Moon-Ho Kang

A High-speed Digital Laser Grating Projection System for the Measurement of 3-dimensional Shapes

In the non-contact 3-dimensional (3D) shape measurements, the fringe pattern projection method based on the phase-shifting technique has been considered very effective for its high speed and accuracy. The digital fringe projector in particular has great flexibility in generating fringe patterns since the patterns can be controlled easily by the computer program. In this work, we have developed a high-speed digital laser grating projection system using a laser diode and a polygon mirror, and evaluated its performance. It has been demonstrated that all the optical measurements required to find out the profile of a 3D object could be carried out within 31 ms, which confirmed the validity of our 3D measurement system. The result implies the more important fact that the speed in 3D measurement can be enhanced remarkably since, in our novel system, there is no device like a LCD or DMD whose response time limits the measurement speed.

Ultra High-speed 3-dimensional Profilometry Using a Laser Grating Projection System

The grating projection method with phase-shifting technique is very useful in measuring the 3-dimensional (3D) shape with high accuracy and speed. In this work, we have developed an ultra high-speed digital laser grating projection system using a high-power laser diode and a highsensitivity CMOS camera. With our system, the optical measurement required to find out the profile of a 3D object could be carried out within 2.6 ms, which is a significant (~10 times) improvement compared with those of the previous studies.

A Study on the Calculation of Reference Impedances in Domestic Low-Voltage Power System

The reference impedances which is about 95% supply impedance value of residential consumers` supply impedances was published by IEC in 1980. The reference impedances are the standard values for use in determining the voltage disturbance characteristics of electrical equipment like the flicker. In IEC 60725, the reference impedances for premises having service current capacities less than 100A per phase and for service current capacities more than 100A per phase are recommended. And these reference impedances are targeted for the countries using 50Hz power frequency. Because of the frequency difference, the reactance values of the reference impedances will be increased in 60Hz power system like Korea, And also the reference impedances are different significantly each other according to declared voltage variation, power consumption and service wire length etc. Therefore It is needed to calculate the reference impedances suitable for domestic low-voltage power system. In this paper, the reference impedances for service current capacities less than 100A in 220/380V, 60Hz single-phase two wire and three-phase four wire low-voltage system are calculated, And the equations for service current capacities more than 100A to calculate the modulus value of maximum supply impedances are suggested base on IEC 60725 and the reference impedances for those are calculated on service current of 100A per phase.

Phase error compensation for three-dimensional shape measurement based on a phase-shifting method

Abstract In this paper, a prediction and compensation method for the error in the phase measured by using the proportionality between two wavelengths in the TW-PMP (Two-wavelength Phase Measuring Profilometry) is proposed and experimental results are shown to verify the usefulness of the proposed method. For sample object, firstly, a phase-shifting with a quite large number of steps is adopted in measurement, compared with the conventional phase-shifting method, secondly, a 3-3 step phase-shifting method is used to measure the same object which is applied to high-speed 3D shape measurement, and then, measured results from these two phase-shifting methods are compared to calculate measurement noises. From the experimental results applying the proposed compensation method to the measured beat phase and absolute phase, it has proven that noises are decreased by 90% and 17.2% for each case.Key Words : 3D Shape Measurement, Error Compensation, Phase Shifting Technique, Two-wavelength, Phase Measuring Profilometry, Phase Error

A FPGA-based Development of Ultrasonic Level Meter for Measuring Oil Levels of Vehicle Transmissions

Abstract In this paper a ultrasonic level meter for accurately and simply measuring oil levels of vehicle transmission is developed and its effectiveness is shown by experiments. By using a FPGA, all digital signal processes for the oil level calculation is fulfilled, and the programming on a FPGA project IDE enables very short developing time. And besides, analog circuits including a transmit/receive switch, multi-stage active filters and an envelope detect circuit are designed to process low-level ultrasonic echo signal. Under experiments, the designed level meter has proven to have the accuracy of about within 1[mm] scale. Key Words : Ultrasonic, Oil Level Meter, Vehicle Transmission, FPGA(Field Programmable Gate Array) * Corresponding Author : Moon-Ho KangTel: +82-10-8837-5349 email: mhkang64@gmail.com접수일 12년 07월 27일 수정일 (1차 12년 08월 30일, 2차 12년 10월 30일) 게재확정일 12년 11월 08일 1. 서론 차량의 누유, 변속충격 및 변속성능 이상의 일차적인 원인이 변속기 오일레벨의 변동 및 오염도에 기인하므로 변속기의 적정한 오일레벨과 상태는 매우 중요하다. 이를 위해 변속기 출하시 조립 라인에서 변속기내에 적정한 량의 오일이 있는지를 검사하는데, 현재는 변속기의 중량을 측정하는 방식을 사용하고 있다. 이 경우, 변속기 부품(하우징, 케이스, 기어류 등)들의 중량차이가 큼에도 불구하고, 일률적으로 기준 중량을 설정하여 전체 중량에서 기준 중량을 차감하는 방법을 사용하기 때문에 정확하게 오일레벨을 측정하기가 어렵다. 본 논문에서는 종래의 자동차 변속기 오일레벨 측정방식을 개선하여 오일레벨을 정확하고 손쉽게 측정하여, 차량의 품질을 향상시키고 효율적인 A/S에 기여할 수 있는 초음파 오일레벨 측정기를 개발하고 실험을 통해 유용성을 보인다. 종래의 초음파를 통한 비파괴 측정 사례들을 분석하여[1-3] 초음파 프로브를 변속기 오일 케이스 하부에 부착함으로서 변속기에 어떠한 변형도 없이 정밀한 오일레벨 측정이 가능하고, 저렴하여 기존의 변속기 조립라인이나 A/S에 신속히 적용할 수 있는FPGA(Field Programmable Gate Array)를 기반으로 한 새로운 오일레벨 측정기를 개발하였다. FPGA로는 Xilinx 사의 XC3S200을 사용하여[4] 오일

A Study on Flicker Management Standard for Distribution Power System in Korea based on IEC 61000-3-7

Voltage variation caused by large loads such as arc furnace and large motors, which use the large and instantaneous currents, can cause the voltage flicker. The flicker irritates the human`s eyes and also has an adverse effect on protection device, rotating machine and electronic device etc, therefore the flicker needs to be managed effectively. Recently, the Korea power quality standard has been established on the IEC standards. This paper presents the flicker management standard for distribution power system and suggests the flicker transfer coefficients for Korea power system based on the IEC 61000-3-7.

Field Test and Evaluation for a Wireless Vehicle Detector with Two Anisotropic Magneto-Resistive Sensors

This paper shows field test and evaluation results for a wireless vehicle detector with anisotropic magneto-resistive (AMR) sensors. The detector consists of two AMR sensors and mechanical and electronic apparatuses. The AMR sensor senses disturbance of the earth magnetic field caused by a vehicle moving over the sensor and then produces an output indicative of the moving vehicle. In this paper, vehicle speeds are calculated by using two AMR sensors fixed on a board, with constant distance. To test and evaluate the accuracy of the detector in real traffic situations, the detector was installed on a local highway and vehicle speeds and volumes were measured both in a free running and a highly congested traffic. The measurements from the detector are compared with the reference measurements obtained from a traffic camera with the Mean Absolute Percentage Errors (MAPE), which has proved the usefulness of the detector in the field.