The Continuous Stream Model of Computation for Real-Time Control

Fontanelli, Daniele; Palopoli, Luigi; Abeni, Luca

doi:10.1109/rtss.2013.23

Cited by 15 publications

(15 citation statements)

References 29 publications

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“…Also, they do not define/provide the concept of meaningful finite states that capture the coupling between cyber and physical subsystems described in R3. There are also some models that allow deadline misses [21,22], but they also does not fully address R2 and R3. Therefore, we need a more general task model that captures both the stability and efficiency of CPSes.…”

Section: Why Not Existing Task Models?mentioning

confidence: 99%

Development and use of a new task model for cyber-physical systems: A real-time scheduling perspective

Lee

Shin

2017

Journal of Systems and Software

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In a typical cyber-physical system (CPS), the cyber/computation subsystem controls the physical subsystem, and therefore the computer society has recently paid considerable attention to CPS research. To keep such a CPS stable, feedback control with periodic computation tasks has been widely used, and its theoretical guarantee of stability has been made with periodic real-time task models that enforce strict periodic control updates. However, some control update misses are usually allowed (e.g., via system over-design) in certain physical subsystem states (PSSes) without causing system instability, and the resources required for strict periodic control updates can thus be reduced or used for other purposes, achieving efficient controls for the entire CPS in terms of the operational cost, such as fuel consumption or tracking accuracy. In this paper, we propose a new periodic, fault-tolerant CPS task model, which not only expresses efficiency and stability of the underlying physical subsystem, but also generalizes existing periodic real-time task models, by capturing a tolerable number of control update misses in different PSSes. To demonstrate the utility of this model, we develop a new scheduling mechanism that prioritizes jobs (i.e., periodic invocations) of a set of tasks not only by the nature of each task, but also by the number of consecutive prior job deadline misses. Based on its analysis in terms of stability and efficiency, we also propose a priority-assignment policy that lowers the system operation cost without compromising stability. Our in-depth analysis and simulation results show that the scheduling mechanism and its analysis, as well as the priorityassignment policy under the proposed model not only generalize the existing periodic real-time task models, but also significantly lower the system operation cost without losing stability.

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Section: Why Not Existing Task Models?mentioning

confidence: 99%

Development and use of a new task model for cyber-physical systems: A real-time scheduling perspective

Lee

Shin

2017

Journal of Systems and Software

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“…al. propose a new model for real-time control applications [24] to investigate stochastic stability, but ignoring the dependencies among stochastic variables. In our previous work [25], we have considered the analysis and design of bandwidth-efficient control servers while guaranteeing stability.…”

Section: Related Workmentioning

confidence: 99%

Analysis and Design of Real-Time Servers for Control Applications

Aminifar

Bini

Eles

et al. 2016

IEEE Trans. Comput.

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Abstract-Today, a considerable portion of embedded systems, e.g., automotive and avionic, comprise several control applications. Guaranteeing the stability of these control applications in embedded systems, or cyber-physical systems, is perhaps the most fundamental requirement while implementing such applications. This is different from the classical hard real-time systems where often the acceptance criterion is meeting the deadline. In other words, in the case of control applications, guaranteeing stability is considered to be a main design goal, which is linked to the amount of delay and jitter a control application can tolerate before instability. This advocates the need for new design and analysis techniques for embedded real-time systems running control applications. In this paper, the analysis and design of such systems considering a server-based resource reservation mechanism are addressed. The benefits of employing servers are manifold: providing a compositional and scalable framework, protection against other tasks' misbehaviors, and systematic bandwidth assignment and co-design. We propose a methodology for designing bandwidth-optimal servers to stabilize control tasks. The pessimism involved in the proposed methodology is both discussed theoretically and evaluated experimentally.

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“…In [FPA13], the authors propose another execution model for realtime control applications to investigate stochastic stability, but ignoring the dependencies among stochastic variables, hence no hard stability guarantees.…”

Section: State Of the Artmentioning

confidence: 99%

“…However, since then, the problem of designing such servers in a systematic manner was the main obstacle in using these servers. Current practice either considers simplified fluid execution models [FPG13] or ignores the dependencies among stochastic variables, which leads to lack of hard stability guarantees [FPA13]. In Chapter 4, we not only address the problem of optimal control server design to guarantee stability with the minimum bandwidth usage, but also provide analytical bounds on the amount of pessimism involved in our proposed approach.…”

Section: Optimal Stabilizing Control Serversmentioning

confidence: 99%

“…Recently, Fontanelli et al proposed a new model for real-time control applications [FPA13] to investigate stochastic stability, but ignoring the dependencies among stochastic variables. In [ABEP14], we extend the work in this chapter towards a different direction, presenting a controller-server co-design approach where the controller is determined in a unified process along with the server parameters.…”

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confidence: 99%

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Analysis, Design, and Optimization of Embedded Control Systems

Aminifar

2016

Linköping Studies in Science and Technology. Dissertations

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T oday, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account.In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems.Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a controlscheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidthefficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, v a novel online scheduling policy to stabilize control applications is proposed. The research presented in this thesis has been partially funded by CUGS (the National Graduate School in Computer Science in Sweden), Ericsson's Research Foundation, eLLIIT (Excellence Center at Linköping-Lund on Information Technology), and the Swedish Research Council.Populärvetenskaplig Sammanfattning I dag omfattar många inbyggda system flera styrapplikationer som delar samma plattform. Dessa system används inom exempelvis bilindustrin, processindustrin och flygelektronik, för att nämna några. Det är välkänt att en sådan resursdelning leder till komplexa tidsbeteenden som försämrar kvaliteten på regleringen och i värsta fall kan även stabiliteten förloras.I denna avhandling betraktar vi inbyggda styrsystem, där flera styrapplikationer delar samma behandlingsenhet. Här har vi valt att fokusera på reglering-schemaläggning co-designproblemet. Till skillnad från traditionella inbyggda system där regleringsparametrarna och schemaläggningsparametrarna optimeras separat, behöver vi nu för inbyggda styrsystem optimera dessa samtidigt, vilket ger upphov till nya metoder. Denna avhandling är ytterligare ett steg mot effektiv design och optimering av inbyggda styrsystem.vii

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The Continuous Stream Model of Computation for Real-Time Control

Cited by 15 publications

References 29 publications

Development and use of a new task model for cyber-physical systems: A real-time scheduling perspective

Development and use of a new task model for cyber-physical systems: A real-time scheduling perspective

Analysis and Design of Real-Time Servers for Control Applications

Analysis, Design, and Optimization of Embedded Control Systems

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