Flight Simulation Model Research Articles

Computational Aerodynamic Modeling Tools for Aircraft Loss of Control

This paper summarizes the status of ongoing NASA research supported over the past eight years to advance computational capabilities for modeling civil aircraft loss of control due to airframe damage or wing stall. The research is motivated by a desire to exploit the capabilities of computational methods to create augmented flight simulation models that improve pilot training for such loss-of-control scenarios. Flight of aircraft with either airframe damage or operating near and beyond the stall boundary encounters additional nonlinear aerodynamic influences on stability and control from dynamic motions that, if not included in flight simulation models, may lead to incorrect pilot responses. In the present work, both low- and high-fidelity computational methods are explored for analyzing such nonlinearities. The challenge of creating nonlinear reduced-order models from high-fidelity computational data is also addressed. At the beginning, few guidelines were available for computing or modeling the dynamic stability characteristics of civil aircraft in nonlinear stalled flight regimes. To accelerate progress, additional resources were leveraged through participation in two NATO task groups consisting of a diverse international body of computational aerodynamicists and flight simulation experts. As a result, a large body of knowledge has been generated, documenting the state of the art for computing and modeling the highly nonlinear stability characteristics of an unmanned air combat vehicle. This knowledge was infused directly into the NASA loss-of-control work through parallel application studies with the NASA Generic Transport Model. From this, it is concluded that the Reynolds-averaged Navier–Stokes formulation should suffice for capturing the representative behavior of civil aircraft stall for training purposes. Furthermore, promising approaches have been identified for creating nonlinear reduced-order models from computational data that can potentially augment flight simulation models for loss-of-control scenarios.

Guidance and control system using constrained adaptive backstepping method for space transportation

This study presents a new guidance and control system using a constrained adaptive backstepping method for a space transportation system. In this method, the effects of input saturations by actuator dynamics (e.g. magnitude, rate and bandwidth) are considered to introduce the compensators on the basis of pseudo control hedging. The stability of the proposed entire system is guaranteed by the Lyapunov’ stability theorem. To confirm the realization and robustness of the proposed system, Monte Carlo simulations (MCSs) were performed. In addition, to obtain optimized control performance, a parameter optimization algorithm combined with the MCSs was introduced. Finally, automatic landing simulations using the six degrees-of-freedom nonlinear flight simulation model of the NASA’s Space Shuttle Orbiter were performed to verify the effectiveness of the proposed technique.

Modeling and flight simulation of unmanned aerial vehicle enhanced with fine tuning

This paper focuses on the complete process of building full six-degree-of-freedom, low cost, high fidelity simulation model of a small-unmanned aerial vehicle starting from scratch. The configuration used in this study is currently available propeller-driven radio controlled model airplane. Modeling its six-degree-of-freedom motion includes experimental measurements of geometric and inertia model, modeling of the propulsion system, estimation of the aerodynamic model, and experimental identification of control surfaces actuator model. The complete propulsion simulation model is validated by the wind tunnel test data of the airplane propulsion system. Piloted flight results for the airplane specific longitudinal maneuver with elevator control input are presented to highlight the results of the simulation model. The present work indicates that airplane parameter estimation from flight test data improves the accuracy of the developed flight simulation model.

Euler–Lagrange as Pseudo-metric of the RRT algorithm for optimal-time trajectory of flight simulation model in high-density obstacle environment

SUMMARYThis paper introduces a solution to the problem of steering an aerodynamical system, with non-holonomic constraints superimposed on dynamic equations of motion. The proposed approach is a dimensionality reduction of the Optimal Control Problem (OCP) with heavy path constraints to be solved by Rapidly-Exploring Random Tree (RRT) algorithm. In this research, we formulated and solved the OCP with Euler–Lagrange formula in order to find the optimal-time trajectory. The RRT constructs a non-collision path in static, high-dense obstacle environment (i.e. heavy path constraint). Based on a real-world aircraft model, our simulation results found the collision-free path and gave improvements of time and fuel consumption of the optimized Hamiltonian-based model over the original non-optimized model.

Experimental Validation of a Flight Simulation Model for Slightly Flexible Aircraft

The paper presents a methodology for modeling the coupled flight dynamics with aeroelasticity in the time domain. The equations of motion are based on linearized mean-axes formulation. Unsteady, incremental aerodynamics due to elastic deformations are modeled in the time domain, applying the strip theory and a indicial function. The methodology is demonstrated with a prototype of the utility aircraft Stemme S15. Comparisons between the simulation and the flight-test data regarding the added aeroelastic dynamics have indicated that the model is suited for the flight control law and aircraft design, and that care must be taken in modeling the control surface lift slope for low-aspect-ratio lifting surfaces.

