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Technical Paper

Acoustic characteristics prediction and optimization of wheel resonators with arbitrary section

2020-04-14
2020-01-0917
Tire cavity noise of pure electric vehicles is particularly prominent due to the absence of engine noise, which are usually eliminated by adding Helmholtz resonators with arbitrary transversal section to the wheel rims. This paper provides theoretical basis for accurately predicting and effectively improving acoustic performance of wheel resonators. A hybrid finite element method is developed to extract the transversal wavenumbers and eigenvectors, and the mode-matching scheme is employed to determine the transmission loss of the Helmholtz resonator. Based on the accuracy validation of this method, the matching design of the wheel resonators and the optimization method of tire cavity noise are studied. The identification method of the tire cavity resonance frequency is developed through the acoustic modal simulation and test. A scientific transmission loss target curve and fitness function are defined according to the noise characteristics.
Technical Paper

Characteristics of Transient NOx Emission of HEV under Real Road Driving

2020-04-14
2020-01-0380
To meet the request of China National 6b emission regulations which will be officially implemented in China, firstly including the RDE emission test limits, the transient emissions on real road condition are paid more attention. Several non-plug-in hybrid light-duty gasoline vehicles (HEV) sold in the Chinese market were selected to study real road emissions employed fast response NOx analyzer from Cambustion Ltd. with a sampling frequency of 100Hz. The concentration of NOx emissions before and after the TWC (Three Way Catalyst) of the hybrid vehicle were also sampled and analyzed, and the working efficiency of the TWC in real road driving process was investigated.
Technical Paper

Study on thermal management strategy of the exhaust gas of diesel engines based on in-cylinder injection parameters

2020-04-14
2020-01-0621
Due to high thermal efficiency, reliability and durability, less fuel consumption, and less carbon dioxide (CO2) emission, diesel engines are widely used in both stationary and mobile applications. However, an inherent combustion mode of diesel engines results in harmful emissions like hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM), the emissions can cause substantial damage to the human health and environment, so there are strict emission regulations to limit the harmful emissions. Diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) are important exhaust gas aftertreatment devices to oxidizing the HC, CO and PM in order to meet the requirements of emission regulations.
Technical Paper

An FxLMS controller for active control engine mount with experimental secondary path identification

2020-04-14
2020-01-0424
Active engine mounts (AEMs) notably contribute to ensuring superior performance of vehicle’s noise, vibration, and harshness. This paper incorporates a filtered-x-least-mean-squares (FxLMS) controller into the active control engine mount system to attenuate the transmitted force to the body. To avoid the error caused by substituting the load cell for acceleration transducer, the FIR model of the secondary path was obtained by experiment. Finally, a hardware-in-the-loop testing system is built to verify the performance of the active engine mount. It can be found from the test results that the vibration is reduced notably after control, which demonstrates the effectiveness of the active engine mount and the controller in vibration attenuation.
Technical Paper

Correlation of Objective and Subjective Evaluation in Automotive Brake Pedal Feel

2018-10-05
2018-01-1889
In order to establish the correlation between objective and subjective evaluation of brake pedal feel for passenger cars, road tests of brake pedal feel were carried out and an evaluation method was proposed. In the road tests, subjective scores and objective measurements were obtained under the conditions of uniform and emergency braking. The objective measurements include pedal preload, low deceleration pedal force and travel, moderate deceleration pedal force and travel, brake response time and brake linearity. Using the theory of analytic hierarchy process (AHP), the design process of the evaluation method was established. Key setups including the hierarchical structure model, the judgement matrix and the score calculation method of objective measurements were described in detail. Then, the correlation between subjective and objective scores was analyzed. It can be concluded that the evaluation method is effective and it can be applied to brake pedal feel assessment and adjustment.
Technical Paper

