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Novel approach of crater detection by crater candidate region selection and matrix-pattern-oriented least squares support vector machine

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Chinese Journal of aeronautics 2013年第2期26卷 385-393页

作者： Ding Meng Cao Yunfeng Wu Qingxian college of Civil Aviation Nanjing University of Aeronautics and Astronautics college of Automation engineering Nanjing University of Aeronautics and Astronautics

Impacted craters are commonly found on the surface of planets, satellites, asteroids and other solar system bodies. In order to speed up the rate of constructing the database of craters, it is important to develop crater detection algorithms. This paper presents a novel approach to automatically detect craters on planetary surfaces. The approach contains two parts： crater candidate region selection and crater detection. In the first part, crater candidate region selection is achieved by Kanade-Lucas-Tomasi （KLT） detector. Matrix-pattern-oriented least squares support vector machine （MatLSSVM）, as the matrixization version of least square support vector machine （SVM）, inherits the advantages of least squares support vector machine （LSSVM）, reduces storage space greatly and reserves spatial redundancies within each image matrix compared with general LSSVM. The second part of the approach employs MatLSSVM to design classifier for crater detection. Experimental results on the dataset which comprises 160 preprocessed image patches from Google Mars demonstrate that the accuracy rate of crater detection can be up to 88%. In addition, the outstanding feature of the approach introduced in this paper is that it takes resized crater candidate region as input pattern directly to finish crater detection. The results of the last experiment demonstrate that MatLSSVM-based classifier can detect crater regions effectively on the basis of KLT-based crater candidate region selection.

关键词： Crater candidate region Crater detection algorithm Kanade–Lucas–Tomasi detector Least squares support vector machine Matrixization

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Universal design of three-dimensional porous graphene-iron based promotors for kinetically rationalized lithium-sulfur chemistry

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Journal of Energy Chemistry 2025年第1期100卷 192-200页

作者： Hua Gao Yunfeng Zhang Menglei Wang Ruoxuan Yang Shuai Feng Xuan Cao Yaping Zhang Zhongyuan Lu Yingze Song State Key Laboratory of Environment-Friendly Energy Materials School of Materials and Chemistry Southwest University of Science and Technology School of Material Science and engineering Henan University of Technology college of Chemistry and Chemical engineering Taishan University

Lithium-sulfur （Li-S） batteries are widely deemed to be one of the most potential candidates for future secondary batteries because of their remarkable energy ***,notorious polysulfide shuttling and retarded sulfur reaction kinetics pose significant obstacles to the further application of Li-S *** rationally designed highly active electrocatalysts can facilitate polysulfide conversion,the universal and scalable synthesis strategies need to be ***,a universal synthetic strategy to construct a series of three-dimensional （3D） porous graphene-iron （3DGr-Fe） based electrocatalysts involving 3DGr-FeP,3DGr-Fe3C,and 3DGr-Fe3Se4is exploited for manipulating the Li-S redox *** has been observed that the implementation of a 3D porous Gr architecture leads to the well-designed conductive networks,while the uniformly dispersed iron nanoparticles introduce an abundance of active sites,fostering the lithium polysulfide conversion,thereby bolstering the overall electrochemical *** Li-S battery with the 3DGr-Fe based electrocatalyst exhibits remarkable capacity retention of 94.8%upon 100 times at 0.2 ***,the soft-packaged Li-S pouch cell based on such a 3DGr-Fe electrocatalyst delivers superior capacity of 1060.71 mA h g-1and guarantees for the continuous 30 min work of fan *** investigation gives comprehensive insights into the design,synthesis,and mechanism of 3DGr-Fe based electrocatalysts with high activity toward efficient and durable Li-S batteries.

关键词： Lithium-sulfur battery Universal synthesis 3D graphene-iron based promotor Electrocatalysis

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Variable thrust directional control technique for plateau unmanned aerial vehicles

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Science China(Information Sciences) 2016年第3期59卷 204-207页

作者： Yin WANG Daobo WANG college of Astronautics Nanjing University of Aeronautics and Astronautics college of Automation engineering Nanjing University of Aeronautics and Astronautics

In order to increase the lift force of the unmanned aerial vehicles(UAV) in plateau areas, the UAV is commonly equipped with high span chord ratio wings. However, it may decrease the maneuverability of the aircraft, and thus increasing the risk of flight in complex terrain regions. Thrust vector control is a direct force flight control technique, which enhances the maneuverability and introduces the residual of the flight control system. In this paper, we develop a novel variable thrust direction mechanism, which provides the normal propeller UAV with the capability of directional force control. We propose a combinational flight control strategy for the newly developed UAV. Simulations and real flight test demonstrate the performance of the proposed technique in increasing the maneuverability of the conventional propeller UAV.

