JPH10138894A - Automatic brake control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly avoid an obstacle by furnishing a steering avoiding capacity computing means to compute steering avoiding capacity to show capacity to avoid the obstacle by steering of a vehicle in accordance with operating quantity of steering and a control means to control forwarding force of the vehicle in accordance with the steering avoiding capacity. SOLUTION: A signal from a steering angle sensor 14 to detect a steering angle by a steering 12, a signal from a radar 16 to detect a distance to an obstacle, signals of a wheel speed sensor 20 of a front wheel 18 and a wheel speed sensor 24 of a rear wheel 22, etc., are input to a control device 10. The control device 10 carries out automatic braking by judging obstacle information in accordance with these input signals and issuing a command to a brake hydraulic actuator 26 as required. Additionally, in the case when obstacle avoiding operation by steering of a driver is detected by the steering angel sensor 14, the control device 10 computes lateral force generated on front and rear wheels 18, 22 from steering quantity and carries out braking control in accordance with it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic braking control device for a vehicle that automatically applies a brake according to a situation at the time of detecting an obstacle ahead of the vehicle.

[0002]

2. Description of the Related Art Conventionally, in order to prevent a collision or a rear-end collision, an obstacle in front of a vehicle is detected, and if the distance between the obstacle and the vehicle is further reduced, it is determined to be dangerous. A technique has been proposed in which a warning is issued to a driver or an automatic braking is performed when approaching beyond a distance (threshold).

For example, in Japanese Patent Application Laid-Open No. Hei 6-298022, a forward object (preceding vehicle) obtained by radar is disclosed.
A device that performs automatic braking based on the distance (inter-vehicle distance) from the vehicle, relative speed, and own vehicle speed is disclosed. More specifically,
This device calculates a first threshold value that can prevent a rear-end collision with a preceding vehicle by braking and a second threshold value that can prevent a rear-end collision with a preceding vehicle based on a self-vehicle speed, an inter-vehicle distance, and a relative speed. I have. Then, even if the detected inter-vehicle distance is smaller than the first threshold, the braking is not performed when the detected distance is larger than the second threshold, and the automatic braking is performed only when the detected distance becomes equal to or less than the first and second thresholds. I'm trying to do it.

[0004]

However, in the conventional automatic braking control device including the device described in the above publication, the driver performs an obstacle avoiding operation before reaching the threshold value for performing the automatic braking. Even if the amount of operation is insufficient, it is necessary to avoid collision by applying automatic braking.

Further, for example, when a driver performs an obstacle avoiding operation by steering, if a braking force is automatically applied without considering the steering avoiding operation, a steering avoidance capability capable of avoiding an obstacle by steering. May not be able to be secured effectively.

That is, when the driver performs an obstacle avoiding operation by steering, it is necessary to perform braking control in consideration of the steering avoiding operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and when a driver is performing an obstacle avoiding operation by steering, it is necessary to ensure that the steering avoiding ability is sufficiently effective and to perform automatic braking. An object of the present invention is to provide an automatic braking control device for a vehicle that can avoid obstacles reliably.

[0008]

SUMMARY OF THE INVENTION As shown in FIG. 1, the present invention provides an automatic braking control device for a vehicle which detects an obstacle in front of the vehicle and performs automatic braking. Steering avoidance operation detecting means for detecting an object avoidance operation, steering avoidance ability calculating means for calculating a steering avoidance ability indicating an ability of the vehicle to avoid an obstacle by steering based on the operation amount of the steering, and steering avoidance operation; This problem has been solved by providing control means for controlling the forward force of the vehicle based on the ability.

According to the present invention, when it is detected that the driver has performed an obstacle avoiding operation by performing steering such as sudden steering, the steering avoiding ability of the vehicle is calculated based on the operation amount, Since the forward force of the vehicle is controlled according to the steering avoidance ability, the steering avoidance ability can be effectively secured. Therefore, the avoidance distance that a collision can be avoided even when approaching so far is reduced, and an obstacle can be reliably avoided.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In a preferred embodiment of the present invention, a lateral force generated by a wheel is employed as an index of the steering avoidance ability, and the control means controls a forward / rearward force generated by the wheel by braking, thereby increasing a forward force of the vehicle. Control (claim 2).

When the driver turns the steering wheel to avoid an obstacle by steering, a lateral force is generated on the wheels. From this lateral force, using a so-called friction circle,
By calculating the maximum braking force that can be generated on the wheels, the longitudinal force of the wheels is controlled by the braking force, and the forward force of the vehicle is controlled to reduce the distance that can avoid a collision. Things.

This will be described below with reference to the drawings.

FIG. 2 shows the relationship between the force acting on the wheel T and the so-called friction circle C. The wheel T forms a steering angle α with the direction F of the vehicle body by the steering of the driver. Therefore, the direction Fw of the wheel on which the longitudinal force such as the driving force and the braking force acts is shifted from the direction F of the vehicle body by the steering angle α. The lateral force Y generated on the wheel T acts in a direction perpendicular to the wheel.

