JP2005162045A - Braking control system for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control an anti-skid operation appropriately at the time of an automatic braking operation. <P>SOLUTION: When the contact between a vehicle concerned and an object ahead is judged unavoidable by steering at the time of the automatic braking operation, ("NO" in Step 24), a target slip rate S<SP>*</SP>is set at S<SB>2</SB>larger than normal S<SB>1</SB>, thereby limiting the operation of the anti-skid control and enhancing the braking performance of the automatic braking. On the other hand, the contact between the vehicle and the object ahead is judged avoidable by steering ("Yes" in Step 24), the target slip rate S* is set at normal S<SB>1</SB>, thereby executing the normal anti-skid control and enhancing the stability and controllability of the vehicle body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides an anti-skid control that suppresses the braking force of a wheel when the wheel tends to lock, and a braking force that automatically generates a braking force when a forward object that may come into contact with the host vehicle is detected. The present invention relates to a vehicle brake control device that performs control.

By the way, when automatic braking is performed by detecting a front object that may come into contact with the host vehicle, if the braking force of the wheels is suppressed by anti-skid control, the stability and maneuverability of the vehicle body will be improved. The distance will increase. For this reason, when operating an automatic brake, the braking performance is more important than the stability and maneuverability of the vehicle body, and there are some which limit the operation of the anti-skid control so as not to extend the braking distance (Patent Document). 1).
JP-A-11-263209

However, as in the conventional example described in Patent Document 1, when automatic braking is performed, if the operation of anti-skid control is always limited, the driver can avoid steering with a front object. In addition, there is a problem that the stability and controllability of the vehicle body cannot be improved.
Therefore, the present invention has been made paying attention to the above problem, and an object of the present invention is to provide a vehicle brake control device that can more appropriately perform anti-skid control when performing automatic braking.

  In order to solve the above problems, the vehicle braking control apparatus according to the present invention is such that when the front object exists on the own vehicle path and the host vehicle generates a braking force, the own vehicle cannot avoid steering the front object. Only when it is judged, the operation of the anti-skid control is limited.

  According to the vehicle brake control device of the present invention, when a forward object is present on the own vehicle path and a braking force is generated on the own vehicle, only when it is determined that the own vehicle cannot avoid steering the forward object, By limiting the operation of the skid control, the braking performance can be improved and the vehicle can be decelerated as much as possible. On the other hand, if it is determined that the host vehicle can avoid the steering of the front object, by enabling the normal anti-skid control, the stability and controllability of the vehicle body when the driver tries to avoid the steering of the front object can be improved. Can be improved.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
The master cylinder 2 that converts the amount of operation of the brake pedal 1 by the driver into hydraulic fluid pressure is supplied to each wheel cylinder 5i (i = FL to RR) through the automatic brake hydraulic pressure unit 3 and the anti-skid hydraulic pressure unit 4 in order. The brake force is generated in each wheel 6i by the brake fluid pressure supplied to each wheel cylinder 5i.

  The automatic brake hydraulic pressure unit 3 is configured to increase the master cylinder pressure regardless of the driver's brake operation by driving a solenoid valve, a pump, or the like (not shown). Further, the anti-skid hydraulic pressure unit 4 is configured such that each wheel cylinder pressure can be individually increased, held, and reduced by driving a solenoid valve, a pump, etc. (not shown). These automatic brake hydraulic unit 3 and anti-skid hydraulic unit 4 are driven and controlled by a controller 9 which will be described later.

A scanning type laser radar 7 is provided at the lower part of the vehicle body. The infrared laser beam is emitted forward while changing the angle within a predetermined angle range, and the infrared laser beam is reflected by an object and received. The distance D to the detection point and the relative speed Vr are measured according to the time until the detection is performed, and the scanning angle with respect to the vehicle longitudinal direction is further detected. Specifically, as shown in FIG. 2, the distance D and the relative speed Vr from the front object and the scanning angles θ _L and θ _{R of} the left edge and the right edge are output. Not only the laser radar 7 but also a millimeter wave radar that detects the inter-vehicle distance D and the relative speed Vr from the frequency difference using the Doppler effect may be used.

