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A survey of recent results in networked control systems
 PROCEEDINGS OF THE IEEE
, 2007
"... Networked Control Systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. In this paper we review several recent results on estimation, analysis, and controller synthesis for NCSs. The re ..."
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Cited by 300 (11 self)
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Networked Control Systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. In this paper we review several recent results on estimation, analysis, and controller synthesis for NCSs. The results surveyed address channel limitations in terms of packetrates, sampling, network delay and packet dropouts. The results are presented in a tutorial fashion, comparing alternative methodologies.
Optimal LQG control across packetdropping links
 Systems & Control Letters
, 2007
"... Abstract We examine two special cases of the problem of optimal Linear Quadratic Gaussian control of a system whose state is being measured by sensors that communicate with the controller over packetdropping links. We extend the LQG separation principle using a standard LQR statefeedback design, ..."
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Cited by 77 (7 self)
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Abstract We examine two special cases of the problem of optimal Linear Quadratic Gaussian control of a system whose state is being measured by sensors that communicate with the controller over packetdropping links. We extend the LQG separation principle using a standard LQR statefeedback design, along with an optimal algorithm for propagating and using the information across the unreliable link. Our design is optimal for any arbitrary packet drop pattern. Further, the solution is appealing from a practical point of view because it can be implemented as a small modification of an existing LQG control design.
Control and Communication Challenges in Networked Realtime Systems
, 2007
"... A current survey of the emerging field of networked control systems is provided. The aim is to introduce the fundamental issues involved in designing successful networked control systems, to provide a snapshot assessment of the current state of research in the field, to suggest useful future researc ..."
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Cited by 62 (4 self)
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A current survey of the emerging field of networked control systems is provided. The aim is to introduce the fundamental issues involved in designing successful networked control systems, to provide a snapshot assessment of the current state of research in the field, to suggest useful future research directions, and to provide a broad perspective on recent fundamental results. Reflecting the goals of the Special Issue itself, this paper surveys relevant work from the areas of systems and control, signal processing, detection and estimation, data fusion, and distributed systems. We discuss appropriate network architectures, topics such as coding for
Scheduling and Feedback CoDesign for Networked Control Systems
 PROC. IEEE CONF. ON DECISION AND CONTROL, LAS VEGAS
, 2002
"... Feedback control systems wherein the control loops are closed through a realtime network are called networked control systems (NCSs). The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Driving our research e#ort into NCSs is the ..."
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Cited by 58 (6 self)
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Feedback control systems wherein the control loops are closed through a realtime network are called networked control systems (NCSs). The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Driving our research e#ort into NCSs is the point of view that the design of both the communication protocols and the interacting controlled system should not be treated as separate. In the codesign approach we propose, network issues such as bandwidth, quantization, survivability, reliability and message delay will be considered simultaneously with controlled system issues such as stability, performance, fault tolerance and adaptability. Thus, we study network scheduling when a set of NCSs are connected to the network and arbitrating for network bandwidth. We first define the basic concepts of network scheduling in NCSs. Then, we apply the rate monotonic scheduling algorithm to schedule a set of NCSs. We also formulate the optimal scheduling problem under both ratemonotonicschedulability constraints and NCSstability constraints, and give an example of how such optimization is carried out. Next, the assumptions of ideal transmission are relaxed: we study the above network scheduling problem with networkinduced delay, packet dropouts, and multiplepacket transmissions taken into account.
Eventtriggering in distributed networked control systems
"... Abstract—This paper examines eventtriggered data transmission in distributed networked control systems with packet loss and transmission delays. We propose a distributed eventtriggering scheme, where a subsystem broadcasts its state information to its neighbors only when the subsystem’s local sta ..."
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Cited by 57 (7 self)
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Abstract—This paper examines eventtriggered data transmission in distributed networked control systems with packet loss and transmission delays. We propose a distributed eventtriggering scheme, where a subsystem broadcasts its state information to its neighbors only when the subsystem’s local state error exceeds a specified threshold. In this scheme, a subsystem is able to make broadcast decisions using its locally sampled data. It can also locally predict the maximal allowable number of successive data dropouts (MANSD) and the statebased deadlines for transmission delays. Moreover, the designer’s selection of the local event for a subsystem only requires information on that individual subsystem. Our analysis applies to both linear and nonlinear subsystems. Designing local events for a nonlinear subsystem requires us to find a controller that ensures that subsystem to be inputtostate stable. For linear subsystems, the design problem becomes a linear matrix inequality feasibility problem. With the assumption that the number of each subsystem’s successive data dropouts is less than its MANSD, we show that if the transmission delays are zero, the resulting system is finitegain stable. If the delays are bounded by given deadlines, the system is asymptotically stable. We also show that those statebased deadlines for transmission delays are always greater than a positive constant. Index Terms—Distributed systems, eventtriggering, networked control systems (NCS). I.
