Small-sized Unmanned Aerial Vehicles Research Articles

Research Progress of High-Speed Data Transmission Technology for Lightweight and Small-Sized Unmanned Aerial Vehicle Platforms

With the continuous development of science and technology, UAV technology has been widely used in various fields. As an essential part, light and small UAV platforms have the advantages of being small, lightweight, and easy to operate and thus have been widely used in aerial photography, monitoring, rescue, and other fields. However, the traditional data transmission method can no longer meet the demand for the data transmission speed and stability of small and light UAV platforms. Wireless optical communication has the advantages of being high-speed and license-free, as well as having a large bandwidth strong anti-interference ability, and good confidentiality. Therefore, this paper aims to study high-speed data transmission technology for light and small UAV platforms to improve their transmission speed and stability. In this paper, the characteristics and advantages of UAV airborne laser communication are first elaborated to illustrate the advancements and importance of data transmission technology based on light and small UAV platforms. Then, the composition of a UAV airborne laser communication system is clarified to illustrate the feasibility of conducting airborne laser communication research. Then, the current domestic and international research status of people on light and small UAV airborne laser communication high-speed data transmission systems is reviewed, and its key technical features are analyzed. Finally, the prospects for its application and development trend are investigated.

Detection Range Estimation of Small UAVs at a Given Probability of Their Identification

The results of the development of a scientific and methodological apparatus that provide an assessment of the detection range of small-sized unmanned aerial vehicles are presented. The general problems of radar detection of small objects are considered. A mathematical formulation of the research problem is carried out from the stand-point of detecting radar signals in noise based on a probabilistic approach. Substantiated are the parameters of radar stations, which are of the most significant importance for increasing the reliability of detecting objects with a small effective scattering surface. The functional dependences of the detection range of small unmanned aerial vehicles on the value of the signal-to-noise ratio in the channel and the sensitivity of the receiving devices are given. The dependence of the detection range on the wavelength of radiation from radar stations has been studied. A quantitative assessment of the probabilities of correct detection of small targets and false alarms is presented for various values of the decision threshold. Nomograms have been developed to assess the capabilities of detectors of unmanned aerial vehicles of the Phantom 3 type. The requirements for the structure of radar signals used to detect small targets are substantiated.

Development of Obstacle Detection System Based On the Integration of Different Based Sensor for Small-Sized UAV

Due to the physical size and weight limits of small unmanned aerial vehicles (UAVs), developing a reliable obstacle detection a system that can provide an effective and safe avoidance path is extremely difficult. Prior work has tended to use a vision-based sensor as the primary detecting sensor however, this has resulted in a high reliance on texture appearance and a lack of distance sensing capabilities. Furthermore, due to the inability to detect the free region, vision-based sensor detection systems have difficulty developing a trusted safe avoidance path. However, most wide spectrum range sensors are bulky and expensive, making them unsuitable for small UAVs. This projectaims to construct an obstacles detection system with the integration of various based sensors for a small UAV. The potential obstacles are identified by categorizing feature points identified in image frame. The suggested approach was tested in a real-world setting for both of the observed scenarios, which included various obstacles configurations. Two types of scenarios are experimented in this project consists of single frontal obstacles and presence of side obstacles alongside the frontal obstacles. On top of that, the position of the side obstacle is aligned to the frontal obstacle and then will be positioned in the increment of 20cm further from the frontal obstacle in order to analyze the outcome of the proposed algorithm. The proposed detection system had a possibility to be a trustworthy system even after utilizing the depth perception technique, however this does not imply that the proposed system is faultless. The results show that the suggested algorithm system detects and distinguishes between the potential obstacles and free region for a single frontal obstacle perfectly. However, there were improvements that should be implemented with the proposed system's ability of detection for multiple obstacles.

