JP3038894B2 - Anti-skid brake control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid brake control method for preventing locking of wheels during braking, and in particular, appropriately performs anti-skid control on a low μ road. The present invention relates to an anti-skid brake control method that enables the control.

(Prior Art) In this kind of anti-skid brake control method, when a wheel tends to lock at the time of braking, the brake pressure of the wheel is reduced to eliminate the lock tendency. , By properly controlling the brake pressure,
The aim is to shorten the braking distance while ensuring the steering performance.

In order to properly perform such anti-skid control, first, it is necessary to determine whether or not the wheels have a tendency to lock. In this determination, the actual vehicle speed must be accurately detected. . However, since it is difficult to directly detect the actual vehicle speed, a pseudo reference vehicle speed is usually used instead of the actual vehicle speed when performing anti-skid control.

When the reference vehicle speed is under non-anti-skid control,
It is obtained based on the third or fourth wheel speed from the high speed side of the wheel speed of each wheel, usually the third wheel speed. On the other hand, during anti-skid control, It is determined based on the first or second, usually second, wheel speed from the high speed side.

Therefore, when the non-anti-skid control is being performed, whether or not to start the control, that is, whether or not one of the wheels has a tendency to lock, is determined by comparing the reference vehicle speed at that time with the wheel speed. When the anti-skid control is being performed, the control is performed based on the reference vehicle speed at that time.

(Problems to be Solved by the Invention) By the way, if the reference vehicle body speed is obtained based on the wheel speed selected as described above, the vehicle is traveling on a low μ road under non-anti-skid control, for example, when the front wheels are not driven. When the rear wheels are driving wheels, the reference vehicle speed is determined based on the wheel speed of the front wheels, even if the rear wheels are spinning. When the anti-skid control is started and the anti-skid control is started, in this case, the reference vehicle body speed is determined based on the second wheel speed from the high speed side among the wheel speeds, that is, the wheel speed of the rear wheel in a spin state. The speed will be set.

For this reason, in the above situation, the reference vehicle speed rapidly increases before and after the start of the anti-skid control, and the speed difference between the front wheel speed and the reference vehicle speed is very large. Becomes Therefore, in this case, since it is erroneously determined that the front wheel is locked, the brake pressure of the front wheel is excessively reduced, and there is a possibility that the braking force of the front wheel cannot be sufficiently obtained. .

The present invention has been made based on the above-described circumstances, and an object of the present invention is to reduce the reference vehicle speed even when the anti-skid control is started in a situation where the drive wheels are spinning. The present invention is to provide an anti-skid brake control method capable of effectively executing the anti-skid control by appropriately setting the anti-skid brake control.

(Means for Solving the Problems) The present invention determines the reference vehicle body speed based on the third or fourth low-speed wheel speed from the high-speed side of each wheel speed during normal driving, and determines the reference vehicle speed during braking. When the wheels tend to lock in view of the vehicle speed, the reference vehicle speed is determined based on the first or second high-speed wheel speed from the high-speed side of each wheel speed, and anti-skid control is performed based on the reference vehicle speed. In the anti-skid brake control method for controlling the increase and decrease of the brake pressure at the wheel to prevent the locking of the wheel, the method according to the present invention employs the method according to the present invention when the anti-skid control is started. The deviation between the wheel speed of the driving wheel and the wheel speed of the non-driving wheel is determined. When the deviation is equal to or greater than a predetermined value, the reference vehicle speed is determined based on the low-speed wheel speed, and the anti-skidding is performed. Control is performed.

(Operation) As described above, according to the anti-skid brake control method of the present invention, when starting the anti-skid control,
If the deviation between the wheel speed of the driving wheel and the wheel speed of the non-driving wheel is equal to or greater than a predetermined value, that is, when traveling on a low μ road, there is a situation where spin occurs in the driving wheel. Since the reference vehicle speed is determined based on the low-speed wheel speed, in this case, the reference vehicle speed is not determined based on the wheel speed of the spinning drive wheel. Therefore, in this case, since the reference vehicle speed is close to the actual vehicle speed, the subsequent anti-skid control can be appropriately performed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, there is shown an anti-skid brake control device applied to an automobile. In this case, the automobile can be switched to two-wheel drive (2WD) or four-wheel drive (4WD) to run. Here, the power transmission path will be briefly described. In the case of 2WD, the driving force of the engine 1 is controlled by the transmission 2, the propeller shaft 6, the rear differential 7,
In addition, in the case of 4WD, the transmission is transmitted from the transmission 2 through the front wheel drive shaft 3 to the rear wheels 5L and 5R via the rear wheel drive shaft 8. The driving force of the engine 1 can be transmitted to 4L and 4R.

