Simulation Exploration Experience: A Communication System and a 3D Real Time Visualization for a Moon base simulated scenario

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1 2014 IEEE/ACM 18th International Symposium on Distributed Simulation and Real Time Applications Simulation Exploration Experience: A Communication System and a 3D Real Time Visualization for a Moon base simulated scenario Alberto Falcone, Alfredo Garro Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES) University of Calabria Rende (CS), Italy {alberto.falcone, alfredo.garro}@dimes.unical.it Francesco Longo, Francisco Spadafora Department of Mechanical, Energy and Management Engineering (DIMEG) University of Calabria Rende (CS), Italy {francesco.longo, francisco.spadafora}@unical.it Abstract The paper presents UNICOM, a project based on HLA (High Level Architecture) that aims at providing: (i) flexible communication services to the entities populating a Moon base simulated scenario and (ii) a real-time 3D visualization of this scenario by connecting the MÄK RTI (Run Time Infrastructure) and Unity 3D. UNICOM has been developed in the context of the 2014 edition of the Simulation Exploration Experience (SEE), an event organized by the Simulation Interoperability Standards Organization (SISO), in collaboration with NASA and other research and industrial partners, with the objective to promote the adoption of the HLA standard and compliant tools by involving university teams in the distributed simulation of a Moon base. The paper aims also to share the experience of the University of Calabria Team in participating to the SEE initiative so to encourage and guide the participation of new teams to the next editions of this exciting event. Keywords Distributed Simulation; High Level Architecture; Communication Services; Model-based Design; 3D visualization. I. INTRODUCTION Modeling and Simulation (M&S) is gaining a central role in many application domains, ranging from Energy to Aerospace, due to the increasing complexity of system requirements and thus of the related engineering problems [3]. Specifically, M&S methods, tools, and techniques can effectively support the analysis and design of modern systems by enabling the evaluation and comparison of different design choices against requirements through virtual testing; this opportunity becomes even crucial when complete and actual tests are too expensive to be performed in terms of cost, time and other resources [8, 9, 18, 19]. Moreover, as systems result from the integration of components which are often designed and manufactured by different organizations belonging to different engineering domains (including mechanical, electrical, control, and software), great benefits can derive from the possibility to perform simulations which involve components independently developed and running on different and possibly geographically distributed machines [6]. Indeed, distributed simulation promotes an effective cooperative, integrated and concurrent approach to complex systems analysis and design [6]. In this context, mature international standards and related technologies are available such as the IEEE High Level Architecture (HLA) [12, 13, 15, 17]. HLA represents a reference solution for distributed simulation as it allows several simulation systems (called Federate) to work together through a Run Time Infrastructure (RTI) that is a sort of service bus able to provides information, synchronization, and coordination services to the connected Federates [10, 12, 14, 16]. To promote the adoption of distributed simulation practices, standards, and technologies, since 2011, the Simulation Interoperability Standards Organization (SISO), in collaboration with NASA and other research and industrial partners, has been organizing an annual event, formerly named Smackdown and now renamed Simulation Exploration Experience (SEE) [4]. The main objective of SEE is to provide undergraduate and postgraduate students with practical experience of participation in international projects related to M&S and, especially, to the HLA standard and compliant tools, by involving them in the simulation of a Moon base. Participating universities at SEE 2014, held in Tampa from the 13th to the 16th of April, were: University of Alabama in Huntsville (UAH), Penn State University, University of Nebraska, California Polytechnic Institute, University of Bordeaux, University of Munich, University of Brunel, University of Genoa, and University of Calabria. The UAH team contributed with three HLA Federates: (i) a communication satellite constellation (Comm Sat), (ii) a cargo drone for materials transport (Cargo Transport), and (iii) a mass driver used to launch the cargo drone into the Moon's orbit (Lunar Mass Driver). The team of the Penn State University developed a space vehicle that includes communication, thermal and power subsystems (Lunar Shuttle). The University of Nebraska team created a vehicle that can transfer cargo between facilities and the lunar shuttle (Cargo Rover). The team of the Munich University developed an outpost located at Libration Point Two (L2-Outpost). The California Polytechnic Institute team created an elevator from the Moon base to the L2-Outpost (Space Elevator). The team of the Bordeaux University created a facility to store the supplies (Supply Depot). The University of Brunel team /14 $ IEEE DOI /DS-RT

