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This article presents analysis and model validation of a single cantilever frequency up-conversion mechanism under stochastic excitation when configured as an electromagnetic energy harvester. The results show that the mechanism is able to achieve an increase in the root mean square velocity of the cantilever end when excited at frequencies below the natural frequency of the beam in the range of 3–7 Hz, as compared to a simple cantilever. The maximum observed gains in root mean square velocity from the experiment varied from 69% at a fundamental excitation frequency of 7 Hz to 153% at 3 Hz for cantilevers with natural frequencies in the range of 8.5–13.3 Hz as compared to a simple cantilever device with the same range of natural frequency. Comparison between the experimental and simulation results demonstrates that the mathematical model of the mechanical system is able to predict the response under such excitation conditions with 99% of the points in the parameter space being fitted at the 95% confidence level. Configured as an electromagnetic harvester based on low-frequency vibration, the device has been shown in the experiment to have a potential gain in average power delivery of 91.5% compared to a simple cantilever structure.

This paper presents a low frequency vibration energy harvester with contact based frequency up-conversion and hybrid electromagnetic–piezoelectric transduction. An electromagnetic generator is proposed as a power source for low power wearable electronic devices, while a second piezoelectric generator is investigated as a potential power source for a power conditioning circuit for the electromagnetic transducer output. Simulations and experiments are conducted in order to verify the behaviour of the device under harmonic as well as wide-band excitations across two key design parameters—the length of the piezoelectric beam and the excitation frequency. Experimental results demonstrated that the device achieved a power output between 25.5 and 34 μW at an root mean squared (rms) voltage level between 16 and 18.5 mV for the electromagnetic transducer in the excitation frequency range of 3–7 Hz, while the output power of the piezoelectric transducer ranged from 5 to 10.5 μW with a minimum peak-to-peak output voltage of 6 V. A multivariate model validation was performed between experimental and simulation results under wide-band excitation in terms of the rms voltage outputs of the electromagnetic and piezoelectric transducers, as well as the peak-to-peak voltage output of the piezoelectric transducer, and it is found that the experimental data fit the model predictions with a minimum probability of 63.4% across the parameter space.

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