Performance analysis according to the combination of energy storage system for fuel cell hybrid vehicle

The need for the unmanned ground combat vehicle (UGCV), which is used for the surveillance, reconnaissance and targeting during extremely dangerous condition on the battlefield, has steadily increased, and the transition from manned ground combat vehicles to unmanned ground combat vehicles is expected to reduce the loss of lives during battle. The UGCV needs many types of capabilities to achieve satisfactory performance. This paper focuses on the modeling and control of the power system of the UGCV, and proposes the fuel cell hybrid system (FCHS) for the power system of the UGCV. The fuel cell hybrid system has many advantages in stealth drive and the system efficiency. In addition, the FCHS is much quieter than the engine generator and generates much less heat. The benefits of the FCHS are advantageous for use in Army operations, which require ‘silent watch’ capability and the ability to operate without showing up on an enemy’s radar screen. The FCHS has a fuel cell and uses an energy storage system (ESS) as a power source. The ESS (e.g., batteries or ultracapacitors) helps the fuel cell supply power to the electric drive system and also recovers energy during deceleration. The ESS makes it possible to improve the efficiency and dynamic characteristic of the power system. In this paper, the FCHS is composed of different combinations of component models. The component sizes are chosen to satisfy performance requirements. In order to determine the power distribution between the fuel cell and the ESS, a power management strategy based on the required power and the SOC (state of charge) of the ESS is proposed. Batteries and ultracapacitor, components of the ESS, have different characteristics. Accordingly, varying the combination of ESS components can change the performance of the power system. The performance of the FCHS with respect to different combinations of ESS is analyzed using simulated results.     

Reaction characteristics of the diesel oxidation catalyst of particulate matters from the diffusion flame of a oiler burner

The objective of this experimental study is to investigate the characteristics of the size distribution and the number concentration of PM (particulate matters) emitted from the diffusion flame of a boiler burner, which has the same type of combustion as a diesel engine. This study is performed to investigate the emission characteristics of nanoparticles generated from diffusion combustion in diesel fuel, and it considered fuel factors and the reaction characteristics of the nanoparticles on the DOC (Diesel oxidation catalyst). The factors examined in this experiment included the sulfur content in the fuel, the blend of the diesel fuel containing biodiesel and bio-ethanol, and the concentration of engine oil (0.1% and 1.0%) blended with diesel fuel. The particle size distribution of the nanoparticles exhausted from the boiler burner was measured by an SMPS (scanning mobility particle sizer). The number concentration of PM that were smaller than 70 nm in diameter greatly increased in the rear of the DOC when fuel containing 250 ppm of sulfur was used. The experiment also suggested that the particle number concentration in both the front and rear of the DOC was lower when ULSD (ultra low sulfur diesel) fuel blended with biodiesel and bio-ethanol, which are oxygenated fuels, was used than when only ULSD fuel was used. The higher the content of engine oil in the fuel, the higher the particle number concentration was in the front and rear of the catalyst. When the first dilution air temperature is increased from 30°C to 180°C, the nanoparticle number concentration dramatically dropped in the rear of the catalyst when fuel containing 250 ppm of sulfur was used, while the particle size distribution remained almost the same when the fuel with engine oil was used.     

Development of evolutionary cone type LSD for SUV/RV utilizing the axiomatic approach and the ultrasonic nano crystal surface modification technology

Surface topology, cone angle and the forces acting on the cone of the clutch type limited slip differential (LSD) are major design parameters for the bias ratio and the noise condition. Therefore much research has been dedicated to these developments but the results have been used to submit patents. A new cone type limited slip differential for sport utility vehicles and recreational vehicles, which has a very simple structure and easy compliance with the vehicle performance, has been developed by the axiomatic approach and the ultrasonic nano crystal surface modification (UNSM) technology. The design criteria and optimal value of the design parameters are determined by the axiomatic approach utilizing CAE tools. Test methodologies in a test rig and in a vehicle were also developed. Test results showed good performance of bias ratio and noise level but durability is still under testing. This study is an extension of F2006P266, FISITA 2006.     

Design of Integrated Chassis Control logics for AFS and ESP

The performance of most electronic chassis control systems in the past has been optimized individually. Recently, a great research effort has been dedicated to the integration of chassis control systems in an effort to improve the vehicle performance. This involves orchestration of individual control modules so that they can jointly contribute to the enhancement of their control effect. In this research, two integrated control logics for AFS (Active Front Steering) and ESP (Electronic Stability Program) have been developed. Of the two logics, one uses a supervisor that rules over the individual modules. The other logic uses a CL (Characteristic Locus) method, which is a frequency-domain multivariable control technique. The two logics have been tested under various driving conditions to investigate their control effects. The results indicate that the proposed integrated control logics can yield vehicle performance that is superior to that of the individual control modules without any integration scheme.     

