Seong-Kyu Cheon

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.

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.

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.

Design of an ultrasonic motor which has Nib shaped stator

In this study, simple ultrasonic motor of plate type stator was proposed. Stator of the proposed ultrasonic motor was composed of an elastic plate and ceramics. The elastic plate has one tip in the middle. The two ceramics were attached on the side surfaces of the elastic plate. The both polarization directions were directed to the upward outside directions. When two AC voltages which have basically 90 degree phase difference were applied to the two ceramics, elliptical displacements of the stator tips were obtained. FEA simulation(ATILA) was used to analyze elliptical displacement characteristics of the friction line tips depending on the width and thickness of elastic body and ceramic. Optimize the elliptical displacement by synchronizing the two resonant frequencies. Based on the FEA results, one model of motor which showed effective characteristics at contact line was chosen and fabricated. The output characteristics of the prototype motor based on the analysis data were measured. And characteristics of the motor were compared with the simulated results.

A Study on the Torque Characteristics Depending on the Elastic Body Materials of a Hexadecagon Shaped Ultrasonic Motor

In this study, novel ultrasonic rotary motor of 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 rotor of cylindrical shaft was inserted inside of the ring stator, central lines of the sixteen sides of the stator hold the shaft by the slight pressures(frictions). This slight pressure was a preload of the motor and it could be controlled by radius and thickness 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), depending on materials of the elastic ring. Based on the FEM results, one model of motor which showed maximum displacement at contact points was chosen and fabricated. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, EL20ET0.5CT0.5CW2 model showed 115[rpm] speed about input voltage of 60[Vrms] at 65.6[kHz]. And the maximum torque of 6[gfcm] was obtained. From these results, the hexadecagon shaped ultrasonic motor can be used to actuator for optical device which needs detailed position control. Also it can be used to medical and portable device by reducing size and weight.

Design of a Honeycomb Shaped Piezoelectric Energy Harvester

In this paper, design of a hexagon shape piezoelectric generator was done by using Finite Element Method (FEM) and generating characteristics of the prototype generator were experimented. The generating device was composed of a thin hexagonal steel plate and a frame-shaped hexagonal ceramic which was attached on the steel plate. This structure has a merit to lessen the stress of ceramic when vibration is applied on the center of the plate. The output of the hexagon generator can be improved, because its area is larger than foursquare area when perimeter is same. Also, when array the generators on a surface it can get high efficiency compared with a round shape device, because there is no wasting space. The generator was named as honeycomb shape piezoelectric generator, because merits of this structure are similar to the merits of honeycomb of a bee. Design and analysis of the generator was done by simulating the output characteristics according to the change of parameters by using FEM program. Output characteristics were determined by varying the width, thickness and the number of lamination of the ceramics. The generating characteristics of the fabricated honeycomb shape generator were measured and compared with the FEM results.