Rotary-wing Unmanned Aerial Vehicle Research Articles

Dynamic Aerial Wireless Power Transfer Optimization

Unmanned aerial vehicle (UAV)-enabled wireless power transfer (WPT) is a viable solution to remotely charge several energy receivers (ERs) in areas with intermittent access to a source of energy. However, given the limited available energy in the on-board battery of the UAV, which is mainly required to suffice propulsion energy consumption, the UAV struggles to roam seamlessly for long intervals. A key challenge is thus to efficiently use the limited battery energy, and accordingly prolong the UAV’s endurance, via controlling the underlying associated parameters such as cruising velocity. To further extend the battery lifetime, the UAV can also harness other sources of sustainable energy, such as sunlight, via solar energy harvesting. This paper studies a UAV-enabled WPT system, where a rotary-wing UAV transfers radio frequency (RF) wireless energy to several ERs at known locations. To offer uninterrupted seamless service, the UAV also harvests solar energy using solar panels. Considering the propulsion energy consumption of the UAV, we maximize the minimum average power received among all ERs over a finite cycle duration by jointly optimizing the UAV’s time allocation between harvesting and charging, flight trajectory as well as velocity, and transmit power allocation. Due to the non-convexity of the problem, we utilize the block coordinate descent (BCD) and successive convex approximation (SCA) methods. Numerical results show that the proposed solution outperforms benchmark schemes.

Sum-rate maximization for UAV-enabled two-way relay systems

In this paper, an Unmanned Aerial Vehicle (UAV)-enabled two-way relay system with Physical-layer Network Coding (PNC) protocol is considered. A rotary-wing UAV is applied as a mobile relay to assist two ground terminals for information interaction. Our goal is to maximize the sum-rate of the two-way relay system subject to mobility constraints, propulsion power consumption constraints, and transmit power constraints. The formulated problem is not easy to solve directly because it is a mixed integer non-convex optimization problem. Therefore, we decompose it into three sub-problems, and use the mutation arithmetic of the Genetic Algorithm (GA) and Successive Convex Approximation (SCA) to dispose. Besides, a high-efficiency iterative algorithm is proposed to obtain a locally optimal solution by jointly optimizing the time slot pairing, the transmit power allocation, and the UAV trajectory design. Numerical results demonstrate that the proposed design achieves significant gains over the benchmark designs.

A Multichannel Wireless UAV Charging System With Compact Receivers for Improving Transmission Stability and Capacity

This article presents a multichannel wireless rotary-wing unmanned aerial vehicle (UAV) charging system with compact receivers for improving transmission stability and capacity. The multichannel scheme and associated landing structure are proposed according to the application challenges. It contains multiple null-cross-coupled transmission paths to improve charging capability, and the structure stabilizes the charging. Compact and shielding-free receivers are embedded to avoid affecting the airflow and the weight of the flight. Misalignment-tolerant unipolar coils are designed based on transmission and field characteristics, which cooperate with the scheme for efficient coupling and restrained leakage flux. The output characteristics of the multichannel system are analyzed based on theoretical modeling and simulation. A multichannel output estimation control strategy is implemented, based on the deduced mapping relations and transmitter-side information, to regulate output currents and eliminate circulating currents. It is realized without real-time massive communication or measuring on board, and the parallel channels avoid influences of faulty channels. A multichannel experimental prototype is established and tested to prove the feasibility of the design, which can be applied to rotary-wing UAV autonomous charging flexibly.

Biplane Trajectory Tracking Using Hybrid Controller Based on Backstepping and Integral Terminal Sliding Mode Control

A biplane quadrotor is a hybrid type of Unmanned Aerial Vehicle (UAV) that has advantages of both fixed-wing and rotary-wing UAVs. In this study, we design controllers using (i) Backstepping Control (BSC), (ii) Integral Terminal Sliding Mode Control (ITSMC), and (iii) Hybrid control (ITSMC + BSC), where the ITSMC controls attitude and BSC controls the altitude subsystems as per the mathematical model of biplane quadrotor. The performance of these controllers is evaluated based on the autonomous trajectory tracking containing all possible maneuvers and operation modes that the biplane quadrotor can perform. Performance analysis reveals that the BSC-based controller is susceptible to a steady-state error in altitude tracking when mass is changed. In contrast, the ITSMC and the “hybrid” controllers achieve smooth tracking in a finite time. Furthermore, the “hybrid” controller outperforms the other designs, reducing tracking error and faster convergence time.

