• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.7-13
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• 2013

The portion of lighting power consumption for our country is up to 20~30% of the total amount. Currently, most of the DSM(Demand side management) of lighting power is delivered in supply of high efficient lighting to customers. On the contrary, applications of lighting power to power load leveling are still rare. In this paper, the simulations for various control types of lighting power for load leveling are tried, and we obtained the cost effective and optimal control method through that. This simulation was executed in test office with fluorescent light by us based on applying 8 control types(on, off & dimming), considering customers' satisfaction, for instance, minimum intensity of illumination allowed. According to the result of this test, we found that mixed type(chessboard(on-off) plus dimming control(10%)) is most effective.

• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.645-654
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• 2000

In this paper, low level control algorithms of a metal belt CVT are suggested. A feedforward PID control algorithm is adopted for line pressure based on a steady state relationship between the input duty and the line pressure. Experimental results show that feedforward PID control of the line pressure guarantees a fast response while reducing the pressure undershoot which may result in belt slip. For ratio control, a fuzzy logic is suggested by considering the CVT shift dynamics and on-off characteristics of the ratio control valve. It is found from experimental results that a desired speed ratio can be achieved at steady state in spite of the fluctuating primary pressure. It is expected that the low level control algorithms for the line pressure and speed ratio suggested in this study can be implemented in a prototype CVT.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.465-472
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• 1987

Two kinds of discontinuous control methods i, e., simple on-off(SOF) control and pulsating on-off(POF) control methods are implemented and compared each other for a low cast hydraulic position-control system which utilizes a solenoid-operated directional valve instead of a servovalve. Experimental work was carried out to investigate effects of control parameters and loading conditions on step response characteristics of the system for each control method. The results show that much higher accuracy and much better transient response characteristics can be achieved by POF controller than those by SOF controller. The results may be used as basic data in the selection of control parameters as well as in the design of the hydraulic position-control system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.3
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• pp.137-142
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• 2013

A small air-conditioner or chiller for a constant temperature bath normally uses a constant speed compressor. The constant speed compressor is relatively inexpensive, but it uses on/off control for capacity modulation. The on/off control has several disadvantages, specifically energy loss and large temperature fluctuation. Continuous operation with a bypass system can be an alternative to on/off control, for capacity modulation. In this study, a heat pump system having a hot-gas bypass and a liquid bypass was adopted. The performance of the bypass-type heat pump was measured, by varying the bypass valve opening. The differences of the COP between the hot-gas bypass and the liquid bypass, in the cooling and heating operations, were within 2% and 1%, respectively. The liquid bypass showed a wider range of capacity control in the cooling operation but the hot-gas bypass showed a wider range of capacity control in the heating operation.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.859-863
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• 2005

This paper describes the improvement of power control characteristics of ship's emergency lighting power supply(SELPS), by which electric power is controlled extensively, and power ON-OFF is controlled and system parameter monitored in remote distance by PC serial communication. Proposed system is composed of step-down converter(SDC), emergency power supply circuit(EPSC), half bridge(HB) inverter, fluorescent lamp(FL) starting circuit, microprocessor control and multi communication circuit. Experimental works confirm that relative system stops when over current is detected and speedy and stable emergency power is supplied when main power source cut-off, and controls input power up to 35[$\%$] by adjusting pulse frequency of the HB inverter, and ON-OFF control of multiple SELS, real time transmission and monitor of parameters as to voltage, current, and power values are performed appropriately by PC communication.

