• 한국항공우주학회지
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• 제39권7호
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• pp.618-626
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• 2011

무인항공기가 복잡한 지형이나 위험 지역에서 안전한 비행을 하기 위해서는 요구되는 경로를 정밀하게 추종할 수 있는 제어기법이 필요하다. 경로추종을 위해 사용되는 PID 제어기에서는 경로의 곡률을 앞먹임하여 추종성능을 개선할 수 있다. 한편 경로를 정밀 추종하기 위해서는 제어기의 이득을 크게 하는 것이 필요하나 비행체의 응답속도가 느린 경우 큰 경로 추종 이득을 사용할 경우 성능 저하 또는 불안정성이 발생할 수 있다. 여기서는 응답지연을 고려하여 앞먹임을 갖는 PID제어기의 설계방법을 고려하였다. 앞먹임에 필요한 경로정보를 간단히 얻기 위해 주어진 경로를 3차 스플라인 방법을 적용하여 3차 다항식으로 나타내었다. 설계한 제어기의 추종성능을 평가하기 위해 높은 고도에서 운용되는 느린 횡방향 동특성을 갖는 무인항공기에 대해 비선형 시뮬레이션을 수행하였다. 제어기에서는 횡방향 동특성을 1차 모델로 가정하여 반영하였다. 시뮬레이션을 통하여 동특성을 고려한 경우는 비행체가 주어진 경로를 매우 정밀하게 추종함을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.991-995
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• 2002

차량 실내에서 발생하는 엔진 부밍 소음은 엔진의 진동이 샤시로 전달되어 구조 진동의 형태로 발생하는 구조소음이다. 본 연구에서는 이러한 엔진 부밍 소음과 그 원인이 되는 엔진 진동 사이의 관계를 알아보고자 엔진 마운트 중 한 위치에서 차체로 전달되는 엔진 진동을 줄일 경우 실내 엔진 부밍 소음의 변화를 고찰하였다. 이를 위하여 제어용 구동기를 제작하고 feed-forward 와 feed-back 제어기를 혼합한 hybrid 제어기를 적용하여 실차 실험을 수행하였다.

• 한국정밀공학회지
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• 제13권2호
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• pp.133-145
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• 1996

This paper presents an indirect cutting force measuring system, which uses the current signals from the AC servo drive units of the horizontal machining center, with its applications to the adaptive regulation of the cutting forces in various milling processes and to the on-line monitoring of tool breakage. A typical model for the feed-drive control system of a horizontal machining center is developed to analyze cutting force measurement from the drive motor. The pulsating milling forces can be measured indirectly within the bandwidth of the current feedback control loop of the feed-drive system. It is shown that the indirectly measured cutting force signals can be used in the adaptive controller for cutting force regulation. The whole scheme has been embedded in the commercial machining center and a series of cutting experiments on the face cutting processes are performed. The adaptive controller reveals reliable cutting force regulating capability against the various cutting conditions. It is also shown that the tool breakage in milling can be detected within one spindle revolution by adaptively filtering the current signals. The effect of the cutter run-out has been considered for the reliable on-line detection of tool breakage.

• 전력전자학회논문지
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• 제9권3호
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• pp.275-284
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• 2004

본 논문은 동적전압보상기(DVR)의 제어를 위한 우수한 성능의 디지털제어기를 제시하고 제어이득(Control Gain)의 설정에 관하여 논한다. DVR계통의 전력회로를 분석하여 DVR의 운전한계를 찾고 그에 따른 제어목표 및 제어기 구조를 제시한다. 디지털 제어기는 인버터의 PWM 스위칭과 함께 제어시스템의 시간지연을 야기한다. 이러한 시간 지연은 제어시스템의 전달함수를 1차수 높게 하여 제어시스템을 더한층 복잡하고 불안정하게 한다. 본 논문은 제어기의 시간지연을 고려하여 제안된 제어기의 이득을 설정하는 방법을 제시하고 인버터의 스위칭 주파수와 관련하여 출력측 필터요소의 설계지침을 제시한다. 제안된 설계방법에 의하여 전디지털화(Full Digital Control) 된 DVR 시스템을 제작하여 이론을 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.434-437
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• 1989

