Aircraft Simulation Research Articles

Lateral-directional stability and control augmentation system design for civil aircraft simulator

Abstract In this paper, we first introduce the necessity, history, and classification of stability and control augmentation systems. The structure of the lateral-directional stability and control augmentation control system in the normal mode is studied, and a comparison of advantages and disadvantages of several design schemes including yawing rate feedback, rolling rate feedback, and sideslip angle feedback is given. Lateral-directional stability and control augmentation control law for a certain type of civil aircraft simulator is designed. Finally, the stability and control augmentation system is simulated and the simulation results are analyzed, which shows that the handling qualities of the aircraft with stability and control augmentation system are better than those without it.

Directional control law functional analysis and design for civil aircraft simulator

Abstract Functional analyses of directional flight control law for a typical civil aircraft are conducted, including directional maneuver, rudder limiter, coordinated turn, Yaw Damper, Thrust Asymmetrical Compensation, Gust Alleviation, manual rudder trim, etc. Through inputs of doublet, step input, and sweeping frequency, open loop control characteristics are analyzed based on a linearized state-space matrix. Simulink block architecture of a closed-loop directional control law is constructed, aiming to fulfill flight control functions, including pedal-to-rudder control, Yaw Damper, coordinated turn, and gain-tuned rudder limiter. Simulations for the previously designed closed-loop directional control law are performed to verify the characteristics of directional handling qualities in the aspect of the Yaw Damper, directional static and dynamic stability, maneuverability, and sweeping frequency.

Longitudinal SCAS design and simulation for civil aircraft simulator

Abstract In this paper, the principle and benefits of stability and control augmentation system (SCAS) are introduced. Four schemes of the longitudinal SCAS for civil aircraft in normal mode are analyzed and compared. One of them, i.e., C * response type, is selected. Its architecture is determined. Then, based on a typical civil aircraft, the flight control law of the longitudinal SCAS is designed. A simulation model of the longitudinal SCAS is established through MATLAB software. Finally, the simulation and verification of the longitudinal SCAS model is carried out. The simulation results show that the designed longitudinal SCAS is feasible and can be applied to engineering practice. Compared with either normal load or pitch rate command response type, with proportional and integral feedback for mixed control signals of pitch rate and normal load, C * not only improves the short period characteristics but also effectively separates phugoid and short period frequencies, thus achieving high control accuracy.

An automatic hybrid mesh generation method for combustion fluid dynamics simulations

PurposeAutomatic mesh generation is still a challenge problem for combustion fluid dynamics simulations because of the high-quality requirement and complexity of geometries. This paper aims to find an efficient automatic analysis model creation and mesh generation method to save the time for pre-processing in numerical simulations.Design/methodology/approachBased on the previous work, we explore effective model processing and mesh generation methods from practical engineering applications. Considering the automation and high quality requirement, we construct an automatic mesh generation procedure for combustion fluid dynamics problems.FindingsThe numerical results show that the procedure we proposed in this paper can automatically generate high quality mesh for combustion fluid dynamics simulations. The strategy of fluid model construction is time-saving and with high-precision. The mesh generation method in our procedure is automatic and efficient.Practical implicationsThe procedure proposed in this paper is applicable to the practical engineering application model, such as aircraft simulation, aeroengine simulation and so on. The procedure has been integrated into an numerical simulation software.Originality/valueThe method proposed in this paper has very practical application value. It can be used in the practical application and saves a lot of manual processing time for numerical stimulation specialists.

Study on Aerodynamic Interference of Tilt-rotor Aircraft at Different Rotor Deflection Angles

This paper presents a numerical simulation of a tiltrotor aircraft developed in the United States, examining the aerodynamic interference between the rotors, wings, and fuselage in three flight conditions: forward flight, transition mode, and hover. The study investigates the distribution of the velocity field, pressure field, vorticity field, and streamlines around the aircraft at different rotor tilt angles.

Getting Along With Autonomous Teammates: Understanding the Socio-Emotional and Teaming Aspects of Trust in Human-Autonomy Teams

Trust plays a critical role in both effective teamwork and the effective use of autonomous technologies, and therefore holds paramount importance in human-autonomy teaming (HAT). Using qualitative analysis of the interviews from an 8-hr-long experiment conducted in an aircraft simulation environment, this study identifies the socio-emotional and team-related qualities that humans desire in their autonomous teammate for them to trust it.

