Loading...
 首页  期刊介绍 期刊订阅 联系我们
 
最新录用  |  预出版  |  当期目录  |  过刊浏览  |  阅读排行  |  下载排行  |  引用排行  |  百年期刊

ISSN 1000-0585
CN 11-1848/P
Started in 1982
  About the Journal
    » About Journal
    » Editorial Board
    » Indexed in
    » Rewarded
  Authors
    » Online Submission
    » Guidelines for Authors
    » Templates
    » Copyright Agreement
  Reviewers
    » Guidelines for Reviewers
    » Online Peer Review
  Office
    » Editor-in-chief
    » Office Work
    » Production Centre
  • Table of Content
      , Volume 60 Issue 2 Previous Issue    Next Issue
    For Selected: View Abstracts Toggle Thumbnails
    SPECIAL SECTION: ELECTRIC VEHICLE
    Active synchronizing control of transmission shifting without a synchronizer for electric vehicles
    TIAN Feng, WANG Lijun, SUI Liqi, ZENG Yuanfan, ZHOU Xingyue, TIAN Guangyu
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 101-108.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.032
    Abstract   PDF (9917KB) ( 474 )
    Motor coupled mechanical transmissions without synchronizers for electric vehicle applications have high transmission efficiencies, compact structures and low manufacturing costs. However, the synchronization of the sleeve to the ring gear is slow and can produce shift shock and failure. Active control of the driving motor torque is used here to provide "zero speed difference" and "zero angle difference" tracking control of the relative speed and angle between the ring gear and the sleeve. An optimal torque synchronizing control algorithm is used to avoid gear striking caused by frequent switching between the motor drive and the brake quadrants during the active synchronizing control using minimum working quadrant switching of the motor. Vehicle tests show that the active synchronizing control algorithm provides fast, stable shifting and shortens the power interruption time of the shifting process to less than 300 ms.
    Figures and Tables | References | Related Articles | Metrics
    Nonlinear dynamics analyses of gear shifting with gear vibrations
    SUI Liqi, TIAN Feng, LI Bo, ZENG Yuanfan, TIAN Guangyu, CHEN Hongxu
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 109-116.   DOI: 10.16511/j.cnki.qhdxxb.2019.21.033
    Abstract   PDF (2908KB) ( 589 )
    The dynamic characteristics of a sleeve and a gear ring during shifting of an electric drive mechanical transmission were studied using a nonlinear dynamic model that included the coupled vibrations of the drive gears. The model used a nonlinear contact model to describe the impact of the sleeve and the gear ring during engaging with nonlinear vibrations of the drive gears with clearances described using the concentrating mass method of gear dynamics. The two nonlinear processes were coupled by the dynamics equations. The various engaging conditions of the sleeve and the gear ring were summarized into five states with their coupled dynamics equations. Then, the dynamic characteristics of the system were simulated using the Runge-Kutta method. The results are consistent with experimental data. Analyses of the impact force between the sleeve and the gear ring shows that with even only a slight difference between the relative rotational speed and the contact angle, the impact force can reach 23 800 N. The results are of great significance for optimizing sleeves and gear rings for improving gear shifting quality.
    Figures and Tables | References | Related Articles | Metrics
    Control of a tire-cornering based differential steering system
    SONG Jian, ZHAO Wenzong, DAI Yaqi, CHENG Shuai, LI Fei
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 117-123.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.044
    Abstract   PDF (1245KB) ( 653 )
    Differential steering based on the tire cornering characteristics is applicable to large-radius curves. This paper presents a model of an independently driven four wheel electric vehicle. The state-space equation for the differential steering system is used to analyze the stability and controllability and to analyze the factors influencing the steering ability. A steady-state steering torque model is used in a control method based on fuzzy inference feedforward compensation. Simulations show that the control algorithm not only improves the system response time but is also adaptable to different steering needs at different speeds.
