Air Vehicles Research Articles

Experimental investigation of unmanned air vehicle rotor aeroacoustics using benchmark geometries

A series of benchmark and off-the-shelf unmanned air vehicle rotors with diameters around 12 inches was tested in the newly-built anechoic chamber at the Łukasiewicz Research Network - Institute of Aviation, as well as in an open field. The aerodynamic performance of the rotors was assessed using thrust and torque meters embedded in a custom testing rig, and their acoustic characteristics, including directivity, were determined using a column of free-field microphones. The characteristics of the anechoic chamber, including the spatial distribution of background noise and the anechoic condition, were evaluated in detail, and the comparison with open-field measurements enabled confirmation of its suitability for testing of low Reynolds number rotors. The measurements of rotor performance were compared with published results, and the agreement between the data sets validated the methodologies employed in this study. Furthermore, a new benchmark is defined based on an 8-inch commercial rotor, for which broadband noise is more significant than for larger diameters. A full set of aeroacoustic characteristics is presented, broadening the range of available benchmark cases.

Low-Carbon Incentive Guidance Strategy for Electric Vehicle Agents Based on Carbon Emission Flow

The cleanliness of charging power determines whether electric vehicles can fully utilize their low-carbon properties. This paper, taking into account the impact of temperature on the energy consumption of electric vehicle air conditioning, uses the Monte Carlo algorithm to calculate the typical daily charging load of electric vehicle clusters in different seasons. Secondly, based on the Shapley value carbon responsibility allocation method, a reasonable range of carbon emission responsibilities for different electric vehicle agents is calculated, and a tiered carbon pricing method is proposed accordingly. Then, using carbon emission flow theory, we calculate the carbon emissions generated by the different agents’ charging amounts and corresponding carbon emission costs. Finally, a low-carbon incentive guidance model is constructed with the signal of tiered carbon prices and the goal of minimizing operating costs to re-optimize the charging load distribution of electric vehicles. Case studies showcase that the proposed method is effective in reducing power system carbon emissions and electric vehicle charging costs.

Abrasion resistance of a carbon fiber reinforced composite based on a nanoclay epoxy nanocomposite matrix

AbstractIn this paper, the abrasion resistance of a carbon fiber composite based on epoxy nanocomposite matrix filled with layered‐silicate clay nanoparticles was evaluated. In the first step of the work, the clay‐epoxy nanocomposite was first studied to assess the dispersion and the performance, and then to select the best content for the fiber composite production. The nanocomposite mixture was prepared by finely dispersing clay nanoparticles into the epoxy monomer through mechanical stirring, then the hardener was added. After this step, the fiber reinforced composite was produced by vacuum infusion, and then the properties were evaluated. The abrasion resistance has been assessed using different approaches. A test was specifically designed to simulate the impact of abrasive powders which could potentially be found in the atmosphere and crash into aircraft or air vehicles (such as for instance volcanic ashes). The results showed that the presence of nanoclay reduces the weight loss of the sample with the impacted surface, which can be clearly correlated to a damage reduction.Highlights Sandblasting tool made to mimic impact of abrasive powder on composite surface Presence of nanoclay does not significantly affect the vacuum infusion process Layered‐silicate nanoparticles lead to improve composites abrasion resistance

Plasma disinfection procedures for surfaces in emergency service vehicles: a field trial at the German Red Cross

