Object-oriented Modeling Language Research Articles

Virtual design on the heat pump refrigeration cycle: challenges and approaches

Virtual product design (VPD) of the refrigeration cycle has long been a major subject of many engineers and manufacturers. Issues should be the question of how simulation gets close to the real world in virtual ways. It is especially true when we consider variable refrigerant flow (VRF) heat pumps, having various types of indoor unit combinations, long and complicated piping configurations, and simultaneous cooling and heating functions under extreme weather conditions. In this regard, model-based systems engineering (MBSE) or model-based design (MBD) guides a methodology to make a virtual model easily. Now, there are plenty of engineering platforms and tools to make a strong simulation model, which provides interfacing technology among multiple physics, different dimensions, and codes in different languages. In the study, the authors share their experience in the virtual design for a VRF heat pump system including the architecture, multiple physics, and the connection with the control SW. Modelica, an acausal and object-oriented modeling language, constructs the backbone of the model to describe the dynamic behavior of refrigerants and to combine external components in the form of functional mock-up units (FMUs). The developed virtual model is validated against measured data, showing it can reproduce all the essential physics of interest both in qualitative and quantitative ways.

Accounting and Monitoring System of Electricity Expenditures Based on Geospatient Data Consumers Location

The purpose of the research is considers the development and implementation of a system of accounting and monitoring of electricity costs with visualization of geospatial location data by consumers, which provides technical accounting and analysis of the structure of electricity consumption, estimation of electricity consumption for the tasks of planning production volumes and purchasing electricity from producing companies based on consumer expenditure statistics, prevention of losses associated with unauthorized electricity extraction.Methods. When creating a project and software implementation of a system for monitoring and controlling energy consumption, methods of system analysis, methods of designing software for information systems, a unified object-oriented modeling language Unified Modeling Language (UML), DBMS SQLServer, development environment Microsoft Visual Studio Code (VS Code.) were used.Results. During the project, software for a monitoring and control system for electricity consumption with visualization of geospatial data on the location of consumers was developed and implemented.Тhe project was implemented, tested and introduced into the activities of JSC АtomЕnergoSbyt when planning and accounting for electricity supplies to consumers.Тhe testing results showed that the software system fully satisfies the functional requirements, is ready for use and was demonstrated at the exhibition center.Conclusion. А system for recording energy consumption data with visualization of the territorial location of consumers has been developed in order to control consumption and payments. Тhe developed system will solve the problem of delay in receiving readings from metering devices in the data collection system. Visualization of energy resource con- sumption data by objects and their territorial location with linked personal accounts, meters and consumption volumes will allow you to quickly control the volume of supplies and energy consumers. availability of payment, which will reduce unproductive losses and unauthorized connections.For the company JSC Аtomenergosbyt, operational visualization of consumer data makes it possible to analyze the coverage of consumers by territorial basis and plan new connections.

Physical modeling and simulation of electro-mechanical actuator-based TVC systems for reusable launch vehicles

This paper presents the high-fidelity physical modeling of a Thrust Vector Control (TVC) system operated by Electro-Mechanical Actuators (EMAs) for Reusable Launch Vehicles (RLVs). In contrast to simplified, often linear, models, high-fidelity physical models enable a better assessment of the actual system performance and a deeper verification of the on-board software robustness against disturbances, unmodeled dynamics or degradation. This aspect is essential to enable the reusability concept as driven by long-term reliability requirements. Moreover, critical systems like Fault Detection, Isolation and Recovery (FDIR) logic, whose robustness and efficacy are often difficult to prove, can be thoroughly tested without requiring hardware experiments with eventual invasive modifications for fault injections. This work captures the whole dynamics of the EMA and TVC components, including the power drive electronics, the electrical motor, and the mechanical transmission for the EMA, as well as the mechanical properties of the engine nozzle acting as a load. The resulting differential algebraic equation system is modeled in the Modelica acausal object-oriented modeling language. An ad-hoc framework is implemented to guarantee flexibility and modularity, which allows models with different fidelity levels to be easily exchanged to achieve the simulation objectives and needed accuracy level. The impact of the different models on the closed-loop TVC dynamics is analyzed in both the frequency and time domain, and then benchmarked with a realistic RLV mission. The results show that the high-fidelity physical models provide a better understanding of the more complex effects governing the TVC dynamics and can, in turn, effectively improve its requirement definition process.