Further, the vehicle is provided with a wheel rotation sensor 8i that detects a wheel speed Vwi of each wheel 6i.
Various signals from the laser radar 7 and the wheel rotation sensor 8i are input to a controller 9 composed of, for example, a microcomputer. The controller 9 performs the automatic brake control process of FIG. 3 and the anti-skid control process of FIG. To control the driving of the automatic brake hydraulic unit 3 and the anti-skid hydraulic unit 4.
The automatic brake control process is executed as a timer interruption process every predetermined time (for example, 10 msec), and first, as shown in FIG. 3, various data are read in step S1. Specifically, the distance D to the front object and the relative speed Vr, the scanning angles θ _L and θ _{R of} the left and right edges, and the vehicle body speed V calculated by the anti-skid control process described later are read.

In the subsequent step S2, it is determined whether or not the host vehicle may come into contact with the front object according to the following equation (1). Here, T is a dead time (for example, 0.2 s) from when the driver depresses the brake pedal until deceleration is generated, and a is a deceleration (for example, 8. which is generated by the driver's brake operation). 0 m / s ² ). The relative speed Vr is a positive value when the host vehicle approaches a front object.
D <Vr × T + Vr ² / 2a (1)

  When the relationship between the distance D and the relative speed Vr satisfies the above equation (1), it is determined that there is no possibility that the host vehicle is in contact with the front object, and the process proceeds to step S3. In step S3, the automatic brake hydraulic pressure unit 3 is deactivated to deactivate the automatic brake. In subsequent step S4, the limit flag F is set to “0” in order to activate the anti-skid control as usual. After resetting, it returns to the predetermined main program.

  On the other hand, when the relationship between the distance D and the relative speed Vr satisfies the above formula (1), it is determined that the host vehicle may come into contact with the front object, and the process proceeds to step S5. In step S5, the automatic brake is operated by controlling the automatic brake hydraulic pressure unit 3 so as to generate a braking force of a predetermined magnitude, and in the subsequent step S6, whether or not the operation of the anti-skid control is limited. 4 is executed, and then the process returns to the predetermined main program.

Here, in the restriction determination process of FIG. 4, first, in step S10, the lateral movement amount Y _N necessary for the host vehicle to avoid contact with the front object is calculated. First, as shown in FIG. 2, the width of the host vehicle is Wb, the offset amount from the center of the vehicle width where the laser radar 7 is attached is Ws, and the host vehicle makes contact with the front object as shown in FIG. The amount of lateral movement Y _L to the left and the amount of lateral movement Y _R to the right necessary for avoidance are calculated according to the following (2).
Y _L = D × tan θ _L + Wb / 2 + Ws
Y _R = D × tan θ _R + Wb / 2 + Ws (2)

Then, as shown in the following formula (3), the smaller one of the lateral movement amount Y _L to the left side and the lateral movement amount Y _R to the right side is selected as the lateral movement amount Y _N.
Y _N = min [Y _L , Y _R ] (3)
In the subsequent step S11, referring to the control map of FIG. 6, the time Ty required for the own vehicle to move laterally by Y _N is calculated according to the vehicle body speed V and the lateral movement amount Y _N. Here, in the control map of FIG. 6, the horizontal axis represents the horizontal movement amount Y _N , the vertical axis represents the horizontal movement required time Ty, and the horizontal movement required time Ty increases from 0 when the horizontal movement amount Y _N increases from zero. In addition, the rate of increase in the required lateral movement time Ty is set to increase as the vehicle body speed V decreases.

  In a succeeding step S12, it is determined whether or not contact with a front object can be avoided by steering. Specifically, it is determined whether the time (= D / Vr) until contact with the front object is greater than the time required for lateral movement Ty. When this determination result is D / Vr> Ty, it is determined that the contact with the front object can be avoided by steering, and the process proceeds to step S13, and the restriction flag F is set to “0” in order to operate the anti-skid control as usual. After the reset to, the restriction determination process is terminated. On the other hand, when the determination result is D / Vr ≦ Ty, it is determined that the contact with the front object cannot be avoided by steering, the process proceeds to step S14, and the limit flag F is set to “1” in order to limit the anti-skid control. After setting, the restriction determination process is terminated.

