Estimation of maximum road friction coefficient based on Lyapunov method

With the real time and accurate information of motor torque and rotation speed of the four-in-wheel-motordrive electric vehicles, a slip based algorithm for estimating maximum road friction coefficient is designed using Lyapunov stability theory. Modified Burckhardt tire model is used to describe longitudinal slip property of the tire. By introducing a new state variable, a nonlinear estimator is proposed to estimate the longitudinal tire force and the maximum road friction coefficient simultaneously. With the appropriate selection of estimation gain, the convergence of the estimation error of the tire longitudinal force and maximum road friction coefficient is proved through Lyapunov stability analysis. In addition, the error is exponentially stable near the origin. Finally the method is validated with Carsim-Simulink co-simulation and real vehicle tests under multi working conditions in acceleration situation which demonstrate high computational efficiency and accuracy of this method.     

Transient design waves for green-water loading on bulk carriers

The wave surface profiles associated with extreme relative motion between a slender stationary vessel and the adjacent wave surface are investigated for long-crested head seas. The methodology is based upon an established statistical relationship for a Gaussian random process which indi-cates that in the vicinity of an extreme event the most probable shape of the time history approaches that of the autocorrelation function. Attention is given to the relative motion at a longitudinal position which is representative of the No. 1 hatch cover location on a bulk carrier. Second-order corrections to the wave surface profiles are used to provide estimates of nonlinear relative motions. It is shown that extreme relative motion at the hatch cover location is associated with the vessel encountering a steep-fronted wave with pronounced asymmetry in the horizontal and vertical directions. In order to evaluate the exceedence probabilities, it is hypothesized that the peaks of the nonlinear relative motions are closely correlated with the peaks of an underlying linear process. The overall methodology is applied to an investigation of relative motion exceedence probabilities for vessel lengths of 250 m and 300 m over a range of survival seastates. Received: July, 1999 / Accepted: November, 1999     

巡回出租车市场卫星派遣车队最适规模之研究

出租车乃公共运输系统中最具经营弹性之运输工具,在经济活动频繁之都会地区广为旅行者所欢迎。近年,由于信息与通讯科技的发展,以及日益增高的行车成本,应用卫星派遣俨然已成为出租车市场的趋势与潮流。研究以双层规划数学分析模型描述巡回暨卫星派遣出租车市场之营运绩效,考虑社会福利最大与营运者利润最大的双阶层目标,研析最适车队规模和卫星派遣出租车比例,并针对使用卫星派遣服务之乘客数量,分析出租车市场结构的变化。     

Vibration transmission reduction from a centrifugal turbo blower in a fuel cell electric vehicle

This paper presents a multi-body flexible dynamic analysis of a centrifugal turbo blower for a fuel cell electric vehicle (FCEV) based on the application of computer-aided engineering (CAE) to predict the acceleration at the mount position of the blower. This predicted acceleration is validated by using the measured acceleration data. The numerical simulation for the multi-body flexible dynamics of the blower is used not only to identify the most effective mount among four mounts in an FCEV by controlling the complex stiffness of the isolator, but also to suggest the range of complex stiffness of the isolator at the most effective mount. This numerical simulation technology can be useful for the estimation of the variation of vibration transmission for the structural modification of the turbo blower.     

Application of slim A-pillar to improve driver’s field of vision

The importance of vehicle safety cannot be exaggerated in today’s mobile societies. Many manufacturers, associates related to vehicles and universities make an effort to improve vehicle safety by developing new technologies, applying high strength steel to the body structure etc. However, the majority of these efforts are focused on decreasing injury. It is absolutely important to minimize injury, but a more important aspect is coping with vehicle accidents. That is, As undeniably important as it is to minimize potential injuries, it is critical that experts focus on developing ways to keep drivers out of situations likely to lead to crashes in the first place. The purpose of this paper is to determine what the most critical factor is when coping with an unfamiliar driving situation. The answer is to provide a wide-open field of vision, especially for the driver. The driver’s field of vision is obstructed by the vehicle’s A-pillar. To solve this, the A-pillar obstruction angle, which is the angle between the driver’s eyes and the A-pillar should be decreased. This paper purposes three-methods for decreasing this angle structurally and applying a slim A-pillar which is as the best solution to decrease the A-pillar obstruction angle and ensure the drivers field of vision at the same time     

Development of electrostatic diesel particulate matter filtration systems combined with a metallic Flow-Through Filter and electrostatic methods