Computational fluid dynamics-based virtual flight simulation of a flying wing micro air vehicle

In this article, a computational fluid dynamics -based computational method is developed to simulate the virtual flight of a flying wing micro air vehicle. The virtual flight simulation model is composed of unsteady Reynolds averaged Navier-Stokes equations, motion equations, and flight control equations. The flow solver is established based on low Mach number preconditioning method, momentum source method, implicit dual time-stepping algorithm, and lower upper symmetric Gauss–Seidel iteration scheme on hybrid dynamic meshes. S-A turbulence model is also introduced to close the Reynolds averaged Navier-Stokes equations. Fourth-order Adams prediction-correction method is adopted to couple computational fluid dynamics and rigid body dynamics. The multidisciplinary computational method is validated as a reliable tool for virtual flight simulation through simulating wing-rock motion of a delta wing. Finally, the developed method is used to simulate the virtual flight of the micro air vehicle. The effectiveness of the computational method is proved in the virtual flight simulation.

The Effect of Airflow over Mountains on Flight Safety

A flight simulation model is established, which is composed of airflow over mountains model, pilot model and flight dynamics model. It is simulated that Boeing 747 aircraft in landing configuration gets through airflow over mountains induced by simple and complexterrain. The simulation results indicate that the main flight safety problems in airflow over mountains are angle of attack increasing and height losing or severe bumpiness. Pilot needs to pay attention to the change trend of the angle of attack and flight height.

The impact of radio-tags on Ruby-throated Hummingbirds (Archilochus colubris)

ABSTRACT Radiotelemetry has advanced the field of wildlife biology, especially with the miniaturization of radio-tags. However, the major limitation when radio-tagging birds is the size of the animal to which a radio-tag can be attached. We tested how miniature radio-tags affected flight performance and behavior of Ruby-throated Hummingbirds (Archilochus colubris), possibly the smallest bird species that has been fitted with radio-tags. Using eyelash adhesive, we fitted hatch-year individuals (n = 20 males, n = 15 females) with faux radio-tags of 3 sizes that varied in mass and antenna length (220 mg, 12.7 cm; 240 mg, 12.7 cm; and 220 mg, 6.35 cm), then filmed the birds in a field aviary to quantify activity budgets. We also estimated flight range using flight simulation models. When the 3 radio-tag packages were pooled for analysis, the presence of a radio-tag significantly decreased both flight time (∼8%) and modeled flight range (∼23%) in comparison to control birds. However, a multiple-comparison anal...

High-Altitude Gas Balloon Trajectory Prediction: A Monte Carlo Model

The high-altitude gas balloon is an indispensable tool in atmospheric science, meteorology, and other applications requiring stratospheric observations. A prerequisite of the effectiveness of many types of balloon operations is an accurate trajectory forecasting capability. In particular, targeted flights, sample return missions, or flights of expensive instruments (whose recovery is essential) rely on such models. In this paper, the authors describe a new balloon flight simulation model, which takes into account a range of environmental, physical, and operational uncertainties to generate a predicted trajectory equipped with landing site location error estimates. A key source of error in such models is the incomplete understanding of the drag opposing the rise of balloons in the free atmosphere; here the authors propose a new stochastic drag model based on empirical data derived from thousands of radiosonde flights. Other sources of prediction error are also examined, affecting the accuracy of the flight-path forecast, such as uncertainties in the wind profile and balloon envelope manufacturing variability. The authors show how integrating these elements into a process that generates Monte Carlo ensembles of simulated trajectories has yielded a practically useful flight planning tool, which we have made available to the ballooning community as a free online service.

A closed loop experiment of collective bounce aeroelastic Rotorcraft–Pilot Coupling

This work presents an experimental study that investigated the possibility of destabilising a rotorcraft by coupling the biomechanical behaviour of human subjects with the dynamics of the vehicle. The results of a study focused on the behaviour of pilots holding the collective control inceptor in a flight simulator are discussed. The motion of the flight simulation model was restricted to the heave axis, and augmented to include an elastic mode of vibration in addition to the rigid heave degree of freedom. Four different pilots flew several alternative model configurations with different elastic mode frequency and different collective pitch gearing ratios. This resulted in several observable unstable pilot–vehicle interactions at frequencies that cannot be traced back to the rotorcraft dynamics. Unstable oscillatory events evolving into limit cycle oscillations occurred most often at frequencies related to the biomechanics of the flight simulator occupant. They appeared to be task dependent and, in some cases, the trigger could be attributed to specific events. Additionally, it was found that the presence of collective friction alleviates but does not completely eliminate the unstable interactions between the pilot and the rotorcraft. Although not statistically meaningful because of the small set of human subjects available for the study, the results confirmed that the biomechanics transfer function of the pilot is the most influential aspect of the pilot–vehicle system that gives rise to the adverse vertical bounce phenomenon. Additionally, this study gave useful insight into the vehicle parameters that can adversely influence the involuntary interaction of pilots with rotorcraft.

