A Formal Approach to the Distributed Software Control for Automated Multi-Axis Manufacturing Machines

Background

Petri nets and automata are the most used to describe discrete event system control. Modeling and analysis of discrete event systems with controllable and uncontrollable events, turned on and off by the supervisor, were proposed based on automata theory (Ramadge & Wonham, 1987). However, finite automata present some drawbacks such as the difficulty to model parallelism, synchronization and resource sharing. Although control commands generation was related to state transitions, since the connection of several finite automata is no longer a finite automaton, the communication specifications between modules can not be achieved using the finite automata framework (Lima & Saridis, 1996; Stadter, 1999; Silva et al., 2014). In spite of a great number of researches concerning advanced methods and tools to analyze the distributed models, these models are mostly constructed by empirical methods based on the knowledge of experts and customized for a particular application. Most approaches are limited by the combinatorial explosion that occurs when attempting to model complex systems.

On the other hand, Petri nets incorporate the notion of a distributed state of a system and a rule of state change (Murata, 1989; David & Alla, 1992), providing a mathematical formalism and a graphic tool for the formal representation of a system whose dynamics is characterized by concurrency, synchronization, nondeterministic decision, mutual exclusion and conflict. Computerized automation systems have the same, typical and most important features as industrial distributed systems.