• 동력기계공학회지
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• 제2권2호
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• pp.55-59
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• 1998

In practice, the property of nonlinearity is contained in all physical systems. In other word, all physical systems are nonlinear to some degree. Therefore it is important that we acquires a facility for analyzing feedback control systems with varying degrees of nonlinearity. To operate the system linearly over wide range of variation of signal amplitude and frequency, the system requires components of an extremely high quality. Such a system would probably be impractical in the view points of cost, space and weight. In this context of view, it is worth noting that the nonlinearities may be intentionally introduced into a system in order to compensate for the effects of other undesirable nonlinearities or to obtain better performance than what could be achieved using linear element only. A simple example of an intentional nonlinearity is the use of a nonlinear damped system to optimize response in accordance with the magnitude of error. In this paper, an on-off type nonlinear controller is introduced and the applicability and validity of a simple on-off controller are presented by the experimental result.

• 항공우주시스템공학회지
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• 제10권4호
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• pp.11-16
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• 2016

본 논문에서 채널 안내로를 비행하는 가변스팬 날개의 공력특성에 관한 실험연구를 수행하였다. NACA 0012익형을 가진 가변스팬 날개를 제작하였으며 선형서보모터를 사용하여 작동시켰다. 날개의 가로세로비, 지면효과, 날개와 펜스사이의 거리가 날개의 공력특성에 미치는 영향을 조사하였다. 연구결과 지면 및 펜스 모두 항공기 날개의 양력을 증가시켰으며 지면효과와 달리 펜스는 날개의 항력에 큰 영향을 미치지 않았다. 가변스팬 메커니즘이 플랩사용이 제한되는 상황에서 효과적인 고양력 장치로 사용가능할 것으로 판단된다.

• Korea-Australia Rheology Journal
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• 제13권3호
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• pp.141-148
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• 2001

In this research, experimental studies leave been performed on the hydrodynamic interaction between a spherical particle and a plane wall by measuring the force between the particle and wall. To approach the system as a resistance problem, a servo-driving system was set-up by assembling a microstepping motor, a ball screw and a linear motion guide for the particle motion. Glycerin and dilute solution of polyacrylamide in glycerin were used as Newtonian and non-Newtonian fluids, respectively. The polymer solution behaves like a Boger fluid when the concentration is 1,000 ppm or less. The experimental results were compared with the asymptotic solution of Stokes equation. The result shows that fluid inertia plays all important role in the particle-wall interaction in Newtonian fluid. This implies that the motion of two particles in suspension is not reversible even in Newtonian fluid. In non-Newtonian fluid, normal stress difference and viscoelasticity play important roles as expected. In the dilute solution weak shear thinning and the migration of polymer molecules in the inhomogeneous flow field also affect the physic of the problem.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권8호
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• pp.557-564
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• 2000

A very simple control approach using neural network for the robust position control of a Permanent Magnet Synchronous Motor(PMSM) is presented. The linear quadratic controller plus feedforward neural network is employed to obtain the robust PMSM system approximately linearized using field-orientation method for an AC servo. The neural network is trained in on-line phases and this neural network is composed by a feedforward recall and error back-propagation training. Since the total number of nodes are only eight, this system can be easily realized by the general microprocessor. During the normal operation, the input-output response is sampled and the weighting value is trained multi-times by error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. In addition, the robustness is also obtained without affecting overall system response. This method is realized by a floating-point Digital Signal Processor DS1102 Board (TMS320C31).

• 조명전기설비학회논문지
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• 제16권2호
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• pp.71-80
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• 2002

영구자석형 선형동기전동기(PMLSM)는 고속, 고추력의 직선추진이 가능하므로 산업현장에서 위치결정장치나 물류반송시스템 및 공작기계 등의 선형 서보 시스템에 이용이 되고 있다. 본 논문에서는 PMLSM의 AC 서보화를 위해 동기 프레임상에서 제어구조가 미리 설정된 스위칭 함수에 따라 불연속적으로 변화되는 가변구조 전류제어방식 및 간접 벡터제어이론을 기본으로하여 도달시간을 제거하고, 구동시스템의 추력 이용도를 높이기 위해 파라미터 변동과 한정된 외란에 거의 영향을 받지 않으며 오버슈트가 없는 고속응답을 실현하기 위해 슬라이딩 모드제어 알고리즘을 제안하여 PMLSM의 위치제어에 적용하고자 한다.

