Precision measurement method of full-cycle torsion angle based on Moiré fringe

Due to the leakage of frequency spectrum caused by applying fast Fourier transform to the Moiré fringe image, it becomes challenging to achieve accurate 360° full-cycle measurements. A measurement method of full-cycle torsion angle based on Moiré fringe was proposed and a set of torsion angle measurement system was built. The Moiré fringe images with different widths were acquired by a CMOS camera at 1° intervals, and then the grating frequency spectrum information could be obtained by adopting fast Fourier transform (FFT). In addition, the 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 to achieve precision measurement of full-cycle torsion angle. Experimental results show that the system can quickly and accurately realize the full-cycle measurement of the torsion angle with the advantage of wide measurement range, and its maximum error rate is 0.243 3%.