Energy harvesting: vibration powered generators with non-linear compliance

Generating power from ambient vibrations is one of a number of techniques that have been proposed to provide a renewable power source for electronic circuits. Typical applications include wireless sensors to monitor parameters inside the human body or conditions inside a large civil structure.Because of the applications vibration powered generators have to be small and it can be difficult to produce sufficient power in such a small volume unless the device is careful optimised. Vibration powered generators use a resonant mass/spring arrangement to amplify the small vibrations to a useable level and the proposed research will investigate how this resonant system behaves when the spring element has a non-linear compliance i.e. force is no longer proportional to frequency. This is important since non-linearities can occur because of manufacturing, particularly at small scales, and because of magnetic or electrostatic forces.The proposed research will provide analytical techniques to design vibration powered generators with non-linear spring elements and hence improve their performance, making them applicable in a wider variety of applications.