Browsing by Author "Human, Carlo"

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    A design framework for aggregation in a system of digital twins
    (Stellenbosch : Stellenbosch University, 2022-04) Human, Carlo; Basson, AH; Kruger, K; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH SUMMARY: The digital twin (DT) concept has become a popular means of capturing and utilising data related to physical systems and has been applied in many domains. The data provided within DTs allow for the integration of services and models to improve understanding and decision-making related to the physical system. Through aggregation, multiple DTs can be combined to represent larger, more complex system, while maintaining the separation of concerns. The design framework presented in this dissertation aims to enable systematic, effective decisions when designing a system of DTs to represent a complex physical system. In particular, this framework adopts hierarchical aggregation as one of its primary enablers and it considers the use of a services network, such as a service-oriented architecture, as well. The design framework is intended to be broadly applicable, by remaining vendor-neutral, and it enables traceability of design choices. The approach starts with an analysis of physical system complexity to identify key needs related to managing complexity. A suitable requirements classification is then introduced to help translate the needs into requirements that the system of DTs should satisfy. Hierarchical aggregation is also introduced as a primary architectural approach to manage complexity. Hierarchical aggregation allows for the separation of concerns, computational load distribution, incremental development and modular software design. The design framework is arranged in six steps: 1) needs and constraints analysis, 2) physical system decomposition, 3) services allocation, 4) performance and quality considerations, 5) implementation considerations and 6) verification and validation. The dissertation then introduces a general reference architecture that combines a system of DTs (which follows hierarchical aggregation principles) with a services network to allow for reliable and adaptable service provisioning. The design framework is then discussed in the context of the general reference architecture. The design steps of the design framework are then moulded into six design patterns, which simplify the design process by focussing of key quality attributes. The quality attributes considered for the respective design patterns are performance efficiency, reliability, maintainability, compatibility, portability and security. The use of the design framework and design patterns are then demonstrated and validated through three case studies, two high-level case studies and one detailed case study. The high-level case studies consider a water distribution system and a smart city, respectively. The detailed case study considers a heliostat field. The dissertation concludes that the design framework, as well as the design patterns, enable a systematic approach to designing a system of DTs. The design framework can also be applied to numerous and varying domains, such as the case studies considered.