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An Efficient Path Planning Methodology Based on the Starting Region Selection

Tsinghua University-Huajian Zhou
Hunan University-Xin Chen, Zhaobo Qin, Liang Chen
  • Technical Paper
  • 2020-01-0118
To be published on 2020-04-14 by SAE International in United States
Automated parking is an efficient way to solve parking difficulties and path planning is of great concern for parking maneuvers [1]. Meanwhile, the starting region of path planning greatly affects the parking process and efficiency. The present research of the starting region are mostly determined based on a single algorithm, which limits the flexibility and efficiency of planning feasible paths. This paper, taking parallel parking and vertical parking for example, proposes a method to calculate the starting region and select the most suitable path planning algorithm for parking, which can improve the parking efficiency and reduce the complexity. The collision situations of each path planning algorithm are analyzed under collision-free conditions based on parallel and vertical parking. The starting region for each algorithm can then be calculated under collision-free conditions. After that, applicable starting regions for parking can be obtained, and each of those regions corresponds to a parking path planning algorithm. However, there always exists overlapped starting regions, which can be applied to multiple parking path planning algorithms. In order to select the most…
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Instantaneous PLII and OH* Chemiluminescence Study on Wide Distillation Fuels, PODEn and Ethanol Blends in a Constant Volume Vessel

Tsinghua University-Longxi Cui, Yue Ma, Xiao Ma, Shijin Shuai
Birmingham University-Hongming Xu
  • Technical Paper
  • 2020-01-0340
To be published on 2020-04-14 by SAE International in United States
The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere. Comparing with WD, the soot amount of WDEP decreased for 55% and 27% at 870 K and 920 K. For the case of 920 K and 15.8% of ambient oxygen, the soot amount…
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Mechanical Response of Laterally-Constrained Prismatic Battery Cells under Local Loading

Tsinghua University-Feiyu Xiao, Bobin Xing, Yong Xia
  • Technical Paper
  • 2020-01-0200
To be published on 2020-04-14 by SAE International in United States
The crash safety of lithium-ion batteries has received great attention in recent years because of their growing popularity in electric vehicles. However, the safety issues of prismatic batteries have not been thoroughly studied; in particular, the mechanical responses of prismatic battery cells with lateral constraints under varied loading conditions still remain unclear.In this study, indentation tests are conducted to study the mechanical response of prismatic battery cells. Fixtures providing lateral constraint which simulates the real packing situation in battery module are designed. Firstly, the effects of lateral constraints on coupled mechanical and electrical responses of prismatic battery cells are analyzed and discussed. Secondly, dynamic indentation tests of prismatic cells with lateral constraints are carried out. The response of the stacked batteries under local loading is revealed. Thirdly, non-destructive X-ray computed tomography imaging technique is employed to detect the fracture patterns in battery cells caused by indentation.The results of indentation tests indicate that the indentation depth and the peak force for the battery internal failure are affected by the side constraint conditions and the responses of…
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The Review of Vehicle Purchase Restriction in China

Tsinghua University-Feiqi Liu, Han Hao, Fuquan Zhao, Zongwei Liu
  • Technical Paper
  • 2020-01-0972
To be published on 2020-04-14 by SAE International in United States
In the past two decades, rapidly expanding economy in China led to burst in travel demand and pursuit of quality of life. It further promoted the rapid growth of China's passenger car market. China had already become the largest vehicle sales country, exceeding the U.S. in 2010. By the end of 2018, there had been over 240 million cars in China, with over 200 million passenger cars. The surge of car ownership has also brought a series of problems, like traffic congestion, long commuting time, insufficient parking space, etc. Therefore, some local governments in China introduced vehicle purchase restriction policies to control the growth and gross of vehicle stock. Different cities issued different rules. Lottery and auction mechanisms both exist. There are also differences in classification and licensing of electric vehicles. However, with the recent slowdown of economic development, China's car sales began to decline in 2018, and the trend of 2019 is also not optimistic. As a result, the central government issued document, indicating that it is strictly forbidden to introduce new restrictions on…
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Decision making and trajectory planning of a novel vehicle lane-changing control method inspired by automatic parallel parking

