EXTENDING THE KNITTING TECHNIQUE TO PETRI-NET SYNTHESIS OF AUTOMATED MANUFACTURING SYSTEMS

The modelling or synthesis of ordinary Petri nets has been recognized as a key step for applying Petri nets to performance analysis, control and simulation of industrial production systems. This paper addresses this synthesis problem by adopting a global and incremental synthesis approach: the knitting technique for manufacturing systems. The knitt ing technique has been applied to Petri net modelling and anlaysis of communication networks. The idea behind this technique is to introduce details in an incremental way, i.e. by adding new paths and/or cycles to a Petri net. At each step the Petri net model grows according to c ertain rules which will guarantee such system properties as boundednes s, liveness and reversibility. Thus the cumbersome anlaysis for these properties can be avoided while designers can still build up a Petri n et model for a complicated system. The knitting rules are divided into two types: TT and PP with a number of variations. This paper formulat es and discusses these rules in the context of manufacturing. The theo retical results on the preservation of system properties using the pro posed rules are presented. The results are illustrated through Petri n et modelling of an automated manufacturing system which consists of tw o robots, five machines and two automatic guided vehicles. This approa ch is compared with other existing synthesis approaches and its distin guishing advantages are indicated in the conclusion. Future research a long this direction is also discussed.