Concurrent control systems: from Grafcet to VHDL

Abstract

The automated production systems (APS) are composed of concurrent interacting entities, so any model should exhibit parallel and sequential behaviours. The Grafcet is now well established in manufacturing to specify the awaited behaviour of the APS. Moreover programmable components increase modularity and allow a higher integration rate of circuits. The paper studies the hardware implementation of a Grafcet specification into such a component. Those components have to be programmed using a hardware description language. We therefore focus on inherent problems of such an approach and we study different kinds of possible solutions to automatically translate a Grafcet specification into a VHDL program. In particular, we introduce a solution based on synchronous language works about symbolic research of stability states. This compiler only accepts the stable grafcets. In addition to automatically generating a VHDL code, this solution provides a way to check some safety properties on Grafcet.