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991.
Y. -M. Kim Y. -G. Kim S. -W. Kim C. -K. Park T. -W. Park 《International Journal of Automotive Technology》2010,11(5):673-680
The performance of brakes has become important due to increased train speeds. The brake system of a train must possess a large
brake force to stop the train safely within a limited stopping distance. However, an excessive brake force deteriorates the
ride comfort and causes the train to skid. Therefore, it is necessary to control the brake force within the adhesion force
limit. This paper presents an analytical method to estimate the relationship between the brake and adhesion forces of a disc
brake system. This method has been applied to the actual disc braking control system of the Korea High-Speed Train (HSR350x),
and the adhesion force is estimated in an actual skid condition. 相似文献
992.
P. Karthikeyan D. B. Sonawane S. C. Subramanian 《International Journal of Automotive Technology》2010,11(4):507-515
A properly functioning brake system is critical for ensuring the safe operation of any vehicle on roadways. Commercial vehicles
such as trucks, tractors-trailers and buses are equipped with an air brake system that uses compressed air as the energy transmitting
medium. This paper presents a model-based control scheme for an electropneumatic brake system for use in commercial vehicles.
A mathematical model for an electropneumatic brake system was developed and corroborated with experimental data. A control
scheme was developed based on this model and was used to regulate the pressure of air inside the brake chamber according to
a desired pressure trajectory. This control scheme was implemented on an experimental test bench, and its performance was
studied for various values of the controller parameter. The control scheme was tested for various desired pressure trajectories
reflecting actual brake operation. 相似文献
993.
Using the recent anthropometry of the North American population, human body models were developed for seat comfort simulation.
The external geometry of the models was acquired from the three-dimensional whole body laser scan of recruited volunteers
in a driving position. The selection criteria for volunteers with standard size and shape were derived from a statistical
factor analysis of the Size USA database. As a practical application of the model in a design process, comfortable driving
postures were constructed by adopting the cascade prediction model (CPM), which takes into account both interior package layout
and the driver’s anthropometry. The detail modeling process of finite element modeling and its validation results against
volunteer measurements are introduced. 相似文献
994.
High tension bolts in critical joints in internal combustion engines are susceptible to fatigue failure. Computeraided bolted
joint design procedures require knowledge of the dependence of bolt fatigue limit on the mean stress and ultimate tensile
strength. This dependence is investigated with staircase fatigue limit tests. The test results show that when the bolt fatigue
limit is estimated with the nominal stress of the bolt, it decreases with increasing tensile strength and nominal mean stress.
However, there is a range of the nominal mean stress where the bolt fatigue limit is almost constant. The test results are
interpreted with finite element analysis. 相似文献
995.
Recently, as climate changes have manifested worldwide, every country is making efforts to prevent ozone depletion and global
warming. In the automotive industry, R-134a refrigerant is widely used in air conditioning systems because it has zero ozone
depletion potential (ODP). Unfortunately, its global warming potential (GWP) is high. Therefore, alternative refrigerants
are needed as a replacement for R-134a. R-152a is considered to be one of the better alternative refrigerants due to zero
ODP and low GWP. In this paper, the performance of an automotive air conditioning system using R-134a and one using R-152a
are compared experimentally at the bench level. The experimental apparatus simulated a real automotive air conditioning system
consisting of a cabin and engine room structure. The cooling capacity, condensing capacity, coefficient of performance (COP)
and power consumption characteristics of the automotive air conditioning system are evaluated by changing the air velocity
entering the condenser and the compressor rotation speed with the optimized refrigerant charge amount. Also, the performance
of the R-152a system was investigated by changing the thermostatic expansion valve which is set of values. The results of
this study show that the R-152a system is slightly better than the R-134a system, not only under driving conditions but also
under idling condition. R-152a refrigerant thus shows promise as an alternative refrigerant to replace the current standard,
R-134a, in automotive air conditioning systems. 相似文献
996.
Design of conformal cooling channels for an automotive part 总被引:2,自引:0,他引:2
The cooling system plays a crucial role in determining the productivity and quality of an injection molding process. With
the current growth of Solid Freeform Fabrication (SFF) techniques, mold designers have been striving for not only improvement
in cooling system performance but also for a method to do so automatically. In this paper, a method is proposed for developing
a conformal cooling system that facilitates uniform cooling over the entire mold surface with minimum cycle time. Based on
the temperature distribution after the filling stage, the mold surface is split into zones which will be cooled by optimized
subconformal channels obtained from the optimization process. The optimization process in which the objective function is
stated as minimization of the cooling time with boundaries ensuring a realistic design will optimize the cooling system layout
in terms of cooling channel size and location. Finally, all subcooling channels are combined to generate the entire conformal
cooling system for the injection mold. 相似文献
997.
