Aircraft Maneuvers Research Articles

Numerical Analysis of Rotor/Propeller Aerodynamic Interactions on a High-Speed Compound Helicopter

In the context of the development of high-speed compound helicopters, the main rotor may not be an efficient propulsive device at high speeds and adding a propulsive propeller is a means to enable higher speed. On such configuration, at low speed, the propellers are in strong interactions with the main rotor wake which affects their performance and aircraft maneuverability. The present work numerically investigates the aerodynamics of the rotor/propeller interaction on rotorcraft similar to the Racer from Airbus Helicopters. Through the comparison of two different levels of fidelity for three different advance ratios, it is shown that at high advance ratio, a simple free wake model is suitable to give most of the interaction effects, while in hover, a full computational fluid dynamics (CFD) unsteady computation is necessary to better capture all the unsteadiness of the interaction. The detailed analysis of CFD results also outlines the different behaviors of the propeller when it is fully inside the rotor wake or out of it, and therefore the need for a precise control of the rotorcraft in the transition between hover to fast forward flight.

Survival of Unmanned Aerial Vehicles by Luring Pursuers in Angle Constrained Interception

In this paper, a sliding mode control-based cooperative guidance strategy for a team of two unmanned aerial vehicles (aircraft), which ensures their survival against pursuers, is proposed. The pursuing interceptors are assumed to employ augmented proportional navigation guidance. The cooperating aircraft maneuver in a way to lure their respective pursuers to an impact angle constrained collision. The problem of controlling impact angle is first transformed to that of tracking line-of-sight angle and its rate, and then the same is achieved by enforcing sliding mode on appropriate chosen switching surface. Furthermore, the allocation of aircraft’s lateral accelerations is performed in a way to minimize the instantaneous aerodynamic drag acting on both unmanned aerial vehicles. Numerical simulations are presented to validate the effectiveness of the proposed guidance strategy under different engagement geometries.

Discontinuous maneuver trajectory prediction based on HOA-GRU method for the UAVs

<abstract> <p>With the rapid development of artificial intelligence technology, the intelligence and autonomy of Unmanned Aerial Vehicles (UAVs) have been significantly improved. Because the real trajectory data is often discontinuous and random, the current aircraft maneuver trajectory prediction methods are far from meeting the practical requirements of the autonomous air tasks. Especially, in order to occupy a better position rapidly where it is easier to attack the enemy, a fast and accurate maneuver trajectory prediction method for the UAVs is proposed in this paper. Firstly, the prediction model of aircraft maneuvering trajectory is built by extracting characteristic information from the historical trajectory. Aiming at the problem of slow optimization speed and easy to fall into local optimization, a global aircraft maneuver trajectory prediction method based on the Hummingbird Optimization Algorithm (HOA) and Gated Recurrent Unit (GRU) is proposed. Then, the implementation process of the maneuver trajectory prediction method based on the above HOA-GRU network for the UAVs is presented. Finally, the aircraft maneuver trajectory prediction method is applied to a simulation training system with the discontinuous and random air task data. The simulation results show that the proposed method can predict the maneuver trajectory of the UAVs with discontinuous data in real time with less error and less time.</p> </abstract>

Investigations of the algorithms linear properties for strapdown inertial navigation systems

The basic operation principles of the strapdown inertial navigation systems (SINS) without platform and models of the measuring sensors errors, including offsets of zero signals, errors of scale factors and cross-links connections, are considered. The influence of various components of these errors and their linear combinations on the numeration accuracy of coordinates, velocity and orientation angles is investigated by the method of mathematical modeling of the SINS operation at one and a half hour intervals. To assess the linear properties of SINS algorithms, a quantitative measure is introduced — the value of the numeration error deviation, caused by a linear combination of input errors, relative linear combination of errors caused by separate input errors, as a percentage is expressed. Numerical estimates for typical trajectories of a maneuverable aircraft are obtained for this value. The obtained results can serve as the basis for the formation of technical requirements, used at the design and testing of aviation navigation systems and complexes. Keywords strapdown inertial navigation system, potential of the gravity field, gravitational acceleration, apparent acceleration, numeration errors, math modeling

