Wyniki wyszukiwania - Biblioteka Nauki

1

Expressiveness of Petri Nets with Stopwatches. Dense-time Part

100%

Magnin M. , Molinaro P. , Roux O.-H.

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tom Vol. 97, nr 1/2

111-138

EN

With this contribution, we aim to draw a comprehensive classification of Petri nets with stopwatches w.r.t. expressiveness and decidability issues. This topic is too ambitious to be summarized in a single paper. That is why we present our results in two different parts. The scope of this first paper is to address the general results that apply for both dense-time and discrete-time semantics. We study the class of bounded Petri nets with stopwatches and reset arcs (rSwPNs), which is an extension of T-time Petri nets (TPNs) where time is associated with transitions. Stopwatches can be reset, stopped and started. We give the formal dense-time and discrete-time semantics of these models in terms of Transition Systems. We study the expressiveness of rSwPNs and its subclasses w.r.t. (weak) bisimilarity (behavioral semantics). The main results are following: 1) bounded rSw- PNs and 1-safe rSwPNs are equally expressive; 2) For all models, reset arcs add expressiveness. 3) The resulting partial classification of models is given by a set of relations explained in Fig. 7: in the forthcoming paper, we will complete these results by covering expressiveness and decidability issues when discrete-time nets are considered. For the sake of simplicity, our results are explained on a model such that the stopwatches behaviors are expressed using inhibitor arcs. Our conclusions can however be easily extended to the general class of Stopwatch Petri nets.

2

Timed Automata with non-Instantaneous Actions

100%

Barbuti R. , De Francesco N. , Tesei L.

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tom Vol. 47, nr 3,4

189-200

EN

In this paper we propose a model, timed automata with non-instantaneous actions, which allows representing in a suitable way real-time systems. Timed automata with non-instantaneous actions extend the timed automata model by dropping the assumption that actions are instantaneous: in our model an action can take some time to be completed. We investigate the expressiveness of the new model, comparing it with classical timed automata. In particular, we study the set of timed languages which can be accepted by timed automata with non-instantaneous actions. We prove that timed automata with non-instantaneous actions are more expressive than timed automata and less expressive than timed automata with e edges. Moreover we define the parallel composition of timed automata with non-instantaneous actions. We point out how the specification by means of a parallel timed automaton with non-instantaneous actions is, in some cases, more convenient to represent reality.

3

A formal approach to modelling of real-time systems using RTCP-nets

88%

Szpyrka M. , Szmuc T. , Matyasik P. , Szmuc W.

Foundations of Computing and Decision Sciences

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2005

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tom Vol. 30, No. 1

61-71

EN

The paper deals with an application of formal methods for modelling of real-time systems. The main objective of this approach is to support development of these systems in order to ensure that the produced software artefacts are correct, as well as to improve the development process. The Real-Time Coloured Petri nets (RTCP-nets), which are a subclass of time coloured Petri nets, are used as a modelling tool. To make the nets more suitable for modelling and analysis RTCP-nets are derived from coloured Petri nets. Applications of RTCP-nets as a modelling and verification tool are strongly supported by the so-called Adder Tools. The formal description of RTCP-nets is not presented here since the paper focuses on the main properties of these and the supporting facilities of the Adder Tools. The approach is illustrated by a practical example, that shows the expressiveness of RTCP-nets for modelling and verification of real-time systems. 1 1Supported by KBN Research Project No 4 T11C 035 24

4

Expressiveness of Petri Nets with Stopwatches. Discrete-time Part

75%

Magnin M. , Molinaro P. , Roux O.-H.

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tom Vol. 97, nr 1/2

139-176

EN

With this contribution, we aim to draw a comprehensive classification of Petri nets with stopwatches w.r.t. expressiveness and decidability issues. This topic is too ambitious to be summarized in a single paper. That is why we present our results in two different parts. In the first part of our work, we established new results regarding to both dense-time and discrete-time semantics. We now focus on the discrete-time specificities. We address the class of bounded Petri nets with stopwatches and reset arcs (rSwPNs), which is an extension of T-time Petri nets (TPNs) where time is associated with transitions. Stopwatches can be reset, stopped and started. We recall the formal dense-time and discrete-time semantics of these models in terms of Transition Systems. We study the expressiveness of rSwPNs and its subclasses w.r.t. (weak) bisimilarity (behavioral semantics). The main results are following: 1) Discrete-time bounded TPNs, discrete-time bounded rSwPNs and untimed Petri nets are equally expressive; 2) The resulting (final) classification of models is given by a set of relations explained in Fig. 7. While investigating expressiveness, we exhibit proofs that can be easily extended to the resolution of decidability issues. Among other results, we prove that, for bounded rSwPNs, the state and marking reachability problems - undecidable with dense-time semantics - are decidable when discrete-time is considered. Table 1 gives a synthesis of the main decidability results for these models. For the sake of simplicity, our results are explained on a model such that the stopwatches behaviors are expressed using inhibitor arcs. Our conclusions can however be easily extended to the general class of Stopwatch Petri nets.

