N. Iriondo

Graphical Modeling of PLC-based Industrial Control Applications

Industrial process measurement and control systems (IPMCS) are used in most of the industrial sectors to achieve production improvement, process optimization and time and cost reduction. Integration, reuse, flexibility and optimization are demanded to adapt to a rapidly changing and competitive market. In fact, standardization is a key goal to achieve integration in this type of applications. The international standardization efforts have lead to the definition of the IEC 1131 standard. Part 3 of this standard defines a software model for defining automation projects as well as 5 programming languages, emphasizing software reuse. The Technical Committee 6 for XML belonging to the international organization PLCopen, has defined an XML based interface for importing/exporting automation projects. This work presents a graphical modeling tool that guides the user through the definition of the IEC1131-3 automation project, as a PLC programming tool does. But, internally, it stores the information about the automation project as a XML file. From it, it is possible to extract information, export the automation project to different programming tools or to translate it to PLCopen XML format, using different XML technologies.

Automatic Generation of the Supervisor Code for Industrial Switched-Mode Systems

This paper describes a methodology for the design and implementation of supervisors for switched-mode systems, which is a typical class of hybrid systems in industrial process applications. Many works can be found in the literature addressing formal modeling and control techniques for switched-mode systems, but they commonly deal with control design and simulation. The focus of this paper is to automate the design of supervisors for industrial switched-mode processes composed by multirate loops, in order to automatically generate the code of the supervisor. Its function is to detect changes in the process operation mode and to switch to the control algorithm accordingly. The target control equipment is the programmable logic controllers (PLCs) and, thus, the software architecture generated follows the IEC 61131-3 standard. The tool developed captures information related to the overall control system (inputs and outputs and control algorithms), as well as to the discrete dynamic of the switched-mode process from the simulation model and automatically generates the supervisor code as well as a time-driven schedule for every supervisors mode. The improvement of the overall system performance using the switched-mode supervisor is analyzed experimentally through a performance index.

Implementing Non-Linear Strategies for PID in IEC 61131-3 ST Language

Industrial process measurement and control systems (IPMCS) are used in most of the industrial sectors to achieve production improvement, process optimization and time and cost reduction. Integration, reuse, flexibility and optimization are demanded to adapt to a rapidly changing and competitive market. The standardization of high level programming languages for programmable logic controller (PLCs) allows implementing more advanced control strategies in PLC based control applications. In this paper, antiwindup (AW) and bumpless transfer (BT) mechanisms for PID control have been selected to be implemented as reusable functional block (FB) program organization unit (POU). In particular, the final objective of the work is to design a mode switching supervisor for hybrid control systems.

An Integrated System for Supervisory Process Control using ADA

Abstract The paper presents an integrated software package for supervisory process control using ADA language. This system performs process control using classical and heuristic controllers, supervision in order to detect abnormal situations and on-line monitoring. Using ADA language, the definition of the different processes (control, supervision and monitoring) can be easily implemented using the concurrent programming techniques inherent to the language. Specifically, a rule-based system which compensates for dead-zone phenomena in a position control servomechanism is developed. The supervisor module is designed to detect and avoid undesirable on-linear control phenomena such as steady state errors, limit cycling or excursions into unwanted zones. It constitutes an intelligent compensator for system input nonlinearities which may be generalized to other non-linearity types.

Bumpless transfer multi-controller architecture for switched-mode processes

Switched mode systems are defined as those represented by a finite set of linear subsystems and a set of logic rules orchestrating the switching among them. Current Programmable Logic Controller (PLCs) and the IEC 61131-3 standard allows a systematic design of multi-controller architecture to improve the behavior of such type of industrial systems. This paper describes the implementation of Bumpless Transfer (BT) mechanisms within multi-rate control architecture for switched mode systems. By detecting the system state and the feasible next states, the supervisor decides the control algorithms that are active, in tracking mode or in wait state. The steps to design the complete architecture are presented and experimental results that validate the architecture are shown.

PLC based Supervision of Industrial Switched Processes

Abstract This paper presents a methodology for the design of supervisors for mode switching systems, one class of hybrid system that frequently appears in industrial process applications. The classical continuous control methods are based on designing controllers that are only valid for an operation point for which are designed. The switching among different controllers can optimize transient response and meet multiple objectives. The main goal of this work is to automatically generate the code of the regulation level loops supervision which will be executed on a Programmable Logic Controller (PLC) and following the guidelines for software development provided by the IEC-61131 standard. The tool developed for achieving this automatic code generation processes information about the process operation, the functional specifications and the control algorithms used in each mode. This information is captured from the different view models of the overall control system and through a user interface.

On the Application of Fuzzy Logic in the Design of Supervisors for Real-Time Control Systems

Abstract This work deals with the use of fuzzy logic techniques in order to include heuristic knowledge about the system under study into a supervisor module. The goal of the supervisor is to track the system operation between different states (such as different operation points, operation under hard nonlinearities, restricted zones, etc.). As the design is to be applied in real-time control system applications, the fuzzy supervisor is optimised in the sense of fast and reliable processing. The paper proposes a methodology for its design and shows its application on a servo-positioning system.

Fuzzy Logic and Its Application on the Design of Supervised Real-Time Control Systems

Abstract This paper proposes new control techniques for non-linear systems introducing heuristics in order to improve performance of classical controllers. The heuristics is implemented by means of a rule-based supervisor and a fuzzy controller. The system operation is divided into a set of so called ‘states’ then the supervisor detects a system state change and switch to the control algorithm associated (e.g. a linear control algorithm for normal operation and fuzzy controller for the zone with specific-non-linear behaviour).