Next, the anti-skid control process is executed as a timer interrupt process every predetermined time (for example, 10 msec). As shown in FIG. 7, first, in step S20, the setting state of the limit flag F and each wheel speed Vwi are read. Include.
In subsequent step S21, the vehicle body speed V is estimated based on each wheel speed Vwi, and then the slip ratio Si of each wheel 6FL to 6RR is calculated according to the following equation (4).
Si = (Vwi−V) / V (4)

  In a succeeding step S22, it is determined whether or not each slip ratio Si is smaller than a predetermined value Sa. When this determination result is Si <Sa, it is determined that the wheel does not have a tendency to lock, and the process proceeds to step S23, and the anti-skid hydraulic unit 4 is set in a non-driven state to make the anti-skid in a non-operating state. Return to the predetermined main program. On the other hand, when the determination result is Si ≧ Sa, it is determined that the wheel has a locking tendency, and the process proceeds to step S24.

In step S24, it is determined whether or not the limit flag F is reset to “0”. When the determination result is F = 0, the target slip ratio S ^* of the wheel is set to normal S ₁ (eg, S ₁ = 10%) in step S25, and then the process proceeds to step S26. On the other hand, when the determination result is F = 1, in order to limit the operation of the anti-skid control, in step S27, the wheel target slip rate S ^* is larger than the above-described normal S ₁ S ₂ (for example, S ₂ = 20%) and then the process proceeds to step S26.

In step S26, a target value of each wheel cylinder pressure is calculated according to the difference between the actual slip ratio Si and the target slip ratio S ^*, and the anti-skid hydraulic pressure unit 4 is driven and controlled based on the target value. After the braking force of the wheels is suppressed, the program returns to a predetermined main program.
As described above, the processing in steps S1 to S5 and the automatic brake hydraulic pressure unit 3 correspond to the braking force control means, the processing in steps S10 to S14 corresponds to the steering avoidance determination means, and the processing in steps S20 to S23, S25, and S26. And the anti-skid hydraulic unit 4 correspond to the anti-skid control means, and the processes in steps S24 and S27 correspond to the limiting means.

Next, operations and effects of the first embodiment will be described.
Now, it is assumed that it is determined whether or not there is a possibility that the host vehicle is in contact with a front object. When the relationship between the distance D to the front object and the relative speed Vr does not satisfy the expression (1) (determination in step S2 is “No”), there is no possibility that the host vehicle is in contact with the front object. Then, the automatic brake is deactivated (step S3).

At this time, since the limit flag F is reset to “0”, the anti-skid control operates as usual. That is, when the driver suddenly brakes or the friction coefficient of the road surface is low such as a rainy road, a snowy road, and a frozen road, the slip ratio Si of each wheel becomes a predetermined value Sa or more ( The determination in step S22 is “Yes”), the target slip ratio S ^* is set to the normal S ₁ (step S25), and the braking force of the wheel is determined according to the difference between the target slip ratio S ^* and the actual slip ratio Si. Is suppressed (step S26). As a result, the wheels can be prevented from being locked, so that the stability of the vehicle body is improved and obstacles can be easily avoided by the steering operation.

On the other hand, if the relationship between the distance D to the front object and the relative speed Vr satisfies the above equation (1) (the determination in step S2 is “Yes”), the host vehicle may come into contact with the front object. The automatic brake is activated (step S5).
At this time, if it is determined that steering of the host vehicle cannot avoid the contact with the front object (the determination in step S12 is “No”), and the limit flag F is set to “1”, the slip ratio of the wheels is automatically braked. Si is when it becomes a predetermined value or more Sa, changing the target slip ratio S ^* to a larger S ₂ than S ₁ (step S27). As a result, the difference between the actual slip ratio Si and the target slip ratio S ^* is reduced and the amount of suppression of the braking force, that is, the amount of pressure reduction is reduced, so that the anti-skid control operation is limited. As a result, the braking performance by automatic braking is improved and the vehicle can be decelerated as much as possible.

On the other hand, there is room for the vehicle to avoid steering with the front object, and when the driver tries to avoid contact with the front object by steering operation, the stability of the vehicle body is more stable than the braking performance by automatic braking. It is desirable to improve the maneuverability preferentially.
Therefore, in this embodiment, when it is determined that the steering with the front object can be avoided (the determination in step S12 is “Yes”) and the limit flag F is reset to “0”, the slip of the wheel is caused by automatic braking. When the rate Si is equal to or greater than the predetermined value Sa, the target slip rate S ^* is set to normal S ₁ (step S25). As a result, the anti-skid control restriction is canceled and the anti-skid control is performed as usual, so that the stability and controllability of the vehicle body is improved when the driver tries to avoid contact with the front object. be able to.

