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Technical Paper

An Outer Loop of Trajectory and an Inner Loop of Steering Angle for Trajectory Tracking Control of Automatic Lane Change System

2019-11-04
2019-01-5029
Automatic Lane Change (ALC) function is an important step to promote the currently popular Advanced Driver Assistance Systems (ADAS) within a single lane. The key issue for ALC is accurate steering angle and trajectory tracking during the lane changing process. In this paper, an MPC controller with a receding horizon is designed to track the desired trajectory. During the tracking process, other objectives such as safety and smoothness are considered. Considering of the practical mechanism and parameter uncertainties, an SMC controller is designed to track the target steering angle. For validation, a Hardware-in-the-Loop (HIL) experiment platform is established, and experiments of different control algorithms under different conditions are carried out successively. Comparisons of the experiment results of MPC+SMC and PID+SMC schemes indicate that both the trajectory error and the steering angle error of the former combination are smaller.
Technical Paper

Proton Exchange Membrane Fuel Cell Fault Rapid Diagnosis Method Based on Electrochemical Impedance Spectroscopy and Fuzzy C-Means Algorithm

2019-11-04
2019-01-5032
Water management is a key research direction for the performance and lifetime of proton exchange membrane fuel cell (PEMFC) stacks. The paper is aimed to develop an online fault diagnosis method that distinguishes different degrees of flooding and drying within a fuel cell stack by unobservable variables. In our research, the equivalent circuit model is established and electrochemical impedance spectroscopy (EIS) is utilized. The mathematical methods are used to extract the fault features. Fuzzy C-means is used to classify the selected features and the diagnostic rules are automatically extracted from the data. Through verification, the interpretability and computational efficiency of the proposed method are achieved.
Technical Paper

Parameter Identification for One-Dimension Fuel Cell Model Using GA-PSO Algorithm

2019-11-04
2019-01-5041
When studying on how to identify the proton exchange membrane fuel cell model parameters accurately and quickly, the model frequently used is a lumped parameter model. Compared to this kind of model, one-dimensional dynamic proton exchange membrane fuel cell model can correlate the physical parameters with output characteristics of fuel cell to predict the effects of design parameters, materials and environmental conditions, thus reducing the need for experimentation. However, there is little literature about parameter identification for one-dimensional dynamic models currently. In this paper, a one-dimension dynamic proton exchange membrane fuel cell model with many assumptions for reducing the complexity of calculation is realized in Matlab-Simulink environment. The model consists of five interacting subsystems.
Technical Paper

Study on Air Pressure-Flow Decoupling Control in Fuel Cell System Based on Feedforward Algorithm

2019-11-04
2019-01-5042
Proton exchange membrane fuel cell (PEMFC) system is considered to be one of the ideal replacement for conventional Internal Combustion Engines (ICE) due to its zero emission, low operating temperature and high power density. The high-pressure PEMFC system has become the future development direction because the higher gas pressure can effectively improve the performance and power density of stack. However, the high gas pressure can lead to the damage of membrane electrode assembly (MEA) and even the failure of fuel cell stack. As the air supply system is a nonlinear system, the flow and pressure have a strong coupling relation. For this problem, firstly, the mathematical model of air supply system is established in MATLAB/Simulink. Then a dual-loop control strategy is used in controller.
Technical Paper

Composite Steering Strategy for 4WS-4WD EV Based on Low-Speed Steering Maneuverability

2019-11-04
2019-01-5052
A composite steering control strategy, which combines four-wheel steering (4WS) and differential steering, is proposed in this paper, to optimize steering maneuverability in the conditions where the vehicle speed is below 15 Km/h, mainly for U-turning and parking conditions. A dynamic model is developed for the steering system and the tire system. Taking different steering wheel inputs into consideration, a 4WS control strategy proportional to the front wheel steering angle is quoted to improve the steering maneuverability in the low speed conditions and guarantee the manipulability by controlling the side slip of the vehicle. Based on the 4WS system, this paper explores the possibility of further improving the low-speed maneuverability of the vehicle through differential steering. And the differential steering control strategy is developed, including four hub-motor output modes. A composite steering controller is designed based on the 4WS-4WD electric vehicle platform.
Technical Paper

Durability Performance of Polymer Electrolyte Membrane Fuel Cells under Open-Circuit Voltage

