A METHODOLOGY TO SUPPORT EARLY STAGE OFF-THE-SHELF NAVAL VESSEL ACQUISITIONS

This paper describes a research programme to construct a Model-Based Systems Engineering (MBSE) methodology that supports acquiring organisations in the early stages of Off-the-Shelf (OTS) naval vessel acquisitions. A structured approach to design and requirements definition activities has been incorporated into the methodology to provide an easily implemented, reusable approach that supports defensible acquisition of OTS naval vessels through traceability of decisions. The methodology comprises two main parts. Firstly, a design space is developed from the capability needs using Set-Based Design principles, Model-Based Conceptual Design, and Design Patterns. A key idea is to employ Concept and Requirements Exploration to trim the design space to the region of OTS designs most likely to meet the needs. This region can be used to specify Request for Tender (RFT) requirements. Secondly, the methodology supports trades-off between the OTS design options proposed in the RFT responses using a multi-criteria decision making method. The paper includes an example implementation of the methodology for an indicative Offshore Patrol Vessel capability.

THE USE OF A FUZZY LOGIC SET-BASED DESIGN TOOL TO EVALUATE VARYING COMPLEXITIES OF LATE-STAGE DESIGN CHANGES

Advanced design methods, such as set-based design (SBD), can provide a structured approach to evaluating the design space in order to make accurate and informed decisions towards reaching a globally optimal design. The set-based communications required to appropriately implement SBD are counter-intuitive to the point-based communications of a typical design process. The use of a hybrid agent fuzzy logic design tool can help to facilitate the SBD process by ensuring the use of set-based communication of design variables. The design tool uses automation of certain aspects such as data collection and analysis while still allowing for input from human designers. One important advantage of using SBD is the ability to delay decisions until later in the design process when more information is known. This paper focuses on the robustness of the SBD process and its ability to handle late-stage design changes of varying complexity. Multiple SBD experiments instituting design changes of varying magnitude late in the design process were conducted using a hybrid agent fuzzy logic SBD tool. A simplified planing craft design was utilized for the experiments. Conclusions regarding the robustness of the SBD process under late-stage design changes were determined and outlined using information gathered by the SBD tool.

System Design Priority Order Considering Uncertainty in Early Stages

Herein, we have confirmed the importance of formulating product proposals and product-development processes equipped to cope effectively with uncertainty in the early design stage. The objective of this study was to derive the target performance and design priority order taking into account uncertainties in system design. Following the concept of set-based design, the approach adopted was to secure a set of solutions as design space that satisfy the target variables demands, dividing the design space into several clusters and evaluating each of the clusters, then gradually narrowing the cluster as the design progresses, and finally extracting the solution space that is desirable. Priority order of design was developed based on the strategy of increasing the degree of freedom of the subsequent process. The effectiveness of the proposed method was verified using the model of a plug-in hybrid vehicle. From the results, we confirmed the existence of a trade-off between design and target variables preference and development risk, that it is possible to determine the extent to which the solution space can be narrowed, that the shape of the solution space determines the design priorities, and we were able to derive a desirable design priority order according to the target performance.

Quantitative Set-Based Design to Inform Design Teams

System designers, analysts, and engineers use various techniques to develop complex systems. A traditional design approach, point-based design (PBD), uses system decomposition and modeling, simulation, optimization, and analysis to find and compare discrete design alternatives. Set-based design (SBD) is a concurrent engineering technique that compares a large number of design alternatives grouped into sets. The existing SBD literature discusses the qualitative team-based characteristics of SBD, but lacks insights into how to quantitatively perform SBD in a team environment. This paper proposes a qualitative SBD conceptual framework for system design, proposes a team-based, quantitative SBD approach for early system design and analysis, and uses an unmanned aerial vehicle case study with an integrated model-based engineering framework to demonstrate the potential benefits of SBD. We found that quantitative SBD tradespace exploration can identify potential designs, assess design feasibility, inform system requirement analysis, and evaluate feasible designs. Additionally, SBD helps designers and analysts assess design decisions by providing an understanding of how each design decision affects the feasible design space. We conclude that SBD provides a more holistic tradespace exploration process since it provides an integrated examination of system requirements and design decisions.