Experimental investigation on turbulence effects on unsteady aerodynamics performances of two horizontally placed small-size UAV rotors

Wind turbulent disturbance is one of the critical challenges to flying unmanned aerial vehicles (UAVs); especially when the size, weight, and power on board such aircraft are limited. Therefore, to shed light on such turbulent wind effects on UAVs' aerodynamic performances, wind tunnel experiments were conducted on the single- and multi-rotor configurations by varying the turbulence intensity up to 15%, while setting the wind velocity at 5 m/s. The turbulent disturbances were generated inside the wind tunnel using two different passive grids. One is with 29% blockage, and the other is 49%. As the single-rotor experimental tests were conducted, the onset turbulence was found to give rise to a significant change in thrust and the power coefficient in the presence of a lower revolution per minute (rpm). However, at higher rpm, only the wind effect is observed to be the dominant contributor to the aerodynamic performance. Additionally, three different rotor spacings are experimentally examined to measure the propeller wake interactions at the same velocity and different onset turbulence intensities. It was experimentally found that a significant wake interaction occurs between 0.5 D (diameter) and 1.25 D below the propellers, depending on the rotor spacing and the flow conditions. The present work opens up an experimental approach to examine the unsteady aerodynamic performance of multi-rotor UAVs in the presence of wind disturbances, i.e. at different turbulence intensities.

Pathloss and Airframe Shadowing Loss of Air-to-Ground UAV Channel in the Airport Area at UHF- and L-Band

In air-to-ground unmanned aerial vehicle (UAV) communications, an accurate channel propagation model is very important for the evaluation and design of communication systems. For this purpose, we have conducted several channel measurement campaigns in the airport area at UHF- and L-band (around 433 MHz and 1.518 GHz). In the line-of-sight (LoS) case, we give the distance-dependent pathloss models for both frequenciy bands. Meanwhile, it is found that the measured pathloss in the LoS scenario has a good agreement with the two-ray propagation model at short link distances. This is because of the strong ground reflection path. In the non-LoS (NLoS) case, we propose the elevation-dependent pathloss model at UHF-band based on the field measurement results. On the other hand, considering that the airframe of the UAV can block the wave propagation during the 3-D rotation in the air and the taking off and landing procedures, we specifically analyze the statistical characteristics of the airframe shadowing loss for the two cases and provide the loss distribution models for the fixed-wing, small-sized UAVs made of wood structure and carbon fiber skins.

Dual-antenna GPS-based UAV Attitude Determination Method and Accuracy Analysis

Accurate attitude information of small-sized unmanned aerial vehicles (UAVs) is required to obtain absolute azimuth information of a target via an airborne electro-optical imaging system. The direct attitude solution method of dual-antenna Global Position System (GPS) is investigated in this paper to address this need. We analyzed the attitude measurement principle of the direct method, gave the error estimation model, and estimated the inner and outer precision through simulation. The simulation results demonstrated that to achieve the requirement of UAV yaw angle error within 1°, the baseline length should be no less than 1 m. The applicability of the model and algorithm was confirmed.

Comparison studies on aerodynamic performances of a rotating propeller for small-size UAVs

A better prediction of key aerodynamic parameters of a propeller is necessary to improve the performances of unmanned aerial vehicles (UAVs) in different operating environments. In this work, we conduct a systematic investigation on an APC 1045 multi-rotor propeller to analyze its aerodynamic performances with wind tunnel tests, blade element momentum theory (BEMT) and 3D computational fluid dynamics (CFD). The theoretical BEMT model provides accurate and reliable estimation at the advance ratios ≤0.567, whereas the method begins to stall at advance ratios ≥0.661. Conversely, the results obtained from CFD simulations agree well with the experiments at all advance ratios, with the differences in thrust- and power coefficients around 5% and 4%, respectively. The present work compares the aerodynamic parameters while varying the freestream velocity to investigate the limitations and advantages of the use of the aforementioned three different methods. Given the limitation of the BEMT, it is found to be reliable enough to estimate the aerodynamic parameters of a small-scaled fixed-pitch propeller. In addition, a more comprehensive investigation of the BEMT shows that increasing advance ratio decreases the lifting portion of the propeller blade, i.e. incurring more losses associated with the hub and tip.

