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Nowadays, embedded systems appear more and more as distributed systems structured as a set of communicating components. Therefore, they show a less deterministic global behavior than centralized systems and their design and analysis must address both computation and communication scheduling in more complex configurations. We propose a modeling framework centered on data. More precisely, the interactions between the data located in components are expressed in terms of a so-called observation relation. This abstraction is a relation between the values taken by two variables, a source and an image, where the image gets past values of the source. We extend this abstraction with time constraints in order to specify and analyze the availability of timely sound values.
The formal description of the observation-based computation model is stated using the formalism of transition systems, where real time is handled as a dedicated variable. As a first result, this approach allows to focus on specifying time constraints attached to data and to postpone task and communication scheduling matters. At this level of abstraction, the designer has to specify time properties about the timeline of data such as their freshness, stability, latency… As a second result, a verification of the global consistency of the specified system can be automatically performed. The verification process can start either from the timed properties (e.g. the period) of data inputs or from the timed requirements of data outputs (e.g. the latency). Lastly, communication protocols and task scheduling strategies can be derived as a refinement towards an actual implementation.
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The paper presents features and implementation of a shared redundant approach to increase the reliability of networked control systems. Common approaches based on redundant components in control system use passive or active redundancy. We deal with quasi-redundant subsystems (shared redundancy) whereas basic features are introduced in the paper. This type of redundancy offers several important advantages such as minimizing the number of components as well as increasing the reliability. The example of a four-rotor mini-helicopter is presented in order to show reliability improving without using any additional redundant components. The main aim of this paper is to show the influence of the load increasing following different scenarios. The results could help to determine the applications where quasi-redundant subsystems are a good solution to remain in a significant reliability level even if critical failure appears.
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Even if hardware improvements have increased the performance of embedded systems in the last years, resource problems are still acute. The persisting problem is the constantly growing complexity of systems, which increase the need for reusable developement framework and pieces of code. In the case of PDAs and smartphones, in addition to classical needs (safety, security), developers must deal with quality of service (QoS) constraints, such as resource management.
Qinna was designed to face with these problems. In this paper, we propose a complete framework to express ressource constraints during the developpement process. We propose a component-based architecture, which generic components and algorithms, and a developpement methodology, to manage QoS issues while developing an embedded software. The obtained software is then able to automatically adapt its behaviour to the physical resources, thanks to \g{degraded modes}. We illustrate the methodology and the use of Qinna within a case study.
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Service-oriented architectures (SOA) become more and more important in networked embedded systems. The main advantages of Service-oriented architectures are a higher abstraction level and interoperability of devices. In this area, Web services have become an important standard for communication between devices. However, this upcoming technology is only available on devices with sufficient resources. Therefore, embedded devices are often excluded from the deployment of Web services due to a lack of computing power, insufficient memory space and limited bandwidth. Furthermore, embedded devices often require real-time capabilities for communication and process control. This paper presents a new table driven approach to handle real-time capable Web services communication, on embedded hardware through the Devices Profile for Web Services.
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High-performance platforms are required by modern applications that make use of massive calculations. Actually, low-cost and high-performance specific hardware (e.g. GPU) can be a good alternative along with CPUs, which turned to multiple cores, forming powerful heterogeneous desktop execution platforms. Therefore, self-adaptive computing is a promising paradigm as it can provide flexibility to explore different computing resources, on which heterogeneous cluster can be created to improve performance on different execution scenarios. One approach is to explore run-time tasks migration among node's hardware towards an optimal system load-balancing aiming at performance gains. This way, time requirements and its crosscutting behavior play an important role for task (re)allocation decisions. This paper presents a self-rescheduling task strategy that makes use of aspect-oriented paradigms to address non-functional application timing constraints from earlier design phases. A case study exploring Radar Image Processing tasks is presented to demonstrate the proposed approach. Simulations results for this case study are provided in the context of a surveillance system based on Unmanned Aerial Vehicles (UAVs).
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Nowadays developments in Wireless Sensor and Actuators Networks (WSAN) applications are determined by the fulfillment of constraints imposed by the application. For this reason, in this work a characterization of WSAN applications in health, environmental, agricultural and industrial sectors are presented. Two cases study are presented, in the first a system for detecting heart arrhythmias in non-critical patients during rehabilitation sessions in confined spaces is presented, as well as an architecture for the network and nodes in these applications is proposed; while the second case presents experimental and theoretical results of the effect produced by communication networks in a Networks Control System (NCS), specifically by the use of the Medium Access Control (MAC) algorithm implemented in IEEE 802.15.4.
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A precise localization is required in order to maximize the usage of Mobile Sensor Network. As well, mobile robots also need a precise localization mechanism for the same reason. In this paper, we showed a combination of various localization mechanisms for precise localization in three different levels. Localization can be classified in three big categories: wide area and long distance localization with low accuracy, medium area and distance localization with medium accuracy, and small area short distance localization with high accuracy. In order to present localization methods, traditional map building technologies such as grid maps or topological maps can be used. We implemented mobile sensor vehicles and composed mobile sensor network with three levels of localization techniques. Each mobile sensor vehicles act as a mobile sensor node with the facilities such as autonomous driving, obstacle detection and avoidance, map building, communication via wireless network, image processing, extensibility of multiple heterogeneous sensors, and so on. For localization, each mobile sensor vehicle has abilities of the location awareness by mobility trajectory based localization, RSSI based localization and computer vision based localization. With this set of mobile sensor network, we have the possibility to demonstrate various localization mechanisms and their effectiveness. In this paper, the result of computer vision based localization, sensor mobility trail based localization and RSSI based localization will be presented.
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A control engineering environment called CPDev for programming small controllers in ST, FBD and IL languages of IEC 61131-3 standard is presented. The environment consists of a compiler, simulator and hardware configurer. It is open in the sense that: (1) code generated by the compiler can be executed by different processors, (2) low-level components of the controller runtime program are developed by hardware designers, (3) control programmers can define libraries with functions, function blocks and programs.
Of the three IEC languages, ST Structured Text is a basis for CPDev. FBD diagrams are translated to ST. IL compiler uses the same code generator. The runtime program has the form of virtual machine which executes universal code generated by the compiler. The machine is an ANSI C program with some platform-dependent components. The machines for AVR, ARM, MCS51 and x86 processors have been developed so far. Applications include two controllers for small DCS systems and PC equipped with I/O boards. CPDev may be downloaded from http://cpdev.prz-rzeszow.pl/demo.
