The objective of this work is to develop MEMS vibration energy harvesters for tire pressure monitoring systems
(TPMS), they can be located on the rim or on the inner-liner of the car tire. Nowadays TPMS modules are powered by
batteries with a limited lifetime. A large effort is ongoing to replace batteries with small and long lasting power sources
like energy harvesters . The operation principle of vibration harvesters is mechanical resonance of a seismic mass,
where mechanical energy is converted into electrical energy. In general, vibration energy harvesters are of specific
interest for machine environments where random noise or repetitive shock vibrations are present. In this work we present
the results for MEMS based vibration energy harvesting for applying on the rim or inner-liner.
The vibrations on the rim correspond to random noise. A vibration energy harvester can be described as an under
damped mass-spring system acting like a mechanical band-pass filter, and will resonate at its natural frequency . At
0.01 g2/Hz noise amplitude the average power can reach the level that is required to power a simple wireless sensor node,
approximately 10 μW .
The dominant vibrations on the inner-liner consist mainly of repetitive high amplitude shocks. With a shock, the seismic
mass is displaced, after which the mass will “ring-down” at its natural resonance frequency. During the ring-down
period, part of the mechanical energy is harvested. On the inner-liner of the tire repetitive (one per rotation) high
amplitude (few hundred g) shocks occur. The harvester enables an average power of a few tens of μW , sufficient to
power a more sophisticated wireless sensor node that can measure additional tire-parameters besides pressure.
In this work we characterized MEMS vibration energy harvesters for noise and shock excitation. We validated their
potential for TPMS modules by measurements and simulation.