Small-scale Unmanned Aerial Vehicles Research Articles

Design, Aerodynamic Calculation and Manufacturing using CFRP and Additive Manufacturing of a small Tilt-Rotor UAV for Railway Inspection

The present paper aims to develop a small scale Unmanned Aerial Vehicle for railway inspection. The development process and structure manufacturing aimed at a low complexity technological process both to meet market requirements and to be economically efficient. To define the architectural structure and its components in the design process, a NACA 0024 aerodynamic profile was selected out of two proposed airfoils. The novelty of this concept is the double benefit of the wing, which serves as a cargo bay while uses a low-cost manufacturing technology, incorporating the 3D printing process. Further, a simplified preliminary aerodynamic calculation was performed, the model was manufactured using composite materials reinforced with carbon fibre while other key components have been obtained using the 3D printing technology. In the end, the manufacturing process was a success and the unmanned aerial vehicle was designed and manufactured specifically that its flight envelope meets the requirements of the mission.

A UAV Video Dataset for Mosaicking and Change Detection From Low-Altitude Flights

In recent years, the technology of small-scale unmanned aerial vehicles (UAVs) has steadily improved in terms of flight time, automatic control, and image acquisition. This has lead to the development of several applications for low-altitude tasks, such as vehicle tracking, person identification, and object recognition. These applications often require to stitch together several video frames to get a comprehensive view of large areas (mosaicking), or to detect differences between images or mosaics acquired at different times (change detection). However, the datasets used to test mosaicking and change detection algorithms are typically acquired at high-altitudes, thus ignoring the specific challenges of low-altitude scenarios. The purpose of this paper is to fill this gap by providing the UAV mosaicking and change detection dataset. It consists of 50 challenging aerial video sequences acquired at low-altitude in different environments with and without the presence of vehicles, persons, and objects, plus metadata and telemetry. In addition, this paper provides some performance metrics to evaluate both the quality of the obtained mosaics and the correctness of the detected changes. Finally, the results achieved by two baseline algorithms, one for mosaicking and one for detection, are presented. The aim is to provide a shared performance reference that can be used for comparison with future algorithms that will be tested on the dataset.

Determination of coordinates of terrestrial targets with the use of small UAVs on the basis of an improved pseudolongdimensional method

In this article the feasibility of using an improved pseudolongdimensional method to determine the coordinates of terrestrial targets using small-scale unmanned aerial vehicles (UAVs), which is used to identify the coordinates of an object on the ground in real-time without involving of powerful computable technique, is justified.The analysis of existing methods for determining the coordinates of terrestrial objects using unmanned aerial vehicles is carried out and an algorithm for determining them based on an improved pseudolongdimensional method using small- scale unmanned aerial vehicles is proposed.The determining the coordinates of terrestrial objects using existing unmanned aerial vehicles is carried out by comparing the image, which was obtained from a located on the unmanned aerial vehicles video camera, with an electronic territory map, on which the observation takes place. The coordinates of the point on the terrain are determined after reaching of maximum coincidence of specified images. The accuracy and timing the coordinates of the point depends on the quality of the image, the number of images, the angle and other factors.An algorithm for determining the coordinates of terrestrial targets using small-scale unmanned aerial vehicles based on an improved pseudolongdimensional method was proposed based on the analysis of the unmanned aerial vehicles work to identify the coordinates of the point on the terrain. The pseudolongdimensional method is used in modern satellite navigation receivers, which is solved by using methods of "least squares", "successive approximations" and etc.The analysis of the accuracy estimation shows that the errors of the coordinate’s determination of the target by the proposed method will depend only on the accuracy of determining the current coordinates of small- scale the unmanned aerial vehicles at the points, where the picture was taken, and the accuracy of the measuring of the corresponding values of the range to the target. To determine the coordinates of a target there is no need for large amounts of memory and powerful computing resources.

Rotor interactional effects on aerodynamic and noise characteristics of a small multirotor unmanned aerial vehicle

Small scale unmanned aerial vehicles using multirotor propulsion systems have received considerable attention for a wide range of military and commercial applications in recent years. In the multirotor configuration, the rotor interaction phenomenon occurs severely because the rotors are located in close proximity to each other. Therefore, the separation distance between the adjacent rotor tips has a strong effect on the wake structures and flow fields, which consequently play an important role in determining the aerodynamic performance and noise level of the multirotor vehicle. In the present study, numerical simulations of a quadcopter under hover flight conditions are conducted to investigate the mutual rotor-to-rotor interactional effects on the aerodynamic performance, wake structures, and sound pressure level using the nonlinear vortex lattice method with the vortex particle method and acoustic analogy based on Farassat’s formulation 1A. Calculations for the multirotor configurations with different separation distances show that the average thrust force decreases significantly and force fluctuation is found to increase dramatically as the rotor spacing gets smaller. In addition, the wake geometry and induced flow structure behind the rotor tend to be radially dragged down toward the center of the vehicle due to the existence of the adjoining rotor, which consequently results in strong wake-to-wake interaction and the formation of asymmetric wake structures although the multirotor operates under the hovering condition. It is also observed that unsteady loading introduced by rotor interaction leads to a considerable increase in the sound pressure level, particularly the normal direction of the rotor plane.