An Integrated Imitation and Reinforcement Learning Methodology for Robust Agile Aircraft Control with Limited Pilot Demonstration Data

In this paper, we present a methodology for constructing data-driven maneuver generation models for agile aircraft that can generalize across a wide range of trim conditions and aircraft model parameters. Maneuver generation models play a crucial role in the testing and evaluation of aircraft prototypes, providing insights into the maneuverability and agility of the aircraft. However, constructing the models typically requires extensive amounts of real pilot data, which can be time-consuming and costly to obtain. Moreover, models built with limited data often struggle to generalize beyond the specific flight conditions covered in the original dataset. To address these challenges, we propose a hybrid architecture that leverages a simulation model, referred to as the source model. This open-source agile aircraft simulator shares similar dynamics with the target aircraft and allows us to generate unlimited data for building a proxy maneuver generation model. We then fine-tune maneuver generation model to the target aircraft using a limited amount of real pilot data. Our approach combines techniques from imitation learning, transfer learning, and reinforcement learning to achieve this objective. To validate our methodology, we utilize real agile pilot data provided by Turkish Aerospace Industries (TAI). By employing the F-16 as the source model, we demonstrate that it is possible to construct a maneuver generation model that generalizes across various trim conditions and aircraft parameters without requiring any additional real pilot data. Our results showcase the effectiveness of our approach in developing robust and adaptable maneuver generation models for agile aircraft.

Design and Assessment of Fighter Pilot Assistance Systems for Air-to-Air Refuelling with Probe-and-Drogue-Equipment

Air-to-air refuelling (AAR) with a probe-and-drogue system is a highly demanding process for fighter pilots. In the frame of the project “Future Air-to-Air Refuelling” (F(AI)2R) the German Aerospace Center (DLR) is designing concepts for assistance systems to support fighter pilots during this manoeuvre. The AAR process was examined using a hierarchical task analysis (HTA) based on a literature review and semi-structured interviews with Eurofighter-, Tornado- and test pilots. “Situation Awareness Requirements” (SAR), which represent relevant parameters for the situation awareness of the fighter pilot were derived from the HTA and rated by pilots according to their relevance. The collected data was then used to design different concepts of pilot assistance systems using a morphological box and a decision matrix. The concepts were visualised as storyboards, assessed by test pilots of the “Wehrtechnische Dienststelle 61” (WTD 61) and optimized based on their feedback. In this paper, the used methodology as well as the results of the HTA and SAR analysis are presented. Besides that, storyboards for pilot assistance systems displaying the overtake speed “German Patent No. 10.2022.110.505” and the “Contact Assistance, Status and Warning System” (CASWS) “German Patent No. 10.2022.123.653” are described. Additionally, the planned implementation using a HoloLens 2 is explained and the strategy for the subsequent simulator study on the DLR fighter aircraft simulator “Military AiR vehicle Simulator – Fast Integration Testbed” (MARS-FIT) is described.

Individual Differences in Fatigued Performance

Cognitive fatigue is a prevalent issue across multiple military operational domains, resulting in degraded mission performance and costly mishaps. One approach to mitigating the effects of fatigue in operational environments is to develop technology, such as biomathematical, physiological, and cognitive models, that can help individuals assess and predict their fatigue and its impacts on performance. We can further enhance the accuracy of these models by incorporating individual difference metrics that allow for increased individualization. In the current study, we examine how individual differences in circadian typology, typical sleep duration, sleep duration need, and hardiness relate to fatigued performance during a 24-hr long mobility aircraft simulator session with mobility aircrews. Specifically, we examine individual difference relationships with performance on three cognitive tasks, the Psychomotor Vigilance Test, the N-back task, and the Change Signal Task, which measure processes crucial to operational performance: attention, working memory, and executive functioning.

