Development of probabilistic pedestrian fatality model for characterizing pedestrian-vehicle collisions

Pedestrian-related accidents are considered to be the most serious of traffic accidents due to the associated high fatality rates. In Korea, pedestrian fatalities accounted for approximately 40% of all traffic-related fatalities in 2004. Significant efforts have been made to develop effective countermeasures for pedestrian-vehicle collisions. A basis for devising such countermeasures is to understand the characteristics of pedestrian-vehicle collisions. This study develops a pedestrian fatality model capable of predicting the probability of fatality in pedestrian-vehicle collisions. Binary logistic regression and a probabilistic neural network (PNN) are employed to estimate the probability of pedestrian fatality. Pedestrian age, vehicle type and collision speed are used as independent variables of the fatality model. The models developed herein are valuable tools that can be used to direct safety policies and technologies associated with pedestrian safety.     

Effect of residual stress on impact damage in a dissimilar laminated plate at a biaxial bending mode

Systematic investigations have been performed on the mechanisms that lead to impact damage in a dissimilar laminated plate with a thermal residual stress at a biaxial bending mode. Glass/polymer laminated plates are often used as blast-proof safety screens, and bullet-proof windows, and in windshields in the automotive and the aerospace and aeronautical fields. Their many advantages, the development of new materials, and the need for high-performance, low-weight structures ensure that laminated plate construction will continue to be in demand. In this work, the impact damage in glass/Al alloy laminated circular plates cured at RT and 80°C was investigated using an instrumented long bar impact tester at a biaxial bending mode. A circular plate was cured at different curing temperatures to form a thermally induced residual stress at the bonding interface. To improve the damage tolerance of laminated circular plates, various geometric (thickness ratio of the inner to outer layer) and material parameters are considered by determining their effects of maximizing impact absorbed energy. The measured impact force profiles and the impulse of the force explained the impact damage behaviors induced in the laminated circular plates. We show that a compressive residual stress could reduce the initiation of radial cracks and the impact damaged area of the laminated plate in the outer layer. Greater an inner layer thickness results in smaller a damaged area. A design guideline for effective dissimilar laminated plate construction is proposed.     

Low cost design of parallel parking assist system based on an ultrasonic sensor

This paper presents a low cost design and implementation of a parallel parking assist system (PPAS) based on ultrasonic sensors. Generally, a PPAS requires several types of sensors, such as an ultrasonic sensor, camera sensor, radar sensor and laser sensor for parking space detection. However, our proposed PPAS only requires two ultrasonic sensors on the front and lateral sides for parking space detection. Moreover, a steering angle sensor and wheel speed sensor installed in the vehicle are used to obtain vehicle position information for localization in ultrasonic range data. The hardware architecture of the PPAS based on an electronic control unit (ECU) module, sensor modules and a human machine interface (HMI) module was proposed. Moreover, the software architecture of the PPAS is based on system initialization, scheduling, recognition and a control algorithm. In particular, a novel sensor algorithm was proposed to minimize the vehicle corner error of the ultrasonic sensor. A prototype of the PPAS based on the proposed architecture was constructed. The experimental results demonstrate that the implemented prototype is robust and successfully performs parking space detection and automatic steering control. Finally, the low cost design and implementation of the PPAS was possible due to the cheap ultrasonic sensors, simple hardware design and low computational complexity of the proposed algorithm.     

Driving environment assessment using fusion of in- and out-of-vehicle vision systems

Because the overall driving environment consists of a complex combination of the traffic Environment, Vehicle, and Driver (EVD), Advanced Driver Assistance Systems (ADAS) must consider not only events from each component of the EVD but also the interactions between them. Although previous researchers focused on the fusion of the states from the EVD (EVD states), they estimated and fused the simple EVD states for a single function system such as the lane change intent analysis. To overcome the current limitations, first, this paper defines the EVD states as driver’s gazing region, time to lane crossing, and time to collision. These states are estimated by enhanced detection and tracking methods from in- and out-of-vehicle vision systems. Second, it proposes a long-term prediction method of the EVD states using a time delayed neural network to fuse these states and a fuzzy inference system to assess the driving situation. When tested with real driving data, our system reduced false environment assessments and provided accurate lane departure, vehicle collision, and visual inattention warning signals.     

Influence of oxygenate content on particulate matter emission in gasoline direct injection engine

The relationship between the oxygen content in gasoline and the particulate emission (particle number and weight) was investigated. In order to study the influence of the engine configuration on the particulate emission, four vehicles were tested in which the following systems were installed: Vehicle 1 was equipped with direct injection system which uses central mounted outwardly opening injectors. Vehicle 2 and 3 used direct injection with a side mounted multihole injectors and Vehicle 4 had port fuel injection system. Methyl tert-butyl ether (MTBE) was used as the oxygen booster. The oxygen content in the gasoline was varied from 1 to 3 wt%, which corresponds with an MTBE dosage from 3.55% to 16.11%. This study used fuel that contained the same octane number with a 2% oxygen content without oxygen components, and it was used as the reference fuel in order to distinguish the effect of the oxygen content increases and the octane boosts that result from the MTBE. All vehicle tests were performed on a roller type chassis dynamometer using the New European Driving Cycle (NEDC) and Federal Test Procedure-75 (FTP-75) cycle. The experiment results demonstrate that the oxygen content increases in the gasoline reduced the particulate emission in vehicles with direct injection engines. An equivalent phenomenon was observed in a vehicle with a port fuel injection engine, but its absolute particle number was much smaller than that of the gasoline direct injection engine. The amount of reduction of the particle number in the start (cold) phase of the test cycle was significant compared with the later (hot) phase engine operation. However, particulates were emitted even though the engine was fully warmed up, especially when the engine was highly loaded. Other factors such as fuel economy or other exhaust emissions were not significantly affected by the oxygen content.     

