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111.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(12):1835-1859
A planar suspension system (PSS) is a novel automobile suspension system in which an individual spring–damper strut is implemented in both the vertical and longitudinal directions, respectively. The wheels in a vehicle with such a suspension system can move back and forth relative to the chassis. When a PSS vehicle experiences asymmetric road excitations, the relative longitudinal motion of wheels with respect to the chassis in two sides of the same axle are not identical, and thus the two wheels at one axle will not be aligned in the same axis. The total dynamic responses, including those of the bounce, pitch and the roll of the PSS vehicle, to the asymmetric road excitation may exhibit different characteristics from those of a conventional vehicle. This paper presents an investigation into the comprehensive dynamic behaviour of a vehicle with the PSS, in such a road condition, on both the straight and curved roads. The study was carried out using an 18 DOF full-car model incorporating a radial-spring tyre–ground contact model and a 2D tyre–ground dynamic friction model. Results demonstrate that the total dynamic behaviour of a PSS vehicle is generally comparable with that of the conventional vehicle, while PSS exhibits significant improvement in absorbing the impact forces along the longitudinal direction when compared to the conventional suspension system. The PSS vehicle is found to be more stable than the conventional vehicle in terms of the directional performance against the disturbance of the road potholes on a straight line manoeuvre, while exhibiting a very similar handling performance on a curved line. 相似文献
112.
Madan Mohan Guin Hiroharu Kato Hajime Yamaguchi Masatsugu Maeda Masaru Miyanaga 《Journal of Marine Science and Technology》1996,1(5):241-254
Determination of the flow structure near the wall is essential for a clear insight into the phenomenon of skin friction reduction
by microbubbles in a turbulent boundary layer. An important parameter, is the bubble concentration or void fraction in the
wall region in drag-reducing conditions. The purpose of this paper is to show drag-reducing effects due to microbubbles in
a water channel and, more importantly, to show the dependence of the drag-reduction values on the near-wall void fraction.
A two-dimensional channel with an aspect ratio of 10 was specially built for this purpose with provisions for air injection
through porous plates. Skin friction was directly measured by a miniature floating element transducer with a 5-mm circular
sensing disk mounted flush on the top wall 67 channel-heights downstream of the injector. The wall friction in the presence
of air bubbles was found to be reduced under the same bulk velocity when compared with the value without air. Detailed void
fraction profiles across the channel were obtained by a sampling probe and a fiber-optic probe. Better collapse of the drag
reduction data, independent of different profile shapes, was found when plotted against the near-wall void fraction than against
a cross-sectional mean void fraction. While this dependence reconfirms that the phenomena are essentially inner-region dependent,
the lack of influence of the bubble distribution patterns away from the wall implies lack of outer region influence. 相似文献
113.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(2):217-234
An adaptive sideslip angle observer considering tire–road friction adaptation is proposed in this paper. The single-track vehicle model with nonlinear tire characteristics is adopted. The tire parameters can be easily obtained through road test data without using special test rigs. Afterwards, this model is reconstructed and a high-gain observer (HGO) based on input–output linearisation is derived. The observer stability is analysed. Experimental results have confirmed that the HGO has a better computational efficiency with the same accuracy when compared with the extended Kalman filter and the Luenberger observer. Finally, a road friction adaptive algorithm based on vehicle lateral dynamics is proposed and validated through driving simulator data. As long as the tires work in the nonlinear region, the maximal friction coefficient could be estimated. This algorithm has excellent portability and is also suitable for other observers. 相似文献
114.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(1):139-164
Progress in reducing actuator delays in pneumatic brake systems is opening the door for advanced anti-lock braking algorithms to be used on heavy goods vehicles. However, little has been published on slip controllers for air-braked heavy vehicles, or the effects of slow pneumatic actuation on their design and performance. This paper introduces a sliding mode slip controller for air-braked heavy vehicles. The effects of pneumatic actuator delays and flow rates on stopping performance and air (energy) consumption are presented through vehicle simulations. Finally, the simulations are validated with experiments using a hardware-in-the-loop rig. It is shown that for each wheel, pneumatic valves with delays smaller than 3 ms and orifice diameters around 8 mm provide the best performance. 相似文献
115.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(8):1047-1065
Vehicle stability and active safety control depend heavily on tyre forces available on each wheel of a vehicle. Since tyre forces are strongly affected by the tyre–road friction coefficient, it is crucial to optimise the use of the adhesion limits of the tyres. This study presents a hybrid method to identify the road friction limitation; it contributes significantly to active vehicle safety. A hybrid estimator is developed based on the three degrees-of-freedom vehicle model, which considers longitudinal, lateral and yaw motions. The proposed hybrid estimator includes two sub-estimators: one is the vehicle state information estimator using the unscented Kalman filter and another is the integrated road friction estimator. By connecting two sub-estimators simultaneously, the proposed algorithm can effectively estimate the road friction coefficient. The performance of the proposed estimation algorithm is validated in CarSim/Matlab co-simulation environment under three different road conditions (high-μ, low-μ and mixed-μ). Simulation results show that the proposed estimator can assess vehicle states and road friction coefficient with good accuracy. 相似文献
116.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1601-1620
ABSTRACTTires are used by the customers during several tens of thousands of kilometres, and before their replacement, the driver will encounter a continuous variation of tread depth due to the tire wearing. Although the wet braking labelling demonstrates the performance of the tire in the new stage, it is known that the wet traction evolves with tire wear. In this paper, an in-depth comparison of the wet grip performance of new and worn tires will be conducted, based on the regulatory wet braking test. For this purpose, we propose an original approach to analyse braking test results, which allows breaking down and quantifying the relative importance of the mechanisms involved during this test. This study demonstrates that two main mechanisms are taking place during the entire test: rubber friction and hydroplaning mechanisms. The µ value obtained at low speeds reflects the friction potential of the tested tires while the decline of performance at higher speeds is attributed to hydroplaning mechanisms. This analysis is conducted on numerous tires and demonstrates that current regulatory test applied on new tires is focussing mainly on the rubber friction mechanism. The same test applied on worn tires exhibits both rubber friction and hydroplaning mechanisms. The mechanisms decomposition shows that the source of the performance decline from new to worn status varies greatly, some tires having most of their performance loss due to hydroplaning, some others due to rubber friction drop. 相似文献
117.
118.
针对杭州至兰州高速公路巫山—奉节的A20标K54+010~+150段,由于开挖路堑边坡引起的工程滑坡,在对滑坡的发展过程及变形破坏特征等进行调查研究的基础上,分析了产生滑坡的原因,并提出了清方卸载、排水和抗滑桩等综合处治措施。工程实践证明,坡体稳定,社会经济效益效果较好。 相似文献
119.
曲线箱形梁桥是空间复杂受力结构体系,预应力钢束产生的径向分布力是预应力混凝土曲线箱梁产生扭矩的主要原因之一。采用组合有限元法和简化方法分析曲线箱梁中预应力所产生的效应,得出预应力作用产生的内力和变形的变化趋势,为进一步完善曲线预应力混凝土箱梁桥的设计提供了依据。 相似文献
120.