Development Of Hub Loading And Unloading Robot Workstation Based On Machine Vision

In order to meet the requirements of strength and lightweight,aluminum alloy motorcycle wheel hub is usually made of steel spline sleeve and aluminum alloy wheel hub matrix composite casting.The difference of thermal properties between the two metals is easy to lead to excessive joint clearance,which affects the safety of the hub.The research group has developed the quality inspection equipment for the engagement of the spline sleeve of the friction wheel.By applying periodic load on the spline shaft,the clearance of the bimetal parts of the defective hub is exposed in a certain way,and then identified by vision.The equipment basically meets the requirements of Jinfei group’s aluminum alloy motorcycle wheel hub inspection index,but the manual loading and unloading method of assembling wheel hub and spline shaft is difficult to meet the inspection rhythm demand of nearly 200 million wheels per year.The spline sleeve and spline shaft must meet the requirements of assembly accuracy in order to achieve accurate assembly.However,the reality is that the spline shaft may produce circumferential rotation in the process of periodic loading,which makes the angle of each hub change during assembly.These factors bring difficulties to the automatic loading and unloading of spline hub and the assembly of shaft hole.In this project,a robot hub loading and unloading workstation with visual guidance function is developed(1)Aiming at the robot workstation needs to adapt to the handling requirements of a variety of models and different sizes of spline hub,a dual station hub fixture is designed.At the same time,according to the spline shaft hole matching accuracy and load size,the workstation and key parts are designed;(2)Canny algorithm which combines adaptive median filter and quadrilateral Sobel template is developed to extract spline edge with high accuracy and reliability.At the same time,it is compared with the traditional edge detection algorithm;(3)Aiming at the problems of traditional template matching algorithm,such as long time consuming,large amount of calculation,and easily affected by the rotation and scaling of target image(spline axis),a template matching algorithm based on gradient vector similarity measure function accelerated by image pyramid is developed.The template matching effect of target spline axis under different interference factors is studied,and the effectiveness of the new algorithm is verified by experiments;(4)Based on the research of spline shaft edge extraction and template matching core algorithm,the fully integrated automatic control system and visual processing software are further developed,and the robot hub loading and unloading workstation with visual guidance function is built.The visual matching function of shaft and sleeve is verified through experiments,and the automatic loading of hub is realized.On the basis of the above research,three innovations are put forward(1)An image edge detection method based on adaptive template and median filter is proposed.(2)A template matching method based on image pyramid and gradient vector similarity measure function is proposed.(3)A loading and unloading workstation for spline hub is designed,which integrates robot system,visual guidance system and hub detection equipment to realize the assembly of complex edge hole shaft.Through the research of core algorithm,the development of hardware and software and the comprehensive performance test,the following conclusions are obtained(1)Compared with other traditional edge detection algorithms,the proposed algorithm can filter impulse noise more effectively and improve the integrity and clarity of the edge.(2)The proposed template matching method not only shortens the matching time,but also makes the template matching process have strong anti-interference ability to illumination transformation,image rotation and scaling factors.The total time consumption of edge detection algorithm and template matching algorithm can be controlled at about 1700 ms,which can meet the requirements of 1800 ms in workstation design.(3)After the accuracy test,it can be concluded that the workstation can realize the loading and unloading of spline hub and the assembly of shaft hole,and the assembly process accuracy can reach 0.046 mm,which can meet the requirements of 0.05 mm when the workstation is designed.