• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1500-1503
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• 2002

In this paper, we proposed windmill type ultrasonic motor which has modified shape of Endcap. The motor was especially designed by FEM for high speed. As results, displacements of the windmill and the clover type motor was compared. Using clover type motor, more smooth rotation of rotor was achieved. If Z component of the displacement of the clover type motor can be applied for linear motor.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.100-102
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• 2002

In this paper the driving characteristic for a traveling-wave type ultrasonic motor is described. For driving of ultrasonic motor, a two-phase resonant inverter and Digital IC was made. The driving circuit simulation results are compared with measured frequencis and amplitudes.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.607-612
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• 2001

Rotary ultrasonic motors are based on the traveling wave generated by piezo materials attached on the stator. Large scale model of an annular ring was built to understand the fundamental mechanism involved in the rotary ultrasonic motors. Traveling wave on the structure can be generated by superposing two standing waves. Precise matching of the amplitudes and phase shift between two standing waves in time and space is the key to the success of generating a traveling wave.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1285-1286
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• 2007

In this study, novel structured thin ultrasonic rotary motor has been proposed. Ultrasonic motors are based on an elliptical motion on the surface of elastic body. ATILA ver. 5.2.4 was used for optimizing stator. The motor was fabricated by using designed stator. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, 860[rpm] speed was obtain by input voltage of 16[Vrms] at 92.5[kHz].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.300-302
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• 1999

The standing waves of the fourth bending mode of vibration and first longitudinal mode of vibrator were utilized to construct a ultrasonic linear motor. The geometrical dimensions of the vibrator were determined by Euler-Bernoulli theoty. FEM(finite element method) employed to calculate the vibration mode of the metal-piezoceramic composite thin plate vibrator. ANSYS was used to design positions of the projections and calculate displacement of vibrator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.411-414
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• 2000

An ultrasonic linear motor was composed of a slider and a stator vibrator including piezoelectric material and elastic material. The ultrasonic linear motors mainly consist of an ultrasonic oscillator which generates elliptical oscillations. Elliptical oscillations are generated by synthesizing two degenerated modes. Direction of vibratory displacement was analyzed by employing the finite element method. So, we could recognize that the direction of the slider's movement was controlled by changing the Phase difference of the drive voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.129-131
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• 1999

Driving generator of USMs(ultrasonic motors) with low noise, high efficiency was designed and fabricated. It was focused on merits such as size-reduction, thermal resistance, To control revolution speed, input frequency was varied. Output of generator had frequency range of 39.1 ∼ 43.5 MHz and voltage of 120 V. USM with resonant frequency 40.3 kHz exhibited a maximum torque of 2.5 kg $.$ cm and a maximum revolution speed of about 130 rpm.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.4
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• pp.91-100
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• 2009

In this paper, we propose autonomous intelligent wheelchair system which recognize the commands using the gaze recognition and avoid the detected obstacles by sensing the distance through range sensors on the way to driving. The user's commands are recognized by the gaze recognizer which use a centroid of eye pupil and two reflection points extracted using a camera with infrared filter and two infrared LEDs. These are used to control the wheelchair through the user interface. Then wheelchair system detects the obstacles using 10 ultrasonic sensors and assists that it avoid collision with obstacles. The proposed intelligent wheelchair system consists of gaze recognizor, autonomous driving module, sensor control board and motor control board. The gaze recognizer cognize user's commands through user interface, then the wheelchair is controled by the motor control board using recognized commands. Thereafter obstacle information detected by ultrasonic sensors is transferred to the sensor control board, and this transferred to the autonomous driving module. In the autonomous driving module, the obstacles are detected. For generating commands to avoid these obstacles, there are transferred to the motor control board. The experimental results confirmed that the proposed system can improve the efficiency of obstacle avoidance and provide the convenient user interface to user.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.17-23
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• 1998

A simplified experiment was performed to figure out the atomization characteristics of highly viscous liquid of rice-bran oil by applying ultrasonic energy to improve the atomization of spray droplets. A spray system, an ultrasonic system, and three kinds of pintle-type nozzles(pin-edge angle: 5 , 10 , 15 ) were manufactured. To investigate the effects of ultrasonic energy on the atomization of a highly viscous liquid, a phase doppler particle analyzer was used for the measurement and calculation of spray droplets data. Nozzle opening pressures were chosen of 3 levels, i.e, 10, 13, 16 MPa. As a result, it could be concluded that the ultrasonic energy was effective to improve the spray atomization when applied to the fuel by means of 3 different nozzles because of the effects of the liquid fuel cavitation and relaxation between molecules caused by ultrasonic energy. The improvement rate of the spray atomization by the ultrasonic spray atomization by the ultrasonic spray compared with the conventional spray was about 10% increase in the case of pintle type nozzles. With the increase of pin-edge angles the distribution lines by nozzle opening pressures are declined for both conventional and ultrasonic sprays. This means that the increase of the pin-edge angle improves the atomization of sprays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.94-94
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• 2009

전기 에너지를 기계적 에너지 변환하고 또한, 기계적 에너지를 전기 에너지로 변환할 수 있는 압전 세라믹스는 압전 변압기 (piezoelectric transformer), 초음파모터, 센서등과 같은 응용분야에 넓게 사용되고 있다. 특히, 압전 변압기의 설계와 제조방법에 대해서는 이미 상당히 많은 연구가 수행되어 왔다. 특히, 전원장치에 있어서는 현재 주요부품으로 사용되고 있는 권선형 변압기와 같은 전자 변환기의 대체품으로서 누설손실이 없는 압전세라믹스 소재의 특성을 이용한 압전변압기의 개발과 응용연구가 국내외적으로 활발히 진행 중이다. 하지만 지금 까지 널리 사용된 PZT계 압전 세라믹스는 환경문제에 있어서 문제점을 가지고 있다. $1200^{\circ}C$ 이상에서 소결되는 PZT계열의 압전세라믹스 소재를 사용한 전자부품의 60~70%이상이 PbO로 구성되어 있기 때문에 $1000^{\circ}C$ 부근에서 급격한 휘발특성을 보이는 PbO로 인한 환경오염문제가 대두되고 있다. 압전변압기, 초음파모터등에 사용될 수 있는 무연계 압전재료 중에 PZT 압전소자의 기능을 대체할 만한 물질로는 높은 큐리온도와 우수한 압전특성을 보이는 $(Na,K)NbO_3$세라믹스가 가장 유력한 것으로 알려져 있다. 즉, 압전변압기용 조성 세라믹스는 높은 에너지 변환효율을 위해서 전기기계 결합계수($k_p$)가 커야 되며, 발열에 의한 온도 상승을 억제하기 위하여 기계적 품질계수($Q_m$)가 큰 것이 바람직하다. 또한, 높은 전류를 발생하기 위해서는 유전상수가 커, 압전변압기의 출력측 정전용량을 크게 하여야 한다. 본 연구에서는 무연계 압전세라믹스를 개발하고, 이를 이용한 전력밀도(power density)가 높은 무연계 압전변압기를 제작하여 그에 대한 전기적 특성을 조사하였다. 따라서 본 연구에서는 무연 압전변압기용 압전 세라믹스를 개발하기 위해 뛰어난 압전 및 유전특성을 가진 무연$(Na,K)NbO_3$계 세라믹스를 기본조성으로 하였고, KCN을 복합 첨가하여 볼 변화에 따른 미세구조, 압전 및 유전특성을 조사하고. 가장 우수한 조성으로 비납 압전변압기를 제작하여 전기적특성을 조사하였다.