Contributors to this issue

Contributors to this issue     

Experimental validation of a mathematical model of a reed-valve reciprocating air compressor from an automotive-braking system

Mathematical simulation is the process of designing a model of a real system and then conducting experiments with the simulation to understand the system’s behavior. Mathematical simulation is widely used for investigating and designing compressors, and with a minimal number of simplifying assumptions, mathematical models can be used in conjunction with modern computing tools to solve complicated problems. A considerable amount of previous research has focused on the mathematical modeling of reciprocating air compressors used in automotive braking. The aim of the present work was to experimentally validate the mathematical model for such compressors. We present a simplified and effective mathematical model for estimating compressor performance, and this model can easily be executed using personal computers. Parameters such as compressor speed, discharge pressure and clearance volume were evaluated in terms of their effect on the thermodynamic behavior of compressors. The model can predict cylinder pressure, cylinder volume, cylinder temperature, valve lift and resultant torque at different crank angles; it can also predict the free air delivered and the indicated power of the compressor. Therefore, the model has been validated using experimental results.     

Method for analyzing epicyclic gearboxes

This paper presents a method for analyzing epicyclic gearboxes by evaluating the speeds, torques and power of the external elements in epicyclic gear mechanisms, as well as the total ratios of the gear box. The method is based on the equations that describe each epicyclic gear mechanism and rules that assign appropriate codes to the external elements. The method emphasizes how power flows are transmitted through the epicyclic gears, as well as power losses. Analysis of an epicyclic gear box is performed to illustrate the proposed method.     

公路路域景观美学评价

公路路域景观美学感知是营造高质量公路景观环境的重要内容之一.基于公路使用者角度,采用"心理物理学"法定量评价了不同公路路域景观组成的美学感知状况.研究发现:公路路域景观美学质量与人工设施特色性、公路与人工设施距离、人工设施与周围环境融合度、路域植被盖度、景观质地、路域水体大小、路域植被种类、景观多样性、景观自然性、景观开阔性、景观完整性、景观生动性、天象特征和公路在视域内显著度呈显著相关关系;本文的评价模型中仅考虑路域植被类型与景观完整性两个自变量.依据评价结果,提出了五点有助于公路景观设计和决策的路域景观美学建设的建议.     

Comparison of Feedforward and Feedback Control for 4WS

A system incorporating feedforward plus feedback control was configured such that it would follow the target yaw rate found by calculation. Selection of optimum values for the control system constants made it possible to separate control of the steering input response characteristic from control of vehicle stability against external disturbances. The former is controlled by the feedforward control function and the latter by the feedback control function; the values of the two functions can be set independently.     

Walking infrastructure design assessment by continuous space dynamic assignment modeling

For the planning and design of walking infrastructure, characterized by the fact that the pedestrians can choose their paths freely in two‐dimensional space, applicability of traditional discrete network models is limited. This contribution puts forward an approach for user‐optimal dynamic assignment in continuous time and space for analyzing for instance walking infrastructure in a two‐dimensional space. Contrary to network‐based approaches, the theory allows the traffic units to choose from an infinite non‐countable set of paths through the considered space. The approach first determines the continuous paths using a path choice model. Then, origin‐destination flows are assigned and traffic conditions are calculated. The approach to determine a user‐optimal assignment is heuristic and consists of a sequence of all‐or‐nothing assignments. An application example is presented, showing dynamic user equilibrium traffic flows through a realistic transfer station. The example is aimed at illustrating the dynamic aspects of the modeling approach, such as anticipation on expected flow conditions, and predicted behavior upon catching or missing a connection.     

概念阶段应用超静定力学规划车顶抗压性能的研究

近几年北美和中国的翻滚事故致死人数和死亡率居高不下,对社会和交通人身安全造成了恶劣影响,而翻滚伤害又与车顶抗压强度有关。应用超静定力学分析法预测各个路径的受力,进而明确关键力学路径,通过梁结构弯矩提高的理论,选取关键力学路径中受压侧的板件厚度作为正交试验的因素,分析各因素对车顶抗压强度和质量的贡献度。研究发现,连接中立柱内板和顶盖中横梁的接头支架对车顶抗压性能的贡献度最大。通过对接头支架进一步的优化设计,在提高车顶抗压性能的情况下,实现轻量化。     

Experimental study of an electro-mechanical CVT ratio controller

This paper introduces an electro-mechanical, dual acting pulley, continuously variable transmission (EMDAPCVT) and presents its real time ratio controller using a proportional-derivative-plus-conditional-integral (PDPCI) controller. The ratio controller system is developed based on primary (input) and secondary (output) pulley position controllers. Each position controller has two PID parameters, releasing and clamping, which are determined experimentally using a relay feedback method. A PC-based ratio controller system is implemented using Matlab/Simulink® software and a Keithley DAS-1602 data acquisition system card. The experimental results show that the PDPCI controller system can control the CVT ratio adequately.     

弹性地基板模态试验及地基动参数识别

用脉冲锤击法进行了弹性地基上自由板的自由振动模态试验,并用Me scope软件分析传递函数,得到了7阶位移模态和应变模态。在此基础上,对试验结果进行了初步的分析并总结了弹性地基板振动测试的场地经验。对用优质LR12-2元建立的厚板ADS1元进行了Vlasov地基上矩形板的有限元分析,同时对Vlasov地基上板的振型进行了分析,利用刚体模态进行了Winkler地基参数识别,并利用2阶频率,根据模态振型匹配的原则进行双参数地基参数的识别。结果表明:该有限元分析程序具有较强的通用性,地基板的振型呈模态密集区的形式。