Implementation of a toolbox for the generation of flight profiles for use in simulator studies

Motion sickness is a phenomenon which can produce various symptoms in affected individuals. During development of new aircraft types and cabin layouts, it is important to consider this phenomenon early on, to reduce resulting effects. For research on this topic, German Aerospace Center uses the simulator environment Air Vehicle Simulator together with the Advanced Future Cabin. The Air Vehicle Simulator is a full flight simulator with an interchangeable cockpit module. One of those modules is the Advanced Future Cabin, a realistic replica of an aircraft cabin. Good standardization of the test conditions is required to ensure objectivity and reliability of motion sickness studies in this simulator environment. A specialized software infrastructure is used to replay pre-recorded flight profiles, which are then reproduced by the simulator’s motion, visual and audio systems. Using this replay approach, complete flight profiles can be reproduced very well. However, when parts of the flight profile need exact reproduction within a flight profile or across multiple flight profiles, the approach to record pilot-in-the-loop simulation sessions becomes problematic, as flying the exact same twice is almost impossible. As an improved approach, a toolbox has been implemented, which automates the generation of flight profiles, enabling easier and more precise research on motion sickness in the simulator. The toolbox replaces the pilot-in-the-loop simulation with an automated control of the underlying aircraft simulation model. This leads to greatly improved accuracy of inputs to the simulation model and thus very good reproducibility even of flight profile segments. In this manuscript, details of the toolbox implementation and its validation are discussed.

Design and Flight Simulation Verification of the Dragonfly eVTOL Aircraft

Recently, electric vertical take-off and landing (eVTOL) aircraft have become a top priority for urban air transportation due to their ability to overcome urban ground traffic congestion. In this research, a new type of scaled lift–cruise ‘Dragonfly’ has been designed. The ‘Dragonfly’ combines the characteristics of an octocopter and a fixed-wing aircraft. Compared with the same type of eVTOL aircraft, it has a longer wingspan and a more stable aircraft structure, it can not only take off and land vertically without the need for a runway, but also fly quickly in a straight line and hover in mid-air. In order to ensure the success of the flight test, it was also simulated in this paper. A simulation scenario highly fitting with the flight test environment of eVTOL is designed in the Gazebo simulation platform, and then combined with the PX4 flight control platform, the system SITL of the constructed aircraft simulation model is carried out on the Gazebo platform, Finally, simulation flight test data for accurate analysis are obtained, the accuracy and stability of the control algorithm are fed back, and scientific support for the follow-up ‘Dragonfly’ aircraft hardware-in-the-loop simulation and physical flight test is provided.

Adaptive dynamic programming base on MMC device of a flexible high-altitude long endurance aircraft

Flexible high-altitude long endurance (HALE) aircraft face challenges such as the delay effect caused by aeroelasticity and low efficiency during high-altitude cruising. This paper addresses a new active control scheme that replaces traditional aerodynamic control surfaces with longitudinal and lateral moving masses and adopts an observer-based adaptive dynamic programming (ADP) control strategy, aiming to solve the attitude control of HALE aircraft with flexible wings. Firstly, considering the account of unsteady aerodynamics, attitude angular velocity, and moving masses, complete dynamic model is established for a flexible aircraft, in order to more accurately describe the state of the HALE aircraft. This model includes two moving masses to replace traditional ailerons and elevators. It is difficult to design attitude control strategies considering the delay effects and unknown dynamic disturbances of HALE aircraft. To this end, the actor-critic structure of the ADP approach is designed to achieve the near-optimal control strategy of the system, which eliminates the need for prior knowledge of model parameters. A fixed time disturbance observer (FTDO) is proposed to estimate the future tracking error information and unknown disturbances to improve the control performance of the attitude. Finally, the stability of the system is proved via the Lyapunov technique and a comprehensive simulation of HALE aircraft is provided. The simulation results show that the proposed control algorithm can enable the aircraft attitude angles to quickly response and maintain stability under gust wind. Compared with a single ADP control strategy, this paper's algorithm has advantages in response speed and error.

Research on longitudinal control technology in the transition section of tilt-rotor aircraft based on linear active disturbance rejection control

To solve the problem of strong coupling and control redundancy in the transition section of the tilt-rotor, this paper presents a longitudinal control method based on linear active disturbance rejection control (LADRC), verified by simulation. Firstly, the nonlinear dynamics model of tilt-rotor aircraft based on the mechanism method is established, and the model’s accuracy is verified by comparing the trim result with the generic tilt-rotor aircraft simulation (GTRS) model verified by flight test in XV-15. Then, the control and redundant rudder surface assignment strategies for tilt-rotor aircraft are proposed. Then, the vertical and vertical control law of tilt-rotor aircraft is designed, the linear expansion state observer (LESO) model is analyzed and derived, and the linear active disturbance rejection controller suitable for attitude loop control of tilt-rotor is designed. The altitude and velocity loops are controlled. Finally, the proposed linear active disturbance rejection control (LADRC) controller is verified by simulation, and the whole process of tilting transition is simulated. The results show that the proposed control strategy and the controller designed in this paper have strong anti-disturbance ability, fast response speed, and high control precision and can be used in the transition section of tilt-rotor aircraft. The vertical direction shall be well controlled.

