• Journal of Power Electronics
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• 제19권5호
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• pp.1224-1234
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• 2019

Hybrid rotor position estimation methods that integrate a fundamental model and high frequency (HF) signal injection are widely used for the wide speed-range sensorless control of interior permanent-magnet synchronous machines (IPMSMs). However, the direct transition of two different schemes may lead to system fluctuations or system instability since two estimated rotor positions based on two different schemes are always unequal due to the effects of parameter variations, system delays and inverter nonlinearities. In order to avoid these problems, a seamless transition strategy to define and construct a virtual q-axis inductance is proposed in this paper. With the proposed seamless transition strategy, an estimated rotor position based on a fundamental model is forced to track that based on HF signal injection before the transition by adjusting the constructed virtual q-axis inductance. Meanwhile, considering that the virtual q-axis inductance changes with rotor position estimation errors, a new observer with a two-phase phase-locked loop (TP-PLL) is developed to accurately obtain the virtual q-axis inductance online. Furthermore, IPMSM sensorless control with maximum torque per ampere (MTPA) operations can be tracked automatically by selecting the proper virtual q-axis inductance. Finally, experimental results obtained from an IPMSM demonstrate the feasibility of the proposed seamless transition strategy.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1424-1430
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• 2013

This paper presents design procedure of the magnetic bearings used for high-speed electric machines and flywheel energy storage systems. Magnetic bearing can be categorized by inner-rotor type and outer-rotor type according to the position of the rotary disc. These two types are applicable based on application environments such as application space, required attraction force, and controllability. Magnetic bearing is generally designed based on the ratio (geometrical coefficient or geometrical efficiency) of pole width to rotor journal radius but proper ratio is only decided by the analysis. This is the difficulty of the magnetic bearing design. In this paper, proper design technology of the inner-rotor type and outer-rotor-type eight pole magnetic bearings is introduced and compared with the FEM analysis results, which verifies the proposed design procedure is suitable to be applied to the design of the magnetic bearings for the industrial applications and flywheel energy storage system.

• 한국전자거래학회지
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• 제21권4호
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• pp.29-40
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• 2016

음성 사용자 인터페이스(VUI)는 인간에게 가장 친숙하고 편안한 인터페이스이다. VUI는 이미 스마트폰에 적용되어 있으며 최근에는 클라우드 및 AI 기술의 발전으로 VUI 적용 제품은 더욱 확대되고 있다. 그러나 가장 많이 보급되어 있는 스마트폰의 경우에도 VUI를 사용하는 사용자는 매우 적은 상황이다. 본 연구의 목적은 현재 스마트폰에서 사용되고 있는 VUI의 이용 현황 및 사용자 인식을 조사하고 문제점을 파악하여 향후 VUI 사용성 제고를 위한 연구 방향을 제시하는 것이다. 163명의 대학생들을 대상으로 스마트폰 VUI의 사용 현황에 대한 설문 조사를 수행하였다. 조사 결과 VUI의 인지도는 높지만 사용률은 매우 낮았으며, 많은 사용자가 음성 인식 속도, 반응 속도 및 작동 방법에 대해 불편함을 느끼고 있는 것으로 나타났다. 대부분의 사용자가 호기심에서 VUI를 사용해봤지만 일부만이 계속 사용하고 있는 것으로 조사되었으며, 많은 사용자들이 기계에게 말하는 것과 다른 사람들이 듣는 것에 거부감을 가지고 있었다. 본 연구의 결과는 VUI의 활용도를 제고하기 위한 향후 연구에 도움이 될 것으로 기대된다.

