Browsing by Author "El Fassi, Soufiane"

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    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.
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    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
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    Data Supporting "Managing Assumption-Driven Design Change via Margin Allocation and Trade-offs"
    (Cranfield University, 2023-10-24 15:45) Chen, Xin; El Fassi, Soufiane; Riaz, Atif; Guenov, Marin; Van heerden, Albert; Jimeno Altelarrea, Sergio
    Results of design of experiment study produced in "Managing Assumption-Driven Design Change via Margin Allocation and Trade-offs". Presented as Figures 16, 17, and 18 in the paper.
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    Managing assumption-driven design change via margin allocation and trade-offs
    (Taylor and Francis, 2023-10-11) El Fassi, Soufiane; Chen, Xin; Riaz, Atif; Guenov, Marin D.; van Heerden, Albert S. J.; Jimeno Altelarrea, Sergio
    Assumptions are commonly introduced to fill gaps in knowledge during the engineering design process. However, the uncertainty inherent in these assumptions constitutes a risk that ought to be mitigated. That is, assumptions can negatively impact the system if they turn out to be invalid. Adverse effects may include system failure, violation of requirements, or budget and schedule overruns. In this paper, the relationships between assumptions and margins are made explicit, with the purpose of aiding risk mitigation, as well as accommodating future opportunities such as product evolvability. To this end, a novel assumption management framework is proposed, which consists of a taxonomy of margins, an algorithm for change absorber localisation, and an interactive approach for margin trade-off. The proposed framework is demonstrated with a conceptual aircraft design use case, which shows that the most relevant margins can be identified, given a revision of a set of assumptions. It is also demonstrated that the application of the method allowed the margins to be adjusted according to the confidence in the assumptions, while maintaining satisfaction of all design constraints, without unacceptable compromise of system performance.