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321.
S. O. Kang S. O. Jun H. I. Park K. S. Song J. D. Kee K. H. Kim D. H. Lee 《International Journal of Automotive Technology》2012,13(4):583-592
This research aims to develop an actively translating rear diffuser device to reduce the aerodynamic drag experienced by passenger cars. One of the features of the device is that it is ordinarily hidden under the rear bumper but slips out backward only under high-speed driving conditions. In this study, a movable arc-shaped semi-diffuser device, round in form, is designed to maintain the streamlined automobile??s rear underbody configuration. The device is installed in the rear bumper section of a passenger car. Seven types of rear diffuser devices whose positions and protrusive lengths and widths are different (with the basic shape being identical) were installed, and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. The main purpose of this study is to explain the aerodynamic drag reduction mechanism of a passenger car cruising at high speed via an actively translating rear diffuser device. The base pressure of the passenger car is increased by deploying the rear diffuser device, which then prevents the low-pressure air coming through the underbody from directly soaring up to the rear surface of the trunk. At the same time, the device generates a diffusing process that lowers the velocity but raises the pressure of the underbody flow, bringing about aerodynamic drag reduction. Finally, the automobile??s aerodynamic drag is reduced by an average of more than 4%, which helps to improve the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. 相似文献
322.
If a driver passes over a pedestrian lying on the road and flees, it is considered a crime. In several cases, even if the
driver fled and was arrested, he/she often asserts that they did not know that the victim was a human being. However, the
investigation agency often believes that a driver can certainly recognize when he/she passes over a person. Accordingly, such
cases frequently lead to disputes due to the lack of criteria for recognizing when a driver was involved in run-over accidents.
In this study, tests were conducted both to identify if drivers can recognize whether their vehicles passed over a person
and to examine how they feel at the time. A silicon dummy, which was manufactured to have the same characteristic as the human
chest, was used in this study. According to the method specified in ISO2631, the vibration delivered to the driver was measured,
and eighteen participants drove a vehicle over the silicon dummy to experience how the vibrations felt. When the passenger
car for the test ran over the dummy at speeds ranging from 10 km/h to 60 km/h, all participants recognized the delivered vibration,
and the VDV that was delivered to the participants ranged from 1.81 m/s
1.75 to 2.38 m/s
1.75. The participants thought that the object they drove over was a stone or a piece of wood. This indicates that the driver
certainly can recognize the vibrations generated from passing over a human chest even though it feels like a solid object. 相似文献
323.
The intake system in an automotive engine has a short duct compared with that of the exhaust system. The filtered-x LMS (FX-LMS)
algorithm has been applied to the active noise control (ANC) system in a short acoustic duct. This algorithm design is based
on the FIR (finite impulse response) filter; however, it has a slow convergence issue due to a large number of zero coefficients.
To improve the convergence performance, the step size of the LMS algorithm was modified from fixed to variable. However, this
algorithm is still not suitable for the ANC system of a short acoustic duct because the reference signal is affected by the
backward acoustic wave propagated from a secondary source. Therefore, the recursive filtered-u LMS algorithm (FU-LMS) based
on the infinite impulse response (IIR) is developed to consider backward acoustic propagation. Generally, this algorithm has
a stability problem. The stability issue was improved using an error-smoothing filter. In this paper, the recursive LMS algorithm
with a variable step size and smoothing error filter is designed. This recursive LMS algorithm, the FU-VSSLMS algorithm, uses
an IIR filter. With fast convergence and good stability, this algorithm is suitable for the ANC system in a short acoustic
duct, such as the intake system of an automotive engine. This algorithm is applied to the ANC system of a short acoustic duct.
The disturbance signals used as primary noise source are a sinusoidal signal embedded in white noise and the chirp signal,
which has a variable instantaneous frequency. The test results demonstrate that the FU-VSSLMS algorithm has a superior convergence
performance when compared with the FX-LMS and FX-LMS algorithms. The algorithm can be successfully applied to the ANC system
in a short duct, such as the intake duct. 相似文献
324.
K. Jeon H. Hwang S. Choi S. Hwang S. B. Choi K. Yi 《International Journal of Automotive Technology》2012,13(7):1067-1075
This study presents a few fail-safe control strategies based on reliability evaluation scenarios for the electronic brake systems of green cars in several critical cases. CarSim and MATLAB Simulink were used to develop the FCEV model with regenerative braking involving EWBs and EMBs. The proposed reliability evaluation scenarios were simulated, and a few fail-safe control algorithms were verified using the proposed reliability evaluation scenarios with the developed FCEV simulation model. The reliability evaluation scenarios were developed using a combination of driving modes and FMEA results for these electronic brake systems. 相似文献
325.
Idle stop and go (ISG) is a low cost but very effective technology to improve fuel efficiency and reduce engine emissions by preventing unnecessary engine idling. In this study, a new method is developed to improve the performance of conventional ISG by monitoring traffic conditions. To estimate frontal traffic conditions, an ultra-sonic ranging sensor is employed. Several fuzzy logic algorithms are developed to determine whether the engine idling is on or off. The algorithms are evaluated experimentally using various data gathered in real areas with traffic congestion. The evaluation results show that the method developed can reduce the chance of false application of ISG significantly while improving fuel efficiency up to 15%. 相似文献
326.