• 대한기계학회논문집A
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• 제40권11호
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• pp.913-918
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• 2016

자동차 엔진과 변속기 블록 등의 가공과정에서 잔류하는 기름때를 제거하기 위한 부품 세척장비는 정교한 제어장치 없이도 정확한 수류방향 절환이 원활히 이루지는 3 방향 절환밸브를 사용한다. 그러나, 밸브의 복잡한 유로 및 바텀플러그 형상으로 인해 유속변화가 심하게 발생하여 공동현상이 나타날 수 있다. 본 연구에서는 3 방향 절환밸브 내의 유동특성을 해석적으로 평가하였으며, 바텀플러그 하부에서 나타나는 공동현상을 공동화지표와 POC(Percent of cavitation)를 도입하여 정량화하였다. 공동현상의 저감을 위해 바텀플러그 형상을 매개변수화하고, 해석의 수렴성 개선과 해석시간을 단축시킬 수 있는 단순 유한요소모델을 이용하여 유동해석을 통한 형상최적설계를 실시하였다. 또한, 연구팀에서 보유하고 있는 유동시험설비와 ISA-RP75.23 규격에 맞게 제작된 시편을 이용하여 공동현상 가시화 실험을 실시하여 해석결과를 검증하였다.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1863-1872
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• 2006

In FMS (Flexible Manufacturing System) and CIM (Computer Integrated Manufacturing), machine-tools have been the target of integration in the last three decades. The conventional concept of integration is being changed into the autonomous manufacturing device based on the knowledge evolution by applying advanced information technology in which an open architecture controller, high-speed network and internet technology are included. In the advanced environment, the machine-tools is not the target of integration anymore, but has been the key subject of cooperation. In the near future, machine-tools will be more improved in the form of a knowledge-evolutionary intelligent device. The final goal of this study is to develop an intelligent machine having knowledge-evolution capability and a management system based on internet operability. The knowledge-evolutionary intelligent machine-tools is expected to gather knowledge autonomically, by producing knowledge, understanding knowledge, reasoning knowledge, making a new decision, dialoguing with other machines, etc. The concept of the knowledge-evolutionary intelligent machine is originated from the machine control being operated by human experts' sense, dialogue and decision. The structure of knowledge evolution in M2M (Machine to Machine) and the scheme for a dialogue agent among agent-based modules such as a sensory agent, a dialogue agent and an expert system (decision support agent) are presented in this paper, with intent to develop the knowledge-evolutionary machine-tools. The dialogue agent functions as an interface for inter-machine cooperation. To design the dialogue agent module in an M2M environment, FIPA (Foundation of Intelligent Physical Agent) standard platform and the ping agent based on FIPA are analyzed in this study. In addition, the dialogue agent is designed and applied to recommend cutting conditions and thermal error compensation in a tapping machine. The knowledge-evolutionary machine-tools are expected easily implemented on the basis of this study and shows a good assistance to sensory and decision support agents.

• 대한기계학회논문집A
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• 제34권11호
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• pp.1733-1740
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• 2010

대형 드럼세탁기의 낙하 충격에 대한 포장재의 동적 거동 분석을 수행하였다. 해석에는 충격 해석에 널리 쓰이고 있는 LS-DYNA를 사용하였으며, 자유 낙하 시의 충격 가속도와 유효 응력, 그리고 고속 카메라를 통한 포장재 압축 변형 비교를 통해 해석 결과의 신뢰성을 검증하였다. 완충 특성 및 포장재 구조 에 대한 파라미터 분석을 통해 기존 포장 구조에 대한 설계 개선안을 도출하였으며, 유통 시험을 통해 유효성을 검증하였다. 본 연구에서 사용한 해석 기법 및 분석 방법 등을 통해, 향후 드럼 세탁기의 완충 성능 및 재료비 개선에 효과적으로 기여할 수 있을 것으로 기대된다.

• 한국기계가공학회지
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• 제18권9호
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• pp.29-35
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• 2019

The structure of the machinery industry due to the 4th industrial revolution is changing from precision and durability to intelligent and smart machinery through sensing and interconnection(IoT). There is a growing need for research on prognostics and health management(PHM) that can prevent abnormalities in processing machines and accurately predict and diagnose conditions. PHM is a technology that monitors the condition of a mechanical system, diagnoses signs of failure, and predicts the remaining life of the object. In this study, the vibration generated during machining is measured and a classification algorithm for normal and fault signals is developed. Arbitrary fault signal is collected by changing the conditions of un stable supply cutting oil and fixing jig. The signal processing is performed to apply the measured signal to the learning model. The sampling rate is changed for high speed operation and performed machine learning using raw signal without FFT. The fault classification algorithm for 1D convolution neural network composed of 2 convolution layers is developed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.962-977
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• 2019

