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Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

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Chinese Journal of Aeronautics 2013年第1期26卷 151-160页

作者： shi zhongke Fan Li School of Automation Northwestern Polytechnical University

To investigate the longitudinal motion stability of aircraft maneuvers conveniently, a new stability analysis approach is presented in this paper. Based on describing longitudinal aerodynamics at high angle-of-attack （a ＆lt; 50 ） motion by polynomials, a union structure of two-order differential equation is suggested. By means of nonlinear theory and method, analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight. Applying the theories of bifurcations, many kinds of bifurcations, such as equilibrium, Hopf, homoclinic （heteroclinic） orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived. The bifurcation curves divide the parameter plane into several regions; moreover, the complete bifurcation diagrams and phase portraits in different regions are obtained. Finally, our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium. The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.

关键词： Bifurcation High angle of attack Longitudinal motion Polynomials Stability

An overview on flight dynamics and control approaches for hypersonic vehicles

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Science China(Information Sciences) 2015年第7期58卷 7-27页

作者： XU Bin shi zhongke School of Automation Northwestern Polytechnical University National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical University

With the capability of high speed flying, a more reliable and cost efficient way to access space is provided by hypersonic flight vehicles. Controller design, as key technology to make hypersonic flight feasible and efficient, has numerous challenges stemming from large flight envelope with extreme range of operation conditions, strong interactions between elastic airframe, the propulsion system and the structural *** paper briefly presents several commonly studied hypersonic flight dynamics such as winged-cone model,truth model, curve-fitted model, control oriented model and re-entry motion. In view of different schemes such as linearizing at the trim state, input-output linearization, characteristic modeling, and back-stepping, the recent research on hypersonic flight control is reviewed and the comparison is presented. To show the challenges for hypersonic flight control, some specific characteristics of hypersonic flight are discussed and the potential future research is addressed with dealing with actuator dynamics, aerodynamic/reaction-jet control, flexible effects,non-minimum phase problem and dynamics interaction.

关键词： hypersonic flight vehicle linearizing at the trim state input-output linearization back-stepping non-minimum phase

Application of a fourth-order relaxation scheme to hyperbolic systems of conservation laws

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Acta Mechanica Sinica 2006年第1期22卷 84-92页

作者： Jianzhong Chen zhongke shi EO.Box615 Northwestern Polytechnical UniversityXi'an 710072 China

A fourth-order relaxation scheme is derived and applied to hyperbolic systems of conservation laws in one and two space dimensions. The scheme is based on a fourthorder central weighted essentially nonoscillatory （CWENO） reconstruction for one-dimensional cases, which is generalized to two-dimensional cases by the dimension-by-dimension approach. The large stability domain Runge-Kutta-type solver ROCK4 is used for time integration. The resulting method requires neither the use of Riemann solvers nor the computation of Jacobians and therefore it enjoys the main advantage of the relaxation schemes. The high accuracy and high-resolution properties of the present method are demonstrated in one- and two-dimensional numerical experiments.

关键词： Hyperbolic systems of conservation laws Relaxation schemes CWENO reconstruction

Identification of reduced-order model for an aeroelastic system from flutter test data

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Chinese Journal of Aeronautics 2017年第1期30卷 337-347页

作者： Tang Wei Wu Jian shi zhongke School of Automation Northwestern Polytechnical University

Recently, flutter active control using linear parameter varying（LPV） framework has attracted a lot of attention. LPV control synthesis usually generates controllers that are at least of the same order as the aeroelastic models. Therefore, the reduced-order model is required by synthesis for avoidance of large computation cost and high-order controller. This paper proposes a new procedure for generation of accurate reduced-order linear time-invariant（LTI） models by using system identification from flutter testing data. The proposed approach is in two steps. The well-known poly-reference least squares complex frequency（p-LSCF） algorithm is firstly employed for modal parameter identification from frequency response measurement. After parameter identification,the dominant physical modes are determined by clear stabilization diagrams and clustering technique. In the second step, with prior knowledge of physical poles, the improved frequencydomain maximum likelihood（ML） estimator is presented for building accurate reduced-order model. Before ML estimation, an improved subspace identification considering the poles constraint is also proposed for initializing the iterative procedure. Finally, the performance of the proposed procedure is validated by real flight flutter test data.

