Showing papers in "Research in Engineering Design in 2018"

Process models in design and development

Abstract: Many models of the design and development process have been published over the years, representing it for different purposes and from different points of view. This article contributes an organising framework that clarifies the topology of the literature on these models and thereby relates the main perspectives that have been developed. The main categories of model are introduced. Their contexts, advantages, and limitations are considered through discussion of selected examples. It is demonstrated that the framework integrates coverage of earlier reviews and as such provides a new perspective on the literature. Finally, key characteristics of design and development process models are discussed considering their applications in practice, and opportunities for further research are suggested. Overall, the article should aid researchers in positioning new models and new modelling approaches in relation to state-of-the-art. It may also be of interest to practitioners and educators seeking an overview of developments in this area.

Design theory: a foundation of a new paradigm for design science and engineering

Abstract: In recent years, the works on Design Theory (and particularly the works of the Design Theory SIG of the Design Society) have contributed to reconstruct the science of design, comparable in its structure, foundations and impact to Decision Theory, Optimization or Game Theory in their time. These works have reconstructed historical roots and the evolution of design theory, conceptualized the field at a high level of generality and uncovered theoretical foundations, in particular the logic of generativity, the " design-oriented " structures of knowledge, and the logic of design spaces. These results give the academic field of engineering design an ecology of scientific objects and models, which allows for expanding the scope of engineering education and design courses. They have contributed to a paradigm shift in the organization of R&D departments, supporting the development of new methods and processes in innovation departments, and to establishing new models for development projects. Emerging from the field of engineering design, design theory development has now a growing impact in many disciplines and academic communities. The research community may play significant role in addressing contemporary challenges if it brings the insights and applicability of Design Theory to open new ways of thinking in the developing and developed world.

Pareto-optimization of complex system architecture for structural complexity and modularity

Abstract: Due to ever-increasing complexity of cutting-edge engineering systems, the need for managing structural complexity and modularity of such systems is becoming important. The complexity of the overall system architecture is mostly decided during the initial concept generation stage, when configurations of major modules within the system are determined. In this paper, we present a multi-objective optimization framework for (1) minimizing the variation in complexity allocation to individual modules, while (2) maximizing for the degree of modularity. The optimization framework was applied to a case study, where a trailing bogie system for railroad train was optimized for structural complexity allocation among individual modules and overall system modularity. The modularity maximizing decomposition is shown to induce a large variation in module-level complexity distribution with a small fraction of modules sharing a disproportionately large chunk of overall system complexity, while equitable distribution of module-level complexity leads to erosion in the degree of modularity achieved for the resulting system decomposition.

Multi-criteria fuzzy decision support for conceptual evaluation in design of mechatronic systems: a quadrotor design case study

Abstract: Designing mechatronic systems is known to be a very complex and tedious process due to the high number of system components, their multi-physical aspects, the couplings between the different domains involved in the product, and the interacting design objectives. This inherent complexity calls for the crucial need of a systematic and multi-objective design thinking methodology to replace the often-used sequential design approach that tends to deal with the different domains and their corresponding design objectives separately leading to functional but not necessarily optimal designs. Thus, a new approach based on a multi-criteria profile for mechatronic systems is presented in this paper for the conceptual design stage. Additionally, to facilitate fitting the intuitive requirements for decision-making in the presence of interacting criteria, three different methods are proposed and compared using a case study of designing a vision-guided quadrotor drone system. These methods benefit from three different aggregation techniques such as Choquet integral, Sugeno integral and fuzzy-based neural network. To validate the decision yielded by the results of global concept score for each aggregation methods, a computer simulation of a visual servoing system on all design alternatives for quadrotor drone has been performed. It is shown that although the Sugeno fuzzy can be a useful aggregation function for decisions under uncertainty, but the approaches using Choquet fuzzy and fuzzy integral-based neural network seem to be more precise and reliable in a multi-criteria design problem where interaction between the objectives cannot be overlooked.