UAV-Involved Wireless Physical-Layer Secure Communications: Overview and Research Directions

Due to their flexible deployment and on-demand mobility, small-scale unmanned aerial vehicles (UAVs) are anticipated to be involved in widespread communication applications in the forthcoming fifth-generation networks. However, the confidentiality of UAV communication applications is vulnerable to security threats due to the broadcast nature and dominant line-of-sight channel conditions, and physical-layer security can be applied for secrecy performance enhancement in such a context. On the other hand, it is also promising to exploit UAVs to cooperatively protect secure communications. This article provides an overview of the recent research efforts on UAV-involved secure communications at the physical layer. We focus on the design of secure transmission schemes according to different roles of UAVs and the optimization of introduced degrees of freedom by the unique characteristics of UAVs. We also propose some future research directions on this topic.

Analysis of Ground Effect for Small-Scale UAVs in Forward Flight

The letter investigates how the behavior of small-scale unmanned aerial vehicles (UAVs) is influenced by the system's close proximity to the ground/rigid surfaces both at hover and in forward flight. We perform an extensive experimental study where a quadrotor is tasked with flying in forward velocities in the range of 0–8 m/s and at altitudes that range between 0.05–0.5 m. Experimental data are used to evaluate four existing ground effect models. Results suggest that existing models for helicopters and in-hover multi-rotors cannot fully describe the forward motion of a quadrotor when it operates close to ground. We introduce two new data-driven models for rotorcraft operating in ground effect both at hover and in forward flight, and evaluate the proposed models with another quadrotor of different size. The proposed models simultaneously consider several operating conditions, which are parameterized by the vehicle's forward velocity and altitude. The models link the thrust produced when operating in ground effect and hovering out of ground effect as forward velocities vary. This information can be incorporated into flight controllers for robust and adaptive UAV flights, and can benefit motion planners for safe and energy efficient near-ground trajectory planning.

Efficient privacy-preserving authentication framework for edge-assisted Internet of Drones

In recent years, small-scale unmanned aerial vehicles (UAVs), or drones, have demonstrated their promising capabilities in supporting a range of applications, such as surveillance, inspection, package delivery, precision agriculture, etc. Given an increasing number of UAVs in the low-altitude airspace, connecting UAVs to form the Internet of Drones (IoDs) is a promising trend to enhance the flying safety as well as the service quality of UAVs. However, due to the open-access communication environment, IoD also raises security and privacy concerns, including authentication threat as well as the leakage of identity, location, and flying routes.In order to address the security and privacy concerns in IoD, this paper proposes an efficient privacy-preserving authentication framework. By utilizing the lightweight online/offline signature design, our framework assures the authentication efficiency when deploying on resource-constrained small-scale UAVs. Considering the high mobility of UAVs, a predictive authentication approach is investigated with mobile edge computing (MEC) in our framework to further reduce the authentication cost for potential authentication activities. Meanwhile, by designing a buffer pseudonym and public key update strategy, our framework enables the protection of privacy in terms of UAVs’ identity, location, and flying routes. Thorough analysis is carried out to demonstrate the fulfillment and feasibility of our framework in terms of security, privacy, and efficiency.

Energy Harvesting Performance of Plate Wing from Discrete Gust Excitation

Energy harvesting from aeroelastic response tends to have a wide application prospect, especially for small-scale unmanned aerial vehicles. Gusts encountered in flight can be treated as a potential source for sustainable energy supply. The plate model is more likely to describe a low aspect ratio, thin plate wing structure. In this paper, the Von Kármán plate theory and 3D doublet lattice method, coupled with a piezoelectric equation, are used to build a linear state-space equation. Under the load of “one-minus-cosine” discrete gust, the effects of flow speed and gust amplitude, thickness of piezoelectric ceramic transducer (PZTs) layers, and mounted load resistance are investigated. Results reveal that the PZTs layers on the wing root of the leading edge can obtain the highest electrical parameters. The flow velocity, thickness of the PZTs layers and load resistance are used to optimize energy harvesting data.

