CERES :: Browsing by Author "Guenov, Marin D."

Browsing by Author "Guenov, Marin D."

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Open Access
Aircraft systems architecting: a functional-logical domain perspective
(American Institute of Aeronautics and Astronautics, 2016-06-17) Guenov, Marin D.; Molina-Cristobal, Arturo; Voloshin, V.; Riaz, Atif; van Heerden, Albert S. J.; Sharma, Sanjiv; Cuiller, C.; Giese, Tim
Presented is a novel framework for early systems architecture design. The framework defines data structures and algorithms that enable the systems architect to operate interactively and simultaneously in both the functional and logical domains. A prototype software tool, called AirCADia Architect, was implemented, which allowed the framework to be evaluated by practicing aircraft systems architects. The evaluation confirmed that, on the whole, the approach enables the architects to effectively express their creative ideas when synthesizing new architectures while still retaining control over the process.
Open Access
Airship-assisted space launch.
(2004-03-01T00:00:00Z) Guenov, Marin D.; Peyron, Vincent
Introduction Being lighter-than-air, airships do not seem to be an obvious platform choice for dropping of heavy objects. We have challenged the idea and this paper presents the summary of a speculative concept which utilises airships as a reusable first stage of a space launch system. The inspiration behind the concept was that if not much cheaper, the airship-assisted space launch will be environmentally friendlier- an argument which is likely to become even more important with time. During the development of the concept we have used as a base for comparison the Orbital Sciences Corp. Pegasus XL concept, which is currently the single operational aircraft-based space launch system. Alongside the challenges of estimating weight and cost of the very large airship required (approximately 728,000 m 3 ), the work presented in this paper concentrates mainly on the process of releasing the space launch vehicle from the airship.
Open Access
Assumption management in model-based systems engineering: an aircraft design perspective.
(2021-12) El Fassi, Soufiane; Riaz, Atif; Guenov, Marin D.
Early design of complex systems is characterised by significant uncertainty due to lack of knowledge, which can impede the design process. In order to proceed with the latter, assumptions are typically introduced to fill knowledge gaps. However, the uncertainty inherent in the assumptions constitutes a risk to be mitigated. In fact, assumptions can negatively impact the system if they turn out to be invalid, such as causing system failure, violation of requirements, or budget and schedule overruns. Within this context, the aim of this research was to develop a computational approach to support assumption management in model-based systems engineering, with an explicit consideration of the uncertainty in assumptions. To achieve the research aim, the objectives were to: (1) devise methods to enable assumption management in a model-based design environment; and (2) devise methods to manage risk of change due to invalid assumptions, with an explicit consideration of both assumptions and margins. The scope was limited to the early stages of aircraft design. To evaluate this research, a demonstration was performed based on two use cases to assess whether the methods work as intended. The developed methods were demonstrated to industry experts in order to obtain feedback on expected usefulness in practice, thus assessing the impact of this research. The experts concluded that the proposed methods are innovative, useful and relevant to industry, where these methods can lead to: (i) fewer undesired iterations, due to earlier identification and management of risks associated with assumptions; and (ii) a better margin balance, due to timely and interactive margin revision. Future work includes further industrial evaluation, extending the research scope and studying the scalability and associated costs of the proposed methods.
Open Access
An assumption network-based approach to support margin allocation and management
(Cambridge University Press, 2020-05-31) El Fassi, Soufiane; Guenov, Marin D.; Riaz, Atif
Presented is an approach to support margin allocation and management via a graph-theoretical network of assumptions. In contrast to the document-centric approach, the network captures assumptions dependencies, and enables an algorithmic process supporting margin allocation and management. Ultimately, this methodology is intended to assist decision-makers in managing assumptions and examining their impact on an architecture. Explicitly linking margins to assumptions allows to support mitigating their risk of invalidity. The approach is demonstrated with a conceptual aircraft design example
Open Access
Building safety into the conceptual design of complex systems. An aircraft systems perspective.
