Micro-Patterned Electret Power Generator for Simultaneous Oscillation and Rotatory Detection in Railways

This paper presents a novel micro electret power generator as self-powered railway sensor for both horizontal oscillation detection and rotation speed monitoring. Both the electret material and counter electrode are micro-patterned with square-shaped blocks and connected diagonally. By this way, capacitance variation can be maximized in either horizontal oscillation or axial rotation. From the experiment results, they show obvious differences between the waveforms from two types of motions. Therefore, both the rotation of the iron wheel and the change of the track in railway can be precisely detected and distinguished. The experimental results show that the peak value of the output voltage can reach 121.94 V when the rotation speed is 600 rpm in the rotating mode and 132.96 V in the sliding mode. The self-powered sensing system can not only achieve stable and continuous output signals, but also adapt to the multi-directional working environment. The outcomes of this work offer new insights of realizing single structured electret power generator for multifunctional applications.