Flight Stability Research Articles

Effect of Bending Deformation on the Lateral Force of Spinning Projectiles with Large Aspect Ratio

The bending deformation can affect the lateral force of spinning projectiles with large aspect ratios, thus interfering with their flight stability. Based on the established spin–deformation coupling motion model, the unsteady Reynolds averaged Navier–Stokes (URANS) equations are solved to simulate the flow over a large−aspect−ratio projectile undergoing spin and spin−deformation coupling motion by using the dual−time stepping method and dynamic mesh technique, obtaining the lateral force. Furtherly, the flow mechanism is analyzed for the changed lateral force induced by the bending deformation. The results indicate that the variation of transient lateral force for the head of a projectile is consistent with that of the deformation−induced additional sideslip angle; affected by the deformation−induced compression wave and expansion wave, the time−averaged lateral force for the middle of a projectile will be increased at small angles of attack, but changed little at large angles of attack; at small angles of attack, the change trend of transient lateral force for the tail of a projectile is similar to that of additional angle of attack caused by the deformation; at large angles of attack, the characteristic of phase lag is presented between the transient lateral force for the tail of a projectile and the additional sideslip angle.

Research on Variable-Swept Hybrid Aerial Underwater Vehicle Plunge-Diving Control Based on Adaptive Dynamic Surface Control

The variation in aerodynamic parameters during the process of a variable sweepback hybrid aerial underwater vehicle (HAUV) affects flight stability. During the air–water trans-media locomotion, there are medium mutations and solid–liquid gas coupling phenomena, resulting in the complex dynamic process of HAUV. To ensure stable control during the trans-media process of a variable sweepback vehicle, this study proposes a neural-network-based adaptive dynamic surface control method for aircraft flight-path angle. This method aims to establish an effective control model for the entire process of air to media transition, in response to the characteristics of uncertainty and external disturbances in the process of variable backsweeping in the air and media transition. By utilizing the multibody dynamics method, the dynamic equations for variable-swept vehicles are established and transformed into a rigorous feedback system with model uncertainty. The adaptive dynamic surface method in this paper introduces a first-order filter, which overcomes the “differential explosion” problem in traditional backstepping control design through differential filtering; the unknown parameters present in the model are estimated online through adaptive laws, and the uncertain parts of the system are overcome through nonlinear damping items. By analyzing Lyapunov stability, the semi-global stability of the required closed-loop system can be obtained, and adjusting the controller parameters can make the tracking error infinitely small. Numerical simulations are conducted to illustrate the tracking control of flight-path angles for different plunge-diving angle rates and strategy of ingress. The results show that HAUV with variable-swept configuration with different strategy has a great effect on the stability of plunge-diving locomotion; the designed controller can effectively track the target trajectory and has a certain degree of robustness and adaptability.

Numerical Analysis of Bioinspired Tails in a Fixed-Wing Micro Air Vehicle

Bird tails play a key role in aerodynamics and flight stability. They produce extra lift for takeoff and landing maneuvers, enhance wing functions and maintain stability during flight (keeping the bird from yawing, rolling and pitching, or otherwise losing control). This paper investigates the use of bioinspired horizontal stabilizers for Micro Air Vehicles (MAVs) involving a Zimmerman wing-body geometry. A selection of five tail shapes of the main types existing in nature is presented, and a parametric analysis is conducted looking into the influence of the most relevant tail geometric parameters to increase the longitudinal static stability of the vehicle. Based on the parametric study, a smaller subset of candidate tail designs are shortlisted to perform a detailed aerodynamic analysis. Then, steady RANS CFD simulations are conducted for a higher-fidelity study of these candidate tail designs to obtain an optimum of each tail type. The criterion for selection of the optimum tail configuration is the maximum aerodynamic efficiency, CLCD , as well as a high longitudinal static stability. The squared-fan tail provides the highest aerodynamic efficiency while maintaining a high longitudinal stability of the vehicle. In conclusion, this paper provides an innovative study of improving longitudinal stability and aerodynamics through the implementation of bioinspired horizontal stabilizers in vehicles with these characteristics.

