• 한국자동차공학회논문집
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• 제14권5호
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• pp.17-24
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• 2006

Anti-lock brake system(ABS) are designed to prevent wheel lock on all wheels of the vehicle by sensing wheel angular speed, processing the speed sensor signals in suitable digital electronic control circuits and comanding electrohydraulic actuators to control brake pressure. This study considers a control of ABS using wheel circumferential acceleration thresholds which avoids dangerous wheel locking due to excessive brake pressure during the vehicle braking and discusses the 3-channels, 3-sensors ABS system that employs "independent control" technique for the front wheels and "select low" technique for the rear wheels. The validities of the ABS such as vehicle stability, steerability and stopping distance during braking are assured through the vehicle tests on uniform asphalt straight roads.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.30-37
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• 2004

There have been continuous efforts on automating welding processes. This automation process could be said to fall into two categories, weld seam tracking and weld quality evaluation. Recently, the attempts to achieve these two functions simultaneously are on the increase. For the study presented in this paper, a vision sensor is made, a vision system is constructed and using this, the 3 dimensional geometry of the bead is measured on-line. For the application as in welding, which is the characteristic of nonlinear process, a fuzzy controller is designed. And with this, an adaptive control system is proposed which acquires the bead height and the coordinates of the point on the bead along the horizontal fillet joint, performs seam tracking with those data, and also at the same time, controls the bead geometry to a uniform shape. A communication system, which enables the communication with the industrial robot, is designed to control the bead geometry and to track the weld seam. Experiments are made with varied offset angles from the pre-taught weld path, and they showed the adaptive system works favorable results.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.802-811
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• 1996

Farmers need alternatives for weed control due to the desire to reduce chemicals used in farming. However, conventional mechanical cultivation cannot selectively remove weeds located in the seedline between crop plants and there are no selective heribicides for some crop/weed situations. Since hand labor is costly , an automated weed control system could be feasible. A robotic weed control system can also reduce or eliminate the need for chemicals. Currently no such system exists for removing weeds located in the seedline between crop plants. The goal of this project is to build a real-time , machine vision weed control system that can detect crop and weed locations. remove weeds and thin crop plants. In order to accomplish this objective , a real-time robotic system was developed to identify and locate outdoor plants using machine vision technology, pattern recognition techniques, knowledge-based decision theory, and robotics. The prototype weed control system is composed f a real-time computer vision system, a uniform illumination device, and a precision chemical application system. The prototype system is mounted on the UC Davis Robotic Cultivator , which finds the center of the seedline of crop plants. Field tests showed that the robotic spraying system correctly targeted simulated weeds (metal coins of 2.54 cm diameter) with an average error of 0.78 cm and the standard deviation of 0.62cm.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.1140-1145
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• 1989

A general dynamic iterative learning control scheme is proposed for a class of nonlinear systems. Relying on stabilizing high-gain feedback loop, it is possible to show the existence of Cauchy sequence of feedforward control input error with iteration numbers, which results in a uniform convergance of system state trajectory to the desired one.

• 한국항행학회논문지
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• 제19권1호
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• pp.7-14
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• 2015

본 논문에서 국내 공항별 비행장 관제시뮬레이터(ATCS; aerodrome traffic control simulator)를 구축하기 위한 모델을 제안한다. ATCS는 관제사의 직무교육과 새로운 관제시스템 교육을 위한 연구기능 등으로 활용된다. 이런 기능들을 수행하기 위해, 우리는 ATCS를 교육, 연구 그리고 통합관리 시스템 등의 세 가지 유형으로 분류하였고 국내 공항별 근무 환경과 교육 환경 등으로 분석하였다. 따라서 우리는 국내 공항별 구축 모델을 균등형, 차등형, 그리고 센터형 등으로 제안하고 각 시스템에 대한 장단점을 분석한다. 또한 우리는 ATCS 구축 모델을 구축 비용과 유지 보수비용, 활용성 그리고 확장성 등의 항목으로 검토하였다. 그에 따라 국내 공항에 비행장관제시뮬레이터 구축이 적합한 차등형을 제안하였다.

• 한국멀티미디어학회논문지
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• 제7권5호
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• pp.737-743
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• 2004

본 논문에서는 비균일 부하의 다중 셀 CDMA시스템에서 복수의 서비스 종류를 고려한 효율적인 호 수락제어 기법을 제안한다. CDMA 시스템에서는 각 셀에서 동시에 통화할 수 있는 이동 가입자들의 수는 각 기지국이 수신하는 총 간섭량에 따라 제약을 받고, 또한 서비스 받는 이동 가입자의 수는 각 기지국마다 균일하지 않게 분포될 수 있다. 본 연구에서는 등가대역 개념을 이용한 호 수락 제어 방법을 사용하며, 신규 호의 차단율 및 핸드오프 호의 절단율을 감소시키기 위해 차단율(blocking rate)과 절단율(dropping rate)에 따라 각 셀의 대역폭을 가변시켜 신규 호와 핸드오프 호를 처리한다. 본 논문에서 제안하는 기법의 성능은 컴퓨터 시뮬레이션을 수행 해 본 결과, 이동 가입자의 수용 용량을 증가시킬 수 있음을 확인하였다.

