Aircraft Model Research Articles

The influence and application of nonlinear aerodynamics on static derivatives in transonic regime

This paper details two static aeroelastic analysis methods applied to a passenger aircraft model with high aspect ratio wing. The influence of nonlinear aerodynamic force on static aeroelastic derivatives in the transonic regime is analysed. The traditional aerodynamic influence coefficient (AIC) matrix method can produce fast and reliable aerodynamic force and is widely used in aeroelastic analysis. However, the AIC matrix computed by linear aerodynamics will lead to some errors in transonic regime because of the nonlinear effect of aerodynamics. By generating the correction matrices, the AIC matrix is modified, and the accuracy of transonic static aeroelastic correction of aerodynamic data can be improved. The static derivatives are compared to the results of the computational fluid dynamics (CFD) / computational structural (CSD) interaction method.

Research on Dynamic Characteristics Analysis and Control Law Design Method of Model Aircraft in Wind Tunnel–Based Virtual Flight Testing

In the three-degree-of-freedom virtual flight test, the scaled model has no translational motion, which will result in the model’s dynamics being different from that of free flight, and this difference will directly affect its effectiveness in simulating free flight and the design of the flight control law. In this paper, the longitudinal and lateral-directional dynamic characteristics of virtual flight are studied from the three aspects of modal characteristics, disturbance response characteristics, and control response characteristics. The dynamic characteristic difference between the virtual flight test and free flight is analyzed. In addition, the scaling ratio of the model will also lead to differences in the flight control law design methods of virtual flight and full-size aircraft. The control law design method of the virtual flight test is established by studying the similarity relation of control law parameters between full-size aircraft and the scaled model, and the correctness of similar design of closed-loop control law parameters of the scaled model is verified by a virtual flight test. Finally, the attitude control law parameters obtained from the virtual flight test are applied to the six-degree-of-freedom flight simulation of a full-size aircraft, and the simulation results show that the three-axis attitude control law designed based on the virtual flight test also has good performance in the six-degree-of-freedom flight of the full-size aircraft, and the response of attitude angle and angular rate are approximately the same for both.

Incipient Fault Detection and Reconstruction Using an Adaptive Sliding-Mode Observer for the Actuators of Fixed-Wing Aircraft

This paper proposes a new method of detection and reconstruction of the incipient fault of fixed-wing actuators based on an adaptive sliding-mode observer. First, a mathematical model of a fixed-wing aircraft is derived under certain assumptions, considering nonlinear terms and system disturbances. Second, by introducing a nonsingular coordinate transformation, the incipient faults are separated from the disturbances. For a subsystem with no disturbances, the Luenberger observer can estimate the incipient fault. For a subsystem with disturbances, the sliding-mode observer is robust against these disturbances. The Lyapunov stability theory guarantees dynamic error convergence and system stability. The evaluation function was designed to realize residual evaluation and threshold judgment. Third, based on the concept of equivalent output injection, an adaptive sliding-mode observer method is proposed to reconstruct actuator faults precisely under the condition of the uncertain system structure. The design steps of the proposed reconstruction method are introduced in the form of a linear matrix inequality problem, which provides an effective method for calculating the design parameters. Finally, the simulation results of the De Havilland DHC-2 “Beaver” aircraft demonstrate the correctness and effectiveness of the proposed method.

An energy systems model of large commercial liquid hydrogen aircraft in a low-carbon future

