Remote access of a programmablelogical Control (PLC) is the prerequisite for an effective maintenance. We present an architecture for the development of tools supporting the installation, configuration, maintenance, ...
详细信息
ISBN:
(纸本)0769513727
Remote access of a programmablelogical Control (PLC) is the prerequisite for an effective maintenance. We present an architecture for the development of tools supporting the installation, configuration, maintenance, supervision, and diagnosis of remote PLCs via the Internet. The developed architecture, called Virtual PLC, consists of a set of extensible components describing a real PLC. The Virtual PLC uses Java (TM) Technology to be platform independent. The Virtual PLC enables developers to rapidly implement tools for remote diagnosis, supervision and maintenance of a real PLC.
The transition between the Supervisory Control Theory (SCT) and its implementation in programmable logic controllers (PLCs) is not straightforward. This is mainly due to the fact that the SCT is stated in an event bas...
详细信息
ISBN:
(纸本)0780367332
The transition between the Supervisory Control Theory (SCT) and its implementation in programmable logic controllers (PLCs) is not straightforward. This is mainly due to the fact that the SCT is stated in an event based asynchronous setting whilst PLCs are signal based and synchronous. Based on Petri nets, the PLC programming language Sequential Function Chart (SFC) seems to be the ideal choice for this transition. However, the transition requires detailed knowledge of how the PLC and SFCs work. We present different execution models for SFCs and compare them with the international standard IEC 1131-3.
Ladder diagrams (LDs) have been widely used in industrial control systems as a programming language for programmable logic controllers (PLCs). However, the synthesis of LD itself mainly depends on the experience of th...
详细信息
ISBN:
(纸本)0780370902
Ladder diagrams (LDs) have been widely used in industrial control systems as a programming language for programmable logic controllers (PLCs). However, the synthesis of LD itself mainly depends on the experience of the industrial engineer, which often results in unstructured or inflexible design. Hence, in this paper, we propose a ladder diagram transformation (LDT) algorithm which systematically produces LDs. for PLCs based on discrete event models (DEMs) to enhance the structured and flexible design mechanism. Moreover, the LDT algorithm is convenient and easy to be implemented. The LDT algorithm is illustrated by considering the control of a point to point (PTP) control system.
In this communication tile hardware implementation of a quasi-sliding algorithm, based on Zero Average Dynamics (ZAD), to a DC-AC converter is reported. Tile algorithm fulfils the requirement of fixed frequency switch...
详细信息
ISBN:
(纸本)0780370619
In this communication tile hardware implementation of a quasi-sliding algorithm, based on Zero Average Dynamics (ZAD), to a DC-AC converter is reported. Tile algorithm fulfils the requirement of fixed frequency switching as well as of similar sliding properties concerning reaching and robustness. The complexity of the algorithm, (several cases have to be considered involving non-linear arithmetic) renders an analogue implementation difficult. Consequently, a digital electronic implementation has proved to be the most appropriate solution, which is achieved by means of a Field programmable Cate Array and all external EEPROM memory. Experimental results for resistive loads validate theoretical predictions.
The case-study presented in this paper is aimed at assessing the dependability of a programmablelogic Controller (PLC) devoted to safety functions. This case study has been brought to our attention by a national envi...
详细信息
ISBN:
(纸本)0769512488
The case-study presented in this paper is aimed at assessing the dependability of a programmablelogic Controller (PLC) devoted to safety functions. This case study has been brought to our attention by a national environmental agency and has been partially abstracted and anonymized to protect proprietary information. The PLC consists of a triplicated channel with a (2 : 3) majority voting logic and is modeled by means of a recently proposed extension of the classical Fault Tree (FT) formalism called Parametric Fault Tree (PFT). In the PFT replicated units are folded and parameterized so that only one representative of the various similar replicas is explicitly included in the model. The quantitative analysis of the PFT assumes s-independence among components and is based on combinatorial formulas. In order to include dependencies both in the failure and repair process, the PFT is directly converted into a particular class of High Level Petri Nets, called SWN. The paper illustrates the PFT formalism and the automatic conversion algorithm from a PFT into a SWN. Moreover it is shown how various kind of dependencies can be accommodated in the obtained SWN model.
