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arXiv 2019年

作者： Lee, Sangil Kim, Haram Kim, H. Jin Automation and Systems Research Institute Department of Mechanical and Aerospace Engineering Seoul National University Seoul Korea Republic of

In this work, we propose an edge detection algorithm by estimating a lifetime of an event produced from dynamic vision sensor (DVS), also known as event camera. The event camera, unlike traditional CMOS camera, generates sparse event data at a pixel whose log-intensity changes. Due to this characteristic, theoretically, there is only one or no event at the specific time, which makes it difficult to grasp the world captured by the camera at a particular moment. In this work, we present an algorithm that keeps the event alive until the corresponding event is generated in a nearby pixel so that the shape of an edge is preserved. Particularly, we consider a pixel area to fit a plane on Surface of Active Events (SAE) and call the point inside the pixel area closest to the plane as a intra-pixel-area event. These intra-pixel-area events help the fitting plane algorithm to estimate life time robustly and precisely. Our algorithm performs better in terms of sharpness and similarity metric than the accumulation of events over fixed counts or time intervals, when compared with the existing edge detection algorithms, both qualitatively and quantitatively. Copyright © 2019, The Authors. All rights reserved.

关键词： Cameras

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Robust Real-time RGB-D Visual Odometry in Dynamic Environments via Rigid Motion Model

Robust Real-time RGB-D Visual Odometry in Dynamic Environmen...

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2019 IEEE/RSJ International Conference on Intelligent Robots and systems (IROS)

作者： Sangil Lee Clark Youngdong Son H. Jin Kim Department of Mechanical and Aerospace Engineering Automation and Systems Research Institute Seoul National University Seoul Republic of Korea

In the paper, we propose a robust real-time visual odometry in dynamic environments via rigid-motion model updated by scene flow. The proposed algorithm consists of spatial motion segmentation and temporal motion tracking. The spatial segmentation first generates several motion hypotheses by using a grid-based scene flow and clusters the extracted motion hypotheses, separating objects that move independently of one another. Further, we use a dual-mode motion model to consistently distinguish between the static and dynamic parts in the temporal motion tracking stage. Finally, the proposed algorithm estimates the pose of a camera by taking advantage of the region classified as static parts. In order to evaluate the performance of visual odometry under the existence of dynamic rigid objects, we use self-collected dataset containing RGB-D images and motion capture data for ground-truth. We compare our algorithm with state-of-the-art visual odometry algorithms. The validation results suggest that the proposed algorithm can estimate the pose of a camera robustly and accurately in dynamic environments.

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Comparative study on the machine learning-based techniques for magnetorheological elastomer dynamic properties prediction

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AIP Conference Proceedings 2024年第1期3124卷

作者： Kasma Diana Saharuddin Mohd Hatta Mohammed Ariff Irfan Bahiuddin Saiful Amri Mazlan Nurhazimah Nazmi Ubaidillah Ubaidillah Advanced Vehicle System (AVS) Research Group Malaysia Japan International Institute of Technology (MJIIT) Universiti Teknologi Malaysia 54100 Kuala Lumpur Malaysia Department of Mechanical Engineering Vocational College Universitas Gadjah Mada Yogyakarta Indonesia Engineering Materials & Structures (eMast) ikohza Malaysia Japan International Institute of Technology (MJIIT) Universiti Teknologi Malaysia 54100 Kuala Lumpur Malaysia Pattern Recognition and Robotics Automation iKohza Malaysia Japan International Institute of Technology (MJIIT) Universiti Teknologi Malaysia 54100 Kuala Lumpur Malaysia Mechanical Engineering Department Faculty of Engineering Universitas Sebelas Maret JI. Ir. Sutami 36A Kentingan Surakarta 57126 Indonesia

