REAL-TIME SYNCHRONIZATION OF MULTIAXIS HIGH-SPEED MACHINES, FROM SFC SPECIFICATION TO PETRI-NET VERIFICATION

The paper considers the co-ordination and control of flexible, indepen dently driven, multiaxis, high-speed machinery in which mechanical com plexity has been exchanged for sophistication in control. The control of such machines is a hybrid control problem and the paper addresses t he specification and design of the discrete event part of the controll er. It focuses on the design of synchronisation logic for the event-dr iven real-time co-ordination and synchronisation of the machine. For s uch time-critical and system-critical applications, it is imperative t hat system behaviour is fully understood and unambiguous. The paper pr oposes a method for inferring system behaviour and performing formal v erification of machine systems specified using a subset of the industr y standard IEC 1131 sequential function charts (SFC). It shows how an SFC-based design can be translated to an equivalent Petri net model, t hereby allowing Petri net theory and analysis techniques to probe its behaviour and verify its functionality. The approach is demonstrated b y considering the design of synchronisation logic for a prototype six- axis high-speed packaging machine which incorporates both time-critica l and system-critical functions.