• 제어로봇시스템학회논문지
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• 제6권3호
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• pp.309-316
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• 2000

A coordination method for a macro/micro robot with separate controllers is proposed and evaluated. The macro/micro robot system generally has independent controllers for the macro and the micro robot respectively. A controller for the coordination of the macro and the micro robot has been designed based on the stable independent controller of each system. The method and trajectory generation method is also proposed to track the moving desired position rapidly. The control method and trajectory generation method is also proposed to track the moving desired position rapidly. The control strategy has been implemented to the macro/micron robot system to evaluate the performance. The experimental results show that the proposed method for maintaining the micro robot within its workspace has uniform performance over the various range of the bandwidth and the proposed trajectory generator is shown to be efficient.

• Journal of Astronomy and Space Sciences
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• 제37권3호
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• pp.199-208
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• 2020

This paper presents a kinematic ephemeris generator for Korea Pathfinder Lunar Orbiter (KPLO) and its performance test results. The kinematic ephemeris generator consists of a ground ephemeris compressor and an onboard ephemeris calculator. The ground ephemeris compressor has to compress desired orbit propagation data by using an interpolation method in a ground system. The onboard ephemeris calculator can generate spacecraft ephemeris and the Sun/Moon ephemeris in onboard computer of the KPLO. Among many interpolation methods, polynomial interpolation with uniform node, Chebyshev interpolation, Hermite interpolation are tested for their performances. As a result of the test, it is shown that all the methods have some cases that meet requirements but there are some performance differences. It is also confirmed that, the Chebyshev interpolation shows better performance than other methods for spacecraft ephemeris generation, and the polynomial interpolation with uniform nodes yields good performance for the Sun/Moon ephemeris generation. Based on these results, a Kinematic ephemeris generator is developed for the KPLO mission. Then, the developed ephemeris generator can find an approximating function using interpolation method considering the size and accuracy of the data to be transmitted.

• 한국정밀공학회지
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• 제23권8호
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• pp.64-71
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• 2006

In this paper, a uniform speed controller for an ultrasonic rotary motor is developed using the phase-difference method. The phase difference method uses traveling waves to drive the ultrasonic motor. The traveling waves are obtained by adding two standing waves that have a different phase to each other. A compact phase-difference driver system is designed and integrated by combining VCO(Voltage Controlled Oscillator) and phase shifter. Theoretically the relationship between the phase difference in time and the rotational speed of the ultrasonic motor is sine function, which is verified by experiments. Then a series of experiments under various loading conditions are conducted to characterize the motor's performance that is the relationship between the speed and torque. Proportional-integral control is adopted for the uniform speed control. The proportional control unit calculates the compensating phase-difference using the rotating speed which is measured by an encoder and fed back. Integral control is used to eliminate steady-state errors. Differential control for reducing overshoot is not used since the response of ultrasonic motor is prompt due to its low inertia and friction-driving characteristics. The developed controller demonstrates reasonable performance overcoming disturbing torque and the changes in material properties due to continuous usage.

• 한국전자파학회논문지
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• 제14권3호
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• pp.268-275
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• 2003

본 논문에서는 멀티 미디어 서비스를 지원하는 VSG-CDMA 시스템의 역방향 링크 용량을 전력 제어와 사용자 분포에 따라 두 모델로 가정하여 해석적으로 분석한다. 분석 모델 I은 완벽한 전력제어와 사용자의 균일 분포로 가정하여 블록킹 확률식을 계산하고 1 %의 블록킹 확률에 일치하는 최대 음성과 데이터 사용자수를 산출한다. 분석 모델 II은 전력제어오차와 사용자의 비균일(셀 경계 부분에 위치)분포로 가정하여 분석한다. 모델 I의 분석 결과는 5 MHz의 광대역 VSG-CDMA 시스템 용량의 상한선(upper bound)이며 모델 II의 분석 결과는 시스템 용량의 하한선(lower bound)을 제시한다. 또한 모델 II에서 데이터 활동율과E$_{b}$/N$_{o}$ 값에 따른 사용자 용량을 분석하여 VSG-CDMA 시스템의 성능 개선 방안을 제안한다.