• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.670-674
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• 2016

The control performance of hybrid PWM inverter using a phase current measurement is presented in this paper. The hybrid PWM technique consists of space vector pulse width modulation (SVPWM) and six-step voltage control operation. The SVPWM is performed to reduce the harmonic components in the low speed region, and the six-step modulation is applied to increase the maximum speed of the IPMSM in the high speed region. Therefore, it is possible to obtain a great performance in both the low speed range and high speed range. However, the six-step modulation cannot be completely implemented, since the inverter that includes the lag-shunt sensing method has an immeasurable current region. In this paper, a quasi-six-step modulation using a modified voltage vector is proposed. The validity and usefulness of the proposed PWM technique is verified by MATLAB/Simulink and experimental results.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.195-196
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• 2012

This paper describes combustion tuning methodology of double-swirl gas turbine combustor using six sigma tools. This methodology is consist of five steps-Define, Identify, Design, Optimize and Verify (DIDOV). First, the NOx reduction target was defined in the step design; second, the current status of the plant was diagnosed in the step of identify; third, the vital few control parameters to achieve the defined target were determined by analyzing the correlation between the control parameters and NOx emissions in the step of design; fourth, the optimum condition was derived from one of the six sigma tools in the step of optimize; finally, the optimum condition was verified by applying the condition to the gas turbine combustor in the step of verify. As a result of the suggested method, averaged NOx emissions were reduced by more than 70% and the standard deviation was improved by more than 60%. Thus, this methodology can be attributed to the efficient reduction of NOx emission with saving combustion tuning time.

• 전력전자학회논문지
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• 제26권4호
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• pp.263-270
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• 2021

Active AC/DC converters with PWM operation are utilized to regulate rectified DC bus voltage of a permanent magnet synchronous generator in the maritime DC power system. A DC bus voltage regulation strategy that exploits the six-step operation is proposed in this study. Compared with that of the PWM operation, switching loss of the converter can be significantly reduced under the six-step operation. Moreover, conduction loss can also be reduced due to the high modulation index and reduced flux-weakening current of the six-step operation. A controller is used for the proposed DC bus voltage regulation strategy to verify its validity with the simulation and experimental setup. The simulation and the experimental test results showed that the converter loss reduces to a maximum of 70% and 19%, respectively.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 추계 학술대회
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• pp.157-163
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• 2006

There are big differences in six sigma applications between manufacturing processes and transactional processes. This paper analyzes the differences between two areas by examining 18 six sigma case studies in Korean companies. To characterize six sigma cases, a step-by-step checklist is developed based on 12-step DMAIC methodology proposed by US six sigma academy. On the basis of those characterized data, the differences between two areas are analyzed. The most significant differences is that statistical tools are widely used in manufacturing processes, but qualitative tools are used in transactional processes during improvement phase.

• 대한안전경영과학회지
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• 제15권1호
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• pp.283-292
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• 2013

This paper aims to propose a new steps of hypothesis testing using analysis process and improvement process in the six sigma DMAIC. The six sigma implementation models proposed in this paper consist of six steps. The first step is to establish a research hypothesis by specification directionality and FBP(Falsibility By Popper). The second step is to translate the research hypothesis such as RHAT(Research Hypothesis Absent Type) and RHPT(Research Hypothesis Present Type) into statistical hypothesis such as $H_0$(Null Hypothesis) and $H_1$(Alternative Hypothesis). The third step is to implement statistical hypothesis testing by PBC(Proof By Contradiction) and proper sample size. The fourth step is to interpret the result of statistical hypothesis test. The fifth step is to establish the best conditions of product and process conditions by experimental optimization and interval estimation. The sixth step is to draw a conclusion by considering practical significance and statistical significance. Important for both quality practitioners and academicians, case analysis on six sigma projects with implementation guidelines are provided.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.230-231
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• 2016

본 논문은 공간벡터 변조 방법에서부터 Six-step 동작까지의 새로운 과변조 방법을 제시하였다. 극전압을 푸리에 시리즈를 이용하여 분석하였고 지령 상전압에서부터 펄스 폭 변조 스위칭 신호까지의 알고리즘을 제안하였다. Matlab 시뮬레이션을 통해 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.175-176
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• 2007

본 논문은 매입형 영구자석 동기 전동기의 준 식스스텝 운전(Quasi six-step operation)을 위한 약자속 제어에 대한 새로운 방법을 제안한다. 제안된 방법은 전향 경로(feedforward path)와 궤환 경로(feedback path)로 구성되고 전향 경로는 1차원 참조표로 구성되며 궤환 경로는 전류제어기 출력과 과변조에 의해 제한된 전압의 차이를 이용한다. 제안된 방법을 통해 약자속 제어와 안티 와인드업(anti-windup) 제어가 동시에 이루어질 수 있다. 또한 제한된 직류단 전압 조건에서 식스 스텝(six-step) 운전에서 낼 수 있는 전동기의 최대 토크에 가까이 출력 토크를 발생시키면서 전류 제어를 계속할 수 있는 준 식스 스텝 운전이 가능하다. 제안된 방법의 유효성을 컴퓨터 시뮬레이션과 실험의 결과를 통해 입증하였다.

• International Journal of Quality Innovation
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• 제2권1호
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• pp.58-68
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• 2001

Six Sigma was introduced into Korea in 1997, and it is regarded as a fascinating management strategy in many Korean companies. First of all, the reasons why Six Sigma is fascinating are given and a smart way to introduce Six Sigma is illustrated. Seven step procedures to introduce Six Sigma are explained. Next, the differences of problem-solving processes for project team activities for R&D, manufacturing, and service areas are compared. Third, a typical process for R&D Six Sigma is proposed, and major activities and scientific methods at each process step are suggested. Fourth, some differences between Six Sigma project team and quality circle team are presented. Finally, a Six Sigma model for e-business is proposed and briefly explained.

• 로봇학회논문지
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• 제2권1호
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• pp.55-63
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• 2007

Mobile robots traveling on rough terrain need several algorithms to overcome obstacles. In this paper, we propose the step-type obstacle traversal algorithm to adapt the mobile robot with six arms and wheels to travel on rough terrain. Obstacle traversal is composed of two different stages: planning and control. In planning stage, the required joint torque of each arm as well as the interference between the wheels and the arms are analyzed to guarantee traversing obstacles. Control stage includes such steps as checking distance to obstacle, determining the height and length of obstacle, performing arm motion according to sensed torque data, and evaluating safety at every instance. The proposed algorithm is designed and implemented for CALEB 1 six legged robot developed in the laboratory and verified by simulation and experiment in outdoor environment.

• 품질경영학회지
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• 제36권4호
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• pp.37-46
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• 2008

There are big differences in six sigma projects between manufacturing processes and transactional/service processes. This paper analyzed the differences between the two areas by examining 18 six sigma case studies in Korean companies. To characterize six sigma case studies, step-by-step questions and check criteria were developed based on 12 step DMAIC methodology. On the basis of those characterized data, the differences between two areas were analyzed. Significant differences were found in the number of CTQs, validation of measurement systems, methods to determine improvement objectives, the methods to elicit improvement plans and types of control systems. The most significant difference was that statistical tools were widely used in manufacturing processes, but qualitative tools were used in transactional/service processes during improvement phase.