The demand for thorough disinfection within ambulances is essential, given the in-vehicle medical procedures and the potential high risk of infections due to patients' open wounds. One solution that can address this hygiene challenge involves the application of reactive products generated from atmospheric (air) oxygen and water vapor, activated through the use of cold plasma. Cold plasma's charged particles perforate the cell membranes of microorganisms. This process does not work in human cells, as proteins in the form of enzymes within the body break down the cold plasma and protect the cells. The study was done on an ambulance that was contaminated in eight places. Samples were taken from each site, and two surfaces measuring approximately 8 × 8 cm were carefully sealed and marked. These surfaces were deliberately contaminated by applying an Enterococcus faecium suspension of 8.5 × 107 CFU/mL using a sterile cotton swab. It was followed by the disinfection procedure, that was initiated with the PLASMOCAR device. It was positioned on the front workspace and operated for a duration of 30 min, utilizing the vehicle's onboard voltage. Throughout the operation, all doors and windows were closed and the vehicle's air conditioning system remained active. After the completion of the disinfection process, samples were collected from the surfaces for bacterial counts. A reduction of 3.73 log levels in initial bacteria was accomplished within the rescue vehicle for Enterococcus faecium, equivalent to a 10–fourfold reduction in bacteria, eliminating up to 99.99% of the initial microorganisms. This success makes the process well-suited and convenient as an ongoing "background" procedure to enhance the established disinfection procedures. The established disinfection procedures outlined in the hygiene plan must be promptly implemented whenever mechanical surface cleaning is required. The use of PLASMOCAR offers an extra layer of protection and security, significantly decreasing the risk of microorganism transmission through cross-contamination and aerosols. This is a significant benefit for the well-being of both staff and patients.

STRUCTURAL DEFORMATION ANALYSIS ON MORPHING MAV WING

Micro air vehicles (MAV) and the notion of morphing are always changing to suit their mission characteristics. To achieve twist morphing, however, the process underlying the application of the morphing force and its related aerodynamic load is not well understood. In this study, the structural deformation of the washout twist morphing wing MAV was investigated, and the association between wing deformation, morphing force, and membrane inflation owing to aerodynamic force was clarified. Several numerical simulations of washout TM wings were undertaken and compared to those of rigid and membrane wings. The results demonstrated that twist morphing is associated with considerable wing deformation. In comparison to the TM 3N, TM 1N, and baseline wing, the TM 5N wing was the most distorted. The deformation of the wing structure was substantially influenced by the morphing force applied to the wing. Larger morphing power led to a greater degree of wing distortion.

Scarab Beetle‐Inspired Embodied‐Energy Membranous‐Wing Robot with Flapping‐Collision Piezo‐Mechanoreception and Mobile Environmental Monitoring

AbstractThe mechanoreception system in bionic micro air vehicles, akin to insect sensory neurons, handles internal and external stimulus information. However, current onboard mechanoreception methods add weight and necessitate additional power. Employing the embodied energy design paradigm, a lightweight intelligent membranous wing is proposed, mimicking the scarab beetle's hindwing morphology and kinematics. This wing serves multiple functions, including aerodynamic load‐bearing, flight piezo‐mechanoreception, and power supply. The beetle's semi‐tubular costa structure is replicated, featuring a compliant leading edge for upstroke aerodynamic load resistance. Inspired by beetle hindwing veins and membranes, the bionic wing with three membranous fields: anal, medial, and apical, using heat lamination of multilayer materials is fabricated. The bionic wing's aerodynamic performance closely mirrors that of a real beetle hindwing, enabling various flight maneuvers and validating its real‐flight potential. As a piezo‐mechanoreception receptor for micro air vehicles, the bionic intelligent wing senses flapping frequency, wing deformations, and collisions through voltage signals from piezoelectric materials in the three membranous fields. Energy harvested from flapping‐wing motion powers onboard light intensity and ultraviolet sensors for mobile 3D environmental monitoring. This integration of aerodynamics, mechanoreception, and power supply via embodied flapping energy offers a novel approach for designing future intelligent flapping‐wing micro air vehicles.

Surface Properties of Double-Fin Generated Shock-Wave/Boundary-Layer Interactions

