Flight Stability Research Articles

Numerical investigations of vortex formation on a generic multiple-swept-wing configuration

For an improvement of the flight stability characteristics of high-agility aircraft, the comprehension of the vortex development, behavior and break down is important. Therefore, numerical investigations on low aspect ratio, multiple-swept-wing configurations are performed in this study to analyze the influence of the numerical method on the vortex formation. The discussed configurations are based on a triple- and double-delta wing planform. Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations and delayed detached eddy simulations (DDES) are performed for both configurations. The simulations are executed at Re = 3.0times 10^6, symmetric freestream conditions, and an angle of attack of alpha = 16^circ, for consistency with reference wind tunnel data. For the triple-delta-wing configuration, the results of the DDES show a satisfying accordance to the experiments compared to URANS, especially for the flow field and the pitching moment coefficient. For the double-delta-wing configuration, the URANS simulation provides reliable results with low deviation of the aerodynamic coefficients and high precision for the flow field development with respect to the experimental data.

The damping properties of the foam-filled shaft of primary feathers of the pigeon Columba livia

The avian feather combines mechanical properties of robustness and flexibility while maintaining a low weight. Under periodic and random dynamic loading, the feathers sustain bending forces and vibrations during flight. Excessive vibrations can increase noise, energy consumption, and negatively impact flight stability. However, damping can alter the system response, and result in increased stability and reduced noise. Although the structure of feathers has already been studied, little is known about their damping properties. In particular, the link between the structure of shafts and their damping is unknown. This study aims at understanding the structure-damping relationship of the shafts. For this purpose, laser Doppler vibrometry (LDV) was used to measure the damping properties of the feather shaft in three segments selected from the base, middle, and tip. A combination of scanning electron microscopy (SEM) and micro-computed tomography (µCT) was used to investigate the gradient microstructure of the shaft. The results showed the presence of two fundamental vibration modes, when mechanically excited in the horizontal and vertical directions. It was also found that the base and middle parts of the shaft have higher damping ratios than the tip, which could be attributed to their larger foam cells, higher foam/cortex ratio, and higher percentage of foam. This study provides the first indication of graded damping properties in feathers.

Проектирование рамы автономного летательного аппарата с применением композиционных материалов

The paper considers approaches to creating a new type of unmanned aircrafts - quadcopters. It is stated that the efficiency of a quadcopter directly depends on its frame design and the structural materials used. The approaches to designing the aircraft frame using computer-aided design tools (SolidWorks package) are described. The stress maps obtained during the strength study for the frame beam made of carbon fiber allow asserting a large margin of structural strength. The strength calculation carried out predetermined the need to take into account the influence of additional factors (the air flow created by the traction screws). The existing restrictions on the maximum size of the rotating propellers predetermined the design of the quadcopter frame taking into account the maximum number of possible aerodynamic effects that determine the stability of flight characteristics by minimizing interference from air turbulence, as well as from possible natural phenomena. The designed quadcopter frame has special aerodynamic surfaces that allow for a stable flight path in a volatile air environment. The generated torque is determined by the characteristics of the traction screw motors. The influence of the isosurface air flow on the design of the quadcopter was evaluated.

Cascaded PID Control System for UAV with Gain Factor Prediction Using ML

Abstract: Drones are not inherently stable, necessitating the use of a flight controller. If the UAV is properly tuned, the drone will fly steadily; otherwise, it won’t. Hence, we have used a PID (proportional, integral, differential) controller for a stable flight. A well-functioning PID controller should enable amazing climbs and long-range flights. But, when used singly, PID controllers can provide poor performance, resulting in a long settling time, overshoot, and oscillation. Here, we propose a new approach to maneuver UAVs using a PID control system and overcome the shortcomings of using PID controllers in UAVs. This disadvantage is resolved using the Machine Learning polynomial regression model. The gain factors in a PID control system, which is otherwise ideally constant, should be changed in order to reduce the minor instabilities for a smooth flight. Our method has been elaborated and illustrated with suitable diagrams in the following work. When simulated in Gazebo on a Robot Operating System (ROS), our technique is proven to be successful. Keywords: Control Systems, PID, UAV, Drones, Polynomial Regression, Gain Factor, Prediction Algorithm.

