Research And Design Of Soft PLC For CNC System

In the era of technology and economic globalization, increasing the technological content ofproducts, reducing capital investment and shortening project processing time are goals thatusers continue pursuit. So the increasingly high requirements for the system processing speed,openness are necessary. In order to achieve these goals, we need to adopt new technologies,improve software and hardware continuously, such as the introduction of high-speedprocessing performance of the PC and good openness into the control field.In this paper, based on PC open type full software CNC system based on software PLC,we developed a set of procedures to realize the logic control of NC machine tool. Soft PLCbased on PC-platform development integrated with the PC software and hardware and controlsoftware, both has the traditional PLC function, but also has the PC operation monitoring andmanagement functions. The design of the soft PLC system met IEC61131-3programmingstandard language, using C language and GTK+graphics library in the Linux+RTAIenvironment, and realized the soft PLC ladder diagram programming interface as well asother major functions of the development system. For the ladder program, we designed therelated data structures to realize the ladder data storage.In the part of the compiler, we studied the conversion of the ladder program to theinstruction table, starting with the ladder is mapped to the AOV, and then using the dual stackdepth first search algorithm to traverse the ladder diagram tree, and the use of the ladderdiagram and corresponding instruction set of semantic relations to traverse the ladder diagramand ladder diagram into instruction code. It does not need to convert the ladder topology forthe other tree, entering the ladder will be able to output the instruction set code.This project uses a hardware abstraction layer technology, in-depth study of thecommunication mechanism of the soft PLC and CNC systems, completed the design of thecommunication module, and finally to achieve a soft PLC in the NC system.