2 developed three federates: (i) a real-time simulation of an astronaut that delivers regolith from a mine to a factory (Astronaut), (ii) a factory that extracts oxygen and other volatiles from the lunar regolith, based on SIMUL8 (Factory), and (iii) an agent based simulation of lunar regolith mining based on REPAST (Mine). The University of Genoa team produced: (i) an asteroid defense system (IPHITOS), which include an asteroid detection system and a missile base, and (ii) a medical facility (SISMA) that constantly checks the health status of astronauts. Finally, the University of Calabria, contributed with the UNICOM project with the aim to offer flexible communication services to the other entities populating the Moon base as well as 3D real-time visualization services. This paper describes the UNICOM project with the following three main objectives: (i) present and discuss the main encountered issues (and related solutions) in the development of components for HLA-based distributed simulation; (ii) propose an effective solution for providing HLA-based simulation with advanced 3D real-time visualization capabilities; (iii) share the experience of the University of Calabria Team in participating to the SEE initiative so to encourage and guide the participation of new teams to the next editions of this exciting event. The rest of the paper is structured as follows: Section II presents the simulation scenario used as a reference in the development of UNICOM; Section III describes the Agile software development process exploited for the UNICOM project by the University of Calabria Team; Section IV describes both the architecture and behavior of the UNICOM HLA Federate developed to provide flexible communication services to the entities populating the SEE 2014 Moon base scenario; Section V describes the solution implemented for providing a 3D real-time visualization of the simulated scenario by connecting the MÄK RTI [15] and Unity 3D (a leading 3D visualization engine by Unity Technologies) [1]; finally, Section VI concludes the paper and delineates future work. II. THE ASTEROID ALERT SCENARIO The simulation scenario, chosen for proving the effectiveness of the communication and visualization services provided by UNICOM in the context of the 2014 edition of SEE, concerns an emergency situation in which an asteroid is on a collision course with the Moon: the Asteroid Alert Scenario. In this case, the only way to avoid the impact is to intercept and destroy the asteroid with a missile. These activities are handled by the IPHITOS missile base (an HLA federate developed by the University of Genoa, Italy) that through UNICOM alerts the other entities of the emergency situation. In particular, UNICOM sends an Asteroid Alert - ongoing message in broadcast to all the entities that populate the human settlement. Each receiving entity may react to the emergency situation in different ways; e.g. the L2 Outpost federate, developed by the University of Munich, reacts by preparing for a possible evacuation and this decision is notified to the other entities through UNICOM. When the missile (hopefully) intercepts and destroys the Asteroid an Asteroid Alert - all-clear message is send by IPHITOS through UNICOM so to notify the other entities that the emergency is passed. Concerning the visualization services provided by UNICOM in the context of the above described scenario, each sent message is traced by a visible path in the simulated world; the chosen solution consists in drawing enlarging toroids centered on the UNICOM Antenna (see Sections IV and V) whose color depends on the type of message (e.g. red for the alert, yellow for possible protection actions, green for the all-clear). Moreover, UNICOM has in charge to visualize the IPHITOS missile base, the trajectory of the missile and the asteroid. These capabilities are enabled by the joint exploitation of Unity 3D and the MÄK RTI (see Section V). The Asteroid Alert Scenario covers a portion of the whole simulation scenario that has been presented during the SEE 2014 event [20] and that has involved all the entities populating the Moon base that were developed by the participating teams (see Section I). III. THE DEVELOPENT PROCESS The design and implementation of UNICOM has been centered on typical Software Engineering methods and, in particular, on an Agile software development process [11]: after a high-level planning and analysis necessary to outline the scope of the project, the Team has gone through a series of weekly iterations in each of which analysis, design, development and testing activities have been performed (see Figure 1). The objectives to reach in each iteration have been established on the basis of the results achieved in the previous ones, the feedbacks coming from the weekly SEE Technical Meetings, the discussions on the SEE 2014 Google Group, and pairwise interactions with other teams. Fig. 1. The exploited Agile software development process. In order to implement a parallel work organization, some members of the UNICAL Team have worked on the communication aspects of UNICOM, while others have focused on the visualization aspects. This work organization

