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Abstract
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This project was aimed at developing and demonstrating a new type of self-de-icing LED signals for highway and railroad intersections, as a replacement for the existing LED signal lights that remain too cold on the signal lens to deice or melt snow and could cause accidents in snowy conditions.
The work of this project was divided into three stages. Stage 1 work focused on laboratory development and testing of the new self-de-icing LED signals. The self-de-icing LED signals adopt an innovative system architecture of "Integrated Light and Heat Arrangement of LEDs in Low Profile", which was tested in the laboratory to enhance the lighting and heating performance while reducing costs. Necessary equipment, components and materials were procured to develop and build prototypes. Three types of new light engines (R, Y, G) in low profile, each equipped with 96 medium-power LEDs, were designed in-house and custom-made with assistance from the industrial partner. On top of each LED, a Fresnel lens (diameter: 15 mm, focal length: 11.5 mm, thickness: 1.5-2.0 mm) was mounted with a gap of 1⁄4" for light collimation. New signal housing was custom made by a plastic molding company using UV stabilized polycarbonate materials. Two new LED drivers (one for red light and the other for green/yellow light), which were integrated with a remote temperature sensor for controlling the signal power output in light of the ambient air temperature and an on/off switch for winter and summer modes, were self-designed and custom-made by an electronics company. As a result, the prototype signals (R, Y, G) consist of a new signal housing, three new light engines in different light color (R, Y, G), two custom-made LED drivers integrated with a remote temperature sensor, new signal lens integrated with 96 small Fresnel lenses for light collimation of individual LEDs, and insulation materials as part of the innovative system architecture. Four generations of prototype signals in Red, Yellow, and Green were developed and tested in the laboratory with continuous improvements on their heating and lighting parameters with the desired specifications.
Work in Stage 2 focused on closed-course performance and reliability tests of the fully working prototypes mounted on the roof of the University of Kansas engineering complex, and follow-up improvements on any identified issues. Fully functional prototypes have been under continuous testing on the roof, powered by a real traffic control cabinet. Based on the test results, new plastic housing with desired changes were designed and tested in the laboratory with satisfactory performance. Some issues with the second generation LED drivers were resolved with needed changes, and the ambient temperature sensor of the drivers was improved for switching power output at 4°C with acceptable tolerances. Second generation LED driver samples were tested thoroughly in the cold room and on the roof and, based on the test results, improvements were made for developing the third generation LED drivers. New Fresnel lenses made by another manufacturer with lower price and higher quality control were procured and tested in the laboratory with satisfactory results. A total of 21 new LED drivers of the third generation were tested for their field performance and further improvements needed for the control of the yield rate in production. The industrial partner assisted in the production of finalized LED light engines while several other contracted companies have been producing all other metal, glass, and plastic parts needed for assembling the final porotypes for field tests. The fourth generation prototypes were tested in a controlled cold room for the performance of the ambient temperature sensor connected to the LED driver. The power output of the LED drivers was adjusted. The signal housing was also revised for quick assembly.
Work in the third and final stage involved field testing of the developed prototypes on identified highway signalized intersections and/or rail track sections. New fully functional prototypes for field tests were assembled and continuously tested in the laboratory in preparation for field tests. Also, a field monitoring system consisting of a Raspberry PI computer, three cable cameras, four temperature sensors, USB flash drivers, power supplies, and mounting accessories, was built in- house and continuously tested in the laboratory and on the roof for field installation. The prototypes, once validated in the closed-course setting, were installed on pole-mounted side signals as backup to the existing primary signals and commissioned. Real-time performance for melting snow and deicing was monitored by a field monitoring system for year- around data recording. The first field test site was set up in Kansas at the intersection of County Rd 458 (or 1200 Rd) /US- 59. All new equipment including the performance monitoring system for data recording were installed on side signals facing north. More prototypes of the final products are in preparation for other test sites. Seven states (Kansas, California, Michigan, New Jersey, Wisconsin, Pennsylvania, and Maryland) are participating in field testing and evaluation of the prototypes. On-site demonstration of the prototype signals would also be held for project partners and state DOTs to initiate the implementation process. |