Comparative analysis of vehicle brake data in the ministry of transport test on the roller brake tester and on flat ground

This study performs a comparison between what occurs when braking on a Ministry of Transport (MOT) brake tester and on flat ground. The tire pressure is changed, but the other parameters remain constant. The results from this research and from the in-depth comparative study conducted by the mechanical engineering staff in the mechanical laboratory at the Miguel Hernández University in Elche have led to the following main conclusions: By varying the tire pressure, false results can be obtained with the MOT brake tester, which means that, if the tires are inflated at a low pressure but the brakes are in good condition, the vehicle will not pass the MOT. Conversely, if the brakes are in poor condition but the tire pressure is higher than what is recommended by the manufacturer, a false pass is produced. This article shows that the MOT brake testing equipment is often wrong and inexact, and the data and graphs presented prove that the tire pressure is a determining factor when assessing the condition of brakes.     

Topology optimization of gas flow channel routes in an automotive fuel cell

An efficient topology optimization method for fluid-structure problems was developed in an effort to determine the optimum flow channel route in a fuel cell bipolar plate from first principles. This study describes the derivation and solution of new mathematical equations for topology optimization combining a density-based algorithm, the interpolation method of moving asymptotes (MMA), and the incompressible Navier-Stokes equation with a term representing the chemical reaction between hydrogen and the catalyst. The present method is based on the finite element method with a newly developed reaction rate equation. In this model, a topology variable of 0 represents viscous flow, whereas a value of 1 indicates porous flow. The flow velocity and pressure were obtained from the Navier-Stokes equation and constraints and element matrices for sensitivity analyses during the optimization. MMA was utilized to calculate the optimum flow routes in the design domain. The influence of the key design parameter q and the pressure drop on the optimum topology were also investigated. The channel topology became smoother with decreasing q, and the number of channels increased with increasing pressure drop.     

Fuel consumption of fuel cell hybrid vehicles considering battery SOC differences

Fuel cell hybrid vehicles (FCHVs) have become one of the most promising candidates for future transportation due to current energy supply problem and environmental problem. Fuel economy is an important factor in FCHVs. In order to properly evaluate the fuel economy of an FCHV, the initial battery state of charge (SOC) and the final battery SOC have to be identical so that the effect of the battery energy usage on the fuel economy is neglected. In the simulation or in the real driving, however, the final battery SOC is usually different from the initial battery SOC, and the final battery SOC often depends on the power management strategy. To consider the difference between the two battery SOC values, the concept of equivalent fuel consumption is presented by two methods. One is based on the relationship between delta SOC and delta fuel consumption, and the other is based on the optimal control theory. Two rule-based power management strategies for an FCHV are presented, and for each strategy, the fuel economy is evaluated based on the two methods. The characteristics of the two methods are discussed and compared, and the superior one is selected based on the comparison.     

基于车激动力响应互相关指标的桥梁基础冲刷诊断方法

针对当前桥梁基础冲刷诊断和检测方法过程复杂、成本高且受环境影响大等问题,提出一种基于车激动力响应互相关指标的桥梁基础冲刷诊断方法。该方法通过桥墩和桥跨不同测点的纵向加速度响应自由衰减段信号的互相关分析,建立基础冲刷诊断指标体系,实现冲刷定位和均匀性诊断。首先,依据互相关函数幅值向量置信度判据指标进行基础冲刷初判;然后,通过响应互相关函数幅值向量因子变化率向量进行冲刷定位,再根据横桥向互相关函数幅值变化率向量诊断冲刷均匀性;并通过统计评估方法提高诊断精度;最后,结合1座连续梁桥算例进行多种冲刷工况的数值仿真分析,对所提方法的有效性和适用性进行验证。结果表明：该方法能够很好地实现基础冲刷的定位和均匀性诊断,指标具有较高敏感性;同时具有较好的抗噪性能,通过所提出诊断指标体系的综合使用可消除噪声对诊断结果的干扰。该方法具有诊断结果精度高、过程简便易行、无需进行复杂且误差较大的模态识别、允许试验测试参数和条件适量变化等优点,可嵌入常规桥梁荷载试验同步开展,具有很好的工程应用潜力和实用价值。     

Insights into vehicle trajectories at the handling limits: analysing open data from race car drivers

Race car drivers can offer insights into vehicle control during extreme manoeuvres; however, little data from race teams is publicly available for analysis. The Revs Program at Stanford has built a collection of vehicle dynamics data acquired from vintage race cars during live racing events with the intent of making this database publicly available for future analysis. This paper discusses the data acquisition, post-processing, and storage methods used to generate the database. An analysis of available data quantifies the repeatability of professional race car driver performance by examining the statistical dispersion of their driven paths. Certain map features, such as sections with high path curvature, consistently corresponded to local minima in path dispersion, quantifying the qualitative concept that drivers anchor their racing lines at specific locations around the track. A case study explores how two professional drivers employ distinct driving styles to achieve similar lap times, supporting the idea that driving at the limits allows a family of solutions in terms of paths and speed that can be adapted based on specific spatial, temporal, or other constraints and objectives.     

