• Journal of Biosystems Engineering
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• 제28권2호
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• pp.117-126
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• 2003

This study was conducted to develop precision control system fur cold storage facility that could offer safe storage environment for green grocery. For that reason of neuro-fuzzy control system with learning ability algorithm and single chip neuro-fuzzy micro controller was developed for cold storage facility. Dynamic characteristics and hunting of neuro-fuzzy control system were far superior to on-off and fuzzy control system. Dynamic characteristics of temperature were faster than on-off control system by 1,555 seconds(123% faster) and fuzzy control system by 460 seconds(36.4% faster). When system was arrived at steady state. hunting was ${\pm}$0.5$^{\circ}C$ in on-off control system, ${\pm}$0.4$^{\circ}C$ in fuzzy control system, and ${\pm}$0.3$^{\circ}C$ in neuro-fuzzy control system. Hunting of humidity and wind velocity was also controlled precisely by 70 to 72.5% and 1m/s For storage experiment with onion, characteristics of neuro-fuzzy control system were tested. Dynamic characteristics of neuro-fuzzy control system made cold storage facility conducted precooling ability and minimized hunting.

• Ocean Systems Engineering
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• 제4권1호
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• pp.63-82
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• 2014

Declutching control is applied to a hemispherical wave energy converter with direct linear electric Power-Take-Off systems oscillating in heave direction in both regular and irregular waves. The direct linear Power-Take-Off system can be simplified as a mechanical spring and damper system. Time domain model is applied to dynamics of the hemispherical wave energy converter in both regular and irregular waves. And state space model is used to replace the convolution term in time domain equation of the heave oscillation of the converter due to its inconvenience in analyzing the controlled motion of the converters. The declutching control strategy is conducted by optimal command theory based on Pontryagin's maximum principle to gain the controlled optimum sequence of Power-Take-Off forces. The results show that the wave energy converter with declutching control captures more energy than that without control and the former's amplitude and velocity is relatively larger. However, the amplification ratio of the absorbed power by declutching control is only slightly larger than 1. This may indicate that declutching control method may be inapplicable for oscillating wave energy converters with direct linear Power-Take-Off systems in real random sea state, considering the error of prediction of the wave excitation force.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1736-1740
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• 2003

POSCO Kwang-Yang Works #2 Cold Rolling Mill RCL has the main hydraulic system that controlled on/off control method. In the aspect of the consumption of electrical energy this system has some problem. So, we present a continuous control method instead of on/off control method that controls the pressure of main hydraulic system with saving the electric energy.

• 전력전자학회논문지
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• 제12권1호
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• pp.98-106
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• 2007

본 논문에서는 개선된 온라인 턴 오프각 제어방식을 이용하여 스위치드 릴럭턴스 전동기의 성능최적화를 위한 온라인 전류제어방식을 제안한다. 성능최적화를 위한 제어방식은 에너지효율의 최대화와 토크리플 저감이라는 두가지 측면에서 접근하며, 두 가지 조건을 모두 만족할 수 있는 최적의 턴 오프 위치각은 제안된 알고리즘의 연산방식을 통해 획득된 턴 오프각 제어기를 통해 구현됨으로서 SRM의 성능최적화를 이룬다. 제안된 제어기는 토크와 전류 특성, 자속변동의 정보와 같은 복잡한 데이터베이스나 SRM이 가지는 고유의 자화곡선을 요구하지 않는다는 장점을 가지며 제안된 연산 제어기를 시뮬레이션과 실험을 통해 실제 적용가능성과 그 타당성을 입증한다.

• Journal of Microbiology and Biotechnology
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• 제8권2호
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• pp.165-170
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• 1998

Lipase-catalyzed esterification of n-butyl oleate was carried out in n-hexane as a model reaction. The optimal activity of Candida rugosa lipase was shown in a water activity ($a_w$) range of 0.52 to 0.65 at $30^{\circ}C$. The water produced from the esterification was removed by a tubular type pervaporation system. The rate of ester formed from the enzymatic esterification was allowed to be the same as the rate of water removal by maintaining an optimal $a_w$ of the reaction system using an on-off dewatering control device. The reaction rate and yield with a$a_w$ control were increased two folds higher than the respective values for the uncontrolled reaction.

• 설비공학논문집
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• 제8권1호
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• pp.76-87
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• 1996

Energy analysis for the hot water heating control system of apartment house complex is accomplished by computer simulation. Mathematical model of a boiler, pipe network and a unit-house is developed. The effects of heating control methods on the heating performance and energy consumption of the system are investigated. The heating control methods considered in this study are a continuous heating control, and on-off heating control and an intermittent heating control methods. For each control method, the effects of an outdoor temperature, indoor temperature sensing position and the capacities of the boilers and circulating pumps on the heating performance and energy consumption are obtained and "the best" control method is recommended.commended.