Tsinghua University-Liangyao Yu, Ze Ru, Zhenghong Lu, Guanqun Liang, Cenbo Xiong, Abi Lanie, Ruyue Wang
  • Technical Paper
  • 2020-01-0134
To be published on 2020-04-14 by SAE International in United States
With the development of automation technology in automobiles, lane-changing systems have been developed and applied to improve environmental adaptability of advanced driver assistant system (ADAS) as well as driver comfort. Lane-changing control consists of three steps: decision making, trajectory planning and trajectory tracking. Decision making and trajectory planning are usually integrated in recent studies, where decision making is related to potential trajectories so that environmental adaptability is improved. However, current methods are not perfect due to weaknesses like high computation cost, low robustness to uncertainties, etc. In this paper, a novel lane changing control method is proposed, where lane-changing behavior is analogized to parallel parking behavior. The focus of this study lies on decision making and trajectory planning. In the perspective of host vehicle with lane-changing intention, the space between vehicles in the target adjacent lane can be regarded as dynamic parking space. A decision making and trajectory planning algorithm of parallel parking is adapted to deal with lane-changing condition. The adopted algorithm is based on rules which checks lane-changing feasibility and generates desired path…
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Super-Twisting Second-Order Sliding Mode Control for Automated Drifting of Distributed Electric Vehicles

Tsinghua University-Xiaohui Hou, Junzhi Zhang, Weilong Liu, Yuan Ji
  • Technical Paper
  • 2020-01-0209
To be published on 2020-04-14 by SAE International in United States
Studying drifting dynamics and control could extend the usable state-space beyond handling limits and maximize the potential safety benefits of autonomous vehicles. Distributed electric vehicles provide more possibilities for drifting control with better grip and larger maximum drift angle. Under the state of drifting, the distributed electric vehicle is a typical nonlinear over-actuated system with actuator redundancy, and the coupling of input vectors impedes the direct use of control algorithm of upper. This paper proposes a novel automated drifting controller for the distributed electric vehicle. First, the nonlinear over-actuated system, comprised of driving system, braking system and steering system, is formulated and transformed to a square system through proposed integrative recombination method of control channel, making general nonlinear control algorithms suitable for this system. On this basis, a super-twisting second-order sliding mode controller is designed to generate the desired virtual control input, pushing the vehicle to the performance and operating limits while keeping in the quasi-equilibrium state. Finally, an online control allocation is designed to translate the virtual control input to the longitudinal and lateral…
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Comparison of spray collapses from multi-hole and single-hole injectors using high-speed photography

Tsinghua University-Lu Xinhui, Yi Gong, Xiao Ma, Shijin Shuai, Omar Awad
Harbin Institute of Technology-Yitao Shen
  • Technical Paper
  • 2020-01-0321
To be published on 2020-04-14 by SAE International in United States
In this paper, the differences between multi-hole and single-hole spray contour under the same conditions were compared by using high-speed photography. The difference between the contour area of multi-hole and that of single-hole spray was used as a parameter to describe the degree of spray collapse. Three dimensionless parameters (i.e. degree of superheat, degree of undercooling, and nozzle pressure ratio) were applied to characterize inside-nozzle thermodynamic, outside-nozzle thermodynamic and kinetic factors, respectively. In addition, the relationship between the three dimensionless parameters and the spray collapse was analyzed. A semi-empirical equation was proposed for evaluation of the degree of collapse based on dimensionless parameters of flash and non-flash boiling sprays respectively.
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Effect of Oil Viscosity and Driving Mode on Oil Dilution and Transient Emissions Including Particle Number in Plug-in Hybrid Electric Vehicle