In the first embodiment, the amount of suppression of the braking force by the anti-skid control is reduced by changing the target slip ratio S ^* . However, the present invention is not limited to this. In short, since it is only necessary to reduce the braking force suppression amount by the anti-skid control, the target value of each wheel cylinder pressure may be calculated and then corrected to a small value.
In the first embodiment, when it is determined that there is no possibility that the host vehicle is in contact with a front object, the automatic brake is simply deactivated. However, the automatic brake is activated. If the braking force suddenly drops from the state where the vehicle is on, the operator may feel uncomfortable. Therefore, when it is determined that there is no possibility of contact from the state where it is determined that there is a possibility of contact with the front object, the automatic brake hydraulic pressure unit 3 so that the braking force by the automatic brake is gradually reduced. May be driven and controlled.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, anti-skid control is performed in accordance with the wheel slip speed ΔVi.
Therefore, the second embodiment is the same as the first embodiment except that the above-described anti-skid control process of FIG. 7 is changed to the anti-skid control process of FIG. Omitted.
In the anti-skid control process of FIG. 8, first, in step S30, the setting state of the restriction flag F and each wheel speed Vwi are read.
In subsequent step S31, the vehicle body speed V is estimated based on each wheel speed Vwi, and then the slip speed ΔVi of each wheel 6FL to 6RR is calculated according to the following equation (5).
ΔVi = Vwi−V (5)

  In the subsequent step S32, it is determined whether or not each slip speed ΔVi is smaller than a predetermined value ΔVa. When this determination result is ΔVi <ΔVa, it is determined that the wheel does not tend to lock, and the process proceeds to step S33, and the anti-skid hydraulic unit 4 is brought into a non-driving state to make the anti-skid non-operating state. Return to the predetermined main program. On the other hand, when the determination result is ΔVi ≧ ΔVa, it is determined that the wheel has a locking tendency, and the process proceeds to step S34.

In step S34, a target slip speed ΔV ^* is calculated according to the vehicle body speed V and the limit flag F with reference to a control map as shown in the flowchart. The control map, the horizontal axis vehicle speed V, and the vertical axis between the target slip speed [Delta] V ^*, increased target slip speed [Delta] V ^* with an increase in vehicle speed V, F when limitation flag F is F = 1 The increase rate of the target slip speed ΔV ^* is set to be larger than when 0.

In the subsequent step S35, a target value of each wheel cylinder pressure is calculated according to the difference between the actual slip speed ΔVi and the target slip speed ΔV ^*, and the anti-skid hydraulic pressure unit 4 is driven and controlled based on this target value. To suppress the braking force of the wheel and return to a predetermined main program.
As described above, when the restriction flag is F = 1, the control map referred to in step S34 corresponds to the restriction means, and the other steps S30 to S35 and the anti-skid hydraulic unit 4 correspond to the anti-skid control means. ing.

As described above, according to the second embodiment, when the wheel slip speed ΔVi is equal to or higher than the predetermined value ΔVa by automatic braking, it is possible to avoid steering when it is determined that steering with a front object cannot be avoided. The target slip speed ΔV ^* is made larger than when judged (step S34). As a result, the difference between the actual slip speed ΔVi and the target slip speed ΔV ^* is reduced and the amount of braking force suppression is reduced, so that the anti-skid control operation is limited. As a result, the braking performance by automatic braking is improved and the vehicle can be decelerated as much as possible.
On the other hand, when it is determined that steering can be avoided, the normal target skid speed ΔV ^* corresponding to the vehicle body speed V is set and normal anti-skid control is performed, so the driver avoids steering with the front object. When trying to do so, the stability and maneuverability of the vehicle body can be improved.
Other functions and effects are the same as those of the first embodiment described above.