5

Wybrane zagadnienia szeregowania zadań wieloprocesorowych dla dedykowanych procesorów

75%

Gajer M.

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tom Vol. 49, z. 2

163-173

PL

Systemy czasu rzeczywistego stanowią obecnie dobrze określoną i wyodrębnioną grupę systemów komputerowych. W systemach takich najważniejszą sprawą jest dochowywanie nałożonych na realizację zadań ograniczeń czasowych. Spełnienie wymogów czasowych wymusza często konieczność zastosowania w miejsce sekwencyjnych procesorów systemów wieloprocesorowych, które są w stanie dostarczyć wymaganego poziomu pracy obliczeniowej. Jednakże zastosowanie rozwiązań wieloprocesorowych powoduje konieczność rozwiązania niełatwego problemu szeregowania zadań wieloprocesorowych. W artykule po wstępnym wprowadzeniu w problematykę szeregownia zadań wieloprocesorowych, dokonano szczegółowej analizy przypadku szeregowania zadań wieloprocesorowych dla czterech dedykowanych procesorów. Rozważania teoretyczne zostały uzupełnione o wyniki symulacji komputerowych.

EN

In many modern computer systems multiprocessor solutions are more often applied. This concerns especially computer systems that are used in the real-time applications. At present the real-time systems constitute the well-defined class of computer systems. The real-time systems are getting more and more popular in many fields of industry and communication. The real-time systems are used to control telecommunication devices and systems, defense systems, avionics and modern factories. In fact many modern facilities cannot do without them. For example without the real-time systems there would be no nuclear power plants, space ships, jet aircrafts, modern factories with robots etc. The program realized by the real-time computer systems is divided into special tasks performing given functions. In the case of the real-time systems a very important matter is to guarantee that all the task are to be finished before their deadline points. In the case of the hard real-time systems any exceeding task deadline is absolutely intolerable. Such event if happens may lead to uncontrollable behavior of the system, which can cause a disaster, for example an aircraft carsh, a loss of human life etc. To guarantee that the task deadlines will be always met, the task scheduling theory was developed. The main goal of the task scheduling theory is to demonstrate at the system development phase that under all the possible to foreseen circumstances the task deadlines will always be met. There does not exist one universal task scheduling algorithm for all kinds of task. There are separate algorithms for periodic tasks and tasks that are event-triggered. Also there are different algorithms for tasks that are preemptive and for tasks that are not preemptive. There exist also quite different algorithms for tasks that are dedicated for one processor only and for so-called multiprocessor tasks that require for their execution two or more processor at the time. As was earlier mentioned in the case of the real-time systems the most important factor is whether the tasks meet the predefined time constraints. In order to meet the hard time constraints cery often a multiprocessor system is used in stead of a sequential system with only one processor. The multiprocessor system is expected to deliver much more computational power than a single processor system, however, the usage of a multiprocessor system requires simultaneously to solve a non-easy problem of multiprocessor task scheduling. In the paper a brif introduction to the problems of multiprocessor task scheduling is given. Further the case of scheduling a set of independent multiprocessor tasks for four dedicated processors is examined. Multiprocessor systems with four processors are very popular at the present time. For example the Texas Instruments TMS320C80 is a single-chip multiprocessor system composed of four DSP processors. Earlier Texas Instruments offered a personal computer boards with four TMS320C40 processors. The proposed algorithm of multiprocessor task scheduling was called a Divide Uniprocessor Task (DUT) algorithm, because all the tasks dedicated for a single processor are grouped together and then the whole set is divided into two subsets, one of which has the length as close as possible to the execution time of compatible tasks dedicated for orther three processors. In the paper the process of multiprocessor task scheduling is illustrated with examples and the results of computer simulations are also presented.

6

Control of delivery of water capsule for the explosive generation of water spray

75%

Śmigielski G. , Lewandowski D. , Dygdala R.

Automatyka / Automatics

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2013

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tom Vol. 17, no. 2

253--262

EN

This article presents the structure of the system which makes possible the release of a water capsule from the helicopter and the detonation of water situated inside the capsule at the defined height over the target (the place of fire) in order to cover the land of a adequate area with the produced aerosol. The moment of the release and detonation is defined on the basis of the current velocity of a flight and the position of the capsule.