Development of Unmanned Aerial Vehicle for Detecting the Forest Fires

In recent years, forest fires can be brought under control in line with the information obtained from Unmanned Aerial Vehicles (UAVs), which play an important role in determining the progression of fires, detecting heat points and determining intervention locations. In this study, if the UAV detects the fire by autonomously positioning in the area where the fire is located, the point where the fire reaches the most intense temperature is determined with the help of the thermal camera, and it is ensured that the fireball is dropped to the target with a 100% success rate. The requirements of the UAV, which will be produced in order to realize this task, such as fast, load-carrying and stable flight are also taken into consideration. In addition to being economical and long-lasting of the materials inside, it will be able to fly efficiently in most weather conditions (foggy, dark, etc.). In the construction of the UAV, a domestic Electronic Speed Controller (ESC) with a unique design is produced to meet the sufficient current. With this acquisition, ESC, which will meet the requirements by sending sufficient current to more than one Brushless DC (BLDC) motor, has been tested on our Radio Controlled (RC) aircraft and included in the project.

Trajectory Tracking of a Quadcopter UAV using PID Controller

UAVs or Drones are aircraft with no onboard pilot to control the flight. They are introduced in a few categories such as single-rotor, multi-rotors, fixed-wing, and hybrid VTOL. As for multirotor drones, quadcopters are the most well-known either commercially or in the research field. Due to its advantages, a quadcopter has been chosen to perform various tasks across various fields such as entertainment, military, meteorological reconnaissance, civil and emergency responses. As the demand for quadcopters has diverged, the required features of quadcopters have also diverged. One of the current features required by quadcopters is the ability to track trajectories. However, due to its nature of non-linearity, under-actuated and unstable, controlling quadcopter for an accurate and stable performance is quite a challenge. Despite the various proposed methods throughout the past decades, PID controller is still used as either the main controller or the base controller in most cases of industrial control, including quadcopter, mainly due to its simplicity and robustness. However, to design a proper PID controller for quadcopter system is a challenge as it defies the control inputs of four with its six degree-of-freedom form, in which six inputs are required to be controlled to ensure a stable and accurate flight. This paper derived a mathematically model of a quadcopter with Newton-Euler’s equation. Some assumptions on the body and structure of the quadcopter are taken into account to make the modelling possible. Then, a manually tuned PID controller is designed to achieve the objective of controlling the operation and stability of the quadcopter during its flight. The designed controller is tested with five different trajectories which are circular, square, lemniscate, zigzag, and spiral. The results show the proposed controller successfully tracks the desired trajectories, which prove PID controller can be used to control a quadcopter.

Aerial Torsional Work Utilizing a Multirotor UAV with Add-on Thrust Vectoring Device

Aerial manipulation aims to combine the versatility and the agility of aerial platforms with the manipulation capabilities of robotic arms. Their fast deployment allows for their implementation in maintenance tasks and support during disaster situations. However, the under-actuated nature of multirotor UAVs limits the magnitude and direction of the forces an aerial vehicle can safely exert during manipulation tasks. In this paper, the problems associated with UAVs and torsional tasks constraints regarding valve turning are addressed. An add-on thrust vectoring device which enhances manipulation options available to a conventional multirotor UAV is developed and described. The proposed system allows for a partial decoupling of the attitude and velocity vector of a multirotor. This permits stable translational flight and higher torque capabilities for torsional tasks. The separation of attitude and the velocity vector that allows for the design of a passive mechanism for valve operation is presented in this paper as well. The experimental results illustrate the forces and torques that can be generated in the evaluated operation modes.

