• 한국정밀공학회지
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• 제30권11호
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• pp.1153-1160
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• 2013

SMISMO valve configuration is now starting to draw attention of the researchers of the construction equipment industry to increase the fuel efficiency of their equipment like excavators and wheel-loaders. An open-loop control strategy for grading operation of hydraulic excavator systems using SMISMO valve configuration is investigated in this paper. Tabor's algorithm for 1 d.o.f. SMISMO system under the assumption of quasi-static operation is revealed as not adequate for multi d.o.f. system with large moment of inertia even though the motion of the system is slow. New parameters are proposed in this paper. It modifies Tabor's open-loop control strategy for the grading operation of hydraulic excavators using SMISMO valve configuration. A simulation-based parameter tuning method is also proposed. It uses GA (Genetic Algorithm) to find the best parameter values. Simulation study for a practical hydraulic excavator shows the validity of the proposed open-loop control strategy.

• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.1-9
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• 2018

The spool displacement of directional control valve can be considered as the standard signal to measure the bandwidth frequency of a directional control valve. When the spool displacement is not available, the metering-orifice system is implemented in this research as an alternative way of measuring the 90 degrees phase bandwidth frequency of the hydraulic directional control valve. The inertia effect on the transmission line oil induces the phase lead of the valve load pressure when compared with the phase of spool displacement. The capacitance effect of the oil induces the phase lag of the valve load pressure. The phase of the load pressure can be adjusted to be the same as that of the spool displacement by controlling the opening area of the metering orifice. A series of experiments were conducted to verify the effectiveness of the metering orifice. The 90 degrees phase bandwidth frequency measured from the valve load pressure was significantly deviated in some cases from the frequency of the spool displacement. The metering orifice was hard to be applied to measure the -90 degrees phase bandwidth frequency of the high precision.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.153-158
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• 2007

Since the introduction of Nanoimprint in the mid-1990s, Nanoimprint lithography, a low-cost, non-convential method, has been the dominant lithography technology that guarantees high-throughput patterning of nanostructures. Based on the mechanical embossing mechanism, Nanoimprint lithography creates the nanopatterns on the polymer material cast on the substrate. In essence, the process needs nanofabrication equipment for printing with the adequate control of temperature, pressure and control of parallels of the stamp and substrate. This article introduce the possibility and reality of the thermal control on the hot plate using a CFD code. Numerical computation has been conducted for assessing the feasibility of a hot plate($120{\times}120\;mm2$). PID control is adopted to ensure high temperature uniformity in several zones. Parallel experiments have also been performed for verifying thermal performance. Not only show the results the optimum number of thermocouples related to controllers but also suggest that the thermal simulation using a CFD code would be an alternative method to design and develop the thermal control equipment in the financial aspect.

• 융합보안논문지
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• 제17권2호
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• pp.69-80
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• 2017

IT시대의 고도화로 인한 사이버 범죄는 지능화, 다양화, 고도화 되고 있는 가운데 보안 관제의 역할은 더욱 중요해졌다. 과거 방화벽이나 IDS 등 보안 장비에만 의존하던 방식과는 달리 실시간 감시를 통해 사이버 공격에 대한 대응을 하는 보안 관제 업무가 광범위해지고 그 역할 또한 중요하게 되었다. 현재의 사이버 위협에 대해 보안 장비만으로는 안정적인 방어를 할 수 없기 때문에 보안 장비를 운영 및 감시하고 실시간적인 대응을 할 수 있는 보안 관제의 업무가 필수 요소가 된 것이다. 본 연구에서는 네트워크 보안시스템을 효율적으로 구성하는 방법과 보안시스템을 실시간 운영하는 보안관제의 현황과 개선방안에 대해 다루고자 한다.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3618-3622
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• 2012

본 연구에서는 LCD 생산라인에서 장기적으로 정체상태에 있는 모듈의 수율을 높이고, 현재 TFT-LCD 생산공정에 필수적인 고압의 실리콘주입 장비 및 정밀 제어시스템을 개발하였다. 본 개발을 통하여 향후 본격생산을 준비중인 차세대 디스플레이 생산라인뿐만 아니라 중국으로 이전중인 LCD 생산 설비의 라인 환경에서 장비의 효율을 최대한 발휘함으로써 신규 투자비용을 최소화하고 최대의 효과를 창출할 수 있도록 세부 동작 시퀀스를 제어하기 위한 H/W와 S/W 시스템을 생산라인에 실장하였다. 또한, Fast-evacuating을 위한 Vacuum pump 구조를 제안하고 Pump control 회로 설계 및 실험을 통해 제품화하였다.

