This article addresses a multi-pursuer single-evader pursuit-evasion game where the free-moving evader moves faster than the pursuers. Most of the existing works impose constraints on the faster evader, such as limited moving area and moving direction. When the faster evader is allowed to move freely without any constraint, the main issues are how to form an encirclement to trap the evader into the capture domain, how to balance between forming an encirclement and approaching the faster evader, and what conditions make the capture possible. In this article, a distributed pursuit algorithm is proposed to enable pursuers to form an encirclement and approach the faster evader. An algorithm that balances between forming an encirclement and approaching the faster evader is proposed. Moreover, sufficient capture conditions are derived based on the initial spatial distribution and the speed ratios of the pursuers and the evader. Simulation and experimental results on ground robots validate the effectiveness and practicability of the proposed method.

This paper studies the problem of distributed formation maneuver control of multi-agent systems via complex Laplacian. We will show how to change the translation, scaling, rotation, and also the shape of formation continuously by only tuning the positions of the leaders in both 2-D and 3-D spaces, where the rotation of formation in 3-D space is realized by changing the yaw angle, pitch angle, and roll angle of formation sequentially. Compared with real-Laplacian-based methods, the first advantage of the proposed complex-Laplacian-based approach is that each follower requires fewer neighbors and lesser communication. The second advantage is that non-convex and non-generic nominal configurations are allowed and the uniqueness of the complex-constraint-based target formation can be guaranteed by the non-collocated nominal agents. The third advantage is that more formation shapes can be realized by only tuning the positions of the leaders. Two simulation examples are given to illustrate the theoretical results.

In this article, we propose a general graph optimization-based framework for localization, which can accommodate different types of measurements with varying measurement time intervals. Special emphasis will be on range-based localization. Range and trajectory smoothness constraints are constructed in a position graph, then the robot trajectory over a sliding window is estimated by a graph-based optimization algorithm. Moreover, convergence analysis of the algorithm is provided, and the effects of the number of iterations and window size in the optimization on the localization accuracy are analyzed. Extensive experiments on quadcopter under a variety of scenarios verify the effectiveness of the proposed algorithm and demonstrate a much higher localization accuracy than the existing range-based localization methods, especially in the altitude direction.

This paper investigates the localization problem of a network in 2-D and 3-D spaces given the positions of anchor nodes in a global frame and inter-node relative measurements in local coordinate frames. It is assumed that the local frames of different nodes have different unknown orientations. First, an angle-displacement rigidity theory is developed, which can be used to localize all the free nodes by the known positions of the anchor nodes and local relative measurements (local relative position, distance, local relative bearing, angle, or ratio-of-distance measurements). Then, necessary and sufficient conditions for network localizability are given. Finally, a distributed network localization protocol is proposed, which can globally estimate the locations of all the free nodes of a network if the network is infinitesimally angle-displacement rigid. The proposed method unifies local-relative-position-based, distance-based, local-relative-bearing-based, angle-based, and ratio-of-distance- based distributed network localization approaches. The novelty of this work is that the proposed method can be applied in both generic and non-generic configurations with an unkn

In this article, we consider the formation tracking problem of nonholonomic multiagent systems only using relative bearing measurements between the agents. Such a practical and important yet challenging issue has been taken into limited consideration by existing approaches, which usually requires additional measurements such as relative positions. The contributions of this article are two-fold. First, a fully distributed reference velocity estimator is proposed. Under the proposed adaptive estimator, each agent can estimate the time-varying reference velocity asymptotically. Second, an input-to-state stable controller is designed according to the bearing rigid theory. Under the proposed controller, the formation with bearing-only constraints can be achieved. Finally, the proposed scheme is demonstrated and its effectiveness is verified by presenting some simulation and experimental tests.

To steer a team of multiple mobile agents to desired collective maneuvers so that the geometric pattern, translation, orientation, and scale of formation can be changed continuously, this article studies the formation maneuver control of single-integrator and double-integrator multiagent systems by a leader–follower strategy. Unlike most existing results requiring generic configurations or convex configurations, the proposed control algorithms can be applied to either nongeneric or nonconvex configurations. Distributed control algorithms are designed for the leaders and followers over directed graphs, respectively, where the formation’s maneuver parameters, such as geometric pattern, translation, orientation, and scale of formation are decided by the first leader. It is worth noting that the closed-loop tracking errors converge to zero globally. Some numerical simulations are given to illustrate the theoretical results.