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Impact angle constrained fuzzy adaptive fault tolerant IGC method for Ski-to-Turn missiles with unsteady aerodynamics and multiple disturbances

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Journal of Systems Engineering and Electronics 2022年第5期33卷 1210-1226页

作者： GUO Hang WANG Zheng FU Bin CHEN Kang FU Wenxing YAN Jie Research Center for Unmanned System Strategy Development Northwestern Polytechnical UniversityXi’an 710072China Unmanned System Research Institute Northwestern Polytechnical UniversityXi’an 710072China

An impact angle constrained fuzzy adaptive fault tolerant integrated guidance and control method for Ski-to-Turn(STT)missiles subject to unsteady aerodynamics and multiple disturbances is proposed.unsteady aerodynamics appears when flight vehicles are in a transonic state or confronted with unstable airflow.Meanwhile,actuator failures and multisource model uncertainties are introduced.However,the boundaries of these multisource uncertainties are assumed unknown.The target is assumed to execute high maneuver movement which is unknown to the missile.Furthermore,impact angle constraint puts forward higher requirements for the interception accuracy of the integrated guidance and control(IGC)method.The impact angle constraint and the precise interception are established as the object of the IGC method.Then,the boundaries of the lumped disturbances are estimated,and several fuzzy logic systems are introduced to compensate the unknown nonlinearities and uncertainties.Next,a series of adaptive laws are developed so that the undesirable effects arising from unsteady aerodynamics,actuator failures and unknown uncertainties could be suppressed.Consequently,an impact angle constrained fuzzy adaptive fault tolerant IGC method with three loops is constructed and a perfect hit-to-kill interception with specified impact angle can be implemented.Eventually,the numerical simulations are conducted to verify the effectiveness and superiority of the proposed method.

关键词： integrated guidance and control(IGC) impact angle constraint unsteady aerodynamics fault tolerant control(FTC) actuator failures

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Comparative Study of Machine Learning Modeling for unsteady aerodynamics

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Computers, Materials & Continua 2022年第7期72卷 1901-1920页

作者： Mohammad Alkhedher Mechanical Engineering Department Abu Dhabi UniversityAbu DhabiUnited Arab Emirates

Modern fighters are designed to fly at high angle of attacks reaching 90 deg as part of their routine maneuvers.These maneuvers generate complex nonlinear and unsteady aerodynamic loading.In this study,different aerodynamic prediction tools are investigated to achieve a model which is highly accurate,less computational,and provides a stable prediction of associated unsteady aerodynamics that results from high angle of attack maneuvers.These prediction tools include Artificial Neural Networks(ANN)model,Adaptive Neuro Fuzzy Logic Inference System(ANFIS),Fourier model,and Polynomial Classifier Networks(PCN).Themain aim of the predictionmodel is to estimate the pitch moment and the normal force data obtained from forced tests of unsteady delta-winged aircrafts performing high angles of attack maneuvers.The investigation includes three delta wing models with 1,1.5,and 2 aspect ratios with four determined variables:change rate in angle of attack(0 to 90 deg),non-dimensional pitch rate(0 to.06),and angle of attack.Following a comprehensive analysis of the proposed identification methods,it was found that the newly proposed model of PCN showed the least error in modeling and prediction results.Based on prediction capabilities,it is seen that polynomial networks modeling outperformed ANFIS and ANN for the present nonlinear problem.

关键词： unsteady aerodynamics supermaneuverability identification neuro-fuzzy polynomial networks neural networks

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Panel/full-span free-wake coupled method for unsteady aerodynamics of helicopter rotor blade

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Chinese Journal of Aeronautics 2013年第3期26卷 535-543页

作者： Tan Jianfeng Wang Haowen School of Aerospace Tsinghua University

A full-span free-wake method is coupled with an unsteady panel method to accurately predict the unsteady aerodynamics of helicopter rotor blades in hover and forward flight. The unsteady potential-based panel method is used to consider aerodynamics of finite thickness multi-bladed rotors, and the full-span free-wake method is applied to simulating dynamics of rotor wake. These methods are tightly coupled through trailing-edge Kutta condition and by converting doublet-wake panels to full-span vortex filaments. A velocity-field integration technique is also adopted to overcome singularity problem during the interaction between the rotor wake and blades. Helicopter rotors including Caradonna–Tung, UH-60A, and AH-1G rotors, are simulated in hover and forward flight to validate the accuracy of this approach. The predicted aerodynamic loads of rotor blades agree well with available measured data and computational fluid dynamics （CFD） results, and the unsteady dynamics of rotor wake is also well simulated. Compared to CFD, the present method obtains accurate results more efficiently and is suitable to rotorcraft aeroelastic analysis.

