• Title, Summary, Keyword: Elliptical trajectory

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Analysis of the elliptical shooting trajectory for tuna purse seine (참치선망어선의 타원형 투망궤적 분석)

  • LEE, Da-Yun;LEE, Chun-Woo;CHOI, Kyusuk;JANG, Yongsuk
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.56 no.1
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    • pp.1-10
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    • 2020
  • In the previous study, a shooting trajectory assuming that the purse seine shooting trajectory is a circle was proposed based on the speed and direction of the movement of the fish school. However, in practice, a trajectory that is closer to an elliptical shape than a circular one is often formed. In this study, the existing circular trajectory and the elliptical trajectory methods were compared under the same conditions to confirm the effectiveness of elliptical shooting trajectory. In addition, changes in the eccentricity of ellipses were derived to assess which type of ellipse was appropriate as a shooting trajectory. When a high-speed fish school moves in a straight line, an elliptical shooting trajectory with the eccentricity of 0.7 to 0.9 will be reasonable, and for middle-low speed fish school, an elliptical shooting trajectory with the eccentricity of 0.4 to 0.6 will be more useful than a circle shooting trajectory.

Compensating the Elliptical Trajectory of Elliptical Vibration Cutting Device (타원궤적 진동절삭기의 타원궤적 보정)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.789-795
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    • 2011
  • In elliptical vibration cutting (EVC), cutting performance is largely affected by the shape of an elliptical path of the cutting tool. In this study, two parallel piezoelectric actuators were used to make an elliptical vibration cutting device. When harmonic voltages of $90^{\circ}$ out-of-phase are supplied to the EVC device, creation of an ideal elliptical trajectory whose major and minor axes are parallel to the cutting and thrust directions is anticipated from a kinematic analysis of the EVC device, however, the paths we experimentally observed showed significant distortions in its shape ranging from skew to excessive elongation of the major axis of the ellipse. To compensate distortions, an analytical model describing the elliptical path of the cutting tool was developed and verified with experimental results, and based on the analytical model, the distorted elliptical paths created at 100 Hz, 1 kHz, and 16 kHz were corrected for skew and elongation.

Elliptical Vibration Cutting with Variable Trajectory for Ultra-precision Micro-Machining (초정밀 미세가공을 위한 궤적 변화에 따른 타원 궤적 진동 절삭)

  • Kim, Gi-Dae;Loh, Byoung-Gook
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.11
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    • pp.52-58
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    • 2007
  • A cutting device capable of generating various shapes of the cyclic elliptical trajectory of a cutting tool was proposed and micro v-grooving experiments were performed to investigate the characteristics of elliptical vibration cutting (EVC). The proposed cutting device is comprised of a pair of parallel piezoelectric actuators with which harmonic voltages of varying phase difference and magnitude are supplied, creating various shapes of the elliptical tool path. The attributes of the elliptical locus involving the direction of the axis of an ellipse, the rotational direction and amplitudes of a trajectory were fine-tuned for stable operation of the EVC. The EVC characteristics performed with brass and copper revealed reduction in the cutting resistance and suppression of burr formation, resulting in the enhancement of form accuracy of machined micro-features. While the effect of the EVC increases with the increase of excitation frequency and the amplitude, it is found that a change in the cutting force decreases as the amplitude of an elliptical locus increases.

Kinematical Characteristics of Vibration Assisted Cutting Device Constructed with Parallel Piezoelectric Stacked Actuators (평행한 적층 압전 액추에이터로 구성된 진동절삭기의 기구학적 특성 고찰)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1185-1191
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    • 2011
  • The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

Kinematical Analysis and Vibrational Characteristics of Orthogonal 2-dimensional Vibration Assisted Cutting Device (직교형 2차원 진동절삭기의 기구학적 해석 및 진동 특성 고찰)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.9
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    • pp.903-909
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    • 2012
  • In elliptical vibration cutting(EVC) where the cutting tool traces a micro-scale 2-dimensional elliptical trajectory, the kinematical and vibrational characteristics of the EVC device greatly affect cutting performance. In this study, kinematical and vibrational characteristics of an EVC device constructed with two orthogonally-arranged stacked piezoelectric actuators were investigated both analytically and experimentally. The step voltage was applied to the orthogonal EVC device and the associated displacements of the cutting tool were measured to assess kinematical characteristics of the orthogonal EVC device. To investigate the vibrational characteristic of the orthogonal EVC, sinusoidal voltage was applied to the EVC device and the resulting displacements were measured. It was found from experiments that coupling of displacements in the thrust and cutting directions and the tilt of the major axis of the elliptical trajectory exists. In addition, as the excitation frequency is in vicinity of resonant frequencies the distortion in the shape of the elliptical trajectory becomes greater and change in the rotation direction occurs. To correct the shape distortion of the elliptical trajectory, the shape correcting procedure developed for the parallel EVC device was applied for the orthogonal EVC device and it was shown that the shape correcting method successfully corrects distortion.

Characteristics of Pulse Width Modulation(PWM) Excitation of Ultrasonic Elliptical Vibration Cutting Device (초음파 진동절삭기의 펄스폭변조 가진 특성)

  • Loh, Byoung Gook;Kim, Gi Dae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.1
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    • pp.59-65
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    • 2014
  • To obtain an elliptical trajectory at the cutting edge during elliptical vibration cutting, sinusoidal voltage excitations of two piezoelectric actuators have commonly been used. In this study, PWM excitation, which is relatively simple to generate, was employed and its characteristics were investigated. In experimental and analytical analyses, we found that for PWM excitation, the integer-multiple frequencies of the excitation voltage distorted the shape of the elliptical trajectory, whereas at a duty ratio(DR) of 50%, the distortion of the elliptical trajectory was minimized due to disappearance of the first overtone. When the magnitude of the maximum excitation voltage was maintained at the same level for both PWM and sinusoidal excitation, PWM (DR=50%) excitation produced a greater vibration amplitude than sinusoidal excitation but resulted in more rapid saturation of a high-frequency power amplifier.

Elliptical Trajectory Analysis of Ultrasonic Linear Motor (초음파 리니어 모터의 타원궤적 해석)

  • 김태열;김범진;박태곤;김명호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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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.

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Elliptical Trajectory Analysis of Ultrasonic Linear Motor using ANSYS (ANSYS를 이용한 초음파 리니어 모터의 타원궤적 해석)

  • Choi, Myeong-Il;Park, Tae-Gone;Kim, Myong-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.292-295
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    • 2002
  • Transducer for linear ultrasonic motor with symmetric and anti-symmetric modes was studied. The transducer was composed of two Langevin-type vibrators that cross at right angles with each other at tip. In order to excite two vibration modes, two Langevin-type vibrators must have 90-degree phase difference with each other. As a result, tip of transducers moves in elliptical motion. In this paper, elliptical trajectory of transducer was analyzed by employing the finite element method.

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Design and Fabrication of Novel Linear Ultrasonic Motor (선형초음파 모터의 설계 및 제작)

  • 이동균;한득영;윤석진
    • Journal of the Korean Ceramic Society
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    • v.40 no.10
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    • pp.981-984
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    • 2003
  • A novel linear ultrasonic motor for precision position control was designed and fabricated. It was composed of two piezoelectric actuators with longitudinal ultrasonic fluctuations and shaking beam. When two AC electric fields (Usinwt, Ucoswt) were applied to piezoelectric actuators respectively, the middle part of shaking beam had an elliptical trajectory. According to experimental results, the generative force was proportional to pre-load force but the speed of slider was in inverse proportion. And the bar of shaking beam had a same trajectory with simulation result.