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Influence of vibration on mechanical polishing micro-structured surface using discrete element method

International Journal of Machining and Machinability of Materials 2020年第1期22卷 24-46页

作者： Wang, Guilian Lv, Bingrui Liu, Li Liu, Bin Zhou, Haibo Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology Tianjin300384 China Tianjin Laboratory of Control Theory and Applications in Complicated System Tianjin300384 China School of Electrical and Electronic Engineering Tianjin University of Technology Tianjin300384 China

A model using discrete element method (DEM) was conducted to simulate vibration assisted mechanical polishing micro-structured surface process by particle flow code in three dimensions (PFC3D). The effect laws of vibration frequency and amplitude on abrasive grains and polishing force were researched in detail according to the simulation results. The effects of vibration on the particles average motion velocity in one fluid cell were researched, and the simulation results show that average velocity increases with increase of vibration frequency and amplitude on the whole. The effects of vibration on the unbalanced force acting on the workpiece surface were quantified at first. The changes of average unbalanced force obviously increase for low feed rate with increase of frequency and increase approximately linearly with increase of amplitude. It is concluded that vibration with high frequency and great amplitude can significantly increase machining efficiency and improve surface quality in micro-structured surface polishing. Copyright © 2019 Inderscience Enterprises Ltd.

关键词： Finite difference method

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TICNet: Three-Branch Real-Time Semantic Segmentation Network with Intensive Compensation of Railway Track Scenes

TICNet: Three-Branch Real-Time Semantic Segmentation Network...

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Machine Learning and Computer Application (ICMLCA), International Conference on

作者： Yiwen Bai Lu Yang Lei Zhang Yajing Song School of Transportation Science and Engineering Beihang University Beijing China Tianjin Key Laboratory for Advanced Mechanical System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin China Traffic Control Technology Co. Ltd Beijing China

ISBN: (数字)9798331530334

ISBN: (纸本)9798331530341

With the rapid development of railway traffic system, real-time semantic segmentation plays a crucial role in railway track scene monitoring. However, most of the existing methods use lightweight convolution to reduce the computational complexity, which results in reduced accuracy. To solve this problem, this paper proposes a real-time semantic segmentation network called TICNet, which is specifically used for accurate segmentation of railway track scenes. TICNet uses a novel three-branch structure designed for efficient feature extraction and accurate segmentation. Results on the RailSem19 dataset show that TICNet has a segmentation accuracy of 62.36% mIoU with an inference speed of 81.2 FPS, which is significantly better than many existing methods.

关键词： Accuracy Convolution Semantic segmentation Semantics Focusing Machine learning Feature extraction Real-time systems Computational complexity Monitoring

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Optimization of experiment teaching in the course of mechanical principle 3

Optimization of experiment teaching in the course of mechani...

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3rd International Conference on Education Technology Management, ICETM 2020

作者： Hao, Pujun Liu, Jingna Ma, Wenpeng Wu, Ruiqin 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 Tianjin Key LABORATORY for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China

ISBN: (纸本)9781450388757

Based on experience of former teaching reformation and philosophy of "Emerging Engineering Education", an experimental teaching reformation program that includes restructured knowledge system, modularization of experimental teaching process and diversified evaluation system is proposed. It is found that students have deeper and comprehensive understanding on knowledge and more enthusiasm in experimental process. Finally students have definite self-cognition about their division of labor in teamwork. Through gathering statistics, the effectiveness of reformation program is verified and this program can enrich practical experience of experimental teaching reformation. © 2020 ACM.

关键词： Optimization

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Energy-aware Trajectory Optimization for UAV-enabled wireless powered WSN

Energy-aware Trajectory Optimization for UAV-enabled wireles...

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Fully Actuated system Theory and Applications (CFASTA), Conference on

作者： Feihang Qiu Jing Guo Huineng Diao Xu Zhang School of Mechatronic Engineering and Automation Foshan University Foshan China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen China Shenzhen Key Laboratory of Control Theory and Intelligent Systems Southern University of Science and Technology Shenzhen China

ISBN: (数字)9798350373691

ISBN: (纸本)9798350373707

Unmanned Aerial Vehicle enabled (UAV-enabled) wireless powered Wireless Sensor Networks (WSN) provide an effective way to deploy massive and passive sensors for environmental monitoring in harsh environments. This study focuses on maximizing the total energy received by all Sensor Nodes (SNs) through the optimization of the UAV trajectory. An energy-aware smoothing trajectory method is proposed by considering the dynamic energy requirements of SNs. First, the optimization problem (P1) is formulated according to the mathematical model. Second, the B-spline method is introduced to turn the smoothing problem into a solvable problem (P2). Finally, problem (P2) is solved under the constraints to obtain the trajectory solution. Simulation results indicate the proposed method can adjust the overall trajectory according to the SNs demands. Meanwhile, according to the wake-up distance and energy-aware, the trajectory of some nodes can be locally adjusted without affecting other trajectory segments.

关键词： Wireless communication Wireless sensor networks Smoothing methods Simulation Autonomous aerial vehicles Mathematical models Trajectory

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LCFNet: Loss Compensation Fusion Network for Real-Time Semantic Segmentation of Urban Road Scenes

LCFNet: Loss Compensation Fusion Network for Real-Time Seman...

