12th International Modelica Conference

Session 6: Poster Session

Title: Large Scale Training through Spoken Tutorials to Promote and use OpenModelica
Authors: Kannan Moudgalya, Bhargava Nemmaru, Kaushik Datta, Priyam Nayak, Rahul Jain, Peter Fritzson and Adrian Pop
Abstract:The step-by-step self-teaching approach through audio-video tutorials, known as Spoken Tutorials, has been very successful. About 3.4 million students in India have taken at least one course during the past 6-year period, of which 1.6 million students have attended the rapidly expanding course programme during 2016. This programme has now been expanded by a newly developed course in Modeling and Simulation with Modelica using the OpenModelica open source tool, primarily via the OMEdit graphical user interface. The spoken tutorial programme is exclusively based on free and open source software. This paper gives an introduction to the spoken tutorial approach and presents the recently developed spoken tutorial series for Modelica using OpenModelica. Feedback of participants shows that this series is an effective tool for self-learning of OpenModelica. The paper also presents a new web version that generalises the interactive DrModelica course material, OMWebbook: it enables students to learn Modelica, do text-based modeling exercises, and run simulations without needing to install a Modelica tool. OMWebbook is also planned to be covered in a future update to the spoken tutorial course on Modelica.
Links: Full paper

Title: EMOTH The EMobility Library of OTH Regensburg
Authors: Alexander Grimm and Anton Haumer
Abstract:The importance of E-Mobility is rapidly increasing, not only for private vehicle traffic but also for public transport. In and around Regensburg, Germany there are a lot of automotive companies. Therefore E-Mobility is an important topic in the curriculum of several courses of study at the East-Bavarian Technical University of Applied Sciences Regensburg (OTH). One Master of Applied Research student at OTH has chosen the topic to develop an open-source simulation tool for electric vehicles – the EMOTH Library – based on Modelica and to refine several aspects of the library during the one and a half year of the master course. After one semester, the basic version of the library is available and will be presented in this paper.
Links: Full paper, Additional material

Title: Simulating a Variable-structure Model of an Electric Vehicle for Battery Life Estimation Using Modelica/Dymola and Python
Authors: Moritz Stüber
Abstract:A variable-structure model (VSM) of a battery electric vehicle used for simulating the ageing of the battery pack is presented. The operating principle of the software used to simulate the models is described and a brief summary of the state of science and technology regarding the simulation of VSMs is given. By comparing the performance of the VSM to a conventional model, it is found that the simulation time does not necessarily decrease when replacing a model with a variable-structure version. However, the VSM has advantages regarding the handling of the result files and the possibility to analyse the results.
Links: Full paper

Title: Model Reduction Techniques Applied to a Physical Vehicle Model for HiL Testing
Authors: Romain Gillot, Alessandro Picarelli, Mike Dempsey and Stephen Gallagher
Abstract:To build a full vehicle model entirely based on physical equations is a challenge. To have this model to run fast enough so that it is suitable for Hardware-in-the-Loop testing is even more challenging. The level of detail in the physical representation of the vehicle can always be increased at the cost of simulation time. Even if the performance of the hardware is constantly improving, we still have to compromise. As part of the MORSE (MOdel based Real-time Systems Engineering) project, model reduction techniques are developed and applied to a vehicle model. The results in terms of accuracy and simulation speed are then investigated.
Links: Full paper

Title: Towards Virtual Validation of ECU Software using FMI
Authors: Lars Mikelsons and Roland Samlaus
Abstract:Connected, Automated, Electrified. These three trends in the automotive industry require rethinking of the use of simulation respectively models. The use of models for evaluation of new concepts or stimulating the unit-under-test (in HiL testing), already firmly rooted in the development process of software functions, will not be sufficient to realize visions like autonomous driving or update-over-the-air. One key enabler for such technologies is virtual validation, i.e. the validation or release of software functions in a pure virtual setup. That is, simulation is not only a tool to shorten the development cycle, but one of the key technologies to release future software functions, e.g. highly automated or autonomous driving. In this contribution a feasibility study for the validation of FMI-based virtual ECUs (vECUs) in a co-simulation setup is presented. Thereby, the powertrain and the vECU are represented by FMUs, while the tool CarMaker is used for vehicle dynamics. On the base of the gained experience requirements for the FMI standard are formulated that would allow to go for virtual validation of future software functions.
Links: Full paper

