Aircraft Simulation Model Research Articles

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.

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.

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.

Conceptual design of a pilot assistance system for customised noise abatement departure procedures

The departure of an aircraft is commonly the flight phase with the highest thrust level in a flight, which leads to considerable noise levels on the ground. The departure procedures are characterised by the thrust reduction altitude, the acceleration altitude, and the control of airspeed and aircraft configuration within each take-off segment. Thrust reduction and acceleration altitudes are typically constant and are not adjusted to particular operational key parameters (e.g., take-off mass, reduced take-off thrust) or weather conditions. However, the parameters differ between individual flights and affect flight performance as well as the noise levels on the ground. This paper presents the conceptual design of a pilot assistance system which aims to reduce the noise on the ground by identifying a custom thrust reduction and acceleration altitude for existing noise abatement departure procedures. The pilot assistance system is based on an aircraft simulation model and a noise simulation and is aimed to be utilised during pre-flight planning on ground. A key part of the noise evaluation is that the local population distribution around the airport is considered. An overview of the ongoing research at the German Aerospace Center is provided. The conceptual design and preliminary results are presented and discussed using an exemplary take-off for three wind conditions.

SDC-based dynamic inversion controller for a fixed-wing aircraft

This work presents dynamic model inversion controller which uses state dependent coefficient matrices, and is applied for a fixed-wing aircraft attitude and velocity control problem. Numerical validation of the proposed controller is done using a Cessna 172 aircraft simulation model for several scenarios of atmospheric disturbances.

Stochastic modeling of aircraft flight parameters in terminal control area based on automatic dependent surveillance-broadcast (ADS-B) data

A critical step in developing good traffic management (ATM) system simulation model is to build a kinematic model of an aircraft movement that can represent the actual conditions. This study aims to obtain flight parameters for aircraft operating in the terminal control area of Soekarno-Hatta International Airport using Automatic Dependent Surveillance-Broadcast (ADS-B) data, which is openly available on Flight Radar24. Flight parameters were measured for several flight phases, such as take-off, initial climb, climb, cruise, descend, and final approach. In addition to these flight phases, flight parameters at waypoints on the arrival and departure were also measured. Furthermore, all flight parameters are modeled stochastically through the probability distribution function (PDF) approach. The best model for each parameter is obtained using the Maximum Likelihood method (MLE) with some relevant Kosmolgrove Smirnov Test criteria. The use of ADS-B data along with the stochastic model presented in this paper provides comprehensive information on flight behavior, which can be further utilized for an aircraft simulation model of an Air Traffic Management system.

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.

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.

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.

Routing Protocols for the Aircraft AD HOC Networks

The communication between the aircraft-to-aircraft and aircraft-to-ground can be established with the support of Aircraft Ad hoc Networks (AANET). Routing in the aircraft ad hoc networks is a challenging task due to its unique attributes such as very high mobility of the aircraft nodes and dynamic topology. Few research works had developed routing environment and protocols for the dynamic topology based AANET. This paper analyses the developments of the routing protocols for the aircraft ad hoc networks. This paper extensively discusses the routing protocols and comparative analyses of the performance metrics namely throughput, packet delivery ratio, end to end delay, routing overhead, and number of handoffs. Further, this work deliberates the aircraft ad hoc networks simulation environment, aircraft’s velocity, different radio propagation models of aircraft simulation model. Various challenges and issues of routing protocols are extensively analyzed and compared with existing methodologies in this paper.

Feedback linearization and backstepping: an equivalence in control design of strict-feedback form

Abstract This paper investigates an equivalence between feedback linearization and backstepping control. Implications from equivalence are that stability and performance properties of one method are the same for another method. Thus, a property known to exist only for one method could be used to prove property also holds for another. Also, a suspected advantage of one method over the other could be proven to be a false conjecture. Control laws in both approaches are achieved by coordinate transformations and non-linear feedbacks. Further, resulting non-linear feedback control law achieved by feedback linearization method matches exactly with non-linear controller achieved by the backstepping control design. This equivalence is a general analytical match within the specific class of non-linear dynamic systems under investigation. Demonstrations are considered and validated via flight control of longitudinal dynamics of a high performance aircraft simulation model. Algorithms are tested and evaluated with analytical models and non-linear closed-loop simulation.

