Research On FPGA-based Phase Grating Interference Sensor Signal Processing System

Wide-range, high-precision displacement sensor plays an essential role in the field ofadvanced manufacturing, which is in extensive demand. Phase grating interference (PGI)displacement sensor which uses diffraction grating pitch as the measurement benchmarkmaintains both high resolution and accuracy in wide-range measurement. Signal processingsystem is one of the most important aspects to ensure the accuracy of a sensor, this thesisfocuses on the research of PGI displacement sensor and develops a kind of FPGA-based PGIdisplacement sensor signal processing system, the main work of the thesis is as follows:1. The principle of PGI displacement sensor is analysed, and its signal processingprocess is designed.2. The signal processing and acquisition circuit of PGI displacement sensor is designed,which includes photodiode current to voltage conversion circuit, differential amplificationcircuit, zero-calibration amplification circuit, analog to digital conversion circuit,optocoupler isolation circuit and PCI bus interface circuit, etc.3. The sine signal decoding and counting technique based on FPGA is implemented.The analog to digital conversion programme, the digital filter, decoder and counter oforthogonal signal, PCI local bus interface are completed by FPGA programming andWindows PCI driver encapsulation is done by Windows programming.4. The hysteresis is compensated which is caused by hysteresis comparator and maylead to counting error. The main errors of tangent subdivision method are analysed.5. The comparison experiment with dual-frequency laser interferometer is carried out toverify the accuracy of PGI displacement sensor.