Novel method of energy harvesting in rotating wheel is presented. Unlike the previous results of shock induced energy harvesting with a device fixed beneath a tire1–3, this device is placed on a rim. So it shows a lot of enhanced features like better stability, less rolling noise, and simple process for tire exchange. We could charge an electrical energy of 16 mJ in Li ion battery connected to the device after 200 cycles for 10 minutes, which means that 0.08 mJ per each cycle despite of the poor charging efficiency and mechanical instability at this stage. Basic idea is to increase the rotation speed of voice coil generator by restricting the rotation using magnetic force until enough centrifugal force is achieved at high rotation speed of wheel. So the high power output characteristics of this device will be useful for many applications such as tire pressure monitoring systems (TPMS).
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