3 lead on the development of two separate but strongly integrated modules (i.e. HLA federate): (i) UNICOM Communication, and (ii) UNICOM Visualization. The development of the two UNICOM federates has been documented by internal technical reports. In particular, the requirements and both the structural and behavioral design of the two federates have been modeled by using SysML and UML diagrams [5]. External documentation has also been produced and made available on the SEE 2014 Google Group to enforce and enable an effective cooperation with the other teams. In the following Sections the two UNICOM federates are described in details by highlighting their architecture, behavior and peculiar aspects also with references to the typical issues encountered in the development of components for HLA-based distributed simulation [13]. IV. THE UNICOM COMMUNICATION FEDERATE The UNICOM Communication federate provides flexible communication functionalities to the other entities populating a Moon base (e.g. broadcasting of alert and all-clear messages during the Asteroid Alert simulation scenario); its architecture and operation are described in the following. A. Architecture The architecture of the UNICOM Communication federate is shown in Figure 2 by using a UML Class Diagram; in the following its main classes are briefly described. The AbstractUnicomFederate class manages the lifecycle of the UNICOM Communication federate; it includes the management of the simulation time and the synchronization among the objects connected to the RTI. This abstract class is extended by the BaseUnicomFederate and Mode01UnicomFederate that implement the basic and the mode01 operation mode respectively (see Section IV.B). The AbstractUnicomFederateAmbassador class implements the methods that are called by the RTI for interacting with the federate (RTI callback methods); along with the RTI Ambassador interface, which is used by the federate to access the RTI services. Moreover, the AbstractUnicomFederateAmbassador class handles the interactions with the other federates through the use of the Controller class. The SimulationConfig class is used to load the configuration parameters of the UNICOM Communication federate, which are stored in a property file. These parameters include the position of the Antenna expressed in Cartesian Coordinates, the UNICOM FOM module (see below for a description), the selected operation mode (basic, mode01), and others parameters of the Antenna such as: gain, frequency, etc. (see Section IV.C). The information that can be shared and exchanged between UNICOM and the other federates, participating to the Moon base simulated scenario, are defined in a Federation Object Model (FOM) that can result from the merging of several FOM modules [12, 16]. Fig. 2. The Architecture of the UNICOM Communication federate

4 Indeed, a UNICOM FOM module has been defined to model the information provided and handled both by the UNICOM Communication and Visualization federates. Specifically, the UNICOM FOM module is composed of one object class called UNICOM that inherits from the PhysicalEntity class provided by the Smackdown Entity FOM module, and three interactions: broadcastasteroidalert, broadcastl2potential Evacuation and transmissionongoing whose meaning is auto-explicative (see Section II). All these interactions have the same structure that provides a single parameter (called message) containing the payload of the message; specifically, it can be ongoing or all-clear for the broadcastasteroidalert interaction, and ongoing or aborted for the broadcastl2potentialevacuation interaction. The simulation time is managed by a java thread called runningthread in the AbstractUnicomFederate class that handles the federation logical time. Note that the logical time represents the current time within the simulation and typically do not match the wall-clock time and is only closely related to the scenario time (see [7] for a discussion). The above described architecture allows managing adequately the simulation time and the interactions among UNICOM Communication and the other federates during the Asteroid Alert simulation scenario (see Section II). B. Behavior In this section, with reference to the Asteroid Alert scenario, the behavior of the UNICOM Communication federate is described by presenting and commenting UML 2.0 behavioral diagrams. The activities performed by the UNICOM Communication federate are shown in Figure 3 through a UML Activity Diagram. In particular, in the Asteroid Alert scenario (see Section II), the UNICOM Communication federate can receive only two types of interactions: AsteroidAlert and L2PotentialEvacuation coming from the IPHITOS and L2- Outpost federates respectively. Incoming interactions are processed by UNICOM based on two operation mode (see Figure 3): Basic mode, a message is sent by UNICOM to all the entities (represented in the simulation by HLA objects/federates) that populate the human settlement. The sent message is broadcastasteroidalert when the incoming interaction is AsteroidAlert ; broadcastl2potentialevacuation if the incoming interaction is L2PotentialEvacuation ; Mode01 mode, UNICOM retrieves