D. O. Kang S. J. Heo M. S. Kim W. C. Choi I. H. Kim 《International Journal of Automotive Technology》2012,13(1):109-122
This study presents the robust design optimization process of suspension system for improving vehicle dynamic performance
(ride comfort, handling stability). The proposed design method is so called target cascading method where the design target
of the system is cascaded from a vehicle level to a suspension system level. To formalize the proposed method in the view
of design process, the design problem structure of suspension system is defined as a (hierarchical) multilevel design optimization,
and the design problem for each level is solved using the robust design optimization technique based on a meta-model. Then,
In order to verify the proposed design concept, it designed suspension system. For the vehicle level, 44 random variables
with 3% of coefficient of variance (COV) were selected and the proposed design process solved the problem by using only 88
exact analyses that included 49 analyses for the initial meta-model and 39 analyses for SAO. For the suspension level, 54
random variables with 10% of COV were selected and the optimal designs solved the problem by using only 168 exact analyses
for the front suspension system. Furthermore, 73 random variables with 10% of COV were selected and optimal designs solved
the problem by using only 252 exact analyses for the rear suspension system. In order to compare the vehicle dynamic performance
between the optimal design model and the initial design model, the ride comfort and the handling stability was analyzed and
found to be improved by 16% and by 37%, respectively. This result proves that the suggested design method of suspension system
is effective and systematic. 相似文献
327.
S. M. Zhang F. Tian G. F. Ren L. Yang 《International Journal of Automotive Technology》2012,13(5):693-699
The paper presents an innovative method combining artificial neural networks (ANNs) with Fuzzy PID to demonstrate the advantages of this control approach for meeting both NOx emission requirements and NH3 slip targets. An ANN model was utilized to simulate the formation of NOx emissions under various engine operating conditions. Next, an effective closed-loop control strategy with a type of feedback known as fuzzy PID is adopted for on-line, real-time control of 32.5% aqueous urea dosing in the exhaust stream. The new strategy explores the benefits by simulation and testing in the environments of Matlab/Simulink and ESC/ETC, respectively. The notable achievement of considerable NOx reduction and an acceptably small NH3 slip is obtained based on this new, feasible and effective strategy. 相似文献
328.
In order to explore the control method of the intake air state in utility tunnels when the outside fresh air humidity is too high, taking the ventilation works of a utility tunnel section in Pingtan comprehensive experimental area as the research background, this paper proposes the control method of intake air state parameters for ventilation and dehumidification in utility tunnels under normal and accident conditions, by means of the effective ventilation and dehumidification duration prediction model, the evolutionary multi-objective algorithm (EMOA), and in combination with the ventilation control requirements. The results show that the intake air state parameter controller can be adjusted freely according to the different requirements of decision makers for ventilation fan working duration and dehumidifier working temperature and moisture content, and the optimized appropriate control objectives can be achieved, which is conducive to the real-time decision-making of the intake air state parameter control for ventilation and dehumidification in utility tunnels. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
329.
G. Xie S. D. Iwnicki 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2008,46(1):117-128
A new model for simulating rail roughness growth on tangent track is presented in this paper. The model consists of three relatively independent components: (1) a time-domain vehicle/track interaction model; (2) a 2D non-Hertzian and non-steady wheel/rail contact model; and (3) a wear model. Wheel/rail contact forces for a given initial roughness obtained from the vehicle/track interaction model are used by the contact model to calculate the contact patch size, normal pressure and tangential stresses with material removal assumed to be linearly proportional to the friction work in the contact patch. The roughness profile is updated and fed back into vehicle/track interaction model. The 2D contact model is initially compared with a 3D model for various wavelength of initial sinusoidal roughness. Long term roughness growth is then simulated with the 2D contact model. Simulation shows that all initial sinusoidal roughness of wavelengths between 20-100 mm are levelled out. The wavelength-fixing mechanism, that has previously been used to explain the cause of corrugation, is not found in the present investigations. 相似文献
330.
Karen Mayor Richard S.J. Tol 《Transportation Research Part D: Transport and Environment》2010,15(1):26-36
We use a model of international and domestic tourist numbers and flows to investigate the effect of various climate policy instruments implemented in Europe on arrivals and emissions for the countries concerned. We find that these schemes do not fulfil their desired effects. The introduction of aviation into the European trading system results in a fall in the number of tourists travelling into the European Union in favour of other destinations. It also causes a significant welfare loss with only a small reduction in emissions. The flight taxes in the Netherlands and the UK result in different substitution effects across destinations (depending on the zones being taxed) but both policies do have the same consequence of inducing global welfare losses and also reducing visitor numbers to the countries. We find that when these policies are combined their effects are additive. Welfare impacts are robust to variations in the underlying assumptions and changes in the scope of the taxes examined have the expected effects. 相似文献