Special Issue "Unmanned Aerial Vehicles (UAVs) II"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editor

Dr. Sunghun Jung
E-Mail Website
Guest Editor
Determent of Smart Mobile Convergence System, Chosun University, Gwangju, 61452, Korea
Interests: energy-efficient path planning, battery-state estimation, unmanned-system algorithm and SW development
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Unmanned aerial vehicle (UAV) services such as sensing, mapping, goods and equipment delivery, inspection, and monitoring have started to grow rapidly with the rapidly falling prices of both drones and the sensors mounted on them. Many of these services involve the gathering of data and their processing with complex algorithms either in real time or in the cloud, and precise navigation and path-planning of the drones. We invite articles on all aspects of these problems involving UAV services, including data processing and sensor fusion, obstacle and collision avoidance, trajectory generation for single UAVs or groups of UAVs, communications and networks among UAVs, mission planning for various purposes, and so on.

Articles may be submitted in all the areas that currently abound in the news: inspection of farms, vineyards, ranch animals, petrochemical refineries, oil pipelines, and battlefields; delivery of pesticides and herbicides, food in restaurants, and packages to remote areas and residences; the cutting edge of photography, filming, and journalism; the mapping of various fields—optical, magnetic, acoustic, and chemical; and reconnaissance and tactical bombing in battlefield. Most of these applications have so far been performed by single UAVs, though use of a multiplicity of UAVs can significantly improve performance.

Dr. Sunghun Jung
Guest Editor

Manuscript Submission Information

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Keywords

  • unmanned aerial vehicle (UAV)
  • data processing and sensor fusion
  • obstacle and collision avoidance
  • trajectory generation
  • communications and networks
  • mission planning

Published Papers (11 papers)

