Research On Multiple Holes Alignment For Stereo Workpiece With Complex Shape

The riveting work of the holes in hydraulic workpiece is currently completed manually.Because the riveting process is difficult risky,relying only on workers’ experience will lead to inefficiency,and the product consistency will be difficult to be guaranteed.The riveting process parameters and riveting quality are difficult to control.In order to increase productivity and quality consistency,it is necessary to introduce an automatic riveting machine to realize automatic riveting of riveting holes in the workpiece.The automatic riveting process can be divided into two steps: the alignment of the hole and the plug,the pressing of the plug.The alignment of the hole and the plug is the key in the whole riveting process.In addition,improving the alignment accuracy of the hole can not only avoid damage to the product during the pressing process of the plug,but also improve the quality of riveting.In this thesis,a multiple holes alignment method was proposed,which can be used in precise alignment of holes and plugs in automatic riveting process of automatic riveting machine.In this dissertation,the existing alignment methods were introduced first,and then the multi-axis alignment system was designed.The alignment process of the system could be divided into 2 steps: coarse alignment by multi-DOF system and precise alignment by vision-aided system.Then,the coarse alignment system and precise alignment system were described in detail.Finally,the experimental platform for multi-hole alignment was built and experimental study was carried out on the platform.The experimental results showed that the alignment accuracy can be achieved in the range of 10 microns by this system,and the alignment accuracy requirements of the automatic riveting machine can be satisfied.The innovations of the thesis are:1.Based on robot kinematics and vision detection technology,a multiple holes alignment system and its method of combining multi-DOF system and vision system is presented.2.Subpixel detection method based on improved Sobel operator and cubic spline interpolation is used to optimize the quality of edge detection and improve the positioning accuracy of hole axis.