• Journal of Bio-Environment Control
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• v.8 no.3
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• pp.152-163
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• 1999

It is required to analyze the controlled response of air temperature in greenhouse according to control techniques for precise control. In this study, a mathematical model was established for air heating of greenhouse with hot-water heating system The parameters of the model were decided by regression analysis using reference data measured at the greenhouse being heated In the simulation for the digital control of air temperature in the greenhouse, the mathematical model to evaluate the control performances was used. Tested control methods were ON-OFF contpol, p control, rl control and PID control. The mathematical model represented by inside air temperature ( T$_{i}$), hot-water temperature (T$_{w}$) in heating pipe and outside air temperature (T$_{o}$) was expressed as a following discrete time equation ; T$_{i}$($textsc{k}$＋1)＝ 0.851.T$_{i}$($textsc{k}$)＋0.055.T$_{w}$($textsc{k}$)＋0.094.T$_{o}$($textsc{k}$) Control simulations for various control methods showed the settling time, the overshoot and the steady state nor as follows; infinite time, 3.5$0^{\circ}C$, 3.5$0^{\circ}C$ for ON-OFF control : 30min 2.37$^{\circ}C$, 0.51$^{\circ}C$ for P control; 21min, 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PI control; 18min 0.0$0^{\circ}C$, 0.23$^{\circ}C$ for PID control, respectively. PI and PID controls appeared to be optimal control methods. There was no effect of differential gain on the heating process but much effect of integral gain on it.on it.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.335-339
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• 2000

In the weaving process, tension control of the warp is important. The variation of the warp tension cause irregularities of the weft density and low quality of the woven fabrics. Due to the fact that the warp tension varies in depending on the difference between take-up velocity and let-off velocity, it is necessary to regulate the velocity of let-off in relation to that of take-up for keeping the warp tension. Futhermore, the diameter of warp beam changes in the weaving process. The changing diameter of warp beam cause changing inertia of warp beam and the velocity of the let-off. It makes the control of such a system more complex. In this paper, we propose a fuzzy controller for the warp tension control. From the computer simulation, it was observed that a developed fuzzy controller has a better performance than that of conventional PI controller.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.585-591
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• 1998

In the case of reinforced concrete beams strengthening by steel plate, sometimes these beams collapse due to the stress concentration at the ends of steel plates before the design expected failure. This kind of failure is called premature failure. This study analyzes the behavior of strengthened RC beams to control premature failure of these plated beams with either changing the geometries at the ends of plates or strengthening steel plates beside the ends. The results from the former cases show that, the effect of expanded plates sections at the ends was very small, and the beams which are rounded the ends of plates effectively increased the initial rip-off loads about 14% compared with control beam but the ultimate loads was almost same. However, the beams in the latter cases effectively increased the initial and the ultimate rip-off loads with changing failure mode, especially around 14~19% in the ultimate rip-off load comparing with control beam.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.286-288
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• 2007

The proposed method offers an improved control method for high power density AC/DC adapter by using more energy efficient electrical equipments. Power factor corrector (PFC) topology is based on boost topology with boundary conduction mode (BCM). DC/DC topology is based on half-bridge topology with newly introduced off-time control method, which helps to reduce size of the semiconductor and the magnetic devices. Test results with 85W AC/DC adapter (18.5V/4.6A) design shows that the measured efficiency is 90% with power density of $36W/in^3$. It also show low no load power consumption of about 0.5W.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.447-454
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• 2011

This paper reports a filtered velocity feedback(FVF) controller, which is an alternative to direct velocity feedback(DVFB) controller. The instability problems due to high frequency response under DVFB can be alleviated by the suggested FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The FVF controller and the dynamics of clamped beams under forces and moments are first formulated. The effects of the design parameters(cut-off frequency, gain, and damping ratio) on the stability and the performance are then investigated. The cut-off frequency should be selected not to affect the system stability. The magnitude of the open loop transfer function(OLTF) at the cut-off frequency should be small. As increasing the gain of the FVF controller, the magnitude of the OLTF is increased, so that the closed loop response can be reduced more. The enhancement of the OLTF at the cut-off frequency is reduced but the phase behavior around the cut-off frequency is distorted, as the damping ratio is increased. The control performance is finally estimated for the clamped beam. More than 10 dB reductions in velocity response can be achieved at the modal frequencies from the first to eighth modes.