Research on Intelligent System of Computer Aided Ideological and Political Course Teaching

This paper focuses on the design scheme of the auxiliary teaching system for ideological and political theory courses using J2EE architecture design. In this paper, the overall planning of the system's architecture, work flow, system function, data structure, etc. is carried out, and it is designed and implemented in detail. The system adopts B/S three-tier structure and uses JSP technology to design dynamic pages. Consider using JavaBean to encapsulate the key code of the program from the aspects of system security and code reusability. Use CASE tools and object-oriented modeling language in system design. Through UML modeling language, use VISIO, ROSE and other modeling tools to analyze and design the system to generate conceptual models and entities of the system. Through requirement analysis and detailed design, the user login module, network course module, online examination module, learning resource module and exchange forum module are finally realized. Finally, the thesis assists the realization of the functions of each module of the teaching system, and carries out corresponding tests and verifications, and the system is in the testing stage and plays a great role in practice.

The development of the application for support the intellectual analysis of texts of the humanities and socio-economic cycle

The article is devoted to the consideration of the problems of didactic design of teaching materials by a teacher of disciplines of the humanities and socio-economic cycle associated with the study of a significant amount of information from various sources, the need to select a number of literary sources taking into account their specifics for different educational tasks and types of educational activities, as well as ranking the most important didactic units for the formation of working programs of disciplines. The possibilities of using automation tools for the analysis of text materials are revealed, which will allow a teacher engaged in the didactic design of a particular discipline to conduct a syntactic analysis of methodological materials, significantly reduce the complexity of this process when developing, making changes and adapting courses of social and humanitarian orientation. As a result of the analysis of the subject area, the authors determined a list of functional requirements, based on which the results of the physical and logical design of the system were presented, including a database model, system architecture, as well as a deployment diagram using an object-oriented modeling language.

Advanced GNC-oriented modeling and simulation of Vertical Landing vehicles with fuel slosh dynamics

This paper introduces a flexible framework to enable high-fidelity simulations of the fuel slosh dynamics for verification of the Guidance, Navigation and Control (GNC) algorithms. The sloshing phenomenon must be tackled during the control system design phase and the GNC software run and validated within appropriate simulation frameworks. Equivalent mechanical models can well approximate sloshing under specific assumptions, allowing the derivation of the multibody vehicle’s equations of motion; however, while suitable for analysis and control synthesis purposes, this approach presents several limitations for implementation as a simulation model. In this work, the multibody plant embedding slosh dynamics is modeled by means of the DLR’s Vertical Landing Vehicles Library (VLVLib) written using the object-oriented Modelica modeling language. The advantages of using Modelica are explored throughout the paper. Given that control synthesis, analyses and simulation campaigns are usually performed in the Matlab/Simulink environment, a core point of the proposed solution is to achieve a good synergy within the latter and the Modelica plant model with the least readaptation burden for the developer. The strategies to achieve a full integration and verification tool chain are illustrated. The potential of this approach is demonstrated via two different test cases: a lunar landing scenario of the ALINA spacecraft developed by PTS, and CALLISTO reusable rocket demonstrator.