关键词： unmanned aerial vehicle thrust vectoring control combination control plateau application pro peller engine

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Simulation of 3D parachute fluid–structure interaction based on nonlinear finite element method and preconditioning finite volume method

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Chinese Journal of aeronautics 2014年第6期27卷 1373-1383页

作者： Fan Yuxin Xia Jian college of Aerospace engineering Nanjing University of Aeronautics and Astronautics

A fluid–structure interaction method combining a nonlinear finite element algorithm with a preconditioning finite volume method is proposed in this paper to simulate parachute transient dynamics. This method uses a three-dimensional membrane–cable fabric model to represent a parachute system at a highly folded configuration. The large shape change during parachute inflation is computed by the nonlinear Newton–Raphson iteration and the linear system equation is solved by the generalized minimal residual（GMRES） method. A membrane wrinkling algorithm is also utilized to evaluate the special uniaxial tension state of membrane elements on the parachute canopy. In order to avoid large time expenses during structural nonlinear iteration, the implicit Hilber–Hughes–Taylor（HHT） time integration method is employed. For the fluid dynamic simulations, the Roe and HLLC（Harten–Lax–van Leer contact） scheme has been modified and extended to compute flow problems at all speeds. The lower–upper symmetric Gauss–Seidel（LUSGS） approximate factorization is applied to accelerate the numerical convergence speed. Finally,the test model of a highly folded C-9 parachute is simulated at a prescribed speed and the results show similar characteristics compared with experimental results and previous literature.

关键词： Flow fields analysis Fluid–structure interaction Nonlinear structural dynam-ics Numerical analysis Parachute inflation

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Attitude tracking control for variable structure near space vehicles based on switched nonlinear systems

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Chinese Journal of aeronautics 2013年第1期26卷 186-193页

作者： Wang Yufei Jiang Changsheng Wu Qingxian college of Automation engineering Nanjing University of Aeronautics and Astronautics

An adaptive robust attitude tracking control law based on switched nonlinear systems is presented for a variable structure near space vehicle （VSNSV） in the presence of uncertainties and disturbances. The adaptive fuzzy systems are employed for approximating unknown functions in the flight dynamic model and their parameters are updated online. To improve the flight robust performance, robust controllers with adaptive gains are designed to compensate for the approximation errors and thus they have less design conservation. Moreover, a systematic procedure is developed for the synthesis of adaptive fuzzy dynamic surface control （DSC） approach. According to the common Lyapunov function theory, it is proved that all signals of the closed-loop system are uniformly ultimately bounded by the continuous controller. The simulation results demonstrate the effectiveness and robustness of the proposed control scheme.

关键词： Attitude control Fuzzy control Robust control Switched nonlinear systems Variable structure near space vehicle

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A salient edges detection algorithm of multi-sensor images and its rapid calculation based on PFCM kernel clustering

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Chinese Journal of aeronautics 2014年第1期27卷 102-109页

作者： Xu Guili Zhao Yan Guo Ruipeng Wang Biao Tian Yupeng Li Kaiyu college of Automation engineering Nanjing University of Aeronautics and Astronautics

Multi-sensor image matching based on salient edges has broad prospect in applications, but it is difficult to extract salient edges of real multi-sensor images with noises fast and accurately by using common algorithms. According to the analysis of the features of salient edges, a novel salient edges detection algorithm and its rapid calculation are proposed based on possibility fuzzy C-means （PFCM） kernel clustering using two-dimensional vectors composed of the values of gray and texture. PFCM clustering can overcome the shortcomings that fuzzy C-means （FCM） cluster- ing is sensitive to noises and possibility C-means （PCM） clustering tends to find identical clusters. On this basis, a method is proposed to improve real-time performance by compressing data sets based on the idea of data reduction in the field of mathematical analysis. In addition, the idea that kernel-space is linearly separable is used to enhance robustness further. Experimental results show that this method extracts salient edges for real multi-sensor images with noises more accurately than the algorithm based on force fields and the FCM algorithm; and the proposed method is on average about 56 times faster than the PFCM algorithm in real time and has better robustness.

