The Research And Development Of Software Plc In Open Computer Numerical Control System

SoftPLC technology is the gradual rise of international industrial automation, anew PC-based control technology. PLC compared with the traditional hard andsoftPLC has a more powerful data processing capabilities and networkcommunications capabilities and has an open architecture. In recent years, with therapid development of computer technology, industrial automation of open controllerand the system needs more pressing, hardware and software architecture closedtraditional hard-PLC encountered challenges. SoftPLC applications open architecture,has a good network of communications capabilities, able to complete more complexcontrol tasks, to meet and achieve current and future areas of industrial automationcontrol system openness and flexibility requirements, and it is for the future ofindustrial automation to a higher level of integration provides a reliable technicalsupport.For the present situation and development trend of software PLC, not difficult tofind PC-based PLC platform for embedded software can take full advantage ofhardware and software resources of the PC, and directly program adopting ladderdiagram or language, possesses favorable man-machine interface. In the NC system, itis gradually replaced in the field of hardware PLC as a new method for control ofauxiliary functions.This paper first analyzes the status of the CNC system and the development trendof openness, then proposed the concept of the software PLC. According to theanalyzation of the principle and architecture about software PLC, and referencing tothe IEC1131-3 international criterion, research and design the architecture and systemplatform of the software PLC. According to the structure of software PLC, integratesoftPLC editor development system by using VC++. The system can complete thePLC ladder diagram and instruction sheet edited compilation features two languages,PLC process simulation, ladder, and two languages of instruction list betweenconversion and gives a ladder program editing and conversion with the commandlanguage program examples.Software PLC discussed in this article exists in the upper and lower computer of CNCsystem. The upper computer software PLC completes user PLC programes download,interfaces environment. After syntax checking and logical checking, user program iscompiled and is saved as intermediate file with general data structure. The downloaded intermediate file is running under DOS environment in lower computer inreal time.