Aircraft Simulation Research Articles

Research on Trim Simulation and Flight Test of a General Electric Aircraft

In order to study the stable flight of an electric aircraft in the whole flight speed range, taking the manned electric aircraft as an example, the method and principle of Longitudinal Trim for high aspect ratio aircraft are presented. Based on the wind tunnel test data, the torque produced by different gravity centers and tension lines as input parameters, and ignoring the influence of lateral and heading parameters, the three-degree-of-freedom motion equation of the aircraft is established, the difference of the performance parameters before and after the trim state is analyzed, which reflects the flight characteristics of the aircraft in a comprehensive way, and is compared with the flight test data. The simulative simulation data and the flight test data are in good agreement and have certain feasibility, it provides a reference for analyzing the performance parameter modification of other high aspect ratio electric aircraft in the future.

The task of increasing the number of training situations as one of the areas for improving the ergatic software and hardware systems “Aviation simulator”

Currently, the ergatic software and hardware complex, called the “flight simulator”, is used worldwide for professional training of crew members in piloting an aircraft in special flight conditions. Flight and integrated flight simulators include a visual environment simulator that synthesizes for a pilot a three-dimensional image of the external environment behind the simulator’s cabin, which allows pilots to be trained in visual landing on a runway model, while solving aeronautical problems. Simulators of the visual environment developed earlier could not synthesize recognizable areas of the area more than 400 × 400 km in size necessary for training in solving problems of self-driving. Therefore, simulators for the training of navigators were separately developed, teaching the determination of the location of the model of an aircraft in the model of the environment according to the models of radio engineering means of aircraft. Modern optical-technical-software systems for the synthesis of three-dimensional models of the external environment allow us to develop new and modernize existing flight and complex flight simulators by adding training to the crew of the aircraft in solving problems of aircraft navigation. The analysis carried out by the authors of this article showed that for this it is necessary to solve the problem of selecting objects that should become benchmarks and their placement according to the model of a large area. Solutions are proposed that allow us to solve the tasks and develop a model of a recognizable piece of the earth’s surface that is sufficient to solve the problems of piloting and self-driving training on an aircraft simulator.

Pilot’s mental workload nonlinear correlation among objective and subjective measurements

In the aviation framework, the workload evaluation is influenced by human factors effects both for pilots and ground operators. Nevertheless, the measurement of workload is of great importance to prevent human errors due to fatigue. In the present work, correlation analysis has been carried out to investigates the relationship between subjective and objective workload measurements. An experimental campaign was conducted using a full flight business aircraft simulator. Particular attention has been paid to the NASA-TLX subscales contribute. In terms of objective measurements, three different indexes gathered from heart rate variability have been considered. As the main result, the frequency-domain index reveals a large correlation effect with the workload subscale for the maneuvers taken into account.

Large eddy simulation of aircraft at affordable cost: a milestone in computational fluid dynamics

Abstract While there have been numerous applications of large eddy simulations (LES) to complex flows, their application to practical engineering configurations, such as full aircraft models, have been limited to date. Recently, however, advances in rapid, high quality mesh generation, low-dissipation numerical schemes and physics-based subgrid-scale and wall models have led to, for the first time, accurate simulations of a realistic aircraft in landing configuration (the Japanese Aerospace Exploration Agency Standard Model) in less than a day of turnaround time with modest resource requirements. In this paper, a systematic study of the predictive capability of LES across a range of angles of attack (including maximum lift and post-stall regimes), the robustness of the predictions to grid resolution and the incorporation of wind tunnel effects is carried out. Integrated engineering quantities of interest, such as lift, drag and pitching moment will be compared with experimental data, while sectional pressure forces will be used to corroborate the accuracy of the integrated quantities. Good agreement with experimental $C_L$ data is obtained across the lift curve with the coefficient of lift at maximum lift, $C_{L,max}$ , consistently being predicted to within five lift counts of the experimental value. The grid point requirements to achieve this level of accuracy are reduced compared with recent estimates (even for wall modelled LES), with the solutions showing systematic improvement upon grid refinement, with the exception of the solution at the lowest angles of attack, which will be discussed later in the text. Simulations that include the wind tunnel walls and aircraft body mounting system are able to replicate important features of the flow field noted in the experiment that are absent from free air calculations of the same geometry, namely, the onset of inboard flow separation in the post-stall regime. Turnaround times of the order of a day are made possible in part by algorithmic advances made to leverage graphical processing units. The results presented herein suggest that this combined approach (meshing, numerical algorithms, modelling, efficient computer implementation) is on the threshold of readiness for industrial use in aeronautical design.

