Method for converting PLC program into common Petri net

Abstract

The invention provides a method for converting a PLC program into a common Petri net. The method is characterized by: aiming at a PLC ladder diagram program, simulating a ladder diagram contact and a coil as a node; simulating a lead as a directed edge; establishing a PLC directed graphical model of the ladder diagram program; defining a path in a directed graph; according to a path relation, converting the PLC directed graph into the Petri net. In the invention, automatic conversion from the PLC ladder diagram program to a common Petri net model can be realized. Because an excitation condition of the common Petri net is concise, a logic thinking mode is simple, visual and understandable and the obtained Petri net model can complete simulate a dynamic behavior of a PLC control system, PLC program analysis and error correction can be conveniently achieved and PLC program logic is more precise.

Description

technical field [0001] The invention relates to a mathematical modeling method of a programmable logic controller (PLC) program, which is a powerful tool for PLC program simulation and verification, especially a method for converting a programmable logic controller program into a common Petri net. technical background [0002] Programmable logic controller (PLC) is a typical controller hardware in industrial control systems, widely used in the monitoring of steel, petroleum, chemical, electric power and transportation systems. However, the development of PLC programs faces high complexity problems: with the support of fieldbus technology, the scale and structure complexity of industrial control systems grow rapidly, such as subway traffic control systems and nuclear power control systems, etc., and the number of states of the system varies with the number of sensors The number of and executive agencies is increasing exponentially, and the state of the logistics system consis...

AI Technical Summary

Problems solved by technology

However, the development of PLC programs faces high complexity problems: with the support of fieldbus technology, the scale and structure complexity of industrial control systems grow rapidly, such as subway traffic control systems and nuclear power control systems, etc., and the number of states of the system varies with the number of sensors The number of and executive agencies is increasing exponentially, and the state of the logistics system consisting of only 5 automatic navigation vehicles reaches millions, so the PLC program design faces inherently high computational complexity

[0003] The high computational complexity brings two major engineering problems: (1) The program design and debugging workload is cumbersome and huge, and the program development cycle and development cost are difficult to control; (2) Traditional program debugging cannot verify each state (the number of states is exponential Growth), the correctness and reliability of the program cannot be guaranteed, and program errors may cause serious accidents, such as train collisions, European Ariana 5 rocket explosions, and American Threc-5 radioactive medical accidents, etc.

[0005] The method that has been reported at present is to give the method of converting a single instruction or a simple ladder diagram program into an extended Petri net, which cannot automatically convert a common ladder diagram program, and needs to list a large number of logical relationships when actually simulating and converting a ladder diagram program method, which increases the workload, and the behavior analysis of the extended Petri net is more complicated, which increases the possibility of errors; another method is to use the structural elements of the extended Petri net to describe the basic logic instructions of the PLC ladder diagram, and then Complete the conversion of PLC ladder diagram language

The key to this method is to define transition as a specific event, but from a logical perspective, the operation of the entire network structure is not simpler than the PLC ladder diagram program, and the Petri network structure cannot operate by itself during simulation

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