Title: Parameter Estimation based on FMI
Authors: Rüdiger Kampfmann, Danny Mösch and Nils Menager
Abstract:In order to stay competitive the requirements on machinery in the producing industry have enormously increased. Within the automation industry these demands, like higher throughput or better energy efficiency, result in increasing complexity of the installed plants. Additionally, Industry 4.0 and the Internet of Things continuously increase the amount of software. Using model-based development methods is one approach to deal with this complexity. But model-based methods can also be utilized during the operational phase of a plant in order to generate additional value for the plant operator. Introducing smart services based on the usage of physical models enables new control and diagnosis features, e.g. the utilization of inverse plant models for feedforward control or comparing the output of a model with measurements of the plant in order to prove for correct behavior. For all these services the accuracy of the considered models is crucial. With an inexact model neither the future behavior can be foreseen nor the control quality can be improved. The used models don't have to be built up from scratch, existing models already created for sizing can be reused. However, these models cannot be used directly. First a reparametrization is necessary, because effects like friction or manufacturing tolerances cannot be taken into account correctly during sizing. For this special kind of problem dedicated optimization algorithms are available for parameter estimation, which take randomly distributed measurement errors and the special structure of this problem class into account. In this paper a work flow for parameter estimation based on open source tools is presented, in which the considered models are provided as Functional Mock-up Unit. Afterwards the performance of this work flow is demonstrated on a real industrial problem: A three arm Delta Robot.
Links: Full paper

Title: Generic FMI-compliant Simulation Tool Coupling
Authors: Edmund Widl and Wolfgang Müller
Abstract:The Functional Mock-up Interface (FMI) specification provides a simple yet effective definition for co-simulation APIs. Even though the number of simulation tools supporting the export of Functional Mock-up Units (FMU) is growing steadily, there is a considerable number of well-established tools that do not. This paper addresses this issue by introducing a generic and adaptable way of coupling established simulation tools in an FMI-compliant manner. The proposed concept has been implemented as part of the FMI++ library, which is used as basis for FMI-compliant wrappers for the TRNSYS simulation tool and the MATLAB environment. These examples demonstrate the potential of the proposed approach to include well-established simulation tools with minimal effort. This not only enables researchers and engineers to include a diverse range of tools more easily into their work flow, but is also an incentive for tool developers to provide FMI-compliant wrappers.
Links: Full paper

Title: FMI and IP protection of models: A survey of use cases and support in the standard
Authors: Erik Durling, Elias Palmkvist and Maria Henningsson
Abstract:FMI is increasingly being adopted as a standard for exchanging simulation models within and between organizations. Such models often represent significant investments for the model creator. There is thus a large interest in protecting intellectual property while collaborating and sharing simulation model in the form of FMUs. This paper presents a collection of use cases and issues related to IP protection of model contents that have been identified in interviews with industrial representatives. The requirements in each use case are described, along with an investigation of how well the use cases can be managed within the current version of the FMI standard, and proposed extension of the standard.
Links: Full paper

Title: Model-based virtual sensors by means of Modelica and FMI
Authors: Mikel Gonzalez Cocho, Oscar Salgado, Jan Croes, Bert Pluymers and Wim Desmet
Abstract:This paper presents an application case for the estimation of forces using Modelica and the FMI. For that purpose state estimation and model-based virtual sensors are used. These techniques are presented and the development of the state estimation and virtual sensor library for Modelica and the FMI is discussed. This library is developed in Python where the package pyFMI is used with models exported with the FMI 2.0 for model exchange. The technique is used for the estimation of forces and the friction coefficient in a scaled test bench of a vertical transportation system. The model of this test bench is explained and the results of the estimation of forces and the friction coefficient are discussed.
Links: Full paper

Title: Dymola-JADE Co-Simulation for Agent-Based Control in Office Spaces
Authors: Ana Constantin, Artur Löwen, Ferdinanda Ponci, Kristian Huchtemann and Dirk Müller
Abstract:This paper presents an application of coupling Modelica under Dymola and JADE to test novel agent-based control for office spaces. The office space with a coupled energy system and weather boundary conditions are modeled in Dymola. The agent platform is programmed in JADE, where the agents communicate with each other to control the technical equipment used to deliver thermal energy to the room. Heating experiments, run for a one room scenario, using a radiator, show better system reaction to the comfort desires of the user when compared to a control with a thermostatic valve, while having similar energy consumption. While the agents run in real time, the simulation in Dymola runs more quickly. We focus on the particularities of the connection for co-simulation to insure smooth transferability of the experiments from simulation to field test, where the energy system as well as the agent platform would be running in real time.
Links: Full paper

