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Steady-state Optimization of Modelica Models and Functional Mockup Units with Pyomo
Full text linkThis paper describes two ways on how to interface Functional Mockup Units (FMUs) and Modelica models through the Pyomo’s foreign function interface with Pyomo. Pyomo is a Python-based, open-source optimization modeling language with a diverse set of optimization capabilities. Modelica has arguably much better modeling capabilities than Pyomo, but Pyomo integrates excellent optimization solvers, such as Ipopt (Wächter et al. 2006), and provides a good optimization infrastructure. The Interface has been developed in the context of a NAWI, (National Alliance Water Innovation) Hub project in collaboration with the University of Connecticut and Sandia National Labs. The optimization has been set up and tested within Modelon’s Modelica platform Modelon Impact. An unpublished, detailed multi-effect desalination plant developed by Prof. Matt Stuber in the context of (Stuber et al., 2015) has been used to demonstrate the capabilities, as well as simple test models, and design models from Modelon’s commercial Libraries
Modelica as Model Aggregator for Holistic Architecture Validation of Electric Vehicles
Full text linkAutomotive OEMs and suppliers are facing recent challenges in the development process, induced by ever shortened product cycles, further distributed development as well as increasing demands for virtual testing and certification using virtual proving grounds or digital twins.
This paper presents a real-life demonstration of a federated, seamlessly integrated design process for a complex cyberphysical system (electric truck), where simulation is used for early-stage performance validation and decision making. Since holistic, but abstract architecture models created in systems engineering discipline contain relevant information with respect to logical system structure and allocated requirements, the simulation domain will benefit from a cross domain linking of model artefacts. By aligning system interfaces across model abstractions and augmenting logical models with physical information, behavioural model templates for design can be generated in a smart, traceable and automated fashion. With the additional information of requirements allocated to certain architectural components in those abstract architecture models, it is demonstrated how scenario-based component and system simulation will contribute to analysis tasks like architecture exploration or specific design optimization in efficient, continuous engineering environments
Evaluating Capabilities of MT Systems in Translating Idiomatic Expressions Using a Specialized Dataset
Full text linkMultiword expressions (MWEs) are generally problematic for machine-translation systems. In this paper, we (i) describe a set, available on CLARIN-IS, of appr. 1,000 idiomatic MWEs which have been translated into English; (ii) use the set as a template for a hidden evaluation set, to be used in a new leaderboard for Icelandic language technology, and (iii) evaluate -- using both automatic and manual approaches -- four MT systems' abilities to translate MWEs from Icelandic to English using both datasets. We find that traditional transformer-based MT systems evaluated commonly fail when translating idiomatic expressions, while LLMs do much better
Validation of Dynamic Simulation Models using Metamorphic Testing and Given-When-Then Patterns
Full text linkAs the maritime industry evolves, there is a focus onsimulation-driven design, testing, and validation usingnovel technology solutions. Simulation models designed torepresent the behaviour and features of real systems areincreasingly available for testing during the early phaseof the full development, but in many cases, their testingsuffers from the availability of test oracles. Metamorphictesting has become increasingly used in differentapplication domains as an approach to test systems when anexplicit test oracle is unavailable. In order to increaseits adoption by domain experts, we combine metamorphictesting with Behaviour Driven development for theverification and validation of simulation models. Thetool-based approach facilitates automated test generationbased on domain-specific custom metamorphic transformationsto generate meaningful test inputs for metamorphic inputrelations. The method also uses features and scenariosextracted from system requirements and domain expertise todefine metamorphic output relations. By automating testgeneration based on system behaviours as features,scenarios, metamorphic transformations, and outputcandidates for metamorphic relations in a Gherkin-likeformat, the tool enables practitioners to verify modelsbased on domain-specific constraints and metamorphicrelation checks. Our preliminary evaluation shows that thetool can detect MR violations in the simulation modelsunder test and that automated test generation providesimproved coverage
Development and Experimental Validation of an Unglazed Photovoltaic-Thermal Collector Modelica Model that only needs Datasheet Parameters
Full text linkThis work introduces the first validated, user-friendly,and accurate open-source photovoltaic-thermal (PVT)collector model in Modelica, tailored for system-levelsimulation and optimization. Current state-of-the-art PVTcollector Modelica models are largely limited tooversimplified, steady-state representations that fail tocapture the dynamic thermal behavior inherent to real PVTsystems. A comprehensive Modelica model is developed basedon the ISO 9806 standard (test method for the quasi-dynamicthermal performance of solar thermal collectors), coupledwith an electrical system model through an internal heattransfer coefficient. The model calibration reliesexclusively on manufacturer datasheet parameters, therebyeliminating the need for parameter estimation frommeasurement data. The model is validated using experimentalresults from an unglazed PVT collector, demonstratingstrong agreement for various (weather) conditions. Thefindings highlight that, while steady-state models maysuffice for conventional solar thermal collectors (STCs),accurate PVT modeling necessitates a dynamic approach,particularly for the thermal aspects. The electrical outputof the PVT collector is less sensitive to transienteffects. In addition to the model formulation andvalidation, this work presents a user-friendly automatedcalibration method based on manufacturer data, andcritically addresses the limitations and potentialtrade-offs of using exclusively datasheet-derivedparameters, thereby providing a transparent tool for PVTsystem simulation, design, and optimization within theopen-source IDEAS library
