Vibration energy harvesting in automobiles to power wireless sensors

Automobiles may include sensors for obtaining information regarding various physical parameters, such as ultrasonic sensors for distance detecting during reversing. Usually these sensors are powered by wire connection with the batteries of the automobiles. However, while more and more sensors are installed to the automobiles, the wire connection turns to be troublesome. Furthermore, some embedded sensors cannot be powered by wire connection, such as the tire pressure monitoring sensors. Therefore, powering these distributed or embedded wireless sensors from ambient energy becomes attractive. It will reduce the installment trouble and maintenance costs. This work reports on vibration levels detected in automobiles during road test as a potential energy source for automobile sensors. The measurement results showed that the vibrations in the automobiles are large enough for useful vibration harvesting. A piezoelectric vibration harvester was designed and equipped with a power interface circuit. The test demonstrates that sufficient energy is harvested to possibly supply a wireless sensor. It is also shown that significant increases in harvested energy may be obtained by improving the harvesting device design.