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Fast and precise location measurement of joint multiple ellipses based on inverse transformation of perspective projection

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Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica 2023年第12期44卷

作者： Liu, Chuankai Lei, Junxiong Liu, Qian Sun, Jun Su, Jianhua Hu, Xiaodong Li, Dongsheng School of Electrical Engineering and Automation Jiangxi University of Science and Technology Ganzhou341000 China Beijing Aerospace Control Center Beijing100190 China Key Laboratory of Science and Technology on Aerospace Flight Dynamics Beijing100190 China Institute of Automation Chinese Academy of Sciences Beijing100194 China

Cooperative target measurement is an important positioning method for many kinds of operation tasks such as spacecraft rendering，docking，capture and maintenance. However，the current positioning method based on co⁃ operative target has some problems，such as complex operation of target extraction and vulnerability to interferences，which result in poor timeliness，stability，and positioning accuracy. To solve the above problems，a location method of circular cooperative target is proposed based on inverse transformation of perspective projection. Firstly，target con⁃ tour points are projected into the space by inverse projection of the imaging beam to form a plurality of elliptical cones composed of ray clusters. Then，an optimization model of position and posture residuals is constructed based on the relative relationship between multiple circular outlines of the cooperative target and elliptical conical ray clusters. Fi⁃ nally，an accurate pose of the target is obtained by the Levenberg-Marquadt algorithm. The measurement proposed does not need to fit the ellipse according to target contour points，which improves the calculation efficiency and avoids the accuracy error caused by ellipse fitting. The joint adjustment of multiple ray clusters greatly reduces the influence of noise and error points on position and posture accuracy，and improves the robustness and anti-interference of the al⁃ gorithm. The experimental results show that the proposed algorithm has high accuracy，computing efficiency and ro⁃ bustness at different distances and noise environments，and can provide strong support for rapid，stable and accurate visual measurement of cooperative targets in the scenes of capture and rendezvous and docking of the space manipulator. © 2023 AAAS Press of Chinese Society of Aeronautics and Astronautics. All rights reserved.

关键词： Inverse problems

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A new Stroh formalism for gradient electro-mechanics with applications to Lamb waves in piezoelectric and flexoelectric coupled plates

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Journal of Applied Physics 2024年第11期135卷 114103-114103页

作者： Zhu, Feng Li, Nian Pan, Ernian Qu, Yilin College of General Aviation and Flight Nanjing University of Aeronautics and Astronautics Liyang213300 China State Key Laboratory of Mechanics and Control for Aerospace Structures College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China Suzhou HunterSun Electronics Co. Ltd. Suzhou215124 China Department of Civil Engineering College of Engineering Disaster Prevention & Water Environment Research Center Institute of Pioneer Semiconductor Innovation National Yang Ming Chiao Tung University 1001 University Road Hsinchu300 Taiwan School of Marine Science and Technology Northwestern Polytechnical University Xi'an710072 China Unmanned Vehicle Innovation Center Ningbo Institute of NPU Ningbo315048 China

In this paper, a new Stroh formalism for gradient electro-mechanics is derived for the first time, which is both mathematically concise and numerically powerful, applicable to generally coupled anisotropic material systems. Based on this new formalism, the complicated Lamb wave in flexoelectric and piezoelectric plates is investigated. The dispersion equation is obtained by solving the eigenvalue problem along with the unconditionally stable dual-variable and position method. From the obtained dispersion equation, the dispersion curves and mode shapes of the Lamb wave are calculated by the 1D form of the multidimensional moduli ratio convergence method. Two important and interesting features are observed from our analysis: One is the difference in the mode shape symmetry between the piezoelectric and flexoelectric cases, and the other is the size-dependent property of the flexoelectric effect as observed by nondimensionalization. These features are further illustrated by comparing the dispersion curves and wave-mode shapes among the three different material models (purely piezoelectric, purely flexoelectric, and flexoelectric and piezoelectric coupled). The newly derived Stroh formalism offers a robust, concise, and unified approach for dealing with strain gradient electro-mechanic materials with crystal systems of general anisotropy. The present work also explains the physical mechanism of symmetry breaking observed, as induced by flexoelectric coupling in piezoelectric materials. © 2024 Author(s).

关键词： Surface waves

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In-Plane Semi-Linear Cloaks with Arbitrary Shape

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Acta Mechanica Solida Sinica 2019年第3期32卷 277-286页

作者： Dengke Guo Zheng Chang Gengkai Hu Key Laboratory of Dynamics and Control of Flight Vehicle Ministry of Education School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China College of Science China Agricultural University Beijing 100083 China

Soft materials with semi-linear strain energy function can be used as smart transformation media to manipulate elastic waves via finite pre-deformation. However, the intrinsic cons train ts involved in such materials limit the shapes of t ransformation devices to very sim - pie cases. In this work, combining theoretical and numerical analyses, we report an approach of achieving the in-plane elastodynamic cloak with arbitrary shape. We demonstrate that with the appropriate out-of^plane st retch applied on the semi-linear material, cloaking effec t can be achieved for both P- and SV-waves in the symmetrie plane of a 3D domain, and the performance of the cloak with arbitrary cross section can be guaranteed for relatively small in-plane rot at ion. In addition, we propose an empirical formula to predic t the deformation limit of the cloaks with semi-linear materials. This work may stimulate the experimental research on softmatter- based transformation devices. Potential applications can be anticipated in nondestructive testing, structure impact protection, biomedical imaging and soft robotics.