Next, a third embodiment of the present invention will be described with reference to FIGS.
In the third embodiment, the operation of the anti-skid control is limited by changing the threshold value of the slip state in which the suppression of the braking force is started by the anti-skid control.
Therefore, the third embodiment is the same as the first embodiment except that the above-described anti-skid control process of FIG. 7 is changed to the anti-skid control process of FIG. Omitted.

In the anti-skid control process of FIG. 9, first, in step S40, the setting state of the restriction flag F and each wheel speed Vwi are read.
In the following step S41, the wheel acceleration αwi of each wheel is calculated based on the sampling period of the wheel speed Vwi and the data for each sampling.
In subsequent step S42, the vehicle body speed V is estimated based on each wheel speed Vwi, and then the slip ratio Si of each wheel 6FL to 6RR is calculated according to the above-described equation (4).

  In a succeeding step S43, it is determined whether or not the restriction flag F is reset to “0”. When the determination result is F = 0, the process proceeds to step S44 to perform normal anti-skid control, and then returns to a predetermined main program. In this step S44, referring to a control map as shown in FIG. 10A, any one of a braking force pressure increase command, a hold command, and a pressure decrease command is determined based on the wheel acceleration αwi and each slip ratio Si. Output to the anti-skid hydraulic unit 3.

Here, the control map of FIG. 10 (a), the wheel acceleration αwi outputs a holding command when a predetermined value .alpha.w ₁ is greater than the acceleration region, the wheel acceleration αwi is small and the slip ratio Si than a predetermined value .alpha.w ₁ given outputs a pressurization command when greater than the value S _3, small and the slip ratio Si than the predetermined value .alpha.w ₂ of wheel acceleration αwi is deceleration region outputs a holding command when less than the predetermined value S _3, the wheel acceleration αwi The pressure increasing command is set to be output when the slip ratio Si is smaller than the predetermined value S _{3 in} the range of the predetermined value αw ₂ to αw ₁ .

On the other hand, when the determination result in step S43 is F = 1, in order to limit the operation of the anti-skid control, the wheel acceleration αwi and each slip ratio are referred to with reference to a control map as shown in FIG. Based on Si, one of a braking force pressure increasing command, a holding command, and a pressure reducing command is output to the anti-skid hydraulic pressure unit 3. Here, the control map of FIG. 10B is obtained by changing the threshold value of the slip ratio Si for starting the output of the pressure reduction command to a predetermined value S ₄ larger than the predetermined value S ₃ described above.
As described above, the processes of steps S40 to S42 and S44 and the anti-skid hydraulic pressure unit 4 correspond to the anti-skid control means, and the processes of steps S43 and S45 correspond to the limiting means.

Next, operations and effects of the third embodiment will be described.
Now, it is assumed that when the automatic brake is activated, it is determined that the host vehicle cannot avoid contact with the front object, and the limit flag F is reset to “1”. At this time, in order to make it difficult to start the output of the decompression command, the threshold of the slip ratio at which the output of the decompression command is started is changed from normal S ₃ to S ₄ to limit the operation of the anti-skid control (step S45). As a result, when the slip ratio Si of the wheel increases due to automatic braking, it becomes difficult to start the output of the decompression command, that is, it is difficult to start suppression of the braking force. It can be decelerated as much as possible.

On the other hand, if it is determined that the vehicle can avoid steering with a front object and the limit flag F is reset to “0”, the threshold of the slip ratio at which the decompression command is output is set to normal S ₃ (Step S44). As a result, the anti-skid control restriction is canceled and the anti-skid control is performed as usual, so that the stability and controllability of the vehicle body is improved when the driver tries to avoid contact with the front object. be able to.

In the third embodiment, the braking force is reduced according to the wheel slip rate S. However, the present invention is not limited to this, and the braking force is reduced according to the wheel slip speed ΔV. The braking force may be started or the braking force may be reduced according to both the slip ratio S and the slip speed ΔV.
In the third embodiment, in order to limit the operation of the anti-skid control, only the threshold value for starting the output of the decompression command is changed, but the present invention is not limited to this. That is, the threshold for starting the output of the pressure reduction command is changed, and the amount of suppression of the braking force by the anti-skid control is reduced as in the first embodiment and the second embodiment described above, so that the anti-skid control is activated. You may restrict.