Sliding-Mode Control for Flight Stability of Quadrotor Drone Using Adaptive Super-Twisting Reaching Law

In this study, a sliding-mode controller is designed using an adaptive reaching law with a super-twisting algorithm. A dynamic model of a drone is designed with a quadrotor that has four motors and considers disturbances and model uncertainties. Given that the drone operates as an under-actuated system, its flight stability and maneuverability are influenced by the discontinuous signal produced by the reaching law of the sliding-mode control. Therefore, this study aims to improve the sliding-mode control and stability of drone flight using the proposed adaptive law, which is based on exponential properties. The discontinuous signal of a conventional strategy is overcome using the super-twisting algorithm, and the drone rapidly reaches equilibrium using the proposed adaptive law that utilizes the sliding surface value. The proposed control strategy covers a higher dimension than the conventional sliding-mode control strategy; the system stability is proven using the strict Lyapunov function. The reaching time estimation results are introduced and used to compare the respective reaching times of the control strategies. To verify the superior performance of the proposed control method, multiple experiments are conducted under various situations and realizations. The simulation results prove that the proposed control method achieved a superior rapid response, stable maneuvering, and robustness with shorter reaching time.

Fast terminal synergetic control for morphing quadcopter with time-varying parameters

To enhance flexibility and improve versatility, recent research has focused on the development of variable structure vehicles. In line with this, this paper introduces a morphing quadcopter with time-varying parameters that enables independent rotation of its arms around the main body. This study highlights the influence of these parameters on the geometric properties, dynamics, flight stability, and control of this aerial robot, while considering nonlinear functions, unknown parameters, and external disturbances. The system dynamics are derived using Newton-Euler formalism, and a robust control approach based on synergetic theory is proposed. The distinctive features of this strategy are demonstrated through finite-time convergence, enhanced control accuracy, and effective chattering suppression. In the control aspect, a Synergetic Controller (SC) is initially developed and further improved by incorporating fast finite-time convergence of the state variables. A comparative study is conducted, quantitatively and qualitatively, among four controllers: BackStepping (BS) controller, Sliding Mode Controller (SMC), SC, and Fast Terminal Synergetic Controller (FTSC). The FTSC exhibits numerous advantages, including rapid tracking towards desired states, adaptability to varying system parameters and uncertain external disturbances, as well as suitability for digital implementation. To conduct a significant comparative study, a Genetic Algorithm is employed to select the optimal gains for each control technique. Additionally, to imitate the real situation as much as possible, external disturbances are considered in the performed numerical simulation. Overall, the results demonstrate that the proposed control technique outperforms in terms of accuracy and robustness. It offers superior control performance and effective handling of system variations and external disturbances, making it a promising approach for the morphing quadcopter system.

Modeling, Control and Implementation of Adaptive Reconfigurable ROtary Wings (ARROWs)

Inspired by the self-rotating motion of the descending maple seeds, we introduce a novel modular aerial robotic platform—ARROWs. With customized wing and control modules, ARROWs can be easily reassembled into different configurations. Unlike conventional multirotor aerial vehicles which rely on the direct thrust from propellers, ARROWs can generate more lift by their revolving wings. However, the complex dynamics causes difficulties in flight controller development. In this work, we first analyze the flight dynamics by considering a combination of effects from the propeller, aerodynamic force on the wing, as well as self-rotating motion. As a result, a cascaded flight controller with a unified framework is designed based on reduced flight dynamics and relaxed hovering conditions to achieve stable flights in all proposed configurations. In addition, a set of inertial measurement units is employed for each flight module to estimate the flight configuration to overcome the dynamic uncertainties caused by manual re-construction. Finally, our proposed platform and flight control strategy are validated using several flight experiments in 12 different configurations (include both centrosymmetric and centrally asymmetric cases). The results show an average position error of 8.9 cm with a deviation of 2.4 cm among all configurations in hovering tests.

