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This article investigates the targeted bipartite consensus problem of opinion dynamics in cooperative–antagonistic networks. Each agent in the network is assigned with a convergence set to represent a credibility interval, in which its opinion is trustworthy. The network topology is characterized by a signed switching digraph. The objective is to achieve the bipartite consensus targeted within these credibility intervals. A gradient term is introduced in the opinion dynamics besides the consensus term. Under the assumption that the underlying graph is uniformly jointly strongly connected and structurally balanced, it is first shown that the considered opinion dynamics reaches the targeted bipartite consensus within the intersections of the convergence sets associated with two antagonistic groups. Next, by relaxing the connectivity condition to uniform joint quasistrong connectivity, the targeted bipartite consensus result is also proven with an additional convergence set assumption. Numerical examples are provided to validate the proposed theoretical results. [ABSTRACT FROM AUTHOR]

In signed networks, the cooperation and antagonism cause great difficulties for their behavior analysis, especially, when they are subject to time-varying topologies. This is different from unsigned networks involving only cooperations, of which behavior analysis can be feasibly achieved based on the nonnegative matrix theory. With these facts, this article first bridges a relation between signed and unsigned networks and then takes advantage of the relation for the behavior analysis of signed networks under directed switching topologies. In particular, a solution is provided for the connection of signed and unsigned networks via solving a class of linear dynamic systems, which is obtained by separating antagonisms from cooperations. The solution makes it possible to employ the convergence results for unsigned networks to address the convergence issues for signed networks. If the joint spanning tree condition is met, then switching signed networks can achieve the quasi-interval bipartite consensus. Moreover, the established results can be applied to signed networks with both continuous-time and discrete-time dynamics. [ABSTRACT FROM AUTHOR]

Due to the sensors’ latency, unsynchronized clocks, triggering, and data jams, there usually exists an inevitable time offset between image streams and inertial measurement unit (IMU) data sequences in visual-inertial systems. Such a time offset has a significant effect on the robustness and accuracy of the system. In this article, an online temporal calibration algorithm is proposed based on a modified projection model. In particular, we introduce the time offset as an estimated state variable in an extended Kalman filter (EKF)-based visual-inertial odometry (VIO). In addition, in order to align camera and IMU measurements in the time domain, the projection model is sophisticatedly given, and we propose a systematic method to obtain features’ virtual observations with respect to the time offset. Our approach is general and can be easily applied to different EKF-based VIO frameworks. Experimental results demonstrate that the time offset is calibrated quickly and accurately even compared with other existing offline tools, and the proposed online temporal calibration method significantly improves the performance of VIO. [ABSTRACT FROM AUTHOR]

This paper investigates the coordinated attitude synchronization and tracking problems of multiple rigid-body spacecraft subject to inaccurate inertial parameters. Two adaptive distributed control algorithms are developed based on communications among spacecraft connected through a switching communication network, which allow each switching subgraph to be disconnected. In the first place, by introducing an adaptive strategy for the inertial parameters, a distributed attitude synchronization control algorithm is designed. In particular, a gain selection criteria is specified for the asymptotic attitude synchronization under uniform joint connectivity. In the second place, for the coordinated attitude tracking problem, we first develop a distributed observer for each spacecraft to estimate the reference information associated with a leader over a switching network with uniform joint quasi-strong connectivity. Then, we propose an adaptive tracking scheme such that each spacecraft tracks the estimated information. Finally, numerical examples are given to validate the effectiveness of two proposed adaptive distributed control algorithms. [ABSTRACT FROM AUTHOR]

This paper proposes a distributed formation control approach for a team of vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) subject to switching topologies. The communication topology among UAVs is allowed to be with weak connectivity, in the sense of satisfying a uniformly jointly connected assumption. Since VTOL UAV systems are typically underactuated, a hierarchical framework is introduced such that a distributed control scheme can be established using neighboring positions and velocities. In particular, a distributed command force is developed to fulfill the formation objective, and an applied torque is synthesized for the attitude to track the command attitude. This command attitude is extracted from the command force by using a backstepping idea. In addition, an auxiliary system with appropriate parameters is introduced to preserve thrust saturation constraint, to guarantee nonsingular command attitude extraction and to avoid usage of neighboring acceleration information. With proper choices of Lyapunov functions, explicit selection criteria for the control parameters are formulated to ensure the asymptotic stability of the closed-loop system. Simulations and experiments are provided to validate the proposed theoretical results. [ABSTRACT FROM AUTHOR]

This brief considers the synchronization problem of coupled nonlinear dynamical systems over time-varying interaction graphs. We first show that infinite joint connectivity is necessary for achieving globally asymptotic synchronization. We then show that the commonly used Lipschitz condition on the nonlinear self-dynamics is not sufficient to ensure synchronization even for an arbitrarily large coupling strength. A sufficient synchronization condition is established in terms of the times of connectivity, the integral of the Lipschitz gain, and the network parameters. [ABSTRACT FROM AUTHOR]