FLIGHT DYNAMICS AND STABLE CONTROL ANALYSES OF MULTI-BODY AIRCRAFT

Multi-body aircraft is a new concept aircraft consisting of multiple small unmanned aerial vehicles hinged-connected by wing tips. This concept aircraft can integrate the performance and advantages of two types of flying platforms: small unmanned aerial vehicles and high-altitude long endurance unmanned aerial vehicles. It has great development potential. Based on the Newton-Euler equation and on the lifting line method, it establishes a multi-body aircraft flight dynamics model, and analyzes the trim and stability characteristics of the multi-body aircraft system that allowing the relative degree of freedom of rolling motion with the dual-aircraft combination. The results show that, different from the traditional configuration aircraft, the multi-body aircraft system has an unstable relative motion flight mode, which is dominated by relative rolling motion. This configuration aircraft cannot fly stably in an uncontrolled situation. Based on the completion of the dynamics modeling, the Proportion-Integration-Differentiation control method is used for stable control. The stable control loop is designed separately for each single aircraft to achieve the purpose of stable flight. The simulation results show that the control method is effective and can quickly stabilize the divergent flight dynamics system.

Demonstration of tethered hovering flight of HTTP-3AT hybrid rocket

This study demonstrated the performance of flight control systems of a hybrid rocket in a hovering flight test by developing a rocket designated HTTP-3AT powered by High Test Peroxide (HTP, a term used for concentrated hydrogen peroxide, H2O2). Hybrid rocket excels in system simplicity, operational safety, oxidizer storability, cost, and throttling capability compared to current solid and liquid rocket engine systems. Although issues such as the severe oxidizer-to-fuel (O/F) ratio shift during combustion and difficulty in gimbaled thrust vector control (TVC) caused by the lengthy chambers need to be solved, hybrid rocket propulsion is nevertheless a promising propulsion technology for future space exploration. To achieve accurate orbit insertion, thrust magnitude control and TVC of the rocket engines are necessary. However, no organizations have successfully implemented this technology on a practical hybrid rocket, not even using this technology for hovering flight tests. On September 8th, 2020, a hovering flight test of HTTP-3AT was conducted, achieving a steady hover 3 m above ground for 25 s utilizing both attitude and position controls. This test showed that a hybrid rocket could achieve a stable hovering flight with the capability of vertical takeoff and vertical landing (VTVL), demonstrating excellent throttling control and TVC capabilities of hybrid rocket propulsion.

Flight Stability of Rigid Wing Airborne Wind Energy Systems

The flight mechanics of rigid wing Airborne Wind Energy Systems (AWESs) is fundamentally different from the one of conventional aircrafts. The presence of the tether largely impacts the system dynamics, making the flying craft to experience forces which can be an order of magnitude larger than those experienced by conventional aircrafts. Moreover, an AWES needs to deal with a sustained yet unpredictable wind, and the ensuing requirements for flight maneuvers in order to achieve prescribed control and power production goals. A way to maximize energy capture while facing disturbances without requiring an excessive contribution from active control is that of suitably designing the AWES craft to feature good flight dynamics characteristics. In this study, a baseline circular flight path is considered, and a steady state condition is defined by modeling all fluctuating dynamic terms over the flight loop as disturbances. In-flight stability is studied by linearizing the equations of motion on this baseline trajectory. In populating a linearized dynamic model, analytical derivatives of external forces are computed by applying well-known aerodynamic theories, allowing for a fast formulation of the linearized problem and for a quantitative understanding of how design parameters influence stability. A complete eigenanalysis of an example tethered system is carried out, showing that a stable-by-design AWES can be obtained and how. With the help of the example, it is shown how conventional aircraft eigenmodes are modified for an AWES and new eigenmodes, typical of AWESs, are introduced and explained. The modeling approach presented in the paper sets the basis for a holistic design of AWES that will follow this work.

