Modeling and control of flatness in cold rolling mill using fuzzy petri nets

Today, having a good flatness control in steel industry is essential to ensure an overall product quality, productivity and successful processing. Flatness error, given as difference between measured strip flatness and target curve, can be minimized by modifying roll gap with various control functions. In most practical systems, knowing the definition of the model in order to have an acceptable control is essential. In this paper, a fuzzy Petri net method for modeling and control of flatness in cold rolling mill is developed. The method combines the concepts of Petri net and fuzzy control theories. It focuses on the fuzzy decision making problems of the fuzzy rule tree structures. The method is able to detect and recover possible errors that can occur in the fuzzy rule of the knowledge-based system. The method is implemented and simulated. The results show that its error is less than that of a PI conventional controller.<br /

A compact Petri net representation and its implications for analysis

This paper explores a property-independent, coarsened, multi-level representation for supporting state reachability analysis for a number of di erent properties. This multi-level representation comprises a reachability graph derived from a highly optimized Petri net representation that is based on task interaction graphs and associated property-speci c summary information. This highly optimized representation reduces the size of the reachability graph but may increase the cost of the analysis algorithm for some types of analyses. This paper explores this trade-o. To this end, we have developed a framework for checking a variety of properties of concurrent programs using this optimized representation and present empirical results that compare the cost to an alternative Petri net representation. In addition, we present reduction techniques that can further improve the performance and yet still preserve analysis information. Although worst-case bounds for most concurrency analysis techniques are daunting, we demonstrate that the techniques that we propose signi cantly broaden the applicability of reachability analyses.