• International Journal of Control, Automation, and Systems
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• 제4권3호
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• pp.325-332
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• 2006

The dynamic responses of human standing postural control were investigated when subjects were exposed to long-term horizontal vibration. It was hypothesized that the motion of standing posture complexity mainly occurs in the mid-sagittal plane. The motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced anterior/posterior (AP) motion. The platform acceleration and the trunk angular velocity were used as the input and the output of the system, respectively. A method was proposed to identify the complexity of the standing posture dynamics. That is, during AP platform motion, the subject's knee, hip and neck were tightly constrained by fixing assembly, so the lower extremity, trunk and head of the subject's body were individually immovable. Through this method, it was assumed that the ankle joint rotation mainly contributed to maintaining their body balance. Four subjects took part in this study. During the experiment, the random vibration was generated at a magnitude of $0.44m/s^2$, and the duration of each trial was 40 seconds. Measured data were estimated by the coherence function and the frequency response function for analyzing the dynamic behavior of standing control over a frequency range from 0.2 to 3 Hz. Significant coherence values were found above 0.5 Hz. The estimation of frequency response function revealed the dominant resonance frequencies between 0.60 Hz and 0.68 Hz. On the basis of our results illustrated here, the linear model of standing postural control was further concluded.

• 한국정밀공학회지
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• 제22권5호
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• pp.103-112
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• 2005

This paper presents one-axis high precision scanning system and illustrates the design of modified $X-Y-{\theta}$ stage as a tracker using VCM and commercialized air bearings for it. The scanning system for 100nm resolution is composed of the 3-axis stage and one axis long stroke linear motor stage as a follower. In this study a previous proposed and presented structure of VCM for the fine stage is modified. The tracker has 3 DOF($X-Y-{\theta}$ motions by four VCM actuators which are located on the same plane. So 4 actuating forces are suggested and designed to create least pitch and roll motions. This article will show about the design especially about optimal design. The design focus of this fine stage is to have high acceleration to accomplish high throughput. The optimal design of maximizing acceleration is performed in restrained size. The most sensitive constraint of this optimal design is heat dissipation of coil. There are 5 design variables. Because the relationship between design variables and system parameters are quite complicated, it is very difficult to set design variables manually. Due to it, computer based optimal design procedure using MATLAB is used. Then, this paper also describes the procedures of selecting design variables for the optimal design and a mathematical formulation of the optimization problem. Based on the solution of the optimization problem, the final design of the stage is also presented. The results can be verified by MAXWELL. The designed stage has the acceleration of about 5 $m/s^{2}$ with 40kg total mass including wafer chuck and interferometer mirror. And the temperature of coil is increased $50^{\circ}C$. In addition, the tracker is controlled by high precision controller system with HP interferometer for it and linear scaler for the follower. At that time, the scanning system has high precision resolution about 5nm and scanning resolution about 40nm in 25mm/s constant speed

• 전력전자학회논문지
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• 제9권6호
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• pp.602-611
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• 2004

본 논문에서는 속도 오차의 최소화와 안정된 응답 특성을 가진 선형 영구자석형 동기 전동기를 이용한 시스템을 구성하기 위해서 속도 오차와 속도 오차의 미분항을 입력 변수로 하고 PI 룩업-테이블(look up table)을 이용한 퍼지(fuzzy) 기반 자기동조(self-tuning) PI 속도 제어기를 제안 하였다. 부하가 변동되는 제어 환경이나 시스템에 비선형성 외란이 가해지는 경우, 고정된 최초의 이득 설정 또는 NC 공작기에서 사용되는 속도에 따른 가변이득 조절 방식만으로는 원하는 제어특성을 기대하기가 어렵다. 본 연구의 타당성을 검증하기 위해서 기존의 고정이득 방식 및 속도 변동량에 따른 가변이득 방식을 제안한 방식과 시뮬레이션 및 4상한 운전 실험을 통해 비교함으로써 제안된 방식이 기존의 방식들보다 안정되고 빠른 속도 응답특성을 가짐을 확인하였다.

• Earthquakes and Structures
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• 제12권4호
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• pp.425-436
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• 2017

Vibration control using a tuned mass damper (TMD) is an effective technique that has been verified using analytical methods and experiments. It has been applied in mechanical, automotive, and structural applications. However, the damping of a TMD cannot be adjusted in real time. An excessive mass damper stroke may be introduced when the mass damper is subjected to a seismic excitation whose frequency content is within its operation range. The semi-active tuned mass damper (SATMD) has been proposed to solve this problem. The parameters of an SATMD can be adjusted in real time based on the measured structural responses and an appropriate control law. In this study, a stiffness-controllable TMD, called a leverage-type stiffness-controllable mass damper (LSCMD), is proposed and fabricated to verify its feasibility. The LSCMD contains a simple leverage mechanism and its stiffness can be altered by adjusting the pivot position. To determine the pivot position of the LSCMD in real time, a discrete-time direct output-feedback active control law that considers delay time is implemented. Moreover, an identification test for the transfer function of the pivot driving and control systems is proposed. The identification results demonstrate the target displacement can be achieved by the pivot displacement in 0-2 Hz range and the control delay time is about 0.1 s. A shaking-table test has been conducted to verify the theory and feasibility of the LSCMD. The comparisons of experimental and theoretical results of the LSCMD system show good consistency. It is shown that dynamic behavior of the LSCMD can be simulated correctly by the theoretical model and that the stiffness can be properly adjusted by the pivot position. Comparisons of experimental results of the LSCMD and passive TMD show the LSCMD with less demand on the mass damper stroke than that for the passive TMD.