Discrete Event Systems (DESs) are systems whose state-space is discrete and the evolution is driven by the abrupt occurrence of discrete events, that is, with instantaneous duration in time, and in non regular lifetimes. Computational systems, manufacturing systems and traffic systems are examples of Discrete Event Systems. Many Discrete Event Systems such as manufacturing cells are composed by sub-systems which have to obey a set of coordination constraints in order to work together. The Supervisory Control Theory, proposed by Ramadge and Wonham, in 1989, was based on formal languages and finite state automata and establishes the necessary and sufficient conditions for the existence of a minimally restrictive supervisor and supplies a formal methodology for its computation. The practical use of this approach is, however, limited by the state-space explosion with the growth of the number of subsystems. Even though this problem can be alleviated with the use of modular control, the controller complexity could nevertheless make it difficult do be implemented in practice. As an alternative to the complexity of Ramadge and Wonham approach, some researches have explored the simplicity and the graphic power of Petri Nets.
However, in more complex manufacturing systems, the resources used for the manufactured product transformation, as well as the product characteristics changes through the process may lead the Petri Nets models to a great complexity and very difficult analysis. Consequently, we see that the use of High Level Petri Nets becomes attractive. This type of modeling keeps the graphical and analysis power of Petri Nets, added to the possibility of a detailed definition of the processes types and manufactured product characteristics. In this work is shown an analysis of tree types of High Level Petri Nets: Coloured Petri Nets, Predicate-Transition Petri Nets and Object Petri Nets, and their applicability to flexible manufacturing systems. In this paper are discussed some aspects of flexible manufacturing systems, as well is described a real system to be modeled and presents the High Level Petri Nets, showing the cited system modeling using each type of Petri Net.