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This paper assesses the vibratory energy harvesting performance of a tuned inertial mass electromagnetic transducer (TIMET) through hardware-in-the-loop (HIL) testing under random vibration. The TIMET has been developed by adding a tuning spring and an extra rotational inertial mass to a conventional electromagnetic transducer (ET) with a motor. The authors have already shown that the energy harvesting efficiency of the TIMET can be increased by taking advantage of the mechanical resonance effect of the rotational inertial mass due to the tuning spring through numerical simulation studies. In addition, further improvement in power generation of the TIMET can be achieved theoretically by controlling the current to the motor based on the appropriately developed algorithms. In this paper, the superiority of the TIMET over the ET under random disturbances when the current to the motor is controlled by the algorithms proposed for the ET in the literature is experimentally verified. Moreover, the accuracy of the numerical simulation using the developed device models is validated by comparing with the test results.

This paper proposes a novel vibration energy harvesting device employing a tuned variable inerter. The inerter is a device that can produce an amplified inertial mass effect by ball screw or rack and pinion mechanisms. Originally, the inerter was developed for suspensions in automobiles, and various kinds of inerter technologies have been widely studied not only in structural control but also in energy harvesting so far. As an example of such devices, the tuned inertial mass electromagnetic transducer has been proposed, and its effectiveness as an energy harvesting device has been shown already. However, at the same time, previous studies suggested that further performance improvement is possible if the inerter is variable according to changes in disturbance conditions. Thus, in this research, a prototype which can change the value of the inerter is designed, and a system to change the inerter based on the dominant frequency detected online by the fast Fourier transform of the measured data is developed. Then, it is shown through experimental studies that the proposed device can improve the energy harvesting performance compared to the existing tuned inertial mass electromagnetic transducer for disturbances with varying dominant frequencies.

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