The prototype piezoelectric sensor to fit up the outside of engine was manufactured for measuring equivalent indicated mean effective pressure (Equivalent IMEP). Equivalent IMEP is correlative with indicated mean effective pressure (IMEP) got from ordinary cylinder pressure diagram. The insulation resistance at 150 degrees was 1 G ohms over, and the sensitivity was 1 V/MPa over when feedback capacitance was 1000 pF. The prototype sensor mounted a single cylinder engine and measured equivalent IMEP, the correlation coefficient of IMEP between equivalent IMEP was about 0.99.

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CO emission sources from diesel combustion with multiple fuel injections were analyzed by using in-cylinder CO-LIF imaging and numerical simulation. The major source of CO emission under low-load conditions is the over-diffusion of pilot sprays, and that under high-load condition is the shortage of oxygen in the rich regions at the frame front. As an example of CO reduction techniques, a new piston-cavity with a stepped lip which reduces the squish flow velocity was introduced. Its effects on CO emission were validated by exhaust emission tests and simulations.

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The recent engine equipped with various devices such as variable nozzle turbocharger, EGR or DPF can satisfy environmental regulations. However, introduction of many technologies causes ECU parameters to increase and engine system to be complicated, which makes determining optimum ECU setting with conventional calibration method difficult. For that reason, calibration method based on experimental engine models is taken notice. The objective of this study is construction of high robustness and high quality experimental engine models containing physical laws such as extended Zeldovich mechanism or soot formation theories. And it is shown that the models to which physical laws are applied have possibility to predict exhaust emissions qualitatively and have robustness to the number of measured data.

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Exhaust gas temperature is an important factor in NOx, THC and PM emissions of engines. Especially 2D temperature and concentration distribution plays an important role for the engine efficiency. In this study, the theoretical and experimental research has been conducted in order to develop the noncontact and fast response 2D temperature and concentration distribution measurement method. The method is based on a computed tomography method using absorption spectra of water vapor at 1388nm. It has been demonstrated that the method has been successfully applied to engine exhausts to measure 2D temperature distributions.

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The key challenges of passenger car today are to reduce carbon dioxide and to clean up exhaust gas emission. HCCI engine needs the following for practical use: wider operating range, combustion changing, and robustness control for different usage situation (e. g. fuel quality, parts variant). In this report, detection technology of combustion fluctuation and combustion noise on HCCI combustion mode was studied for constructing robustness control. The feature of this technology is to estimate combustion fluctuation and noise with rotational fluctuation of crankshaft and engine Vibration. As a result of bench engine test, an availability of this technology was confirmed.

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The objective of this study is to be clear the influence of the oxidation deterioration of FAME on the property of elastomer, NBR and FKM, by using the soaking test by neat FAME and FAME blend with changing of degree in oxidation deterioration. And the Hansen solubility parameter (HSP) has been applied to the study of the NBR and FKM solubility and swelling by methyl oleate mixed with formic acid, acetic acid, propionic acid, oleic acid, which are formed by oxidation deterioration of FAME. Form the result, NBR increases in mass and volume, and decreases in tensile strength by the oxidized FAME immediately, and FKM also increases in mass and volume by long soaking time.

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This paper describes the influence of cold flow improver(CFI) and antioxidant addition in FAME on low temperature behavior, oxidation stability and exhaust characteristic. From the experimental results, it is found that antioxidant have no influence on low temperature behavior. On the other hand, the results show that by CFI addition in FAME with amine type antioxidant the oxidation stability can be improve. Also, there are no changes in exhaust emission characteristics by addition of CFI and antioxidant.

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The effect of reducing agents for NO reduction activities were compared between NH₃ and urea on zeolite-type SCR catalysts such as Fe-, Cu- and Ce-zeolite type catalysts using the model-gas reactor. As a result, NO reduction performances had a similar tendency between both reducing agents. To investigate urea decomposition behavior, the FTIR analysis was operated on the surface of the Fe-zeolite catalyst during NO reduction. Then NH₃ was produced at a low enough temperature (130-160 ºC) on the catalyst surface. Therefore, it is considered that the reducing agent species (NH₃ or urea) showed almost no difference for the NO reduction activity.

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In a membrane filter consisting of nanoscaled SiC-particles with surface-oxide-layer including a single-nanoscaled Pt-particle, oxidation rate of soot trapped on the surface became higher than that without Pt-particle though both apparent activation energies are much the same. Through Thermal Desorption Spectroscopy experiment, the number of oxygen adsorbed on the surface of the oxide layer with Pt-particle is larger than that without Pt. As a result, the reaction rate might be increased by a high frequency collision between the adsorbed oxygen and soot.