PL

Artykuł prezentuje budowę systemu, który umożliwia automatyczne uwolnienie ze śmigłowca kapsuły wodnej i zdetonowanie ładunku umieszczonego wewnątrz niej na określonej wysokości nad celem (miejscem pożaru) tak, aby wytworzony aerozol pokrył teren o wymaganej powierzchni. Moment uwolnienia, a także detonacji jest określany na podstawie aktualnej prędkości lotu oraz pozycji kapsuły.

7

Schedulability timing analysis of exchange information for real-time system

75%

Mrozek M. , Majcher A.

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tom nr 4

49-58

EN

This paper presents a schedulability timing analysis for a two-processor real-time system. This system enables to work with other devices in the dispersed industrial network with a protocol of data transmission Modbus RTU. A method of transmission information between a master microprocessor and a slave microprocessor of the system was described. An optimisation method, with the help of specialist software TimesTool, was done, which is used for modelling and schedulability analysis of embedded real-time systems.The simulation tests shortened the time needed for working out the method and decreased the numbers of errors in the designed system.

PL

W artykule przedstawiono analizę czasową zadań wykonywanych w dwuprocesorowym systemie czasu rzeczywistego. System ten charakteryzuje się możliwością współpracy z innymi urządzeniami w rozproszonej sieci przemysłowej z odpowiednim protokołem transmisji danych (Modbus RTU). Dokonano analizy czasowej zadań wymiany informacji między mikroprocesorem głównym i mikroprocesorem komunikacyjnym. Przy wykorzystaniu specjalistycznego oprogramowania TimesTool do modelowania i analizy zadań w systemach czasu rzeczywistego zoptymalizowano metodę wymiany informacji między mikroprocesorem głównym i mikroprocesorem komunikacyjnym systemu. Zastosowanie badań symulacyjnych skróciło czas opracowywania metody, zmniejszając liczbę błędów w projektowanym systemie.

8

A lightweight approach to two-person interaction classification in sparse image sequences

51%

Kasprzak W. , Piwowarski P. , Do V. K.

Annals of Computer Science and Information Systems

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2022

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tom Vol. 30

181--190

EN

A lightweight neural network-based approach to two-person interaction classification in sparse image sequences, based on predetection of human skeletons in video frames, is proposed. The idea is to use an ensemble of “weak” pose classifiers, where every classifier is trained on a different time-phase of the same set of actions. Thus, differently than in typical assembly classifiers the expertise of “weak” classifiers is distributed over time and not over the feature domain. Every classifier is trained independently to classify time-indexed snapshots of a visual action, while the overall classification result is a weighted combination of their results. The training data need not any extra labeling effort, as the particular frames are automatically adjusted with time indices. The use of pose classifiers for video classification is key to achieve a lightweight solution, as it limits the motion-based feature space in the deep encoding stage. Another important element is the exploration of the semantics of the skeleton data, which turns the input data into reliable and powerful feature vectors. In other words, we avoid to spent ANN resources to learn feature-related information, that can be already analytically extracted from the skeleton data. An algorithm for merging-elimination and normalization of skeleton joints is developed. Our method is trained and tested on the interaction subset of the well-known NTU-RGB+D dataset , although only 2D skeleton information is used, typical in video analysis. The test results show comparable performance of our method with some of the best so far reported STM and CNN-based classifiers for this dataset, when they process sparse frame sequences, like we did. The recently proposed multistream Graph CNNs have shown superior results but only when processing dense frame sequences. Considering the dominating processing time and resources needed for skeleton estimation in every frame of the sequence, the key to real-time interaction recognition is to limit the number of processed frames.

9

UDP/IP/Ethernet network as an integration layer for distributed avionic application: a case study

51%

Samolej S. , Rogalski T.

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tom Vol. 39, nr 1

65--76

EN

The paper discusses an application of standard UDP/ IP/Ethernet local area network as a communication layer for real-time distributed avionic application. The main objective of the paper is to propose and discuss hardware/software network configurations which improve the control device's data exchange even if the network must conduct another data intensive stream services.

PL

W artykule rozważane jest zastosowanie standardowej lokalnej sieci komputerowej klasy UDP/IP/Ethernet jako platformy komunikacyjnej dla pokładowej rozproszonej aplikacji czasu rzeczywistego. Głównym przedmiotem analiz prowadzonych w pracy jest dobór konfiguracji sprzętowo-programowych dla sieci, w których należy zachować przepustowość dla danych procesowych systemu sterowania przy obecności innych znaczących transferów danych.