Product family platform selection using a Pareto front of maximum commonality and strategic modularity

Abstract: Product family design offers a cost-effective solution for providing a variety of products to meet the needs of diverse markets. At the beginning of product family design, designers must decide what can be shared among the product variants in a family. Optimal design formulations have been developed by researchers to find one optimal component sharing solution based on commonality, cost or technical performance of a product family. However, these optimization methods may not be able to apply in consumer product design because some metrics (e.g., visual appeal and ergonomics) of a consumer product cannot be formulized. In this paper, we suggest a tradeoff between commonality and the quality of the modular architecture in product family platform selection. We introduce a method for designers to identify multiple component sharing options that lie along a Pareto front of maximum commonality and strategic modularity. The component sharing options along the Pareto front can be evaluated, compared, and further modified. We demonstrate the method using a case study of product family platform selection of high-end and low-end impact drivers and electric drills. In the case study, the quality of the modular architecture is evaluated using a design structure matrix (DSM) for each of product variants. Three architectures along the Pareto front with maximum commonality, optimal modularity, and a balanced solution of the two metrics are highlighted and further examined to validate the effectiveness of our method.

Predicting requirement change propagation through investigation of physical and functional domains

Abstract: Requirements play a critical role in the design process and are important to the project’s success. The design process is iterative, and requirements are constantly changed and updated to reflect stakeholders’ expectations, design changes, regulations, and resource limitations. Since requirements drive product development from initial development of concepts to final production of the finished product, mismanaged requirement changes can lead to monetary and time losses. The ability to assess a requirement change, predict its propagation, and evaluate the impact early in the design process will enable engineers to make informed decisions regarding change implementation. Prior research performed by Morkos culminated in the Automated Requirement Change Propagation Prediction (ARCPP) tool to mitigate issues due to requirement change propagation. The ARCPP tool utilized syntactic natural language data, part of speech (POS) elements in requirement statements, as relators to form relationships between requirements. The resulting requirement network serves to predict change propagation as a result of an initiating requirement change using the performance metric of the tool, requirement review depth. Whereas the prior research proved that change propagation can be predicted using requirements, the purpose of this research is to understand why requirements can be used. Specifically, what parts of a requirement affect its ability to predict change propagation? This is performed by addressing three key research questions (RQs): (1) Is the requirement review depth affected by the number of relators selected to relate requirements, (2) Is the requirement review depth affected by the frequency of relators selected to relate requirements, and (3) Which element of a requirement, the physical or functional domain, is responsible for instigating change propagation? The results indicate that the review depth, an indicator of the performance of the ARCPP tool, is not affected by the number and frequency of relators, but rather by the ability of relators in capturing the propagating relationships. Further, the physical domain is found to contribute more towards predicting change propagation than the functional domain. Finally, a recommendation on selecting the number of requirement relators is presented.

A comprehensive end-of-life strategy decision making approach to handle uncertainty in the product design stage

Abstract: This study employs fuzzy logic to evaluate uncertain component end-of-life (EOL) options in the design stage. Determining EOL strategies during the product design stage can be complex. For example, EOL strategies for retired bicycle components are various and may change with geographic location. Thus, adopting fixed EOL strategies in the product design stage may not always be appropriate; the element of uncertainty should be considered. Limited research has examined uncertainty of EOL strategies during the design stage. Moreover, the evaluation of EOL strategies in a comprehensive manner has not been shown in a realistic case study. These facts motivate this investigation. Fourteen evaluation criteria are used to generate a comprehensive framework for assessing seven EOL strategies. The evaluation process generates the likelihood for each of these strategies by aggregating fuzzy set operations and a left–right fuzzy ranking method. Using SUMPRODUCT calculation for these weights/probabilities and input sustainability value (i.e., cost, environmental impact and labor time), expected values are derived to represent the sustainability values for each EOL strategy. A Technique-for-Order-of-Preference-by-Similarity-to-Ideal-Solution (TOPSIS) based method is employed to identify the appropriate EOL strategy for each component/product. A refrigerator is used as a case study to illustrate the methodology. This study addresses the uncertainty involved in identifying an EOL strategy for a specific product component during the design stage through the use of fuzzy logic. The method closes a gap in the current EOL strategy assessment criteria and introduces a comprehensive evaluation framework to capture multiple strategic perspectives by incorporating 14 key evaluation criteria.

