation model.On this basis,the key design parameters which affect the dynamic characteristics are determined by single factor analysis method,which is used as the input parameter of the fast calculation model.Combined with the approximate modeling technology,the training data and test data are obtained through the simulation model,so as to obtain the corresponding mathematical models and their accuracy of different modeling methods.The mathematical model with the highest accuracy is selected as the fast calculation model of the corresponding dynamic characteristics.By combining the approximate life model with the fast calculation model of dynamic characteristics,the mathematical model describing the corresponding relationship between the design parameters and the life of electromagnetic relay is established,which lays the foundation for the expansion of small samples in the process of reliability evaluation.Finally,the reliability evaluation method of aerospace electromagnetic relay is studied.In order to solve the problem that the traditional reliability evaluation process such as hypothesis test and graph test specifies the distribution type and the result is not unique,this paper proposes a method to determine the best distribution type based on fuzzy comprehensive evaluation theory,which realizes the rapid and unique determination of the distribution type of life data.At the same time,in order to make the reliability evaluation process meet the "law of large numbers",the small sample life data is expanded by combining the manufacturing process data and the established mathematical model.In order to reflect the randomness of the small sample expansion process,the confidence feature is introduced into the load characteristic curve.Taking the capacitive load type as an example,the reliability curve and load characteristic curve of a certain type of aerospace electromagnetic relay are evaluated,and the accuracy of the reliability evaluation results is verified by actual samples.Based on the reliability evaluation process established in this paper,a tolerance optimal allocation method is proposed,which can improve the life reliability of aerospace electromagnetic relay to the target value.