2019-11-04
2019-01-5076
Polymer electrolyte membrane fuel cells (PEMFCs) are a good candidate for fuel cell electric vehicles (FCEVs) due to their high efficiency, high power density and zero-emission. However, the lifetime is one of the main barriers to overcome before their commercialization. The durability testing methods for PEMFCs are main include electrocatalyst cycle, catalyst support cycle, membrane electrode assembly (MEA) chemical stability, membrane mechanical cycle and so on. In addition, there is little research about MEA chemical stability test, which applies a continuous open-circuit voltage (OCV) to produce more free radicals and these will have a bad influence on PEMFCs. Based on this, the durability of PEMFC was studied under OCV operation at 30% relative humidity (RH), 90 °C and 150 kPa inlet pressure. The electrochemical performances such as in-situ cyclic voltammetry (CV), linear sweep voltage (LSV) and cell polarization were used to evaluate the durability of PEMFC.
Technical Paper

Research on Control Algorithm of Air Supply System for High-Pressure PEMFC Engine

2019-04-02
2019-01-0379
The Proton Exchange Membrane Fuel Cell (PEMFC) is the most widely used engine in fuel cell vehicles. For PEMFC, whether the supply of oxygen for cathode is adequate or not is a critical factor for its net output power and service life, and the proper control of air supply mass flow and pressure can effectively improve its system performance and efficiency. At present, fuel cells need to reduce the mass and volume and increase the power density. Therefore, it is necessary to increase the air supply pressure for PEMFC. But at the same time, many auxiliary devices are appended to the system to provide high-pressure air, such as air compressor, intercooler, and back pressure valve, which make the control of the entire air supply system very complicated. So an excellent control algorithm is needed.
Technical Paper

DC/DC Modeling and Current Harmonic Analysis in Fuel Cell Hybrid Power System

2019-04-02
2019-01-0375
Fuel cells directly convert the energy stored in hydrogen into electrical energy through an electrochemical reaction, and the only reaction product is water, which can improve the energy efficiency and reduce the pollution caused by fossil fuels. The fuel cell hybrid power system used in vehicles usually consists of a fuel cell stack and a power battery module, and the DC/DC converter is the key component to connect them together. The current ripples caused by the system have been confirmed to have detrimental effects on the fuel cell’s reliability and lifespan. In addition, it is one of the key factors that reduce the system efficiency. So, it is necessary to analyze the current ripple in the system and maintain it at a low level. In this paper, a brief review on the different kinds of converters used in vehicles has been made. Then, with the help of MATLAB/SIMULINK, a simulation model of the hybrid power system based on 4-phase interleaved parallel topology is established.
Technical Paper

Real-Time Testing Technology of Powertrain System in Proton Exchange Membrane Fuel Cell Electric Vehicles: A Review

2019-04-02
2019-01-0371
The proton exchange membrane fuel cell (PEMFC) vehicle is one kind of new energy vehicle with fuel cell as power source, which has environmental friendliness, high power density and quick refueling. However, the productlization testing in powertrain system, especially for subsystems and key parts, is one of the critical technical challenges, which restricts the industry development and large-scale commercialization of fuel cell electric vehicles (FCEVs). In this paper, comprehensive testing requirement and latest testing technologies were reviewed, the development status and directions of testing technologies in FCEV powertrain system were presented. Based on comprehensive analysis, X-in-the-Loop (XiL) testing technology was proposed, and it is quite helpful to improve Real-time testing performance and functions for FCEV powertrain system. Furthermore, real-time and reliability as the two key factors for the XiL application was deeply analyzed and discussed.
Technical Paper

Voltage and Voltage Consistency Attenuation Law of the Fuel Cell Stack Based on the Durability Cycle Condition

2019-04-02
2019-01-0386
Based on the durability cycle test of fuel cell stack and the characteristics of cyclic working conditions, this paper defines the characteristic current point and studies the attenuation rule of the fuel cell stack voltage over time under the characteristic current point. The results show that the voltage of the fuel cell stack appears to be linear downward under the characteristic current point. and the voltage attenuation rate of the fuel cell stack increases quadratically with the increase of the current density in addition to the open-circuit voltage point. Then the coefficient of variation is introduced in statistics as the index to characterize the voltage consistency attenuation of the fuel cell stack, and its variation rule is explored. The results show that the voltage consistency of vehicle fuel cell stack decreases seriously with the increase of running time under the condition of durable cycling.
Technical Paper

