New level of vehicle comfort and vehicle stability via utilisation of the suspensions anti-dive and anti-squat geometry

In this article a novel vehicle dynamics control concept is designed for a vehicle equipped with wheel individual electric traction machines, electronically controlled brakes and semi-active suspensions. The suspension's cross-couplings between traction forces and vertical forces via anti-dive and anti-squat geometry is utilised in the control concept to improve driving comfort and driving stability. The control concept is divided into one main and two cascaded branches. The main controller consists of a multivariable vehicle dynamics controller and a control allocation scheme to improve the vehicle's driving comfort. The cascaded feedback loops maintain the vehicle's stability according to wheel slip and vehicle sideslip. The performance of the combined vehicle dynamics controller is compared to a standard approach in simulation. It can be stated that the controller piloting semi-active suspensions together with brake and traction devices enables a superior performance regarding comfort and stability.     

为进行能源管理并强化车体结构所采用的结构粘合剂

1简介在汽车制造过程中,作为一种金属连接的方式,结构粘合剂的应用正处于迅猛发展阶段。结构粘合剂可增强粘接结构的刚性、耐久性和抗冲撞性。此外．该粘合剂的使用使得相容性差的金属之间的粘接变得容易,因此从成本高低和车体质量大小方面加大了车体结构优化设计的可能性。     

Estimation of link performance functions from incomplete flow data

Despite the pivotal importance of link performance functions to models of transport systems, relatively little work has been done on practical aspects of estimating these functions from observed data. Furthermore it is difficult to find any examples in the literature of estimated urban link performance functions faithfully reproducing theoretical travel time-flow relationships. One reason for the paucity of research in this area is the difficulty and expense of obtaining the requisite data. The increase in automatic collection of traffic flow data goes part way to resolving this problem, but matching such flows to manually recorded travel times can present considerable statistical difficulties in the estimation procedure. This paper considers the estimation of link performance functions from a combination of automatically recorded traffic counts and travel collected by hand, using a non-standard statistical methodology. The study is motivated by a set of data of precisely this type, from the UK city of Leicester.     

Learning from Los Angeles: transport,urban form,and air quality

Los Angeles is well known around the world as an automobile-oriented low density community, yet recent transportation policies have emphasized greater capital investment in rail transportation than in highways, and recent policies have attempted to discourage automobile usage through transportation demand management. While these policies have accomplished small shifts toward public transport and somewhat lower dependence upon singly occupied automobilies for work commuting, the financial costs of these policy changes has been very large in relation to their benefits. Proper pricing of transportation alternatives, more creative use of new and emerging transportation technologies, and the provision of many more opportunities for simpler private sector transport services, would all appear to be more promising as cost-effective approaches to coping with congestion in Los Angeles than the current regional transportation policies.     

Railway Vehicle Modelling by the Constraint Equation Method*

A method for the dynamic analysis of railway vehicles is proposed. The method is based on both the using of constraint equations, and on the building of the mathematical model by means of the initial data.

The calculation models are nonlinear, due both to the connecting elements, and to the wheel-rail contact modelling. Solving of differential equations is achieved by time step integration. The method has been applied to the analysis of a freight wagon and a train unit.     

Lifestyles and transportation needs of the elderly in Los Angeles

This study examined the trip-making behavior of persons over 65 years of age residing in Los Angeles County. To date, the major shortcoming of most research concerned with the transportation needs of the elderly is that the aged have been treated as a homogeneous group without recognizing the various lifestyles of the senior population. The two most easily distinguishable groups of elderly persons within the county are those residing in the inner-city and those around the urban fringe. Although many elderly are still found in gray ghettos there is currently a trend toward a more suburban generation of retirees. Four areas were selected within the county that reflected these two living patterns of the elderly. A comparative analysis of trip patterns and socio-economic data was completed. It was found that the suburban elderly are characterized as (1) having higher incomes, (2) residing predominantly in single-family units and (3) being reliant upon automobile transportation. As is typical of a large proportion of those over 65 years of age, many of the suburban elderly cannot drive. Studies of the transportation needs of this group indicate that without transit alternatives they may well become society's most transit-deprived segment. On the other hand, while the inner-city elderly may have a wider range of transportation options, they also have a distinct economic disadvantage which preludes their accessibility to opportunities. An analysis of modal choices, trip purposes and the frequency of travel exhibited many similarities and some significant differences in the travel behavior as well as problems of these two groups.In addition to investigating travel patterns a survey of taxi-cab use on weekends and weekdays was undertaken. Elderly persons represent a substantial proportion of taxi-cab patrons. Their use of taxis is further indicative of the change that occurs in mobility patterns upon reaching retirement. This mode of transportation is presently the only type of demand-responsive service available to the senior population in some parts of the county.This report was produced as part of a program of Research and Training in Urban Transportation sponsored by the Urban Mass Transportation Administration of the U.S. Department of Transportation. The results and views expressed are the independent products of university research and are not necessarily concurred in by the Urban Mass Transportation Administration of the Department of Transportation.     

Cohort analysis of driving cessation and limitation among older adults

Automobiles are central to participation in economic, social, and cultural activities in the United States. The ability to drive as one ages is fundamental to the quality of life among older adults. Driving rates decline significantly with age. Researchers using cross-sectional data have studied the reasons former drivers have stopped driving, but few have followed individuals over time to examine changes in relationships among driving cessation, socio-demographics, and health conditions. We used longitudinal data from a national sample of 20,000 observations from the University of Michigan Health and Retirement Study (HRS) to examine relationships among demographic variables, health conditions, and driving reduction and driving cessation. Longitudinal data allow analysis of generational differences in behavior, a major advantage over cross-sectional data which only allow comparisons of different people at one point in time. We found, like many other studies, that personal decisions to limit and eventually stop driving vary with sex, age, and health conditions. In addition, unlike most previous studies, we also found that those relationships differ by birth cohort with younger cohorts less likely to stop and limit their driving than their older counterparts. The findings indicate an evolution in the association between driving cessation and its causes.

     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.