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Numerical analysis was conducted on diesel particulate filter coated with NH₃-SCR catalysts to downsize catalyst volume and to improve the characteristics of the NOx reduction due to controlling heat loss. Firstly, we analyzed deteriorated NOx reduction performance due to the soot loading on SCR catalyst and confirmed the validity of the model. In addition, we discussed about the catalyst design by changing the distribution of catalyst and wall thickness in the filter by using numerical code developed.

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In order to select optimum diesel engine systems and develop new control logic, a zero-dimensional diesel combustion model for Total Engine Simulation System (TESS) has been developed. It is possible to predict fuel efficiency and exhaust emission with relatively high accuracy considering its high computational speed. This paper presents model improvements in heat loss, in-cylinder flow, turbulence and soot of the combustion model. Furthermore validation results of prediction accuracy at a wide range of operating points and engine displacement are shown.

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The authors' group has been developed an LDA flow rate meter for a fuel injection rate measurement. The LDA flow rate meter can realize simultaneous measurements of the fuel injection rate and of the spray characteristics. The various diameters of pipe that is the measuring section of LDA flow meter are tested for improving the measurement accuracy of the high-pressure fuel injection rate. In addition, the oscillation in the flow rate is separated, and the injection rates are re-calculated. It is pointed out that the oscillation is caused by shocks when the injector valve is opening and closing.

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Gasoline direct injection (DI) has been widely utilized in high-compression-ratio engines and supercharged engines to improve the thermal efficiency. One of the most important quality problems in DI gasoline engines is the spark plug fouling due to dispersed fuel droplets under the fuel-rich condition during the cold start. To understand and solve this problem, we developed a new method to measure the amount of fuel droplets around the spark plug using a spark-plug-type optical sensor based on the light extinction. We confirmed that we could measure the amount of fuel droplets using this sensor. We found that the amount of fuel droplets strongly correlated with the number of cycles which the engine was operated until it could not restart at the pre-delivery test and the number of misfires during the warm-up. Therefore, the development of the spark plug antifouling performance is accomplished by controlling the amount of fuel droplets around the spark plug.

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Engine tests were conducted along with chemical kinetics modeling to investigate the effects of 40% Jatropha-derived biodiesel on combustion and emission characteristics over a wide range of engine operating conditions in a passenger car diesel engine. Emissions measurements and heat release analyses showed that biodiesel can significantly reduce PM (particulate matter) without significantly influencing heat release rates, NOx emission and brake thermal efficiency under the conditions in the NEDC. For comparison with experimental results, we utilized a zero-dimensional reaction model with detailed chemical kinetics to identify the effects on engine combustion and emissions.

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Two different 2-stage turbocharging strategies, featured by the different low pressure turbine flow rate and controlling strategy of the air handling devices, were compared in order to improve the practical fuel consumption and the exhaust emissions in a heavy duty diesel engine. As the results, combination of the selected turbochargers that obtained a higher boost pressure in a broad engine speed and load range and the higher compression ratio can achieve simultaneous improvement in exhaust emissions and fuel consumption with actual driving conditions, i.e. mileage.

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The effect of fuel properties on diesel combustion and exhaust emissions characteristics were investigated by using Computational Fluid Dynamics which includes detailed elementary reaction processes. Chemical effects are examined by increasing the content of aromatic components and physical effects are done by deactivating the evaporation characteristics. As a result, the soot formed is increased with the increase of aromatic component up to 40% at constant physical properties. When evaporation properties were deteriorated by replacing original physical properties with those of higher HCs, soot emission was decreased due to longer ignition delay time.

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This study is to clarify the effect of the variable valve timing control by means of a high BMEP heavy duty diesel engine equipped with 2-stage turbocharging system. Test was done in various engine operating points. In conclusion, at low speed and low load condition, BSFC is improved with late IVC because of decreasing friction loss with lower effective compression ratio. While BSFC is not so improved only with late IVC in high load condition, there is a potential to improve BSFC combined late IVC with advanced fuel injection timing, resulting in a higher degree of constant volume combustion with maintaining peak cylinder pressure lower than the constraint. Furthermore, it was found that excess air ratio plays an important role to control engine performance and exhaust emissions in any cases.

