Abstract: Based on the principle of laser Doppler velocimetry, this study proposes a hybrid frequency resolution methodology combining fast Fourier transform (FFT) and continuous Fourier transform (CFT), achieving enhanced measurement accuracy for wire rod velocity. By combining autocorrelation detection, FFT spectrum estimation, CFT spectrum refinement, and energy center estimation spectrum correction, this method achieves effective noise reduction, high signal-to-noise ratio and spectral resolution, thereby improving the accuracy of wire rod speed measurement. The simulation and experimental results show that the signal-to-noise ratio of the collected signal is improved after single autocorrelation, and the average absolute error of speed measurement is less than 0.01 m/s. Compared with Welch spectrum estimation, this method has a smaller absolute error and higher accuracy in speed measurement under different speed conditions. The on-site production tests show that the speed measurements of different sections meet the requirements of high-speed wire rod production control, confirming the applicability of this method.

Key words: laser technology, laser Doppler velocimetry, fast Fourier transform, continuous Fourier transform, wire rod, spectrum refinement and correction