JP3320768B2 - Automatic vehicle braking system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic braking system for a vehicle which automatically brakes each wheel when avoiding contact with an obstacle in front of the vehicle. The present invention relates to an improvement of feedback control of brake pressure so that deceleration becomes a target deceleration.

[0002]

2. Description of the Related Art Conventionally, as an automatic braking device for a vehicle of this type, for example, as disclosed in Japanese Patent Publication No. 39-2565 and Japanese Patent Publication No. 39-5668, an optical method or an ultrasonic And continuously detect the distance and relative speed between the host vehicle and the obstacle ahead of the vehicle, judge the possibility of contact from the detection result, and activate the actuator when there is a possibility of contact It is known to automatically apply a brake to each wheel to avoid contact with a forward obstacle.

[0003] In such an automatic braking device, feedback control is incorporated so that the actual deceleration of the host vehicle becomes a target deceleration set in order to avoid contact. For example, Japanese Patent Laid-Open Publication No. 52-112238 discloses a deceleration detecting means for detecting the actual deceleration of the own vehicle, and comparing the actual deceleration of the own vehicle detected by the detecting means with the target deceleration. A correction circuit that corrects a control signal for the actuator according to the comparison value is provided, and the operation of the actuator is feedback-controlled by the corrected control signal. This feedback control does not necessarily control the actual deceleration of the own vehicle and the target deceleration completely to coincide with each other. When the difference becomes within a predetermined value, the brake pressure due to the operation of the actuator is reduced. A dead zone region for regulating the increase / decrease pressure regulation is provided.

[0004]

However, the actual rate of increase in deceleration generated during automatic braking is not constant, and varies greatly depending on factors such as the number of occupants of the vehicle and the state of the running road surface. For this reason, when the width of the dead zone is set to be narrow, even when the actual deceleration of the own vehicle enters the dead zone, it is likely to be changed beyond the dead zone. The overshoot of the deceleration is accompanied by a delay in the behavior of the vehicle from the time when the actuator is activated to the time when the vehicle actually appears as a deceleration. On the other hand, if the width of the dead zone is set wide, there is a problem that the accuracy of the feedback control is deteriorated.

The present invention has been made in view of the foregoing, and an object of the present invention is to change the width of the dead zone in accordance with the actual rate of increase in deceleration occurring during automatic braking, thereby providing feedback control. While increasing the accuracy of
It is an object of the present invention to provide an automatic braking device for a vehicle that can prevent an actual deceleration from becoming vibrating near a target deceleration due to the number of occupants, road surface conditions, and the like.

[0006]

In order to achieve the above object, a solution of the present invention is to automatically increase the brake pressure of each wheel under predetermined conditions, and to set the actual deceleration of the vehicle to a target value. In the automatic braking device for a vehicle configured to feedback-control the brake pressure so as to achieve deceleration, the difference between the actual deceleration of the own vehicle and the target deceleration during the feedback control is within a dead band region having a predetermined width. A dead zone region setting means for regulating the increase / decrease of the brake pressure; a deceleration increase rate detecting means for detecting an increase rate of the actual deceleration of the own vehicle during the automatic braking control ; and the actual deceleration. When the increase ratio of the dead zone is larger than a predetermined value, the dead zone region width changing means for changing the width of the dead zone so that the width of the dead zone becomes larger than when the increase ratio is smaller than the predetermined value. And obtain configuration.

[0007]

[Action] By the above configuration, in the present invention, during automatic braking, the rate of increase deceleration actual is detected by the detecting means, the width of the dead zone is changed by changing means based on the detection result. That is, when the rate of increase in the actual deceleration is large, the width of the dead zone is widened, thereby preventing an overshoot in which the deceleration increases beyond the dead zone. Also, when the rate of increase of the actual deceleration is small, the width of the dead zone becomes narrower,
The accuracy of the feedback control increases. That is, sometimes
The width of the dead zone changes according to the constantly changing road conditions
Brake control prevents vibration control
Is done.

[0008]

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

1 and 2 show an automatic braking device for a vehicle according to an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram of the automatic braking device, and FIG. 2 is a block diagram of the automatic braking device. It is.

