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POTENTIAL OF A TEST ENVIRONMENT FOR RAIL APPLICATIONS R.Rütters, B. Schäfer, T. Engelhardt, D. Abel Institute of Automatic Control, RWTH Aachen University

ENC GNSS 2010

Considering the described features, Galileo will 1. Abstract be a step towards applications that will use safety critical position information. The use of The introduction of the European navigation Galileo within train control systems, for in- satellite system Galileo promises advantages in stance, is expected to result in an augmenta- terms of accuracy, availability and reliability tion of line capacity and a reduction of infra- compared to today’s systems, like GPS and structure costs. GLONASS. These advantages can be essential when using global navigation satellite systems RWTH Aachen University intends to contribute (GNSS) in safety critical applications. Presently to the use of satellite navigation in safety critical RWTH Aachen University is building two Gali- applications like train control. Therefore the test facilities within the project ‘Galileo Galileo testbed railGATE [1] is currently being above’1. These facilities offer the to built. It is part of Galileo above, a project deal- develop innovative GNSS-based applications ing with the construction of two testbeds for au- for automotive and rail prior to the launch of the tomotive and rail. These testbeds permit the Galileo system. In this paper special topics of evaluation and testing of Galileo-based applica- Galileo are introduced in general and the Gali- tions that demand high accuracy and high reli- leo testbed ‘railGATE’ is presented. An initial ability of the GNSS signal. The aim of the project dealing with automated shunting opera- linked initial projects is to show the potential of tions is described. train control with GNSS.

2. Introduction 2.2. Potential for railways

2.1. Galileo Like in other modes of transport Galileo has potential for safety critical applications in the rail In addition to GPS and GLONASS, which were sector, too. Presently applications based on established as military systems, Galileo is the GNSS can only be found in non-safety critical European GNSS with focus on civil use. Pres- areas, like passenger information systems and ently the system is being built and FOC (full traffic management, energy and fleet manage- operational capability) is expected in 2016. ment. [2] Galileo will be the first system with guaranteed availability. Beside the Open Service (OS), High requirements with regard to accuracy, special services for commercial users are pro- availability and reliability have to be met when vided by the Commercial Service (CS). using GNSS signals in the railway domain. Track selective positioning is essential for many It is crucial for safety critical applications to applications. 2 m accuracy is necessary for a have reliable information. Galileo is planned to usual track distance of 4 m. This can be provide integrity information integrated in the achieved by augmentation systems and sensor system. This service will be called Safety-of- fusion. The availability of the position infor- Life-Service (SoL). mation can be augmented by exploiting the characteristic of rail-bound traffic, namely the

movement in one dimension along the track. 1 Sponsored by the Space Agency of the German Aerospace Centre (DLR) with funding by the Federal Ministry of Economics Together with a digital track map, fewer satel- and Technology, in compliance with a resolution of the German Parliament (project/grant no. 50 NA 0902).