Wings and halteres act as coupled dual oscillators in flies

The mechanics of Dipteran thorax is dictated by a network of exoskeletal linkages that, when deformed by the flight muscles, generate coordinated wing movements. In Diptera, the forewings power flight, whereas the hindwings have evolved into specialized structures called halteres, which provide rapid mechanosensory feedback for flight stabilization. Although actuated by independent muscles, wing and haltere motion is precisely phase-coordinated at high frequencies. Because wingbeat frequency is a product of wing-thorax resonance, any wear-and-tear of wings or thorax should impair flight ability. How robust is the Dipteran flight system against such perturbations? Here, we show that wings and halteres are independently driven, coupled oscillators. We systematically reduced the wing length in flies and observed how wing-haltere synchronization was affected. The wing-wing system is a strongly coupled oscillator, whereas the wing-haltere system is weakly coupled through mechanical linkages that synchronize phase and frequency. Wing-haltere link acts in a unidirectional manner; altering wingbeat frequency affects haltere frequency, but not vice versa. Exoskeletal linkages are thus key morphological features of the Dipteran thorax that ensure wing-haltere synchrony, despite severe wing damage.

Flight Dynamics Modeling, Trim, Stability, and Controllability of Coaxial Compound Helicopters

Coaxial compound helicopters feature high-speed characteristics that are not possessed by conventional helicopters. The aim of this paper is to develop a flight dynamics model of coaxial compound helicopters and investigate the trim, stability, and controllability. A flight dynamics model including a coaxial rotor model and a propeller model is introduced. Based on the flight dynamics model, the trim of hover and level flights of a coaxial compound helicopter is performed. Considering the influence of flapping motions, stability and control derivatives are assessed under the small disturbance hypothesis by using a numerical differentiation method. Then, stability and response of the coaxial compound helicopter are presented. The results of trim show good agreement with those of the reference, which verifies the flight dynamics model. The speed static stability derivative is stable in whole trim range, while the angle of attack static stability derivative is unstable. The yawing control with collective differential of the coaxial compound helicopter will induce serious roll effect in high-speed flights.

Inflight head stabilization associated with wingbeat cycle and sonar emissions in the lingual echolocating Egyptian fruit bat, Rousettus aegyptiacus.

Sensory processing of environmental stimuli is challenged by head movements that perturb sensorimotor coordinate frames directing behaviors. In the case of visually guided behaviors, visual gaze stabilization results from the integrated activity of the vestibuloocular reflex and motor efference copy originating within circuits driving locomotor behavior. In the present investigation, it was hypothesized that head stabilization is broadly implemented in echolocating bats during sustained flight, and is temporally associated with emitted sonar signals which would optimize acoustic gaze. Predictions from these hypotheses were evaluated by measuring head and body kinematics with motion sensors attached to the head and body of free-flying Egyptian fruit bats. These devices were integrated with ultrasonic microphones to record sonar emissions and elucidate the temporal association with periods of head stabilization. Head accelerations in the Earth-vertical axis were asymmetric with respect to wing downstroke and upstroke relative to body accelerations. This indicated that inflight head and body accelerations were uncoupled, outcomes consistent with the mechanisms that limit vertical head acceleration during wing downstroke. Furthermore, sonar emissions during stable flight occurred most often during wing downstroke and head stabilization, supporting the conclusion that head stabilization behavior optimized sonar gaze and environmental interrogation via echolocation.

Application of a new type of annular shaped charge in penetration into underwater double-hull structure

A new type of annular shaped charge was utilized to enhance penetration performance into underwater structures in this paper. Explosive Formed Projectile (EFP) which can be formed by a shaped charge with a spherical segment liner was proved having a stable flight at a large stand-off distance and causing a large penetration diameter into structures. Therefore, underwater tests of double hull subjected to shaped charges with annular and spherical segment liners were first conducted. Subsequently, the damage characteristics of two layers subjected to these two shaped charges associated with underwater explosion were compared and analysed. The first layer was first penetrated by the projectiles, which resulted in the initial hole. With the effect of the subsequent shock wave and explosive products the hole was enlarged and four big petals were formed around the hole. The maximum dimensions of the crevasse and the deflection caused by the annular projectile associated with underwater explosion were 2.6 and 1.3 times than those by EFP. As for the second layer, although the annular projectile partially penetrated into the shell, it caused a larger plastic deformation than EFP. The comparison results indicate that the proposed annular shaped charge caused more severe damage to the underwater double-hull than the traditional one.

