符合ISO 26262車用電池管理系統之可靠度評估

Abstract

電動車因具有低汙染、節能、低噪音等優點，漸漸被大眾廣泛使用，然而，其動力來源－蓄電池有能量損耗及儲存的問題，會影響使用者的生命安全。而安全一直是車輛產業非常關注的焦點，車用電機/電子產品或其零組件的安裝與使用者的生命財產安全息息相關，為了避免車輛危害帶來重大損失，國際標準組織(International Organization for Standardization, ISO)專為車用電機/電子發佈ISO 26262標準。本論文以電池管理系統(Battery Management System, BMS)為案例，示範符合ISO 26262標準之執行流程，並評估電池管理系統之可靠度。首先介紹電池基本概念以及電池管理系統的功能；接著說明ISO 26262組成架構與功能安全管理，並進一步介紹概念階段以及硬體架構評估所需推動的工作或實施項目；最後透過ISO 26262功能安全標準來發展一電池管理系統，使其能符合功能安全設計的要求；同時亦建立一個完整的功能安全管理流程，以利產品達到高安全、高可靠度以及高品質的境界。此外，本研究亦探討電池管理系統的失效模式與影響分析，並使用MIL-HDBK-217F N2或FIDES Guide 2009兩種可靠度預估模型，計算電池管理系統與其零組件之可靠度和平均失效時間(Mean Time to Failure, MTTF)。研究結果發現，本論文所探討的電池管理系統平均失效時間為3.79年，而依照失效模式之影響程度將各零組件予以排列，失效嚴重程度依序為電池組過熱、ECU訊號異常、ECU燒毀與電池組爆炸等。

Owing to their low pollution, energy saving, low noise, and other benefits, electric vehicles will be widely used in the near future. However, the batteries of and electric vehicle encounter a few problems including energy loss and storage limitation. Their failures would threaten lives of the driver and passengers of a vehicle and should be paid attention to safety has always been a major concern in the automotive industry. The electric or electronic devices are closely related to the safety of a vehicle. In order to avoid losses caused by failure of a vehicle, the International Organization for Standardization published ISO 26262 which is functional safety standard entitled “Road Vehicles – Functional Safety.” To demonstrate how ISO 26262 can be fulfilled, a battery management system (BMS) used in an electric vehicle is studied from reliability engineering point of view in this thesis. First, the BMS used in an electric vehicle is introduced. The overall architecture and functional safety management of ISO 26262 is introduced briefly afterwards. Emphasis is placed on the concept phase and assessment of the hardware architectures. The required work to implement ISO 26262 to a product is highlighted in particular. Finally, an example of implementing ISO 26262 to the introduced BMS and is carried out. The purpose is to create a completion functional safety management toward the high safety, reliability and quality target to meet ISO 26262 standard for the BMS. In addition, the failure mode and effect analysis (FMEA) of the BMS is performed. The reliability and mean time to failure (MTTF) of the BMS and its components are evaluated. The result shows the MTTF of the studied BMS is 3.79 years. Based on FMEA, it’s found that critical failure modes of the BMS are overheating of battery packs, abnormal signal of the electric control unit (ECU), burned-out ECU, and the explosion of battery packs etc., in sequential order of seriousness.