Ways to Determine the Structural Resource of Highly Maneuverable Aircraft

This paper emphasizes the importance of monitoring aircraft structural fatigue and proposes as paramount the analysis of military aircraft structural constitutive materials aging process, during flight. Aircraft structural health monitoring is defined as an evaluation process for the integrity of key structural components with the sole purpose of enhancing flight safety and mitigating maintenance risks and loses. Nowadays, aircraft are predominantly built from composite materials with at least two layers with different mechanical properties, which combined, result in a new composite material with highly superior resilience and elastic properties. Even though there are great advantages of using composite materials, when it comes to operating military aircraft, a mere visual inspection cannot be sufficient for observing or identifying structural damages within the composite layers of the aircraft. The focus of this study is on improving the process of monitoring the structural condition of highly maneuverable military jet aircraft by using the strain gauge marks methods. Monitoring aircraft structural condition can be easily implemented, both during maintenance and flight missions, by using a wide array of sensors that can generate specific sets of instructions for all processes involved in enhancing flight and maintenance safety. The main concern of implementing a structural evaluation, within aircraft maintenance processes, sits on preventing and not ameliorating incidents and accidents during flight. As a result of the continuous research and testing, it has been proved that the operational resource of the aircraft structure, provided by the manufacturer, can be easily reached in a lot lesser flight hours than initially anticipated, by engaging the aircraft in specific operational missions and, therefore, inflicting pronounced fatigue on the aircraft structure.

Identification of the key design inputs for the FEM-based preliminary sizing and mass estimation of a civil aircraft wing box structure

FEM-based preliminary structural sizing has been successfully carried out for a typical single-aisle wing box structure using MSC Nastran, by considering various load cases representing typical aircraft manoeuvres, engine loads, landing and ground handling conditions. The strength, buckling and fatigue criteria have been applied as the design constraints for sizing. The resultant total mass and the structural (static and modal) behaviour of the sized wing box model have been verified against a validated high-fidelity wing box model. A sensitivity analysis has been performed to evaluate the influence of the number of design fields and the selected design inputs (i.e. load cases and design constraints) on the accuracy of sizing and mass estimation of the wing box. This sensitivity analysis has also been extended to the static and modal behaviour of the wing box structure obtained from sizing. It provides an insight into the significance of considering the buckling and fatigue constraints, aircraft rolling loads, engine loads and landing loads in sizing, in addition to the commonly-applied 2.5 g aircraft pull-up loads under the strength constraint. The findings of this study highlight the trade-off between the sizing efficiency and accuracy of a civil aircraft wing for modelling purposes.

Situational Awareness and Problems of Its Formation in the Tasks of UAV Behavior Control

Situational awareness formation is one of the most critical elements in solving the problem of UAV behavior control. It aims to provide information support for UAV behavior control according to its objectives and tasks to be completed. We consider the UAV to be a type of controlled dynamic system. The article shows the place of UAVs in the hierarchy of dynamic systems. We introduce the concepts of UAV behavior and activity and formulate requirements for algorithms for controlling UAV behavior. We propose the concept of situational awareness as applied to the problem of behavior control of highly autonomous UAVs (HA-UAVs) and analyze the levels and types of this situational awareness. We show the specifics of situational awareness formation for UAVs and analyze its differences from situational awareness for manned aviation and remotely piloted UAVs. We propose the concept of situational awareness as applied to the problem of UAV behavior control and analyze the levels and types of this situational awareness. We highlight and discuss in more detail two crucial elements of situational awareness for HA-UAVs. The first of them is related to the analysis and prediction of the behavior of objects in the vicinity of the HA-UAV. The general considerations involved in solving this problem, including the problem of analyzing the group behavior of such objects, are discussed. As an illustrative example, the solution to the problem of tracking an aircraft maneuvering in the vicinity of a HA-UAV is given. The second element of situational awareness is related to the processing of visual information, which is one of the primary sources of situational awareness formation required for the operation of the HA-UAV control system. As an example here, we consider solving the problem of semantic segmentation of images processed when selecting a landing site for the HA-UAV in unfamiliar terrain. Both of these problems are solved using machine learning methods and tools. In the field of situational awareness for HA-UAVs, there are several problems that need to be solved. We formulate some of these problems and briefly describe them.

Experimental and computational investigation of flow boiling in microgravity

This study explores use of Computational Fluid Dynamics (CFD) to predict near-saturated flow boiling of FC-72 in microgravity. The computational method employs transient analysis to predict detailed interfacial behavior and heat transfer characteristics along a rectangular channel heated along two opposite walls. Predicted results are validated against experimental temperature measurements and high-speed video images captured during a series of parabolic aircraft maneuvers for three sets of operating conditions which include variations of both mass velocity and wall heat flux. The computational method is based on the multi-phase volume of fluid (VOF) model, which is combined with appropriate phase change and turbulence models, and accounts for both shear-lift force on bubbles and conjugate heat transfer along the heating walls. A key advantage of the CFD method is ability to capture details that are very difficult to measure experimentally, including detailed spatial variations of bubble shape, void fraction, mixture fluid temperature, liquid velocity, and vapor velocity, results for which are presented for each of the three test cases. Different flow regimes predicted along the heated length exhibit a number of dominant mechanisms including bubble nucleation, bubble growth, coalescence, vapor blankets, interfacial waviness, and residual liquid sub-layer, all of which agree well with experiment. Vapor velocity is shown to increase appreciably along the heated length because of increased void fraction, while liquid velocity experiences large fluctuations. Non-equilibrium effects are accentuated with increasing mass velocity, contributing minor deviations of fluid temperature from simulations compared to those predicted by the analytical method. Predicted wall temperature is fairly uniform in the middle of the heated length but increases in the entrance region, due to sensible heat transfer in the subcooled liquid, and decreases toward the exit, mostly because of flow acceleration resulting from increased void fraction.