Shock-Wave/Boundary-Layer Interaction (SBLI) is ubiquitous in high-speed air vehicles. SBLI surface flowfield properties of crossing shocks induced by symmetric Double-Fins (DFs) at fin angles of 8° and 10° at Mach 2 are experimentally investigated; a 10° Single-Fin (SF) is also explored as a comparison. Surface visualization is used to capture distinct flowfield structures such as separation and upstream influence. Steady and unsteady Pressure-Sensitive Paints (PSPs) are used to obtain global surface pressure fields. Characteristics of DF-SBLI surface topology are discussed by comparing the corresponding SF-SBLI. The effect of fin angle on DF-SBLI is characterized, and unsteady dynamics of the pressure field are examined. Spectral Proper Orthogonal Decomposition (SPOD) is performed on unsteady PSP, and traveling surface pressure waves and their frequency-dependent behavior are discussed. Dispersion relation of surface pressure waves is revealed by performing two-dimensional space–time Fourier transform on unsteady PSP, and the results are compared with the phase velocity distributions obtained from SPOD. Accompanying group velocity behavior is examined for distinct SBLI regions wherein wave propagation is found dependent on its frequency. Steady surface pressures along the centerline are compared with previous experimental data. Fin-tip spacing is found to be an essential parameter for scaling of upstream influence length.

Experimental and Numerical Studies on an Automobile Air Conditioning System With the Refrigerants R134a, R1234yf, and R1234ze(E)

Abstract The Montreal Protocol of 1987 has put the chlorofluorocarbons (CFCs) into the category of ozone-depleting substances. The hydrofluorocarbons (HFCs), synthesized as alternatives to CFCs, though possess zero ozone-depleting potential, have high global warming potential (GWP). Despite this, numerous applications currently employ HFCs for refrigeration and air conditioning. The 2016 Kigali amendment to the Montreal Protocol suggested a phase out of the HFCs, and this process will go on until 2036 in developed nations and until 2047 in developing nations to accomplish a condition of 85% decrease in the use of HFCs. The refrigerant R134a used in mobile air conditioning has a global warming potential (GWP100) of 1300, which prompted researchers to look for new low GWP refrigerants. Recent research has revealed that the HydroFluoroOlefin (HFO) refrigerants R1234yf and R1234ze(E) with a GWP100 of 4 or less show promise for application in the automobile air conditioning (AAC) field. The AAC requires special attention due to frequent leakages of HFC caused by vibration-induced pipe failures. In this research, the low GWP refrigerants R1234yf and R1234ze(E) are considered to explore the AAC system performance, and comparisons are made with the currently used refrigerant R134a. The numerical simulations are performed by including and excluding liquid-to-suction heat exchanger/internal heat exchanger (IHX). The results show that the use of IHX is advantageous for both R1234yf and R1234ze(E). Even though R134a performed better, R1234yf with IHX is a better low GWP alternative in the current AAC system working with R134a without IHX, with only a slight compromise in the system performance and the performance of R1234yf is better than R1234ze(E). Finally, the numerical simulation results are validated against the experimental results for R134a and R1234yf and found that most of the results agree within 10% deviation for system without IHX and within 15% deviation for system with IHX. Thus, if the AAC systems change to R1234yf with an IHX, the directives set out in the Kigali amendment of 2016 to Montreal Protocol (namely the discontinuation of HFCs for refrigeration) will be satisfied without any significant loss in the performance.

A Numerical Study on the Influence of Transverse Grooves on the Aerodynamic Performance of Micro Air Vehicles Airfoils

Micro Air Vehicles (MAVs) airfoils usually operate at low Reynolds number conditions, where viscous drag will consume a large amount of propulsion power. Due to the small dimensions, many drag reduction methods have failed, resulting in limited current research. To develop an effective method of reducing viscous drag, transverse grooves were placed on the surface of MAVs airfoils in this study, and a numerical investigation was implemented to uncover the corresponding flow control law as well as the mechanism. Research has shown that transverse grooves have an impact on the drag and lift of airfoils. For drag, properly sized transverse grooves have the effect of reducing drag, but under high adverse pressure gradients or when the continuous arrangement of grooves is excessive, the optimal drag reduction effect achieved by the grooves is weakened, and even the drag increases due to the significant increase in pressure difference. In severe cases, it may also cause strong flow separation, which is not conducive to MAV flight. For lift, the boundary vortex in the groove has the ability to reduce the static pressure near the groove. However, high adverse pressure gradients or too many grooves will thicken the boundary layer and increase the blockage effect, resulting in a large static pressure on the grooved side of the airfoil (with an increase in drag). From the perspective of circulation, the static pressure changes on the suction and pressure surfaces have opposite effects on lift. Considering the comprehensive aerodynamic performance of the airfoil, we designed a high lift-to-drag ratio airfoil with grooves, which increased the lift-to-drag ratio by 33.747% compared to the smooth airfoil. Based on the conclusions, we proposed preliminary design criteria for grooved airfoils, providing guidance for subsequent research and applications.

