Design Of Visual Inspection System Based On EtherCAT Technology

With the development of industrial 4.0,intelligent manufacturing and intelligent factory are known by the public.Industrial manufacturing began developing towards automation and intelligent.And the Internet,robotics,image processing and machine learning began to be widely used in industrial manufacturing.The traditional dedicated robot controller is strong and the interface is closed.It is difficult for the user to develop it for the second time.It needs special technical support,high development cost and having great difficult with debugging.The open motion controller has the advantages of modularity,scalability and so on.The user interface is rich and easy to use.The development of open motion controllers makes it’s easier upgrading industrial production lines.And large companies in the motion control industry have begun to research open motion controllers.The computer vision processing is applied on the basis of the motion controller without affecting the motion control task which saves hardware costs and improves system integration.The correctness of the motion controller’s task results requires not only the correct logical operation but also the timely output.In this paper,through referenceing the literature,I choosed to use of Xenomai to improve the standard Linux operating system,from Preempt-RT,RTAI,Xenomai.It provides support for different vendors’ ARM chips and is compatible with other real-time operating systems API.Eventually I achieved the Linux+Xenomai dual-core system on the NXP i.MX6Q CPU.Out tests summed that task scheduling latency in the user space can reach 5 μs,kernel space 4 μs,kernel timer task response delay is only 2 μs.It performed as well as commercial real-time operating systems.In addition,since Xenomai is an open source project,it can be used completely free of charge.The motion controller utilizes EtherCAT network bus technology,the most popular network bus in the current motion control industry.The EtherCAT master can be used directly with the CPU’s network control unit,without special equipment support.In addition,it has advantage of high efficiency,good synchronization.The shielded twisted pair cable is used for connection,so it has anti-interference ability.This paper studies in the communication of the EtherCAT bus and the principle of time synchronization between master and slave devices.The master uses an open source program,the IgH EtherCAT Master,which is a fully functional master station,and completely open source.So we can custom it according to our needs.By referenceing to papers,I successfully transplant the master station on i.MX6Q.I also modified the standard Linux network driver for the EtherCAT master,for receiving and sending datagrams.The minimum communication task cycle of the EtherCAT master station in this paper can reach 120 μs,and the difference of the synchronization clock of slave stations can achieve less than 1 μs.It can meet the needs of most motion control applications.The camera for the automatic production line is just like eyes to people,the image processing algorithm likes people’s visual perception of the brain area.This paper implements the sorting function on the EtherCAT based master station.I Filtered the Image getting form the camera to remove salt and pepper noise caused by strong electric signal.Then I transformed the image for the RGB color space to the HSL space to make it easier for processing.The artifacts can be separated from the background by color and brightness information.In this paper,I propose an improved recursive cluster method,which improves the speed of image processing.The direction of the work pieces are calculated by the image’s second order center moment.Last step,getting the work pieces’ coordinate of the robotics’ world coordinate system.Finally,we programmed a simple human-computer interaction interface using Q,so that we can easily control and monitor the task.