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801.
Simon?P.?BlaineyEmail author John?Armstrong Andrew?S.?J.?Smith John?M.?Preston 《Transportation》2016,43(3):425-442
This paper describes an integrated methodology for identifying potential ‘quick wins’ for mode shift from road to passenger rail transport. Firstly, a procedure for analysing rail’s relative competitiveness in the market for passenger transport between large urban areas is developed and then applied to a UK case study. The purpose of such analysis is to allow the identification of flows where rail is currently relatively uncompetitive (in terms of journey time in particular) and to assess the reasons for this poor performance, so that the issues which suppress rail use may be addressed. In parallel, a framework, methodology and tool for the assessment of existing and potential capacity (trains, seats, TEUs, etc.) is developed for both passenger and freight traffic, to identify and address network constraints. An illustrative example of the use of these demand and capacity assessment tools is then presented, with the tools used to identify and evaluate flows where rail demand is suppressed by poor service quality and where spare capacity exists which would allow the passenger rail service to be improved without requiring significant investments in infrastructure. The effects of such improvements on demand are predicted, and the cost implications of operating such additional services are discussed. The analysis suggests that there may be significant potential for increasing rail’s mode share by providing additional inter-urban services where rail currently offers an inferior service. 相似文献
802.
J. -S. Jo S. -H. You J. Y. Joeng K. I. Lee K. Yi 《International Journal of Automotive Technology》2008,9(5):571-576
The Vehicle stability control system is an active safety system designed to prevent accidents from occurring and to stabilize
dynamic maneuvers of a vehicle by generating an artificial yaw moment using differential brakes. In this paper, in order to
enhance vehicle steerability, lateral stability, and roll stability, each reference yaw rate is designed and combined into
a target yaw rate depending on the driving situation. A yaw rate controller is designed to track the target yaw rate based
on sliding mode control theory. To generate the total yaw moment required from the proposed yaw rate controller, each brake
pressure is properly distributed with effective control wheel decision. Estimators are developed to identify the roll angle
and body sideslip angle of a vehicle based on the simplified roll dynamics model and parameter adaptation approach. The performance
of the proposed vehicle stability control system and estimation algorithms is verified with simulation results and experimental
results. 相似文献
803.
In order to prevent the uncontrolled release of seatbelt buckles due to high acceleration caused by pretensioners, anti-g
buckles that have pendulum-shaped g-masses to block the releasing motion are commonly adopted in seatbelt systems. However,
even with the wide applications of anti-g buckles, the underlying operational principles of anti-g buckles have yet to be
investigated. This work studies conditions for the engagement of the g-mass to prevent inertial release, and conditions for
maintaining a blocked state under very high acceleration. Using a multibody model of an anti-g buckle, the effects of various
design parameters on the performance of the anti-g buckle have been examined. It turns out that design variables associated
with the geometry of the g-mass and its contacting surface configuration play important roles. In order to account for the
dynamic interaction between driver and seatbelt, a multibody model of a seatbelt system is combined with a dummy model to
form a single dynamic system. Using the measured displacement of the buckle during the explosion of a pretensioner as the
driving condition for simulation, dynamic analysis of the seatbelt with driver interaction has been carried out. Through comparison
with measured and computed accelerations of webbing, which shows good agreement, the validity of the model has been demonstrated.
The dynamic model for seatbelt and driver can be used as a design tool for the development of anti-g buckles. 相似文献
804.
Increasing fuel economy has been a central issue in the development of new cars, and one of the important strategies to improve
fuel economy is to decrease vehicle weight. In order to obtain this goal, researchers have sought to make bumpers lighter
without sacrificing strength, ability to absorb impact, or passenger safety. In this study, the effects of structural variables
on the torsional stiffness of a body bumper impact beam were analyzed for possible weight reduction. To this end, the effects
of variation of section height, increase of impact beam thickness and the addition of stays in a bumper impact beam were carefully
investigated and compared. Among these, the most effective way to increase the torsional stiffness of the bumper impact beam
was found to be increasing the section height. In addition, the potential for overall weight reduction of the impact beam
was examined by comparing the crash capability of a bumper using conventional steels with that of high-strength steel (boron
steel) with a tensile strength of 1.5 GPa. This analysis could serve as a guide to design for optimal bumper impact beam development. 相似文献
805.
S. J. Kim S. G. Kim K. S. Oh S. K. Lee 《International Journal of Automotive Technology》2008,9(6):703-711
The excitation force of a powertrain is one of major sources of interior noise in a vehicle. This paper presents a novel approach
to predict the interior noise caused by the vibration of the powertrain by using the hybrid TPA (transfer path analysis) method.
Although the traditional transfer path analysis (TPA) is useful for the identification of powertrain noise sources, it is
difficult to modify the structure of a powertrain by using experiments for the reduction of vibration and noise. In order
to solve this problem, the vibration of the powertrain in a vehicle is numerically analyzed by using the finite element method
(FEM). The vibration of the other parts of the vehicle is investigated by using experiments based on vibrato-acoustic transfer
function (VATF) analysis. These two methods are combined for the prediction of interior noise caused by a powertrain. Throughout
this research, two papers are presented. This paper presents a simulation of the excitation force of the powertrain exciting
the vehicle body based on numerical simulation. The other paper presents a prediction of interior noise based on the hybrid
TPA, which uses the VATF of the car body and the excitation force predicted in this paper. 相似文献
806.