• 조명전기설비학회논문지
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• 제25권4호
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• pp.16-23
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• 2011

Since the first lighting light source was invented, lighting has turned into superior-quality lighting considering the amenity of occupants, and the characteristics of a light source has developed rapidly. So this research confirmed the lighting performance of a dimmer control system and an ON-OFF control system via the existing light source, and analyzed the basic lighting environment of Permanent Supplementary Artificial Lighting of Interiors(PSALI) through the physical comparison and evaluation of a LED lamp substituted for a fluorescent lamp used in a dimmer control system, showing that the lighting physical quantity characteristics of an ON-OFF control system and a dimmer control system are similar to each other and that they are effective in terms of energy saving. Besides, it was shown that introducing a LED light source to a dimmer control system improves lighting environments and largely reduces energy consumption.

• Journal of Biosystems Engineering
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• 제14권4호
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• pp.229-241
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• 1989

The purposes of this study were to develop an electronic-hydraulic draft control system for tractor implements, to investigate the control performance of the system and the possibility of adaptation to the conventional tractor. Experiments were carried out to investigate the responses of the system to the step and sinusoidal inputs in draft control. The effects of control mode, hydraulic flow rate, reference deadband, and proportional constant on control performance of the system were investigated. Moreover, the effects of filtering signals from draft sensor were also investigated. The following conclusions were derived from the study; 1. In draft control, there were hunting problems in controlling the implement without filtering the draft signals. Filtering was performed by a control program of electronic controller and the control performance and stability of the system were improved significantly. 2. For the draft control system operated on on-off control mode, draft was controlled within ${\pm}27-{\pm}55kg_f$ to the reference draft when the hydraulic flow rates were 5-15 l/min. For the draft control system operated on PWM control, draft was controlled within ${\pm}27kg_f$ to the reference draft regardless of hydraulic flow rates. 3. In the frequency responses of the draft control system, control performance on PWM control mode was not better than on on-off control mode because of characteristics of hydraulic valve and drafe sensor. As the hydraulic flow rates increased for the system operated on on-off control mode, the corner frequency of amplitude attenuation increased, but the corner frequency of phase-angle change remained nearly the same. But, the system was unstable beyond the frequency of 3.1 rad/s. 4. The electronic-hydraulic hitch control system developed in this study showed superior control performance, stability and convenience compared to conventional mechanical-hydraulic hitch control system. It is considered to be a superior replacement for the conventional mechanical-hydraulic hitch control system.

• Journal of Power Electronics
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• 제16권4호
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• pp.1256-1267
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• 2016

Distributed stray inductance exerts a significant influence on the turn-off voltages of power switching devices. Therefore, the design of low stray inductance bus bars has become an important part of the design of high-power converters. In this study, we first analyze the operational principle and switching transient of a T-type converter. Then, we obtain the commutation circuit, categorize the stray inductance of the circuit, and study the influence of the different types of stray inductance on the turn-off voltages of switching devices. According to the current distribution of the commutation circuit, as well as the conditions for realizing laminated bus bars, we laminate the bus bar of the converter by integrating the practical structure of a capacitor bank and a power module. As a result, the stray inductance of the bus bar is reduced, and the stray inductance in the commutation circuit of the converter is reduced to more than half. Finally, a 10 kVA experimental prototype of a T-type converter is built to verify the effectiveness of the designed laminated bus bar in restraining the turn-off voltage spike of the switching devices in the converter.

• 한국군사과학기술학회지
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• 제8권4호
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• pp.130-135
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• 2005

This paper presents application possibility of Lightweight Piezoceramic Composite Actuator(LIPCA) to suppress vibration of dynamic structures as an actuator. LIPCA is composed of a piezoelectric layer, a carbon/epoxy layer and glass/epoxy layers. When compared to the bare piezoelectric ceramic(PZT), LIPCA has advantages such as high performance, durability and reliability. In this study, performances of LIPCA have been estimated in an active vibration control system. Experiments were performed on an aluminum beam with cantilever configuration. In this test, strain gages and single LIPCA are attached on the aluminum beam with epoxy resin. Digital ON-OFF control algorithm is applied into the system to exhibit performance of LIPCA as actuator in active vibration control system. First, we performed static actuation test of bare PZT and LIPCA in order to show the superiority of LIPCA. Secondly, we carried out beam vibration control test using LIPCA. The results showed LIPCA could suppress free vibration of the aluminum beam, which means that LIPCA can be applied as an actuator to control vibration of dynamic structures.