Title: Failure Modes of Tearing and a Novel Robust Approach
Authors: Ali Baharev, Arnold Neumaier and Hermann Schichl
Abstract:State-of-the-art Modelica implementations may fail in various ways when tearing is turned on: Completely incorrect results are returned without a warning, or the software fails with an obscure error message, or it hangs for several minutes although the problem is solvable in milliseconds without tearing. We give three detailed examples and an in-depth discussion why such failures are inherent in tearing and cannot be fixed within the traditional approach. Without compromising the advantages of tearing, these issues are resolved for the first time with staircase sampling. This is a non-tearing method capable of robustly finding all well-separated solutions of sparse systems of nonlinear equations without any initial guesses. Its robustness is demonstrated on the steady-state simulation of a particularly challenging distillation column. This column has three solutions, one of which is missed by most methods, including problem-specific tearing methods. All three solutions are found with staircase sampling.
Links: Full paper

Title: Towards Adjoint and Directional Derivatives in FMI utilizing ADOL-C within OpenModelica
Authors: Willi Braun, Kshitij Kulshreshtha, Rüdiger Franke, Bernhard Bachmann and Andrea Walther
Abstract:Algorithmic differentiation has proven to be an efficient method for evaluating derivative information for implementations of mathematical functions. In the context of the Functional Mockup Interface (FMI) the reverse mode of algorithmic differentiation shows immense promise. FMI is increasingly used for model-based applications, such as parameter estimation or optimal control. The paper motivates the exploitation of algorithmic differentiation and proposes an extension of FMI for the evaluation of adjoint directional derivatives. Attempts to interface algorithmic differentiation libraries with Modelica tools have been made. Instead of generating code for the target language which is instrumented with algorithmic differentiation library API and then compiled, in this new approach the intermediate representation used by the library is generated directly. This avoids compilation of the target language that often takes a large fraction of the overall simulation time. It also avoids model execution in order to create such an internal representation at runtime. The initial results are presented here.
Links: Full paper

Title: PDEModelica and Breathing in an Avalanche
Authors: Jan Šilar, Filip Ježek and Jiří Kofránek
Abstract:This paper presents a Modelica language extension for partial differential equations (PDE) called PDEModelica. Support for this extension is implemented in OpenModelica. This support is limited to 1-dimensional problems and the first and second partial derivatives. PDEModelica is introduced by a string equation model and later by a real life model of respiration during a snow burial. This model describes CO2 advection and diffusion in snow described by advection-diffusion PDE.
Links: Full paper, Additional material

Title: Multirotor Aerial Vehicle modeling in Modelica
Authors: Muhamed Kuric, Nedim Osmic and Adnan Tahirovic
Abstract:This paper presents a generalized multirotor aerial vehicle (MAV) modeling framework which includes rigid body dynamics, gyroscopic effects and motor dynamics. We illustrate how this model can be used to derive any MAV platform constructed with an arbitrary number of rotors by using the quadrotor case as an example. Based on this result, we design the first Modelica-based MAV simulator. We validate the proposed design by using a simple altitude and attitude stabilization control system through a Modelica simulation setup.
Links: Full paper

Title: Rotating Machinery Library for Diagnosis
Authors: Tatsuro Ishibashi, Bing Han and Tadao Kawai
Abstract:This paper presents our new rotating machinery library. Diagnosing the complex system accurately based on stochastic method requires an enormous amount of data, both with and without faults. Acquiring operation data with all kinds of faults for each components is very hard and costly. To generate data for rotating machinery diagnosis, we developed rotating machinery library using Modelica. It provides the basic components such as rotor, shaft, bearing, coupling, housing and support. Its component models are implemented on basis of rotor dynamics theory. This library makes it possible accessing rotating machinery operation data with various faults such as unbalanced rotor, shaft bending and ball bearing faults. To validate our models, we compared both Modelica simulation and experiment with a rotor kit as a test case.
Links: Full paper

