Full-cycle torsion angle measurement method based on Moiré fringe

Due to the spectral leakage caused by applying fast Fourier transform to the Moiré fringe pattern, it becomes challenging to achieve accurate 360° full-range measurements. A measurement method for full circle torsion angle based on Moiré fringe was proposed and a set of torsion angle measurement system was built. Moiré fringe images with different widths were acquired by with a CMOS camera at 1° intervals, then grating spectrum information could be obtained used fast Fourier transform (FFT). In addition, frequency spectrum was corrected by the Hanning-window energy centrobaric method (HnWECM), and the real and effective information of torsion angle represented by moiré fringe image could be obtained for the achievement of complete cycle torsion angle measurement. Experimental results show that the system can quickly and accurately realize the full-circle measurement of the torsion angle with the advantage of widely measurement range, and its maximum error is 0.021 9°.