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RAMS analysis of GNSS based localisation system for the train control application
Abstract and Figures
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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... In railway transport, users speak of safety integrity to encompass a larger number of safety lifecycle requirements. The term integrity itself refers to the integrity of the train, that is, the fact that the train has not split and in the further implementation of positioning and unification systems may characterize such functions as diagnostics and reporting of rolling stock failures [23][24][25][26]. ...
... Over the past two decades, several projects have been carried out with research aimed at developing solutions to implement GNSSs in railway applications. The first major projects were APOLO [26,52], GADEROS [53], LOCOPROL [54], GaLoROI [25], and 3inSat [55]. The above projects were implemented in the first decade of the 2000s. ...
This article characterizes and presents Global Navigation Satellite Systems in relation to rail transportation applications. Due to the review character of this article, a synthesis of the literature discussing issues related to the possibility of implementing satellite positioning systems in the framework of their use in the management and control of railway traffic was made. On the basis of the literature review, the area of potential implementation of Global Navigation Satellite Systems was identified, as well as assumptions regarding the architecture of such systems being defined, along with the definition of criteria for assessing the impact of the use of satellite systems on rail traffic safety. The purpose of the above is to direct the development of rail guidance and control systems to systems that enable precise localization of rail vehicles, thereby optimizing the use of rail infrastructure through the implementation of efficient and cost-effective localization systems. This article goes on to characterize existing Global Navigation Satellite Systems and future directions related to the use of new satellite constellations. The basis of this review is the last twenty years of scientific publications on the subject of research issues related to the use of satellite positioning in railway systems. Based on the review of the state of the art and the results of the analysis, it was determined that the most frequently mentioned area of use of satellite positioning systems is the European Train Control System, the functionality of which enables the implementation of the transportation process based on so-called moving block spacing. The results of this review of the current state of knowledge will direct those responsible for the development and implementation of modern systems in the direction and control of railway traffic.
... 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.
... 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). ...
This paper highlights a promising application of the analysis technique of probabilistic verification. We prove that it is able and suitable to analyse GNSS based positioning in aviation sectors for aircraft guidance. In particular, the focus is a widely used formal method called probabilistic model checking, and its generalisation to the analysis of quantitative aspects of a specific civil flight. We construct a formal model of the GNSS based positioning system for this application in the probabilistic π-calculus, a process algebra which supports modelling of concurrency, uncertainty, and mobility. After that, we encode our model in language of the PRISM symbolic probabilistic model checker. We then formalise and analyse the logical properties that relate to the dependability of the underlying system to check the system reliability and availability. We demonstrate how model specification and verification techniques can be successfully applied to the reliability and availability analysis of our case study.
... 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. ...
Railways have already introduced satellite-based localization systems for non-safety related applications. Driven by economic reasons, the use of these systems for new services and, in particular, their introduction in signaling system is seriously investigated today and tested all around the world. Because of the weight of their history, their strong normative context, and the high requested level of safety, the introduction is relatively slow. The aim of this paper is to provide a survey of past and current programs dealing with global navigation satellite systems as a basis to introduce main issues relative to context, standards, performance requirements, and safety proofs. Links with aeronautical concepts are also presented, illustrating the transposable principles and the limits due to the land transport environment.
In the future, many new challenges will arise in the transportation sector, one of which is the increasing urbanisation. This often leads to a reduced availability of public rail transport or even its discontinuation in rural areas. This shortcoming could be addressed by introducing an on-demand rail service with small-sized trains. The focus on on-demand rail transport in rural areas can have strong positive scaling effects and is currently very prominent politically. In order to assess the potential of such a transport service, a status survey of the current equipment and technical possibilities must first be carried out. With this, the possibilities and open challenges of the different components can be debated. These include, for example, the introduction of a smart traffic management system or the communication between the infrastructure and the vehicles or between the vehicles themselves. It can be seen that the technical possibilities that are already available show considerable potential, despite some unresolved issues. It is imperative that the potentials be used, as they entail more attractive connections in rural areas, technological progress through pilot projects and the addressing of major challenges of the future decades.
The accurate and reliable localization of the trains is one decisive factor for a lot of specific location-based railway applications. Considering the cost-efficiency of construction and maintenance, the Global Navigation Satellite System (GNSS) is an effective approach for train localization systems which aim to replace the track-side Balises with on-board sensors. Thus, the accumulative error of the odometer is calibrated by the GNSS receivers and the autonomy of the on-board equipment is surely improved. In order to cope with the uncertainties in raw sensor measurements, the Bayesian filtering frame is adopted to obtain an accurate estimation of the train's state. Based on that, an enhanced particle filter solution is presented to realize iterative estimation. In this method, the cubature Kalman filter (CKF) is involved to generate the proposal distribution by using the track constraint, which indicates a modified kinematical model and an extended measurement model. The coupling of track constraint is designed to generate the importance proposal distribution for the update stage of the sequential importance sampling. Results from simulation with field data demonstrate the capability of the track-constrained particle filter for train localization using GNSS and odometer, which is with great potential for enabling the next generation GNSS-based railway systems.
The development of electrical trains has been requiring advances in the construction of components that are usually supervised by smart systems. Safety aspects are given to redundant capabilities of the new equipments to overcome failures. The new components must obey to internationally recognized standards. For that reason, the electrical supply and the mechanical contacts between train and rails are the key issues to be supervised. The current ISO/IEC/IEEE 1451 is basically helpful for the electrical supply by means of the dedicated transducers. In this paper, a new voltage/current transducer for the train supply is shown and analyzed paying the attention on its reliability, availability, maintainability, and safety approach performed in an innovative way with a specific reference to guidelines of the ISO/IEC/IEEE 1451. At this aim, an extensive theoretical and experimental analysis has been performed using dedicated algorithms developed for the purposes of this research considering reliability aspects according to commercial and defense industry needs.