Liquid hydrogen (LH2) aircraft have the potential to achieve carbon neutrality. However, if the hydrogen is produced using electricity grids that utilise fossil fuel, they have a non-zero carbon dioxide (CO2) emission associated with their well-to-wing pathway. To assess the potential of LH2 in aviation decarbonisation, an energy systems comparison of large commercial LH2, liquified natural gas (LNG), conventional Jet-A and LH2 dual-fuel aircraft is presented. The performance of each aircraft is compared towards 2050, over which three system changes occur: (1) LH2 aircraft technology develops; (2) both world average and region-specific grid electricity, which is used to produce the hydrogen, decarbonises; and (3) the International Air Transportation Association (IATA) emissions targets, which are used to restrict the passenger-range performance of each aircraft, tighten. In 2050, the emissions of all aircraft are thus constrained to 0.063 kg-CO2/p-km, relative to 0.110 kg-CO2/p-km for the unconstrained Jet A fuelled Boeing 787-8. It is estimated that, in this year, an LH2 aircraft powered by fuel cells and sourcing world average electricity can travel 6000 km, 20% further than the conventional Jet A aircraft that is also constrained to meet the IATA targets, but not as far as the LNG aircraft. At its maximum range, the LH2 aircraft carries 84% of the Jet A passenger demand. Analysis using region-specific hydrogen indicates that LH2 aircraft can travel further than LNG aircraft in North America only, accounting for 17% of the global demand. 1.59 times the current aviation energy consumption is required if all conventional aircraft are replaced with LH2 designs. Under stricter emissions constraints than those outlined by the IATA, LH2 outperforms LNG in Europe and the Americas, accounting for 41% of the global demand. Also in these regions, the range, energy consumption and passenger capacity of LH2 aircraft can be improved upon by combining the advantages of LH2 with LNG in dual-fuel aircraft concepts. The use of LH2 is therefore advantageous within several prominent niches of a future, decarbonising aviation system.

Synthesis of fluorinated copolymers and their applications as pressure‐responsive materials

AbstractPressure‐sensitive paints (PSPs) have been demonstrated to be very important for aerodynamics research. In order to improve the pressure sensitivity and adhesion ability of PSP, herein, a series of fluorine‐containing copolymers compositing of an oxygen and pressure‐responsive probe derived from platinum(II)‐5,10,15,20‐tetrakis‐(2,3,4,5,6‐pentafluorophenyl)‐porphyrin (PtTFPP) named as poly[(tBs)a‐co‐(TFEM)b‐co‐(PtTFPP‐1MA)c] were synthesized and investigated as PSPs. These PSPs were constructed with different fluorine ratios for the investigation of the effect of fluorine contents on PSPs. Especially, PSP (F0.33) with the trifluoroethyl methacrylate (TFEM) molar ratio of 33% in the copolymers could adhere well to the surface of an aircraft model. F0.33 showed high oxygen sensitivity (I0/I100 = 32.87), reasonable response time to oxygen (44 s), high pressure sensitivity (SP = 0.75%/kPa at 20°C) and low temperature response (ST = −0.77%/°C at 100 kPa). F0.33 was further sprayed on the surface of a delta wing of an aircraft model and its pressure response was verified in a wind tunnel. The data from F0.33 film at the same wind speed and position were close to the pressure data measured by using traditional method using open pressure holes, showing the potential application of these PSPs.

A composite approach to modelling aircraft noise contours for improved annoyance prediction

Aircraft noise contours are an essential tool for land-use planning around aerodromes. They are intended as predictors of the effects of aircraft noise on communities, mainly in terms of aircraft noise annoyance. In practicality, these contours often fail to encompass a large percentage of the severely annoyed population at the prescribed noise thresholds for the onset of significant annoyance. This paper proposes a novel approach to modelling noise exposure contours that can improve their predictive power. Using Toronto Pearson Airport as a case study, data from a 2020 noise annoyance questionnaire and calculated noise levels from 25 noise monitoring terminals were used to examine the relationships between severe annoyance and noise exposure for six different airport operational scenarios, representative of both average and alternate traffic configurations. The findings indicate that a composite scenario that models noise exposure for both average and alternate traffic configurations is more predictive of severe annoyance than an average type scenario alone.

FEM-based optimal design and testing of synchronous magnetic coupling for aerospace Starter/Generator applications

Improvements in high energy density rare-earth permanent magnets make it innovative to develop magnetic couplings for Starter/Generator applications in the light of more electric aircraft to ensure magnetically insulated contactless power transmission between decoupled shafts for safe operation. Although there are essential studies on magnetic couplings in the literature, especially those for aerospace Starter/Generator structures are rarely encountered. However, methodologies considering system constraints and examining design parameters of couplings are in demand. In response to such a need, this paper proposes the novel design of highly reliable synchronous radial magnetic couplings with torque requirements of 6 and 12 N·m to isolate Starter/Generator and piston engine shafts in model aircraft. The preliminary volume is obtained analytically. Simulations are executed by optimetric approaches in Ansys Maxwell 2D. Optimisation techniques are compared in Maxwell 3D to get the final shape. The retaining sleeve of 0.5 mm is suggested. Loss of synchronisation in the event of the piston shaft failure or exceeding the maximum torque of the coupling is also examined. The torque fluctuation at load changes is 0.1%. Performance tests are conducted on the direct dynamic test bench. Absolute error margin is 37% for the Virtual Work method, 13% for 2D FEM and 6% for 3D FEM. The coupling efficiency is 93.8% at the maximum operating speed and the critical angle, and 96.9% at the minimum torque angle and the minimum operating speed.