the list of the objects/federates to notify; if the list is empty then the flow of activities ends; otherwise, for each object/federate to be notified: (i) its location represented in term of Cartesian Coordinates are analyzed; (ii) if the location of the object/federate is in the coverage area of the UNICOM Antenna (see Section IV.C) an AsteroidAlert or L2PotentialEvacuation interaction (according to the incoming interaction) is sent to it; otherwise, it is too far away to be informed by UNICOM about the emergency situation; (iii) the list of subscribed objects/ federates is updated. A 3D visualization of the ongoing communication is provided as described in Section V. In Figure 4 the sequence of messages exchanged to complete the startup phase of the UNICOM Communication federate is shown by using a UML Sequence Diagram. Fig. 3. Activities performed by the UNICOM Communication federate

5 Fig. 4. UNICOM Communication: the startup phase. The lifecycle of the UNICOM Communication federate consists of four phases as shown in Figure 5. In the initialization state, the UNICOM Communication federate loads the configuration parameters from a config file using the SimulationConfig class. A transition to the startup state happens if the configuration parameters are valid and during the state transition a connection to the federation execution platform (HLA RTI) is performed. If the configuration parameters are invalid a state transition to the shutdown state is performed. In this latter state, all the resources engaged by the UNICOM federate are de-allocated and the lifecycle terminates. In the startup state, the UNICOM federate checks the connection status. If the connection is not established the lifecycle ends with a transition to the shutdown state. Otherwise, UNICOM publishes its interactions ( broadcastasteroidalert, broadcastl2potentialevacuation and transmissionongoing ), subscribes the interactions published by IPHITOS ( asteroidalert ) and L2Outpost ( L2PotentialEvacuationNotification ) federates, registers its object instance on the RTI platform, and activates the time management thread. If all the actions in the startup state are successfully terminated, a transition to the running state is performed. The running state represents a UML AND-Decomposition state containing two concurrent sub-states: Simulation Time Management and Interactions Management. These sub-states become active simultaneously whenever the composite state becomes active. The Simulation Time Management sub-state handles the simulation time through three states: (i) Waiting: the UNICOM Communication module waits for the TAG (Time Advance Grant) Callback from the RTI. When the callback is received a transition to the processing and update data is performed; (ii) processing and update data: the logical time is updated, the data received from the RTI platform are processed, and then a transition to the make TAR request state is performed; (iii) make TAR (Time Advance Request) request: the UNICOM Communication federate requests to the RTI platform the grant for the next logical time. The Interactions Management sub-state handles the interactions coming from the IPHITOS and the L2Outpost federates. When an interaction is received, a transition from the waiting for interaction state to the processing interaction state is performed. In the processing interaction state the interaction is processed and a transition to the sent interaction is made. In the sent interaction state the UNICOM Communication federate (depending to its operation mode) sends an interaction in broadcast to the federates that populate the moon-base or to a subset of them. Fig. 5. UNICOM Communication: lifecycle

6 When the simulation ends a transition from the running state to the shutdown state is performed and, during the state transition, the UNICOM Communication federate is disconnected from the RTI platform. C. UNICOM Base Station To provide its services, UNICOM is equipped with an Antenna mounted on a tower. The tower is a square-based structure provided with an Omni-directional Antenna that works in Band S (i.e. with frequencies that range from 2 to 4 GHz); see Figure 11 for a possible space-qualified commercial Antenna by Cobham that can be chosen for the purpose. TABLE I. SELECTED ANTENNA FEATURES The receivers can be equipped with the Compact Microstrip Monopole Antenna (CMMA) proposed by NASA (Glenn Research Center, Cleveland) [2]. UNICOM currently works in two different ways: (i) Basic, i.e. the message can be received by all the subscribing entities; (ii) Mod01, i.e. an entity can receive the signal from the Antenna if it is in its line of sight (at the moment, the orography of the terrain has not been considered), see Figure 6 and Section IV.B for details. Fig. 7. UNICOM Visualization federate: enabling technologies. The first step in the implementation of the UNICOM Visualization federate has thus consisted in developing a Java module that joins to the Federation execution, subscribes and publishes the objects and interactions, advances the time, and receives all the messages of the other federates. As the Java module is just a bridge between the SEE Federation and Unity, four different messages that the federate has to send