Modeling Cyber-Physical Production Systems with SystemC-AMS

The heterogeneous nature of SystemC-AMS makes it a perfect candidate solution to support Cyber-Physical Production Systems (CPPSs), i.e., systems that are characterized by a tight interaction of the cyber part with the surrounding physical world and with manufacturing production processes. Nonetheless, the support for the modeling of physical and mechanical dynamics typical of production machinery goes far beyond the initial application scenario of SystemC-AMS, thus limiting its effectiveness and adoption in the production and manufacturing context. This paper starts with an analysis of the current adoption of SystemC-AMS to highlight the open points that still limit its effectiveness, with the goal of pinpointing current issues and to propose solutions that could improve its effectiveness, and make SystemC-AMS an essential resource also in the new Industry 4.0 scenario

SystemC-AMS Simulation of Energy Management of Electric Vehicles

Electric vehicles (EV) are rapidly invading the market, since they are clean, quiet and energy efficient. However, there are many factors that discourage EVs for current and potential customers. Among them, driving range is one of the most critical issues: running out of battery charge while driving results in serious inconvenience even comparable to vehicle breakdown, as an effect of long fuel recharging times and lack of charging facilities. As a result, the dimensioning of the energy subsystem of an EV is a crucial activity. The choice of the power components and of the adopted policies should thus be validated at design time through simulations, that estimate the vehicle driving range under reference driving profiles. It is thus necessary to build a simulation framework that takes into account an EV power consumption model, dependent on the characteristics of the vehicle and of the driving route, plus accurate models for all power components, including batteries and green power sources. The goal of this paper is to achieve early EV simulation, so that the designer can estimate at design time the driving range of the vehicle, validate the adopted components and policies and evaluate alternative configurations

Efficient Modelling and Simulation Methodology for the Design of Heterogeneous Mixed-Signal Systems on Chip

