城市道路交通状态分析方法回顾与展望

阐述了城市道路交通状态分析的必要性,通过对实时交通状态进行科学分析和划分,为区域路网的交通流控制、诱导等提供交通管理决策支持。并对现有的交通状态分析方法进行评述,提出了进一步的研究方向。     

增压中冷柴油机燃用F-T柴油的燃烧波动特性分析

为了分析柴油机燃用F-T柴油的燃烧波动特性,在增压中冷直喷柴油机上对燃用F-T柴油和0号柴油的中高转速和负荷工况进行了对比试验研究。研究表明:在同一工况下,与0号柴油相比,燃用F-T柴油的燃烧始点较早,燃烧压力峰值较低,压力波动幅值较小;对燃烧压力进行频谱分析可以看出,F-T柴油的燃烧压力波动一阶主频率小于0号柴油的主频率,两种燃料的一阶主频率均随转速的增加而增大,随着负荷的增加有降低的趋势,且负荷对F-T柴油的影响较0号柴油更加显著。从燃烧振动噪声源的角度考虑,燃用F-T柴油有利于降低柴油机的燃烧噪声和缸内燃烧时的爆发冲击载荷。     

Analysis of the car body stability performance after coupler jack-knifing during braking

This paper aims to improve car body stability performance by optimising locomotive parameters when coupler jack-knifing occurs during braking. In order to prevent car body instability behaviour caused by coupler jack-knifing, a multi-locomotive simulation model and a series of field braking tests are developed to analyse the influence of the secondary suspension and the secondary lateral stopper on the car body stability performance during braking. According to simulation and test results, increasing secondary lateral stiffness contributes to limit car body yaw angle during braking. However, it seriously affects the dynamic performance of the locomotive. For the secondary lateral stopper, its lateral stiffness and free clearance have a significant influence on improving the car body stability capacity, and have less effect on the dynamic performance of the locomotive. An optimised measure was proposed and adopted on the test locomotive. For the optimised locomotive, the lateral stiffness of secondary lateral stopper is increased to 7875?kN/m, while its free clearance is decreased to 10?mm. The optimised locomotive has excellent dynamic and safety performance. Comparing with the original locomotive, the maximum car body yaw angle and coupler rotation angle of the optimised locomotive were reduced by 59.25% and 53.19%, respectively, according to the practical application. The maximum derailment coefficient was 0.32, and the maximum wheelset lateral force was 39.5?kN. Hence, reasonable parameters of secondary lateral stopper can improve the car body stability capacity and the running safety of the heavy haul locomotive.     

A vehicle stability control strategy with adaptive neural network sliding mode theory based on system uncertainty approximation

Modelling uncertainty, parameter variation and unknown external disturbance are the major concerns in the development of an advanced controller for vehicle stability at the limits of handling. Sliding mode control (SMC) method has proved to be robust against parameter variation and unknown external disturbance with satisfactory tracking performance. But modelling uncertainty, such as errors caused in model simplification, is inevitable in model-based controller design, resulting in lowered control quality. The adaptive radial basis function network (ARBFN) can effectively improve the control performance against large system uncertainty by learning to approximate arbitrary nonlinear functions and ensure the global asymptotic stability of the closed-loop system. In this paper, a novel vehicle dynamics stability control strategy is proposed using the adaptive radial basis function network sliding mode control (ARBFN-SMC) to learn system uncertainty and eliminate its adverse effects. This strategy adopts a hierarchical control structure which consists of reference model layer, yaw moment control layer, braking torque allocation layer and executive layer. Co-simulation using MATLAB/Simulink and AMESim is conducted on a verified 15-DOF nonlinear vehicle system model with the integrated-electro-hydraulic brake system (I-EHB) actuator in a Sine With Dwell manoeuvre. The simulation results show that ARBFN-SMC scheme exhibits superior stability and tracking performance in different running conditions compared with SMC scheme.     

A system dynamics model of CO2 mitigation in China’s inter-city passenger transport

Mitigation of greenhouse gas emissions from transportation has become increasingly important and challenging especially for developing countries. This paper takes the inter-city passenger transport in China as a case, and develops a system dynamics model for policy assessment and CO₂ mitigation potential analysis. It is found that the future demand for China’s inter-city passenger transport is expected to be large, with the turnover volume growing at a rate of 9% per annum and amounting to 6600 billion p-km in 2020. Major emissions reduction potential exists in inter-city passenger transport. In 2020, comparing to the case without any specific policies stressing mitigation, the reduction of CO₂ emissions ranges from 26% to 32% under those scenarios with policy controls. Sensitivity analysis reveals that the CO₂ mitigation will be best achieved by accelerating the development of railway network, together with slowing down the extension of highway network and imposing fuel taxes.     

地铁车辆车轴新型超声波探伤仪的研究

介绍了微电脑车轴超声波探伤仪的工作原理.给出了超声波发射电路、超声波接收放大电路、衰减量显示电路、AD9850和AD603芯片的基本工作原理及应用.该超声探伤仪引入了直接数字合成技术,可以使超声回波图更清晰、更准确,具有集成度高、响应速度快、探测精度高、分辨率高,图象清晰等特点.高速数据采集和现场可编程门阵列技术的运用解决了以前超声波设备采样频率与计算机通信的瓶颈,可以提高测量精度,在不退轮的情况下能够准确判断车轴的缺陷,减少误判和漏判的概率.     

非线性系统同步的反向设计

反向设计是将Lyapunov函数的选取与控制的设计相结合的一种回归设计方法。将该方法用于同步系统的设计,给出了一个具体可行的同步设计过程。在同步设计中,不管是几阶系统均只需一个控制项。不仅适用于一般的非线性系统的同步,还适用于一些混沌系统（如有外激励的van der pol系统、Duffing系统、Chua电路、Bossler系统等）的同步。控制项中不出现求导项,便于该方法的实施。作为算例,给出了van der pol系统及Chua电路的同步设计。     

平板橡胶支座上梁的倾覆稳定性计算

针对橡胶支座上的混凝土简支梁,在偏心荷载作用下的横向倾覆稳定性问题进行了探讨。特别是橡胶支座变形对梁体横向稳定性的影响进行了分析,建立了考虑支座变形梁体横向稳定性的计算方法,使支座上梁体横向稳定性检算更接近于实际。     

汽车造型设计的线型分析方法

讨论了现有汽车造型设计分析方法的优缺点,根据实际情况归纳出影响造型的主要工程技术因素。介绍了一种全新的造型设计分析方法—线-型分析法。该方法通过判定、提取形体表面的关键造型线,并对不同的车型的关键线进行对比分析,使设计人员能够快速、准确地把握造型风格的核心,判断最新趋势,从而指导后面的造型设计工作。最后以大众品牌的几个主要车型为案例,应用线-型分析方法,归纳总结了新一代大众汽车在造型方面的主要特点,映证了本文提出的分析方法的可行性。     

燃料含硫量对柴油机颗粒物排放的影响研究

利用一台电控高压共轨欧Ⅲ柴油机,采用离子色谱法精确测取了颗粒排放物中硫酸盐的含量,对不同含硫量的柴油进行了颗粒物排放和硫酸盐的测量比较.结果表明,对于无催化转换装置的重型柴油机而言,与含硫量约为800×10-6的柴油相比,采用含硫量约为273×10-6的柴油时其颗粒排放降低了4.7%;开发无尾气后处理装置的电控柴油机,为满足欧Ⅲ排放标准,重点是柴油机本身燃烧系统的开发和控制润滑油消耗.