THE SYSTEM OF SUPPORT FOR THE DIDACTIC DESIGN OF ACADEMIC DISCIPLINES OF THE HUMANITIES AND SOCIO-ECONOMIC CYCLE

The article presents a software package that allows to support the design of teaching materials by a teacher of disciplines of the humanities and socio-economic cycle. The problems of the organization of didactic design by a university teacher with the need to compile directly by an expert teacher supporting lecture notes and other methodological materials, including the need to select a number of literary sources taking into account their specifics for different educational tasks and types of educational activities, are presented. The problems of adaptation and development of methodological materials to changes in the ontology of the subject area are discussed, for example, in connection with changing trends in the scientific environment, when established positions are transformed, which creates a problem for the teacher to additionally engage in didactic design and adjust teaching materials. Thus, there is an urgency of automatic analysis of text materials, which will significantly reduce the complexity of this process when developing, making changes and adapting courses of humanitarian and socio-economic orientation. The step-by-step process of transition from the competence-oriented requirements of the subject area to the functional requirements of the information system is analyzed, on the basis of which a decision-making model was formulated that closely imitates the process of didactic design, subject to automation, and allows using software tools to control its logic. The results of the infological and physical design of the system are presented, including a database model and a deployment diagram using an object-oriented modeling language. Methods and tools of software implementation of the application are discussed with justification of the relevance of their choice for the software solution of the task. The results of the system's operation confirm its functional suitability, and the results of testing allow us to judge a significant reduction in the complexity of the didactic design process by the teacher. The developed tool can be widely used both in the development of educational and methodological materials of the main literature, and for the methodological equipment of the organization of independent work of students.

DOOML: A New Database & Object-Oriented Modeling Language for Database-Driven Web Application Design and Development

A database driven web application is a very common software solution to rising business problems. Modeling the database and the software architecture can be challenging, hence there not being one combined modeling language for database and software architecture, specifically suited for web application development. In this paper we present Database object-oriented Modeling Language (DooML) and its primary Archetype Diagram: a notation for specifying the design of a database schema and corresponding object-oriented software architecture. It combines the syntax for drawing Entity Relationship Diagrams, the Relational Model and Universal Modeling Language Class Diagrams as well to create a mixed diagram, stating database design as well as software design specifications. By default, DooML ensures that the approach of advanced web application development is model-driven and both database-oriented as well as object-oriented.

Validated open-source Modelica model of direct evaporative cooler with minimal inputs

Direct evaporative coolers (DECs) are a low-energy cooling alternative to conventional air conditioning in hot-dry climates. The key component of DEC is the cooling pad, which evaporatively cools the air passing through it. While detailed numerical models of heat and mass transfer have been proposed for the cooling pad, these require many input parameters that are not readily accessible. Alternatively, simplified models lack accuracy and are confined to common types of cooling pad. To address these limitations, we developed and validated a physics-based model, that only needs the nominal data to compute the heat and mass transfer with considerable accuracy. The proposed model is implemented in Modelica, an equation-based object-oriented modeling language. For comparison, a basic lumped model from EnergyPlus based on the efficiency curve of the cooling pad is also implemented. The physics-based model exhibits <2% error from the experimental data and the lumped model exhibits a 12.3% error.

Experiments and Comparison of Digital Twinning of Photovoltaic Panels by Machine Learning Models and a Cyber-Physical Model in Modelica

We present two approaches for digital twinning in the context of the forecast of power production by photovoltaic panels. We employ two digital models that are complementary: the first one is a cyber-physical system, simulating the physical properties of a photovoltaic panel, built by the open- source object-oriented modeling language Modelica. The second model is data-driven, obtained by the application of machine learning techniques on the data collected in an installation of the equipment. Both approaches make use of data from the weather forecast of each day. We compare the results of the two approaches. Finally, we integrate them in more sophisticated hybrid systems that get the benefits of both.

MoHydroLib: An HMU Library for Gas Turbine Control System with Modelica

Modelica is an open-source, object-oriented equation-based modeling language. It is suitable for describing sophisticated dynamic systems (symmetry/asymmetry) as it uses mathematical acausal equations to express physical characteristics. The hydraulic mechanical units (HMU) of gas turbine engine control systems couple the contents of mechanical, hydraulic, symmetry, and other multidisciplinary fields. This paper focuses on the Modelica description method of those HMU models. The content of this work is threefold: firstly, the division form of basic elements in HMU is defined, and the method for describing these element models with Modelica is proposed; secondly, the organization of the element models is defined by using the inheritance characteristics of Modelica, and a lightweight (small code scale) component model is designed; and finally, the causal/acausal connections are designed according to bond graph theory, and the elements and components are integrated into a prototype modeling library. In this paper, the modeling library is verified by comparing simulation results of five typical HMU subsystem models with commercial modeling and simulation software.

