A Comparison of Adaptive LQG and Nonlinear Controllers for Vehicle Suspension Systems

A design feature of many computer-controlled suspension systems, is their ability to adapt control law parameters to suit prevailing road conditions. Here, for systems employing high bandwidth actuators and state variable feedback control, the benefits of such adaptation are shown to be at best marginal. An optimal adaptive LQG system is compared with a fixed structure nonlinear feedback controller in the context of a simple quarter-vehicle suspension model. Performance comparisons are made, and trends considered under more realistic conditions. In consequence the overall usefulness of this type of adaptation is called into question.     

The coastal barrier resources act of 1982: An assessment of legislative intent,process, and exemption alternatives

Recent coastal barrier legislation demonstrates a growing national concern to protect fragile undeveloped coastal barriers and to prevent the expenditure of federal monies used in promoting their development. The Coastal Barrier Resources Act of 1982 bases designations of undeveloped coastal barriers on previous federal legislation and Department of the Interior rule‐making. This paper examines the legislative intent of Congress and how it was interpreted through the designation process. Alternative strategies to achieve exemption from the Coastal Barrier legislation are discussed as a process, and an analysis is made of an exemption as it occurred in Texas.     

中国的先行者

州数码在北京、上海、广州设有主要分销中心，在各省和省会城市设有10个分销点。为了进一步加强在三、四线城市的覆盖力度神州数码于2005—06年在分销网络中又增加了29个城市,其大陆的分销商总数达到了8．225个，同比增长35％。     

Performance indicators for public transit connectivity in multi-modal transportation networks

Connectivity plays a crucial role as agencies at the federal and state level focus on expanding the public transit system to meet the demands of a multimodal transportation system. Transit agencies have a need to explore mechanisms to improve connectivity by improving transit service. This requires a systemic approach to develop measures that can prioritize the allocation of funding to locations that provide greater connectivity, or in some cases direct funding towards underperforming areas. The concept of connectivity is well documented in social network literature and to some extent, transportation engineering literature. However, connectivity measures have limited capability to analyze multi-modal public transportation systems which are much more complex in nature than highway networks.In this paper, we propose measures to determine connectivity from a graph theoretical approach for all levels of transit service coverage integrating routes, schedules, socio-economic, demographic and spatial activity patterns. The objective of using connectivity as an indicator is to quantify and evaluate transit service in terms of prioritizing transit locations for funding; providing service delivery strategies, especially for areas with large multi-jurisdictional, multi-modal transit networks; providing an indicator of multi-level transit capacity for planning purposes; assessing the effectiveness and efficiency for node/stop prioritization; and making a user friendly tool to determine locations with highest connectivity while choosing transit as a mode of travel. An example problem shows how the graph theoretical approach can be used as a tool to incorporate transit specific variables in the indicator formulations and compares the advantage of the proposed approach compared to its previous counterparts. Then the proposed framework is applied to the comprehensive transit network in the Washington–Baltimore region. The proposed analysis offers reliable indicators that can be used as tools for determining the transit connectivity of a multimodal transportation network.     

An analysis of the retail and lifecycle cost of battery-powered electric vehicles

Regulators, policy analysts, automobile manufacturers, environmental groups, and others are debating the merits of policies regarding the development and use of battery-powered electric vehicles (BPEVs). At the crux of this debate is lifecycle cost: the annualized initial vehicle cost, plus annual operating and maintenance costs, plus battery replacement costs. To address this issue of cost, we have developed a detailed model of the performance, energy use, manufacturing cost, retail cost, and lifecycle cost of electric vehicles and comparable gasoline internal-combustion engine vehicles (ICEVs). This effort is an improvement over most previous studies of electric vehicle costs because instead of assuming important parameter values for such variables as vehicle efficiency and battery cost, we model these values in detail. We find that in order for electric vehicles to be cost-competitive with gasoline ICEVs, batteries must have a lower manufacturing cost, and a longer life, than the best lithium-ion and nickel–metal hydride batteries we modeled. We believe that it is most important to reduce the battery manufacturing cost to $100/kWh or less, attain a cycle life of 1200 or more and a calendar life of 12 years or more, and aim for a specific energy of around 100 Wh/kg.     

国内汽车厂家竞逐上市

为了赢得新客户和增加市场份额，中国的国内汽车制造商与国外品牌的竞争日趋白热化，而很多国内制造商已经成功取得了竞争优势。当前，以比亚迪、奇瑞和吉利等为首的国内品牌已经占到中国乘用车年销量的近1／3。一场横扫中国7000多家汽车经销商的销量比赛正进行得如火如茶。而同时，另一场不为大众消费者所瞩目的擂台赛也正愈演愈烈。众多中国汽车制造商正在计划或已经将公司在上海、深圳或香港的证券交易所公开上市。     

Dynamic stability in following seas: predictive and experimental approaches

This article presents work based on the development of a performance-based stability assessment method. It describes a numerical method used to determine the survival limit for a dynamic intact stability assessment procedure. The numerical method utilises a time-domain vessel motion program to assess the limit for a range of vertical centres of gravity (KG). The appropriateness of the numerical predictions was examined through comparison with model experiment results. Free-running model tests were conducted in regular following waves at discrete KGs. A comparison between the survival limits determined through the numerical and experimental methods is presented. The current International Maritime Organisation (IMO) stability criteria are also evaluated against the numerical and experimental dynamic performance-based stability assessment methods.     

站在北美港口的角度 看跨太平洋集装箱班轮航线

2004年是温哥华港务局作为第一家北美的港口获准在中国正式建立办事处的第十个年头.     

Minimizing vehicle post impact path lateral deviation using optimized braking and steering sequences

This paper investigates the optimal control of a vehicle, after a light impact during a traffic accident. To reduce the risk of secondary events, the control target is set: to minimize the maximum lateral deviation from the initial path. In previous analysis path control was achieved by the active control of individual wheel braking. The present paper examines potential benefits from the additional control of front steering angles. Numerical optimization is used to determine optimal control sequences for both actuator configurations. It is found that steering provides significant control benefits, though not for all post-impact kinematics. For all cases considered, the optimal control operates at the boundary of the control domain of available forces and moments. This domain is expanded when steering is available, and there exists an expanded range of conditions for which coupled control of yaw moments and lateral forces is the most effective control strategy. The sensitivity of vehicle response to the individual actuator controls is studied; it reveals this sensitivity is related to the actuator bandwidth and the lack of any dynamic cost in the longitudinal direction. This motivates a further analysis which includes longitudinal and lateral dynamics in the cost function. This is broadly related to real-world crash risks. Further, different versions of such cost functions are compared as a basis for implementation in a closed-loop controller.