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Repeated clamping locking device for magnetic bearing flywheel

Guangxue Jingmi Gongcheng/Optics and Precision Engineering 2012年第8期20卷 1802-1810页

作者： Liu, Qiang Fang, Jian-Cheng Key Laboratory of Inertial Technology Beihang University Beijing 100191 China National Defense Key Science Laboratory of Novel Inertial Instrument and Navigation System Technol. Beihang University Beijing 100191 China

As the integral carbon fiber slice for a locking device is not easy to disassemble and the one-off locking device can not repeat locking/unlocking in a magnetic bearing flywheel, a novel repeated clamping locking device based on a separate elastic slice as release mechanism was presented. The composition, operating principles and the scheme of elastic slice for the device were introduced. To be equivalent the elastic slice for a cantilever beam-mass mode, the static and dynamic analysis was performed for the device. Upon this, the structure parameters of high sensitivity were selected as design variables, and the structural strength, unlocking force and the first resonance frequency were concerned. Then, the software of multidisciplinary design optimization (iSIGHT) was used for the optimization of elastic slice. The results indicate that the total mass of elastic slices has been reached to the minimum of 207 g corresponding to 10 elastic slices, which is reduced by 56.6% compared with initial mass of 477 g. According to optimization results, a locking device was manufactured and it is verified by sine-swept vibration and random vibration. The verification shows that the locking device can protect magnetic bearing flywheels and has great significance and values for space applications of magnetic bearing flywheels.

关键词： Flywheels

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TS-ENAS:Two-Stage Evolution for Cell-based Network Architecture Search

arXiv

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arXiv 2023年

作者： Zou, Juan Wu, Shenghong Xia, Yizhang Jiang, Weiwei Wu, Zeping Zheng, Jinhua Engineering Research Center of Hunan Province for Optimization and Security of Intelligent System Key Laboratory of Intelligent Computing and Information Processing Ministry of Education of China Key Laboratory of Hunan Province for Internet of Things and Information Security Xiangtan University Hunan Province Xiangtan411105 China The College of Aerospace Science and Engineering National University of Defense Technology Hunan Changsha410073 China

Neural network architecture search provides a solution to the automatic design of network structures. However, it is difficult to search the whole network architecture directly. Although using stacked cells to search neural network architectures is an effective way to reduce the complexity of searching, these methods do not able find the global optimal neural network structure since the number of layers, cells and connection methods is fixed. In this paper, we propose a Two-Stage Evolution for cell-based Network Architecture Search(TS-ENAS), including one-stage searching based on stacked cells and second-stage adjusting these cells. In our algorithm, a new cell-based search space and an effective two-stage encoding method are designed to represent cells and neural network structures. In addition, a cell-based weight inheritance strategy is designed to initialize the weight of the network, which significantly reduces the running time of the algorithm. The proposed methods are extensively tested and compared on four image classification dataset, Fashion-MNIST, CIFAR10, CIFAR100 and ImageNet and compared with 22 state-of-the-art algorithms including hand-designed networks and NAS networks. The experimental results show that TS-ENAS can more effectively find the neural network architecture with comparative performance. Copyright © 2023, The Authors. All rights reserved.

关键词： Image classification

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Numerical Investigation on Thermal Characteristics and Energy Efficiency of Lithium-Ion Battery Under Different Charging Stresses

SSRN

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SSRN 2024年

作者： Xie, Wenlong Gao, Xinlei Zhang, Zhengjie Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China Department of Mechanical Engineering Imperial College London LondonSW7 2AZ United Kingdom School of Transportation Science and engineering Beihang University Beijing100191 China

