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171.
A robust H
∞ preview control is investigated for an active suspension system with look-ahead sensors. The uncertain system is described
by a state-space model with linear nominal parts and additional nonlinear time-varying norm-bounded uncertainties. Proof of
robust stability and a feedback-type robust H
∞ preview controller are derived by augmenting the dynamics of the original system and previewed road input. As, however, the
augmented previewed road input gives the system a much larger dimension than the original system, much more computation time
is required for solving of Riccati equations. To resolve this problem, a decomposed robust H
∞ preview controller is proposed. Robust stability and performance variations for system uncertainties are shown using a numerical
example of a quarter-car model. 相似文献
172.
T. H. Hwang K. Park S. -J. Heo S. H. Lee J. C. Lee 《International Journal of Automotive Technology》2008,9(1):17-27
The performance of most electronic chassis control systems in the past has been optimized individually. Recently, a great
research effort has been dedicated to the integration of chassis control systems in an effort to improve the vehicle performance.
This involves orchestration of individual control modules so that they can jointly contribute to the enhancement of their
control effect. In this research, two integrated control logics for AFS (Active Front Steering) and ESP (Electronic Stability
Program) have been developed. Of the two logics, one uses a supervisor that rules over the individual modules. The other logic
uses a CL (Characteristic Locus) method, which is a frequency-domain multivariable control technique. The two logics have
been tested under various driving conditions to investigate their control effects. The results indicate that the proposed
integrated control logics can yield vehicle performance that is superior to that of the individual control modules without
any integration scheme. 相似文献
173.
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
174.
Numerical study of a light-duty diesel engine with a dual-loop EGR system under frequent engine operating conditions using the doe method 总被引:1,自引:0,他引:1
J. Park K. S. Lee S. Song K. M. Chun 《International Journal of Automotive Technology》2010,11(5):617-623
Exhaust gas recirculation (EGR) is an emission control technology that allows for a significant reduction in NOx emissions
from light- and heavy-duty diesel engines. The primary effects of EGR are a lower flame temperature and a lower oxygen concentration
of the working fluid in the combustion chamber. A high pressure loop (HPL) EGR is characterized by a fast response, especially
at lower speeds, but is only applicable if the turbine upstream pressure is sufficiently higher than the boost pressure. On
the contrary, for the low pressure loop (LPL) EGR, a positive differential pressure between the turbine outlet and the compressor
inlet is generally available. However, a LPL EGR is characterized by a slow response, especially at low and moderate speeds.
In this study, of the future types of EGR systems, the dual-loop EGR system (which has the combined features of the high-pressure
loop EGR and the low-pressure loop EGR) was developed and was optimized under five selected operating conditions using a commercial
engine simulation program (GT-POWER) and the DOE method. Finally, significant improvements in the engine exhaust emissions
and performance were obtained by controlling several major variables. 相似文献
175.
Design of active suspension and electronic stability program for rollover prevention 总被引:1,自引:0,他引:1
This paper presents a method for the design of a controller for rollover prevention using active suspension and an electronic
stability program (ESP). Active suspension is designed with linear quadratic static output feedback control methodology to
attenuate the effect of lateral acceleration on the roll angle and suspension stroke via control of the suspension stroke
and tire deflection of the vehicle. However, this approach has a drawback in the loss of maneuverability because the active
suspension for rollover prevention produces in vehicles an extreme over-steer characteristic. To overcome this drawback of
the active suspension based method, ESP is designed. Through simulations, the proposed method is shown to be effective in
preventing rollover. 相似文献
176.
S. -J. Park S. -W. Chae E. -S. Kim 《International Journal of Automotive Technology》2010,11(3):441-445
Neck fracture is a major cause of death in traffic accidents. This pattern of injury normally occurs in a frontal collision
or overturn of a vehicle. This study investigates the case of a neck fracture from a low-speed collision. In the examined
case, the passenger in the front seat of the car fractured his neck and died. He did not have his seatbelt on when the vehicle
slipped on a frozen road surface on a downward slope of a hill and impacted into the shoulder of the road at low speed. In
this type of collision, an occupant’s body will be impacted by the windshield or other interior trim of the car. However,
in this case, rather unusually, neither body tissue nor fiber remained although the collision involved a broken windshield.
Thus, the reason for the passenger death was unidentified. This study applied the computer simulation package Madymo for analyzing
the accident. The result of the simulation was that the passenger, who did not wear a seatbelt, moved forward due to inertia.
The upper part of the passenger then rotated and lifted when the knee contacted with the dashboard. By evaluating the structural
deformation of the vehicle at the front, we deduced that the collision velocity was 30 km/h. Through a computational experiment
that was undertaken using Madymo 7.0, NIC was estimated to be 240 m2/s2. This result far exceeded the threshold for neck injuries. In particular, in comparison with whiplash injuries, when the
passenger’s head directly impacts the roof following a rear-end collision, the bending moment through hyperextension of the
neck is greatly increased. In this study, we concluded that the manner of death was the hyperextension of the neck, as the
passenger’s head contacted the roof from underneath. 相似文献
177.
As more electrical equipment is installed and larger currents are required in vehicles, the automotive ground system becomes
more important to guarantee the stable operation of the equipment and efficient power consumption. In this paper, an automotive
ground system is analyzed in a steady-state condition, and a simulation model for estimating its ground voltage distribution
is described. The automotive ground system is divided into an engine compartment ground and a body ground, and it is modeled
as an equivalent resistor network, which is suitable for simulation. By using the developed model, ground voltages are simulated
and measurements are taken with a real car. A comparison of the simulation and measurement results shows good agreement, and
the validity of the model is confirmed. Then, the factors that dominate the ground voltage level are discussed. 相似文献
178.
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
179.
Dong Won Yi Soung Hie Kim Hyung Rim Choi Nam-Kyu Park Tae-Woo Lee 《Maritime Policy and Management》2000,27(2):155-167
It is an important matter closely connected with saving logistics costs, as well as encouraging national competitive power, to improve the productivity of container terminals by efficient utilization of container terminal resources. In this respect, this paper tries to suggest a conceptual model for sharing container terminal resources, taking as a case study the Gamman Container Terminal (GCT) in the port of Pusan. In so doing, it identifies what kinds of resources can be systematically shared from the viewpoint of their common use and draws some problems resulting from terminal operation by four operators at GCT. The model does not imply the conception that each terminal has its own resources individually, but recommends that tentatively-called Container Terminal Resource Management Center (CTRMC) should be established and operated in order to save operation and investment costs and improve operational efficiency. In addition, the continuous acquisition and life-cycle support (CALS) concept is imbedded in the model so that it can control the supply and demand of resources efficiently by sharing the database, through which the CTRMC can automatically identify the status of the excess or deficit of a certain resource in each berth at GCT. 相似文献
180.
Traffic density can be accurately measured by counting the number of vehicles within 1 km; however, it is often calculated between macroscopic traffic parameters using the fundamental equation because of difficulty of observing traffic density directly in the field. Measuring density in this way may be inaccurate and may bias the analysis because the relationship between these traffic parameters can vary across the study sites. The purpose of this study is to find a method for measuring traffic density from aerial photography that is easy and accurate, and for this purpose, we investigated whether the measuring length (i.e., the length of a section of roadway from which observations of traffic are simultaneously collected) can be shorter than 1 km and yet retain the same measured traffic density. We divided an aerial photograph into several 20‐m unit sections, counted the number of vehicles manually, and examined measured traffic density according to central limit theory. According to the results of this study, with the number of 20‐m unit sections for observing traffic density at 15 (the measuring length is 300 m), the measured traffic density was almost the same as the density of a representative section of 1 km. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献