ANALISA DESAIN KEKUATAN STUKTUR PART KONEKTOR DAN TUBE FRAME UAV VTOL MENGGUNAKAN FINITE ELEMENT ANALYSIS

UAV The purpose of this study was to determine the effect of the use of carbon fiber and aluminum materials on the structural strength of the tube and connector parts by considering the safety factor obtained from the analysis results. This study uses the finite element method with the help of solidworks software. The research was conducted in stable flight conditions, namely the UAV's gravity was the same as the UAV's lift. From the results of the frame design, the weight mass is 25.6 kg. From the simulation results, the tube with carbon fiber material and aluminum 6061 alloy both have good strength because the maximum stress values ​​that occur are 15.71 MPa and 15.64 MPa, and these values ​​are still below the yield stress of carbon fiber material which is 551 MPa and aluminum 6061 alloy material, namely 55.1 MPa, with a safety factor obtained of 35 for carbon fiber and 3.5 for aluminum 6061 alloy, and a maximum displacement of 0.056 mm for carbon fiber and 0.812 mm for aluminum 6061 alloy. Whereas the connectors with carbon fiber and aluminum 6061 alloy materials also have good strength because the maximum stress values ​​that occur are 4,266 MPa and 4,139 MPa, and these values ​​are still below the yield stress of carbon fiber material and aluminum 6061 alloy material. with a safety factor obtained of 130 on carbon fiber and 3.5 on aluminum 6061 alloy, and the maximum displacement is 3,734 x 10-5 mm on carbon fiber and 5,416 x 10-4 mm on aluminum 6061 alloy. The use of carbon fiber material in tubes and connectors has better strength than aluminum 6061 alloy, due to the safety factor the value obtained is greater.

Feasibility Investigation of Attitude Control with Shape Memory Alloy Actuator on a Tethered Wing

This study is aimed at assessing the feasibility of employing an innovative, smart-material-based control effector for an inflatable wing. A shape memory alloy (SMA) actuator is primarily investigated as a control effector in this work for its advantages of a simple actuation mechanism and a high force-to-weight ratio. This paper presents the design, control strategy and simulation results of the SMA actuator used as a stability augmentation system for a small-scale prototype kite. Stable flight of the kite is achieved during open wind tunnel tests using the SMA actuator. Based on experimental and simulation analyses, it is evident that the current SMA actuator is better for low-frequency actuations rather than stability augmentation purposes, as its performance is sensitive to practical conditions. The study also discusses potential improvements and applications of the SMA actuator.

Performance Evaluation of a Quadcopter by an Optimized Proportional–Integral–Derivative Controller

This paper presents an analysis of a quadcopter’s stability and its sensors’ data reading using an IMU (inertial measurement unit). Firstly, the angular velocity and acceleration data are read by an Stm® development board embedded with an Stm32f401ccu6 microcontroller. The altitude of the measurement instrument platform was determined using an MS5611 barometric pressure sensor combined with a temperature sensor. The quadcopter’s control was achieved by connecting a brushless DC motor to the Stm® board, which received four PWM (pulse-width modulation) signals via the output port. An electronic governor was utilized to control the brushless DC motor, while a pre-existing remote control was designated as the transmitter. The quadcopter receiver received a 2.4 GHz signal from the transmitter using the BLE (Bluetooth low-energy) protocol, which was used to ensure the simultaneous operation of the four brushless DC motors. Finally, a PID (proportional–integral–derivative) controller was employed for parameter adjustment. The collected PID parameter program was developed in the Simulink software as a simulation platform, allowing for the execution of the Simulink model on the Stm® MCU. The Stm® module facilitates monitoring of the performance of the UAV (unmanned aerial vehicle) and enables immediate parameter adjustments to ensure flight stability. This research aims to reduce calculation errors in sensor and controller usage and improve the efficacy of the remote machine module for future industrial applications.

Vision-based Propeller Damage Inspection Using Machine Learning

Unmanned Aerial Vehicles (UAVs) play an increasingly pivotal role in day-to-day rescue operations, offering crucial aerial support in challenging terrain and emergencies, such as drowning. Drone hangars are strategically deployed to ensure swift response in remote locations, overcoming range-limiting constraints posed by battery capacity. However, the UAV's airworthiness, typically ensured through conventional inspections by a technical individual, is paramount to guarantee mission safety. Over time, UAVs are prone to degradation through contact with the external environment, with propellers often being the cause of flight instability and potential crashes. This paper presents an innovative approach to automate UAV propeller inspection to avert incidents preemptively. Leveraging visual recordings and deep learning methodologies, we train a Convolutional Neural Network (CNN) model using both passive and active learning strategies. Our approach successfully detects physical damage on propellers with an impressive accuracy of 85.8%, promising a significant improvement in maintaining UAV flight safety and effectiveness in rescue operations.

