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CNN Feature Boosted SeqSLAM for Real-Time Loop Closure Detection

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Chinese Journal of Electronics 2018年第3期27卷 488-499页

作者： BAI Dongdong WANG Chaoqun ZHANG Bo YI Xiaodong YANG Xuejun College of Computer National University of Defense Technology State Key Laboratory of High Performance Computing National University of Defense Technology National institute of defense technology innovation

This paper proposes an efficient and robust Loop closure detection(LCD) method based on Convolutional neural network(CNN) feature. The primary method is called SeqCNNSLAM, in which both the outputs of the intermediate layer of a pre-trained CNN and the outputs of traditional sequence-based matching procedure are incorporated, making it possible to handle the viewpoint and condition variance properly. An acceleration algorithm for SeqCNNSLAM is developed to reduce the search range for the current image, resulting in a new LCD method called A-SeqCNNSLAM. To improve the applicability of A-SeqCNNSLAM to new environments, O-SeqCNNSLAM is proposed for online parameters adjustment in A-SeqCNNSLAM. In addition to the above work, we further put forward a promising idea to enhance Seq SLAM by integrating the both CNN features and VLAD’s advantages called patch based Seq CNNSLAM(P-SeqCNNSLAM), and provide some preliminary experimental results to reveal its performance.

关键词： Simultaneous localization and mapping(SLAM) Loop closure detection(LCD) Convolutional neural network(CNN) SeqSLAM SeqCNNSLAM A-SeqCNNSLAM O-SeqCNNSLAM P-SeqCNNSLAM

A survey on numerical simulations of drag and heat reduction mechanism in supersonic/hypersonic flows

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Chinese Journal of Aeronautics 2019年第4期32卷 771-784页

作者： Xiwan SUN Wei HUANG Min OU Ruirui ZHANG Shibin LI College of Aerospace Science and Engineering National University of Defense Technology National innovation institute of defense technology Chinese Academy of Military Sciences

Along with the survey on experimental investigations drawing attention to the drag and heat reduction mechanism, the authors simultaneously focus on the recent advances of numerical simulations on the schemes applied to supersonic/hypersonic vehicles. The CFD study has evolved as an irreplaceable method in scheme evaluation and aircraft optimization. Similar to our previous experimental survey, the advances in drag and heat reduction schemes are reviewed by similar kinds of mechanism in this article, namely the forward-facing cavity, the opposing jet, the aerospike, the energy deposition and their combinational configurations. This review article puts an emphatic eye on the flow conditions, numerical methods, novel schemes and analytical conclusions given in the simulations. Further, the multi-objective design optimization concept has also been illustrated due to the observable advantages of using CFD over experimental method, especially those performances conducted in drag reduction and thermal protection practice, and this would possess reference value in the design of aircraft system.

关键词： Aerospike Drag and heat reduction Energy deposition Forward-facing cavity Opposing jet

Lazy Scheduling Based Disk Energy Optimization Method

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Tsinghua Science and technology 2020年第2期25卷 203-216页

作者： Yong Dong Juan Chen Yuhua Tang Junjie Wu Huiquan Wang Enqiang Zhou School of Computer Science National University of Defense TechnologyChangsha 410073China National innovation institute of defense technology Beijing 100091China

Reducing the energy consumption of the storage systems disk read/write requests plays an important role in improving the overall energy efficiency of high-performance computing *** propose a method to reduce disk energy consumption by delaying the dispatch of disk requests to the end of a time window,which we call time window-based lazy *** prove that sorting requests within a single time window can reduce the disk energy consumption,and we discuss the relationship between the size of the time window and the disk energy consumption,proving that the energy consumption is highly likely to decrease with increasing window *** exploit this opportunity,we propose the Lazy Scheduling based Disk Energy Optimization(LSDEO)algorithm,which adopts a feedback method to periodically adjust the size of the time window,and minimizes the local disk energy consumption by sorting disk requests within each time *** implement the LSDEO algorithm in an OS kernel and conduct both simulations and actual measurements on the algorithm,confirming that increasing the time window increases disk energy *** the average request arrival rate is 300 and the threshold of average request response time is 50 ms,LSDEO can yield disk energy savings of 21.5%.