(2021-06) Jimeno Altelarrea, Sergio; Guenov, Marin D.; Riaz, Atif
Safety is a critical consideration during the design of an aircraft, as it constrains how primary functions of the system can be achieved. It is essential to include safety considerations from early design stages to avoid low-performance solutions or high costs associated with the substantial redesign that is commonly required when the system is found not to be safe at late stages of the design. Additionally, safety is a crucial element in the certification process of aircraft, which requires compliance with safety requirements to be demonstrated. Existing methods for safety assessment are limited in their ability to inform architectural decisions from early design stages. Current techniques often require large amounts of manual work and are not well integrated with other system engineering tools, which translates into increased time to synthesise and analyse architectures, thus reducing the number of alternative architectures that can be studied. This lack of timely safety assessment also results in a situation where safety models evolve at a different pace and become outdated with respect to the architecture definition, which limits their ability to provide valuable feedback. Within this context, the aim is to improve the efficiency and effectiveness of design for safety as an integral part of the systems architecting process. Three objectives are proposed to achieve the stated aim: automate and integrate the hazard assessment process with the systems architecting process; facilitate the interactive introduction of safety principles; and enable a faster assessment of safety and performance of architectures. The scope is restricted to the earlier (conceptual) design stages, the use of model-based systems engineering for systems architecting (RFLP paradigm) and steady-state models for rapid analysis. Regarding the first objective, an enabler to support the generation of safety requirements through hazard assessment was created. The enabler integrates the RFLP architecting process with the System-Theoretic Process Analysis to ensure consistency of the safety assessment and derived safety requirements more efficiently. Concerning the second objective, interactive enablers were developed to support the designer when synthesizing architectures featuring a combination of safety principles such as physical redundancy, functional redundancy, and containment. To ensure consistency and reduce the required amount of work for adding safety, these methods leverage the ability to trace dependencies within the logical view and between the RFLP domains of the architecture. As required by the third objective, methods were developed to automate substantial parts of the creation process of analysis models. In particular, the methods enable rapid obtention of models for Fault Tree Analysis and subsystem sizing considering advanced contextual information such as mission, environment, and system configurations. To evaluate this research, the methods were implemented into AirCADia Architect, an object-oriented architecting tool. The methods were verified and evaluated through their applications to two aircraft-related use cases. The first use case involves the wheel brake systems and the second one involves several subsystems. The results of this study were presented to a group of design specialists from a major airframe manufacturer for evaluation. The experts concluded that the proposed framework allows architects to define and analyse safe architectures faster, thus enabling a more effective and efficient design space exploration during conceptual design.
Open Access
Complexity and cost effectiveness measures for systems design
(2002-04-01T00:00:00Z) Guenov, Marin D.
This paper proposes two measures intended to aid high level decision makers in comparing alternatives during pre-competitive studies or during the architectural design process of composite systems. The first measure is a complexity estimate and is based on Boltzmann’s entropy concept. It measures the distribution of functional couplings in the system’s decomposition. The second measure is intended to estimate the costs and benefits of a functional coupling related to system’s perfo
Open Access
Component-driven computational design of complex engineering systems.
(2018-08) Bile, Yogesh Hanumant; Guenov, Marin D.; Molina-Cristobal, Arturo
During the conceptual design of complex systems, architects study a number of different options, which comprise the architectural design space. Usually, new system architectures (SAs) are created by modifying existing ones, e.g., by deleting existing and/or adding new elements. Once the concept is synthesised, the architect wishes to swiftly find the effect of the proposed architectural changes at system level. This would involve sizing of the modified sub-systems, and then, obtaining the system level performance. In turn, this involves time-consuming activities, such as re-arrangement (orchestration) of computational tasks and models. Also, depending on the results, the architect may undertake further modifications. When doing this, a means to navigate across the RFLP (Requirements-Functional-Logical-Physical) views of the SA may be required, in order to trace elements affected by these modifications. Generally, several iterations are involved between architecting and sizing during conceptual design, which, if manually performed, result in a tedious and time-consuming process. There are existing methods which address this problem, but these have significant limitations in that they are usually system specific and often involve an excessive amount of time-consuming manual tasks. Within this context, the research aim is to improve the efficiency of the architectural design space exploration (ADSE) process, by automating repetitive computational tasks, thus enabling the designer to swiftly and interactively explore multiple SA options. A novel method, comprised of two parts, has been developed