Automated Optical Inspection Of Tabs Welding Defects In Lithium Batteries

Laser welding process is widely used in the welding of lithium-ion battery cell lugs and Protection Circuit Module.Generally,different types of welding defects appeared inevitably with welded products due to the instability of laser energy,mechanical vibration and uneven material,these defects were checked manually in the traditional visual inspection way before the machine vision technology were used.However,the diverse demand and the insufficient specific algorithms still make defects inspection process face some problems that the real-time performance and inspection accuracy can not meet the demand of production.Focusing to ameliorate the inspection accuracy and real-time performance,this thesis develops a defects inspection system taking a DSP image processing unit as the core.The overall structure and design options are proposed,and the specific development of the lithium battery cell lugs-PCM welding defects inspection system are carried out—focusing on higher inspection accuracy and better real-time algorithms,after finishing above-mentioned work the thesis verifies the performance of the system through a test.The proposed inspection system can avoid the host computer executing all tasks including image processing,which will improve the realtime performance of the system because of the high performance of digital image processor.Besides,the defects inspection algorithm is specifically designed to ensure a high inspection accuracy.In specific research,the thesis explores the overall structure of the inspection system on the basis of production requirements and inspection objects features.Based on the advantages of high-speed image processing of DSP and high-speed transmission and timing control of embedded industrial cameras,an embedded lithium battery inspection scheme-including system hardware components,as well as the various components of the interface program-is designed.Embedded industrial camera designed to acquire solder joints image and control acquisition period has a camera output interface playing a role of transmitting the original image to image processing module for real-time processing.Multiple images are required in solder joints defects inspection process,so the system uses a number of large-capacity SDRAM and FLASH to ensure a high real-time performance.The thesis proposes a complete set of image processing algorithm including filtering,fusion,automatic threshold segmentation,edge detection,morphological processing,geometric transformation and template matching algorithm to extract the location,shape and size of solder joints accurately.On this basis,the thesis develops defects inspection program with solder joints position labeling,morphological marking and size calculation functions.The accuracy of the algorithm is verified finally on a defects inspection device.In addition,in accordance with the production requirements,a host computer software for parameter setting,equipment control and result display is designed.An online inspection and analysis of mobile phone battery cell lugs-PCM welding is completed on the integrated system.The experiment proved that the system developed has a relatively large improvement in defects inspection speed and accuracy aspects,and the inspection accuracy is 98.5%.