Vibration power generation harnesses weak environmental vibrations and converts them into electrical energy. In this study, a vibration power generator based on a magnetostrictive material (Fe-Ga) was investigated. The generator was designed with a cantilever beam structure, offering advantages in simplicity, robustness, and high-power generation capacity compared with piezoelectric systems. The change in magnetic flux within the coil is attributed to two factors: the change in the magnetoresistance of the magnetostrictive material owing to applied stress, and the variation in air-gap reluctance caused by fluctuations in the air-gap length. In our previous research, we focused on air-gap magnetoresistance variation and proposed a vibro-generator with a narrower air gap. Modifying the air-gap structure increased the generator’s air-gap magnetoresistance variation at the same amplitude, enhancing power generation. In this study, we introduced an auxiliary magnetic circuit to a narrow-gap-type vibration power generator. The main and auxiliary magnetic circuits had opposing flux directions and trends, which maximized the change in flux in the coil. Based on the study’s experimental results, the maximum output power generated by the multiple magnetic circuit vibro-generator was 149% and 46.3% higher than that of conventional vibro-generators and narrow-gap-type vibration generators, respectively. The multiple magnetic-circuit structure can enhance the power generation efficiency of the vibration generator, thereby increasing the application potential of the equipment.
The periodic inspection of a bridge requires visual observation and hammering, which is very costly. In addition, the inspection is sometimes difficult, depending on the place of installation. Consequently, there is a need for remote health monitoring of structures using wireless modules. However, nowadays, these monitoring systems use batteries for power supply and need periodic battery replacement. As a solution, we investigate vibration generators using magnetostrictive materials (Fe-Ga alloy) as a power source for remote health monitoring. Using this system, we can inspect infrastructures without maintenance such as changing batteries. The generator features a simple structure, robustness, and high output and is close to practical application. In this paper, we propose an extra-large magnetostrictive vibration power generator that can generate practical power using a low frequency (10~20 Hz), such as bridge vibration. It is 300 mm in length, 5 kg in weight, and uses a Fe-Ga alloy plate with dimensions of 40 × 4 × 125 mm3 . First, we improve the output of the generator by adding a reinforcing plate and adjusting the bias magnetic field. Next, we confirmed the generation of an instantaneous maximum power of 0.58 W and effective power of 0.22 W under sinusoidal vibration (18.5 Hz, 0.2 G). Furthermore, we reproduced bridge vibration and evaluated the characteristics of the extra-large generator. Finally, we confirmed that 88 mJ of energy was stored in the storage capacitor from reproduced vibration of the bridge in 5 s.
In recent years, the periodic inspection of aging transport infrastructure has become a global problem incurring significant costs and requiring the extensive use of manpower. As a solution, we propose a magnetostrictive vibration power generator that makes use of vehicle-induced highway vibrations to power a battery-free low power wide area (LPWA) module incorporating a titanium wire sensor. This system makes use of an LPWA module with a transmission range of over 1 km, and a titanium wire sensor which was inexpensive, easy to install, and could be used to inspect aging infrastructure. Using this system, infrastructure inspection, can be conducted without the need for conventional maintenance on the system, such as battery replacement. Our main research objective was the magnetostrictive vibration power generator. The generator was suitable for supplying power to the system because it was simple, robust, and was capable of high power output. First, the generator was scaled up to increase the output power in order to generate practically useful electric power with highway vibrations. The large generator was 150 mm×60 mm×50 mm in size and 0.6 kg in weight, incorporating a 16 mm×2 mm×50 mm plate of iron-gallium (Fe-Ga) alloy. We then reproduced the highway vibrations experimentally in a laboratory to ascertain the generator characteristics. We confirmed that it generated a peak voltage of 7 V, instantaneous maximum power of 36 mW, and total energy output of 52 mJ from the simulated highway vibrations over a period of 5 min. Finally, we field tested the system and succeeded in activating the battery-free LPWA modules within 16.5 min using vehicleinduced highway vibrations.
In this study, a magnetostrictive vibrational power generator was proposed for high-frequency vibration occurring in a machine tool and high-efficiency power conversion circuit for a battery-free wireless sensor. A conventional device was miniaturized according to the scale effect, and a device composed of a Fe-Ga alloy plate, of 2 × 0.25 × 8 mm3 with a frame of 0.5 mm thickness, was fabricated and evaluated. As a result, a generated voltage of 2 V and effective power of 234 μW were confirmed at a vibration of 522 Hz and 10 m/s2 . In addition, the operating principle was verified in the power conversion circuit composed of an LC circuit (resonant circuit), a diode and a storage capacitor. As a result, it was confirmed that by using a large inductance, the Q value could be increased, and a considerable amount of energy could be stored in a 330 μF capacitor.
We study magnetostrictive vibration based power generator using iron-gallium alloy (Galfenol). The generator is advantages over conventional, such as piezoelectric material in the point of high efficiency highly robust and low electrical impedance. Generally, the generator exhibits maximum power when its resonant frequency matches the frequency of ambient vibration. In other words, the mismatch of these frequencies results in significant decrease of the output. One solution is making the spring characteristics nonlinear using magnetic force, which distorts the resonant peak toward higher or lower frequency side. In this paper, vibrational generator consisting of Galfenol plate of 6 by 0.5 by 13 mm wound with coil and U shape-frame accompanied with plates and pair of permanent magnets was investigated. The experimental results show that lean of resonant peak appears attributed on the non-linear spring characteristics, and half bandwidth with magnets is 1.2 times larger than that without. It was also demonstrated that the addition of proof mass is effective to increase the sensitivity but also the bandwidth. The generator with generating power of sub mW order is useful for power source of wireless heath monitoring for bridge and factory machine.
Vibrational power generator extracts electrical energy from ambient vibration. Author invented novel configuration using magnetostrictive material. The device is based on parallel beams of iron-gallium alloy and magnetic material, and features high efficiency, high robustness, and low electrical impedance. In this paper, author proposes U-shape generator for universal use. It consists of the parallel beams and fixed and free end beams forming U-shape frame flexibly modified for variety of mechanical input. Miniature U-shape prototype using Fe-Ga rod 6 by 0.5 by 13 mm3 exhibited average power of 3.7 mW under vibration of 166 Hz and 2.5 G. L-shape type was demonstrated to generate electromotive force by two directional vibrations. In switch type, maximum energy of 0.7 mJ was retrieved by one pushing force. The performances are sufficient to drive wireless module for heath monitoring and remote control.
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