URLLC in UAV-enabled multicasting systems: A dual time and energy minimization problem using UAV speed, altitude and beamwidth

Realizing ultra-high reliability for short packets in sixth-generation (6G) networks is a crucial task for network designers as classical Shannonian capacity bounds become obsolete. Moreover, for multiuser communications, due to distinct aerodynamics, the trajectory design for a fixed-wing unmanned aerial vehicle (UAV) fundamentally differs from rotary-wing UAVs, which poses a challenge for systems designers. This paper addresses these challenges and relies on a fixed-wing UAV-enabled multicasting system to deliver common short blocklength ultra-reliable and low-latency (URLLC) packets to the ground nodes (GNs) using a Snake Traversal trajectory path. To accomplish this task, we consider the fly-and-communicate protocol for the UAV, where the UAV sweeps a large rectangular area to disperse a common file to GNs with obscure positions. In this vein, we investigate the dual time and energy minimization problems by presenting a quasi-optimal design of the UAV’s flying speed, altitude, and antenna beamwidth. Simulation results of numerical search reveal the optimal altitude and half-power beamwidth, which minimize the completion time and energy consumption, respectively. Moreover, for optimized beamwidth, the UAV speed monotonically increases with the altitude, whereas both the completion time and energy consumption monotonically decrease with the altitude. We also analyze the effects of the blocklength and decoding error probability on optimal UAV speed, completion time, and energy consumption. Additionally, simulation results show that for the completion time, the percentage difference between minimum UAV altitude hmin and maximum UAV altitude hmax is 195.252%, whereas for the energy consumption, the percentage difference at hmin and hmax is 196.912%. Similarly, for the completion time, the percentage difference at minimum UAV antenna beamwidth θmin and maximum UAV antenna beamwidth θmax is 181.586%, whereas for the energy consumption the percentage difference at θmin and θmax is 189.269%. This demonstrates the efficacy of the proposed technique is almost two times in reducing the completion time and the energy consumption effectively between the minimum and the maximum values of the UAV altitude and the UAV antenna beamwidth. Lastly, the results show that for both the blocklength and decoding error probability, the UAV speed monotonically increases, while completion time and energy consumption monotonically decrease.

Adaptive backstepping controller design of quadrotor biplane for payload delivery

Performance of the UAVs for a particular application can be enhanced by hybrid design, where take-off, hover, and landing happen like rotary-wing UAVs, and flies like fixed-wing UAVs. A backstepping controller and an adaptive backstepping controller are designed for trajectory tracking and payload delivery in a medical emergency or medical substance delivery like vaccine delivery in the presence of wind gust. Simulation results show that the backstepping controller effectively tracks the trajectory during the entire flight envelope, including take-off, hovering, the transition phase, level flight mode, and landing. A comparison between Backstepping, Integral Terminal Sliding Mode (ITSMC) and Adaptive Backstepping controllers for payload delivery show that the adaptive backstepping controller effectively tracks the altitude and attitude. ITSMC is capable of tracking the desired trajectory for a change in the mass but has sluggish response. The backstepping controller generates a steady-state error in altitude during the mass change in biplane quadrotor.

Simulation analysis and experimental research on the safety distance of UAV inspection on transmission lines

In recent years, unmanned aerial vehicle (UAV) inspection has become one of the main means of daily operation and maintenance of overhead transmission lines. Since the key components of the UAV inspection system are composed of electronic components, it relies on data communication to realize data link transmission. In the actual operation process, the complex electromagnetic field environment has an obvious impact on its control and communication performance, especially when inspecting near the DC line. In this paper, combined with the research on the safety assurance technology of UAV inspection operations, the electromagnetic field simulation model of the UAV inspection operation on DC transmission lines is established. The electromagnetic field distribution around the wire is analyzed when the UAV is at different inspection distances, and the influence range and degree of the DC electromagnetic field on UAV inspection system are obtained. A true test platform for the inspection safety distance of the ±500 kV line UAV inspection was built, and the inspection safety distance test and research of the small rotary-wing UAV with a typical size, structure, and material was carried out. Through the test, when the current of the transmission line is 3 kA, the minimum safety distance of the UAV inspection operation of the ±500 kV DC transmission line straight tower is 3 m, and the distance is corrected in combination with the current. The research results of this paper can provide technical support for the inspection operation of small multi-rotor UAVs on ±500 kV transmission lines.