Design of construction and instrumentation of the Zlín aircraft simulator

Flight simulators play an important role in pilot training around the world. They contribute to increasing the safety of air traffic, allow you to practice dangerous situations and non-standard procedures and thus prepare pilots for dangers during real flight. The article deals with the design and arrangement of the instrument part of the simulator, while the design is based mainly on the flight manual of the aircraft Zlín. The result of our work is the design of the structure, instrumentation of the simulator and the subsequent construction of the simulator. The created frame of the simulator construction, as a fixed platform, is used to place the computer technology and accessories of the simulator. The simulator will serve students of the Department of Air Transport for training procedures during the flight on a given type of aircraft, getting acquainted with the aircraft equipment, or training in non-standard and emergency situations.

Integrated Design of Fault Estimation and Fault-Tolerant Control for Closed-Loop Systems With Uncertain Short Delay

In this paper, an integrated design scheme of fault estimation (FE) and fault-tolerant control (FTC) is presented for a closed-loop system with uncertain short delay. Firstly, a closed-loop system with uncertain short delay is modeled as a system with uncertain parameters, and a bi-directional robustness interaction of uncertainty between the observer and the control system is analyzed. Then a fault estimation observer and a fault-tolerant controller are constructed, and the integrated design problem is converted into a robust control problem for the augmented system under $H_{\infty }$ performance index. Furthermore, the parameters of the fault estimation observer and fault-tolerant controller are solved by Lyapunov function and relaxation methods. Finally, the effectiveness and superiority of the proposed method are verified by an aircraft simulation.

Optimal calculation method of aircraft infrared physical imaging simulation

In order to meet the needs of high-precision simulation images in the development process of infrared imaging detection system, the infrared physical imaging radiation transmission model for aircraft was established, and the ray tracing method was used to realize the simulation calculation of radiance image. Aiming at the difference between the reflection characteristics of the aircraft skin and the distribution characteristics of the radiation source, an optimization method for skin radiance calculation using direct lighting multi-importance sampling was proposed. Aiming at the characteristics of strong emission ability and weak extinction ability of aircraft exhaust plume, an optimization method for exhaust plume radiance calculation using combining integration was proposed. The correctness and effectiveness of the physical imaging model and calculation optimization method were verified through simulation experiments. The relative error of the skin radiation calculation is better than 0.05%, and the relative error of the tail flame radiation calculation is better than 0.1%. Compared with the traditional ray tracing method, the calculation optimization method has a faster convergence speed and stronger adaptability. Infrared imaging simulation and radiation characteristics analysis of stealth aircraft were carried out. The simulation results show that infrared stealth technology can reduce the radiation intensity in the mid-waveband and long-waveband, and increase the reflected radiation intensity in the short-waveband.

DEPARTURE TRAJECTORY OPTIMIZATION FOR NOISE ABATEMENT PROCEDURE IN SOEKARNO-HATTA INTERNATIONAL AIRPORT

Air traffic noise emission has been a growing concern for communities living within the vicinity of airports due to a massive increase in air traffic volume in recent years. This work focuses on the noise annoyance problem by optimizing one of the RNAV trajectories, which aims to minimize the noise footprint of a flying aircraft in a low altitude trajectory. Optimal control theory is applied to minimize the number of awakenings caused by a departing aircraft while constraining the relative increase of fuel consumption with regard to a fuel-minimal trajectory. The aircraft simulation model is based on the BADA 3 database, while the noise is modeled according to the ANP database, both published by EUROCONTROL. The methodology is demonstrated for the Soekarno-Hatta International Airport (CGK) in Jakarta; the result shows the comparison between fuel-minimal trajectories and noise-minimal trajectories for seven aircraft types representing the fleet mix at CGK. The number of awakenings of the noise-minimal trajectories is reduced by 30.33%, with an additional of 5% fuel consumption for the seven aircraft types when compared to the fuel-minimal trajectory.

