STAND-LOOP SIMULATION OF AIR TRAFFIC CONTROL SYSTEMS

Introduction

Air Traffic Management (ATM) systems are examples of systems whose successful introduction is impossible without a lot of researches including simulation. This is primarily due to the complexity of the system and the value of real tests. Simulation helps to predict the impact of changes from the very beginning and avoids economic loss in the event of an ineffective concept or functionality. Simulation in ATM plays increasingly important role. A set of simulation tools are developed and widely used around the world. These tools perform simulation both with human in the loop and in automatic mode without human in the loop (fast-time simulation). Simulation tools are widely used for testing and validation of new ATM concepts and technologies, for the evaluation of new airborne procedures, for the evaluation of the airspace structure, etc. Simulations with human in the loop can be conducted both on real air traffic control simulators (e.g. INDRA ATC simulators, Thales-ATM TopSky-ATC simulators, etc.) and on special designed research stands (simulation tools). The examples of such research stands are "TSim" (Si-ATM), "BEST ATC Simulation" (MICRO NAV), "TOPSIM" (ATRiCS), "Airlab" (Thales-ATM), "Integrated ATM Laboratory" (MITRE), "NAVSIM" (4d-Aerospace), "NARSIM"+"TRS" (NLR), etc.

Russian State Research Institute of Aviation Systems (GosNIIAS for short) developed the Research Stand for hardware-in-the-loop and humanin-the-loop simulation of Air Traffic Management System (KIS UVD for short) [3]. KIS UVD includes air and ground components of the ATM. This Research Stand allows to conduct researches on all phases of flight -from gate to gate. The stand is designed for demonstration, simulation and research of new technologies in air traffic management system, new airborne procedures and avionics.

Currently KIS UVD is used for:

• Testing of Prospective Airborne Surveillance Applications, such as Conflict Detection (CD) [4], Airborne Conflict Management (ACM) [5], Enhanced Visual Acquisition(EVAcq) [4], ReRoute (RR), Enhanced Visual Approach (EVApp) [4], Airport Surface Situational Awareness (ASSA) [4], Final Approach and Runway Occupancy Awareness (FAROA) [4],In-Trail Procedure (ITP) [5][6] , Flight-Deck Interval Management (FIM) [7][8].

• Testing of interaction between the pilot and ATC controller based on CPDLC;

• Simulation of new arrival and departure management technologies (AMAN,DMAN);

• Simulation of Advanced Surface Movement Guidance and Control System (A-SMGCS);

• Testing of new algorithms of air traffic flow management (ATFM);

• Evaluation of the airspace structure.

The stand allows conducting distributed simulation across multiple host computers or workstations.

Configuration of models or workstations involved in the simulation may vary depending on the research goals. The stand can include both mathematical models and human-in-theloop and hardware in the loop simulators (e.g. cockpit simulators, ATC workstation, etc.). Depending on the stand configuration the simulation can be conducted in two modes: real-time mode and fast-time mode. Real-time mode is used for humanin-the-loop demonstrations and experiments, fasttime mode is used for fast multiple run simulation without human interaction.

Stand Components

Currently the following mathematical models and workstations are developed and can be connected to the stand (both own and third-party developments) for simulation ( Figure 1):

Figure 1. Research Stand Components

Сoсkpit Simulator

At the same time several cockpit simulators can take part in simulation. Currently three types of cockpit simulators can be connected to the simulation environment: 1) MS-21 prototype cabin developed by

Pseudo-Pilot Workstation

It is a simplified alternative to the cockpit simulator. The main objectives -testing and demonstration of prospective airborne functions and interaction with the air traffic controller (ATCO).

