符合ISO 26262之馬達動力系統可靠度分析

Reliability Analysis of Motor-Drive Systems for Fulfillment of ISO 26262

馬維君(Wei-Chun Ma)

指導教授 ： 吳文方

國立臺灣大學/工學院/機械工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603460

摘要

由於電動車 逐漸成為未來趨勢，馬達動力系統廣泛應用於車輛中，一旦失效產生，可能影響駕駛與乘客安危，因此車輛功能安全需求備受矚目。由於汽車電子/電機系統功能安全標準ISO 26262已納入歐盟規範，並將於2018年拓展涵蓋範圍至其他車輛產業，為配合國內車廠及相關產業導入此國際標準，本論文以馬達動力系統為研究對象，執行符合ISO 26262標準之評估流程，探討組件和系統之可靠度。文中首先介紹ISO 26262組成架構，並進一步說明概念階段與硬體架構評估階段之工作內容；接著定義馬達動力系統，並透過文獻之蒐集，執行相關危害分析與風險評估，藉以訂定關鍵組件之汽車安全完整性等級(Automotive Safety Integrity Level, ASIL)；最後再探討關鍵組件是否符合所訂之功能安全目標。本論文以美國海軍可靠度手冊所載資料作為可靠度評估之依據，首先估算各關鍵組件與系統之失效率與平均失效時間，而後再與ISO 26262標準硬體架構評估階段所預先設定之安全目標相互比對。本論文也依據ISO 26262之特定要求，探討關鍵組件之失效模式，執行失效模式與影響性分析(Failure Mode and Effect Analysis, FMEA)。本研究結果顯示，馬達動力系統中，失效率較高的組件依序為定子、軸承及轉子。結果也顯示，若欲提升系統之可靠度，較顯著的方法依序為提升定子繞組之可靠度、降低馬達操作溫度以及減少軸承接觸之水氣含量。而在失效模式與影響性分析方面，本論文發現各關鍵組件中，較需注意之失效模式依序為軸承脫軸、定子繞組短路與轉子斷條。

關鍵字

馬達動力系統 ； ISO 26262 ； 失效模式與影響性分析 ； 可靠度 ； 平均失效時間

並列摘要

Electric vehicles have gradually become the trend of future transportation. It is expected that more and more motor-drive systems will be used along with the development of electric vehicle. The failure of motor-drive system threatens the lives of drivers and passengers, and hence the automotive functional safety requirements have gained much attention in recent years. The functional safety standard ISO 26262 for automotive electronic and electrical systems has been included in EU regulations, and its coverage will be expanded from small vehicles to all passenger vehicles in 2018. To help engineers of the domestic automotive industry understand more about ISO 26262 and to demonstrate how to implement the international standard, a motor-drive system is studied in this thesis. First, the framework as well as the composition of ISO 26262 is introduced. The concept design stage and the assessment of hardware architecture are explained in detail. A motor-drive system is defined, and related hazard analysis and risk assessment are carried out in order to assign appropriate automotive safety integrity levels to key components of the motor-drive. Whether each of the key components would reach its functional safety goals is examined. The reliability manual of US Navy is used as the basis of reliability assessment. To begin with, the failure rates and mean times to failure of the key components as well as the system are evaluated. The failure rates are then compared with the originally set safety goals. The failure modes of key components are identified following the specific requirement of ISO 26262, and the failure mode and effect analysis is performed. The research result shows that, for the studied motor-drive system, components that have higher failure rates are the stator, bearings, and the rotor in descending sequence. It is also found that if the reliability of the system is to be increased, the more significant actions are enhancing the reliability of stator winding, reducing the operating temperature of the motor, and reducing the moisture content of the bearing. In failure mode and effect analysis, it is identified the failure modes that should be paid more attention to are bearing running out of the shaft, stator winding short circuit, and broken rotor bars.

並列關鍵字

motor-drive system ； ISO 26262 ； failure mode and effect analysis ； reliability ； mean time to failure

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