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Anti-disturbance control of hypersonic flight vehicles with input saturation using disturbance observer

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Science China(Information Sciences) 2015年第7期58卷 28-39页

作者： CHEN Mou REN BeiBei wu QinXian JIANG ChangSheng College of Automation Engineering Nanjing University of Aeronautics and Astronautics Department of Mechanical Engineering Texas Tech University

This paper proposes an anti-disturbance control scheme for the near space vehicle(NSV) based on terminal sliding mode(TSM) technique and disturbance observer method. To tackle the system uncertainty and the time-varying unknown external disturbance of the NSV, a disturbance observer based on TSM technique is designed which can render the disturbance estimate error convergent in finite time. Furthermore, an auxiliary design system is introduced to analyze the input saturation effect. Based on the developed disturbance observer and the auxiliary design system, an anti-disturbance attitude control scheme is developed for the NSV using the TSM technique to speed up the convergence of all signals in closed-loop system. For the closed-loop system,the stability is rigorously proved by using the Lyapunov method and we guarantee the finite time convergence of all closed-loop system signals in the presence of the integrated affection of the system uncertainty, the input saturation, and the unknown external disturbance. Simulation study results are given to show the effectiveness of the developed TSM anti-disturbance attitude control scheme using the disturbance observer and the auxiliary system for the NSV.

关键词： near space vehicles anti-disturbance control sliding mode control input saturation disturbance observer

Poincaréand Logarithmic Sobolev Inequalities for Nearly Radial Measures

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Acta Mathematica Sinica,English Series 2022年第8期38卷 1377-1398页

作者： Patrick CATTIAUX Arnaud GUILLIN Li Ming wu Institut de Mathématiques de Toulouse CNRS UMR 5219UniversitéPaul Sabatier118 Route de NarbonneF-31062 Toulouse Cedex 09 Laboratoire de Mathématiques Blaise Pascal CNRS UMR 6620UniversitéClermont-AuvergneAvenue des LandaisF-63177 Aubiere

Poincaréinequality has been studied by Bobkov for radial measures,but few are known about the logarithmic Sobolev inequality in the radial *** try to fill this gap here using different methods:Bobkov's argument and super-Poincaréinequalities,direct approach via L_(1)-logarithmic Sobolev *** also give various examples where the obtained bounds are quite *** bounds obtained by Lee–Vempala in the log-concave bounded case are refined for radial measures.

关键词： Radial measure log-concave measure Poincaréinequality logarithmic Sobolev inequality super-Poincaréinequality

A self-adaptive correction method for perspective distortions of image

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Frontiers of Computer Science 2019年第3期13卷 588-598页

作者： Lihua wu Qinghua SHANG Yupeng SUN Xu BAI School of Measurement and Communication Harbin University of Science and Technology Harbin 150080 China

Frequently, the shooting angles available to photograph an object are limited, and the resultant images contain perspective distortions. These distortions make more difficult to perform subsequent tasks like feature extraction and information identification. This paper suggested a perspective correction method that extracts automatically distortion features through edge detection. Results showed that this method is powerful in correcting images with perspective distortions. The corrected image has virtually little information missing, clear features and high recovery rate.

关键词： perspective correction perspective transformation Hough transform edge detection

Hydrothermal synthesis and characterization of NiS flower-like architectures

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Particuology 2012年第6期10卷 783-788页

作者： Hai Zhou Baoliang Lv Dong wu Yuhan Sun Key Laboratory of Carbon Materials Institute of Coal ChemistryChinese Academy of Sciences Graduate University of the Chinese Academy of Science Low Carbon Conversion Center Shanghai Advanced Research InstituteChinese Academy of Sciences

Under the influence of thiocyanate anions （SCN-） and cetyltrimethyl ammonium bromide （CTAB）, NiS flower-like architectures were successfully synthesized by a one-step hydrothermal method. The syn-thesized flower-like architectures, with a multilayered and highly ordered texture, have diameters of several micrometers. X-ray powder diffraction （XRD） shows that the NiS flower-like architectures are rhombohedral crystalline. On the basis of condition-dependent experiments, the diffusion-limited aggregation （DLA） model and cage effect were used to explain the growth process of rhombohedral crystalline NiS flower-like architectures. Magnetic measurements showed that the coercivity （He） of the as-obtained NiS flower-like architectures was 102.14 Oe.

关键词： Nanostructures Chemical synthesis Electron microscopy Magnetic properties

Kinematic Comparison of Forward and Backward Swimming and Maneuvering in a Self-Propelled Sub-Carangiform Robotic Fish

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Journal of Bionic Engineering 2014年第2期11卷 199-212页

作者： Zhengxing wu Junzhi Yu Min Tan Jianwei Zhang State Key Laboratory of Management and Control for Complex Systems Institute of Automation Chinese Academy of Sciences Beijing 100190 P. R. China Department of Informatics University of Hamburg Hamburg Germany

We make a thorough kinematic comparison of forward and backward swimming and maneuvering on a self-propelled robot platform that uses sub-carangifbrm swimming as the primary propulsor. An improved Central Pattern Generator （CPG） model allowing free adjustment of phase relationship and directional bias is employed to achieve flexible swimming and smooth transition. Considering the characteristics of forward swimming in carangiform fish and backward swimming in anguilliform fish, various backward swimming patterns for the sub-carangiform robotic fish are suitably created by reversing the direction of propagating propulsive waves. Through a combined use of the CPG control and closed-loop swimming direction control strategy, flexible and precise turning maneuvers in both forward and backward swimming are implemented and compared. By contrast with forward swimming, backward swimming requires a higher frequency or an increased lateral displacement to reach the same relative swimming speed. Noticeably, the phase difference shows a greater impact on forward swimming than on backward swimming. Our observations also indicate that the robotic fish achieves a larger turning rate in forward maneuvering than in backward maneuvering, yet these two maneuvers display comparable turning precision.

