Flight testbeds with multiple unmanned aerial vehicles (UAVs) are especially important to support research on multi-vehicle-related algorithms. The existing platforms usually lack a generic and complete solution allowing for software and hardware design. For such a purpose, this paper presents the design and implementation of a comprehensive multi-camera-based testbed for 3-D tracking and control of UAVs. First, the testbed software consists of a multi-camera system and a ground control system, which performs image processing, camera calibration, 3-D reconstruction, pose estimation, and motion control. In the multi-camera system, the positions and orientations of UAVs are first reconstructed by using epipolar geometric constraints and triangulation methods and then filtered by an extended Kalman filter (EKF). In the ground control system, a classical proportional-derivative (PD) controller is designed to receive the navigation data from the multi-camera system and then generates control commands to the target vehicles. Then, the testbed hardware employs smart cameras with field-programmable gate array (FPGA) modules to allow for real-time computation at a frame rate of 100 Hz. Lightweight quadcopter Parrot Bebop drones are chosen as the target UAVs, which does not require any modification to the hardware. Artificial infrared reflective markers are asymmetrically mounted on target vehicles and observed by multiple infrared cameras located around the flight region. Finally, extensive experiments are performed to demonstrate that the proposed testbed is a comprehensive and complete platform with good scalability applicable for research on a variety of advanced guidance, navigation, and control algorithms.

This article proposes a new multivehicle cooperative localization approach that combines time of arrival (TOA) with a heuristic simulated annealing extended Kalman filter (SA-EKF) to enhance positioning accuracy and robustness in urban canyons. The method incorporates a path loss model to account for the complex communication environment between vehicles, using TOA measurements for distributed EKF estimation. The integration of a simulated annealing strategy within the method is instrumental in circumventing local minima, thereby facilitating global optimisation. Furthermore, an adaptive weighted filtering correction mechanism is employed to enhance estimation accuracy and system stability. Experimental results conducted on the SUMO simulation platform and in real-world scenarios demonstrate that the proposed method offers certain advantages over existing approaches in complex, noisy environments.

Accurate and flexible calibration is a prerequisite for visual sensor networks to retrieve metric information from image data. This paper presents the design and implementation of an accurate and flexible calibration method for a class of visual sensor networks intended for 3D measurement and tracking in large volumes. The proposed method employs a generic camera model that is applicable for wide-angle lens cameras as well as for conventional cameras. It does not require all the employed cameras to share a common field of view, and only pairwise overlap is needed. In the calibration process, the poses between stereo cameras are first initialized using essential matrix decomposition and then optimized by the Levenberg-Marquardt algorithm. A weighted vision graph is proposed to select optimal transformation paths among cameras by using Dijkstra’s shortest path algorithms for multi-camera calibration. Then, the global coordinates are constructed using a four-marker calibration triangle. Finally, a Unity3D-based virtual platform, in which the total number and configurations of cameras, as well as the environment scene, can be arbitrarily edited, is designed to test the proposed calibration algorithms. Extensive experiments based on synthetic and real data are performed to demonstrate the effectiveness of the proposed multi-camera calibration method. Experimental results show that the multi-camera calibration method is accurate and easy-to-implement in the presence of noise.

In visual simultaneous localization and mapping (SLAM) systems, traditional methods often excel due to rigid environmental assumptions, but face challenges in dynamic environments. To address this, learning-based approaches have been introduced, but their expensive computing costs hinder real-time performance, especially on embedded mobile platforms. In this article, we propose a robust and real-time visual SLAM method towards dynamic environments using acceleration of feature extraction and object detection (AFO-SLAM). First, AFO-SLAM employs an independent object detection thread that utilizes YOLOv5 to extract semantic information and identify the bounding boxes of moving objects. To preserve the background points within these boxes, depth information is utilized to segment target foreground and background with only a single frame, with the points of the foreground area considered as dynamic points and then rejected. To optimize performance, CUDA program accelerates feature extraction preceding point removal. Finally, extensive evaluations are performed on both TUM RGB-D dataset and real scenes using a low-power embedded platform. Experimental results demonstrate that AFO-SLAM offers a balance between accuracy and real-time performance on embedded platforms, and enables the generation of dense point cloud maps in dynamic scenarios.

With the advancement of sensor technology, distributed processing technology, and wireless communication, Visual Sensor Networks (VSNs) are widely used. However, VSNs also have flaws such as poor data synchronization, limited node resources, and complicated node management. Thus, this paper proposes a sensor placement optimization method to save network resources and facilitate management. First, some necessary models are established, including the sensor model, the space model, the coverage model, and the reconstruction error model, and a dimensionality reduction search method is proposed. Next, following the creation of a multi-objective optimization function to balance reconstruction error and coverage, a clever optimization algorithm that combines the benefits of Genetic Algorithms (GA) and Particle Swarm Optimization (PSO) is applied. Finally, comparison studies validate the methodology presented in this paper, and the combined algorithm can enhance optimization effect while relatively reducing running time. In addition, a sensor coverage method for large-range target space with obstacles is discussed.

In adversarial environments, unmanned aerial vehicle (UAV) swarms often face challenges such as node failures, battle damage, and strong electromagnetic interference, which may result in network failures and disruptions to physical formation. To address the issue of node failures, this paper proposes a distributed self-healing algorithm to recover corrupted swarm configurations. First, a distributed flocking method is employed to achieve self-organized formation and velocity alignment within the UAV swarm. Next, a concept named “level” is introduced, along with a level generation and diffusion mechanism to establish a stable level distribution across the swarm. This mechanism enables the evaluation of the importance of each UAV in the swarm. Based on the level distribution, a distributed recursive self-healing strategy is developed to construct healing paths that repair the damage caused by failed nodes. Finally, a series of simulations are conducted to demonstrate the effectiveness of the proposed algorithm.