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Chinese Journal of Aeronautics 2024年第10期37卷 275-293页

作者： Qi YU wanchun chen Wenbin YU School of Astronautics Beihang UniversityBeijing 102206China

In the scenario that a solid-fuel launch vehicle maneuvers in outer space at high angles of attack and sideslip for energy management,Approximate Analytical Solutions(AAS)for the threedimensional(3D)ascent flight states are derived,which are the only solutions capable of considering time-varying Mass Flow Rate(MFR)at *** uneven MFR makes the thrust vary nonlinearly and thus increases the difficulty of the problem *** AAS are derived based on a 3D Generalized Ascent Dynamics Model(GADM)with a normalized mass as the independent *** simplify some highly nonlinear terms in the GADM,several approximate functions are introduced carefully,while the errors of the approximations relative to the original terms are regarded as minor ***,a finite series with positive and negative exponents,called Exponent-Symmetry Series(ESS),is proposed for function approximation to decrease the highest exponent in the AAS so as to reduce computer round-off *** calculate the ESS coefficients,a method of seeking the Optimal Interpolation Points(OIP)is proposed using the leastsquares-approximation *** to the artful design of the approximations,the GADM can be decomposed into two analytically solvable subsystems by a perturbation method,and thus the AAS are obtained ***,to help implement the AAS,two indirect methods for measuring the remaining mass and predicting the burnout time in flight are put forward using information from *** results verify the superiority of the AAS under the condition of time-varying MFR.

关键词： Approximate analytical solutions 3D ascent trajectory Solid-fuel launch vehicle Uneven thrust Energy management

Robust entry guidance using multi-segment linear pseudospectral model predictive control

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Journal of Systems Engineering and Electronics 2017年第1期28卷 103-125页

作者： Liang Yang wanchun chen Xiaoming Liu Hao Zhou School of Astronautics Beihang UniversityBeijing 100191China

This paper presents a robust entry guidance algorithm for the high lift-to-drag ratio entry vehicle that employs the recently developed pseudospectral model predict control in a segmented manner. Here, the guidance commands are the longitudinal lift-to-drag (L/D) and bank reversal commands, which are calculated by successively solving multiple segment linear algebraic equations. These equations are derived using the linear pseudospectral method, control parametrization and calculus of variations. The method uses orthogonal polynomials and computes the updates through a series of analytical formulae, which makes it accurate and computationally effective. Moreover, it is able to adjust the number of bank reversals by providing the precise bank reversal point so as to fully exploit the potential of lateral maneuver. The method also employs proportional navigation and polynomial guidance after the last bank reversal to meet multiple terminal constraints. High-fidelity numerical simulations with various destinations are carried out to demonstrate its applicability. Furthermore, Monte Carlo simulations are also conducted to show that the proposed algorithm consistently offers very stable and robust performances and has superior performances in computational efficiency, guidance accuracy and lateral trajectory shaping capability in comparison with other typical methods. © 1990-2011 Beijing Institute of Aerospace Information.

关键词： Calculations Computational efficiency Drag Electronic guidance systems Intelligent systems Lift drag ratio Linear algebra Linear equations Monte Carlo methods

Analytical game strategies for active UAV defense considering response delays

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Defence Technology（防务技术） 2024年第12期42卷 191-210页

作者： Xiaopeng Gong wanchun chen Wengui Lei Jinyang Wang Zhongyuan chen Yunyun Li School of Astronautics Beihang UniversityBeijing 100191China Beijing Electro-Mechanical Engineering Institute Beijing 100074China

In the realm of aerial warfare,the protection of Unmanned Aerial Vehicles(UAVs) against adversarial threats is *** order to balance the impact of response delays and the demand for onboard applications,this paper derives three analytical game strategies for the active defense of UAVs from differential game theory,accommodating the first-order dynamic *** targeted UAV executes evasive maneuvers and launches a defending missile to intercept the attacking missile,which constitutes a UAVMissile-Defender(UMD) three-body game *** explore two distinct operational paradigms:the first involves the UAV and the defender working collaboratively to intercept the incoming threat,while the second prioritizes UAV self-preservation,with independent maneuvering away from potentially sacrificial *** with model linearization and order reduction,the Collaborative Interception Strategy(CIS) is first derived via a linear quadratic differential game *** upon CIS,we further explore two distinct strategies:the Informed Defender Interception Strategy(IDIS),which utilizes UAV maneuvering information,and the Unassisted Defender Interception Strategy(UDIS),which does not rely on UAV maneuvering ***,we investigate the conditions for the existence of saddle point solutions and their relationship with vehicle maneuverability and response *** simulations demonstrate the effectiveness and advantages of the proposed strategies.

关键词： Active defense Unmanned aerial vehicles(UAVs) Three-body game Differential game Analytical game strategy Response delays

Optimal terminal guidance for exoatmospheric interception

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Chinese Journal of Aeronautics 2016年第4期29卷 1052-1064页

作者： Yu Wenbin chen wanchun Yang Liang Liu Xiaoming Zhou Hao School of Astronautics Beihang University

In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be considered or neglected by properly adjusting a parameter in the cost function. To make this problem analytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

关键词： Exoatmospheric interception Explicit guidance Guidance Optimal control Proportional navigation Pulsed guidance

Study on flow characteristics of solid/liquid system in lysozyme crystal growth

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Chinese Science Bulletin 2007年第9期52卷 1196-1204页

作者： CUI HaiLiang YU Yong chen wanchun KANG Qi National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Institute of Physics Chinese Academy of Sciences Beijing 100080 China

