On line prediction of roll grinding chatter based on EMD component and wavelet packet energy entropy
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摘要: 针对轧辊磨削颤振时的时频域单一处理方法存在部分特征丢失的问题,提出了时频域相结合的方法对信号进行特征处理,并利用智能算法实现轧辊磨削颤振的在线预测。首先,利用经验模态分解( empirical mode decomposition,EMD)方法对振动传感器信号进行分解获得各固有模态函数(intrinsic mode function,IMF),剔除“虚假分量”后计算表征轧辊磨削颤振的时域特征。然后,利用小波包能量熵对声发射传感器信号求解频率段节点能量熵值,获得表征轧辊磨削颤振的频域特征。最后,将上述时频域特征降维后代入智能算法模型实现对轧辊磨削加工的在线预测。结果表明:LV-SVM模型的磨削颤振分类平均准确率达92.75%,模型平均响应时间为0.776 5 s;验证了时频域特性的EMD和小波包能量熵方法的LV-SVM在线预测轧辊磨削颤振的有效性。Abstract: To address the issue of partial feature loss in the single processing method within the time-frequency domain for roll grinding chatter, a combined time-frequency domain method is proposed to process signal feature. An intelligent algorithm is used to achieve online prediction of roll grinding chatter. Firstly, the empirical mode decomposition (EMD) method is utilized to decompose the vibration sensor signals, extrating the intrinsic mode function (IMF) while removing "spurious components" to calculate time domain characteristics associated with roll grinding chatter. Then, wavelet packet energy entropy is used to solve the frequency band node energy entropy values of acoustic emission sensor signals, obtaining frequency domain features characterizing the roll grinding chatter. Finally, the time-frequency domain features after dimension reduction is substituted into the intelligent algorithm model for online prediction of the roller grinding process. The results show that the the LV-SVM model achieves an average classification accuracy of 92.75%, with an average response time of 0.776 5 s. This verifies the validity of EMD and LV-SVM based on wavelet packet energy entropy in the time-frequency domain for online prediction of roller grinding chatter.
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表 1 机床及砂轮基本参数
Table 1. Basic parameters of machine tool and grinding wheel
参数 规格或取值 机床型号 MM1300 × 3000 头架转速 n1 / (r·min−1) 18~140 主轴最高转速 n2 / (r·min−1) 8000 可加工最大工件长度 L1 / mm 1677 砂轮架移动分辨率 L2 / mm 0.001 砂轮架重复定位精度 L3 / mm 0.002 砂轮外径 × 内径 × 厚度 400 mm × 200 mm × 20 mm 砂轮线速度 vs / (m·s−1) 35 砂轮中氧化铝磨粒粒度代号 F120/140 砂轮修整方式 金刚石笔修整 修整比 R 0.7 每次修整量 L4 / μm 1.5 液压传动速度 v1 / (m·s−1) 0.1~4.0 快速进给量 ap / μm 50 表 2 输入特征IMFrms数据集δvar
Table 2. Input characteristic IMFrms dataset δvar
类型 序号 δvar Imf1 Imf2 Imf4 Imf5 总和 无颤振 1 0.011 3 0.005 1 0.006 3 0.010 5 0.033 2 2 0.008 1 0.004 2 0.006 8 0.011 2 0.030 3 … … … … … … 29 0.007 1 0.003 1 0.002 2 0.002 4 0.014 8 30 0.007 1 0.003 0 0.002 4 0.002 0 0.014 5 有颤振 1 0.009 1 0.005 6 0.002 5 0.002 0 0.019 2 2 0.009 5 0.005 1 0.002 3 0.002 0 0.018 9 … … … … … … 29 0.010 3 0.004 8 0.003 2 0.002 1 0.020 4 30 0.010 1 0.004 9 0.002 9 0.002 2 0.020 1 表 3 输入特征IMFrms数据集 δstd
Table 3. Input characteristic IMFrms dataset δstd
类型 序号 δstd Imf1 Imf2 Imf4 Imf5 总和 无颤振 1 0.011 4 0.005 1 0.006 3 0.010 5 0.033 3 2 0.008 1 0.004 2 0.006 8 0.011 2 0.030 3 … … … … … … 29 0.007 1 0.003 1 0.002 2 0.002 4 0.014 8 30 0.007 1 0.003 0 0.002 4 0.002 0 0.014 5 有颤振 1 0.009 1 0.005 6 0.002 5 0.002 0 0.019 2 2 0.009 5 0.005 1 0.002 3 0.002 0 0.018 9 … … … … … … 29 0.010 3 0.004 8 0.003 2 0.002 1 0.020 4 30 0.010 1 0.004 9 0.002 9 0.002 2 0.020 1 表 4 小波包能量熵计算值
Table 4. Wavelet packet energy entropy calculation value
类型 序号 单个节点处小波包熵值 EEN H0 H1 H2 H3 H4 H5 H6 H7 无颤振 1 0.273 8 0.103 5 0.102 1 0.227 7 0.225 4 0.124 4 0.122 4 0.140 3 2 0.279 7 0.112 9 0.106 5 0.228 8 0.227 4 0.125 6 0.123 6 0.141 8 … … … … … … … … … 29 0.285 9 0.132 7 0.108 6 0.229 6 0.226 3 0.126 0 0.125 2 0.142 6 30 0.286 5 0.147 4 0.110 8 0.226 3 0.222 9 0.124 8 0.123 2 0.139 2
有颤振1 0.530 7 0.480 4 0.244 1 0.347 7 0.341 4 0.200 4 0.196 4 0.223 8 2 0.529 4 0.479 7 0.251 5 0.358 8 0.352 2 0.208 5 0.204 9 0.232 6 … … … … … … … … … 29 0.530 4 0.466 3 0.245 9 0.362 2 0.355 6 0.210 0 0.207 6 0.235 8 30 0.526 1 0.412 0 0.245 6 0.399 1 0.397 1 0.241 2 0.236 4 0.269 3 -
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