An appropriate simulation environment for testing real-time software applications, especially PLC (PLC: programmablelogic Controller) programs, is demanded in recent time for many reasons. One of the them might be. f...
详细信息
ISBN:
(纸本)0780367367
An appropriate simulation environment for testing real-time software applications, especially PLC (PLC: programmablelogic Controller) programs, is demanded in recent time for many reasons. One of the them might be. found in the altered conditions of cooperation (teamwork, teleworking, etc.) under which PLC software projects have to be carried out. Most areas of automation engineering lack for largely formalizable procedures, in particular within the specification and testing phase, and almost no tools are available for the development of real-time software. The consequence is that PLC programs are usually not developed before the facility to be controlled is installed, and putting it into operation is often the only test. The results are unacceptable waste of time during the. installation phase, unacceptable high risks, and unacceptable. high costs of the outcome. Due to the availability of simulation tools including real-time hardware and software platforms open interesting perspectives pertaining to an integrated approach of analysis and design of PLC programs and the corresponding testing environments.
This paper describes system design techniques using a low power CoolRunner(TM) CPLD to reduce overall system power consumption. Utilizing a CoolRunner(TM) CPLD to off load operations from the system microprocessor kee...
详细信息
ISBN:
(纸本)0780366778
This paper describes system design techniques using a low power CoolRunner(TM) CPLD to reduce overall system power consumption. Utilizing a CoolRunner(TM) CPLD to off load operations from the system microprocessor keeps the processor in a power saving mode longer and contributes to significant power savings.
Experimental data characterizing indoor electric and magnetic fields radiated by power line communication (PLC) systems and used for the calculation of a local transfer function (coupling factor) are presented. It is ...
详细信息
ISBN:
(纸本)0780365690
Experimental data characterizing indoor electric and magnetic fields radiated by power line communication (PLC) systems and used for the calculation of a local transfer function (coupling factor) are presented. It is shown that the indirect determination of electric field using magnetic field measurements and assuming a plane wave approximation may result in an underestimation of the electric field. Additionally, it is shown that the radiated field magnitudes vary significantly as a function of the position of the observation point and of the network load. A first evaluation of the indoor electromagnetic field radiated by PLC systems using NEC2 is presented and compared with experimental data.
The language sequential function charts (SFC) is a programming and structuring language for programmable logic controllers (PLC). It is defined in the IEC 611313 standard and includes various interesting concepts such...
详细信息
ISBN:
(纸本)0769512879
The language sequential function charts (SFC) is a programming and structuring language for programmable logic controllers (PLC). It is defined in the IEC 611313 standard and includes various interesting concepts such as parallelism, hierarchy, priorities, and activin, manipulation. Although SFCs are perpetually used in the engineering community for programming and the design of embedded control systems, there are hardly any specific verification approaches for them. Existing approaches for Petri Nets, Grafcets, or (UML-)Statecharts do not really apply to SFCs, whose structures are similar, but include distinct features. In this work,we present a method to model-check SFCs. This is done by defining a translation of SFCs into the native language of the Cadence Symbolic Model Verifier (CaSMV). This translation is specifically tailored to cover all the concepts of SFCs and can be performed automatically. Moreover we demonstrate our approach by an application to a control process in chemical engineering.
In the paper, the problem of the modeling and design of a control system for transporting systems in batch processes is addressed. In particular, it is shown that with a careful modeling of transporting systems as agg...
详细信息
ISBN:
(纸本)0780367227
In the paper, the problem of the modeling and design of a control system for transporting systems in batch processes is addressed. In particular, it is shown that with a careful modeling of transporting systems as aggregate resources and with a suitable hierarchical control architecture, the problem complexity can be strongly reduced with respect to known approaches. In addition, the implementation phase can be easily carried out as well. Supervisory control theory is here adopted as a design technique, and exploited to the extent to which it is convenient in the perspective of the design and implementation of industrial automation systems. Though the ideas here discussed are quite general, they have been exemplified with a batch process drawn from the literature.
暂无评论