Turbulence Modeling for Leading-Edge Vortices: An Enhancement Based on Experimental Data

Low-aspect ratio wing planforms, such as delta wings, experience the predominance on their aerodynamic characteristics of large-scale leading-edge vortices separating around the leading edges. Due to their important application for highly maneuverable aircraft, the physical and aerodynamic understanding related to the vortex flow is of primary relevance. The investigation process is routinely performed with numerical simulations employing Reynolds-averaged Navier–Stokes equations. As the vortex grows in intensity, the limitation of ordinary models reduces the accuracy grade. Scale-resolving or more complex turbulence models can increase the accuracy, but the computational cost prohibits the application to a large envelope of cases. In the context of this work, the enhancement of a one-equation eddy-viscosity model is employed. The model is improved by formulating additional vortex source terms exclusively active inside the vortex-flow region and by employing a calibration procedure that is integrated into an iterative automated process where experimental data are used as targets for optimizing the model. The accuracy is enhanced for a cluster of cases around the calibration target, and it shows the potential of the application to large datasets that include several geometric and flow condition variations.

Assessment of the Method of Merging Landing Aircraft Streams in the Context of Fuel Consumption in the Airspace

The most important directions in the field of sustainable development of air transport concern increasing the capacity of airports and improving the global civil aviation system, improving air traffic safety, and developing procedures to optimize the operation of the aviation system. An important area is environmental protection and measures to minimize the negative impact of civil aviation activities on the environment. Air traffic and the operation of airports generate adverse environmental effects, including greenhouse gas emissions, air pollution, and noise emissions. Due to the high intensity of aircraft maneuvers, the authors analyzed aircraft traffic in the area approaching the airport. It is essential to correctly line up for aircraft reporting from different entry points to the approach area to avoid waiting for landing. Misalignment of landing aircraft negatively impacts airport capacity, increases fuel consumption through more prolonged waiting times in space, and directly impacts air pollution. There are different ways to organize landing aircraft flows and other ways to merge these flows. The article aims to assess the method of combining the streams of landing aircraft and estimate the impact of such an organization on the increased fuel consumption of aircraft and thus on air pollution. The authors proposed a measure for assessing the quality of the landing queue, which was defined as the increase in flight time of aircraft in the approach area in relation to the nominal time, which was adopted as minimization. In order to obtain the results of research works, a model using a Petri net was developed, allowing for flexible mapping of concurrent processes and their effect analysis. Various methods of combining the streams of landing aircraft have been adopted: three-stage, two-stage, and single-stage. Then, simulation experiments were carried out, allowing the determination of whether the method of combining the streams of landing planes has an impact on the quality of the landing queue measured with the proposed index. The obtained results of the assessment can be used to estimate the increased fuel consumption of the aircraft.

A neural network learning-based global optimization approach for aero-engine transient control schedule

Transient performance of aero-engine determines the maneuverability of aircraft. The optimal control schedule can tap the potential transient performance with subject to each constraint. Thus the transient time can be minimized with the optimal transient control schedule. This transient schedule is described by a strong constrained and nonlinear problem. It is therefore challenging to present an optimal method to achieve the best transient schedule. Motivated by solving this problem, a surrogate-assisted optimization framework is presented by using the learning capability of neural networks. It is achieved by presenting a sequential ensemble radial basis function (RBF) neural network-based optimization (SERO) algorithm. The advantage of the RBF neural network such as excellent prediction accuracy is taken and integrated into the surrogate-assisted optimization algorithm to improve the algorithm performance. With the application of the proposed scheme, the global optimization schedule is guaranteed for aero-engine transient control. Numerical validation is finally carried out by applying the presented optimization framework to a mixed-flow aero-engine transient control schedule. It is demonstrated that the SERO approach can minimize the transient process time despite any constraint at any time.