Flow Structures and Aerodynamic Behavior of a Small-Scale Joined-Wing Aerial Vehicle under Subsonic Conditions

Flow behavior and aerodynamic performance of a small-scale joined-wing unmanned aerial vehicle (UAV) was studied experimentally and numerically under various pitch and yaw angle combinations in subsonic flow conditions. Selected numerical results are compared against experimental results obtained using surface oil flow visualizations and force measurements, with additional simulations expanding the range of combined pitch and yaw configurations. Under zero-yaw conditions, increasing the pitch angle leads to the formation of symmetric ogive vortex roll-ups close to the fuselage and their significant interactions with the fore-wing. Additionally, contributions to lift and drag coefficients under zero-yaw conditions by the key UAV components have been documented in detail. In contrast, when the UAV is subjected to combined pitch and yaw, no clear evidence of such ogive vortex roll-ups can be observed. Instead, asymmetric flow separations occur over the fuselage’s port side and resemble bluff-body flow behavior. Additionally, these flow separations become more complex, and they interact more with the fuselage and fore- and aft-wings when the yaw angle increases. Lift and drag variations due to different pitch and yaw angle combinations are also documented. Finally, rolling and yawing moment results suggest that the present UAV possesses adequate flight stability unless the pitch and yaw angles are high.

A novel estimation method for weight and center-of-gravity via the aircraft trim data

Aircraft weight and center-of-gravity are significant parameters that affect flight stability and controllability, and unreasonable CG position may cause serious flight accidents. However, there is no airborne sensor can directly measure aircraft weight and center-of-gravity. In view of this, a novel estimation method for weight and center-of-gravity via the aircraft trim data is introduced. Specifically, the trim data calculation process for the aircraft with variable center of mass is given. Then, an inverse interpolation approach based on the binary search algorithm is presented to estimate the aircraft weight and center-of-gravity, and an improved moving average filter is introduced to eliminate the adverse effect on estimation results caused by the high-frequency noise of airborne sensors. Some simulations are given to demonstrate the validity of the proposed estimation method, and it can be drawn from the result that the aircraft longitudinal CG position estimation error is within 0.05 %MAC.

ENSURING SPEED STABILITY OF THE UNMANNED AERIAL VEHICLE IN DIF-FERENT FLIGHT MODES

The publication deals with the issue of ensuring the stability of an unmanned aerial vehicle flight by speed. An analysis of the physical essence of the process of ensuring the unmanned aerial vehicle stability by speed is presented. Attention is paid to the flight modes in which the operator (external pilot) may encounter difficulties in the practical piloting of the unmanned aerial vehicle. The possible causes of abnormal situations when flying the unmanned aerial vehicle at speeds close to the borderline low are analyzed. Possible actions of the operator (external pilot) to return the unmanned aerial vehicle to the operating speed range from the area of instability are considered. The article shows the features of stability and controllability of an unmanned aerial vehicle in a route flight mode. Attention is paid to the complexity of piloting and safety of flight in the second modes. The article demonstrates the method of determining the boundary between the first and second flight modes. The features of unmanned aerial vehicle management and ensuring stability in the first and second modes are shown. The issue of dynamic stability of the unmanned aerial vehicle is investigated. Numerical modeling of the longitudinal movement of the unmanned aerial vehicle in free, uncontrolled flight was carried out, trajectories for the unmanned aerial vehicle of the selected configuration with a change in speed and angle of inclination of the trajectory in time were obtained. Graphs of movement trajectories with changes in speed and height over time were constructed, graphs of transient processes were constructed for cases of stable and unstable flight modes. An analysis of the external factors that most affect the flight parameters in various conditions of unmanned aerial vehicle use was carried out.