Designing and Realizing of UAV Simulation System

This paper discusses an Unmanned Aerial Vehicle simulation system design and implementation, which focuses on the system design, system management, software development, and the information flow management of the whole system. To simulate battlefield environments, this system provides a clear and visual expression way for complex system design. Besides, it provides services for the design, integration testing, experiment, verification and evaluation of complex system. The main tasks of the system include: establish flight control simulation model; construct three-dimensional visual environment model and three-dimensional entity model; In the case of aircraft loading, drive various kinds of simulation modules, use related model of aircraft task / path planning module; display the typical use of aircraft system visually, as combining with three-dimensional visual simulation environment. Based on VC++ and MultiGen Creator/Vega, this simulation system probes into three-dimensional modeling technology and visual simulation-driven. It proposes general techniques route, improves work efficiency and has a wide range of application.

Radiative Heating Uncertainty for Hyperbolic Earth Entry, Part 1: Flight Simulation Modeling and Uncertainty

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Radiative Heating Uncertainty for Hyperbolic Earth Entry, Part 1: Flight Simulation Modeling and Uncertainty

Radiative Heating Uncertainty for Hyperbolic Earth Entry, Part 1: Flight Simulation Modeling and Uncertainty

In-Bore Yaw Effects on Lateral Throw-off and Aerodynamic Jump Behavior for Small Caliber Projectiles Firing Sidewise From Air Vehicles

The present study investigates the effects of in bore-yaw phenomenon on lateral throw-off and aerodynamic jump behavior for small caliber rotational symmetric (both in configuration and mass distribution) projectiles launched horizontally at supersonic firing speeds and various altitudes from high-subsonic air vehicles. The ammunition used is the caliber .50 API M8 bullet type firing from M2 machine automatic gun. The projectile is considered to be eccentrically engraved, tilted as it enters the rifling, and it is assumed that the tilt persists throughout its passage through the rifled barrel of the used weapon system. The modified linear 6-DOF flight simulation modeling is applied for the bullet free-flight trajectory predictions. The coupled epicyclic pitching and yawing motion analysis for the first 100 m of the examined trajectories are taken into account.

Realization and Evaluation of IIR Seeker via Hardware-in-the-Loop Simulation

The simulation is indispensable for systems design and analysis especially flight control systems. Among the simulation techniques is the Hardware-in-Loop-Simulation (HILS) which links the hardware and software for synthesis with the objective of overcoming any of the simplifying assumptions during modeling. The benefits of this type of simulation are to cut down the required number of flight trials and to increase the confidence level of realizability of the system design. Therefore, this paper addresses the implementation and evaluation of Image Infra-Red (IIR) seeker system, where the system integration is carried out via HILS for research and development (RDthermal camera, video tracker, and steering system are analyzed and tested individually. Interfacing problems are deeply analyzed and figured out in the assembled overall system for performance evaluation of IIR seeker. The real thermal target coordinates provided from IIR seeker are applied to a six-degrees-of freedom (6DOF) flight simulation model for homing guidance systems. The experimental setup associated with the system is presented from which the simulation and experimental results highlight the effect of various components constituting the IIR seeker. Smoothing filters are proposed to enhance the interception of targets performing uncertainrandom maneuvers and to overcome the dynamics of the video tracker and the steering system towards achieving missile-target interception with good trajectory.

Modelling, Control and Simulation of a Six-DOF Motion Platform for a Flight Simulator

This paper encompasses a study on the modelling, design and simulation of a motion platform for a flight simulator. The motion platform has a hexapod configuration with six degrees-of-freedom, designed on a biologically inspired concept. A dynamical model of the proposed motion platform is formulated using the principles of flight simulation and Stewart platform modeling. In the first test case, the proposed dynamical model is evaluated in terms of motion requirements for a Level-C flight simulator through real-time simulations using SimMechanics and xPC Target software. X-Plane (a commercial flight simulator package) is used to provide the flight dynamical model for a Level-C flight simulator. In the second test case, a computed torque-based controller incorporating the proposed dynamical model is tested in both forward and inverse dynamics modes to track the flight dynamics of an aircraft. Finally, the paper draws conclusions about the significance and performance of the proposed system in terms of motion cueing errors.