Performance models of passenger aircraft and propulsion systems based on particle swarm and Spotted Hyena Optimization methods

Performance models of passenger aircraft and propulsion systems based on particle swarm and Spotted Hyena Optimization methods

Constrained Dynamics of an Aerial Manipulator Interacting With Flexible Cantilever Beams

Aerial manipulation poses complex challenges for aircraft design, modeling, and control, especially when dealing with nonlinear continuous systems. This article explores the coupled dynamics of a fully actuated aerial vehicle when interacting with a cantilever beam undergoing large deflections, focusing on achieving a more accurate model and identifying the challenges involved in this task. The analysis can be applied to prolonged interactions, such as tree branch deflection or long reach manipulation. Based on the Udwadia–Kalaba formulation, the presented model follows a relatively simple and systematic approach for imposing constraints without Lagrange multipliers. The resulting constrained equation of motion is obtained in closed form and captures the essential characteristics of the interaction: kinematic constraints and geometric nonlinearities. Furthermore, simulation and experiments demonstrate the feasibility and performance limitations of using a linear motion controller and how end-effector configuration can affect stability.

Safety and Efficiency Evaluation Model for Converging Operation of Aircraft and Vehicles

To explore the mixed traffic characteristics of vehicles and aircraft on the airport surface and solve the problem of real-time conflict detection at key intersections. According to the actual taxiing procedures and airport control rules in China, this paper focus on abstracting the mixed motion process of aircraft and vehicles in the maneuvering area, defining the convergent cross-safety operation scenario. To quantify the driver’s attention to safety separation and the degree of conservatism in adjusting speed, the vehicle deceleration rate and acceleration rate are defined with α as the exponent. Under the same spacing, the vehicle deceleration rate is directly proportional to α, and α is named the vehicle safety sensitivity. At the same time, the rules of speed change of vehicles and aircraft will be designed, and a convergent operation model of aircraft and vehicles will be proposed. Based on real-time speed and separation dynamic assessment of safety and efficiency under different traffic strategies, the computer simulation results show that vehicle safety sensitivity and deceleration rules determine the sequence of vehicles and aircraft when they are passing through in the short term and can affect the proportion of mixed traffic flow in the long run. The safety probability of vehicles passing the intersection first is negatively correlated with vehicle safety sensitivity, while the safety probability of aircraft passing the intersection first is correlated positively with vehicle safety sensitivity. The efficiency of passing without conflict with mixed traffic has an inverse relationship with vehicle safety sensitivity. When the vehicle safety sensitivity takes the value in the interval [0.4, 0.6], a mixed traffic flow with higher safety and efficiency, better stability, and a balanced ratio of locomotives can be obtained.

Physics-Inspired Hybrid Method for the Conducting Target's RCS Extrapolation in the Frequency Domain

A physics-inspired hybrid method for extrapolating the conducting target's radar cross section (RCS) versus frequency is presented. Inspired by physical optics, we propose using the nonlinear least squares method to capture the global trend of the conducting target's RCS and using Gaussian process regression to automatically extrapolate the remaining local fluctuations. Experiments based on simulated and measured data are carried out to verify the proposed method. This method achieves a maximum root-mean-square error of only 0.444 dBsm on the simulated data of an electrically large aircraft model, and 0.065 dBsm on the measured data of a combinatorial model. These results fully demonstrate its high extrapolation accuracy.