A digital thread approach to support manufacturing-influenced conceptual aircraft design

Abstract: This paper proposes and demonstrates the integration of manufacturing and production considerations with traditional aircraft design metrics to support affordability-based design. To enable the necessary multi-disciplinary trades, a digital thread approach is proposed that integrates detailed models and analyses. The digital thread refers to linking models from various disciplines through common inputs and data flows with the goal of speeding design time and enabling trades across traditionally isolated disciplines. When used within an overarching design process, the production cost, rate, and efficiencies of non-conventional designs in variable demand environments can be quantified and traded early in the design process. In particular, the methodology is demonstrated using a wingbox design problem such that aircraft performance considerations, production rate, manufacturing cost, and financial planning metrics can be traded within a parametric, visual trade-off environment. The environment, combined with a multi-objective optimization routine, facilitates effective affordability-based tradespace exploration during the early stages of the design of non-traditional aircraft (e.g., those utilizing composite structures) under demand variability. An F-86 Sabre redesigned wingbox using three separate manufacturing concepts is used as a proof-of-concept for this research.

A failure analysis method for designing highly reliable product-service systems

Abstract: Recently, product-service systems (PSSs), which create value by integrating a physical product and a service, have been attracting attention. In PSSs, it is critical for a provider to offer highly reliable products and services. To do so, the provider needs to effectively and efficiently detect possible failures, and then, take adequate measures against them in the conceptual design stage. However, in current studies on product failure analysis, service aspects are not covered in analyzing failure causes and developing measures. On the other hand, product aspects are hardly considered in existing methods of service failure analysis. To fill the gap, this paper proposes a method for failure analysis in PSS design called PSS failure mode and effect analysis (PSS FMEA). Especially, this paper extends the framework of FMEA, and then, a procedure for PSS FMEA is introduced so that designers can analyze failures and develop measures in consideration of both product and service aspects. Furthermore, the proposed method supports designers in finding new business opportunities. The proposed method was applied to a real offering of products and services by a cleaning machine provider and found effective.

Empirical approaches to quantifying effort, fatigue and concentration in the conceptual design process

Abstract: Recently, physiological signals such as eye-tracking and gesture analysis, galvanic skin response (GSR), electrocardiograms (ECG), and electroencephalograms (EEG) have been used by design researchers to extract significant information to describe the conceptual design process. We study a set of video-based design protocols recorded on subjects performing design tasks on a sketchpad while having their EEG monitored. We propose empirical approaches to quantify effort, fatigue, and concentration during the conceptual design process. To perform this analysis, we extract EEG features that convey information on effort, fatigue, and concentration. We argue that all three are relevant in the conceptual design process. Such an analysis has the merit of being fully automated, readily integrable in engineering systems and not being subjected to the subjectivity of the domain expert performing the analysis like in subjective rating frameworks. Our analysis leads to four hypotheses: (1) effort and fatigue are subjected to ice-breaking and end of task phenomena; (2) fatigue and effort follow a capacity model; (3) fatigue is multidimensional; and (4) concentration follows a modal shift model.