Modeling, Simulation, and Cruise Characteristics of Wingtip-Jointed Composite Aircraft

In this paper, multibody dynamic modeling and a simulation method for the wingtip-jointing process of a new-concept composite aircraft system are investigated. When the wingtips of two aircraft are jointed, the resultant wingtip-jointed aircraft is regarded as variable-geometry multiple rigid bodies, and a seven-degree-of-freedom non-linear dynamic model is established by mathematical derivation. The slip-meshing method is adopted to analyze the unsteady aerodynamic influence. We also present specific aerodynamic database acquisition methods under the quasi-steady assumption. Based on this, the simulation results indicate that the longitudinal and lateral movements are highly jointed and complex. A new composite aircraft system is investigated, in order to meet the balance requirement. With the lift–drag ratio (K) considered, the piecewise cubic Hermite interpolation (PCHIP) method, with a sufficient sample size, was utilized to help the cruise strategy optimization analysis under fixed altitude and speed conditions. Meanwhile, distribution of cruise characteristics with different sampling values of composite flight characteristic parameters were also analyzed. The research results can be used as a reference for new-concept composite aircraft model establishment, simulation, and multibody dynamic characteristic investigation.

Research on Air Flight Simulation Control Law of Large Aircraft

The air flight simulator, also known as the variable stability aircraft, can make the dynamic characteristics of the machine change or simulate the response characteristics of different objects in a large range through the variable stability telex system. This paper is devoted to the research of the air flight simulation control law of large aircraft, and designs the five degree of freedom variable stability control law: to control the elevator, rudder and aileron of the basic aircraft, and to design the three-degree-of-freedom variable stability control law. The control of the direct lift surface and the automatic throttle was added, and the five-degree-of-freedom variable stability control law was designed to simulate the trajectory characteristics and velocity characteristics. Finally, the variable stability control law is verified based on the target aircraft simulator.

System Identification and LQR Controller Design with Incomplete State Observation for Aircraft Trajectory Tracking

This paper presents a controller design process for an aircraft tracking problem when not all states are available. In the study, a nonlinear-transport aircraft simulation model was used and identified through Maximum Likelihood Principle and Extended Kalman Filter. The obtained mathematical model was used to design a Linear–Quadratic Regulator (LQR) with optimal weighting matrices when not all states are measured. The nonlinear aircraft simulation model with LQR controller tracking abilities were analyzed for multiple experiments with various noise levels. It was shown that the designed controller is robust and allows for accurate trajectory tracking. It was found that, in ideal atmospheric conditions, the tracking errors are small, even for unmeasured variables. In wind presence, the tracking errors were proportional to the wind velocity and acceptable for small and moderate disturbances. When turbulence was present in the experiment, state variable oscillations occurred that were proportional to the turbulence intensity and acceptable for small and moderate disturbances.

Modeling and simulation of mass-actuated flexible aircraft for roll control

Moving mass control (MMC) is a flight control technique that provides several unique advantages over conventional aerodynamic control surfaces, particularly for near space vehicles. In this study, we propose an MMC strategy for roll control of low-speed flexible HALE aircraft. Two internal moving masses are used to produce rolling moment rather than conventional ailerons. The complete equations of motion of the flexible aircraft carrying moving mass are first derived in terms of quasi-coordinates. A simplified model integrated with unsteady aerodynamic loads is obtained for roll control. The effect of moving mass positions on rigid-body motion and aeroelasticity couplings are analyzed. The feasibility of the mass-actuation concept for roll control of the flexible aircraft is primarily proven. The roll control ability and aeroelastic characteristics can be improved through the reasonable design of the moving mass system. The dynamic behavior of the system, while the mass travels along the wing, is simulated, implying that the elastic motion induces the delay effect in the roll motion of the flexible model compared with the rigid model. A roll rate control system is designed and analyzed to demonstrate the feasibility of using moving masses in real-time flight control.

A Novel Hybrid Robust Control Design Method for F-16 Aircraft Longitudinal Dynamics

This paper presents a hybrid robust control design method for a third-order lower-triangular model of nonlinear dynamic systems in the presence of disturbance. In this paper, a novel control design is presented systematically to synthesize a robust nonlinear feedback controller, called backstepping sliding mode control (BSMC), for the proposed system by a combined approach of backstepping design and sliding mode control. In this approach, a family of the “sliding surface” is introduced in state transformations. Then, a smooth switching function of the sliding surface is introduced and enforced to include in virtual feedbacks and a real control law from the control selection phrases of the backstepping design loop. The achieved control method proves a well-tracking command with asymptotic stability, provides a robustness in the presence of uncertainties, and eliminates completely a chattering phenomenon. The application of flight-path angle control corresponding to the longitudinal dynamics of a high-performance F-16 aircraft simulation model is implemented. Under some assumptions, full nonlinear longitudinal dynamics is reformed into a lower-triangular system for a direct application to formulate a control law. A closed-loop system is achieved for in-flight simulation with different flight profiles for a comparison of the existing methods. Also, an external disturbance on different loading/unloading conditions in flight is applied to verify and validate robustness of the proposed control method.