Aircraft Performance Simulation of 19-Passenger Commuter Aircraft: A Comparison between Normal and Amphibious Category

This article presents calculating flight performance aspects and simulations of flight characteristics during a flight mission of the 19-passenger commuter aircraft, with a focus on the comparison between the normal and amphibious category aircraft. The objective is to analyse the flight characteristics (warm up, takeoff, cruise, descent, landing) and capabilities of both aircraft configurations. The significant difference between the two aircraft lies in the presence of float components in the 19-passenger Amphibious aircraft. The calculation process, both manual and simulation-based, involves utilizing constraint analysis and mission analysis to determine the weight fraction values for each flight phase. The results of the constraint analysis indicate that the amphibious category aircraft has higher values (35% - 80%) compared to the normal category aircraft. Meanwhile, the calculations using aircraft engine design (AEDsys) software reveal nearly identical reductions in weight fraction for each phase, with the amphibious category aircraft having a significant decrease in the final weight fraction of 0.87836. The fuel weight used is 2129 lb or 965.70 kg (8 barrels) with a range of approximately 372 nm or about 690 km and a flight time of approximately 2.4 hours. The drag polar values obtained using Parametric cycle analysis software at an altitude of 3,048 meters (10,000 ft) show that the normal category aircraft has a smaller coefficient drag (CD) value. Further validation of the findings from this performance simulation study can be conducted through direct experimental validation during flight to be utilized for optimizing aircraft performance.

Flight Simulation of Fire-Fighting Aircraft Based on Multi-Factor Coupling Modeling of Forest Fire

Forest fires can develop rapidly and may cause a wide range of hazards. Therefore, aerial firefighting, which has the ability to respond and reach fire fields quickly, is of great significance to the emergency response to and subsequent extinguishing of forest fires. The burning of forest fires generates a lot of heat and smoke, which changes the air flow environment and vision over the region and brings challenges to aerial firefighting. In the present work, aerial forest firefighting simulation was divided into the forest fire spread model, the air flow model and the aircraft flight dynamic and automatic control model. Each model was constructed based on a physical method. An integrated framework was designed to realize the interaction among fire fields, airfields, and aircraft, and is verified. The proposed framework can be used for the emergency response decision of aerial forest fire fighting and subsequent fire-fighting mission planning.

Numerical simulation of aircraft arresting process with an efficient full-scale rigid-flexible coupling dynamic model

The arresting process of carrier-based aircraft is widely recognized as a challenging task, characterized by the highest accident rate among all carrier-based aircraft operations. Dynamic simulation plays a crucial role in assessing the intricate responses of the arresting process, favoring the design of carrier-based aircraft. An efficient and accurate rigid-flexible coupling model for analyzing the dynamic response of the arresting process is proposed. By combining the dynamic characteristics of airframe, landing gear, arresting hook and arresting gear system, the rigid-flexible coupling dynamic model is established to reflect the relative motion of the coupling parts and arresting load. The dynamic model is verified through simulations of landing gear landing drops and by comparing the arresting simulation results with corresponding data in the US military standard. Additionally, simulations of the arresting process under different off-center distance and aircraft yaw angle are conducted to obtain the dynamic response of the aircraft during the arresting process. The result indicates that the rigid-flexible coupling dynamic model proposed is effective for analyzing the arresting dynamics response of carrier-based aircraft. The axial force of the arresting cable on both sides of the hook engagement point, pitch and yaw angle of aircraft are inconsistent under yaw and off-center arresting. The analysis method and obtained results provide valuable references for assessing the dynamic responses of carrier-based aircraft during arresting process and offer valuable in-sights in the design of carrier-based aircraft.