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Research

Open AccessFeature PaperArticle
Advantages of Gamma-Radiometric and Spectrometric Low-Altitude Geophysical Surveys by Unmanned Aerial Systems with Small Scintillation Detectors
Appl. Sci. 2021, 11(5), 2247; https://doi.org/10.3390/app11052247 - 04 Mar 2021
Viewed by 367
Abstract
Unmanned aerial systems (UAS) for airborne gamma-ray surveys in radioecological and geological research are being increasingly used, since they provide radiation safety for personnel and high survey performance. Improvement of detection modules is one of the main directions in which UAS-gamma is developing. [...] Read more.
Unmanned aerial systems (UAS) for airborne gamma-ray surveys in radioecological and geological research are being increasingly used, since they provide radiation safety for personnel and high survey performance. Improvement of detection modules is one of the main directions in which UAS-gamma is developing. Semiconductor detectors are used increasingly as they have a small mass and are convenient for light unmanned aerial vehicles (UAVs). Simultaneously, in our opinion, the potential of traditional scintillation detectors is not exhausted because they are cheaper and more affordable. Radiometric and spectrometric detection modules based on scintillation detectors can even be created at home. The main disadvantage of scintillation detectors is the need for large crystals with significant mass to obtain high data quality. Traditional aerial gamma surveys with operated aircraft systems use scintillation detectors with a volume of tens or hundreds of litres. In this paper, we present the comparison result of radiometric and spectrometric surveys with small volume detectors made at different altitudes and ground surveys. We prove that with properly designed and applied ultralight UAS for aerial gamma spectrometry it is possible to obtain high-quality and informative data. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Deep Reinforcement Learning Based Resource Management in UAV-Assisted IoT Networks
Appl. Sci. 2021, 11(5), 2163; https://doi.org/10.3390/app11052163 - 01 Mar 2021
Viewed by 450
Abstract
The resource management in wireless networks with massive Internet of Things (IoT) users is one of the most crucial issues for the advancement of fifth-generation networks. The main objective of this study is to optimize the usage of resources for IoT networks. Firstly, [...] Read more.
The resource management in wireless networks with massive Internet of Things (IoT) users is one of the most crucial issues for the advancement of fifth-generation networks. The main objective of this study is to optimize the usage of resources for IoT networks. Firstly, the unmanned aerial vehicle is considered to be a base station for air-to-ground communications. Secondly, according to the distribution and fluctuation of signals; the IoT devices are categorized into urban and suburban clusters. This clustering helps to manage the environment easily. Thirdly, real data collection and preprocessing tasks are carried out. Fourthly, the deep reinforcement learning approach is proposed as a main system development scheme for resource management. Fifthly, K-means and round-robin scheduling algorithms are applied for clustering and managing the users’ resource requests, respectively. Then, the TensorFlow (python) programming tool is used to test the overall capability of the proposed method. Finally, this paper evaluates the proposed approach with related works based on different scenarios. According to the experimental findings, our proposed scheme shows promising outcomes. Moreover, on the evaluation tasks, the outcomes show rapid convergence, suitable for heterogeneous IoT networks, and low complexity. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Lightweight Unmanned Aerial System for Time-Domain Electromagnetic Prospecting—The Next Stage in Applied UAV-Geophysics
Appl. Sci. 2021, 11(5), 2060; https://doi.org/10.3390/app11052060 - 26 Feb 2021
Cited by 1 | Viewed by 561
Abstract
Nowadays in solving geological problems, the technologies of UAV-geophysics, primarily magnetic and gamma surveys, are being increasingly used. However, for the formation of the classical triad of airborne geophysics methods in the UAV version, there was not enough technology for UAV-electromagnetic sounding, which [...] Read more.
Nowadays in solving geological problems, the technologies of UAV-geophysics, primarily magnetic and gamma surveys, are being increasingly used. However, for the formation of the classical triad of airborne geophysics methods in the UAV version, there was not enough technology for UAV-electromagnetic sounding, which would allow studying the geological environment at depths of tens and hundreds of meters with high detail. This article describes apparently the first technology of UAV-electromagnetic sounding in the time domain (TDEM, TEM), implemented as an unmanned system based on a light multi-rotor UAV. A measuring system with an inductive sensor—an analogue of a 20 × 20 or 50 × 50 m receiving loop is towed by a UAV, and a galvanically grounded power transmitter is on the ground and connected to a pulse generator. The survey is carried out along a network of parallel lines at low altitude with a terrain draping at a speed of 7–8 m/s, the maximum distance of the UAV’s departure from the transmitter line can reach several kilometers, thus the created technology is optimal for performing detailed areal electromagnetic soundings in areas of several square kilometers. The results of the use of the unmanned system (UAS) in real conditions of the mountainous regions of Eastern Siberia are presented. Based on the obtained data, the sensitivity of the system was simulated and it was shown that the developed technology allows one to collect informative data and create geophysical sections and maps of electrical resistivity in various geological situations. According to the authors, the emergence of UAV-TEM systems in the near future will significantly affect the practice of geophysical work, as it was earlier with UAV-magnetic prospecting and gamma-ray survey. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Roll Control of Morphing Aircraft with Synthetic Jet Actuators at a High Angle of Attack
Appl. Sci. 2021, 11(2), 505; https://doi.org/10.3390/app11020505 - 06 Jan 2021
Viewed by 338
Abstract
