• International Journal of Automotive Technology
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• 제8권4호
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• pp.477-481
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• 2007

In this article we present a new, reference model based, unified strategy for engine control. Three main modes are considered: first is the driver control mode where the driver controls the engine via the pedal position; second is the dashpot mode, that is, when the driver takes his foot off the pedal; and, lastly is the idle speed control mode. These modes are unified so that seamless transitions between modes now becomes possible. The unification is achieved due to the introduction of a reference model for the engine speed whereby only the desired engine speed is different for different modes while the structure of the control system remains the same for all the modes. The scheme includes an observer that estimates unknown engine load torque. A proof of robustness with respect to unknown load disturbances both within the operating modes and during intermode transitions is given.

• 신재생에너지
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• 제2권2호
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• pp.23-27
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• 2006

The power split hybrid powertrain is considered to be one of the most prospective configuration for the hybrid electric vehicle (HEV). Toyota Prius, representing this type of vehicle, showed outstanding performances in fuel efficiency, emission reduction and acceleration. The excellence is largely due to the fact that it utilizes almost all operation modes of HEV. Those modes include ZEV (Zero Emission Vehicle) driving, idle stop, fuel cut-off, power assist, active charging, regenerative braking and so forth. In this paper, a few of the mode operations were simulated using AVL Cruise. Also, control logics to operate the powertrain in each mode were developed. The states of powertrain components were displayed and analyzed. By controlling the three components (engine, motor and generator), it was possible to run the powertrain in several hybrid operation modes.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.547-550
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• 2006

The power split hybrid power train is considered to be one of the most prospective configuration for the hybrid electric vehicle (HEV). Toyota Prius, representing this type of vehicle, showed outstanding performances in fuel efficiency, emission reduction and acceleration. The excellence is largely due to the fact that it utilizes almost all operation modes of HEV. Those modes include ZEV (Zero Emission Vehicle) driving, idle stop, fuel cut-off, power assist, active charging, regenerative braking and so forth. In this paper, a few of the mode operations were simulated using AVL Cruise. Also, control logics to operate the powertrain in each mode were developed. The states of powertrain components were displayed and analyzed. By controlling the three components (engine, motor and generator), it was possible to run the powertrain in several hybrid operation modes.

• 전력전자학회논문지
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• 제21권1호
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• pp.19-26
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• 2016

In this study, a bidirectional DC-DC converter for idle stop and go (ISG) is developed to reduce fuel consumption. A three-phase non-isolated half-bridge converter is selected through a design method by considering efficiency and volume. According to the state of charge of the batteries at both the low-voltage and high-voltage sides, buck mode, which charges a low-voltage battery from the generated motor energy, and boost mode, which provides power to the motor from the low- and high-voltage battery sides, are required in the ISG system. Hence, an autonomous and seamless bidirectional control method using a variable current limiter is proposed for mode change. A 1.8 kW engineering sample of the proposed converter has been built and tested to verify the validity of the proposed concept. The maximum efficiencies, including gate driver and control circuit losses, are 96.4% in charging mode and 96.1% in discharging mode.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권7호
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• pp.283-292
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• 2013

기존 서버 클러스터에서는 고성능을 보장하기 위해, 실시간 요청 수량에 관계없이 모든 서버를 항상 On 한다. 그 방법에서는 QoS를 보장하지만 일부 서버들이 Idle할 때 서버 전력을 낭비하게 된다. 서버들이 소모하는 에너지를 절약하기 위해, 서버가 필요하지 않을 경우 해당 서버의 전력을 Off 하게 하는 서버 전력 제어 방법이 제안되었다. 서버 전력 제어 방법은 서버의 Power가 실제로 어느 시점에 Off 되느냐에 따라 정적인 방법과 동적인 방법이 있다. 정적인 방법에서는 특정 서버가 Off 하기로 결정된 다음 일정 시간 지연 후 그 서버가 Off 된다. 동적인 방법에서는 그 서버에서 수행중인 모든 서비스가 종료된 다음에 해당 서버가 Off 된다. 이는 가변 시간 지연 후 서버가 Off 되는 방법에 해당된다. 정적 종료방식은 단점이 있다. 반복 실험을 통해 수작업으로 최적의 시간 지연을 알아내기 위해서는 많은 시간이 소요된다. 본 논문에서는 정적 종료 방식의 단점을 극복하는 동적 종료 방식을 제안한다. 제안된 방식은 최적의 지연 시간으로 자동적으로 접근하므로 좋은 전력 절약을 하면서 QoS를 보장하는 것을 가능하게 해준다. 30대의 PC 클러스터를 이용하여 실험이 수행되었다. 실험결과는 제안하는 동적 종료 방법이 기존의 정적 종료 방법과 비교할 때 에너지 절감측면에서는 비슷하지만 QoS 측면에서 우수함을 보여준다.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제22권6호
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• pp.296-301
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• 2016

