Feng Ju

A Quality Flow Model in Battery Manufacturing Systems for Electric Vehicles

Improving quality in large volume battery manufacturing systems for hybrid and electric vehicles is of significant importance. In this paper, we present a flow model to analyze and improve product quality in electrical vehicle battery assembly lines with 100% inspections and repairs for defective parts. Specifically, a battery assembly line consisting of multiple inspection stations is considered. After each inspection, defective parts will be repaired and sent back to the line. A quality flow model is introduced to analyze quality propagations along the battery production line. Analytical expressions of final product quality are derived and structural properties, such as monotonicity and sensitivities, are investigated. A bottleneck identification and mitigation method is introduced to improve quality performance. Finally, a case study is presented to illustrate the applicability of the method.

Virtual Battery: A Battery Simulation Framework for Electric Vehicles

The battery is one of the most important components in electric vehicles. In this paper, a virtual battery model, which provides a framework of battery simulation for electric vehicles, is introduced. Using such a framework, we can model and simulate the performance of a battery during its usage, such as battery charge, discharge, and idle status, the impacts of internal and external temperature, the manufacturing quality on joints, the cell capacity and balance management, etc. Such a framework can provide a quantitative tool for design and manufacturing engineers to predict the battery performance, investigate the impacts of manufacturing process, and obtain feedback for improvement in battery design, control, and manufacturing processes. Note to Practitioners-Automotive battery manufacturing has become more and more important due to the need of alternative energy source to gasoline powered engines. Although substantial amount of attention has been paid to study both individual battery cells and the battery pack as a whole, a battery model which includes interactions of all its components (cells, joints, external inputs, etc.) is not available, and the impact of manufacturing quality on battery performance has not been investigated. In this paper, a virtual battery simulation framework is developed to evaluate battery performance under different circumstances, involving the issues of cell capacity, temperature, driving profile, the joint (manufacturing) quality, etc. Such a framework can help battery design and manufacturing engineers to evaluate battery performance, investigate the impacts of manufacturing practices, and provide feedback for improvement.

Quality flow model in automotive paint shops

Abstract Improving paint quality is of significant importance for vehicle manufacturing. In this paper, a quality flow model is presented to analyse and improve quality in automotive paint shops. Specifically, we study the vehicle-painting process with multiple inspection stations. After each inspection, vehicles failed to achieve quality requirement will be repaired before moving to the next operation. In such systems, the quality variations may propagate along the painting process. To address this, a three-state quality flow model has been developed, and analytical formulas to evaluate product quality have been derived. In addition, to improve quality performance, a bottleneck analysis method has been introduced to identify the most critical stage that impedes product quality in the strongest manner. Two case studies at automotive paint shops are introduced to illustrate the applicability of the method.

Modeling, analysis, and improvement of integrated productivity and quality system in battery manufacturing

A battery manufacturing system typically includes a serial production line with multiple inspection stations and repair processes. In such systems, productivity and quality are tightly coupled. Variations in battery quality may add up along the line so that the upstream quality may impact the downstream operations. The repair process after each inspection can also affect downstream quality behavior and may further impose an effect on the throughput of conforming batteries. In this article, an analytical model of such an integrated productivity and quality system is introduced. Analytical methods based on an overlapping decomposition approach are developed to estimate the production rate of conforming batteries. The convergence of the method is analytically proved and the accuracy of the estimation is numerically justified. In addition, bottleneck identification methods based on the probabilities of blockage, starvation, and quality statistics are investigated. Indicators are proposed to identify the downtime and quality bottlenecks that remove the need to calculate throughput and quality performance and their sensitivities. These methods provide a quantitative tool for modeling, analysis, and improvement of productivity and quality in battery manufacturing systems and can be applied to other manufacturing systems ameanable to investigation using integrated productivity and quality models.

Computer modeling of lung cancer diagnosis-to-treatment process.

We introduce an example of a rigorous, quantitative method for quality improvement in lung cancer care-delivery. Computer process modeling methods are introduced for lung cancer diagnosis, staging and treatment selection process. Two types of process modeling techniques, discrete event simulation (DES) and analytical models, are briefly reviewed. Recent developments in DES are outlined and the necessary data and procedures to develop a DES model for lung cancer diagnosis, leading up to surgical treatment process are summarized. The analytical models include both Markov chain model and closed formulas. The Markov chain models with its application in healthcare are introduced and the approach to derive a lung cancer diagnosis process model is presented. Similarly, the procedure to derive closed formulas evaluating the diagnosis process performance is outlined. Finally, the pros and cons of these methods are discussed.

