Real-time systems are systems which interact permanently with their environment by receiving external informations and producing output commands on it. They are commonly met in factories for the control of industrial ...
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Real-time systems are systems which interact permanently with their environment by receiving external informations and producing output commands on it. They are commonly met in factories for the control of industrial processes. In this case, they are often implemented with programmable controllers (PC). The GRAFCET language, which is derived from Petri-Nets, is often used for programming such PC. Unfortunately, it is not based on a single semantics, which complicates programs verification, programs exchange and programs simulation. We have expressed its semantics with synchronous processes, implemented them with the synchronous language SIGNAL and investigated methods to make proofs on it.
The paper deals with a theoretically known, but in practice seldom used procedure for the nonparametric model identification. The essential point of the method is in applying the Pseudo Random Bynary signal and evalua...
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The paper deals with a theoretically known, but in practice seldom used procedure for the nonparametric model identification. The essential point of the method is in applying the Pseudo Random Bynary signal and evaluating the crosscorrelation function between input and output signals which results in the estimated impulse response of the process. The method was improved by applying the signals twice in succession, which resulted in all signals to become periodic. It turned out that the period of 127 (7 bit PRBS register) is sufficient for practical application). The static gain of the process was estimated by averaging low frequency cross power density spectrum and the bias of the estimated impulse response was eliminated. Automatic detection of inappropriate frequency range of the signals enables the procedure to be applied as selftunning method for PID controller’s tuning by Chien Hrones Reswick rules. Due to these rules the method is applicable to proportional overdamped processes only. The method has proven itself as a very robust method against all kinds of disturbances and initially chosen sampling time. Implementation of the method in IDR 052 software for Mitsubishi programmable Logic controllers and application to the Elwe hydraulic plant are described.
We have applied the model checker using the computation tree logic (CTL) to automatic verification of the sequential control system, of which mechanism is defined by the rules in series. The rule transition graph and ...
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We have applied the model checker using the computation tree logic (CTL) to automatic verification of the sequential control system, of which mechanism is defined by the rules in series. The rule transition graph and the modified CTL formulas were introduced to determine if the system satisfies the specifications.
Just as a good number of people use Esperanto to understand each other, road equipment may use a Road Common Language for telmatics. It is an enourmous advantage for Traffic Managers when specifying R. C. L. for traff...
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Just as a good number of people use Esperanto to understand each other, road equipment may use a Road Common Language for telmatics. It is an enourmous advantage for Traffic Managers when specifying R. C. L. for traffic data collection, videosurveillance, variable message signs, tunnels, emergency call networks, and central computers. For the first time, MARIUS, the totally renovated Marseille motorway network control system, uses the same language to exchange data between hundreds of elements connected via copper cables, optical fibers, X25media or telephone. Here is a new generation of traffic control systems supported by many manufacturers under the aegis of the French Administration.
An universal methodology and a system to program PLCs are presented. The system front end is a Graphical User Interface (GUI), supporting the relay ladder language and a simulator. The GUI is an user-friendly environm...
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An universal methodology and a system to program PLCs are presented. The system front end is a Graphical User Interface (GUI), supporting the relay ladder language and a simulator. The GUI is an user-friendly environment with menus, icons and a point and click interface. After the GUI, an Intermediate Literal Language (ILL) implements a virtual PLC. ILL fIles are then used by specific parser-drivers (developed with lex and yacc utilities), to translate ILL definitions into real PLC statements. Object-oriented programming techniques, based on C++, are used, along with Blaise Win++ class library. The system runs as a Microsoft Windows application.
The International Electrotechnical Commission is currently standardising four compatible languages for designing and implementing programmable logic controllers (PLCs). The language family includes a diagrammatic nota...
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The International Electrotechnical Commission is currently standardising four compatible languages for designing and implementing programmable logic controllers (PLCs). The language family includes a diagrammatic notation that supports the idea of software ICs to encourage graphical design techniques and systematic software reuse. This paper presents an interactive system with a graphical interface for constructing and validating PLC software. The semantics of a graphical design is defined by a mapping associating each design with an executable formal specification. The specification provides the basis for rigorous proofs and early tests of critical properties of a new design. A realistic example illustrates these features.
Control of manufacturing systems can be defined in terms of synchronizing physical objects. These objects typically belong to a limited number of classes, exhibiting similar behavior whithin each class, examples inclu...
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Control of manufacturing systems can be defined in terms of synchronizing physical objects. These objects typically belong to a limited number of classes, exhibiting similar behavior whithin each class, examples include machines and buffers. In this paper we propose the following for feasible development of fabrication systems control: • Separate the control of the individual device from the synchronization of the whole system. • This can be achieved by bulding internal objects, software models of the physical devices, the external objects. • Encapsulate the control of the physical device, by building these objects in two distinct parts, a general and a specific part. • The internal objects communicate by messages, specially designed for expressing the synchronizing aspects, including prioritys and various addressing formats. • One object needs to be application specific, a controller that administers the message handling. Furthermore, we discuss this approch in relation to MMS, which utilizes a similar scheme, though not so intent on handling the synchronizing functions of a discrete event manufacturing system. Lastly, we illustrate our method by describing an FMS workcell involving buffers, robots and machines.
A fault-tolerant resource allocation procedure aimed at automatic modification of Petri net-based control models is presented. The recovery scheme is based on the assumption that some of the system shared resources ma...
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A fault-tolerant resource allocation procedure aimed at automatic modification of Petri net-based control models is presented. The recovery scheme is based on the assumption that some of the system shared resources may be replaced by others, e.g. in case of their malfunctioning. The method encompasses a new deadlock avoidance algorithm which guarantees deadlock freedom of the control models. Its application for development of controls for computer integrated assembly cells is shown in an example.
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