Seong-Su Jeong

Ubiquitous magneto-mechano-electric generator

Stray magnetic field considered as harmful noise for the human body can be a ubiquitous energy source. We are surrounded with 50/60 Hz parasitic magnetic noise arising from power delivery infrastructure, but it cannot be readily utilized by traditional electromagnetic harvesters. Here, we introduce a novel magneto-mechano-electric (MME) generator with a colossal power density that can turn on 35 LEDs and drive a wireless sensor network under a weak magnetic field of 5–7 × 10−4 T at a low frequency of 60 Hz. The MME generator is a cantilever structured magnetoelectric (ME) laminate composite in which the 〈011〉 oriented anisotropic single crystal fiber composite (SFC) is bonded to Ni plate and Nd permanent magnet proof mass. The ME laminate composite has a strong ME coupling (αME ∼ 160 V cm−1 Oe−1) even without magnetic bias due to the intrinsic property of Ni. The MME generator is also found to exhibit a colossal output power density of 46 mW cm−3 Oe−2 under a weak magnetic field of 1.6 × 10−4 T at 60 Hz. This MME generator can be a ubiquitous power source for wireless sensor networks, low power electric devices, and wireless charging systems by harvesting tiny amounts of parasitic magnetic energy from our living environment.

Design of a Piezoelectric Energy-Harvesting Shock Absorber System for a Vehicle

Only ∼20% of a vehicles fuel consumption is used for overcoming air drag force and friction with the road. Vibration energy produced during driving is dissipated by shock absorbers in the vehicle suspension. A new Piezoelectric Energy-Harvesting Shock Absorber (PEHSA) system for vehicles has been developed to act as an energy harvester that converts vibration energy to electrical energy. Cylindrical piezoelectric transducers are combined with the cylinder of the shock absorber to generate electricity from changes in fluid pressure produced by piston vibrations. A multiphysics simulation was performed using COMSOL Multiphysics to determine the characteristics of the PEHSA system.

Generating characteristics of a cross-shaped piezoelectric generator depending on elastic body material and leg length

The dependence of the generation characteristics of a cross-shaped piezoelectric generator on the material and leg length of the elastic body was studied. The generator consisted of a centrosymmetric thin cross-shaped elastic body and four rectangular piezoelectric ceramics that were attached to the upper surfaces of the four legs of the elastic body. Vibrations from a vibrating source were applied to the center of the elastic body. The centrosymmetric structure of the cross-shaped generator guarantees more stable and multiplied generation than a cantilever-type generator since the four legs of the generator resonate at the same frequency. The resonance and output characteristics of the generator were analyzed by using a finite element method (FEM) program. Generators were fabricated on the basis of analysis results and attached to a frequency controllable vibrator for determining their output characteristics. Further, experimental results were compared with simulated results. The speed of sound in the materials depends on the Young’s modulus and density of the materials. Accordingly, the resonance frequency of the generator decreased with a decrease in the velocity of sound in the material. The resonance frequency of the generator also decreased with an increase in the leg length. By changing the generator parameters, the resonance frequency of the generator can be controlled.

Design and Fabrication of Three Touch Point Thin Ultrasonic Rotary Motor

A novel structure three touch points thin ultrasonic rotary motor has been proposed to enable the actuator to use in small mobile equipment. A thin stator of simple structure is advantageous to use in tight spaces. Also, three points of contact enables to stable driving. Twelve ceramics plates were attached on upper and bottom side of the metal plate. When three phase alternating current sources are applied to the stator, elliptical displacements are generated at three inner edges of the stator. Modeling of the ultrasonic motor was done and the displacement characteristics were defined by using finite element analysis program. The effectiveness of the proposed design was verified by experiments. Characteristics of the motor such as speed, and input voltage were measured by using the driver and measurement equipment. Maximum displacement was appeared at frequency of minimum impedance. The resonance frequency was inversely proportional to the ceramic length. The maximum speed of 220 [rpm] was obtained at the resonance frequency, 76.4 [kHz]. The speed increase somewhat linearly with increasing applied voltage.

Driving Characteristics of the Thin-Type Ultrasonic Motor Using Microcontroller

This paper represented driving characteristic of a thin-type ultrasonic motor by fabricating and utilizing two kinds of drivers which could generate sinusoidal wave, square wave, respectively. A thin brass plate was used as a cross shaped vibrator and sixteen ceramic plates were attached on upper and bottom side of the brass plate. From the thin stator, elliptical displacements of the four contact tips were obtained. When two harmonic voltages which have 90° phase difference were applied to the ceramics, the symmetric and anti-symmetric displacements were generated at inside of the tips to make the elliptical motion. A finite element analysis (ATILA) was used for simulating the motional pattern of contact tips of the stator. The characteristics of the motor such as speed, torque, and current consumption were measured by applying sinusoidal waves through driving equipment which composed of function generator and power amplifier. As a result, the speed and the torque changed linearly at both driving frequency of 88.6 ∼ 87.6[kHz] and voltage of 24∼36[V]. Two-drivers which generate sinusoidal waves and square waves were designed and compared through some experiments in order to be put to practical use. In conclusion, the drivers had similar characteristic of speed-torque at alike frequency and voltage range. The square wave driver was recommended to control the motor linearly among two drivers by reason of practical use and simplification of driver.

