Networked control systems are often subject to limited communication resources. By only communicating output measurements when needed, event-triggered control is an adequate method to reduce the usage of communication resources while retaining desired closed-loop performance. In this work, a novel event-triggered control (ETC) strategy for a class of nonlinear feedback systems is proposed that can simultaneously guarantee a finite $\mathcal{L}_{p}$ - gain and a strictly positive lower bound on the inter-event times. The new ETC scheme can be synthesized in an output-based and/or decentralized form, takes the specific medium access protocols into account, and is robust to (variable) transmission delays by design. Interestingly, in contrast with the majority of existing event-generators that only use static conditions, the newly proposed event-triggering conditions are based on dynamic elements, which has several advantages including larger average inter-event times. The developed theory leads to families of event-triggered controllers that correspond to different tradeoffs between (minimum and average) inter-event times, maximum allowable delays and $\mathcal{L}_{p}$ - gains. A linear and a nonlinear numerical example will illustrate all the benefits of this new dynamic ETC scheme.

Output-Based and Decentralized Dynamic Event-Triggered Control With Guaranteed $\mathcal{L}_{p}$- Gain Performance and Zeno-Freeness

http://carmenere.ucsd.edu/jorge/publications/data/2014_NoCo-auto.pdf

Distributed event-triggered coordination for average consensus on weight-balanced digraphs

Multi-agent systems' cooperation to achieve global goals is usually limited by sensing, actuation, and communication issues. At the local level, continuous measurement and actuation is only approximated by the use of digital mechanisms that measure and process information in order to compute and update new control input values at discrete time instants. Interaction with other agents takes place, in general, through a digital communication channel with limited bandwidth where transmission of continuous-time signals is not possible. This technical note considers the problem of consensus (or synchronization of state trajectories) of multi-agent systems that are described by general linear dynamics and are connected using undirected graphs. The proposed event-triggered consensus protocol not only avoids the need for continuous communication between agents but also provides a decentralized method for transmission of information in the presence of time-varying communication delays, where each agent decides its own broadcasting time instants based only on local information. This method gives more flexibility for scheduling information broadcasting compared to periodic and sampled-data implementations.

Periodic Event-Triggered Synchronization of Linear Multi-Agent Systems With Communication Delays

http://www.rug.nl/staff/m.cao/2014_automatica_event.pdf

Asynchronous decentralized event-triggered control

This paper studies a distributed event-triggered communication and control strategy that solves the multi-agent average consensus problem. The proposed strategy does not rely on the continuous or periodic availability of information to an agent about the state of its neighbors, but instead prescribes isolated event times where both communication and controller updates occur. In addition, all parameters required for its implementation can be locally determined by the agents. We show that the resulting network executions are guaranteed to converge to the average of the initial agents' states, establish that events cannot be triggered an infinite number of times in any finite time period (i.e, no Zeno behavior), and characterize the exponential rate of convergence. We also provide sufficient conditions for convergence in scenarios with time-varying communication topologies. Simulations illustrate our results.

http://carmenere.ucsd.edu/jorge/publications/data/2014_NoCo-acc.pdf

Zeno-free, distributed event-triggered communication and control for multi-agent average consensus

The paper presents a reconfigurability analysis of multirotor unmanned aerial vehicles (UAVs) with four and six rotors. A method for structural reconfigurability analysis is introduced, which is then applied to a structural model of the multirotors. The failures lead either to a blockage or to the complete loss of a rotor. The analysis shows that, independent of the systems' parameters, a quadrotor is not able to hover with a failed actuator, while the reconfigurability of hexrotors strongly depends on the configuration of the clockwise and counter clockwise rotating rotors. The results concerning the reconfiguration of a rotor loss in a hexrotor system are evaluated in simulations, where the reconfiguration is performed by using the virtual actuator technique.

Structural reconfigurability analysis of multirotor UAVs after actuator failures

Decentralized event-based control: Stability analysis and experimental evaluation

This paper presents experimental results that have been obtained by applying an active fault-tolerant control (FTC) framework to multirotor UAVs subject to actuator failures. The proposed fault-tolerant control scheme combines a bank of observers for diagnosis with the concept of the virtual actuator for control reconfiguration. Therefore, an evaluation method for fault detection and isolation is presented, which guarantees that the diagnosis result is always adequate for control reconfiguration. The experiments with a hovering multirotor UAV subject to a rotor failure validate the applicability of the proposed FTC scheme under real-time constraints and in the presence of natural uncertainties, measurement noise and process disturbances.

http://ieeexplore.ieee.org/iel7/7602795/7739711/07739739.pdf

Daniel Vey

Papers

Structural reconfigurability analysis of multirotor UAVs after actuator failures

Decentralized event-based control: Stability analysis and experimental evaluation

Experimental evaluation of an active fault-tolerant control scheme for multirotor UAVs

Control reconfiguration of physically interconnected systems by decentralized virtual actuators

Plug-and-play reconfiguration of decentralised controllers of interconnected systems