Brief paper: A state-feedback approach to event-based control
TL;DR: An upper bound of the difference between both loops is derived, which shows that the approximation of the continuous state-feedback loop by the event-based control loop can be made arbitrarily tight by appropriately choosing the threshold parameter of the event generator.
Abstract: This paper proposes a new method for event-based state-feedback control in which a control input generator mimics a continuous feedback between two consecutive event times. The performance of the event-based control system is evaluated by comparing this loop with the continuous state-feedback loop. An upper bound of the difference between both loops is derived, which shows that the approximation of the continuous state-feedback loop by the event-based control loop can be made arbitrarily tight by appropriately choosing the threshold parameter of the event generator.
Citations
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01 Dec 2012
TL;DR: An introduction to event- and self-triggered control systems where sensing and actuation is performed when needed and how these control strategies can be implemented using existing wireless communication technology is shown.
Abstract: Recent developments in computer and communication technologies have led to a new type of large-scale resource-constrained wireless embedded control systems. It is desirable in these systems to limit the sensor and control computation and/or communication to instances when the system needs attention. However, classical sampled-data control is based on performing sensing and actuation periodically rather than when the system needs attention. This paper provides an introduction to event- and self-triggered control systems where sensing and actuation is performed when needed. Event-triggered control is reactive and generates sensor sampling and control actuation when, for instance, the plant state deviates more than a certain threshold from a desired value. Self-triggered control, on the other hand, is proactive and computes the next sampling or actuation instance ahead of time. The basics of these control strategies are introduced together with a discussion on the differences between state feedback and output feedback for event-triggered control. It is also shown how event- and self-triggered control can be implemented using existing wireless communication technology. Some applications to wireless control in process industry are discussed as well.
1,642 citations
Cites background from "Brief paper: A state-feedback appro..."
...A formal analysis can be found in the more recent work [43], which extends the work in [44] that assumed availability of the full state....
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...It is also worthwhile to mention the connection of the usage of model-based predictions to the work in [19], where the relevance of generalized holds was mentioned, and the work in [44], [43] in which the term signal generator was used based on model-based predictions (although in absence of a resource-constrained controller-to-actuator channel)....
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TL;DR: Simulation results have shown that the proposed event-triggering scheme is superior to some existing event- triggering schemes in the literature.
Abstract: This note is concerned with event-triggered H∞ controller design for networked control systems. A novel event-triggering scheme is proposed, which has some advantages over some existing schemes. A delay system model for the analysis is firstly constructed by investigating the effect of the network transmission delay. Then, based on this model, criteria for stability with an H∞ norm bound and criteria for co-designing both the feedback gain and the trigger parameters are derived. These criteria are formulated in terms of linear matrix inequalities. Simulation results have shown that the proposed event-triggering scheme is superior to some existing event-triggering schemes in the literature.
1,326 citations
Cites background or methods from "Brief paper: A state-feedback appro..."
...Our event generator is also implemented based on dissipation inequalities as in [10], [15]–[17], [19]–[21]....
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...It should be noted that, some existing [10], [12],...
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...Remark 2: Different from a continuous event generator (CEG) which is an event generator with a continuous supervision of the state [10], [15]–[17], [19]–[21], the event generator with the algorithm (3) only supervises the difference between the states sampled in discrete instants having no interest in what happens in between updates....
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...Compared with the event-triggered scheme in [10], [15]–[17], [19]–[21], the selftriggered scheme can provide additional energy savings for the sensor and also less complexity in the implementation....
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...In [10], the event-triggered control with constraint was proposed for linear systems with an external disturbance, where the threshold of the event generator is a constant....
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10 Dec 2013
TL;DR: The PETC strategies developed in this paper apply to both static state-feedback and dynamical output-based controllers, as well as to both centralized and decentralized (periodic) event-triggering conditions.
Abstract: Event-triggered control (ETC) is a control strategy that is especially suited for applications where communication resources are scarce. By updating and communicating sensor and actuator data only when needed for stability or performance purposes, ETC is capable of reducing the amount of communications, while still retaining a satisfactory closed-loop performance. In this paper, an ETC strategy is proposed by striking a balance between conventional periodic sampled-data control and ETC, leading to so-called periodic event-triggered control (PETC). In PETC, the event-triggering condition is verified periodically and at every sampling time it is decided whether or not to compute and to transmit new measurements and new control signals. The periodic character of the triggering conditions leads to various implementation benefits, including a minimum inter-event time of (at least) the sampling interval of the event-triggering condition. The PETC strategies developed in this paper apply to both static state-feedback and dynamical output-based controllers, as well as to both centralized and decentralized (periodic) event-triggering conditions. To analyze the stability and the L2-gain properties of the resulting PETC systems, three different approaches will be presented based on 1) impulsive systems, 2) piecewise linear systems, and 3) perturbed linear systems. Moreover, the advantages and disadvantages of each of the three approaches will be discussed and the developed theory will be illustrated using a numerical example.