关键词： robotic fish backward swimming Central Pattern Generator (CPG) swimming locomotion control

Book Review: Introduction to Artificial Intelligence. Ed. by Fei wu and Yunhe Pan

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Frontiers of Digital Education 2024年第3期1卷 272-273页

作者： Fei wu College of Computer Science and Technology Zhejiang UniversityHangzhou 310058China

Artificial intelligence(AI)is a strategic technology and an important driving force leading the scientific and technological revolution and industrial *** has the potential to enhance every technology as it resembles enabling technologies like the combustion engine or *** believe the nature of AI is *** other words,the power of AI lies in augmenting its ability to accelerate research exponentially and the possibilities are endless.

关键词： driving strategic electricity

Superfluid states in α–T_(3) lattice

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Chinese Physics B 2021年第6期30卷 137-142页

作者： Yu-Rong wu Yi-Cai Zhang School of Physics and Materials Science Guangzhou UniversityGuangzhou 510006China

The superfluid states of attractive Hubbard model in α–T_(3) lattice are investigated. It is found that one usual needs three non-zero superfluid order parameters to describe the superfluid states due to three sublattices. When two hopping amplitudes are equal, the system has particle–hole symmetry. The flat band plays an important role in superfluid pairing near half filling. For example, when the filling factor falls into the flat band, the large density of states in the flat band favors superfluid pairing and the superfluid order parameters reach relatively large values. When the filling factor is in the gap between the flat band and upper band, the superfluid order parameters take small values due to the vanishing of density of states. The superfluid order parameters show nonmonotonic behaviors with the increase of filling factor. At last, we also investigate the edge states with open boundary conditions. It is shown that there exist some interesting edge states in the middle of quasi-particle bands.

关键词： superfluid states flat band α–T_(3)lattice particle–hole symmetry

Interactive multigraph visualization and exploration with a two-phase strategy

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Journal of Systems Engineering and Electronics 2014年第5期25卷 886-894页

作者： Huaquan Hu Lingda wu Chao Yang Hanchen Song Science and Technology on Information Systems Engineering Laboratory National University of Defense Technology Equipment Academy

While it is very reasonable to use a multigraph consisting of multiple edges between vertices to represent various relationships, the multigraph has not drawn much attention in research. To visualize such a multigraph, a clear layout representing a global structure is of great importance, and interactive visual analysis which allows the multiple edges to be adjusted in appropriate ways for detailed presentation is also essential. A novel interactive two-phase approach to visualizing and exploring multigraph is proposed. The approach consists of two phases： the first phase improves the previous popular works on force-directed methods to produce a brief drawing for the aggregation graph of the input multigraph, while the second phase proposes two interactive strategies, the magnifier model and the thematic-oriented subgraph model. The former highlights the internal details of an aggregation edge which is selected interactively by user, and draws the details in a magnifying view by cubic Bezier curves; the latter highlights only the thematic subgraph consisting of the selected multiple edges that the user concerns. The efficiency of the proposed approach is demonstrated with a real-world multigraph dataset and how it is used effectively is discussed for various potential applications.

关键词： visual analytics information visualization multigraph visualization multiple edges aggregation graph magnifier model.

2.5-Dimensional modeling of EM logging-while-drilling tool in anisotropic medium on a Lebedev grid

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Petroleum Science 2023年第1期20卷 249-260页

作者： Zhen-Guan wu Hu Li Xi-Zhou Yue School of Geoscience and Technology Southwest Petroleum UniversityChengduSichuan610500China Maxwell Dynamics Inc. HoustonTX77074USA Well-tech R&D Institute China Oilfield Services LimitedBeijing101149China

A 2.5D finite-difference(FD)algorithm for the modeling of the electromagnetic(EM)logging-whiledrilling(LWD)tool in anisotropic media is *** FD algorithm is based on the Lebedev grid,which allows for the discretization of the frequency-domain Maxwell's equations in the anisotropic media in 2.5D scenarios without *** leads to a system of linear equations that is solved using the multifrontal direct solver which enables the simulation of multi-sources at nearly the cost of simulating a single source for each *** addition,near-optimal quadrature derived from an optimized integration path in the complex plane is employed to implement the fast inverse Fourier Transform(IFT).The algorithm is then validated by both analytic and 3D *** results show that two Lebedev subgrid sets are sufficient for TI medium,which is common in geosteering *** number of quadrature points is greatly reduced by using the near-optimal quadrature method.

关键词： 2.5D modeling Electromagnetic logging-while-drilling Anisotropic medium Lebedev grid