Global Navigation Satellite Systems (GNSS) are ready for various railway applications, especially the safety-related applications such as train detection and train localisation for the purpose of train control. Every safety-related application for railway should comply with a wide range of railway standards. In order to integrate GNSS into train localisation, a stand-alone satellite-based localisation unit should be developed. Then the demonstration of GNSS quality of service (QoS) should be implemented in consistent with EN50126 (Reliability, Availability, Maintainability and Safety, RAMS) standard. The RAMS standard seeks to evaluate massively the dependability (RAM) and safety aspects during the lifecycle before they are put into operation. However currently there is no RAMS evaluation method for GNSS-based localisation for railways available. In this paper, we propose a procedure and a model for evaluating GNSS in terms of railway RAMS, using the GNSS data derived from a large number of test runs along a railway line in the High Tatra mountains in Slovakia. We start by evaluating the accuracy, availability and then reliability as a whole to represent the QoS along this line. Since the localisation unit depends heavily on GNSS itself (especially satellites, signal in space and receivers), we investigate typical environment scenarios along this line in detail, for example open area, forest, etc. We evaluate quantitatively each scenario according to reliability and availability aspects, and on this basis we analyse the safety risks when GNSS is unreliable but available.
This paper proposes a fusion framework to locate trains travelling on
track routes. The input data are gained from two independent sensor
devices, namely, a Global Navigation Satellite System and an eddy
current sensor device. The sensor data are fused by an Extended Kalman
Filter gaining precise information about the train location. This
positioning system combines the sensor devices with the fusion approach
to perform a robust location even in the case of noise or when a sensor
fault occurs. Additionally, some future fusion strategies to extend the
existing location system are presented.
Data fusion schemes for train localization and parting detection for the “Train Collision Avoidance System” (TCAS) in Indian Railways are described and evaluated. The requirements and constraints for the application are reviewed and the relevance of related technologies reported with the TCAS problem is discussed. The autonomous component of train localization in TCAS should (i) determine the longitudinal (along track) position of the train, (ii) provide reliable velocity measurement for automated braking and (iii) detect accidental train parting by comparing the longitudinal positions of the engine and the last carriage. This paper examines whether the above duties can be performed during GPS outage and GPS dark regions, without using track-side aids. The system engineering issues for selecting sensors and short-listing of data fusion options are discussed in the context of the above requirements. A number of data fusion solutions including a new proposed scheme for longitudinal localization are discussed and compared with two solutions reported earlier. A novel scheme for detecting train parting situation, based on fusion-filters and fault detection approach is also described and its performance evaluated. All the reported schemes use odometer and accelerometer. Parametric performance analyses are performed to select appropriate algorithms, sensor specification and tuning parameters. Representative simulation results are included.
Satellite-based localization technologies are strategic opportunities in railway applications because they offer new possibilities of service and have advantages that current technologies relying mainly on infrastructures deployed along tracks cannot equal. GNSSs (Global Navigation Satellite Systems) can, in particular, offer localization services in ERTMS (European Rail Traffic Management System), the system developed within the European railway community to harmonize, at European scale, railway signalling and control/command systems. However, using GNSS in such safety applications is slowed down when trying to comply with railway standards. Indeed, demonstrations of RAMS properties (Reliability, Availability, Maintainability, Safety) are required on new solutions embedded in trains. They aim at verifying if all dependability (RAM) and safety aspects are controlled over the lifecycle of the solutions before using them operationally. No RAMS evaluation technique exists for systems based on signal propagation and subject to failures provoked by environment effects. The major challenge is so to develop proof methods that will give means to fulfil the railway certification process. In this article, we propose a procedure to work in that direction after having presented the advantages, the possibilities and the challenges to use GNSS in rail transportation. The procedure is based on experiments for the evaluation of RAMS properties related to satellite-based localization units. We apply the method to different position measurements obtained in several typical railway environments. The obtained results are discussed according to the dependability and safety points of view.
Three commonly used analytical techniques for reliability
evaluation are fault trees, binary decision diagrams (BDD) and Markov
chains. Each of these techniques have advantages and disadvantages and
the choice depends on the system being modeled. Fault trees have been
found to be the most popular choice in terms of building an analytical
model of a system. It provides a compact representation of the system
and is easily understood by humans. However, fault trees lack the
modeling power and solution time increases exponentially with the size
of the system being modeled. In this paper, we present a new exciting
hybrid approach, called the modular approach, for the efficient analysis
of both static and dynamic fault trees. It provides a combination of BDD
solution for static fault trees and Markov chain solution for dynamic
fault trees coupled with the detection of independent subtrees. The
algorithms used for modularization, integrating the results obtained
from the separate solution of the independent modules (subtrees) and
incorporating coverage modeling are discussed in detail in this paper.
The modular approach is applied to an example system to demonstrate the
potential of this research
This paper describes a methodology to construct dependability
models using generalized stochastic Petri nets (GSPN) and stochastic
reward nets (SRN). Algorithms are provided to convert a fault tree (a
commonly used combinatorial model type) model into equivalent GSPN and
SRN models. In a fault-tree model, various kinds of distributions can be
assigned to components such as defective failure-time distribution,
nondefective failure-time distribution, or a failure probability. The
paper describes subnet constructions for each of these different cases,
and shows how to incorporate repair in these models
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).