Use of Unmanned Aerial Vehicles for 3D topographic Mapping and Monitoring the Air Quality of Open-pit Mines

Recently remarkable advancement development of unmannedaerial vehicles (UAVs) has been observed and their applications have beenshown in many fields such as agriculture, industry, and environmentalmanagement. However, in the mining industry, the application of UAVtechnology remains potential. This paper presents a low-cost unmannedaerial vehicle technology-based system for 3D mapping and air qualitymonitoring at open-pit mine sites in Vietnam. The system includes severaldust sensors that are mounted on a low-cost rotary-wing type UAV. Thesystem collects a variety of data, mainly images and airborne pollutantconcentrations. To evaluate the performance of the proposed system, fieldtests were carried out at the Coc Sau coal mine. Based on the imagestransmitted to the ground monitoring station, large scale 3D topographicmaps were successfully modeled. In addition, sensors mounted on theUAV system were able to monitor the levels of environmental variablesassociated with the air quality within the pit such as temperature, dust, CO,CO2, and NOx. The field test results in this study illustrate the applicabilityof the low-cost UAV for the 3D mapping and the air quality monitoring atlarge and deep coal pits with relatively high accuracy.

Discrete space-based route planning for rotary-wing UAV formation in urban environments

The route planning problem for rotary-wing UAV formation is studied in discrete urban environments. First, a discrete-space consensus algorithm (DSCA) integrating asynchronous planning and grouping mechanism is developed to make the rotary-wing UAVs converge to the desired formation. Then the DSCA is combined with the improved rapidly-exploring random tree (IRRT) algorithm to enable the rotary-wing UAV formation to avoid the obstacles. Finally, the time information of waypoints is complemented by resolving the conflicts among multiple rotary-wing UAVs, thus reducing the rotary-wing UAVs’ time gap of reaching the destinations. The proposed method extends the original consensus theory in the discrete space and for the obstacle avoidance issue. Also, it is valid in the route planning problem for rotary-wing UAV formation considering the real urban environments.

An Object Detection Algorithm for Rotary-Wing UAV Based on AWin Transformer

The increasing use of rotary-wing UAVs poses security risks, which makes image detection of rotary-wing UAVs a critical issue. This paper proposes an object detection algorithm for rotary-wing UAVs based on a transformer network. A self-attention mechanism is used to utilize the local contextual information to extract the features of the rotary-wing UAV more effectively, which improves the accuracy of object detection. Meanwhile, a new self-attention mechanism is designed, in which the query vector and the key vector of the surrounding annular area are calculated separately and then concatenated by different heads of attention. Experimental results show that, compared with existing algorithms, the proposed algorithm improves the mean average precision by 1.7% on the proposed rotary-wing UAV dataset.

Learning Nonlocal Quadrature Contrast for Detection and Recognition of Infrared Rotary-Wing UAV Targets in Complex Background

Learning Nonlocal Quadrature Contrast for Detection and Recognition of Infrared Rotary-Wing UAV Targets in Complex Background

Design of a class of generalized parallel mechanisms for adaptive landing and aerial manipulation

In this paper, the concept of adaptive landing and aerial manipulation mechanism (ALAM) is proposed. The mechanism can be installed on a rotary-wing unmanned aerial vehicle (UAV), allowing the UAV to land on uneven terrain and perform aerial manipulation. Based on the Lie group, the design principles of the ALAM are proposed by combining the advantages of the generalized parallel mechanism. The design procedure of the mechanism is introduced. Then, the structure synthesis is performed for the ALAMs with 1 to 3 degrees of freedom (DOF) generalized moving platform. In order to evaluate the landing performance of the mechanism, two general indexes for evaluating landing adaptability and stability are established based on three typical structured terrains. Multi-objective parameter optimization of a 3T1R ALAM is carried out. Finally, a prototype is developed and validated for its workspace range and landing performance.

