Crash protection of Hybrid Electrical Vehicles for amending the KMVSS No. 91

This paper explores issues related to the electrical safety of Hybrid Electrical Vehicles (HEVs) during and after various crash events. Japanese and American federal regulations regarding occupant protection against high voltages in Electric Vehicles (EVs) and HEVs were surveyed and analyzed in this study. Front, side and rear impact tests for two types of HEVs were conducted to investigate electrolyte spillage, the retention of the propulsion battery system and the electrical isolation of the occupant. The test results met the related criteria. The test procedures and the criteria for occupant protection established through this study were amended to Korean Motor Vehicle Safety Standard (KMVSS) No. 91 to add the crash protection of the EVs and the HEVs.     

Prediction of the dimensional deformation of the addendum and dedendum after the warm shrink fitting process using a correction coefficient

The warm shrink fitting process is generally used to assemble automobile transmission parts (shafts/gears). However, this process causes a deformation in the addendum and dedendum of the gear depending on the fitting interference and gear profile, and this deformation causes additional noise and vibration between the gears. To address these problems, the warm shrink fitting process is analyzed by considering the error in the dimensional deformation of the addendum and dedendum found when comparing the results of a theoretical analysis and finite element analysis (FEA). A correction coefficient that reduces this error is derived through an analysis of the difference in the cross-sectional area between the shapes used for the theoretical analysis and that of the actual gear, and a closed-form equation to predict the dimensional deformation of the addendum and dedendum is proposed. The FEA method is proposed to analyze the thermal-structural-thermal coupled field analysis of the warm shrink fitting process (heating-fitting-cooling process). To verify the closed-form equation using the correction coefficient, measurements are made of actual helical gears used in automobile transmissions. The results are in good agreement with those given by the closed-form equation.     

Modified lateral control of an autonomous vehicle by look-ahead and look-down sensing

This paper presents a modified lateral control method for an autonomous vehicle with both look-ahead and look-down sensing systems. To cope with sensor noise and modeling uncertainty in the lateral control of the vehicle, a modified LMI-based H lateral controller was proposed, which uses the look-ahead information of the lateral offset error measured at the front of vehicle and the look-down information of the vehicle yaw angle error between the reference lane and the centerline of the vehicle. To verify the safety and the performance of the lateral control, a scaled-down vehicle was developed, and the positioning of the vehicle was estimated with USAT. The proposed controller, which uses both look-ahead and look-down information, was tested for lane changing and reference lane tracking with both simulation and experiment. The simulation and experimental results show that the proposed controller has better tracking and handling performance compared with a controller that uses only the look-ahead information of the target heading angle error.     

Effect of fuel stratification on initial flame development: Part 3-high swirl condition

This paper discusses the final investigation into the effect of fuel stratification on flame propagation. In previous works, the characteristics under the no port-generated swirl condition and the low-swirl condition were considered. For this purpose, the initial flame development and propagation were visualized under different axially stratified states in a modified optical single-cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and through the mean absolute deviation of the propagation direction. The results show that the LML is expanded remarkably under the high-swirl cases up to the highest relative AFRs of 1.71 and 1.75 between 140 and 160CA. In addition, similar to the low-swirl condition, the flame-flow interaction determines the direction of flame propagation, and the governing roles of the two factors vary according to the swirl level; the flow is more important at the higher swirl conditions, and the flame is more important at the lower swirl condition. Finally, fast and stable flame propagation can be achieved under the preferably stratified condition, which is induced by the suitable combination of the high swirl and injection timing.     

Design framework for FlexRay network parameter optimization

Because the FlexRay protocol has more than 70 configuration parameters and these parameters correlate with each other, designing a FlexRay network is a complex and difficult task. In this study, we propose a design framework that optimizes the two main FlexRay network parameters that are highly relevant to the application algorithm. The design process is composed of two steps for optimizing parameters. In the first step, the static slot length is optimized using a frame-packing algorithm. This algorithm binds network signals into static frames based on their periods and signal groups. In the second step, the communication cycle length is optimally designed with frame-scheduling algorithm and worst-case reponse time analysis. Based on the frame-scheduling algorithm, the response times are analyzed. The proposed design framework was applied to a unified chassis control system as a case study, and the analytical results were verified.     

Comprehensive lateral driver model for critical maneuvering conditions

A new comprehensive driver model is presented for critical maneuvering conditions with more accurate dynamic control performance. In order to achieve a safe maneuvering mode, a new path planning scheme to maintain stability of the vehicle was designed. A new steering strategy, considering the errors of vehicle position and yaw angle between the real track and the planned path, was established to obtain the steering angle. Therefore, the vehicle can be adjusted to accurately follow the desired path with the driver model, and the stability of the vehicle and the smoothness of the steering angle input were comprehensively considered. Simulation results were used to validate the control performance in comparison with the optimal preview driver model proposed by Macadam.     

Engine performance and toxic gas analysis of biobutanol-blended gasoline as a vehicle fuel

A comprehensive study evaluating the performance of biobutanol-blended gasoline in passenger cars was conducted because biobutanol is considered a better biofuel than bioethanol as it has no water solubility and it has a higher caloric value, giving it a higher energy value. Several kinds of samples—suboctane gasoline, 8 volume percentage and 16 volume percentage biobutanol—blended gasoline, and a 10 volume percentage MTBE-blended market sample (as the oxygencontaining gasoline)-were tested to evaluate the engine performance in terms of the detergency of the intake valves and combustion chambers, power, emissions, and fuel efficiency. Additionally, the toxicity of the emissions from these biobutanolblended samples was tested in order to assess the viability of biobutanol as one of the competitive potential substitutes for MTBE as an oxygenator in the near future. The results show that biobutanol-blended gasoline samples had relatively better detergency, relatively higher power, and similar levels of emissions compared with those of MTBE-blended gasoline. Formaldehyde was emitted from all of the samples at almost the same levels and within the error range, whereas biobutanolblended gasoline samples emitted approximately three times the amount of acetaldehyde than did the suboctane gasoline. This study shows that biobutanol is one of the best alternative bioalcohol fuels for use in the near future.     

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.     

Application of Inverse Models to Vehicle Optimization Problems

This paper presents a nonlinear inverse model of a road vehicle which simulates combined steering and braking/driving. The inputs to the model are the lateral and longitudinal acceleration of the vehicle's sprung mass center. The simulation returns the steering wheel angle and brake/drive torques required to obtain the desired accelerations. An example is presented which demonstrates the utility of inverse models for optimization purposes.