Using Modelica for advanced Multi-Body modelling in 3D graphical robotic simulators

This paper describes a framework to extend the 3D robotic simulation environment Gazebo, and similar ones, with enhanced, tailor-made, multi-body dynamics specified in the Modelica language. The body-to-body interaction models are written in Modelica, but they use the sophisticated collision detection capabilities of the Gazebo engine. This contribution is a first step toward the simulation of complex robotics systems integrating detailed physics modelling and realistic sensors such as lidar and cameras. A proof-of-concept implementation is described in the paper integrating Gazebo collider and the Modelica MultiBody library, and the results obtained when simulating the interaction of an elastic sphere with a rigid plane are shown

Modelica in Area of Thermodynamic and Energy Systems Applications with a Focus on ClaRa Library

The focus of this investigation is the development of an advanced transient model to describe the operation of a coal fired power plant which supplies electric power for a pyrometallurgy unit. Particular attention was paid to the effects of so called „downswings“ (cut-off the electric arc). The performance of the unit during such failures (accumulation of energy in steam boiler during fast transient of turbine power output) was investigated using a dynamic model. The modelling of the power plant was performed on the object-oriented, multi-domain modelling language Modelica and free ClaRa library

The OpenModelica integrated environment for modeling, simulation, and model-based development

OpenModelica is a unique large-scale integrated open-source Modelica- and FMI-based modeling, simulation, optimization, model-based analysis and development environment. Moreover, the OpenModelica environment provides a number of facilities such as debugging; optimization; visualization and 3D animation; web-based model editing and simulation; scripting from Modelica, Python, Julia, and Matlab; efficient simulation and co-simulation of FMI-based models; compilation for embedded systems; Modelica- UML integration; requirement verification; and generation of parallel code for multi-core architectures. The environment is based on the equation-based object-oriented Modelica language and currently uses the MetaModelica extended version of Modelica for its model compiler implementation. This overview paper gives an up-to-date description of the capabilities of the system, short overviews of used open source symbolic and numeric algorithms with pointers to published literature, tool integration aspects, some lessons learned, and the main vision behind its development.Fil: Fritzson, Peter. Linköping University; SueciaFil: Pop, Adrian. Linköping University; SueciaFil: Abdelhak, Karim. Fachhochschule Bielefeld; AlemaniaFil: Asghar, Adeel. Linköping University; SueciaFil: Bachmann, Bernhard. Fachhochschule Bielefeld; AlemaniaFil: Braun, Willi. Fachhochschule Bielefeld; AlemaniaFil: Bouskela, Daniel. Electricité de France; FranciaFil: Braun, Robert. Linköping University; SueciaFil: Buffoni, Lena. Linköping University; SueciaFil: Casella, Francesco. Politecnico di Milano; ItaliaFil: Castro, Rodrigo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; ArgentinaFil: Franke, Rüdiger. Abb Group; AlemaniaFil: Fritzson, Dag. Linköping University; SueciaFil: Gebremedhin, Mahder. Linköping University; SueciaFil: Heuermann, Andreas. Linköping University; SueciaFil: Lie, Bernt. University of South-Eastern Norway; NoruegaFil: Mengist, Alachew. Linköping University; SueciaFil: Mikelsons, Lars. Linköping University; SueciaFil: Moudgalya, Kannan. Indian Institute Of Technology Bombay; IndiaFil: Ochel, Lennart. Linköping University; SueciaFil: Palanisamy, Arunkumar. Linköping University; SueciaFil: Ruge, Vitalij. Fachhochschule Bielefeld; AlemaniaFil: Schamai, Wladimir. Danfoss Power Solutions GmbH & Co; AlemaniaFil: Sjolund, Martin. Linköping University; SueciaFil: Thiele, Bernhard. Linköping University; SueciaFil: Tinnerholm, John. Linköping University; SueciaFil: Ostlund, Per. Linköping University; Sueci

Integrated model concept for district energy management optimisation platforms

District heating systems play a key role in reducing the aggregated heating and domestic hot water production energy consumption of European building stock. However, the operational strategies of these systems present further optimisation potential, as most of them are still operated according to reactive control strategies. To fully exploit the optimisation potential of these systems, their operations should instead be based on model predictive control strategies implemented through dedicated district energy management platforms. This paper describes a multiscale and multidomain integrated district model concept conceived to serve as the basis of an energy prediction engine for the district energy management platform developed in the framework of the MOEEBIUS project. The integrated district model is produced by taking advantage of co-simulation techniques to couple building (EnergyPlus) and district heating system (Modelica) physics-based models, while exploiting the potential provided by the functional mock-up interface standard. The district demand side is modelled through the combined use of physical building models and data-driven models developed through supervised machine learning techniques. Additionally, district production-side infrastructure modelling is simplified through a new Modelica library designed to allow a subsystem-based district model composition, reducing the time required for model development. The integrated district model and new Modelica library are successfully tested in the Stepa Stepanovic subnetwork of the city of Belgrade, demonstrating their capacity for evaluating the energy savings potential available in existing district heating systems, with a reduction of up to 21% of the aggregated subnetwork energy input and peak load reduction of 24.6%.The research activities leading to the described developments and results, were funded by the European Uniońs Horizon 2020 MOEEBIUS project, under grant agreement No 680517. Authors would like to ex-press their gratitude to the operator of the Vozdovac district heating system (Beogradske elektrane) for the specifications used to develop and calibrate the models, and to Solintel M&P, SL for developing the initial versions of the EnergyPlus models (including only the geometrical and constructive definition of the buildings), in the framework of the MOEEBIUS project