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To achieve higher thermal efficiency of a gasoline engine, numerical simulations were conducted. The effects of air-fuel mixture formation in partially premixed compression ignition (PaPC) as well as fuel ignitability on auto-ignition combustion under boosted and high EGR ratio air charge condition were studied. From the simulations, it was showed that EGR with boosted air charge could make the oxidation process remained in a partially oxidized state which is desired for PaPC combustion. Thermal efficiency of the PaPC engine is expected to be up to around 50% by selecting fuel ignitability, fuel injection timing and the quantity and EGR ratio.

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A Cu-Zeolite SCR system was experimentally compared with a Fe-Zeolite one in terms of NOx conversion efficiency over a wide range of exhaust gas temperatures in a heavy-duty diesel engine. The test results show that the Cu-Zeolite SCR can reduce NOx more effectively due to increased NH₃ adsorption at lower temperatures than the Fe-Zeolite type. In addition, N₂O tends to be formed in a DOC located downstream of the SCR system depending on slipping NH₃ from it as well as on the lower temperatures. A simplified catalytic reaction model developed in this study can explain these SCR and N₂O formation reactions.

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It is well known that HCCI combustion has low ignition timing controllability and that this characteristic has been a major obstacle for automobile manufacturers to apply this combustion into production engines. In this study, to overcome the drawback, diesel injection was used to control and stabilize the combustion. The experiment results indicate that this combustion concept is effective to stabilize HCCI combustion. At medium load conditions, while attaining extremely low NOX and PM emissions, high thermal efficiencies were achieved. Simulation results showed reasonable agreement with the experiment results, thus visualization of the combustion was realized.

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The effects of branched structure on the low-temperature oxidation mechanism of hydrocarbon fuel have been investigated by using a steady-state analysis. This analysis shows that both quaternary and tertiary carbon decrease the ratio to chain branching process among the reaction path of alkylperoxy radicals (ROO). A quaternary carbon affects mainly intramolecular hydrogen shift reactions of ROO and cyclic-ether formation reactions of hydroperoxy (QOOH) radical. On the other hand, a tertiary carbon affects HO₂ elimination reaction of ROO and intramolecular hydrogen shift reaction of hydroperoxyalkylperoxy (OOQOOH) radical. These kinetic effects elucidate the correlations between chemical structure and ignition delay time for alkane molecule presented in our previous study.

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Palm oil butyl ester (PBE) has lower pour point compared with palm oil methyl ester (PME). In this study, to reduce NOx and smoke emissions of PBE, emulsified PBE was made and its fuel properties and combustion characteristics were investigated using a single cylinder DI diesel engine, and were compared with PME, emulsified PME, JIS no.2 diesel fuel. From the experimental results, NOx and smoke emissions of emulsified PBE reduce simultaneously in comparison with PBE. Emulsified PBE has better emulsification stability, almost the same thermal efficiency and NOx emission, and slightly higher HC, CO and smoke emissions compared with emulsified PME.

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Using a detailed chemical kinetic model of normal heptane, a constant-volume ignition process of a highly-diluted mixture was analyzed. When the N₂ concentration increases or the fuel concentration decreases to a considerable extent, an ignition process starting with the LTO phase indicates double peaks of heat release in the thermal ignition preparation phase. The H₂O₂ loop reactions mainly contribute to heat release in a low-temperature region of the thermal ignition preparation phase, and H + O₂ + M = HO₂ + M mainly contributes to heat release in a high-temperature region of the phase. H₂O₂ is accumulated during the LTO and NTC phases, and then drives the H₂O₂ loop reactions to increase the temperature in the thermal ignition preparation phase. When the heat capacity of a mixture per unit fuel concentration increases, H₂O₂ is consumed in a lower-temperature region, and the heat release by the H₂O₂ loop reactions stagnates at a lower temperature. Thus, a gap of heat release between the low-temperature and high-temperature regions of the thermal ignition preparation phase is generated. Because the rate of H + O₂ = OH + O cannot overtake the rate of H + O₂ + M = HO₂ + M, CO + OH = CO₂ + H proceeds slowly with H + O₂ + M = HO₂ + M in the final stage of the ignition process rather than with the branching chain reaction.

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In order to reduce piston frictions in the automobile engine, we have examined the various surface characteristics and surface treatment of pistons. As a result, we confirmed that it is most effective to smooth the piston skirt surfaces for friction reduction, which is approximately 15% reduction in frictions. So we have developed the new surface treatment technology applicable for mass production, and confirmed its effect.

