Design Of Intelligent Conversion Module For DNC System Based On CAN Communication

Manufacturing industry is the industrial foundation of the country,whose development level directly reflect the comprehensive national power of a country.The arriving of the “Internet+ Manufacturing industry” mode closely integrates computer networking technology and manufacturing industry to form a new networked manufacturing mode,which could Improve the economic efficiency of enterprises.Numerical control machine tools are important equipments in modem manufacturing industry,whose output and technological level could reflect the technological level and competitiveness of a country's manufacturing industry.At present,there are still massive middle and low grade economy numerical control machine tools without networking function,which limits the improvement of the manufacturing industries developmental level.The networked manufacturing of numerical control machine tools uses different network to establish the Distributed Numerical Control(DNC)system,which could realize the real-time control of one computer to several numerical control machine tools,this could improve the use ratio of the equipment and reduce the production cost.In the DNC system structured by CAN bus,since the dispatch deviation could lead to communication contention aware in the control process of the upper computer over multiple numerical control machine tools even in the scheduling range.The protocol conversion module designed in this paper added the first-in first-out(FIFO)storage submodule,the intelligent representation of the module constructs a double-layer communication network,which can judge the storage status of the FIFO memory,the module sends the status signal to the upper computer,when the status is full the upper computer switches to other modules,when the status is empty the upper computer switches to the module,ensure that the normal operation of numerical control machine tools at the same time improve the efficiency of the use of equipment.Receive the status of numerical control machine tools to ensure the normal transmission of data.Took the communication contention aware as research point CAN bus rate,program consumption rate,data transmission efficiency and other parameters to carry out modeling calculation to get the upper and lower bounds of FIFO-memory,analyzed the variation of environmental parameters to the upper and lower bounds,and by setting a reasonable threshold value the control of upper computer over numerical control machine tool could be accomplished effectively and the communication contention aware could be avoided.The interfaces of the majority of the middle and low grade economy numerical control equipments are RS232 C and RS48,while the general protocol conversion module could only realize the data transition of one of the interfaces.The protocol conversion module designed in this paper could achieve the transition of the functions of CAN-RS232 C and CAN-RS485,users could choose the appropriate conversion interface according to their need.Finally,the corresponding hardware and software were designed aiming at the design requirements,and the reliability is studied according to the design requirement of operating environment.The protocol conversion module designed in this paper could be used in different DNC system to carry out format conversion on data between different buses,and the rationality of the design is verified through simulation and on-site operation of each module.