Jing Feng

Bio: Jing Feng is an academic researcher from National University of Defense Technology. The author has contributed to research in topics: Reliability (statistics) & Deblurring. The author has an hindex of 9, co-authored 33 publications receiving 206 citations.

Reliability Assessment of Metallized Film Capacitors using Reduced Degradation Test Sample

Abstract: Metallized film capacitor is a type of product with a long lifetime and high reliability. It is difficult to assess the lifetime and reliability using the traditional statistical inference method which is based on the large number of testing data. This paper presents a new testing methodology, called T-performance degradation test, by dividing the test process into several stages. In each stage, the sample size of working capacitors under test decreases stage by stage until the test lasts enough time with few survival capacitors. Leveraging the T-performance degradation data, this paper further presents a reliability assessment model to predict the lifetime of the high-performance capacitors. Finally, the reliability assessment model is demonstrated on a type of high-performance metallized film capacitors used in the energy module of the laser facility. Copyright © 2012 John Wiley & Sons, Ltd.

Residual life estimation under time-varying conditions based on a Wiener process

Abstract: Residual life (RL) estimation plays an important role in prognostics and health management. In operating conditions, components usually experience stresses continuously varying over time, which have an impact on the degradation processes. This paper investigates a Wiener process model to track and predict the RL under time-varying conditions. The item-to-item variation is captured by the drift parameter and the degradation characteristic of the whole population is described by the diffusion parameter. The bootstrap method and Bayesian theorem are employed to estimate and update the distribution parameters of ‘a’ and ‘b’, which are the coefficients of the linear drifting process in the degradation model. Once new degradation information becomes available, the RL distributions considering the future operating condition are derived. The proposed method is tested on Lithium-ion battery devices under three levels of charging/discharging rates. The results are further validated by a simulation method.

Online estimation of state-of-health for lithium ion batteries based on charge curves

Abstract: Usable capacity refers to the maximum capacity in theory that a fully charged battery can release, and is often used as an indicator in state of health (SOH) estimation for lithium ion batteries. The traditional method for measuring usable capacity is mainly based on voltage data in the discharge process with a constant current. However, the discharge current of a lithium ion battery in operation always fluctuates due to load changes, which makes the traditional method difficult for realizing online capacity measurement. To overcome the above problems, a novel approach is proposed in this paper to estimate the usable capacity and SOH of lithium ion batteries based on the charge curve. The time intervals between two voltages and currents during charging are used as the health factors to predict the usable capacity, which is then used to perform the SOH estimation. Experiments are implemented based on data provided by the NASA Ames Prognostics Center of Excellence. Results confirm that the proposed method performs well in online estimation of SOH.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Reliability of Capacitors for DC-Link Applications in Power Electronic Converters—An Overview

Abstract: DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.