Centrifugal Pump Model of the DLR Thermofluid Stream Library
Full text linkModeling pumps in 1D flows in Modelica is not new. In thispaper a new approach is presented that can be used forgeneral centrifugal pumps as well as centrifugal pumpsbased on measurement data for the DLR Thermofluid StreamLibrary. The presented model is based on dimensionlessnumbers for good scaling. This approach allows to predictthe pump behavior also for pumps where no measurement dataexist based on data from similar pumps. The models aredesigned with focus on numerically robustness. They avoidnon-linear equation systems and work for zero mass flowrate and/or zero angular velocity. Furthermore care hasbeen taken that extrapolation of the pump data outside thedata range is robust without interpolation artifacts. Apump surge example demonstrates that the TFS can handleinstationary behavior like limit cycles by default withoutany further modifications needed
Simulation of Embodied Cyber Physical System Based on Modelica/MWORKS: A Case Study of Intelligent Unmanned Surface Vessel
Full text linkThis paper proposes a new paradigm of the EmbodiedCyber-Physical System (Embodied CPS, ECPS) to address theissues of the disconnection between physical laws andintelligent decision-making and the insufficientinteraction with dynamic environments in the modeling andsimulation of traditional CPS. ECPS achieves unifiedmodeling of physical laws and autonomous decision-makingthrough the "perception-decision-action" closed loop.Toverify ECPS, an embodied space framework based onModelica/MWorks is designed. Through three majortechnological innovations: constructing an embodied domainmodeling specification and embedding the Navier-Stokesequations into the training of the policy network;expanding the syntax and semantics of Modelica,encapsulating physical constraint reinforcement learningcomponents, and establishing a gradient interactionprotocol between the Physics-Informed Neural Network (PINN)and Modelica equations; building a digitaltwin-hardware-in-the-loop co-simulation platform based onthe FMI/SSP protocol to establish a collaborativeverification link between high-precision physicalsimulation and real-time decision-making.Taking theUnmanned Surface Vehicle (USV) as the carrier, thefull-process method from dynamic modeling, reinforcementlearning strategy training to virtual-real environmentco-simulation is demonstrated. Experiments verify theeffectiveness of this framework in achieving theclosed-loop coupling of physical simulation and intelligentdecision-making under complex sea conditions, providing amethodological foundation for interpretable modeling andverifiable simulation in the development of embodiedintelligence
On the precise and efficient representation of industrial controllers in Modelica
Full text linkThis paper highlights some still-open issues in theModelica representation of industrial controllers,particularly when simulation efficiency must balance withfidelity to their real-world implementation as digitalcomponents of cyber-physical systems. The treatise focuseson PID controllers due to their predominant role, thoughthe ideas readily extend to virtually any other controlstructure. The aim is to stimulate discussion around thisimportant yet often overlooked topic, while also suggestingdirections for future development
Integrating a Seasonal Thermal Energy Storage FMU in a MATLAB/Simscape Thermal Source Network Model
Full text linkThe integration of Functional Mock-up Units (FMUs) enableseffective multi-domain co-simulation and model exchange,offering new possibilities for energy systems modellingconsidering thermo-hydraulic aspects. This paper presents acase study on incorporating an FMU of a seasonal thermalenergy storage (sTES), developed in Modelica/Dymola, into aMATLAB/Simscape model of a thermal source network (TSN).While traditional thermo-hydraulic models are typicallyconfined to a single simulation environment, this studydemonstrates the feasibility and advantages of FMU-basedinteroperability between Modelica/Dymola andMATLAB/Simscape.A key focus is the methodological approach for integratingFMUs into Simscape, addressing interface requirements,solver settings, and model coupling challenges. Toillustrate the impact of FMU integration, the authorspresent simulation results for exemplary operationscenarios: TSN operation with and without an sTES.Additionally, our simulation results offer valuableinsights into the influence of sTES on TSN operation andsystem layout
MultiEnergySystem: A Modelica Library for Dynamic Modeling and Simulation of District Heating and Gas Networks
Full text linkThis paper presents the MultiEnergySystem Library (MESL),an open-source Modelica library designed for the dynamicsimulation of integrated district heating and gas/hydrogennetworks. MESL introduces a fully equation-based fluidproperty formulation, ensuring model interpretability andenabling compatibility with control and optimizationapplications. The library includes dedicated models forhydrogen blending studies and supports gas qualityindicators such as Wobbe Index (WI), Higher Heating Value(HHV), and Specific Gravity (SG). District heating modelshave been experimentally validated using data from areal-world test facility, and these datasets are providedto support reproducibility. While MESL currently focuses onthermal and gas domains, planned expansions include a morecomprehensive electrical package and experimentalvalidation of hydrogen components. The paper describes thelibrary’s design and validation strategy, concluding withillustrative case studies and ongoing development plans