Abstract

Safe railway operation requires a reliable localization of trains in the railway network. Hence, this paper aims to improve the accuracy and reliability of train-borne localization systems proposed recently. Most of these approaches are based on a global navigation satellite system (GNSS) and odometers. However, these systems turned out to have severe shortcomings concerning accuracy and availability. The authors believe that the ability to detect turnouts and the branching direction thereon is the most valuable clue for improvement. Knowing the branching direction provides topological information about the train position. Thus, it complements the geographical information of GNSS and the longitudinal position information of odometers in an ideal way. With such a sensor setup a track-selective localization would be possible even if GNSS is unavailable or disturbed. Therefore, this paper compares the individual benefits of different sensor principles for turnout detection such as inertial measurement units (IMUs), cameras, and lidar (light detection and ranging) sensors. As a consequence, the authors focus on lidar sensors. For those the authors define requirements, review the market, and report the results of a case study in a tramway scenario. The authors proved that it is possible to detect rails, turnouts, and platforms. Finally the authors discuss the findings intensively and give an outlook on further research.

Highlights

  • Infrastructure-based positioning systems as, e.g., described in [1] rely on a multitude of sensors along the track

  • Most train-borne localization systems are based on global navigation satellite system (GNSS) receivers, odometers, and digital track maps [1, 3,4,5,6,7,8,9]

  • We motivated the necessity of a turnout detector and identified lidar sensors as the most promising choice to complement those systems

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Summary

Introduction

828 Computers in Railways XIV require continuous maintenance, suffer from low accuracy and cause a standstill in the case of theft or vandalism [2]. Most train-borne localization systems are based on global navigation satellite system (GNSS) receivers, odometers, and digital track maps An odometer provides the distance covered along the track Tachometers such as the eddy current sensor (ECS) [5, 9, 10] and accelerometers as used, e.g., in inertial measurement units (IMUs) [3, 4, 6,7,8] are alternatives. The map contains information about the railway network, e.g., on geography, geometry, and topology Those systems have severe shortcomings concerning accuracy and availability. Systematic errors of the GNSS position due to multipath effects and jammers, as well as the unavailability of GNSS signals in tunnels, deep valleys, and forests hamper precise localization Those systems cannot guarantee a longitudinal position accuracy of up to 25 cm as stated, e.g., in [1].

Review of different sensor principles for turnout detection
Review of lidar sensors for detecting railway infrastructure
Case study of a lidar sensor in a tramway scenario
Discussion and recommendations for the sensor configuration
Conclusions and future work
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