Flight Experiment Research Articles

Flight performance and wing morphology in the bat Carollia perspicillata: biophysical models and energetics.

Studies on functional performance are important to understand the processes responsible for the evolution of diversity. Morphological trait variation within species influences the energetic cost of locomotion and impacts life history traits, with ecological and evolutionary consequences. This study examined wing morphology correlates of flight performance measured by energetic expenditure in the Seba's short-tailed bat, Carollia perspicillata. In the flight experiments, nature caught bats (59 females, 57 males) were allowed to fly for 3 min in a room. After each flight, thermographic images were taken to measure body temperature, and biophysical models were used to calculate sensible heat loss as a measure of energetic expenditure. Wing morphological traits were measured for each individual and associated with heat loss and power required to fly on performance surfaces. Wing morphological traits explained 7-10% of flight energetic cost, and morphologies with the best performance would save the energy equivalent to 9-30% of total daily requirements. The optimal performance areas within the C. perspicillata morphospace were consistent with predicted selection trends from the literature. A trade-off between demands for flight speed and maneuverability was observed. Wing loading and camber presented sexual dimorphism. These morphological differences are likely associated with more economical but less maneuverable flight in females, leading them to fly more often in open areas along the forest edge. Our findings demonstrate how small scale changes in wing morphology can affect life history strategies and fitness.

Operation quality control of rapeseed strip aerial seeding system via under-constrained seeding technique

Due to the strong aerodynamic disturbance induced by high-speed rotating rotors and under-constrained seeding condition, it is difficult to control the width of landing seeds in target area during the aerial seeding process. In this study, based on the multi-rotor plant protection unmanned aerial vehicle (UAV) platform, the strategy of under-constrained seeding at a low dropping height is employed to realize the strip aerial seeding of rapeseed. Firstly, the spatial-temporal characteristics of downwash flow field in forward flight state are verified via the high-fidelity computational fluid dynamics method. Afterwards, the migration mechanism of falling seeds and operation parameter optimization are investigated by employing the gas-solid coupling simulation technique. Finally, flight experiments are carried out based on multi-rotor UAV platform to verify the validity of simulation results, where the image processing technique is used to accurately obtain the coordinates and distribution characteristics of landing seeds. The result indicates that the strip effect could be further improved with a higher flight speed and lower dropping height, for instance, the strip width of 95 % landing seeds could be controlled within 81.1 mm when the flight speed and dropping height are 3.5 m/s and 0.5 m respectively. The research results can provide a suggestion for scientific setting of operation parameters of aerial seeding system.

Reflectometry diagnostics for atmospheric entry applications: state-of-the-art and new developments

Insight into the plasma properties of high-speed ionized flows is key for the validation of predictive aerothermodynamic tools for atmospheric entry applications, namely plasma radiation which will be highly dependent on the flow electron densities, which accordingly need to be accurately estimated. We performed an extensive review on past re-entry microwave diagnostics, including both in-flight and ground-test experiments. This work assesses the peculiar characteristics of entry plasmas, and derives functional requirements for microwave diagnostics tailored for such applications. A preliminary analysis, including a simulation of electromagnetic environment for the RAM-C II flight experiment, obtained through a CFD code coupled to an electromagnetic propagation code, is presented. The obtained results outline the adequacy of such diagnostics for improving verification and validation for high-speed entry plasma flows.

Development of flapping wing robot and vision-based obstacle avoidance strategy.

Due to the flight characteristics such as small size, low noise, and high efficiency, studies on flapping wing robots are being actively conducted. In particular, the flapping wing robot is in the spotlight in the field of search and reconnaissance. Most of the research focuses on the development of flapping wing robots rather than autonomous flight. However, because of the unique characteristics of flapping wings, it is essential to consider the development of flapping wing robots and autonomous flight simultaneously. In this article, we describe the development of the flapping wing robot and computationally efficient vision-based obstacle avoidance algorithm suitable for the lightweight robot. We developed a 27 cm and 45 g flapping wing robot named CNUX Mini that features an X-type wing and tailed configuration to attenuate oscillation caused by flapping motion. The flight experiment showed that the robot is capable of stable flight for 1.5 min and changing its direction with a small turn radius in a slow forward flight condition. For the obstacle detection algorithm, the appearance variation cue is used with the optical flow-based algorithm to cope robustly with the motion-blurred and feature-less images obtained during flight. If the obstacle is detected during straight flight, the avoidance maneuver is conducted for a certain period, depending on the state machine logic. The proposed obstacle avoidance algorithm was validated in ground tests using a testbed. The experiment shows that the CNUX Mini performs a suitable evasive maneuver with 90.2% success rate in 50 incoming obstacle situations.