Systems on Chip (SoCs) and Systems in Package (SiPs) are key parts of a continuously broadening range of products, from chip cards and mobile phones to cars. Besides an increasing amount of digital hardware and software for data processing and storage, they integrate more and more analogue/RF circuits, sensors, and actuators to interact with their (analogue) environment. This trend towards more complex and heterogeneous systems with more intertwined functionalities is made possible by the continuous advances in the manufacturing technologies and pushed by market demand for new products and product variants. Therefore, the reuse and retargeting of existing component designs becomes more and more important. However, all these factors make the design process increasingly complex and multidisciplinary. Nowadays, the design of the individual components is usually well understood and optimised through the usage of a diversity of CAD/EDA tools, design languages, and data formats. These are based on applying specific modelling/abstraction concepts, description formalisms (also called Models of Computation (MoCs)) and analysis/simulation methods. The designer has to bridge the gaps between tools and methodologies using manual conversion of models and proprietary tool couplings/integrations, which is error-prone and time-consuming. A common design methodology and platform to manage, exchange, and collaboratively develop models of different formats and of different levels of abstraction is missing. The verification of the overall system is a big problem, as it requires the availability of compatible models for each component at the right level of abstraction to achieve satisfying results with respect to the system functionality and test coverage, but at the same time acceptable simulation performance in terms of accuracy and speed. Thus, the big challenge is the parallel integration of these very different part design processes. Therefore, the designers need a common design and simulation platform to create and refine an executable specification of the overall system (a virtual prototype) on a high level of abstraction, which supports different MoCs. This makes possible the exploration of different architecture options, estimation of the performance, validation of re-used parts, verification of the interfaces between heterogeneous components and interoperability with other systems as well as the assessment of the impacts of the future working environment and the manufacturing technologies used to realise the system. For embedded Analogue and Mixed-Signal (AMS) systems, the C++-based SystemC with its AMS extensions, to which recent standardisation the author contributed, is currently establishing itself as such a platform. This thesis describes the author's contribution to solve the modelling and simulation challenges mentioned above in three thematic phases. In the first phase, the prototype of a web-based platform to collect models from different domains and levels of abstraction together with their associated structural and semantical meta information has been developed and is called ModelLib. This work included the implementation of a hierarchical access control mechanism, which is able to protect the Intellectual Property (IP) constituted by the model at different levels of detail. The use cases developed for this tool show how it can support the AMS SoC design process by fostering the reuse and collaborative development of models for tasks like architecture exploration, system validation, and creation of more and more elaborated models of the system. The experiences from the ModelLib development delivered insight into which aspects need to be especially addressed throughout the development of models to make them reusable: mainly flexibility, documentation, and validation. This was the starting point for the development of an efficient modelling methodology for the top-down design and bottom-up verification of RF Systems based on the systematic usage of behavioural models in the second phase. One outcome is the developed library of well documented, parameterisable, and pin-accurate VHDL-AMS models of typical analogue/digital/RF components of a transceiver. The models offer the designer two sets of parameters: one based on the performance specifications and one based on the device parameters back-annotated from the transistor-level implementation. The abstraction level used for the description of the respective analogue/digital/RF component behaviour has been chosen to achieve a good trade-off between accuracy, fidelity, and simulation performance. The pin-accurate model interfaces facilitate the integration of transistor-level models for the validation of the behavioural models or the verification of a component implementation in the system context. These properties make the models suitable for different design tasks such as architecture exploration or overall system validation. This is demonstrated on a model of a binary Frequency-Shift Keying (FSK) transmitter parameterised to meet very different target specifications. This project showed also the limits in terms of abstraction and simulation performance of the "classical" AMS Hardware Description Languages (HDLs). Therefore, the third and last phase was dedicated to further raise the abstraction level for the description of complex and heterogeneous AMS SoCs and thus enable their efficient simulation using different synchronised MoCs. This work uses the C++-based simulation framework SystemC with its AMS extensions. New modelling capabilities going beyond the standardised SystemC AMS extensions have been introduced to describe energy conserving multi-domain systems in a formal and consistent way at a high level of abstraction. To this end, all constants, variables, and parameters of the system model, which represent a physical quantity, can now declare their dimension and associated system of units as an intrinsic part of their data type. Assignments to them need to contain besides the value also the correct measurement unit. This allows a much more precise but still compact definition of the models' interfaces and equations. Thus, the C++ compiler can check the correct assembly of the components and the coherency of the equations by means of dimensional analysis. The implementation is based on the Boost.Units library, which employs template metaprogramming techniques. A dedicated filter for the measurement units data types has been implemented to simplify the compiler messages and thus facilitate the localisation of unit errors. To ensure the reusability of models despite precisely defined interfaces, their interfaces and behaviours need to be parametrisable in a well-defined manner. The enabling implementation techniques for this have been demonstrated with the developed library of generic block diagram component models for the Timed Data Flow (TDF) MoC of the SystemC AMS extensions. These techniques are also the key to integrate a new MoC based on the bond graph formalism into the SystemC AMS extensions. Bond graphs facilitate the unified description of the energy conserving parts of heterogeneous systems with the help of a small set of modelling primitives parametrisable to the physical domain. The resulting models have a simulation performance comparable to an equivalent signal flow model

Principes et réalisation d'une interface de synchronisation interopérable entre modèles de calcul SystemC AMS pour le prototypage virtuel optimisé de systèmes multi-disciplines