In FIG. 1, reference numeral 1 denotes a master back which increases the stepping force of a brake pedal 2 by a driver, and 3 denotes a master cylinder which generates a brake pressure according to the stepping force increased by the master back 1. The brake pressure generated in the master cylinder 3 is first sent to a hydraulic actuator unit 4 of an automatic braking device, and then is passed through a hydraulic actuator unit 5 of an anti-skid brake device (ABS) to four wheels (only one wheel is shown in the figure). Each brake device 6
It is supplied to.

The hydraulic actuator section 4 of the automatic braking device has a shutter valve 11, a pressure increasing valve 12, and a pressure reducing valve 13 for cutting off the communication between the master cylinder 3 and the brake device 6 side. One valve 1
Each of 1 to 13 is composed of an electromagnetic two-port two-position switching valve. A motor-driven oil pump 14 is provided between the pressure increasing valve 12 and the master cylinder 3.
An accumulator 15 for storing the pressurized oil discharged from the compressor 4 and maintaining the same at a constant pressure is provided. When the shutter valve 11 is in the open position, the brake device 6 of each wheel is operated according to the depression force of the brake pedal 2.
Brake is applied. On the other hand, when the shutter valve 11 is in the closed position, the pressure increasing valve 12 is in the open position, and the pressure reducing valve 1 is in the open position.
3 is switched to the closed position, the pressure oil from the accumulator 15 is supplied to the brake device 6 of each wheel to increase the brake pressure, and the pressure increasing valve 12 is closed and the pressure reducing valve 13 is opened. When each is switched, the pressure oil is returned from the brake device 6 and the brake pressure is reduced.

The hydraulic actuator unit 5 of the ABS has a three-port two-position switching valve 21 provided for each wheel, and is applied to each brake device 6 by switching the valve 21 when the ABS is activated. The brake pressure is controlled so that each wheel does not lock. Although the configuration of the hydraulic actuator unit 5 is not described in detail, the hydraulic actuator unit 5 includes a motor-driven oil pump 22 and accumulators 23 and 24 in addition to the switching valve 21. The brake device 6 for each wheel includes a disk 26 that rotates integrally with the wheel, and a caliper 27 that receives the brake pressure from the master cylinder 3 and clamps the disk 26.

On the other hand, in FIG. 2, reference numeral 31 denotes an ultrasonic radar unit provided at a front portion of the vehicle body. The ultrasonic radar unit 31, which is not shown in detail in the drawing, transmits an ultrasonic wave from a transmitting unit as is well known. While transmitting toward an obstacle such as a vehicle in front of the own vehicle, the receiving unit receives a reflected wave that is reflected by hitting the front obstacle,
An operation unit 32 that receives a signal from the radar unit 31
Calculates the distance and the relative speed between the host vehicle and the obstacle ahead of the vehicle based on the delay time from the transmission time of the radar reception wave. Reference numerals 33 and 34 denote a pair of radar head units provided on the left and right sides of the front part of the vehicle, respectively. The respective radar head units 33 and 34 transmit pulsed laser light from a transmitting unit toward an obstacle in front of the vehicle. In addition, the receiving unit receives the reflected light that is reflected upon hitting the obstacle in front of the vehicle.
Receives signals from the radar head units 33 and 34 through the signal processing unit 35, and calculates the distance and the relative speed between the host vehicle and the obstacle ahead of the vehicle based on the delay time from the point of emission of the laser reception light. It has become. Then, the arithmetic unit 32 calculates the radar head units 33, 3
Priority is given to the calculation results of distance and relative speed by the system of 4,
The calculation results of the distance and the relative speed by the system of the ultrasonic radar unit 31 are used in an auxiliary manner. The relative speed detecting means 36 is constituted.

The transmitting and receiving directions of the pulse laser light by the two radar head units 33 and 34 are provided so as to be changeable in the horizontal direction by a motor 37.
The operation of is controlled by the calculation unit 32. Numeral 38 denotes an angle sensor for detecting the transmission / reception direction of the pulse laser beam from the rotation angle of the motor 37. The detection signal of the angle sensor 38 is input to the arithmetic unit 32, and the radar head unit 33, The transmission and reception directions of the pulsed laser light are added to the calculation of the distance and the relative speed by the 34 systems.

