A Scalable and Secure System Architecture for Smart Buildings

Recent years has seen profound changes in building technologies both in Europe and worldwide. With the emergence of Smart Grid and Smart City concepts, the Smart Building has attracted considerable attention and rapid development. The introduction of novel information and communication technologies (ICT) enables an optimized resource utilization while improving the building performance and occupants' satisfaction over a broad spectrum of operations. However, literature and industry have drawn attention to certain barriers and challenges that inhibit its universal adoption. The Smart Building is a cyber-physical system, which as a whole is more than the sum of its parts. The heterogeneous combination of systems, processes, and practices requires a multidisciplinary research. This work proposes and validates a systems engineering approach to the investigation of the identified challenges and the development of a viable architecture for the future Smart Building. Firstly, a data model for the building management system (BMS) enables a semantic abstraction of both the ICT and the building construction. A high-level application programming interface (API) facilitates the creation of generic management algorithms and external applications, independent from each Smart Building instance, promoting the intelligence portability and lowering the cost. Moreover, the proposed architecture ensures the scalability regardless of the occupant activities and the complexity of the optimization algorithms. Secondly, a real-time message-oriented middleware, as a distributed embedded architecture within the building, empowers the interoperability of the ICT devices and networks and their integration into the BMS. The middleware scales to any building construction regardless of the devices' performance and connectivity limitations, while a secure architecture ensures the integrity of data and operations. An extensive performance and energy efficiency study validates the proposed design. A "building-in-the-loop" emulation system, based on discrete-event simulation, virtualizes the Smart Building elements (e.g., loads, storage, generation, sensors, actuators, users, etc.). The high integration with the message-oriented middleware keeps the BMS agnostic to the virtual nature of the emulated instances. Its cooperative multitasking and immerse parallelism allow the concurrent emulation of hundreds of elements in real time. The virtualization facilitates the development of energy management strategies and financial viability studies on the exact building and occupant activities without a prior investment in the necessary infrastructure. This work concludes with a holistic system evaluation using a case study of a university building as a practical retrofitting estimation. It illustrates the system deployment, and highlights how a currently under development energy management system utilizes the BMS and its data analytics for demand-side management applications.

Ontology-based system to support industrial system design for aircraft assembly

Jinzhi Lu, Xiaochen Zheng

The development of an aircraft industrial system is a complex process which faces the challenge of digital discontinuity in multidisciplinary engineering due to various interfaces between different digital tools, leading to extra development time and costs. This paper proposes an ontology-based system, aiming at functionality integration and design process automation, by Models for Manufacturing methodology principles. A tool-agnostic modelling, simulation and validation platform with Discrete Event Simulation and 3D simulation is enabled and demonstrated in a real case study. An ontology layer collecting the domain knowledge enables integration of the proposed system, accelerating the design process and enhancing design quality. Copyright (c) 2022 The Authors.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

ELSEVIER2022

Modelling global behaviour with scenarios in object-oriented analysis

The first object-oriented analysis methods focused on the specification of the classes of a system and on the static relationships between them. Dynamic relationships between classes and the functional view of the system as a whole were neglected, and no models were offered for capturing system requirements. This changed with the publication of use case driven approaches such as OOSE (1992) and Fusion (1994). Modelling global behaviour by scenarios in both requirements analysis and design has since been adopted by many object-oriented methods. Scenarios are also called use cases, system operations or business processes, and they are modelled using different notations. Some of the analysis methods that use scenarios have common characteristics, namely i) the similarity of the relationship between the entities of a data model and the scenarios of a flat scenario model with a matrix, and ii) the assumption that the externally visible behaviour of the system can be subdivided into more or less independent scenario types. In the following, we will refer to these characteristics by the term matrix approach. While in many projects the matrix approach has been used successfully, several difficulties arise when more complex systems are modelled: relationships and similarities between different scenario types cannot be expressed, the dependencies between scenario types are not modelled, only one abstraction level can be represented, and the apparently seamless transition from the analysis to the design model may result in a low quality object model with a strong bias towards data modelling. These difficulties lead us to propose an enhanced scenario modelling technique (called SEAM) which overcomes some of the weaknesses of the matrix approach. This modelling technique includes composition, aggregation, specialisation and extension hierarchies of services, and is based on the paradigm of interacting objects (which can be atomic objects, subsystems or systems) offering services. Scenario types, showing the possible interaction sequences for a specific service, can be modelled on several abstraction levels, and can describe the services of any kind of object (and thus also the global behaviour of a whole system) from both an internal and external point of view. We describe the concepts and the notation of SEAM, and we show how it can be integrated into the Fusion method. The difficulties that may arise in projects using methods based on the matrix approach are not only due to the limitations of scenario modelling techniques. A major factor is the often contradictory definition of the analysis model goals, which leads to clashes of intent. Therefore we discuss the nature of such intent clashes and analyse how the different software development methods deal with them. Finally we give an overview of the various notations and basic concepts used by different scenario modelling techniques, and we provide summaries of current, mostly objectoriented, approaches to modelling global behaviour.