The design of embedded systems is currently an increasingly complex problem. These systems tend to become heterogeneous in the sense that they require the integration of components described by means of different physical/engineering disciplines, for example, electrical, optical, thermal, mechanical, chemical, or biological. Besides, these disciplines can be described under different time domains, for example, Discrete Event (DE), Discrete Time (DT), or Continuous Time (CT). To address this problem, designers require modeling and simulation tools to describe the system’s components under different time domains and synchronize them in the same simulation environment. We explore the possibilities of modeling, simulating and synchronizing multi-disciplinary systems in the same environment, using as reference the SystemC Analog/Mixed-Signal (AMS) simulation standard. We analyze the method introduced in SystemC AMS for synchronizing the DE and DT domains, and we identify its drawbacks. Besides, we introduce a new formalization of the synchronization problem, which is used to detect issues in a model before simulation. We propose a simulator prototype called SystemC Multi-Disciplinary Virtual Prototyping (MDVP), which is implemented as an extension of SystemC. It allows the modeling, and the generic hierarchical elaboration and simulation of multi-disciplinary systems, by means of different Models of Computation (MoCs). To build the MDVP simulator, we introduce a synchronization principle to handle interactions between MoCs. In addition, we introduce a methodology to add, in the simulator prototype, MoCs described under different time domains. We apply this methodology to add a Timed Data Flow MoC in SystemC MDVP. This MoC implements the DT semantics introduced by the SystemC AMS standard, and is based on the synchronization principle between the DE and DT domains. Using the TDF MoC, we implement and simulate a case study of a vibration sensor model and its digital front end circuit. This case study includes a feedback loop and several interactions between the DE and DT domains.La conception de systèmes embarqués devient de plus en plus complexe. Ces systèmes sont hétérogènes dans le sens où ils nécessitent l’intégration de composants décrits au moyen de plusieurs disciplines scientifiques, par exemple, l’électricité, l’optique, la thermique, la mécanique, la chimie ou la biologie. De plus, ces disciplines peuvent être représentées dans des domaines temporels différents, par exemple, le domaine des événements discrets, celui du temps discret, ou celui du temps continu. Face à cette situation, les concepteurs ont besoin d’outils de modélisation et de simulation efficaces pour décrire le comportement d’un système hétérogène dans un environnement de simulation unique. Nous examinons la possibilité de modéliser, de simuler et de synchroniser les systèmes multi-disciplines dans le même environnement, en utilisant comme référence la norme de simulation « SystemC Analog/Mixed-Signal (AMS) ». Nous analysons la méthode introduite par SystemC AMS pour synchroniser le domaine des événements discrets avec celui du temps discret, et nous identifions ses inconvénients. Nous proposons une formalisation du problème de synchronisation qui permet de détecter les problèmes existants dans un modèle avant la simulation. Nous proposons un prototype de simulateur appelé « SystemC Multi-Disciplinary Virtual Prototyping (MDVP) », qui est implémenté comme une extension de SystemC. Il permet la modélisation, l’élaboration, et la simulation hiérarchique de systèmes multi-disciplines au moyen de plusieurs modèles de calcul. Pour concevoir le simulateur MDVP, nous introduisons un nouveau principe de synchronisation entre plusieurs modèles de calcul. En outre, nous introduisons une méthodologie pour ajouter, dans le prototype de simulateur, des modèles de calcul représentés par plusieurs domaines temporels. Nous appliquons cette méthodologie pour ajouter un modèle de calcul « Timed Data Flow (TDF) » dans SystemC MDVP. Ce modèle de calcul repose sur la sémantique du temps discret introduite par SystemC AMS, et sur la formalisation du principe de synchronisation entre le domaine des événements discrets et celui du temps discret. Nous mettons en œuvre le modèle de calcul TDF, dans le cas d’un capteur de vibrations et son circuit numérique. Ce modèle comporte une boucle d’asservissement et plusieurs interactions entre le domaine des événements discrets et celui du temps discret

UVM-SystemC-AMS based framework for the correct by construction design of MEMS in their real heterogeneous application context

Each new embedded system tends to integrate more sensors with tight software-driven control, digitally assisted analog circuits, and heterogeneous structure. A more responsive simulation environment is needed to support the co-design and verification of such complex architectures including all its digital hardware/software and analog/multi-physical aspects using Multi-Disciplinary Virtual Prototyping (MDVP). Taking a Micro-Electro-Mechanical System (MEMS) vibration sensor as an example, we introduce a reusable framework based on the state-of-the-art technologies SystemC AMS, Finite Elements/Reduced-Order modeling, and UVM to design, simulate, and verify such systems in their real application context

Goddard Laboratory for Atmospheric Science, collected reprints 1978-1979, volume 1

A ready reference is presented to 61 papers by members of the Laboratory published between January 1, 1978 and December 31, 1979. To avoid unnecessary duplication, only abstracts or introductions of NASA reports and conference proceedings are included with reprints of articles from various journals