On appropriate microstate descriptions in entropy modelling

Using an information-theoretic approach to entropy modelling, expressions for the possible number of microstates are derived from the sets of choices available to households and firms in given location/transport planning situations. In planning applications, the urban space is usually subdivided into discrete zones, and various classes of householders and firms are grouped into separate activities. Nevertheless, the location sites within zones may vary considerably in accessibility, price and quality, and amenity v. cost trade-offs between location and travel many differ markedly between individuals within the same activity group. The inclusion of such variations within a random utility framework is demonstrated to be equivalent to maximizing entropy with the microstates disaggregated to the level where these variations occur. Using constraints based on spatial conditions, observed behaviour and planning policy, entropy maximization is used to determine the most probable macrostate according to each choice set specification. The resulting distributions are compared and their revelance discussed.     

A capacity related reliability for transportation networks

A capacity related reliability for transportation networks with random link capacity is introduced. It is defined as the probability that the road network can accommodate a certain level of traffic demand, and is built on the concept of network reserve capacity. Network reserve capacity is defined as the largest multiplier applied to an existing origin-destination demand matrix that can be allocated to a transportation network in a user-optimal way without violating the link capacities. Due to large variability associated with link capacities, a probabilistic approach is adopted to model the different physical and operational factors that often degrade the capacity of roadways. A Monte Carlo simulation procedure is developed to estimate the capacity related reliability measure. Numerical results are provided to demonstrate the feasibility of the approach.     

轮轨系统中使用直线电动机技术的可能性

德国铁路为提高现有以及今后动车的功率,研究了轮轨系统中使用直线电动机技术的可能性.首要的问题是,用直线电动机产生的附加切向力提高牵引力.接着的另一个项目是,研究直线电动机产生的附加法向力分量是否能提高传递到轮轨接触点上的牵引力或制动力,以及是否能降低轻型导向的端部控制车对侧风的敏感性.     

SCR control strategy based on ANNs and Fuzzy PID in a heavy-duty diesel engine

The paper presents an innovative method combining artificial neural networks (ANNs) with Fuzzy PID to demonstrate the advantages of this control approach for meeting both NOx emission requirements and NH3 slip targets. An ANN model was utilized to simulate the formation of NOx emissions under various engine operating conditions. Next, an effective closed-loop control strategy with a type of feedback known as fuzzy PID is adopted for on-line, real-time control of 32.5% aqueous urea dosing in the exhaust stream. The new strategy explores the benefits by simulation and testing in the environments of Matlab/Simulink and ESC/ETC, respectively. The notable achievement of considerable NOx reduction and an acceptably small NH3 slip is obtained based on this new, feasible and effective strategy.     

Design methodology to reduce the chest deflection in US NCAP and EURO NCAP tests

There have not been many studies on the factors that affect chest deflection, although the US NCAP thoracic injury criterion was recently shifted from the 3-msec clip to chest deflection. This study explored these factors and proposed a design methodology for the factors to minimize chest deflection. Because injuries can become severe if the driver crashes against the vehicle interior, this study also sought a solution using a penalty function to prevent crashes with the interior and minimize injuries. First, a MADYMO model was made to simulate US NCAP and EURO NCAP tests by one-to-one and stochastic verifications. Second, a sensitivity analysis was conducted to find the major factors that affect chest deflection. Lastly, the factors identified via the sensitivity analysis were optimized to propose design guidelines that helped vehicles receive high star ratings in US NCAP and EURO NCAP tests and helped minimize the possibility of hard contact between the driver and the vehicle interior by utilizing a penalty function and the Taguchi method.     

Development of a control strategy based on the transmission efficiency with mechanical loss for a dual mode power split-type hybrid electric vehicle

In this study, a control strategy for a dual mode power split-type hybrid electric vehicle (HEV) is developed based on the powertrain efficiency. To evaluate the transmission characteristics of the dual mode power split transmission (PST), a mechanical loss model of the transmission (TM loss) is constructed. The transmission efficiency, including the TM loss, is evaluated for the dual mode PST. Two control strategies for the dual mode PST are proposed. An optimal operation line (OOL) control strategy is developed to maintain a high engine thermal efficiency by controlling the engine operation point on the OOL. A speed ratio (SR) control strategy is proposed to obtain a greater transmission efficiency by shifting the engine operation point when the dual mode PST operates near the mechanical points. Using the TM loss and the proposed control strategies, a vehicle performance simulation is conducted to evaluate the performance of the two control strategies for dual mode PST. The simulation results demonstrate that, for the SR control strategy, the engine efficiency decreases because the engine operates beyond the OOL. However, the transmission efficiency of the dual mode PST increases because the PST operates near the mechanical point where the PST shows the greatest transmission efficiency. Consequently, the fuel economy of the SR control strategy is improved by 3.8% compared with the OOL control strategy.     

Development of a fail-safe control strategy based on evaluation scenarios for an FCEV electronic brake system

This study presents a few fail-safe control strategies based on reliability evaluation scenarios for the electronic brake systems of green cars in several critical cases. CarSim and MATLAB Simulink were used to develop the FCEV model with regenerative braking involving EWBs and EMBs. The proposed reliability evaluation scenarios were simulated, and a few fail-safe control algorithms were verified using the proposed reliability evaluation scenarios with the developed FCEV simulation model. The reliability evaluation scenarios were developed using a combination of driving modes and FMEA results for these electronic brake systems.     

Nonlinear tire-road friction control based on tire model parameter identification

A hierarchical control structure is a more suitable structural scheme for integrated chassis control. Generally, this type of structure has two main functions. The upper layer manages global control and force allocation, while the bottom layer allocates realized forces with 4 independent local tire controllers. The way to properly allocate these target forces poses a difficult task for the bottom layer. There are two key problems that require attention: obtaining the nonlinear time-varying coefficient of friction between the tire and different road surfaces and accurately tracking the desired forces from the upper layer. This paper mainly focuses on longitudinal tire-road friction allocation and control strategies that are based on the antilock braking system (ABS). Although it is difficult to precisely measure longitudinal tire-road friction forces for frequently changing road surface conditions, they can be estimated with a real-time measurement of brake force and angular acceleration at the wheels. The Magic Formula model is proposed as the reference model, and its key parameters are identified online using a constrained hybrid genetic algorithm to describe the evolution of tire-road friction with respect to the wheel slip. The desired wheel slip, with respect to the reference tire-road friction force from the top layer, is estimated with the inverse quadratic interpolation method. The tire-road friction controller of the extended anti-lock braking system (Ext-ABS) is designed through use of the nonlinear sliding mode control method. Simulation results indicate that acceptable modifications to changes in road surface conditions and adequate stability can be expected from the proposed control strategy.     

Forme urbaine et mobilité domicile-travail dans 13 aires urbaines françaises : une analyse multiéchelle

This article provides a multi-scale analysis of the links between commuting patterns and urban form by using both morphological and more classical indicators of urban form (like density). Thirteen French urban areas of more than 500,000 inhabitants (excluding Paris) are compared. The findings highlight the complexity of the links between urban form and commuting patterns because the same indicators of urban form do not have the same influence according to the spatial scale. Even if the influence of the morphological indicators is lower than that of more classical socioeconomic variables (income level, motorization rate), our study discusses the various and multi-scale consequences of urban development on daily travel behaviour.