State Observer for Optimal Control using White-box Building Models

In order to improve the energy efficiency of buildings, optimal control strategies, such as model predictive control (MPC), have proven to be potential techniques for intelligent operation of energy systems in buildings. However, in order to perform well, MPC needs an accurate controller model of the building to make correct predictions of the building thermal needs (feedforward) and the algorithm should ideally use measurement data to update the model to the actual state of the building (feedback). In this paper, a white-box approach is used to develop the controller model for an office building, leading to a model with more than 1000 states. As these states are not directly measurable, a state observer needs to be developed. In this paper, we compare three different state estimation techniques commonly applied to optimal control in buildings by applying them on a simulation model of the office building but fed with real measurement data. The considered observers are stationary Kalman Filter, time-varying Kalman Filter, and Moving Horizon Estimation. Summarizing the results, all estimators can achieve low output estimation error, but on the other hand only Moving Horizon Estimation is capable to keep the state trajectories within the limits thanks to the constraints at expenses of the computational time. As a first step towards real implementation of white-box MPC, in this paper, we have compared different state estimation techniques commonly applied to optimal control in buildings. We selected three different state observers available from the literature and compared their estimation error and robustness against initial conditions and noise in a numerical case study by using a virtual test bed model of a real building

Evaluating Recharge Options for Phase Change Material Storage of a Personal Conditioning System

Buildings consume about two-fifths of the primary energy in the United States with space heating and cooling taking up one-third of that fraction. Global warming and the associated climate changes have necessitated a rethinking of our energy consumption patterns. Roving Comforter (RoCo) is one such technology being developed with this objective. It enables buildings to save 10-30% of HVAC (Heating, Ventilating, and Air Conditioning) loads by enabling elevation of temperature set-points without compromising occupant comfort. The cooling operation involves an R134a vapor compression cycle operation, which stores the condenser heat into a phase change material (PCM) based thermal storage. Previous studies focused on enhancing the PCM to reduce the recharge time by thermosiphon operation by 40% without a significant increase in the weight of the thermal storage. This enhanced PCM storage needs to be recharged before the next cooling operation, which may be conducted in two different ways. A gravity-assisted two-phase thermosiphon operation consumes very less power but takes a longer recharge time (6 hours) in comparison to a reverse heat pump operation which consumes more power in a much shorter operation time (2.5 hours). The current article uses a validated dynamic models of thermosiphon and heat pump in Modelica to evaluate the overall coefficient of performance for combined cooling and recharge operations. Reduced recharge time from the heat pump recharge leads to increased frequency of the cooling operation enabling savings on building HVAC energy. All these factors are considered in making design recommendations for future prototypes of RoCo, which will save additional energy and provide longer cooling operation to the current prototypes. The modeling framework discussed in the article being generic may be used by researchers investigating vapor compression cycle integration strategies with PCM thermal storages. The article provides interesting insights and quantification of benefits obtained from various strategies adopted for improvement over the first prototype

Modelling and Simulation of the Fifth-Generation District Heating and Cooling

District heating and cooling are efficient systems for distributing heat and cold in urban areas. They are a key solution for planning future urban energy-efficient systems due to their high potential for integrating renewable energy sources. The systems also play an important role in community resilience, which makes them a multidisciplinary research topic. The continuous development of these systems has now reached the fifth-generation whereby end-customers can benefit from the intrinsic synergies this generation offers. A typical Fifth-Generation District Heating and Cooling (5GDHC) system consists of connected buildings that together have simultaneous heating and cooling demands. Local heat pumps and chillers in decentralised substations modulate the low network temperature to the desired building supply temperatures. The demands are potentially balanced by the means of recovering local waste heat from chillers, while also utilising heat pumps to provide direct cooling. The heat carrier fluid in the distribution pipes can therefore flow in either direction in the so-called bidirectional low-temperature network. A balancing unit is incorporated to compensate for network energy imbalances. The exchange of energy flows is realised at different stages within the individual building and across connected buildings. Numerous factors influence the quantity and quality of the exchanged energy flows. Demand profiles in each building, the efficiency of building energy systems, and control logics of system components are some examples of these factors. Investigating this generation using traditional computational tools developed using imperative programming languages is no longer suitable due to system complexity, size variability, and changes adopted in different use cases. Modelica is a free open-source equation-based object-oriented language used for the modelling and simulation of multi-domain physical systems. Models are described by differential-algebraic and discrete equations. The mathematical relations between model variables are encapsulated inside an icon that represents the model. Different component models interface variables through standardised interfaces and connection lines. Large complex systems are composed by the visual assembly of components in a Lego-like approach. Models developed in Modelica can be easily inherited for rapid virtual prototyping and/or edited to adopt changes in the model use. This dissertation has a fourfold objective. Firstly, it demonstrates the development of a simulation model for an installed 5GDHC system located in Lund, Sweden. Secondly, it characterises the components that constitute a 5GDHC system. Thirdly, it unravels the exchange of energy flows at different system levels and describes, in a logical progression, the modelling of 5GDHC with Modelica. Fourthly, it presents ethical risk analyses of the different role-combinations that may arise in 5GDHC business models. The developed model is used in performing annual simulations and to evaluate the system performance under two different substation design cases. The results indicate that adding a direct cooling heat exchanger in each substation can reduce the electric energy consumption at both substation and system levels by about 10 and 7 %, respectively. Moreover, the annual waste heat to ambient air can be decreased by about 17 %. The dissertation fosters an ethical discourse that engages the public and all who take part in the multidisciplinary research on 5GDHC to guarantee safe operation and appropriate services. Future research will build on the models presented in this dissertation to investigate different network temperature and pressure control strategies, in addition to adopting several design concepts for balancing units and thermal energy storage systems