Feedback Control Utilizing Packet Dropping Network Links
 In Proc. of the IEEE Conference on Decision and Control
, 2002
"... The increasing availability of network connectivity has prompted the study of computerbased control methodologies that are implemented centrally or distributively using existing network infrastructure as the communications backbone. Recent work has looked at the stability of networked control syste ..."
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Cited by 55 (1 self)
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The increasing availability of network connectivity has prompted the study of computerbased control methodologies that are implemented centrally or distributively using existing network infrastructure as the communications backbone. Recent work has looked at the stability of networked control systems (i.e., control systems in which feedback loops are closed through networks) and focused on performance guarantees under networked induced delays and varying data packet rates. In this work, we extend these ideas in a probabilistic setting by modeling a packet dropping network as an erasure channel and by developing bounded variance stabilization schemes.
Optimal control of LTI systems over unreliable communication links
, 2006
"... In this paper, optimal control of linear timeinvariant (LTI) systems over unreliable communication links is studied. The motivation of the problem comes from growing applications that demand remote control of objects over Internettype or wireless networks where links are prone to failure. Dependin ..."
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Cited by 53 (3 self)
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In this paper, optimal control of linear timeinvariant (LTI) systems over unreliable communication links is studied. The motivation of the problem comes from growing applications that demand remote control of objects over Internettype or wireless networks where links are prone to failure. Depending on the availability of acknowledgment (ACK) signals, two different types of networking protocols are considered. Under a TCP structure, existence of ACK signals is assumed, unlike the UDP structure where no ACK packets are present. The objective here is to meansquare (m.s.) stabilize the system while minimizing a quadratic performance criterion when the information flow between the controller and the plant is disrupted due to link failures, or packet losses. Sufficient conditions for the existence of stabilizing optimal controllers are derived.
Stabilization of networked control systems with data packet dropout and transmission delays: continuoustime case,”
 European Journal of Control,
, 2005
"... AbstractAn iterative approach is proposed to model networked control systems (NCSs) with arbitrary but finite data packet dropout as switched linear systems. This enables us to apply the rich theory of switched systems to analyzing such NCSs. Sufficient conditions are presented on the stability an ..."
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Cited by 52 (1 self)
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AbstractAn iterative approach is proposed to model networked control systems (NCSs) with arbitrary but finite data packet dropout as switched linear systems. This enables us to apply the rich theory of switched systems to analyzing such NCSs. Sufficient conditions are presented on the stability and stabilization of NCSs with packet dropout and network delays. Stabilizing state/output feedback controllers can be constructed by using the feasible solutions of some linear matrix inequalities. The merit of the iterative approach is that the controllers can make full use of the previous information to stabilize NCSs when the current state measurements can not be transmitted by the network channel instantly. A simulation example is worked out to illustrate the effectiveness of the proposed approach.
Data Transmission over Networks for Estimation and Control
"... We consider the problem of controlling a linear time invariant process when the controller is located at a location remote from where the sensor measurements are being generated. The communication from the sensor to the controller is supported by a communication network with arbitrary topology compo ..."
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Cited by 45 (9 self)
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We consider the problem of controlling a linear time invariant process when the controller is located at a location remote from where the sensor measurements are being generated. The communication from the sensor to the controller is supported by a communication network with arbitrary topology composed of analog erasure channels. Using a separation principle, we prove that the optimal LQG controller consists of an LQ optimal regulator along with an estimator that estimates the state of the process across the communication network mentioned above. We then determine the optimal information processing strategy that should be followed by each node in the network so that the estimator is able to compute the best possible estimate in the minimum mean squared error sense. The algorithm is optimal for any packetdropping process and at every time step, even though it is recursive and hence requires a constant amount of memory, processing and transmission at every node in the network per time step. For the case when the packet drop processes are memoryless and independent across links, we analyze the stability properties and the performance of the closed loop system. The algorithm is an attempt to escape the more commonly used viewpoint of treating a network of communication links as a single endtoend link with the probability of successful transmission determined by some measure of the reliability of the network. I.
Stability of networked control systems with large delays
 in Proc. of the 46th IEEE Conf. on Decision and Control
, 2007
"... Abstract — We consider the stabilization problem for Networked Control Systems (NCSs) with uncertain, timevarying networkinduced delays and a bounded number of subsequent packet dropouts. A discretetime model, describing a NCS with packet dropouts and timevarying delays, that can be both smalle ..."
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Cited by 42 (8 self)
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Abstract — We consider the stabilization problem for Networked Control Systems (NCSs) with uncertain, timevarying networkinduced delays and a bounded number of subsequent packet dropouts. A discretetime model, describing a NCS with packet dropouts and timevarying delays, that can be both smaller and larger than the sampling interval, is presented. Based on this NCS model sufficient LMI conditions are proposed for the stability analysis and controller synthesis problem for two different controllers, i.e. a feedback controller that depends on both the state and the past control inputs and a statefeedback controller. The applicability of both controllers is compared. Moreover, the stability and controller synthesis LMIs allow for a performance analysis in terms of a lower bound for the transient decay rate of the response. The results are illustrated by application to a typical motion control example. I.