A multifunctional electromagnetic device for vibration energy harvesting and rail corrugation sensing

A multifunctional electromagnetic device for harvesting rail vibration energy and sensing rail corrugation is proposed. Firstly, the optimal coil position is investigated theoretically and verified through experiments. Then, experimental frequency-sweeping tests are carried out to understand the response characteristics of the harvester. Two sections of a metro line with/without rail corrugations are selected to measure rail roughness and vibration. Using the field-measured rail vibration as excitations, the response characteristics of the harvester are investigated through indoor experiments. Experimental results demonstrate that occurrences of corrugation can be identified through time-frequency analysis of the electromotive forces of the harvester. Besides, electrical load tests under normal rail vibration demonstrate that this harvester will yield its maximum power of 18.6 mW (average power: 1.5 mW) when the resistance of the external electrical load is close to the internal resistance of the coil. The capability to energise small commercial electronic devices is verified by charging a supercapacitor, and driving LEDs, a digital clock, and a thermo-hygrometer to work, respectively. The capabilities of the harvester for powering low-power electronics and sensing rail corrugation pave the wave for designing a self-powered sensing node for rail corrugation monitoring.