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Technical Paper

3D Automotive Millimeter-Wave Radar with Two-Dimensional Electronic Scanning

2017-03-28
2017-01-0047
The radar-based advanced driver assistance systems (ADAS) like autonomous emergency braking (AEB) and forward collision warning (FCW) can reduce accidents, so as to make vehicles, drivers and pedestrians safer. For active safety, automotive millimeter-wave radar is an indispensable role in the automotive environmental sensing system since it can work effectively regardless of the bad weather while the camera fails. One crucial task of the automotive radar is to detect and distinguish some objects close to each other precisely with the increasingly complex of the road condition. Nowadays almost all the automotive radar products work in bidimensional area where just the range and azimuth can be measured. However, sometimes in their field of view it is not easy for them to differentiate some objects, like the car, the manhole covers and the guide board, when they align with each other in vertical direction.
Technical Paper

A Comparative Study of Different Wheel Rotating Simulation Methods in Automotive Aerodynamics

2018-04-03
2018-01-0728
Wheel Aerodynamics is an important part of vehicle aerodynamics. The wheels can notably influence the total aerodynamic drag, lift and ventilation drag of vehicles. In order to simulate the real on-road condition of driving cars, the moving ground and wheel rotation is of major importance in CFD. However, the wheel rotation condition is difficult to be represented exactly, so this is still a critical topic which needs to be worked on. In this paper, a study, which focuses on two types of cars: a fastback sedan and a notchback DrivAer, is conducted. Comparing three different wheel rotating simulation methods: steady Moving wall, MRF and unsteady Sliding Mesh, the effects of different methods for the numerical simulation of vehicle aerodynamics are revealed. Discrepancies of aerodynamic forces between the methods are discussed as well as the flow field, and the simulation results are also compared with published experimental data for validation.
Journal Article

A Comprehensive Validation Method with Surface-Surface Comparison for Vehicle Safety Applications

2017-03-28
2017-01-0221
Computer Aided Engineering (CAE) models have proven themselves to be efficient surrogates of real-world systems in automotive industries and academia. To successfully integrate the CAE models into analysis process, model validation is necessarily required to assess the models’ predictive capabilities regarding their intended usage. In the context of model validation, quantitative comparison which considers specific measurements in real-world systems and corresponding simulations serves as a principal step in the assessment process. For applications such as side impact analysis, surface deformation is frequently regarded as a critical factor to be measured for the validation of CAE models. However, recent approaches for such application are commonly based on graphical comparison, while researches on the quantitative metric for surface-surface comparison are rarely found.
Technical Paper

A Control Allocation Strategy for Electric Vehicles with In-wheel Motors and Hydraulic Brake System

2015-04-14
2015-01-1600
Distributed drive electric vehicle (EV) is driven by four independent hub motors mounted directly in wheels and retains traditional hydraulic brake system. So it can quickly produce driving/braking motor torque and large stable hydraulic braking force. In this paper a new control allocation strategy for distributed drive electric vehicle is proposed to improve vehicle's lateral stability performance. It exploits the quick response of motor torque and controllable hydraulic pressure of the hydraulic brake system. The allocation strategy consists of two sections. The first section uses an optimal allocation controller to calculate the total longitudinal force of each wheel. In the controller, a dynamic efficiency matrix is designed via local linearization to improve lateral stability control performance, as it considers the influence of tire coupling characteristics over yaw moment control in extreme situations.
Technical Paper

A Development And Test Environment for Automotive LIN Network

2008-06-23
2008-01-1519
“LIN-BOX” is designed as a development tool for simulation, implementation and test of the automotive LIN (Local Interconnect Network) control devices or entire network. The tool can be used to simulate master and/or slaves around LIN system. The configurable signal processing makes it possible to simulate and test the communication behavior. LIN-BOX monitors the bus traffic in the vehicle. The data on LIN bus can not only be shown on various windows but also written into log files. LIN-BOX has been used by several cases for debugging and validation, the result shows that it is a powerful tool for LIN cluster design, simulation and test.
Technical Paper

A Lattice Boltzmann Simulation of Gas Purge in Flow Channel with Real GDL Surface Characteristics for Proton Exchange Membrane Fuel Cell