关键词： Elastic waves Cloak Hyperelasticity Semi-linear Arbitrary shape

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A Strength Model of the 3D Arrangement of BCC Lattice Structure Based on Boundary Conditions

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Advanced Engineering Materials 2025年

作者： Tao, Yuan Yao, Weixing Zhao, Qia Xie, Xiang Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics Nanjing210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing210016 China

Numerous studies have shown that the strength of lattice structures varies with the layout of the structure, and traditional models are no longer fully applicable for predicting the strength of structures. To study the impact of the array configuration of unit cells with varying numbers in different 3D directions on the strength of lattice structures, this article treats each strut of the cubic lattice structure as an independent element. It considers the influence of boundary conditions on the lattice structure and analyzes force distribution on struts at different positions. The distribution of struts with various types of failure points in different array configurations is obtained, along with the strength at each failure points for individual struts. Furthermore, the overall structural strength is predicted, and a strength analysis model based on the array configuration of unit cells with different numbers in 3D directions is proposed. Seven types of unit cells, all with identical dimensions but different unit cell arrangements in the 3D directions, are 3D printed for body-centered cubic lattice structures, and their compressive strength is tested. The final prediction results are found to be in good agreement with the experimental results, confirming the validity of the proposed model. © 2025 Wiley-VCH GmbH.

关键词： Compressive strength

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3D reconstruction using 0.1THz Bessel CT imaging system

3D reconstruction using 0.1THz Bessel CT imaging system

引用

International Conference on Infrared and Millimeter Waves

作者： Wei Liu Qiulin Yang Defeng Liu Sishi Shen Shutao Yang Kejia Wang Zhengang Yang Jinsong Liu AVIC Beijing Changcheng Aeronautic of Measurement and Control Technology Research Institute Beijing China Aviation Key Laboratory of Science and Technology on Special Condition Monitoring Sensor Technology Beijing China Wuhan National Laboratory for Optoelectronics(WNLO) Huazhong University of Science and Technology Wuhan China School of Optics and Electronic Information(OEI) Huazhong University of Science and Technology Wuhan China

Zero-order terahertz Bessel beams are diffractom-free. Therefore, unlike the traditional Gaussian beam CT, the terahertz zero-order Bessel beam used in terahertz CT imaging can improve the depth of field of the imaging system. At the same time, the imaging system has high lateral resolution. Bessel beam CT was used to scan a variety of samples at the same time and the reconstruction results were obtained. The reconstructed sections and three-dimensional structures of the scanned samples were clearly seen.

关键词： Three-dimensional displays Image resolution Computed tomography Imaging Image reconstruction

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Fourth-Order Conservative Transport on Overset Grids Using Multi-Moment Constrained Finite Volume Scheme for Oceanic Modeling

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Journal of Ocean University of China 2020年第4期19卷 747-760页

作者： GU Juan PENG Xindong DAI Yongjiu CHE Yuzhang College of Global Change and Earth System Science Beijing Normal UniversityBeijing 100875China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China College of Air Traffic Management Civil Aviation Flight University of ChinaGuanghan 618307China School of Atmospheric Sciences Sun Yat-Sen UniversityGuangzhou 510275China Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information TechnologyChengdu 610103China Department of Mechanical Engineering Tokyo Institute of TechnologyTokyo 152-8550Japan

With an increase in model resolution,compact high-order numerical advection scheme can improve its effectiveness and competitiveness in oceanic modeling due to its high accuracy and scalability on massive-processor *** provide high-quality numerical ocean simulation on overset grids,we tried a novel formulation of the fourth-order multi-moment constrained finite volume scheme to simulate continuous and discontinuous problems in the Cartesian *** some degrees of freedom over each cell and derivatives at the cell center,we obtained a two-dimensional(2D)cubic polynomial from which point values on the extended overlap can achieve fourth-order ***,this interpolation causes a lack of conservation because the flux between the regions are no longer equal;thus,a flux correction is implemented to ensure conservation.A couple of numerical experiments are presented to evaluate the numerical scheme,which confirms its approximately fourth-order accuracy in conservative transportation on overset *** test cases reveal that the scheme is effective to suppress numerical oscillation in discontinuous problems,which may be powerful for salinity advection computing with a sharp gradient.

