Abstract
Currently, it is still a challenge to study the degradation mechanisms of the space traveling wave tube amplifier (TWTA) with no failure and small sample tests. Given that the Copula functions are used to describe the correlation of multiple performance characteristics, this paper develops a bivariate hybrid stochastic degradation model to evaluate the in-orbit reliability of TWTA. Firstly, based on the impact analysis of the life of TWTA, helix current and anode voltage are selected as the performance degradation parameters. Secondly, stochastic processes with random effects based on the one-dimensional Wiener process and Gamma process are applied to describe the degradation of TWTA’s helix current and anode voltage, respectively, and the corresponding marginal distribution function is obtained. Then, the Copula function is utilized to describe the correlation between two different performance parameters of TWTA. Meanwhile, this paper also proposed a two-step method to estimate the reliability level of TWTA based on its in-orbit telemetry data through a two-step method, which contains a Markov Chain Monte Carlo (MCMC) algorithm and a maximum likelihood estimation (MLE) algorithm. Besides, the Bayes-Bootstrap sampling method is also used to improve the evaluation accuracy to overcome the defect of an in-orbit small sample of TWTA. Finally, a TWTA degradation case with a set of telemetry data is carried out, and the results show that the method proposed in this paper is more applicable and more accurate than other methods.
Highlights
Space traveling wave tube amplifier (TWTA) is a key component of spacecraft transponders and spacecraft transmitters
Step 1: Parameter estimation of the marginal distribution According to the edge distribution of the performance degradation data of the TWTA, the likelihood function of the edge distribution as shown in Equations (21) and (22) can be obtained, and the estimated value can be obtained by the Markov Chain Monte Carlo (MCMC) method [25], which is used to estimate unknown parameters in the likelihood function of marginal distributions referred to in the Wiener process and the Gamma process, respectively
In engineering, it is generally agreed that the life of the TWTA is mainly determined by the cathode’s life, while the helix current is a comprehensive index of the TWTA, and its variation is affected by many factors
Summary
Space TWTA is a key component of spacecraft transponders and spacecraft transmitters. The data-driven methods are used to predict the probability density function (PDF) and cumulative distribution function (CDF) of the product’s life through its historical failure data and the existing observation data These methods do not rely on the operating principle of the product and the inherent failure mechanism, mainly including neural networks, support vector machines, statespace models, and stochastic processes. Performance degradation-based methods are one of the essential data-driven methods based on the fact that the hidden life information is reflected by one or multiple performance characteristics, and they have been recognized as an effective and important approach for the reliability evaluation of the high-reliability and long-life products They provide a reference to carry out the research on PHM of TWTA. Through in-depth research on the failure mechanisms of the TWTA, helix current and anode voltage are selected as the in-orbit performance characteristic parameters, and the data are used to study the performance degradation of the TWTA
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