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Intelligent feedforward gust alleviation based on neural network

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Chinese Journal of aeronautics 2024年第3期37卷 116-132页

作者： Yitao ZHOU zhigang wu chao yang School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China

This paper proposes a neural network-based intelligent feedforward gust alleviation framework,which includes a neural network identification model and a neural network controller.A neural network training dataset is formed by collecting flight data and the gust data encountered during the aircraft flight.A neural network identification model is first trained to accurately predict the aircraft’s ***,based on the output of the identification model and the collected flight data,the parameters of the time-delay neural network controller are obtained through a learning *** simulation results show that the designed intelligent controller has good gust alleviation effects for both continuous turbulence excitation and discrete gust *** example,when the aircraft is 40000 kg and the flight speed is 0.81Ma,the controller achieves a 67.82%reduction in wingtip acceleration and a 35.90%reduction in center of mass acceleration under continuous turbulence *** considering the measurement uncertainties,such as noise existing in the collected data,the trained controller can still achieve an acceptable gust alleviation ***,considering a flight in which the aircraft mass is constantly changing,the intelligent controller,which continuously learns from new flight data,maintains a good gust alleviation effect throughout the flight.

关键词： Gust alleviation Intelligent control Feedforward control Neural networks Time-varying aircraft

Active flutter suppression of nonlinear fin-actuator system via inverse system and immersion and invariance method

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Chinese Journal of aeronautics 2024年第4期37卷 343-362页

作者： Jin LU zhigang wu chao yang Chinese Aeronautical Establishment Beijing 100029China School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China

Structural nonlinearities such as freeplay will affect the stability and even flight safety of the fin-actuator *** is a lack of a practical method for designing Active Flutter Suppression (AFS) control laws for nonlinear fin-actuator systems.A design method for the AFS controller of the nonlinear all-movable fin-electromechanical actuator system is established by combining the inverse system and the Immersion and Invariance (I&I) ***,the composite control law combining the inverse system principle and internal model control is used to offset the nonlinearity and dynamics of the actuator,so that its driving torque can follow the ideal ***,the ideal torque of the actuator is designed employing the I&I *** unfavorable oscillation of the fin is suppressed by making the output torque of the actuator track the ideal *** simulation results reveal that the proposed AFS method can increase the flutter speed of the nonlinear finactuator system with freeplay,and a set of controller parameters is also applicable for wider freeplay within a certain *** power required for the actuator does not exceed the power that can be provided by the commonly used aviation *** method can also resist a certain level of noise and external disturbance.

关键词： Aeroelasticity Active flutter suppression Fin-actuator system Freeplay Inverse system Immersion and invariance

Application of output feedback sliding mode control to active flutter suppression of two-dimensional airfoil

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Science china(Technological Sciences) 2010年第5期53卷 1338-1348页

作者： yang chao,SONG Chen,wu zhigang & XIE ChangChuan School of Aeronautic Science and Engineering,beijing university of aeronautics & astronautics,beijing 100191,china School of Aeronautic Science and Engineering Beijing University of Aeronautics & Astronautics

The effectiveness of the sliding mode control(SMC) method for active flutter suppression(AFS) and the issues concerning control system discretization and control input constraints were studied using a typical two-dimensional *** airfoil has a trailing-edge flap for flutter *** aeroelastic system involves a two-degrees-of-freedom motion(pitch and plunge),and the equations were constructed by utilizing quasi-steady aerodynamic *** control system,designed by the output feedback SMC method,was incorporated to suppress the pitch-plunge ***,the system discretization and the flap deflection constraints were ***,a classical Runge-Kutta(RK) algorithm was utilized for numerical *** results indicated that the close-loop system with the SMC system could be stable at a speed above the flutter ***,when the flap deflection limits are reached,the close-loop system with the simple discretized control system loses ***,control compensation developed by theoretical analysis was proposed to make the system stable *** parameter perturbations and the time delay effects were also discussed in this paper.

