GRAFCET diagrams are powerful modeling tools that enable the detailed definition of discrete event system behaveior through structured and hierarchical designs. These diagrams incorporate partial GRAFCET and facilitate interaction between them through forcing or encapsulation. GRAFCET are widely recognized and extensively used in automation engineering. Methodologies that automatically generate control software from GRAFCET diagrams allow engineers to focus on optimizing system performance and significantly reduce sources of error during the implementation stage. Several methodologies exist for code generation from GRAFCET using the IEC 61131-3 programming standard, effectively addressing scenarios involving a single programmable device. However, the issue remains open for the more recent IEC 61499 programming standard, which is designed to simplify the development of distributed control applications that operate on multiple devices. This paper aims to contribute to the development of methodologies that facilitate the generation of control code from discrete event system models, particularly GRAFCET, resulting in IEC 61499 standard compliant code. The goal is to produce code that supports straightforward and transparent distribution across multiple control devices within a plant.

Ponencia presentada en: 20th International Conference on Informatics in Control, Automation and Robotics (ICINCO 2023) Roma, 13-15 november, 2023.

In this work, the implementation of SSOD sampling strategy under the principles stated in standard IEC 61499 is addressed. The implementation is then tested in an experimental distributed control system, in which this sampling strategy will be used. This framework will be used to test experimentally the validity of the sampling strategy as well as the control algorithms and tuning rules proposed in previous literature about SSOD applied on networked control systems.

The control software of manufacturing systems has to interact with the mechanical and electrical machine parts, hence, their engineering is closely interrelated. A high-level model of this system can provide an abstract view on the system's behavior and is therefore beneficial for any engineering discipline. The language GRAFCET was developed as a domain-specific tool for specifying the operation of a production system. GRAFCET models can be structured hierarchically to regulate the behavior of a subsystem with forcing orders and enclosing steps. Based on a Grafcet, control software can be implemented in the executable modeling language IEC 61499. In this paper, we describe a step-by-step approach for implementing hierarchical features of GRAFCET with IEC 61499 models. The resulting application is well-structured and thus maintainable.

A Grafcet is a standardized model for describing the behavior of systems which is popular among automation engineers. As the Grafcet standard excludes implementation details, the models are typically translated to automation software. Such software was traditionally programmed in one of the languages specified in IEC 61131-3. Nowadays, automation software is increasingly modelled in IEC 61499 which facilitates designing distributed control systems. In this paper, we define a standardized translation methodology, so that automation engineers can benefit from the advantages of IEC 61499 while continuing to use Grafcet. We discuss the differences between Grafcet and IEC 61499. We translated a Grafcet model into an IEC 61499 application to illustrate the process and derive guidelines for application designers. For the core concepts of Grafcet, we present the corresponding structure in IEC 61499.

This paper presents a study about the performance of event-based PID controllers implemented in the standard IEC-61499. The implementation details are addressed and experimental results are given. The main goal is to evaluate the benefits and drawbacks of using the event-based controllers under this standard in substitution of the periodic controllers that has been used so far. Both the computational cost of the control algorithms and the close loop performance when using periodic and event based controllers are analyzed in order to compare these two approaches.

In this paper we analyse the conditions that produce oscillations in event based PID controllers. A Symmetric Send-On-Delta scheme (SSOD) is assumed, and the describing function is the tool used to address the problem. Once the conditions for oscillations are established, a new robustness to oscillations performance measure is introduced. Then a very simple and intuitive rule of thumb is given about how to tune PID controllers to avoid the limit cycles. The rule presented here entails with the classical concept of phase margin, providing the key to design SSOD based PID by using continuous PID tuning methods. The proposed ideas are tested in simulations with a batch of models widely used in PID design methods testing.