Coupling Mid-Fidelity Aerodynamics and Multibody Dynamics for the Aeroelastic Analysis of Rotary-Wing Vehicles

A mid-fidelity aerodynamic solver based on the vortex particle method for wake modeling, DUST, is coupled through the partitioned multi-physics coupling library preCICE to a multibody dynamics code, MBDyn, to improve the accuracy of aeroelastic numerical analysis performed on rotary-wing vehicles. In this paper, the coupled tool is firstly validated by solving simple fixed-wing and rotary-wing problems from the open literature. The transient roll maneuver of a complete tiltrotor aircraft is then simulated, to show the capability of the coupled solver to analyze the aeroelasticity of complex rotorcraft configurations. Simulation results show the importance of the accurate representation of rotary wing aerodynamics provided by the vortex particle method for loads evaluation, aeroelastic stability assessment, and analysis of transient maneuvers of aircraft configurations characterized by complex interactional aerodynamics. The limited computational effort required by the mid-fidelity aerodynamic approach represents an effective trade-off in obtaining fast and accurate solutions that can be used for the preliminary design of novel rotary-wing vehicle configurations.

Sliding mode control of directly excited structural dynamic model of twin-tailed fighter aircraft

The buffeting phenomenon can lead to long-term damage in aeroelastic bodies due to fatigue. It can also restrict the maneuverability of aircrafts. In this work, the buffeting problem of the twin-tails of a fighter aircraft is tackled. A nonlinear model of the twin-tails is utilized, and the buffeting load is simulated using a wind disturbance model that combines discrete wind gust and Von-Karman wind turbulence. An integral sliding mode controller is developed to suppress the vibrations of the twin-tails. Simulation studies demonstrate the effectiveness of the sliding mode controller at suppressing the vibrations the twin-tails.

Discrete-to-deep reinforcement learning methods

Neural networks are effective function approximators, but hard to train in the reinforcement learning (RL) context mainly because samples are correlated. In complex problems, a neural RL approach is often able to learn a better solution than tabular RL, but generally takes longer. This paper proposes two methods, Discrete-to-Deep Supervised Policy Learning (D2D-SPL) and Discrete-to-Deep Supervised Q-value Learning (D2D-SQL), whose objective is to acquire the generalisability of a neural network at a cost nearer to that of a tabular method. Both methods combine RL and supervised learning (SL) and are based on the idea that a fast-learning tabular method can generate off-policy data to accelerate learning in neural RL. D2D-SPL uses the data to train a classifier which is then used as a controller for the RL problem. D2D-SQL uses the data to initialise a neural network which is then allowed to continue learning using another RL method. We demonstrate the viability of our algorithms with Cartpole, Lunar Lander and an aircraft manoeuvring problem, three continuous-space environments with low-dimensional state variables. Both methods learn at least 38% faster than baseline methods and yield policies that outperform them.

Distributed State Estimation for Stochastic Linear Hybrid Systems With Finite-Time Fusion

Building on the classical interacting multiple model algorithm, this article develops a novel distributed approach for solving the problem of distributed state estimation for stochastic linear hybrid systems. In our distributed framework, a network of sensors is employed and each of them measures only a portion of the system outputs, thus, the system may not necessarily be observable for any individual sensor. To tackle with this, we develop an effective data fusion scheme that enables the sensor network to collectively measure the output of the hybrid system, by leveraging the communication between neighboring sensors. Consequently, each sensor only needs to process a relatively small set of data and is able to locally and identically observe the states (both the continuous states and discrete modes) of stochastic linear hybrid systems. Stability of the proposed distributed algorithm is proved theoretically, in the sense that the covariance of estimation error is lower and upper bounded. Finally, the performance of the proposed algorithm is demonstrated via illustrative simulations on a maneuvering aircraft tracking problem.

Design and co-simulation of a nose wheel steering system for a civil aircraft

In order to automate the ground maneuvering of a civil regional aircraft and improve the efficiency of the air transport system, a fly-by-wire nose wheel steering system (NWSS) was designed. A rack and pinion steering mechanism integrated with a single actuator mechanism was proposed. The basic control circuit diagram with integrated test, the electro-hydraulic system diagram, and the mathematical model of the steering system were established and analyzed. A co-simulation model of the system was built to verify the control law. The results show that the properties of the prototype meet the design requirements. Given the importance of the NWSS, the simulation results can be used to optimize the basic design parameters. This methodology can also be used for other types of aircraft.