COTS and Design Pattern Based High Fidelity Flight Simulator Prototype System

Flight simulator is among the most sophisticated software systems in existence. It is highly distributed, has rigorous timing requirements, and must be amenable to frequent updates to maintain high fidelity with the ever- changing vehicle and environment it is simulating. Current flight simulation framework and software developing pattern are complicated to use and time consuming. We have accomplished a flight simulator prototype system based on a new distributed real-time simulation framework and non-flight-certified Commercial-off-the-shelf (COTS) solutions and have proved its fidelity and coordination characters as a flight training device. The distributed real- time simulation framework uses mediator design pattern as an information broker among flight simulation models of a sub-system which minimizes model interdependencies, improves the extendibility for the simulator and makes the maintenance easier. Meanwhile, the simulation models and executable code in the simulator were generated through COTS software and run on a PC cluster by which the difficulties of programming tasks are descend. The simulation modeling process and virtual prototype of the motion system are also expatiated. The validation methods and contrasting simulation results are presented finally to show the feasible design to carry out flight simulation with high quality.

Extracting micro air vehicles aerodynamic forces and coefficients in free flight using visual motion tracking techniques

This paper describes a methodology to extract aerial vehicles’ aerodynamic characteristics from visually tracked trajectory data. The technique is being developed to study the aerodynamics of centimeter-scale aircraft and develop flight simulation models. Centimeter-scale aircraft remains a largely unstudied domain of aerodynamics, for which traditional techniques like wind tunnels and computational fluid dynamics have not yet been fully adapted and validated. The methodology takes advantage of recent progress in commercial, vision-based, motion-tracking systems. This system dispenses from on-board navigation sensors and enables indoor flight testing under controlled atmospheric conditions. Given the configuration of retro-reflective markers affixed onto the aerial vehicle, the vehicle’s six degrees-of-freedom motion can be determined in real time. Under disturbance-free conditions, the aerodynamic forces and moments can be determined from the vehicle’s inertial acceleration, and furthermore, for a fixed-wing vehicle, the aerodynamic angles can be plotted from the vehicle’s kinematics. By combining this information, we can determine the temporal evolution of the aerodynamic coefficients, as they change throughout a trajectory. An attractive feature of this technique is that trajectories are not limited to equilibrium conditions but can include non-equilibrium, maneuvering flight. Whereas in traditional wind-tunnel experiments, the operating conditions are set by the experimenter, here, the aerodynamic conditions are driven by the vehicle’s own dynamics. As a result, this methodology could be useful for characterizing the unsteady aerodynamics effects and their coupling with the aircraft flight dynamics, providing insight into aerodynamic phenomena taking place at centimeter scale flight.

Flight Simulation Model for Small Scaled Rotor Craft-Based UAV

Abstract: Many control system designs have been developed for controlling the dynamicprocess of aerospace vehicles. Yet, among those designs, few are readily suitable forapplying. Moreover, most of the applicable aerospace control designs are built through flighttests that perform real processes on available real vehicles. The need to use real vehicles in thecontrol design cycle poses a high risk and is prohibitively cost. To solve this problem, a realtimesimulation concept that employs cheap, practical, and rapid-to-build modular hardware,which can simulate a nearly real process in lab’s environment, is proposed in this researchwork. This paper elaborated the integration of nonlinear model for small scale helicopter,“Yamaha R-50”, with the sensors, servos, and wind models into a modular Simulink model.The Simulink model performed a real-time computing process and behaved like therepresented helicopter dynamic system. The overall scheme of flight simulation can play asignificant role in the efficient control system design for aerial vehicles.

FAA AC120-63 Level C급 KA-32T 비행 시뮬레이션 모델 개발

Flight simulation model for helicopter simulator is one of the most important models which affect flight performance and handling quality. It is typical to develop the model based on the raw data and models from the helicopter designers/manufacturers. The approaches in this study were to develop the basic model based on the available resources regarding helicopter operation/maintenance and to tune and validate it based on the flight test results. The basic model was developed with maintenance manuals, flight manuals, analyses, measurements, papers and so on considering that KA-32T data could not be obtained from the manufacturer. The flight test for KA-32T was performed and the reference data for the simulation validation tests were acquired. The flight simulation model was validated to have the fidelity compatible with level C of FAA AC120-63 after comparison and tuning with flight test results.