Research On Integrated CNC System Based On Petri Net

Opening,networking and intellectualization are the future developmental trends of numerical control technology.As products become more and more diversified,NC functions become more and more complex,and the voice of reconfigurable,portable and scalable CNC systems is getting higher and higher.With the rapid development of software and hardware technology in recent years,the research of open CNC system can lay the foundation for the application of the large amount of computation and the application of the stronger real-time performance of CNC system.Further research on integrated CNC system will be carried out to change the corresponding structure of existing machine tools and systems,improve the integration degree,and lay the foundation for the future industrial automated integrated control.This thesis is based on the high-performance universal multi core processor platform and uses real time Industrial Ethernet to develop integrated CNC system.Firstly,the software integration scheme of CNC system is analyzed,and the advantages and disadvantages of reconstructing the NC system,the virtual machine technology and the container technology to realize the integrated numerical control are compared,and the numerical control integration scheme based on the container virtualization technique is determined.In order to reduce the coupling and improve the integration,according to the function,the CNC system is divided into several functional modules,such as interpreter module,discretization module,planning module,acc/dec module,interpolation module,and position module.Each module is operated on one container separately and unified scheduling by scheduling module to make the maximum processing efficiency and resource utilization.And the scheduling module can also cache the data generated by each module and accept the request of the user.In order to connect the CNC system in the virtual environment and the network drive module in the host computer,a communication module which has the function of data cache is designed.Compared with the integrated CNC system software,the hardware design which uses the real-time industrial Ethernet Power Link communication protocol,connects all the servo drives and the IO devices is simple.In order to ensure the correctness and reliability of the CNC system development process,the methods of the formal software modeling is used to model and analyze the system.For multi task concurrent CNC systems,it has a natural advantage using Petri network modeling.Next,the colored Petri nets is used to model CNC system at different levels.First,the top-level Petri net model of CNC system is established,and the top-level model includes CNC part and scheduling part.For the numerical control part,the function submodule can continue to be modeled.For the scheduling module,the priority preemptive task scheduling strategy is adopted.Two task scheduling strategies based on task dependency and data stream are designed,and two scheduling strategies are modeled and analyzed by Petri nets.Finally,the experimental platform of integrated CNC system is built.Firstly,the external environment test of the CNC system,including the virtual environment,the realtime environment and the communication module connecting the two,is used to test the performance of the three parts in real time.Then,for internal test of the CNC system,the actual operation effect of the two task scheduling strategies is compared,and the result of Petri net modeling analysis is verified.Finally,the experimental parameters of integrated CNC system are determined based on the above analysis and test,and machining experiments are carried out to verify the feasibility of CNC system integration.