1 lites are needed to calculate the position solu- GATE is being installed and will be in regular tion. service at the end of 2010. The focus of avia- tionGATE is the use of Galileo pseudolite sys- A safety critical application for Galileo in the rail tems for the start and landing phase of planes. sector is train control. In higher levels of the European Train Control System (ETCS) a train needs to determine its position autonomously. 4. The railGATE The combination of Galileo with an odometry For the project railGATE RWTH Aachen Uni- platform is a reasonable alternative for existing versity is building a so-called pseudolite sys- systems, especially on regional lines [3]. Be- tem. This system allows positioning with a tween 2005 and 2008 the GRAIL consortium specified accuracy of 0.8 m (1 σ, carrier phase developed a strategy for the introduction of solution); the update rate will be 20 Hz. Com- GNSS in the rail sector particularly for ETCS, plex scenarios can be demonstrated in the test funded by the Galileo Supervisory Authority environment because of the system’s ability to (GSA) [4]. The consortium revealed potentials serve multiple users. The pseudolite transmit- concerning the enhancement of the odometry ters will be placed on poles that already exist or platform accuracy, as well as train integrity have to be erected. The new poles will have a check. height up to 60 m in order to guarantee an op- timal coverage of the test area. Applications Another use case for GNSS in the railway do- can be tested in the test environment before main is being developed by the German Aero- the start of Galileo. After FOC, the system can space Centre (DLR), especially for regional also be used as an addition to Galileo. Applica- lines. The Railway Collision Avoidance System tions can be tested in arbitrary and reproducible (RCAS) was presented in May 2010. scenarios. The feasibility of an automated shunting system The railGATE will be installed in the Siemens based on GNSS will be demonstrated at RWTH Test- and Validationcenter Wegberg- Aachen University. The first steps are de- Wildenrath (PCW, [6]). PCW is used by many scribed in section 5. European manufacturers for testing not only vehicles but also infrastructure elements. On its 3. Galileo Testbeds 28 km of railway tracks the PCW allows tests of nearly any kind of vehicle, from trams to high To establish the use of GNSS sensors in safety speed trains, under realistic conditions and in- critical applications, still a large research effort dependent of constraints encountered on regu- has to be made. To contribute to this work, Gal- lar tracks. Therefore PCW offers ideal condi- ileo test environments are built. The Space tions for research activities. Agency of the German Aerospace Centre (DLR) funds the installation of Galileo Test En- vironments (GATEs). There will be five GATEs in Germany. Each has a different focus. The GATE in Berchtesgaden [5] is the first GATE in Germany and is operational since 2008. The focus is mainly the development of receivers and applications in general. Users have the chance to test their equipment with regard to Galileo specification. In the sea port of Rostock maritime Galileo applications can be tested with the Sea Gate. Within the project a Galileo- based docking assistant was developed for the “Mecklenburg-Vorpommern” ferry as a refer- ence application. The application is based on Figure 1: Siemens Test- and Validationcenter Wegberg-Wildenrath, © Siemens AG the Sea Gate’s accuracy of 0.5 m. In the re- search airport of Braunschweig the aviation- Figure 2 shows the track system of PCW as

2 well as the position of the eight pseudolite bust mobile box, that can be installed on any poles. A special challenge is the partly dense kind of ground-based vehicle. Additionally the vegetation of the area. For railGATE six of eight user segment can use multiple data sources. It poles have to be newly erected. First system can combine pseudolite and GNSS satellite da- tests are planned for springtime 2011. railGATE ta. For example, these modes of operation in- is expected to be fully operational in autumn clude information from GPS satellites and 2011. EGNOS in any reasonable combination.

4.1. Technical Properties Like regular navigation satellite systems railGATE is divided into three segments:

• transmitting segment / space segment • user segment • monitor and control segment

A wireless network will be installed for commu- nication purposes. All components send their data to a central server that records all data for replay and evaluation of tests.

A. Transmitting segment / space segment RailGATE consists of eight pseudolites, which cover the area with signals similar to the Galileo SIS ICD. The message broadcast by the pseu- dolites is freely scalable and thus can be adapted to specific application purposes. A Figure 2: Illustration of the railGATEs pseudo- pseudolite consists of the components: lites, © RWTH/IRT

• Galileo signal generator C. Monitor and control segment (MCS) • Timing unit for synchronizing individual The MCS consists of a reference receiver with- pseudolites among each other in the testbed and a central server that records • Communication component for commu- and analyses data. It monitors and controls the nication between the pseudolites and pseudolites in terms of timing, e.g. It can also the control station provide information for a differential working mode of the system. The MCS can influence B. User segment and degrade the system purposefully, if a spe- In the user segment standard Galileo receivers cial GNSS scenario is needed. The incoming are used, that are capable of receiving the data is visualized. For example it will be possi- pseudolite signals. The raw data is processed ble to monitor the position of each receiver in by a computer-based evaluation unit that calcu- the testbed. Relevant system data, like accura- lates the user position. Presently no navigation cy are also shown to the operator. message is defined for local elements in the SIS ICD. Therefore the user segment needs 5. Initial project the information of the pseudolites’ position to be able to calculate a user position from the The initial project rail has two focuses. First it pseudorange measurements. This is done by has to proof the proper function of railGATE; the evaluation unit. The data is then provided to secondly it is a first step towards the use of a user in the standard NMEA format. The user Galileo pseudolites in a rail application. The segment calculates actual data on time, posi- project goal is an accurate satellite-based stop- tion, speed and direction of the user’s motion. ping at a defined point. This is a basic function The user segment has to work in a rough envi- of the automated shunting system described in ronment, therefore it will be a compact and ro- [7]. To make the transport of cargo on rails