At this time, assuming that the braking force B is applied to the wheel T, the resultant force R of the lateral force Y and the braking force B = √ (Y ²
+ B ² ) is the vehicle weight W and the road surface friction coefficient μ
Cannot be exceeded. That is, the following inequality (1) holds.

√ (Y ² + B ² ) ≦ μW (1)

Therefore, the resultant force of all the forces acting in the horizontal plane between the wheel T and the ground (in this case, the resultant force of the lateral force Y and the braking force B) remains within a circle having a radius μW shown in the figure. In this sense, μW is called a maximum frictional force, and the circle C is called a friction circle.

If the lateral force Y is constant with the magnitude shown in the figure, Bmax in the figure is the maximum braking force that can be generated at the wheel T at this time. This maximum braking force Bmax can be calculated by the following equation (2).

Bmax = {(μW) ² −Y ² } (2)

Therefore, when the lateral force Y is generated on the wheel T by the steering of the driver, the avoidance distance can be reduced most effectively by braking the wheel T with the braking force of the maximum braking force Bmax. Can be.

If the vehicle weight W is a determined value and the road friction coefficient μ and the lateral force Y can be detected, the maximum braking force Bmax can be calculated by the above equation (2).

For example, in the case of a two-wheel drive vehicle, the road surface friction coefficient μ can be determined by comparing the wheel speeds of the drive wheel and the driven wheel.

It is also known that when the front wheels are turned at the steering angle α, the lateral forces Yf and Yr generated on the front wheels and the rear wheels are theoretically obtained by the following equations (3) and (4). ing.

Yf = {(2mKfKr) / Δ｝ [(IV / 2Kr) S ² + ｛(Lr ² + (I / m)｝ S + VLr] α (3) Yr = ｛(2mKfKr) / Δ｝ [｛ LfLr− (I / m)｝ S + VLf] α (4) where Δ = mIVS ² + ｛2 m (Lf ² Kf + Lr ² Kr) + 2I (Kf + Kr)｝ S + [｛4KfKr (Lf + Lr) ² / V- ² mV (LfKf-LrKr)] (5) where m: inertial mass of the vehicle I: yaw inertia moment of the vehicle V: vehicle speed Kf: cornering power of the front wheel tires (for two right and left wheels) Kr: cornering power of the rear wheel tires ( Lf: distance between the center of gravity of the vehicle and the front axle Lr: distance between the center of gravity of the vehicle and the rear axle S: Laplace operator

Further, as shown in FIG. 3, when the lateral force is only Y, the braking force that can be generated is Bmax, but as shown by Bo in FIG. When braking is applied, the resultant force R of the lateral force Y and the braking force Bo protrudes from the friction circle C, the lateral force Y is ignored, and steering cannot be performed.

On the other hand, as shown in FIG. 4, when the braking force B having the maximum frictional force μW is applied first, even if the driver attempts to generate the lateral force Y by steering, the lateral force Y is also controlled. Since the resultant force R with the power B exceeds the friction circle C, the lateral force Y cannot be generated accordingly. That is, also in this case, the wheels are locked and the vehicle does not turn.

According to the present invention, by utilizing a friction circle,
The automatic braking control is performed by obtaining an appropriate braking force according to the lateral force Y generated by the driver's steering, thereby effectively using the lateral force Y as the steering avoidance ability to reduce the avoidance distance. is there.

Next, a more specific embodiment of the present invention will be described with reference to FIGS. In this embodiment, when the driver performs an obstacle avoidance operation by steering, the lateral force is estimated and calculated based on the steering amount, and the braking force that can be generated by the front and rear wheels is calculated based on the lateral force. It controls braking.

FIG. 5 is a schematic configuration diagram of an automatic braking control device to which the present invention is applied.

In FIG. 5, a control unit (ECU) 10 includes a signal from a steering angle sensor 14 for detecting a steering angle α by the steering 12 and a signal from a radar 16 for detecting a distance to an obstacle. , Signals from the wheel speed sensor 20 of the front wheel 18 and the wheel speed sensor 24 of the rear wheel 22 are input.

The control device 10 determines obstacle information based on these input signals, and issues a command to the brake hydraulic actuator 26 to perform automatic braking as necessary.

When the steering angle sensor (steering avoidance operation detecting means) 14 detects an obstacle avoidance operation by the driver's steering, the control device 10 determines the front and rear wheels 1 from the steering amount.
The lateral force generated in steps 8 and 22 is calculated, and the braking control is performed based on the calculated lateral force. That is, the control device 10 plays a role of a steering avoidance ability calculation unit and a control unit.