Multi-objective design and optimization of wings

Nowadays, with the fast development of technology, aircrafts have been successful advanced. As we all know, wings are one of the most significant parts of the aircrafts, therefore, multi-objective design and optimization of wings has become a critical issue among many researchers. This paper mainly introduces several approaches to improve the wing in different conditions, including optimization design of civil airplanes, design and optimization of aircraft wing structure at low Reynolds numbers, Wing Design and Aerodynamic Characteristics of Biomimetic Flapping Wing Micro Air Vehicles and so on, the purpose of this article is to give a brief introduction to these relatively new research methods and make the public understand more about this field. The primary approaches of this article are literature analysis and review. This paper finds that algorithm and artificial intelligence are fundamental to improving wings, and all the design needs to reduce the amount of energy as much as possible, which is also the most important requirement.

Analysis of the Pneumatics principles of several aircrafts

In recent years, the advancement of science and technology, particularly the development of flight control technology, has driven the progress of aircraft technology, which facilitates the rapid development of many kinds of aircraft. Pneumatics, the mechanics of gas flow, is used to study aerodynamics. In the design and manufacturing of aircraft, gas flow has a significant impact on the movement, control, attitude, stability, and other aspects of the aircraft. This paper describes the basic Pneumatics principles in aircraft design: aerodynamics is the discipline that studies the interaction between airflow and aircraft, it is the core foundation of aircraft external shape design, a pivotal discipline in overall design, and a prerequisite for conducting design analyses in fields, it plays a crucial role in aircraft design and force analysis for the aircraft, and this paper also introduces the aerodynamic layout design and aerodynamic characteristics of tilt-rotor Unmanned Aerial Vehicle (UAV), multi-rotor aircraft and bionic flapping wing aircraft, so as to offer some references for future study of air vehicles.

Earwig-inspired foldable origami wing for micro air vehicle gliding.

Foldable wings serve as an effective solution for reducing the size of micro air vehicles (MAVs) during non-flight phases, without compromising the gliding capacity provided by the wing area. Among insects, earwigs exhibit the highest folding ratio in their wings. Inspired by the intricate folding mechanism in earwig hindwings, we aimed to develop artificial wings with similar high-folding ratios. By leveraging an origami hinge, which is a compliant mechanism, we successfully designed and prototyped wings capable of opening and folding in the wind, which helps reduce the surface area by a factor of seven. The experimental evaluation involved measuring the lift force generated by the wings under Reynolds numbers less than 2.2 × 104. When in the open position, our foldable wings demonstrated increased lift force proportional to higher wind speeds. Properties such as wind responsiveness, efficient folding ratios, and practical feasibility highlight the potential of these wings for diverse applications in MAVs.

Assessing the mechanical and static aeroelastic performance of cellular Kirigami wingbox designs

Adaptive wings configurations have been evaluated for morphing airframe applications during the last two decades. Constructions with flexible hinges can be in particular a solution for small top medium-scale air vehicles, while novel Kirigami technologies help to produce flexible and complex structures by enabling novel geometric paradigms. In this study, a cellular Kirigami wingbox with an adaptive hinge is designed and manufactured. The mechanical properties of the wingbox are numerically evaluated, considering the shear modulus of the cellular elements patterning the wingbox. Thus, the equivalent torsional, flexural stiffness, as well as the shear center location of the whole wingbox structure are calculated. The analysis is parametrized against various possible internal cell angles and cell thickness values that define the Kirigami cellular tessellation of the wingbox. The static divergence speed is also evaluated by means of the same parametrization. This study shows the feasibility of using a Kirigami wingbox concept for morphing/adaptive small to medium-scale from a structural and aeroelastic perspective.

