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| 2. |
- Claesson, Vilgot, 1968
(författare)
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Efficient and Reliable Communication in Distributed Embedded Systems
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of distributed computing elements has grown in the embedded systems arena, consequently the use of shared communication media linking these computers has garnered increasing attention. Two prominent and contemporary media sharing approaches include variations of controlled and contention based media access paradigms, with the time-triggered (TT) and the event-triggered (ET) approaches, respectively, being prominent manifestations of these paradigms. For these mentioned TT and ET approaches, the thrust of this thesis is on investigating and analyzing efficient realizations of such. A desired attribute in embedded systems, with safety and real-time requirements, is the basic capability to coordinate and synchronize system time and events. This directly relates to the establishment of a predictable communication base, which subsequently becomes the basis to provide for predictable communication at the system level. Focusing on bus-based communication protocols, we present a novel synchronization approach targeting efficiency and low communication overhead as the main drivers for TDMA environments. Existing techniques require explicit transfer of node id information for synchronization. In this novel approach, the synchronization process utilizes the implicit information in each node's unique message length as node identifier. Furthermore, our initial startup synchronization approach is fault-tolerant, and has a bounded startup time. We also present a re-synchronization strategy that incorporates recovering nodes into synchronization. The event-triggered and the time-triggered media access paradigms have spawned discrete followings with much debated pros and cons regarding their relative flexibility, bandwidth efficiency and predictability features. The event-triggered approach is commonly perceived as providing high flexibility. Similarly, the time-triggered approach is expected to provide a higher degree of predictable communication access to the media. One part of this thesis is to objectively and quantitatively assess the capabilities and limitations of each of these paradigms. More importantly, we quantify the spread of their differences, and provide system design guidelines for suggested best usage for each approach. The focus of this work is on response times of the communication system, and the schedulability of the communication system in collaboration with tasks in the nodes. Focusing on efficiency, the second component of this thesis, deals with introducing modifications in the time-triggered approach to efficiently accommodate event-triggered communication using the time-triggered operations as a base.
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| 3. |
- Claesson, Vilgot, 1968, et al.
(författare)
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The Event-Triggered and Time-Triggered Medium-Access Methods
- 2003
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Ingår i: Proceedings - 6th IEEE International Symposium on Object-Oriented Real-Time Distributed Computing, Hakodate, Japan, 14-16 May 2003. - 0769519288 ; , s. 131-134
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Konferensbidrag (refereegranskat)abstract
- The processes of accessing a shared communication media have been extensively researched in the dependability and real-time area. For embedded systems, the primary approaches have revolved around the event-triggered and the time-triggered paradigms. In this paper, our goal is to objectively and quantitatively outline the capabilities and limitations of each of these paradigms. The event-triggered approach is commonly perceived as providing high flexibility, while the time-triggered approach is expected to provide for a higher degree of predictable communication access to the media. We have quantified the spread of their differences, and provide a summary discussion about suggested best usage for each approach. The focus of our work is on the response times of the communication system, and also on the schedulability of the communication system in collaboration with tasks in the nodes.
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| 4. |
- Gäfvert, Magnus, et al.
(författare)
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Investigation and requirements of a computer control system in a heavy-duty truck
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report, which is the first in a series of three reports, an existing computer control system in a heavy-duty truck from Volvo Truck Corporation has been investigated. The aim of the report and of the DICOSMOS case study at Volvo Technological Development is to design and study a future computer control system for a truck and semi-trailer vehicle combination. The functionality in focus is vehicle dynamics control, VDC, which assists the driver to maintain control of his vehicle in difficult situations.
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| 5. |
- Gäfvert, Magnus, et al.
(författare)
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Proposal for a distributed computer control system in heavy-duty trucks
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In designing safety-critical real-time distributed control-systems a great potential lies in combining methods within the areas of dependable computer systems and control theory. In this report a brake system on a heavy-duty truck is used as a case study to discuss the choice of distribution level of the computer system and the control algorithms. The distrubution levels of these system aspects are othogonal in the sense that they may be chosen independently for a certain system configuration. A system configuration is obtained by mapping a specific control algorithm architecture on a computer/communications architecture. To explore different system architectures the combinations of three different distribution levels for the control algorithms and computer/communication systems are investigated with respect to dependability and required information exchange. The result is a proposal on the choice of final distribution level of the brake system.
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| 6. |
- Gäfvert, Magnus, et al.
(författare)
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Truck Model for Yaw Dynamics Control
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes the derivation of a nonlinear model of a tractor-semitrailer combination vehicle. The purpose of the model is validation of yaw-control algorithms. The model include 4 DOF in lateral, longitudinal, and yaw motion. It is formulated as a state-spece model with 5 state variables. Additional states are added with the rotational dynamics of the wheels. The model includes a static description of load-transfer, and a fairly detailed tyre model. A linearized version of the model is also presented. The nonlinear model is implemented in Simulink (TM). Validation is performed by comparison with a multibody model. Examples of simulation outputs are given.
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| 7. |
- Hult, Gunnar, 1952-, et al.
(författare)
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Sweden - Aeronautics RTD Programme and Research Agenda
- 2012
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Ingår i: Proceedings of the Sixth European Aeronautics Days. - Amsterdam : IOS Press. - 9781614990628 ; , s. 432-436
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Konferensbidrag (refereegranskat)abstract
- The Aeronautics RTD programme in Sweden was in the past dominated by the needs for the development of military aircraft and this programme is still continued to support the Gripen but with a lower level of effort. The national Aeronautical Programme (NFFP) started in 1994 and is now in its fifth phase (2009-2012). Its objectives are to: (i) strengthen Swedish competitiveness; (ii) strengthen the capability to participate in international research cooperation; (iii) support Swedish Armed Forces.
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| 8. |
- Jhumka, Arshad, 1974, et al.
(författare)
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On Systematic Design of Globally Consistent Executable Assertions in Embedded Software
- 2002
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Ingår i: SIGPLAN Notices (ACM Special Interest Group on Programming Languages). - : Association for Computing Machinery (ACM). - 0730-8566 .- 0362-1340 .- 1558-1160. ; 37:7, s. 75-84
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Konferensbidrag (refereegranskat)abstract
- Over the design of software (SW) used in provisioning of dependable services, Executable Assertions (EAs) are seeing increasing usage in aiding detection of data errors. Given the requirements for provision of service despite faults, early detection of system states that can potentially lead to system failure is valuable. We address the issue of ascertaining whether localized EAs in individual modules add up complementarily to implement a global EA/property. We first show that detection of globally compliant EAs is NP-complete. Thus, we develop a two-pass approach for our objective. In the first pass, we introduce the consistency property of EAs and use it to ascertain global conformity across all EAs. The second pass, analogous to predicate transformers, generates globally consistent EAs when any inconsistency is flagged in the first pass. We show the applicability of our approach on a real embedded system. Initial results obtained show that our framework is able to detect inherent vulnerabilities (due to placement of mismatched EAs) that were previously undetected. Our intent is automation of this approach, which can be incorporated in a compiler.
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