to achieve the aim. In the first part, a graph-theoretic approach is employed to enable architectural element dependency analysis. Here, the relationships between the architectural elements are stored as a graph. Algorithms, such as ‘Depth First Search’ and ‘Transitive Closure’ are then applied to assist the architect in tracing the dependencies between elements that might be affected by a proposed change to other elements of the SA. In the second part, the architecture is assessed to find the system level performance. The inputs needed for rapid assessment include the functional and logical views of the SA, and the requisite steady-state computational models associated with each of the ‘logical’ components. The assessment process itself consists of three steps. In the first step, the sequence of the sub-systems is automatically generated by extracting a sub-systems source-sink ‘Dependency Structure Matrix (DSM)’ from the logical view, followed by the application of an algorithm which determines the systems’ sizing sequence. In the second step, the individual sub-systems and system level workflows are constructed. Here, the computational workflow (a network of computational models) is represented as a bipartite graph. A maximum matching enumeration algorithm is used to find all possible workflows for a given model set, and another algorithm, to choose from these the most computationally efficient one, i.e., the workflow with the lowest number of reversed variables. In the third step, the workflows produced in the second step and subsystems ’sizing sequence obtained in the first step are combined to produce a complete workflow. To demonstrate and evaluate the proposed enablers, the author developed a prototype object-oriented architecting tool. The enablers were individually and collectively verified on representative test-cases. Comparison with the existing methods confirmed the claimed advantages of the proposed approach, namely, reducing the number of manual activities, which results in swifter and interactive ADSE process. Feedback obtained from experts in the aircraft industry during an initial qualitative evaluation session confirmed the usefulness of the proposed method.
Open Access
Computational design process modelling
(2006-12-01T00:00:00Z) Guenov, Marin D.; Libish; Tang, Dunbing; Lockett, Helen L.
In the conceptual design phase, relatively simple equations and functions (or compiled code) are used to describe the aircraft and to perform trade-off studies. The latter require an optimal execution sequence in order to reduce computational cost and design time, respectively. The focus of this paper is the dynamic derivation of the optimal computational plan for each study so that the designer could focus on designing the aircraft rather than managing the process flow. Two methodologies, the Design Structure Matrix (DSM) and the Incidence Matrix are used for the computational process modeling. The incidence matrix describes the relationship between variables and equations/models. The DSM has been used to express the dependency relationships between the models and also, after manipulation, to produce the solution process. The designer specifies the independent (known) variables first. Then the variable flow is modeled using the Incidence Matrix Method (IMM). It determines how data flows through the models, and also identifies any strongly connected components (SCCs). The second step is to rearrange all equations/models hierarchically in order to reduce the feedback loops in each of the identified SCCs. This is achieved by the application of a genetic-based algorithm. Subsequently all SCCs and noncoupled models are assembled into a macro model which forms a global DSM. The global DSM is further rearranged to obtain an upper triangular matrix which defines the final model execution sequence. A simple aircraft sizing example is presented to illustrate the proposed method and algorithm. Advantages of the method include improved efficiency and the ability to deal with both algebraic and numerical models as well as with multiple outputs per model.
Open Access
Computational engineering design under uncertainty: an aircraft conceptual design perspective
(Cranfield University, 2009-07) Padulo, Mattia; Guenov, Marin D.
Presented in this thesis is a novel methodology for aircraft design optimization in the presence of uncertainty, with emphasis on the conceptual design stage. In the initial part of the thesis, the uncertainty typologies of interest for aircraft design are identied within a broader epistemological framework. The main implications for non-deterministic computational design are also outlined. The focus is then restricted to uncertainties that can be modeled by probability theory. In this context, a methodology is developed to enhance robust design optimization (RDO). Firstly, the problem is formulated in order to relax, when required, the common RDO assumption about the normality of objectives and constraints. Secondly, starting from engineering considerations about the risk related with design unfeasibility, suitable estimates of tail conditional expectation are introduced in the set of robustness metrics. The proposed formulation requires the estimation of mean and variance of objec¬tives and constraints. To calculate such moments, a novel uncertainty propaga¬tion technique is proposed, which achieves a favorable trade-obetween the ac-curacy of the estimates and the required computational cost. Peculiar features of the propagation technique are exploited to couple the propagation and the opti¬mization phases for the classes of gradient-based methods and the derivative-free pattern search methods. Also analyzed are the possible advantages achievable when the two types of algorithms are hybridized. The usefulness of the proposed methodology for conceptual design optimization is demonstrated with the aid of two engineering design problems, concerning the sizing of passenger aircraft and the design of transonic airfoils.