Open-Loop Characteristics Analysis and Control of High Speed On-Off Valve

2018-10-05
2018-01-1868
In the process of ABS control, the Anti-lock braking system (ABS) of the vehicle adjusts the wheel cylinder brake pressure through the hydraulic actuator so as to control the movement of the wheel. The high-speed on-off valve (HSV) is the key components of the Anti-lock braking system. HSV affects the performance of the hydraulic actuator and the valve response characteristics affects the Anti-lock braking system pressure response as well as braking effect. In this paper, the electromagnetic field theory and flow field theory of HSV are analyzed, and simulation analysis of electromagnetic field characteristics of HSV is done by ANSYS. Combined with the ANSYS analysis results, a precise physical model of HSV is constructed in AMESim. Meanwhile, the valve response characteristics are analyzed. Moreover, the influence of different wheel cylinder diameter and PWM carrier frequency on hydraulic braking force characteristics are analyzed.
Technical Paper

Coordinated Control under Transitional Conditions in Hybrid Braking of Electric Vehicle

2018-10-05
2018-01-1869
In the hybrid brake system of electric vehicle, due to the limitation of the motor braking force when the motor is at high speed and the failure of the regenerative braking force when the motor is at low speed, there are three transitional conditions in hybrid braking: the hydraulic brake system intervenes the braking, the hydraulic brake system withdraws the braking and the regenerative braking force withdraws the braking. Due to the response speed of the hydraulic system is slower than that of the motor, there is a large braking impact (the derivative of braking deceleration) in the transitional conditions of hybrid braking, which deteriorates the smoothness and comfort in braking. Aiming at the impact caused by the poor cooperation between the hydraulic braking force and the motor braking force, a coordinated strategy of double closed-loop feedback and motor force correction is proposed in this paper.
Technical Paper

Study on Brake Disc Dynamics under Asymmetric Thermal Loads

2018-10-05
2018-01-1901
In order to explore the generation mechanism of hot-spots on the automotive brake disc, disc tests under non-frictional thermal loads are carried out on the brake dynamometer test bench. In the tests, the oxy-acetylene flame is used as the heat source, and the distribution characteristics of the disc temperature and displacement are measured and analyzed. To confirm the mechanism of the disc deformation, a disc thermal buckling model using finite element method is established, and the key factors for the disc thermal buckling under thermal loads are further analyzed. It is found that the temperature circumferential gradient is small but the temperature radial gradient is large. The disc presents waviness deformation mode with 5th order in circumferential direction, which is the first thermal buckling mode of the disc. A method using spatial frequency spectrum has been proposed to find the critical time and load of thermal buckling.
Technical Paper

Precise Steering Angle Control of Lane Change Assist System

2017-09-23
2017-01-2002
After obtaining the optimal trajectory through the lane change decision and trajectory planning, the last key technology for the automatic lane change assist system is to carry out the precise and rapid steering actuation according to the front wheel angle demand. Therefore, an automatic lane change system model including a BLDCM (brushless DC motor) model, a steering system model and a vehicle dynamics model is first established in this paper. Electromagnetic characteristics of the motor, the moment of the inertia and viscous friction etc. are considered in these models. Then, a SMC (Sliding Mode Control) algorithm for the steering system is designed to follow the steering angle input. The control torque of the steering motor is obtained through the system model according to steering angle demand. After that, the control current is calculated considering of electromagnetic characteristics of the BLDCM. Debugging and optimization of the control algorithm are done through simulations.
Technical Paper

The Trajectory Planning of the Lane Change Assist Based on the Model Predictive Control with Multi-Objective

2017-09-23
2017-01-2004
The automatic lane change assist system is an intelligent driving assistance technology oriented to traffic safety, which requires trajectory planning of the lane change maneuver based on the lane change decision. A typical scene of lane change for overtaking is selected, where the front vehicle in the same lane and the rear vehicle in the left lane are deemed to be potential dangerous vehicles through the lane change. Lane change trajectory equation is first established according to the general law of steering wheel angle through lane changes. Based on the relative position, velocity and acceleration information of the dangerous vehicles and the lane change vehicle, motions of these surrounding dangerous vehicles are predicted. At the same time, a multi-objective optimization function is established based on the relative longitudinal safety boundary. The objectives are the minimum safety distance, the lane change time and the front wheel angle.
Technical Paper

The Effect of High-Power Capacitive Spark Discharge on the Ignition and Flame Propagation in a Lean and Diluted Cylinder Charge

