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861.
A. Goodarzi M. Naghibian D. Choodan A. Khajepour 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(12):1671-1687
Active safety systems of a vehicle normally work well on tyre–road interactions, however, these systems deteriorate in performance on low-friction road conditions. To combat this effect, an innovative idea for the yaw moment and roll dynamic control is presented in this paper. This idea was inspired by the chase and run dynamics animals like cheetahs in the nature; cheetahs have the ability to swerve while running at very high speeds. A cheetah controls its dynamics by rotating its long tail. A three-dimensional stabilizer pendulum system (3D-SPS) resembles the rotational motion of the tail of a cheetah to improve the stability and safety of a vehicle. The idea has been developed in a stand-alone 3D stabilizer pendulum system as well as in an integrated control system, which consists of an ordinary differential braking direct yaw control (DYC) and active steering control that is assisted by the 3D-SPS. The performance of the proposed 3D-SPS has been evaluated over a wide range of handling manoeuvres by using a comprehensive numerical simulation. The results show the advantage of 3D-SPS over conventional control approaches, which are ineffective on low-friction road conditions and high lateral acceleration manoeuvres. It should however be noted that the best vehicle dynamics performance is obtained when an integrated 3D-SPS and DYC and AFS is utilised. 相似文献
862.
Some gears in an automobile transmission have to be mounted by being press-fitted on a shaft instead of splines. The torque capacity of the press-fitted gear will be proportional to the radial interference. The excessive interference, however, will increase the gear radial deformation. In this paper, the press- and shrink-fit and the subsequent torque capacity test were investigated by finite element analysis, theoretically and experimentally. The static and dynamic coefficient of friction were determined. 相似文献
863.
This study proposes a design for an idle speed controller to compensate for varying engine load and friction torque in passenger car diesel engines. An active disturbance rejection control (ADRC) framework, comprised of a disturbance compensator and a feedback controller, is applied to an idle speed controller to compensate for disturbances such as engine load and friction torque. In addition, a feedforward compensator is designed into the ADRC framework to improve disturbance rejection performance. The proposed controller is validated by engine and vehicle experiments and the experiment results are compared with a commercial controller. 相似文献
864.
J. H. Seo E. D. Lee J. W. Lee B. K. Han 《International Journal of Automotive Technology》2016,17(4):665-670
This study reports on the effect of vehicle tumble-home (side body inclination) on roof strength. The steep inclination of the side body of a vehicle increases its roof strength. Comprehensive analysis of the impact of high roof strength driven by the steep inclination on dynamic roof strength in rollover is described. Here, we have developed a numerical model using the ADAMS, which is capable of characterizing both of the static and the dynamic roof strength. According to the FMVSS 216 protocol, we achieve the strength to weight ratio (SWR; static roof strength) by applying loading plates to the roof of a vehicle. The Controlled Rollover Impact System (CRIS) allows us to quantitatively characterize the displacements of the top end of A-pillar and B-pillar, thus determining the dynamic roof strength by comparing the results. We demonstrated that the roof intrusion was one of the most critical causes which lead to injuries of occupants fastening seat belts. Our analysis revealed that the increase of the side body inclination of vehicles enhanced the static roof strength whereas it could not reduce the roof displacement (intrusion) in the dynamic rollover. 相似文献
865.
S. M. Yang S. H. Yoo D. S. Gi S. B. Choi K. S. Kim N. T. Jeong S. U. Choi M. W. Suh J. H. Lee 《International Journal of Automotive Technology》2016,17(4):671-679
While a screw is a fastening element that can tighten the two parts at low cost, the loosening of the screw is generated due to external forces such as repetitive load, vibration, and thermal stress. This phenomenon decreases the initial clamping force, and this can be a serious problem to the safety of the product. However, while fastening parts are handled through experiment and experience, there is a lack of research on the screw loosening of plastic fastening parts. For example, vehicles have various fastening parts. Among the fastening elements, screws are typically used for tightening parts of the vehicle door trim. Vehicle interior materials are mainly composed of plastic parts. Especially, the temperature of the vehicle interior changes from a sub-zero temperature to 100 degrees (°C) due to solar radiation. Unlike metals, plastic materials are commonly susceptible to the environment. In this study, the fastening screw of automotive door trim parts is selected. First, a screw loosening mechanism is implemented through Computer Aided Engineering (CAE) analysis and the influences of degradation are then analyzed. Secondly, the selecting method of clamping force is suggested through the analysis result of reduction according to the tightening torque. 相似文献
866.
Despite the widespread use of synthetic data in discrete choice analysis, little is known about how the methodology used to
generate synthetic datasets influences the properties of parameter estimates and the validity of results based on these estimates.
That is, there are two potential sources of biases when using synthetic discrete choice data: (1) bias due to the method used
to generate the dataset; and, (2) bias due to parameter estimation. The primary objective of this study is to examine bias
due to the underlying data generation method. This study compares three methods for generating synthetic datasets and uses
design of experiments and analysis of variance methods to investigate the ability to recover estimates for “true” logsum parameters
for nested logit models. The method that uses nested logit probabilities to generate the chosen alternative results in unbiased
parameter estimates. The method that is based on Gumbel error component approximations reveals that while the error components
themselves are unbiased, subtle empirical identification problems can arise when these error components are combined with
synthetically generated utility functions. The method that is based on normal error component approximations reveals that
all logsum coefficients are biased upwards; the bias dramatically increases for those nests that have a low choice frequency
and is most pronounced for those nests with high correlations among alternatives. Based on the results of the analysis, several
recommendations for the generation of synthetic datasets for discrete choice analyses are provided. 相似文献
867.
868.
The workshop considered system development as a key element of improving the performance of public transport. The main theme was the governance of decision making, design and development of public transport projects. A first main finding is that governance should be improved to keep focus on the original values for which the projects are started. Many projects lose sight of their original aims through the long and often problematic process from inception to operation. A second main finding is that the technological choice, mainly between rubber on tarmac and steel on rails, can be postponed, as both technologies start to overlap in their capacities. A stronger focus on functional needs in the earlier phases of the projects could help. Finally, as the different technologies provide similar options and can be used interchangeably, communicating the service they provide in other ways then through vehicle and infrastructure technology becomes more important. 相似文献
869.
Airline alliances are a global transportation issue which is the subject of increasing attention in the literature. A simple simulation model of air carrier competition in a network is constructed to examine the economic welfare effects of different levels of alliance between the carriers serving the network. The simulations confirm that consumers derive benefits from improved access to passenger markets. However, in many cases, carriers tend to gain from a limited alliance such as code-sharing. This suggests that closer alliances may be driven by other considerations such as raising barriers to entry or the cross-subsidisation of international routes through greater control of the domestic market. 相似文献
870.
Based on a comprehensive review of the literature and preliminary testing performed on a subgrade soil, a testing methodology for repeated load testing was established. This testing protocol was verified using data from subgrade soil. The successful application of this testing protocol on the two subgrade soils proves that it can provide consistent, reliable results. A power model was used to fit the accumulated axial strain over load repetitions with the first hundred cycles excluded from the data set. A number of factors influencing the accumulation of permanent deformation were investigated. The results indicate that confining pressure, load frequency and density are relatively minor contributors to deformation accumulation. Moisture content, deviator stress and first cycle freeze-thaw are major factors governing permanent deformation. The effects of stress history resulting from staged loading are dependent upon the level of applied deviator stress. The interpretation of the rich and consistent deformation data derived from this testing protocol provide valuable insights for transportation engineers relative to the design, construction, operation and maintenance strategy of highway subgrades as well as railway roadbeds. 相似文献