Research On Key Technologies Of Bus-based High-grade CNC System For Aviation Manufacturing

For a long time,due to the slow development of domestic high-end CNC systems,it is impossible to form a batch of supporting applications in the field of aviation manufacturing,which makes domestic aviation manufacturing enterprises rely heavily on foreign CNC systems,and the situation has become very passive.At the same time,it also buried the hidden danger of national defense security in aviation enterprises,which directly affects the production secrets and security.Independent security of high-end CNC system is the bottleneck to ensure national defense security and high-end equipment industry chain security.Under the background of Sino-US trade war and the "ZTE Event",it is particularly important for high-end manufacturing industry,including aviation manufacturing industry,to have independent,controllable,safe and reliable high-end CNC system.In the “Outline of National Medium and Long Term Science and Technology Development Plan”and”Made in China 2025”,the development of high-grade CNC systems with independent intellectual property rights is one of the important research objectives.At the same time,"High-grade CNC machine tools and basic equipment manufacturing" National Science and technology major projects will also be high-grade CNC system as an important part of the task of CNC devices.Based on the analysis of the development status and trend of advanced and high-end CNC systems at home and abroad,aiming at the requirements of high-end CNC systems in the field of aviation manufacturing,this paper studies the key technologies of high-end CNC systems for aviation manufacturing,studies the relevant technical solutions of domestic high-end CNC systems with independent intellectual property rights,and integrates them into the LanTian CNC system to make it work.Performance and performance meet the processing requirements of high-end CNC system in domestic aviation manufacturing field.Around the above problems,the research work in this paper is as follows:1.Design and Implementation of Open CNC System Architecture.The most important part of software openness is the open architecture of CNC system,whichincludes the division of system software components and the connection and constraint between components.Component technology has natural advantages in supporting interoperability between software modules,while ensuring real-time and openness.In the opening of hardware implementation platform,the most important is the communication mode of analog or bus between CNC system and servo driver.Obviously,the emerging real-time Ethernet is an effective way to completely change the motion controller and drive structure of CNC system.This research combines real-time Ethernet technology with component technology,develops an open architecture of CNC system based on Real-time Ethernet by using component model,gives full play to their respective advantages,and improves the openness of CNC system at the software and hardware levels respectively.2.Design and Implementation of EtherCAT Master in Open CNC System.In the CNC system using traditional fieldbus,the position loop is closed in the motion controller,and the motion controller outputs the control instructions indicating the speed to the servo driver.After the servo driver receives the input,the final control current is sent to the motor through the internal speed loop and the torque loop.At the same time,the encoder feeds the position information back to the servo driver and the motion controller.This communication process is usually one-way,from the controller to the driver.In a real-time Ethernet bus-based system,the servo driver closes all servo control loops in itself,so the communication between the motion controller and the bus driver becomes bidirectional.Therefore,the architecture of CNC system can be fundamentally changed by using real-time Ethernet bus.With this architecture,motion controller can be separated from bus driver while maintaining the quality and performance of itself.The motion controller and driver are integrated into a unified interface to meet the openness and interoperability of the open architecture.In this study,EtherCAT is used as the communication network between open CNC system and servo driver,and the EtherCAT master is designed by using finite state machine,which solves the problem of huge time overhead caused by waiting when many instances access EtherCAT.Finally,the efficiency and real-time performance of themaster are verified by testing.3.Research on Synchronization Method of EtherCAT Master-slave in Open CNC System.In open CNC system,a simple and efficient linear topology structure is usually chosen as its control network.The EtherCAT master station is integrated in the CNC system,which can represent the master node on the network,while the slave station is realized by the servo driver controlling the movement of each axis,representing the slave node on the network.In this way,the motion control of CNC system for each axis can be converted into the control of master station and slave station in EtherCAT network.On the one hand,in order to ensure the synchronization among the axes,it is required that the execution actions among the slaves in the EtherCAT network keep synchronization;on the other hand,in order to ensure the synchronization among the CNC system and the axes,it is required that the execution actions among the master and slaves in the EtherCAT network keep synchronization.In this study,distributed clock mechanism is used to solve the synchronization of actions between slave stations.At the same time,a synchronization method for local application of EtherCAT master and slave stations is proposed to solve the synchronization between CNC system and each axis.This method can effectively avoid the loss of data caused by the asynchronization of local application of master and slaves.Finally,the efficiency and adaptability of the local synchronization method of EtherCAT master-slave station are verified by test experiments.4.Research on Synchronization and Anti-backlash Control Strategy of Four Motor Drives in Open CNC System.In this paper,the gantry platform driven by four motors though the gears and racks on both sides is taken as the research object,a control strategy of synchronization and anti-backlash based on open CNC system is proposed.The strategy takes an open CNC system based on RTE(Real-Time Ethernet)as the main execution platform and the RTE as the carrier of data exchange.A two-axis synchronous control method is used to adjust the position of the two axes,so that the displacements on both sides of the gantry platform are consistent.At the same time,an anti-backlash control method of two-motor driving is used to eliminatebacklash,so that to ensure the transmission accuracy.In addition,in order to improve the control frequency and accuracy of the open CNC system,the interpolation of CNC system is separated into two processes: rough interpolation and fine interpolation.The period of the rough interpolation is consistent with the original cycle of the system and the period of fine interpolation is to match the minimum control period of servo driver.'S' test results show that the proposed control strategy can keep the two ends of the gantry platform in good position synchronization.