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New continuously variable valve phase and lift/duration mechanism for widely available automobile engines has been developed. The mechanism enables to continuously change the phase and lift/duration simultaneously during the engine operation. Multi-body dynamics simulation oriented study predicted the unexpected problems for the initial designs and enables to improve the system without experiment. The prototype mechanism on the single cylinder head is successfully operated up to 7000 rpm, the targeted range of engine speed. The development process to find the new mechanism and design components are described in this paper.

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Oil consumption through piston cylinder characteristics under an engine brake condition are investigated by means of varying specifications of piston rings. An oil consumption amount is evaluated by a weight of an oil adhered to the inner walls of the engine cylinder and the intake pipe. As the results, reduction in size of the top ring gap is the most effective to decrease the oil consumption. The oil behavior around the piston indicates that the reduction of the top ring gap directly acts influence not on choking the passage of an oil flow. To clarify the reason, a pressure of a piston 2nd land and an axial movement of piston rings are analyzed with a newly developed ultra-small sized data logger. The results indicate that the reduction of the top ring gap heightens the 2nd land pressure by changing the top ring movement and the gas flow around the ring, and it inhibits the oil inflow from the 3rd land area.

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Cylinder bore shape under engine operating condition has much effect on lubricating oil consumption. This study aims at evaluating the conformability of oil-ring on cylinder bore under engine operating condition and clarifying the mechanism of lubricating oil consumption via the oil ring sliding surface. Laser-Induced-Fluorescence method was adopted to the three-piece-type oil-ring, and oil-film thickness was successfully measured. It was found that oil-film became thicker around the bottom dead center. Findings suggested that the cylinder bore shape, the piston tilting and vaporization of oil on the cylinder affected the oil-film thickness at the oil-ring sliding surface.

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Synchromesh mechanisms are commonly applied to transmissions because it can effectively help shift change process. Dynamic behavior of transmissions with synchromesh mechanism has not been investigated although the dynamic behavior of the synchromesh mechanism influences the vehicle behaviors. In this study, a mathematical model for a transmission with the synchromesh mechanism is proposed to analyze the dynamic behaviors during the shift changing motions. The model consists of inertias, torsion stiffness, frictions, and a model for the synchromesh mechanism. In order to confirm the validity of the proposed model, the model is applied to an experimental setup which is controlled by a PC. As the results of experiments and simulations, it is confirmed that the proposed model can qualitatively evaluate the dynamic behavior during the shift change motions.

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The project discussed in this paper developed a new electronically controlled all-wheel-drive system that replaces dual-pump system exploiting front-rear wheel rotation speed difference. The new system has hydraulic circuit with an electric hydraulic pump and a solenoid control valve. The use of electronic control has further optimized rear wheel driving force, the realization of increased responsiveness has made it possible to do away with a one-way cam, and a low-friction BRG has been employed. These and other innovations in the new system have made it possible to reduce weight and friction.

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With the spread of electric vehicles such as plug-in hybrid vehicles and electric vehicles, it is feared that the electric power of houses and the society will be overloaded. In this research, human behavior is analyzed by using the floating car data and the power consumption data. On the basis of the results, we propose a new method of optimal energy management of vehicles for the electric power of society and houses. It is confirmed that the amount of electric energy by proposed method is one fifth less than those of non-charging management.

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This paper discusses the levels of deterioration in Li-ion batteries that are acceptable in different types of electric-driven vehicles. Simulation-based analysis of the adverse effects of battery deterioration on vehicle performance was carried out, and acceptable degrees of battery deterioration are proposed based on the criteria of 20% loss of performance (20% reduction in cruising range for BEVs, 20% increase in fuel consumption for HEVs and 20% increase in CO₂ emissions for PHEVs).

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Lithium-ion Batteries (LiB) are increasingly used in automobiles and buildings since around 2010. Although the lifetime of several years is long enough for LiB used in small electronic devices, a life time of more than 10 years will be required for LiB in infrastructures However, many LiB users are reporting uncertainty of the life time of LiB. This is one of the major problems which prevent LiB from spreading to society. Therefore, it is important to predict the degradation of battery performance and the lifetime of LiB based on the present performance. It will decide proper installation place of used battery and how to use them in the future. The authors developed an evaluation model of used LiBs. The model contains two elements: (1) degradation speed database of experiments and (2) the modeling of use pattern and condition of LiB.

