A Study on the Modeling and Its Validation for Pedestrian's Knee Ligaments

基于人体模型THUMS中的膝韧带模型,改进了材料参数和单元属性.采用近年较新的生物力学实验数据,逐个验证韧带模型在不同应变率下的生物逼真度.结果表明,膝韧带ACL、PCL、MCL和LCL在不同应变率下的拉力与位移关系曲线与试验结果吻合较好,说明模型具有较好的生物逼真度,能较准确地模拟韧带的损伤和拉伸响应.     

Numerical investigation of a DI diesel spray flame using a detailed chemical reaction mechanism

Emission standards have grown increasingly stricter, consequently triggering greater interest in issues surrounding environmental pollution. In particular, soot and NOx released from DI diesel vehicles is considered to be the main source of air pollution in urban environments. However, the mechanics of fuel spray formation and the influence of the operating parameters on the resulting spray flame are not yet fully understood. In this study, the original KIVA code was modified to incorporate a detailed chemical reaction mechanism involving various species and multiple reaction steps to better understand the spray characteristics. n-Heptane, C₇H₁₆, was used as the representative fuel for diesel fuel, and the reaction mechanism for this fuel was composed of 66 species and 274 elementary reaction steps. The accuracy of the predicted results was demonstrated primarily by a comparison with experimental results. The numerical prediction of a specific operating condition for the parametric investigation correlates well with the experimental results.     

A comparative study on the power characteristics and control strategies for plug-in hybrid electric vehicles

A comparative study was performed on two types of plug-in hybrid electric vehicles (PHEVs): the GM Volt and the Toyota Prius Plug-in Hybrid. First, the powertrain models of the two vehicles were derived. Based on the dynamic models, a detailed component control algorithm was developed for each PHEV. Specifically, a control algorithm was proposed for motor generator 1 (MG1) and MG2 to achieve optimal engine operation. Additionally, an energy management strategy for selecting the operation mode was developed from the viewpoint of fuel economy, battery state of charge and vehicle velocity. Using the dynamic model of the control algorithm for each PHEV, simulations were performed, and the simulation results were verified by comparing them with those obtained using the Powertrain System Analysis Toolkit simulator for the plug-in Prius. Based on the simulation results, a comparative study was performed, and it was found that the role and capacity of MG1 and MG2 and the mode selection algorithm must be determined depending on the configuration of the PHEV.     

Influence of the accelerating operation mechanism on the combustion noise in DI-diesel engines

This paper focuses on the mechanisms of combustion noise during the accelerating operation of multi-cylinder diesel engines using testing technology for the transient conditions of IC engines. Based on impact factors, such as the gas dynamic load and cylinder pressure oscillations, tests and analysis of the combustion noise during transient and steady-state conditions for different loads are made on four-cylinder naturally aspirated engines, turbocharged engines, EGR-introduced engines, and high pressure common rail engines. The laws of combustion noise difference for the same engine speed and load are researched during transient and steady-state conditions. It is found that during transient conditions, the maximum pressure rise rate and the high frequency oscillation amplitude of the cylinder pressure are all higher than those observed during steadystate conditions for the same engine speed and load. With their joint action, the combustion noise during transient conditions is greater than that during steady-state conditions. Turbocharging is useful in reducing the combustion noise during transient conditions. Turbocharging has a better effect on the control over the combustion noise during transient conditions with a constant engine speed and an increasing torque than in conditions with a constant torque and an increasing engine speed. One of the main reasons for different control effects on the combustion noise is that turbocharging causes different wall temperatures inside combustion chambers. The introduction of the appropriate EGR is helpful in the reduction of the combustion noise during transient conditions. The key to the control of combustion noise with EGR during transient conditions is whether a real-time adjustment to the EGR rate can be made to achieve the optimization of the EGR rates for different transient conditions. By means of analyzing the differences in the combustion noise between the transient and steady-state conditions for different pilot injection controls, we obtain a strategy for controlling the combustion noise during transient conditions with a pilot injection. Compared with the steady-state conditions, a larger pilot injection quantity and a longer interval between the main injection and pilot injection should be selected for transient conditions, and this is verified through tests.     

Sensitivity analysis for reducing critical responses at the axle shaft of a lightweight vehicle

Critical responses are frequently detected at the coupled torsional beam axle (CTBA) of a lightweight vehicle. However, the freedom to modify the design of the axle shaft is limited because the suspension system must satisfy other vehicle requirements such as steering performance. Conventional sensitivity analysis cannot provide practical information about the resonant behavior because the analysis only identifies the contribution of the axle shaft to the behavior. This paper presents a novel sensitivity analysis based on transmissibility ratios (TRs). The vehicle components other than the axle shaft that can be modified to control the critical spectra are identified using acceleration responses. A multi-body vehicle model is constructed to simulate the proposed design modifications, and the simulation results show that the vibration of the axle shaft is considerably reduced by the modifications. Because the TRs on the CTBA are effectively minimized through the modified design strategy, the resonant response from the axle shaft can be controlled efficiently.     