An Integrated Framework for Autonomous Sensor Placement With Aerial Robots

Aerial manipulators have the unique ability to cover wide-spread areas within a single mission, making them ideal for the transport and placement of sensors required to build an instrumented environment. Recent work in the field has focused on controllers for aerial interaction that account for compliance during contact-based tasks, omitting integration concerns that are critical to an automated solution. Furthermore, state-of-the-art flying base manipulators are often mechanically and computationally complex, reducing their endurance. Within this work, we present an interactive framework for autonomous sensor placement that incorporates both mechanical and software based compliance, optimised for use on a simple coplanar quadrotor. Under appropriate actuation and perception constraints, we detail the development of a control, perception, and motion planning strategy to enable sensor placement that relies solely on onboard computation and sensing, thus presenting a fully contained and accessible sensor placement approach capable of robust interaction with the environment. An extended finite-state machine is developed to facilitate automated mission planning. Extensive flight experiments are performed to validate the effectiveness of each sub-system, as well as the integrated solution. Experiments result in trajectory tracking errors under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10 \,\mathrm{mm}$</tex-math></inline-formula> as well as onboard mass estimation errors under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.7 $</tex-math></inline-formula> % for sensors of various weights. A statistical analysis of 162 flight experiments shows the proposed framework's ability to autonomously place sensors within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10 \,\mathrm{cm}$</tex-math></inline-formula> of the target with a success rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$93.8 $</tex-math></inline-formula> % and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$95 $</tex-math></inline-formula> % confidence interval of (89%, 97%), thus confirming the robustness of our approach. <xref ref-type="fn" rid="fn1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¹</xref>

Optimal Elastic Wing for Flapping-Wing Robots Through Passive Morphing

Flapping wing robots show promise as platforms for safe and efficient flight in near-human operations, thanks to their ability to agile maneuver or perch at a low Reynolds number. The growing trend in the automatization of these robots has to go hand in hand with an increase in the payload capacity. This work provides a new passive morphing wing prototype to increase the payload of this type of UAV. The prototype is based on a biased elastic joint and the holistic research also includes the modelling, simulation and optimization scheme, thus allowing to adapt the prototype for any flapping wing robot. This model has been validated through flight experiments on the available platform, and it has also been demonstrated that the morphing prototype can increase the lift of the robot under study by up to 16% in real flight and 10% of estimated consumption reduction.

Micro-Drone Ego-Velocity and Height Estimation in GPS-Denied Environments Using an FMCW MIMO Radar

In the context of autonomous navigation, the vehicle trajectory estimation and the detection of surrounding obstacles are two critical functionalities that must be robust to difficult environmental conditions (e.g., fog, dust, and snow) and the unavailability of infrastructure signals (e.g., GPS). With the advantage of remaining operable in low-visibility conditions, radar sensors are good candidates to detect obstacles in an autonomous navigation context. In this article, we show that radars can also be successfully used for real-time trajectory estimation. We address the case of an autonomous micro-drone intended for the exploration of piping networks and embedding a frequency-modulated continuous wave (FMCW) multi-input multioutput (MIMO) radar. We show that using a beamforming technique to virtually steer the radar field of view (FOV), we can simultaneously estimate the horizontal and vertical velocities of the drone as well as its height. These results are first validated through simulations based on experimental drone flight data and a radar simulator. Then, using an Infineon 77-GHz FMCW radar, we show, through real-world experiments, the high performance attainable with our solution.

Real-Time Robust Receding Horizon Planning Using Hamilton–Jacobi Reachability Analysis

Safety guarantee prior to the deployment of robots can be difficult due to unexpected disturbances in runtime. This article presents a real-time receding-horizon robust trajectory planning algorithm for nonlinear closed-loop systems, which guarantees the safety of the system under unknown but bounded disturbances. We characterize the forward reachable sets (FRSs) of the system based on the Hamilton–Jacobi reachability analysis as a means for safety verification. For the online computation of the FRSs, we approximate nonlinear systems as LTV systems with linearization errors and compute ellipsoids that encompass the FRSs in continuous time. Using the proposed ellipsoidal approximation of the FRSs, we formulate a computationally tractable robust planning problem that can be solved online. Consequently, the proposed method enables real-time replanning of a reference trajectory with safety guarantees even when the system encounters unexpected disturbances in runtime. The flight experiment of obstacle avoidance in a windy environment validates the proposed robust planning algorithm.