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In order to improve the driving performance of electric vehicles with in-wheel motors, we have proposed a traction control system adaptive to road conditions. The feedback gain and the time constant of the control system are adaptively adjusted by the estimated slip ratio and friction coefficient during driving. The simulation and the pre-experimental results demonstrated that the control system achieves high acceleration performance in normal road conditions, as well as restrains wheel slip on slippery roads. This paper, applying the proposed system to the experimental electric vehicle, reports the experimental results of anti-slip control on slippery road surface. In addition, about the estimation error of slip ratio, we discussed its influence on slip restraint performance.

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A stability factor for force control is obtained theoretically. The stability factor is the ratio of the following two terms. One is the natural frequency of rotational motion of steering system around kingpin axis. The other is that of a vehicle around the vertical axis through its center of gravity. From the stability factor distribution of actual vehicles, its target value is proposed. To satisfy the value, a design method for steering system parameters on plots is also proposed. As a result, enough stable vehicles under force control can be designed theoretically and visually without numerical simulations.

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International standards for safety evaluation tests of lithium-ion batteries, which are beginning to be installed in those vehicles, are IEC 62660-2 for cells and ISO 12405-1 and ISO 12405-2 for battery packs and systems. We conducted safety evaluation tests to verify the relevance of the test method. In this paper we report on the high-temperatre endurance tests results. The IEC high-temperatre endurance test specifies that cells should be heated to 130 ºC in a convective constant temperature bath, but we also heated them to 150 ºC. Some cells ignited while cooling from 150 ºC to ambient temperature. Some cells may also ignite even after being heated to the 130 ºC test temperature specified in IEC, so the cell temperature should fall to at least 50 ºC before the IEC test is terminated.

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We conducted hydraulic sequential tests of new domestic standard ”KHK S 0128” for existing VH3 and VH4 tanks. No problem was found in carrying out these tests. No unexpected phenomena occurred in the VH4 tank. However, in the liner of the VH3 tank leaked. The temperature and pressure control regulations of the procedure are not detailed in the accelerated stress test, one of the sequential tests. The control procedure affects the results, so, it is necessary to investigate the influence of the temperature and pressure control procedure.

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It is investigated that how characteristics of steering wheel torque exert influence on behavior of driver-vehicle system by using driving simulator. In addition to friction and damping of steering system, tire cornering power contributes to static and dynamic characteristics of not only vehicle motion but also steering wheel torque. It is revealed that the characteristics of steering wheel torque are associated with handling and stability of the driver-vehicle system. In particular, the characteristics can improve a repeatability of steering behavior of driver in repetitive cornering on same course, which correlates to subjective evaluation of handling.

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The vehicle, of which the four-wheel steering was controlled such that the vehicle’s body headed outward compared to the conventional vehicle during high speed cornering, gave better feeling of confidence. The purpose of this paper is to clarify the cause of the feeling. The simulation based on the look-ahead driver model shows that the vehicle heading outward makes the steering return correction decrease and makes the steering velocity at the initial positioning lower compared to the vehicle heading inward. The simulation result was validated by the experiment using the driving simulator. Many drivers feel confidence because the vehicle positioning becomes easier when the vehicle heads outward in cornering.

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It is 4DOF model considering inputs from steering wheel and road. Torque and angle as steering inputs, and king-pin lift torque, side force at road cant and curvature as road inputs are considered. The equivalent cornering power involving the compliance as compliance coefficient is used. Also, the cornering coefficient presented dividing the equivalent cornering power by axle load is used for being responsible to loading weight validation. Simulated results are shown with actual express way running data.

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In the first report, a study of dynamic contact patch measurement technology was presented and contact behavior in terms of dynamic adhesive & slippage regions for improving eco-tire’s cornering power/force was described. However, since the proposed methodology visualizes global contact stress distributions by averaging a number of measurement signals, the effects of a complicated tread pattern design represented by lug grooves, sipes, and so on tend to be mitigated. In order for taking these effects into account, the measurement and visualization methodology of detailed tread pattern behavior in a contact patch has been developed. As its application, the new tread pattern design of the latest eco-tire for the improvement of compatibility between braking performance and low rolling resistance has been proposed and verified.

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As the number of automobiles in the world is increasing, problems associated with environment and safety are becoming serious matter. One of the solutions to these problems is an autonomous platooning of trucks. In such applications control gains are typically tuned manually. The optimal values change due to the freight or over the years. Therefore, when the control performance decreases, gain tuning is needed again. In this paper, a fuzzy inference based self-tuning method of steering control gains is proposed. This proposed method leverages a relationship among a meander cycle, amplitude of a vehicle and control gains. Its effectiveness is experimentally evaluated.

