This paper's aim is to present a novel design technique for distributed estimation in networked systems. The problem assumes a network of interconnected agents each one having partial access to measurements from a linear plant and broadcasting their estimations to their neighbours. The objective is to reach a reliable estimation of the plant state from every agent location. The observer's structure implemented in each agent is based on local Luenberger-like observers in combination with consensus strategies. The paper focuses on the following network related issues: delays, packet dropouts and communication policy (time and event-driven). The design problem is solved via linear matrix inequalities and stability proofs are provided. The technique is of application for sensor networks and large scale systems where centralized estimation schemes are not advisable and energy-aware implementations are of interest. Simulation examples are provided to show the performance of the proposed methodologies.

This brief tackles the problem of designing suboptimal H₂/H_∞ controllers for linear networked control systems (NCS) subject to time-varying delays and packet dropouts. The formulation provides state feedback NCS controllers allowing to tradeoff performance and disturbance rejection. The control objective consists in designing an H₂ suboptimal control minimizing a quadratic performance index, with a disturbance rejection constraint (H_∞ constraint). To characterize the network, only the lower and upper bounds for the delay, as well as the maximum number of consecutive dropouts are required. The approach relies on the formulation of the problem in terms of the minimization of a single scalar parameter, that can be cast as a standard linear matrix inequality (LMI) problem, yielding a suboptimal cost-guaranteed solution. As a difference from previous works, the solution provided is independent of initial conditions. Stability and robustness properties of the proposed controller are theoretically demonstrated and tested on an experimental testbed consisting in the stabilization of a robot arm in the proximities of the unstable upright position. The application shows good performance and disturbance rejection capabilities even for stringent network conditions.