一种基于图像处理的旋切原木直径测量方法

摘要

[目的]提出一种基于图像处理的旋切原木直径测量方法,为旋切原木直径测量提供非接触式的技术支持.[方法]增添650 nm红色激光器和940 nm不可见激光器作为辅助光源,采用树莓派官方摄像头和带有滤光片装置的USB高清工业摄像头进行图像采集,利用图像处理技术探究5种计算方法(计算激光线下弧线像素点个数、计算激光线骨架像素点个数、计算激光线周长像素点个数取平均值、计算激光线X轴方向像素点个数和通过激光线计算拟合圆直径)和6种数据拟合方法(傅里叶拟合、指数拟合、高斯拟合、Polynomial拟合、Power拟合和Sum of Sine拟合)下能够满足测量精度的最优方案.[结果]对比各计算方法采用不同数据拟合方法的拟合优度,可得到拟合优度最佳的2种方案:计算激光线X轴方向像素点个数并采用Sum of Sine拟合方法,其决定系数为0.999 8,标准差为1.638;计算激光线X轴方向像素点个数并采用傅里叶拟合方法,其决定系数为0.999 8,标准差为1.881.在原木测量误差分析中对拟合优度相差较小的2种方法(傅里叶拟合和Sum of Sine拟合)进一步对比,傅里叶拟合的平均绝对误差范围为1.7％,标准差为2.11,方差为4.45;Sum of Sine拟合的平均绝对误差范围为1.5％,标准差为4.35,方差为18.95.[结论]计算激光线X轴方向像素点个数并采用傅里叶拟合方法,在满足旋切机用原木直径测量精度要求的同时,拟合优度最佳.%[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.