Conceptual design of sacrificial sub-systems: failure flow decision functions

• Published in: Research in engineering design Vol. 29; no. 1; pp. 23 - 38
• Main Authors: Short, Ada-Rhodes, Lai, Ann D., Van Bossuyt, Douglas L.
• Format: Journal Article
• Language: English
• Published: London Springer London 2018; Springer Nature B.V
• Subjects: CAE) and Design; Complex systems; Computer architecture; Computer-Aided Engineering (CAD; Conceptual design; Decision making; Design; Design engineering; Designers; Engineering; Engineering Design; Failure; Iterative methods; Mars exploration; Mathematical models; Modelling; Original Paper; Propagation; Survivability; Systems design; Failure modeling; Failure flow decision-making; Functional modeling; Design methodology
• ISSN: 0934-9839; 1435-6066
• DOI: 10.1007/s00163-017-0258-3

This paper presents a method to conceptually model sacrificing non-critical sub-systems, or components, in a failure scenario to protect critical system functionality through a functional failure modeling technique. Understanding the potential benefits and drawbacks of choosing how a failure is directed in a system away from critical sub-systems and toward sub-systems that can be sacrificed to maintain core functionality can help system designers to design systems that are more likely to complete primary mission objectives despite failure events. Functional modeling techniques are often used during the early stage of conceptual design for complex systems to provide a better understanding of system architecture. A family of methods exists that focuses on the modeling of failure initiation and propagation within a functional model of a system. Modeling failure flow provides an opportunity to understand system failure propagation and inform system design iteration for improved survivability and robustness. Currently, the ability to model failure flow decision-making is missing from the family of function failure and flow methodologies. The failure flow decision function (FFDF) methodology presented in this paper enables system designers to model failure flow decision-making problems where functions and flows that are critical to system operation are protected through the sacrifice of less critical functions and flow exports. The sacrifice of less critical system functions and flows allows for mission critical functionality to be preserved, leading to a higher rate of mission objective completion. An example of FFDF application in a physical design is a non-critical peripheral piece of electrical hardware being sacrificed during an electrical surge condition to protect critical electronics necessary for the core functionality of the system. In this paper, a case study of the FFDF method is presented based on a Sojourner class Mars Exploration Rover (MER) platform.