EPFL1997

On the dependability of nanoscale circuits and systems

Milos Stanisavljevic

The invention of the integrated circuit and the manufacturing progress as well as continuing progress in the manufacturing process are the fundamental engines for the implementation of all technologies that support today's information society. The vast majority of microelectronic applications presented nowadays use the well-established CMOS process and fabrication technology which exhibit high reliability rates. The hypothesis of reliable components has mostly been taken in the development of electronic systems fabricated in the past four decades. The steady downscaling of CMOS technology has led to the development of devices with nanometer dimensions. For future nano-circuits, emerging nanodevices and their associated interconnects, the expected higher probabilities of failures, as well as the higher sensitivities to noise and variations, could make future chips prohibitively unreliable. The systems to be fabricated will be made of unreliable components and achieving 100% correctness will not be only extremely costly, but might be plainly impossible. The global picture is that reliability emerges as one of the most significant threats to the design of future integrated computing systems. Building reliable systems out of unreliable components will require increased cooperative involvement of the logic designers and architects, where high-level techniques will rely upon lower levels support based on novel modeling including component and system reliability as design parameters. An architecture suitable for circuit-level and gate-level redundant modules and exhibiting significant immunity to permanent and random failures, as well as unwanted fluctuation of the fabrication parameters is presented, which is based on a four-layer feed-forward topology, using averaging and thresholding as the core voter mechanisms. The architecture with both fixed and adaptable threshold is compared to triple and R-fold modular redundancy techniques, and its superiority is demonstrated based on numerical simulations as well as analytical developments. A chip implementation of the architecture is realized. Other applications of the architecture like delay variations minimization are identified and explored. A novel general method enabling introduction of fault-tolerance, and evaluation of circuit and architecture reliability is proposed. The method is based on the modeling of probability density functions (PDFs) of unreliable components and their subsequent evaluation for a given reliability architecture. PDF modeling, presented for the first in the context of realistic technology and arbitrary circuit size, is based on a cutting-edge reliability evaluation algorithm and offers scalability, speed and accuracy. Fault modeling has also been developed to support PDF modeling. In the second part of the thesis a new methodology that introduces reliability in existing design flows is proposed. The methodology consists of partitioning the whole system into reliability-optimal partitions and applying reliability evaluation and optimization at local and system level. System level reliability improvement of different fault-tolerant techniques is studied in depth. Optimal partition size analysis and redundancy optimization have been performed for the first time in the context of a large-scale system, showing that a target reliability can be achieved with low to moderate redundancy factors (R < 50) even for high defect densities (device failure rate up to 10-3). The optimal window of application of each fault-tolerant technique with respect to defect density is presented as a way to find the optimum design trade-off between the reliability and power/area. R-fold modular redundancy with distributed voting and averaging voter is selected as the most promising candidate for the implementation in trillion-transistor logic systems. Finally, a realistic circuit example of the methodology implementation is verified using simulations.

EPFL2009

Modelling global behaviour with scenarios in object-oriented analysis

EPFL1997

On the dependability of nanoscale circuits and systems

Milos Stanisavljevic

EPFL2009