• 유공압시스템학회논문집
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• 제3권4호
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• pp.21-28
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• 2006

The proportional control solenoid valves as well as the PWM solenoid valves operated by electric signal play an important role in the hydraulic system for automatic transmissions to improve the shift quality. However it is not generally available for the performance data because most of the automotive parts manufacturer don't release the specific test results, especially dynamic performance that is essential to design a shift control algorithm. In this research, a performance test equipment that can be applied to various types of pressure control solenoid valve was developed. It was implemented by 8-bit micro-controller with many useful functions such as adjustable PWM carrier frequency, embedded function generator, current controller, data monitoring and acquisitions, etc. for the test of dynamic performance of solenoid valve as well as the steady-state pressure characteristics. The performance test results for the direct type proportional control solenoid valve show not only the validity of overall functions but also its usefulness as a hydraulic valve tester.

• 드라이브 ㆍ 컨트롤
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• 제11권3호
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• pp.47-54
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• 2014

Clutches are an integral part of the automatic transmission for changing gears. Modern automatic transmissions make extensive use of wet multiple-disc clutches employing hydraulic actuation mechanism with electronic control. Although nowadays, highly advanced shifting algorithm implements the superior shift quality and transmission efficiency, its performance should be based on smooth, reliable engagement with a reasonably durable friction material as well as stable clutch piston dynamics. Particularly, clutch filling control is the crucial part of shifting process because only the open-loop control is available due to the lack of measurement. In this paper, the effect of clutch-fill control parameters on clutch piston dynamics is experimentally investigated by using clutch piston test equipment which enables the clutch piston to actuate similar to real shifting conditions. The experimental analysis results can be expected to be utilized for the calibration of proportional solenoid valve as reference current profile data in vehicle test.

• 드라이브 ㆍ 컨트롤
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• 제14권4호
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• pp.29-36
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• 2017

Electronic control technologies that have long been developed for passenger cars spread to construction equipment and agricultural vehicles because of its outstanding performance achieved by embedded software. Especially, system program of transmission control unit (TCU) plays a crucial role for the superb shift quality, driving performance and fuel efficiency, etc. Since the control algorithm is embedded in software that is rarely analyzed, development of such a TCU cannot be conducted by conventional reverse engineering. Transmission simulator is a kind of electronic device that simulates the electric signals including driver operation command and output of various sensors installed in transmission. Standalone TCU can be run in normal operation mode with the signals provided by transmission simulator. In this research, transmission simulator for the tracked vehicle TCU is developed for the analysis of shift control algorithm from the experiments with standalone TCU. It was confirmed that shift experimental data for the simulator setup conditions can be used for the analysis of control algorithms on proportional solenoid valves and shift map.

• Journal of Power Electronics
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• 제19권1호
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• 한국산학기술학회논문지
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• 제13권11호
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• pp.5434-5441
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• 2012

국내 철도 저밀도 지선구간에서는 주요노선에 적용되고 있는 고가의 지상설비들이 운용됨에 따라 적자로 운영되는 등 효율성 측면에서 문제가 되고 있어, 열차 차상에서 직접 선로변 설비를 제어할 수 있는 새로운 개념의 차상중심 열차제어시스템의 개발에 대한 필요성이 대두되고 있다. 이에 따라 본 논문에서는 국내의 앞선 정보통신기술(ICT)을 접목하여 지상설비를 최소화하는 동시에 기존 시스템을 대체가능한 차상제어시스템을 제안하였으며, 개념 및 상세설계 결과와 모형시험환경 구축을 통한 기능 확인 수행내용을 제시하였다.