Tsinghua University-Qinhao Fan, Yunfei Wang, Jianhua Xiao, Zhi Wang
Shell (Shanghai) Technology Limited-Weizi Li, Tian Jia, Bin Zheng
  • Technical Paper
  • 2020-01-0362
To be published on 2020-04-14 by SAE International in United States
Plug-in electric vehicle (PHEV) has a promising prospect to reduce greenhouse gas (GHG) emission and optimizes engine operating in high-efficiency region. According to the maximum electric power and all-electric range, PHEVs are divided into two categories, including “all-electric PHEV” and “blended PHEV” and the latter provides a potential for more rational energy distribution because engine participates in vehicle driving during aggressive acceleration not just by motor. However, the frequent use of engine may result in severe emissions especially in low state of charge (SOC) and ahead of catalyst light-off. This study quantitatively investigates the impact of oil viscosity and driving mode (hybrid/conventional) on oil dilution and emissions including particle number (PN). Two cycles, WLTC (World-wide Harmonized Light Duty Driving Test Cycle) and continuous ECE 15 (European Driving Cycle), were adopted and initial SOC was controlled in the range of 10-13%, which can induce more engine start events. Oil dilution is detected through method of ASTM D3525-04 to identify dilution rate under different conditions. Results show that both in WLTC and ECE 15, frequent engine start…
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A Personalized Deep Learning Approach for Trajectory Prediction of Connected Vehicles

Tsinghua University-Yahui Liu, Hong Wang
Nanyang Technological University-Yang Xing, Chao Huang, Chen Lv
  • Technical Paper
  • 2020-01-0759
To be published on 2020-04-14 by SAE International in United States
Forecasting the motion of the leading vehicle is a critical task for connected autonomous vehicles as it provides an efficient way to model the leading-following vehicle behavior and analyze the interactions. In this study, a personalized time-series modeling approach for leading vehicle trajectory prediction considering different driving styles is proposed. The method enables a precise, personalized trajectory prediction for leading vehicles with limited inter-vehicle communication signals, such as vehicle speed, acceleration, space headway, and time headway of the front vehicles. Based on the learning nature of human beings that a human always tries to solve problems based on grouping and similar experience, three different driving styles are first recognized based on an unsupervised clustering with a Gaussian Mixture Model (GMM). The GMM generates a specific driving style for each vehicle based on the speed, acceleration, jerk, time, and space headway features of the leading vehicle. Then, a personalized joint time-series modeling (JTSM) method based on the Long Short-Term Memory (LSTM) Recurrent Neural Network model (RNN) is proposed to predict the trajectory of the front vehicle.…
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Modelling of a combined system of hydraulic magnetorheological fluid damper with braking-by-wire system

Tsinghua University-Cenbo Xiong, Liangyao Yu, Zhenchuan Li, Zhenghong Lu, Abi Lanie
  • Technical Paper
  • 2020-01-0988
To be published on 2020-04-14 by SAE International in United States
A hydraulic chamber is embedded in serial with the accumulator of a normal mono-tube magnetorheological fluid damper (MRFD). The damper stiffness can be adjusted by changing the initial accumulator volume with the hydraulic chamber. This hydraulic chamber is connected to an electric pump and controlled by the braking-by-wire system. Some signals and control parameters of the braking system are shared with the suspension system. A modified bi-viscosity magnetorheological fluid (MRF) model that explicitly includes the parameter of control current is adopted to determine the viscous forces of the damper. A dynamic model of this hydraulic MRFD is subsequently set up based on the hydro dynamic system and the MRF model. In this scheme, both the MRF viscosity and the damper stiffness can be continuously adjusted at the same time. A theoretical model combining the vehicle dynamics, the braking-by-wire system and the hydraulic MRFD is established based on which the control principles of the hydraulic MRFD according to the braking intensity are revealed. Simulations are carried out to study the parametric influences of this combined braking…