Study on Combined Prediction Model for Surface Roughness in Milling Process
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摘要: 加工过程产生的粗糙度数据序列会包含多种特征,而单一的预测模型不能同时捕捉多种数据特征,难以提高预测精度。因此,从加工过程中粗糙度数据特征的复杂性出发,提出了一种基于支持向量机(SVM)和BP神经网络算法(BP)的组合预测模型,来同时捕捉数据的线性特征和非线性特征;在组合预测过程中为充分发挥两种预测算法的最佳性能,采用粒子群优化算法(PSO)对支持向量机的参数和BP神经网络中的权值进行优化。通过蠕墨铸铁的铣削实验,实现不同切削用量下的表面粗糙度精准预测,并与PSO-SVM、PSO-BP算法以及切削加工表面粗糙度理论模型进行对比,验证了该组合模型的优越性。Abstract: The roughness data sequence generated in machining process will contain a variety of features, and a single prediction model cannot simultaneously capture multiple data features, and it is difficult to improve the prediction accuracy. Therefore, a combined prediction model based on support vector machine (SVM) and BP neural network algorithm (BP) considering the complexity of data features in machining process is proposed, which can simultaneously capture the linear characteristics and nonlinearity of data features. In order to full play the two prediction algorithms, particle swarm optimization (PSO) is used to optimize the parameters of the support vector machine and the weights in the BP neural network. Through milling experiments, and comparing with PSO-SVM, PSO-BP algorithm and the model for surface roughness, the superiority of the combined model (PSO-SVM+PSO-BP) is verified.
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Key words:
- combined model /
- prediction of surface roughness /
- parameters optimization /
- milling
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表 1 实验切削用量及粗糙度值
实验组数 切削速度/ (m·min-1) 进给量/ (mm·min-1) 粗糙度实际值/μm 1 226 180 1.409 2 2 226 360 2.507 0 3 226 540 3.659 0 4 226 720 4.433 2 5 226 900 4.120 3 6 452 180 0.340 3 7 452 360 0.786 7 8 452 540 1.550 5 9 452 720 2.382 2 10 452 900 3.227 2 11 678 180 0.331 8 12 678 360 0.430 2 13 678 540 0.557 0 14 678 720 0.645 3 15 678 900 0.794 0 16 904 180 0.323 8 17 904 360 0.529 8 18 904 540 0.478 5 19 904 720 0.717 3 20 904 900 0.773 2 表 2 PSO在SVM和BP算法中的参数设
参数名 SVM中的PSO参数值 BP中的PSO参数值 种群数量 20 20 迭代次数 200 100 学习因子(c1, c2) c1=1.5
c2=1.7c1=1.494 45
c2=1.494 45适应度函数 均方误差EMS 均方根误差ERMS 表 3 各模型对测试样本预测值及相对误差
样本号 表面粗糙度预测值/μm 相对误差ER/% PSO-SVM+PSO-BP PSO-SVM PSO-BP 理论模型 PSO-SVM+PSO-BP PSO-SVM PSO-BP 理论模型 13 0.544 6 0.597 4 0.624 9 0.758 0 2.223 7 7.246 0 12.187 9 36.094 4 14 0.697 5 0.597 4 0.703 5 0.945 2 8.094 5 7.429 1 9.013 1 47.866 1 15 0.794 9 0.694 5 0.780 0 1.140 6 0.119 5 12.528 3 1.768 0 43.656 5 16 0.323 9 0.423 9 0.333 0 0.214 1 0.030 4 30.909 5 2.834 4 33.868 3 17 0.497 4 0.597 4 0.439 9 0.372 8 6.119 5 12.752 0 16.970 3 29.634 5 18 0.491 8 0.578 6 0.603 1 0.515 6 2.784 2 20.916 4 31.682 3 7.755 6 19 0.716 3 0.617 0 0.690 1 0.649 0 0.141 4 13.989 7 3.787 0 9.519 3 20 0.773 3 0.672 9 0.698 4 0.775 8 0.010 1 12.978 2 9.670 9 0.341 4 表 4 各预测模型的评价指标计算结果
模型 EMAP/% ERSM/% PSO-SVM+PSO-BP 2.440 4 2.27 POS-SVM 14.843 6 8.56 PSO-BP 10.989 2 7.56 理论模型 26.092 0 19.32 -
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