권두언

하주식 한국해사문제연구소 1990 (月刊)海洋韓國 Vol.207 No.-

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선박에 있어서의 내연기관구동발전기의 속도안정도에 관한 연구

하주식,노창주 대한전기학회 1975 전기의 세계 Vol.24 No.4

The speed characteristics of the diesel engines driving alternators are very important because it is directly concerned to the quality of electric power especially when electric power is supplied by a single alternator. In this paper, the speed characteristics of th diesel engine, equipped with a centrifugal mechanical governor, driving an alternator is dealt when load changes stepwise. The all coefficients included in the block diagram of the speed control system are estimated by actual experiments and the effects of gain change of the governor in the speed characteristics are examined theoretically and experimentally. The obtained result seems to be satisfactory and very useful for the improvement of quality of electric power supplied by a single alternator driven by the diesel engine especially for electric power system of ships.

수종의 시판 청량음료가 치아표면 법랑질 침식에 미치는 영향에 관한 실험적 연구

하주식,김종열 대한치과의사학회 2000 대한치과의사학회지 Vol.19 No.11

규범모델 추종방식에 의한 회전계통의 적응속도제어에 관한 연구

하주식,송문현 한국마린엔지니어링학회 1995 한국마린엔지니어링학회지 Vol.19 No.3

Recently, in the field of industrial servo-systems, several methods have been proposed for tracking the reference input fastly and finely without overshoot. These methods, however, are established under hypothesis that structure and parameters of the plant are known accurately and they are time invariant. In practice, it is difficult to obtain the values of plant's parameters accurately and usually plants change with time and operation conditions. In this paper a method to construct the nominal model tracking adaptive control system is proposed. The system is composed of the nomial model which produces a ideal response and the model tracking system with the fuzzy adaptive controller. If the actual plant is equal to the controlled object in the nominal model, the output of the plant is the same as that of the nominal model and the fuzzy adaptive controller becomes idle. However, when the plant changes, the fuzzy adaptive controller of the tracking system operates in order for the output of the plant to track the ideal response. Through the computer simulations under various conditions, it is confirmed that the proposed model tracking system is very effective.

선박의 자동화와 Computer이용의 현황과 문제점

하주식 대한전기학회 1981 전기의 세계 Vol.30 No.12

실측선위의 정도개선과 항법계산의 전산화에 관한 연구

하주식,윤여정 한국항해항만학회 1983 한국항해학회지 Vol.7 No.2

This paper concerns the applications of the Kalman filter to navigation and the develment of computer programs of the navigational calculations. Methods to apply the Kalman filter to celestial fix, fix by cross bearing and cocked hat are proposed, and numerical simulations under various noise conditiions are conducted. The accuracy of the optimal positions obtained by the Kalman filter is compared with that of the fixed positiions by radial error method. In the case of celestial fix, an algorithm to estimate the optimal positions by using the linear Kalman filter is presented. The optimal positions by the Kalman filter are compared with the running fixes and with the most probable positions obtained from a single line of position. It is confirmed that the resutls of the proposed method are more accurate than the others. In practical piloting, bearings are generally measured intermittently and the measurement process is nonlinear. It is, therefore, difficult for us to apply the Kalman filter to fix by cross bearing. In order to be used in such an unfavorable case, the extended Kalman filter is revised and the aplicability of the revised extended Kalman filter is checked by numerical simulation under various noise conditions. In a cocked hat, an inside or outside fix is dependent only upon azimuth spread, if the error of each line of position is assumed to be equal both in magnitude and sign. A new technique of selecting a ship's position between an inside fix and an outside fix in a cocked hat by using fix determinant derived from the equation of three lines of position is also presented. The relations among the optimal position by Kalman filter, incentre (or excentre) and random error centtre of the cocked hat are discussed theoretically and the accuracy of the optimal position is compared with that of the others by numerical simulation.

適應制御裝置에 關한 硏究

하주식,최경삼,김승호,Ha, Joo-Shik,Choi, Kyung-Sam,Kim, Seung-Ho 한국마린엔지니어링학회 1979 한국마린엔지니어링학회지 Vol.3 No.1

