20.1 INTRODUCTION

Petri nets are useful tools for modelling systems with control flow. In particular they aid in modelling systems with concurrency, and parallelism. A set of routines have been developed at UWO to serve as the basis for a manufacturing simulation. The routines will support a number of various Petri net functions. The basic operation of the Petri net may be simulated. As well the EOR transitions will also be modelled. An attempt has been made to add ‘colors’ to the tokens, but at the present there is insufficient information (i.e., no references) to verify the implementation.

The routines have been written in a user friendly way to allow simple application interface. Places and Transitions are specified with textual names. A brief theory of petri nets follows.

•These are like state diagrams, except multiple states can be active at the same time.

•Other techniques, such as GRAFCET, are based on Petri nets.