An effective method for detection and elimination of avalanche effect problem

Abstract

The Supervisory control theory (SCT) is a general framework for the synthesis of supervisors (controllers) for discrete events systems (DES). The SCT makes use of automata theory and formal languages. Given a plant automaton model and a specification for the controlled behavior, a RW (Ramagde-Wonham) supervisor is obtained as an automaton. Programmable Logic Controllers (PLCs) are widely used in modern industrial systems to carry out control tasks. Although there are a lot of methods proposed for PLC based implementation of RW supervisors, there are still very few industrial applications. This is due to a number of important problems, one of which is called avalanche effect. In this paper, two contributions are provided to tackle with the avalanche effect problem. The first one is an algorithm proposed for the determination of the events that cause avalanche effect in a given supervisor. The second one is a very simple and effective avalanche effect elimination method (AEEM). The applicability of these two contributions is shown by examples.