关键词： multi-moment constrained finite volume scheme oceanic modeling overset grid conservation numerical transport

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Global Dynamics and Optimal Design of a New Highly Efficient Nonlinear Energy Sink Based on Magnetic-Elastic Impacts with Negative Stiffness

Research Square

引用

Research Square 2021年

作者： Li, Shuangbao Wang, Tingting Chen, Jianen Research Institute of Science and Technology Innovation Civil Aviation University of China Tianjin300300 China College of Science Civil Aviation University of China Tianjin300300 China Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China

A new highly efficient elastic-impact bistable nonlinear energy sink (EI-BNES) based on magnetic-elastic impacts with negative stiffness and bistability is proposed and optimized through global dynamical analysis. The EI-BNES has better robustness and higher energy dissipation rates with nearly more than 96.5% for broadband impulsive excitations than the traditional cubic NESs and single bistable NESs. The structure of negative stiffness impacts is realized by reasonable layout of permanent ring magnets and springs. A two-degree-of-freedom (two-DOF) elastic-impact system is established to describe the coupled nonlinear interaction between the main structure and the attached EI-BNES. A global Melnikov reduction analysis (GMRA) is proposed to study global dynamics and homoclinic bifurcations of the reduced two-dimensional subsystem, which is used to explain the mechanism of nonlinear targeted energy transfer (TET) and detect the threshold of impulsive amplitudes of EI-BNES for in-well and compound motions between in-well and cross-well resonance responses. A special type of saddle-center equilibrium points is also found in the non-smooth system of the EI-BNES and can be used to effectively increase the energy dissipation rates. The optimal design criterion of the tuned EI-BNES for better dissipation performance is also first discussed based on the GMRA and numerical techniques for calculating the Melnikov function of the non-smooth systems. The effectiveness of the analytical GMRA is also verified by numerical simulations. © 2021, CC BY.

关键词： Stiffness

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Superhydrophobic flexible sensors: A review of fabrication methods and applications

引用

Materials Today Chemistry 2025年 47卷

作者： Qiang He Yujie Liu Zehua Xu Jiwen Wang Yangyang Jia Guangfei Wang Anling Li College of Civil Aviation Safety Engineering Civil Aviation Flight University of China Guanghan 618307 Sichuan China Civil Aircraft Fire Science and Safety Engineering Key Laboratory of Sichuan Province Guanghan 618307 China Sichuan Key Technology Engineering Research Center for All-electric Navigable Aircraft Guanghan 618307 Sichuan China

Flexible sensors have garnered extensive application in fields such as smart wearables, biomedical devices, and industrial production owing to their exceptional flexibility and high sensitivity. However, in complex environments (e.g., underwater, humid, acidic/alkaline conditions), conventional flexible sensors face significant technical bottlenecks, including susceptibility to signal interference and surface corrosion, severely limiting their long-term stability and reliability. Superhydrophobic surfaces, characterized by their unique wettability properties, offer an innovative solution to these challenges. By endowing flexible sensors with self-cleaning, low-adhesion, corrosion resistance, and anti-interference capabilities, superhydrophobicity significantly enhances their applicability in harsh environments. This review systematically summarizes recent advances in superhydrophobic flexible sensors. Initially, the limitations of conventional flexible sensors in practical applications are introduced. Subsequently, the theoretical foundations of superhydrophobic surface wettability and the types/characteristics of flexible sensors are presented. Furthermore, diverse fabrication strategies for superhydrophobic flexible sensors are critically discussed, encompassing techniques such as spraying, dip-coating, sandwich structure design, and laser etching, with a systematic evaluation of their respective advantages and disadvantages. Additionally, the innovative applications of these sensors in three major domains—smart wearables, vibration monitoring, and gas detection—are analyzed. Finally, the review identifies current shortcomings in fabrication technologies and outlines prospective future research directions, serving as a valuable reference for understanding the latest developments and applications of superhydrophobic flexible sensors.

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Probabilistic reach-avoid reachability in nondeterministic systems with time-varying targets and obstacles

arXiv

引用

arXiv 2021年

作者： Liao, Wei Liang, Taotao Wei, Xiaohui Yin, Qiaozhi Key laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and Astronautics NanjingJiangsu China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics NanjingJiangsu China

The probabilistic reachability problems of nondeterministic systems are studied. Based on the existing studies, the definition of probabilistic reachable sets is generalized by taking into account time-varying target set and obstacle. A numerical method is proposed to compute probabilistic reachable sets. First, a scalar function in the state space is constructed by backward recursion and grid interpolation, and then the probability reachable set is represented as a nonzero level set of this scalar function. In addition, based on the constructed scalar function, the optimal control policy can be designed. At the end of this paper, some examples are taken to illustrate the validity and accuracy of the proposed method. Copyright © 2021, The Authors. All rights reserved.

关键词： Numerical methods

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Correction: a novel non-vacuum packaged triaxial accelerometer with differential dual-axis resonantors and torsional elements

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Microsystem Technologies 2023年第1期30卷 45-45页

作者： Li, Jinhui Xia, Dunzhu Wang, Songli Yang, Xiuhua Zhang, Bing Key Laboratory of Micro-lnertial Instruments and Advanced Navigation Technology Ministry of Education Nanjing China School of Instrument Science and Engineering Southeast University Nanjing China Xi’an Flight Automatic Control Research Institute of Aviation Industry Xi’an China

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