Extraction of landslide morphology based on Topographic Profile along the Direction of Slope Movement using UAV images

The landslide morphology is quickly and accurately extracted from Unmanned Air Vehicle (UAV) images. It is of great significance for emergency rescue and quantitative evaluation of landslide disasters. However, due to the complexity of landslide morphology, choosing the reasonable extraction thresholds is a challenging issue. A threshold selection method of Topographic Profile along the Direction of Slope Movement (TP-DSM) was proposed. Firstly, a hierarchical extraction rule sets for landslide morphology was constructed by integrating multi-feature information such as spectral, texture, geometry, topography and space of UAV images. Second, TP-DSM was proposed to select the optimal elevation thresholds for classifying different landslide morphology. Finally, the thresholds were introduced into the rule sets to achieve effective extraction of landslide morphology. This study uses Digital Orthophoto Map (DOM) and Digital Elevation Model (DEM) generated by UAV images as data sources, and the landslide in Luquan County, Yunnan Province, China as the Study area, the results show that the overall accuracy (OA) of landslide morphology extraction was 89.58%, and the Kappa coefficient was 0.88, which is effective and more consistent with the reality. The proposed method can also be applied to other potential locations.

A 3D navigation algorithm switching between waypoint and Bezier curves based local plans for micro air vehicles

Micro Air Vehicles (MAVs) are playing an increasingly prominent role in our lives. Numerous studies have been conducted on autonomous mobility. In this study, an architecture has been developed for 3D mapping and 3D navigation for MAVs. The flight time of a MAV is considerably shorter than ground vehicles. Therefore, they are expected to perform tasks more efficiently and with higher performance. MAVs can plan a route to a given target and follow this path using the developed 3D navigation algorithm. Tracking paths produced by classical waypoint-based planners is slow. For this reason, a local path planner based on Bezier curves has been developed for MAVs, with path planning represented as a curve on the low-level control card. Since it is not always possible to reach the given target with a single curve, the multi-hop Bezier curves approach has been proposed. Particularly in environments with low complexity, this approach yields very effective results. In cases where the Bezier path cannot be generated in high-complexity environments, a metric has been developed to measure the complexity, allowing for a switch between waypoint and multi-hop Bezier curves based local plans on the environment complexity metric. Thanks to these developed methods, the aim is to extend the flight time of MAVs by optimizing their battery usage. Within the scope of this study, all experiments were conducted in the ROS-GAZEBO simulation environment. Firstly, waypoint-based local planning methods such as Dijkstra and A*, which will function within the navigation algorithm, were implemented to operate in 3D, and performance tests were conducted in the designed simulation environments. Subsequently, a multi-hop Bezier curves-based local planner was developed, and performance comparisons were made with waypoint-based methods using the same simulation environments, taking into account environmental complexity parameters.

POD-Galerkin FSI Analysis for Flapping Motion.

FSI simulations of flapping motions have been widely investigated to develop a flapping-wing micro air vehicle. Because an intensive parametric study is important for the product design, a computationally efficient model is required. The purpose of the present study was to develop a reduced-order model of flapping motion. Among the various methods available to solve FSI problems, we employed the Dirichlet-Neumann partitioned iterative method, in which three sub-systems (fluid mesh update, fluid analysis, and structural analysis) are executed. In the proposed analysis system, first, snapshot data of structural displacement, fluid velocity, fluid pressure, and displacement for the fluid mesh update were collected from a high-fidelity FSI analysis. Then, the snapshot data were used to create low-dimensional surrogate systems of the above three sub-systems based on the POD under Galerkin projection (i.e., the POD-Galerkin method). In numerical examples, we considered a two-dimensional FSI problem of simplified flapping motion. The problem was described via two parameters: frequency and amplitude of flapping motion. We demonstrated the effectiveness of the presented reduced-order model in significantly reducing computational time while preserving the desired accuracy.

