Reliability Analysis of Motor-Drive Systems for Fulfillment of ISO 26262
Date Issued
2016
Date
2016
Author(s)
Ma, Wei-Chun
Abstract
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.
Subjects
motor-drive system
failure mode and effect analysis
reliability
mean time to failure
Type
thesis
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