터보제트 복합추진시스템 흡입구의 배압 영역별 내부유로 유동박리 및 블리드 유량 변화 분석

Inlet performance with the back pressure in the TBCC(Turbine-Based Combined Cycle) is analyzed in order to study a stable start of the turbojet engine. A reliable back-pressure boundary condition using total pressure extrapolation method is proposed to investigate the inlet performance and to obtain the turbojet compressor effect in high accuracy. Numerical results show that the location of flow separation of subsonic diffuser can be decided by the subsonic diffuser angle and the bleed effect. In low back-pressure, the total pressure recovery of the turbojet is very low because the terminal shock has relatively strong strength. In high back-pressure, the mass capture ratio is low because of the large amount of the bleed flow rate. Considering the stable flight of TBCC, a range of back pressure may exist even in the critical condition depending on the performance of the engine itself.

Anti‐swing control and trajectory planning of quadrotor suspended payload system with variable length cable

AbstractDifferent from the quadrotor suspended payload system with fixed length cable, the system with variable length cable can load and unload cargoes more efficiently under many conditions. This paper presents a method of modeling, control, and trajectory planning for a quadrotor suspended payload system with variable length cable. In order to effectively reduce the swing of the slung payload under the quadrotor, a coupled dynamic model and an integral backstepping control scheme for the system are designed, and a basic trajectory planning is carried out. The presented coupled dynamic model is composed of two parts, one is the dynamic equation of the quadrotor with payload pull, and the other is the dynamic model of the payload pendulum angles with variable length cable related with quadrotor flight acceleration. Meanwhile, the interaction forces between them are calculated. Based on the coupled dynamic model of the system, a cascade control scheme with trajectory planning is designed. The attitude and position control loop of the system adopt the integral backstepping algorithm to solve the reliable flight of quadrotor with slung payload. At the same time, the flight trajectories are generated by trajectory planning as the reference input of the control system, which can further reduce the payload swing. Simulation results show that the proposed scheme can realize stable and reliable flight of the quadrotor and limit the pendulum angles within the desired range to reduce the payload swing.

Analysis of How the Bonding Force between Two Assemblies Affects the Flight Stability of a High-speed Rotating Projectile

Analysis of How the Bonding Force between Two Assemblies Affects the Flight Stability of a High-speed Rotating Projectile

Development of Medical Drone for Blood Product Delivery: A Technical Assessment

Drone is the well-known technology in military and amateur application. Recently, the drone was used to deliver goods and parcels. There is an increasing need for urgent delivery of medical supplies in low resource setting due to traffic congestion and terrain obstacles. The delivery of blood in emergency cases such as postpartum hemorrhaging is challenging and can be delayed due to geographical condition in underserved area. Postpartum hemorrhaging needs an immediate blood transfusion with proper blood product to save the life of mother and baby. To address to this need, a drone that can deliver blood supply to the desired location may be a good option. Therefore, research has been conducted to identify the baseline of drone specifications for blood delivery. A Hexacopter with the ArduPilot firmware and a Lithium-Polymer battery of 16,000 mAh were used to study the applicability of blood products delivery using drone. Using several tests to assess drone limitations, experimental data was obtained and analyzed using distinctive methods. The results indicated that the thrust-to-weight ratio of the drone play a paramount role for the drone performance and flight time. The GPS guidance performance showed a reliable and stable flight with only a slight deviation of ±6 meters during the tests. Finally, a test flight was conducted to simulate the actual test location from Queen Elizabeth Hospital and Hospital Wanita dan Kanak-Kanak, Likas, Sabah. The developed drone reached a flight time of 25 minutes covering 8.38 km with 4.3 kg take-off weight.

Aerial Tele-Manipulation with Passive Tool via Parallel Position/Force Control

This paper addresses the problem of unilateral contact interaction by an under-actuated quadrotor UAV equipped with a passive tool in a bilateral teleoperation scheme. To solve the challenging control problem of force regulation in contact interaction while maintaining flight stability and keeping the contact, we use a parallel position/force control method, commensurate to the system dynamics and constraints in which using the compliant structure of the end-effector the rotational degrees of freedom are also utilized to attain a broader range of feasible forces. In a bilateral teleoperation framework, the proposed control method regulates the aerial manipulator position in free flight and the applied force in contact interaction. On the master side, the human operator is provided with force haptic feedback to enhance his/her situational awareness. The validity of the theory and efficacy of the solution are shown by experimental results. This control architecture, integrated with a suitable perception/localization pipeline, could be used to perform outdoor aerial teleoperation tasks in hazardous and/or remote sites of interest.