to Unity have been introduced: Discover Object Message, to communicate when a new object is discovered in the Federation; Update Attributes Message, to communicate when an object updates its attributes; Remove Object Message, to communicate when an object is removed; Interaction Received Message, to communicate when an interaction is received. The Java module encodes the information of the message to be sent in an XML-formatted string and send it to the Unity 3D module (see Figure 8 for an example). Fig. 6. Line of sight in the UNICOM Operation Mode Mod01. V. THE UNICOM VISUALIZATION FEDERATE The UNICOM Visualization federate is able to provide a 3D real-time visualization of the Asteroid Alert simulation scenario (see Section II) through Unity 3D (connected through the MÄK HLA) [1, 15]. Currently the UNICOM Visualization federate is set to provide the 3D real-time visualization of the missile base (provided by the IPHITOS federate), of the Antenna as well as of the messages sent through the UNICOM Communication federate, and of the trajectory of the missile and asteroid. Potentially, the UNICOM Visualization federate is able to handle the 3D visualization of the entire Moon base scenario (of the federates connected through MÄK-HLA). A. A Java-based Bridge Module for Unity 3D HLA implementation actually supports mainly C++ and Java languages; to integrate HLA with Unity 3D, that uses the C# language, an ad-hoc bridge Federate that communicate with Unity has been developed in Java (see Figure 7). Fig. 8. Example of an XML-based Update Attributes Message. Each message includes all the attributes and parameters of the considered object or interaction so as that Unity can handle it in the correct way. As sketched in Figure 9, the communication between the Java module and Unity is established by a TCP/IP connection, where the Java module is the server and Unity is the client. Fig. 9. Java-Unity3D Communication

7 B. Architecture The architecture of the UNICOM Visualization federate is shown in Figure 10 by using a UML Class Diagram; in the following its main classes are briefly described. The architecture implements a modular and flexible structure that allows reusing the code to visualize the entire Moon base scenario with affordable effort. BridgeConnection is the class who connects to the Java module by the TCP/IP protocol, and receives the XML-based string messages (see Section V.B). This class calls the handlemessage method of the IManager and passes the string message. IManager receives the string message and, by using a XML parser, understands the type of the message. If it is a Discover Object Message, the IManager looks for an HLAGameObject with the same name of the discovered object and instantiates the object. With a Remove Object Message, the IManager deletes the object. If the message is an Update Attributes Message, the IManager looks for the already instantiated object with the same name and queues the HLA Message in the MessageBuffer of the object. The last type of the message is the Interaction Received Message, in this case the IManager passes the message to the InteractionManagerAbstract. InteractionManagerAbstract has to implement the activities required when an Interaction Received Message is received; this class typically instantiates an HLAGameObject that behaves in a specific way. HLAGameObject manages a Unity 3D counterpart of an object published in the Federation; it implements the MonoBehaviour interface and has a MessageBuffer object. Each HLAGameObject has to be provided with a 3D model to visualize the object in the 3D simulated environment. Acceleration, Position) during the simulation. For each of these objects a related HLAGameObject with a 3D model for its visualization has been developed (see Figures 11 and 12). Fig. 11. Control Base and Antenna Visualization. UNICOM Communication publishes a trasmissingongoing interaction with a message parameter that specifies the type of the message (see Section IV). Fig. 12. Missile on the launch pad, Asteroid and Control Base. The trasmissingongoing interaction indicates to the UNICOM Visualization federate that the UNICOM Antenna located on the Control Base is transmitting a radio signal. To provide an intuitive visualization of this signal, enlarging toroids centered on the Antenna (miming the signal propagation) are drawing by using different colors; specifically: red, for representing an ongoing asteroid alert; yellow, for a potential (or aborted) evacuation of the L2- Outpost; green, for announcing that the asteroid has been destroyed by the missile or it is no more a threat (see Figure 13 and 14 and Section IV.A). Fig. 10. The Architecture of the UNICOM Visualization federate. C. Visualization of the Asteroid Alert Scenario For the SEE 2014 event, the UNICOM Visualization federate interacts with the UNICOM Communication federate and IPHITOS federate of the University of Genoa. IPHITOS publishes an Asteroid, a Missile and a Control base object, and update their attributes (i.e. Velocity, Fig. 13. Visualization of an ongoing asteroid alert situation

