Lateral dynamics of motorcycles towing single-wheeled trailers

A motorcycle towing a single-wheel trailer may provide useful transport for light cargo on narrow tracks and off-road use, particularly in rural areas of developing countries. Four designs of such trailers are described. Linear models are derived for the lateral dynamics of an off-road motorcycle towing this type of trailer straight ahead at constant speed. The trailers were tested behind an instrumented motorcycle. Linear autoregressive models were fitted to the experimental data using system identification techniques. Analytical and experimentally derived models largely agreed on frequency, damping and shape of the weave, wobble and trailer sway normal modes. The trailers made the motorcycle's steering heavier but the analytical models did not predict this. The location of the articulation axes between the motorcycle and the trailer were found to be critical for stability. The best trailer design handled well with loads up to 200 kg and speeds up to 70 km/h.     

Lateral Dynamics of an Offroad Motorcycle by System Identification

An instrumented offroad motorcycle was run at a range of speeds in approximately straight lines whilst the rider excited its lateral dynamics by shaking the steering. Autoregressive models were fitted to the resulting multiple output time series data using system identification. The method allowed statistical estimation of state space models to represent the dynamics of an unstable or marginally stable vehicle under manual control. A symbolic algebra computer package was used to derive an analytical state space model to describe the lateral dynamics of the motorcycle. Results from the experiments and analysis compared well with respect to frequency, damping and modal shape of weave and wobble modes, frequency response and model order.     

瑞士和其他国家人口稠密城市的无轨电车的现状和未来

瑞士和其他国家正致力于发展现代化的地区和城市公共交通系统.日益增长的交通需要,要求继续在技术、政治、经济和环境等方面对各种有轨和其他交通工具进行试验评价.此外,还对无轨电车的使用条件及今后的发展轨迹进行了分析.     

基于FPGA的MVB1类设备网卡的设计

考虑到MVB1类设备网卡支持简单的过程数据传送(功能代码为0～4)和设备状态响应(功能代码15)，不支持消息数据、过程数据强制功能的情况，提出利用FPGA(现场可编程门阵列)开发MVB1类设备网卡。这样，在完成通信功能的同时，可以无需外加CPU即完成一些简单的IO、AD等功能，也可以设计出总线方式与CPU相连。实践证明MVB1类设备网卡采用PC104接口与宿主CPU连接，具有110个256位的过程数据通信能力；用FPGA开发MVB1类设备网卡比用MVBC芯片更具优势。     

Preparing highway emissions inventories for urban scale modeling: A case study in Philadelphia

Highway emissions represent a major source of many pollutants. Use of local data to model these emissions can have a large impact on the magnitude and distribution of emissions predicted and can significantly improve the accuracy of local scale air quality modeling assessments. This paper provides a comparison of top–down and bottom–up approaches for developing emission inventories for modeling in one urban area, Philadelphia, in calendar year 1999. A bottom–up approach relies on combining motor vehicle emission factors and vehicle activity data from a travel demand model estimated at the road link level to generate hourly emissions data. This approach can result in better estimates of levels and spatial distribution of on-road motor vehicle emissions than a top–down approach that relies on more aggregated information and default modeling inputs.     

Offshore export versus in situ fractionated mineralization: a 1-D model of the fate of the primary production of the Rías Baixas (Galicia, NW Spain)

A linked hydrodynamic mineralization model is described and used to evaluate offshelf fluxes and fractionated mineralization of particulate phytogenic materials in the coastal upwelling system of the Rías Baixas (NW Spain), under three different typical situations of the upwelling season. The simulations made indicate that the intensity of upwelling controls: (a) net community production (NCP); (b) particulate organic matter (POM) accumulation; (c) in situ mineralization; and (d) matter export in the ‘Rías Baixas.’ Under strong upwelling conditions, there is an important horizontal offshelf flux, having only a small mineralization effect on NCP; if weak upwelling conditions are simulated, POM export is dramatically reduced and in situ mineralization is significantly enhanced; finally, under average upwelling conditions, the offshelf export of POM is about one third of the POM accumulation inside the domain, evidencing its importance in the productivity enhancement of near-shore areas. According to our sensitivity tests, the net vertical velocity (water velocity plus sinking velocity) has a critical role in the C/N/P stoichiometry of POM.     

