• 한국공작기계학회논문집
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• 제13권4호
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• pp.87-94
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• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. The high speed usually results in thermal displacement and structural deformation. To minimize the thermal effect, precision machine tools adopt a high precision cooling system. This study proposes a temperature control for an oil cooler system using Pill control with fuzzy logic. In the cooler system, refrigerant flow rate is controlled by rotational speed of a compressor, and outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error and difference between the outlet temperature and the reference temperature. Here, ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional Pill control. The experimental results show that the proposed method has advantages of faster response and smaller overshoot.

• 융합신호처리학회논문지
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• 제14권2호
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• pp.130-135
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• 2013

최근 공작기계 분야에서 가공속도와 가공정밀도 같은 시스템 성능이 한층 요구되고 있다. 특히 가공속도가 증가함에 따라 공작기계와 수가공 분야의 공작물 가공 부위에 유해한 열 발생을 초래하게 된다. 이 열은 가공 정밀도를 저하시키는 주된 원인으로 작용한다. 따라서 온도를 제어하는 오일쿨러는 공작기계에서 필수적이다. 일반적으로 두 가지 대표적인 제어기법인 핫가스 바이패스 방식과 압축기 가변속 제어 방식이 오일쿨러에 채택 되었다. 본 논문에서는 오일 출구 온도를 설정값으로 유지하기 위해 압축기의 속도를 제어하였다. 공작기계의 정밀 가공이 요구되는 추세에 맞추어 ${\pm}0.1^{\circ}C$의 고정도 온도 제어가 가능한 오일쿨러가 요구된다. 그러나 정밀 온도제어가 가능한 오일쿨러는 가격이 고가이다. 그러므로 본 논문에서는 on/off(릴레이) 제어방식 대신에 PID 제어기와 위상각 전력제어 방식을 사용하여 정밀 온도제어가 가능한 오일쿨러용 제어기를 제안한다. 제안한 제어기를 제작하고, $23^{\circ}C$, $24^{\circ}C$ 그리고 $25^{\circ}C$에서 실험하였다.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.687-692
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• 2016

엔진에 터보차져를 사용하게 되면 엔진의 출력도 향상되지만 동시에 엔진의 온도도 높아지게 된다. 특히 피스톤의 경우는 냉각이 문제가 된다. 이러한 문제를 해결하기 위하여 오일 젯을 사용하는데, 오일 젯은 오일을 피스톤의 밑 부분에 분사하여 피스톤을 냉각시키는 것이다. 오일 젯이 사용된다면, 오일의 분사로 인하여 오일 유량의 증가및 피스톤으로부터의 열전달에 의하여 높아진 오일 온도 문제를 해결하기 위하여 오일 펌프 용량 증대와 오일 쿨러의 사용이 필요하다. 그러나 용량 증대 오일 펌프와 오일 쿨러를 사용하면 엔진의 마찰 토크가 증가하는 원인이 된다. 본 연구에서는 오일 젯, 오일 쿨러 및 오일 펌프의 용량 증대로 인하여 엔진의 마찰 토크가 증가하는 정도에 대하여 연구하였다. 또한 각 부품의 사양을 변경함에 따라 마찰 토크가 얼마나 영향을 받는가도 측정되었다. 저속에서는 오일 펌프와 오일 쿨러에 의한 영향이 크고 고속에서는 오일 쿨러에 의한 영향이 큼을 알 수 있었다.

• 한국생산제조학회지
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• 제8권1호
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• pp.89-99
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• 1999

The automatic design of shell & tube type oil cooler can be used in real industrial environments. Since the automatic design system is intended to be used in small companies, it is designed to be operated well under environments of CAD package in the personal computer. It has adopted GUI in design system, and has employed DCl language. Design parameters to be considered in the design stage of shell and tube type oil cooler are type of oil cooler, outer diameter, thickness, length of tube, tube arrangement, tube pitch, flow rate, inlet and outlet temperature, physical properties, premissive pressure loss on both sides, type of baffle plate, baffle plate cutting ratio, clearance between baffle plate outer diameter and shell inner diameter and clearance between baffle plate holes. As a result, the automatic design system of shell & tube type oil cooler is constructed by the environment of CAD software using LISP. We have built database of design data for various kinds of shell & tube type oil coolers. The automatic design system have been assessed and compared with existing specification of design. Good agreement with Handbook of heat exchanger and design dta of real industrial environments has been found.

• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.451-454
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• 2003

The Oil Coolers is very important unit for the stable thermal performance in machine tools, semiconductor equipments and high precision measuring systems. To select a proper oil cooler for the temperature control of core unit in a machine, not only cooling ability but also static and dynamic sensitivity of temperature sensors are considered. In this paper, the relationship between cooling ability and inflow oil temperature is identified. The cooling ability is increased with the increase of inflow oil temperature. The oil temperature control errors of a cooler are influenced by mainly sensitivity of temperature sensors and heating velocity in a machine. The validity of error cause analysis for temperature control is proved by real cooling experiments with inflow and outflow temperature sensors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1006-1011
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• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. Such high speed usually results in thermal displacement and structural deformation. To minimize such thermal effect, most precision machine tools adopt high precision cooling system. This study proposes a temperature control for an oil cooler system using PI control with fuzzy logic. In a cooler system, the refrigerant flow rate is controlled by rotational speed of the compressor, where the outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error, difference between the outlet temperature and the reference one. Here, the ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional PID control. The experimental results show that the proposed method has advantages of smaller overshoot and smaller steady state error.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1237-1242
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• 2004

In this study, single-phase heat transfer experiments were conducted with oil cooler with offset strip fin using water. An experimental water loop has been developed to measure the single-phase heat transfer coefficient in a vertical oil cooler. Downflow of hot water in one channel receives heal from the cold water upflow of water in the other channel. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the on cooler with offset strip fin remains turbulent. The present data show that the heat transfer coefficient increases with the Reynolds number. Based. On the present data, empirical correlation of the heat transfer coefficient was proposed. Also, performance prediction analysis for oil cooler were executed and compared with experiments. ${\varepsilon}-NTU$ method was used in this prediction program. Independent variables are flow rates and inlet temperature. Compared with experimental data, the accuracy of the program is within the error bounds of ${\pm}5$% in the heat transfer rate.

• 한국기계가공학회지
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• 제2권4호
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• pp.11-16
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• 2003

Recently, CNC lathe is in need of higher speed for precision works. So more intensive and compact heat exchanger is necessary to cool down the heat in short time from drills and works during high speed working. In this study, to increase heat transfer coefficient per unit volume, inner groove tube is designed and compact oil cooler, 57% volume of conventional type, is manufactured. The heat transfer performance is experimented and is compared with the performance of conventional type.

• 동력기계공학회지
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• 제20권4호
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• pp.83-90
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• 2016

This study proposes a high-performance PI controller design method for an oil cooler system in conjunction with zero position adjustment and the characteristic parameters in its closed loop control system. The characteristic parameters included PI gains are decided by design specifications such as settling time and overshoot. The fine tuning on decided gains was performed by adjustment the zero position to get more desirable control performances. The simulations and experimental results show that the proposed PI controller design for an oil cooler system was possible to accomplish good control performances and to satisfy the design specifications.