8 REFERENCES Fig. 14. Visualization of the all-clear communication and the asteroid explosion. VI. CONCLUSIONS The paper has presented the experience of the University of Calabria Team in participating to the 2014 edition of the SEE (Simulation Exploration Experience) event (formerly named Smackdown ). Specifically, the Team has been in charge of the development of solutions able to provide flexible communication services to the other entities populating a Moon base simulated scenario as well as 3D real-time visualization services. The outcome of Team s work has consisted in two HLA Federate: UNICOM Communication and UNICOM Visualization. The former is able to simulate surface-to-surface communications among the entities populating the Moon base by using the basic publish/subscribe mechanisms provided by HLA; the latter provides an effective solution, based on popular tools such as Unity, for adding 3D real-time visualization capabilities to HLA-based distributed simulation. To achieve the results presented in the paper, the UNICAL team has faced with several difficulties mainly related to the coordination and collaboration issues that inevitably arise when several and geographically distributed teams are jointly involved in a project with tight deadlines. Despite the difficulties encountered, the UNICAL team has pursued with determination its objectives and has been honored with the SEE 2014 Awards for Outstanding achievement in Distributed Teamwork, Collaboration and Interactivity. The Team is currently working on the further experimentation, refinement and enhancement of the proposed solutions with the aim to participate to the next edition of SEE. Hopefully, the experience and related solutions shared by the University of Calabria Team could encourage and guide the participation of new teams to the next editions of this exciting and challenging event. ACKNOWLEDGMENT Authors would like to thank the other members of the SEE 2014 University of Calabria Team that were involved in the development of the UNICOM federates: Pasquale Legato, James Brucato, Alessandro Chiurco, Rina Mary Mazza, and Andrea Tundis. Authors would also like to thank all the people involved in the organization of SEE as well as the members of the other teams for their support and cooperation. [1] 3D Game Engine, Unity3D, available from: accessed May [2] F. Barr, A. Zaman, and F. Miranda, A Compact, Broadband Antenna For Planetary Surface-Tosurface Wireless Communications, in Microwave And Optical Technology Letters, Vol. 48, No. 3, pp , March [3] L.G. Birta, G. Arbez, Modelling and Simulation, Exploring Dynamic System Behaviour, 2nd edition. Springer-Verlag London Limited, [4] P. R. Elfrey, G. Zacharewicz, M. Ni, Smackdown: Adventures in Simulation Standards, Eds. S. Jain, R.R. Creasey, J. Himmelspach, K.P. White, and M. Fu, Proceedings of the 2011 Winter Simulation Conference. [5] S. Friedenthal, A. Moore, R. Steiner, A Practical Guide to SysML, Second Edition: The Systems Modeling Language, The MK/OMG Press, Morgan Kaufmann, [6] R.M. Fujimoto, Parallel and distributed simulation systems, New York, NY: Wiley, [7] R.M. Fujimoto, "Time Management in the High Level Architecture." Simulation, Vol. 71, No. 6, pp , [8] A. Garro, J. Groß, M. Riestenpatt Gen. Richter, and A. Tundis, Reliability Analysis of an Attitude Determination and Control System (ADCS) through the RAMSAS method, in Journal of Computational Science, Vol. 5, No. 3, pp , 2014, Elsevier B.V., Amsterdam, The Netherlands. [9] A. Garro, A. Tundis, On the Reliability Analysis of Systems and SoS: the RAMSAS method and related extensions, in IEEE Systems Journal (IJS), IN PRESS, 2014, IEEE Systems Council. [10] C. Gervais, J. B. Chaudron, P. Siron, R. Leconte, D. Saussié, Real- Time Distributed Aircraft Simulation through HLA, in Proceedings of the 2012 IEEE/ACM 16th International Symposium on Distributed Simulation and Real Time Applications, IEEE Computer Society, [11] J. Highsmith, Agile Software Development Ecosystems, The Agile Software Development Series, ed. A. Cockburn and J. Highsmith, Addison-Wesley, [12] IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) - Federate Interface Specification, IEEE Standard [13] F. Kuhl, R. Weatherly, J. Dahmann, Creating Computer Simulation Systems: An Introduction to the High Level Architecture, Prentice Hall, [14] G. Lasnier, J. Cardoso, P. Siron, C. Pagetti, P. Derler, Distributed simulation of heterogeneous and real-time systems, Distributed Simulation and Real Time Applications (DS-RT), 2013 IEEE/ACM 17th International Symposium on. IEEE, [15] MÄK, VR-Forces: The complete simulation toolkit, available from: accessed January [16] B. Möller, The HLA Tutorial v1.0, Pitch Technologies, Sweden, [17] Pitch Technologies, The simulation toolkit, available from: accessed January [18] L. Rogovchenko-Buffoni, P. Fritzson, A.Garro, A. Tundis, and M. Nyberg, Requirement Verification and Dependency Tracing During Simulation in Modelica, in Proceedings of the 8th EUROSIM Congress on Modelling and Simulation (EUROSIM 2013), Cardiff, Wales, UK, September, [19] L. Rogovchenko-Buffoni, A. Tundis, M. Z. Hossain, M. Nyberg. and P. Fritzson, An integrated toolchain for model based functional safety analysis, in Journal of Computational Science, Vol. 5, No. 3, pp , 2014, Elsevier B.V., Amsterdam, The Netherlands. [20] Simulation Exploration Experience, available from: accessed May