A steering angle sensor 41 detects a steering angle.
42 is a vehicle speed sensor for detecting the vehicle speed, 43 is a front and rear G sensor for detecting the front and rear acceleration (front and back G) of the vehicle, 44 is a road surface μ sensor for detecting the road surface friction coefficient (μ). 44 and the arithmetic unit 3
The signals of the distance and the relative speed between the host vehicle and the front obstacle obtained in 2 are input to the contact possibility determination unit 45. The contact possibility determining unit 45 determines the possibility of contact between the own vehicle and the preceding obstacle based on the distance and the relative speed between the own vehicle and the preceding obstacle. When it is determined that there is a possibility of contact by the unit 45, a signal is output from the determination unit 45 to the control unit 50 that controls the operation of the hydraulic actuator unit 4 of the automatic braking device so that the contact is avoided. The brakes are automatically applied to each wheel. Reference numeral 46 denotes an alarm display unit provided on an instrument panel in the vehicle compartment. The alarm display unit 46 is provided with an alarm buzzer 47 and a distance display unit 48 that receive signals from the contact possibility determination unit 45, respectively. I have.

The contact possibility judging section 45 first uses a threshold map as shown in FIG. 3 which is stored in advance to perform sudden braking (both with full braking) in order to avoid contact with an obstacle ahead. ) Is calculated. Next, a predetermined distance is added to each of the threshold values L0 to calculate a distance at which gentle braking is performed before sudden braking and a distance at which an alarm is issued by the alarm buzzer 47.
Here, rapid braking or full braking refers to applying a brake at the maximum deceleration (about 0.8 G), and gentle braking refers to deceleration lower than the maximum deceleration (about 0.3 to 0.4 G).
G) means to apply a constant brake. Further, the distance to apply gentle braking is set to be several times longer than the distance to apply sudden braking, and the distance to issue an alarm is set to be longer than the distance to apply gentle braking.

In the threshold map shown in FIG. 3, a threshold line A indicates that a vehicle in front as an obstacle in front of the vehicle stops when it comes into contact with an obstacle ahead of the vehicle and stops. This is the same as when the preceding obstacle is a stationary object (that is, when the relative speed V1 is the same as the own vehicle speed v0) regardless of the relative speed V1. It takes a value (numeric expression v0 ² / 2μg). The threshold line B represents the following distance (numeric expression V1) required to avoid contact with the preceding vehicle when the vehicle is fully braked.
(2v0−V1) / 2 μg), and the threshold line C indicates the inter-vehicle distance required to avoid contact with the preceding vehicle when the preceding vehicle applies gentle braking with a deceleration μ / 2g, vehicle distance required for the threshold line D to avoid contact between the vehicle when the preceding vehicle is kept constant speed (numeric expression V1 ² /
2 μg). Furthermore, although the threshold line E cannot avoid contact with the preceding vehicle even when the own vehicle applies automatic braking,
Indicates the distance between vehicles that can reduce the impact force at the time of contact. When the threshold line is set on the horizontal axis (that is, when the threshold value L0 is always set to zero), automatic braking is not applied and this is canceled.

The contact possibility judging section 45 selects one threshold line from the five types of threshold lines A to E according to the driving state of the vehicle, and selects this threshold line. In the line, a threshold value L0 corresponding to the relative speed V1 between the host vehicle and the preceding obstacle (preceding vehicle) is calculated. For example, by selecting a threshold line B when the own vehicle speed v0 is a high vehicle speed, a threshold line D when the own vehicle speed v0 is a middle vehicle speed, and a threshold line E when the own vehicle speed v0 is a low vehicle speed. The threshold value L0 of the possibility of contact is changed to a larger value as the vehicle speed becomes higher.