Open Access
Computational framework for interactive architecting of complex systems
(Wiley, 2020-02-17) Guenov, Marin D.; Riaz, Atif; Bile, Yogesh H.; Molina-Cristobal, Arturo; van Heerden, Albert S. J.
Presented is a novel framework for interactive systems architecture definition at early design stages. It incorporates graph‐theoretic data structures, entity relationships, and algorithms that enable the systems architect to operate interactively and simultaneously in different domains. It explicitly captures the “zigzagging” of the functional reasoning process, including not only allocated, but also the derived functions. A prototype software tool, AirCADia Architect, was implemented, which allowed the framework to be demonstrated to and tried hands‐on by practicing aircraft systems architects. The tool enables architects to effectively express their ideas when interactively synthesizing new architectures, while still retaining control over the process. The proposed approach was especially acknowledged as the way forward for rationale capture.
Open Access
Computational techniques for aircraft evolvability exploration during conceptual design.
(2018-02) Van Heerden, Albert Stevan Johan; Guenov, Marin D.; Molina-Cristobal, Arturo
Evolvability is a critical consideration during the design of an aircraft. It refers to the extent to which a baseline design could be reused, or `easily' modified to create descendant designs that would meet future requirements. Since a major fraction of the cost of an aircraft programme is determined by decisions made during conceptual design, it is essential that the design space is explored thoroughly during this stage to find evolvable designs. Existing computational methods to perform such exploration exist, but are limited in two respects. The first of these is that, with existing techniques, derivatives are usually generated by applying pre-specified modifications to a selected baseline, such that each derivative in a study is only linked to a single baseline. The designer must therefore evaluate large numbers of baseline-derivative pairs to adequately capture the evolution options available. The second limitation concerns an absence of appropriate down-selection criteria to narrow down the number of design points when evolvability is considered. The work presented in this thesis addresses these limitations. The aim was to develop computational techniques that would enable aircraft designers to explore the evolvability of their designs more efficiently and effectively during the conceptual design stage. The scope was limited to civil transport aircraft and specifically to airframes. The work is applicable to both single- and twin-aisle aircraft, but the focus was, to a small degree, more on single-aisles. The research resulted in two main contributions: 1) a framework to provide a means to link all derivatives to all the baselines; and 2) a set of techniques to filter out inferior designs systematically. The framework builds on the premise that the degree of `similarity' between two ,designs could be used as an estimate for the redesign e ort (i.e. resource expenditure) required to change one of these into the other. Case studies involving existing aircraft families were conducted to determine which design changes could be considered `reasonable'. Based on this information, a set of techniques to assess airframe similarity was developed, which involves automatically predicting possible commonality across two designs. Several algorithms were devised to achieve this, including one that solves a longest common subsequence problem to find common body segments and a simple optimisation procedure to find common wing elements. Notably, these techniques can be used to compare aircraft with dissimilar configurations. For testing purposes, the framework was applied to several existing and future aircraft. The results showed that the predicted commonality matches published information regarding commonality and design re-use between designs. The framework essentially removes the need to model each future design option based on a specific starting design. The design filtering techniques involve the application of set-based design to facilitate systematic down-selection of potential designs. Specifically, it is demonstrated how established set-based design criteria could be adapted to prune an evolvability design space progressively. To demonstrate the usefulness of the research, it was applied to an example, concerning design candidates for a new single-aisle, environmentally friendly passenger aircraft. The results of this study were presented to a panel of design specialists from Airbus UK. The panel concluded that the proposed similarity assessment provides reasonable initial estimates for redesign e ort and that the overall approach adds value to the evolvability exploration process.
Open Access
Computational workflow management for conceptual design of complex systems: an air-vehicle design perspective
(Cranfield University, 2007) Balachandran, Libish Kalathil; Guenov, Marin D.
