• 로봇학회논문지
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• 제14권1호
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• pp.58-64
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• 2019

The paper proposes a stiffness measurement device composed of a measurement part including six indenters and a fixing part including four fixtures. The device is able to make simultaneously measurements of the stiffness of human arm. The six indenters make use of both position and force control schemes sequentially whenever needed. In addition, the loadcells and the digital encoders are attached to the indenters and electric motors, respectively, so that the data can be provided in real time. On the end of the indenter, two-axis potentiometer is attached in order to measure the angle difference between the applied force axis and the axis normal to the skin of human arm, and to convert the force measured on the loadcell into the actual applied force to skin. For this purpose, the mapping between the voltage output and the angle of potentiometer was obtained by fitting it for each axis. Ultimately, the measurement device was able to measure the stiffnesses of six regions of human arm.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1017-1023
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• 2019

The increase of the alternate current frequency results in increased rotational speed of the electrical motors and connected pumps. The consequence for the reactor coolant pumps is increased flow in primary coolant system. Increase of the current frequency can be initiated by the subsynchronous resonance phenomenon (SSR). This paper analyses the implications of the SSR and consequential increase of the frequency on the nuclear power plant safety. The Simulink $MATLAB^{(R)}$ model of the steam turbine and governor system and RELAP5 computer code of the pressurized water reactor are used in the analysis. The SSR results in fast increase of reactor coolant pumps speed and flow in the primary coolant system. The turbine trip value is reached in short time following SSR. The increase of flow of reactor coolant pumps results in increase of heat removal from reactor core. This results in positive reactivity insertion with reactor power increase of 0.5% before reactor trip is initiated by the turbine trip. The main parameters of the plant did not exceed the values of reactor trip set points. The pressure drop over reactor core is small discarding the possibility of core barrel lift.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.380-383
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• 2014

허브(hub) BLDC(Brushless Direct Current) 전동기란 아우터로터 타입 고효율 전동기로 다극의 영구자석으로 이루어진 회전자가 바퀴의 구동축이 되는 직접구동용 모터를 말하며, 휠인 모터로도 불린다. 본 연구에서는 BLDC 허브 모터 구동을 위한 벡터제어 기법 속도 제어기를 dsPIC30f2010 16비트 마이크로 컨트롤러를 이용하여 설계한다. 특히 복잡한 연산 시간을 줄이는 벡터 제어 방법을 제안하고, MOSFET 인버터 구동기를 직접 설계하여 경제성을 높인다.

• 드라이브 ㆍ 컨트롤
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• 제18권3호
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• pp.8-15
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• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• The Journal of Asian Finance, Economics and Business
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• 제9권4호
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• pp.399-408
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• 2022

Corporate governance and innovation have been a hot topic in recent boardroom talks, whether in the trade or manufacturing industries. Governance innovations are highly significant for the survival of the motor vehicle industry like Honda, Nissan, New General Motors, and Toyota. The study chooses the motor vehicle industry which crosses the age of a century and sufficient corroborative support exists with the perspective of distinctive objectives. Using the population of all the automobile companies listed on the Pakistan stock exchange (PSX), we distill automobile companies to evaluate the firm performance using the panel data regression approach. The results show that there is a significant relationship between gender diversity, audit committees, and firm performance. Further, board size also has a positive impact on firm performance. We identify that the governance mechanism of firms found in default of the frequency of audit committee meetings. By considering results, only limited knowledge of finance directors and also very few numbers of female directors are on the board. Empirical findings of this work might be useful for policymakers in attempting to draft a corporate governance framework better able to monitor the financial performance of firms through female directors and also serve as a catalyst for the regulators of electric vehicles.

• Earthquakes and Structures
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• 제24권1호
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• pp.1-9
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• 2023

A model for calculating structure interacted mechanics is proposed. A structural interaction model and controller design based on tuned mass damping (TMD) was developed to control the induced vibration. A key point is to introduce a new analytical model to evaluate the properties of the TMD that recognizes the motion-dependent nonlinear response observed in the simulations. Aiming at the problem of increased current harmonics and low efficiency of permanent magnet synchronous motors for electric vehicles due to dead time effect, a dead time compensation method based on neural network filter and current polarity detection is proposed. Firstly, the DC components and the higher harmonic components of the motor currents are obtained by virtue of what the neural network filters and the extracted harmonic currents are adjusted to the required compensation voltages by virtue of what the neural network filters. Then, the extracted DC components are used for current polarity dead time compensation control to avert the false compensation when currents approach zero. The neural network filter method extracts the required compensation voltages from the speed component and the current polarity detection compensation method obtains the required compensation voltages by discriminating the current polarity. The combination of the two methods can more precisely compensate the dead time effect of the control system to improve the control performance. Furthermore, based on the relaxed method, the intelligent approach of stability criterion can be regulated appropriately and the artificial TMD was found to be effective in reducing cross-wind vibrations.

