排序方式: 共有127条查询结果,搜索用时 453 毫秒
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公路隧道设计中的几个问题 总被引:3,自引:1,他引:3
公路隧道在提高公路标准,保护生态环境和提高运营效率中起着重要作用。以山区公路隧道为出发点,就隧道设计范围、洞口设计、纵坡取值及持殊设计等方面阐述个人观点,供同行探讨。 相似文献
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Xiao-Yun Lu J. Karl Hedrick 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(9):653-669
This paper addresses modelling, longitudinal control design and implementation for heavy-duty vehicles (HDVs). The challenging problems here are: (a) an HDV is mass dominant with low power to mass ratio; (b) They possess large actuator delay and actuator saturation. To reduce model mismatch, it is necessary to obtain a nonlinear model which is as simple as the control design method can handle and as complicated as necessary to capture the intrinsic vehicle dynamics. A second order nonlinear vehicle body dynamical model is adopted, which is feedback linearizable. Beside the vehicle dynamics, other main dynamical components along the power-train and drive-train are also modelled, which include turbocharged diesel engine, torque converter, transmission, transmission retarder, pneumatic brake and tyre. The braking system is the most challenging part for control design, which contains three parts: Jake (engine compression) brake, air brake and transmission retarder. The modelling for each is provided. The use of engine braking effect is new complementary to Jake (compression) brake for longitudinal control, which is united with Jake brake in modelling. The control structure can be divided into upper level and lower level. Upper level control uses sliding mode control to generate the desired torque from the desired vehicle acceleration. Lower level control is divided into two branches: (a) engine control: from positive desired torque to desired fuel rate (engine control) using a static engine mapping which basically captures the intrinsic dynamic performance of the turbo-charged diesel engine; (b) brake control: from desired negative torque to generate Jake brake cylinder number to be activated and ON/OFF time periods, applied pneumatic brake pressure and applied voltage of transmission retarder. Test results are also reported. 相似文献
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Qing Wu Maksym Spiryagin Colin Cole Chongyi Chang Gang Guo Alexey Sakalo 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(3):343-365
This paper presents the results of the International Benchmarking of Longitudinal Train Dynamics Simulators which involved participation of nine simulators (TABLDSS, UM, CRE-LTS, TDEAS, PoliTo, TsDyn, CARS, BODYSIM and VOCO) from six countries. Longitudinal train dynamics results and computing time of four simulation cases are presented and compared. The results show that all simulators had basic agreement in simulations of locomotive forces, resistance forces and track gradients. The major differences among different simulators lie in the draft gear models. TABLDSS, UM, CRE-LTS, TDEAS, TsDyn and CARS had general agreement in terms of the in-train forces; minor differences exist as reflections of draft gear model variations. In-train force oscillations were observed in VOCO due to the introduction of wheel–rail contact. In-train force instabilities were sometimes observed in PoliTo and BODYSIM due to the velocity controlled transitional characteristics which could have generated unreasonable transitional stiffness. Regarding computing time per train operational second, the following list is in order of increasing computing speed: VOCO, TsDyn, PoliTO, CARS, BODYSIM, UM, TDEAS, CRE-LTS and TABLDSS (fastest); all simulators except VOCO, TsDyn and PoliTo achieved faster speeds than real-time simulations. Similarly, regarding computing time per integration step, the computing speeds in order are: CRE-LTS, VOCO, CARS, TsDyn, UM, TABLDSS and TDEAS (fastest). 相似文献
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Qing Wu Colin Cole 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(12):1688-1714
This paper discusses the evolution of longitudinal train dynamics (LTD) simulations, which covers numerical solvers, vehicle connection systems, air brake systems, wagon dumper systems and locomotives, resistance forces and gravitational components, vehicle in-train instabilities, and computing schemes. A number of potential research topics are suggested, such as modelling of friction, polymer, and transition characteristics for vehicle connection simulations, studies of wagon dumping operations, proper modelling of vehicle in-train instabilities, and computing schemes for LTD simulations. Evidence shows that LTD simulations have evolved with computing capabilities. Currently, advanced component models that directly describe the working principles of the operation of air brake systems, vehicle connection systems, and traction systems are available. Parallel computing is a good solution to combine and simulate all these advanced models. Parallel computing can also be used to conduct three-dimensional long train dynamics simulations. 相似文献
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In this paper, a set of longitudinal velocity and distance controllers with switching logic is proposed for an active driver
safety system, and validation via hardware-in-the-loop simulation (HILS) is presented. Since the desired velocity and distance
are given discretely and arbitrarily by a driver, there are usually discontinuities or discrete jumps between the desired
and current vehicle state immediately after the switching. To minimize performance degradation resulting from this discrete
jump, dynamic surface control (DSC) with an input-shaping filter is applied for both velocity and distance control. Furthermore,
while much cost and effort are usually necessary for the experimental validation of a longitudinal controller, the validation
of the longitudinal controller via HILS is performed with a minimum of effort. In the HILS, the various switching scenarios
and desired discrete inputs in terms of velocity and distance are considered and the corresponding performance of the controller
is shown in the end. 相似文献
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地铁盾构隧道,尤其是大型跨江海的水下地铁盾构隧道,局部埋深通常要大于普通地铁盾构隧道,而且要承受较高的水压力作用;盾构隧道作为特长线性结构,其纵向刚度较小,对于外部荷载的变化较为敏感,由此产生的不均匀变形是隧道工程中不可忽视的问题。文章针对武汉地铁越长江盾构隧道工程,通过三维数值计算探讨了埋深变化、水压变化、地层变化及穿越刚性结构物等因素对越江盾构隧道纵向不均匀变形及受力状态的影响。 相似文献
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大跨径梁式桥的主要病害 总被引:28,自引:8,他引:28
论述了预应力混凝土大跨径梁式桥的两种主要病害,一是跨中下挠,二是梁体开裂。分析了跨中下挠、垂直裂缝、斜裂缝、纵向裂缝的原因,并叙述了预防对策。这些对策主要是:梁有足够的正截面和斜截面强度;设计中要控制恒载挠度(包括徐变挠度)在一个较小值;在梁纵向两悬臂端施加水平力对顶后合龙;三维分析箱梁主拉应力并布置预应力束;预留体外备用钢束;混凝土加载龄期不小于7天;竖向预应力应两次张拉以保证有效预应力。 相似文献