Air Traffic Controller's Workstation

The KIS UVD stand includes 2 air traffic controller working position -"MK-2000" (Softaero, Russia). Such working positions are used by controllers in Moscow Air Traffic Control Centre. In addition to the basic functions the enhanced working position implements advanced functions: 1) receiving and analyzing recommendations from arrival manager (AMAN) systems to delay arrival traffic enroute; 2) MONA function -"the purpose of MONA is to assist the controller in the routine monitoring of the traffic situation, warning the controller when aircraft deviate from their planned route or clearances, reminding the controller of actions that need to be performed, and keeping the trajectories updated with the progress of the flights" [9]; 3) receiving and sending CPDLC-messages; 4) decision support functions during the performance of perspective procedures (ITP, ReRoute, ACM, etc.) Federation. An enhanced version of this ATFM system is integrated into research stand as a part of Central Flow Management Unit Workstation ( Figure 3). System analyses the airspace usage, keeps updated flight plans based on incoming data from the ATC and surveillance systems, performs trajectory prediction and distributes actual flight plan data to other components of the research stand. Based on actual flight plan data system analyses traffic demand and regulates traffic flow by setting ground delays in order to avoid exceeding airport or ATC sector capacity. Regulation measures (delays) are calculated based on optimization algorithm.

Central Flow Management Unit Workstation

Figure 3. ATFM System User Interface

AMAN Workstation

Arrival Manager (AMAN) system prototype provides assistance in metering and sequencing arrival traffic flow [10]. AMAN is intended to solve the "bottleneck" problem of the ATM systemproblems on the surface of aerodrome and in the terminal area. The conflicts (violations of separation standards) in the terminal area and on the runway are predicted based on actual flight plans and on trajectory prediction. AMAN assists to regulate arrival traffic flow. Regulation measures are en-route speed changing, STAR route and STAR en-route transition changing. AMAN recommendations are sent to ATC controller and controller decides accept or reject them. This technology was implemented in the KIS UVD stand.

The main feature of AMAN prototype is automatic optimization algorithm. This algorithm allows to obtain conflict-free arrival traffic flow. Figure 4 demonstrates AMAN user interface.

DMAN Workstation

Departure Manager (DMAN) system prototype provides assistance in metering and sequencing departure traffic flow. DMAN provides control of the departing air traffic flow and prediction of separation standards violations on the threshold of the runway and in the terminal area. DMAN helps to regulate departing air traffic flow by setting ground delays and changing SID route or SID en-route transition. As well as AMAN DMAN has tools for manual regulation departing flow and automatic optimization algorithm. DMAN interacts with A-SMGCS system which controls all of operations on the surface of airport. Figure 5 demonstrates DMAN user interface.

Figure 5. DMAN User Interface

A-SMGCS Workstation

Advanced Surface Movement, Guidance and Control Systems (A-SMGCS) prototype ( Figure 6) is intended to control all of operations on the surface of airport:

1) control of the movement both the aircraft and ground vehicle;

2) detection and prevention of dangerous situations (collision avoidance system);

3) appointment of a parking place; 4) appointment of taxi routes; 5) appointment of tasks for ground vehicle.

The control all of operation on the surface of airport can be performed either automatically when the task of the operator is only monitor the process simulation, or in semi-automatic mode, in which the operator is responsible for handling incoming queries from the models of aircraft and issues the appropriate control commands.

Figure 6. A-SMGCS User Interface

Video Surveillance System at the Airport The video surveillance system prototype ( Figure 7) is designed for to improve the situational awareness of the crew and traffic control services on the movement of aircrafts and ground vehicles on the airfield. The main objective of the model is to analyze the video stream from the external observation cameras of the aerodrome for the detection of all moving aircrafts and ground vehicles including not equipped with ADS-B (Automatic dependent surveillance-broadcast). This prototype also helps to find out how many cameras are required and where they should be installed in the real airport to get best coverage.

Figure 7. Video Surveillance System

1F5-4

Virtual Tower

The virtual tower is designed to simulate the real and the synthetic view from an airport tower. Figure 8 demonstrates virtual tower system, The lower row of monitors displays a model of the real view which receives data directly from the air traffic model and which takes into account simulation time of day and weather conditions at the airport. The topper row of monitors displayed a model of the synthetic sight which receives data from the ground surveillance model and video surveillance system at the airport.

Figure 8. Virtual Tower

Ground Vehicles Model

Ground vehicles model simulates ground vehicle movements on the airport surface. Ground vehicles model provides: 1) moving on a given route from parking place to the appointed place and back; 2) detection of obstacles on the path and the reaction to them; 3) service appointed aircraft. Ground vehicles model simulates airstairs, fuel truck, pushback tug, passenger bus, luggage trolley, escort vehicle, snow cutter and other.