• 해양환경안전학회지
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• 제29권6호
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• pp.697-703
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• 2023

최근 대기오염으로 인한 환경오염을 줄이고자 국제 산업계의 노력의 일환으로 국제해사기구(IMO)의 규제 발효등으로 이어지고 있다. IMO는 EEXI,EEDI,CII 등 선박에서 나오는 대기오염을 줄이기 위해 각종 규제를 발효시키고 선박에서 소모되는 전력을 줄여 에너지를 절약하는 방안을 추진하고 있다. 선박에서 사용되는 전력의 대부분은 전동기가 차지한다. 선박에 설치된 전동기 중 큰 부하를 차지하는 기관실 송풍기는 수요와 관계없이 정속운전으로 운전하기 때문에 주파수제어를 통한 에너지절감을 기대할 수 있다. 본 연구에서는 발전기의 과급기에 연소공기를 공급하는 발전기 송풍기의 전동기 주파수를 제어하여 에너지 절감에 대한 실효성을 입증하였다. 송풍기 주파수 입력에 따른 과급기출구 온도의 출력 데이터를 기반으로 시스템을 모델링하고, 과급기 출구온도를 목표값으로 하여 주파수를 제어하는 PI 제어계를 형성하여 과급기 설계기준 출구온도를 유지하면서 송풍기의 주파수 제어를 통해 연간 15,552kW 전력소모량을 절감하였다. 송풍기 팬 주파수 제어를 통한 에너지절감액의 유효성은 하계(4월~9월) 및 동계(3월~10월) 기간동안 검증하였으며 이를 토대로 실습선의 연간 6,091천원의 유류비 절약과 이산화탄소 8.5Ton, SOx 2.4kg, NOx 7.8kg의 대기오염물질 저감을 달성하였다.

• 한국자기학회지
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• 제22권3호
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• pp.109-115
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• 2012

지난 5년간 NdFeB계 이방성 본드자석은 25 MGOe의 높은 자기특성을 강점으로 기존 페라이트 영구자석을 갈음하면서 모터의 경량화라는 새로운 패러다임을 주도했고 자동차용과 전동공구용 모터산업분야에서 두드러진 약진을 보였다. 또한 차체중량감소를 통한 연비향상이라는 자동차산업의 기술동향에 정확히 초점을 두고 기존모터의 50 % 경량화라는 새로운 변혁을 이끌어 냈다. 그러나 2010년 7월에 중국이 희토류원소의 수출규제를 발표함에 따라 2011년 희토류 원자재는 또 한 차례의 폭등을 기록하였고 그 여파는 전방 수요산업에 심각한 충격으로 던져지고 있다. 각 희토류 주요 소비국들은 자원 확보, 희토류 최소사용부품개발 및 희토류 대체 신기술개발 강화에 총력을 다하는 모습이다. 이러한 환경적 변화가 이방성 본드자석 분야에는 중희토류 원소인 Dy의 사용량을 줄이면서 보자력을 향상시키고자하는 기술적 도전을 유발하였고 모터고속화 응용분야에 탐색을 시도하게 하였다. 본 글에서는 희토류 자원문제에 대한 각국 희토류자석산업의 대응과 NdFeB 이방성 본드자석으로 대표되는 Aichi Steel사의 MAGFINE 자성분말에 대해 최근의 개발 동향 및 응용분야에 대해 소개하고자 한다.

• International Journal of Fluid Machinery and Systems
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• 제4권4호
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• pp.367-374
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• 2011

Water hammer pumps can effectively use the water hammer phenomenon in long-distance pipeline networks that include pumps and allow fluid transport without drive sources, such as electric motors. The results of experiments that examined the effect of the geometric form of water hammer pumps by considering their major dimensions have been reported. In addition, a paper has also been published analyzing the water hammer phenomenon numerically by using the characteristic curve method for comparison with experimental results. However, these conventional studies have not fully evaluated the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps. Therefore, as a first stage for the understanding of water hammer pump performance in comparison with the characteristics of typical turbo pumps, the previous paper experimentally examined how the hydrodynamic characteristics were affected by the inner diameter ratio of the drive and lifting pipes, the form of the air chamber, and the angle of the drive pipe. To understand the behavior of the components attached to the valve chamber and the air chamber that affects the performance of water hammer pumps, the previous study also determined the relationship between the water hammer pump performance and temporal changes in valve chamber and air chamber pressures according to the air chamber capacity. For the geometry of components attached to the drain valve, which is another major component of water hammer pumps, this study experimentally examines how the water hammer pump performance is affected by the length of the spring and the angle of the drain pipe.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.23-30
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• 2014

This paper proposes a dead time compensation method for an AC motor drive using phase current polarity information which is detected based on a digital programmable low-pass filter (PLPF). The polarity detection using the PLPF is an alternative solution of a conventional method which uses a general low-pass filter (LPF) and hysteresis bands in order to avoid jittering due to noises. The PLPF not only adjusts its cutoff frequency according to the synchronous frequency of AC motors but also eliminates a gain attenuation and phase delay which are main problems of the general LPF. Through the PLPF, a fundamental component signal without gain and phase distortions is extracted from the measured raw current signal with noise. By use of the fundamental component, the polarity of current is effectively detected by reducing the hysteresis band. Finally, the proposed method compensates the dead time effects by adding or subtracting average voltage value to voltage references of the controller according to the detected current polarity information. The proposed compensation method is experimentally verified by compared with the conventional method.