The Simulation of Aircraft Ditching Based on ALE Method

Ditching is an emergency measure for landing on the water when the aircraft cannot continue to fly in an accident. In order to verify the performance of the aircraft ditching, this paper carry out a simulation study on ditching of fixed-wing aircraft on the water. First determine the simulation method, material model and constitutive equation, and then analyze the influence of the sinking speed and attitude changes on the ditching of the aircraft. The simulation method adopts arbitrary Lagrange-Euler method (ALE). The results show that as the sinking speed increases, the load will increase accordingly. As the initial attitude angle increases, the vertical acceleration gradually decreases, and the longitudinal acceleration is basically the same, the pressure acting area gradually moves backward, and the pressure area gradually decreases. It is necessary to take appropriate local strengthening measures on the dangerous region.

Mathematical Modelling of Gimballed Tilt-Rotors for Real-Time Flight Simulation

This paper introduces a novel gimballed rotor mathematical model for real-time flight simulation of tilt-rotor aircraft and other vertical take-off and landing (VTOL) concepts, which improves the previous version of a multi-purpose rotor mathematical model developed by ZHAW and Politecnico di Torino as part of a comprehensive flight simulation model of a tilt-rotor aircraft currently implemented in the Research and Didactics Simulator of ZHAW and used for research activities such as handling qualities studies and flight control systems development. In the novel model, a new formulation of the flapping dynamics is indroduced to account for the gimballed rotor and better suit current tilt-rotor designs (XV-15, V-22, AW-609). This paper describes the mathematical model and provides a generic formulation as well as a specific one for 3-blades proprotors. The method expresses the gimbal attitude but also considers the variation of each blade’s flapping due to the elasticity of the blades, so that the rotor coning angle can be represented. A validation of the mathematical model is performed against the available literature on the XV-15 Tilt-rotor aircraft and a comparison between the previous model is provided to show the improvements achieved. The results show a good correlation between the model and the reference data and the registered performance allow real-time flight simulation with pilot and hardware in the loop.

Data Fusion and Tracking in a Simulated Multiradar Air Command and Control System

Radars play a crucial role in military air operations. They allow the detection with great accuracy of aircrafts flying at long distances. The exploitation of radars within an air command and control (C2) operational center is made possible through the use of operational information systems. The process of detecting an aircraft’s position, direction and speed from radar measurements to identify possible threats lies in the field of data fusion and especially in tracking. The implementation and testing of tracking algorithms require realistic radar data, and especially data that correspond to extreme radar phenomena that might occur in air C2 data fusion systems. A simulation of a parameterizable multi radar network that lies under an air C2 system has been developed. After simulating radar data, several sensor data fusion algorithms have been implemented and applied, with aim to find a solution that best fits in the specific problem and the environment of study. Specifically, Kalman filters, gating, nearest neighbor, interactive multiple filter and joint probability data association (IMMJPDA) have been implemented and evaluated. The simulation of both aircraft and radar data allowed for the evaluation of the performance of these algorithms. The results showed that IMMJPDA is a solution that handles well radar tracking even in extreme simulated scenarios.

Decoding pilot behavior consciousness of EEG, ECG, eye movements via an SVM machine learning model

To decode the pilot’s behavioral awareness, an experiment is designed to use an aircraft simulator obtaining the pilot’s physiological behavior data. Existing pilot behavior studies such as behavior modeling methods based on domain experts and behavior modeling methods based on knowledge discovery do not proceed from the characteristics of the pilots themselves. The experiment starts directly from the multimodal physiological characteristics to explore pilots’ behavior. Electroencephalography, electrocardiogram, and eye movement were recorded simultaneously. Extracted multimodal features of ground missions, air missions, and cruise mission were trained to generate support vector machine behavior model based on supervised learning. The results showed that different behaviors affects different multiple rhythm features, which are power spectra of the [Formula: see text] waves of EEG, standard deviation of normal to normal, root mean square of standard deviation and average gaze duration. The different physiological characteristics of the pilots could also be distinguished using an SVM model. Therefore, the multimodal physiological data can contribute to future research on the behavior activities of pilots. The result can be used to design and improve pilot training programs and automation interfaces.

