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Engineering Research


Robotics and Mechatonics Lab: Railroad


Real-time Measurement of Track Modulus


Sponsor: Federal Railroad Administration
Collaborator: Dr. Richard Arnold, UNL

raliroad raliroad
2005 AREMA Presentation
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The safety of vehicles traveling on railroad track is subject to the condition and quality of the track. Track modulus is one of several indicators for the quality and performance of railroad track. It is the ratio of vertical rail deflection and the contact pressure between the rail base and track foundation. Track modulus describes the vertical support condition of the track and is affected by all components of the track structure under the rail. The goal of this project is to develop a real-time, on-board, non-contact track modulus measurement system. Currently there is one vehicle that can measure track modulus, and this vehicle is limited to speeds under 10 mph. The only other methods of measuring track modulus involve taking static measurements, which are time consuming and difficult to make. Currently there is not a system capable of measuring track modulus at normal track speeds.

raliroad The measurement system, shown to the left, uses two rail cars. A liquid tanker car houses the sensor system, and acts as the loading vehicle. The second car, a renovated caboose, contains all controls and data-acquisition equipment.
The sensor systems are mounted on the trucks of the tanker car nearest the caboose. The systems are positioned so that their center is located 4 feet in front of the contact point of the wheel, directly above the rail. raliroad
raliroad Two line lasers and a video camera make up the sensor system. A sample of the camera image is shown to the left. As the cars move over the rail, the rail deflects, causing the distance between the laser lines to change. This distance is used to find deflection of rail and track modulus.

Instrument Shroud

raliroad In early tests sunlight drowned out the laser lines on the rail, making it difficult to extract quality data from the video. As part of my U.C.A.R.E. research I designed the system shown to the left to combat sunlight. The shroud is lightweight and quickly disassembled.

To block light out, Recreational Vehicle splash stop bristles surround the sensor system, with double layers used on the front and back to ensure consistent performance. A .04" aluminum plate covers the top of the system.
Analyzing data in early tests was inefficient because the position of each image was estimated from the speed of the train, or from markings on the rail. raliroad
raliroad An odometer was designed to run off an existing pulley system on the wheel of the caboose. The gear ratio of the system increases the angular velocity of the wheel by a factor of 5, and at maximum speed the odometer rotates 2500 rpm. The system uses a photoelectric rotary encoder to relate the rotation of the wheels to a distance that is displayed on each image.