Aerodynamic design optimization of rear body shapes of a sedan for drag reduction

This study proposes an aerodynamically optimized outer shape of a sedan by using an Artificial Neural Network (ANN), which focused on modifying the rear body shapes of the sedan. To determine the optimization variables, the unsteady flow field around the sedan driving at very fast speeds was analyzed by CFD simulation, and fluctuations of the drag coefficient (C _D ) and pressure around the car were calculated. After consideration of the baseline result of CFD, 6 local parts from the end of the sedan were chosen as the design variables for optimization. Moreover, an ANN approximation model was established with 64 experimental points generated by the D-optimal methodology. As a result, an aerodynamically optimized shape for the rear end of the sedan in which the aerodynamic performance is improved by about 5.64% when compared to the baseline vehicle is proposed. Finally, it is expected that within the accepted range of shape modifications for a rear body, the aerodynamic performance of a sedan can be enhanced so that the fuel efficiency of the sedan can be improved. The YF SONATA, a sedan manufactured by Hyundai Motors Corporate, played a major role in this research as the baseline vehicle.     

Study of an optimized gas strut layout to improve opening and closing quality

The most important factor in gas strut design is determining an optimized layout. If the layout is not optimized, vehicle operators will have a suboptimal experience when opening and closing the tailgate. A poor layout of the gas struts causes operators to work excessively when they open/close the tailgate, and vehicle owners will incur additional expenses due to deterioration in the body quality of the vehicle. Thus, an optimized gas strut layout is very important, even if it does not seem interesting. This paper describes the tailgate operation process and focuses on determining an optimized gas strut layout for opening/closing the tailgate easily.     

Analysis process of a steering system using a concept model for idle vibration

This paper describes the development of an optimal design process for a steering column system and supporting system. A design guide is proposed at the initial concept stage of the development process to obtain sufficient stiffness of the steering system while reducing the idle vibration sensitivity of the system. Case studies on resonance isolation are summarized, where vibration modes among the systems are separated by applying a vibration mode map at the initial stage of the design process. This study also provides design guidelines for an optimal dynamic damper system using a CAE (computer aided engineering) analysis. The damper FE (finite element) model is added to the vehicle model to analyze the relation between the frequency and the sensitivity of the steering column system. This analysis methodology makes it possible to achieve target performance in the early design stage and reduction of damper tuning activity after the proto car test stage. Through the proposed steering column system development process, a lightweight vehicle with high stiffness is possible prior to the proto build stage. Furthermore, the improved process is expected to contribute to reducing the overall development period and the number of proto car tests necessary to achieve the desired steering system performance.     

Prediction of fatigue life and estimation of its reliability on the parts of an air suspension system

Air suspension systems have been implemented in various commercial vehicles, such as buses and special purpose trucks, because of the comfortable ride and easy height control. An evaluation of the durability of vehicle parts has been required for service life and safety starting in the early stages of design. The cyclic load applied to the vehicle can cause fatigue failure of parts, such as the suspension frame. This paper presents a method to predict the fatigue life of the suspension frame at the design stage of the air suspension system used in a heavy-duty vehicle. To estimate the fatigue life using the SN method, the Dynamic Stress Time History (DSTH) is necessary for the part of interest. DSTH can be obtained from the results of the flexible body dynamic analysis using the Belgian road simulation and the Modal Stress Recovery (MSR) method. Furthermore, the reliability of the predicted fatigue life can be evaluated by considering the variations in material properties. The probability and distribution of the expected life cycle can be obtained using experimental design with a minimum number of simulations. The advantage of using statistical methods to evaluate the life cycle is the ability to predict replacement time and the probability of failure of mass-produced parts. This paper proposes a rapid and simple method that can be effectively applied to the design of vehicle parts.     

Lane-following method for high speed autonomous vehicles

This paper presents a steering control method for lane-following in a vehicle using an image sensor. With each image frame acquired from the sensor, the steering control method determines target position and direction, and constructs a travel path from the current position to the target position either as an Arc-path or S-path. The steering angle is calculated from the travel path thus generated, and the vehicle follows the travel path via motor-control. The method was tested using a vehicle dubbed as KAV (Korea Autonomous Vehicle) along an expressway (Seoul Inner Beltway) trajectory with a variety of radii (50 m ∼ 300 m) while traveling at a speed of 60 km/h to 80 km/h. Compared with an experienced human driver, the method showed little much difference in performance in terms of lane-center deviation. The proposed method is currently employed for high speed autonomous driving as well as for stop and go traffic.     