Modelica-based modeling and simulation of district cooling systems: A case study

While equation-based object-oriented modeling language Modelica can evaluate practical energy improvements for district cooling systems, few have adopted Modelica for this type of large-scale thermo-fluid system. Further, to our best knowledge, district cooling modeling studies have yet to include hydraulics in piping networks alongside plant models featuring realistic mechanical systems and controls. These are critical details to include when looking to make energy and control improvements in many physical system installations. To fill these gaps, this study released new open-source district cooling models at the Modelica Buildings Library and leveraged these models for a real-world case study at the University of Colorado Boulder. The site includes six buildings connected to a central chiller plant featuring a waterside economizer. Several energy saving strategies are pursued based on the validated model, including control setpoint optimization, equipment modification, and pump setpoint adjustments. Results indicate that a combination of the studied measures can save the campus annually 84.6 MWh of energy, 8.9% of electricity costs, 58.0 metric tons of carbon dioxide emissions, while the waterside economizer cuts down chillers’ run times by 201 days/year, reducing maintenance costs and extending chiller life.

Cyber–physical system modeling with Modelica using message passing communication

Modelica is an object-oriented modeling language whose design and features facilitate the description of cyber–physical systems (CPS). Message passing communication (MPC), seen as the transmission of impulses of information between model components, eases the description of the discrete-event parts of CPS models. However, Modelica does not currently supports MPC. Modelica supports an equation-based component connection rationale, where Modelica tools automatically transform component connections into model equations, following a physical modeling approach. The differences between MPC and Modelica connections are analyzed. A proposal for supporting MPC in Modelica is presented, inspired by the coupled PDEVS model communication approach. The presented MPC proposal is based on the definition of structures to manage messages, named buffers, interface ports and communication channels. Also, an implementation of the proposed MPC mechanism in the form of a new free Modelica library, named MSGLib, is presented. MSGLib includes functionality to manage and dynamically store messages, and describe component communications. Two examples, a pick and place system and a robotic arm, are presented to demonstrate the use of the library, and its combination with other Modelica models.

Технология программной имплементации цифрового двойника в контур IoT управления HVAC-системой

The development of application software for cyber-physical systems of buildings involves the widespread use of Internet of Things (IoT) integration platforms. In practice, the flexible functionality of IoT platforms often leads to additional costs for software enhancement of existing and connection of new units, in particular digital twins. The paper proposes a technological solution for the implementation of a digital twin of the ventilation process in the IoT control loop of heating, ventilation and air conditioning (HVAC) systems for buildings and industrial facilities. The implementation and execution of the digital twin in the form of a dynamic simulation model in the object-oriented modelling language Modelica in the OpenModelica environment is considered. The IoT platform InfluxData, based on the TICK stack, is considered as an example of an integration environment. It is a horizontally-oriented IoT platform that contains the mechanism for collecting data from devices and the InfluxDB time-series database for storing metrics. To integrate simulation models on Modelica with InfluxDB, an OMPython server is proposed. In this case, the integration scripts are executed in the Python language, which as a result extends the traditional capabilities of the IoT platform significantly to the level of a digitally twinned control system. This HVAC control involves adapting control loops by taking into account the dynamics of the air distribution process over the ventilation network, evaluating and compensating for process inertia. The publication was prepared within the framework of the Academic Fund Program at the HSE University in 2020–2021 (grant № 21-04-039).

Quantitative risk assessment of a hydrogen refueling station by using a dynamic physical model based on multi-physics system-level modeling