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A new yaw-moment control method which generates stabilizing moment during the G-Vectoring control command has positive acceleration value and the driver’s accelerator pedal input is zero was developed. A new hybrid control which is comprised with G-Vectoring control （GVC）, Electric stability control （ESC） and this new control was constructed, and it was installed into test vehicle and tested on snowy surface. We confirmed the control has very high potential for improvement in both agility and stability.

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It is understood that rolling resistance coefficient (RRC) is one of the most important characteristics for fuel consumption. The influence that tyre temperature has on tyre characteristics is well known. This paper proposes a way to represent tyre thermal characteristics by simple experimental formula and shows the effect of the thermal characteristics on vehicle performance in actual driving. In addition, suitable inflation air pressure is discussed to achieve a good balance between cornering characteristics and rolling resistance.

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We have developed a new multi-link rear suspension that has a simple link configuration and a lower link that features a connecting bushing mechanism. This innovative new connecting bushing mechanism not only helps to provide better handling stability by ensuring high stiffness and an adequate level of compliance steer, but also helps to improve ride comfort by suitably controlling the behavior of tires when they encounter irregularities in the road surface, thereby providing a safe and comfortable driving experience suitable for a high-performance passenger vehicle. The new link layout enabled us to reduce the number of components compared with current multi-link suspensions. We have also achieved weight reductions by precisely controling the load transmitted to links and suspension members.

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Future Steel Vehicle (FSV) is a program to provide steel solution for the concept design of environmental friendly vehicles in 2020. This program has been conducted by WorldAutoSeel (WAS) which is a consortium of 17 major steel companies all over the world. WAS set the target of FSV for Well to Wheel CO₂ emission less than 100g/km and 35% weight reduction of body in white. Utilizing Advanced High Strength Steel and cutting edge forming technologies the challenging target was achieved.

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Computer aided optimization methods were applied to the major structural design prossess of the FSV (Future Steel Vehicle). Based on the design space with the original styling and powertrain layout for BEV (Battery Electric Vehicle), the topology optimization was carried out to obtain the major load path. The 3G (Geometry, Grade, Gauge) optimization was carried out for body structure design and subsequent major subsystem design. The proposed optimized model showed efficient enegy management performance with significant weight reduction.

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WorldAutoSteel(WAS) launched Future Steel Vehicle (FSV) program in 2008. FSV will address the global environmental and regulatory concerns through the application of multi-grade advanced high-strength all steel bodystructures in vehicle design for Battery Electric Vehicles (BEV). The objective of the FSV program is to meet year 2015-2020 performance criteria while achieving a 35% mass reduction target in addition to a detailed project cost analysis. This paper presents the various advanced high-strength steel materials and their forming methods which applied in FSV program, and their selection criteria for the main structure parts considering the weight and cost reduction potentials.

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WorldAutoSteel(WAS) launched its FutureSteelVehicle (FSV) program with the aim to show auto-OEMs how latest and future steel grades & technologies can provide light body structures for Electrical Vehicles(EV). The objective was to develop detailed design concepts and fully optimize a radically different steel body structure for a compact battery electric vehicle in production in the 2015-2020 time frame. This paper discloses the final outcomes of FSV and its joining and assembly technologies, while meeting 2015-2020 crash performance objectives as well as stiffness, NVH and total life cycle greenhouse gas emissions targets . This is achieved using advanced & ultra high strength steels and engineering design optimization .

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Multidisciplinary Design Optimization (MDO) using Design of Experiments (DoE) and approximation model is a very efficient methodology for reducing weight of car body structure. However, one of the important issues on MDO is reduction of a large number of samples of DoE to generate high accurate approximation model, especially for non-linear phenomena such as crashworthiness. This paper proposes a Sequential DoE to reduce the number of samples. It is an additional sampling method and puts appropriate sample points in discrete design space for multi-approximation model. It can finally reduce the number of sample by half of the conventional method.

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To utilize urethane foam's characteristics well for seat's ride-comfort, we've thought of making a better shape of pad's back face. To verify its effects, in using both of measuring with actual pieces and FEM analysis, we paid special attention to urethane foam's inner stress status. We consider relationship between urethane foam's inner stress and seat's ride-comfort, adding to results of experimenting with test pieces simulating conditions, which generates inner-stress.

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