Denis D'Aoust


Wayside Inspection Devices Inc. (WID)
United States

Integrating wheel sensors into laser based wayside monitoring systems


  • Usage of wheel sensors as a key component of the TBOGI system
  • TBOGI-HD, a laser based wayside monitoring system


TBOGI-HD is laser based wayside monitoring system manufactured by Wayside Inspection Devices Inc. (WID) in Rigaud, Canada that scans passing trains to directly measure by optical means the angle of attack (AOA) and tracking position (TP) of each axle of the train. Measurement data of each axle is combined for each bogie to calculate derived bogie performance parameters as well as bogie lateral instability (hunting).

A key component of the TBOGI systems are the wheel sensors that are used to detect the presence of a train, toggle the data acquisition on and off, measure axle speed, measure distance between axles and detect the direction of travel of the axle.

TBOGI was originally designed to operate with wheel sensors commonly used with hot box detectors in North America. These wheel sensors are passive devices producing a sinusoidal pulse by each passing wheel, the amplitude of the pulse being speed sensitive. Several inherent limitations of this type of sensor, described in the presentation, led to adopting eddy current type of railway wheel sensors manufactured in Europe, and more recently, the integration of the Frauscher Wheel Sensor RSR110.

WID developed a hardware interface specifically for the RSR110 packaged in a small DIN rail mountable enclosure. The hardware interface described in the presentation provides the analogue signal conditioning (current to voltage amplifier and comparator) to digitise the output of the two sensors inside the RSR110 and logic combination of the two sensors to create a narrow sensing zone required by TBOGI-HD. The development the hardware interface optimized for TBOGI permitted the integration of the RSR110 without having to make costly hardware modifications to the TBOGI data acquisition and processing unit and minimised the firmware modifications (also discussed in the presentation). Packaging the hardware interface into a small external enclosure also permitted retrofitting the RSR110 in older TBOGI-HD systems with just a firmware upgrade.


Denis D’Aoust is a professional engineer with 35 years of experience creating ground breaking instrumentation systems for the railroad industry. After graduating from McGill University with a B.Eng. Electrical, he worked 14 years in the research department of Canadian Pacific Railroad. In 1996 he co-founded Wayside Inspection Devices Inc. (WID), which supplies condition monitoring systems to railroads on five continents. Denis D’Aoust is currently President of WID.

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