Communication Scheduling And Application Of The FML System Based On CAN Field Bus

At present, there are a large number of low-standard CNC machine tools in our country,because this kind of numerical control machine tool only has RS232communication interfaceand its memory capacity is small, so it can’t establish a seamless connection with thetechnology of CAD/CAM and other advanced manufacture technologies in the use. In orderto improve the level of manufacturing and production efficiency of Chinese enterprises, fullplay to the performance and efficiency of NC machine tool available should be given with thedevelopment of high-grade CNC machine tools at the same time. In this paper, we build up aflexible production line which CAN field bus is as its communication medium and DNCtechnology will be used in order to connect low-grade NC machine tools with the network. Bydoing so, low small capacity of CNC machine tool edge transmission side’s processing isachieved, the efficiency of the use of this kind of CNC machine tools is improved, theinformation management of the underlying devices is realized.This paper focuses on the building of flexible production line communication networkconstruction and communication scheduling of system. CAN bus is used as thecommunication medium for building the connection between the DNC control host and CNCmachines in flexible production lines to achieve communication. The protocol conversionbetween DNC control host and CAN bus is through PC-CAN communication card, thecommunication between CAN bus and the numerical controlled machine tools is throughCAN-RS232protocol conversion module. According to the flexible production line’s work,real time communication process of communication network is analyzed and a mathematicalmodel system to avoid communication conflicts is built. By analyzing the influence ofparameters such as the rate of CAN bus and the application rate of system on the size of thesystem, the method of making sure the upper and lower limit values of the underlyingcommunication network protocol conversion module in the flexible production line is givenunder the case that the system’s scale and the protocol conversion module are bothdetermined. The scheduling priorities of the nodes in the communication are determined bythe state of the node and the consumption deadline of NC program. DNC control host decidethe sequence of sending the NC program to the nodes according to the priorities of the node.Finally, an important component of CAN-RS232Z protocol on the flexible production line ofthe bottom network conversion module for the reliability analysis. Finally, the reliabilityanalysis of CAN-RS232Z protocol conversion module which is the important part of theunderlying communication networks in the flexible production line is made.