• 한국소음진동공학회논문집
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• 제13권11호
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• pp.860-867
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• 2003

This paper presents a systematic method measuring a velocity disturbance to design the robust seek loop system of optical disk drives. The velocity disturbance caused by the rotation of a disk has a greater influence on the performance of the seek control loop as the rotational speed increases. Thus, it needs to measure the extent of the velocity disturbance and design the seek control loop based on the measured data. The measurement method of the velocity disturbance is a real-time . method using a measurable velocity and a velocity controller output and is a robust method considering actuator uncertainties. The loop gain adjustment algorithm is introduced to compensate for the actuator uncertainties. The proposed method is implemented by an experimental digital system and is evaluated through an experiment.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.425-428
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• 2008

A new type of cross-coupled planar microwave filter using coupled microstrip square open-loop resonators diplexer pro-posed. A method for the rigorous calculation of the coupling coefficients of basic four pole electric and magnetic coupling structures encountered. Simple empirical models are derived for estimation of the coupling coefficients. Experiments are performed to verify the theory. And a method for diplexer matching is conjugate matching that has characteristic better than open matching method.

• 한국컴퓨터산업학회논문지
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• 제8권3호
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• pp.167-172
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• 2007

일반적으로 응용프로그램에서 병렬성 추출에 대한 핵심 부분은 루프이다 따라서 본 논문에서는 Loop Interchange를 자동으로 처리할 수 있는 병렬컴파일러를 구현하고자한다. Loop Interchange는 반복문에서 cedar Fortran의 CDOALL문장을 바깥쪽으로 보냄으로서 특히 더 많은 병렬화 효과를 얻을 수 있기 때문이다. 이는 향후 선형변환과 혼합하여 더욱 효과적인 실행 결과를 기대하고 불완전 중첩루프에 적용하는 방법의 연구에 기여할 것으로 판단된다.

• 조명전기설비학회논문지
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• 제29권7호
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• pp.14-21
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• 2015

Distribution systems are operated in radial structure, but temporal loop structure could be founded the live load transfer. Main purposes of reconfiguration of distribution network are load balancing, loss minimization and voltage drop maintaining. In the loop structure, huge loop current can be flowed between two substations in case of large voltage angle difference. Protection devices of distribution line can be triped by this huge loop current. So, precise calculation of loop current is very important for secure switching. This paper proposes a novel calculation method of loop current using the voltage angle differences measured at the tie switches. Feasibility of the propose method has been verified by various case studies based on Matlab simulation.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.237-254
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• 2005

The vast mechanical systems could be classified as closed loop system, open loop system and open & closed (switching) system. In the closed loop system, the kinematics and dynamics of 3-D mechanisms will be reviewed and closed form solutions using the direction cosine matrix method and reflection transformation method will be introduced. In the open loop system, kinematic & dynamic analysis methods regarding the redundant system which has more degrees of freedom in joint space than those of task space are reviewed and discussed. Finally, switching system which changes its phase between closed and open loop motion is investigated with the principle of dynamical balance. Among switching systems, the human gait in biomechanics and humanoid in robotics are presented.

• 한국소음진동공학회논문집
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• 제20권10호
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• pp.900-906
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• 2010

This note proposes vibration-free motor control through modified LQG/LTR methodology. A conventional LQG/LTR method is a design tool in the frequency domain. However, unlike the conventional one, the proposed one is a time response based design method. This feature is firstly designed by parameterized settling time control gain through the target loop design procedure and the feature is secondly realized by loop transfer recovery. In order to show convergence to the target loop transfer functions, asymptotic behaviors of the open and the closed loop transfer functions are shown. At the conclusion, it is verified that the proposed method is robustly stable to parametric uncertainties through ${\mu}$-plot.

• 전력전자학회논문지
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• 제24권1호
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• pp.49-55
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• 2019

This study proposes a robust control of a fin position servo system using the H-infinity loop-shaping method. The fin position control system has a proportional (P) position controller and a proportional-integral (PI) controller. In this work, the position control loop requires a wide bandwidth. No current control loop exists due to the compact design of the system. Hence, the controller parameters are difficult to determine using the traditional cascade design method. The $H_{\infty}$ controller design method is used to design the controller's gain to achieve good performance and robustness. First, the transfer function of the system, which can be divided into tunable and fixed parts, is derived. The tunable part includes the position P controller and speed PI controller. The fixed part includes the rest of the system. Second, the optimized controller parameters are calculated using Matlab $H_{\infty}$ controller design program. Finally, the system with optimized controller is tested by simulation and experiment. The control performance is satisfactory, and the $H_{\infty}$ controller design method is proven to be valid.

• Journal of Communications and Networks
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• 제7권3호
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• pp.248-257
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• 2005

In this paper, we develop design procedures for carrier tracking loop for orthogonal frequency division multiplexing (OFDM) systems or other systems of blocked data. In such communication systems, phase error measurements are made infrequent enough to invalidate the traditional loop design methodology which is based on analog loop design. We analyze the degradation in the OFDM schemes caused by the tracking loop and show how the performance is dependent on the rms phase error, where we distinguished between the effect of the variance in the average phase over the symbol and the effect of the phase change over the symbol. We derive the optimal tracking loop including optional delay in the loop caused by processing time. Our solution is general and includes arbitrary phase noise apd additive noise spectrums. In order to guarantee a well behaved solution, we have to check the design against margin constraints subject to uncertainties. In case the optimal loop does not meet the required margin constraints subjected to uncertainties, it is shown how to apply a method taken from control theory to find a controller. Alternatively, if we restrict the solution to first or second order loops, we give a simple loop design procedure which may be sufficient in many cases. Extensions of the method are shown for using both pilot symbols and data symbols in the OFDM receiver for phase tracking. We compare our results to other methods commonly used in OFDM receivers and we show that a large improvement can be gained.

• 전력전자학회논문지
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• 제8권6호
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• pp.561-568
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• 2003

PWM 인버터의 출력전압을 제어하는 방식에는 2가지 제어기법이 있다. 첫 번째 방법은 전류제어기를 사용하여 출력전압을 제어하는 이중 제어루프를 갖는 제어방식이며, 두 번째 방법은 단일루프만으로서 출력전압을 제어하는 제어방식이다. 일반적으로 3상 PWM 인버터의 제어기는 각상 제어 PI제어기, 2상 정지좌표계 PI제어기, 동기 좌표계 PI제어기로 구성되며, 각상제어 PI제어기를 이용하여 3상의 독립된 출력측 전압 및 전류를 제어하도록 구성된다. 단일루프 전압제어기는 높은 출력 임피던스의 경우 이중제어루프 도다 더 낮은 성능을 나타내기만, 낮은 출력임피던스의 경우에는 또는 부하범위에서 좋은 제어성능을 나타낸다. 또한 시뮬레이션과 실험을 통하여 이를 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1632-1633
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• 2007

This paper presents a new method of designing digital controller based on closed-loop identification of a pulse width modulation (PWM) converter system. We consider the control system structure which is composed of both current control loop and voltage control loop. The current controller can be designed independently of voltage loop. Whereas voltage controller can not do easily due to the PWM switching component which is nonlinear in nature. Furthermore, the control objective of inner loop is to track the sine wave of 60 Hz, but the outer loop shall maintain the constant DC voltage irrespective to load change. To systematically design outer loop controller, we propose a method finding linear approximate model of the nonlinear inner loop part including current controller by closed loop identification. Based on the identified model, we show that a simple digital voltage controller can be directly designed and it has good performance.