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171.
We propose a semiparametric approach that can capture the nonlinearity of deterministic components of the utility functions
in discrete choice models and demonstrate it by analyzing travel mode choice behaviour for an interregional trip. The proposed
smoothing spline-based specification method can be used to make ex ante evaluations regarding the parametric specifications of the deterministic utility functions in discrete choice models. 相似文献
172.
173.
Uncontrolled expansion of combustion wave in spark ignited internal combustion engine causes knock effect which seriously degrades efficiency and lifetime of the engine. Thus, accurate knock detection and control are essential for obtaining a desired performance from the engine. Usually, knock sensor is used to detect this phenomenon but it has limited accuracy especially at engine high-speed rotations because of natural vibration and external noises. In this study an effective method based on Non-Local Mean (NLM) algorithm has been proposed to improve the knock detection accuracy. This method is evaluated based on four different indicators and four engine cylinders. The results show 52.9 % improvement in knock detection. Also feasibility of real time execution of this method based on embedded hardware has been studied. 相似文献
174.
Alan J. Horowitz 《Transportation》2010,37(4):689-703
This paper describes a group of techniques for disaggregating origin–destination tables for travel forecasting that makes
explicit use of observed traffic on a network. Five models within the group are presented, each of which uses nonlinear least-squares
estimation to obtain row and column factors for splitting trip totals from and to larger geographical areas into smaller ones.
The techniques are philosophically similar to Fratar factoring, although the solution method is quite different. The techniques
are tested on a full-sized network for Northfield, MN and are found to work effectively. 相似文献
175.
Eunhyek Joa Kwanwoo Park Youngil Koh Kilsoo Kim 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(4):579-603
This paper presents a tyre slip-based integrated chassis control of front/rear traction distribution and four-wheel braking for enhanced performance from moderate driving to limit handling. The proposed algorithm adopted hierarchical structure: supervisor – desired motion tracking controller – optimisation-based control allocation. In the supervisor, by considering transient cornering characteristics, desired vehicle motion is calculated. In the desired motion tracking controller, in order to track desired vehicle motion, virtual control input is determined in the manner of sliding mode control. In the control allocation, virtual control input is allocated to minimise cost function. The cost function consists of two major parts. First part is a slip-based tyre friction utilisation quantification, which does not need a tyre force estimation. Second part is an allocation guideline, which guides optimally allocated inputs to predefined solution. The proposed algorithm has been investigated via simulation from moderate driving to limit handling scenario. Compared to Base and direct yaw moment control system, the proposed algorithm can effectively reduce tyre dissipation energy in the moderate driving situation. Moreover, the proposed algorithm enhances limit handling performance compared to Base and direct yaw moment control system. In addition to comparison with Base and direct yaw moment control, comparison the proposed algorithm with the control algorithm based on the known tyre force information has been conducted. The results show that the performance of the proposed algorithm is similar with that of the control algorithm with the known tyre force information. 相似文献
176.
Jerzy Ejsmont Stanislaw Taryma Grzegorz Ronowski Beata Swieczko-Zurek 《International Journal of Automotive Technology》2018,19(1):45-54
Temperature is a very important factor controlling rolling resistance of road vehicle tyres. There are at least three different temperatures that may be considered as important factors controlling thermal conditions of the rolling tyre. The most common measure of the thermal conditions during tyre rolling is ambient air temperature. The other two are: pavement temperature and “tyre” temperature. Tyre temperature is the most difficult to establish, as temperatures of different parts of rolling tyres differ considerably, thus there is a problem to obtain representative values. In the authors’ opinion, air temperature is the most universal and reliable parameter to measure. The article presents results obtained in the Technical University of Gdańsk during laboratory and road measurements of different car tyres rolling on different pavements. The knowledge of rolling resistance characteristics is important for modelling car dynamics as well as fuel consumption. It is also necessary to establish proper test conditions in the future standardized on-road method of measuring rolling resistance. The results indicate that generally each tyre and pavement combination is influenced by the air temperature in a unique way, but at the same it is possible to propose some general influence factors that may be used to normalize measurements to the standard temperature of 25 °C. 相似文献
177.