Computational evaluation of flight performance of flapping-wing nano air vehicles using hierarchical coupling of nonlinear dynamic and fluid-structure interaction analyses

This study endeavours to introduce an inventive hierarchical coupling methodology for evaluating the flight capabilities of polymer micromachined flapping-wing nano air vehicles (FWNAVs) using advanced computational tools. Furthermore, our objective is to provide a practical demonstration of FWNAVs in both tethered and airborne scenarios. These dual objectives represent the distinctive and pioneering aspects of this research. Such FWNAVs, which are insect-inspired robots, have a 2.5-dimensional structure. An FWNAV comprises a micro piezoelectric drive system and a pair of micro thin flexible wings. The drive system includes a micro transmission and a piezoelectric bimorph actuator. The flight performance of the designed FWNAV is evaluated using a hierarchical coupling approach, where the whole system is decomposed into a micro wing and a micro piezoelectric drive system. The coupling between these parts is modelled as one-way coupling and that between the micro wings and the surrounding air is modelled as strong coupling. In the one-way coupling analysis, nonlinear structural dynamic analysis is conducted for the micro piezoelectric drive system, where the dynamic response is transmitted to the micro wings via the Dirichlet boundary condition. In the strong coupling analysis, strongly coupled fluid-structure interaction analysis is conducted for the micro wings and the surrounding air to consider their strong coupling. The optimisation of flight performance is conducted using fluid-structure interaction analysis to achieve sufficient lift force to support the weight of an FWNAV. The design of a tethered and flyable FWNAV with a size of 10 mm or smaller is demonstrated. This FWNAV can be easily fabricated using polymer micromachining.

Optimized self-excited electrostatic actuators with insulated-electrodes configuration for micro air vehicles

Optimized self-excited electrostatic actuators with insulated-electrodes configuration for micro air vehicles

Comparison of estimating vegetation index for outdoor free-range pig production using convolutional neural networks.

This study aims to predict the change in corn share according to the grazing of 20 gestational sows in a mature corn field by taking images with a camera-equipped unmanned air vehicle (UAV). Deep learning based on convolutional neural networks (CNNs) has been verified for its performance in various areas. It has also demonstrated high recognition accuracy and detection time in agricultural applications such as pest and disease diagnosis and prediction. A large amount of data is required to train CNNs effectively. Still, since UAVs capture only a limited number of images, we propose a data augmentation method that can effectively increase data. And most occupancy prediction predicts occupancy by designing a CNN-based object detector for an image and counting the number of recognized objects or calculating the number of pixels occupied by an object. These methods require complex occupancy rate calculations; the accuracy depends on whether the object features of interest are visible in the image. However, in this study, CNN is not approached as a corn object detection and classification problem but as a function approximation and regression problem so that the occupancy rate of corn objects in an image can be represented as the CNN output. The proposed method effectively estimates occupancy for a limited number of cornfield photos, shows excellent prediction accuracy, and confirms the potential and scalability of deep learning.

Poster] Spatial modelling of midair collision risk using ADS-B data


 The airspace environment is a complex system that is only expected to continue increasing in complexity with the introduction of new types of air vehicles and operations, such as uncrewed aircraft, and the projected growth of air traffic volumes. This increase in complexity brings a need for investigating and developing new models of complex airspace environments to better understand their constituent parts. To address this need, this paper presents a methodology to create a geospatial model of complex airspace environments which can be used to study any geospatially distributed entity part of these environments. The methodology leverages Discrete Global Grid Systems (DGGS) for this purpose, a Geographic Information Systems framework previously utilized in geography and urban planning. The usefulness of the model is demonstrated on a case study geospatial entity which is the risk of midair collisions for many geospatially distributed points in an airspace region of interest. Since such a model needs to be able to work for any type of air vehicle and airspace region in a fully three-dimensional model that is capable of performing time varying analysis in a computationally efficient manner, a rudimentary midair collision risk model was also developed which satisfies these requirements. Air traffic data from the OpenSky Network was collected and integrated in the geospatial model and the midair collision risk model was used to calculate the risk of collisions for many geospatially distributed points in the airspace for four scenarios of ascending airspace complexity. The results from these four scenarios showed that the proposed methodology can be used to study the risk of midair collisions for different points in the airspace for any type of air vehicle and airspace region of interest in a fully three-dimensional model that is capable of performing time varying analysis in a computationally efficient manner.