Assessing the impact of cornering losses on the energy consumption of electric city buses

In view of the increasing electrification of public city transport, an accurate energy consumption prediction for Battery Electric Buses (BEBs) is essential. Conventional prediction algorithms do not consider energy losses that occur during turning of the vehicle. This is especially relevant for electric city buses, which have a limited battery capacity and often drive curvy routes.In this paper, the additional energy consumption during steering of a BEB is modeled, measured, and assessed. A nonlinear steady-state cornering model is developed to establish the additional energy losses during cornering. The model includes large steer angles, load transfer, and a Magic Formula tire model. Model results show that both cornering resistance and tire scrub of the rear tires cause additional energy losses during cornering, depending on the corner radius and vehicle velocity.The energy consumption model is validated with full scale vehicle tests and shows an average deviation of 0.8 kW compared to the measurements. Analysis of recorded real-world bus routes reveals that on average these effects constitute 3.1% of the total powertrain energy. The effect is even more significant for routes crossing city centers, reaching values up to 5.8%. In these cases, cornering losses can be significant and should not be neglected in an accurate energy consumption prediction.     

大型巡航救助船快速性研究

结合大型巡航救助船的功能需求和主尺度特点,对其快速性进行分析。采用计算流体力学(CFD)技术对原型方案的线型进行阻力性能计算。根据计算结果,分别对艏部轮廓线形状、球艏、呆木和支架进行优化,得到最终方案,该方案的阻力相比原型方案大幅减小。对最终方案进行模型试验,模型试验结果与CFD计算结果的吻合度良好,证明该船采用的线型优化方法是可靠、可用的。     

非定常气动荷载对桥上列车行驶安全舒适性影响分析

为了研究非定常气动力荷载对桥上列车行车安全性和舒适性的影响,结合有限元软件ANSYS和多体动力学软件SIMPACK,建立列车-轨道-桥梁三维多体系统模型,计算风-列车-桥梁耦合系统的动力响应;对比分析定常与非定常气动力荷载作用下桥上列车的行驶安全与舒适性,研究非定常气动力荷载作用下不同横向风速对列车行驶安全的影响。研究结果表明:列车行驶速度为200~300km/h,无风荷载情况下,各安全性与舒适性指标值均满足要求且均小于风荷载作用。横风作用下平均风速为20 m/s,考虑非定常气动力荷载的影响不仅会使列车行驶安全评估结果更安全,还会使列车舒适性评估结果偏于保守。平均风速不超过20 m/s,车速控制在250 km/h,桥上列车行车安全、舒适性均满足要求,且平稳性等级可达到"良好"以上。通过对不同横向风速下桥上列车行驶安全分析,给出桥上列车安全行驶的阈值,为列车的安全运营提供依据。     

基于演化博弈的政府鼓励条件下共享停车行为分析

为研究在政府鼓励措施下出行者和车位拥有者参与共享停车时的策略对共享停车匹配结果的影响，建立出行者和车位拥有者演化博弈模型并进行演化稳定状态分析，结合仿真说明不同收益和成本及策略选择对共享停车的影响。研究结果表明：在政府鼓励措施下双方演化博弈中出行者和车位拥有者均能通过不断学习最终演化至稳定均衡状态，但演化速率和演化波动性受双方收益制约；通过分析发现，想要演化至(使用，共享)状态则需要较高初始比例，可以通过提高收益和减少成本等措施诱导出行者和车位拥有者使用共享停车，同时在初始比例较高时收益分配比例对演化过程也有较大影响。研究发现，当共享平台给出合理收益和支出费用时，政府鼓励 政策对共享停车发展起促进作用。     