During the process of lysozyme protein crystallization with batch method,the macroscopic flow field of solid/liquid system was observed by particle image velocimetry(PIV). Furthermore,a normal growth rate of(110) face and local flow field around a single protein crystal were obtained by a long work dis-tance microscope. The experimental results showed that the average velocity,the maximal velocity of macroscopic solid/liquid system and the velocity of local flow field around single protein crystal were fluctuant. The effective boundary layer thickness δeff,the concentration at the interface Ci and the characteristic velocity V were calculated using a convection-diffusion model. The results showed that the growth of lysozyme crystal in this experiment was dominated by interfacial kinetics rather than bulk transport,and the function of buoyancy-driven flow in bulk transport was small,however,the effect of bulk transport in crystal growth had a tendency to increase with the increase of lysozyme concentra-tion. The calculated results also showed that the order of magnitude of shear force was about 10-21 N,which was much less than the bond force between the lysozyme molecules. Therefore the shear force induced by buoyancy-driven flows cannot remove the protein molecules from the interface of crystal.

关键词：溶菌酶晶体生长固体液体系统流动特性

In Situ Observation of KB_(5) Crystal Growth Under Purely Diffusion Gel Systems by Holographic Interferometry

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Chinese Physics Letters 1991年第9期8卷 469-471页

作者： chen wanchun SHEN Yunxue MA Wenyi LI Ming chen Yansong Institute of Physics Academia SinicaBeijing 100080

KB_(5)O_(8).4H_(2)O(KB_(5))crystals have been grown in an agar-agar gel by temperature decrease method for simulating crystal growth in *** and growth have been followed by interferometric holography.A concentration field surrounding the growing crystals was obtained and a Liesegang ring was *** pattern are visualized directly to reveal physical phenomena of purely diffusion crystal growth kinetics.

关键词： Diffusion purely

Progress in Research on Materials Under Microgravity in China

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空间科学学报 2004年第Z1期24卷 138-149页

作者： chen Nuofu chen wanchun LUO Xinghong YE Yude Key Laboratory of Semiconductor Materials Sciences Institute of Semiconductors The Chinese Academy of Sciences Beijing 100083 China National Laboratory of Microgravity Institute of Mechanics The Chinese Academy of Sciences Beijing 100080 China Institute of Physics The Chinese Academy of Sciences Beijing 100080 China National Laboratory of Microgravity Institute of Mechanics The Chinese Academy of Sciences Beijing 100080 China Institute of Metal Research The Chinese Academy of Sciences Shenyang 110016 China Key Laboratory of Semiconductor Materials Sciences Institute of Semiconductors The Chinese Academy of Sciences Beijing 100083 China

Research on materials under microgravity in China began in the 1980s, sparked by Prof. Lanying Lin (academician of CAS), Prof. Xiji Wang (academician of CAS), Prof. Guirong Min (academician of CAS), and Prof. Huabao Lin (academician of CAS), and others. The first semiconductor crystal, first optical crystal, and first alloys were grown in space on board a recoverable satellite in 1987. Since then, microgravity materials science became a new scientific branch in *** and technical activities on space crystal growth and solidification are carried out through two major programs: ground-based studies and orbital experiments. The main results obtained during 2001-2003 are reported below.

关键词： Microgravity, Semiconductor, Metal, Crystal

Growth of α-LiIO_(3) Single Crystal Grown in Space

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Chinese Physics Letters 1991年第4期8卷 191-194页

作者： MAI Zhenhong chen wanchun CUI Shufan MA Wenyi XIE Anyun XU Lu JIN Zecen chen Gang Institute of Physics Academia SinicaBeijing 100080 Department of Applied Physics Beijing Polytechnic UniversityBeijing 100022

α-LiIO_(3) single crystals were grown by the aqueous solution method in a Chinese scientific *** morphology of the crystals grown in space are similar to that of earth-grown *** is found that the growth rates of the positive and negative sides of the space-grown crystals are almost the *** perfection of both crystals grown in space and on earth was examined.

关键词： earth perfect crystals

Progress of Microgravity Material Research During the Period of 2007-2009

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空间科学学报 2010年第5期30卷 504-515页

作者： chen Nuofu Bai Yiming chen wanchun Zhou Yanfei Luo Xinghong Yu Yude Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 Institute of Physics Chinese Academy of Sciences Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion Shanghai Institute of Ceramics Chinese Academy of Sciences Institute of Metal Research Chinese Academy of Sciences School of Renewable Energy North China Electricity Power University

Orbital experimental researches on crystal growth of Mn-doped GaSb and Bi2Se0.21Te2.79 are briefly *** space experiments were completed in September of 2007 on broad the Foton-M3 satellite of ***-based researches on the solidification behaviors of Al-Al3Ni,AlAl2Cu,Ag-Cu eutectic,Al-Pb monotectic and Cu-Co peritectic alloys in a 50-meter-high drop tube were *** experimental results on the ultrasonic field and the temperature recycling induced to chiral symmetry breaking of NaClO3 crystal also were reported in the present paper.

关键词：微重力材料空间实验晶体生长凝固行为包晶合金对称破缺温度诱导

VECTRIX AND SOME OF ITS PROPERTIES SUITED TO FLIGHT DYNAMICS

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Chinese Journal of Aeronautics 1996年第2期9卷 92-97页

作者： chen wanchun Xiao Yelun (School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100083) School of Astronautics Beijing Univ. Aero. and Astronaut. Beijing 100083 China

A vectrix cross-product operator identity is presented which shows thesymmetrical relationship between a column matrix and a vectrix. The kinematics ofvectrices and other commonly used relations are then easily obtained with it. The timederivative of the transformation matrix is extended to a more general form ofexpression. The results can be used conveniently in the modeling of flight dynamics inwhich many reference frames must be used.

关键词： vectors (mathematics) matrix methods operators (mathematics),kinematics dynamic models