Towards Networked Control Systems with guaranteed stability: Using weakly hard real-time constraints to model the loss process

Blind, Rainer; Allgöwer, Frank

doi:10.1109/cdc.2015.7403405

Cited by 22 publications

(23 citation statements)

References 13 publications

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“…Likewise the quality of a control application is still satisfactory if once in a while a sensor data sample is lost and the control algorithm is performed on an old sensor data sample [10]. Results from control engineering [4] could even show Lyapunov stability of the feedback control of an unstable plant that runs in open loop from time to time due to failures. The modern concept of weakly-hard real-time (WHRT) computing systems [2] takes this reality into account.…”

Section: Introductionmentioning

confidence: 96%

Finite ready queues as a mean for overload reduction in weakly-hard real-time systems

Ahrendts

Quinton

Ernst

2017

Proceedings of the 25th International Conference on Real-Time Networks and Systems

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Finite ready queues, implemented by bu ers, are a system reality in embedded real-time computing systems and networks. The dimensioning of queues is subject to constraints in industrial practice, and often the queue capacity is su cient for typical system behavior but is not su cient in peak overload conditions. This may lead to over ow and consequently to the discarding of jobs. In this paper, we explore whether nite queue capacity can also be used as a mean of design in order to reduce workload peaks and thus shorten a transient overload phase. We present an analysis method which is to the best of our knowledge the rst one able to give (a) worst-case response times guarantees as well as (b) weakly-hard guarantees for tasks which are executed on a computing system with nite queues. Experimental results show that nite queue capacity may only a have weak overload limiting e ect. This unexpected outcome can be explained by the system behavior in the worst-case corner cases. The analysis shows nevertheless that a trade-o between weakly-hard guarantees and queue sizes is possible.

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Section: Introductionmentioning

confidence: 96%

Finite ready queues as a mean for overload reduction in weakly-hard real-time systems

Ahrendts

Quinton

Ernst

2017

Proceedings of the 25th International Conference on Real-Time Networks and Systems

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“…In [24], the suitability of weakly hard real-time schedulers [25] has been investigated by deriving sufficient stability conditions for a single NCS, however, without directly taking network utilization and competing traffic into account. Dynamic state-based schedulers for NCS have also been investigated.…”

Section: Introductionmentioning

confidence: 99%

State-dependent priority scheduling for networked control systems

Carabelli¹,

Blind²,

Dürr³

et al. 2017

2017 American Control Conference (ACC)

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Networked control systems (NCS) have attracted considerable attention in recent years. While the stabilizability and optimal control of NCS for a given communication system has already been studied extensively, the design of the communication system for NCS has recently seen an increase in more thorough investigation. In this paper, we address an optimal scheduling problem for a set of NCS sharing a dedicated communication channel, providing performance bounds and asymptotic stability. We derive a suboptimal scheduling policy with dynamic state-based priorities calculated at the sensors, which are then used for stateless priority queuing in the network, making it both scalable and efficient to implement on routers or multi-layer switches. These properties are beneficial towards leveraging existing IP networks for control, which will be a crucial factor for the proliferation of wide-area NCS applications. By allowing for an arbitrary number of concurrent transmissions, we are able to investigate the relationship between available bandwidth, transmission rate, and delay. To demonstrate the feasibility of our approach, we provide a proofof-concept implementation of the priority scheduler using real networking hardware.

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“…It is expected that effective solutions can be provided by other approaches, e.g. based on weakly-hard real-time considerations as suggested by (Blind and Allgöwer (2015)) for the case of switched systems. Others modeling paradigms may be also investigated, e.g., as in (Qiu, Wei, and Karimi (2015)) where time delays are handled inside hybrid systems modeled by Markov jump systems.…”

Section: Robustness Of Lpv Based Varying Samplingmentioning

confidence: 99%

“…However approaches gathering real-time scheduling and feedback control considerations are still quite rare. Let us for example cite (Blind and Allgöwer (2015)) for the analysis of closed-loop stability under weakly-hard scheduling constraints.…”

Section: Joint Control and Schedulingmentioning

confidence: 99%

“…Possible research directions include extended models of the hybrid control system as, e.g., Markov jump systems (Qiu et al (2015)). Another promising way is the translation of the weakly-hard scheduling constraints (gathering aperiodic sampling and time delays) into stability conditions as done in (Blind and Allgöwer (2015)) to model the data loss process in a control loop. Finally the real-time scheduler itself may induce other sporadic events that could disturb the control application.…”

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confidence: 99%

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Real-time control systems: feedback, scheduling and robustness

Simon

Seuret

Sename

2017

International Journal of Systems Science

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The efficient control of real-time distributed systems, where continuous components are governed through digital devices and communication networks, needs a careful examination of the constraints arising from the different involved domains inside co-design approaches. Thanks to the robustness of feedback control, both new control methodologies and slackened real-time scheduling schemes are proposed beyond the frontiers between these traditionally separated fields. A methodology to design robust aperiodic controllers is provided, where the sampling interval is considered as a control variable of the system. Promising experimental results are provided to show the feasibility and robustness of the approach.

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Towards Networked Control Systems with guaranteed stability: Using weakly hard real-time constraints to model the loss process

Cited by 22 publications

References 13 publications

Finite ready queues as a mean for overload reduction in weakly-hard real-time systems

Finite ready queues as a mean for overload reduction in weakly-hard real-time systems

State-dependent priority scheduling for networked control systems

Real-time control systems: feedback, scheduling and robustness

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