by Bob Tuzik, December 1, 2004
As part of its effort to monitor dynamic vehicle/track interaction on the Northeast Corridor, Amtrak commissioned ENSCO, Inc., to develop a Wayside Train/Track Interaction Detection System. The goal was to measure and collect information on vehicle/track forces that would enable Amtrak to determine the causes of track degradation. Amtrak also wanted to identify variations in wheel and truck component conditions for the various types of equipment operating on the corridor. This information would be used to determine and verify safety and maintenance tolerances for higher operating speeds. It would also quantify how much the vehicles used in high-speed operation contributed to track degradation.
The site selected for the system was just east of Midway interlocking near Princeton, N.J. Tracks 3 and 4, which see primarily west bound traffic, were instrumented. While the traffic on track four consists primarily of passenger equipment (with some freight) operating at speeds up to 110 mph, track 3 sees primarily passenger equipment, including the high-speed ACELA equipment that operates at up to 135 mph in that location. In order to capture the data that Amtrak required, ENSCO developed a system consisting of three main parts:
• Vertical and Lateral Strain gages.
• Teknis Electronics’ Wayside Monitoring System (WMS) including the Wheel Condition Monitoring System (WCM).
• Wayside Inspection Devices’ T/BOGI, an optical laser-based system for identifying angle-of-attack and the vehicles’ overall geometry and tracking position.
Data from all three components is integrated into the Wayside Monitoring System database. An AEI reader was included in the system to identify tagged vehicles. The WCM consists of a track-mounted array of accelerometers that measure the motion in the rail as each wheel passes over. Five consecutive cribs are instrumented. During processing of the data, normal rail motion is removed leaving only impact data. This data is recorded for each axle. Each array is connected to a signal processor that interfaces to the AEI reader, the 10 accelerometers, temperature sensors, four wheel sensors and up to 24 channels of strain gage bridges.
Strain gages were integrated into the WCM to measure the vertical and lateral forces generated by individual wheels passing over the site. Vertical strain gage bridges were installed on six consecutive cribs (including the five with accelerometers). Lateral strain gage bridges were installed on three of the cribs (2, 4, and 6).
The T/BOGI system was installed outside of the clearance envelope, several cribs to the west of the WCM array. It consists of an optical assembly and integrated signal conditioner. Two wheel sensors are integrated into the system. Data collected for each axle of the train includes the axle number, speed, direction, angle-of-attack and lateral position. Data from the T/BOGI system can be accessed independently, but it is also integrated into the WMS.
All collected data is stored in the processor at the Midway site. It is transferred off-site to servers at both Amtrak and ENSCO at a user-selected interval (currently just after midnight each day). Data can be accessed and displayed using various system-generated reports. Information is integrated with the AEI system and can be summarized either by train or by vehicle. Multiple passes of a vehicle can be identified and analyzed to predict degradation. Messages and alarms are generated when user-determined thresholds are exceeded.
The data is also incorporated into Amtrak’s Sharable, Expandable Database, which, according to Michael Trosino, Amtrak’s Senior Director of Clearances, Inspections and Tests, will allow Amtrak to identify “bad acting” vehicles and the track degradation and maintenance costs associated with them.