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MmWave Beamforming for UAV Communications with Unstable Beam Pointing

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China Communications 2019年第1期16卷 37-46页

作者： Weizhi Zhong Lei Xu Qiuming Zhu Xiaomin Chen Jianjiang Zhou College of astronautics Nanjing University of Aeronautics and Astronautics College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics

Millimeter wave(mmWave) communications of unmanned aerial vehicles(UAVs) have drawn dramatic attentions for its flexibility on a variety of ***,channel tracking base on the spatial features has been proposed to solve the problem of beam misalignments due to the UAV ***,unstable beam pointing caused by the non-ideal beam tracking environment may impact the performance of mmWave systems *** this paper,an improved beamforming method is presented to overcome this ***,the effect of the beam deviation is analyzed through the establishment of the equivalent data ***,combining the quantification of spatial angle and the improved orthogonal matching pursuit(OMP) algorithm,an optimized beam corresponding to the beam deviation is *** results show that the optimized beam of the proposed approach can effectively improve the spectral efficiency without improving the complexity when the beam pointing is unstable.

关键词： UAV communications mmWave beamforming unstable beam pointing beam tracking orthogonal matching pursuit(OMP)

A Novel 3D Non-Stationary UAV-MIMO Channel Model and Its Statistical Properties

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China Communications 2018年第12期15卷 147-158页

作者： Qiuming Zhu Kaili Jiang Xiaomin Chen Weizhi Zhong Ying Yang College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics College of astronautics Nanjing University of Aeronautics and Astronautics

The wireless communication systems based on Unmanned Aerial Vehicles(UAVs) have found a wide range of applications recently. In this paper, we propose a new three-dimensional(3 D) non-stationary multiple-input multiple-output(MIMO) channel model for the communication links between the UAV and mobile terminal(MT). The new model originates the traditional geometry-based stochastic models(GBSMs) but considers the non-stationary propagation environment due to the rapid movements of the UAV, MT, and clusters. Meanwhile, the upgrade time evolving algorithms of time-variant channel parameters, i.e., the path number based on birth-death processes of clusters, path delays, path powers, and angles of arrival and departure, are developed and optimized. In addition, the statistical properties of proposed GBSM including autocorrelation function(ACF), cross-correlation function(CCF), and Doppler power spectrum density(DPSD) are investigated and analyzed. Simulation results demonstrate that our proposed model provides a good agreement on the statistical properties with the corresponding derived theoretical ones, which indicates its usefulness for the performance evaluation and validation of the UAV based communication systems.

关键词： unmanned aerial vehicles(UAVs) non-stationary channel models geometry-based stochastic models(GBSMs) statistical properties

Observer Design Based on Self-Recurrent Consequent-Part Fuzzy Wavelet Neural Network

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Tsinghua Science and Technology 2016年第5期21卷 544-551页

作者： Xin Wen Xin Li Department of aeronautics and astronautics Shenyang Aerospace University Shenyang 110136 China School astronautics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In this paper, we propose and construct an observer design based on a Self-Recurrent Consequent-Part Fuzzy Wavelet Neural Network（SRCPFWNN） for a class of nonlinear system. We use a Self-Recurrent Wavelet Neural Network（SRWNN） to construct a self-recurrent consequent part for each rule of the Takagi-Sugeno-Kang（TSK） model in the SRCPFWNN and analyze the structure of the fuzzy wavelet neural network model. Based on the Direct Adaptive Control Theory（DACT） and a back propagation-based learning algorithm, all parameters of the consequent parts are updated online in the SRCPFWNN. On this basis, we propose a design method using an adaptive state observer based on an SRCPFWNN for nonlinear systems. Using the Lyapunov function, we then prove the stability of this observer design method. Our simulation results confirm that the observer can accurately and quickly estimate the state values of the system.

关键词： Takagi-Sugeno-Kang (TSK) fuzzy model activation functions state observer nonlinear systems simulation

DIGITAL GENERATION OF TWO-DIMENSIONAL FIELD OF TURBULENCE FOR FLIGHT SIMULATION

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Chinese Journal of aeronautics 1990年第4期5卷 239-245页

作者： Yelun, Xiao Beijing univ of aeronautics and Astronautics Beijing China

In some special cases of flight simulation (e.g. for formation flight, in-flight tanking) it is required to generate a two-dimensional field of turbulence, in which the turbulent wind speeds are stochastic functions of two coordinates (e.g. x in the flight direction and y in the wing span direction). For this purpose a simple and efficient technique for the digital generation of a two-dimensional field of turbulence, i.e. for the production of turbulent speed sequences on a rectangular network, is proposed in this paper. The correlation of the turbulent field so generated is found to be in good agreement with the theoretical correlation of the turbulence model, and thus the feasibility of the proposed method is verified. Two possible operation modes (off-line and on-line) of the turbulence generator in flight simulation are also discussed.