Wire-driven parallel robot suspension system for SDM in a low-speed wind tunnel

A wire-driven parallel robot with eight wires (WDPR-8) acting as the suspension system for an aircraft model in a low-speed wind tunnel is introduced in this paper. A kinematics model for WDPR-8 is established here. A theoretical basis is also provided, through which movement control of the model is achieved by changing the wire length. A model motion control subsystem, a monocular vision measurement subsystem for the model position, and a data acquisition subsystem were also developed for WDPR-8. A prototype of WDPR-8 was built and mounted in a low-speed wind tunnel with an open test section. A six-component strain-gauge balance was installed inside the test model to acquire aerodynamic parameters. The aerodynamic coefficients of the static test show reasonable agreement with reference results. The difference between the test result of WDPR-8 and the results from reference is smaller in the positive angle of attack than the negative angle of attack, and the total difference between WDPR-8 and other facilities is under 10%. Pitch dynamic tests with different amplitudes and frequencies were used to verify the aerodynamic hysteresis phenomena. The research indicates it is successful that the solution of measuring aerodynamic parameters with strain-gauge balance set into the standard dynamic model suspended by WDPR. It demonstrates that WDPR-8 is effective and feasible as a model suspension system in a low-speed wind tunnel. Furthermore, test results without interference correction in accordance with the reference data proves that the interference of Wire-Driven support system to flow field during wind tunnel tests is negligible. Finally, WDPR suspension system introduced in this paper will remarkably improve the efficiency and accuracy in wind tunnel test.

Design and Verification of Short-Distance Landing Control System for a One-Third-Scale Unmanned Supersonic Experimental Airplane

The Aerospace Plane Research Center at the Muroran Institute of Technology is currently conducting research to develop enabling technologies for high-speed aircraft traveling at high altitudes and constructing experimental, small-scale, unmanned supersonic aircraft called Oowashi as a testbed for flight. To confirm the control performance of the aircraft, an experiment using a one-third-scale model of the Oowashi aircraft has been planned. The flight of high-speed aircraft always presents the problem of having to land on an ordinary runway regardless of the aircraft’s high speed at the beginning of the landing process. This paper therefore proposes a new landing control design method that can shorten the landing distance for a high-speed aircraft without increasing the rate of descent. The design method utilizes the newly clarified relationship between an angle of attack and the time constant of flare control system, which is effective to raise glideslope angle during landing. The validity of the method is confirmed by computer simulation assuming the model aircraft equivalent to a one-third-scale model of the Oowashi aircraft.

Conservatism reduction in robust control of Markov jump delay systems

A new method is developed for the robust stabilization of a Markov jump system with general discrete state time-delay and partly unknown transition probabilities. In contrast to most existing literature, a set of numerical testable conditions, rather than a huge matrix inequality, are established for the resulting closed-loop system in order to justify the stochastic stability and disturbance attenuation capability with the aid of a non-monotonic design approach. To be specific, by constructing a stochastic Lyapunov function via the application of an n-samples variation, sufficient conditions for the existence of a dissipative state feedback controller are derived with less conservativeness, that is, with larger stochastic stable region and better attenuation level. Three examples including a numerical example, a pest’s structured population model and an F-404 test aircraft model are presented to demonstrate the advantage and practical potential of the proposed methodology.

Large-Scale Aircraft Pose Estimation System Based on Depth Cameras

In the fields of wind tunnel measurement and aerospace, the real-time pose information of aircraft is an important index. In this paper, we propose a large-scale aircraft pose estimation system, in which depth cameras are used to scan the entire aircraft model in multiple directions. Using a principal component analysis (PCA) featuring vectors as the target coordinate system through a coordinate transformation matrix for the point cloud calibration of aircraft, we merge the complete aircraft model with the point cloud. An intrinsic shape signature (ISS) key point extraction and a signature of histograms of orientations (SHOT) feature description are used to form feature descriptors. The scale of the point clouds is reduced, and coarse registration of the point clouds is performed by feature matching and random sample consensus (RANSAC) mismatching. The robustness of the algorithm is improved, and the initial pose estimation is achieved for the precise registration of point clouds. The experimental results demonstrate that the proposed system can achieve an angle measurement accuracy of 0.05°.