Flow Behaviour Assessment of Smokey SAM Rocket Prototype

This paper presents an aerodynamic assessment on the "Smokey Sam Prototype (TRL-6) Start (X)". Initially, the rocket prototype was designed using OpenRocket open source software, where all of the user's design requirements and objectives are considered. The TRL-6 Smokey Sam Star (X) is expected to fly within 400 m with the operating Mach 0.2, as comparable to US GTR-18A. This research evaluates the aerodynamics performance of the design Smokey Sam prototype rocket using a computational fluid dynamics (CFD) approach. For instance, the CFD study assessed the flight performance and stability once launched, such as lift coefficient, drag coefficient and pitching moment. This research employs K-omega (k-ω) model to express the turbulent properties of the flow. The actual pressure distribution was compared with the conventional rocket material's exact pressure distribution to inspect the best rocket material to sustain the best strength to weight ratio at high-speed trajectory operation. Several observations were made into the modelling process, such as surrounding velocity and pressure. It is found that the flight is in stable mode since the obtained pitching moments are almost zero at all assessed speeds.

Tunnel Gaussian Process Model for Learning Interpretable Flight’s Landing Parameters

Approach and landing accidents have resulted in a significant number of hull losses worldwide. Technologies (e.g., instrument landing system) and procedures (e.g., stabilized approach criteria) have been developed to reduce the risks. This paper proposes a data-driven method to learn and interpret flight’s approach and landing parameters to facilitate comprehensible and actionable insights into flight dynamics. Specifically, two variants of tunnel Gaussian process (TGP) models are developed to elucidate aircraft’s approach and landing dynamics using advanced surface movement guidance and control system (A-SMGCS) data, which then indicates the stability of flight. TGP hybridizes the strengths of sparse variational Gaussian process and polar Gaussian process to learn from a large amount of data in cylindrical coordinates. This paper examines TGP qualitatively and quantitatively by synthesizing three complex trajectory datasets and compared TGP against existing methods on trajectory learning. Empirically, TGP demonstrates superior modeling performance. When applied to operational A-SMGCS data, TGP provides the generative probabilistic description of landing dynamics and interpretable tunnel views of approach and landing parameters. These probabilistic tunnel models can facilitate the analysis of procedure adherence and augment existing aircrew and air traffic controller’ displays during the approach and landing procedures, enabling necessary corrective actions.

On-board cable attitude measurement and controller for outdoor aerial transportation

AbstractDeploying quadcopters for aerial transportation can be cost effective in impromptu material handling applications. However, such applications are limited mainly due to the requirement of onboard localization sensors and associated computation. The current work presents a human-controlled modality to successfully execute spontaneous outdoor flight of a quadcopter with a cable-suspended payload. Stable and smooth flights are achieved through an onboard integration of a custom-built sensor system and a controller to minimize payload oscillations. The feasibility of the proposed modality is demonstrated by conducting outdoor experiments and a case study in an unstructured environment.

Bioinspired Feathered Flapping Wing UAV Design for Operation in Gusty Environment

The flight of unmanned aerial vehicles (UAVs) has numerous associated challenges. Small size is the major reason of their sensitivity towards turbulence restraining them from stable flight. Turbulence alleviation strategies of birds have been explored in recent past in detail to sort out this issue. Besides using primary and secondary feathers, birds also utilize covert feathers deflection to mitigate turbulence. Motivated from covert feathers of birds, this paper presents biologically inspired gust mitigation system (GMS) for a flapping wing UAV (FUAV). GMS consists of electromechanical (EM) covert feathers that sense the incoming gust and mitigate it through deflection of these feathers. A multibody model of gust-mitigating FUAV is developed appending models of the subsystems including rigid body, propulsion system, flapping mechanism, and GMS-installed wings using bond graph modeling approach. FUAV without GMS and FUAV with the proposed GMS integrated in it are simulated in the presence of vertical gust, and results’ comparison proves the efficacy of the proposed design. Furthermore, agreement between experimental results and present results validates the accuracy of the proposed design and developed model.