Magnetorheological elastomers (MRE) have gained popularity due to their ability to control viscoelastic properties by varying the strength of the magnetic field. Due to the obvious nonlinear and complex behavior of MRE, machine learning approaches were used to predict the MRE viscoelastic properties, which are storage and loss modulus. In comparison to the traditional viscoelastic model, which is complex in mathematical derivation, machine learning method easily identifies trends and patterns by mapping the input-output relationship. It can also handle nonlinear problems by training on data. Support vector regression (SVR), Gaussian process regression (GPR), Backpropagation neural network (BP-ANN), and Extreme learning machine (ELM) were introduced and compared to simulate the field-dependent viscoelastic behavior of MRE with frequency and magnetic field strength as model input. As a result, the ELM model produced the highest accuracy, with more than 98 percent accuracy on model generalization capability. Therefore, this demonstrates that machine learning can replace traditional modelling approaches and serve as a basis for material and device development.

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反向连边在大型分层网络中的影响（英文）

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engineering 2024年第5期 240-249页

作者：曹浩森胡斌斌莫小雨陈都鑫高建喜袁烨陈关荣 Tamás Vicsek 管晓宏张海涛 MOE Engineering Research Center of Autonomous Intelligent Unmanned Systems State Key Laboratory of Intelligent Manufacturing Equipment and Technology School of Artificial Intelligence and Automation Huazhong University of Science and Technology School of Mechanical and Aerospace Engineering Nanyang Technological University Jiangsu Key Laboratory of Networked Collective Intelligence School of Mathematics Southeast University Department of Computer Science Rensselaer Polytechnic Institute Department of Electronic Engineering City University of Hong Kong Department of Biological Physics E?tv?s University MOE Key Laboratory for Intelligent Networks and Network Security School of Automation Science and Engineering Xi'an Jiaotong University

Hierarchical networks are frequently encountered in animal groups, gene networks, and artificial engineering systems such as multiple robots, unmanned vehicle systems, smart grids, wind farm networks,and so forth. The structure of a large directed hierarchical network is often strongly influenced by reverse edges from lower-to higher-level nodes, such as lagging birds' howl in a flock or the opinions of lowerlevel individuals feeding back to higher-level ones in a social group. This study reveals that, for most large-scale real hierarchical networks, the majority of the reverse edges do not affect the synchronization process of the entire network; the synchronization process is influenced only by a small part of these reverse edges along specific paths. More surprisingly, a single effective reverse edge can slow down the synchronization of a huge hierarchical network by over 60%. The effect of such edges depends not on the network size but only on the average in-degree of the involved subnetwork. The overwhelming majority of active reverse edges turn out to have some kind of ‘‘bunchingo effect on the information flows of hierarchical networks, which slows down synchronization processes. This finding refines the current understanding of the role of reverse edges in many natural, social, and engineering hierarchical networks,which might be beneficial for precisely tuning the synchronization rhythms of these networks. Our study also proposes an effective way to attack a hierarchical network by adding a malicious reverse edge to it and provides some guidance for protecting a network by screening out the specific small proportion of vulnerable nodes.

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Robust longitudinal attitude control of flapping-wing micro air vehicle based on disturbance observer

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Journal of institute of Control, Robotics and systems 2019年第11期25卷 1000-1006页

作者： Lee, Jonggu Ryu, Seungwan Kim, H. Jin Department of Mechanical and Aerospace Engineering Seoul National University Korea Republic of Automation and Systems Research Institute Seoul National University Korea Republic of

Flapping-wing micro air vehicles (FWMAVs) are interesting flight platforms due to their energy efficiency, camouflage ability and agility. However, these FWMAVs produce limited forces and moments due to their small scale and complex dynamics, so most studies have been conducted in indoor environments where external disturbance is excluded. In order for these bio-inspired robots to perform various tasks in outside, an ability to react robustly to external disturbance is essential. In this paper, we employ a robust controller called disturbance observer for attitude control of a FWMAV. Before designing a controller, we derive the attitude dynamics of the FWMAV based on experimental data. Then, we validate the proposed algorithm with a flight experiment in a laboratory condition with wind disturbance similar to outdoor flight. © 2019, institute of Control, Robotics and systems. All rights reserved.

关键词： Robust control

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Long-term Stability Analysis of Vertical Channel Damping and Kalman Filtering for Inertial Navigation system/Vertical Gauge

Long-term Stability Analysis of Vertical Channel Damping and...

