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Deceleration patterns of an expert driver will be formulated using the perceptual risk index for approach and proximity of a preceding vehicle as an example of comfortable braking pattern. It will be shown that the formulated braking pattern can generate smooth deceleration profile uniformly for many conditions of approaching conditions. In addition, brake initiation timing of expert driver will be successfully formulated using the alternative index. Finally, an automatic braking system will be proposed based on the formulated brake initiation model and the velocity profile. Twenty five expert drivers experienced the automatic braking installed in an experimental car. It will be shown that the proposed system can generate smooth profile and realize secure brake patterns based on subjective evaluation.

A performance index for approach and alienation that estimates driver's status such as inattentive operation from the vehicles behavior as a result of the driver's visual cognition, judgment, and operation is proposed to prevent rear-end crashes. The index is based on the hypothesis that drivers are performing approach detection with change of area of a preceding car on the retina. First, it is shown that safe driving behaviors of experimental results and micro data of traffic accidents with a rear-end collision as danger status can be distinguished using the proposed index. Then, results of basic laboratory experiments with a joystick and a LCD system show that the index reflects changes of the danger level, visual capability, and awareness of the drivers. In addition, a driver model of the deceleration behaviors in preceding-car-following situation is developed by hypothesizing that drivers determine the acceleration and deceleration behavior by the function of the proposed index.

The adaptation of an active control suspension has remarkably improved the vehicle attitude and ride comfort characteristics. Such an active controlled suspension is controlled by actuators and hydro-dynamic equipments like servo valves. The control strategies are composed of feedback control with each cylinder oil pressure, suspension stroke and velocity. In the practical application of these systems, it must be taken into account that the effect of control is much dependent on the time delay of a controller as well as control elements. The object of this study is to confirm preview effects on the response of the system. The aim of preview feedforward control is to compensate the system delay of active control suspension. The control system is constructed of an ordinary feedback loop and a feedforward loop based on a road preview signal.

The object of this study is to investigate the possibility of improving ride comfort, and develop a new damping control system. We supposed and analyzed the ideal damping control for vehicle suspension system using optimal control strategy. The parameter study shows the effect of reducing vehicle acceleration from road excitation. To achieve the same performance with a more simple and lower cost control strategy, we introduce another control strategy called ‘Skyhook model’ proposed by D.Karnopp. Continuously damping control system is developed based on this to avoid some problems that might be caused in the case of a two-stage switching system. Further more, variable control gain depends on vehicle vibration circumstances introduced to realize the adaptation of various road conditions. Using computer simulation and testing the experimental vehicle, effectiveness of this system is evident and the possibility of ride comfort improvement is verified by using this control.

The simplified two-axle tire uniformity tester (abbreviated to “developed tester”, hereunder) has been developed as a compact, light-weight and low-cost tester which enables measurement of uniformity of passenger car tire assemblies. In the developed tester, a radial force and a lateral force of the rolling tire under setting load can be detected continuously and in addition, with high precision. Furthermore, variations of these forces have close relation with the riding comfort and stability and controllability. Therefore, the developed tester can be used as a tool for judging whether or not problems relating to vehicle noise and vibration are attributable to the problem caused by tires.