Ground Surveillance Model

Ground surveillance model simulates the measurement, processing and distribution of the trajectory data (received from either radar facilities or ADS-B) and meteorological data.

Weather Model

The weather model simulates the dynamic growth and disappearance of three type of thunderstorm clouds: Single-cell (Figure 9), Multi-cell and Super-cell. Model simulates also the magnitude and direction of the wind.

Figure 9. Spatial Model of a Single-Cell

Thunderstorm Cloud

Air Traffic Model

The air traffic model is designed to simulate the performance of flights based on flight plan information and ATC controller's commands. The aim is to create a realistic air traffic flow. The input data for the air traffic model are planning data, Aircraft Performance Model (BADA), meteorological data and controller's commands. Model allows to simulate: 1) the movement in the air and on the airport surface on the route given by controller.

2) the following actions of the crew and onboard flight navigation and stabilization systems: the interaction with controllers during the flight;

• calculation of the planned flight path and its adjustment in accordance with the controller's instructions

• on-board flight management system's commands to stabilization system 3) the main characteristics of the stabilization system (dynamics of commands' execution, limit changes of the angle of roll, limit changes of the longitudinal and vertical speed) 4) flight management errors caused by the on-board navigation system and its supporting ground-based components, as well as by stabilization system 5) instrument flight 6) autonomous detection of obstacles on the airport surface and the reaction to them.

ATC System Model

The model simulates the ATC system as a whole, doesn't simulate the work of each controller individually, or the interaction between controllers. This model controls whole air traffic in all phases of flight from gate to gate except the flights controlled by operators of ATC workstation and A-SMGCS.

The following system functions can be modeled: 1) air traffic control, conflict (violations of separation standards) prediction, detection and resolution; 2) testing of advanced CNS functions -ITP, ACM, FIM etc.

Research Manager Workstation

Research Manager workstation is a central element of the stand, it is a core. It performs an integrating function for the entire stand, acting as arbiter, which regulates the progress of the simulation and provides information interaction between all components of the stand. Rich user interface allows to support all phases of experiment:

1.Preparation and choosing the prepared experiment scenarios which contain:

• research air traffic flows (based on archive real flight plans from Main Air Traffic Management Centre of the Unified Air Traffic Management System of the Russian Federation);

• airspace structures (based on actual or archive Russian air navigation structure (AIP));

• meteorological conditions (wind, thunderstorm clouds, etc.);

• ground navigation and surveillance equipment;

• configuration data for each component involved in experiment;

• experiments setting (metrics, experiment duration, parameters of random factors, etc.)

2. Choosing stand configuration and providing components involved in simulation all of the initial data;

3. Controlling the experiment (start, stop, changing speed, etc.) 4. 2D-visualization, 3D-visualization of air situation (Figure 10), indications of the simulation process, etc.

5. Analysis and processing the obtained results.

Figure 10. Example of User Interface of Research Manager Workstation

Technical Implementation

The stand allows conduct distributed simulation. Components of the stand can be located in different buildings and even in different cities. Figure 11 demonstrates hardware and software scheme of the stand. Components interact through the protocol based on TCP/IP. The core technology of communication is based on sockets (method for communication between a client program and a server program in a network). Involved in simulation components should connect to server host. This server host is called message manager. Message manager is a part of Research Manager Workstation. All information exchanges between all components of the research stand are performed through message manager. Also message manager performs time synchronization.

Figure 11. Hardware and Software Scheme of KIS UVD

Use of sockets for interaction makes it easy to include new components to the stand, to the simulation environment. For example, the stand has components that run under various operating systems (Windows, Unix) and have been implemented in different programming languages (Object Pascal, C, C ++, JAVASCRIPT, PHP). And they have no problems to be involved in the simulation.

A large amount of information is stored on the common database. All components can be connected to the database, but it is not necessarily. Use a common database realizes the idea of sharing information and collaborative decision making. The database stores the following information: • the meteorological data (archive information regarding the wind blowing);

• Airport Mapping Database AMDB -highaccuracy digital map ;

• Base of Aircraft Data (BADA) -Aircraft Performance Model created by Eurocontrol;

• experiments setting, scenarios.