Design and Fabrication of Hexadecagon Type Ultrasonic Motor

Ultrasonic rotary motor which has hexadecagon shape stator was proposed. Stator of the hexadecagon ultrasonic motor was composed of an elastic ring and ceramics. The elastic ring had sixteen sides and sixteen angular points. Eight ceramics were attached on the outer surface of the eight sides of the ring. When two sinusoidal voltages which have 90 degree phase difference were applied to each four ceramics, elliptical displacements of inner surface of the ring were obtained. These elliptical displacements of the inner surface rotated the shaft rotor through the frictions. The proposed hexadecagon ultrasonic motor was designed and analyzed by using the finite element method (FEM). Based on the FEM results, the rotational speed of the fabricated motor was measured by changing the driving frequency and voltage. As FEM results, large displacements at contact points of the stator could be obtained from thinner elastic ring and also thinner ceramics. Rotational speed of 61 [rpm] was obtained from the fabricated motor by applying 10 [V] of alternating voltages.

A Study on the Resonance Frequency of the Cross-Shaped Piezoelectric Generator According to Change in Elastic Body Thickness and Tip Mass

Over the past few years, research about generating system with piezoelectric ceramics has been conducted. To compensate problem of low generating power than other harvesters, many researchers have studied about piezoelectric generator for obtaining high output. And until now various types of piezoelectric generator has been developed. Cross-shaped piezoelectric generator using only one vibration source has four elastic body legs which have same vibration mode. So they have same resonance frequency under the vibration. Elastic body thickness and tip mass in design parameters influence on the resonance frequency. The parameters have relation to output characteristics. In this paper, the output characteristics depending on the elastic body thickness and tip mass were studied. The elastic body material used here was SUS304 for high output characteristics. As a result, the resonance frequency was decreased with decreasing thickness. The generator is expected to be used as an energy harvest from at vibration source around the human life.

Characteristics of the Piezoelectric Generator Using Circular Type Bender

The Piezoelectric generator for energy harvesting is usually using rectangular type unimorph or bimorph. In this paper, the characteristic of the piezoelectric generator which has a circular type bender was studied for more efficiently converting the mechanical energy to electrical energy than the rectangular type. The generator consisted of circular type vibrating plate, thin piezoelectric ceramics, stub and mass. The generator was simulated with FEM(finite element method) program as changing size of each part. When the radius of the piezoelectric ceramics and the elastic body were increased and the diameter of the vibrating plate was increased, the resonant frequency was decreased. And the output voltage was increased when the radius of the elastic body was increased. The output voltage was also affected by the distance which is the mass position from center of unimorph. The piezoelectric generator was fabricated from these simulated results. The output power was 4.3[mW] when the weight of mass was 7.2g.

Study on the new type of piezoelectric actuator utilizing smooth impact drive mechanism

ABSTRACT In this paper, the linear piezoelectric actuator utilizing smooth impact drive mechanism (SIDM) was proposed. It is easy to fabricate an actuator because of the simple structure of a bimorph type piezoelectric ceramic cantilever without any rotators or sliders. The cantilever, called as leg, was composed of four rectangular ceramics which were attached on the surfaces of an elastic body. Finite Element Analysis (FEA) was used to optimize the driving characteristics of the actuator. When bipolar rectangular wave with different durations for positive and negative voltages was applied, the piezoelectric actuator was moved by a stick-slip driving mechanism. The actuator was driven by two successive motions of actuator legs, slow forward and rapid backward movement. The driving characteristics of the prototype actuator were measured by the laser Doppler vibrometer.

Generating characteristics of a hump shaped piezoelectric energy harvester

This paper present generating characteristics of a hump shaped piezoelectric energy harvester. The harvester consists of a crooked elastic body plate and two ceramics which are attached on both inclined planes of the elastic body plates. This structure has a merit to lessen the stress of the ceramic because it can protect from direct pressure to the ceramic. And the harvester is easy to fabricate because additional support fixture is not required in this structure. The hump shaped harvester can be used in various industrial fields. Also the harvester can generate electrical power by using vibrations of lower frequency which can be found easily around us. The harvester are analyzed using finite element method program ANSYS. As shown, output voltage of the harvester is increased when ceramic thickness is decreased. By decreasing elastic body thickness, output voltage is increased. By increasing the elastic bodys cap length, output voltage is increased. The harvester is fabricated using the analyzed result of FEM. Generating characteristics of the harvester are defined by comparing analysis results and the experimental results.