Abstract
To overcome the difficulty of accurately determining the load state of a wet ball mill during the grinding process, a method of mill load identification based on improved empirical wavelet transform (EWT), multiscale fuzzy entropy (MFE), and adaptive evolution particle swarm optimization probabilistic neural network (AEPSO_PNN) classification is proposed. First, the concept of a sliding frequency window is introduced based on EWT, and the adaptive frequency window EWT algorithm, which is used to decompose the vibration signals recorded under different load states to obtain the intrinsic mode components, is proposed. Second, a correlation coefficient threshold is used to select the sensitive mode components that characterize the state of the original signal for signal reconstruction. Finally, the MFE of the reconstructed signal is used as the characteristic vector to characterize the load state of the mill, and the partial mean value of MFE is calculated. The results show that the mean value of MFE under different load states varies. To further identify the load state, a characteristic mill load vector is constructed from the MFE values of the reconstructed signal under different load conditions and is used as the input of the AEPSO_PNN model, which then outputs the predicted ball mill load state. Thus, a load state identification model is established. The feasibility of the method is verified based on grinding experiments. The results show that the overall recognition rate of the proposed method is as high as 97.3%. Compared with the back propagation (BP) neural network, Bayes discriminant method, and PNN classification, AEPSO_PNN classification increases the overall recognition rate by 8%, 5.3%, and 3.3%, respectively, which indicates that this method can be used to accurately identify the different load states of a ball mill.
Highlights
As the main type of mechanical equipment used for ore grinding, ball mills are widely used in the beneficiation process in mining operations [1]
High accuracy. the nonstationary and nonlinear characteristics of the vibration signal from the Considering and nonlinear the vibration cylinder of a ball the mill,nonstationary a load identification methodcharacteristics for ball mills isofproposed in thissignal studyfrom basedthe on cylinder of a ball mill, a load identification method for ball mills is proposed in this study based improved empirical wavelet transform (EWT), multiscale fuzzy entropy (MFE), and AEPSO_PNN classification
The fuzzy entropy (FE) of the reconstructed signal is calculated, and five groups of samples are assessed for each type of ball mill load state
Summary
As the main type of mechanical equipment used for ore grinding, ball mills are widely used in the beneficiation process in mining operations [1]. The classification effect of a probabilistic neural network is greatly influenced by the smoothing parameter σ, and if the selection of σ is not appropriate, inaccurate results may be obtained To solve this problem, an adaptive evolutionary particle swarm optimization (AEPSO) algorithm is proposed in this paper to optimize the smoothing parameters in a probabilistic neural network (PNN) so that the optimized network can identify the load state of a ball mill. Considering and nonlinear the vibration cylinder of a ball the mill,nonstationary a load identification methodcharacteristics for ball mills isofproposed in thissignal studyfrom basedthe on cylinder of a ball mill, a load identification method for ball mills is proposed in this study based improved EWT, MFE, and AEPSO_PNN classification.
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