Eloy Garcia

Model-Based Event-Triggered Control for Systems With Quantization and Time-Varying Network Delays

This paper combines two important control techniques for reducing communication traffic in control networks, namely, model-based networked control systems (MB-NCS) and event-triggered control. The resulting framework is used for stabilization of uncertain dynamical systems and is extended to systems subject to quantization and time-varying network delays. The use of a model of the plant in the controller node not only generalizes the zero-order-hold (ZOH) implementation in traditional event-triggered control schemes but it also provides stability thresholds that are robust to model uncertainties. The effects of quantized measurements are especially important in the selection of stabilizing thresholds. We are able to design error events based on the quantized variables that yield asymptotic stability compared to similar results in event-triggered control that consider nonquantized measurements which, in general, are not possible to use in digital computations. With respect to MB-NCS, the stability conditions presented here do not need explicit knowledge of the plant parameters as in previous work but are given only in terms of the parameters of the nominal model and some bounds in the model uncertainties. We consider the joint adverse effects of quantization and time delays and emphasize the expected tradeoff between the selection of quantization parameters and the admissible network induced delays.

Decentralised event-triggered cooperative control with limited communication

This note studies event-triggered control of Multi-Agent Systems (MAS) with first-order integrator dynamics. It extends previous work on event-triggered consensus by considering limited communication capabilities through strict peer-to-peer non-continuous information exchange. The approach provides both a decentralised control law and a decentralised communication policy. Communication events require no global information and are based only on local state errors; agents do not require a global sampling period or synchronous broadcasting as in sampled-data approaches. The proposed decentralised event-triggered control technique guarantees that the inter-event times for each agent are strictly positive. Finally, the ideas in this note are used to consider the practical scenario where agents are able to exchange only quantised measurements of their states.

Model-based event-triggered control with time-varying network delays

In this paper two approaches for reducing communication traffic in a control network, namely, Model-Based Networked Control Systems (MB-NCS) and event-triggered control, are unified under a single framework. The use of a model of the plant in the controller node not only generalizes the Zero-Order-Hold (ZOH) implementation in traditional event-triggered control schemes but it also provides stability thresholds that are robust to model uncertainties. With respect to MB-NCS, the stability conditions presented here do not need explicit knowledge of the plant parameters as in previous work but are given only in terms of the parameters of the nominal model and some bounds in the model uncertainties. The resulting framework is capable of increasing the update time intervals compared with the individual approaches considered in this paper.

Decentralized event-triggered consensus with general linear dynamics

The consensus problem with general linear dynamics and undirected graphs is studied in this paper by means of event-triggered control strategies. A novel consensus protocol is proposed, where each agent implements a model of the decoupled dynamics of its neighbors. Under this control strategy, transmission of information does not occur continuously but only at discrete points in time. The approach presented in this paper provides both a decentralized control law and a decentralized communication policy. We are able to design thresholds that only depend on local information and guarantee asymptotic consensus. Positive inter-event times are guaranteed for particular cases of the linear dynamics. In an extension, a positive constant is added to the thresholds in order to exclude Zeno behavior for general linear dynamics. The difference between agents trajectories can be bounded in this case and bounds on the state disagreement are derived.

Decentralized model-based event-triggered control of networked systems

This paper presents a model-based event-triggered (MB-ET) control framework for stabilization of networked systems. The controller and the events are designed in a decentralized manner, based only on local information. The knowledge of a priori model of the interconnected subsystems or agents is used at every controller node to generate estimates of the state of distant subsystems in order to reduce the frequency at which measurements need to be broadcasted. This framework allows for considerable reduction of bandwidth since every agent broadcasts its local information to other agents only when it is necessary, based on the difference between real and estimated variables. The use of models of the systems in the controller nodes not only generalizes the Zero-Order-Hold (ZOH) implementation in traditional event-triggered control schemes but it also provides stability thresholds that are robust to model uncertainties.

Cooperative aircraft defense from an attacking missile

This paper addresses a three-body pursuit-evasion scenario where an Attacker missile using Pure Pursuit guidance pursues a Target aircraft and a Defender missile launched by a wingman aims at intercepting the Attacker before it reaches the aircraft. An optimal control problem is posed which captures the goal of the Target-Defender team, namely, to maximize the separation between Target and Attacker at the instant of capture of the Attacker by the Defender. The optimal control law provides the heading angles for the Target and the Defender team.

Cooperative control with general linear dynamics and limited communication: Centralized and decentralized event-triggered control strategies

This paper presents event-triggered control techniques for the consensus problem with general linear dynamics. A novel consensus protocol is proposed, where each agent implements a model of the decoupled dynamics of its neighbors. We first provide a simple centralized condition to motivate the problem. Then, the focus is placed on designing decentralized consensus protocols. The decentralized approach proposed in this paper not only avoids the need for continuous communication between agents but also provides a decentralized and asynchronous method for transmission of information. This method gives more flexibility for scheduling information broadcasting compared to periodic and sampled-data implementations. Finally conditions are provided in order to guarantee positive inter-event times.

Active target defense differential game

A pursuit-evasion differential game involving three agents is discussed. This scenario considers an Attacker missile pursuing a Target aircraft. The Target is however aided by a Defender missile launched by, say, its wingman, to intercept the Attacker before it reaches the Target aircraft. Thus, a team is formed by the Target and the Defender which cooperate to maximize the distance between the Target aircraft and the point where the Attacker missile is intercepted by the Defender missile, and the Attacker which tries to minimize said distance. The solution to this differential game provides optimal heading angles for the Target and the Defender team to maximize the terminal separation between Target and Attacker and it also provides the optimal heading angle for the Attacker to minimize the said distance.

Cooperative Aircraft Defense from an Attacking Missile using Proportional Navigation

A three-agent pursuit-evasion scenario where an Attacker missile using Proportional Navigation guidance pursues a Target aircraft is considered in this paper. The Target is aided by a Defender missile which is launched by a wingman and aims at intercepting the Attacker before it reaches the aircraft. An optimal control problem is posed which captures the goal of the Target-Defender team, namely, to maximize the separation between Target and Attacker at the instant of capture of the Attacker by the Defender. The optimal control law provides the heading angles for the Target and the Defender team.

Model-based control of networked systems

1. Introduction.- PART I 2. Model-Based Control Systems: Stability.- 3. Model-Based Control Systems: Output Feedback and Delays.- 4. Model-Based Control Systems with Intermittent Feedback.- 5. Time-Varying and Stochastic Feedback Updates.- 6. Event-Triggered Feedback Updates.- 7. Model-Based Nonlinear Control Systems.- 8. Quantization Analysis and Design.- PART II 9. Optimal Control of Model-Based Event-Triggered Systems.- 10. Performance Analysis using Lifting Techniques.- 11. Reference Input Tracking.- 12. Adaptive Stabilization of Networked Control Systems.- 13. Multirate Model-Based Systems.- 14. Distributed Control Systems.- Appendix.- Index.- References.