1,011 citations
TL;DR: This paper analyzes networked control systems in the presence of denial-of-service (DoS) attacks, namely attacks that prevent transmissions over the network, to characterize frequency and duration of the DoS attacks under which input-to-state stability (ISS) of the closed-loop system can be preserved.
Abstract: The issue of cyber-security has become ever more prevalent in the analysis and design of networked systems. In this paper, we analyze networked control systems in the presence of denial-of-service (DoS) attacks, namely attacks that prevent transmissions over the network. We characterize frequency and duration of the DoS attacks under which input-to-state stability (ISS) of the closed-loop system can be preserved. To achieve ISS, a suitable scheduling of the transmission times is determined. It is shown that the considered framework is flexible enough so as to allow the designer to choose from several implementation options that can be used for trading-off performance versus communication resources. Examples are given to substantiate the analysis.
794 citations
Cites background from "Brief paper: A state-feedback appro..."
...As discussed in [19], [29], and [30], event-based sampling is a very effective solution for saving communication resources....
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TL;DR: This paper proposes a decentralized event-triggering mechanism that will be able to guarantee stability and performance for event-triggered controllers with larger minimum inter-event times than the existing results in the literature.
Abstract: Most event-triggered controllers available nowadays are based on static state-feedback controllers. As in many control applications full state measurements are not available for feedback, it is the objective of this paper to propose event-triggered dynamical output-based controllers. The fact that the controller is based on output feedback instead of state feedback does not allow for straightforward extensions of existing event-triggering mechanisms if a minimum time between two subsequent events has to be guaranteed. Furthermore, since sensor and actuator nodes can be physically distributed, centralized event-triggering mechanisms are often prohibitive and, therefore, we will propose a decentralized event-triggering mechanism. This event-triggering mechanism invokes transmission of the outputs in a node when the difference between the current values of the outputs in the node and their previously transmitted values becomes “large” compared to the current values and an additional threshold. For such event-triggering mechanisms, we will study closed-loop stability and L∞-performance and provide bounds on the minimum time between two subsequent events generated by each node, the so-called inter-event time of a node. This enables us to make tradeoffs between closed-loop performance on the one hand and communication load on the other hand, or even between the communication load of individual nodes. In addition, we will model the event-triggered control system using an impulsive model, which truly describes the behavior of the event-triggered control system. As a result, we will be able to guarantee stability and performance for event-triggered controllers with larger minimum inter-event times than the existing results in the literature. We illustrate the developed theory using three numerical examples.
761 citations
Cites methods from "Brief paper: A state-feedback appro..."
...The analysis is performed for first-order stochastic systems, as analysis of larger-dimensional systems is difficult, and it is shown that the variance of the state is smaller when compared to a sampled-data controller, while having approximately the same number of control updates....
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References
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TL;DR: A new control design methodology is proposed, which relies on the possibility of changing the sensitivity of the quantizer while the system evolves, which yields global asymptotic stability.
Abstract: This paper addresses feedback stabilization problems for linear time-invariant control systems with saturating quantized measurements. We propose a new control design methodology, which relies on the possibility of changing the sensitivity of the quantizer while the system evolves. The equation that describes the evolution of the sensitivity with time (discrete rather than continuous in most cases) is interconnected with the given system (either continuous or discrete), resulting in a hybrid system. When applied to systems that are stabilizable by linear time-invariant feedback, this approach yields global asymptotic stability.
1,533 citations
10 Dec 2002
TL;DR: In this paper, it is shown that Lebesgue sampling gives better performance for some simple systems than traditional Riemann sampling, which is an analog of integration theory and is called event-based sampling.
Abstract: The normal approach to digital control is to sample periodically in time. Using an analog of integration theory we can call this Riemann sampling. Lebesgue sampling or event based sampling is an alternative to Riemann sampling. It means that signals are sampled only when measurements pass certain limits. In this paper it is shown that Lebesgue sampling gives better performance for some simple systems.
961 citations
TL;DR: A new class of feedback control problems is introduced, which cannot be asymptotically stabilized if the underlying dynamics are unstable, and a weaker stability concept called containability is introduced.
Abstract: For part I, see ibid., vol.42, p.1294-8, 1997. In this paper a new class of feedback control problems is introduced. Unlike classical models, the systems considered here have communication channel constraints. As a result, the issue of coding and communication protocol becomes an integral part of the analysis. Since these systems cannot be asymptotically stabilized if the underlying dynamics are unstable, a weaker stability concept called containability is introduced. A key result connects containability with an inequality equation involving the communication data rate and the rate of change of the state.
923 citations
01 Jan 1999
TL;DR: A simple event-based PID controller is presented and it is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation.
Abstract: A simple event-based PID controller is presented. It is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation. Simulations on a double-tank process are presented.
865 citations
TL;DR: In this article, a simple event-based PID controller is presented, and it is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation.
Abstract: A simple event-based PID controller is presented. It is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation. Simulations on a double-tank process are presented.
796 citations