Tractor–semitrailer model for vehicles carrying liquids

This article presents a model for solving solid–fluid interactions in vehicles carrying liquids. A tractor–semitrailer model is developed by incorporating suspension systems and tire dynamics. Owing to the solid–fluid interaction, equations of motion for the vehicle system are coupled. To simplify the complicated solution procedure, the coupled equations are solved separately using two different codes. Each code is analyzed separately; but as the parameters of the two codes depend on each other, the codes must be connected at the end of each time step. To determine the dynamic behavior of the system, different braking moments are applied. As the braking moments increase, braking time decreases. However, it turns out that increasing the braking moment to more than a certain level produces no significant results. It is also shown that vehicles carrying fluids need a greater amount of braking moments in comparison to vehicles carrying solids during braking. In addition, as the level of the fluid inside the tanker increases, from one-third to two-third of the tanker’s volume, the sloshing forces applied to the tanker’s walls increase. It was also concluded that the strategy used in this article to solve for the solid–fluid interaction by incorporating vehicle dynamic effects represents an effective method for determining the dynamic behavior of vehicles carrying fluids in other critical maneuvers.     

载人潜水器在母船上系固时的受力计算及分析

载人潜水器在母船上系固时的安全性是7 000 m载人潜水器母船设计的关键技术之一,准确预报载人潜水器在母船上系固时受到的作用力,对于潜水器系固装置的设计及系固安全性评估至关重要。根据耐波性理论,针对潜水器搭载母船的实际线型和航行海域情况,提出了基于搭载母船耐波性预报的潜水器系固时受力的简便计算方法,该方法可以计算不同海况时的受力情况,能适应潜水器不同存放或维修工况下系固设计的需要,具有较好的工程适用价值。     

An analysis of the effects of French vehicle inspection program and grant for scrappage on household vehicle transaction

The French government has implemented a periodical vehicle inspection program, which aims at maintaining proper functioning of the vehicle and ensuring the emissions control systems installed on the vehicle work properly. Also, an incentive program for scrapping old vehicles was introduced in 1994 through 1996 to promote the replacement of those vehicles with higher emissions by newer vehicles with lower emissions. A hazard-based duration model of household vehicle transaction behavior has been developed in this study to examine the effects of the inspection program and the grant for scrappage on vehicle transaction timing. The model is developed as a competing risks model assuming the following three types of competing risks: replacing one of the vehicles in the household fleet, disposing of one vehicle in the fleet, and acquiring one vehicle to add to the fleet. The empirical analysis is carried out using the panel data of French households' vehicle ownership from 1984 to 1998, obtained by the panel survey called Parc-Auto, which has been conducted by a French marketing firm, SOFRES, since 1976. The long panel observation period facilitates the introduction of macro-economic indicators into the model, enabling the analysis to distinguish the effects of policy measures from macro-economic factors. The empirical results indicate that the expected vehicle holding duration becomes 1.3 years longer under the inspection program than before the program commenced, given that the vehicle is replaced by another vehicle at the end of the holding duration; and that the conditional probability of replacing a vehicle aged 10 years and over becomes 1.2 times higher, and the average holding duration becomes shorter by 3.3 years, when the grant for scrappage is available.     

铁路直线轨道空间振动时变模型研究

采用有限单元法,将轨枕视为线性粘弹性连续支承梁单元,钢轨划分为线性粘弹性点支承梁单元,分别考虑每个单元的横向、纵向、竖向及扭转振动,建立铁路直线轨道结构空间振动模型。运用弹性系统总势能不变值原理,采用轨道不断"增加和缩减"技术,建立直线轨道结构空间振动时变质量、阻尼和刚度矩阵。以国产25Z型客车为例,计算200s时间段上车辆—轨道耦合振动动力响应,与实测结果比较吻合。     

270 km·h-1动力车驱动制动单元悬挂参数的优化

为进一步改善270km·h-1的轮对空心轴式动力车的性能,采用多刚体动力学软件SIMPACK建立了完整的动力车动力学模型,在高、低干扰线路上分析了驱动制动单元车体端、构架端悬挂刚度和耦合减振器阻尼特性对单元各向振动加速度和动力车平稳性能的影响。结果表明优化单元悬挂参数可以改善其工作条件和整车性能,但对轮轨作用力影响不大。相同速度不同级别线路上,单元悬挂参数对动力车性能的影响规律是相似的。     

车内次声的试验研究

文中论述了车内次声的发生机理，并用实测法研究了车内次声的规律性。结果表明，在车内声波的总能量中，次声波的能量占主要成分，听声的能量所占比例极小。随着车的提高，车内次声总声压级也相应提高，120km/h时，开右前窗时次声总声压级达到121dB（IL），闭窗时次声总声压级达到114dB（IL）。次声的声压级峰值频率范围是1．5－9Hz，未发现明显的共振频率和谐波。     

车辆导航系统的研究开发现状与趋势

车辆导航系统是智能交通系统（ITS）建设的一项基础内容，本文对当前国内车辆导航系统的研究与开发现状作了全面调研与分析。对其中的一些关键技术问题作了深入探讨，最后着重对全球定位系统（GPS），地理信息系统（GIS）在车辆导航系统中的应用前景进行了研究，这对车辆导航系统的深入开发及ITS的建设都有重要的意义。     

六自由度汽车运动模拟器机构的位置姿态误差分析

六自由度汽车运动模拟器是可进行汽车驾驶逼真模拟的训练和研究用设备。本文利用微分平移和微分放置变换方法，通过误差传递矩阵的求解来探讨模拟器运动台主要误差源与运动台位置姿态误差之间的关系，建立了六自由度模拟器运动台的位置姿态误差模型。