关键词： high-performance computing system storage systems disk energy savings lazy scheduling disk seek time window

Research on Key Technologies of Network Security Situational Awareness for Attack Tracking Prediction

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Chinese Journal of Electronics 2019年第1期28卷 162-171页

作者： KOU Guang WANG Shuo TANG Guangming Artificial Intelligence Research Center National Innovation Institute of Defense Technology Information Engineering University

This paper analyzed the existing network security situation evaluation methods and discovered that they cannot accurately reflect the features of large-scale,synergetic, multi-stage gradually shown by network attack behaviors. For this purpose, the association between attack intention and network configuration information was deep analyzed. Then a network security situation evaluation method based on attack intention recognition was proposed. Unlike traditional method, the evaluation method was based on intruder. This method firstly made causal analysis of attack event and discovered and simplified intrusion path to recognize every attack phases, then realized situation evaluation based on the attack phases. Lastly attack intention was recognized and next attack phase was forecasted based on achieved attack phases, combined with vulnerability and network connectivity. A simulation experiments for the proposed network security situation evaluation model is performed by network examples. The experimental results show that this method is more accurate on reflecting the truth of attack. And the method does not need training on the historical sequence, so the method is more effective on situation forecasting.

关键词： Multi-stage attack Situation evaluation Network security Intention recognition Causal analysis

Research on Rigid-flexible Coupling Dynamics of Flexible Cone-probe Docking Mechanism

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空间科学学报 2019年第5期39卷 684-693页

作者： HAN Wei JIANG Zhijie HUANG Yiyong CHEN Xiaoqian National innovation institute of defense technology Academy of Military Sciences

In this paper,a new kind of flexible cone composed of the thin-walled plates based on space probecone docking mechanism for small-sized spacecraft is *** theoretical model of docking impact dynamics,which takes into account the additional stiffness terms,is derived based on Lagrange Analytical Mechanics theory and Hertz contact *** element method is employed for the discretization of the thin-walled *** results show that the traditional dynamic model without considering the additional stiffness terms will be difficult to reach steady *** method proposed in this paper can correctly predict the dynamic behavior of the system.

关键词： Probe-cone docking mechanism Flexible cone FEM Impact dynamics Additional stiffness term

Near Infrared Star Centroid Detection by Area Analysis of Multi-Scale Super Pixel Saliency Fusion Map

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Tsinghua Science and technology 2019年第3期24卷 291-300页

作者： Xiaohu Yuan Shaojun Guo Chunwen Li Bin Lu Shuli Lou the Department of Automation Tsinghua University the National innovation institute of defense technology Naval Aeronautical University Yantai University

The centroid location of a near infrared star always deviates from the real center due to the effects of surrounding radiation. To determine a more accurate center of a near infrared star, this paper proposes a method to detect the star's saliency area and calculate the star's centroid via the pixels only in this area, which can greatly decrease the effect of the radiation. During saliency area detection, we calculated the boundary connectivity and gray similarity of every pixel to estimate how likely it was to be a background pixel. Aiming to simplify and speed up the calculation process, we divided the near infrared starry sky image into super pixel maps at multi-scale by Simple Linear Iterative Clustering(SLIC). Second, we detected the saliency map for every super pixel map of the image. Finally, we fused the saliency maps according to a weighted coefficient that is determined by the least square method. For the images used in our experiment, we set the multi-scale super pixel numbers to 100, 150,and 200. The results show that our method can obtain an offset variance of less than 0.27 for the center coordinates compared to the labelled centers.