Title: Modelling and Simulation of the passive Structure of a 5-Axis-Milling Machine with rigid and flexible bodies for evaluating the static and dynamic behaviour
Authors: Michael Schneider, Anton Haumer and Rupert Köckeis
Abstract:Most of the mechanical simulations for industrial usage are done by finite element (FE-) analysis. Milling machines are mechatronic systems, combining electrical, mechanical and control components for machining certain materials. Modelica provides a powerful and strong tool to simulate different physical ares in one model. For this usage a mechanical model of a 5-Axis-Milling Machine is implemented with rigid and flexible bodies. Specific attention will be paid to which components can be modelled rigid without significant deviation in accordance to the real behaviour of the machine. Two classes of implementing flexible bodies in multi body systems are given by the flexible bodies Library, advantages and disadvantages of both classes will be evaluated. At the end a comparision of the static and dynamic behaviour of the passive structure of the model in contrast to a FE-analysis is given.
Links: Full paper

Title: Modeling and Simulation on Environmental and Thermal Control System of Manned Spacecraft
Authors: Sun Lefeng, Jin Jian, Chen Liping, Liu Wei, Zhou Fanli and Liu Qi
Abstract:In order to support crew resides, key air environ-ment parameters of manned spacecraft should be controlled within index range by environmental and thermal control system. In this paper a model of manned spacecraft environmental and thermal control system in Modelica language is developed. Using this simulation model, we analyze air envi-ronment parameters varying trend as the crew metabolic level variation. The results show that crew metabolic level could influence air envi-ronment parameters dramatically. Furthermore, air environment parameters should be analyzed comprehensively due to important affection of air temperature to oxygen partial pressure, carbon dioxide partial pressure and relative humidity. The work in this paper is helpful to provide a new method for analysis of environmental and thermal control system of manned spacecraft.
Links: Full paper

Title: Modeling and simulation of complex ThermoSysPro model with OpenModelica - Dynamic Modeling of a combined cycle power plant
Authors: Baligh El Hefni and Daniel Bouskela
Abstract:ThermoSysPro (TSP) is a generic library for the modeling and simulation of power plants and other kinds of energy systems. TSP library is developed by EDF and released under open source license. The library features multi-domain modeling such as thermal-hydraulics, neutronics, combustion, solar radiation, instrumentation and control. Numerous organizations and individuals worldwide now use TSP. Until recently, the TSP library could be used only under Dymola for the modeling and simulation of complex power plants. But now, with the latest version of OpenModelica (OM), we can simulate complex models of power plants with complex scenarios. To be able to use TSP under OM, some adaptations have been applied in our models, essentially the method used to make inverse computation. The objective of this work is to evaluate the potentiality, capability and efficiency of using OpenModelica tools to perform dynamic studies of power plants. A combined cycle power plant has been chosen as a representative test case of the complexity of this type of study. The paper describes the dynamic model of a combined cycle power plant, whose objective is to study a step variation load from 100% to 50% and a full gas turbine trip, using OM software. Also, the structure of the model, the parameterization data, the results of simulation runs, the difficulties encountered using OM and the comparing between Dymola and OM are presented.
Links: Full paper

Title: A Power-Based Model of a Heating Station for District Heating (DH) System Applications
Authors: Abdulrahman Dahash, Annette Steingrube and Mehmet Elci
Abstract:District Heating (DH) systems are often seen as a good practical approach to meet the local heat demand of the districts due to its ability to provide affordable and low carbon energy to the consumers. Yet, under today’s regulations to renovate the buildings into more energy-efficient ones, the local heat demand is decreasing. Therefore, the operation of DH systems is also affected by the changing heat demand profile, which might lead to less profits for the operators of DH systems. Thus, the operators of DH systems strive for an optimal operation at which the heat demand is met and the profits are maximized. Due to the fact that these systems are complex-physical systems, therefore it is difficult to conduct any experimental investigation on them in order to examine the optimal operation. Accordingly, it is crucial to create fundamental models to investigate the optimal operation of such systems. In this paper, a power-based model is built to represent the heating station as part of a DH system. Then, the model is validated using real data from an existing heating station in Freiburg, Germany. The validation results reveal that the goodness-of-fit for the model is held to be good enough to test it for operational optimization cases.
Links: Full paper