• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.45-46
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• 2006

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve transient control performances such as small rise time, small overshoot, small settling time, etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving transient responses and attenuating the disturbance related with dynamic coupling.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.11-14
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• 2007

An additive servo-system is developed to improve straightness of linear motor stages. For linear motor stages used in the field of high-precision linear motion process, high straightness accuracy is necessary as well as positioning accuracy in the longitudinal axis. In such cases, machining and assembling cost increases to improve the straightness accuracy. An electro-magnetic actuator which is relatively cost effective than any other conventional servo-systems is suggested to compensate the fixed straightness error. To overcome the compensation error due to modeling error and friction disturbance, a sliding mode control is addressed. The effectiveness of the suggested mechanism and the control are illustrated along with some experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.45-50
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• 1995

본 연구에서는 기존에 널리 사용되고 있는 스카이훅 제어 알고리즘(skyhook control algorithm)[3]을 바탕으로 확장 개발된 모드 스카이훅 제어(mode skyhook control) 개념 및 주파수 감응식 제어(frequency dependent control)개념[4][5]을 실용화하기 위하여 응답속도가 20msec이하의 비교적 빠른 응답 속도를 갖는 전자기식 작동기 (electro-magnetic actuator)에 의해 가변되는 4단 반능동형 가변 댐퍼 시스템을 개발한 후, 다음과 같은 성능의 향상을 시험결과를 통하여 보이고자 한다. -저속에서의 승차감 향상과 고속에서의 주행 안정성 향상 -커브 주행 또는 급격한 핸들 작동시의 롤안정성 (rolling stability) 향상 -제동 및 급발진시의 차체 피칭 운동 방지 (anti-dive, anti-squat)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.453-458
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• 2000

Design of an in-process feedback control system has been studied for precision grinding. A grinding system consists of a grinding tool, a turn table and a disk-shaped workpiece on the table is taken as an object. A grinding process model has been deduced which gives some reasoning about the process errors. In the control system the tool position is actively controlled by an electro-magnetic actuator in-process. The ground error is feedback to compose a closed-loop control system and an optimal PID controller is applied. Some control performances such as transient response and disturbance such as transient response and disturbance attenuation have been examined, which convinces the effectiveness of the control. Some methods for implementation of the control. Some methods for implementation of the control have been suggested from a standpoint of practical application.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.911-912
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• 2007

영구자석형 조작기(PMA)의 단점을 보완한 고전압 차단기용 전자석 조작기인 EMFA는 긴 스트로크를 가지는 차단기에도 사용이 가능하며, 특히 진공 차단기(VCB)용 조작기를 비롯하여, 가스 차단기(GCB)에 적용한 모델도 이미 개발되었다. 다양한 모델에 대한 설계 및 연구가 추가적으로 진행되고 있으나, 아직 설계 방법이 정형화되어 있지 않아 모델에 따라 그 형상이 달라지는 경우가 많다. 이러한 점을 개선하기 위해, 본 논문에서 EMFA의 설계 변수를 변화시켜 가며 나타나는 특성을 홀딩력과 자속밀도를 통해 분석하였다. 나아가 이를 바탕으로 설계 방법의 정형화에 대한 실마리를 제공하고자 한다. 해석에는 2차원 유한요소법을 이용하였고, 설계 변수는 조작기의 초기상태를 기준으로 설정하였다.

• Steel and Composite Structures
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• v.33 no.6
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• pp.891-906
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• 2019

This study considers the instability behavior of sandwich plates considering magnetorheological (MR) fluid core and piezoelectric reinforced facesheets. As facesheets at the top and bottom of structure have piezoelectric properties they are subjected to 3D electric field therefore they can be used as actuator and sensor, respectively and in order to control the vibration responses and loss factor of the structure a proportional-derivative (PD) controller is applied. Furthermore, Halpin-Tsai model is used to determine the material properties of facesheets which are reinforced by graphene platelets (GPLs). Moreover, because the core has magnetic property, it is exposed to magnetic field. In addition, Kelvin-Voigt theory is applied to calculate the structural damping of the piezoelectric layers. In order to consider environmental forces applied to structure, the visco-Pasternak model is assumed. In order to consider the mechanical behavior of structure, sinusoidal shear deformation theory (SSDT) is assumed and Hamilton's principle according to piezoelasticity theory is employed to calculate motion equations and these equations are solved based on differential cubature method (DCM) to obtain the vibration and modal loss factor of the structure subsequently. The effect of different factors such as GPLs distribution, dimensions of structure, electro-magnetic field, damping of structure, viscoelastic environment and boundary conditions of the structure on the vibration and loss factor of the system are considered. In order to indicate the accuracy of the obtained results, the results are validated with other published work. It is concluded from results that exposing magnetic field to the MR fluid core has positive effect on the behavior of the system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.997-1005
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• 2008

Linear motor stage is a useful device in precision engineering field because of its simple power transmission mechanism and accurate positioning. Even though linear motor stage shows fine positioning accuracy along travel axis, geometric dependent errors which relay on machining and assembling accuracy should be addressed to increase total positioning performances. In this paper, we suggests a cost effective yaw error compensation servo-system which is mounted on platform of the stage and nullify travel position dependent yaw error. This paper also provides a method of designing a sliding mode control which is robust to existing friction disturbance and model uncertainties. The reachability condition of slinding mode control for the yaw error compensating servo-system has been established. From some experimental results by using an experimental set-up, the sliding mode control showed its effective in disturbance rejection and its performance was superior to conventional linear controls.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.111-115
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• 2009

The method of test for observing the combustion instability and controling the instability actively by using secondary injection of fuel through flame stabilizer was studied by constructing model combustor of supersonic engine. The frequency of combustion instability was detected by measuring the pressure of combustor using pressure sensor and by optical sensing of flame intensity. Electro-magnetic valve was adopted as actuator for active control and the characteristics of modulated fuel was studied by measured pressure of valve outlet and scattering signal of spray at secondary fuel injection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1201-1207
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• 2010

In this study, a fatigue testing system capable of performing load-controlled tension-tension tests for micro-specimens was developed by using an electro-magnetic actuator. Using this system, fatigue testing as well as tensile testing can be performed over a wide range of loading frequencies. Further, a new laser interferometric strain/displacement gage was used during fatigue testing to obtain high-resolution measurements of the cyclic deformation of thin films. Since the testing machine and the displacement gage are stable and show quick responses, the displacement can be measured instantaneously and continuously during fatigue testing, and high-resolution results can be obtained.