Journal of the Korea Institute of Information and Communication Engineering (한국정보통신학회논문지)

The Korea Institute of Information and Commucation Engineering (한국정보통신학회)
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FPGA Implementation of RVDT Digital Signal Conditioner with Phase Auto-Correction based on DSP

RVDT용 DSP 기반 위상 자동보정 디지털 신호처리기 FPGA 구현

  • Kim, Sung-mi (Department of Electronic Engineering, Chonbuk National University) ;
  • Seo, Yeon-ho (Department of Electronic Engineering, Chonbuk National University) ;
  • Jin, Yu-rin (Department of Electronic Engineering, Chonbuk National University) ;
  • Lee, Min-woong (Department of Electronic Engineering, Chonbuk National University) ;
  • Cho, Seong-ik (Department of Electronic Engineering, Chonbuk National University) ;
  • Lee, Jong-yeol (Department of Electronic Engineering, Chonbuk National University)
  • Received : 2017.02.21
  • Accepted : 2017.05.14
  • Published : 2017.06.30
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Abstract

A RVDT is a sensor that measures angular displacement and the output signal of RVDT is a DSBSC-AM signal. For this reason, a DSBSC-AM demodulation processor is required to determine the angular displacement from the output signal. In this paper, DADC(Digital Angle to DC) which extracts the angular displacement from the output signal of a RVDT is implemented based-on modified Costas Loop usually used in the demodulation of DSBSC-AM signal by using FPGA. DADC can used with both 4-wire and 5-wire RVDTs and can exactly compensate the phase difference between the input excitation and output signals of a RVDT unlike the conventional analog RVDT signal conditioners which require external components. Since digital signal processing technique that can enhance the linearity is exploited, DADC shows 0.035% linearity error, which is smaller than 0.005% that of a conventional analog signal conditioner. The DADC are tested in an integrated experimental environment which includes a commercial RVDT sensor, ADC and an analog output block.

RVDT(Rotary Variable Differential Transformer)는 각도 변위를 측정하는 센서로써 출력 신호는 DSBSC-AM(Double SideBand Suppressed Carrier AM) 신호이기 때문에 출력 신호로부터 각도 변위를 알아내기 위하여 DSBSC-AM 복조 과정이 필요하다. 본 논문에서는 DSBSC-AM 신호의 복조기인 코스타스 루프를 수정하여 RVDT 출력 신호로부터 각도 변위를 추출하는 DADC(Digital Angle to DC)를 FPGA(Field Programmable Gate Array)로 구현하였다. 본 논문에서 설계된 DADC는 4선식과 5선식 RVDT에 적용가능하며, 코스타스 루프의 사용으로 기존의 아날로그 신호처리기와는 달리 외부의 소자를 사용하지 않고 RVDT 입력여기신호와 출력신호 사이의 위상 차이를 정확하게 보정할 수 있다. 또한 선형성 향상을 위하여 디지털 신호처리 기법이 적용되어 DADC는 기존의 아날로그 신호처리기의 선형성 오차 0.05%보다 적은 0.035%의 선형성 오차를 보였다. 구현된 DADC의 기능과 성능 테스트는 상용 RVDT 센서와 ADC(Analog to Digital Converter), 아날로그 출력단으로 구성된 통합 실험환경을 구성하여 진행하였다.

Keywords

References

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