关键词： turbulence turbulent coordinates verified stochastic rectangular generator transformed minimization intuitive

SIMULATION RESEARCH ON THE AFTERBURNING DYNAMIC CHARACTERISTICS OF ENGINE CONTROL SYSTEM

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Chinese Journal of aeronautics 1990年第1期5卷 23-33页

作者： Kejiu, Mao Xu, Wang Beijing univ of aeronautics and Astronautics Beijing China

Static and dynamic mathematical models for a new type of engine and its actual hydraulic control system are proposed. A nonlinear mathematical model is used for the engine and afterburner fuel control system. With programs formed on the basis of these models, the static and dynamic close loop characteristics of this engine control system under afterburning condition have been analyzed in detail. Satisfactory results and valuable conclusions have been obtained. The results are useful for solving many practical problems of the engine control system.

关键词： Control Systems Hydraulic Drive Dynamics Mathematical Models

Exploration and Study on Similarity Theory

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Journal of Systems Engineering and Electronics 1992年第1期3卷 9-20页

作者： Chuanyuan, Wen Beijing univ of aeronautics & Astronautics Beijing China

This paper introduces the similarity theory as the theoretical foundation of system simulation. The concepts of similarity theory, similarity styles and similarity methods are discussed.

关键词： Calculations System theory

EXPERIMENTAL AND THEORETICAL INVESTIGATION OF PSEUDOELASTIC HYSTERESIS IN SHAPE MEMORY ALLOYS

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Acta Metallurgica Sinica(English Letters) 1999年第3期12卷 235-240页

作者： Gong, S.K. Xu, H.B. Beijing univ of aeronautics and Astronautics Beijing China

The pseudoelastic hysteresis loop associated with phase equilibrium and the stress relaxation on the yield line were investigated, and the theoretical description was confirmed by deformation controlled load-deformation measurements on CuZnAl single crystals. It was found that in a loading-unloading process, the states of shape memory alloys run through a hysteresis loop, and the points that trigger the internal yield and recovery inside the pseudoelastic hysteresis loop define a line that traverses the hysteresis loop from the upper left to the lower right corner. This line was interpreted as a line of unstable phase equilibrium according to the thermodynamic arguments, which determines also the tendency for stress relaxation on the yield line section and for a stress growth on the recovery line section.

关键词： Aluminum copper alloys Hysteresis Stress relaxation

DEFORMATION　AND　FRACTURE　MECHANISMS　OF　TWO－PHASE　TiAl－BASED　ALLOYS　WITH　FULLY　LAMELLAR　MICROSTRUCTURE

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 359-368页

作者： Y. G .Zhang, C. Q. Chen (Beijing university of aeronautics and astronautics, Beijing 100083, China)Q. Xu (Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences. Beijing,China)M. C. Chaturvedi (The university of Manitoba, Winnipeg, Manito Beijing univ of aeronautics and Astronautics Beijing China

A two-phase TiAl-based alloy with fully lamellar structure has been deformed al room temperature and the deformed microstructures have been examined in dtails by optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy(TEM) . Deformation mechanisms in the γ-TiAl phase has been defined and the role of grain boundaries in the deformation and fracture has been assessed Some of the mechanisms of interactions between twinning or gliding dislocations and three types of γ γ domain boundaries or γ α_2 interface in a lamellar grain have been identified and resistance of the various domain boundaries or the interface to the propagation of twinning has been evaluated

关键词： TiAl Deformation mechanism Lamellae Twinning

REFLECTION AND TRANSMISSION OF WATER WAVES BY POROUS VERTICAL PLATES

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Journal of Hydrodynamics 1992年第4期4卷 58-65页

作者： Wang, Jinun Beijing univ of aeronautics and Astronautics Beijing China

Reflection and transmission of small amplitude surface waves were studied. Two vertical porous plates with the spacing L are fixed in the middle of an infinitely long channel of constant depth. An incident wave propagates in the negative x direction toward the porous plates. Analytical solutions were obtained for surface wave profiles. The results indicate that when the spacing L is a quarter-wavelength plus a multiple of the half-wavelength of incident wave, the amplitude of reflected wave and transmitted wave are reduced to the minimum. On the other hand, when the spacing L is a multiple of the half-wavelength of incident wave, the amplitude of reflected wave and transmitted wave have maximum values. For the two cases, energy dissipation caused by the two porous plates and water between them were discussed.

关键词： Energy dissipation Porous materials Reflection Surface waves Water waves