预应力CFRP板加固钢板轴心受拉行为分析

首先分析比较预应力的施加方法和锚固方式,然后基于一维线弹性理论,对预应力碳纤维增强复合材料(CFRP)板加固钢板体系的受力过程进行分阶段分析,得到在张拉预应力和受载工况下CFRP板、钢板、胶层的应力分布解析式及CFRP有效粘结长度公式、弹性压缩带来的预应力损失值;最后利用ANSYS中Solid95三维单元进行有限元模拟对比分析。结果表明:直接张拉CFRP板能有效控制预应力及其加固效果,比间接法施加预应力有更多优势;采用高强螺栓连接的平板夹具锚传递大部分荷载,改善了非预应力粘贴加固界面的薄弱特点;该理论分析及有限元模型是可靠、有效的。     

高速铁道车辆的主动稳定性系统

介绍了高速铁道车辆的主动稳定性控制系统.利用整车滚动试验台对稳定性控制器的性能进行了试验.     

Assessment of the pedestrian friendliness of a vechicle using subsystem impact tests

Annually, thousands of unprotected pedestrians are killed or suffer serious injuries in accidents with moving vehicles. Numerous automobile organizations have performed research on pedestrian safety. The European Enhanced Vehicle- Safety Committee (EEVC), Working Group 17 (WG17) proposed three component subsystem tests to evaluate the friendliness of a vehicle to pedestrians: the legform to hood test, the upper legform to bonnet leading edge test and the headform to bonnet top test. In assessing the pedestrian friendliness of a vehicle, the present study adopted the WG17 regulations of the three component subsystem tests. We herein describe in detail a finite element subsystem model built to analyze the pedestrian friendliness of a vehicle using LS-DYNA. The first objective of this study was to simulate these three component subsystem impact tests and evaluate car front aggressiveness. The second objective was to analyze the frontal structures of a vehicle and, based on the simulation results, identify dangerous areas and provide suggestions for vehicle front design that may decrease pedestrian injuries. The analysis of these models and the results obtained may be used to help evaluate the pedestrian friendliness of a vehicle and guide the future development of pedestrian-friendly vehicle technologies.     

Hydroplaning simulations for tires using FEM,FVM and an asymptotic method

Hydroplaning tires have been frequently simulated using commercial explicit FEM (Finite Element Method) codes. However, these simulations are slow, and the result of the lift force is so oscillatory that the hydroplaning speed cannot be accurately determined. Thus, in the author’s previous study, a new methodology using FDM (Finite Difference Method) code and an FE tire model iteratively was proposed. However, this full iteration method still required a long computation time, especially for patterned tires. Thus, in this study, the full iteration methodology was modified such that no iteration or only one additional iteration was needed at each speed. Then, by applying the full iteration method, no iteration method and one iteration method, the hydroplaning speeds of a straight-grooved tire were determined, and it was noted that the hydroplaning speed obtained from the one iteration method was almost the same as that obtained from the full iteration method. Moreover, the hydroplaning speeds of two patterned tires were determined using the one iteration method, and they were compared with the hydroplaning speeds obtained experimentally.     

Estimation of the adhesion force for a disc brake in a skid control condition

The performance of brakes has become important due to increased train speeds. The brake system of a train must possess a large brake force to stop the train safely within a limited stopping distance. However, an excessive brake force deteriorates the ride comfort and causes the train to skid. Therefore, it is necessary to control the brake force within the adhesion force limit. This paper presents an analytical method to estimate the relationship between the brake and adhesion forces of a disc brake system. This method has been applied to the actual disc braking control system of the Korea High-Speed Train (HSR350x), and the adhesion force is estimated in an actual skid condition.     

Improved method for analyzing automotive transmission parts (shaft/gear) manufactured using the warm shrink fitting process

There are three sub-processes associated with the assembly of an automobile transmission: heat fitting, shrink fitting, and combination fitting. In the heat fitting stage, the gear is heated to a specified temperature and then squeezed towards the outer diameter of the shaft. The stress of the heat-fitted gear depends on the yield strength of the gear. In the shrink fitting process, the gear is typically squeezed towards the shaft at room temperature using a press. An alternate method, known as warm shrink fitting, heats the already warm gear and safely squeezes it toward the shaft. The warm shrink fitting process for automobile transmission parts is becoming more commonplace, but the additional heating can cause the dimensions of the assembled parts (shaft/gear) to change with respect to both the outer diameter and the profile of the gear. As a result, there may be additional noise and vibration between gears. To address these problems, we analyzed the warm shrink fitting process using the contact pressure caused by fitting interference between the outer diameter of the shaft and the inner diameter of the gear, fitting temperature, and the profile tolerance of the gear as design parameters. In this study, a closed form equation for predicting the contact pressure and fitting load is proposed. This equation is used to develop an optimization technique for the warm shrink fitting process. The reliability of the model was verified using experimental results measured in the field, and FEM with thermal-structural coupled field analysis. Actual loads measured in the field showed good agreement with the results obtained by theoretical and finite element analysis, and expansion of the outer diameters of the gears agreed well with the results.