Flow separation and dynamic stall occurring at a high angle of attack will lead to difficulty in control and maneuverability for morphing aircraft. This study proposes a novel active flow control technology using a synthetic jet actuator for the roll motion of morphing [...] Read more.
Flow separation and dynamic stall occurring at a high angle of attack will lead to difficulty in control and maneuverability for morphing aircraft. This study proposes a novel active flow control technology using a synthetic jet actuator for the roll motion of morphing aircraft. With the help of the computational fluid dynamics method and vortex lattice method, the roll control model of morphing aircraft undergoing large shape change at a high angle of attack is established. In this model, both the array of the actuator with an optimized cavity shape and morphing span, which are subject to the input saturation constraint, are used to mimic the conventional control surface. Integrated flight control based on the sliding mode control method is designed to ensure the desired closed-loop asymptotic stability, wherein the radial basis function neural network is employed to provide the compensation induced by the input saturation constraint. To demonstrate the effectiveness of the control scheme, various control strategies for different combinations of input are proposed to maintain the roll motion. The numerical results show that the designed control law could track the target signal well, which suggests that the virtual control surface is an effective tool for maintaining the high flight performance of morphing aircraft. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Design and Experimentation of an Aerial Seeding System for Rapeseed Based on an Air-Assisted Centralized Metering Device and a Multi-Rotor Crop Protection UAV
Appl. Sci. 2020, 10(24), 8854; https://doi.org/10.3390/app10248854 - 10 Dec 2020
Viewed by 404
Abstract
To improve the overall mechanization level of rapeseed production in China, especially in some hilly regions where ground machinery cannot enter the fields or can only enter with very low economic benefits, a special aerial seeding system for rapeseed based on a miniature [...] Read more.
To improve the overall mechanization level of rapeseed production in China, especially in some hilly regions where ground machinery cannot enter the fields or can only enter with very low economic benefits, a special aerial seeding system for rapeseed based on a miniature air-assisted centralized metering device was designed and tested in this study. Unlike existing commercial aerial seeding systems, the proposed seed meter was a miniaturized version derived from the traditional air-feeding seed meter on ground planters. The new version contained a redesigned seed feeding component to overcome problems of serious air backflow to the seed box and difficult seed feeding after miniaturization. Three groups of experiments were designed and conducted to optimize the parameters of the seed meter and test its performance. Results from the orthogonal experiment showed that the seed feeding component performed best when the seed layer thickness was 45 mm, the rotational speed of the gear disc was 45 r/min, and the airflow pressure was 2450 Pa. Results from the static workbench test showed that the designed seeding system had a maximum average total sowing efficiency of 537.17 g/min, with the maximum values of the stability variation coefficient of total seeding rate (seven ports) and the consistency variation coefficient between each port was 2.37% and 4.89%, respectively. Field tests further proved that the designed aerial seeding system could work stably, uniformly, and efficiently, so that the agronomic requirements of rape crop planting could be well met. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Distance and Visual Angle of Line-of-Sight of a Small Drone
Appl. Sci. 2020, 10(16), 5501; https://doi.org/10.3390/app10165501 - 09 Aug 2020
Viewed by 605
Abstract
Determining the distance of the line-of-sight (LOS) of a small drone is essential in both regulating drone operation and drone operator training considering public safety. A field experiment was conducted to determine the LOS distance and visual angle of a small drone. Human [...] Read more.
Determining the distance of the line-of-sight (LOS) of a small drone is essential in both regulating drone operation and drone operator training considering public safety. A field experiment was conducted to determine the LOS distance and visual angle of a small drone. Human participants were requested to observe a drone in one of the predetermined locations in the air. They responded whether they could see and hear the drone using a five-point scale. It was found that auditory signals were insignificant in drone detection because most of the participants could not hear the drone while they could still see the drone in most of the test locations. Logistic regression analyses were conducted to predict the probability of catching the drone visually. Two models were built considering the “definitely yes” and “definitely or probably yes” criteria of visual detection. These models may be used to estimate the LOS distance and visual angle. Assuming a 50% probability of visual catching and the “definitely or probably yes” criterion, the distance and visual angle of the LOS for the Mavic Air drone without a protector were approximately 307 m and 0.065°, respectively. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Real-Time Visual Tracking of Moving Targets Using a Low-Cost Unmanned Aerial Vehicle with a 3-Axis Stabilized Gimbal System
Appl. Sci. 2020, 10(15), 5064; https://doi.org/10.3390/app10155064 - 23 Jul 2020
Cited by 1 | Viewed by 789
Abstract
Unmanned Aerial Vehicles (UAVs) have recently shown great performance collecting visual data through autonomous exploration and mapping, which are widely used in reconnaissance, surveillance, and target acquisition (RSTA) applications. In this paper, we present an onboard vision-based system for low-cost UAVs to autonomously [...] Read more.
