A dynamic traffic assignment model for a continuum transportation system

A predictive continuum dynamic user-optimal (PDUO-C) model is formulated in this study to investigate the dynamic characteristics of traffic flow and the corresponding route-choice behavior of travelers within a region with a dense urban road network. The modeled region is arbitrary in shape with a single central business district (CBD) and travelers continuously distributed over the region. Within this region, the road network is represented as a continuum and travelers patronize a two-dimensional continuum transportation system to travel to the CBD. The PDUO-C model is solved by a promising solution algorithm that includes elements of the finite volume method (FVM), the finite element method (FEM), and the explicit total variation diminishing Runge-Kutta (TVD-RK) time-stepping method. A numerical example is given to demonstrate the utility of the proposed model and the effectiveness of the solution algorithm in solving this PDUO-C problem.     

Defect control at nanoscale and flux pinning enhancement in MgB2 superconductor

Defect control at nanoscale of MgB2 by doping various nanoparticles including Ti,C,nano-diamond,and HoB4,and their roles played to enhance flux pinning force in MgB2 arc compared and analyzed.These nan...     

Dynamic modeling of the electro-mechanical configuration of the Toyota Hybrid System series/parallel power train

The hybridization of the conventional thermal vehicles nowadays constitutes a paramount importance for car manufacturers, facing the challenge of minimizing the consumption of the road transport. Although hybrid power train technologies did not converge towards a single solution, series/parallel power trains with power-split electromechanical transmissions prove to be the most promising hybrid technology. In fact, these power trains show maximum power train overall efficiency and maximum fuel reduction in almost all driving conditions compared to the conventional and other hybrid power trains. This paper addresses the model and design of the electro-mechanical configuration of one of the most effective HEV power trains: case study of the 2nd generation Prius. It presents the simulation work of the overall operation of the Toyota Hybrid System (THS-II) of the Prius, and explores not only its power-split eCVT innovative transmission system but also its overall supervision controller for energy management. The kinematic and dynamic behaviors of the THS-II power train are explained based on the power-split aspect of its transmission through a planetary gear train. Then, the possible regular driving functionalities that result from its eCVT operation and the energy flow within its power train are outlined. A feed-forward dynamic model of the studied power train is next proposed, supervised by a rule-based engineering intuition controller. The energy consumption of the THS-II proposed model has been validated by comparing simulation results to published results on European, American and Japanese regulatory driving cycles.     

Optimization of intake port design for SI engine

It is well known that in-cylinder flow is very important factor for the performance of SI engine. An appropriate in-cylinder flow pattern can enhance the turbulence intensity at spark time, therefore increasing the stability of combustion, reducing emission and improving fuel economy. In this paper, the effect of intake port design on in-cylinder flow is studied. It is found a vortex existed at the upper side of intake port of a production SI engine used in the study, during the intake stroke, which will reduce both tumble ratio and volumetric efficiency. A minor modification on intake port is made to eliminate the vortex and increase tumble ratio while keeping volumetric efficiency at the same level. It is demonstrated that the increase in tumble in the new design results in a 20 per cent increase in the fuel vaporization. In this study, both KIVA and STAR-CD are used to simulate the engine cold flow, as well as ICEM CFD and es-ice used as pre-processor respectively due to the complexity of engine geometry. Simulation results from KIVA and STAR-CD are compared and analyzed.     

Hybrid vehicle power management modeling and refinement

The power management strategy in many hybrid vehicles is based on expert rules and thresholds. These rule-based strategies can result in good efficiency in term of fuel economy and emissions if their thresholds and rules are accurate. However, due to the complexity and the non-linearity of the hybrid powertrain, determining accurate thresholds and rules is neither explicit nor straightforward, and experts in most cases fail to define these thresholds and rules with enough accuracy. Based on this fact, the objective of this paper is to propose a method to improve this rule-based strategy by refining its thresholds and rules. To achieve this, we used an optimization method (dynamic programming) to calculate the optimal power management, determine the optimal control signals, and extract efficient thresholds and rules that can be used in real time. Finally, simulation results for the three strategies (optimal, simple and refined strategy) are shown and discussed.     

Highly reliable driving workload analysis using driver electroencephalogram (EEG) activities during driving

Traffic accidents are caused by various factors, which can be classified into human factors, vehicle factors and environmental factors. Recently, human factors have been drawing particular attention as efforts are being made to enhance the safety performance of vehicles and improve road conditions. Driving distraction caused by an increased driving workload is a representative human factor. Various studies in the past have attempted to quantify the driving workload by using EEG activities. However, they have failed to consider vibration properties generated from vehicle engines. A number of noise signals were included in brainwave signal processing, which resulted in a failure to obtain reliable outcomes. Thus, this study suggests driver EEG activities free of vehicle engine secondary vibration in order to develop a method that analyzes the driving workload with high statistical reliability. By using the analytical method developed in this study, standard values of driving workload for straight and left-turn driving that has statistical significance could be calculated. The analytical method for driving workload created by this study can be applied to HVI and road design.     

Robustness analysis of ESC ECU to characteristic variation of vehicle chassis components using HILS technique

The ESC system, since its introduction in the mid 90s, has greatly contributed to prevention of vehicle accidents with its capability of maintaining vehicle stability in severe driving conditions. Due to its significant advantages, many nations are now adopting regulations that mandate installation of the ESC system in all classes of passenger vehicles — from mini to luxury. Accordingly it became important to know whether an ESC ECU can yield good performance on a wide range of vehicle parameter changes. In this paper, robustness analysis was conducted to study how characteristic variation of the main chassis components affect the performance of the ESC ECU. This analysis was carried out using a HILS system built on an actual ESC ECU. The variation range of each chassis component was carefully selected considering the component’s design criteria adopted in automotive industries. Based upon the robustness analysis results, the allowable variation ranges of the chassis components for ensuring sound performance of an ESC ECU were proposed.     

Effectiveness of ECE R66 and FMVSS 220 standards in rollover crashworthiness assessment of paratransit buses

The main objective of the presented study was to compare the effectiveness of two standard test procedures for evaluating bus roof integrity: the dynamic rollover test according to UN-ECE Regulation 66 (ECE-R66), and the quasi-static symmetric roof loading according the Federal Motor Vehicle Safety Standard 220 (FMVSS 220). Both tests were applied to a selected Paratransit Bus. The investigation was carried out primarily using a numerical study backed up by experimental validation tests on components and full scale rollover tests. A sensitivity analysis using LS-OPT? was performed to identify the most important structural components influencing the response of the bus in these two tests. The results obtained from this study show that the final outcome of the crashworthiness assessment of the selected paratransit bus depends on the selection of the evaluation standard. Although the two tests are used for the same purpose of roof integrity evaluation, their results are divergent and may lead to different conclusions. The paper presents a discussion on the effectiveness of both standards in evaluating the rollover crashworthiness.