    Figures and Tables | References | Related Articles | Metrics
    Dynamic torque characteristics of the band brake of a continuous automatic transmission
    LI Fei, SONG Jian, FANG Shengnan, LU Zhenghong, NGUYEN Truong Sinh
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 124-131.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.025
    Abstract   PDF (6915KB) ( 192 )
    A band brake is the shift actuator in a continuous automatic transmission with the band brake dynamics significantly influencing the shift quality. A static model, a finite element model and tests were used to investigate the relationship between the brake torque and the braking force. Tests of a brake drum rotated clockwise and counterclockwise were compared with simulations. The results show that the dynamic braking torque is related to the rotational speed, normal force and dynamic friction coefficient. When the brake drum is rotated forward, the self-energy effect increases the braking torque generated by the brake band with a longer static zone and better braking stability. When the drum is reversed, there is no obvious static zone, while the relationship is more linear and suitable for control. The test results are used to define the control parameters of the empirical equation for the dynamic brake band braking torque for smooth control of the brake band.
    Figures and Tables | References | Related Articles | Metrics
    Dynamic torque allocation for in-wheel motor driven vehicle based on energy consumption optimization
    CHEN Hao, YUAN Liangxin, ZHENG Sifa, LIAN Xiaomin
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 132-138.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.041
    Abstract   PDF (2729KB) ( 291 )
    In-wheel motor driven vehicles can provide independent control of the driving torque to each wheel and easy access to feedback information. This paper presents a dynamic torque allocation method based on the torque vectoring control system of an in-wheel motor driven vehicle. The vehicle energy consumption is used as the objective function. Changes in the real-time capabilities of the motors and the driver's demands are used to build a constrained nonlinear optimization model. The optimization problem is decomposed into parts while the feasible torque space is discretized to resolve the contradiction between the constraint changes and the real-time requirement of the online optimization. A MATLAB/Simulink-Cruise simulation platform is used to verify the algorithm's feasibility and robustness for a new European driving cycle (NEDC) and an urban driving cycle. The simulations show that this method effectively reduces the vehicle energy consumption and has good fault tolerance.
    Figures and Tables | References | Related Articles | Metrics
    Electrochemical impedance equivalent circuit model for zinc-air fuel cells
    CHEN Dongfang, PEI Pucheng, SONG Xin, REN Peng
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 139-146.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.042
    Abstract   PDF (4056KB) ( 372 )
    The physicochemical processes in zinc-air fuel cells can be represented by an equivalent circuit model. However, the impedance distribution of anode and cathode is not taken accounted in the existing models. A whole cell model including the anode and cathode impedances is presented and a simplified version is developed that neglects the effect of the anode. The influences of the cell structure, performance degradation, storage condition, conductive agent in the zinc anode, and structural changes in the air cathode on the impedance are investigated with the model fitting experimental data with chi-square test results all less than 0.01. The impedances predicted by the model are then used to analyze the impedance change mechanism. The results show that this model can be used to study metal-air batteries.
    Figures and Tables | References | Related Articles | Metrics
    HYDRAULIC ENGINEERING
    Review of water body information extraction based on satellite remote sensing
    LI Dan, WU Baosheng, CHEN Bowei, XUE Yuan, ZHANG Yi
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 147-161.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.038
    Abstract   PDF (2003KB) ( 1338 )
    The spatial and temporal distributions of water bodies are of great significance for monitoring the use of water resources. The most common remote sensing applications are classifying the surface cover types and analyzing changes in the spatial distributions of these water resources. In recent years, satellite remote sensing data has been used to extract key features such as the location, area, morphology and river width especially for large water bodies or for those in inaccessible regions in high mountains. This not only saves manpower and promotes safety, but also improves work efficiency. This study analyzes methods for using satellite remote sensing data for water body information extraction with reviews of the reflection characteristics of water bodies in various spectral regions of the electromagnetic spectrum; water extraction methods based on radar and optical remote sensing data at home and abroad since 1980; the working principles, advantages and disadvantages of various water information extraction methods; and some challenges of water information extraction applying remote sensing and the key issues to solve these problems. Finally, this paper forecasts future applications of remote sensing for water body information extraction.
