Structured Approach to Build-in Design Robustness to Improve Product Reliability

Abstract

Robustness is defined as the degree to which a system or component can function correctly in the presence of invalid inputs or stressful environmental conditions. The objective of robustness is to deliver high reliability to customers. Robustness ensures that product design is immune to and can gracefully handle invalid inputs and stressful environmental conditions without any disruption or degradation of service to the end user. Robustness can be systematically built into any system, regardless of hardware or software, by following an end−to−end approach that encompasses product requirements, design, development, and testing. This chapter provides a structured approach to design in robustness by mapping baseline use case scenarios as ‘sunny day’ scenarios, identifying potential failures using P−diagrams and Design Failure Modes & Effects Analysis (or, “rainy day” scenarios), and proactively embedding design controls to strengthen product robustness and minimize field failures. The authors describe an innovative way to prioritize design improvements not just by traditional Risk Priority Number (RPN) of design failures but by considering the actual magnitude of risk reduction, as well as by factoring in cost of design improvements in prioritization decisions. Robustness once built−in product design must be validated through vigorous robustness testing to provide objective evidence of design robustness and support decision-making regarding product readiness for release. A comprehensive approach to robustness testing is described along with guidance on how to design a comprehensive suite of robust test cases for high reliability.