Soft PLC Research Based On Open Numerical Control System

NC technology is playing a very important role in the manufacturing field. With the development of open numerical control system, based on PC and realized with software has been the tendency of modem PLC.Based on PC, this paper develops compiled system and simulative running system of soft PLC. This paper uses SIPROM as source program of machine logic. In the compiled system, the paper describes symbolic structure of the SIPROM language word with regular expression. Based on the FA theory, this paper presents a lexical analysis method by using morphology table. After comparing some common syntax analysis methods, this paper choosing the LR(1) analyzer. The paper breaks the syntax analysis to two parts: symbol- expression syntax analysis and word-expression syntax analysis, and can makes those two parts transferring each other. This method has the strongpoint of LR(1) analyzer, at the same time reduces the syntax analysis table. By using the syntax-lead semantic analysis, this paper can accomplish syntax analysis and semantic analysis in one time scan. The intermediate code created by the compiler is very compact and is propitious read by the running system because the paper uses reverse polish representations, hi the simulative running system, the paper uses the hardware PLC principles and the OO method to white the running program. The simulative running system can easily add I/O port and other functions, so it has good expansibility.In a word, the compiled system and the running system have high efficiency of running. It has the great advantage comparing with hardware PLC.It has been proved that the soft PLC is adapt to be used in the open numerical control system.