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Train Positioning Systems

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

 

  • MS9000 – 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.