Six degrees of freedom flight simulation of tilt-rotor aircraft with nacelle conversion

This paper presents six degrees of freedom flight simulation with mode conversion between airplane mode and helicopter mode as an application for realizing Digital Flight of the tiltrotor aircraft. The tiltrotor aircraft has the characteristics of both helicopters and propeller planes with changing the flight mode by tilting the engine nacelles. However, much less work with continuously changing these modes has been done so far. In this paper, the main components such as rotors, engine nacelles, fixed wings and a fuselage are considered. In order to perform large deformations of mesh geometry such as the rotation of the rotor and nacelle as well as the change of the position and attitude of the aircraft, the computational domain is decomposed into multiple domains corresponding to each component. Independently moving these domains makes possible to perform the characteristic behavior of a tiltrotor aircraft. To deal with rotations of multiple decomposed domains, the multi-axis sliding mesh approach is applied. As the solver for simulating unsteady flow driven by complicated moving boundaries, the unstructured Moving-Grid Finite-Volume method is adopted. Based on this solver, the Moving Computational Domain method enables the aircraft to fly in any size of region without restriction of mesh size. The airframe is treated as a rigid body, and the coupled simulations considering interaction with surrounding fluid of the aircraft are demonstrated. The result shows complicated fluid phenomena around the tiltrotor aircraft that occur when it flies with mode change.

Identification and Modeling of the Airbrake of an Experimental Unmanned Aircraft

This paper presents the modeling, system identification, simulation and flight testing of the airbrake of an unmanned experimental aircraft in frame of the FLEXOP H2020 EU project. As the aircraft is equipped with a jet engine with slow response an airbrake is required to increase deceleration after speeding up the aircraft for flutter testing in order to remain inside the limited airspace granted by authorities for flight testing. The airbrake consists of a servo motor, an opening mechanism and the airbrake control surface itself. After briefly introducing the demonstrator aircraft, the airbrake design and the experimental test benches the article gives in depth description of the modeling and system identification referencing also previous work. System identification consists of the determination of the highly nonlinear (saturated and load dependent) servo actuator dynamics and the nonlinear aerodynamic and mechanical characteristics including stiffness and inertia effects. New contributions relative to the previous work are a unified servo angular velocity limit model considering opening against the load or closing with it, the detailed construction and evaluation of airbrake normal and drag force models considering the whole deflection and aircraft airspeed range, the presentation of a unified aerodynamic - mechanic nonlinearity model giving direct relation between airbrake angle, dynamic pressure and servo torque and the transfer function-based modeling of stiffness and inertial effects in the mechanism. The identified servo dynamical model includes system delay, inner saturation, the aforementioned load dependent angular velocity limit model and a transfer function model. The servo model was verified based-on test bench measurements considering the whole opening angle and dynamic load range of the airbrake. New, unpublished measurements with gradually increasing servo load as the servo moves are also considered to verify the model in more realistic circumstances. Then the full airbrake model is constructed and tested in simulation to check realistic behavior. In the next step the airbrake model integrated into the nonlinear simulation model of the FLEXOP aircraft is tested by flying simulated test trajectories with the baseline controller of the aircraft in software-in-the-loop (SIL) Matlab simulation. First, the standalone airbrake simulation is compared to the SIL results to verify flawless integration of airbrake model into the nonlinear aircraft simulation. Then deceleration times with and without airbrake are compared underlining the usefulness of the airbrake in the test mission. Finally, real flight data is used to verify and update the airbrake model and show the effectiveness of the airbrake.

A multi-time scale solution strategy for an elastomeric aircraft

This paper develops a multi-time scale kinetics solution strategy for the flight dynamic simulation of elastomeric aircraft. The combination of computational fluid dynamics (CFD) solver and reduced-order model is utilized to calculate the aerodynamics of elastic aircraft. CFD is applied to the aerodynamic solution of rigid motion, and reduced-order model is to the elastic deformation. The governing equations of rigid-body dynamics and structure dynamics are decoupled in time-scale, and their time step sizes can be set differently. This method overcomes the problem of large difference in characteristic times between rigid-body dynamics and structure dynamics, and improves the calculation efficiency of CFD based multi-disciplinary coupling solution. For current work, the multi-time scale kinetics solution method is applied to the simulation of store separation problem considering elastic deformation of carrier aircraft. The autoregressive with exogenous input model is employed to establish the generalized aerodynamic model of carrier. By comparison, the time responses of store obtained by the multi-time scale kinetics solution method are in good agreement with those by traditional CFD based multi-disciplinary coupling simulation, which validates high precision of the new method. Furthermore, the calculation amount of the new coupled calculation method is reduced by about an order of magnitude compared with that of the traditional method. The multi-time scale kinetics solution method can provide an effective solution strategy for similar engineering problems.