关键词： aeroelasticity flutter airfoil sliding mode control output feedback control

Design optimization and testing of a morphing leading-edge with a variable-thickness compliant skin and a closed-chain mechanism

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Chinese Journal of aeronautics 2024年第7期37卷 285-300页

作者： zhigang WANG Xiasheng SUN Yu yang Wenjie GE Daochun LI Jinwu XIANG Panpan BAO Qi wu Andrea DA RONCH School of Aeronautical Science and Engineering Beihang UniversityBeijing 100191China National Key Laboratory of Strength and Structural Integrity Aircraft Strength Research Institute of ChinaXi’an 710065China School of aeronautics and astronautics Shanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Faculty of Engineering and Physical Sciences University of SouthamptonSouthampton SO171JBUK

Climate warming and the increased demand in air travels motivate the aviation industry to urgently produce technological *** of the most promising innovations is based on the smoothly continuous morphing leading-edge *** study proposes a two-step process for the design of a morphing leading-edge,including the optimization of the outer variable-thickness composite compliant skin and the optimization of the inner kinematic *** the compliant skin design,an optimization of the variable thickness composite skin is proposed based on a laminate continuity model,with laminate continuity constraint and other manufacturing *** laminate continuity model utilizes a guiding sequence and a ply-drop sequence to describe the overall stacking sequence of plies in different thickness regions of the complaint *** the inner kinematic mechanism design,a coupled four-bar linkage system is proposed and optimized to produce specific trajectories at the actuation points on the stringer hats of the compliant skin,which ensures that the compliant skin can be deflected into the aerodynamically optimal ***,a morphing leading-edge is manufactured and *** results are compared with numerical predictions,confirming the feasibility of the morphing leading-edge concept and the overall proposed design approach.

关键词： Optimization Design Morphing wing Compliant skin Kinematics Leading-edge Control surfaces

Aeroelastic dynamic response of elastic aircraft with consideration of two-dimensional discrete gust excitation

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Chinese Journal of aeronautics 2020年第4期33卷 1228-1241页

作者： yang yang chao yang zhigang wu School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

Design loads generally require a one-dimensional discrete gust profile without consideration of the spanwise effect,and this profile cannot represent the true gust field *** a high aspect ratio aircraft,two-dimensional gusts may cause critical load conditions,and approaches for calculating dynamic responses under two-dimensional discrete gust excitation are rarely *** this paper,a spanwise non-uniform vertical discrete gust field is established based on a onedimensional‘1-cos’gust profile in reference to a DARPA proposal,while frequency and hybrid approaches to the dynamic response analysis of flexible aircraft under this two-dimensional gust excitation are *** techniques have been applied to a high aspect ratio aircraft to assess the different response characteristics with a comparison between one-dimensional and two-dimensional discrete gust field *** results show that the two-dimensional discrete gust model produces a higher bending moment than that of the one-dimensional ***,the critical load conditions that are derived from the two-dimensional discrete gust for high aspect ratio aircraft should be seriously *** to the analysis,an active control scheme to alleviate the bending loads caused by the two-dimensional gust is designed,and alleviation effects in different gust conditions are compared.

关键词： Aeroservoelastic Discrete gust Gust response Gust response alleviation Two-dimensional gust

Structural Nonlinear Flutter Characteristics Analysis for an Actuator-fin System with Dynamic Stiffness

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Chinese Journal of aeronautics 2011年第5期24卷 590-599页

作者： yang Ning wu zhigang yang chao School of Aeronautic Science and Engineering Beihang University Beijing 100191 China

The flutter characteristics of an actuator-fin system are investigated with structural nonlinearity and dynamic stiffness of the electric motor. The component mode substitution method is used to establish the nonlinear governing equations in time domain and frequency domain based on the fundamental dynamic equations of the electric motor and decelerator. The existing describing function method and a proposed iterative method are used to obtain the flutter characteristics containing preload freeplay nonlinearity when the control command is zero. A comparison between the results of frequency domain and those of time domain is studied. Simulations are carried out when the control command is not zero and further analysis is conducted when the freeplay angle is changed. The results show that structural nonlinearity and dynamic stiffness have a significant influence on the flutter characteristics. Limit cycle oscillations （LCOs） are observed within linear flutter boundary. The response of the actuator-fin system is related to the initial disturbance. In the nonlinear condition, the amplitude of the control command has an influence on the flutter characteristics.

