关键词: 原木直径测量, 图像处理, 激光器, 标定拟合

Abstract: [Objective] A non-contact log diameter measurement method for a rotary cutting machine based on image processing technology was proposed in this paper with the aim to provide technical support for the non-contact, low-cost measurement of log diameter for a rotary cutting.[Method] In this study, a red line laser of 650 nm source and an invisible line laser source of 940 nm were added as auxiliary light sources, a Raspberry Pi camera and a USB-interface driverless high-definition industrial camera were selected for different laser light sources to acquire the images, respectively. Five methods of calculation(calculate arc length method,calculate perimeter length method,skeletal method,circle-fitting method,calculate the number of pixels in X axis, and six kinds of fitting method (Fourier fitting method, Exponential fitting method, Gaussian fitting method, Polynomial fitting method, Power fitting method, Sum of Sine method) were adopted when exploring which method is the best way to measure the diameter of the log on the premise of satisfying the precision requirements.[Result] By comparing the goodness of the different fitting method, two schemes of best fitting goodness can be obtained. They're respectively the method of calculating the number of pixels in X axis of laser line and applying the fitting method of Sum of Sine, the coefficient of determination was 0.999 8 and the standard deviation was 1.638. And the method of calculating the number of pixels in X axis of laser line and applying the fitting method of Fourier, the coefficient of determination was 0.999 8 and the standard deviation was 1.881. Furthermore, during the error analysis of log measurements to compare the two method, Fourier fitting and Sum of Sine fitting, had less difference in goodness of fitting. The average absolute error range of the Fourier fitting method was 1.7%, the standard deviation was 2.11, and the variance was 4.45. The average absolute error range of the Sum of Sine fitting method was 1.5%, the standard deviation was 4.35, and the variance was 18.95.[Conclusion] The scheme of calculating the number of pixels in X axis of laser line and applying the fitting method of Fourier can obtain the best goodness of fitting while satisfying the measurement precision of the diameter of the log for the rotary cutting machine.

Key words: log diameter measurement, image processing, laser, calibration and fitting