A Method for Generating a Well-Distributed Pareto Set in Nonlinear Multiobjective Optimization

A method is presented for generating a well-distributed Pareto set in nonlinear multiobjective optimization. The approach shares conceptual similarity with the Physical Programming-based method, the Normal-Boundary Intersection and the Normal Constraint methods, in its systematic approach investigating the objective space in order to obtain a well-distributed Pareto set. The proposed approach is based on the generalization of the class functions which allows the orientation of the search domain to be conducted in the objective space. It is shown that the proposed modification allows the method to generate an even representation of the entire Pareto surface. The generation is performed for both convex and nonconvex Pareto frontiers. A simple algorithm has been proposed to remove local Pareto solutions. The suggested approach has been verified by several test cases, including the generation of both convex and concave Pareto frontiers

Enabling interactive safety and performance trade-offs in early airframe systems design

Presented is a novel interactive framework for incorporating both safety and performance analyses in early systems architecture design, thus allowing the study of possible trade-offs. Traditionally, a systems architecture is first defined by the architects and then passed to experts, who manually create artefacts such as Fault Tree Analysis (FTA) for safety assessment, or computational workflows, for performance assessment. The downside of this manual approach is that if the architect modifies the systems architecture, most of the process needs to be repeated, which is tedious and time consuming. This limits the exploration of the design space, with the associated risk of missing better architectures. To overcome this limitation, the proposed framework automates parts of the safety and performance analysis in the context of the Requirement, Functional, Logical, and Physical (RFLP) systems engineering paradigm. Safety analysis is carried out by automatic creation of FTA models from the functional and logical flow views. Regarding performance analysis, computational workflows are first automatically created from the logical flow view, and then executed for a set of flight conditions over the range of the mission in order to determine the most demanding condition. Finally, performance characteristics of the subsystems, such as weights, power offtakes, ram drag etc. are evaluated at the most demanding flight condition, which enables the architect to compare architectures at aircraft level. The framework is illustrated with a representative example involving the design of an environmental control system of a civil aircraft, where the safety and performance trade-off is conducted for multiple ECS architectures

Neutral description and exchange of design computational workflows

Proposed in this paper is a neutral representation of design computational workflows which allows their exchange and sharing between different project partners and across design stages. This is achieved by the de-coupling of configuration and execution logic. Thus, the same underlying workflow can be executed with different (fidelity) models and different software tools as long as the inputs and outputs of the constituent process are kept the same. To this purpose, an object model is proposed to define different simulation objects, their scope, and hierarchy in the simulation process. An XML based computer readable representation of workflows based on the proposed object model, is also suggested. The application of the proposed representation is demonstrated via a case study involving the exchange of workflows between two design partners. The case study also demonstrates how the same workflow can be executed using different execution tools and involving different fidelity models

A set-based approach for coordination of multi-level collaborative design studies

Presented in this paper is a framework for design coordination of hierarchical (multi-level) design studies. The proposed framework utilizes margin management and set-based design principles for handling the challenges associated with vertical and horizontal design coordination. The former is based on flexible constraints/margins, while the latter is handled by intersecting feasible design spaces across different teams. The framework is demonstrated with an industrial test-case from the UK ATI APPROCONE (Advanced PROduct CONcept analysis Environment) project

Towards automating the sizing process in conceptual (airframe) systems architecting

Presented is a method for automated sizing of airframe systems, ultimately aiming to enable an efficient and interactive systems architecture evaluation process. The method takes as input the logical view of the system architecture. A source-sink approach combined with a Design Structure Matrix (DSM) sequencing algorithm is used to orchestrate the sequence of the sub-system sizing tasks. Bipartite graphs and a maximum matching algorithm are utilized to identify and construct the computational sizing workflows. A recursive algorithm, based on fundamental dimensions of additive physical quantities (e.g., weight, power, etc.) is employed to aggregate variables at the system level. The evaluation, based on representative test cases confirmed the correctness of the proposed method. The results also showed that the proposed approach overcomes certain limitations of existing methods and looks very promising as an initial systems architectural design enabler

Application of axiomatic design and design structure matrix to the decomposition of engineering systems, Systems Engineering 8(1

ABSTRACT A design decomposition-integration model, named COPE, is proposed in which Axiomatic Design Matrices (DM) map Functional Requirements to Design Parameters while Design Structure Matrices (DSM) provide structured representation of the system development context. In COPE, the DM and the DSM co-evolve. Traversing between the two types of matrices allows for some control in the application of the system knowledge which surrounds the decision making process and the definition of the system architecture. It is argued that this approach describes better the design process of complex products which is constrained by the need to utilise existing manufacturing processes, to apply discrete technological innovations and to accommodate work-share and supply chain agreements. Presented is an industrial case study which demonstrated the feasibility of the model. © 2004 Wiley Periodicals, Inc. Syst Eng 8: [29][30][31][32][33][34][35][36][37][38][39][40] 200