基于自适应滤波算法的树木年轮测量方法

Annual-ring Measurement Method Based on Adaptive Filtering Algorithm

为提高树木年轮测量仪的测量精度,提出了一种自适应低通滤波算法对年轮测量仪的直流电机电流信号进行滤波处理。普通低通滤波算法滤波系数固定,当树木年轮宽度发生变化时,既可能保留了部分噪声信号,又可能滤去部分有效的树木年轮信号,因此降低了年轮测量仪的测量精度。自适应低通滤波算法的滤波系数可随滤波器输入值和输出值的变化自动进行调整,提高了噪声滤除效果,减少了有效信号损失。使用自主研发的年轮测量仪测量了大、中、小3种径阶的60个落叶松圆盘,记录直流电机原始电流信号,分别采用自适应低通滤波算法和普通低通滤波算法对原始电流进行滤波处理,根据滤波后的电流波形图,预估圆盘年龄,并计算2种滤波算法的年轮识别正确率。结果表明,自适应低通滤波器年轮识别正确率的平均值为89.66%,普通低通滤波器年轮识别正确率的平均值为75.84%;当平均年轮宽度变窄时,自适应低通滤波器的年轮识别正确率从95.61%下降到82.02%,下降了13.59个百分点,而普通低通滤波器的年轮识别正确率从86.37%下降到62.30%,下降了24.07个百分点。表明自适应低通滤波器年轮识别正确率高,自适应能力强,年轮识别精度稳定。

In order to improve the accuracy of annual-ring measuring instrument,a new adaptive low-pass filtering algorithm was proposed to filter the direct current(DC)motor current signal of annual-ring measuring instrument.The filter coefficients of ordinary low-pass filtering algorithm were fixed.When the annual-ring width was changed,the current fileted by ordinary low-pass filter may not only retain part of the noise signal,but also filter part of the effective annual-ring signal,which reduced the accuracy of the annual-ring measuring instrument.The filter coefficients of the adaptive low-pass filter algorithm can be adjusted automatically with the changes of the input and output values of the filter,which can improve the effect of noise filtering and reduce the loss of effective signals.Totally 60 larch discs,including large,medium and small diameter orders were measured by self-manufactured annual-ring measuring instrument.The original current signals of DC motor were recorded.The adaptive low-pass filtering algorithm and the ordinary low-pass filtering algorithm were used to filter the original current signals of DC motor respectively.According to the filtered current waveform,the disc age was estimated,and the annual-ring recognition accuracy of the two filtering algorithms was calculated.The average annual-ring recognition accuracy of adaptive low-pass filter was 89.66%,and that of ordinary low-pass filter was 75.84%.The average annual-ring recognition accuracy of adaptive low-pass filter was 13.82 percentage points higher than that of ordinary low-pass filter.When the average ring width became more narrow,the annual-ring recognition accuracy of the adaptive low-pass filter was decreased by 13.59 percentage points from 95.61%to 82.02%,while that of the ordinary low-pass filter was decreased by 24.07 percentage points from 86.37%to 62.30%.The experiment results showed that the adaptive low-pass filter had high annual-ring recognition accuracy,strong self-adaptive ability and stable annual-ring recognition accuracy.