The decisions taken during the aircraft conceptual design stage are of paramount importance since these commit up to eighty percent of the product life cycle costs. Thus in order to obtain a sound baseline which can then be passed on to the subsequent design phases, various studies ought to be carried out during this stage. These include trade-off analysis and multidisciplinary optimisation performed on computational processes assembled from hundreds of relatively simple mathematical models describing the underlying physics and other relevant characteristics of the aircraft. However, the growing complexity of aircraft design in recent years has prompted engineers to substitute the conventional algebraic equations with compiled software programs (referred to as models in this thesis) which still retain the mathematical models, but allow for a controlled expansion and manipulation of the computational system. This tendency has posed the research question of how to dynamically assemble and solve a system of non-linear models. In this context, the objective of the present research has been to develop methods which significantly increase the flexibility and efficiency with which the designer is able to operate on large scale computational multidisciplinary systems at the conceptual design stage. In order to achieve this objective a novel computational process modelling method has been developed for generating computational plans for a system of non-linear models. The computational process modelling was subdivided into variable flow modelling, decomposition and sequencing. A novel method named Incidence Matrix Method (IMM) was developed for variable flow modelling, which is the process of identifying the data flow between the models based on a given set of input variables. This method has the advantage of rapidly producing feasible variable flow models, for a system of models with multiple outputs. In addition, criteria were derived for choosing the optimal variable flow model which would lead to faster convergence of the system. Cont/d.
Open Access
Covariance structural models of the relationship between the design and customer domains
(Taylor & Francis, 2008-02-01T00:00:00Z) Guenov, Marin D.
This paper addresses the problem of modelling and mapping of difficult to quantify customer needs to technical requirements and subsequently to design parameters. Proposed is a covariance structural equation model, which incorporates a confirmatory and a structural component. The former is used for the decomposition of the qualitative customer needs, modelled as latent variables, onto a generally larger number of measurable technical requirements. The structural component maps the technical requirements to design parameters. The concept is illustrated by an example. The model is confined to the linear dependence between the variables, but in general the approach can handle a number of non-linear relations through variable transformation. The conclusion is that the proposed synthetic procedure, named SEMDES (Structural Equation Models for the Design of Engineering Systems) represents a sufficiently rich and generic structure capable of bridging the gap between the customer and the design domains.
Open Access
Design exploration for engineering design optimisation : an aircraft conceptual perspective
(Cranfield University, 2010-11) Nunez, Marco; Guenov, Marin D.
Most of the efforts in optimisation so far have been focused on the development of novel or the improvement of existing numerical methods for an effective computation of optimal solutions. Particular attention has been put on balancing multiple conflicting objectives, handling the interaction between different disciplines, reducing computational cost and managing uncertainty. Nonetheless, specific issues of this design methodology still remain to be properly addressed. In this research, attention is concentrated on advancing engineering optimisation as a tool for design exploration. The work is put in the context of conceptual aircraft design. The overall aim of the present research is to develop a methodology that allows the designer to effectively conduct an exploration and analysis of alternative design solutions via a set of methods that can be used separately or conjointly. The initial part of the thesis introduces two novel methods for assisting the formulation of an optimisation problem, which generally is assumed to be given a priori. Nonetheless, the correctness of the optimisation statement, which is not addressed by established optimisation methods, turns out to be decisive for the feasible design set determination. The designer is thus provided with an adaptive formulation of functional and designvariable constraints, which allows the exploration of further promising solutions initially not contained in the feasible design set. Meaningless results or the loss of important solutions can therefore be partially avoided. In a second instance, attention is focused on the visualisation needs for design exploration. A suitable visualisation methodology has been developed to make the large multidimensional results of complex design optimisation procedures fully readable and explanatory. This is achieved by integrating advanced visualisation techniques which provide the designer with diverse perspectives of the data under study and allow him/her to conduct a number of analysis tasks on it, without the need to be an expert in numerical optimisation methods. Last, but not least, a methodology to address conceptual design change problems is proposed. The decision-maker is enabled to formally state the new design requirements and priorities introduced by the conceptual change via an adequate problem reformulation. All the data previously collected can thus be re-used and exploited to drive an effective exploration of alternative design solutions through design space regions of interest. The evaluation of the proposed methodologies has been carried out with a number of test cases. Analytical examples have been used for the assessment of effectiveness, whereas codes representative of aircraft sizing procedures have been adopted to evaluate the methodologies functionality. A visualisation user interface prototype has also been developed for demonstration and evaluation purposes.
