In this paper, we present a nonlinear electromagnetic energy harvesting device that has a broadly resonant response. The nonlinearity is generated by a particular arrangement of magnets in conjunction with an iron-cored stator. We show the resonant response of the system to both pure-tone excitation and narrow-band random excitation. In addition to the primary resonance, the superharmonic resonances of the harvester are also investigated and we show that the corresponding mechanical upconversion of the excitation frequency may be useful for energy harvesting. The harvester is modeled using a Duffing-type equation and the results are compared with the experimental data.
In this paper we present a nonlinear electromagnetic energy harvesting device that has a broadly resonant response. The nonlinearity is generated by a particular arrangement of magnets in conjunction with an iron-cored stator. We show the resonant response of the system to both pure-tone excitation and narrow-band random excitation. In addition to the primary resonance, the super-harmonic resonances of the harvester are also investigated and we show that the corresponding mechanical up-conversion of the excitation frequency may be useful for energy harvesting. The harvester is modeled using a Duffing-type equation and the results compared to the experimental data.
A fundamental drawback of vibration-based energy harvesters is that they typically feature a resonant mass/spring mechanical system to amplify the small source vibrations; the limited bandwidth of the mechanical amplifier restricts the effectiveness of the energy harvester considerably. By extending the range of input frequencies over which a vibration energy harvester can generate useful power, e.g. through adaptive tuning, it is not only possible to open up a wider range of applications, such as those where the source frequency changes over time, but also possible to relax the requirements for precision manufacture or the need for mechanical adjustment in situ. In this paper, a vibration-based energy harvester connected to a generalized electrical load (containing both real and reactive impedance) is presented. It is demonstrated that the reactive component of the electrical load can be used to tune the harvester system to significantly increase the output power away from the resonant peak of the device. An analytical model of the system is developed, which includes non-ideal components arising from the physical implementation, and the results are confirmed by experiment. The −3 dB (half-power) bandwidth of the prototype energy harvester is shown to be over three times greater when presented with an optimized load impedance compared to that for the same harvester presented with an optimized resistive only load.
This paper describes how an inerter-based device for structural vibration suppression can be realized using an electromagnetic transducer such as a linear motor. When the motor shaft moves, a difference of voltage is generated across the transducer coil. The voltage difference is proportional to the relative velocity between its two terminals. The electromagnetic transducer will exert a force proportional to current following the Lorentz principle if the circuit is closed around the transducer coil. If an electronic circuit consisting of a capacitor, an inductance and a resistance with the appropriate configuration is connected, the resulting force reflected back into the mechanical domain is equivalent to that achieved by a mechanical inerter-based device. The proposed configuration is easy to implement and very versatile, provided a high quality conversion system with negligible losses. With the use of electromagnetic devices, a new generation of vibration absorbers can be realized, for example in the electrical domain it would be relatively uncomplicated to synthesize multi-frequency or real time tunable vibration absorbers by adding electrical components in parallel. In addition by using resistance emulators in the electrical circuits, part of the absorbed vibration energy can be converted into usable power. Here an electromagnetic tuned inerter damper (E-TID) is tested experimentally using real time dynamic substructuring. A voltage compensation unit was developed in order to compensate for coil losses. This voltage compensation unit requires power, which is acquired through harvesting from the vibration energy using a resistance emulator. A power balance analysis was developed in order to ensure the device can be self sufficient. Promising experimental results, using this approach, have been obtained and are presented in this paper. The ultimate goal of this research is the development of autonomous electromagnetic vibration absorbers, able to harvest energy, convert it into usable power, and use it for vibration control and health monitoring.
SUMMARY Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure. Traditionally, this energy is dissipated through the devices as heat. In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated. The energy‐dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy. That gives the possibility of controlled damping force whilst generating useful electrical energy. Both analytical and experimental results from an adaptive and a semi‐active tuned mass damper/harvester are presented. The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression. Copyright © 2014 John Wiley & Sons, Ltd.
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