J. Kim N. Kim S. Hwang Y. Hori H. Kim 《International Journal of Automotive Technology》2009,10(6):733-742
A motor control strategy for an input-split hybrid electric vehicle (HEV) is proposed. From a power characteristic analysis,
it is found that the powertrain efficiency decreases for speed ratios at which power circulation occurs. Using dynamic models
of an input-split HEV powertrain, a motor-generator control algorithm for obtaining high system efficiency is designed by
inversion-based control. The performance of the control algorithm is evaluated by the simulator which is developed based on
PSAT, and simulation results are compared with the test results. It is found that, even if the engine thermal efficiency is
sacrificed by moving the engine operation point from the OOL for the control strategy, improved overall powertrain system
efficiency can be achieved by the engine operation that gives a relatively high efficiency from the viewpoint of the overall
powertrain efficiency. The control algorithm developed can be used in design of future electric vehicles. 相似文献
998.
S. Y. Kim H. C. Choi W. J. Won S. Y. Oh 《International Journal of Automotive Technology》2009,10(1):103-113
Because the overall driving environment consists of a complex combination of the traffic Environment, Vehicle, and Driver
(EVD), Advanced Driver Assistance Systems (ADAS) must consider not only events from each component of the EVD but also the
interactions between them. Although previous researchers focused on the fusion of the states from the EVD (EVD states), they
estimated and fused the simple EVD states for a single function system such as the lane change intent analysis. To overcome
the current limitations, first, this paper defines the EVD states as driver’s gazing region, time to lane crossing, and time
to collision. These states are estimated by enhanced detection and tracking methods from in- and out-of-vehicle vision systems.
Second, it proposes a long-term prediction method of the EVD states using a time delayed neural network to fuse these states
and a fuzzy inference system to assess the driving situation. When tested with real driving data, our system reduced false
environment assessments and provided accurate lane departure, vehicle collision, and visual inattention warning signals. 相似文献
999.
Physical-chemical properties of ethanol-diesel blend fuel and its effect on the performance and emissions of a turbocharged diesel engine 总被引:1,自引:0,他引:1
Z. -Q. Chen X. -X. Ma S. -T. Yu Y. -N. Guo J. -S. Liu 《International Journal of Automotive Technology》2009,10(3):297-303
This paper deals with the main physical-chemical properties of ethanol-diesel blend and the effects of ethanoldiesel blends
(up to 15% volume) on engine performance (full load torque vs. engine speed, BSEC vs. torque at 1400 r/min and 2300 r/min,
and effect of start of injection angle) and emissions in ECE R49 tests (steady 13 points) using a 6.6 L inline 6-cylinder
turbocharged direct injection diesel engine. The results show that an increase in ethanol fraction results in decreased viscosity
of the blend fuel and very high distillation characteristics in the low temperature range. Solvents can improve the solubility
of ethanol-diesel blends. The engine power was degraded proportional to the ethanol content (10% and 15%) due to the LHV (low
heating value) of the blends. The higher latent heat of vaporization and lower CN (cetane number) of ethanol, which results
from the steady state emissions of CO, HC, and SOF (soluble organic fraction), were much higher in the ECE R49 tests at low
loads. Soot (solid mass) emissions were improved. The particulate matter emissions were significantly increased with higher
blend volumes, and NOx emissions slightly increased with higher ethanol volumes. By increasing the injection angle properly,
the performance parameters of the diesel engine were improved, but NOx emissions were deteriorated slightly. 相似文献
1000.
In order to plan bus operations, it is necessary for transit planners to understand what factors may influence travelers’ choice of buses for travels within a city. The proposed method involves various scenarios of a hypothetical bus operation which was rated by a group of individuals. Analysis of Covariance technique is employed to analyze people's sensitivities to their perceived levels of bus service characteristics. The technique involves:
-
testing for the significant effects of varying levels of service characteristics upon people's intentions to use bus service, and
-
assessing differences among various population segments in their sensitivity patterns towards bus service characteristics.