感应电动机无速度传感器矢量控制在铁道机车车辆传动方面的应用

铁道机车车辆牵引领域中的转矩控制是利用脉冲发生器(PG)来检测牵引感应电动机的转子频率.从提高牵引系统可靠性、降低成本和维修费用以及减小感应电动机尺寸的观点出发,最好不使用PG.为此,一直在研究把无速度传感器控制方法应用于牵引感应电动机的控制,提出了应用无速度传感器的控制策略.文章叙述了铁道机车车辆牵引的新控制方法并出示一些研究试验的结果.     

用于城市交通的直线电机推进系统

现代城市交通系统必须提供连发列车间隔时间短的高水平服务.线路的设计必须灵活并且允许存在局部陡峭路际,从而最大程度地降低交通系统成本.不管气候如何,交通系统都务必要保证列车准点到站.直线感应电机(LIM)推进系统在理论上能满足运行要求,而且其加速度和制动力都不依赖于轮轨粘着,其拓扑结构是短一次侧在车上而长二次侧在地面.为了设计可行的交通系统,必须要考虑LIM拓扑的影响.设计时需考虑气隙问题、反应轨结构改变问题、法向力及直接驱动的操作问题.LIM推进系统已经开发出两代,并在5个先进的交通系统中成功应用.     

The anachronism in maritime law that is general average

The concept of general average is of great antiquity. It has fruitfully served the maritime community of the last two millennia, but the justification for its continued existence in the 21^st century is questionable. This article examines the proposition that general average is an anachronism and should be abolished — a cry that has been heard for well over a hundred years but has failed to materialise. In the article, the arguments for retaining general average are marshalled alongside the demands for its demise. Current developments in the revision of the York-Antwerp Rules are discussed. In conclusion, the resilience of general average as an age-old equitable maritime principle is recognized. But the author points to the sophistication in the modern regime of marine insurance in support of discarding general average and allowing maritime losses to lie where they fall; to be indemnified independently by the insurer of each interest in a maritime adventure without contribution from co-adventurers or their insurers.     

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电力是现今大部份铁道系统的动力来源． 可靠、有效率及安全的电力输送对整体铁道服务质素尤为重要，跟其它大型工程系统一样，铁道供电系统的设计，运作及筹划相当倚重计算机仿真．本文将回顾铁道供电系统仿真的模型及一般常规，并通过模拟结果例子及实际应用，介绍最新的模拟方式发展．本文亦对铁道供电系统仿真的未来挑战作出评论．     

Customer loads of two-wheeled vehicles

Customer usage profiles are the most unknown influences in vehicle design targets and they play an important role in durability analysis. This publication presents a customer load acquisition system for two-wheeled vehicles that utilises the vehicle's onboard signals. A road slope estimator was developed to reveal the unknown slope resistance force with the help of a linear Kalman filter. Furthermore, an automated mass estimator was developed to consider the correct vehicle loading. The mass estimation is performed by an extended Kalman filter. Finally, a model-based wheel force calculation was derived, which is based on the superposition of forces calculated from measured onboard signals. The calculated wheel forces were validated by measurements with wheel–load transducers through the comparison of rainflow matrices. The calculated wheel forces correspond with the measured wheel forces in terms of both quality and quantity. The proposed methods can be used to gather field data for improved vehicle design loads.     

Steering torque control using variable impedance models for a steer-by-wire system

This paper presents a novel sensor-less steering torque control method for applications to the steer-by-wire system. A steer-by-wire system has not any mechanical link to connect a steering wheel and a rack and pinion gear module. Instead of mechanical devices, two electric motors are used on each side. A one motor is attached to the steering wheel and the other is set on rack and pinion. The motor on the steering wheel works as a deliverer between a steering torque and load torque from the road. In this paper, we focus on motion control related to the steering feel based on impedance control. Therefore, the model of rack and pinion is not considered in this work. In most power steering systems, a torque sensor is used to set impedance effect on driver’s steering feel. In this paper, we proposed a novel steering control method without using any torque sensors. The effectiveness of a proposed method is confirmed from experimental results.     

Integration of GPS and monocular vision for land vehicle navigation in urban area

For land vehicle navigation in urban area, Global Positioning System (GPS) receivers often suffer from the lack of positioning accuracy, availability, and continuity due to insufficient number of visible satellites and multipath errors. To mitigate this problem, this paper proposes an efficient hybrid positioning method combining a single frequency GPS receiver and a monocular vision sensor. The proposed method is advantageous in that it requires only low-cost hardware and no external map aiding. Compared with existing vision-based methods, the proposed method directly measures absolute heading angle based on the images of straight road segments. For the reason, the proposed method is resilient to multipath errors. The performance of the proposed method is evaluated by the experiments with field-collected real measurements; one with good satellite visibility and the others with poor satellite visibility. Comparison with existing positioning methods demonstrates the feasibility of the proposed method in urban area.     

Influence of rail pressure on a two-stage turbocharged heavy-duty diesel engine under transient operation

The demand for continually improving the transient performance of diesel engines requires higher rail pressure and more efficient turbocharger. Before the test, a two-stage turbocharger with a turbine by-pass valve (TBV) had been matched reasonably with the base engine. In order to reduce smoke emission under the typical 5-second transient process of constant speed and increasing torque, the influence of rail pressure on combustion, emissions and performance characteristics was experimentally investigated. The results showed that the two-stage turbocharger was helpful in improving transient performance. Moreover, the full-stage rail pressure (FSRP) strategies (increasing rail pressure during the whole transient process) could reduce smoke emission when the TBV was closed. However, smoke deteriorated once TBV opening got larger. Then the sectional-stage rail pressure (SSRP) strategies (increasing rail pressure from a pre-set load to 100 % load) were presented under small TBV opening to improve in-cylinder thermal condition. Hence, the air-fuel mixing process was improved at medium and large loads. Then the maximum decline of smoke opacity peak was 56.3 %, which happened under 10 % TBV opening. In addition, fuel consumption of FSRP strategies got worse under larger TBV opening. However, this deterioration situation could be effectively restrained by the utilization of SSRP strategies.     

Deregulation of inter‐city coach services in Britain

Public transport in Britain has traditionally operated under conditions of regulation. The 1930 Road Traffic Act imposed controls upon the quantity and quality of transport regulations, with an abolition of the quantity controls associated with inter‐city coach services. The principal objectives of the Act were to eliminate restriction upon entry to the market and to promote competition between coach operators.

This paper is based on research which was undertaken to establish the impact of the 1980 Transport Act upon express (inter‐city) coach services in Britain. The effects of the legislation are examined in relation to the experience of various coach operators, British Rail, and the inter‐city traveller. This provides evidence of the way in which the supply of, and demand for, public transport behaves in a competitive, deregulated environment. It is shown that at least in net terms, the consumer has enjoyed short‐term benefits. Greater uncertainty surrounds the long‐term situation. The main competition has been confined to the principal trunk routes and has taken place between the state‐owned undertaking of National Express and British Rail. The outcome of deregulation for the private sector has been disappointing.

The paper identified similarities which exist between inter‐city and local public transport services. In this context, the lessons derived from express deregulation are employed to suggest likely developments in the deregulation of stage carriage (local) services in Britain.