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International Conference on Electrical engineering/Electronics, Computer, Telecommunications and Information Technology, ECTI-CON

作者： Chan Gook Park Jaehyuck Cha Hojin Ju Department of Mechanical and Aerospace Engineering Automation and Systems Research Institute Seoul National University Seoul Korea Automation and Systems Research Institute Seoul National University Seoul Korea

This paper deals with inertial navigation system (INS) aided by a vertical gauge (VG) for unmanned vehicles in two different schemes, vertical channel damping (VCD) and Kalman filter (KF). As the altitude error of standalone INS goes to diverge quickly, a VG can play a key role in an integrated navigation. A conventional technique to integrate INS with a VG is the VCD scheme which only corrects the vertical channel states by separating them from those of the horizontal channels. On the other hand, in this paper, it is shown that a KF scheme without separation of them can also reduce the horizontal position estimation errors as well by only using a VG. The navigation results of the two different schemes through numerical simulations are compared. Providing the simulation results on the both of correct and incorrect KF measurement error model, it shows the performance of KF scheme considerably depends on the model accuracy.

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Lithium insertion in Si electrodes studied by first principles method

Lithium insertion in Si electrodes studied by first principl...

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作者： Wu Ruiqi Liu Fengbin Si Lina Zhao nan Yan Hongjuan Chen Jianguo School of Mechanical and Materials Engineering North China University of Technology Beijing Aerospace Unmanned Vehicles System Engineering Research Institute

Si has been considered as one of the most potential new-generation anode materials for high-capacity lithium-ion batteries. However, the lithiation and delithiation of lithium ions during the charge-discharge processes of the Si electrode would give rise to almost four-fold volume expansion, causing structural changes and cracks of the conductive network, limiting the application of Si-based anode material. In this paper, the lithium ions inserting into Si material at various positions and at different doping concentrations of lithium ions was studied by first-principles method. The stability of different insertion sites, the structural changes, band structures and density of States after Li insertion were analyzed. It has been found that the lithium ions doping is an interstitial doping rather than a substitutional one and the tetrahedral center(Td) site is the most stable insertion position. From the band structure analysis, it can be seen that the Si material with the insertion of lithium ions becomes metal-like, and as the concentration changes, silicon changes from an indirect gap semiconductor to a direct gap semiconductor. When the concentration reaches 12.5%, the structural expansion rate increases obviously. This work provides a strategy for the improvement of the Si based anode material used in high-capacity lithium-ion batteries.

关键词： Lithium insertion in Si electrodes studied by first principles method

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Simulative and experimental study of dynamic characteristics of pressure relief valve based on amesim

Simulative and experimental study of dynamic characteristics...

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CSAA/IET International Conference on Aircraft Utility systems (AUS 2020)

作者： F. Teng P. He H. Zhang H. Hu X. Wang X. Liu Aerospace System Engineering Shanghai 201109 Shanghai China AVIC Jiangxi Hongdu Aviation Industry Group Company Ltd 330000 Nanchang China Beihang University School of Automation Science and Electrical Engineering 100191 Beijing China Research Institute for Frontier Science Beihang University 100191 Beijing China

A simulation model for the dynamic characteristics of pressure relief valve was established based on AMESim in this paper to solve the problem of the abnormal outlet pressure fluctuation during the −40℃ environmental test of the pressure relief valve of the booster delivery system of a certain type of launch vehicle. By calibrating the model with test data and parameters of the valve and test system and using the Stribeck friction model, the simulation successfully reproduced the pressure fluctuation phenomenon, located the cause of the failure and showed the main reason for the long-term drop in pressure. To solve the problem, the proposed improvement scheme of the high-pressure sealing structure was simulated and verified by experiments.