A novel approach to include sustainability concepts in classical DFMA methodology for sheet metal enclosure devices

Abstract: Nowadays sustainable design is a mandatory requirement in the product development process. For this reason, design methodologies are addressed to establish a close relationship between environmental, social and economic impact indicators and product features from early design stages, especially in those features related to its manufacturing. In this paper, the design for manufacturing and assembly—DFMA methodology is adapted to sheet metal enclosure devices, integrating functional and component relationships to minimize particular sustainability indicators such as energy consumption, carbon footprint, number of parts, required amount of material, assembly time and manufacturing costs. Savings with the proposed method are achieved following specific sub-tasks oriented to define new simplified product components, considering changes in manufacturing processes and re-defining mechanical connections between parts. Traditional DFMA approaches consider manufacturing and assembly issues related to a reduction of product complexity and economic savings. The proposed method aims to examine the benefits in life cycle stages such as raw material consumption, service, maintenance, upgrading and end of life—EOL. The methodology is validated through a redesign of a sheet metal industrial clock, in which the sustainability impacts are calculated from a comparison of an existent product vs. a new product development. The implementation of the method in the case study demonstrate reductions of more than 25% in product mass, consumed energy and CO2 footprint, and more than 50% in theoretical assembly time and product complexity. Sustainability indicators of the proposed method are selected from literature analysis and taking into account attributes of sheet metal enclosure devices.

A systematic approach for supporting the adaptation process of discrete manufacturing machines

Abstract: Automated manufacturing machines in the discrete manufacturing domain frequently face changes in requirements, such as volatile customer demands or changes in product variants. Due to this, machines need to become more flexible to cope with these changing conditions. Therefore, manufacturing machines have to undergo adaptation processes during their operational phase. The adaptation processes might include mechanical, electrical, and software changes. In industrial practice, experts individually perform these adaptation processes without methodological support, which is time-consuming and highly error-prone. This article proposes a systematic approach for supporting the different phases of the adaptation process. The producibility check of a production request based on a suitable skill model of the system is addressed as well as the automatic generation of adaptation options. Furthermore, the article provides concepts for analyzing the impact, effort and benefit of the generated adaptation options. Additionally, a multi agent architecture is presented for the implementation of the proposed adaptation approaches. The entire assistance concept was applied to a lab-size production machine to validate the applicability of the approach.

Design for invention: annotation of functional geometry interaction for representing novel working principles

Abstract: In some mechanical engineering devices the novelty or inventive step of a patented design relies heavily upon how geometric features contribute to device functions. Communicating the functional interactions between geometric features in existing patented designs may increase a designer’s awareness of the prior art and thereby avoid conflict with their emerging design. This paper shows how functional representations of geometry interactions can be developed from patent claims to produce novel semantic graphical and text annotations of patent drawings. The approach provides a quick and accurate means for the designer to understand the patent that is well suited to the designer’s natural way of understanding the device. Through several example application cases we show the application of a detailed representation of functional geometry interactions that captures the working principle of familiar mechanical engineering devices described in patents. A computer tool that is being developed to assist the designer to understand prior art is also described.

Redesign methodology for mechanical assembly

Abstract: Design for assembly is the concept of carrying out critical thought early in the design stage to create assembly easement at the production stage. In the aerospace industry, products have very long lives, frequently being optimised rather than introducing new products. This has meant older products, which are stable income generators, have not benefited from the latest design for assembly methods and manufacturing technology suffers from obsolescence. It has been established that a large percentage of overall product cost is determined at the design stage; thus, existing products suffer from preloaded costs. This paper takes existing design for assembly methodologies and analyses them with respect to the unique challenges involved in legacy product redesign. Several novel factors that contribute to redesign analysis are identified such obsolescence impact and a holistic operation difficulty assessment. A tool is developed to identify potential redesign for assembly projects. The tool is demonstrated through the application of real data and comparing against business decisions. The tool was found to provide a strong indication of where profitable projects may be launched.

