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This article provides an introduction to event-triggered coordination for multi-agent average consensus. We provide a comprehensive account of the motivations behind the use of event-triggered strategies for consensus, the methods for algorithm synthesis, the technical challenges involved in establishing desirable properties of the resulting implementations, and their applications in distributed control. We pay special attention to the assumptions on the capabilities of the network agents and the resulting features of the algorithm execution, including the interconnection topology, the evaluation of triggers, and the role of imperfect information. The issues raised in our discussion transcend the specific consensus problem and are indeed characteristic of cooperative algorithms for networked systems that solve other coordination tasks. As our discussion progresses, we make these connections clear, highlighting general challenges and tools to address them widespread in the event-triggered control of networked systems.

In this paper two approaches for reducing communication traffic in a control network, namely, ModelBased Networked Control Systems (MB-NCS) and eventtriggered 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. I. INTRODUCTIONN Networked Control Systems (NCS) a digital communication network is used to transfer information among the components of a control system. NCS can also help to improve efficiency, flexibility, and reliability of the network interconnected system reducing reconfiguration and maintenance costs [1]. In contrast, the protocols used to establish an ordered communication between nodes and the number of control systems and different applications that share the communication network introduce time delays and loss of information. These situations force us to revaluate the tools that are commonly used in control design in order to account for limited feedback information in the analysis and design of NCS compared to traditional point-to-point control systems. Extensive research has been done in the area of NCS as described in [2] and references therein. Reducing the amount of communication between sensor and controller nodes without compromising the stability of the control system has been a topic of many papers. In particular, Walsh, et al.[3] introduced a network control protocol TryOnce-Discard (TOD) to allocate network resources to the different nodes in a Networked Control System, all of them may access the network at any time assuming each access occurs before the Maximum Allowable Transfer Time (MATI). The work in [4]-[5] uses more efficiently the packet structure, that is, reduction on communication is obtained by sending packets of information using all data bits available (excluding overhead) in the structure of the packet.Both authors are with the