Vibration reduction of H/Shaft using an electromagnetic damper with mode change

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.     

Modeling multi-unit vehicle dynamics for low-speed path-following assessment off-highway

This paper proposes a non-linear dynamics model for articulated vehicles. This model is able to capture common low-speed behaviours of any articulated vehicles off-highway, such as operating for a corner or roundabout on a cambered or slippery surface. It can be used to assess the low-speed manoeuvrability of articulated vehicles under such manoeuvres and conditions. The vehicle model was validated by comparing its path tracking performance to that of the field tests.     

Driver behavior formulation in intersection dilemma zones with phone use distraction via a logit-Bayesian network hybrid approach

Use of cellular phone while driving is one of the top contributing factors that induce traffic crashes, resulting in significant loss of life and property. A dilemma zone is a circumstance near signalized intersections where drivers hesitate when making decisions related to their driving behaviors. Therefore, the dilemma zone has been identified as an area with high crash potential. This article utilizes a logit-based Bayesian network (BN) hybrid approach to investigate drivers' decision patterns in a dilemma zone with phone use, based on experimental data from driving simulations from the National Advanced Driving Simulator (NADS). Using a logit regression model, five variables were found to be significant in predicting drivers' decisions in a dilemma zone with distractive phone tasks: older drivers (50–60 years old), yellow signal length, time to stop line, handheld phone tasks, and driver gender. The identified significant variables were then used to train a BN model to predict drivers' decisions at a dilemma zone and examine probabilistic impacts of these variables on drivers' decisions. The analysis results indicate that the trained BN model was effective in driver decision prediction and variable influence extraction. It was found that older drivers, a short yellow signal, a short time to stop line, nonhandheld phone tasks, and female drivers are factors that tend to result in drivers proceeding through intersections in a dilemma zone with phone use distraction. These research findings provide insight in understanding driver behavior patterns in a dilemma zone with distractive phone tasks.     

A tool to aid redesign of flexible transport services to increase efficiency in rural transport service provision

Rural areas generally have lower and more dispersed demands for travel which cannot sustain conventional public transport services and consequently have a greater number of flexible and demand responsive transport services operating. These services usually operate on a stand-alone basis, are often subsidized and are typically only accessible by certain passenger types or for specific trip purposes. This generally results in uncoordinated and inefficient transport provision overall. The Flexible integrated transport services (FITS) system featured in this paper has been designed to address this problem. FITS can be used as a planning tool to assess potential benefits from relaxing operating constraints (e.g., a service's operating boundaries), which can potentially suggest service redesign. It also includes the capacity to assign subsidy payments on a trip by trip basis to increase cost efficiency whilst meeting a greater proportion of transport needs. The case study in the paper focusses on transport to health in the Aberdeenshire and Morayshire areas of Scotland in the UK. Despite flexible transport operators receiving public funds to meet passenger needs, this is currently being supplemented by public bodies paying large amounts in taxi fares in instances where there is a statutory obligation to provide travel but where no other suitable transport service exists. The results demonstrate the potential substantial savings which could be realized by allowing transport operators to redesign their services by relaxing constraints and by the reassignment of subsidies: resulting in more passenger demands being met and a reduction in public spending on taxi fares.     

Train-Track Interaction and Mechanisms of Irregular Wear on Wheel and Rail Surfaces

Summary High-frequency train-track interaction and mechanisms of wheel/rail wear that is non-uniform in magnitude around/along the running surface are surveyed. Causes, consequences and suggested remedies to relieve the problems are discussed for three types of irregular wheel/rail wear: (1) short-pitch rail corrugation on tangent tracks and large radius curves, (2) wheel corrugation as caused by tread braking, and (3) wheel polygonalisation. The state-of-the-art in modelling of dynamic train-track interaction in conjunction with prediction of irregular wear is reviewed.