Research On Moiré Fringe Signal Subdivision Technology Based On Incremental Optical Encoder

Incremental optical encoder is one of the most widely used position detection devices and mostof the encoder is grating type sensor. Moiré fringe signal subdivision is the key technology to realizehigh precision grating measurement. Improving the detection accuracy of the sensor with advancedmoiré fringe signal subdivision method but not changing structures of the sensor has important valuein engineering. Therefore, based on the analysis of the moiré fringe measurement principle and theexisting subdivision technology, two electric subdivision methods were deeply discussed: time-spaceconversion subdivision method and the quadrature PLL subdivision method. Meanwhile, systematicand in-depth researches were launched:Two essential models of displacement measurement and the commonly used subdivisiontechnology were discussed to clarify the view of space-time in displacement measurement. Based onthe idea of “measuring space by time”, this paper proposes the method of time-space conversionsubdivision for the first time. This method makes full use of the advantage of high precision timemeasurement and has such advantages as, high subdivision factor, unification of subdivision anddirection discrimination, easy to integration etc.Based on the research of the PLL principle, the quadrature PLL subdivision method was adoptedto overcome the drawbacks of traditional PLL subdivision method. It can prove the feasibility of themethod through theoretical analysis and simulation experiment.Experiments were carried out to inspect the performance of the method. Hardware platformbased on FPGA and DSP was built and it was also completed in the design and debugging of severalcircuit modules, such as modulation circuit, time measurement based on FPGA etc. The testingenvironment for new subdivision methods was established. Displacement measurement experimentsand error analysis for time-space conversion subdivision method were carried out and theexperimental results verified the effectiveness of the proposed method.