객체 기반 스토리지 솔루션은 비정형 데이터를 효과적으로 처리할 뿐만 아니라 보안, 확장성에서 기존 블록 스토리지보다 장점을 갖고 있다. 그러나 전력관리 관점에서, 객체 기반 스토리지가 기록하는 많은 수의 사본들은 여러 서버들을 유휴상태에서 불필요한 전력을 소모하게 하는 문제가 있다. 이 문제를 해결하기 위해서는 작업량에 따라 유휴상태 서버들의 전원모드를 변화시키는 전력관리기법의 적용이 필요하다. 본 논문에서는 프락시 서버에서 보내는 작업량 정보를 기반으로 스토리지 서버의 전력 상태를 동적으로 전환하는 전력관리 기법을 제안한다. 실험 결과, 제안한 전력관리 기법은 오픈스택 기반 스위프트 객체 스토리지에서 전체 전력 소모량을 12% 감소시키는 것으로 나타났다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 가을 학술발표논문집 Vol.31 No.2 (3)
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• pp.322-324
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• 2004

IEEf 802.11 Point Coordination Function (PCF) mode is defined to support time bounded traffic, such as VoIP in wireless LANs. The poll scheduling plays an important role in IEEE 802.11 PCF mode operation. This paper proposed a Multicast Polling Scheme to increase the performance of wireless LANs. Moreover, we proposed a polling schedule scheme for our proposed multipoll to serve real-time traffic. The results show that the proposed mechanism is more efficient than the original IEEE 802.11 PCF.

• Journal of Power Electronics
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• 제14권4호
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• pp.796-805
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• 2014

A digital controller with a low-power approach for point-of-load synchronous buck converters is discussed and compared with its analog counterpart to confirm its feasibility for system integration. The tri-mode digital controller IC in $0.35{\mu}m$ CMOS process is presented to demonstrate solutions that include a PID, quarter PID, and robust RST compensators. These compensators address the steady-state, stand-by, and transient modes according to the system operating point. An idle-tone free condition for ${\Sigma}-{\Delta}$ DPWM reduces the inherent tone noise under DC-excitation. Compared with that of the traditional approach, this condition generates a quasi-pure modulation signal. Experimental results verify the closed-loop performances and confirm the power-saving mechanism of the proposed controller.

• Journal of Power Electronics
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• 제18권6호
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• pp.1627-1633
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• 2018

A constant voltage AC-DC converter based on digital assistant technology is proposed in this paper, which has rapid dynamic response capability. The converter operates in the PFM (Pulse Frequency Modulation) mode. According to the load state, the compensation current produced by the digital compensation module was injected into the CS pin to adjust the switching pulse width dynamically and improve the dynamic response. The control chip is implemented based on NEC $1{\mu}m$ 5V/40V HVCMOS process. A 5V/1.2A prototype has been built to verify the proposed control method. When the load jumps from idle to heavy, the undershoot time is only 7.4ms.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.137-143
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• 2013

This paper presents development of variable speed generation (VSG) system with energy saving function. The rubber tyred gantry crane (RTGC) requires the power from diesel-engine. Significant fuel savings by reducing the engine speed can be achieved, because all of operation modes except hoisting are required lower power than rated value of engine. When low speed operation output voltage of generator is decrease until acceptable range of motor driver inverters and auxiliary load supplier. According to power demand engine speed is varying from 20 to 60Hz, and voltage is varying between 210Vac and 480Vac. When idle mode or low power operation dc/dc converter operates by constant output voltage control and inverters dc site voltage is compensated by it. This paper proposed 3-phase interleaved boost converter which has the same structure as the commercially available 3-phase inverter and current sharing capability. 400kW interleaved converter is designed and a performance of converter is evaluated through several experiments with a RTGC system. Energy saving VSG system can cut down fuel consumption by 36% and 21.3% at idle and unidirectional load operations.