The operation of the present embodiment will be described below with reference to the flowcharts of FIGS.

First, at step 100, the vehicle speed is calculated based on the signals from the wheel speed sensors 20 and 24, and the steering angle sensor 14 is used to calculate the driver's steering speed.
The steering angle α by two operations is input.

In the next step 102, the road surface friction coefficient μ is calculated based on the input front and rear wheel speeds.

In the next step 104, the lateral forces Yf and Yr generated at the front and rear wheels 18 and 22 are calculated by the equations (3) to (5).

In the next step 106, the front and rear wheels 18, 18 are calculated by the equation (2) using the lateral forces Yf and Yr just calculated.
The braking forces Bf and Br that can be generated at 22 are calculated.

In the next step 108, it is determined whether or not the driver is avoiding steering of an obstacle by sudden steering or the like. This is determined based on whether the steering angle α and the steering angular velocity dα calculated from the steering angle α are smaller than the steering angle threshold c and the steering angular velocity threshold k1, which are threshold values, respectively. As a result, when the steering angle α and the steering angular velocity dα are both lower than the respective thresholds c and k1, it is determined that the steering is not avoided, and when one of them is equal to or larger than the threshold, the steering is avoided. Is determined. If it is determined that steering avoidance has not been performed, the steering avoidance flag F is turned off in the next step 110.

When it is determined that the steering avoidance is being performed, it is determined in the next step 112 whether or not the steering avoidance flag F is on. If the steering avoidance flag F is not turned on, the routine proceeds to step 114, where the steering angular velocity dα is compared with the steering angular velocity threshold k2 which is larger than the steering angular velocity threshold k1 in the determination of step 108, and the driver really does not steer. Check again to see if you have If the steering angular velocity dα does not exceed the steering angular velocity threshold k2, it is determined that steering avoidance has not been performed, and a signal for releasing automatic braking is output in the next step 116.

On the other hand, if the steering angular velocity dα exceeds the steering angular velocity threshold k2, it is determined that the driver is performing steering avoidance, and the steering avoidance flag F is turned on in the next step 118. Then, in step 120, the braking oil pressure is controlled through the actuator 26 so that the braking force of the front and rear wheels 18, 22 becomes the desired value calculated in step 106. As a result, the longitudinal force of the wheels is controlled, the forward force of the vehicle is controlled, and the obstacle avoiding operation is effectively performed.

Thereafter, the automatic braking control is continued, but the avoidance operation of the driver is completed, and the steering angle α or the steering angular velocity dα is settled. In step 108, the respective steering angle thresholds c and k1 are set. When it becomes smaller, the steering avoidance flag F is turned off in step 110, and the process proceeds to step 116 via steps 112 and 114 to cancel the automatic braking control.

As described above, according to the present embodiment, when the driver tries to steer sharply to avoid an obstacle, it is possible to apply the maximum braking force that can be generated to the wheels within a range that does not reduce the steering avoidance ability. It is possible to reduce the avoidance distance by effectively using the steering avoidance ability by controlling the forward force of the vehicle.

[0043]

As described above, according to the present invention, when the driver is performing the steering avoidance operation, the steering avoidance ability is calculated based on the steering amount, and the braking force is calculated based on the steering avoidance ability. To control the forward force of the vehicle, it is possible to achieve both steering avoidance and braking avoidance, perform optimal avoidance control, and reduce the avoidance distance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a force acting on a wheel and a friction circle.

FIG. 3 is an explanatory diagram showing a braking force that can be generated when a lateral force is first generated in a friction circle;

FIG. 4 is an explanatory diagram showing a lateral force that can be generated when a braking force is first generated in a friction circle.

FIG. 5 is a schematic configuration diagram of an automatic braking control device according to an embodiment of the present invention.

FIG. 6 is a flowchart illustrating control according to the embodiment of the present invention.

FIG. 7 is a flowchart showing control according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Control device (ECU) 12 ... Steering 14 ... Steering angle sensor 16 ... Radar 18 ... Front wheel 20 ... Wheel speed sensor 22 ... Rear wheel 24 ... Wheel speed sensor 26 ... Brake hydraulic actuator

Claims (2)

[Claims] 1. An automatic braking control device for a vehicle that detects an obstacle in front of the vehicle and performs automatic braking, comprising: a steering avoidance operation detecting means for detecting an obstacle avoidance operation by a driver's steering; , A steering avoidance ability calculating means for calculating a steering avoidance ability indicating an ability of the vehicle to avoid an obstacle by steering, and a control means for controlling a forward force of the vehicle based on the steering avoidance ability. An automatic braking control device for a vehicle. 2. The vehicle according to claim 1, wherein a lateral force generated by a wheel is adopted as an index of the steering avoidance ability, and the control means controls a forward force of the vehicle by controlling a longitudinal force generated by the wheel by braking. Automatic braking control device for a vehicle.