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I studied the driver steer characteristics in the severe lane change with a drift. And, I studied the technique by which the performance of running in the vehicle at the severe lane change with a drift was improved. It has been understood that the severe lane change with a drift is a steer proportional to the body slip angle unlike the grip running. Moreover, I have understood importance in the vehicle movement performance improvement the cornering force characteristic where the maximum cornering force of the tire was exceeded. Next, I have understood the differentiation steer assistance is more effective.

In general, the longitudinal position of the center of gravity of a vehicle has a great influence on lateral acceleration in critical cornering. Most rear-wheel-drive vehicles (front engine, rear-wheel drive) have a tendency to be over-steered because the driving power acts on the rear wheels, and so the forward weight distribution is large. As such, the vehicle has an under-steer tendency in this respect and an overall balance is achieved. On the other hand, because formula cars are very light compared to general vehicles, the used area of the vertical wheel load-maximum cornering force characteristic, differs greatly from general vehicles. That is, although general vehicles use a nonlinear area for the vertical wheel load-maximum cornering force characteristic of the tire, a comparatively light formula car uses an almost linear area in the vertical wheel load-maximum cornering force characteristic of the tire.

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.

In this research, we examine the three controls inside-outside wheel braking force and driving force, camber angle, and the derivative steering assistance to determine how angle differences affect cornering performance and controllability. This is accomplished by comparing body slip angle area differences in a closed loop examination of the grip to drift area using a driving simulator. The results show that inside-outside wheel braking force and driving force control in the area just before critical cornering occurs has a significant effect on vehicle stability. We also clarified that controlling the camber angle enhances grip-cornering force, and confirmed that the sideslip limit could be improved in the vicinity of the critical cornering area. Additionally, when the counter steer response was improved by the use of derivative steering assistance control in the drift area exceeding the critical cornering limit, corrective steering became easier.

In a new technology called “in wheel motor,” in which the motor is installed in the wheel, the electric vehicle can become more compact, which leads to a new type of mobility. Moreover, the front wheel steering is controlled by an electrical unit instead of the traditional mechanical unit of a steering wheel inside the car. In such a “steer-by-wire” method, the motor uses an electric signal. Because the degrees-of-freedom of this steer control are increased and a variety of steer controls based on the electric signal are possible, further improvement of the control stability is needed. In other words, the steer control technique can pose a problem for drivers, and so further research in this area is needed. That is, proportional derivative steering assistance can improve emergency evasion performance and the steering delay upon counter steering. Moreover, rear-wheel active steering can improve vehicle response during emergency evasion maneuvers.

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 this study, an effective technique for improving drift running performance was examined. Basically, a driver model with counter steering was examined with the assumption that the body slip angle, along with the body slip angle velocity, served as feedback. Next, the effectiveness of adding front wheel steer angle velocity feedback to steering angle compensation as a drift running performance improvement technique of a vehicle was analyzed.

To improve both the sensing of grip critical cornering and drift control, it is desirable to increase the body slip angle at critical cornering. To discover why this facilitates driver control, the gaze of the driver was monitored, and the relationship between the gaze movement of the driver and the vehicle behavior was investigated. It was found that the driver steered by gazing at the target course in the direction of the inside forward of the vehicle in the grip driving area. On the other hand, the gaze movement of the driver corresponded to the change in the body slip angle in the grip critical cornering area-drift cornering area. That is, in the drift driving area, it was found that the drift was controlled by gazing at the direction of the drift angle of the outside forward of the vehicle, feeding back the body slip angle, and sensing the change from the grip critical cornering to the drift area.

In this study, a steering model and vehicle velocity control model were applied for a driver in drift cornering in order to maintain an intentional drift angle at the time of cornering. The driver was assumed to steer based on feedback from the body slip angle and the body slip velocity during drift cornering. It is found that the driver not only controls the drift angle at the time of the drift cornering but also controls the turn radius by changing vehicle velocity. Moreover, at the return from drift cornering to the straightaway, feedback is based on not only the body slip angle but also the body slip angle velocity, which is differentiated steer based on the phase is advanced.

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.

The relation of the front wheel steering angle to the steering wheel angle in electric vehicles is changing due to the “steer-by-wire” method, which is based on an electric signal. With this method, excellent maneuverability is possible in various driving situations. Therefore, this steer control method technique is considered in this study. It was clarified that steer-bywire requires an improvement in the control stability in emergency maneuvers and the delay of counter steering in drift cornering without causing a sense of driver incompatibility. (Here, the sense of incompatibility was defined as feeling by which the harmony between the steer intention of the driver and the vehicle movement was lost.) (Here, the drift cornering shows cornering done in the area with counter steering where the rear wheel exceeded the maximum cornering force.) One control stability method is Proportional Derivative (PD) steering assistance, which is dependent on the anticipated driving situations.

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.

A driving simulator capable of duplicating the critical sensations incurred during a spin, or when a driver is engaged in drift cornering, was constructed by Mitsubishi Heavy Industries, Ltd., and Hiromichi Nozaki of Kogakuin University. Specifically, the simulator allows independent movement along three degrees of freedom and is capable of exhibiting extreme yaw and lateral acceleration behaviors. Utilizing this simulator, the control characteristics of drift cornering have become better understood. For example, after a J-turn behavior experiment involving yaw angle velocity at the moment when the drivers attention transitions to resuming straight ahead driving, it is now understood that there are major changes in driver behavior in circumstances when simulator motions are turned off, when only lateral acceleration motion is applied, when only yaw motion is applied, and when combined motions (yaw + lateral acceleration) are applied.

Various studies have been done into the steering models that describe how the driver steers the vehicle. However, no steering models for critical cornering have been developed. In this paper, the steering characteristic was investigated by monitoring the gaze of the driver during critical cornering. The direction of the steering model during critical cornering was considered. Since the driver can readily perceive the vehicle body slip angle if body sensory information is combined with visual information, it is important for the driver to be able to look at the target course easily and to control the drift well. Drivers exhibit the tendency to position their gaze point on a difficult corner exit to drive when body sensory information is combined with visual information. Thus, it was found that the driver can perceive the roll motion and visual feedback the body slip angle, and drive while stabilizing the vehicle from the corner exit to back straight.

In recent years, the conversion of vehicles to electric power has been accelerating, and if a full conversion to electric power is achieved, further advancements in vehicle kinematic control technology are expected. Therefore, it is thought that kinematic performance in the critical cornering range could be further improved by significantly controlling not only the steering angle but also the camber angle of the tires through the use of electromagnetic actuators. This research focused on a method of ground negative camber angle control that is proportional to the steering angle as a technique to improve maneuverability and stability to support the new era of electric vehicles, and the effectiveness thereof was clarified. As a result, it was found that in the critical cornering range as well, camber angle control can control both the yaw moment and lateral acceleration at the turning limit.

The following has been understood for the change in the steer characteristic and the amount of perspiration in the drift cornering when not only visual information but also body sensory information is added. When body sensory information joins visual information as for the driver, it has been understood that the amount of perspiration increases overall and can do the drift control continuing with a moderate tension. In the drive only of visual information, the driver comes to arrive easily at spin because the drift control is difficult. And, it has been understood that the amount of perspiration increases greatly compared with the case to give body sensory information, and becomes the one with a very high risk. Moreover, the driver can control an adequate drift compared with driving only visual information in feed back body sensory information on the roll angle to the steer.