Optimizing controller location in networked control systems with packet drops

Robinson, Craig; Kumar, P. R.

doi:10.1109/jsac.2008.080508

Cited by 45 publications

(42 citation statements)

References 25 publications

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“…In this work we generalize this and allow each actuator a i , (i ∈ {1, 2, ..., m}) to maintain a (possibly) vector state 4 denoted by…”

Section: The Wireless Control Networkmentioning

confidence: 99%

“…Furthermore, transmissions in the network must be scheduled carefully to avoid packet dropouts due to collisions between neighboring nodes. These issues can be detrimental to the goal of maintaining stability of the closed loop system if not explicitly accounted for, and substantial research has been devoted to understanding the performance limitations in such settings (e.g., [2], [3], [4]). These works typically adopt the convention of having one or more dedicated controllers or state estimators located in the system, and study the stability of the closed loop system assuming that the sensorestimator and/or controller-actuator communication channels are unreliable (dropping packets with a certain probability, for example).…”

Section: Introductionmentioning

confidence: 99%

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Topological Conditions for In-Network Stabilization of Dynamical Systems

Pajić

Mangharam

Pappas

et al. 2013

IEEE J. Select. Areas Commun.

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Abstract-We study the problem of stabilizing a linear system over a wireless network using a simple in-network computation method. Specifically, we study an architecture called the "Wireless Control Network" (WCN), where each wireless node maintains a state, and periodically updates it as a linear combination of neighboring plant outputs and node states. This architecture has previously been shown to have low computational overhead and beneficial scheduling and compositionality properties. In this paper we characterize fundamental topological conditions to allow stabilization using such a scheme. To achieve this, we exploit the fact that the WCN scheme causes the network to act as a linear dynamical system, and analyze the coupling between the plant's dynamics and the dynamics of the network. We show that stabilizing control inputs can be computed in-network if the vertex connectivity of the network is larger than the geometric multiplicity of any unstable eigenvalue of the plant. This condition is analogous to the typical min-cut condition required in classical information dissemination problems. Furthermore, we specify equivalent topological conditions for stabilization over a wired (or point-to-point) network that employs network coding in a traditional way -as a communication mechanism between the plant's sensors and decentralized controllers at the actuators.

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“…In this work we generalize this and allow each actuator a i , (i ∈ {1, 2, ..., m}) to maintain a (possibly) vector state 4 denoted by…”

Section: The Wireless Control Networkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Topological Conditions for In-Network Stabilization of Dynamical Systems

Pajić

Mangharam

Pappas

et al. 2013

IEEE J. Select. Areas Commun.

View full text Add to dashboard Cite

show abstract

“…Even in the few works that consider networked control over arbitrary topologies (e.g., [11], [12]), an assumption is made that there is a single actuation and a single sensing point on the plant. Under this assumption, those papers recommend placing the controller at the actuation point, so that the controller will know all of the inputs that are applied to the plant, and can thus correctly estimate the state from the information that it receives from the sensing point (via the other nodes).…”

Section: Multiple Sensing/actuation Pointsmentioning

confidence: 99%

“…To control all plants simultaneously, each node groups all of its (possibly vector) states into a single transmission packet. 11 Upon reception of the different states from each of its neighbors, each node updates its different internal states using the appropriate linear combinations. This enables a completely decoupled computation of the matrices that guarantee stability for each of the plants, although physically realized by the same WCN.…”

Section: Compositionalitymentioning

confidence: 99%

“…12 While this direct attempt to cast the controller design problem as a LMI does not work in our context, we note that problems of the above form appear in the design of static output feedback controllers with sparsity constraints on the gain matrix [28]. Although this is a computationally difficult problem in general (e.g., various versions of this problem are NP-hard [29]- [31]), various numerical approximation algorithms have been proposed in the literature 11 Usually this is not a severe limitation even for low-bandwidth, 802.15.4 networks (where each transmission can carry up to 1024 b). In these networks, if each plant is controlled using the scheme where a node maintains a scalar 16-b state value, then up to 64 plants can be controlled in parallel.…”

Section: Stabilizing the Closed-loop Systemmentioning

confidence: 99%

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The Wireless Control Network: A New Approach for Control Over Networks

Pajić

Sundaram

Pappas

et al. 2011

IEEE Trans. Automat. Contr.

149

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Abstract-We present a method to stabilize a plant with a network of resource constrained wireless nodes. As opposed to traditional networked control schemes where the nodes simply route information to and from a dedicated controller (perhaps performing some encoding along the way), our approach treats the network itself as the controller. Specifically, we formulate a strategy for each node in the network to follow, where at each time-step, each node updates its internal state to be a linear combination of the states of the nodes in its neighborhood. We show that this causes the entire network to behave as a linear dynamical system, with sparsity constraints imposed by the network topology. We provide a numerical design procedure to determine appropriate linear combinations to be applied by each node so that the transmissions of the nodes closest to the actuators will stabilize the plant. We also show how our design procedure can be modified to maintain mean square stability under packet drops in the network, and present a distributed scheme that can handle node failures while preserving stability. We call this architecture a Wireless Control Network, and show that it introduces very low computational and communication overhead to the nodes in the network, allows the use of simple transmission scheduling algorithms, and enables compositional design (where the existing wireless control infrastructure can be easily extended to handle new plants that are brought online in the vicinity of the network).

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Optimal controller location in wireless networked control systems

Xin

Cao

Chen

et al. 2013

Intl J Robust & Nonlinear

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SUMMARYThe control performance of wireless networked control systems (WNCS) has been shown to heavily depend on the packet delivery quality of both the sensor‐to‐controller and controller‐to‐actuator communications. Such quality relies on the relative distance between the wireless transmitter and receiver, which naturally raises the challenging problem of controller placement in WNCS for optimal control performance. In this paper, we investigate the optimal controller location (OCL) problem in WNCS based on linear‐quadratic‐Gaussian control strategy. For the one‐hop network case where the controller can only be placed at either the sensor side or the actuator side, we derive a simple yet effective criterion to determine the OCL. For the more general multi‐hop case where the controller can be located at either one of the sensors, relays, or actuators, we obtain the necessary and sufficient condition under which the closed‐loop system is guaranteed to be stable. On the basis of these results, we further transform the OCL problem into an optimization problem that can be solved efficiently. Numerical results are provided to verify our analysis. Copyright © 2013 John Wiley & Sons, Ltd.

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Optimizing controller location in networked control systems with packet drops

Cited by 45 publications

References 25 publications

Topological Conditions for In-Network Stabilization of Dynamical Systems

Topological Conditions for In-Network Stabilization of Dynamical Systems

The Wireless Control Network: A New Approach for Control Over Networks

Optimal controller location in wireless networked control systems

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