Simulation

As already mentioned, simulation can be conducted in two modes: with human in the loop and without human in the loop (fast-time simulation). First mode allows to demonstrate controller-pilot interaction when advanced airborne procedures are performed, it allows to validate new technologies, new user interfaces.

The second mode allows to conduct researches by multiple fast-time simulation with statistics collection.

Aircraft's departure time from airports, speed on airways' segments, availability of certain airborne equipment and etc. could be appointed as a variable parameter during a series of statistical experiments. For example, in research of advanced airborne procedures the departure time was a normally distributed random variable with mean equals to scheduled time and with mean square deviation which is set in the experiment settings.

In order to estimate the potential benefits of the advanced concepts and technologies introduction it is accepted in the world practice to assess the performance characteristics and metrics enshrined in international documents [11][12]. Performance characteristics and metrics used in researches on the stand KIS UVD were selected as a result of the analysis of these documents as well as from materials of international air navigation conferences and from published research papers [13][14][15][16][17][18][19].

Currently the following performance characteristics are estimated:

• Airspace access;

• Airspace capacity;

• Efficiency;

• Environment;

• The flexibility of air traffic control;

• The predictability of air traffic;

• Safety. Table 1 demonstrates the performance characteristics and metrics. The process of research on the KIS UVD stand consists of several stages. 3. Data processing. The last stage is a data processing. Researcher analyses results, constructs diagrams and makes conclusions. To assist this stage the Research Manager Workstation allows to export experiments data to Microsoft Excel, then using the capabilities of this mathematical package researcher can obtain additional metrics, build charts and graphs. Based on the metrics researcher draws conclusions about the impact of the new procedures, technologies on the performance characteristics. Therefore the results of research are:

• calculated metrics;

• comparative visualization of the data (graphs, histograms, etc.);

• quantification of changes in the performance characteristics;

• the conclusions drawn on the basis of received information.

Conducted Researches

The following researches were conducted on the KIS UVD stand: 1) Testing of interaction between the pilot and ATC controller based on digital datalink -CPDLC;

2) Testing of the Arrival Management (AMAN) system prototype that provide assist in metering and sequencing arrival air traffic flow in airport Sheremetyevo (SVO);

3) Assessment of the potential benefits from the use of electric taxiing system by simulation of ground movement on airport Sheremetyevo (SVO) surface;

4) Assessment the influence on air traffic characteristics advanced ADS-B-based functions

• In-Trail Procedure (ITP), which enables aircraft that desire flight level changes in procedural airspace to achieve these changes on a more frequent basis, thus improving flight efficiency while maintaining safe separation from other aircraft;

• Flight-Deck Interval Management (FIM) procedure, a set of airborne capabilities designed to support a range of interval management operations whose goal is precise inter-aircraft spacing;

• Airborne Conflict Management (ACM) procedure, which enables aircraft to detect, prevent and resolve air traffic conflicts, thus performing self-separation;

• SURF procedure -airborne traffic situational awareness on airport surface.

5)

Testing of the Departure Management (DMAN) system prototype that provide assist in sequencing departure air traffic flow in airport Sheremetyevo (SVO), testing of DMAN/A-SMGCS systems interaction and collaborative decision making;

1F5-9 6) Assessment of the potential benefits from the use various ATFM procedures.

Conclusion

Research Stand for hardware-in-the-loop and human-in-the-loop simulation of Air Traffic Management System allows conducting distributed simulation from gate to gate. The stand is designed for research, accompanying the development of new functions, procedures, technologies. Stand perform simulation both with human-in-the-loop and in automatic mode without human in the loop (fast-time simulation). KIS UVD stand allows testing of interaction between the pilot and ATC controller, testing new ATM technologies (CDM, ATFM, AMAN, DMAN, SMAN). Also KIS UVD stand is a tool for demonstration of new technologies, tool for analyzing the characteristics of human-machine interface (both pilot and controller) and fast-time simulation tool for assessment of the potential benefits of new technologies and procedures.

[18] J.