Method for converting ladder diagram into PLC (Programmable Logic Controller) program command

Abstract

The invention relates to a method for converting a ladder diagram into a PLC (Programmable Logic Controller) program command, which comprises the following steps of: 1, presenting a topological structure of a ladder diagram by using a directed graph; 2, traversing a transposed graph GL <T> by using a depth-first search method, storing a topological sorting relation of parallel-connection peaks and coil peaks in a queue Q; 3, carrying out breadth-first search on the parallel-connection peaks according to a connection relation of the directed graph GL, carrying out depth-first search on serial-connection peaks adjacently connected with the parallel-connection peaks, generating an AND expression of the directed graph GL on the whole serial-connection path and an OR expression of the serial-connection peaks; 4, generating a final expression of the maximum combining item of the parallel-connection peaks; 5, carrying out breadth-first search on a connection relation graph Gp by using the Q,figuring out an OR expression of the corresponding parallel-connection peaks and verifying, finally, constructing the maximum combining item into the AND expression to form a final result; 6, judgingwhether a queue Q' is empty; and 7, processing a starting peak. The invention can be widely applied to the process of converting the ladder diagram into the PLC program command.

Description

technical field [0001] The invention relates to a method for generating program instructions, in particular to a method for converting ladder diagrams into PLC program instructions. Background technique [0002] Programmable logic controller (Programmable Logic Controller, PLC) is the most commonly used general control equipment in the field of industrial control, and the ladder diagram is a necessary programming language for PLC. Although the ladder diagram is intuitive and easy to use, it cannot be run directly on the PLC. It is necessary to convert the ladder diagram into an instruction table to make the PLC control the controlled object according to the control logic of the ladder diagram. There are many ways to convert from ladder diagram to instruction list, but by far the better method is to convert the ladder diagram into a binary tree or some tree-like data structure, and then use some rules and some simple linear data structures, such as stacks Or queue, repeatedl...

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Problems solved by technology

[0003] However, the above method has the following disadvantages: 1. The conversion from the ladder diagram to the tree structure is relatively complicated, and must be completed with the help of auxiliary vertices, so that the generated results lack optimization.

2. The ladder diagram with complex topological connection structure cannot be converted, so the conversion range is limited

3. The structure of the tree-based conversion program is complex, and the calculation relationship between vertices and edges is more complicated during the conversion process. It is difficult to analyze the time complexity of the conversion process. Use on a large scale

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