METHODOLOGICAL APPROACH TO THE ASSESSMENT OF SPATIAL AND TEMPORAL PARAMETERS OF AN UNMANNED AERIAL VEHICLE DURING FLIGHT TESTS

During flight tests of unmanned aerial vehicles (UAVs), the assessment of individual parameters, such as: range and flight duration (spatial and temporal parameters) is associated with the involvement of a significant resource (time, space, material and technical, etc.), which often raises problematic questions regarding their implementation. At the same time, in most cases, the customer usually puts forward fundamental and clear requirements to ensure the required range and duration of the flight. These indicators generally characterize the capabilities of complexes to perform tasks as intended. However, during the conducted tests, for a number of complexes, they were not fully evaluated (confirmed), including due to unfavorable conditions for conducting tests, as well as the presence of space and time limitations, first of all, the imperfection of the existing testing facilities. Given the above, the article substantiates, builds and analyzes the practical implementation, based on the results of a flight experiment, of a methodological approach to the operational assessment of certain flight characteristics, primarily the range and duration of flight during UAV flight tests. At the same time, an increase in the reliability of the data obtained is achieved through the use of the proposed complex indicator and savings in material and time resources due to the optimization of the program of the relevant test flights. The previously proposed complex indicator - the coefficient of technical perfection of the UAV, which simultaneously takes into account the perfection of the design, aerodynamic layout and efficiency of the power plant, allows to verify the reliability of the values of the parameters of the maximum range and duration of the UAV flight obtained during flight tests The theoretical and practical calculation (during a flight experiment) of the coefficient of technical perfection of a UAV with an electric propulsion system based on the experimentally obtained characteristics of the maximum range and duration of flight is presented and compared.

A smooth control allocation method for a distributed electric propulsion VTOL aircraft test platform

AbstractDistributed electronic propulsion (DEP) aircraft with vertical take‐off and landing (VTOL) ability mostly equipped with multiple redundant tiltable propulsors, which are used to provide not only thrusts, but also control torque in all flight mode. The features make the control allocation problem of these aircraft both complex and important. Therefore, this paper proposes: (і) a prototype platform for DEP VTOL aircraft that allows researchers to design and analyse control allocation strategies, and (іі) a uniform hierarchical control allocation method that can be adapted to both MC and FW modes. The platform contains ten fully actuated thrusters, which are distributed in the scaled geometry of a typical DEP‐VTOL aircraft. The proposed control allocation strategy uses hierarchical structure to avoid high‐dimensional matrix operations for the redundant actuators. The additional constraints on the thrust and tilt angles of the actuators are addressed by adopting cascade generalized inversion (CGI) to force decompensation (FD)‐based methods by a coordinate transformation. A novel smooth strategy through Schur Complement is also presented to achieve steady and smooth transition from MC to FW mode. Finally, the proposed method is implemented in the authors’ novel platform in both simulations and flight experiments to demonstrate its effectiveness and smoothness.

Simulation Study on Thermal Wake Characteristics of Underwater Vehicle under Rotary Motion

The high temperature cooling water generated by the power system of underwater vehicle is discharged through the discharge port and mixed with seawater to form a thermal wake, whose thermal characteristics can be easily detected by infrared submersible technology. In order to explore the characteristics of the thermal wake of the underwater vehicle when it rotates in fresh water, this paper uses the finite volume method to establish a three-dimensional scaled SUBOFF mathematical model, and then combines the overlapping grid technology to numerically simulate the rotation of the underwater vehicle in the background waters. The thermal wake experimental platform is established to verify the reliability of the numerical simulation method by comparing the direct flight experiment with the simulation results. The near-field cooling water trajectory and far-field wake spatial evolution behind the rotary body are analyzed, and the abnormal characteristics of water surface temperature are obtained. The results show that the thermal wakes on the turning side and the deviation side are greatly affected by the vortex caused by the body, and have great differences in morphology, motion trajectory and temperature characteristics. When the thermal wakes on both sides rise to the water surface, an arc-shaped water surface temperature anomaly area composed of two high-temperature hot spots is formed.

