Hydroplaning simulation of a tire in thin water using fem and an estimation method and its application to skid number estimation

To simulate the hydroplaning of a tire, many analytical studies have been performed using commercial explicit FE (Finite Element) codes such as MSC.DYTRAN and LS-DYNA. However, most previous studies on this subject have addressed simulation of hydroplaning for water more than 5 mm deep. Additionally, because a great number of Eulerian elements and Lagrangian elements are typically used to analyze hydroplaning and because multiple analyses should be performed for various water depths, long CPU times are required. In this study, it was found that the traction force and the lift and drag forces between the tire and the road surface could be easily estimated for water shallower than 5 mm using an exponential function based on tire rolling FE simulation results. Furthermore, changes in skid resistance, expressed as SN (skid number), could be estimated for various water depths and vehicle speeds using the method proposed in this study, and the results were proven to be in good agreement with results obtained using the ASTM E274 Pavement Friction Tester.     

Conceptual design of economic hybrid vehicle system using clutchless geared smart transmission

Most hybrid vehicles employ the continuously variable transmission (CVT or eCVT) currently as their choice of the transmissions. Recently, an automated geared transmission (AGT) or dual clutch transmission (DCT) is being tried for some hybrid vehicles for the better fuel economy than the CVT hybrid. However, this AGT or DCT is using automated clutches which require the hydraulic power in addition to the slippage in the clutch plate invoking some energy loss as well as wear. Also, they require a motor with significant power to match to the engine power. The clutchless geared smart transmission (CGST) has no clutch and the clutch function is performed by a planetary gear system controlled by a motor-generator. The hybrid vehicles proposed here using CGST may have some merits in durability, fuel efficiency, and cost since they do not have clutches. The motor used for the clutch function can be also working for power merge with the engine in propelling the vehicle. The proposed hybrid system can be either mild hybrid or full hybrid by adopting a different capacity of battery with much smaller motor-generator due to the planetary gear system compared to the other type hybrid vehicles. In this study, the prospects of newly proposed CGST hybrid system are examined in practical aspects compared with AGT hybrid or DCT hybrid systems.     

Research on control strategy for differential steering system based on H mixed sensitivity

The differential steering system (DSS) of electric wheel vehicle gets rid of the restrictions of traditional steering system completely. As an ideal steering technology, it not only realizes the perfect combination of the road feel and the steering portability, but also realizes the harmony and unification between the steering maneuverability and safety. The structure and basic theory of the DSS of electric wheel vehicle are discussed in this paper. Based on these, the dynamic model of the steering system is built. Considering of the uncertainties and disturbances existing in the model, the H_∞ mixed sensitivity control theory is applied to achieve better tracking performance and road feel in the process of steering. Then, a H_∞ mixed sensitivity controller is designed to restrain the effect of the road disturbance and model uncertainties. The simulation results indicate that the DSS with the designed controller can effectively restrain the effect of noises and disturbances caused by random motivation from road, torque sensor measurement and model parameter uncertainty, and enable the driver to obtain satisfactory road feel.     

Modeling and control strategy development of a parallel hybrid electric bus

This paper presents the system modeling, control strategy design, and experiment validation of a parallel hybrid electric bus with an automatic manual transmission (AMT) and a dry clutch. The mathematical model representation and the system architecture of the powertrain are first described. Next, a complete control scheme including energy management strategy and coordinated control of the AMT and the clutch is presented. The controller and powertrain models are then integrated in a way that the power management and the hybrid driveline perform in real world. The analysis and validation through model simulation and comparison with experiment data are conducted. A good agreement between the model and experiment demonstrates the efficacy and credibility of the integrated model. The integrated model is employed in both simulation and bench-test assessments for the development of a hybrid control unit. The results indicate that the model-based design methodology is beneficial to systematically analyzing and understanding the dynamics of hybrid electric powertrain.     

Design and implementation of a new clamping force estimator in Electro-Mechanical Brake systems

In this paper, an improved clamping force estimator is proposed for Electro-Mechanical Brake (EMB) systems by using the motor rotor position information and the hysteresis characteristics of mechanical parts in the EMB. A cascaded type of a force/position control system with a force sensor or an estimator was designed and implemented to control the clamping force and to keep the clearance gap in EMB systems. The EMB Hardware-In-the-Loop-Simulation (HILS) results show that the proposed force estimator yields better estimation performance than the existing estimator and that the clamping force control system based on the estimator can be also used for the fault tolerant control of the system.     

沥青混合料级配曲线研究进展

级配曲线是由富勒模型中最大粒径和形状系数两个参数来确定的,富勒模型能够很好地拟合使用性能良好的级配.级配曲线图是由形状系数和最大粒径组成的直角坐标系,它可以表示出级配范围、砂石比和相关的性能参数.该文分析了Superpave沥青混合料力学和水稳性能的试验结果,提出了根据级配曲线推荐的集料设计出满足路面各项性能的自由设计理念.