This paper describes the speed control of d.c. servo motor by PID method in loads. PID algorithm has mainly been used in industrial circles In spite of the development of various control theory. D.C. motor speed is controlled by a microprocessor (Z-80). The speed control of d.c. motor is experimented in transient and steady state. In this study, feedforward controller Is used for dealing with loads. When it is possible to measure loads, this feed forward controller is used with another controller. And also, satisfying control effect Is gotten by using it In system with loads. Therefore, It is proved through experiment that a new designed controller can control the speed of d.c. servo motor.

• Transactions on Control, Automation and Systems Engineering
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• 제2권4호
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• pp.274-284
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• 2000

In this paper, the design methodology of digital fuzzy controller(DFC) for the systems with time-delay is presented and the qualitative effects of the quantizers in digital implementation of a fuzzy controllers are investigated. We propose the fuzzy feed-back controller whose output is delayed with unit sampling period and period and predicted. the analysis and the design problem considering time-delay become very easy because the proposed controller is syncronized with the sampling time. The stabilization problem of the digital fuzzy system with time-delay is solved by linear matrix inequality(LMI) theory. Furthermore, we analyze the stability of the quantized fuzzy system. Our results prove that when quantization os taken into account, one only has convergence to some small neighborhood about origin. We develop a fuzzy control system for backing up a computer-simulated truck-trailer with the consideration of time-delay and quantization effect. By using the proposed method, we analyze the quantization effect to the system and design a DFC which guarantees the stability of the control system in the presence of time-delay.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.60-66
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• 2006

This paper presents a new way achieving better welding results of gas mental arc welding (GMAW) system by using a decentralized control method. In this paper, the GMAW system is considered as two separated subsystems such as a power source of GMAW (PS-GMAW) and a wire feed unit (WFU). The mathematical modeling of PS-GMAW and WFU are presented. Based on the modeling of two subsystems, a sliding mode controller and a proportional controller is designed for controlling the PS-GMAW and the WFU, respectively. Two decentralized controllers have to be designed to control the out welding arc of the GMAW to be stable and tracking the setting value accurately during the welding process. Furthermore, the simulation and experimental results are shown to prove the effectiveness of the proposed controllers.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1898-1913
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• 2006

This paper deals with the design of a yaw rate controller based on gain-scheduled H$\infty$ optimal control, which is intended to maintain the lateral stability of a vehicle. Uncertain factors such as vehicle mass and cornering stiffness in the vehicle yaw rate dynamics naturally call for the robustness of the feedback controller and thus H$\infty$ optimization technique is applied to synthesize a controller with guaranteed robust stability and performance against the model uncertainty. In the implementation stage, the feed-forward yaw moment by driver's steer input is estimated by the disturbance observer in order to determine the accurate compensatory moment. Finally, HILS results indicate that the proposed yaw rate controller can satisfactorily improve the lateral stability of an automobile.

• 한국정밀공학회지
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• 제34권4호
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• pp.265-272
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• 2017

Velocity ripple in manufacturing processes reduces productivity and limits the precision of the product. In practice, the frequency and phase of velocity ripples always change minutely, which makes it impossible to compensate for the ripple by simply inserting an opposite feed-forward signal in the system. In this study, an active-phase compensation algorithm was developed to enable the velocity-ripple controller to track the phase change of the ripples in real time. The proposed controller can compensate for the velocity ripple whatever its cause, including disturbance by the torque ripple. The algorithm consists of three functional modules: the velocity-ripple extractor, the synchronized integrator, and the phase shifter. Experimental results showed that the proposed controller clearly reduces velocity ripples with phase variation.

• Journal of Power Electronics
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• 제16권3호
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• pp.1176-1189
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• 2016

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.