Hakki Eres

Application of value-driven design to commercial aeroengine systems

Value-Driven Design provides a framework to enhance the systems engineering processes for the design of large systems. By employing economics in decision making, Value-Driven Design enables rational decision making in terms of the optimum business and technical solution at every level of engineering design. This paper explains the application of ValueDriven Design to the aero-engine system through two case studies, which were conducted through workshops under the Rolls-Royce plc Advanced Cost Modeling Methodologies project. The Surplus Value Theory was utilized to provide a metric that can trade-off component designs with changes in continuous and discrete design variables. Illustrative results are presented to demonstrate how the methodology and modeling approach can be used to evaluate designs and select the value-enhancing solution.

A prescriptive approach to qualify and quantify customer value for value-based requirements engineering

Recently, customer-based product development is becoming a popular paradigm. Customer expectations and needs can be identified and transformed into requirements for product design with the help of various methods and tools. However, in many cases, these models fail to focus on the perceived value that is crucial when customers make the decision of purchasing a product. In this paper, a prescriptive approach to support value-based requirements engineering (RE) is proposed, describing the foundations, procedures and initial applications in the context of RE for commercial aircraft. An integrated set of techniques, such as means-ends analysis, part-whole analysis and multi-attribute utility theory is introduced in order to understand customer values in depth and width. Technically, this enables identifying the implicit value, structuring logically collected statements of customer expectations and performing value modelling and simulation. Additionally, it helps to put in place a system to measure customer satisfaction that is derived from the proposed approach. The approach offers significant potential to develop effective value creation strategies for the development of new products.

Criteria for assessing the Value of Product Service System Design Alternatives: an Aerospace Investigation

Growing from data collected within a major EU research project in the aerospace domain, the paper proposes a candidate approach to assess the value of Product Service System design alternatives in a preliminary design phase. A framework composed of six main families of value criteria is proposed to support the product/service development team in evaluating the responsiveness and trade-off between alternative designs that target lifecycle commitment, with respect to the impact on perceived values and stated needs and expectations. A visualization approach is also proposed to quickly communicate the value contribution of the design alternatives at the decision gate.

Replacing target setting by value models in the ‘house of quality’ for value-based requirements specifications:

Setting targets for engineering characteristics is common practice in the ‘house of quality’ for establishing requirements specifications. However, if deployed arbitrarily, this practice is prone to errors and can often yield irrational results. Three potential methodological problems have been identified, regarding the setting of independent targets for each engineering characteristic, setting fixed targets and cascading down targets from the system level to the component level have been identified. In this article, targets are categorised as constraints and goals because of their different implications for value trade-offs. Then, a ‘multi-attribute utility theory’ based approach is proposed, in which a system value model is developed in order to replace the setting of targets for system engineering characteristics and component value models are further derived to replace the setting of targets for component engineering characteristics. These value models enhance the traditional approach to requirements specification so that value-based requirements specifications can be developed. A case study is deployed to demonstrate the applicability of the approach in the civilian aerospace context for the development of requirements for commercial aircraft. The benefits of the proposed approach are twofold: (1) value becomes an explicit construct and (2) value can be rationally modelled and simulated in the ‘house of quality’ in order to establish value-based requirements specifications. Furthermore, identified methodological problems in terms of setting engineering characteristic targets at any level are mitigated.

Value driven conceptual design of unmanned air system for defense applications

The work presented culminates in the development of a value driven conceptual design assessment framework for a small Unmanned Air System (UAS) to be utilized in a defence application. In the field of Multi-Disciplinary Design Optimisation, most recent systematic search has been devoted to fixed topology parametric geometries, pertaining to a single concept, with very little stress put on the optimization of variable topologies describing alternative design concepts. The search is conducted in a highly novel manner, generating a broad range of combinations of UAS configurations and geometries by systematically searching alternative concepts and design configurations through the parameterization of the aircraft geometric topologies. Moreover, the “value” of proposed solutions is assessed in an objective way both from performance and economic perspectives, while the optimal solution is identified based on the user’s needs after relaxing all of the design constraints. During the multi-criteria decision analysis, the quantification/conversion of the linguistic preferences of the user between the various attributes to numerical values has disclosed some deficiencies introduced by the unjustifiable numerical scales used in the Analytic Hierarchy Process (AHP) and a novel value model for consistent value assessment is introduced, synthesizing the AHP assessment methodologies with multi-attribute value-focused analysis.