The thermal characteristics of lithium-ion batteries during the charging process significantly impact their electrochemical performance and safety, particularly under high-rate or extreme temperature conditions. In this study, an electrochemical-thermal coupling model for a 2.5 Ah LiNi0.8Co0.1Mn0.1O2 18650 lithium-ion battery is proposed and experimentally validated. The heat generation and variation patterns of the electrodes at different charging rates and temperatures are evaluated, and the influence mechanisms of various electrode design parameters on charging energy efficiency are elucidated. The results reveal that high-rate charging increases the proportion of irreversible heat in the total heat generation, primarily due to the increase in ohmic heating at the positive electrode. Ambient temperature is less sensitive to heat generation than the C-rate, but low temperatures can also increase irreversible heat and are associated with an increase in positive polarization heat. Analyzing thermal characteristics at the electrode level can contribute to the optimization of battery design and the improvement of thermal safety. Electrode architectures, including electrode thickness, active material porosity, particle radius and negative/positive electrode capacity (N/P) ratio, are determined to analyze their effects on the heat generation of various components within the battery. Thick electrodes or active materials with high porosity induce significant ohmic heating and increase irreversible heat, with a slight effect on reversible heat, which is detrimental to energy efficiency. Large particle radii primarily increase reaction heat and polarization heat, and a high N/P ratio reduces the battery heat generation and is related to the reduction of negative reaction heat. Notably, variations in both two parameters have limited impact on to energy efficiency. Therefore, implementing appropriate thermal management across various charging scenarios is crucial for achievin

关键词： Lithium-ion batteries

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Stability and energetics of two-dimensional surface crystals in liquid AuSi thin films and nanoscale droplets

引用

Physical Review Materials 2021年第7期5卷 074003-074003页

作者： Hailong Wang Mengyuan Wang Alireza Shahabi Alain Karma Moneesh Upmanyu CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China Hefei Anhui 230027 China Group for Simulation and Theory of Atomic-Scale Material Phenomena (stAMP) Department of Mechanical and Industrial Engineering Northeastern University Boston Massachusetts 02115 USA Department of Physics Northeastern University Boston Massachusetts 02115 USA

We employ atomic-scale computational frameworks to study the surface crystallization in AuSi films and droplets as a function of composition, temperature, and size. Above the melting point, the surfaces of both thin films and droplets undergo a first-order transition from a two-dimensional (2D) Au2Si crystalline phase to a laterally disordered yet stratified layer. The thin film surfaces exhibit an effective surface tension that increases with temperature and decreases with Si concentration, while for droplets in the size range 10–30 nm, the bulk Laplace pressure alters the surface segregation as it occurs with respect to a strained bulk. Above the transition, the size effect on the surface tension due to the stratified surface layer is small, while the crystalline surface layer below the transition is strained and composed of 2D crystallites separated by extended grain boundary scars that lead to large fluctuations in its energetics. As a specific application, all-atom simulations of AuSi droplets on Si(111) substrate subject to Si surface flux show that the supersaturation dependent surface tension destabilizes the contact line via formation of a precursor wetting film on the solid-vapor interface and has ramifications for size selection during droplet-catalyzed routes for nanowire growth. Our study sheds light on the interplay between stability and energetics of surfaces in this unique class of binary alloys and offers pathways for exploiting their surface structure for varied applications such as catalytic nanocrystal growth, dealloying, and polymer crystallization.

关键词： Crystal forms Growth Interface & surface thermodynamics Nanocrystals Structural phase transition 2-dimensional systems Surfaces Molecular dynamics

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Understanding the Limitations of Thick Electrodes on the Rate Capability of High-Energy Density Lithium-Ion Batteries

SSRN

引用

SSRN 2024年

作者： Xie, Wenlong Zhang, Zhengjie Gao, Xinlei Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China School of Transportation Science and engineering Beihang University Beijing100191 China Department of Mechanical Engineering Imperial College London LondonSW7 2AZ United Kingdom

As a core component of transportation electrification, lithium-ion batteries need to address two critical challenges: achieving high energy density and enabling fast charging. However, changes in electrode thickness could result in a trade-off between these two characteristics. Herein, the impact of electrode thickness on the electrochemical performance, thermal behavior, as well as energy and power density of LiNi0.8Co0.1Mn0.1O2(NCM)/graphite batteries are investigated through mathematical modeling. Underutilization of active materials of the thick electrode is identified as the primary limitation on rate capability, which can be attributed to the slow solid-state diffusion and poor electrolyte transport within the electrode, especially the enlarged concentration gradients in the solid phase and the lithium depletion in the electrolyte phase during high-rate charging. Evolutions of local current density and heat generation rate along the electrode thickness are compared, identifying the underlying mechanism of inducing uneven reaction kinetics inside the battery. The trade-off between the energy and power density as a function of electrode thickness is investigated based on the limitations of charge transfer and mass transport. Furthermore, the rate-limiting factors under various application requirements are elucidated. This study will provide guidance for the electrode design of high-energy-density batteries with fast-charging capabilities. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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Non-holonomy in im torque control

