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RAMS analysis of GNSS based localisation system for the train control application


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Global Navigation Satellite Systems (GNSS) is usually used in non-safety-related applications for various transportation modes. In order to employ GNSS (Global Navigation Satellite Systems) for train control application, numerous projects study if performance of GNSS can satisfy the railway safety requirements. In the railway context, multiple obstacles in local environments can cause different signal perturbations that lead to negative consequences on the position accuracy. Reinforcing the position quality for safety-related applications is necessary. In this context, the European Project - GaloROI is on going. Its working principle is based on the combination of data from GNSS receiver and an Eddy Current Sensor (ECS). According to the development process of GaLoROI system, the dependability and safety analysis is an essential mission in order to prove if it satisfy the safety railway standards. In this paper, we present a procedure for predictive RAMS analysis of a localisation unit based on the combination of GNSS & ECS for the application ”control the braking loop”. Besides capturing multiple local impacts on satellite signal quality, this approach allows us to analyse complex behaviours of the sensor fusion component and also to take into account the reliability parameters of hardware components.
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... Availability requirements are identified as the most challenging obstacles towards GNSS aided positioning systems in [2]. Many approaches [3][4][5][6] can be used to analyse availability properties. Among them, simulation, analytical analysis, and quantitative analysis are popular and practical. ...
... Because of the detailed nature of the model and the corresponding state space size, we first consider a small number of satellites (N ¼4, 5,6,7,8). It is possible, though, that availability properties analysed in these small models will also be exhibited by a more large size (e.g., 17 satellites). ...
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... In [15,16], the authors presented a statistical wide-band analysis for low-elevation satellites based on measured data for channel characterization considering urban, suburban, rural, lightly wooded and heavily wooded environments. In [17][18][19], a narrow-band technique was applied for detecting the Global Navigation Satellite System (GNSS) availability in different geographical areas. Moreover, in [1], a method for optimizing the accuracy of GNSS receivers in urban environments in particular was developed by modeling signals with pseudorange error only. ...
... Moreover, in [1], a method for optimizing the accuracy of GNSS receivers in urban environments in particular was developed by modeling signals with pseudorange error only. The geometrical model used for the urban environments in the aforementioned references ( [1,[17][18][19]) was the conventional street canyon model. ...
The effects of high-rise buildings on satellite propagation in the vicinity of urban canyons are investigated. A comparison between a conventional canyon model (CCM) and two modified canyon models (MCMs), which take into account the presence of high-rise buildings, is presented for both narrow-band and wide-band signal cases. The narrow-band is developed using ray tracing (RT) and includes the direct wave, the specular reflection from building walls and ground and the diffracted waves. In addition, multiple shadow boundaries are defined and used to carry out uniform theory of diffraction (UTD) calculations. The incident shadow boundary (ISB) is the dominant boundary and is used to determine the line of sight 1 region for all cases, while wall and ground reflection shadow boundaries are used to obtain higher precision due to multiple reflections. The wide-band model is developed by applying a channel transfer function to the data obtained from the RT method. The proposed models are used to predict the received signal in a realistic urban environment from satellites. The models are applicable to any satellite link application such as GNSS (Global Navigation Satellite Systems), LEO (Low Earth-Orbiting), HAPS (High Altitude Platform Systems), etc., and results are obtained for a satellite transmitting two linearly polarized signals at a frequency of 1.625 GHz. It is found that the presence of high-rise buildings next to a street canyon can significantly alter the visibility of satellites which in turn lead increase in path loss. Consequently, ignoring high-rise buildings in the proximity of a street canyon can lead to a path loss difference of as much as 30dB.
... The increasing demand for navigation has led to a growing number of GPS applications in the vehicles. In addition to positioning and velocimetry, attitude determination is of critical importance for the emerging control system in vehicles for earth and space [1]- [4], including course-keeping and collision avoidance [5], [6]. Compared with the conventional inertial navigation system [7]- [9], GPS has obvious advantages in terms of maintenance-free, long-term stability and high precision. ...
A multiantenna global positioning system over fiber (GPS-over-fiber) system with real-time line bias monitoring is proposed for attitude determination of vehicles. In the proposed system, GPS signal transmission from multiple antennas to the receiver is achieved via radio-over-fiber links. A phase-derived range measurement scheme is applied to monitor the line bias variation between different optical fibers. Then the carrier phase single difference (SD) model, instead of the carrier phase double difference (DD) model, is used to improve the pitch and roll precision of the GPS-based attitude determination system. Experimental results show that the precision of the pitch and roll is improved by over three times compared with the conventional DD model while the precision of the heading is not reduced.
... The relations between these events are here simplified using classical logical gates (AND, OR) and one type of dynamic gate (DUR-duration-gate). This eFT is then translated following specific rules [106] into a Petri Net model whose transitions integrate appropriate failure probability distributions. The PN can finally be executed with a dedicated simulation tool. ...
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GPS/GNSS based train position locator for railway signalling
  • A Filip
  • L Bazant
  • H Mocek
  • J Cach
A. Filip, L. Bazant, H. Mocek & J. Cach, GPS/GNSS based train position locator for railway signalling, Computers in Railways VII, 2000, ISBN 1-85312-826-0
Railway applications specification and demonstration of reliability, availability, maintainability and safety (RAMS) Part 2: Guide to the application of EN50126-1
EN 50126-2, 2007. Railway applications specification and demonstration of reliability, availability, maintainability and safety (RAMS) Part 2: Guide to the application of EN50126-1. CENELEC European technical report (European Committee for Electrotechnical Standardization).
Railway applications communication, signalling and processing systems safety related electronic systems for signalling
EN 50129, 2003. Railway applications communication, signalling and processing systems safety related electronic systems for signalling. CENELEC European standard (European Committee for Electrotechnical Standardization).