2019-04-02
2019-01-0389
Gas purge is considered as an essential shutdown process for a PEMFC (Proton Exchange Membrane Fuel Cell), especially in subfreezing temperature. The water flooding phenomenon inside fuel cell flow channel have a marked impact on performance in normal operating condition. In addition, the residual water freezes in the subzero temperature, thus blocking the mass transfer from flow channel to porous media. Therefore, the gas purge course is of primary importance for improvement of performance and durability. The water droplet residing in the flow channel can be purged out due to shearing force of gas. In fact, the flow channel is not completely flat due to surface roughness of gas diffusion layer (GDL), meaning the water droplet may climb over obstacles. Moreover, the water droplet may block the flow channel and then be sheared into films on the surface of GDL.
Technical Paper

A Lithium-Ion Battery Optimized Equivalent Circuit Model based on Electrochemical Impedance Spectroscopy

2015-04-14
2015-01-1191
An electrochemical impedance spectroscopy battery model based on the porous electrode theory is used in the paper, which can comprehensively depict the internal state of the battery. The effect of battery key parameters (the radius of particle, electrochemical reaction rate constant, solid/electrolyte diffusion coefficient, conductivity) to the simulated impedance spectroscopy are discussed. Based on the EIS analysis, a lithium-ion battery optimized equivalent circuit model is built. The parameters in the equivalent circuit model have more clear physical meaning. The reliability of the optimized equivalent circuit model is verified by compared the model and experiments. The relationship between the external condition and internal resistance could be studied according to the optimized equivalent circuit model. Thus the internal process of the power battery is better understood.
Technical Paper

A Lumped Parameter Model Concerning the Amplitude-Dependent Characteristics for the Hydraulic Engine Mount with a Suspended Decoupler

2019-04-02
2019-01-0936
This paper presents a novel lumped parameter model(LPM) and its parameter identification method for the hydraulic engine mount(HEM) with a suspended decoupler. In the new model the decoupler membrane’s variable stiffness caused by being contact with the metallic cage is considered. Therefore, the decoupler membrane in the model can be taken as a spring. As a result, two parameters of the decoupler’s variable stiffness and the equivalent piston area are added. Then the finite element method is employed to analyze the suspended decoupler membrane’s variable stiffness characteristics under the contact state with the metallic cage. A piecewise polynomial is used to fit the decoupler membrane’s variable stiffness. To guarantee the symmetry of the stiffness, the polynomial only keeps the odd power coefficients.
Technical Paper

A Method of Acceleration Order Extraction for Active Engine Mount

2017-03-28
2017-01-1059
The active engine mount (AEM) is developed in automotive industry to improve overall NVH performance. The AEM is designed to reduce major-order signals of engine vibration over a broad frequency range, therefore it is of vital importance to extract major-order signals from vibration before the actuator of the AEM works. This work focuses on a method of real-time extraction of the major-order acceleration signals at the passive side of the AEM. Firstly, the transient engine speed is tracked and calculated, from which the FFT method with a constant sampling rate is used to identify the time-related frequencies as the fundamental frequencies. Then the major-order signals in frequency domain are computed according to the certain multiple relation of the fundamental frequencies. After that, the major-order signals can be reconstructed in time domain, which are proved accurate through offline simulation, compared with the given signals.
Technical Paper

A New Kind of Road Structure-Borne N&V Prediction Method Based on Combination of High-Frequency Parameterized Model of Bushes, Multi-Body Calculation on Adams and Finite Element Model

2018-04-03
2018-01-0139
Road NVH are becoming one of important performance controlled during passenger vehicle NVH development, especially for these EV vehicles due to lack of traditional gasoline or diesel engines noise sources. Generally speaking, traditional CAE and multi-body dynamic approaches have several drawbacks respectively, such as it is extremely difficult to get precise inputs as excitation to CAE model and non-linear parts in suspensions perform complex high frequency dynamic characteristics that is hard to be dealt with in multi-body software. Therefore, structure-borne road noise prediction has become one of difficult NVH problems in vehicle industry and eagerly, needs a systematic and scientific method. Under this circumstance, a new kind of high frequency road N&V co-simulation method has been introduced here to predict road NVH performance for one brand vehicle. This new approach includes three steps.
Technical Paper

A New Method of Comprehensive Evaluation Research and Application on Vehicle Engine Exhaust System