Combined Technologies for Efficiency Improvement on a 1.0 L Turbocharged GDI Engine

2019-04-02
2019-01-0233
The CO2 reduction request for automotive industry promotes the efforts on the engine thermal efficiency improvement. The goal of this research is to improve the thermal efficiency on an extremely downsized 3-cylinder 1.0 L turbocharged gasoline direct injection engine. Effects of compression ratio, exhaust gas recirculation (EGR), valve timing and viscosity of oil on fuel economy were studied. The results show that increasing compression ratio, from 9.6 to 12, can improve fuel economy at relative low load (below 12 bar BMEP), but has a negative effect at high load due to increased knock intensity. EGR can significantly reduce the pumping loss at low load, optimize combustion phase and reduce exhaust gas temperature. Therefore, the fuel consumption is reduced at all test points. The average brake thermal efficiency (BTE) benefit percentage is 3.47% with 9.6 compression ratio and 5.33 % with 12 compression ratio.
Technical Paper

Simulation Investigation of Working Process and Emissions on GDI Engine Fueled with Hydrous Ethanol Gasoline Blends

2019-04-02
2019-01-0219
Compared with ordinary gasoline, using ethanol gasoline blends as fuel of Internal Combustion Engine is beneficial for the performance of power, economy and emission of engine. However, the fuel ethanol blended in ethanol gasoline blends currently is usually anhydrous ethanol, which requires dewatering implementer in production process, and the cost is high. Therefore, the production cost can be significantly reduced by replacement of anhydrous ethanol with hydrous ethanol while exerting the advantage of ethanol gasoline blends. In this study, computation fluid dynamics (CFD) software CONVERGE is employed to establish a simulation model of an actual gasoline direct injection (GDI) engine, and investigate the effect of burning hydrous ethanol gasoline blends and different injection strategy on combustion process and emission, and the validity of the model was validated by experiments.
Technical Paper

Analysis of the Statistical Energy Consumption and Its Application to an Economic Evaluation of Plug-In Hybrid Electric Vehicles

2019-04-02
2019-01-0933
The energy consumption depends not only on the structures of vehicles but also on their operating conditions. For vehicles with the same structure, the operating conditions will vary from driver to driver. In this paper, considering the difference of operating conditions, the concept of statistical energy consumption is proposed to reveal the statistical law of actual vehicle energy consumption. In this paper, a plug-in hybrid electric vehicle (PHEV) is taken as the research object. Based on the distribution law of three vehicle use factors, i.e. vehicle mass, daily driving distance and driving aggression, Monte Carlo method is used to simulate and calculate the statistical energy consumption and statistical comprehensive energy consumption. Then, the energy consumption values that only considered the daily driving distance is calculated.
Technical Paper

Lumped Parameter Transient Thermal Model of Motor Considering Temperature and Flow Rate of Cooling Water

2019-04-02
2019-01-0890
The influence of heat flow and cooling water characteristics on motor temperature cannot be accurately reflected by the traditional motor temperature analysis method. In order to study the motor and its key components’ temperature characteristics under different temperatures and flow rates of cooling water, this paper establishes the lumped parameter transient thermal model which includes cooling water module, based on a 50kW permanent magnet synchronous motor. The transient and steady temperature is calculated through this model together with the motor loss calculation module in the electric drive system model. The influence of different temperature and flow rate of cooling water on motor and its key components’ temperature characteristics is compared. During the modeling process, the motor body is divided into 14 parts, based on the internal heat flow path of the motor. The thermal resistance of each key component and cooling water is calculated.
Technical Paper

Topology Optimization of Metal and Carbon Fiber Reinforced Plastic (CFRP) Structures under Loading Uncertainties

2019-04-02
2019-01-0709
Carbon fiber reinforced plastic (CFRP) composite materials have gained particular interests due to their high specific modulus, high strength, lightweight and perfect corrosion resistance. However, in reality, CFRP composite materials cannot be used alone in some critical places such as positions of joints with hinges, locks. Therefore, metal reinforcements are usually necessary in local positions to prevent structure damage. Besides, if uncertainties present, obtained optimal structures may experience in failures as the optimization usually pushes solutions to the boundaries of constraints and has no room for tolerance and uncertainties, so robust optimization should be considered to accommodate the uncertainties in practice. This paper proposes a mixed topology method to optimize metal and carbon fiber reinforced plastic composite materials simultaneously under nondeterministic load with random magnitude and direction.
Technical Paper