关键词： Aeroelastic system Flutter test Maximum likelihood Reduced-order model Subspace identification

Optimal design of a scaled-up PRO system using swarm intelligence approach

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Science China(Information Sciences) 2021年第12期64卷 175-188页

作者： Yingxue CHEN zhongke shi Bin XU Mohammad Hasan SHAHEED School of Power and Energy Northwestern Ploytechnical University School of Automatic Northwestern Polytechnical University School of Engineering and Materials Science Queen Mary University of London

In this study, the pressure-retarded osmosis(PRO) process is optimized using Harris hawks optimization(HHO)-based maximum power point tracking(MPPT) technology. To make the practical implementation of salinity-gradient-based energy harvesting using PRO feasible, MPPT is envisaged to play a substantial role. Therefore, this study focuses on the development of a novel MPPT controller using swarm intelligence. The HHO algorithm is the latest approach that mimics the unique chasing strategy of Harris hawks in nature. To test the cost effectiveness of the proposed method, two case studies with various operational scenarios are presented. Compared with the performance of selected well-known and recent approaches, such as perturb & observe, incremental mass resistance, and whale optimization algorithm techniques, that of the proposed metaheuristic-based MPPT technique is found to be highly *** also show that the proposed algorithm can overcome other methods’ limitations, such as low tracking efficiency; low robustness when encountered in various operational conditions, including temperature and salinity; and steady-state oscillations. Furthermore, the proposed MPPT strategy is suitable for use in other fields of renewable energy harvesting.

关键词： maximum power point tracking (MPPT) swarm intelligence metaheuristic algorithms pressure-retarded osmosis (PRO) Harris hawks optimization (HHO)

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High-resolution central difference scheme for the shallow water equations

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Acta Oceanologica Sinica 2005年第5期24卷 39-45页

作者： CHEN Jianzhong shi zhongke HU Yanmei Northwestern Polytechnical University Xi＇an 710072 China College of Science Chang＇an University Xi＇an 710064 China

A two-dimensional nonoscillatory central difference scheme was extended to the shallow water equations. A high-resolution numerical method for solving the shallow water equations was presented. In order to prevent oscillation, the nonlinear limiter is employed to approximate the discrete slopes. The main advantage of the presented method is simplicity comparable with the upwind schemes. This method does not require Riemann solvers or some form of flux difference splitting methods. Furthermore, the discrete derivatives of flux can be approximated by the component-wise approach and thus the computation of Jacobian can be avoided. The method retains high resolution and high accuracy similar to the upwind results. It is applied to simulating several tests, including circular dam-break problem, shock focusing problem and partial dam-break problem. The results are in good agreement with the numerical results obtained by other methods. The simulated results also demonstrate that the presented method is stable and efficient.

关键词： shallow water equations central difference scheme high-resolution scheme

Dynamics modeling and control of large transport aircraft in heavy cargo extraction

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控制理论与应用（英文版） 2011年第2期9卷 231-236页

作者： Feng, Yanli shi, zhongke Tang, Wei College of Automation Northwestern Polytechnical University Xi'an Shaanxi 710072 China

In this paper,a novel version of six-degree-of-freedom nonlinear model for transport aircraft motion in cargo extraction is developed and validated by the theoretical mechanics and flight *** this model constraint force and moment reflecting the flight dynamic effects of inner moving cargo are formulated.A methodology for a control law design in this phase is presented,which linearizes the aircraft dynamics making use of piecewise linearization and utilizes robust control technique for interval system to achieve specified handling qualities with robustness to *** simulations demonstrate adequate effectiveness and excellent robustness of the proposed controller.

关键词： Cargo extraction Transport aircraft Flight dynamic model Equilibrium Interval system Robust control

A Novel Nonlinear Model Predictive Control Method Based on LMI and Feedback Linearization

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A Novel Nonlinear Model Predictive Control Method Based on L...

Variable Structure Control of Catastrophic Course in Airdropping Heavy Cargo

第25届中国控制与决策会议

作者： Rui Pang zhongke shi School of automation Northwestern Polytechnical University

ISBN: (纸本)9781467355322

Nonlinear model predictive control （NMPC） mainly deals with complex dynamic systems with different kinds of nonlinearities, which is much more difficult to solve than normal linear model predictive. The non-convex optimization method inside MPC is its main challenging problem. A LMI based NMPC method is proposed combined with nonlinear feedback linearization can efficiently convert complex non-convex optimization problem to convex. The method minimizes the upper bound of cost function instead of itself, which can stabilize the whole system and achieve the control performance. A high angle of attack （HAOA） aircraft controller design example is illustrated in the end to demonstrate the validity of proposed method.

关键词： NMPC LMI convex optimization feedback linearization

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Chinese Journal of Aeronautics 2009年第5期22卷 520-527页

作者： Zhang Huiyuan shi zhongke Department of Automatic Control Northwestern Polytechnical University Xi 'an 710072 China

The mathematical model of a transport aircraft would be subjected to a sudden change when heavy cargo is dropped off in airdropping, which exerts serious influences upon the safety of the aircraft. A variable structure controller is specially designed for handling the airdrop process. The nonlinear system is linearized by input-output feedback linearization using differential geometry theories. On this basis, an inner loop system for velocity and attitude tracking control is designed by using the exponentially approaching rule of the variable structure theory. The whole flight control system is integrated with the outer loop flight altitude control. Digital simulation evidences the applicability of the system to potentially catastrophic course in airdropping heavy cargo and provides robustness against system parameter perturbation.

关键词： flight control airdrop nonlinear control system variable structure control feedback linearization sliding mode control