2018-04-15
2018-01-5011
During current design process of vehicle engine exhaust system, the frequently-used approach mainly concerns an individual component, which usually results in not meeting the overall design requirements or unreasonable design parameters. Here a concept of comprehensive evaluation metrics for vehicle engine exhaust system was established, of which a new weight factor assignment method was proposed, named change rate method, as the core of evaluation system to be especially studied. Taking muffler as an instance, six weight factor assignment schemes were adopted to compare with each other. And the rationality and practicability of the change rate assignment method was verified by the muffler noise experiments. The results show that, the change rate method makes the weight assignment more scientific and rigorous. And the new method can reflect the wishes of designers and completely displays the performance comparison and evaluation between schemes.
Technical Paper

A Novel Battery Impedance Model Considering Internal Temperature Gradient

2018-04-03
2018-01-0436
Battery models are often applied to describe the dynamic characteristics of batteries and can be used to predict the state of the battery. Due to the process of charging and discharging, the battery heat generation will cause the inhomogeneity between inner battery temperature and surface temperature. In this paper, a novel battery impedance model, which takes the impact of the battery internal temperature gradient on battery impedance into account, is proposed to improve the battery model performance. Several experiments are designed and conducted for pouch typed battery to investigate the electrochemical impedance spectroscopy (EIS) characteristics with the artificial temperature gradient (using a heating plate). Experimental results indicate that the battery internal temperature gradient will influence battery EIS regularly.
Journal Article

A Novel ZSB-PAM Power Regulation Method Applied in Wireless Charging System for Vehicular Power Batteries

2015-04-14
2015-01-1194
Wireless charging system for vehicular power batteries is becoming more and more popular. As one of important issues, charging power regulation is indispensable for online control, especially when the distance or angle between chassis and ground changes. This paper proposes a novel power regulation method named Z-Source-Based Pulse-Amplitude-Modulation (ZSB-PAM), which has not been mentioned in the literatures yet. The ZSB-PAM employs a unique impedance network (two pairs of inductors and capacitors connected in X shape) to couple the cascaded H Bridge to the power source. By controlling the shoot-through state of H bridge, the input voltage to H bridge can be boosted, thus the transmitter current can be adjusted, and hence, charging current and power for batteries. A LCL-LCL resonant topology is adopted as the main transfer energy carrier, for it can work with a unity power factor and have the current source characteristic which is suitable for battery charging.
Journal Article

A Potential Field Based Lateral Planning Method for Autonomous Vehicles

2016-09-14
2016-01-1874
As one of the key technologies in autonomous driving, the lateral planning module guides the lateral movement during the driving process. An integrated lateral planning module should consider the non-holonomic constraints of a vehicle, the optimization of the generated trajectory and the applicability to various scenarios. However, the current lateral planning methods can only meet parts of these requirements. In order to satisfy all the performance requirements above, a novel Potential Field (PF) based lateral planning method is proposed in this paper. Firstly, a PF model is built to describe the potential risk of the traffic entities, including the obstacles, road boundaries and lines. The potential fields of these traffic entities are determined by their properties and the traffic regulations. Secondly, the planning algorithm is presented, which comprises three modules: state prediction, state search and trajectory generation.
Technical Paper

A Progress Review on Gas Purge for Enhancing Cold Start Performance in PEM Fuel Cell

2018-04-03
2018-01-1312
Cold start capability is one of remaining major challenges in realizing PEMFC (Proton Exchange Membrane Fuel Cell) technology for automotive applications. Gas purge is a common and integral shutdown procedure of a PEMFC automotive in subzero temperature. A dryer membrane electrode assembly (MEA) can store more water before it gets saturated and ice starts to penetrate in the open pores of porous media, thus enhancing cold start capability of a PEMFC. Therefore, gas purge is always performed prior to fuel cell shutdown to minimize residual water in a PEMFC. In the hope of improving effectiveness of purge in a PEMFC vehicle, two important purge parameters are evaluated including purge time and energy requirement. In practice, an optimized gas purge protocol should be developed with minimal parasitic energy, short purge duration and no degradation of components. To conclude, the cold start capability and performance can be consolidated by proper design of gas purge strategies.
Technical Paper

A Steerable Curvature Approach for Efficient Executable Path Planning for on-Road Autonomous Vehicle