J. N. Kim H. Y. Kim S. S. Yoon S. D. Sa 《International Journal of Automotive Technology》2008,9(6):649-657
A fully three-dimensional model was used to investigate the optimal value for intake valve lift in a CAI engine. Uniform mixing
in the engine is a key parameter that affects the auto-ignition reliability and thermal efficiency. The method of intake of
the air supply often determines the uniformity (or quality) of the fuel-air mixture. In this paper, four strategies were applied
for controlling the swirl intensity of intake air. The variation of the intake valve lift induces different swirling and tumbling
intensities. Both experimental data and 1D WAVE software (Ricardo, Co.) were coupled with the 3D model to provide pressure and temperature boundary conditions. The initial condition of the
EGR mass fraction was also provided by the 1D model. The benchmark scenario (Case 1) was considered as a valve lift with 2
mm for all intake valves. We found that an intake valve lift of 6 mm with the other intake valve closed (i.e., Case 5) yielded
the largest swirling (helical motion in the axial direction) and tumbling, which in turn rendered optimal fuel-gas mixing.
We also found that fuel distribution affected the auto-ignition sites (or spot). The better the mixing, the greater the gas
temperature and combustion efficiency achieved, as seen in Case 5. The NOx level, however, was increased due to the gas temperature.
The optimal operating condition is selected from the viewpoints of environmental protection and combustion efficiency. 相似文献
807.
Analysis of disc brake instability due to friction-induced vibration using a distributed parameter model 总被引:1,自引:0,他引:1
Y. -G. Joe B. -G. Cha H. -J. Sim H. -J. Lee J. -E. Oh 《International Journal of Automotive Technology》2008,9(2):161-171
This paper deals with friction-induced vibration of a disc brake system with a constant friction coefficient. A linear, lumped,
and distributed parameter model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are
used to investigate the dynamic stability, and, in order to verify simulations which are based on the theoretical model, an
experimental modal test and dynamometer test are performed. The comparison of experimental and theoretical results shows good
agreement, and the analysis indicates that modal coupling due to friction forces is responsible for disc brake squeal. Also,
squeal type instability is investigated, using a parametric analysis. This indicates which parameters have influence on the
propensity of brake squealing. This is helpful for validating the analysis model and establishing confidence in the experimental
results of the modified system. These results may also be useful during system development or diagnostic analysis. 相似文献
808.
Because the characteristics of rubber bushing significantly affect the accuracy of vehicle dynamics simulations, they should
be accurately modeled in the vehicle suspension model. In this paper, a new nonlinear bushing model for automotive bushing
components is developed to improve the accuracy of vehicle dynamics analysis. Bushing components were first tested to capture
the nonlinear and hysteretic behavior of typical elements by using a MTS 3-axis elastomer tester. A simple Bouc-Wen hysteretic
differential model was modified to generate a more precise rubber bushing model. A sine wave, step input, and random excitations
are imposed on the bushing. The ADAMS program is used to calculate sensitivity and the VisualDOC program is employed to find
the optimal parameters for the bushing model. An error function is designed to find optimal parameters of the model. Parameter
identification is carried out to satisfy the static and dynamic characteristics due to sine and step excitation inputs. It
was proved that the proposed model could predict the bushing forces under sine, step, and random inputs well. The errors are
within 10% in the overall range. To show the validity of the proposed model, a numerical example was also carried out. Because
the bushing forces due to random excitation input show good agreement with experiments, the proposed bushing model is available
in the vehicle dynamics simulation. 相似文献
809.
A. Broatch J. M. Luján S. Ruiz P. Olmeda 《International Journal of Automotive Technology》2008,9(2):129-140
Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine
warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions.
Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly
unfavorable for the combustion progress. Additionally, the catalytic converter is ineffective due to the low engine temperature.
In conjunction with adequate engine settings (fuel injection and fresh air control), either the glow plugs or the intake air
heater are activated during a portion of the engine warm-up period, so that a nominal engine temperatures is reached faster,
and the impact of these difficulties is minimized. Measurement of gaseous pollutants during engine warm-up is currently possible
with detectors used in standard exhaust gas analyzers (EGA), which have response times well-suited for sampling at such transient
conditions. However, these devices are not suitable for the measurement of exhaust emissions produced during extremely short
time intervals, such as engine starting. Herein, we present a methodology for the measurement of the cumulative pollutant
emissions during the starting phase of passenger car DI Diesel engines, with the goal of overcoming this limitation by taking
advantage of standard detectors. In the proposed method, a warm canister is filled with an exhaust gas sample at constant
volumetric flow, during a time period that depends on the engine starting time; the gas concentration in the canister is later
evaluated with a standard EGA. When compared with direct pollutant measurements performed with a state-of-art EGA, the proposed
procedure was found to be more sensitive to combustion changes and provided more reliable data. 相似文献
810.
J. A. Calvo V. Díaz J. L. San Román D. García-Pozuelo 《International Journal of Automotive Technology》2008,9(4):467-472
In order to safely maintain a vehicle, it is necessary to verify the most important systems that affect safety during Periodic
Motor Vehicle Inspections (PMVIs). In a previous paper, a test method and validation criteria were suggested by the authors
to verify shock absorber status during PMVIs, as they are a fundamental component that may wear out during a vehicle’s life.
In this paper, variations of the performance of the vehicle’s brakes resulting from shock absorber wearing have been analyzed,
in order to confirm whether the suggested criteria is valid for taking into account longitudinal forces and pitch movement
on the vehicle. A simulation-based study was conducted with several configurations of a worn damper on a vehicle driving on
two virtual roads: smooth and undulating. The results confirmed that the damping coefficient established as an acceptable
value to verify the shock absorber status in PMVIs is also valid considering the forces involved in a braking maneuver. 相似文献