浮置板轨道结构对地铁车辆轨道耦合系统动力性能影响分析

以北京地铁6号线车辆为样本,研究了浮置板轨道对于车辆轨道耦合动力学模型的影响。建模时将浮置板轨道考虑成柔性体,用有限元实体单元建模,并利用模态叠加法进行求解。仿真后得出如下结论:与轨道不平顺引起的冲击相比,采用浮置板轨道后所产生的枕跨冲击、过渡冲击、轨道板冲击并不明显。车辆在浮置板轨道上行驶时,其竖向悬挂系统能够较好地降低轮轨的冲击力;轨道垫板刚度的主要影响是频率在60~150 Hz范围内的振动,对低频振动影响较小。随着轨道垫板刚度的变大,轮轨垂向力和轮重减载率逐渐变大,但其对轮轴横向力和脱轨系数影响很小,对车体振动几乎没有影响。轨道垫板刚度的主要影响是频率在10 Hz左右的轨道板的振动,对浮置板钢弹簧支承力的影响较小,即对路基的减振效果影响较小。     

考虑居住区位的公共交通出行行为分析模型

为探讨不同层面居住区位对公共交通出行行为的影响，基于计划行为理论与群体动力理论，构建涵盖居住区位与心理影响因素共同作用的多水平结构方程模型.模型同时考虑个体层面与社区层面变量对出行选择的影响，利用Mplus软件标定模型参数.结果表明，不同层面变量对出行行为意向的影响存在差异.个体层面变量对行为意向的影响程度由大到小依次为：居住区位(0.665)、主观规范(0.664)、行为态度(0.577)、知觉行为控制(0.547).社区层面变量的影响程度为：行为态度(0.736)大于居住区位(0.646).     

服役转臂节点刚度对运营车辆动力学影响研究

运用SIMPACK软件建立CRH3型高速动车组模型,结合试验获得服役120万km转臂节点刚度变化范围,在考虑2种抗蛇行减振器、3种磨耗踏面与3种钢轨廓形匹配的实际运营工况下,仿真分析服役转臂节点刚度变化对车辆动力学性能的影响。结果表明:120万km服役转臂节点纵向刚度分布范围为90~150 MN/m,主要变化率在-10%~0%之间。在服役转臂节点刚度变化范围内,增大转臂节点纵向刚度可以降低车辆非线性临界速度及运行平稳性,并增大轮轨磨耗,其影响程度与轮轨匹配关系以及抗蛇行减振器种类关系紧密。为保证车辆运行稳定性及平稳性,建议避免使用60N(min-wear)钢轨,适当减小转臂节点刚度以及使用T60抗蛇行减振器。     

减振轨道对地铁车辆动力学性能的影响研究

为研究地铁A型车辆在不同等级减振轨道上行车时的动力学特性,基于车辆-轨道耦合动力学理论,以深圳地铁某线路实际铺设的不同等级减振轨道为研究对象,建立考虑不同等级减振轨道的地铁A型车辆-轨道垂向耦合动力学模型,采用数值仿真的方法分析不同等级减振轨道下车辆-轨道耦合系统的动力学特性。结果表明:相对于铺设其他两种等级减振轨道,铺设高等和特殊减振轨道时车体的垂向振动加速度均方根值增幅超过30%,车体垂向Sperling平稳性指标增幅超过5%;钢轨垂向位移增加明显且钢轨垂向位移的标准差增加了约3倍。主要结论为:采用高等级减振轨道会一定程度恶化车辆动力学性能和乘客乘车环境,在实际选取不同等级减振轨道时应综合考虑地铁车辆的行车动力学性能。     

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.     

Optimization of curving performance of rail vehicles

The curving performance of a transit rail vehicle model with 21 degrees of freedom is optimized using a combination of multibody dynamics and a genetic algorithm (GA). The design optimization is to search for optimal design variables so that the noise or wear, arising from misalignment of the wheelsets with the track, is reduced to a minimum level during curve negotiations with flange contact forces guiding the rail vehicle. The objective function is a weighted combination of angle of attack on wheelsets and ratios of lateral to vertical forces on wheels. Using the combination of the GA and a multibody dynamics modelling program, A’GEM, the generation of governing equations of motion for complex nonlinear dynamic rail vehicle models and the search for global optimal design variables can be carried out automatically. To demonstrate the feasibility and efficacy of the proposed approach of using the combination of multibody dynamics and GAs, the numerical simulation results of the optimization are offered, the selected objective function is justified, and the sensitivity analysis of different design parameters and different design parameter sets on curving performance is performed. Numerical results show that compared with suspension and inertial parameter sets, the geometric parameter set has the most significant effect on curving performance.