Design recovery for ladder diagram with information of controlled plant

SFC (sequential function chart), which is a graphical tool for control logic and can also represent the order for events to be controlled explicitly, has been presented as a programming language of sequential control. Since even a nonspecialist can understand SFC, it will be the main tool of sequential control. In spite of this excellent characteristic of SFC, ladder diagrams (LD) are still used in various industrial applications. In this paper, we regard LD and controlled plant as one closed loop, and propose the algorithm for picking up order of events based on the closed-loop system. We try to model the plant by means of temporal logic