Life prediction of Ni-Cd battery based on linear Wiener process

Predicting the life of Ni-Cd battery for electric multiple units (EMU) can not only improve the safety and reliability of battery, but also reduce the operating costs of EMU. For this reason, a life prediction method based on linear Wiener process is proposed, which is suitable for both monotonic and non-monotonic degraded systems with accurate results. Firstly, a unary linear Wiener degradation model is established, and the parameters of the model are estimated by using the expectation-maximization algorithm (EM). With the established model, the remaining useful life (RUL) of Ni-Cd battery and its distribution are obtained. Then based on the unary Wiener process degradation model, the correlation between capacity and energy is analyzed through Copula function to build a binary linear Wiener degradation model, where its parameters are estimated using Markov Chain Monte Carlo (MCMC) method. Finally, according to the binary Wiener process model, the battery RUL and its distribution are acquired. The experimental results show that the binary linear Wiener degradation model based on capacity and energy possesses higher accuracy than the unary linear wiener process degradation model.