Design And Bench Tests Of A Smart Railroad Tie For Energy Harvesting

This paper presents the design, modeling and bench testing of a smart railroad tie for energy harvesting from the motion of railway track. The system is intended for applications that require trackside power in remote locations, such as wayside electrical devices and safety equipment, signal lights, crossing gates, wireless communication, as well as rail health monitoring systems. The smart tie, which is designed to have similar dimensions to a conventional railroad tie, is installed in the same manner as a standard tie on the track. In particular, the mechanical energy harvesting module and its corresponding power management unit can be both embedded inside a composite, concrete or wooden tie, in order to shield the components from the harsh environment and protect the system against any potential theft or vandalism. Different from other railway track harvesters that typically harvest energy from bidirectional track deflections, the proposed smart tie only harvests the kinetic energy of the track when the wheels push it downwards, which resolves the preload and installation challenges of bidirectional harvesting and increases the overall system reliability. A nonlinear analytical model is developed to analyze the dynamic characteristic of the system and the simulation is conducted to predict the performance. Bench tests are subsequently carried out under both harmonic and recorded tie displacement inputs to validate the model and assess the harvesting performance. During the bench tests, the generator shaft was observed to start rotation at 0.1 mm vibration amplitude, indicating that the overall prototype has a relatively small backlash. In-lab test results indicate that an average power of 26.1-42.2W on 4 Ohms and 2 Ohms external loads were achieved under simulated tie movement recorded from a service track.