Research And Design Of Multi-axis Motion Real-time Control System Based On EtherCAT Communication

Since entering the information age,the industry has vigorously developed Ethernet fieldbus technology,Ethernet fieldbus technology has high performance instability,adaptability and reliability,which can suitable for a variety of complex industrial control field.However,with the continuous improvement of the industry's requirements for real-time communication control,the traditional Ethernet fieldbus has been difficult to meet the requirements of today's industrial control.EtherCAT,which developed by Beckhoff Company in Germany,because of its advantages of stable performance,high communication efficiency and high synchronization,has been gradually used in various industrial control fields.In this thesis,the EtherCAT Ethernet communication protocol is used to control multiple servo shafts,and have systematically studied the EtherCAT communication protocol.Based on the open source master station SOEM,the multi-axis motion control program is written,and the real-time control test platform of "PC master station + multi-servo slave station" has been built.Real-time performance and multi-axis motion function have been tested.Firstly,by consulting and investigating the development status of motion control at home and abroad in recent years,with the deeply analysis of the basic working principle of EtherCAT communication protocol,data frame structure,synchronization mode and so on.Combining the motion control data of TWINCAT soft master station and slave station,there is a deep analysis with the basic composition of EtherCAT master station.Wireshark software is used to analyze the control data packets generated in the communication process of the master and slave stations.The specific operations of the master station on the data link layer are clarified by analyzing a series of initial configuration of the master and slave equipment and communication messages related to the clock synchronization of the master and slave stations,which lays a foundation for the design of the multi-axis control program in this thesis.Secondly,based on the Windows system and Linux system,the open source master SOEM has been built.After analyzing and comparing the performance of the master station under different systems,the Linux+SOEM master station scheme has been selected.Considering its real-time performance,the RTAI real-time kernel was installed to improve the real-time performance of communication.Slave servo equipment is selected,and ESI(Slave Device Description File)is analyzed to determine the specific configuration of FMMU,PDO,SM and hardware device interface of the servo slave station.Due to the need of the motion of multiple axes control,it is necessary to design the interpolation algorithm.Based on the point-by-point comparison method and the digital integration method,the linear and circular interpolation algorithm of the plane is designed.At the same time,the digital integration method is also used to design the spatial circular interpolation.In order to make the motion process smooth enough,trapezoidal velocity planning and S-type velocity planning were completed respectively,and the acceleration and displacement curves were simulated by MATLAB.Then,according to the specific content of the description file of the slave device,initialize the multiple slave devices,distribute the clock and con Figure.the state machine,which lays a good foundation for the subsequent control of the servo slave movement.Firstly,the control program have been designed to control the motion of the slave servo driver,and specifie the relevant parameters such as motion speed and running distance.Then,the multi-axis cooperative motion is carried out.The designed motion control program was tested on the built multi-axis servo control platform,and the communication data packets were intercepted during the communication process.The real-time performance of the control system was tested and verified.Finally,an experimental study is carried out on the multi-axis servo control platform based on EtherCAT communication designed in this thesis,and the specific architecture scheme of the master and slave station equipment in the software and hardware lines is established,which verifies the feasibility of the designed multi-axis control program,and the target of real-time performance on Linux system have been achieved At the same time,it provides a precondition for adding more servo slave stations in the future,and also lays a solid foundation for developing high-performance master station software.