Structural stability of polymer matrix composite panels in fire

Development in advanced composite fabrication technology offers the clear prospect of cost effective application of polymer matrix composites for large load-bearing structures. However, polymer matrix composites can be severely degradated under the thermal condition caused by fire. This paper addresses the compressive load-bearing capacity for polymer matrix composite panels in naval structures and civil infrastructures under the combined thermal–mechanical condition. The failure modes arising from structural instability for single skin and sandwich panels in such combined thermal–mechanical condition are the focus in this study. The thermal field under fire heating and the degradation of mechanical properties with elevated temperature are discussed. Analytical solutions for these mechanical failure modes are presented for design considerations. The approach to the development of a quantitative methodology for fire protection design is discussed in the context of the analyses and the experiments. Design diagrams are constructed to design mechanical loads for given fire protection time, and on the opposite, to design fire protection time for given mechanical loads.     

Radar Health Monitoring for Highway Vehicle Applications

Monitoring the health of the radar sensor on a highway vehicle poses a special challenge. This is because the radar measures the distance to other independent vehicles on the highway and the motion of these other vehicles may be completely unknown to the fault detection system. Traditional observer-based approaches to fault diagnostic system design cannot be used. A number of new approaches are therefore explored in this paper in an attempt to create a reliable fault detection system for the radar. These include: (a) Use of inter-vehicle communication; (b) Use of a geographic database of pre-identified roadside radar targets; (c) Detection of abrupt failures using fuzzy logic and a knowledge of vehicle acceleration abilities; (d) Use of a redundant sensor that is inexpensive but of poor quality. The performance of each of these approaches is evaluated. Experimental results indicate that a combination of approaches (c) and (d) would provide the most reliable method for radar health monitoring. This combination would work effectively even in the absence of inter-vehicle communication in a realistic highway environment.     

降低感应电机直接转矩控制的转矩脉动的控制器

基于磁滞比较器和选择表的感应电机直接转矩控制(DTC),其开关频率可变,且转矩脉动大,特别在低速时.这是因为转矩和磁通的变化率以及转矩和磁通达到其上带和下带所花的时间随运行工况变化.文中提出了一种新型的开关频率固定的转矩控制器.新型控制器结构非常简单,其输出类似于传统的三点式磁滞比较器.就提出的控制器介绍了近似频域分析法,作为控制器参数选择的指南.介绍了感应电机直接转矩控制采用该转矩控制器进行的仿真和实验结果.结果表明提出的控制器可以保持开关频率恒定,并降低了转矩脉动,尤其在低速时.     

Construction of a stochastic model of track geometry irregularities and validation through experimental measurements of dynamic loading

This paper describes the construction of a stochastic model of urban railway track geometry irregularities, based on experimental data. The considered irregularities are track gauge, superelevation, horizontal and vertical curvatures. They are modelled as random fields whose statistical properties are extracted from a large set of on-track measurements of the geometry of an urban railway network. About 300–1000 terms are used in the Karhunen–Loève/Polynomial Chaos expansions to represent the random fields with appropriate accuracy. The construction of the random fields is then validated by comparing on-track measurements of the contact forces and numerical dynamics simulations for different operational conditions (train velocity and car load) and horizontal layouts (alignment, curve). The dynamics simulations are performed both with and without randomly generated geometrical irregularities for the track. The power spectrum densities obtained from the dynamics simulations with the model of geometrical irregularities compare extremely well with those obtained from the experimental contact forces. Without irregularities, the spectrum is 10–50?dB too low.