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A drift-turn experiment to assess the influence of differences in steering wheel gear ratios was undertaken using a driving simulator. It is relatively easy to maintain control of a commercial vehicle if the tire is in contact with the road surface and the steering wheel gear ratio is 15.0:1 to 18.0:1. Conversely, in the event of a change in traction such as the rear wheel meeting a drift area, a steering wheel gear ratio of 7.5:1 to 9.0:1 is required to maintain control of the vehicle, even when the vehicle became unstable. Moreover, the stability of the vehicle deteriorates in drift running if the steering gear ratio is reduced too much. That is, the steering gear ratio in which the drift angle is maintained most easily is in the range 7.5∼9.0. And, a drift performance evaluation index D n=x was determined and was found to agree with the subjective ratings. Thus, evaluating drift control for drift cornering using the drift performance evaluation index was assumed to be effective.

It has been reported that steering systems with derivative terms have a heightened lateral acceleration and yaw rate response in the normal driving range. However, in ranges where the lateral acceleration is high, the cornering force of the front wheels decreases and hence becomes less effective. Therefore, we applied traction control for the inner and outer wheels based on the steering angle velocity to improve the steering effectiveness at high lateral accelerations. An experiment using a driving simulator showed that the vehicle's yaw rate response improved for a double lane change to avoid a hazard; this improves hazard avoidance performance. Regarding improved vehicle control in the cornering margins, traction control for the inner and outer wheels is being developed further, and much research and development has been reported. However, in the total skid margin, where few margin remains in the forward and reverse drive forces on the tires, spinout is unavoidable.

In the cornering performance of a formula car, turning is performed at a considerably high level. However, few studies have investigated the control of the camber angle. Therefore, a mechanism that swings to the negative camber side of the suspension in cornering was examined in the present study. A swinging suspension member structure was assumed when a lateral force acted on the tires, and the momentary rotation center of the swing suspension member was controlled so that the direction of the swing would be to the negative camber side. As a result, compliance of the negative camber was achieved. The layout of a preferable mechanism was first determined by geometrical analysis. The negative camber angle obtained with this mechanism changes according to the length of the link for the fixation of the swing suspension member, the installation position, and the angle. The specifications for achieving a proper compliance negative camber were then clarified.

Proportional Derivative (PD) steering assistance offers potential measures by which the control stability of a vehicle can be rapidly improved. However, for all Proportional Derivative (PD) steering methods, the inconvenience caused by the need to keep turning the steering wheel during cornering is significant. Because the steering return phenomenon of the steering wheel stop like this is not so preferable, it is preferable that the Proportional Derivative (PD) steering assistance is extremely weak (almost 0) in such a usual grip cornering driving. Alternatively, in the drift area of cornering where the grip area of the tires has been exceeded, Proportional Derivative (PD) steering assistance is helpful because the driver can control his counter steering extremely well. Furthermore, only a small amount of Proportional Derivative (PD) steering assistance is required in the drift area.

In this study, we focus on “camber angle control” and “derivative steering assistance” using “steer-by-wire” as maneuverability and stability improvement techniques that are appropriate for the electric vehicle (EV) era. Movements that produce a negative camber angle generate camber thrust, and vehicle motion performance improvements extend from the fact that the tire side force is increased by the camber thrust effect. In our experimental vehicle, a proportional steering angle system was used to create negative camber angle control via an electromagnetic actuator that allowed us to confirm improvements to both the effectiveness and stability of steering control in restricted cornering areas. More specifically, we determined that it is possible to improve critical cornering performance by executing ground negative camber angle control in proportion to the steering angle.