The importance of robust design methodology

Abstract: While a systematic quality strategy is of crucial importance for the success of manufacturing companies, the universal applicability and effectiveness of implemented quality management practices were called into question by a number of major product recalls in recent years. This article seeks to illustrate how already simple analyses and early stage design methods can help to better understand one of the potential reasons for these failures, namely the variation inherent in manufacturing, assembly, and use processes. Usually thoroughly controlled in production, it seems as if particularly the risk of unanticipated variation effects remain largely underestimated and thus unaccounted for in design practice, sometimes with disastrous consequences. To foster the awareness of this variation and to illustrate the benefits of its early consideration in product development, this paper reviews one of the most infamous recalls in automotive history, that of the GM ignition switch, from the perspective of Robust Design. It is investigated if available Robust Design methods such as sensitivity analysis, tolerance stack-ups, design clarity, etc. would have been suitable to account for the performance variation, which has led to a number of fatal product defects and the recall of 30 million vehicles. Furthermore, the disclosed legal case files were examined, offering a unique opportunity to examine how technical malfunctioning of the ignition switch could stay undetected long enough to result in fatalities.

Incorporating end-user models and associated uncertainties to investigate multiple stakeholder preferences in system design

Abstract: The essence of systems engineering lies in enabling rational decision-making that is consistent with the preferences of the system’s stakeholders. Modern approaches, such as value-driven design, attempt to convey the true preferences of the stakeholder using mathematical formulations like value models. A critical step to the formation of value models is the identification of the stakeholders. A primary stakeholder must be identified and then it must be determined how the other stakeholders’ preferences impact the preference of the primary, if they do at all. This paper looks at three stakeholders of an electric vehicle system, all of which could be considered the primary stakeholder dependent on the situation. Novel customer, commercial, and government-oriented value models are created. To understand the impact of customers on the primary stakeholder’s designs, an end-user value-based demand model is developed and a method for integrating end-user preferences into the manufacturer’s value model is demonstrated. Uncertainties associated with the end-users, including those associated with the economy, are quantified and incorporated into a value-based design framework through Monte Carlo simulations. Possible stakeholder risk attitudes are discussed and a rational decision-making strategy to maximize stakeholder’s system value under uncertainty is presented. The resulting designs and the influences of the multiple stakeholders are discussed, showing that the identification and incorporation of the important stakeholders are critical to the systems engineering process and value-based design in particular.

Tolerance analysis of overconstrained and flexible assemblies by polytopes and finite element computations: application to a flange

Abstract: In industrial contexts, overconstrained assemblies are often used to ensure sufficient stiffness and accuracy of assembly. Such architectures are quite usual, however, analysis and synthesis of the tolerance are not easy to define and quantify. In these cases, the compliance of the assembly is not automatic and deformations may often occur, requiring a particular and difficult analysis of the assembly from scientific and computing points of view.The present work addresses such overconstrained mechanisms through a general and a sequential approach. Based on this, it is possible to determine the final assembly condition (with or without interference) as a function of part defects. First, the assembly procedure is performed based on polytope computations, assuming a rigid part behavior. From this, a stochastic simulation is performed and some non-compliant assemblies (assemblies with interferences) are identified. For these assemblies, the rigid behavior of parts is then overcome by means of finite element simulations and a typical procedure is set up to introduce part defects. We then deduce whether the assembly can be made from the load needed to assemble the parts. This procedure is applied to a flange composed of five pin/hole pairs, as this is a highly overconstrained mechanism.

Criticality and propagation analysis of impacts between project deliverables

Abstract: The implementation of a management by deliverables and deadlines is based on detailed planning and strict control of deliverables. It is a strategic decision that reports to the project manager and a key element to the success of complex projects. Based on the modeling of the project elements and their interactions using weighted directed graphs, this article presents some contributions to anticipate potential behavior of the project. Topological and propagation analyses are made to detect and prioritize critical elements and critical interdependencies while enlarging the sense of the polysemous word “critical.” We recommend a set of topological indicators suitable for project elements and interactions, which mainly allow us to discuss “How the impact of a project element affects other elements within the network? What is the collective influence of this element?”. These indicators permit to prioritize project elements and their interactions by detecting the most influential ones taking into account the network structure. For instance, they permit to evaluate the collective criticality of project deliverables and to re-evaluate the priority of the risks associated with these deliverables by coupling the traditional features of individual risks with the topological indicators of the deliverables. Furthermore, some algorithms are applied to extract and visualize the propagation path between two elements within the network. For example, this allows to provide a vision of potential impact propagation between two project deliverables, either they are associated with two milestones or are critical. An application to automotive industry illustrates the benefits of the approach, and some perspectives are drawn for further work.

