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Unmanned Aerial Vehicle (UAV) swarm offers extended coverage and is a vital solution for many applications. A key issue in UAV swarm control is to cover all targets while maintaining connectivity among UAVs, referred to as a multi-target coverage problem. With existing dynamic routing protocols, the flying ad hoc network suffers outdated and incorrect route information due to frequent topology changes. This might lead to failures of time-critical tasks. One mitigation solution is to keep the physical topology unchanged, thus maintaining a fixed communication topology and enabling static routing. However, keeping physical topology unchanged may sacrifice the coverage. In this article, we propose to maintain a fixed communication topology among UAVs, which allows certain changes in physical topology, so that to maximize the coverage. We develop a distributed motion planning algorithm for the online multi-target coverage problem with the constraint of keeping communication topology intact. As the communication topology needs to be timely updated when UAVs leave or arrive at the swarm, we further design a topology-management protocol. Experimental results from the ns-3 simulator show that under our algorithms, UAV swarms of different sizes achieve significantly improved delay and loss ratio, efficient coverage, and rapid topology update. [ABSTRACT FROM AUTHOR]

In this paper, forecast modelling based on modulation feedback is used to investigate the forced response of parametric vibration with a damper. The system is excited by both the periodic coefficient and external force terms, which have different periods. In this study, the forced response is expressed as a linear combination of harmonic components. By applying harmonic balance, the parametric equation is converted into a set of infinite-order linear algebraic equations. Then, by taking the limit to infinity, all coefficients of the harmonic components in the forced response are fully expanded into a series. The advantages of the presented approach are (1) the forced response expressed as a trigonometric series is easier to apply in practice and (2) all coefficients of the harmonic components can be determined by numerical computation. The accuracy of the proposed approach has been verified by comparing resulting phase diagram trajectories with those obtained by the standard Runge-Kutta method. The results show that the presented approach is suitable for the forced response approach and the nonlinear characterization of parametric vibration. [ABSTRACT FROM AUTHOR]