When the distance between the host vehicle and the obstacle ahead of the host vehicle is equal to the distance at which a warning is issued, the contact possibility determination unit 4
An operation command signal is output from 5 to the alarm buzzer 47, and an alarm sounds. Further, when the distance between the host vehicle and the obstacle in front is further reduced and becomes a distance at which gentle braking or rapid braking is performed, a deceleration command signal is output from the contact possibility determination unit 45 to the control unit 50, and the control Under the control of the section 50, the hydraulic actuator section 4 of the automatic braking device operates to apply gentle braking or rapid braking.

As shown in FIG. 4, the control unit 50 controls the target deceleration Gr set by the contact possibility determination unit 45.
A comparison circuit which receives the signal of the vehicle and the detection signal from the deceleration detecting means 51 for detecting the actual deceleration Ga of the own vehicle, and calculates a difference e between the actual deceleration Ga of the own vehicle and the target deceleration Gr. 52, a dead zone for regulating the increase / decrease of the brake pressure when the difference e between the actual deceleration Ga of the host vehicle calculated by the comparison circuit 52 and the target deceleration Gr is within a dead zone of a predetermined width. Upon receiving a signal from the setting means 53 and the dead zone setting means 53, when a difference e between the actual deceleration Ga of the host vehicle and the target deceleration Gr is outside the dead zone, a predetermined duty ratio (control cycle T (Ton / T, the ratio of the time Ton in the ON state of the pressure-intensifying valve 12 or the pressure-reducing valve 13 to the pressure-controlling valve 12). With It has been configured to feedback control such that the actual deceleration Ga of the vehicle becomes a deceleration Gr goal.

The control section 50 receives the detection signal from the deceleration detecting means 51 and calculates the deceleration increase rate in the initial stage of automatic braking by a one-time differentiation method or the like. A calculation unit 5
5 and the deceleration detecting means 51 constitute a deceleration increasing rate detecting means 56 for detecting the actual deceleration increasing rate A. The signal of the increase ratio A calculated by the calculation unit 55 is input to the dead zone region width changing unit 57. The change unit 57 sets the width of the dead zone in the dead zone region setting unit 53 as the increase ratio A increases. Changes are made to expand

FIG. 5 shows a flowchart of the feedback control by the control unit 50. In this flowchart, after starting, first, step S1
After the target deceleration Gr and the current actual deceleration Ga1 are fetched, the difference between the current actual deceleration Ga1 and the actual deceleration Ga0 fetched and stored one control cycle ΔT before is controlled in step S2. The deceleration increase rate A (= (Ga1−Ga0) / ΔT) is calculated by dividing by the period ΔT.

Subsequently, in step S3, it is determined whether or not the increase rate A of the deceleration is equal to or more than a predetermined value a1, and in step S4, whether or not the increase rate A of the deceleration is equal to or more than a predetermined value a2 (<a1). It is determined whether or not each is true. If the increase rate A of the deceleration is a small rise equal to or smaller than the predetermined value a2 (in the area S3 in FIG. 6), the width δ of the dead zone is set to δ3 in step S5, The specified value a1 when the specified value is a2 or more
At the time of the following neutral rising (in the area S2 in FIG. 6), the width δ of the dead zone area is set to δ2 in step S6,
Further, when the increasing rate A of the deceleration is a high rise equal to or more than the predetermined value a1 (in the area S1 in FIG. 6), δ1 is set to the width δ of the dead zone area in step S7. Here, the above three values δ1, δ2, δ3 set to the width δ of the dead zone area
Has the following magnitude relationship:

Δ1>δ2> δ3 Accordingly, the setting of the width δ of the dead zone in the above steps S5 to S7 is such that the width δ of the dead zone is increased in three stages as the increasing rate A of the deceleration is higher. . After setting the dead zone area width δ, a difference e between the target deceleration Gr and the current actual deceleration Ga1 is calculated in step S8.

Subsequently, in step S9, it is determined whether or not the difference e between the target deceleration Gr and the current actual deceleration Ga1 is a positive value, that is, whether the target deceleration Gr and the current actual deceleration are present. The magnitude relationship with Ga1 is determined. If the target deceleration Gr is larger than YES, in step S10, it is determined whether or not the absolute value of the difference e is larger than a half value δ of the width of the dead zone, that is, the actual deceleration at the present time. Speed Ga1
Is determined before entering a dead zone having a predetermined width 2δ centered on the target deceleration Gr as shown in FIG. When this determination is YES, step S11
To increase the brake pressure and return, while the determination is NO
In step S12, the brake pressure is maintained without increasing or decreasing in step S12, and the routine returns.

