Abstract
To expand the applications of vibrational energy harvesters (VEHs) as power sources of wireless sensor nodes, it is of significance to improve the scavenging efficiency for the broadband, low-frequency, and low-level vibrational energy. The output voltages of electromagnetic vibrational energy harvesters (EMVEHs) are usually low, which complicates the power management circuit by an indispensable voltage boosting element. To this end, an impact-based non-resonant EMVEH mainly composed of an outer frame and an inner frame on rollers is proposed. Numerical simulations based on a mathematical model of the harvester are conducted to analyze the effects of structural parameters on the output performance. Under base excitation of 0.1 and 0.3 (where g is the gravitational acceleration, 1 g = 9.8 m · s − 2 ), the experimental maximum root mean square voltages of a harvester prototype across a resistor of 11 kΩ are as high as 7.6 and 16.5 V at 6.0 and 8.5 Hz, respectively, with the maximum output powers of 5.3 and 24.8 mW, or the power densities of 54.6 and 256 μW cm−3. By using a management circuit without a voltage boosting element, a wireless sensor node driven by the prototype can measure and transmit the temperature and humidity every 20 s under base excitation of 0.1 g at 5.4 Hz.
Highlights
IntroductionVibration energy harvesters (VEHs) are promising substitutes to batteries to power wireless sensor nodes and implanted systems due to such advantages as long lives and being maintenance-free [1,2]
Vibration energy harvesters (VEHs) are promising substitutes to batteries to power wireless sensor nodes and implanted systems due to such advantages as long lives and being maintenance-free [1,2].The vibrations in natural environments are typically broadband, low-frequency (0.1–30 Hz), and low-level [3,4,5].The relatively high natural frequencies and narrow bandwidth of the linear resonant VEHs make them inefficient in scavenging ambient broadband and low-frequency vibration energy [5,6]
A type of non-resonant VEHs utilizing the nonlinearity caused by mechanical impacts is attractive in low-frequency and broadband vibration energy scavenging
Summary
Vibration energy harvesters (VEHs) are promising substitutes to batteries to power wireless sensor nodes and implanted systems due to such advantages as long lives and being maintenance-free [1,2]. A type of non-resonant VEHs utilizing the nonlinearity caused by mechanical impacts is attractive in low-frequency and broadband vibration energy scavenging. A VEH based on the impact of a moving mass on piezoelectric bending structures produces an output power of 600 μW under a harmonic base excitation with the displacement amplitude of 10 cm and frequency of 10 Hz [14]. As the rolling friction is usually much lower than the sliding friction, the impact-based VEHs with a rolling mass are preferred in low-level vibration energy scavenging. It may be concluded that the impact-based non-resonant VEHs with a rolling mass are suitable to scavenge low-level, broadband, and low-frequency vibration energy. This paper proposed an impact-based electromagnetic VEH which produces high output voltage even under low-level base excitation, making the voltage boosting element of the management circuit dispensable. Prototypes were fabricated and tested and a prototype was used to power a wireless sensor node
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