A value-focused approach for establishing requirements’ specification of commercial aircraft

Although systems engineering processes and standards are widely used in aircraft development programs, traditional requirements’ engineering practice for commercial aircraft does not explicitly address value perceptions and associated information. In this paper, a value-focused approach is proposed to promote a better understanding of customer-value perceptions and their derivation among different levels for value-based requirements engineering of commercial aircraft. The approach is a four-step process starting from initial customer statements to a customer-value model and leading to a system-value model with associated component-value models. A set of theories and methods are introduced in order to resolve different aspects of the approach regarding the appropriate understanding of customer-value perceptions and the establishment of the value-based requirements’ specification. A case study is used to demonstrate the transformation of airlines’ initial expectation statements into three types of value models. There are two significant benefits of this approach: (a) perceived customer value can be explicitly modeled, simulated, and derived into different levels of the system development and (b) the value model can be subsequently utilized reactively for design evaluations and proactively for design optimization to generate creative design alternatives.

A probabilistic multi-fidelity aero-engine preliminary design optimization framework: technical and commercial perspectives

Conceptual and preliminary design phases of aerospace gas turbines compromise a particularly uncertain and challenging stage of their development. It is at these early design phases when the most critical and influential architectural decisions are made. The outcomes of those decisions have a direct impact on a multitude of the aero-engine design attributes such as performance, weight, specific fuel consumption and life-cycle cost - the factors directly influencing the economic value and market success of a prospective power system. Hence, the commercial success of a specific aero-engine and the technical aspects of the processes used in its design are strongly correlated. This work targets the examination of that relationship and presents a rationale for the development of an Integrated Framework for Uncertainty Quantification and Multi-Objective Optimization. First, the commercial aspects of a typical aerospace design project are considered. Then, the top level structure of aero-engine design process is considered from the technical point of view. Finally, the top-level architecture of the framework is discussed and a brief update on the current development status of its implementation is presented.

Uncertainty quantification via elicitation of expert judgements

The purpose of this paper is to depict one method of quantifying uncertainty about different parameters, which is based on eliciting judgements either from a single expert or from a group of experts. The quantities obtained as a result of the elicitation are therefore used in order to fit probability density functions (PDFs) by using an in-house MATLAB model which uses appropriate fitting techniques similar to the ones suggested in the existing literature. Consequently, an initial framework has been implemented which would first of all allow the comparison of elicited data with the experimental results. The underlying theory behind the elicitation process is being presented and subsequently an aero-engine Fan Blade Off (FBO) case study is presented. The framework is used to illustrate the way in which expert judgements are implemented as inputs into the MATLAB model which is used to predict different parameters of interest associated to FBO events such as probabilities of having a particular speed during an event as well as what are the characteristics of the most likely events to occur. Those are taken into consideration in order to allow the designer to perform relevant and more detailed analysis on the fan subsystem during the preliminary design process.

Co-creation in complex supply chains: the benefits of a Value Driven Design approach

Social Product Development.- Open Source Product Development.- Technological Game Changers for Product Development in the Socio-sphere.- New Business Models for Product Development in the Socio-sphere.In the last decade, as the manufacturing companies reconsidered the overall concept of goods production, their focus shifted from developing ‘products’ to ‘solutions’. In complex supply chains, the combination of products and services that maximize customers’ and stakeholders’ value can be identified only if manufacturers improve their ability to co-create, establishing more interactive relationships with end users, clients and sub-contractors. Methodologies for Value Driven Design (VDD) are emerging as enablers for cross-functional and cross-organizational knowledge sharing, reinforcing early stages design iterations to emphasize the maturation of the requirements across supply chain levels. This chapter highlights the uptake of VDD in a traditionally protective domain, such as the aerospace sector. It describes methods and tools for value assessment, and points toward the most relevant initiatives in this domain. Eventually, it discusses areas of further research to promote the effective use of the VDD methodology while designing complex engineering systems.