Flight safety event management method as illustrated by a guided reactivity model

The article provides a brief analysis of the problems of the existing flight safety management system in the state aviation of the Russian Federation, based on the lack of stable positive dynamics of accidents reduction. Brief conclusions from the analysis of the currently proposed scientific approaches for accidents reduction are given. The most significant practical results in the field of building a safety management system for a particular flight are considered. A new approach to the implementation of on-board flight safety management systems based on event management is proposed. The method of event-based safety management of a particular flight allows us to exclude the real time manifestation of known dangerous factors. To implement it, all processes related to known hazards are described in the form of events and assembled into complete groups of events. Control of the occurrence of the complete groups of events, their analysis and event management are carried out by event management models developed for each dangerous factor. When a certain number of events in one or several complete groups of events is reached, the aviation system protection algorithm, by preventing the occurrence of the remaining one or several events of the complete group, prevents erroneous actions of the crew, which prevents the occurrence of aviation incidents and accidents. As an example of the method implementation, the principle of forming an automated guided reactivity model of the event control contour for the dangerous factor "Violation of the Established Minimum Safe Parameters of the Aircraft Flight" in relation to an arbitrary maneuverable aircraft is considered in the article. The system, having registered the events that determine the group flight, is included into the analysis of dynamic elementary events determining the position of the wingman relating to the leading aircraft inside the event control contour in terms of range, angle of sight and altitude separation. When the parameters of one of the dynamic events approach the boundary of the event control contour, the system uses a recommendation or control action to set limits to the parameters not to go beyond the contour, which prevents the occurrence of erroneous actions of the crew.

ANALYSIS OF SENSITIVITY OF TARGET TRACKING SYSTEMS TO EXTERNAL INTERFERENCE IN MULTICHANNEL RADARS WITH FIXED PARAMETERS

The multichannel and fixed parameters radars for tracking targets with the phased array antennas are widely used in modern military surveillance systems. The modular integration of a phased antenna array with digital processors allows to realize the command and control functions of antenna patterns for tracking multiple targets in the time resolution modes. Tracking of the air targets in range, radial speed and angular coordinates of evaluations and azimuth is provided by means of the multichannel radars without adaptation modes to the characteristics of external influences. Thus, adjusting the algorithms of tracking systems to the maximum maneuverability of the air targets can lead to a significant reduction in the accuracy of surveillance in comparison with the potentially achievable accuracy for such radars of tracking the linear flight targets in the long duration of time. In the case of adjusting the algorithms of tracking systems to either low intensity of flying targets, or lack of the aircraft maneuvering, it is possible to significantly increase the error of the aircraft flying information, and as a result to have a disruption of tracking the air targets. The increase in the parameters of the tracking error in relation to the influence of external interference were obtained as a result of the study. As a result of research, it is possible to assess the feasibility of adapting to certain characteristics of external influences, and provide recommendations for selecting and fixing the parameters of algorithms of tracking systems to ensure their versatility to surveillance targets with both high maneuverability, and implementing the stealth technology.

ВИЗНАЧЕННЯ ПОТРІБНОГО ПИТОМОГО НАВАНТА-ЖЕННЯ НА КРИЛО РАКЕТИ

Wing loading severely affects the mass of a missile as well as its flight performance. For airplanes this parameter must not exceed allowable values calculated from different requirements especially related to such cases as lift-off, landing, cruise flight and aircraft maneuverability. For missiles wing loading is determined considering launch conditions and providing the necessary maneuverability. Appropriate estimation of wing loading at the initial design stages guarantees the minimal mass of an aircraft with all tactical requirements met.Review of available literature, related to missile design, has shown that the problem of optimal wing loading estimation contains lengthy and quite approximate analytical expressions.This article is dedicated to the development of a missile wing loading estimation technique that provides minimal propellant mass fraction and total mass of an aircraft while meeting tactical requirements.Impact of wing loading onto propellant mass fraction, maximal maneuverability and total mass of a missile is considered. The algorithm of optimal wing loading estimation, which provides necessary tactical characteristics of a missile being designed, is proposed. We define simple polynomial approximations of both the trajectory and the velocity profile. Further analysis is being conducted using two considerations: for an air-based missile the value of wing loading has to provide flight during launch without fall movement as well as the maximal maneuverability at the moment when a missile intercepts the target.It is shown that for the wing loading in the range from 300 to 1000 kg/m2 the propellant mass fraction changes rapidly, and inaccurate selection of wing loading may lead to obtaining of an incorrect value of propellant mass fraction. For maximal maneuverability less than 40, inappropriate selection of wing loading may cause significant numerical error. Analysis of relation between wing loading and total mass of a missile revealed that there is a critical value of wing loading which depends on initial data and represents the low limit of an acceptable range.

Learning from nature for healthcare, energy, and environment

Learning from nature for healthcare, energy, and environment