ENERGY CALCULATION OF SMALL-SIZED UAVs AUTOMATIC OPTOELECTRONIC OBSERVATION SYSTEMS

Great popularity of small unmanned aerial vehicles (UAVs) in remote observation tasks requires further improvement of not only the carrier, but also the on-board equipment. Standard means of surveillance for UAVs are television cameras. Thermal imaging cameras are used in more expensive technical solutions. The efficiency of the functioning of these devices primarily depends on spatial and energy resolution of their input units, which containe optical system and detector. Small-sized UAVs operate at short distances. The peculiarity of useful signal formation by optical-electronic surveillance systems (OESS) of such UAVs is the need to primarily ensure sufficient energy sensitivity.
 The article develops a method for determining the energy resolution of short-range automatic UESs with two information channels - television and thermal imaging. It is justified that for simplified calculations it is advisable to use the functions of the noise-equivalent luminance difference and the noise-equivalent temperature difference of the corresponding channel as quality indicators. Examples of energy resolution calculations of television and thermal imaging channels of the OESS with matrix detectors are given. The influence of focal length and of entrance pupil diameter of the lenses on the energy resolution was studied for observation distances from 0.5 km to 2 km. It is shown that, in OESS with variable magnification, lenses with a larger diameter of the entrance pupil are preferred - they provide more uniform energy sensitivity when changing the focal length. The developed calculation methods can be used for multispectral OESS operating in the visible and infrared spectrum ranges.

Aerial Refueling: Scheduling Wireless Energy Charging for UAV Enabled Data Collection

The working scope and working time of small size unmanned aerial vehicles (UAVs) are limited because of the limited battery capacity. In this work, inspired by aerial refueling for aircrafts, we propose a wireless power transmission (WPT) scheme by categorizing the UAVs into charging UAV (CUAV) and mission UAV (MUAV) for charging UAVs without interrupting the mission. In the proposed aerial refueling scheme, mission UAVs (MUAV) can be recharged by charging UAVs on the fly and operate in a perpetual manner. The feasibility of aerially wireless charging for small UAVs is firstly discussed and evaluated. Then we consider a practical application scenario of multiple MUAVs for collecting data from several points of interest, where the MUAVs are recharged by CUAVs. Accordingly, the issue of scheduling the flying path and charging process of each CUAV to minimize the mission time arises. Deep reinforcement learning (DRL) based algorithms for scheduling both single and multiple CUAVs are proposed and deployed. Extensive simulation evaluations demonstrate that, by applying the proposed aerial refueling scheme, CUAVs can explore and optimize the scheduling strategies, thereby improving the system performance in terms of mission completion and charging efficiency.

Improvements of a low-cost CO2 commercial nondispersive near-infrared (NDIR) sensor for unmanned aerial vehicle (UAV) atmospheric mapping applications

Abstract. Unmanned aerial vehicles (UAVs) provide a cost-effective way to fill in gaps between surface in situ observations and remotely sensed data from space. In this study, a novel portable CO2 measuring system suitable for operations on board small-sized UAVs has been developed and validated. It is based on a low-cost commercial nondispersive near-infrared (NDIR) CO2 sensor (Senseair AB, Sweden), with a total weight of 1058 g, including batteries. The system performs in situ measurements autonomously, allowing for its integration into various platforms. Accuracy and linearity tests in the lab showed that the precision remains within ± 1 ppm (1σ) at 1 Hz. Corrections due to temperature and pressure changes were applied following environmental chamber experiments. The accuracy of the system in the field was validated against a reference instrument (Picarro, USA) on board a piloted aircraft and it was found to be ± 2 ppm (1σ) at 1 Hz and ± 1 ppm (1σ) at 1 min. Due to its fast response, the system has the capacity to measure CO2 mole fraction changes at 1 Hz, thus allowing the monitoring of CO2 emission plumes and of the characteristics of their spatial and temporal distribution. Details of the measurement system and field implementations are described to support future UAV platform applications for atmospheric trace gas measurements.

CONSTRUCTION OF SMALL-SIZED DEVICES FOR RADIO-ELECTRONIC SUPPRESSION OF COMPACT UNMANNED AERIAL VEHICLES

This article is devoted to the solving task of developing a jamming device for suppressing small-sized unmanned aerial vehicles. The paper analyzes modern devices and systems for jamming, means of electronic countermeasures for unmanned aerial vehicles, their features and the principle of operation are indicated. The relevance of these devices to date is substantiated. A small-sized device for jamming in the frequency range from 433 to 6 GHz has been developed. Its structural and circuit diagram has been synthesized, the printed circuit board of this device has been designed on a modern element base. Designed, manufactured and tested a transmitting antenna for this device.