Power Management for Hybrid Energy Storage System of Electric Vehicles Considering Inaccurate Terrain Information

Terrain information can significantly impact load power demand, and in turn, on battery life and system efficiency of a hybrid energy storage system (ESS) with battery and supercapacitor. Taking terrain information ahead into consideration for proactive power management is one of the most important ways to improve battery life and overall system efficiency. However, since terrain information is typically available from commercial geographic information systems database, it is by nature inaccurate with uncertainties with respect to the requirements of power management. This is often worsening when combining with commercially low-quality global positioning systems. This paper proposes a novel power management strategy to cope with the inaccuracy and uncertainties of the terrain information with the aim to improve battery life, while maintaining overall system performance. First, the impact of terrain inaccuracy on battery life and system efficiency is analyzed based on two different hybrid ESSs with semiactive topologies. Then, a power management control strategy is developed that actively distributes the power between battery and supercapacitor with adaptation to terrain inaccuracy and uncertainties. The objective of the proposed power management control strategy is to minimize the total cost of the system, including the cost for battery life and energy. Finally, simulation is conducted that has verified the effectiveness of the proposed control strategy.

Systematic continuous improvement model for variation management of key characteristics running with low capability

A systematic continuous improvement model (SCIM) is described in this paper. This model responds to improvements opportunities that were identified in the literature and aerospace companies to aim in variation management of KCs and for developing solutions to improve issues in KCs. This approach helps to identify and improve key characteristics (KCs) in products that most influence in rework and scrap costs, especially in material removal processes. SCIM complies with two purposes; a mathematical method to calculate the rework cost for KCs as a variable in function of expected amount of material to be removed. This cost plus scrap cost is used to prioritise KCs running with low capability; this prioritisation is performed by predicting rework and scrap costs based on historical data of manufacturing processes performance, costs associated to rework and scrap parts out of specification and forecast for product demand. Once critical KCs are identified, the second purpose of this model helps engineers to develop solutions to eliminate what is causing KCs running with low capability; this is possible using knowledge management methodologies to capture, structure and storage solutions developed, in order to reuse them in future similar issues. A case study is presented in this paper to apply this model.

Performance Evaluation of Modularized Global Equalization System for Lithium-Ion Battery Packs

Battery management system has attracted mounting research attention recently, within which cell equalization plays a key role. Although many research and practices have been devoted to developing various structures of cell equalizers, there are still substantial opportunities for performance improvement yet to investigate. In particular, mathematical modeling and systematic analysis of equalizer systems are limited. In this paper, the performance analysis of the modularized global equalizer system for Lithium-ion battery cell equalization is conducted analytically. Specifically, a mathematical model is developed to emulate the equalization dynamics by considering both charging/discharging and energy loss. Analytical formulas are derived to evaluate the performance of the global equalizer. The introduced model is also compared with the state-of-the-art structures in terms of equalization speed and energy loss. Numerical studies show that the modularized global equalization outperforms others by its substantial reduction on energy loss with similar equalization performance and much less equalizers. In addition, a module segmentation guide is provided to facilitate the equalization system design. Lithium-based battery technology offers performance advantages over traditional battery technologies, which makes it promising in application such as automobiles, portable devices, power grid, etc. To ensure the Lithium-ion batteries working efficiently, reliably and safely, battery equalization systems play a critical rule, especially in large volume battery packs. Various equalization structures have been proposed to balance the state of charge within a string of battery cells. In this paper, we first review the state-of-the-art equalization structures in a unified model representation scheme, and then focus on a modularized global equalization structure with much less equalizers. Based on the mathematical models for performance evaluation, the modularized global equalization system outperforms the state-of-the-art structures in terms of energy loss with similar equalization speed. In addition, we provide a module segmentation guide to determine the number of modules in the system design.

Medication Error Propagation In Intensive Care Units

We examined propagation of medication errors at various stages of the medication management process (ordering, transcription, preparation, dispensing, administration and monitoring) in two ICUs of a medical center. We performed a secondary analysis of 1,732 medication events identified in a group of 630 ICU patients. A Markov Chain model showed that errors propagate throughout the medication management process, in particular between the stages of preparation, dispensing and administration.

Modularized global equalization of battery cells for electric vehicles

Battery management system has attracted mounting research attention recently, within which cell equalization plays a key role. Although many research and practices have been devoted to developing system-level structure of cell equalizers, there are still substantial opportunities for performance improvement yet to investigate. This paper proposes a novel architecture for battery cell equalization, referred to as modularized global equalizer. The mathematical model is developed to emulate the equalization dynamics by considering both charging/discharging and energy loss. Analytical formulas are derived to evaluate the performance of the global equalizer. The proposed method is also compared with the state-of-the-art structures in terms of equalization speed and energy loss.