Open Access
Effective multiobjective MDO for conceptual design - An aircraft design perspective
(Cranfield University, 2007) Fantini, Paolo; Guenov, Marin D.
Once the requirements for a new aircraft have been defined, the Conceptual design phase is launched. During this phase one or more designers have the goal of defining and investigating a number of alternative solutions. Through discussion with industry it has become apparent that optimisation tools are seldom used, even though these could greatly enhance the work of the designers. The objective of the work carried forward has been of identifying, comparing and where necessary improving the most suitable techniques, as well as schemes for their integration, in order to perform effectively Multidisciplinary Design and Optimisation (MDO) in the Conceptual phase of the aircraft design. The techniques that have been investigated include: multi-objective optimisation algorithms, MDO algorithms for treating non-hierarchically decomposable systems and Automatic Differentiation (AD). As a result an algorithm for performing multiobjective MDO has been developed. Given a complete model for a complex non-hierarchically decomposable system and given a number of objectives and constraints, the algorithm is capable of determining a set of well distributed solutions, representative of both local and global Pareto frontiers. A number of test cases have been used for evaluating the alternative methodologies and the proposed algorithm. These include a set of complex algebraic test cases typically used for evaluating global optimisation algorithms and a simplified aircraft conceptual design model, which was provided by industry. The results demonstrate the unique capability of the algorithm of determining well distributed solutions on the global and local Pareto frontiers for global multiobjective continuous nonlinear constrained optimisation problems. The results also show this capability when the algorithm is applied to non-hierarchically decomposable systems, as typically encountered when performing MDO. Further work could extend the approach in order to handle mixed discrete/continuous variables.
Open Access
Efficient method for variance-based sensitivity analysis
(Elsevier, 2018-07-05) Chen, Xin; Molina-Cristobal, Arturo; Guenov, Marin D.; Riaz, Atif
Presented is an efficient method for variance-based sensitivity analysis. It provides a general approach to transforming a sensitivity problem into one uncertainty propagation process, so that various existing approximation techniques (for uncertainty propagation) can be applied to speed up the computation. In this paper, formulations are deduced to implement the proposed approach with one specific technique named Univariate Reduced Quadrature (URQ). This implementation was evaluated with a number of numerical test-cases. Comparison with the traditional (benchmark) Monte Carlo approach demonstrated the accuracy and efficiency of the proposed method, which performs particularly well on the linear models, and reasonably well on most non-linear models. The current limitations with regard to non-linearity are mainly due to the limitations of the URQ method used.
Open Access
Enablers for uncertainty quantification and management in early stage computational design. An aircraft perspective
(2017-10) Chen, Xin; Guenov, Marin D.; Molina-Cristobal, Arturo
Presented in this thesis are novel methods for uncertainty quantification and management (UQ&M) in computational engineering design. The research has been motivated by the industrial need for improved UQ&M techniques, particularly in response to the rapid development of the model-based approach and its application to the (early) design of complex products such as aircraft. Existing work has already addressed a number of theoretical and computational challenges, especially regarding uncertainty propagation. In this research, the contributions to knowledge are within the wider UQ&M area. The first contribution is related to requirements for an improved margin management policy, extracted from the FP7 European project, TOICA (Thermal Overall Integrated Conception of Aircraft). Margins are traditional means to mitigate the effect of uncertainty. They are relatively better understood and less intrusive in current design practice, compared with statistical approaches. The challenge tackled in this research has been to integrate uncertainty analysis with deterministic margin allocations, and to provide a method for exploration and trade-off studies. The proposed method incorporates sensitivity analysis, uncertainty propagation, and the set-based design paradigm. The resulting framework enables the designer to conduct systematic and interactive trade-offs between margins, performances and risks. Design case studies have been used to demonstrate the proposed method, which was partially evaluated in the TOICA project. The second contribution addresses the industrial need to properly ‘allocate’ uncertainty during the design process. The problem is to estimate how much uncertainty could be tolerated from different sources, given the acceptable level of uncertainty associated with the system outputs. Accordingly, a method for inverse uncertainty propagation has been developed. It is enabled by a fast forward propagation technique and a workflow reversal capability. This part of the research also forms a contribution to the TOICA project, where the proposed method was applied on several test-cases. Its usefulness was evaluated and confirmed through the project review process. The third contribution relates to the reduction of UQ&M computational cost, which has always been a burden in practice. To address this problem, an efficient sensitivity analysis method is proposed. It is based on the reformulation and approximation of Sobol’s indices with a quadrature technique. The objective is to reduce the number of model evaluations. The usefulness of the proposed method has been demonstrated by means of analytical and practical test-cases. Despite some limitations for several specific highly non-linear cases, the tests confirmed significant improvement in computational efficiency for high dimensional problems, compared with traditional methods. In conclusion, this research has led to novel UQ&M tools and techniques, for improved decision making in computational engineering design. The usefulness of these methods with regard to efficiency and interactivity has been demonstrated through relevant test-cases and qualitative evaluation by (industrial) experts. Finally, it is argued that future work in this field should involve research and development of a comprehensive framework, which is able to accommodate uncertainty, not only with regard to computation, but also from the perspective of (expert) knowledge and assumptions.