The engine mission simulation system: coupled simulation of aircraft and engine in the mission

AbstractWhen designing future aircraft, the entire system including airframe, propulsion system, energy management and mission control must be considered in a coupled approach at an early design stage. To model and study this complex interaction, the Engine Mission Simulation System (EMSS) environment was created in cooperation with the Bundeswehr Technical Center for Aircraft and Aircraft Equipment. EMSS is intended to serve as a digital, flying test bed at the Institute of Jet Propulsion for the rapid and low-cost evaluation of new concepts for propulsion and power supply systems for new and legacy aircraft designs. This tool chain allows a detailed engine simulation under consideration of its flight condition while using an external propulsion and power control system. First, the software architecture of EMSS is discussed, which involves a propulsion simulation in NPSS® coupled with the X-Plane 11 flight simulator via MATLAB®/Simulink®. The aircraft itself is modeled as a six degrees of freedom simulation using the blade element theory, allowing both complex flight maneuvers and unusual aircraft to be easily simulated. The EMSS achieves real-time capability and enables user-friendly pre-design as well as quick trend detection through the ability to perform focused parametric studies. To evaluate the accuracy of the system’s results, the engine model used is validated against experimental data. Subsequently, the aerodynamic characteristics of the aircraft model are verified with a CFD simulation. Finally, a parametric study is used to demonstrate the mission as well as propulsion evaluation capabilities of the Engine Mission Simulation System.

Aircraft Simulations Using the New CFD Software from ONERA, DLR, and Airbus

This paper presents a thorough comparison between RANS simulations performed with the computational fluid dynamics by ONERA, DLR, and Airbus (CODA) new-generation flow solver and reference legacy codes TAU (DLR) and elsA (ONERA) for high-speed cruising NASA Common Research Model (CRM) configurations that were considered in the context of the 5th, 6th, and 7th Drag Prediction Workshops. The solver’s accuracy is assessed with several meshing strategies, including block-structured, hybrid-structured/unstructured, and fully unstructured tetrahedral meshes. This solver features both a cell-centered finite-volume (FV) scheme suited to arbitrary meshes as well as a modern high-order discontinuous Galerkin (DG) scheme. We show that for all cases considered, the FV component recovers an equivalent accuracy compared to elsA (cell-centered FV) on block-structured meshes and TAU (node-centered FV) on hybrid and unstructured meshes. The high-order DG scheme (third-order accurate) is found to significantly enhance the drag prediction on coarse meshes compared to legacy FV methods, both for structured and unstructured meshes.

DESIGN AND IMPLEMENTATION OF REAL-TIME NON-LINEAR DYNAMIC SIMULATION OF FIGHTER AIRCRAFT ON MULTICORE PROCESSOR

Simulation is a system to imitate the operation of various kinds of real-world facilities or processes for training, behavior study or entertainment purposes. Some implementation of fighter aircraft simulation is done sequentially using FORTRAN and MATLAB / Simulink. On the other hand, a multicore (parallel) computer system has been in the personal computer environment, so the multicore computing paradigm should be considered. Intel Threading Building Blocks (TBB) library need to be utilized in multicore programming. This paper discusses the design and implementation of real-time nonlinear dynamic simulation of fighter aircraft on multicore processor. The aircraft model used in this study is F16 data. Implementation of the simulation code is written in C++ with Intel TBB, OpenGL, Open Scene Graph, and Open Dynamic Engine library. The testing results of non-linear dynamics simulation of fighter aircraft show that the speedup on an Intel Core 2 Duo processor is 1.1776 x for elevator doublet input (short period), while speedup on an Intel i7 is 1.5405 x for rudder doublet input (dutch roll). Key Words: multicore computing, real-time simulation, nonlinear dynamic, fighter aircraft model

Piloted Simulation-Based Assessment of Simplified Vehicle Operations for Urban Air Mobility

This work investigates the simplified vehicle operations paradigm, which seeks significant reductions in pilot workload and training requirements through the holistic design of flight control laws, control inceptors, and cockpit displays in the context of vertical takeoff and landing urban air mobility aircraft using piloted flight simulations. Two inceptor layouts, one similar to conventional fixed-wing aircraft and the other similar to conventional rotorcraft, differing in inceptor-to-command mappings, were incorporated into two research flight simulators. A lift-plus-cruise aircraft simulation model, a total energy control system–based fly-by-wire flight control architecture, and identical cockpit displays were used for both setups. Twenty-one participants, divided into three groups based on their prior piloting experience, were used to study pilot performance using representative handling qualities task elements. The piloted simulation data revealed that participants in each group were able to successfully perform the simulation tasks and allowed handling quality ratings to be calculated. They also highlighted instances of control coupling between inceptor axes in each setup for different tasks and the relative ease or difficulty of performing each task with the two inceptor designs.