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Contention-based Multiple Access Architectures for Networked Control Systems
KTH, School of Electrical Engineering (EES), Automatic Control. (Reglerteknik)ORCID iD: 0000-0001-7228-0249
2011 (English)Licentiate thesis, monograph (Other academic)
Abstract [en]

Networked Control Systems (NCSs) use a wireless network for communication between sensors and controllers, and require a Medium Access Controller (MAC) to arbitrate access to the shared medium. Traditionally, a MAC for control systems is chosen primarily based on the delay it introduces in the closed loop. This thesis focuses on the design of a contention-based MAC, in a time-varying, resource-constrained network for closed loop systems.

In this thesis, we advocate the use of a state-aware MAC, as opposed to an agnostic MAC, for NCSs. A state-aware MAC uses the state of the plant to influence access to the network. The state-aware policy is realized using two different approaches in the MAC: a regulatory formulation and an adaptive prioritization.

Our first approach is a regulatory MAC, which serves to reduce the traffic in the network. We use a local state-based scheduler to select a few critical data packets to send to the MAC. We analyze the impact of such a scheduler on the closed loop system, and show that there is a dual effect for the control signal, which makes determining the optimal controller difficult. We also identify restrictions on the scheduling criterion that result in a separation of the scheduler, observer and controller designs.

Our second approach is a prioritized MAC that uses state-based priorities called Attentions, to determine access to the network. We use a dominance protocol called tournaments, to evaluate priorities in a contention-based setting, and analyze the resulting performance of the MAC.

We also consider a NCS that uses a wireless multihop mesh network for communication between the controller and actuator. We design an optimal controller, which uses packet delivery predictions from a recursive Bayesian network estimator.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , vi, 120 p.
Trita-EE, ISSN 1653-5146 ; 2011:006
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-29781ISBN: 978-91-7415-866-3OAI: diva2:397755
2011-02-18, D3, KTH, Lindtedtsv. 5, Stockholm, 15:41 (English)
QC 20110216Available from: 2011-02-16 Created: 2011-02-15 Last updated: 2011-02-16Bibliographically approved

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