A synthesis approach to distributed supervisory control design for manufacturing systems with Grafcet implementation

Abstract

In supervisory control, computational complexity and implementation flexibility represent major challenges when a large number of local components compose a target system. To overcome these difficulties, we propose a formal approach to distributed control synthesis and implementation for automated manufacturing systems (AMS). We assume that the system is modelled with automata in a local modular fashion. Local control specifications are defined for each local subsystem by means of logical equations to construct local controllers (LCs). Then, global control specifications, stated as logical implications, are applied to the LCs, which allows synchronisation and cooperative interaction among the subsystems. This paper makes two contributions. First, it outlines a formal method for constructing minimally restrictive and deadlock-free distributed controllers (DCs). Second, it proposes a method for the interpretation of these DCs into Grafcet, which is a graphical modelling formalism widely used to design the controller’s dynamic behaviour for AMS. An experimental manufacturing system illustrates the approach.

Keywords:

• discrete-event dynamic systems
• manufacturing systems
• supervisory control
• synthesis methods
• Grafcet
• PLC

Notes

1. Grafcet will be mentioned with a capital G when referring to the tool in general, and mentioned with a small g (grafcet) when referring to a specific logic controller model.