Practice teaching design of visual detection for assembly parameters based on an engineering project
[Objective]Integrating actual engineering projects into practical teaching and optimizing practical teaching cases to show complex engineering problems can change the current phenomenon where the practical teaching of engineering majors is disconnected from industries and can improve the quality of engineering candidates'training.Herein,an actual engineering project of vision inspection in the precision manufacturing industry is used as a teaching case for the practical teaching of a machine vision course for intelligent manufacturing majors.This paper proposes a method of converting actual engineering projects into practical teaching cases.[Methods]The hardware of the vision inspection system consisted of a CCD,an image card,a coaxial light source,a motion platform(with servo motors and screws),an industrial computer,and an image processing software system.After the slider and suspension assembly image enhancement was conducted using the image processing software system,threshold segmentation,shape-based Gaussian pyramid template matching,Canny pixel level edge detection,and Zernike matrix subpixel edge detection were used to obtain the subpixel feature contour.After that,the external contour of the slider and three feature holes of the suspension were fitted using the least square method,and the coordinate system was established with the characteristic points of the suspension as a reference to calculate the deviation value(X-dim,Y-dim)of the slider and the suspension assembly.Considering that the technology used in actual engineering projects is a collection of technologies containing multiple knowledge bases,the content of actual engineering projects can be decomposed into three types of teaching experiments in the design of practical teaching cases:basic type,comprehensive type,and innovative type.The basic type experiment is based on basic knowledge and practical ability,covering basic hardware knowledge and a single technical knowledge of image processing.Meanwhile,comprehensive-type experiments allow students to operate through a series of basic experimental projects to complete a measurement project.In the operation process,isolated knowledge points are integrated,forming a complete knowledge network.Innovative type experiments are oriented toward different assembly precision requirements,which require students to consider the hardware conditions comprehensively,determine whether the detection algorithm can meet accuracy requirements,and put forward different design solutions from various perspectives to cultivate innovative thinking and innovative ability.[Results]The results of this practical engineering project's assembly accuracy inspection testing can reach the subpixel level,and it can be decomposed into four practical sessions of 11 experiments with different difficulty requirements.In the design of the above practical teaching plan,students can select corresponding experimental projects according to different knowledge points and the ability to conduct engineering practical training.[Conclusions]Teaching methods for transforming actual engineering projects into practical teaching cases enhance students'sense of engineering experience and help them to master the knowledge points and application skills of machine vision step by step.These promote the construction of undergraduate practical teaching courses,effectively improving students'innovation and engineering practice abilities.
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