Generation of a function-component-parameter multi-domain matrix from structured textual function specifications

Abstract: This study introduces a method to build a multi-domain matrix (MDM), visualizing the intended architecture of a system within the component, function, and parameter domains. The MDM is generated from textual function specifications that are subject to a specific grammatical structure and vocabulary based upon the functional basis and interaction basis as presented in the literature. Two types of functions are distinguished: functions specifying what functionality a particular component provides to another component, and functions specifying the internal working (transformation of flow) of a particular component. The fixed grammar for the specification of the two types of functions allows for the automated derivation of dependencies between components, between functions of components, and between system parameters. A case study on a navigation lock demonstrates that the system architecture generated from function specifications matches the architecture of the real lock system fairly well. As such the method can be used in the early design phase to reveal the product architecture that is embodied in the function specifications of system components. The method may also support modeling of high-definition DSMs of existing engineering systems.

Idea-configuration-evaluation (ICE): development and demonstration of a new prescriptive model of the conceptual engineering design process based on parameter analysis and C–K theory

Abstract: This paper introduces a new prescriptive model of conceptual engineering design. The model is based on the method called parameter analysis (PA) and the relatively new descriptive model called C–K theory. PA was developed based on observations of designers in action, while C–K theory has a strong foundation in logic theory. The new model combines the benefits of C–K theory and PA to overcome the lack of a strong theoretical foundation in PA and the insufficient prescriptive power of C–K theory. The paper describes in detail the process of developing the new model, which was similar to product development. It started with conceptualization in order to define a set of key factors and principles, i.e., the conceptual foundation or the “ideology” of the new prescriptive model. Next, those principles were integrated into a structured systematic procedure to form the new prescriptive model. The conceptual design of a realistic design task is used to demonstrate the application of the new model. The significance of the current work is the contribution to the theory and practice of engineering design, eventually leading to improved design processes and better designed products. Reporting on the experimental testing of the new model will follow in the future.

A rapid Kano-based approach to identify optimal user segments

Abstract: The Kano model of customer satisfaction provides product developers valuable information about if, and then how much a given functional requirement (FR) will impact customer satisfaction if implemented within a product, system or a service. A limitation of the Kano model is that it does not allow developers to visualize which combined sets of FRs would provide the highest satisfaction between different customer segments. In this paper, a stepwise method to address this shortcoming is presented. First, a traditional Kano analysis is conducted for the different segments of interest. Second, for each FR, relationship functions are integrated between x = 0 and x = 1. Third, integrals are inserted into a matrix crossing segments and FRs, where FRs with the highest sum across the chosen segments are identified. Finally, the functions of the chosen segments with the smallest interval, define the FRs appealing to the biggest target group. The proposed extension should assist product developers within to more effectively evaluate which FRs should be implemented when considering more than one combined customer segment. It shows which segments provide the highest possibility for high satisfaction of combined FRs. We demonstrate the approach in a case study involving customers’ preference for outdoor sports equipment.