    Figures and Tables | References | Related Articles | Metrics
    Local climate impact of central heating in the winter based on the WRF-LUCY model
    HUANG Bei, NI Guangheng
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 162-170.   DOI: 10.16511/j.cnki.qhdxxb.2019.22.040
    Abstract   PDF (8942KB) ( 371 )
    Rapid urbanization affects land and atmospheric processes through changes in the underlying surface conditions. At the same time, high-density, high-intensity human activities in urban areas result in large amounts of anthropogenic heat (AH) emissions which impact the local urban climate. Thus, research on the impact of anthropogenic heat on the local urban climate is important for exploring urban land-atmosphere interactions. This study couples weather research and forecasting model (WRF) with the heating results calculated by the large scale urban consumption of energy (LUCY) model. This study analyzes how the high spatial and temporal resolution of the anthropogenic heat emission model used in the WRF model affects the simulation results. The Beijing winter central heating system is used as an example to study the impact of a large anthropogenic heat release on the local climate. The results show that the WRF-LUCY model gives reasonable predictions of the meteorological elements and the urban-rural circulation, that the anthropogenic heat released by the heating causes the air temperature to rapidly increase, and that the temperature rise is greater at night than during the day. This study provides a reliable tool for urban local climate simulations and a scientific basis for urban energy planning and environmental improvement.
    Figures and Tables | References | Related Articles | Metrics
    ELECTRONIC ENGINEERING
    Research progress on drug representation learning
    CHEN Xin, LIU Xien, WU Ji
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 171-180.   DOI: 10.16511/j.cnki.qhdxxb.2019.21.038
    Abstract   PDF (1031KB) ( 432 )
    The drug development process is characterized by large capital density, high risk and long cycles; thus, drug development requires much capital, manpower and resources. While traditional machine learning methods can aid drug development some, they require molecular descriptors as inputs. The selection of the molecular descriptors then greatly impacts the performance of the machine learning models. Therefore, most traditional machine learning methods require complex and time-consuming feature engineering. The emerging deep learning methods can directly learn the features from raw representations of the drugs which bypasses the feature engineering and shortens the drug development cycle. In this paper, the drug representation learning methods are divided into simplified molecular input line entry specification (SMILES) expression based drug representation learning methods and molecular graph based representation learning methods. This paper then surveys the innovations and limitations of various drug representation learning methods. This paper then identifies major challenges in current drug representation learning methods and presents possible solutions.
    Figures and Tables | References | Related Articles | Metrics
    BIOMEDICAL ENGINEERING
    Speech enhancement algorithm for cochlear implants to suppress multi-directional speech noise
    GONG Qin, RAO Cheng, ZHENG Shuo
    Journal of Tsinghua University(Science and Technology). 2020, 60 (2): 181-188.   DOI: 10.16511/j.cnki.qhdxxb.2019.21.022
    Abstract   PDF (1511KB) ( 252 )
    Cochlear implant users often cannot clearly hear sounds in complex sound environments, especially with competing talkers. This paper describes a speech enhancement algorithm based on closely-spaced microphones. The algorithm extracts a delay parameter and defines a mask matrix based on this parameter to distinguish sound sources having different orientations. The model uses a digital signal processor (DSP) to implement the algorithm. Tests indicate that the robust algorithm improves the signal-to-noise ratio. The algorithm has short single-frame run times and can be integrated with commonly used speech coding strategies, which are needed for real-time computing in cochlear implants.
    Figures and Tables | References | Related Articles | Metrics
  News More  
» aaa
  2024-12-26
» 2023年度优秀论文、优秀审稿人、优秀组稿人评选结果
  2023-12-12
» 2022年度优秀论文、优秀审稿人、优秀组稿人评选结果
  2022-12-20
» 2020年度优秀论文、优秀审稿人评选结果
  2021-12-01
» aa
  2020-11-03
» 2020年度优秀论文、优秀审稿人评选结果
  2020-10-28
» 第十六届“清华大学—横山亮次优秀论文奖”暨2019年度“清华之友—日立化成学术交流奖”颁奖仪式
  2020-01-17
» a
  2019-01-09
» a
  2018-12-28
» a
  2018-01-19


  Links More  



Copyright © Journal of Tsinghua University(Science and Technology), All Rights Reserved.
Powered by Beijing Magtech Co. Ltd