Non-holonomy in im torque control

引用

International Workshop on Advanced Motion Control (AMC)

作者： B. Crcar P. Cafuta G. Stumberger H.R. Cortes A.M. Stankovic Electrical Engineering Department Al-Azhar University Cairo Egypt School of Engineering Science and Design Glasgow Caledonian University Glasgow Scotland UK Valley Higher Institute for Engineering and Technology Science Valley Academy Cairo Egypt Tech. University of Delft THE NETHERLANDS State Key Laboratory of ASIC & System Fudan University Shanghai CHN

In the paper IM torque control is studied as an example of non-holonomic system with drift terms. Following the famous Brockett integrator problem several control propositions are introduced. The paper extends the control scheme from the state to the output control in several steps. By introducing adjusted amplitude, frequency and phase modulation of the IM stator current vector, the rotor flux linkage vector is implicitly forced to generate required periodic orbits that satisfy nonholonomic constraint. Improvements in the transient feedback performance, maximal steady-state efficiency, avoidance of singularities and sufficient robustness are actually achieved by making the current modulation dependent from the torque error signal. In the contrast with the original work instead of global only local stability could be assured. Simulation and experimental results illustrate main characteristics of the proposed control

关键词： Torque control Frequency Phase modulation Stators Rotors Couplings Orbits Feedback Steady-state Robustness

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Performance comparation of two kinds of aircraft ram air outlet

Performance comparation of two kinds of aircraft ram air out...

引用

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

作者： L. Zhimao Z. Xinlong W. Boyu P. Houju X. Wenbing S. Hong Shanghai Aircraft Design and Research Institute Environment Control and Oxygen System Department Shanghai 201210 China Jiangsu University of Science and Technology College of energy and power Zhenjiang 212003 China MIIT Nanjing University of Aeronautics and Astronautics Key Laboratory of Aircraft Environment Control and Life Support Nanjing 210016 China

With the development of electronic equipment integration technology, the air demand for cooling in cabin and electronic system is increasing continuously. The ram air outlet plays an important role in the airflow system. In this paper, the three-dimensional modeling of the door-type ram air outlet and the grille-type ram air outlet is carried out. Then, the flow characteristics and resistance characteristics of ram air outlet are analyzed based on structured grid technology. The results show that the flow rate of the door panel ram air outlet is greater than that of the grille-type ram air outlet in the same size, the discharge rate of the door panel outlet is 0.3kg/s more than that of the grille-type outlet under the design condition, and the skin surface temperature at the back of the door panel outlet is 13.5K lower than that of the grille outlet. Therefore, the door-type ram air outlet has better emission characteristics and flow characteristics, which is more suitable for the aircraft in this research. This study provides a technical reference for the design of the civil aircraft.

关键词： aircraft control refrigerators refrigeration skin electric actuators design engineering metal foams heat exchangers cooling

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A unified leader-follower scheme for mobile robots with uncalibrated on-board camera

A unified leader-follower scheme for mobile robots with unca...