The human voice is a convenient method of information transfer between different objects such as between men, men and machine, between machines. The development of information and communication technology, the voice has been able to transfer farther than before. The way to communicate, it is to convert the voice to another form, transmit it, and then reconvert it back to sound. In such a communication process, a vocoder is a method of converting and re-converting a voice and sound. The CELP (Code-Excited Linear Prediction) type vocoder, one of the voice codecs, is adapted as a standard codec since it provides high quality sound even though its transmission speed is relatively low. The EVRC (Enhanced Variable Rate CODEC) and QCELP (Qualcomm Code-Excited Linear Prediction), variable bit rate vocoders, are used for mobile phones in 3G environment. For the real-time implementation of a vocoder, the reduction of sound quality is a typical problem. To improve the sound quality, that is important to know the size and shape of noise. In the existing sound quality improvement method, the voice activated is detected or used, or statistical methods are used by the large mount of data. However, there is a disadvantage in that no noise can be detected, when there is a continuous signal or when a change in noise is large.This paper focused on finding a better way to decrease the reduction of sound quality in lower bit transmission environments. Based on simulation results, this study proposed a preprocessor application that estimates the SNR (Signal to Noise Ratio) using the spectral SNR estimation method. The SNR estimation method adopted the IMBE (Improved Multi-Band Excitation) instead of using the SNR, which is a continuous speech signal. Finally, this application improves the quality of the vocoder by enhancing sound quality adaptively.

• KNOM Review
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• 제21권2호
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• pp.26-34
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• 2018

클라우드 컴퓨팅 및 서비스의 확산으로 인터넷 트래픽과 서비스 품질 향상에 대한 요구가 증가하면서 데이터 센터 내부 서버의 리소스를 보다 효율적으로 사용하는 서버 가상화와 네트워크 가상화 기술에 대한 관심이 증가하고 있다. 트래픽 모니터링을 위해 패킷을 복제하는 기존의 하드웨어 TAP (Test Access Port) 장비는 서버 가상화 환경에서 구성된 가상 데이터 경로 (datapath)에 적합하지 않기 때문에 하드웨어 TAP 장비를 소프트웨어로 구현한 Virtual TAP (vTAP)을 통해 가상 스위치에서 패킷을 복제한다. 그러나 가상 스위치에서 vTAP을 구현하면 호스트 머신의 컴퓨팅 리소스를 가상 스위치 및 가상 머신과 공유하기 때문에 성능 저하 문제가 발생한다. 이 문제를 극복하기 위해 고속 패킷 처리 기술인 eBPF (Extended Berkeley Packet Filter) 기반의 vTAP 구현 기술을 제안하고 기존 방법과 성능을 비교한다.

• Journal of Biosystems Engineering
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• 제1권1호
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• pp.15-15
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• 1976