Mathematical model of inertial-optical autonomous navigation complex of unmanned aerial vehicle

In the article considers the possibility of implementing an autonomous mode in the navigation complex of a small-sized tactical unmanned aerial vehicle, including a strapdown inertial navigation system and an onboard vision system. Due to the fact that the accuracy of such navigation systems significantly depends on changes in the background-target environment and equipment failures, it is proposed to organize automatic adaptation of the system to changes in external conditions and internal factors by controlling the operating modes and parameters of the software that implements optimal estimation algorithms. For this purpose, a model of an onboard inertial-optical autonomous navigation system has been developed in the class of discrete dynamic systems with a random change in structure.

Influence Degree Analysis of Landing Points of Small-sized Fixed-wing Gliding UAV in Short Range

Enhancing the landing accuracy and reducing landing point dispersion of Unmanned Aerial Vehicles (UAVs) with fixed wings is critical for expanding the applications of UAVs in complex terrains. Faced with the requirement for arresting recovery for UAV landings in short range, a UAV with fixed wings is chosen as the research basis. The landing strategy for UAVs has been modified by the addition of wing flaps, dynamic compensation control, and ultrasonic sensors, among other things. Additionally, the simulation model validated the feasibility of the modified landing-recovery strategy. The Monte Carlo method is used to analyze the influence of interference sources, such as constant wind, gust, positioning error, airspeed measurement, mass, air density, processing and assembly, and control error, on landing point dispersion. Simulation results indicate that the modified landing strategy can significantly improve the short landing performance for small-sized UAVs with fixed wings.

Sudden Obstacle Appearance Detection by Analyzing Flow Field Vector for Small-Sized UAV

Achieving a reliable obstacle detection and avoidance system that can provide an effective safe avoidance path for small unmanned aerial vehicle (UAV) is very challenging due to its physical size and weight constraints. Prior works tend to employ the vision based-sensor as the main detection sensor but resulting to high dependency on texture appearance while not having a distance sensing capabilities. The previous system only focused on the detection of the static frontal obstacle without observing the environment which may have moving obstacles. On the other hand, most of the wide spectrum range sensors are heavy and expensive hence not suitable for small UAV. In this work, integration of different based sensors was proposed for a small UAV in detecting unpredictable obstacle appearance situation. The detection of the obstacle is accomplished by analysing the flow field vectors in the image frames sequence. The proposed system was evaluated by conducting the experiments in a real environment which consisted of different configuration of the obstacles. The results from the experiment show that the success rate for detecting unpredictable obstacle appearance is high which is 70% and above. Even though some of the introduced obstacles are considered to have poortexture appearances on their surface, the proposed obstacle detection system was still able to detect the correct appearance movement of the obstacles by detecting the edges.

Prospects for creation and development of robotic systems in the interests of the Ministry of Internal Affairs of Russia

The analysis of foreign experience in the use of robotic technological systems (RTS) shows that there are many possible areas of their practical application in the activities of state enforcement agencies. In the activities of the Russian police small-sized ground-based robotic systems and unmanned aerial vehicles have been used, which expand the capabilities of the internal affairs bodies in the course of resolving official tasks. The article presents the current state of the use of RTS in the Ministry of Internal Affairs of Russia, discusses the main problems to be solved, and considers the prospects for development of police robotic systems. The scope of use of RTS for various purposes is determined, depending on the application environment and the method of basing.