Facing the Challenges of Supercooled Large Droplet Icing: Results of a Flight Test Based Joint DLR-Embraer Research Project

<div class="section abstract"><div class="htmlview paragraph">Today’s airplanes are well equipped to cope with most common icing conditions. However, some atmospheric conditions consisting of supercooled large droplets (SLD) have been identified as cause of severe accidents over the last decades as existing countermeasures even on modern aircraft are not necessarily effective against SLD-ice. In 2014, the new Appendix O to the certification regulations (FAR Part 25 / CS-25) had been issued to guarantee the safe operation of future airplane when encountering SLD conditions. But as the SLD topic is quite new for the majority of aircraft manufacturers and research institutes in a same way, DLR (German Aerospace Center) and Embraer established a joint research cooperation in 2012 to obtain a better understanding of the distinct influences of SLD-ice shapes on aircraft characteristics and to evaluate proper ways for future airplane certification under App. O. Furthermore, one additional scientific goal of the cooperation was to develop and test new tools for the in-flight monitoring of aircraft characteristics as well as the on-board identification of simulation models. During the 4 years of the project, a distinct way to better understand icing-induced degradations on a specific aircraft was followed: first, data of the clean aircraft was gathered in flight test to identify a dynamic simulation model as base for the subsequent evaluations. Second, data of test flights with artificial App. C ice configurations were analyzed and used for the development of distinct modifications of the base aircraft simulation model; a first evaluation of the icing-induced changes of aircraft characteristics was conducted. Third, after the generation of SLD-ice shapes, wind tunnel testing and flight clearance, a second flight test campaign with these artificial SLD-ice shapes delivered the data for an additional model modification and identification. The results of the final data and model evaluation provide the observable degradation of SLD-ice in flight, which is well comparable to results obtained from the App. C ice configurations.</div></div>

Dynamic aircraft simulation model covering local icing effects

A novel $$\Delta $$ -model approach to characterize the changes in longitudinal and lateral aircraft dynamics occuring due to local icing is analytically derived. This model extension is formulated as a separate module in the aircraft flight mechanics simulation and can be used in existing simulation models. Using the former DLR research aircraft VFW 614 ATTAS as example, information about the icing-induced performance and handling degradation is obtained by 3D CFD calculations with numerically generated ice shapes. With the resulting data, $$\Delta $$ -model parameters describing a local aerodynamic degradation are estimated. Simulation of the local wing icing influences on the aircraft’s dynamic behavior show the $$\Delta $$ -model’s capabilities to cover aerodynamic changes during a de-icing process.

An Approach to Develop a Remotely Operated Integrated Avionics Test Suit

AbstractIntegration testing and functional validation & verification are few of the key phases of Aircraft Development Life Cycle. This is performed by integrating the avionic system on complex dynamic test platforms in a controlled lab environment. The avionic systems are in general, composed of a combination of multiple LRUs (Line Replaceable Units) / LRMs (Line Replaceable Modules). Test platforms referred to as Integrated test benches (ITB) comprise of dynamic aircraft simulation models running on multiple host computers, IO servers, breakouts, power supply control units and internal airflow management modules for avionics cooling. This paper proposes a means of making the Integration Test Benches remotely available across multiple locations seamlessly, without incurring substantial cost, thereby eliminating the need for building and maintaining the test benches at multiple locations. This approach explores a novel technique that can be leveraged to make a single bench accessible globally within the organization by leveraging various concepts of IOT (Internet of things) and cloud technology.

Detection and Identification of Loss of Efficiency Faults of Flight Actuators

Abstract We propose linear parameter-varying (LPV) model-based approaches to the synthesis of robust fault detection and diagnosis (FDD) systems for loss of efficiency (LOE) faults of flight actuators. The proposed methods are applicable to several types of parametric (or multiplicative) LOE faults such as actuator disconnection, surface damage, actuator power loss or stall loads. For the detection of these parametric faults, advanced LPV-model detection techniques are proposed, which implicitly provide fault identification information. Fast detection of intermittent stall loads (seen as nuisances, rather than faults) is important in enhancing the performance of various fault detection schemes dealing with large input signals. For this case, a dedicated fast identification algorithm is devised. The developed FDD systems are tested on a nonlinear actuator model which is implemented in a full nonlinear aircraft simulation model. This enables the validation of the FDD system’s detection and identification characteristics under realistic conditions.