Other functions and effects are the same as those of the first embodiment described above.
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
In the fourth embodiment, when the automatic brake is operated, it is determined whether or not at least the contact between the front surface of the vehicle body and the front object can be avoided.
Therefore, in the restriction determination process of the fourth embodiment, as shown in FIG. 11, the same as the first embodiment, except that the steps S11 and S12 of FIG. 4 are changed to the new steps S50 and S51. Therefore, detailed description of the same part is omitted.

First, in step S50, the distance x in the straight traveling direction that travels until the front surface of the vehicle body comes into contact with the front object is estimated, and a travel locus map as shown in FIG. vehicle front lateral movement amount Y _P that can traverse, is calculated in accordance with the vehicle speed V when it.
In a succeeding step S51, it is determined whether or not the lateral movement amount Y _P is equal to or larger than the lateral movement amount Y _N necessary for steering avoidance. When this determination result is Y _P ≧ Y _N, it is determined that at least the front of the vehicle body can avoid steering with the front object, and the process proceeds to step S13. On the other hand, when the determination result is Y _P <Y _N, it is determined that the front side of the vehicle body cannot avoid contact with the front object, and the process proceeds to step S14.

Here, the processes of steps S10, S50, S51, S13, and S14 correspond to the steering avoidance determination means.
As described above, according to the fourth embodiment, when it is determined that the front of the vehicle body cannot avoid the steering with the front object when the automatic brake is operated, the limit flag F is set to “1”. To limit the operation of anti-skid control. On the other hand, when it is determined that at least the front of the vehicle body can avoid contact with the front object, the restriction flag F is reset to “0” to stop the restriction of the anti-skid control.
As a result, even if the side of the vehicle body or the rear part of the vehicle body comes into contact with the front object, at least the contact between the front surface of the vehicle body and the front object can be avoided by steering. Can be improved.
Other functions and effects are the same as those of the first embodiment described above.

It is a schematic block diagram of this invention. It is the figure which showed a mode that a laser radar detected a front object. It is a flowchart which shows an automatic brake control process. It is a flowchart which shows the restriction | limiting determination process of 1st Embodiment. It is the figure which showed the amount of lateral movement required for steering avoidance. It is a control map used for calculation of time required for lateral movement Ty. It is a flowchart which shows the anti-skid control process of 1st Embodiment. It is a flowchart which shows the anti-skid control process of 2nd Embodiment. It is a flowchart which shows the anti-skid control process of 3rd Embodiment. It is a control map which determines the output of a pressure increase command, a holding command, and a pressure reduction command. It is a flowchart which shows the restriction | limiting determination process of 4th Embodiment. It is a travel locus map.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brake pedal 2 Master cylinder 3 Automatic brake hydraulic pressure unit 4 Anti-skid hydraulic pressure unit 5FL-5RR Wheel cylinder 7 Laser radar 8FL-8RR Wheel rotation sensor 9 Controller

Claims (4)

Anti-skid control means that suppresses the braking force of the wheel when the slip state of the wheel exceeds a threshold value, and a braking force that generates a braking force on the host vehicle when a forward object that may come into contact with the host vehicle is detected A vehicle braking control device comprising: control means;
Steering avoidance determining means for determining whether or not the own vehicle can avoid steering with the front object, and when the braking force control means generates braking force on the own vehicle, the steering avoidance determining means A vehicle braking control device comprising: a limiting unit that limits the operation of the anti-skid control unit only when it is determined that steering with the front object cannot be avoided.   The vehicular braking control apparatus according to claim 1, wherein the steering avoidance determining unit is configured to determine whether or not at least a front surface of the vehicle body can avoid steering with a front object.   When the steering avoidance determining means determines that the host vehicle cannot avoid contact with the front object, the limiting means determines that the braking force by the anti-skid control means is greater than when it is determined that steering can be avoided. The vehicular braking control apparatus according to claim 1 or 2, wherein the braking control device is configured to limit the operation of the anti-skid control means by reducing a suppression amount.   When the steering avoidance determining means determines that the vehicle is unable to avoid contact with the front object, the limiting means is configured to reduce the braking force by the anti-skid control means than when it is determined that steering can be avoided. It is comprised so that the action | operation of the said anti-skid control means may be restrict | limited by changing the said threshold value to a big value so that suppression may become difficult to start. The brake control apparatus for vehicles as described.

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