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상용 Single Chip Solution을 이용한 정전용량형 변위 센서 신호 처리 모듈 개발
김종안(J.-A. Kim),김재완(J. W. Kim),엄태봉(T. B. Eom) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
A signal conditioning circuit for capacitive sensors was developed using a commercial single chip solution. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. Up to now, several companies already have succeeded in the development of the capacitive sensors system and they are commercially available in the market. In this research, to construct the signal processing circuits more easily and simply, we used a universal LVDT signal conditioner (AD698). Since the AD698 provides one chip solution for a basic signal processing including modulation and demodulation using various internal components, we can build the processing circuits successfully with minimal additional circuits: a compensation circuits for the drift caused by the bias current of OP amplifiers and a fine adjustment circuit for the elimination of nonlinearity. The signal processing circuits shows nonlinearity less than 0.05% in the comparison with a laser interferometer.
FPGA 모듈을 이용한 Long Range AFM 용 다축 제어 프로그램 개발
이재윤(J. Y. Lee),엄태봉(T. B. Eom),김재완(J. W. Kim),강주식(C.-S. Kang),김종안(J.-A. Kim) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
In general, atomic force microscope (AFM) used for metrological purpose has measuring range less than a few hundred micrometers. We design and fabricate an AFM with long measuring range of 200 ㎜ × 200 ㎜ in X and Y axes. The whole stage system is composed of surface plate, global stage, microstage. By combining global stage and microstage, the fine and long movement can be provided. We measure the position of the stage and angular motions of the stage by laser interferometer. A piezoresistive type cantilever is used for compact and long term stability and a flexure structure with PZT and capacitive sensor is used for Z axis feedback control. Since the system is composed of various actuators and sensors, a real time control program is required for the implementation of AFM. Therefore, in this work, we designed a multi-axis control program using a FPGA module, which has various functions such as interferometer signal converting, PID control and data acquisition with triggering. The control program achieves a loop rate more than 500 ㎑ and will be applied for the measurement of grating pitch and step height.