Translating Grafcet specifications into Mealy machines for conformance test purposes

Abstract

Conformance test is a black-box test technique aiming at checking whether an implementation conforms to its specification. Numerous results have been already obtained in this field for specifications expressed in a formal language. However, these results cannot be applied for conformance test of industrial logic controllers whose specifications are given in standardized specification languages. To contribute to solve this issue, this paper proposes a method to obtain, from a Grafcet specification, an equivalent Mealy machine, without semantics loss. This method permits to describe explicitly and formally all the states and transitions that are implicitly represented in a Grafcet model.

Coupling timed plant and controller models with urgent transitions without introducing deadlocks

“…Some of them ( [2] and [19] for example) start from a model in SFC 2 language [7]; however this language is an implementation and not a specification language (the interested reader is referred to [16] for further details on the semantic differences between Grafcet and SFC); this explains why these approaches were not selected for this work. On the opposite, [11] presents a method to translate an untimed Grafcet specification into three sets of algebraic equations:…”

“…It is not necessary to represent the first and third phases of the PLC cycle (inputs reading and outputs updating) in the formal model of the controller because the inputs/outputs of the Grafcet are modeled as Boolean variables that are shared by the controller and plant models. The possibility of transient evolutions ( [6], [16]) in the Grafcet, due for instance to the always satisfied transition condition of transition t4, imposes that the output values must not be updated as long as the Grafcet has not reached a stable situation. The computation of the output values must then be skipped if the situation is not stable.…”

Building meaningful timed models of closed-loop DES for verification purposes

“…The interested readers are referred to David (1995), Bierel et al (1997), Provost et al (2011) for deeper presentations.…”

Model-Driven Development of Automation and Control Applications: Modeling and Simulation of Control Sequences

“…Other works related to sequential control with modelbased characteristics include [21] that presents an approach to transform Grafcet [22] models to Mealy machines for testing purposes (Grafcet is a conventional means to specify control sequences). Execution semantics of Sequential Function Charts (SFC) [18] have been addressed in [23].…”