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Peter Gurnk, Oldrich Trgl

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Train position in line segment low accuracy. Trackside wires are needed not ... Possibility of using moving blocks higher density of train transportation ... – PowerPoint PPT presentation

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Title: Peter Gurnk, Oldrich Trgl


1
Peter Gurník, Oldrich Trégl
  • Satellite based train location

2
Content
  • Why want we use GNSS?
  • Possible hazards of using GNSS
  • Safety Requirements
  • GNSS implementation
  • Conclusion

3
Why want we use GNSS?
  • Train location is key information for rail
    transport control
  • Track circuits classical concept
  • Train position in line segment low accuracy
  • Trackside wires are needed not cost effective
  • Fixed block low efficiency of using line
  • ATO is hardly applicable without additional
    technology

4
Why want we use GNSS?
  • New concept passive balise odometry
  • Technology supported in ERTMS project - all
    corridor lines in Europe will be equipped with
    balises future interoperability
  • Passive point device - no trackside wires are
    needed
  • High precise positioning control centre has
    real-time information
  • Possibility of using moving blocks higher
    density of train transportation

5
Why want we use GNSS?
  • Balises vs. GNSS positioning
  • Some countries (Russia, Australia) refused to
    join in ERTMS project because of high cost
  • In average 2 balises per km are needed
  • Implementation of ERTMS in Europe could be faster
    if cheaper technology would exists
  • Virtual balise concept integrating GNSS into
    ERTMS-ETCS could spare some balises on the track
  • We need to find a cheap solution for low density
    lines
  • Efficiency of control suburban lines is low
  • Safety could be improved
  • Poor equipped lines mostly no track circuits
  • Information about train position - based on voice
    communication

6
Content
  • Why we want to use GNSS?
  • Possible hazards of using GNSS
  • Safety Requirements
  • GNSS implementation
  • Conclusion

7
Possible hazards of using GNSS
  • GNSS space segment
  • Faulty satellite can cause unboundary error of
    train position
  • GNSS control segment
  • TTA is not guaranteed
  • Examples from past
  • Faulty navigation message data SVN 35, 1997
  • Satellite clock error PRN 22, 2001

8
Possible hazards of using GNSS
  • Transmission SIS
  • Low availability canyons, tunnels, forests
  • High availability in stations is needed poor
    visibility (urban area)
  • Multipaths common in canyons and on the bridges
    upon the lakes / rivers (reflexive surface)
  • Atmospheric delays
  • Jamming weak signal easy to jam
  • Authenticity of message have to be proved

9
Possible hazards of using GNSS
  • Using commercial GNSS receiver
  • Possible systematic error in HW/SW
  • Problematic determination of position
  • Iterative methods
  • Error could transfer to following fixes
  • Undetected error can expose for relative long
    period of time
  • Stability
  • Some algorithms are unstable in some cases
  • Digital filters
  • Based on statistical methods
  • Some errors could remain masked

10
Content
  • Why we want to use GNSS?
  • Possible hazards of using GNSS
  • Safety Requirements
  • GNSS implementation
  • Conclusion

11
Safety Requirements
  • Safety integrity
  • Ability of a safety-related system to achieve its
    required safety functions under all the stated
    conditions within a stated operational
    environment and within a stated period of time
  • SIL - a number which indicates the required
    degree of confidence that a system will meet its
    specified safety functions with respect to
    systematic failures
  • Standards
  • EN 50126 RAMS
  • EN 50129 Electronic systems for signalling
  • EN 50128 Software for railway control and
    protection system
  • EN 50159-2 Safety related communication in open
    transmission systems

12
Safety Requirements
  • Single faults (EN50129)
  • It is necessary to ensure that SIL 3 and SIL 4
    systems remain safe in the event of any kind of
    single random hardware fault which is recognized
    as possible.
  • Reactive fault-safety (EN50129)
  • Maximum total time taken for detection
    negation shall not exceed the specified limit for
    the duration of a transient, potentially
    hazardous condition.

13
Safety Requirements
  • common-cause failures (EN50129)
  • In systems containing more than one item whose
    simultaneous malfunction could be hazardous,
    independence between items is a mandatory
    precondition for safety

14
Safety Requirements
  • GNSS receiver firmware
  • By the EN 50128 is classified as COTS software
  • Requirements for COTS software
  • A strategy shall be defined to detect failures
    of the COTS software and to protect the system
    from these failures
  • The protection strategy shall be the subject of
    validation testing
  • As far as practicable only the simplest
    functions of the COTS software shall be used
  • Its very hard to accept information's from
    commercial GNSS receiver firmware!

15
Content
  • Why we want to use GNSS?
  • Possible hazards of using GNSS
  • Safety Requirements
  • GNSS implementation
  • Conclusion

16
GNSS implementation
  • Integrity Monitoring
  • Main goal is avoid using faulty satellites in
    position calculation
  • WAAS/SBAS
  • Integrity information from WAAS/SBAS will be
    transferred to train using radio channel
    because of poor visibility of GEO in real terrain
  • LAAS
  • Local monitor station stationary receiver with
    good visibility of satellites
  • Only positive confirmed satellites can be
    included to position calculation in mobile unit

17
GNSS implementation
  • Odometry why is useful?
  • To improve availability
  • In some areas (tunnels, canyons, forests) there
    are still low number of visible satellites we
    cant guarantee the integrity or we are unable to
    compute position
  • To improve precision
  • In some areas an odometry CI is better then CI
    derived from GNSS data processing

18
GNSS implementation
  • Accuracy
  • For resolution of parallel track high accuracy
    is needed
  • High accuracy GNSS positioning method (D-GNSS),
    or
  • Using additional location-oriented devices in
    station
  • Balises

19
Content
  • Why we want to use GNSS?
  • Possible hazards of using GNSS
  • Safety Requirements
  • GNSS implementation
  • Conclusion

20
Conclusion
  • GNSS could be solution for low density lines
  • Technology for low-cost positioning is needed
  • Effort to improve safety
  • Future integration to ETCS
  • Concept of virtual balises
  • Non safety-critical applications
  • Conflict-avoiding systems
  • Information system for passengers and management
  • Real-time tracking of trains

21
  • Ing. Peter Gurník
  • gurnik.peter_at_azd.cz

Ing. Oldrich Trégl tregl.oldrich_at_azd.cz
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