Carrier Aircraft Flight Controller Design by Synthesizing Preview and Nonlinear Control Laws

This paper proposes an innovative automatic carrier landing control law for carrier-based aircraft considering complex ship motion and wind environment. Specifically, a strategy is proposed to synthesize preview control with an adaptive nonlinear control scheme. Firstly, incremental nonlinear backstepping control law is adopted in the attitude control loop to enhance the anti-disturbance capability of the aircraft. Secondly, to enhance the glide slope tracking performance under severe sea conditions, the carrier motion is predicted, and the forecasted motion is adopted in an optimal preview control guidance law to compensate influences induced by carrier motion. However, synthesizing the inner-loop and outer-loop control is not that straightforward since the preview control is naturally an optimal control law which requires a state-space model. Therefore, low-order equivalent fitting of the attitude-to-altitude high-order system model needs to be performed; furthermore, a state observer needs to be designed for the low-order equivalent system to supply required states to the landing controller. Finally, to validate the proposed methodology, an unmanned tailless aircraft model is used to perform the automatic landing tasks under variant sea conditions. Results show that the automatic carrier landing system can lead to satisfactory landing precision and success rate even under severe sea conditions.

Ground Crash Area Estimation of Quadrotor Aircraft Under Propulsion Failure

Small unmanned aircraft systems or drones are expected to be used for different applications, such as parcel delivery, inspection, and aerial photography, in urban areas. However, drones usually use an electric system to power up the propulsion, communications, navigation, and flight control system, which means that it is not as reliable as the manned aircraft system and may result in failure during operation and then crash to the ground. At present, there is almost no extensive publication about the high-fidelity modeling used by drones to calculate the crash trajectory and point of crash. The experimental data for modeling and simulation verification of multirotor aircraft are limited. So far, crash trajectory prediction has been limited to point mass or ballistic methods, and these methods are usually only suitable for complete power failure and without any control system. This study intends to investigate the effects of different multirotor drones’ failure modes on its crash trajectory and crash area compared to the ballistic model by using ADAMS and MATLAB cosimulation methods. Conclusions from the study show the crash trajectory, flight distance, and impact speed of the drones under four failure modes, which are quite different from the ballistic trajectory. The findings can potentially contribute to better risk assessment of the multirotor drones for the urban environment operation.

Effect of Anodic Oxidation on Tribological Behavior of 2017A Alloy

Anodic oxidation is used to improve the wear resistance and surface properties of aluminum alloys. In this study, the effect of two different anodic oxidation (hard anodizing and phosphoric coating) on the wear properties of 2017A aluminum alloy used as a model aircraft engine piston was investigated. In order to determine the effect of anodic oxidation, microhardness, friction coefficient, wear resistance, vibration, and worn surface images of the samples were evaluated. It was concluded that anodic oxidation significantly improved the hardness, friction coefficient, and wear resistance of the samples.

Research on Drag Reduction and Heat Prevention of Hypersonic Vehicle Combined Model with Reverse Jet and Slot Blowing

A novel strategy combining reverse jet with slotted blowing is proposed in this paper, and two-dimensional (RANS) is used to numerically investigate the flow characteristics of a reverse jet. The numerical results show the jet from the aircraft head ejects backward, pushing the shock away and reducing aerodynamic heating and shock wave resistance. The jet from the middle slot ejects backward and the effective solution reduces the viscous resistance of the fuselage. This new strategy not only further reduces the total resistance but also provides good thermal protection for the aircraft. Compared with the aircraft model, the stagnation point temperature and resistance are reduced by 25.0% and 28.0%, respectively, with the addition of multiple jets.

Experimental Results for a Low-Reynolds-Number Airfoil in a Low-Turbulence Wind Tunnel

The Pennsylvania State University (PSU) 94-097 airfoil was originally designed in the mid-1990s for use on winglets of high-performance sailplanes. This design problem is difficult because this application requires the airfoil to operate over a wide range of Reynolds numbers, from to . At that time, over two decades ago, to validate the tools as well as the design itself, high-quality measurements of section characteristics and pressure distributions were made in the PSU low-speed low-turbulence wind tunnel with Reynolds numbers from to . In addition to free-transition measurements, potential drag reductions using artificial turbulators were explored. More recently, this model was retested in the same facility at Reynolds numbers down to . In addition, because this airfoil has been successfully employed on model aircraft and unmanned aerial vehicles, its performance using a simulated simple flap/aileron was measured and found to provide the necessary lift coefficient range to support the flight envelope without significant increases in drag. In this regard, it is comparable to similar flapped-equipped airfoils. Finally, as with the results from the original tests, with the exception of the maximum lift coefficient, theoretical predictions using well-known codes are found to be in good agreement with the wind-tunnel measurements.