关键词： aeroelasticity flutter actuators dynamic stiffness structural nonlinearity component mode substitution method describing functions

Identification of nonlinear multi-degree-of freedom structures based on Hilbert transformation

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Science china(Physics,Mechanics & Astronomy) 2014年第9期57卷 1725-1736页

作者： wu zhigang yang Ning yang chao School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics

The modeling method and identified method adapted to multi-degree-of-freedom structures with strucrural nonlinearities are *** component mode synthesis method is used to establish the nonlinear governing equations by extending the connected *** on the modeling method,the Hilbert transform method is applied to identify the nonlinear stiffness of multi-degree-of-freedom *** analysis and identification of a typical folding wing configuration with three freeplay hinges are *** nonlinear governing equation is established based on present methods and the computing results of different stiffness are checked by finite element *** order to illustrate the influence of the nonlinearities,the frequency response characteristics of the structure are analyzed and Hilbert transform is *** Hilbert transform identification method is utilized to identify the nonlinear stiffness of nonlinear hinges in the time domain and several parametric studies are *** addition,the comparison of response is made to illustrate the feasibility of the *** results show that the extending component mode synthesis method in the present work can be used to establish the governing equation with structural *** on the modeling method,the Hilbert transform identified method can be extended to multi-degree-of-freedom structures accurately.

关键词： structural nonlinearity identification Hilbert transformation component mode synthesis method dynamic analysis dynamic response

Identification and robust limit-cycle-oscillation analysis of uncertain aeroelastic system

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Science china(Technological Sciences) 2011年第7期54卷 1841-1848页

作者： DAI YuTing wu zhigang yang chao School of Aeronautic Science and Engineering Beijing University of Aeronautics and AstronauticsBeijing 100191China

Model uncertainty directly affects the accuracy of robust flutter and limit-cycle-oscillation (LCO) analysis. Using a data-based method, the bounds of an uncertain block-oriented aeroelastic system with nonlinearity are obtained in the time domain. Then robust LCO analysis of the identified model set is performed. First, the proper orthonormal basis is constructed based on the on-line dynamic poles of the aeroelastic system. Accordingly, the identification problem of uncertain model is converted to a nonlinear optimization of the upper and lower bounds for uncertain parameters estimation. By replacing the identified memoryless nonlinear operators by its related sinusoidal-input describing function, the Linear Fractional Transformation (LFT) technique is applied to the modeling process. Finally, the structured singular value(μ) method is applied to robust LCO analysis. An example of a two-degree wing section is carded out to validate the framework above. Results indicate that the dynamic characteristics and model uncertainties of the aeroelastic system can be depicted by the identified uncertain model set. The robust LCO magnitude of pitch angle for the identified uncertain model is lower than that of the nominal model at the same velocity. This method can be applied to robust flutter and LCO prediction.

关键词： aeroelasticity robust identification uncertainty structured singular value p limlt-cycle-oscillation

Study on gust alleviation control and wind tunnel test

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Science china Technological Sciences 2013年第3期56卷 762-771页

作者： wu zhigang CHEN Lei yang chao School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics Division of Structural Strength Shanghai Aircraft Design and Research Institute

Aircraft are inevitably affected by gust during flight,which disturbs the regular operations of pilots and worsens the ride *** more grievous cases,flight mission cannot be completed and the flight safety may be *** order to improve the ride quality and the fatigue life of the plane structure under the affect of gust,it is necessary to explore and validate the gust alleviation *** the low-speed wind tunnel test,the gust alleviation active control technology applied to elastic aircraft is *** a large-type passenger plane configuration with high aspect ratio wing,a test system was designed and three gust alleviation control schemes with PID controllers were *** the gust alleviation control low-speed wind tunnel test was carried out in the FD-09 wind *** results showed that at certain speed and gust frequency,all of the 3 control schemes can alleviate the acceleration at fuselage and wing-tip to a certain extent,as well as the bending moment of *** gust alleviation control scheme,which uses aileron,elevator and canard as control surfaces synthetically,gives the most satisfying gust alleviation effect.

关键词： aeroelasticity aeroservoelasticity gust response gust alleviation active control wind tunnel test