Determination of main performance data of an aircraft threedimensional maneuver split-S with a permissible flight envelope limiter

Due to a steady extension of the flight envelope of modern agile combat aircraft, with the growing requirements for state tests, it is increasingly necessary to study the entire flight envelope and specifically, to determine the main performance data of individual maneuvers. Currently, state tests are based on a flight full-scale experiment, which is cost-ineffective in terms of cost, duration, and limit lines of the flight envelope. The accelerating trends to update state tests are semirealistic simulation and complex simulation modeling. The article presents the various techniques to determine main performance data of a three-dimensional maneuver split-S, which include the calculation method, semirealistic simulation, and simulation modeling. The calculation method is understood as calculation formulas expressed from the system of equations for motion of the aircraft mass center. Semirealistic simulation was carried out using a flight-simulation stand by operator pilots. Simulation modeling was conducted using a complex simulation model of an aircraft, consisting of a pilot’s control actions model based on fuzzy logic. The article provides the description, advantages and disadvantages, comparison of the results of each of the techniques. The calculation method, despite its efficiency, is the most inaccurate due to the complexity and inability to define the average flight parameters. Additionally, this method does not take into consideration such factors as the aircraft flight configuration, atmospheric disturbances, the pilot’s command profile, the logic of the permissible flight envelope limiter operation. The results of semirealistic simulation showed that this method is more accurate than the calculation one, but complex and time consuming in terms of the organization and execution of experiments. The analysis of the study illustrated that the most appropriate way to determine main performance data of split-S is simulation modeling on a complex simulation model of the aircraft, because the given method considerably saves financial and time resources used on state flight tests.

Ground Testing of the 16th Materials International Space Station Experiment Materials

External spacecraft materials play an important role in satellite protection from the harsh space environment. Research has shown that the physical, chemical, and optical properties of matter change continuously as a result of exposure to solar radiation and aggressive chemical species produced in Earth’s upper atmosphere. Thorough knowledge of the material properties’ evolution throughout a planned mission lifetime helps to improve the reliability of spacecraft. Moreover, the establishment of correlation factors between true space exposure and accelerated space weather experiments at ground facilities enables accurate prediction of on-orbit material performance based on laboratory-based testing. The presented work aims to evaluate the radiation effects of a low-Earth-orbit environment, namely, exposure to the high-energy electrons and atomic oxygen (AO) of heritage and novel spacecraft material selection. The studied materials represent the “flight duplicates” of samples that are launched as a part of the 16th Materials International Space Station Experiment Flight Facility (MISSE-FF) mission in 2022.

Vision-Based Moving-Target Geolocation Using Dual Unmanned Aerial Vehicles

This paper develops a framework for geolocating ground-based moving targets with images taken from dual unmanned aerial vehicles (UAVs). Unlike the usual moving-target geolocation methods that rely heavily on accurate navigation state sensors or assumptions of the known target’s altitude, the proposed framework does not have the same limitations and performs geolocation of moving targets utilizing dual UAVs equipped with the low-quality navigation state sensors. Considering the Gaussian measurement errors and yaw-angle measurement bias provided by low-quality sensors, we first propose an epipolar constraint-based corresponding-point-matching method, which enables the historical measurement data to be used to estimate the current position of the moving target; after that, we propose a target altitude estimation method based on multiview geometry, which utilizes multiple images, including historical images, to estimate the altitude of the moving target; finally, considering the negative influence of yaw-angle measurement bias on the processes of target altitude estimation and parameter regression, we take advantage of multiple iterations among the two processes to accurately estimate the moving target’s two-dimensional position and the yaw-angle measurement biases of two UAVs. The effectiveness and practicability of the framework proposed in this paper are proved by simulation experiments and actual flight experiments.

Small Signal Magnetic Compensation Method for UAV-Borne Vector Magnetometer System

Aeromagnetic surveys using UAVs (Unmanned Aerial Vehicle) have attracted extensive interest, and aeromagnetic compensation is indispensable to improve the quality of magnetic field. For the vector magnetic sensors fixed on the drone, existing compensation methods are based on that the magnitude of vector magnetic field is a constant, but in theory, even if the center position of the UAV remains unchanged during rotation, the magnitude of the measured vector magnetic field is time-varying, because the interference field generated by the drone is related to its attitude, resulting in residual error after compensation. This paper creates a novel small signal model (SSM) based on the measured results of the vector magnetometer, compensating the permanent and induced interference magnetic field generated by the drone. A high-pass filter is used to separate the UAV interference field from the outputs of a vector magnetic sensor, and compensation parameters are estimated by the least square method. Meanwhile, compensation flight is the UAV-borne vector magnetometer system flying multiple lines in a small area, no need to keep the center of the system fixed while performing rotation operations in the air. Field experiments have been conducted, and the root mean square error of the compensated magnetic field is less than 1 nT. In addition, the subsequent test flight and detection experiment were carried out, showing that the SSM compensation can improve the quality of magnetic field.