An Integrated Delta Manipulator for Aerial Repair: A New Aerial Robotic System

Unmanned aerial vehicles (UAVs) are capable of entering hazardous areas and accessing hardto-reach locations at high altitudes. However, small-scale UAVs are inherently unstable when exposed to challenging environments. Additionally, their ability to accurately interact with infrastructure is limited by the need to stabilize the vehicle precisely in flight.

Drone Cellular Networks: Enhancing the Quality Of Experience of video streaming applications

This article addresses the problem of delay mitigation for video streaming applications in congested cellular macro-cells by using a mobile micro-cell mounted on an Unmanned Aerial Vehicle (UAV). Small-scale UAVs are at a mature stage of development and can carry lightweight commercial micro-cells with small form factor. The mobile micro-cell is used to offload users from a congested macro-cell to optimize the bandwidth usage of video streaming applications. The paper proposes algorithms and comprehensive design criteria for user offload selection (selecting what users need to be offloaded to the micro-cell) and drone positioning (selecting the position of the UAV that minimizes the network delay). The effectiveness of the proposed criteria is evaluated through extensive performance analysis. We show that the performance increases consistently in terms of bandwidth requests mitigation and average delay reduction under different system configurations.

Optimal Design and CFD Analysis of Wing of a Small-Scale UAV to Obtain Maximum Efficiency

In the recent past small-scale Unmanned Aerial Vehicles (or Unmanned Aerial System as it is called presently) have evolved as an important tool in non-conventional fields like agriculture, e-Commerce, policing, medical logistics in addition to military applications. This paper presents the complete methodology (very limited article exists) applied to optimally design the wing of a small scale Unmanned Aerial Vehicle with help of widely used CFD software, ANSYS to maximize its efficiency. In this study, the application of computational methods in the iterative design process is successfully explored. The various design parameters and features of wing also have been explored with help of CFD analysis to derive the advantages. The strength and stiffness analysis of the UAV wing has also been carried out using ANSYS. The modelling of wing and associated parts were carried out on CATIA. The final design of the wing has two spars, 20 ribs a side with mid wing root strengthening, near elliptical planform and has an all composite structure. The wing is lighter in weight as compared to a similar wing made from Aluminum view weight optimization, and strong enough to meet all in-flight load conditions with safety margins. This paper demonstrates the design process/methodology to optimally design an efficient small-scale UAV.

Optimization of dynamic soaring maneuvers to enhance endurance of a versatile UAV

Dynamic soaring is a process of acquiring energy available in atmospheric wind shears and is commonly exhibited by soaring birds to perform long distance flights. This paper aims to demonstrate a viable algorithm which can be implemented in near real time environment to formulate optimal trajectories for dynamic soaring maneuvers for a small scale Unmanned Aerial Vehicle (UAV). The objective is to harness maximum energy from atmosphere wind shear to improve loiter time for Intelligence, Surveillance and Reconnaissance (ISR) missions. Three-dimensional point-mass UAV equations of motion and linear wind gradient profile are used to model flight dynamics. Utilizing UAV states, controls, operational constraints, initial and terminal conditions that enforce a periodic flight, dynamic soaring problem is formulated as an optimal control problem. Optimized trajectories of the maneuver are subsequently generated employing pseudo spectral techniques against distant UAV performance parameters. The discussion also encompasses the requirement for generation of optimal trajectories for dynamic soaring in real time environment and the ability of the proposed algorithm for speedy solution generation. Coupled with the fact that dynamic soaring is all about immediately utilizing the available energy from the wind shear encountered, the proposed algorithm promises its viability for practical on board implementations requiring computation of trajectories in near real time.

Nonlinear dynamic modeling and hybrid control design with dynamic compensator for a small-scale UAV quadrotor

This paper presents a detailed nonlinear dynamic model and the development of a flight control scheme for an unmanned aerial vehicle (UAV) quadrotor. In the dynamic modeling, significant aerodynamic effects arising from the blade deformation of the rotor and the induced momentum are taken into account. The model is capable of representing the quadrotor behavior for more flight regimes, including not only hover but also high-speed and translational flights. Such a model can benefit the controller design from the improvement of the stability as well as the reduction of development period. Furthermore, a hybrid control scheme incorporating optimal linear quadratic regulator (LQR) and robust sliding mode control (SMC) techniques is designed in a hierarchical multiple-layer structure. In actual practice, only partial states of the quadrotor are readily measurable. A reduced-order observer is hence developed and integrated into the compensator to estimate the unmeasured states. The simulation results show that the designed controller can achieve outstanding performance which is greatly superior than conventional control techniques can do.

