• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.19-22
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• 2000

Noncontact measuring methodology of 3-dimensional profile using CCD camera are very attractive because of it's high measuring speed and its's high sensitivity. Especially, when projecting a grid pattern over the object the captured image have 3 dimensional information of the object. Projection moire extract 3-D information with another grid pattern in front of CCD camera. However phase measuring profilometry(PMP) obtain similar results without additional grid pattern. In this paper, new method for grid pattern generation system by polygonal mirror and Laser Diode. This system is applied the projection moire and the PMP.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.244-247
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• 2001

진동을 감소시키는 방법에는 최적의 설계 변수를 선정하는 수동 제어 방법과 피드백 루프(Feedback loop)를 이용하는 능동제어 방법 두 가지가 있다. 이 중 능동제어에 대한 연구가 최근에 활발히 진행되고 있다. 본 연구에서는 능동제어를 위한 진동시스템의 동적해석과 시스템의 모델링에 대해 연구하고자 한다. 진동체로는 외팔보를 선택하였으며 진동체의 진동을 제어하는 장치로는 제어코일과 베이스코일로 구성된 Push-Pull 타입의 전자석 제어회로를 직접 제작하였고 시스템을 모델링하여 전달함수를 구하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2535-2540
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• 2002

ESPI is a noncontact, nondestructive and relatively fast inspection method. For these reasons ESPI is being applied as a valuable tool in the nondestructive evaluation of structural components. Phase shifting ESPI is used more effectively than the traditional ESPI because spatial resolution of small object displacements are improved and numerical phase values are obtained for all pixels in the image. Consequently the quantitative measurement of deformation is possible. ESPI fringe patterns are contaminated with high levels of speckle noise. Therefore the phase image is to be smoothed to remove the noise and obtain a better signal-to-noise ratio. In this study, smoothing is done by phase shifting convolution to avoid smoothing errors close to the 2$\pi$ phase ambiguities in the deformation phase image, and median filter is used as a smoothing filter.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.137-142
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• 2001

Since recent production system becomes that of the small quantity, large volume with high quality production, accurate and high speed inspection system is required. In such situation, noncontact 3D measurement system which utilized CCD cameras is useful technique in terms of system cost, speed of data acquisition, measuring accuracy and application. However, it has low accuracy compared with contact 3D measurement system because of the camera distortion, non uniformity of laser distribution and so on. For those reasons, in this paper precision enhancement method is studied considering radial camera distortion, and laser distribution. A distortion correction method is applied even to the standard lens. The laser slit beam trajectory is determined by 3 method: based of the Gaussian function signal approximation, the median method, the center of gravity method and the peak point of the Gaussian function method.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.2
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• pp.148-153
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• 2013

This study demonstrates a novel hybrid surface polishing process combining non-traditional electrochemical polishing(ECP) with external artificial ultrasonic vibration. ECP, typical noncontact surface polishing process, has been used to improve surface quality without leaving any mechanical scratch marks formed by previous mechanical processes, which can polish work material by electrochemical dissolution between two electrodes surfaces. This research suggests vibration electrochemical polishing(VECP) assisted by ultrasonic vibration for enhancing electrochemical reaction and surface quality compared to the conventional ECP. The localized roughness of work material is measured by atomic force microscopy(AFM) for detailed information on surface. Besides roughness, overall surface quality, material removal rate(MRR), and productivity etc. are compared with conventional ECP.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.183-190
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• 2007

It is well known that abrasive waterjet(AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain the better cutting quality of various materials such as metals, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, AWJ device still has some problems to obtain the high quality of thin workpiece. In this paper, we investigated the optimal microcutting conditions of AWJ, such as maximum pressure, cutting speed and standoff distance of thin multi-layered materials. The experimental results show that AWJ has possibilities and potential to apply to the microcutting of thin multi-layered materials for IT industrial applications.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.154-157
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• 1995

A magnetic levitation control system is nonlinear and very unstable. Thus there should be a stabilizing compensation network and a feedback path. Due to the levitation control a noncontact photoresistor sensor is generally used. One photocell provides a certain amount of variation in length by the ball shadow casted on the cell surface. Furthermore at the boundary of the cell, the linearity of sensitivity deteriorates severely. To overcome the constraints of the length and linearity, an efficient sensor array is deviced and applied in the feedback path of a large-gap magnetic levitation control system. A number of CdS photocells and a summing circuit of the sensor output signals are used for a sensor array. The levitation length of a ball and the transient performances are main objectives of the large-gap suspension system using the sensor array.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.1133-1136
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• 1999

A magnetic levitation control system is inherently nonlinear and very unstable. Thus there should be a stabilizing compensator network and a negative feedback path using noncontact photoresistor or ultrasonic sensors for the levitation operation. Since the photo sensor plays a key role in the system, the steady-state error and transient performance of the overall system depend on the characteristics of the sensors. But the sensor itself also suffers from nonlinearity, and the magnitude of sensor input heavily depends on environmental conditions. To improve the output performance, we added a linearizing circuit for the sensor characteristics and a disturbance cancelation circuit to avoid sensitive output due to extraneous interfering light.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.317-322
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• 2013

This paper presents a new laser lock-in thermography (LLT) technique for nondestructive evaluation. LLT utilizes a modulated continuous wave laser beam as a heat source to obtain high fidelity thermal wave images even at the presence of background heat disturbances. The thermal waves propagating along the surface and through-the-thickness directions of a structure are visualized using newly developed laser lock-in amplitude and phase images, enhancing the detectability of surface and subsurface defects. The LLT technique is numerically investigated and experimentally validated using thermal images obtained from a steel specimen with low emissivity.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.602-607
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• 1990

Spent nuclear fuel is very dangerous substance emitting strong ionizing radiation which is harmful to human body. The remote handling of spent nuclear fuel is essential because people cannot access this substance without protecting radiation. To handle highly radioactive material or nuclear waste, many kinds of teleoperators such as master slave manipulator, electro mechanical manipulator, servo manipulator, mobile robot was developed. The distance and dimension of target object cannot be measured easily when highly radioactive material is handled by teleoperator because one should use lead glass or TV camera and monitor to protect radiation and see target object. During experiments on the remote handling of spent nuclear fuel by electro mechanical manipulator, we often felt that a distance and dimension measurement system is necessary to handle the objects which is in the highly radioactive environment, so we developed a system which is appropriate for this purpose.