Low Frequency Vibration Energy Harvesting Based on Free/Impact Motion

Self-powering of wireless sensors and wireless micro-devices become an important issue nowadays. Problems associated with chemical batteries such as limited life time and minimization restrictions can be solved by using the approach of energy harvesting. In this work a way of vibration energy harvesting utilizing combined free/impact motion associated with electromagnetic transduction is proposed and studied. The study include impact with soft and hard end stops. A harvester with soft end stops shows a unique resonant behavior. However A micro energy harvester with hard end stops (FHH) shows certain characteristics that make it more appropriate for human powered devices. It can harvest significant amount of energy from human motion during daily activities. The performance of FHH is analyzed and tested with human body motion at different body locations during different daily activities.