Numerous accidents in HRSs have been reported worldwide in accident databases; therefore, many researchers have performed quantitative risk assessments (QRAs) of HRSs to enable risk-informed decision making in determining the safety distances or risk mitigation measures. The HRSs, located in urban areas such as Tokyo in Japan, are situated in congested areas with tall buildings and high population density; thus, they have relatively narrow station areas. However, the QRAs are generally suitable for large plants such as nuclear power plants or chemical plants; therefore, relatively small plants or installations, such as HRSs, have not yet been considered as QRA objects. Hence, it is necessary to conduct detailed QRAs with risk analyses and reduce the applied uncertainties for relatively small plants or installations. We applied a model-based approach of risk assessment to model the HRS process using multi-physics system-level modeling and simulated a target system using Modelica—an equation-based, object-oriented modeling language that allows acausal modeling of complex cyber-physical systems The primary aim of this study was to conduct a QRA of an HRS based on multi-physics system-level modeling. First, we modeled the HRS components and physical relationships between the components using basic physical equations. Then, we elucidate a QRA based on the constructed model. The difference in the leakage rates due to the leak positions and dynamic behavior of the model parameters were calculated using the constructed model. Finally, we estimated the individual risks of all the scenarios and compared the resulting risk contours based on the constructed model that includes the hydrogen-fuel dynamic behavior with those based on the traditional model. These results indicate that it is possible to assess whether the risks around the station boundary are acceptable based on the scenario information obtained by evaluating the risks near the station.

Advanced modeling and trajectory optimization of the in-air-capturing maneuver for winged RLVs

Future reusable launch vehicle concepts and their key technologies have been investigated within the DLR research project AKIRA. In this context, several return options for reusable launch vehicles (RLV) were categorized by vertical (SpaceX, Blue Origin) or horizontal landing strategies (Space Shuttle), and then systematically evaluated based on their influence on overall design and technical feasibility. In general, system dynamics, guidance, and control aspects are of special importance within preliminary design studies, in particular if complex and difficult maneuvers like the DLR-patented in-air-capturing method are considered. In this case, the unpowered winged RLV is captured during descent by an aerodynamically controlled capturing device which is connected to an aircraft by a cable. After successful capturing, the launch vehicle is towed back to its landing site.In previous studies, the technical feasibility of the in-air-capturing maneuver was mainly assessed by simulations for an aerodynamically controlled RLV and an aircraft which is assumed to be passive. In contrast to this, we consider an optimal control approach to the problem of in-air-capturing, investigating both passive and active (cooperative) RLV and aircraft operations. To study the risk of failure of the in-air-capturing maneuver, both the initial capturing approach and a subsequent second attempt for recapture after an initial miss are analyzed. For this purpose, a multi-disciplinary multibody modeling and simulation framework based on the object-oriented modeling language MODELICA is used for the consistent flight dynamics modeling of each vehicle including a rigid cable connecting the aircraft and its capturing device. The trajectory optimization results provide an overview of the dynamic behavior of the multibody system for several constraints and flight conditions. Additionally, the results show that for a successful in-air-capturing maneuver with minimum control effort and multiple recapturing attempts, an actively controlled aircraft with drag-increasing subsystems and a cooperative launch vehicle maintaining a suitable flight path angle are recommended. The obtained reference trajectories can be used for future controllability studies and control system design considering a flexible cable and disturbances.

Evolution of the Electricity Distribution Networks—Active Management Architecture Schemes and Microgrid Control Functionalities

The power system transition to smart grids brings challenges to electricity distribution network development since it involves several stakeholders and actors whose needs must be met to be successful for the electricity network upgrade. The technological challenges arise mainly from the various distributed energy resources (DERs) integration and use and network optimization and security. End-customers play a central role in future network operations. Understanding the network’s evolution through possible network operational scenarios could create a dedicated and reliable roadmap for the various stakeholders’ use. This paper presents a method to develop the evolving operational scenarios and related management schemes, including microgrid control functionalities, and analyzes the evolution of electricity distribution networks considering medium and low voltage grids. The analysis consists of the dynamic descriptions of network operations and the static illustrations of the relationships among classified actors. The method and analysis use an object-oriented and standardized software modeling language, the unified modeling language (UML). Operational descriptions for the four evolution phases of electricity distribution networks are defined and analyzed by Enterprise Architect, a UML tool. This analysis is followed by the active management architecture schemes with the microgrid control functionalities. The graphical models and analysis generated can be used for scenario building in roadmap development, real-time simulations, and management system development. The developed method, presented with high-level use cases (HL-UCs), can be further used to develop and analyze several parallel running control algorithms for DERs providing ancillary services (ASs) in the evolving electricity distribution networks.

