AbstractWe consider a stochastic system where the communication between the controller and the actuatoris triggered by a threshold-based rule. The communication is performed across an unreliable link thatstochastically erases transmitted packets. To decrease the communication burden, and as a partial pro-tection against dropped packets, the controller sends a sequence of control commands to the actuator ineach packet. These commands are stored in a buffer and applied sequentially until the next control packetarrives. In this context, we study dead-beat control laws and compute the expected linear-quadratic loss ofthe closed-loop system for any given event-threshold. Furthermore, we provide analytical expressions thatquantify the trade-off between the communication cost and the control performance of event-triggeredcontrol systems. Numerical examples demonstrate the effectiveness of the proposed framework.Index TermsEvent-triggering algorithms; Linear systems; Communication networks; Packet loss; Networkedcontrol
The analysis becomes even more involved when the network is unreliable. Blind and Allg " o wer @cite_4 extended the work of @cite_27 to the case where transmissions from the sensor to the controller take place over an unreliable link. They analytically derived the control cost and the expected inter-event times for different packet loss rates. Rabi and Johansson @cite_36 designed the optimal impulse control and the level triggering mechanism under packet losses with multiple loops sharing a common network. From a different perspective, @cite_6 analyzed the stability of an event-triggered implementation of a controller in the presence of packet losses and limited processing resources. However, in all these works, the unreliable channel appears between sensor and controller, while the controller-actuator communication is lossless.
@cite_36 @cite_27 @cite_4 @cite_6
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For a single control loop with communication rate constraints, Event-triggered control often outperforms periodic control. When multiple loops are being controlled over a shared contention-based medium, however, the advantage of event-triggered policies is less well understood. In this paper, we consider event-triggered impulse control under lossy communication. The sampling events are determined by level crossings of the plant output. It is shown how a stochastic control criterion depends on the level thresholds and the packet loss probability for a class of integrator plants. For multiple control loops, this result is used to derive a design guideline on how to assign the levels that lead to optimal use of the available communication resources. It is shown that the structure of the event generator depends critically on the loss probability. In this work, we analyze event-based control for scalar systems with an impulsive input that resets the state to the origin when applied. The event information is transmitted within packets, which are randomly dropped. We derive the cost as well as the expected times between events and discuss how to change the bounds, which generate the events, after a packet loss. In this paper, optimal control of linear time-invariant (LTI) systems over unreliable communication links is studied. The motivation of the problem comes from growing applications that demand remote control of objects over Internet-type 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 mean-square (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. This paper is concerned with the analysis, design and validation of a reliable management strategy for industrial monitoring and control over wireless sensor network (WSN). First, we investigate the interactions between contention resolution and congestion control mechanisms in Wireless Industrial Sensor Network (briefly WISN). An extensive set of simulations are performed in order to quantify the impacts of several network parameters (i.e. buffer, sensors reporting rate) on the overall network performance (i.e. reliability, packet losses). This calls for cross-layer mechanisms for efficient data delivery over WISN. Second, a reliable sink resource allocation strategy based on log-utility fairness criteria is proposed. It is shown that the resource sink manager can plan strategies to better allocate the available resource among competing sensors. Finally, the analysis, design and validation of a reliable sinks cooperative control for WISN are introduced. A sufficient condition for wireless network stability in presence of multiple sinks and heterogeneous sensors with different time delays is given and it is used for network parameters design. The stability condition and the resulting cooperative control performance in terms of fairness, link utilization, packet losses, reliability and latency are validated by Matlab Simulink-based simulator TrueTime, which facilitates co-simulation of controller task execution in real-time kernels and in the wireless network environment. Copyright © 2009 John Wiley & Sons, Ltd.