20 / 2021-03-14 17:57:49

Theoretical and experimental studies on an electromagnetic vibration energy harvester for rail corrugation sensing

vibration energy harvesting; rail corrugation monitoring; self-powered-and-sensing node

Rail corrugation, a kind of periodical wear on rail surface, can lead to abnormal vibration of vehicle-track components and harsh noises. Inspection and monitoring of rail corrugation is necessary to ensure the safe operation of trains and passengers’ ride comfort. An electromagnetic energy harvester for rail vibration, which also has a sensing capability of identifying the occurrences of rail corrugation, is proposed in this work.

Firstly, the theoretical model of this harvester is built and the optimal position of the coil for the magnetic field is theoretically studied. Then, experimental frequency-sweeping tests are carried out to understand the response characteristics of the harvester. Test results indicate that the harvester performs well in the frequency range below 80 Hz and reaches its maximum instantons power of 237 mW at 16 Hz. Two sections of a metro line with/without rail corrugations are selected to performs field tests. Rail roughness and vibrations of the two sections are measured in situ. The rail roughness of corrugated-rail section has a typical wavelength of 44.1 mm and a wave depth of 22.7μm. It is found that rail vibrations for the normal-rail section varies in a large frequency range from tens of Hz to thousands of Hz, and vibrations for the corrugated-rail section mainly distribute around a fixed frequency of 540 Hz related to the wavelength of corrugation. Using the field-measured rail vibration as excitations, the response characteristics of the harvester is investigated through indoor experiments. Laboratory experimental results demonstrate that the harvester under both normal and corrugated rail vibrations can generate signals with a dominant low-frequency component. However, signals produced by the harvester under corrugated-rail vibration also have a considerable component corresponding to the dominant frequency of excitations. Using such a characteristic, the occurrence of rail corrugation can be identified through the generated signals. Thus, this harvester shows the potential of being made into a self-powered-and-sensing node for rail corrugation monitoring.