• Journal of Drive and Control
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• v.11 no.4
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• pp.53-60
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• 2014

This paper proposes a control scheme to reduce the power consumption of a variable displacement swash-plate type piston pump supplying oil to a valve-controlled hydraulic cylinder at constant pressure. Whenever flow rate demand was absent, the swash plate angle and the pump speed were changed to the minimum values required to compensate for the internal leakage flow. In response to command signals, the pump speed was changed in proportion to the absolute mean value of the speed component for position commands. At the same time, a pressure regulator was activated to maintain constant system pressure by precisely adjusting the pump speed with the swash plate angle fixed at the maximum. The conventional system consisting of a pressure-compensated variable displacement type pump is driven at a constant speed of 1,800rpm. By comparison, computer simulation and experimental results showed that idling power at stand-by status could be reduced by up to 70% by reducing the pump speed from 1,800rpm to 300rpm and the swash plate angle to the minimum.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.143-148
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• 2023

Among the characteristics of SRM, due to nonlinearity, it is difficult to properly operate to form maximum torque and minimum torque pulsation. In addition, in the case of fixed switching angle control, torque formation according to speed variation is unstable, thereby reducing efficiency. Therefore, active switching angle control according to speed variation is required. Therefore, active switching angle control according to speed variation is required. In this paper, a method for improving driving performance by reducing torque ripple by automatic control of the advance angle and increasing output torque was sought from the problem caused by the nonlinearity of the SRM. In addition, the optimal operation of SRM due to the switching variable according to the performance of the hysteretic current controller was examined.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.69-74
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• 2007

In signal processing applications with highly correlated input signals, subband affine projection algorithm and step size controlling is a good solution for improving the slow convergence rate and large computational complexity of LMS-type algorithms. This paper proposes a subband affine projection algorithm using a variable step size. The proposed method achieves fast convergence rate and small steady-state error with a small computational complexity by combining the SAP and step size controlling in a subband structure. Experimental results on highly correlated input signal show that the proposed method is superior to the conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.28 no.3
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• pp.245-250
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• 2009

In communications and signal processing area, a number of least mean square adaptive algorithms have been used because of simplicity and robustness. However the LMS algorithm is known to have slow and non-uniform convergence. Various variable step size LMS adaptive algorithms have been introduced and researched to speed up the convergence rate. A variable step size LMS algorithm using the error difference for updating the step size is proposed. Compared with other algorithms, simulation results show that the proposed LMS algorithm has a fast convergence. The theoretical performance of the proposed algorithm is also analyzed for the steady state.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.602-611
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• 2004

Servo system has commonly adapted PI controller with fixed gains, because of its simplicity and determinative relationship among the parameters. The fixed gains PI system may be applied well to some operation conditions, but not non-linearities, complex and time variant operation conditions. For solving these problems, another conventional method, 'variable gun schedule according to speed', is published. The value of gain is determined according to the absolute value of the mover real speed. In this paper, FSTPIC(Fuzzy Self-Tuning PI Controller) is proposed based on various experiences to rapidly reduce speed error and to secure a good speed response characteristics. The effectiveness of proposed algorithms is demonstrated by comparing to two conventional gain systems via 4-quadrant operation.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.33-36
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• 2001

본 논문은 높은 추력비(전동기 추력/전동기 중량=N/ Kg)를 갖는 영구자석 여자 횡축형 선형 전동기(TFLM)를 가진기 엑츄에이터로 사용하여 부피와 체적을 줄이고 적은 중량이 요구되는 고출력 전동식 가진기 시스템을 유압식을 대체하여 구현하고 가변 변위 및 가변 속도가 가능한 제어 방법을 개발하여 적용하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.709-711
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• 2002

본 논문은 AE32000 프로세서를 특정 응용 목적의 시스템에 최적화시키기 위하여 개발한 방법을 소개한다. 내장형 프로세서 시스템에서는 프로세서가 수행할 작업의 내용이 미리 알려진 경우가 많다. 이와 같이 작업내용이 정해진 경우 최적의 명령어 집합을 정하고 사용하는 것이 시스템의 동작 속도와 제작비용 및 전력 소모에 매우 큰 영향을 줄 수 있다. 각기 다른 목적의 내장형 시스템에 사용할 수 있으며 각 응용 목적에 최적화된 프로세서를 얻기 위해서는 가변 목표형 설계 기법이 요구된다.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.224-226
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• 2008

본 논문에서는 매트릭스 컨버터를 이용하여 풍력을 에너지원으로한 영구자석형 동기 발전기의 계통연계방법을 제안하고 시뮬레이션으로 타당성을 검증한다. 풍속의 변화에 따라 영구자석형 동기발전기 속도가 변하며, 발전기 속도의 변화로 인해 발전전압의 크기와 주파수가 변한다. 이렇게 가변하는 발전 전압과 주파수를 계통전압의 고정된 전압 크기와 주파수로 변환하는 전력변환장치로써 기존의 PWM AC/DC/AC 컨버터 대신에 매트릭스 컨버터를 사용하여 직접적으로 AC-AC 변환을 한다. 매트릭스 컨버터가 가지고 있는, DC 링크단의 대용량 캐패시터가 필요없고; 양방향전력흐름을 제어할 수 있고, 사용자가 원하는 출력전압의 크기, 주파수, 역률을 임의로 제어 할 수 있는 이점을 사용하여 매트릭스 컨버터를 이용한 영구자석형 동기발전기의 계통연계에 대한 시뮬레이션 결과를 소개한다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.1-8
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• 2003

Conventionally used linear or circular interpolator is undesirable for the precision machining of 3D free-form surface as the following reason: the transmission errors due to the huge number of data, discontinuity of segmentation, unsmooth motion speed. To this regard, modern CNC machine tools are designed with the function of machining arbitrary parametric curves. However, these systems don't consider the adaptive federate, which dominates the quality of the machining process. This paper proposes a NURBS interpolator for the constant material removal rate. That is accomplished by the variable federate using curvature of curve. The curvature-compensated feederate system has important Potential applications in ensuring part accuracy and protecting cutting tool. The simulated result show it can be applicable to the real machining.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.64_65
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• 2009

본 논문은 고창의 전력품질 실증시험장에서 계통에 연계된 풍력발전 시뮬레이터를 이용하여 풍력발전기의 특성을 파악하기 위해, 가변 풍속에서 이중여자 풍력발전기의 회전속도와 유효전력의 변화가 계통에 미치는 영향을 분석하였다. 선로의 길이를 40km로 가정하고, 기상청 자료를 근거로 풍속데이터를 이용한 가변풍속 패턴을 설정하여 풍력발전기의 회전속도에 대한 출력특성을 확인하였다.