Dynamic Parse Approach of Ladder Diagram Based on Binary Logic Tree on the Soft PLC System
Guanci Yang, Jing Yang
Journal of Digital Information Management, Vol. 15, No. 5, 2017.
DOI: 
Link: http://dline.info/fpaper/jdim/v15i5/jdimv15i5_1.pdf
Abstract:
This paper mainly aimed to investigate the
compiling problem of ladder diagrams (LDs) that
coordinate with a soft-PLC system running on PCs or
embedded intelligent terminals to accomplish
corresponding control functions. The data structure to
store the LDs was designed according to the series and
the parallel logic relationship among LD instructions. Then
the procedure to compile the LDs into a binary logic tree
was detailed by adopting the principles of the binary tree,
in which the child leaves represent the instructions, and
the father nodes reflect their series or parallel relationship.
Post-order traverse of the binary logic was used to parse
the control logic, and logical expression was employed to
proof the correctness of the transformation. The proposed
method was compared with one algorithm. Statistical
results on time overhead and interrupt response time
showed that the proposed method performs better in most
cases, indicating its superior capability to run the control
logic. Finally, an example of the application in the central
air conditioning control area is discussed as the case
study to illustrate the proposed methodology.