Abstract:

Objective Yarn defects are an important index to evaluate yarn quality, and it is necessary to classify the common yarn defects such as coarse yarn segment, thin yarn segment and neps in a more detailed way to achieve multilevel management of yarn quality. The key to yarn defect grading is how to quantitatively analyze the appearance geometric dimensions such as yarn defect length and diameter. Aiming at the problems of low accuracy and poor reliability of the current quantitative analysis methods for cotton yarn defects, a quantitative analysis method for cotton yarn defects based on heterogeneous integrated learning is proposed.

Methods A two-dimensional dynamic simulation model for yarn defect detection based on capacitance sensor was established to analyze the influence law of yarn defect size on its signal. Following that, the time domain analysis method was adopted to extract the time domain parameters of yarn defect signals as the quantitative analysis characteristics for yarn defects. Then, the support vector regression algorithm, radial basis function neural network algorithm and gradient boosting decision tree were used as primary and meta learners 'respectively' to establish a heterogeneous integrated learning algorithm model for quantitative analysis of yarn defects, which was verified by experiments finally.

Results Based on the capacitive sensor, the dynamic simulation modeling and analysis of yarn defect detection was carried out, and the comprehensive capacitive sensor detection circuit principle and dynamic simulation analysis results showed that the yarn defect length and yarn defect diameter were the key factors affecting the yarn defect signal change, among which the peak change of the yarn defect signal was affected by the superposition coupling of the yarn defect diameter and the yarn defect length, and the duration of the yarn defect signal peak was only affected by the yarn defect length. The results collected by the time domain analysis method showed that the time domain feature parameters of different levels of yarn defects deminstrated obvious differences, proving that the time domain feature parameters could be adopted to estimate the appearance geometry of yarn defects. However, the relationship between the time domain feature parameters and the appearance geometry of the yarn blemishes remained vague and nonlinear. Therefore, a network with strong nonlinear approximation capability was required to map the time domain parameters and the appearance geometry of yarn defects, namely the quantitative analysis algorithm of yarn defects based on heterogeneous integration learning. The root mean square error and mean absolute error of the yarn defect diameter test set were 0.002 1 and 0.001 2, and the root mean square error and mean absolute error of the yarn defect length test set were 0.002 6 and 0.001 4, which represents a greater improvement than other types of single-model algorithms, and the goodness of fit was close to 1.00, which fully demonstrates that the algorithm proposed in this paper has a better fitting effect on the yarn defect diameter and yarn defect length, and the model has stronger reliability.

Conclusion A quantitative analysis method of yarn defects based on heterogeneous ensemble learning is proposed. The method picked the yarn defects signal by capacitive sensor, combined the time domain characteristic parameter extraction algorithm and multi-model heterogeneous ensemble algorithm, and conducted quantitative analysis of non-stationary and nonlinear yarn defects signal. The experimental results confirmed that the yarn defect quantitative analysis model based on integration of heterogeneous learning can improve the appearance of yarn defects quantitative accuracy of geometry size with the method of optimal fitting R² close to 1.00. Compared with the conventional single model algorithm, the accuracy is improved by 10%, indicating the new method has good generalization ability and stability. It provides a more effective quantitative analysis scheme for yarn defects detection system based on electrical signal.

Key words: cotton yarn, yarn defect, quantitative analysis of yarn defect, yarn defect signal, yarn quality, heterogeneous ensemble learning algorithm