关键词： near infrared starry star saliency Simple Linear Iterative Clustering (SLIC)

Review on strategies of space-based optical space situational awareness

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Journal of Systems Engineering and Electronics 2021年第5期32卷 1152-1166页

作者： HU Yunpeng LI Kebo LIANG Yan’gang CHEN Lei College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China Unmanned Systems Research Center National Innovation Institute of Defense TechnologyBeijing 100071China

Space-based optical(SBO)space surveillance has attracted widespread interest in the last two decades due to its considerable value in space situation awareness(SSA).SBO observation strategy,which is related to the performance of space surveillance,is the top-level design in SSA missions *** recognized real programs about SBO SAA proposed by the institutions in the U.S.,Canada,Europe,etc.,are summarized firstly,from which an insight of the development trend of SBO SAA can be *** to the aim of the SBO SSA,the missions can be divided into general surveillance and space object ***,there are two major categories for SBO SSA *** general surveillance strategies for observing low earth orbit(LEO)objects and beyond-LEO objects are summarized and compared in terms of coverage rate,revisit time,visibility period,and image ***,the SBO space object tracking strategies,which has experienced from tracking an object with a single satellite to tracking an object with multiple satellites cooperatively,are also ***,this paper looks into the development trend in the future and points out several problems that challenges the SBO SSA.

关键词： space situation awareness(SSA) space-based space surveillance space-based optical(SBO)observation strategy general surveillance space object tracking

Nonlinear suboptimal tracking control of spacecraft approaching a tumbling target

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Chinese Physics B 2018年第9期27卷 213-222页

作者： Zhan-Peng Xu Xiao-Qian Che Yi-Yong Huang Yu-Zhu Bai Wen Yao College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China National innovation institute of defense technology Chinese Academy of Military ScienceBeifing 100091China

We investigate the close-range relative motion and control of a spacecraft approaching a tumbling target. Unlike the traditional rigid-body dynamics with translation and rotation about the center of mass（CM）, the kinematic coupling between translation and rotation is taken into consideration to directly describe the motion of the spacecraft＇s sensors or devices which are not coincident with the CM. Thus, a kinematically coupled 6 degrees-of-freedom（DOF） relative motion model for the instrument（feature point） is set up. To make the chaser spacecraft＇s feature point track the target＇s, an optimal tracking problem is defined and a control law with a feedback-feedforward structure is designed. With quasi-linearization of the nonlinear dynamical system, the feedforward term is computed from a specified constraint about the dynamical system and the reference model, and the feedback action is derived starting from the state-dependent Ricca equation（SDRE）. The proposed controller is compared with an existing suboptimal tracking controller, and numerical simulations are presented to illustrate the effectiveness and superiority of the proposed method.

关键词： tumbling target 6 degrees-of-freedom(DOF) relative motion suboptimal tracking control state-dependent Ricca equation(SDRE) method

Reconfigurable fault-tolerant control for supersonic missiles with actuator failures under actuation redundancy

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Chinese Journal of Aeronautics 2020年第1期33卷 324-338页

作者： Tong LI Zhenyu JIANG Huabo YANG Cheng HU Shifeng ZHANG Unmanned Systems Research Center National Innovation Institute of Defense TechnologyBeijing 100071China College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China

Aircraft undergoing actuator failures into under-actuation have been seldom studied in *** at addressing actuator failures of Total Loss of Effectiveness(TLOE)as well as Partial Loss of Effectiveness(PLOE)resulting in different system actuations,reconfigurable FaultTolerant Control(FTC)is proposed for supersonic wingless missiles under actuation *** under-actuated system of TLOE failure patterns is solved by transformation to cascade systems through a’shape variable’.Meanwhile,actuator TLOE faults of different unknown failure patterns from proper actuation to under-actuation are accommodated by a reconfigurable adaptive law on a multiple-model *** backstepping technique with the Extended State Observer(ESO)method adopted as a basic strategy is applied to an established symmetric coupled missile system with actuator PLOE faults,modeling errors,and external ***,the nonlinear saturation characteristics of actuators are settled by an auxiliary system with the Nussbaum function *** stability of the control system is analyzed and proven through Lyapunov *** simulations are implemented in the presences of aerodynamic uncertainties,gust disturbance,and actuator *** demonstrate the effectiveness of the proposed method with satisfactory tracking performance and actuator fault tolerance capacity.

关键词： Extended State Observer(ESO) Fault-Tolerant Control(FTC) Input saturation Reconfigurable control Under-actuation control