to instruction list based on nary trees

 

 

ZHOU Wei, ZHANG De li

 

(College of Mechanical and Electrical Engineering, Nanjing University of 

Aeronautics and Astronautics, Nanjing 210016, China)

 

 

Abstract: Aiming at the problem of multiple output of the soft PLC, the conversion algorithm of PLC function block diagram (FBD) to instruction list (IL) based on Nary Trees was proposed and implemented. In this algorithm, firstly, the FBD program is mapped to the Nary Trees. On this basis, through decomposition and reorganization of the Nary Trees, the complex tree structure generation was decomposed into a collection of ordered subtree structure. And then the decomposed tree structures are sequentially visited in the post order traversal way. Depending on the different nodes types which are translated into the corresponding IL, the PLC FBD, finally, was achieved to be converted to the IL. An example was given to illustrate the ideas and implementation steps of the algorithm. Experimental verification of soft PLC host computer system ,based on the IEC61131 3 international standard, was carried out. The experimental result shows that the algorithm is a general conversion algorithm for conversion of complex FBD with multiple outputs into IL. And in the process of the conversion, the algorithm can preferably simplify the procedures, save more memory space and improve the efficiency of PLC FBD compilation conversion.

 

Key words: nary trees; multiple output; programmable logic controller(PLC); function block diagram; decomposition and reorganization