关键词： Free wake method Helicopter rotor Rotor wake unsteady aerodynamics unsteady panel method

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Numerical Study of the unsteady aerodynamics of Freely Falling Plates

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Communications in Computational Physics 2008年第4期3卷 834-851页

作者： Changqiu Jin Kun Xu Institute of Applied Physics and Computational Mathematics P.O.Box 8009Beijing 100088China Mathematics Department Hong Kong University of Science and TechnologyHong KongChina.

The aerodynamics of freely falling objects is one of the most interesting flow mechanics problems.In a recent study,Andersen,Pesavento,and Wang[J.Fluid Mech.,vol.541,pp.65-90(2005)]presented the quantitative comparison between the experimental measurement and numerical computation.The rich dynamical behavior,such as fluttering and tumbling motion,was analyzed.However,obvious discrepancies between the experimental measurement and numerical simulations still exist.In the current study,a similar numerical computation will be conducted using a newly developed unified coordinate gas-kinetic method[J.Comput.Phys,vol.222,pp.155-175(2007)].In order to clarify some early conclusions,both elliptic and rectangular falling plates will be studied.Under the experimental condition,the numerical solution shows that the averaged translational velocity for both rectangular and elliptical plates are almost identical during the tumbling motion.However,the plate rotation depends strongly on the shape of the plates.In this study,the details of fluid forces and torques on the plates and plates movement trajectories will be presented and compared with the experimental measurements.

关键词： Navier-Stokes equations unified coordinate method unsteady aerodynamics falling plate.

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Modeling Technique of the Aircraft unsteady aerodynamics Due to the Travelling Gust

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International Journal of Plant Engineering and Management 2022年第2期27卷 86-102页

作者： JING Zhiwei TANG Chu General Configuration and aerodynamics Design Department Xi′an Aircraft Design InstituteXi′an 710089China Unmanned System Research Institute Northwestern Polytechnical UniversityXi′an 710072China

The main equations for computing the unsteady aerodynamics of the aircraft undergoing the travelling gust are derived.Research and simulation on a specific example aircraft are performed,the results indicate that the modeling technique of the aircraft unsteady aerodynamics is correct,and it can meet the requirements due to the head⁃on and tail⁃on travelling gusts.

关键词： travelling gust elastic aircraft unsteady aerodynamics doublet lattice method

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unsteady aerodynamics Modeling Using SVM and Artificial Neural Network

Unsteady Aerodynamics Modeling Using SVM and Artificial Neur...

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2015年中国智能自动化学术会议

作者： Yichao Jiang Qingjie Zhao Jihong Zhu Beijing Lab of Intelligent Information Technology School of Computer ScienceBeijing Institute of Technology Department of Computer Science and Technology Tsinghua University

Recently, more and more attention has been drawn by the aircraft’s maneuvering problem. This problem is very significant for improving performance of the nonlinear and unsteady modeling methods used for aircrafts at high angles of attack. In this paper, support vector machine(SVM) and artificial neural network are introduced into unsteady aerodynamics modeling. The experimental results show that the generality and precision have been significantly improved using these two methods, which verifies that machine learning methods can be applied to unsteady aerodynamic modeling.

关键词： unsteady aerodynamics Machine learning method System modeling

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aerodynamics and dynamic stability of micro-air-vehicle with four flapping wings in hovering flight

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Advances in aerodynamics 2020年第1期2卷 88-106页

作者： Cheng Cheng Jianghao Wu Yanlai Zhang Han Li Chao Zhou School of Transportation Science and Engineering Beihang UniversityBeijing 100191China The first Aircraft Design Institute Aviation Industry Coorporation of ChinaXi’an 710089China

Recently,a novel concept of flapping Micro-Air-Vehicles(FMAVs)with four wings has been proposed,which potentially utilizes the clap-and-fling effect for lift enhancement and agile maneuvers through an adjustment of wing kinematics.However,the application of the clap-and-fling effect in the four-winged FMAVs is underexplored and the dynamic stability is still unclear.In this paper,aerodynamics and flight dynamic stability of the four-winged FMAVs are studied experimentally and numerically.Results show that the clap-and-fling effect is observed when the flapping frequency is above 18 Hz.Due to the clap-and-fling effect,the lift generation and aerodynamic efficiency are both improved,which is mainly attributed to the fling phase.Further studies show that the clap-and-fling effect becomes weaker as the wing root spacing increases and is almost absent at a wing root spacing of 1.73 chord length.In addition,a wing with an aspect ratio of 3 can increase both lift generation and efficiency due to the clap-and-fling effect.Finally,according to the dynamic stability analysis of the four-winged FMAV,the divergence speed of the lateral oscillation mode is about 4 times faster than that of the longitudinal oscillation mode.Our results can provide guidance on the design and control of four-winged FMAVs.