Micro deformation of automobile hood in dipping process using stiffness

Technicians have been going through trial-and-error processes to solve very small or micro deformation on automobile hood during the painting process. In order to establish a systematic improvement procedure which can replace the time-consuming trial-and-error method to reduce defects, an accurate analysis of how micro deformation occurs during the painting process is needed. We have utilized a stiffness scanning method in automobile hood and reverse engineering to build up a reliable and accurate structural analysis and measurement procedures. We measured the load-stroke data at critical locations on automobile hood through stiffness scanning to determine material constants closest to the measurement by assuming several critical hood parts, such as sealer inside the hood, hemming part, spot weld part, and other uncertain joints, as virtual elastic materials. After setting the difference between analytical and measured load-stroke data as an objective function, we computed and minimized it by using the response surface method and partial differentiation of the object function. As a result, by obtaining the reliability was over 91%, which showed a strong correlation between analysis and measured results. By comparing the actual strain measured in real painting lines with calculated strain, we confirmed the validity of our structural analysis method. It was concluded that the proper analysis tool could be utilized in determination of optimal locations of supports during the painting process.     

Characteristics on NOx adsorption and intermediates of LNT catalyst

Several NOx reduction technologies under development in recent years have now been commercialized, including selective catalytic reduction (SCR) with NH₃ or hydrocarbons, and Lean NOx Trap. The aim of the present study is to investigate characteristics on NOx adsorption according to the oxygen concentration, de-NOx performance according to lean/rich injection cycle and toxic intermediates at LNT downstram for lean-burn gasoline engine. Under oxygen of 6%, NOx storage capacity was the highest, showed the highest NOx conversion of 98%. The reason for this phenomena is because the excited oxygen atoms at high oxygen concentration increased oxidizing power of NO. Under low temperature of 205°C, LNT catalyst showed the least NOx conversion of 14% because its activity became lower, while the generation rate of toxic HNCO was highest as CO which is generated during the rich condition, reacts with NOx stored on Ba site.     

Computational model for analyzing the kinematics and compliance characteristics of a commercial vehicle’s front suspension system

This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper, the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes. In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics and compliance characteristics in the earliest stages of the commercial vehicle design process.     

Robust yaw stability control for electric vehicles based on active front steering control through a steer-by-wire system

A robust yaw stability control design based on active front steering control is proposed for in-wheel-motored electric vehicles with a Steer-by-Wire (SbW) system. The proposed control system consists of an inner-loop controller (referred to in this paper as the steering angle-disturbance observer (SA-DOB), which rejects an input steering disturbance by feeding a compensation steering angle) and an outer-loop tracking controller (i.e., a PI-type tracking controller) to achieve control performance and stability. Because the model uncertainties, which include unmodeled high frequency dynamics and parameter variations, occur in a wide range of driving situations, a robust control design method is applied to the control system to simultaneously guarantee robust stability and robust performance of the control system. The proposed control algorithm was implemented in a CaSim model, which was designed to describe actual in-wheel-motored electric vehicles. The control performances of the proposed yaw stability control system are verified through computer simulations and experimental results using an experimental electric vehicle.     

Safety benefits of integrated pedestrian protection systems

This study developed a methodology for evaluating the effectiveness of an integrated pedestrian protection system (IPPS) based on simulations. The proposed IPPS consists of active and passive vehicular systems for protecting pedestrians, including a pedestrian warning information system (PWIS), an active hood lift system (AHLS), and pedestrian airbag system (PAS). Two simulation methods were applied in the proposed methodology: a driving simulation and a finite element simulation. A driving simulator was used to obtain the change in collision speed, which is a key parameter for evaluating driving behavior when a PWIS is applied. In addition, a well-known simulator for finite element analysis, LSDYNA was used to simulate the impact of a pedestrian on a vehicle hood in a pedestrian-vehicle collision. The head injury criterion (HIC), which is an outcome of LS-DYNA simulations, is a major parameter for evaluating passive safety systems. The probability of pedestrian fatalities by collision speeds and HICs were estimated to quantify the safety benefits of an IPPS based on the statistical analyses. The results showed that an IPPS is capable of reducing pedestrian fatalities by approximately 90 % associated with jaywalking in the midblock and walking on the roadside. The findings of this study can be used to boost the development of various vehicular technologies for pedestrians. The results can be effectively used for policy making and deriving legislative requirements associated with advanced vehicular technologies for enhancing pedestrian safety.