Responses of Nonlinear Electro-Mechanical Energy Harvester by Means of Recurrences

We examine the modal response of an electro-mechanical energy harvesting device based oncharacterisation of the experimental time-series. Mechanical resonator consisting of a flexible beamand a tip magnet and nonlinear switching magnetic transducer defined as composite magnetic ringbased on a soft ferromagnet. To identify the dynamics of the response of the studied harvesting structure and the associated voltage and displacement output we used the Recurrence Quantification Analysis (RQA), estimating the corresponding recurrence rates and recurrence times.

Dynamic Response of Spiral Cantilever Undergoing Magnetic Coupling

Cantilever beams have found intensive and extensive uses as underlying mechanisms for energy transduction in sensors as well as in energy harvesters. In magnetoelectric (ME) transduction, the underlying cantilever beam usually will undergo magnetic coupling effect. As the beam itself is either banded with magnetic transducer or magnets, the dynamic motion of the cantilever can be modified due to the magnetic force between the magnets and ME sensors. In this study, the dynamic response of a typical spiral cantilever beam with magnetic coupling is investigated. The spiral cantilever acts as the resonator of an energy harvester with a tip mass in the form of magnets, and a ME transducer is positioned in the air gap and interacts with the magnets. It is expected that this spiral configuration is capable of performing multiple vibration modes over a small frequency range and the response frequencies can be magnetically tunable. The experimental results show that the magnetic coupling between the magnets and the transducer plays a favorable role in achieving tunable resonant frequencies and reducing the frequency spacings. This will benefits the expansion of the response band of a device and is especially useful in energy harvesting.

Design and Fabrication of Magnetic Sensor Based on the Phase Characteristics of GMI

This article presents a kind of high sensitive magnetic transducer which is based on the phase characteristics of giant magnet-impedance (GMI) effect. Then the development process of this new kind of magnetic transducer is discussed with the ideal condition of the GMI sensor elements (the frequency and the amplitude of the excitation current). Compared with the amplitude characteristics of GMI effect, the transducer can make a 10 to 100 times lower frequency. At the ideal condition, the sensor has a sensitivity of 1.6°/Oe, and we can conclude that the sensor has a potential to detect the weak magnetic.

Damage Detection Using Impedance Measurement With Magnetic Transducer

Impedance method has been explored for damage detection and identification. Typically, when the impedance sensor is integrated onto the mechanical structure to be monitored, its electrical impedance is directly related to the mechanical impedance of the host structure. Thus the change of impedance measurement before and after damage occurrence can be used as the damage indicator. Since the impedance information may be measured at relatively high frequency range, the impedance method could be sensitive to small-sized damage. Generally, piezoelectric transducers are employed in the impedance approach, which can serve as actuator and sensor simultaneously. In this research, a magnetic transducer approach is investigated for impedance based damage detection. To provide design guidelines, the analytical model of the resistive magnetic impedance measurement circuit is formulated. During the formulation, the two-way magneto-mechanical coupling between the transducer and the structure is systematically studied by using the Maxwell’s equations. The preliminary sensor enhancement is achieved by selecting the number of turns of wire in the electrical coil. Moreover, in order to reduce the negative effects of the high inherent inductance and large parasitic resistance of the coil with a large number of turns of wire, a new measurement circuitry is proposed, in which a negative resistive element and a capacitor are introduced to be serially connected with the original resistive circuit. Correlated numerical and experimental studies are carried out to validate the magnetic transducer in impedance based damage detection.