2016-04-05
2016-01-0707
Research studies have suggested that changes to the ignition system are required to generate a more robust flame kernel in order to secure the ignition process for the future advanced high efficiency spark-ignition (SI) engines. In a typical inductive ignition system, the spark discharge is initiated by a transient high-power electrical breakdown and sustained by a relatively low-power glow process. The electrical breakdown is characterized as a capacitive discharge process with a small quantity of energy coming mainly from the gap parasitic capacitor. Enhancement of the breakdown is a potential avenue effectively for extending the lean limit of SI engine. In this work, the effect of high-power capacitive spark discharge on the early flame kernel growth of premixed methane-air mixtures is investigated through electrical probing and optical diagnosis.
Journal Article

Characteristics of Lubricants on Auto-ignition under Controllable Active Thermo-Atmosphere

2016-04-05
2016-01-0889
Downsizing gasoline direct injection engine with turbo boost technology is the main trend for gasoline engine. However, with engine downsizing and ever increasing of power output, a new abnormal phenomenon, known as pre-ignition or super knock, occurs in turbocharged engines. Pre-ignition will cause very high in-cylinder pressure and high oscillations. In some circumstances, one cycle of severe pre-ignition may damage the piston or spark plug, which has a severe influence on engine performance and service life. So pre-ignition has raised lots of attention in both industry and academic society. More and more studies reveal that the auto-ignition of lubricants is the potential source for pre-ignition. The auto-ignition characteristics of different lubricants are studied. This paper focuses on the ignition delay of different lubricants in Controllable Active Thermo-Atmosphere (CATA) combustion system.
Technical Paper

Cycle Resolved Combustion and Pre-Ignition Diagnostic Employing Ion Current in a PFI Boosted SI Engine

2015-04-14
2015-01-0881
An ion current sensor is employed in a 4 cylinder production SI engine for combustion diagnosis during combustion process, knock, and low speed pre-ignition (LSPI) detection. The results show that the ion current peak value and ion current peak phase have strong correlation with the cylinder pressure and pressure peak phase respectively. The COV of ion current integral value is greater than the COV of IMEP at the same operating condition. Results show that the ion current signal is sensitive to different lambdas. Using ion current signal, the knock in any given cylinder can be detected. Importantly, the ion sensor successfully detected the low speed pre-ignition (LSPI) about more than 20 °CA before spark ignition.
Technical Paper

Control Optimization of a Compound Power-Split Hybrid Transmission for Electric Drive

2015-04-14
2015-01-1214
A novel compound power-split hybrid transmission based on a modified Ravigneaux gear set is presented. The equivalent lever diagrams are used to investigate the electric operating modes for the hybrid powertrain, and then its dynamic and kinematic characteristics as well as efficiency characteristics are described in equations. A brake clutch mounted on the carrier shaft is proposed to enhance the electric driving efficiency for the hybrid transmission. Three types of electric operating mode are analyzed by the simplified combined lever diagrams and the system efficiency and torque characteristics for these electric operating modes are compared. A major influence on output torque of the hybrid transmission derived from the torque capability of motors and brake clutch is depicted.
Technical Paper

A Study on Combustion and Emission Characteristics of GDI Engine for HEV at Quick Start

2014-10-13
2014-01-2709
Gasoline Direct Injection (GDI) engines have attracted interest as automotive power-plants because of their potential advantages in down-sizing, fuel efficiency and in emissions reduction. However, GDI engines suffer from elevated unburned hydrocarbon (HC) emissions during start up process, which are sometimes worsened by misfires and partial burns. Moreover, as the engine is cranked to idle speed quickly in HEVs (Hybrid Electric Vehicle), the transients of quick starts are more dramatically than that in traditional vehicle, which challenge the optimization of combustion and emissions. In this study, test bench had been set up to investigate the GDI engine performances for ISG (Integrated Starter and Generator) HEVs during start up process. Based on the test system, cycle-controlled of the fuel injection mass, fuel injection timing and ignition timing can be obtained, as well as the cycle-resolved measurement of the HC concentrations and NO emissions.
Technical Paper

Study on Fuel Injection Parameters Optimization for Common Rail Diesel Engine Fueled with B20 Biodiesel

