Train Positioning Systems / 列車定位系統
Being able to pinpoint the precise position of a train along the tracks can be
used to increase traffic capabilities, GPS systems being the most popular way to
do so at the moment. However, given that satellite signal is not always
available, autonomous navigation systems are required in order to enhance the
availability of this technique. Not only do MEMS sensors provide a cost
effective solution to this problem, but they also prove very effective,
delivering reliable positioning information such as turn detection even at slow
train maneuvering speeds.
Identifying the position of a train
The readings from the accelerometers measuring acceleration have to be precise
in order to determine the orientation and velocity of a moving train without
external references. Knowing the exact position of the train can tremendously
improve the flow of railway traffic. An effective train positioning system can
be very minimalistic in design, featuring only a few sensors per inertial
platform, especially since altitude isn’t usually an issue in the case of
railways.
The MEMS revolution
Although there are many sensing technologies (capacitive, servo-balancing,
piezoresistive, etc.) competing to provide the best solution for today’s train
positioning systems, none offer the same level of performance in terms of
long-term stability, temperature stability and precision as MEMS capacitive
products, which are not only qualified for safety critical applications, but are
also designed to operate in harsh environments and help drive down maintenance
costs.
System architecture
MEMS sensors are combined with other on-board hardware such as digital maps,
Doppler radar, odometers and are used to generate accurate train positioning
information by combining all of these sources and applying a logical
approximation algorithm for matching railway lines and GPS coordinates.
Advantages of our accelerometers
Our MEMS based sensors are very stable, robust and offer extreme bias stability
over time, being characterized by low power consumption, cost efficiency and the
ability to operate successfully in harsh environments. The MEMS sensors we
produce can be integrated into the on-board hardware and provide a measurement
for acceleration which, combined with readings from other train position
information sources, allows for the precise determining of a train’s location.
Colibrys – positioning ourselves at the top
Colibrys produce the best MEMS capacitive accelerometers renowned for high long
term stability, reliability under harsh conditions, devices that have been
successfully tested and implemented in safety critical railway applications.
Our accelerometers for low g acceleration applications are among the best
products out there in term of short-term and long-term stability, with less than
0.15mg for a ±1g full scale range over one year, that is without mentioning the
excellent bias temperature coefficient, low hysteresis and high repeatability.
Last but not least, our products have a killer combination of noise reduction
and bandwidth, determining the resolution or smallest measurable acceleration.
Colibrys products present a low noise level (9µg/√Hz for a ±1g sensor) and, as a
result, are able to measure angles with a typical resolution of 0.0025° (RMS
noise for 1Hz bandwidth).
Colibrys MEMS sensors for Train Positioning Systems
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TS9001 – Robust and low-power
design for a product that guarantees excellent bias stability and superior
reliability. Full scale range between ±1g. This product has been certified
for safety critical applications.
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