Further on the controllability of networked multiple-input-multiple-output systems, an efficient, necessary, and sufficient condition is derived, where the network topology is directed and weighted and the nodes are higher-dimensional linear time-invariant systems. The new condition is easier to verify, which explicitly shows the effects of the network topology, node-system dynamics, external control inputs, and inner interactions on the controllability of the whole networked system. For networked multiple-input-multiple-output systems in several specific topologies, the corresponding conditions are expressed more precisely. The effectiveness of the conditions is demonstrated through several examples.

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In this paper, H−/H∞ multi‐objective fault detection observer design problem for linear discrete‐time systems is studied. Owing to the model inaccuracy in practical situations, system uncertainty is considered as well as the structure of the uncertainty. Sufficient conditions for the existence of the observers to guarantee the fault sensitivity and disturbance robustness in infinite frequency domain are presented. A new iterative linear matrix inequality (LMI) algorithm for the observers are proposed to obtain the solutions. In order to reduce the conservativeness, the observer design problem in finite frequency domain is also investigated. Simulation results illustrate the effectiveness of the proposed methods.