Effects of subsystem mission time on reliability allocation

Abstract

During the early stages of system development, various factors are considered when determining an allocation weight to apportion a system’s reliability requirement to each subsystem. Previous methods have included subsystem mission time as a factor in obtaining the allocation weight in order to allocate a higher failure rate to a subsystem with a shorter mission time than the system’s mission time. This article, first shows that the results obtained from previous methods are misleading, mainly because the allocated failure rate of the subsystem is expressed in the system’s mission time rather than the subsystem’s mission time. It is further shown that if a designer intends to allocate a lower failure rate to a subsystem that has to operate longer in the system, subsystem mission time must not be included as a factor when determining the allocation weight. If a designer wants to allocate the system failure rate equally to each subsystem regardless of a subsystem’s mission time, subsystem mission time must be included as a factor.

Keywords:

• Allocation weight
• subsystem mission time
• unreliability
• constant failure rate

Additional information

Notes on contributors

Kyungmee O. Kim

Kyungmee O. Kim is a Professor in the Department of Industrial Engineering at the Konkuk University, Seoul, Korea. Her research interests include reliability estimation and optimal system design.

Ming J. Zuo

Ming J. Zuo is currently a Full Professor in the Department of Mechanical Engineering at the University of Alberta, Canada. His research interests include system reliability analysis, maintenance modeling and optimization, signal processing, and fault diagnosis. He is Associate Editor of IEEE Transactions on Reliability, Department Editor of IIE Transactions (2005–2008, 2011–present), Regional Editor for the North and South American region of the International Journal of Strategic Engineering Asset Management, and Editorial Board Member of Reliability Engineering and System Safety, Journal of Traffic and Transportation Engineering, International Journal of Quality, Reliability and Safety Engineering, and International Journal of Performability Engineering. He is a Fellow of the Institute of Industrial Engineers, Fellow of the Engineering Institute of Canada, Founding Fellow of the International Society of Engineering Asset Management, and a Senior Member of IEEE.