In analyzing the operational characteristics of a rice whitening machine, the internal radial pressure of the machine was measured using strain gage equipment. Changes in cylinder and feed screw configurations, screen type, cylinder speed and counter-pressure levels were examined to determine their impact on the quality and quantity of milled rice and the performance of the machine. The results are summarized as follows: 1. The internal radial pressure in the whitening chamber varied with the surface condition of the grain being processed. During the first or second pass through the machine, pressure was relatively low, reached a maximum after two to three passes with combinations I and II, three to six with combination III and then began to fall. 2. The pitch of the feed screw and the size of the feed gate opening which determine the rate of entry of grain into the whitening chamber, appeared to be the most important factor aff-::cting the degree of radial pressure, quality and quantity of milled rice and the efficiency of the machine. Using a feed screw with a wide pitch (4.8cm), radial pressure was relatively high and head rice recovery ratio \vere quite low. In this case capacity and machine effic?iency were much higher than obtained when using a feed screw with a narrow pitch (2.3cm). Very significant responses in radial pressure, head rice recovery rates and machine capacity were observed with changes in cylinder speed and counter-pressure levels when using the wide pitch feed screw. 3. The characteristics of the screen which surrounds the whitening chamber had an important effect on whitening efficiency. The existence of small protuberances on the original screen resulted in significant increases in both machine capacity and efficiency but without a significant decrease in head rice recovery or development of excessive radial pressure. Further work is required to determine the effects of screen surface conditions and the shape of the cylinderical steel roller on the rate of bran removal, machine efficiency and recovery rates. The size of the slotted perforations 0:1 the screen affects total milled rice recovery. The opening size on the original screen was fabricated to accommodate the round shape of Japonica rice varieties but was not suitable for the more slender Indica type. Milling Indica varieties with this screen resulted in a reduction in total milled rice recovery. 4. An increase in cylinder speed from 380 to 820 rpm produced a positive effect on head rice recovery for all machine combinations at every level of counter-pressure used in the tests. Head rice recovery was considerably lower at 380rpm using a wide screw pitch when compared to the results obtained at speeds from 600 to 820 r.p.m. The effects of cylinder speed On radial pressure, capacity and machine efficiency showed contrasting results, depending on the width of the feed screw pitch. With a narrow feed screw pitch (2.3cm), a direct proportional relationship was observed bet?ween cylinder speed and both radial pressure and machine efficiency. In contrast, using a 4.8 centimeter pitch feed roller produced a series of inverse relationships between the above variables. Based on the results of this study it is recommended when milling Indica type long grain rice varieties that the cylinder speed of the original machine be increased from 500-600 rmp up to a minimum of 800 rpm to obtain a greater abrasive effect between the grain and the screen. The pitch of the feed screw should be also reduced to decr?ease the level of internal radial pressure and to obtain higher machine efficiency and increased quality of milled rice with increased cylinder speeds. Further study on the interaction between cylinder speed and feed screw pitch is recommended. 5. An increase in the counter pressure level produced a negative effect On the head rice recovery with an increase in radial pressure, capacity, and machine efficiency over all combinations and at every level of cylinder speed. 6. Head rice recovery rates were conditioned primarily by the pressure inside the whitening chamber. According to the empirical cha racteristics curve developed in this study, the relationships of head rice recovery ($Y_h$) and machine capacity ($Y_c$/TEX>) to internal radial pressure ($X_p$) followed an inverse quadratic function and a linear function respectively: $$Y_h^\Delta=\frac{1}{{1.4383-0.2951X_p^\ast+0.1425X_p^{\ast\ast}}^2} , (R^2=0.98)$$$$Y_c^\Delta=-305.83+374.37X_p^{\ast\ast}, (R^2=0.88)$$The correlation between capacity and power consumption per unit of brown rice expressed in the following exponential function: $$Y_c^\Delta=1.63Y_c^{-0.7786^\{\ast\ast}, (R^2=0.94)$$These relationships indicate that when radial pressure increases above a certain range (1. 6 to 2.0 kg/$cm^2$ based On the results of the experiment) head ricerecovery decrea?ses in a quadratic relation with a inear increase in capacity but without any decrease in power consump tion per unit of brown rice. On the other hand, if radial pressure is below the range shown above, power consumption increases dramatically with a lin?ear decrease in capacity but without significant increases in head rice recovery. During the operation of a given whitening machine, the optimum radial pressure range or the correct capacity range should be selected by controlling the feed rate and/or counter-pressure keeping in mind the condition of the grain, particulary the hardness. It was observed that the total number of passes is related to radial pessure level, feed rate and counter-pressure level. The higher theradial pressure the fewer num?ber of pass required but with decreased head rice recovery. In particular, when using high feed rates, the total number of passes should be increased to more than three by reducing the counter-pressure level to avoid decreaseases in head rice recovery (less than 65 percent head rice recovery on the basis of brown rice) at every cylinder speed. 7. A rapid rise in grain temperature seemed to have a close relationship with the pressure generated inside the whitening chamber and, subsequently with head rice reco?very rates. The higher the rate of increase, the lower were the resulting head rice recoveries.