关键词： seals (stoppers) hydraulic systems friction valves computational fluid dynamics calibration computer simulation

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Experimental and numerical investigation on mechanical properties and failure modes of SiC/SiC tapered laminates: Effects of ply drop location

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Composite Structures 2025年 367卷

作者： Liu, Chenyang Zhang, Sheng Zhang, Xu Dong, Chengqian Wang, Fang Gao, Xiguang Song, Yingdong Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China College of Chemical Engineering Nanjing Forestry University Nanjing210037 China Key Laboratory of Aero-engine Thermal Environment and Structure Ministry of Industry and Information Technology Nanjing210016 China State Key Laboratory of Mechanics and Control Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing210016 China Harbin Engineering University Harbin150001 China China Helicopter Research and Development Institute China

aerospace laminated composite structures often require thickness variations along one or more directions in order to satisfy weight and aerodynamic efficiency requirements. Thickness variation is achieved by introducing dropped plies at appropriate locations. However, the influence mechanism of the ply drop location has not been adequately elucidated. In this work, the effect of ply drop location on the mechanical properties of tapered laminates has been investigated by experiment and simulation. Three different ply-drop configurations of tapered laminates were subjected to quasi-static tensile tests. The main failure modes are delamination and ply damage. Delamination can significantly reduce the load-bearing capacity of the structure. The simulation results are in good agreement with the test results in terms of failure load, load–displacement response, and delamination regions. The results demonstrate that the ply drop location affects the order of occurrence of the main failure modes of tapered laminates and the propagation path of ply damage cracks, thereby influencing their mechanical properties. © 2025 Elsevier Ltd

关键词： Tensile testing

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Performance and exergy analysis of an inclined solar still with baffle arrangements

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Heliyon 2023年第4期9卷 e14807页

作者： S Seralathan G Chenna Reddy S Sathish A Muthuram Joshuva Arockia Dhanraj Natrayan Lakshmaiya Karthikeyan Velmurugan Chatchai Sirisamphanwong Rattapon Ngoenmeesri Chattariya Sirisamphanwong School of Aeronautical Sciences Hindustan Institute of Technology and Science Chennai 603103 Tamil Nadu India. Department of Mechanical Engineering Hindustan Institute of Technology and Science Chennai 603103 Tamil Nadu India. Centre for Automation & Robotics (ANRO) Department of Mechatronics Engineering Hindustan Institute of Technology and Science Chennai 603103 Tamil Nadu India. Department of Mechanical Engineering Saveetha School of Engineering Saveetha Institute of Medical and Technical Sciences Chennai India. Center for Alternative Energy Research and Development Khon Kaen University Thailand. Mechanical Engineering Division Faculty of Engineering Khon Kaen University Khon Kaen Thailand. Smart Energy System Integration Research Unit Department of Physics Faculty of Science Naresuan University Thailand. Research and Academic Service Faculty of Science Naresuan University Thailand. Department of Physics and General Science Faculty of Science Nakhon Sawan Rajabhat University Thailand.

This study presents the details of performance and exergy investigations on an inclined solar still with baffle arrangements. The shortage of consumable water creates the transformation of accessible brackish water into consumable water an unavoidable one and this can be accomplished utilizing sun-oriented refining. To remove drinkable water from pungent water, sun-oriented still is broadly utilized. To build the contact season of the pungent water with sunlight-based brilliance, perplex course of action is set to expand the opposition in the stream. This prompts more vanishing of brackish water. Therefore, the objective of this study is to improve freshwater yield. The experimental study is performed for two different mass flow rates (m = 0.0833 kg/min and m = 0.166 kg/min). An increase in the mass flow of water directly deteriorates the yield of fresh water. Highest accumulated freshwater yield is achieved as 2.908 kg/m day during the month of May for m = 0.0833 kg/min. The accumulated freshwater yield improved by 4.23% in comparison with inclined solar still designs. Moreover, the yield is better by 3.49%-61.56% in comparison with various solar still designs. Using RSM, a polynomial statistical model is specified to estimate as well as maximize the freshwater yield of ISSB. The exergy analysis for m = 0.0833 kg/min shows a maximum hourly exergy efficiency of 6.82%.

关键词： Baffle arrangements Exergy efficiency Inclined solar still Performance yield

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