Passive Self-tuning Energy Harvester for Rotational Motion


The energy harvester for variable rotational speed systems can be used to improve tire pressure-monitoring systems. This technology can be used for applications with a single, time-varying dominant frequency. 

Problem Addressed

Conventional resonant vibrational energy harvesters have fixed resonant frequencies and have limited applicability to time-dependent vibrational environments, such as automobile engines or wheels. One drawback of active energy harvester tuning schemes is that they require an additional source of input power or force. Existing passive tuning schemes do not demonstrate improved energy harvester performance.  By using a passive, self-tuning approach, this invention is able to extract energy at a higher efficiency and thus improve existing energy harvesting technologies.


This invention proposes an energy harvester for rotational motion that is self-tuned to resonate with the rotational frequency. As the rotation frequency changes, the resonant frequency of the energy harvester is adjusted by passively varying tension on a vibrating beam. The variation of centrifugal force with rotational speed ensures that the resonant frequency tracks the driving frequency over a broad frequency range. Furthermore, one is able to tune the beam dimensions and the radius at which the system is mounted for optimization. A prototype on a simulated rotating car wheel demonstrated significantly improved performance compared with untuned harvester performance. The self-tuning approach significantly increases the bandwidth of harvesters for rotating systems.


  • Well suited for variable speed systems
  • Relies only on the beam's mechanical behavior
  • Potential to be used to self-tune other types of energy harvesters