• Journal of Information Display
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• 제2권3호
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• pp.44-47
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• 2001

The extracted field emission current can be used to controllably heat microfabricated cold field emission cathode tips. The heating can be sufficient to smooth and recrystallize the tip surface by surface self-diffusion, and at least partially clean the surface of contaminants by thermal desorption. Self-heating not only allows for the achievement and maintenance of stable emission characteristics, but can be used to make the current-voltage characteristics of microfabricated field emitter tips nearly identical to one another. The resulting improvement in emission uniformity will allow for more reliable array operation at increased electron emission current densities.

• International Journal of Control, Automation, and Systems
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• 제5권4호
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• pp.436-443
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• 2007

In this paper, an intelligent method called BELBIC (Brain Emotional Learning Based Intelligent Controller) is used to control of Locally Linear Neuro-Fuzzy Model (LOLIMOT) of Washing Machine. The Locally Linear Neuro-Fuzzy Model of Washing Machine is obtained based on previously extracted data. One of the important issues in using BELBIC is its parameters setting. On the other hand, the controller design for Washing Machine is a multi objective problem. Indeed, the two objectives, energy consumption and effectiveness of washing process, are main issues in this problem, and these two objectives are in contrast. Due to these challenges, a Multi Objective Genetic Algorithm is used for tuning the BELBIC parameters. The algorithm provides a set of non-dominated set points rather than a single point, so the designer has the advantage of selecting the desired set point. With considering the proper parameters after using additional assumptions, the simulation results show that this controller with optimal parameters has very good performance and considerable saving in energy consumption.

• Smart Structures and Systems
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• 제18권6호
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• pp.1251-1267
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• 2016

In this paper, Simple Adaptive Control (SAC) is used to enhance the seismic response of nonlinear tall buildings based on acceleration feedback. Semi-active MR dampers are employed as control actuator due to their reliability and well-known dynamic models. Acceleration feedback is used because of availability, cost-efficiency and reliable measurements of acceleration sensors. However, using acceleration feedback in the control loop causes the structure not to apparently meet some requirements of the SAC algorithm. In addition to defining an appropriate SAC reference model and using inherently stable MR dampers, a modification in the original structure of the SAC is proposed in order to improve its adaptability to the situation in which the plant does not satisfy the algorithm's stability requirements. To investigate the performance of the developed control system, a numerical study is conducted on the benchmark 20-story nonlinear building and the responses of the SAC-controlled structure are compared to an $H_2/LQG$ clipped-optimal controller under the effect of different seismic excitations. As indicated by the results, SAC controller effectively reduces the story drifts and hence the seismically-induced damage throughout the structural members despite its simplicity, independence of structural parameters and while using fewer number of dampers in contrast with the $H_2/LQG$ clipped-optimal controller.

• Transactions on Control, Automation and Systems Engineering
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• 제1권2호
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• pp.94-98
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• 1999

Optical scanning systems use glavanometers to point the laser beam to the desired position on the workpiece. The angular speed of a galvanometer is typically controlled using Proportional+Integral+Derivative(PID) control algorithms. However, natural variations in the dynamics of different galvanometers due to manufacturing, aging, and environmental factors(i.e., process uncertainty) impose a hard limit on the bandwidth of the galvanometer control system. In general, the control bandwidth translates directly into efficiency of the system response. Since the optical scanning system must have rapid response, the higher control bandwidth is required. Auto-tuning PID algorithms have been accepted in this area since they could overcome some of the problems related to process uncertainty. However, when the galvanometer is attached to a larger mechanical system, the combined dynamics often exhibit resonances. It is well understood that PId algorithms may not have the capacity to increase the control bandwidth in the face of such resonances. This paper compares the achieable performance and robustness of a galvanometer control system using a PID controller tuned by the Ziegler-Nichols method and a controller designed by the Quantitative Feedback Theory(QFT) method. The results clearly indicate that-in contrast to PID designs-QFT can deliver a single, fixed controller which will supply high bandwidth design even when the dynamics is uncertain and includes mechanical resonances.

