Progressive Worst Case Scenario Analysis: Improving Functional Safety by Bridging Gaps in FMEA for Effective Implementation of ISO 26262 2016-01-8132

Reliability engineering methods are used to assess risk and eliminate hazards by estimation, elimination, and management of risks of failures. The ISO 26262 functional safety standard gives detailed guidance on reliability engineering methods like Failure Mode and Effect Analysis (FMEA) [7], Fault Tree Analysis (FTA) [8] [2], and etc. While, there are many methods available for reliability engineering; no single method is foolproof for securing safety by eliminating hazards completely. Out of these methods, FMEA is widely being used as an integral part of the product development life cycle [10]. In this method, failure modes of individual components are analyzed considering one failure at a time. FMEA is an efficient method for analyzing failures in simple systems. For complex systems, FMEA becomes impractical. It is also difficult to consider variables in FMEA.

FMEA provides fairly detailed recommended action items to avoid failures and eliminate hazards in average working conditions [3]. But, when exposed to worst case situations, FMEA recommended action items fail to avoid failures in a system. While designing a product, many times it is hard to imagine what design parameters shall be considered to ensure that the product will survive through extreme conditions. The intent of this paper is to propose the use of Progressive Worst Case Scenario Analysis (PWCSA) as an extension of FMEA. The method is redefined to be more aligned with FMEA, and FMEA being a successive stage. However, this method can also be used in isolation i.e. without using FMEA as a prior stage.

This paper defines PWCSA as a structured & measurable probabilistic process for residual risk assessment and containment to facilitate hazard elimination. Worst case testing is usually carried out on individual components of the system. If PWCSA is incorporated into ISO 26262 as a part of the reliability engineering method, it can help to enhance functional safety by influencing specifications for expected performance and safety standards.