| As a resource in nature,wood is one of the most widely used materials during the development of human civilization.However,nowadays,China’s forest resources are scarce,the proportion of juvenile wood is high,and the wood processing and detection level is low,which can not meet the growing demand of the market.Therefore,it is particularly important to increase the research of high-level detection system for wood quality,so as to improve the comprehensive utilization rate of wood,and save resources.In recent years,ultrasonic detection method is widely used to analyze wood quality through its propagation velocity and other characteristics in wood,but it can not identify the location and size of wood internal defects,and the detection effect is poor.The combination of visualization technology and ultrasonic detection technology can directly reflect the distribution of wood internal defects,improve the automation,intelligence and information level of wood testing instruments and equipment which is of practical significance to promote the sustainable development of domestic wood processing enterprises,save costs,and achieve higher economic and social benefits.Based on the dry coupling ultrasonic method,the design,manufacture and result test of log defect detection and visualization system were completed.The main research contents include:(1)Overall scheme design of the system.(2)Hardware circuit design of the system.The comparison and selection of the main chip of the module were completed according to the circuit energy consumption.The overall hardware framework was designed,the module design was expounded,its function and the specific process of realizing the function were analyzed.(3)Software programming of the system.It mainly includes: the environment setting of each software,the main control flow block design of embedded system software,motor drive,excitation signal output,receiver signal processing and other program design.(4)Program design of client interface of the system.The interface design of the client upper computer was realized to connected the upper computer with the lower computer,and configured the parameters such as baud rate and check bit.The corresponding functions were debugged and the transmission results were recorded.(5)Result test of the system.Larch log specimen was taken as the research object,the system was used to debug the test of A/D acquisition module,motor drive module,signal processing module,upper computer and lower computer.The data received by upper computer was formed into data matrixes and imported into the imaging system.The internal medium distribution diagram was displayed on the PC.The log defect graph was optimized by applying the nearest neighbor interpolation algorithm and bilinear interpolation algorithm.The optimized defect graph was processed by contour detection algorithm to obtain the log defect profile.Python software was used to identify and mark the defect contour of the log,and display it on the upper computer.The characteristics and innovations of this research include: rubber is used as dry coupling agent to solve the serious problem of attenuation of traditional ultrasonic signal in the process of transmission.Digital driver M542 C control motor is used to drive the circular scanning platform built,and cross section scanning detection of log specimen is carried out.The scanning platform runs smoothly and reliably,realizing the visualization effect of the internal defects of the log specimen.The edges of the image can be rounded by interpolation algorithm,and the defects can be identified by edge detection algorithm.To sum up,the wood defect detection and visualization system based on dry coupling designed in this subject could detect the defects such as cavities and cracks of log.,It had the advantages of high degree of automation,accurate detection results,good visualization and low cost.The system could provide reference for wood processing and other industries that need to detect wood,it had high application value. |
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