Methods for accurate measurements of small fixed wing UAV inertial properties

ABSTRACTTwo methods have been compared for the determination of the inertial properties of a small, fixed-wing un-manned aerial vehicle. The first method uses the standard single degree of freedom pendulum method and the second method implements a novel, potentially easier, 3 degrees of freedom pendulum method, which yields the entire inertia tensor from a single swing test. Both methods are using system identification of the pendulum motion to estimate the inertial properties. Substantial corrections (up to 25%) have to be applied to the experimental results. These corrections are caused by the acceleration of the pendulum being immersed in the surrounding air, also called the added mass effect. It has been found that the methods presented in literature to determine the corrections for full-scale aircraft do not give the correct results for the small-scale un-manned aerial vehicle under consideration. The only feasible, cost-effective method to generate these corrections utilise swing tests with a geometrically similar object of known inertial properties. It has also been found that the corrections are unique with respect to the experimental methods. Several benchmarking methods, including the innovative use of static and dynamic wind-tunnel test data, give high confidence in the results.

Propeller Design and Loss Mechanisms in Low-Reynolds-Number Flows

To develop a highly efficient propeller for small-scale unmanned aerial vehicles, the influences of induced and profile losses determined by design parameters are investigated at . The propeller blade shapes, such as chord length and twist angle distributions in the spanwise direction, are determined using the Adkins–Liebeck method. For a fixed designated thrust value and a forward velocity, the influences of a propeller normalized radius, a blade number, and a tip speed ratio on the propeller performance are discussed. Results show that the profile loss can be larger than the induced loss. For such a case, it is beneficial to reduce the blade number and the propeller rotational speed to increase the blade chord length and the Reynolds number; consequently, the propeller efficiency increases even if the induced drag increases.

Design and Implementation of a Control and Navigation System for a Small Unmanned Aerial Vehicle

Abstract: This paper describes the development of a control and navigation system for a small scale unmanned aerial vehicle (UAV) using as strategy a combination of classical control and Fuzzy Inference Systems (FIS). In this sense, the air-plane has been modelled through analytical techniques that use empirical estimations to compute the force and moment components acting on the aircraft. The control systems were designed using the aircraft's transfer functions to reach a desirable response for each command. Finally, the navigation control system is designed using a FIS to control the roll of the aircraft and the yaw control system to control the aircraft's heading. A route composed of waypoints is generated following a rummage of a selected area. The control systems are, then, tested in a simulated environment to ensure they accomplish the desired mission when they work together.

Kinematic positioning using a robotic total station as applied to small-scale UAVs

Modern robotic total stations (RTS) have the ability to automatically aim, search and track moving targets at high precision thereby enabling kinematic positioning. However, the internal subsystems of the RTS (distance and direction) exhibit time delays which limit the precision positioning of a moving target. These effects are investigated with tracking experiments on a known circular and linear path. A second part of this research investigates small-scale unmanned aerial vehicles (UAV) which use navigation quality GPS as a priori coordinates for photogrammetric processing of acquired images. RTS kinematic positioning was applied to a UAV in a field trial to improve a priori image coordinates and evaluate the method for direct geo-referencing.

A Flight Dynamics Model for a Small-Scale Flybarless Helicopter

We present a helicopter flight dynamics nonlinear model for a flybarless, articulated, pitch–lag–flap (P–L–F) main rotor (MR) with rigid blades, particularly suited for small-scale unmanned aerial vehicles (UAVs). The model incorporates the MR, tail rotor (TR), fuselage, and tails. This model is further applicable for high bandwidth control specifications and is valid for a range of flight conditions, including the vortex-ring-state (VRS) and autorotation. Additionally, the paper reviews all assumptions made in deriving the model, i.e., structural, aerodynamics, and dynamical simplifications. Simulation results show that this nonlinear model is in good agreement with an equivalent flightlab model, for both static (trim) and dynamic conditions.

Autonomous Navigation of UAV in Foliage Environment

This paper presents a navigation system that enables small-scale unmanned aerial vehicles to navigate autonomously using a 2D laser range finder in foliage environment without GPS. The navigation f...

Adjoint-Based Aerodynamic Shape Optimization for Low Reynolds Number Airfoils

In the past decades, most of the research studies on airfoil shape design and optimization were focused on high Reynolds number airfoils. However, low Reynolds number airfoils have attracted significant attention nowadays due to their vast applications, ranging from micro-aerial vehicles (MAVs) to small-scale unmanned aerial vehicles. For low Reynolds number airfoils, the unsteady effects caused by boundary layer separation cannot be neglected. In this paper, we present an aerodynamic shape optimization framework for low Reynolds number airfoil that we developed based on the unsteady laminar N–S equation and the adjoint method. Finally, using the developed framework, we performed a test case with NACA0012 airfoil as a baseline configuration and the inverse of lift to drag ratio as the cost function. The optimization was carried out at Re = 10,000 and Ma = 0.2. The results demonstrate the effectiveness of the framework.