Edmondo Di Pasquale Daniel Coutellier 《International Journal of Automotive Technology》2017,18(4):631-642
Head on bonnet impact is becoming more and more important in automotive design as regulations on pedestrian safety become more demanding. Despite the relatively low amount of energy involved, these impacts are truly dynamic phenomena as the event duration is comparable with the traveling time of the different wavefronts generated by the impact. In this paper, we show that we can build up a simplified model for the impact based on wave propagation analysis. Using this model, we can analyze head acceleration on existing bonnets or predict it on new ones. Head acceleration in a bonnet impact can thus be estimated over the whole area of the bonnet with a few minutes of CPU. 相似文献
178.
Development of hot stamped center pillar using form die with channel type indirect blank holder 总被引:1,自引:0,他引:1
H. S. Choi B. M. Kim K. J. Nam S. Y. Ha S. H. Cha C. G. Kang 《International Journal of Automotive Technology》2011,12(6):887-894
The hot stamping process has been used in the automotive industry to reduce the weight of the body-in-white and to increase
passenger safety via improved crashworthiness. However, defects such as fracture and wrinkle occur when hot stamping is performed
using a conventional drawing or forming method. In this study, a channel-type indirect blank holder (CIBH) is proposed to
develop a high-strength center pillar in form-type hot stamping, so that the aforementioned drawbacks are overcome. This type
of blank holder plays an important role in reducing severe wrinkling at the flange; such wrinkling leads to folding after
the completion of form-type hot-stamping. First, we investigated the effect of the channel shape on the indirect blank holding
force by using a simplified two-dimensional plane-strain stamping process. Second, we selected the slope angle and corner
radius of the channel as the main shape parameters by finite element analysis and artificial neural network (ANN). It is known
that fracture at the hot formed wall and wrinkle at the flange are significantly affected by the slope angle of the channel,
and the appropriate value for eliminating fracture and wrinkle is determined to be 99°. By performing hot stamping using a
form die with the selected channel, we can manufacture a high-strength center pillar without wrinkle and fracture. 相似文献
179.
AlterationIntroductionThereisastrongini6ractionamongtemPetalrefield,strCssfield,andmicrosttuctutulaltOrationinm8terialsduringtheirhotworking[l'2].Especiallyduringthecoolingprocess,inwhichtemPeratorechangnsgreatly,intendionsbecomemorecomplexbecauseoftransformationoccurmnce.Duringthehotdeformation,thingswillaPpearsuchas:a.hotdeformation,relatedtostressfieId,changesessentiallytheshaPeofmaterialsandcausesthevariationofthecontactstatebetWeenthedieandsample,resultinginchangeofthethermalboundnyco… 相似文献
180.
In the connected vehicles, connecting interfaces bring threats to the vehicles and they can be hacked to impact the vehicles and drivers. Compared with traditional vehicles, connected vehicles require more information transfer. Sensor signals and critical data must be protected to ensure the cyber security of connected vehicles. The communications among ECUs, sensors, and gateways are connected by in-vehicle networks. This paper discussed the state-of-art techniques about secure communication for in-vehicle networks. First, the related concepts in automotive secure communication have been provided. Then we have compared and contrasted existing approaches for secure communication. We have analyzed the advantages/disadvantages of MAC and digital signatures for message authentication and compared the performance and limitations of different cryptographic algorithms. Firewall and intrusion detection system are introduced to protect the networks. The constraints and features of different intrusion detection approaches are presented. After that, the technical requirements for cryptographic mechanism and intrusion detection policy are concluded. Based on the review of current researches, the future development directions of the automotive network security have been discussed. The purpose of this paper is to review current techniques on automotive secure communication and suggest suitable secure approaches to implement on the in-vehicle networks. 相似文献