Recently the adaptive control system, which keeps the control system always optimal by adjusting the control parameters automatically according to the variations of the plant parameters, have become very important in the field of control engineering. The adaptive control systems are usally composed of the plant identification, the decision of the optimal control parameters, and the adjustment of the control parameters. This paper deals with a method of the adaptive control system when PI or PID controller is used in the feed back control system. Its controlled object (the plant) is assumed to be described by the transfer function of $\frac{ke^{-LS}}{1+TS}$ where k, T and L are steady state gain, time constant and pure dead time respectively, and their values are variable in accordance with the change of environmental circumstance. It has been known that a pseudo-random binary signal is quite effective for the measurement of an impulse response of a plant. In adaptive control systems, however, the impulse response itself is not appropriate to determine the control parameters. In this paper, the authors propose a method to estimate directly the parameters of the plant k, T and L by means of the correlation technique using 3 level M-sequence signal as a test signal. The authors also propose a method to determine the optimal parameters of the PI or PID controller in the sense of minimizing the square integral of the control error in the feed back control system, and the values of the optimal parameters are computed numerically for various values of T and L, and the results are examined and compared with those of the conventional methods. Finally the above-mentioned two methods are combined and an algorithm to struct an adaptive control system is suggested. The experiments for the indicial responses by means of both the model of the temperature control system using SCR actuater and the analog simulations have shown good results as expected, and the effectiveness of the proposed method is verified. The M-sequence generator and the time delay circuit, which are manufactured for the experiments, are operated in quite a good condition.

On-off 제어계통을 갖는 냉동기의 최적제어에 관한 연구

하주식,김원녕,김경근,오철,Ha, J.S.,Kim, W.N.,Kim, K.K.,Oh, C. 한국마린엔지니어링학회 1985 한국마린엔지니어링학회지 Vol.9 No.4

In the case of temperature control of air conditioning and refrigerating system, it is possible to operate the system continuously by controlling the cooling capacity of refrigerating machines. But on-off control system has been adopted for refrigerating system which has more large capacity than that required to remove the generated heat. In this on-off control system, it can be considered that there exists some optimum condition for the refrigerating capacity, operating cycle, running hour, and the temperature difference between thermostat setting value and real one. In this paper, an equation was derived to express the temperature variation of the refrigerated object (Nybrine) and later two evaluating functions were derived. One is for the temperature difference and another is for operating cycle and running hour. The weighted sum of these two functions is defined as the criterion function for the evaluation of the control performance of the system, and then the optimum running condition is investigated in the sense of minimizing the criterion function. Experiments showed that the heat balance equation derived for the temperature variation and the estimation of the time constant of the refrigerated system are appropriate. By conclusion, if a proper weighting factor D is selected, the optimum conditions exist for the refrigerating capacity, running hour, and operating cycle in the on-off temperature control of the refrigerating system.

선박 자동화의 현황과 전망 ( Ship Automation - The Present Situation and Prospects for the Future )

하주식 한국마린엔지니어링학회 1985 한국마린엔지니어링학회지 Vol.9 No.4

선박의 자동화와 Computer의 이용

하주식 한국마린엔지니어링학회 1977 한국마린엔지니어링학회지 Vol.1 No.1

박용분야에 있어서 과거 10년간 가장 진보된 것의 하나는 저동화이다. 과거에 있어서 주기관의 성능과 축계의 강도상의 문제등에 대하여 많은 관심을 가졌던 선박관계자가 그 이상으로 자동화에 대하여 관심을 갖게 된 것은 성역화에 의한 승무원의 노동조건을 개선함과 동시에 자동화에 의한 승조원의 수를 삭감하여 운항비를 낮추어야 할 필요성이 절실히 요망되었기 때문이라고 생각된다. 그러나 석유 파동이후, 세계각국이 저성장기를 맞아 선박자동화도 당분간 별 진전이 없을 것으로 보여진다. 그 1 예로서 일본 NK의 발표에 의하면 각 년도별 MO입급선의 전입급선에 대한 비율이 1972년의 35%를 피이크로 하여 1975년도에는 10%로 감소하고 있다. Computer를 탑재한 초자동화선의 운항척수도 점차 증가 되고 그 신뢰성도 인정이 되고는 있지만 1980년대 전반까지는 초자동화선에 대한 반성기가 계속될 것으로 보아지며, 보다더 가격이 저렴하고 이용율이 높은 Mini-Computer의 사용에 의한 단순화, 통일화가 앞으로 촉진될 것으로 생각된다. 본 원고에서는 선박자동화의 현황과 선박의 Computer Control System에 대해서 극히 개괄적으로 또한 피상적으로 소개하는데 그쳤다. 자동화의 각기기에 대해서는 지면상 언급하지 못하였으니 본 원고 말미의 참고문헌이나 이에 대한 전문서적을 참고하여 주기 바란다. 멀지않은 장래 Computer가 선박운항에 필요 불가결한 기기로 등장할 것만은 사실일 것으로 보아지는 바 선박관계자로 하여금 이러한 분야에 관심을 갖도록 하는데 본고가 다소나마 도움이 되기를 바라마지 않는다.