Conceptual design of sacrificial sub-systems: failure flow decision functions

Abstract: This paper presents a method to conceptually model sacrificing non-critical sub-systems, or components, in a failure scenario to protect critical system functionality through a functional failure modeling technique. Understanding the potential benefits and drawbacks of choosing how a failure is directed in a system away from critical sub-systems and toward sub-systems that can be sacrificed to maintain core functionality can help system designers to design systems that are more likely to complete primary mission objectives despite failure events. Functional modeling techniques are often used during the early stage of conceptual design for complex systems to provide a better understanding of system architecture. A family of methods exists that focuses on the modeling of failure initiation and propagation within a functional model of a system. Modeling failure flow provides an opportunity to understand system failure propagation and inform system design iteration for improved survivability and robustness. Currently, the ability to model failure flow decision-making is missing from the family of function failure and flow methodologies. The failure flow decision function (FFDF) methodology presented in this paper enables system designers to model failure flow decision-making problems where functions and flows that are critical to system operation are protected through the sacrifice of less critical functions and flow exports. The sacrifice of less critical system functions and flows allows for mission critical functionality to be preserved, leading to a higher rate of mission objective completion. An example of FFDF application in a physical design is a non-critical peripheral piece of electrical hardware being sacrificed during an electrical surge condition to protect critical electronics necessary for the core functionality of the system. In this paper, a case study of the FFDF method is presented based on a Sojourner class Mars Exploration Rover (MER) platform.

Fixation and distraction in creative design: the repercussions of reviewing patent documents to avoid infringement

Abstract: It is common to conduct a patent search when designing new products for commercial purposes. This paper examines whether reviewing patent documents to avoid infringement can affect design creativity based on an experimental study involving 106 undergraduate engineering students. As part of the study, the participants were divided into three groups and asked to individually design a water kettle in 20 min. Participants from the first group were each given an identical patent document at the start of the experiment and were warned not to infringe the patented design. Participants from the second group were each given another patent document and the same warning. Participants from the third group were not given any patent documentation. The experiment results show that reviewing patent documents prior to ideation, even when done to avoid infringement, can fixate and lead to the inclusion of design features associated with the patent documents reviewed. In addition, reviewing patent documents can also cause distractions and result in the exclusion of design features that may otherwise be included. The findings of this work can contribute towards design pedagogy and the development of processes to handle patent documents in design projects.

Developing an ideation method to be used in cross-functional inter-organizational teams by means of action design research

Abstract: Using ideation methods in an optimal way has a great potential to increase the number of ideas which a team can contribute during the conceptual phase of product development in industry. Previous s ...

A method to evaluate direct and indirect design dependencies between components in a product architecture

Abstract: Methods for evaluating the strength of design dependencies in a product architecture have been widely studied in the literature; however, evaluating the effects of direct and indirect interactions between components/modules remains a challenge. In fact, indirect connections between components/modules are often overlooked in many cases when evaluating design dependencies. Having a more consistent way of defining a product architecture that considers both its direct and indirect connections is important, especially when analyzing redesign complexity and change propagation. In this study, we propose a systematic method to evaluate direct and indirect design dependencies between components in product architectures. Interfaces are classified into six different types based on a thorough review of the literature, and a method for evaluating design dependencies is introduced to estimate the relative importance of interfaces directly from a set of comparable products. Using an electrical circuit analogy, the proposed method can quantify both direct and indirect design dependencies between components within a product architecture. We compare design dependency results for different wireless computer mice to validate the effectiveness of the proposed method. The results show that using the proposed design dependency measure including direct and indirect effects provides more reliable design dependency results.

Designing in young organisations: engineering change propagation in a university design project

Abstract: Engineering change (EC) is an important phenomenon in the design of products and systems, accounting for nearly one-third of the work effort; however, the literature has been focused on mature firms, and few studies have documented the impact of EC beyond them. Hence, we use a case study approach to study EC and its propagation in the context of a university design project as an example of young organisations, and compare it with the existing work done on mature firms. It was found that 33% of the changes that occurred in the case study were planned, and change propagation accounted for 20% of all changes. The propagation of changes was usually one step (67%), and it was concentrated in one independent network (54%). The results were subsequently compared with EC studies done in mature firms, being revealed that EC behaves differently in the context of a university design project; hence, existing change management tools developed to suit mature firms may not be directly suitable for supporting university design projects. The findings from this work can be used as a platform to better understand how EC propagates when designing in young organisations and shape the development of appropriate change management tools.