• 전자공학회논문지SC
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• 제41권3호
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• pp.17-24
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• 2004

동일한 작업을 반복하여 수행하는 불확실한 로봇 시스템을 위한 P형 반복 학습 제어기를 제안한다. 제안된 반복 학습 제어기는 조인트 위치 오차로 구성되는 선형 피드백 제어기와 현재의 조인트 속도 오차로 갱신되는 피드포워드 및 피드백 학습 제어기로 구성된다. 반복 작업 동작이 계속 진행됨에 따라 조인트 위치와 속도 오차는 균일하게 0으로 수렴한다. 반복 횟수에 따라 변화하는 학습 이득을 채택함으로서 반복 횟수 영역에서 임의적으로 수렴 비율을 조절할 수 있는 조인트 위치, 속도 오차한계를 제시하고, 조인트 위치와 속도 오차는 그 한계 내에서 반복 횟수 영역에서 0으로 수렴한다. 기존의 P형 반복 학습 제어기와는 달리 제안된 반복 학습 제어 알고리즘은 학습 이득을 적절하게 설계함으로써 반복 횟수 영역에서 오차 수렴 비율의 분석과 조정을 가능하게 하는 장점이 있다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.113-117
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• 2003

In the industrial field nowadays the information that needs to be handled arc increasing and requires faster speed in contrast with PLC(Programmable Logic Controller) or DCS(Distributed Control System) based control systems these days. The work environment these days are mostly based on PC, so the control systems are wanted in PC. At Fieldbus used automated systems performing distributed process control by PC performs and combines into one system in order to maximize the increase of productivity, lower the expense, planning constructing and maintaining the reliance of automation. These latest automation systems unites process, makes distributed control process able, and can control and supervise at remote PC.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.155-160
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• 1990

This paper presents the new VSMFC (variable structure model following control) algorithm of a system with parameter uncertainty. In contrast to the conventional approach, continuous control inputs am used instead of discontinous ones and modified reachability condition for sliding mode reduces a reaching phase and a newly proposed sliding surfaces are used for the robust control of uncertain system.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 가을 학술발표논문집 Vol.30 No.2 (2)
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• pp.658-660
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• 2003

본 논문에서는 AMBA 기반의 FPD 시스템에 적용 가능한 콘트라스트 컨트롤러를 설계 및 구현하였다. 제안한 콘트라스트 컨트롤러 내부에는 AMBA의 인터페이스 spec을 준수한 AMBA AHB 컨트롤러와 콘트라스트조정 블록, 메모리 컨트롤러. FPD 컨트롤러가 내장되어있다. 구현한 알고리즘은 실시간 처리가 가능하며 콘트라스트의 범위를 조정하는 가중치를 가진 알고리즘으로 기준되는 값을 이용하여 콘트라스트의 효율적인 조정이 가능하다. 콘트라스트 컨트롤러는 VHDL로 설계하였으며 FPGA를 이용한 H/W를 구현하여 TFT-LCD panel에 디스플레이 하여 검증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.959-962
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• 2010

공장 자동화와 로봇공학 등 다양한 산업현장에서 제어 공학은 이용된다. 이러한 제어 공학에서 위치제어와 속도제어를 위해 많은 제어기들이 연구되어 사용되고 있다. 특히, 본 논문에서는 간단하면서 견고한 제어기 중 능동 소자를 이용한 PID (Proportional-Integral-Derivative) 제어기와 수동소자를 이용한 Lead/Lag제어기를 설계하는데 있어 MATLAB 툴을 이용하여 정확한 성능 검증을 수행하려고 한다. 또한, 본 논문에서는 DC 모터를 위해 개선된 PID 및 Lead/Lag제어기 설계하고, 제안한 Lead/Lag 제어기의 효율성을 보여주고자 한다. 제안한 Lead/Lag 제어기는, 단계적인 변수 조정을 통하여 DC 모터 뿐 아니라 복잡한 제어 시스템에 대해서도 효과적으로 응용 가능하다. 결과적으로, 제시된 각 제어기들은 응답시간을 줄인다거나 시스템 에러를 최소화 시키는 등의 산업분야의 문제를 해결하는데 유용하게 사용될 수 있을 것이다.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.1-8
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• 2003

In this paper, a reconfigurable flight control system is designed by applying the sliding mode control scheme. The sliding mode control method is a nonlinear control method which has been widely used because of its merits such as robustness and flexibility. In the sliding mode controller design, the signum function is usually included, but it causes the undesirable chattering problem. The chattering phenomenon can be avoided by using the saturation function instead of signum function. However, the boundary layer of the sliding surface should be carefully treated because of the use of the saturation function. In contrast to the conventional approaches, the thickness of the boundary layer of our approach does not need to be small. The reachability to the boundary layer is guaranteed by the sliding mode controller. The fault detection and isolation process is operated based on a sliding mode observer. To evaluate the reconfiguration performance, a numerical simulation using six degree-of-freedom aircraft dynamics is performed.