2019-04-02
2019-01-0675
A rapid path-planning algorithm that generates drivable paths for an autonomous vehicle operating in structural road is proposed in this paper. Cubic B-spline curve is adopted to generating smooth path for continuous curvature and, more, parametric basic points of the spline is adjusted to controlling the curvature extremum for kinematic constraints on vehicle. Other than previous approaches such as inverse kinematics, model-based prediction postprocess approach or closed-loop forward simulation, using the kinematics model in each iteration of path for smoothing and controlling curvature leading to time consumption increasing, our method characterized the vehicle curvature constraint by the minimum length of segment line, which synchronously realized constraint and smooth for generating path. And Differ from the path of robot escaping from a maze, the intelligent vehicle traveling on road in structured environments needs to meet the traffic rules.
Technical Paper

A Study of Crevice HC Mechanism Based on the Transient HC Test Data and the Double Zone Combustion Model

2008-06-23
2008-01-1652
The effectiveness of after-treatment systems depends on the exhaust gas temperature, which is low during cold-start. As a result, Euro III, Euro IV and FTP75 require that the emissions tests include exhaust from the beginning of cold start. It is proved that 50%∼80% of HC and CO emissions are emitted during the cold start and the amount of unburned fuel from the crevices during starting is much higher than that under warmed engine conditions. The piston crevices is the most part of combustion chamber crevices, and results of mathematical simulations show that the piston crevice contribution to HC emissions is expected to increase during cold engine operation. Based on the transient HC test data and the double zone combustion model, this paper presents the study of the crevice HC Mechanism of the first firing cycle at cold start on an LPG SI Engine. A fast-response flame ionization detector (FFID) was employed to measure transient HC emissions of the first firing cycle.
Technical Paper

A Study of Parameter Inconsistency Evolution Pattern in Parallel-Connected Battery Modules

2017-03-28
2017-01-1194
Parallel-connected modules have been widely used in battery packs for electric vehicles nowadays. Unlike series-connected modules, the direct state inconsistency caused by parameter inconsistency in parallel modules is current and temperature non-uniformity, thus resulting in the inconsistency in the speed of aging among cells. Consequently, the evolution pattern of parameter inconsistency is different from that of series-connected modules. Since it’s practically impossible to monitor each cell’s current and temperature information in battery packs, considering cost and energy efficiency, it’s necessary to study how the parameter inconsistency evolves in parallel modules considering the initial parameter distribution, topology design and working condition. In this study, we assigned cells of 18650 format into several groups regarding the degree of capacity and resistance inconsistency. Then all groups are cycled under different environmental temperature and current profile.
Technical Paper

A Study on Optimization of the Ride Comfort of the Sliding Door Based on Rigid-Flexible Coupling Multi-Body Model

2017-03-28
2017-01-0417
To solve the problem of serious roller wear and improve the smoothness of the sliding door motion process, the rigid-flexible coupling multi-body model of the vehicle sliding door was built in ADAMS. Force boundary conditions of the model were determined to meet the speed requirement of monitoring point and time requirement of door opening-closing process according to the bench test specification. The results of dynamic simulation agreed well with that of test so the practicability and credibility of the model was verified. In the optimization of the ride comfort of the sliding door, two different schemes were proposed. The one was to optimize the position of hinge pivots and the other was to optimize the structural parameters of the middle guide. The impact load of lead roller on middle guide, the curvature of the motion trajectory and angular acceleration of the sliding door centroid were taken as optimization objectives.
Journal Article

A Study on the Bench Test of Friction-Induced Hot Spots in Disc Brake

2015-09-27
2015-01-2694
During light to moderate braking at high speed, the local high temperature phenomenon can be observed on the brake disc surfaces, known as hot spots. The occurrence of hot spots will lead to negative effects such as brake performance fade, thermal judder and local wear, which seriously affect the performance of vehicle NVH. In this paper, based on the bench test of a ventilated disc brake, the basic characteristics of hot spots is obtained and the evolution process of temperature field and disc deformation is analyzed in detail. In temperature field, hot bands appear first and grow, migrate from inner and outer radius to the middle, with the growing temperature fluctuation and finally hot spots appear in the middle radius of the brake disc. The stable SRO waviness forms much earlier than the temperature fluctuation. In the stop brake studied in this paper, the SRO waviness stabilizes in main 7 order state which is lower than the final hot spot order.
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