Experimental study on the characteristics of nano-particle emissions from a heavy-duty diesel engine using a urea-SCR system

Particulate matter in diesel engine exhaust, particularly nano-particles, can cause serious human health problems including diseases such as lung cancer. Because diesel nano-particle issues are of global concern, regulations on particulate matter emissions specify that not only the weight of particulate matter emitted but also the concentration of nanoparticles must be controlled. This study aimed to determine the effects on nano-particle and PM emissions from a diesel engine when applying a urea-SCR system for NO_x reduction. We found that PM weight increases by approximately 90% when urea is injected in ND-13 mode over the emission without urea injection. Additionally, PM weight increases as the NH₃/NO_x mole ratio is increased at 250 °C. In SEM scans of the collected PM, spherical particles were observed during urea injection, with sizes of approximately 200 nm to 1 μm. This study was designed to determine the conditions under which nano-particles and PM are formed in a urea-SCR system and to relate these conditions to particle size and shape via a quantitative analysis in ND-13 mode.     

Vision-based fusion of robust lane tracking and forward vehicle detection in a real driving environment

With the goal of developing an accurate and fast lane tracking system for the purpose of driver assistance, this paper proposes a vision-based fusion technique for lane tracking and forward vehicle detection to handle challenging conditions, i.e., lane occlusion by a forward vehicle, lane change, varying illumination, road traffic signs, and pitch motion, all of which often occur in real driving environments. First, our algorithm uses random sample consensus (RANSAC) and Kalman filtering to calculate the lane equation from the lane candidates found by template matching. Simple template matching and a combination of RANSAC and Kalman filtering makes calculating the lane equation as a hyperbola pair very quick and robust against varying illumination and discontinuities in the lane. Second, our algorithm uses a state transfer technique to maintain lane tracking continuously in spite of the lane changing situation. This reduces the computational time when dealing with the lane change because lane detection, which takes much more time than lane tracking, is not necessary with this algorithm. Third, false lane candidates from occlusions by frontal vehicles are eliminated using accurate regions of the forward vehicles from our improved forward vehicle detector. Fourth, our proposed method achieved robustness against road traffic signs and pitch motion using the adaptive region of interest and a constraint on the position of the vanishing point. Our algorithm was tested with image sequences from a real driving situation and demonstrated its robustness.     

Simulation of a powertrain system for the diesel hybrid electric bus

The plug-in hybrid electric bus (HEB) is designed to overcome the vulnerable driving range and performance limitations of a purely electric vehicle (EV) and have an improved fuel economy and lower exhaust emissions than those of a conventional bus and convention HEBs. The control strategy of the plug-in parallel HEB??s complicated connected propulsion system is one of the most significant factors for achieving a higher fuel economy and lower exhaust emissions than those of the HEV. The proposed powertrain control strategy has flexibility in adapting to the battery??s state of charge (SOC), exhaust emissions, classified driving patterns, driving conditions, and engine temperature. Simulation is required to model hybrid powertrain systems and test and develop powertrain control strategies for the plug-in parallel HEB. This paper describes the simulation analysis tools, powertrain components?? models and modifications, simulation procedure, and simulation results.     

Roof strength performance improvement enablers

Before 2009, rollover in vehicle accidents had not been significantly studied not only because its rate is lower than other types of accidents but also because it had been easy to meet the rollover regulation, the FMVSS 216 Roof Crush Resistance target. The regulation only requires that the strength-to-weight ratio (SWR) be 1.5, i.e., it was acceptable when the roof could withstand a force of only 1.5 times the vehicle??s weight. In other words, rollover is not considered an important safety factor. However, presently, the situation has completely changed. Rollover is now considered a key safety factor. Recently, the number of rollover incidences has been increasing, reaching as much as the number of front, side and rear accidents. Furthermore, the IIHS has begun to require that the roof must withstand a force of 4.0 times the vehicle??s weight, a more severe restriction than FMVSS. To satisfy this requirement, many manufacturers, universities and institutes are studying the topic. This paper focuses on changing the body structure to minimize injury to the occupant when rollover occurs and help rollover safety performance become excellent. This paper draws on a simple analysis that is based on general factors: changes in the material, the addition of welds and additional reinforcements. The best result will be determined, as described by this paper.     

Shape optimization of rubber isolators in automotive cooling modules for the maximization of vibration isolation and fatigue life

Rubber isolators are mounted between a cooling module and a carrier to isolate the car body from vibration due to the rotation of the cooling fan. The isolators should be durable against fatigue loads originating from fan rotation and road disturbance. Thus, the design of rubber isolators is required to maximize both vibration isolation and fatigue life. In this study, the shapes of the rubber isolators are optimally designed using a process integration and design optimization (PIDO) tool that integrates the various computer-aided engineering (CAE) tools necessary for vibration and fatigue analyses, automates the analysis procedure and optimizes the design solution. In this study, we use CAE models correlated to the experimental results. A regression-based sequential approximate optimizer incorporating Process Integration, Automation and Optimization (PIAnO), a commercial PIDO tool, is employed to handle numerically noisy responses with respect to the variation in design variables. Using the analysis and design procedure established in this study, we successfully obtained the optimal shapes of the rubber isolators in two different cooling modules; these shapes clearly have better vibration isolation capability and fatigue lives than those of the baseline designs used in industry.