Open Access
Enabling interactive safety and performance trade-offs in early airframe systems design
(AIAA, 2020-01-05) Jimeno, Sergio; Riaz, Atif; Guenov, Marin D.; Molina-Cristobal, Arturo
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.
Open Access
Evaluation of a collaborative and distributed aircraft design environment, enabled by microservices and cloud computing
(AIAA, 2023-01-19) Chen, Xin; Isoldi, Adriano; Riaz, Atif; Mourouzidis, Christos; Keskin, Akin; Smith, Dale; Guenov, Marin D.; Pachidis, Vassilios
Presented in this paper are the outcomes from the evaluation of a distributed aircraft design environment, based on microservices and cloud computing. The evaluation was performed on a representative airframe-engine optimization case study, including the engine, wing aero-structural geometry, and high-lift devices. The (computational) design process involved multiple distributed design teams and design tools. The latter were implemented with different programming languages and deployed on the Azure cloud service. As a benchmark, the same case study was performed using the traditional email/document-based approach to design collaboration. Compared with the traditional collaboration, the cloud-based approach substantially reduced the time for design iterations between the design teams. This was mainly due to the fast remote access of models/tools on the cloud and automation of data exchange. Also, the exercise indicated that the cloud-based approach is more flexible with regard to orchestrating the computational workflows and optimization studies, while protecting the Intellectual Property (IP) of the collaborating partners.
Open Access
Evolvability and design reuse in civil jet transport aircraft
(Elsevier, 2019-05-10) van Heerden, Albert S. J.; Guenov, Marin D.; Molina-Cristobal, Arturo
A comprehensive investigation of evolvability and design reuse in new and historical civil jet transport aircraft was undertaken. The main purpose was to characterise the techniques and strategies used by aircraft manufacturers to evolve their designs. Such knowledge is essential to devise improved design methods for promoting the evolvability of new aircraft. To perform the study, jet aircraft from three large western manufacturers (Boeing, Airbus, and McDonnell Douglas) were investigated in depth. The academic and industrial literature was combed to find descriptions of design reuse and change across each major model of all three manufacturers. The causes and effects of the changes are explored, and the amenability of the different airframes to change are discussed. The evolution of the payload and range capabilities of the different aircraft was also investigated. From these studies, it was found that the initial approach to derivative designs appears somewhat ad hoc and that substantial modifications were devised in quick succession to increase both range and capacity. From the 1970s, two distinguishable patterns started to appear – a ‘leap and branch’ and a ‘Z’ pattern. The leaps correspond to major changes in both propulsion and airframe, whereas the branches are simple ‘stretches’ or ‘shrinks’. The Z pattern, also documented by other authors, is a progressive increase in range, followed by a simple stretch, and then another increase in range. Design changes were investigated further by grouping them according to the assumed payload-range objectives set for the derivatives. Finally, the maximum changes found for salient geometrical design parameters amongst all the aircraft surveyed were documented. Developing methods to support the creation of leaps (especially across configurations) appears to be one of the most promising avenues for future research.