3 more attractive, the project’s goal is to optimize actions. The research is presently done at the the shunting process on small railroad lines. Institute of Automatic Control of RWTH Aachen The main part of cargo is processed in few University in cooperation with the Institute of huge and highly automated shunting yards. Be- Railway Systems. For the project a test vehicle cause of the high degree of automation these is used. yards are highly efficient. When transporting small amounts of cargo long retention times in The vehicle is equipped with a Diesel aggre- the shunting yards decrease the attractiveness gate and a control unit that executes the driving of this mode of transport. The efficient marshal- commands. The control unit is a rapid control ing in small, local yards seems to bring ad- prototyping system, which can be adapted and vantages in certain constellations. These ad- programmed quickly. The test vehicle has a vantages can be increased if labour cost can large variety of sensors, which can be used for be reduced when the process is further auto- control algorithms. Based on the sensor infor- mated. Considering that rail-bound systems are mation the locomotive’s movements are influ- suitable for automation because of their specific enced. Beside a GNSS receiver (presently properties, the development of an automated GPS, it will be replaced by a railGATE Galileo shunting system is obvious. receiver) the sensors are an optical velocity sensor, a wheel pulse sensor and an inertial measurement unit. Furthermore it has to be fig- ured out which sensors have to be used in ad- dition to the satellite signal to provide the re- quired system performance. At the railGATE test environment, the robustness of the system in different error scenarios will be tested.

[1] R. Rütters, M. Baier: Go-ahead for railGATE. In: COUNTDOWN 10, Issue 2/09, July 2009, P. 49-53, ISSN 1864-6123

[2] M. Schmidt; J. Winter: Anforderungen der GPS- Figure 3: Test Vehicle of RWTH Aachen, basierten Ortung an den digitalen Streckenatlas. © RWTH/IFS SIGNAL + DRAHT, 2000, Issue 4. [3] B. Stadlmann, H. Zwirchmayr: Einfaches Zugleitsys- The system will be semi-automated in the first tem für Regionalstrecken. SIGNAL + DRAHT, 2004, implementation, which means that the shunting Issue 6. operation is done automatically, but every task will be acknowledged by an operator before it is [4] A. Urech, INECO: GRAIL: GNSS Introduction in the executed. The system is subdivided into three RAIL sector. Final Activity Report, December 2008 parts. A disposition system is the main control- [5] G. Heinrichs, E. Löhnert, H. Mundle: GATE - the ler of the system. It optimizes the system’s ac- German Galileo test & development environment for tions and sends information to the other com- receivers and user applications. Proceedings of the ponents. The other components are the shunt- 2nd ESA Workshop on Satellite Navigation User Equipment Technologies, NAVITEC, 2004 ing locomotive with its controller and the Hu- man-Machine-Interface (HMI). The HMI is a [6] Siemens AG: Test- and Validationcenter Wegberg- handheld computer that an operator uses to Wildenrath. interact with the system. All components are www.transportation.siemens.com/mobility/de/pub/sch connected to each other by wireless radio. The ienenverkehr/pruef_und_validationscenter.htm shunting locomotive receives shunting tasks, [7] R. Rütters, B. Schäfer, M. Baier, D. Abel: Validation which are autonomously fulfilled by the control- of Satellite-based Railway Application Systems Using ler. The safety of the automatic shunting sys- the GALILEO Testbed railGATE Exemplified by Au- tem depends on the ability of the locomotive to tomated Train Formation Facilities. In: The 9th Inter- accurately stop at a predefined point. This national Conference on Intelligent Transport System Telecommunications - ITST 2009, October 20/22, guarantees, that a locomotive stops exactly at a 2009, Lille, France, pp. 337-342, ISBN 978-1-4244- car, so it can e.g. be coupled without further 5347-4

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