A Novel Framework for Investigating Design Process Failures with Nuisance Parameters using Influence Structure Diagrams

Abstract

The design of advanced maritime vessels is a complex and wicked process. The complexity arises from numerous systems being developed through multiple interdependent design processes. Product complexity and design difficulty continue to increase as technology advances, but the design methods used in the maritime design community have not kept pace. Research in the design science domain has historically focused on improving design from a product-centric perspective rather than examining and informing the relationship between the product and the design process.

There are significant knowledge gaps regarding the execution of the design process itself and where in the design process emergent failure is likely to occur. Over the previous several decades, military naval ship design has faced especially severe design process failures, including cost and timeline overruns, product failures, and, ultimately, programs being canceled. Navies have lost trillions of dollars and years of effort to these failures due to incomplete or missing information within the design process. The research presented in this thesis focuses on the design process rather than the product to address the impact of emergent design failures.

Novel Influence Structure Diagrams (ISDs), created as part of this research, model the impact of delayed decision-making and decision-making with incomplete or missing information. The ISD is a directed network developed to model the design process of advanced systems. The network contains variable, decision, and utility nodes representing design process stages, with edges representing directional dependencies among those elements. Within the ISD, variable nodes represent the desired or learned knowledge of design elements, decision nodes represent the lock-in of choice associated with certain knowledge elements, and utility nodes represent the design quality based on the connected knowledge. To address design failure issues directly, the concept of Design Nuisance Parameters (DNPs), which are design elements that are assumed to be required for decision-making but are not fully known or understood in time for the decision, are introduced within the ISD structure. Design Nuisance Parameters play a critical role in understanding design process failures by examining the likelihood of DNPs causing emergent design failure using Monte Carlo simulations.

The presented thesis demonstrates the development of the ISD and Design Nuisance Parameter framework, which, in conjunction with several novel entropy metrics, is used to analyze design process failures. This thesis presents a case study focused on the design of an uncrewed surface vehicle that demonstrates the success of the ISD framework, and its associated metrics, in identifying the impact of emergent design failure through delayed and incomplete information in decision-making. The case study walks through over 75 unique cases which involve cascading failure, emergent rework, design churn, and integration failure through real-world scenarios. The presented case study and underlying framework provide a launching point for future research and advancements in reducing the impact of emergent design failure in complex design programs, not limited to the maritime domain, worldwide.