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Previous studies and recent practical aerodynamic evaluations have shown that aerodynamic drag of passenger vehicles with “ground simulation” with moving ground and rotating wheels may increase in some cases and decrease in other cases relative to the fixed ground and stationary wheel conditions. Accordingly, the effects of the ground simulation on the aerodynamic drag should be deeply understood for further drag reduction. Although the previous studies demonstrated what is changed by the ground simulation, the reason for the change has not been fully understood. In this article, the effects of wheels and wheel houses attachment and those by the ground simulation with ground movement and wheel rotation on the aerodynamic drag were investigated by quantification of the underfloor flow that plays a crucially important role on the formation of vortical structure around vehicles.

Our study unveils what smart cars are needed to minimize congestion by traffic stability. We have previously considered pacer cars with single lane road networks based on a car following model, e.g. adaptive cruise control (ACC). However, pacer cars may have a limitation with multi-lane roadways in terms of lane distribution of traffic and shockwave suppression. Therefore, we motivate building a new smart car which extends the capability of pacer cars allowing lane changing at the timing of congestion detection. In essence, the congestion detection plays a role of adjusting the (time) headway of smart cars to determine whether lane changes should be undertaken. Lane changes can be used to uniformize (or equalize) lane distribution for traffic (flow) stability. Our simulation study has suggested that the proposed smart cars enforce the capability of traffic stability more than manual and pacer cars.

This paper presents new technique to estimate the projected operational forces, which is the operational forces with respect to the evaluation location, at the connections of the separated passive substructures with reciprocity. Since the transfer path analysis (TPA) is conducted with respect to the evaluation location, the forces for the substructures are, therefore, also required only to estimate the projected operational forces. In order to estimate the forces, the projected inertance matrix, which is the projection of the inertance matrix onto the subspace with respect to the evaluation location, is estimated without measuring it directly. The acceleration responses at the connections of the passive substructure are measured by the excitation at the evaluation location with the reciprocity. The technique decomposes the acceleration responses into the output and input element vectors on the subspace. With those vectors, the projected inertance matrix is constructed.

Electric vehicles (EVs) have attractive potential not only for energy and environmental performance but also for vehicle motion control because electric motors have quick and measurable torque response. Recently, the authors' laboratory has developed a completely original EV which has active front and rear steering systems and high-torque direct- drive in-wheel motors in the all wheels. In this paper, the main features of this vehicle are briefly introduced and our recent studies on pitching control, slip-ratio control, and yaw-rate and slip-angle control with lateral force sensors are explained with experimental results.

An experimental technique is developed for a vehicle moving steadily in the vicinity of the ground. A towing tank with a steadily advancing carriage is used and the unfavorable effects of the boundary layer on the ground which is inevitable in the case of a wind tunnel are fully removed. Experiments with a box-shaped model and a car model revealed some interesting features of lift, drag and side force at various clearances from the ground. Lift force is the most sensitive to the boundary layer and the lift measured in a wind tunnel may not completely represent lift on the road. The flow with vortices near the bottom surface of the body has one of the most important effects on the forces.

An inexpensive driving simulation system with sufficient fidelity has been developed. The system produces motion cues of four degrees of freedom, visual and auditory cues, and control feel on the steering wheel. This paper describes the features of this newly developed system and gives examples that demonstrate its effectiveness. The motion cues provided in this system are yaw, heave, and lateral and fore/aft accelerations. The lateral and fore/aft accelerations are simulated by tilting the simulator compartment. A computer-processed road image is given through a CRT monitor. The restoring torque of the steering wheel is produced by an electrical servosystem via a coil spring. Cruising sound is given in order to improve speed perception. Since the system uses digital computers, the vehicle characteristics are altered easily by merely rewriting the software. This enables us to simulate special vehicle dynamics such as front & rear wheel steering.