A 3000 cc diesel engine attached to an engine dynamo was used to test three newly developed electrostatic Diesel Particulate matter filtration Systems (DPS 1, 2, and 3) under four steady-state engine operating conditions: idle, 2000 rpm with no load, and 2000 rpm under 25% and 50% loads. Of the two developed alternatives, DPS 1 and DPS 2, DPS 2 comprises an ionization section, electrostatic field additional section and Flow-Through Filter (FTF), which achieved almost 90% removal of particulate matter (PM) under the engine’s operating conditions, and the efficiency of the FTF was maintained between 20% and 50%. Comparing the long-term performance of DPS 2 and DPS 3 (effectively a serial combination of two DPS 2s) with a commercially-available Diesel Particulate Filter (DPF), the DPS 2 and DPS 3 achieved almost the same efficiency for removing PM as the DPF but had significantly improved (75%∼90% lower) differential pressure drops.     

Development of a new sound metric for impact sound in a passenger car using the wavelet transform

Vehicles can experience impacts due to harsh road conditions. Contact with an uneven road surface causes vehicles to vibrate, which generates a loud impact sound. The attenuation of such noise is important because car passengers may complain about the impact noise. However, perfect removal of impact noise is not possible because most of it is caused by external conditions. More research is needed on the objective attributes of impact noise; however, the problem of impact noise is not a simple matter because impact noise is transient in nature and reaches a high level instantaneously. In this paper, a new objective attribute of impact noise is designed using the wavelet transform, which is appropriate for analyzing nonstationary signals, such as an impact signal. The usefulness of the new objective attribute, which is a sound metric, is examined by comparing the mean subjective ratings for real impact noise in passenger cars. The new sound metric has better correlation with the mean subjective rating than currently existing sound metrics.     

Effects of injection parameters on the spray characteristics of swirl and slit injectors using the Mie-scattering method

We investigated the effects of injection parameters such as injection pressure, ambient pressure, and ambient temperature on spray characteristics. We calculated the turbulence occurring point (t _c ), defined as the time required to generate a vortex, and the deceleration point (t _b ), defined as the time when spray penetration begins to decelerate, to elucidate the breakup mechanism of the test injectors. The spray velocity coefficient (C_v) was obtained to evaluate the spray characteristics. As the ambient pressure increases in the case of a slit injector, C_v decreases. We investigated the effects of nozzle tip shape according to injection pressure, ambient pressure, and fuel properties on spray characteristics and provide a C_v value of 0.38 for the swirl injector with a spray angle of 60° and the slit injector under atmospheric conditions. The value of C_v in the case of a slit injector was reduced by increasing the ambient pressure. Our results suggest that C_v of a swirl injector is constant regardless of changes in ambient pressure, injection pressure, and fuel properties. On the other hand, C_v of a slit injector is altered by changes in ambient pressure.     

Design and optimization of an LPG roller vane pump for suppressing cavitation

A roller vane type liquefied petroleum gas (LPG) pump was developed for a liquid phase LPG injection (LPLi) engine. Most of the LPG pumps used in the current LPLi engines are installed inside of the LPG tank, but this pump is intended to be installed outside of the LPG tank to overcome the difficulty of fixing an in-tank pump. Because LPG has a low boiling point and high vapor pressure, it usually causes cavitation in the pump and consequently deteriorates the flow rate of the pump. The purpose of this work is to optimize the design of the roller vane pump in order to suppress cavitation and increase the fuel flow rate by using a computational fluid dynamics (CFD) analysis. In order to achieve these goals, the intake port configuration and the rotor of the roller vane pump were redesigned and simulated using STAR-CD code. Computation was performed for six different models to obtain the optimized design of the roller vane pump at a constant speed of 2600 rpm and a constant pressure difference between the inlet and outlet of 5 bar. The computation results show that an increased intake port cross-section area can suppress cavitation, and the pump can achieve a higher flow rate when the rotor configuration is changed to increase its chamber volume. When the inlet pressure difference is 0.1 bar higher than the fluid saturation pressure, the pump reaches its maximum flow rate.     

卵砾石层管推进工程超挖及卡钻对管材与土壤互制行为的影响研究

非明挖工法在都市施作时,常因困难地质(如卵砾石层)或障碍物而造成施工困难、工期延误或发生灾损。本文主要针对非明挖施工法里的管推进施工法(Pipe-jacking Method),探讨管推进工法施工时可能遭遇的困难,以及施工困难状况下之管材土体互制行为。探讨的施工困难包括超挖、挤压、卡钻等问题。本研究针对超挖范围、卡钻位置、阻力大小以及推进力施加位置等,以ABAQUS有限元素软件进行三维数值仿真,探讨直线推进施工中的问题。