关键词： Four-winged FMAV Clap-and-fling effect Dynamically stability unsteady aerodynamics

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LIFT AND POWER REQUIREMENTS OF HOVERING INSECT FLIGHT

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Acta Mechanica Sinica 2003年第5期19卷 458-469页

作者：孙茂杜刚 InstituteofFluidMechanics BeijingUniversityofAeronautics&AstronauticsBeijing100083China

Lift and power requirements for hovering flight of eight species of insects are studied by solving the Navier-Stokes equation numerically. The solution provides velocity and pressure fields,from which unsteady aerodynamic forces and moments are obtained. The inertial torque of wing mass are computed analytically. The wing length of the insects ranges from 2 mm (fruit fly) to 52 mm (hawkmoth); Reynolds numbers Re (based on mean flapping speed and mean chord length) ranges from 75 to 3 850. The primary findings are shown in the following: (1) Either small (R = 2 mm, Re = 75),medium (R ≈ 10 mm, Re ≈ 500) or large (R ≈ 50 mm, Re ≈ 4 000) insects mainly employ the same high-lift mechanism, delayed stall, to produce lift in hovering flight. The midstroke angle of attack needed to produce a mean lift equal to the insect weight is approximately in the range of 25° to 45°,which is approximately in agreement with observation. (2) For the small insect (fruit fly) and for the medium and large insects with relatively small wingbeat frequency (cranefly, ladybird and hawkmoth),the specific power ranges from 18 to 39W.kg-1 , the major part of the power is due to aerodynamic force, and the elastic storage of negative work does not change the specific power greatly. However for medium and large insects with relatively large wingbeat frequency (hoverfly, dronefly, honey bee and bumble bee), the specific power ranges from 39 to 61W.kg-1 , the major part of the power is due to wing inertia, and the elastic storage of negative work can decrease the specific power by approximately 33%. (3) For the case of power being mainly contributed by aerodynamic force (fruit fly, cranefly,ladybird and hawkmoth), the specific power is proportional to the product of the wingbeat frequency,the stroke amplitude, the wing length and the drag-to-lift ratio. For the case of power being mainly contributed by wing inertia (hoverfly, dronefly, honey bee and bumble bee), the specific power (without elastic storage) is proportional to the product of the cubic

关键词： insects hovering unsteady aerodynamics power requirement computational fluid dynamics

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Unstable unsteady aerodynamic modeling based on least squares support vector machines with general excitation

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Chinese Journal of Aeronautics 2020年第10期33卷 2499-2509页

作者： Senlin CHEN Zhenghong GAO Xinqi ZHU Yiming DU Chao PANG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Common,unsteady aerodynamic modeling methods usually use wind tunnel test data from forced vibration tests to predict stable hysteresis loop.However,these methods ignore the initial unstable process of entering the hysteresis loop that exists in the actual maneuvering process of the aircraft.Here,an excitation input suitable for nonlinear system identification is introduced to model unsteady aerodynamic forces with any motion in the amplitude and frequency ranges based on the Least Squares Support Vector Machines(LS-SVMs).In the selection of the input form,avoiding the use of reduced frequency as a parameter makes the model more universal.After model training is completed,the method is applied to predict the lift coefficient,drag coefficient and pitching moment coefficient of the RAE2822 airfoil,in sine and sweep motions under the conditions of plunging and pitching at Mach number 0.8.The predicted results of the initial unstable process and the final stable process are in close agreement with the Computational Fluid Dynamics(CFD)data,demonstrating the feasibility of the model for nonlinear unsteady aerodynamics modeling and the effectiveness of the input design approach.

关键词： aerodynamics models Forced vibration Input design Least squares support vector machines Nonlinear system System identification unsteady aerodynamics

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CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird

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Journal of Bionic Engineering 2007年第4期4卷 201-208页

作者： M. A. Moelyadi G. Sachs Aeronautics and Astronautics Department Bandung Institute of Technology Ganesha 10 40132 Bandung Indonesia Institute of Flight Mechanics and Flight Control Technische Universitt München Boltzmannstrasse 15 85748 Garching Germany

Dynamic yaw stability derivatives of a gull bird are determined using Computational Fluid Dynamics（CFD） method. Two kinds of motions are applied for calculating the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a good agreement.

关键词： dynamic yaw stability CFD Fourier analysis unsteady aerodynamics reduced frequency

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