Aerial Energy Orchestration for Heterogeneous UAV-Assisted Wireless Communications

The integration of unmanned aerial vehicles (UAVs) into future-generation wireless networks is a promising strategy for complementing terrestrial communication infrastructures that will lead to capacity and coverage improvements. Unfortunately, the energy limitations of the existing off-the-shelf small-size UAVs are significant challenges, especially during long missions. In this article, first, we investigate the communication model of a heterogeneous UAV-assisted wireless network that consists of multiple energy-constrained battery-powered small-size UAVs (a.k.a. follower UAVs) and a large-size UAV (a.k.a. dispatcher UAV) with solar energy harvesting capability. Subsequently, we propose an aerial energy sharing algorithm to improve the lifetime of the system by orchestrating energy balancing among follower UAVs. In particular, the dispatcher UAV having large energy capacity owing to its battery size and solar energy harvesting capability shares its energy with follower UAVs using radio-frequency-based power transfer through beamforming. The proposed energy sharing algorithm considers the placement, available battery capacity, and mission execution time of the follower UAVs to decide the energy sharing points with optimum efficiency. Extensive simulations show that our proposed algorithm outperforms existing algorithms in terms of charging efficiency and energy balancing among UAVs.

Using Aerial and Vehicular NFV Infrastructures to Agilely Create Vertical Services.

5G communications have become an enabler for the creation of new and more complex networking scenarios, bringing together different vertical ecosystems. Such behavior has been fostered by the network function virtualization (NFV) concept, where the orchestration and virtualization capabilities allow the possibility of dynamically supplying network resources according to its needs. Nevertheless, the integration and performance of heterogeneous network environments, each one supported by a different provider, and with specific characteristics and requirements, in a single NFV framework is not straightforward. In this work we propose an NFV-based framework capable of supporting the flexible, cost-effective deployment of vertical services, through the integration of two distinguished mobile environments and their networks: small sized unmanned aerial vehicles (SUAVs), supporting a flying ad hoc network (FANET) and vehicles, promoting a vehicular ad hoc network (VANET). In this context, a use case involving the public safety vertical will be used as an illustrative example to showcase the potential of this framework. This work also includes the technical implementation details of the framework proposed, allowing to analyse and discuss the delays on the network services deployment process. The results show that the deployment times can be significantly reduced through a distributed VNF configuration function based on the publish–subscribe model.

Visual Tracking of Small Unmanned Aerial Vehicles Based on Object Proposal Voting

In this paper, we propose a novel visual tracking method for unmanned aerial vehicles (UAVs) in aerial scenery. To track the UAVs robustly, we present a new object proposal method that can accurately determine the object regions that are likely to exist. The proposed object proposal method is robust to small objects and severe background clutter. For this, we vote on candidate areas of the object and increase or decrease the weight of the area accordingly. Thus, the method can accurately propose the object areas that can be used to track small-sized UAVs with the assumption that their motion is smooth over time. Experimental results verify that UAVs are accurately tracked even when they are very small and the background is complex. The proposed method qualitatively and quantitatively delivers state-of-the-art performance in comparison with conventional object proposal-based methods.

НАВИГАЦИОННО-ПОСАДОЧНЫЙ КОМПЛЕКС БЕСПИЛОТНОГО ЛЕТАТЕЛЬНОГО АППАРАТА С ИСПОЛЬЗОВАНИЕМ ПСЕВДОСПУТНИКОВ

The problem of navigation of an unmanned aerial vehicle at the landing stage in a complex jamming situation is considered. The aim of the work is to develop the structure as well as software and algorithmic support of navigation and landing complex (NPK), using signals from pseudo-satellites (PS) on board a small-sized unmanned aerial vehicle (UAV). Landing is carried out according to a glide-garden approach, while several configurations of models for the location of pseudo-satellites in close proximity to runway are considered. The characteristics of SS location are known in advance with a high degree of accuracy. Estimation errors of aircraft navigation parameters in a horizontal channel of Strapdown inertial navigation system in the conditions when no PS and when one or two PS being used are found.

Investigation of electromagnetic radiation of the control channel of a small-sized unmanned aerial vehicle for attenuation

An urgent problem of our time is to counteract the illegal use of civilian unmanned aerial vehicles (quadrocopter type). The problem of detecting quadrocopters is related to their low visibility, including in the electromagnetic wavelength range. As a result, it is relevant and appropriate to develop a budget device for countering such aircraft. At the initial stage to achieve this goal, we studied the General principles of control of the civil quadcopter “Xiaomi Mi Drone 4k”, determined its most significant unmasking feature (electromagnetic radiation of the control channel), measured the electrical component of the electromagnetic field from its control panel in order to further calculate the signal attenuation coefficient for detecting the operator of an unmanned aerial vehicle.