Launchable rotary wing UAV designs and launch mechanism designs for rotary wing UAV

In recent years, rotary-wing unmanned aerial vehicles have been used in many areas. Rotary wing unmanned aerial vehicle (UAV) can carry different payloads according to their duties. For example; if they carry cameras, they are used for reconnaissance / surveillance, cargo if they carry cargo, agriculture if they carry pesticides, mapping if they carry an advanced camera and mapping system, and communication if they carry a base station or relay. Rotary-wing unmanned aerial vehicles are usually commanded to take off manually by a trained UAV operator. Before takeoff, the rotary-wing unmanned aerial vehicle is prepared for take-off by the UAV operator and this preparation takes approximately five minutes. It takes time for rotary-wing unmanned aerial vehicles to take off from the runway and reach their cruising speed, causing time loss in critical areas. A rotary-wing unmanned aerial vehicle launch assembly and a rotary-wing unmanned aerial vehicle with an opening mechanism that can open the thrust arms after launch and continue to fly can be the solution to this time loss. Rotary-wing drones capable of launching and without the intervention of the UAV operator will play an important role in emergency response and defense, where situational awareness is often required. For example; firefighters responding to fires can take advantage of the ability to quickly launch rotary-wing unmanned aerial vehicles from a stationary or moving fire truck. Thanks to the day / thermal camera on the launched rotary wing unmanned aerial vehicles, valuable information can be obtained about the progress of the fire and the damage caused by the fire. Thanks to rapid awareness, the fire can be intervened and fought faster. Similarly, military personnel can quickly deploy launchable rotary-wing drones for reconnaissance and surveillance and perform their duties. In order to be applicable to various types of missions, it is important that the rotary wing unmanned aerial vehicle be portable and low in volume. Since the launchable rotary-wing unmanned aerial vehicle proposed in the thesis has an arm release mechanism after launch, it can automatically open and generate thrust after launching its arms. In this way, it helps lower volume coverage before being launched. This also reduces air friction during launch. It can be deployed to autonomous systems effortlessly as it has closed package, mobile and self-arm management. Different mechanisms will be studied to create an efficient design. A mechanism that allows it to open its arms in a short time will be used in the self-arm-opening management design. Throwable rotary wing unmanned aerial vehicle and launch mechanism will be designed and 3D printers will be used for prototype.

Investigation of 3D models acquired with UAV oblique images

The concept of oblique image acquisition entered the literature long after the overhead photogrammetric acquisition techniques. The oblique image acquisition technique is applied to model the edge surfaces of buildings that cannot be obtained with vertical (nadir) image acquisition and eliminate the problems that arise in the orthorectification of high-rise buildings in urban areas. Oblique image acquisition by Unmanned Aerial Vehicles (UAV) independent of aerial photogrammetry is considered possible with unique flight plans. How convenient oblique image acquisition with the help of UAVs is and how it affects the final product is a popular topic studied by researchers. In this study, oblique image acquisition was performed using a rotary-wing UAV (Parrot ANAFI) whose camera can move 180°. With the help of the 3D models obtained, the building was drawn in vector and evaluated to scale. As a result, it has been understood that almost all structural deficiencies in the final products can be eliminated by oblique images. However, it has been revealed that there is still a need for other methods for structures that do not have patterns, such as flat walls.

Three-dimensional trajectory optimization for secure UAV-enabled cognitive communications

Unmanned aerial vehicles (UAVs) are envisioned as a promising means of providing wireless services for various complex terrains and emergency situations. In this paper, we consider a wireless UAV-enabled cognitive communication network, where a rotary-wing UAV transmits confidential information to a ground cognitive user over the spectrum assigned to primary users (PUs), while eavesdroppers attempt to wiretap the legitimate transmission. In order to enhance the secrecy performance of wireless communications, the secrecy rate (SR) of the UAV-enabled cognitive communication system is maximized through optimizing UAV three-dimensional (3D) flying trajectory while satisfying the requirements of UAV's initial and final locations and guaranteeing the constraint of maximum speed of UAV and the interference threshold of each PU. However, the formulated SR maximization (SRM) problem is non-convex. For the purpose of dealing with this intractable problem, we employ the difference of two-convex functions approximation approach to convert the non-convex optimization problem into a convex one, which is then solved through applying standard convex optimization techniques. Moreover, an iterative 3D trajectory optimization algorithm for SRM scheme is proposed to achieve the near-optimal 3D trajectory. Simulation results show that our proposed 3D trajectory optimization based SRM algorithm has good convergence, and the proposed SRM scheme outperforms the benchmark approach in terms of the SR performance.

