Adaptive control of the shifting process in automatic transmissions

This paper focuses on the way of keeping shift quality of automatic transmissions consistent in mass production and with mileage accumulation. We investigate the main factors influencing the consistency of shift quality. Test results show that the torque to pressure (T2P) and pressure to current (P2I) characteristics of shifting elements are easily affected. A simulation model of an 8-speed automatic transmission is established to simulate the dynamic process of clutch-to-clutch shift. Simulation results demonstrate that the change of T2P and P2I characteristics has a significant influence on shift quality. In order to compensate for the influences, we develop two adaptive control strategies, i.e., the adaptive control strategies for torque phase and inertia phase. They make use of the measured speed information and time information to evaluate shift quality. Then the control parameters are tuned to adapt to the change of T2P and P2I characteristics. Vehicle tests verify that the developed adaptive control strategies are effective to keep shift quality consistent in mass production and with mileage accumulation.     

基于波叠加原理的辐射声场的计算研究

描述了用波叠加原理来计算任意形状的辐射体的辐射声场的方法。即用叠加来代替Kirchhoff-Helmholtz积分的方法．给定辐射体表面的振动速度就可求解辐射源的强度。进而求解辐射体表面的声压和辐射的声功率．文中对刚性球面上振动活塞源和脉动球源的辐射问题进行了求解。并将之与分析(解析)解进行了对比，结果表明用该方法进行计算时，可以用简单的数字方法产生矩阵元素，从而提高计算速度。结果的精度高。并能克服边界元法声场计算内在的奇异性问题．     

Agricultural vehicles and sustainable safe road traffic: solving conflicts on arterial highways

Addressing the issues of traffic safety in rural areas presents a constant challenge. The mix of light and heavy vehicles and the considerable differences in speed among these traffic participants result in high risks and delays for the faster vehicles. Agricultural vehicles (AVs) in particular have such an impact on traffic, especially when using arterial highways. This paper reviews the problems of safety and delays that AVs cause on arterial highways, and the appropriate mitigation. The concept of 'sustainable safety' in The Netherlands focuses on these problems, because of the proposed construction of parallel roads alongside all arterial highways. However, Dutch accident statistics cannot justify the high costs for the construction of parallel roads alongside 7000 km of arterial highways. Delays experienced by fast traffic are another reason for separating AVs from other road users with parallel roads. Alternative measures alongside the arterial highway, such as passing bays, restricting AVs to travelling at off-peak only and improving the conspicuity of the AVs, may be more cost-effective ways of reducing delays and/or improving traffic safety on arterial highways. Another solution may be to eliminate the need for AVs to use the arterial highway by altering their routes. For this purpose, land reallocation projects (as practised in Holland) can provide a useful tool.     

Changing patterns of urban travel Part 2. public transport and future patterns of travel

This two‐part paper contains most of a report prepared by TRRL for the European Conference of Ministers of Transport, and presented by one of the authors to the Council of Ministers in November 1984. Part 1, which was published in the January‐March 1986 issue of Transport Reviews, looked at the way cities have been changing over the years and the influence of growing car ownership on trip patterns. This part examines the changes in public transport use in more detail, considers the interactions between the various underlying trends, speculates on future travel patterns by both public and private means and considers the likely impact of land use and transport policies.     

National policy towards cars: Singapore

Singapore has experienced rapid growth in car ownership, and private transport accounts for just under half of motorized trips in Singapore. Yet only since 1970 have determined efforts been made to curtail this increase. Simultaneously with this growth, Singapore's land‐use planners had called for the diversion of population growth into outlying residential estates while maintaining the central area's importance as an employment centre. The resulting anticipated concentration of commuter movement suggested a need for controls to restrain car ownership, reduce central‐area congestion and divert road users on to public transport. The policies followed are described. Those against ownership have included heavy road taxes and registration fees, with a system of discounts on the latter to discourage new purchasers except when replacing scrapped cars. Policies against car use include fuel taxes and the Area Licensing Scheme in the city centre, while parking space is also closely regulated. The measures adopted imply a goal of efficiency in promoting Singapore's planning objectives rather than environmental, safety or equity considerations, although the first two of these have lately received much more attention than formerly. The policies’ effect has been a temporary reversal in the growth of car ownership, but this growth has since resumed and recent further fee increases suggest a panic reaction rather than a coordinated strategy. Such coordination appears at present to be hampered by the fragmented administration of matters relating to transport. Other measures relating to car ownership and use in Singapore are also described.     

Hysteresis in travel demand

This paper presents evidence that there is a hysteresis effect in the demand for transport usage with respect to price. Consequently the neoclassical concept of a smooth continuous demand curve is questioned. The author presents a hysteresis model whereby changes in demand and of demand are embraced in a single theory related to generalized cost.     

Bus running time prediction using a statistical pattern recognition technique

Abstract

Given that real-time bus arrival information is viewed positively by passengers of public transit, it is useful to enhance the methodological basis for improving predictions. Specifically, data captured and communicated by intelligent systems are to be supplemented by reliable predictive travel time. This paper reports a model for real-time prediction of urban bus running time that is based on statistical pattern recognition technique, namely locally weighted scatter smoothing. Given a pattern that characterizes the conditions for which bus running time is being predicted, the trained model automatically searches through the historical patterns which are the most similar to the current pattern and on that basis, the prediction is made. For training and testing of the methodology, data retrieved from the automatic vehicle location and automatic passenger counter systems of OC Transpo (Ottawa, Canada) were used. A comparison with other methodologies shows enhanced predictive capability.     

Economies of density and factor substitution in Dublin city bus services — a translog approach

The primary aim of the paper is to determine a short‐run cost function for Dublin City Bus Services (DCS), using a translog approach. The results show that there are significant economies of density in the transit operation. The results also indicate that the structure of DCS is characterised by a homothetic production function and that partial elasticities of substitution are non‐unitary.     

A study of the bi-directional pedestrian flow characteristics at Hong Kong signalized crosswalk facilities

This paper investigates the bi-directional flow characteristics at signalized crosswalk facilities in Hong Kong. Pedestrian flow measurements were conducted at selected signalized crosswalks in Hong Kong urban area with and without the Light Rail Transit (LRT) railway tracks in the median of the carriageway. The pedestrian speed-flow functions for these crosswalk facilities were calibrated. The relationships between the walking speed at capacity and directional distribution of pedestrian flow (or flow ratio) are determined. The effects of different flow ratio on the effective capacity are also investigated. The bi-directional pedestrian flow effects on signalized crosswalk facilities with LRT tracks are found more significant than those without LRT tracks. The result could be used as a basis to improve the assessment of the crosswalk's capacity and to determine the design walking speeds under different flow ratios at signalized crosswalks in Hong Kong and in other Asian cities with similar environments.     

Performance analysis of a CVT clutch system for a hybrid electric vehicle

In this study, the performance of a CVT clutch system for a hybrid electric vehicle was investigated. To analyzed the vehicle performance at restart, the restart delay and driveshaft torque was investigated by simulations and experiments. It was found from the simulation results that the vehicle restart response depends on the clutch pressure buildup time to the point where the clutch torque begins to overcome the vehicle road load, and driving comfort at restart is directly related to the rate change of the clutch pressure.