关键词： DaM reduction Edge detection Fuzzy clustering Possibility fuzzy C2means(PFCM)

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Noncertainty-equivalent observer-based noncooperative target tracking control for unmanned aerial vehicles

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Science China(Information Sciences) 2022年第5期65卷 142-156页

作者： Kenan YONG Mou CHEN Qingxian WU college of Automation engineering Nanjing University of Aeronautics and Astronautics

Target tracking is a typical and challenging scenario that is required to be executed by unmanned aerial vehicles(UAVs) in operational environments. This work investigates the noncooperative target tracking control problem for UAVs. An integrated model is constructed by combining the dynamics of both the line-of-sight variables and the acceleration components. Particularly, the dynamics of the acceleration components, that contain unmeasurable states, characterize the relative motion between the noncooperative target and the UAV. To estimate these states, a globally convergent observer is developed by utilizing the noncertainty-equivalent(NCE) structure. With the integrated model and the NCE observer, an output-feedback target tracking control scheme is proposed using the dynamic surface control technique and the prescribed performance control method. Based on the Lyapunov approach, the relative spatial positions of the target and the UAV are proved to always stay within a specified operation region and ultimately converge to a small terminal region. Finally, simulation results are presented to illustrate the effectiveness of the proposed target tracking control scheme.

关键词： noncooperative target tracking unmanned aerial vehicles noncertainty-equivalent observer prescribed performance control

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Multipoint optimization on fuel efficiency in conceptual design of wide-body aircraft

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Chinese Journal of aeronautics 2018年第1期31卷 99-106页

作者： Xiao CHAI Xiongqing YU Yu WANG college of Aerospace engineering Nanjing University of Aeronautics and Astronautics

Aircraft conceptual design optimizations that maximize the performance at a design condition （single-point） may result in designs with unsatisfying off-design performance. To further improve aircraft efficiency under actual flight operations, there is a need to consider multiple flight conditions （multipoint） in aircraft conceptual design and optimization. A new strategy for multipoint optimizations in aircraft conceptual design is proposed in this paper. A wide-body aircraft is taken as an example for both single-point and multipoint optimizations with the objective of maximizing the specific hourly productivity. Boeing 787-8 flight data was used in the multipoint opti- mization to reflect the true objective function. The results show that the optimal design from the multipoint optimization has a 7.72% total specific hourly productivity increase of entire flight missions compared with that of the baseline aircraft, while the increase in the total specific hourly productivity from the single-point optimal design is only 5.73%. The differences between the results of single-point and multipoint optimizations indicate that there is a good option to further improve aircraft efficiency by considering actual flight conditions in aircraft conceptual design and optimization.

关键词： Aircraft conceptual design Fuel efficiency Multiple missions Optimization Wide-body aircraft

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Applications of scale-adaptive simulation technique based on one-equation turbulence model

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Applied Mathematics and Mechanics(English Edition) 2015年第1期36卷 121-130页

作者： Chang-yue XU Tao ZHOU Cong-lei WANG Jian-hong SUN college of Aerospace engineering Nanjing University of Aeronautics & Astronautics

A modified scale-adaptive simulation （SAS） technique based on the Spalart- Allmaras （SA） model is proposed. To clarify its capability in prediction of the complex turbulent flow, two typical cases are carried out, i.e., the subcritical flow past a circular cylinder and the transonic flow over a hemisphere cylinder. For comparison, the same cases are calculated by the detached-eddy simulation （DES）, the delayed-detached eddy simulation （DDES）, and the XY-SAS approaches. Some typical results including the mean pressure coefficient, velocity, and Reynolds stress profiles are obtained and compared with the experiments. Extensive calculations show that the proposed SAS technique can give better prediction of the massively separated flow and shock/turbulent-boundary-layer interaction than the DES and DDES methods. Furthermore, by the comparison of the XY-SAS model with the present SAS model, some improvements can be obtained.

关键词： turbulence detached-eddy simulation scale-adaptive simulation cylinder

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Survey on nonlinear reconfigurable flight control

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Journal of Systems engineering and Electronics 2013年第6期24卷 971-983页

作者： Xunhong Lv Bin Jiang Ruiyun Qi Jing Zhao college of Automation engineering Nanjing University of Aeronautics and Astronautics

An overview on nonlinear reconfigurable flight control approaches that have been demonstrated in flight-test or highfidelity simulation is presented. Various approaches for reconfigurable flight control systems are considered, including nonlinear dynamic inversion, parameter identification and neural network technologies, backstepping and model predictive control approaches. The recent research work, flight tests, and potential strength and weakness of each approach are discussed objectively in order to give readers and researchers some reference. Finally, possible future directions and open problems in this area are addressed.

关键词： reconfigurable flight control (RFC) nonlinear dynamic inversion (NDI) backstepping neural network (NN) model predictive control (MPC) parameter identification (PID) adaptive control flight control.

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