Mechanical Energy Scavenging for in-Wheel Sensors

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This project proposes to use the centrifugal force imparted to a mass, rotating within a car wheel to wind a clockwork system that can then be used to power in wheel sensors. Power is generated by the spring unwinding and driving a micro-generator.The project will investigate the feasibility of the mechanical spring system to scavenge and store enough energy to power typical in-wheel sensors. At present typical MEMS based electromagnetic and electrostatic vibrational scavenging systems offer power outputs in the 10-100 microWatt range. The energy harvester proposed here offers the possibility of over 1 milliWatt of power. The fully wound spring system stores up to 2.6 milliWatt-hr of energy and with a conversion factor of 50% for the generation; and the system designed to fully unwind over 1 hour, then there will be a 1.3 milliWatt supply for that hour. The system maintains this power level by being continually rewound by the start-stop motion of the car and any cumulative vibrational motion of the wheel in the radial direction. This generated power can be varied in the 10-10000 microWatt range by changing the speed with which the spring unwinds from seconds to hours. The system can therefore provide the short high power burst required for wireless transmission as well as the lower power of the measurement and sleep states. As part of the project the actual real journey dynamics of a car wheel will also be measured using a remote sensor pod attached to the car. This measured data will be made freely available to researchers for use in energy harvester performance modelling via an open access online database.To achieve the project goal the research will draw upon the unique skills and expertise from the Bio-medical & MicroEngineering group and the Vehicle Technology Research Centre, both situated in the School of Mechanical Engineering at the University of Birmingham.