UAV low-altitude obstacle detection based on the fusion of LiDAR and camera

In this paper, aiming at the flying scene of the small unmanned aerial vehicle (UAV) in the low-altitude suburban environment, we choose the sensor configuration scheme of LiDAR and visible light camera, and design the static and dynamic obstacle detection algorithms based on sensor fusion. For static obstacles such as power lines and buildings in the low-altitude environment, the way that image-assisted verification of point clouds is used to fuse the contour information of the images and the depth information of the point clouds to obtain the location and size of static obstacles. For unknown dynamic obstacles such as rotary-wing UAVs, the IMM-UKF algorithm is designed to fuse the distance measurement information of point clouds and the high precision angle measurement information of image to achieve accurate estimation of the location and velocity of the dynamic obstacles. We build an experimental platform to verify the effectiveness of the obstacle detection algorithm in actual scenes and evaluate the relevant performance indexes.

Development and Validation of a LQR-Based Quadcopter Control Dynamics Simulation Model

AbstractThe growing applications involving unmanned aerial vehicles (UAVs) are requiring more advanced control algorithms to improve rotary-wing UAVs’ performance. To preliminarily tune such advanc...

Micro-Doppler Shift and Its Estimation in Rotary-Wing UAV Sub-6 GHz Communications

Rotary-wing unmanned aerial vehicles (UAVs) can be potentially used in wireless communications and therefore attract research from both academia and industry recently. However, most UAV air-to-ground channel models under 6 GHz have ignored the micro-Doppler effects due to the UAV’s propellers. In this letter, we reveal its principle and develop a method to estimate the micro-Doppler, including sounding waveform design, channel modeling, and Doppler frequency estimation. Our simulation results demonstrate that the estimated root-mean-squared error of micro-Doppler is smaller than 18.83 Hz for 963.09 Hz micro-Doppler frequency shift resulting from the rotation of the propellers in the rotary-wing UAV sub-6 GHz communications systems.

Characterizing vertical distribution patterns of PM2.5 in low troposphere of Shanghai city, China: Implications from the perspective of unmanned aerial vehicle observations

The vertical distribution patterns of PM2.5 (particulate matters with diameters ≤2.5 μm) are crucial for understanding the aggregation, dispersion, and regional transport of PM2.5. However, due to the measurement limitation, the vertical observational data o is difficult to be obtained and is relatively insufficient at present stage. With this consideration, two electric-fueled rotary-wing unmanned aerial vehicles (UAVs) are used in this study to reveal the vertical distribution of PM2.5 in Shanghai of China. Totally 53 vertical profiles of PM2.5 concentration and meteorological factors are collected to reveal the vertical distribution pattern of PM2.5. The results indicate that PM2.5 vertical concentration, especially the maximum of the PM2.5 vertical concentration, shows a good correlation with surface PM2.5 concentration, which means it is possible to use surface PM2.5 concentration to extrapolate PM2.5 vertical concentration. In terms of meteorological factors, low wind speed and northerly (or northwesterly) wind direction significantly contribute to the accumulation of high concentration PM2.5 in Shanghai during the winter. Furthermore, the low height of the planetary boundary layer (PBL) facilitates the accumulation of pollutants near the ground, but it is not imperative for the vertically high concentration of PM2.5, since vertically high PM2.5 concentration exists within high PBL as well. It has been concluded that low PBL height is not mandatory for well vertical mixing within it, for the vertically even distribution of PM2.5 occurred under both low and high PBL. In terms of the effect the temperature, although temperature makes a significant contribution to the inverse distribution of PM2.5, no significant linear correlation was found between temperature and PM2.5 vertical distribution. The findings in this study could help to understand the vertical distribution patterns of PM2.5 during the winter, and provide more evidence of how other factors impact these patterns.

New Energy Consumption Model for Rotary-Wing UAV Propulsion

Accurate and convenient energy consumption models (ECMs) for rotary-wing unmanned aerial vehicles (UAVs) are important for UAV communication designs. Existing models are complex and inconvenient to use. In this letter, a simple and easy-to-use model with closed-form expression as a function of the initial velocity, acceleration and time duration is derived. Using this model, the UAV flight control parameters, such as polling force and tilt angle, are analyzed in analytical form. Numerical results show the validity and reliability of the proposed model.