Driver curve speed model and its application to ACC speed control in curved roads

A speed control algorithm for an ACC (Adaptive Cruise Control) system for curved roads is proposed based on driver behavior characteristics. As the foundation of this research, a driver speed model for curved roads is developed using a series of experimental data regarding driver behavior. To adapt the model to each driver’s individual curve speed behavior, the coefficients of the model are identified in real time from the data sequences collected during drivers’ manual operation stage by a self-learning algorithm based on a Recursive Least-Square (RLS) method with a forgetting factor. Using this algorithm, the parameters of the driver model can be identified from the data collected in the manual operation phase, and the identification results are applied during the ACC automatic control phase. Based on the developed model, the ACC speed control algorithm is modified to provide each individual driver with a customized speed profile for the scenario of a curved road with no car ahead. Tests verify the applicability of the modified system.     

Computational and experimental investigation of the unsteady flow structures around automotive outside rear-view mirrors

The unsteady flow field around two automotive outside rear-view mirrors is investigated. This study includes comprehensive experimental and computational approaches in order to characterize the complex flow structures in the wake of the mirrors. The experiments were carried out in a wind tunnel which included the measurements of the instantaneous and averaged velocity fields as well as mean and unsteady surface pressure distributions. The simulations were performed using Large Eddy Simulation (LES). The LES approach (particularly with the dynamic subgrid viscosity model) provided good agreements with the experiments for the velocity and the surface pressure distributions. The experimental and the computational results of this study will be used as a benchmark to validate the current and the future CFD development and the subsequent aero-acoustic computations.     

Experimental study on the impact characteristics of a sandwich composite with an aluminum foam core

The need for composites has been increasing in various industries because composites have good mechanical properties for their weight and superior stiffness and strength. The composites addressed in this study were multi-pore aluminum foam with a specific gravity of 1/10 composed of solid aluminum metal. This composite has excellent impact energy-absorption capability. In this study, impact tests on an aluminum foam core sandwich composite with a porous core were conducted to examine its mechanical properties. The specimen was a sandwich structure with an aluminum foam core, and different impact energies, such as 50J, 70J, and 100J, were applied to the specimen. Consequently, a maximum load of 5.5 kN occurred when the striker penetrated the upper face sheet in all experiments. The maximum load occurred at 4.2 ms for 50J, 3.5 ms for 70J, and 3.0 ms for 100J, indicating that the greater the impact energy was, the shorter the time was until the maximum load. After the maximum load occurred, that is, after the penetration of the upper face sheet, the striker penetrated 10 mm further, causing the core to be damaged in the 50J test, while the lower face sheet remained intact. In the 70J test, the striker penetrated the core and caused damage to the upper face sheet at 10 ms. Finally, in the 100J test, the striker penetrated both the upper face sheet and core and even the lower face sheet at 10 ms. Given the result above, the maximum load occurred when the striker penetrated the upper face sheet and the sandwich composite with aluminum foam core; the load then gradually decreased and then rapidly increased when the striker reached the lower face sheet, and the maximum load lasted slightly longer than the time required for the upper face sheet to be penetrated.     

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.