Do design decisions depend on "dictators"?

Abstract: Design decisions often require input from multiple stakeholders or require balancing multiple design requirements However, leading axiomatic approaches to decision-based design suggest that combining preferences across these elements is virtually guaranteed to result in irrational outcomes This has led some to conclude that a single "dictator" is required to make design decisions In contrast, proponents of heuristic approaches observe that aggregate decisions are frequently made in practice, and argue that this widespread usage justifies the value of these heuristics to the engineering design community This paper demonstrates that these approaches need not be mutually exclusive Axiomatic approaches can be informed by empirically motivated restrictions on the way that individuals can order their preferences These restrictions are represented using "anigrafs"-structured relationships between alternatives that are represented using a graph-theoretic formalism This formalism allows for a computational assessment of the likelihood of irrational outcomes Simulation results show that even minimal amounts of structure can vastly reduce the likelihood of irrational outcomes at the level of the group, and that slightly stronger restrictions yield probabilities of irrational preferences that never exceed 5% Next, an empirical case study demonstrates how anigrafs may be extracted from survey data, and a model selection technique is introduced to examine the goodness-of-fit of these anigrafs to preference data Taken together, these results show how axiomatic consistency can be combined with empirical correspondence to determine the circumstances under which "dictators" are necessary in design decisions

Exploiting latent functional capabilities for resilience in design of engineering systems

Abstract: In this paper, we address latent functional capabilities, capabilities that were neither intended nor recognized in the design process. We propose that latent capabilities can improve the resilience of engineering systems, enabling recovery of performance after disruptive events. Engineering systems are designed to meet their functional requirements, and have a limited ability to avoid critical failures. Normally, redundancies are put in place to reduce the impact of potential disruptions, adding to cost and complexity. An alternative is to uncover latent capabilities that can be used to recover from disruption by altering the function-form mapping. Existing design methods focus on intended, manifest functionality, and do not consider latent capabilities. With basis in design theory, we show that latent capabilities can enhance resilience, and demonstrate this using two illustrative cases. Further, we propose approaches to uncover latent capabilities in systems design, and discuss implications of using latent capabilities to enhance resilience.

Active mission success estimation through functional modeling

Abstract: Through the application of statistical models, the active mission success estimation (AMSE) introduced in this paper can be performed during a rapidly developing unanticipated failure scenario to support decision making. AMSE allows for system operators to make informed management and control decisions by performing analyses on a nested system of functional models that requires low time and computational cost. Existing methods for analyses of mission success such as probabilistic risk assessment or worst case analysis have been applied in the analysis and planning of space missions since the mid-twentieth century. While these methods are effective in analyzing anticipated failure scenarios, they are built on computational models, logical structures, and statistical models that often are difficult and time-intensive to modify, and are computationally inefficient leading to very long calculation times and making their ability to respond to unanticipated or rapidly developing scenarios limited. To demonstrate AMSE, we present a case study of a generalized crewed Martian surface station mission. A crew of four astronauts must perform activities to achieve scientific objectives while surviving for 1070 Martian sols before returning to Earth. A second crew arrives at the same site to add to the settlement midway through the mission. AMSE uses functional models to represent all of the major environments, infrastructure, equipment, consumables, and critical systems of interest (astronauts in the case study presented) in a nested super system framework that is capable of providing rapidly reconfigurable and calculable analysis. This allows for AMSE to be used to make informed mission control decisions when facing rapidly developing or unanticipated scenarios. Additionally, AMSE provides a framework for the inclusion of humans into functional analysis through a systems approach. Application of AMSE is expected to produce informed decision making benefits in a variety of situations where humans and machines work together toward mission goals in uncertain and unpredictable conditions.