Implementasi Diagram UML (Unified Modelling Language) Pada Perancangan Sistem Informasi Penggajian

Companies need an information system that supports and can provide fast and accurate data. This research was conducted as an effort to improve the existing payroll system so that it is more effective and efficient. At this time several companies engaged in the payroll system services are still at their maximum, starting from recording attendance to payroll, making it possible when the process takes place there are errors in payroll, inaccurate reports made and late in searching for the required data. The research information system uses object-oriented Unified Modeling Language (UML) software modeling. Researchers use Unified Modeling Language modeling with the aim that the desired system can be provided properly so that problems in the existing system are resolved. This uml modeling process begins with analyzing the system's needs and implementing it in usecase traffic diagrams by making class diagrams, sequence diagrams, and activity diagrams. UML software modeling also provides benefits in software development and is able to monitor the flow or system flow expected by the company. This research also uses the approach waterfall method, namely analysis, design, code generation program, testing and maintenance in designing. This information system design is the best solution to solve problems that exist in the payroll system. The payroll system that utilizes software to support the process provides a very effective contribution to the company and the development process will still be carried out for existing problems.

Port-Hamiltonian Modeling of Thermofluid Systems and Object-Oriented Implementation With Modelica I: Thermodynamic Part

In this paper, we present the physical foundations and the development of the thermodynamic part of a Modelica library with the fundamental components for modeling thermofluid systems. We have chosen Modelica because it is an object-oriented modeling language that allows an elegant design of the library, with a top-down conception that starts from very general components where we model the thermodynamic properties common to all simple substances and descend by inheritance to model the properties of each particular substance. To model the behavior of each component, we have used: classical thermodynamics to define the equilibrium states, the local equilibrium hypothesis of Classical Irreversible Thermodynamics to model the changes of state, and the port-Hamiltonian approach to obtain the equations of the system dynamics. With this formulation, we implement the thermodynamic behavior of ideal gases (including monatomic gases as a particular case), the 2073 substances defined for the CEA (Chemical Equilibrium with Applications) NASA Glenn computer program, the IAPWS Formulation 1995 for the Thermodynamic Properties of Water Substance for General and Scientific Use, and the Syltherm 800 HTF (Heat Transfer Fluid). We also define graphical symbols for each library component that facilitate modeling complex systems with simple drag-and-drop manipulations, component connection, and parameter selection. These symbols are a slightly modified version of those used in bond graphs to facilitate their reading and the representation of the structure of complex systems. We also show the modeling, simulation, and comparison for accuracy, performance, and scalability of some thermodynamic systems implemented with the Modelica Standard Library (MSL) and the proposed library.

Dynamic Modeling and Simulation of Non-Interconnected Systems under High-RES Penetration: The Madeira Island Case

The defossilization of power generation is a prerequisite goal in order to reduce greenhouse gas emissions and transit for a sustainable economy. Achieving this goal requires increasing the penetration of renewable energy sources (RESs) such as solar and wind power. The gradual shrinking of conventional generation units in an energy map introduces new challenges to the stability of power systems as there is a considerable reduction of stored rotational energy in the synchronous generators (SGs) and the capability to control their power output, which has been taken for granted until today. Inertia and primary reserve reduction have a substantial effect on the ability of the power system to maintain its security and self-resilience during contingency events. Such issues become more evident in the case of non-interconnected islands (NII) as they have unique features associated with their small size and low inertia. The present study examines in depth the NII system of Madeira, which is composed of thermal, hydro, solid-waste, wind and solar generation units, and additional RES integration is planned for the near future. Electromagnetic transient (EMT) simulations are performed for both the current and future states of the system, including the installation of planned variable RES capacities. To alleviate the stability issues that occurred in the high-RES scenario, the introduction of a utility-scale battery energy storage system (BESS), capable of mitigating the active power imbalance due to the power system’s disturbances resultant of RES penetration, is examined. In addition, a comparison between a flywheel energy storage system (FESS) and BESS is shortly investigated. The grid has been modeled and simulated utilizing the open-source, object-oriented modeling language Modelica. The dynamic simulation results proved that battery storage is a promising technology that can be a solution for transitioning to a sustainable power system, maintaining its self-resilience under severe disturbances such as rapid load changes, the tripping of generation units and short-circuits.