When the determination in step S9 is NO, that is, when the actual deceleration Ga1 at this time is equal to the target deceleration G
If it is greater than r, it is determined in step S13 whether the absolute value of the difference e is greater than a half value δ of the width of the dead zone, that is, the actual deceleration Ga1 at the present time exceeds the dead zone. To determine whether the vehicle is in an overshoot state. If this determination is YES, step S
The brake pressure is reduced at 14 and the return is made, while the judgment is N
In the case of O, the brake pressure is maintained without increasing or decreasing in step S15, and the routine returns.

Therefore, according to the feedback control in accordance with such a flowchart, during the automatic braking control,
Kicking changed width δ of the dead zone region in accordance with the actual deceleration of the increase rate A, when the rising high above increase rate A is large, the dead zone width δ is widened, deceleration exceeds the dead zone over Shooting can be prevented from vibrating near the target deceleration. In addition, when the increase rate A is small and the rise is low with little possibility of overshoot, the dead zone region width δ becomes narrow, so that the accuracy of the feedback control can be increased accordingly.

In the feedback control of the above embodiment, the width δ of the dead zone is set to 3 in accordance with the increasing rate A of the deceleration.
In this embodiment, the width δ of the dead zone may be changed in two steps, four steps or more, or continuously.

Further, in the above embodiment, the automatic braking device for applying an automatic brake in order to avoid contact with an obstacle has been described. However, the present invention is not limited to this, and the vehicle may be stopped at a predetermined stop line. Also, the present invention can be similarly applied to an automatic braking device or the like that automatically decelerates to a predetermined legal speed or a safe speed when the vehicle speed is over.

[0030]

As described above, according to the automatic braking system for a vehicle according to the present invention, the rate of increase in the actual deceleration during the automatic braking control is detected, and when the rate of increase is greater than a predetermined value, the predetermined rate is determined. By changing the width of the dead zone so that the width of the dead zone becomes larger than when the value is smaller than the value, the road surface condition that changes every moment
Since the width of the dead zone is corrected in accordance with, it is possible to increase the accuracy of the feedback control, the braking system
The control can be prevented from vibrating. Sand
Chi, it is possible to prevent the actual deceleration due to the influence of such a road surface state is oscillatory in the vicinity of the target deceleration.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an automatic braking device for a vehicle according to an embodiment of the present invention.

FIG. 2 is a block diagram of the automatic braking device.

FIG. 3 is a diagram showing a map for calculating a threshold for avoiding contact.

FIG. 4 is a block diagram of a control unit.

FIG. 5 is a flowchart of feedback control by a control unit.

FIG. 6 is a diagram for explaining the relationship between the increasing rate of deceleration and the width of a dead zone.

[Explanation of symbols]

 36 Distance / relative speed detecting means 45 Contact possibility judging unit 50 Control unit 51 Deceleration detecting means 52 Comparison circuit 53 Dead zone area setting means 56 Deceleration increasing rate detecting means 57 Dead zone area width changing means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 7/12 B60R 21/00 627 B60T 8/32 G01S 17/93 G01S 15/93 G05B 11/36 501

Claims (1)

(57) [Claims] 1. A vehicle configured to automatically increase the brake pressure of each wheel under predetermined conditions and to feedback-control the brake pressure so that the actual deceleration of the host vehicle becomes a target deceleration. In the automatic braking device, when the difference between the actual deceleration of the own vehicle and the target deceleration during the feedback control is within a dead band region of a predetermined width, a dead band region setting means for regulating the increase / decrease pressure adjustment of the brake pressure; A deceleration increase rate detecting means for detecting an actual deceleration increase rate of the own vehicle during the automatic braking control ; and when the actual deceleration increase rate is larger than a predetermined value, when the actual deceleration increase rate is smaller than the predetermined value. And a dead zone width changing means for changing the width of the dead zone so that the width of the dead zone becomes larger than that of the automatic braking system.