Development of hot stamped center pillar using form die with channel type indirect blank holder

The hot stamping process has been used in the automotive industry to reduce the weight of the body-in-white and to increase passenger safety via improved crashworthiness. However, defects such as fracture and wrinkle occur when hot stamping is performed using a conventional drawing or forming method. In this study, a channel-type indirect blank holder (CIBH) is proposed to develop a high-strength center pillar in form-type hot stamping, so that the aforementioned drawbacks are overcome. This type of blank holder plays an important role in reducing severe wrinkling at the flange; such wrinkling leads to folding after the completion of form-type hot-stamping. First, we investigated the effect of the channel shape on the indirect blank holding force by using a simplified two-dimensional plane-strain stamping process. Second, we selected the slope angle and corner radius of the channel as the main shape parameters by finite element analysis and artificial neural network (ANN). It is known that fracture at the hot formed wall and wrinkle at the flange are significantly affected by the slope angle of the channel, and the appropriate value for eliminating fracture and wrinkle is determined to be 99°. By performing hot stamping using a form die with the selected channel, we can manufacture a high-strength center pillar without wrinkle and fracture.     

Piston-temperature measuring system using electromagnetic induction with verification by a telemetry system

The development of an inner-piston-chamber temperature measurement system is a necessary step in engine development or when solving other fundamental problems related to automotive engines. There are various pre-existing measurement methods available, e.g., the linkage method, piston telemetry, templog, and the electromagnetic induction method. In this study, we first redesigned the coil sensor used in the electromagnetic induction method using PEEK and then used Taguchi methods to reduce the number of experiments in the development process and finally utilized piston telemetry via Bluetooth to verify the precision and accuracy of the redesigned PEEK coil sensor and electromagnetic induction method. The results displayed a reproducibility within 0.5 degrees and an accuracy within 2 degrees Celsius.     

Off-set crack propagation analysis under mixed mode loadings

An assessment was carried out herein to study the eccentricity of cracks subjected to mixed-mode loadings. Several loading locations relative to a central line were selected to induce mixed-mode loadings, which were computed using a finite element method. An adaptive meshing technique was adopted during the simulation of crack propagation to ensure the singularity of stress at the tip of the crack. The stress intensity failure criterion was used and programmed, and the node splitting technique was used when the stress intensity factor reached the fracture toughness of the material to simulate crack propagations. It was found that large variations in the stress intensity factor were observed when off-set cracks were used, and that K _II decreased when loading distance increased, but increased when the off-set crack distance was increased. Both crack eccentricity and loading distance played important roles in producing mixed-mode loading, compared to the influence of central cracks. Correction factors were introduced to modify the calculation of stress intensity factors under mixed-mode loadings. Simulations of crack propagation were also conducted to study the effects of crack eccentricities and loading distances. It was found that the crack length, the loading distance relative to the central crack and the crack eccentricity dominated calculations of the integrity of cracked structures.     

License plate extraction method for identification of vehicle violations at a railway level crossing

The primary cause of most railroad accidents is vehicle entry into railway level crossings despite warning messages. To identify drivers who violate railway level crossing regulations, vehicle license plate recognition can be applied at railway level crossings. The purpose of this paper is to present an effective method for extracting the license plate region from vehicle images taken at railway level crossings. The method proposed in this paper uses the variation in the gray-level values across the image of a license plate. For license plate region extraction, the character region is first recognized by identifying the character width and the difference between the background region and the character region. The license plate region is then extracted by finding the inter-character distance in the plate region. In addition, the license plate type is identified by the difference in the gray-level value between the background region and the character region. The proposed method is effective in solving the current challenges in extracting the license plate region from the damaged frames of license plates issued for domestic use, including new types of license plates. According to the experimental results, the proposed method yields a high extraction rate of 99.5% for vehicle license plates.     

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。