Numerical Study of Intake Manifold Water Injection on Characteristics of Combustion and Emissions in a Heavy-Duty Natural Gas Engine

2019-04-02
2019-01-0562
The performances of heavy-duty natural gas engines have been limited by combustion temperature and NOx emissions for a long time. Recently, water injection technology has been widely considered as a technical solution in reducing fuel consumption and emissions simultaneously in both gasoline and diesel engines. This paper focuses on the impacts of intake manifold water injection on characteristics of combustion and emissions in a natural gas heavy-duty engine through numerical methods. A computational model was setup and validated with experimental data of pressure traces in a CFD software coupled with detailed chemical kinetics. The simulation was mainly carried out in low-speed and full-load conditions, and knock level was also measured and calculated by maximum amplitude of pressure oscillations (MAPO).
Technical Paper

Research and Development of an Electromagnetic Actuated Active Suspension

2019-04-02
2019-01-0858
Active suspension could achieve good ride comfort and road holding performance. Traditional active suspension which utilizes air actuator or hydraulic actuator features relatively slow response or high energy consumption. Utilizing Permanent Magnet Synchronous Motor (PMSM) as actuator, the Electromagnetic Actuated Active Suspension (EAAS) benefits quick response and energy harvesting from vibration at the same time. Benchmarked with luxury cars available on the market, design parameters and design boundary are determined. A mechanism includes push bar and bell crank is designed to transfer the rotary motion of PMSM into linear motion of suspension, or verse vice. A prototype of EAAS is built in compromise of limited budget and a test bench is designed and set up. Different from conventional quarter car model, the model of EAAS in this paper is investigated and the total inertial of PMSM, gearbox and suspension control arms are calculated and simplified as an equivalent mass.
Technical Paper

Study on Real-World NOx and Particle Emissions of Bus: Influences of VSP and Fuel

2019-04-02
2019-01-1181
In this study, the real-world NOx and particle emissions of buses burning pure diesel fuel (D100), biodiesel fuel with 20% blend ratio (B20) and liquefied natural gas (LNG) were measured with portable emission measurement system (PEMS). The measurement conducted at 6 constant speed, which ranged from 10km/h to 60 km/h at 10km/h intervals, and a period of free driving condition. The relationship between vehicle specific power (VSP) and NOx/particle emissions of each bus were analyzed. The results show that the change rules of NOx, PN and PM emission factors with the increase of VSP were basically the same for the same bus, but for the bus using different fuel, the change rules may change. In VSP bin 0, the vehicles were mostly in idle condition and the emission factors of NOx, PN and PM of three buses were all in a relatively high level. In low VSP interval, which ranged from bin 0 to bin 4, the emissions of three buses first decreased and then increased with the growth of VSP.
Technical Paper

Experiment Studies of Charging Strategy for Lithium-Ion Batteries

2019-04-02
2019-01-0792
Regarding the lithium-ion batteries used in the electric vehicle, charging time and charging efficiency are the concern of the public. In this paper, a lot of experiments were conducted to investigate the common charging strategies, including the CC-CV (constant current-constant voltage) charging and the pulse current charging, for the LiFePO4 batteries, which are still widely used in commercial vehicles. Charging temperature and the charging current in the CC phase are the main influence factors to be studied for the CC-CV charging strategy, and the contribution of the CC phase and CV phase to the whole charging is analyzed from three aspects, including the time percent, charging energy efficiency and the capacity of battery at different temperatures and charging current.
Technical Paper

Optimization and Implementation of Three-Phase PMSM Current Harmonic Decomposition Technique

2019-04-02
2019-01-0604
With the development of electric vehicle (EV), permanent magnet synchronous motor (PMSM) has received more and more attention. PMSM torque ripple suppression is one of the core technologies of PMSM control. Current harmonic injection method is a commonly used torque ripple suppression method. In order to accurately control the injecting current harmonics, it is necessary to quickly and efficiently decompose the three-phase PMSM current harmonics first. In this paper, an existing instantaneous harmonic decomposition method based on multiple reference coordinates is adopted. First, the causes of the analysis error of the harmonic decomposition technique are analyzed which are divided into internal factors (e.g. analysis errors generated during the discretization of continuous functions) and external factors (e.g. sampling errors). Analysis errors will directly affect the decomposition result.
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