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： Dejun Guo Hesheng Wang Weidong Chen Ming Liu Zeyang Xia Kam K. Leang DARC (Design Automation Robotics & Control) Lab University of Utah Robotics Center Salt Lake City Utah USA State Key Laboratory of Robotics and System (HIT) Key Laboratory of System Control and Information Processing Ministry of Education of China Department of Automation Shanghai Jiao Tong University Shanghai China Department of Electronics and Computer Engineering Hong Kong University of Science and Technology Hong Kong China Institute of Biomedical and Health Engineering Chinese Academy of Sciences Shenzhen China

This paper studies the problem of image-based leader-follower formation control for mobile robots, where the controller is designed independently of the leader's motion. An adaptive control scheme, which is suitable for both omnidirectional and perspective cameras, is proposed. The proposed approach avoids the need for accurate calibration of the extrinsic parameters of the omnidirectional camera as well as the intrinsic and extrinsic parameters of perspective camera. Additionally, the coefficients of the plane where the feature point moves relative to the camera frame can be uncertain. These uncertain constant parameters are estimated using an adaptive estimator. Uniform Semi-global Practical Asymptotic Stability (USPAS) of the system is shown using the Lyapunov approach. Experimental results are presented to demonstrate the effectiveness of the proposed control scheme.

关键词： Cameras Robot vision systems Kinematics Mobile robots Calibration Automation

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Face Detection based-on Depth Information Using HOG-LBP

Face Detection based-on Depth Information Using HOG-LBP

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2016 Sixth International Conference on Instrumentation and Measurement,Computer,Communication and Control (IMCCC2016)(第六届仪器测量、计算机通信与控制国际会议)

作者： Tiemeng Li Fei Lyu Wenjun Hou Yu Lei Chen Xiao Key Laboratory of Network System and Network Culture Beijing University of Posts & Telecommunication School of Digital Media & Design Arts Beijing University of Posts & Telecommunications Beijing Chin Automation School Beijing University of Posts & Telecommunications Beijing China School of Computer Science and Technology Beijing University of Posts & Telecommunications Beijing

ISBN: (纸本)9781509011964

Face detection is one of the key technology for face information ***,face detection is mainly based on the RGB image,which might lead unexpected results when dealing with non-real 2-dimensional face,which printed on clothes and *** work proposes a face detection approach based on features of depth *** used depth camera to obtain the raw depth data,and then mapped it to the 2D image combined with smooth image processing method to get the depth *** improved HOG-LBP algorithm was designed to profiling the features of face depth,and SVM-light was used for machine ***,an online video face detection system was accomplished.

关键词： Face Detection Depth Image HOG-LBP SVM Stereovision

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PBDW method for state estimation: Error analysis for noisy data and nonlinear formulation

arXiv

引用

arXiv 2019年

作者： Gong, Helin Maday, Yvon Mula, Olga Taddei, Tommaso Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China Paris75005 France Institut Universitaire de France Paris75005 France Université Paris-Dauphine PSL Research University CNRS UMR 7534 CEREMADE Paris75016 France IMB UMR 5251 Univ. Bordeaux Talence33400 France Inria Bordeaux Sud-Ouest Team MEMPHIS Talence33400 France

We present an error analysis and further numerical investigations of the Parameterized-Background Data-Weak (PBDW) formulation to variational Data Assimilation (state estimation), proposed in [Y Maday, AT Patera, JD Penn, M Yano, Int J Numer Meth Eng, 102(5), 933-965]. The PBDW algorithm is a state estimation method involving reduced models. It aims at approximating an unknown function utrueliving in a highdimensional Hilbert space from M measurement observations given in the form ym= m(utrue), m = 1, ⋯, M, where mare linear functionals. The method approximates utruewith u = z + η. The background Z belongs to an N-dimensional linear space ZNbuilt from reduced modelling of a parameterized mathematical model, and the update η belongs to the space UMspanned by the Riesz representers of (1, ⋯, M). When the measurements are noisy - i.e., ym= m(utrue) + ϵmwith ϵmbeing a noise term - the classical PBDW formulation is not robust in the sense that, if N increases, the reconstruction accuracy degrades. In this paper, we propose to address this issue with an extension of the classical formulation, which consists in searching for the background z either on the whole ZNin the noise-free case, or on a well-chosen subset KN⊂ ZNin presence of noise. The restriction to KNmakes the reconstruction be nonlinear and is the key to make the algorithm significantly more robust against noise. We further present an a priori error and stability analysis, and we illustrate the efficiency of the approach on several numerical examples. Copyright © 2019, The Authors. All rights reserved.

关键词： Parameterization

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