Improved efficiency of wireless power transfer of RFID based position detection system for railroad vehicles

Abstract

Accurate detection of train position is critical for successful operation of intelligent railroad transportation system. In order to get high precision position information of railroad vehicles, modules and subsystems such as GPS module, wheel sensors, and RFID tags are used for various detection methods. Among the detection methods, position detection based on RFID tags placed onto the sleepers of the track is examined and is analyzed using Eurobal-ise among the commercial systems. Position information stored in the tags is read by a reader placed at the bottom of running railroad vehicle. It is difficult to wire all of the tags to an elec-tric power source so as to supply power directly. Therefore, the readers supply electric power to tags through wireless power-transfer technology. The wireless power transfer mechanism between the reader coil and the tag coil is the magnetic resonance. Power transfer efficiency is significantly affected by the ferromagnetic material (steel) at the bottom of the railroad vehi-cle and the track and by misalignments between the reader coils and the tag coils. To reduce the impact of the installation environment of the readers and tags, this thesis proposed a wire-less power transfer structure that uses a ferrite material around the reader coil and the tag coil. Moreover, to reduce the impact of any misalignments caused by the movement of the reader, a new structure in which two tilting coils are added to the reader coil is proposed. Based on the experimental results and simulation results, performance of the proposed methods is verified. As a result, the proposed models allow substantially higher power transfer efficiency as well as successful high-precision position detection of railroad vehicles.