Abstract
Self-adaptive vibration energy harvesters convert the kinetic energy from vibration sources into electrical energy and continuously adapt their resonance frequency to the vibration frequency. Only when the two frequencies match can the system harvest energy efficiently. The harvesting of vibration sources with a time-variant frequency therefore requires self-adaptive vibration harvesting systems without human intervention. This work presents a self-adaptive energy harvesting system that works completely self-sufficiently. Using magnetic forces, the axial load on a bending beam is changed and thus the resonance frequency is set. The system achieves a relative tuning range of 23% at a center frequency of 36.4 Hz. Within this range, the resonance frequency of the harvester can be set continuously and precisely. With a novel optimized method for frequency measurement and with customized electronics, the system only needs 22 µW to monitor the external vibration frequency and is therefore also suitable for environments with low vibration amplitudes. The system was verified on a vibrational test bench and can easily be tailored to a specific vibration source.
Highlights
Vibration energy harvesters are an alternative to batteries for operating wireless sensor networks (WSN)
For a quick calculation of ∆ f fa, this function was evaluated at 21 points (Figure 5b) and the values were saved in a lookup table (LUT) in the MCU storage
The resonance frequency of the harvester can be changed by a diametrically magnetized tuning magnet that changes the axial mechanical load on a bending beam structure depending on the angle of rotation
Summary
Vibration energy harvesters are an alternative to batteries for operating wireless sensor networks (WSN). The adaptation is carried out by a rotatable diametrically magnetized tuning magnet, which, depending on the angle of rotation, applies a specific axial load to a bending beam harvester and changes the resonance frequency. As mentioned above, gear boxes [12], household devices [13] or, During the tests on the vibrational test bench, the frequency of the harmonic vibration changed at more generally, machines that involve components rotating at variable speeds [30].isAn extensive certain time intervals; thissources simulates the typical situation of aassociated time-variant vibration source. An extensive characterization of behavior that suchinvolve as white noise and rotating thereforeatcall for resonant (narrowband) energy harvesters Our these sources showed that the vibrations associated with them consist of clearly separated harmonics general structure can be individually tailored to the source by changing the beam geometry.
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