Aeroelastic Response of Spinning Projectiles with Large Slenderness Ratio at Supersonic Speed

Obvious aeroelastic deformation occurs in spinning projectiles with large slenderness ratio, which seriously affects flight stability and maneuverability. This paper investigates the aeroelastic response of spinning projectiles with large slenderness ratio under supersonic speed. Based on a dynamic mesh method, an unsteady numerical simulation method is developed to study the aeroelasticity of spinning projectiles by coupling aerodynamics and structural dynamics. The numerical simulation method is well validated by the experimental results of AGARD 445.6 wing flutter. Then, the aeroelastic response of spinning projectiles with large slenderness ratio is numerically explored under different flight conditions. The aeroelastic response is obtained, revealing the presence of beat vibrations and variations in response frequency. Furthermore, the influence mechanism of flight conditions on the aeroelastic response is analyzed. The results suggest that the coupling of the first two modes of the projectile caused by the spinning motion leads to the occurrence of beat vibrations in the aeroelastic response; the coupling degree of the first two modes decreases as the angle of attack increases and it increases with the increase in spinning speed; and the time−averaged deformation caused by the time−averaged aerodynamic force is beneficial to the convergence of the aeroelastic response of spinning projectiles, while the rotation−induced Magnus effect is counterproductive.

Autonomous semi-major axis adjustment for mega constellation continuous coverage

Mega constellations have larger number of satellites and higher distribution density compared with traditional constellations, that lead to huge tracking, telemetry and command (TT&C) requirement, heavy computation load for configuration design, and frequent configuration control due to low-Earth perturbations, collision avoidance emergencies, etc. This paper proposes a novel constellation control scheme for mega constellations with the same semi-major axis, that is based on the inter-satellite boundary constraints. Satellites do not follow the designed configuration, but keep bounded and stable flight with respect to adjacent satellites. The continuous coverage requirement is considered for priority. The inter-satellite continuous coverage constraint is formulated as right ascension of ascending node constraint and relative distance boundary constraint between every two adjacent coplanar satellites. To reduce control consumption, the boundary constraint is kept by adjusting the semi-major axes of coplanar satellites. To that end, the relationship between relative distance boundary and semi-major axis difference is studied. The semi-major axis adjustment strategy for a single satellite is proposed, and the control rules for coplanar satellites are determined. The proposed control method is verified in GW-2 sub-constellation, and is compared with relative station-keeping control method. Results indicate its effectiveness and good performance in control frequency and consumption.

Trajectory tracking control for quadrotor unmanned aerial vehicle with input delay and disturbances

AbstractThis paper aims to solve the tracking control problem for quadrotor unmanned aerial vehicle (UAV) with input delay and disturbances. An appropriate auxiliary system is applied to compensate the effect of the input delay. The nonlinear disturbance observer is utilized to restrain the influence of external disturbances. Then, the controller is designed by backstepping method to ensure the trajectory tracking and steady flight of the quadrotor UAV. We also present simulation and experimental reification results to demonstrate the tracking effect and stable flight of the UAV.

Enhancing Data Discretization for Smoother Drone Input Using GAN-Based IMU Data Augmentation

This study investigates the use of generative adversarial network (GAN)-based data augmentation to enhance data discretization for smoother drone input. The goal is to improve unmanned aerial vehicles’ (UAVs) performance and maneuverability by incorporating synthetic inertial measurement unit (IMU) data. The GAN model is employed to generate synthetic IMU data that closely resemble real-world IMU measurements. The methodology involves training the GAN model using a dataset of real IMU data and then using the trained model to generate synthetic IMU data. The generated synthetic data are then combined with the real data for data discretization. The resulting improved data discretization is evaluated using statistical metrics and a similarity evaluation. The improved data discretization demonstrates enhanced drone performance in terms of flight stability, control accuracy, and smoothness of movements when compared to standard data discretization methods. These results highlight the potential of GAN-based data augmentation for enhancing data discretization and improving drone performance. The proposition of improved data discretization offers a tangible benefit for the successful integration of Advanced Air Mobility (AAM) systems. Enhancing the accuracy and reliability of data acquisition and processing in UAS makes UAS operations safer and more reliable. This improvement is crucial for achieving the goal of automated and autonomous operations in diverse settlement environments, encompassing multiple mobility modes such as ground and air transportation.