Methods for the Uncertainty Quantification of Aircraft Simulation Models

The paper deals with the propagation of uncertainty in input parameters through the aircraft model in clean cruise configuration triggered by the elevator pulse. Assuming aerodynamic coefficients as random variables and processes, the evolution of uncertainties in the aircraft state is estimated with the help of efficient nonintrusive procedures—stochastic collocation and the nonintrusive Galerkin approaches, here contrasted to the slow convergent Monte Carlo integration. These numerical methods are implemented by using the flight simulator in a black-box manner. In this way, the set of samples of aircraft states is simply obtained by solving the corresponding systems of deterministic ordinary differential equations. Additionally, the paper provides the variance-based sensitivity analysis of a flight model carried out with the help of the polynomial-chaos approach.

On the use of optimization for flight control laws clearance: a practical approach

AbstractFollowing the recent interest of using optimization to solve tricky engineering problems, this paper studies the use of multi-objective optimization methods applied to the clearance phase of flight control laws (FCL). The clearance problem is related to prove that aircraft control systems are capable of keeping it flying within flight envelope bounds, regardless of pilot inputs and environmental conditions. Previous work have focused on the technical viability of this approach, dealing with single criterion clearance, but in an real validation phase, there are usually multiple criteria that need to be checked, therefore requiring either multiple runs of a single-objective method, or ideally a multi-objective approach. In this work, the well-known Non-dominated Sorting Genetic Algorithm (NSGA-II) and a internally developed method are both tested against a highly non-linear certified AIRBUS aircraft simulation model. Pareto optimal solutions to the multi-criteria clearance problem were found with higher probability than the current probabilistic Monte-Carlo approach. A hybrid combination of local and global optimization is also evaluated to improve worst-cases.

Autopilot Supported by Nonlinear Model Following Reconfigurable Flight Control System

The reconfigurable flight control system was developed, applying a nonlinear aircraft model following control algorithm to support the autopilot. The model of a six degrees of freedom airplane with nonlinear aerodynamics and second-order dynamics of control system actuators was supplemented by aircraft autopilot based on classical control laws. The autopilot commands the aircraft in normal operations. In failure cases, the control system reconfiguration is performed using comparison of control external loads on damaged aircraft with loads in undamaged aircraft operation. Fuzzy logic method produces the control signals preventing the consequences of failures. The objective of reconfiguration is to continue the performed flight, including maneuvers, and, if this is not possible, to obtain the steady flight. The aircraft simulation model was tested for consistency with the expected flight performance. The selected autopilot functions were validated and reconfiguration applied in selected cases of failures. T...

Piloted Simulator Evaluation Results of New Fault-Tolerant Flight Control Algorithm

A high fidelity aircraft simulation model, reconstructed using the Digital Flight Data Recorder (DFDR) of the 1992 Amsterdam Bijlmermeer aircraft accident (Flight 1862), has been used to evaluate a new Fault-Tolerant Flight Control Algorithm in an online piloted evaluation. This paper focuses on the piloted simulator evaluation results. Reconfiguring control is implemented by making use of Adaptive Nonlinear Dynamic Inversion (ANDI) for manual fly by wire control. After discussing the modular adaptive controller setup, the experiment is described for a piloted simulator evaluation of this innovative reconfigurable control algorithm applied to a damaged civil transport aircraft. The evaluation scenario, measurements and experimental design, as well as the real-time implementation are described. Finally, reconfiguration test results are shown for damaged aircraft models including component as well as structural failures. The evaluation shows that the FTFC algorithm is able to restore conventional control strategies after the aircraft configuration has changed dramatically due to these severe failures. The algorithm supports the pilot after a failure by lowering workload and allowing a safe return to the airport. For most failures, the handling qualities are shown to degrade less with a failure than the baseline classical control system does.