Unmanned Aerial Vehicles (UAVs) have recently shown great performance collecting visual data through autonomous exploration and mapping, which are widely used in reconnaissance, surveillance, and target acquisition (RSTA) applications. In this paper, we present an onboard vision-based system for low-cost UAVs to autonomously track a moving target. Real-time visual tracking is achieved by using an object detection algorithm based on the Kernelized Correlation Filter (KCF) tracker. A 3-axis gimbaled camera with separate Inertial Measurement Unit (IMU) is used to aim at the selected target during flights. The flight control algorithm for tracking tasks is implemented on a customized quadrotor equipped with an onboard computer and a microcontroller. The proposed system is experimentally validated by successfully chasing a ground and aerial target in an outdoor environment, which has proven its reliability and efficiency. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Drone-Based Parcel Delivery Using the Rooftops of City Buildings: Model and Solution
Appl. Sci. 2020, 10(12), 4362; https://doi.org/10.3390/app10124362 - 25 Jun 2020
Cited by 4 | Viewed by 817
Abstract
In general, the demand for delivery cannot be fulfilled efficiently due to the excessive traffic in dense urban areas. Therefore, many innovative concepts for intelligent transportation of freight have recently been developed. One of these concepts relies on drone-based parcel delivery using rooftops [...] Read more.
In general, the demand for delivery cannot be fulfilled efficiently due to the excessive traffic in dense urban areas. Therefore, many innovative concepts for intelligent transportation of freight have recently been developed. One of these concepts relies on drone-based parcel delivery using rooftops of city buildings. To apply drone logistics system in cities, the operation design should be adequately prepared. In this regard, a mixed integer programming model for drone operation planning and a heuristic based on block stacking are newly proposed to provide solutions. Additionally, numerical experiments with three different problem sizes are conducted to check the feasibility of the proposed model and to assess the performance of the proposed heuristic. The experimental results show that the proposed model seems to be viable and that the developed heuristic provides very good operation plans in terms of the optimality gap and the computation time. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Multiobjective Scheduling of Logistics UAVs Based on Variable Neighborhood Search
Appl. Sci. 2020, 10(10), 3575; https://doi.org/10.3390/app10103575 - 21 May 2020
Viewed by 560
Abstract
This study focuses on the issue of logistics Unmanned Aerial Vehicle (UAV) distribution in urban environment and an automatic delivery system to support the delivery of packages. It can effectively integrate existing facilities and be easily deployed. There is a scheduling problem in [...] Read more.
This study focuses on the issue of logistics Unmanned Aerial Vehicle (UAV) distribution in urban environment and an automatic delivery system to support the delivery of packages. It can effectively integrate existing facilities and be easily deployed. There is a scheduling problem in this system with multiple UAVs and multiple flights. We manage to optimize the two objectives of customer satisfaction and total completion time. The scheduling problem is formulated to a Mixed Integer Linear Programming (MILP), and we propose a multiple objectives decision-making method. A special encoding method suitable for the small scale problem is presented and Variable Neighborhood Search (VNS) algorithm framework is used to generate the approximate optimal solution for this problem. In experiments, we calibrate the important parameter and analyze the robustness of the algorithm. The experimental results show that the proposed algorithms are efficient for this problem. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Helicopter Safe Landing Trajectory after Main Rotor Actuator Failures
Appl. Sci. 2020, 10(8), 2917; https://doi.org/10.3390/app10082917 - 23 Apr 2020
Viewed by 566
Abstract
Main rotor actuator failure leads to catastrophic accidents for single main rotor helicopters. This paper focuses on safe landing trajectories after an actuator is locked in place by the remaining actuators, without introducing other control inputs. A general swashplate geometry is described, and [...] Read more.
Main rotor actuator failure leads to catastrophic accidents for single main rotor helicopters. This paper focuses on safe landing trajectories after an actuator is locked in place by the remaining actuators, without introducing other control inputs. A general swashplate geometry is described, and new reconfiguration solutions for the control mixer are presented. The safe landing trajectories are obtained by formulating a nonlinear optimal control problem based on a nonlinear helicopter dynamic model and geometry constraints due to actuator failure. Safe landing trajectory results are shown with various initial forward velocities of all actuator failure cases. The safe initial speed boundaries are also explored by employing speed sweeps. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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Open AccessArticle
Dynamic Event-Triggered Time-Varying Formation Control of Second-Order Dynamic Agents: Application to Multiple Quadcopters Systems
Appl. Sci. 2020, 10(8), 2814; https://doi.org/10.3390/app10082814 - 18 Apr 2020
Cited by 2 | Viewed by 767
Abstract
This paper investigates the problem of the time-varying formation control of a second-order dynamic agent based on a distributed dynamic event-triggered algorithm. In this problem, each agent can exchange the information of its position and velocity with its neighbors via limited communication ability. [...] Read more.
This paper investigates the problem of the time-varying formation control of a second-order dynamic agent based on a distributed dynamic event-triggered algorithm. In this problem, each agent can exchange the information of its position and velocity with its neighbors via limited communication ability. Our approach provides a new dynamic event triggering mechanism to reduce the number of triggering times while maintaining satisfactory control performance. Further, a novel Lyapunov function is proposed to guarantee that the group of agents asymptotically tracks the desired time-varying formation trajectory. The practical applicability of the event triggering mechanism is also indicated by excluding the Zeno behavior in the proposed control algorithm. Finally, the validity and effectiveness of the proposed method are demonstrated via illustrative examples of the time-varying formation flight for six quadcopters. Full article
(This article belongs to the Special Issue Unmanned Aerial Vehicles (UAVs) II)
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