Basic Reliability Engineering Concepts for Automotive Electronic Systems 770225

An effective reliability engineering program recognizes that achievement of operational reliability is a design parameter. Decisions made during the design process influence all subsequent phases of a system's life cycle in the form of part quality, producibility and maintainability. Therefore, deliberate and positive measures must be instituted during the design and development process which enhance inherent reliability and minimize the introduction of latent defects during manufacturing and inspection, and degradation during field use.

This paper presents an overview of reliability for the manager and engineer who has been recently exposed to this engineering discipline that has found widespread application in military systems. It is intended to provide an appreciation for the tools that are available for aiding the automotive industry in achieving a shorter design/development cycle, reducing costs and increasing customer satisfaction.

Fundamental reliability engineering concepts are introduced with a brief review of the reliability/life characteristic, exponential failure model, reliability prediction techniques and system modeling concepts. Testing philosophies, including accelerated and reliability growth testing methodology are described. Finally, the reliability control program elements appropriate to the several system life-cycle phases are defined.

RELIABILITY CONTROL HAS PLAYED a major role in upgrading military electronic system reliability over the past 15-20 years. Theory, methodology and uniform practices have evolved and are continually refined to improve their effectiveness and extend application. In recent years there has been a marked shift from attainment of ultimate reliability to a consideration of total system life-cycle costs. With this approach reliability becomes a design parameter which can be traded off against costs. Low initial reliability will reduce engineering and production costs but result in high field maintenance or retrofit costs. Conversely, high reliability increases front-end costs but reduces maintenance costs. In between there is an optimum point which establishes the degree of reliability control to be exercised over the development and production process. It is in this context that reliability engineering principles can be effectively applied to automotive electronics systems. Large volume production runs permit relatively high engineering costs but manufacturing costs become critical. While ultimate reliability levels are not generally required (except in critical applications as in braking control) to assure a high probability of mission success, the number of repairs required and associated costs during the warranty period is highly important.

Reliability achievement is primarily a management discipline, applied throughout the system development/production cycle. It must establish requirements, then provide the necessary resources, tools and authority to assure that the consequences on reliability are made part of each decision rendered. This paper is intended to aid the newcomer, both manager and technologist, to electronic systems reliability engineering in understanding the basic principles, concepts and theory. The reliability control program elements that must be carried out coincident with hardware development are briefly outlined along with key reliability engineering tools for quantifying and measuring reliability achievement.