Progress in PLC programming for distributed automation systems control

摘要

Industrial automation plants are controlled essentially by PLC-based control systems. PLCs are today mostly programmed in the languages of the IEC 61131–3 standard which are not ready to meet the new challenges of widely distributed automation systems. Currently, different solutions are under development from industry and research: an extension of IEC 61131–3 which includes object oriented programming; the adoption of the new standard IEC 61499 which makes the software execution event-based instead of scan-cycle based as in IEC 61131–3 standard. In this paper it is shown how object oriented programming implicitly makes event-based the PLC software behavior. Moreover, it is shown how supervisory control can help in designing correct software in this context.