FLIGHT DEMONSTRATION OF A GAP/N2O DIRECT INJECTION GAS-HYBRID ROCKET SYSTEM USING A SMALL ROCKET

This paper presents the first trial of a flight demonstration experiment using a direct-injection gas-hybrid rocket (DIGHR) system, with glycidyl azide polymer (GAP) as the solid fuel and nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O) as the oxidizer. In this work, the combustion characteristics of the DIGHR system were studied. GAP is a high-energy material with characteristics such as self-decomposition, high density, and high heat of formation. N&lt;sub&gt;2&lt;/sub&gt;O has high vapor pressure. Therefore, the system does not need to use additional pressurized gas to oxidize the combustion chamber. Consequently, the DIGHR system is characterized by a high-density specific impulse that enables the development of a small thruster system. In this study, a 400 N thrust class DIGHR was developed to use in the flight demonstration and a ground test was conducted before the flight test. The performance of a DIGHR system using gaseous oxygen (GOX) was previously reported, in which all of the experiments confirmed smooth ignition and stable combustion. In addition, the efficiency of the characteristic velocity (C*) decreased to approximately 85&amp;#37; in comparison to a system using GAP/GOX. One reason for this is that the motor sizes were different. The second reason is the use of liquid N&lt;sub&gt;2&lt;/sub&gt;O as an oxidizer. However, these experimental results support the use of a small rocket at an altitude of 100 m. Therefore, a GAP/N&lt;sub&gt;2&lt;/sub&gt;O flight motor was designed and developed for a small hybrid rocket. The DIGHR was launched from the ground to the sea and the experiment was successfully performed.

The practical rules for aircraft parameters identification based on flight test data

&lt;abstract&gt;&lt;p&gt;The mathematical analysis of the problem of irregularity of estimates inherent in the problem of parametric identification of aircraft mathematical models according to flight experiments data is carried out. It is shown that to ensure the reliability of identification results, usually it is not enough to use only observations of the input and output signals of the object, but it is necessary to attract additional information taken from the basic scientific and engineering disciplines related to the subject under study, and apply other special techniques. For the task of estimating the parameters of aircraft models using flight experiment data, the basic rules for performing identification are formulated.&lt;/p&gt;&lt;/abstract&gt;

Исследование влияния освещенности на расчет вегетационных индексов на примере NDVI

The purpose of the research is to study changes of the values of vegetation indices of landscapes depending on their illumination. The most used vegetation index NDVI was chosen as an example. The NDVI index was calculated for the following natural objects: water surface, open soil, forest plantations and a field with growing agricultural crops. The vegetation index was calculated using multi- and hyper-spectral satellite images obtained from local satellite systems Resurs – P and Canopus – V and foreign satellite system Sentinel – 2. Satellite images were selected for the same territories, but completed at various values of cloud cover density. Different values of cloud cover density provided differences in the illumination of the landscapes depicted in the images. The difference between the dates of the space survey did not exceed five days. As a result of the research, a change in the index values was revealed in images of the same object taken under different light conditions. However, the results obtained during the research did not allow us to estimate the amount of the illumination influence on the values of the vegetation index. As one of the results, a program of a field flight experiment was proposed to determine the values of vegetation indices based on multispectral survey materials using UAV at known values of landscape illumination.

Robust Nonlinear Control for the Fully Actuated Hexa-Rotor: Theory and Experiments

This letter addresses a fully-actuated Hexa-rotor’s control under exogenous position and attitude disturbances. For that aim, we propose a nonlinear and robust control based on a backstepping technique for position dynamics and a geometric control for attitude dynamics. We demonstrate that the closed-loop system is globally exponentially stable. To validate the reached stability, we present simulation results using MATLAB/Simulink and software in the loop simulations using the well-known PX4 firmware in a realistic scenario on a virtual environment in Gazebo. Finally, to ultimately demonstrate the effectiveness of our algorithm, we implement it on an own-developed fully-actuated Hexa-rotor platform. Our contributions can be summarized as 1) the design of a robust controller for the fully-actuated Hexa-rotor not presented in the literature, 2) the publication of the controller’s code for the PX4 autopilot software, and 3) drone’s construction and presentation of real flight experiments.

Research on Pilots ’ Mental Workload Classification in Simulated Flight

Abstract The problem of human-computer interaction mental workload in flight driving has great reference value for the prevention of safety hazards in aviation driving. This paper analyzes and studies the classification method of mental workload in flight driving by designing different simulated flight experiment tasks. This study uses a combination of EEG signals and subjective evaluation, through the use of convolutional neural networks and long short-term memory network method of combining EEG signals for research and analysis. The accuracy of EEG signal classification is as high as 94.9 %. NASA-TLX evaluation results show that there is a positive correlation between task load difficulty and evaluation score. The results show that the combination of convolutional neural network and long short-term memory network is suitable for pilots ’ mental workload classification. This study has important practical significance for flight accidents caused by pilots ’ mental workload.