Margin Allocation and Tradeoff in Complex Systems Design and Optimization

Abstract

Presented is an approach for interactive margin management. Existing methods enable a fixed set of allowable margin combinations to be identified, but these have limitations with regard to supporting interactive exploration of the effects of: 1) margins on other margins, 2) margins on performance and 3) margins on the probabilities of constraint satisfaction. To this purpose, the concept of a margin space is introduced. It is bi-directionally linked to the design space, to enable the designer to understand how assigning margins on certain parameters limits the allowable margins that can be assigned to other parameters. Also, a novel framework has been developed. It incorporates the margin space concept as well as enablers, including interactive visualization techniques, which can aide the designer to explore the margin and design spaces dynamically, as well as the effects of margins on the probability of constraint satisfaction and on performance. The framework was implemented into a prototype software tool, AirCADia, which was used for a qualitative evaluation by practicing designers. The evaluation, conducted as part of the EU TOICA project, demonstrated the usefulness of the approach.

Design margins in industrial practice

“…The literature on margins is extensive and reflects that the concepts of margins are studied for particular stages of the design process, for specific domains of products as well as on margins of different types for areas such as performance (Gale 1975;Tan, Otto & Wood 2016), assurance (Hockberger 1976), safety (Möller & Hansson 2008;Iorga, Desrochers & Smeesters 2012), mitigating effects of changes (Tilstra et al 2015;Cansler et al 2016) uncertainty (Thunnissen 2005), excess from standard or platform components (Martin & Ishii 2002, Eckert et al 2019. Example domains include ships (Gale 1975;Hockberger 1976), space systems (Thunnissen 2004), buildings (Jones, Eckert & Gericke 2018), aerospace (Guenov et al 2018, Eckert et al 2019, nuclear facilities (Youngblood 2010) and automotive (Lebjioui 2018). Margin research has tended to concentrate on the conceptual stages, especially for large and complex products such as ships, space systems, aerospace and buildings (Thunnissen 2004(Thunnissen , 2005, although margin concepts such as factors of safety are discussed for the detail design of machine components by Juvinal & Marshek (1991) in their classic textbook and manufacturing tolerances, which responds to uncertainties throughout product development (Morse et al 2018).…”

Models of Margin: From the Mathematical Formulation to an Operational Implementation

“…In the field of complex system design, the topic of margin allocation has been the source of some recent works [10,11]. The idea is to estimate the extra quantity to allocate to each design variable in early design phases.…”

“…The idea is to estimate the extra quantity to allocate to each design variable in early design phases. In [11], the margin on a design variable is defined as the difference between the chosen value and a requirement (either an upper or lower requirement). However, their margin definitions do not encompass the classic indicators such as the monetary risk measure ρ and the capability process Cp, as they cannot be taken on random variables.…”

Evolvability and design reuse in civil jet transport aircraft

“…different types could be traded off with each other) [16]. A framework that could be used to trade off different types of excess is from Guenov et al [25]. In that paper, the word 'margin' is employed, but the approach would apply equally to excess.…”