• Journal of Welding and Joining
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• 제18권5호
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• pp.49-54
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• 2000

High speed rotating arc process, forming a flat bead surface with shallow penetration depth, can be applied to the automatic seam tracking, because the amplitude of current waveform increases at high rotation speed. Two high speed arc rotation mechanisms have been developed in Japan and Germany b rotating the electrode nozzle using an external motor, which are used prevalently for narrow gap and conventional seam welding. In this study, a new rotation mechanism was developed by using a hallow shaft motor designed to be installed in the electrode nozzle. By rotating the welding arc, the amplitude of current waveform increases remarkably since the self-regulation of arc is not fully performed. Experiments show that the arc sensor with high-speed rotation arc has improved its responsiveness and sensitivity.

• 한국생산제조학회지
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• 제25권4호
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• pp.301-306
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• 2016

High speed polishing can kinematically increase the polishing removal rate by using the conventional Preston equation, especially for hard substrates such as sapphire or diamond. However, high speed effects should be clarified beforehand considering the lubrication state and process parameter variations. In this paper, we developed a polishing experimental method and apparatus to determine the lubrication state by measuring the real time friction coefficient using two load cells. Through experiments, we obtained a boundary lubrication state above 0.35 of the friction coefficient by using low table speed and high polishing load, indicating a synchronized stable behavior in polishing head rotation. However, larger Stribeck indexes by a high speed above 200 rpm can generate a hydrodynamic lubrication state below 0.25 of the low friction coefficient. This causes the polishing head rotation to stop. A forced and synchronized head rotation is required for high speed polishing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.959-962
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• 2000

In this study, the micro shaft was fabricated by high speed etching process. The integration of the kinetic energy of circumference and the effect of etching takes less time to fabricate the micro shaft than any other conventional methods. First, the end part of the rod(SKD11) was dipped in chemical solution(FeCl$_3$) and the rod rotated at high speed(3500-10000rpm). Experimental setup was simply composed of high speed motor. chemical solution and $\Phi$ 1 mm rod. The main factors of diameter control are chemical concentration, reaction time and rpm. has a result. the diameter of the dipped rod was decreased by 200${\mu}{\textrm}{m}$ by high speed rotation and its shape and surface was good. From this experiment, we found the possibility to manufacture micro shaft without very expensive equipment.

• 한국기계가공학회지
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• 제15권5호
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• pp.80-85
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• 2016

In recent years, work to improve the power of a tractor has been in development. This study, using the mid-PTO power of a compact tractor, attempted to develop a high-speed mid-mower by setting the rotation to more than 3,000 RPM designed/manufactured major components of the high speed mid-mower. The performance of high-speed mid-mower was evaluated by the precision of straight bevel gears, and durability, the noise of the gearbox, the gearbox internal temperature, the maximum rotation speed of the mid-mowers, and the grass cutting test. Through the performance test results, the maximum number of revolutions of the mid-mower was measured over 3,000RPM, the gearbox noise and gearbox internal temperature satisfied the performance requirements of a high speed mid-mower.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.477-478
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• 2010

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.17-18
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• 2008

• 전력전자학회논문지
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• 제23권1호
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• pp.16-23
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• 2018

PM synchronous motor may be rotated to an arbitrary direction and speed by outside wind under natural condition in cases where the fan is applied outside, such as in vehicle radiators and outdoor air-conditioners. Sensorless controls that cannot detect rotor position requires additional sensorless control algorithm because a rotor is rotated by an external load. In this study, the sensorless control of a PM synchronous motor under naturally rotating condition is proposed. The natural rotation conditions are classified as forward high-speed rotation, reverse high-speed rotation, and low-speed rotation. Experiment results verify the performance of the sensorless control, including the rotor speed and position detection at natural rotation mode and switch to the closed-loop sensorless control.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2061-2066
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• 2011

사이클로이드 감속기는 기계의 회전수를 조절하기위한 장치이다. 사이클로이드 감속기는 큰 토크로 변환시킬 수 있는 장점이 있지만 높은 회전수 에는 적합하지 않다. 한편 200톤 하중이 가해지는 수송기기에 있어서 감속기의 사용한계속도를 찾아내기는 불가능하다. 본 연구에서는 LS-DYNA를 이용하여 마찰손실동력을 수치 해석적으로 검토하였다. 최대토크3.5ton-m에 있어서 회전수 60rpm 그리고 162rpm으로 구동하여 해석을 수행한 결과 다음과 같은 결과를 얻었다. 60rpm회전의 경우 최대응력은 RV gear의 경우 463MPa 핀기어의 경우 507MPa이 발생하였다. 마찰손실동력은 50kW이며, 162rpm의 경우 최대응력값은 RV gear와 핀기어 각각 550MPa, 538MPa이 발생하였다. 손실동력은 175kW이 발생하여 사용이 불가능하다는 것을 알 수 있었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권1호
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• pp.6-14
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• 2011

This paper presents a high-speed QR decomposition architecture for the multi-input-multi-output (MIMO) receiver based on Givens rotation. Under fast-varying channel, since the inverse matrix calculation has to be performed frequently in MIMO receiver, a high performance and low latency QR decomposition module is highly required. The proposed QR decomposition architecture is composed of Sign-Select Lookahead (SSL) coordinate rotation digital computer (CORDIC). In the SSL-CORDIC, the sign bits, which are computed ahead to select which direction to rotate, are used to select one of the last iteration results, therefore, the data dependencies on the previous iterations are efficiently removed. Our proposed QR decomposition module is implemented using TSMC 0.25 ${\mu}M$ CMOS process. Experimental results show that the proposed QR architecture achieves 34.83% speed-up over the Compact CORDIC based architecture for the 4 ${\times}$ 4 matrix decomposition.

• 한국기계가공학회지
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• 제13권4호
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• pp.99-105
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• 2014

The domestic airline industry undertakes the production of finished products by assembling existing self-described components via a design process which involves assembly and production steps, after which many of the finished products are exported. However, high reliability and stability must be guaranteed, because customers require high-precision components at the time of manufacturing. In the aircraft parts industry, the mass production of high-value-added parts is limited. Therefore, a small production scale depending on the part is used, as many types of conventional CNC lathe machines with X-axis and Z-axis as well as Z-axis and C-axis CNC milling are used. The parts also rely on high-pressure air to increase production. The most important factors are good stability during processing, as high-precision parts are required, as noted above. It was found that as the C-axis rotation speed increased, the diameter of the cutting tool decreased with a decrease in the surface roughness, while the workpiece rotation speed increased with an increase in the surface roughness.