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International Conference on intelligent Transportation

作者： Lu Yang Yiwen Bai Fenglei Ren Shiyu Zhang Chongke Bi Tianjin Key Laboratory for Advanced Mechanical System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin China College of Intelligence and Computing Tianjin University Tianjin China

Semantic segmentation is used by intelligent transportation systems to understand and sense the traffic environment. However, achieving semantic segmentation in real-time is a challenge due to the necessity of both high accuracy and fast processing. This is especially valuable for applications such as autonomous driving and industrial robotics. In this paper, we propose a real-time semantic segmentation network, called LCFNet, which makes use of three-branch structure. The LCFNet consists of Lightweight Detail Guidance Fusion (L-DGF) and Lightweight Semantic Guidance Fusion (L-SGF) modules. Both modules aggregate information from various network layers. In the termination of network, a Total Guidance Fusion (TGF) module is proposed for processing information from all three branches. Depth-wise Convolution Pyramid Pooling (DCPP) module is also included to optimize accuracy and simplify computation. The effectiveness of LCFNet is demonstrated on two typical semantic segmentation datasets, Cityscapes and CamVid. On a single NVIDIA GeForce GTX 2080 Ti GPU, LCFNet reaches 77.02% mIoU at 95.97 FPS and 81.17% mIoU at 204.82 FPS, respectively.

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Research on Crack Detection of Nonlinear Rotor Based on Energy Tracks 17

Research on Crack Detection of Nonlinear Rotor Based on Ener...

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17th IEEE International Conference on mechatronics and Automation, ICMA 2020

作者： Zhang, Yu Liu, Jun Han, Zhu Tianjin University of Technology Tianjin Key Laboratory for Advanced Mechanical System Design and Intelligent Control Tianjin300384 China

ISBN: (纸本)9781728164151

In rotating machinery, because of high-speed working characteristics and terrible working conditions with variable cycles and variable loads, it is easy for rotors to cause a crack initiation and propagation, which may cause serious harm or even the life-threatening. The super harmonic component is an important role of the crack detection. But it is difficult to reflect the super harmonic component in the high-speed region after super harmonic resonances. In this paper, the dynamic equation of a nonlinear rotor system with a crack is considered, the potential energy expression of the cracked rotor is derived, and the concept of energy tracks is proposed. In the distortion of energy tracks, the effects of different crack parameters and nonlinear parameters on the vibration characteristics of the rotor system are compared. The results show that the energy trajectory distortion can diagnose the crack fault. It provides a new research method for vibration response analyses and fault diagnoses of cracked rotor system. © 2020 IEEE.

关键词： Crack detection

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Research on Asymmetrical Dual-rotor system Based on the Energy Orbit 17

Research on Asymmetrical Dual-rotor System Based on the Ener...

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17th IEEE International Conference on mechatronics and Automation, ICMA 2020

作者： Han, Zhu Liu, Jun Zhang, Yu Tianjin University of Technology Tianjin Key Laboratory for Advanced Mechanical System Design and Intelligent Control Tianjin300384 China

ISBN: (纸本)9781728164151

Studying the vibration of asymmetrical dual-rotor is very important for aero engines. In this paper, based on the vibration characteristics of an aero-engine, a different novel coupled dynamic model is proposed based on the spring recovery characteristics of rotor. The model dynamic equations of asymmetrical dual-rotor are obtained by the Lagrange equation, and vibration resonance curves of high pressure and low pressure rotors are numerically simulated and theoretically analyzed by using the Runge-Kutta algorithm. The research show that the system occurs combined vibration, harmonic vibration and superharmonic vibration. In addition, the vibration occurring mechanism was investigated and verified in detail through numerical simulation. For the first time, the concept of energy orbit was introduced into the dual-rotor model system. The energy orbit represents the vibration characteristics and energy exchange process of the model system. Energy orbit is a new energy orbit method for analyzing vibration characteristics of rotor system. The new researches of this paper will show a different research direction for complex dual-rotor systems. © 2020 IEEE.

关键词： Equations of motion

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

SSRN

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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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Kinematics Analysis and Machining Path Generation of Mirror Milling system Based on Dual Hybrid Robot

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Hangkong Zhizao Jishu/Aeronautical Manufacturing Technology 2024年第5期67卷 46-52页

作者： Liu, Qi Guo, Mengna Shan, Xianlei Tian, Wenjie Ma, Yue Li, Bin 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 School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China Key Laboratory of Mechanism Theory and Equipment Design Ministry of Education School of Mechanical Engineering Tianjin University Tianjin300072 China

With the focus on one kind of mirror milling system consisting of two hybrid robots, the canonical forward and inverse kinematic model of the mirror milling system is developed by the vector method, in which the forward kinematic has the advantage of high computational efficiency and accuracy compared with the solution method using the Newton iterative method. A method for generating mirrored machining path is proposed, which specifies the positional relationship between the reference coordinate systems of two hybrid robots, and calculates the mirrored symmetric tool and support head paths by setting the desired machining wall thickness of the thin-walled structural part. Two methods for executing mirrored machining path are proposed by employing 10-axis linkage and dual 5-axis linkage respectively. The latter has the features of reconfigurability and modularity compared with the former, which supports single-machine operation of the milling or supporting robot, and satisfies the needs of rapid on-site arrangement and efficient collaborative machining of single or multiple machines in a large workspace. In order to verify the correctness and effectiveness of the proposed kinematic model and methods for generating and executing machining paths, experiments of machining a large scale thin-walled structural component are carried out. The experimental results show that the error of the machined wall thickness can be guaranteed within ±0.18 mm. © 2024 Aeronautical Manufacturing Technology Magazine Office. All rights reserved.

关键词： Milling (machining)

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