2014-10-13
2014-01-2655
As a type of alternative fuel, biodiesel has advantages in reducing greenhouse gases and ensuring energy security. Compared with petroleum diesel, biodiesel has different lower calorific value, oxygen content and octane number that would raise problems when the unoptimized common rail diesel engine is fueled with biodiesel or its petroleum diesel blends. Among these problems, decreasing full load torque output and increasing NOx and BSFC are significantly important. Fuel injection parameter calibration and optimization experiments are carried out in an in-line 6-cylinder 8.82 liter turbocharged and intercooled common rail diesel, which is equipped with Denso ECD-U2 fuel injection system, SCR (Selective catalytic reduction) and DPF (diesel particulate filter). To avoid after-treatment apparatus' coupling influence and re-calibration, emission measure point is set in front of catalysts. The experiment adopts B20 biodiesel as test fuel.
Technical Paper

Effect of Water Injection Temperature on Characteristics of Combustion and Emissions for Internal Combustion Rankine Cycle Engine

2014-10-13
2014-01-2600
The present work discusses a novel oxyfuel combustion method named internal combustion rankine cycle (ICRC) used in reciprocating engines. Water is heated up through heat exchanger by exhaust gas and engine cooling system, and then injected into the cylinder near top dead center to control the combustion temperature and in-cylinder pressure rise rate, meanwhile to enhance the thermo efficiency and work of the combustion cycle. That is because injected water increases the mass of the working fluid inside the cylinder, and can make use of the combustion heat more effectively. Waste heat carried away by engine coolant and exhaust gas can be recovered and utilized in this way. This study investigates the effect of water injection temperature on the combustion and emission characteristics of an ICRC engine based on self-designed test bench. The results indicate that both indicated work and thermal efficiency increase significantly due to water injection process.
Technical Paper

Effect of Ageing Catalyzed Continuously Regenerating Trap on Particulate Emissions from Urban Diesel Bus Based on On-road Test

2014-10-13
2014-01-2802
Durability and performance evaluation of the ageing catalyzed continuously regenerating trap (CCRT) on solid and volatile particles from diesel bus were studied through a set of transient TSI engine exhaust particle sizer spectrometer based on on-road test. Particle characteristics under stepped steady conditions and during regeneration were discussed in detail. Under idle and stepped steady conditions, total particle number and mass Emission Rate (ER) of each test presented rising trends as speed increase. Total number ERs of all tests showed downtrend as the CCRT aging. The particle number size distributions at different ageing stage showed changing characteristics due to developing filter mechanism. Compared with baseline data, the total number reduction rates at idle condition were incremental, from 91.4% to 98.9% as the CCRT ageing. Percentages of nuclei mode concentrations took higher range from 66.6% to 89.9% compared with the baseline data, 43.2-43.7%.
Technical Paper

Analysis and Design of Dual-Motor Electro-Hydraulic Brake System

2014-09-28
2014-01-2532
In this paper, by analyzing multiple electro-hydraulic brake system schemes in detail, the idea of dual-motor electro-hydraulic brake system is proposed. As a new solution, the dual-motor electro-hydraulic brake system can actively simulate pedal feel, make the most of pedal power (from the driver), and reduce the maximum power output of each active power source remarkably, which is a distinctive innovation compared to most current electro-hydraulic brake systems. Following the proposed concept, a general research thought and method is conceived, and then a dual-motor electro-hydraulic brake system is designed. Finally, the simulation model is set up in AMESim software and its feasibility is simulated and verified.
Technical Paper

Mechanism Study on Time-Varying Characteristics of Frictional Squeal in Pin-on-Disc System

2014-09-28
2014-01-2517
Disc brake squeal has always been a great challenge to the automotive industry. Based on the pin-on-disc system, a series of frictional squeal bench tests are carried out, which show significant time-varying characteristics on occurrence, sound pressure and frequency of frictional squeal. To investigate the generation mechanism of time-varying characteristics of frictional squeal, a four-degree-of-freedom (4DOF) lumped parameter model considering the time-varying tangential contact stiffness, the normal contact stiffness and the friction coefficient is established in this paper. Through both the system stability analysis and the transient response analysis, the time-varying frictional squeal is predicted successfully, and the generation mechanism and the key impact factors are also investigated in depth.
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