Multicopters are attracting more and more attention these years. In the design stage, designers and users wonder if an assembled multicopter can meet their performance requirements, such as hovering endurance, system efficiency, maximum load, maximum pitch, and maximum flight distance. However, in practice, they used to evaluate the performance of a multicopter through lots of flight experiments or by experience, which are normally inefficient and costly. This motivates us to propose a comprehensive offline evaluation algorithm of multicopter performance. The performance indices considered are mainly determined by the propulsion system, including motors, propellers, electronic speed controllers, and batteries. Therefore, in the first stage of this research, models are established for the components of a propulsion system. In order to facilitate the application, only technical specifications of components offered by manufacturers are required as the input of the models. Based on the models and their relationships, equations describing performance indices are established and then solved to perform the evaluation. Finally, several examples are given to demonstrate the efficiency of the proposed evaluation method. As a result, a website ( www.flyeval.com) is established, which can provide users with the performance evaluation mentioned in this paper.

Unmanned Aerial Vehicles (UAVs) are now becoming increasingly accessible to amateur and commercial users alike. An air traffic management (ATM) system is needed to help ensure that this newest entrant into the skies does not collide with others. In an ATM, airspace can be composed of airways, intersections and nodes. In this paper, for simplicity, distributed coordinating the motions of Vertical TakeOff and Landing (VTOL) UAVs to pass an airway is focused. This is formulated as a tube passing problem , which includes passing a virtual tube, inter-agent collision avoidance and keeping within the virtual tube. Lyapunov-like functions are designed elaborately, and formal analysis based on invariant set theorem is made to show that all UAVs can pass the virtual tube without getting trapped, avoid collision and keep within the virtual tube. What is more, by the proposed distributed control, a VTOL UAV can keep away from another VTOL UAV or return back to the virtual tube as soon as possible, once it enters into the safety area of another or has a collision with the virtual tube during it is passing the virtual tube. Simulations and experiments are carried out to show the effectiveness of the proposed method and the comparison with other methods.

This study proposes a uniform passive fault-tolerant control (FTC) method for a quadcopter that does not rely on fault information subject to one, two adjacent, two opposite, or three rotor failure. The uniform control implies that the passive FTC is able to cover the condition from quadcopter fault-free to rotor failure without the need for controller switching. To achieve the purpose of passive FTC, the fault of rotors is modeled as a lumped disturbance acting on the virtual control of the quadcopter system. The estimated disturbance is used directly in the passive FTC. At the same time, a modified controller structure is designed to achieve the passive FTC ability for two and three rotor failure. To avoid the control allocation switching from the fault-free control to the FTC, a dynamic control allocation is used. In addition, the closed-loop stability is analyzed in the presence of up to three rotor failure. To validate the proposed uniform passive FTC method, outdoor experiments are performed for the first time , which have demonstrated that the hovering quadcopter is able to recover from one rotor failure using the proposed controller and resume its mission even if two adjacent, two opposite, or three rotors fail, without the need for any rotor fault information or controller switching. Experimental results can be viewed in this video: https://youtu.be/N1OudPXFXnE . Source code is placed on https://github.com/RflyBUAA/DegradedControl.git

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.