Stability analysis of multiple state-based schedulers with CSMA

2015 54th IEEE Conference on Decision and Control (CDC)

Deroo

Hirche

2015

Abstract-In this paper we address the problem of eventbased data scheduling for a class of physically interconnected networked control systems which compete for limited communication resources. The overall interconnected system consists of multiple heterogeneous LTI sub-systems with the physical interconnection being modeled by a directed acyclic graph (DAG). The sub-systems are controlled by a networked controller through a shared communication channel. In order to cope with the limited channel capacity, we introduce a bi-character deterministic-probabilistic scheduling mechanism which dynamically assigns access priorities to each sub-system at each time-step according to an error-dependent priority measure. The sub-systems which are granted channel access then transmit their state information through the communication network. Given an emulation-based control strategy, we prove stability of such networked systems under the proposed scheduling law in terms of f -ergodicity of overall network-induced error. Simulation results illustrate the proposed approach and show a reduction in the error variance compared to standard TDMA and uniform random-access scheduling policies.

Section: Stability Analysismentioning

confidence: 99%

“…Deterministic policies however are not well suited to deal with delays, dropouts, collisions and noisy systems [8]. Alternatively, probabilistic policies have been investigated that consider stochastic NCSs [9], [10]. These methods are better equipped to deal with noise and collisions but also with model uncertainties [11]- [13].…”

Section: Introductionmentioning

confidence: 99%

Event-based data scheduling for a class of interconnected networked control systems

2015 54th IEEE Conference on Decision and Control (CDC)

Deroo

Hirche

2015

“…In the event-based paradigm, events are typically triggered by either deterministic [8], [9], or stochastic policies [10]- [13]. Deterministic policies usually have better performance as they award the channel to the entity with the highest priority.…”

Section: Introductionmentioning

confidence: 99%

“…On the contrary, MATI does not apply to stochastic schemes as the intervals between consecutive transmissions usually cannot be upper bounded uniformly with probability one. This calls for new stability approaches for stochastic NCSs [10]- [13]. Probabilistic policies are more suitable to deal with stochastic systems with model uncertainties and channel imperfections [10], [12], [13], [15].…”

Section: Introductionmentioning

confidence: 99%

Decentralized event-based scheduling for shared-resource Networked Control Systems

2015 European Control Conference (ECC)

Tolić

Hirche

2015

Abstract-In this paper, we introduce a decentralized eventtriggered scheduling scheme for multi-loop Networked Control Systems (NCSs) in which the individual control loops are coupled through a shared communication channel. The proposed scheduling design combines deterministic and probabilistic attributes to efficiently allocate the limited communication resource among the control loops in an event-based fashion. Based on local error thresholds, each control loop determines whether to compete for the channel access. As a result, control loops with higher transmission priorities are more likely to utilize the channel, which in turn leads to more efficient usage of the limited resource. Each eligible subsystem then attempts to transmit at times specified by local waiting times, which are randomly distributed and local-error dependent. In this manner, the probability of data collisions in the communication channel is reduced. If the channel capacity is reached at some time instants, data packets are dropped. We demonstrate stochastic stability of such NCSs in terms of Lyapunov Stability in Probability (LSP). The numerical results show that our approach improves resource utilization and reduces the networked-induced error variance in comparison with timetriggered, random access, and centralized scheduling policies.

“…In the event-based paradigm, events are typically triggered by either deterministic [23,30], or stochastic policies [7,18,24,26]. Deterministic event-based policies award the channel to the entity with the highest priority.…”

Section: Introductionmentioning

confidence: 99%

Adaptive Decentralized MAC for Event-Triggered Networked Control Systems

Vilgelm

Proceedings of the 19th International Conference on Hybrid Systems: Computation and Control

Kellerer

et al. 2016

Control over shared communication networks is a key challenge in design and analysis of cyber-physical systems. The quality of control in such systems might be degraded due to the congestion while accessing the scarce communication resources. In this paper, we consider a multiple-loop networked control system (NCS), where all control loops share a communication network. Medium Access Control (MAC) is performed in contention-based fashion using a multi-channel slotted ALOHA protocol, where each control loop decides locally whether to attempt a transmission based on some error thresholds. We further introduce a local event-based resource-aware scheduling design with an adaptive choice of the error thresholds for a transmission. This leads to a hybrid channel access mechanism where the control loops are deterministically categorized into two sets of eligible and ineligible sub-systems for transmission in an event-based fashion, before a random process to select the available channels. In addition, employing the introduced policy, we show the stability of the resulting NCS in terms of Lyapunov stability in probability. We illustrate numerically the efficiency of our proposed approach in terms of reducing the average networked-induced error variance, and show the superiority of the adaptive event-based scheduler compared to the scheduling design with non-adaptive thresholds.