An edge fitting method for the online measurement of lithium battery coating

Liu Huaiguang; Kong Jianyi; Yang Jintang; Wang Xingdong; Liu Yuanjiong

doi:10.12086/oee.2019.180563

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Liu Huaiguang, Kong Jianyi, Yang Jintang, et al. An edge fitting method for the online measurement of lithium battery coating[J]. Opto-Electronic Engineering, 2019, 46(10): 180563. doi: 10.12086/oee.2019.180563

Citation:

Liu Huaiguang, Kong Jianyi, Yang Jintang, et al. An edge fitting method for the online measurement of lithium battery coating[J]. Opto-Electronic Engineering, 2019, 46(10): 180563. doi: 10.12086/oee.2019.180563

An edge fitting method for the online measurement of lithium battery coating

Key Laboratory of Metallurgical Equipment and Control Technology, Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081, China

Fund Project: Supported by National Natural Science Foundation of China (51875418), Hubei Provincial Technology Innovation Project (2017ACA180), and Natural Science Foundation of Hubei Province (2017CFC830, 2018CFC795)

More Information

Corresponding author: Liu Huaiguang, E-mail: lhg81219@163.com

Received Date 31 October 2018

Revised Date 19 December 2018

Published Date 18 October 2019

Abstract

Abstract

Edge detection is a key step for the online vision measurement of lithium battery coating (LBC). However, as the vibration and rectification in LBC production, the virtualization and curling of edges could occur. In order to improve the accuracy and efficiency of on-line measurement of LBC, this paper proposed a staged edge location method according to the production characteristics of LBC, and achieved the swift and accurate detection of edges. Firstly, a cross neighborhood operator is used to detect the edge preliminarily to improve the ability of week edge detection. Then, local extreme values difference (LEVD) algorithm with selective peak sort algorithm is proposed to guarantee for the ability of edge-preserving and anti-noise of edge projection and to improve the efficiency of edge detection. Finally, piecewise cubic spline interpolation combined with segmented linear fitting method is provided to realize the sub-pixel location of the edge. The experimental results show the effectiveness of the method.
- lithium battery coating /
- vision measurement /
- edge detection /
- oriented projection /
- linear fitting

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References

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Overview

Overview

Overview: Lithium battery has been widely used in various industries. The coating quality is an important key that affects the performance of the battery. At present, the dimension of the coating of batteries in production mainly depends on manual sampling inspection with soft ruler, which is low-efficiency and has poor real-time performance. This paper focused on the study of the on-line vision dimension measurement technology of the lithium battery coating (LBC) in production, discussed the design of visual measurement system, and proposed a method of progressive location and segmental fitting of coating edges according to the characteristics of LBC production. As traditional boundary operators are noise-sensitivity and poor-robustness, this paper provided an across-neighborhood operator to detect the direction edges of coating. This operator has larger dimension and improved his sensitive to gradual edges. Then, a method of local extreme values difference (LEVD) was performed on the vertical projection of the boundary image. LEVD was operated in local neighborhood of each nonzero projection and search maximum and minimal projected value to mark edge projection, hence reducing the noise peak interference and obtaining a more accurate boundary projection curve. In order to obtain the boundary position, the peaks above a set threshold were fused according to the neighborhood judging rules and sorted by selective sorting algorithm (SPS) with the desired edge number, obtaining the initial location of coating boundary at u direction. In order to obtain more accurate edges of LBC, a segmented edge fitting method was proposed in this paper. First, an edge image was divided into several segments (6 parts in this paper) in the vertical direction, and a number of pixel values in the local range of the u points of the coarse boundary were taken along the gradient direction for each segment to form a boundary fitting vector. Then, the cubic spline curve fitting with the first boundary condition was used for each segment fitting vector. After that, the second derivative of the fitting curve was derived and equal to zero to find the maximum gradient point. Finally, the line fitting for each segment boundary point was done by means of oblique cutting to form the final accurate fitting boundary of LBC. Based on the proposed method, an online measurement system of LBC was developed and applied to the production practice. The field operation realized the high precision measurement with 0.2 pixel, and experimental results prove that the edge fitting method is robust, efficient and suitable for the production needs.