A wheel brake 9 is mounted on each of the front wheel 4 and the rear wheel 5.
Are connected to the hydraulic brake circuit 10.

The hydraulic brake circuit 10 includes a tandem-type master cylinder 12 with a vacuum brake booster operated by a brake pedal 11, and a front wheel brake line 13 is provided from one pressure chamber (not shown) of the master cylinder 12. A rear wheel brake line 14 extends from the other pressure chamber (not shown). The front and rear wheel brake lines 13 and 14 extend through the control valve device 15, and the front wheel brake line 13 is connected to the wheel brakes 9 of the respective front wheels 4, with the distal end branched left and right. The rear brake line 14 is also connected to the wheel brakes 9 of the rear wheels 5 with the leading end branched right and left.

In the front wheel brake line 13, anti-skid valve devices 16 are interposed at portions of the corresponding front wheel branched toward the wheel brake 9, respectively. In the site before branching, 1
Two anti-skid valve devices 16 are inserted.

Further, a hydraulic pump 17 is connected to the control valve device 15, and the hydraulic pump 17 pressurizes the hydraulic fluid sucked from the hydraulic tank 18 to a predetermined pressure, and during the anti-skid brake control, It can be supplied to the wheel brake 9 of each wheel via the control valve device 15.

That is, when the anti-skid control is started during braking,
Each wheel brake 9 has a hydraulic pump, not a hydraulic fluid from the master cylinder 12, due to the operation of the control valve device 15.
The dynamic pressure from 17 is supplied, and the brake pressure in the wheel brake 9, that is, the braking force, can be controlled by appropriately operating each anti-skid valve device 16. .

In order to control the brake pressure of each wheel brake 9 by the above-described anti-skid control, a wheel speed sensor 19 is disposed on each of the wheels 4, 5, and a wheel speed signal from the wheel speed sensor 19 is transmitted to a controller. Supplied to 20.

In addition to the wheel speed sensor 19, the controller 20 is connected with a deceleration sensor 21 for detecting the vehicle body deceleration G and various switches for setting the driving system of the automobile.
For example, these switches have a 4W to select between 2WD and 4WD.
There are a D select switch, a center differential lock switch for locking the function of the center differential, a rear differential lock switch for locking the function of the rear differential 7, and the like.

In FIG. 1, a return line from each wheel brake 9 to the hydraulic fluid tank 18 is not shown in order to simplify the drawing.

Next, the anti-skid brake control method performed by the controller 20, that is, the reference vehicle speed VREF of the vehicle body
Will be described with reference to the flowcharts of FIGS. 2 to 5.

Reference Vehicle Speed Calculation Routine In the description from step S1 in FIG. 2, various flags described later are set to OFF (OF
F), and a reference vehicle speed calculation routine and a drive control routine (not shown) of the anti-skid valve device 16 executed subsequently to the calculation routine are:
It is executed repeatedly every predetermined control cycle time.

First, in step S1, during anti-skid control (ABS
It is determined whether or not the brake pedal has been depressed since the start of this routine, or immediately after the depression (N).
0), and in step S2, the spin flag FS is turned off, and the flag F1 is turned on (ON). And
In the next step S3, among the wheel speeds VW obtained from the wheel speed sensors 19, the third highest wheel speed VW from the top is selected as the selected wheel speed SVW.

In the next step S4, the selected wheel speed SVW becomes the reference wheel speed VF
Then, the detected deceleration MUG is read from the deceleration sensor 21, and appropriate filtering is performed on the reference wheel speed VF and the detected deceleration MUG. In this step, the calculated deceleration G1 of the vehicle body is also calculated by differentiating the reference wheel speed VF.

Next, when the process proceeds to the steps after step S5 in FIG. 3, the determinations in steps S5, S6, and S7 are performed. In this case, the determination results in steps S5 and S6 still remain, and
Since the determination result of step S7 is positive (Yes), the process proceeds to the next steps S8 and S9, and the determination in these steps is performed.

In step S8, the calculated deceleration G1 and the detected deceleration MUG satisfy the following equation, and this state is maintained for a predetermined time T1 (for example,
It is determined whether or not the operation is continued for 100 msec).

G1> MUG + α (for example, α = 0.25 g) In step S9, the calculated deceleration G1 is set to a constant value CG.
(For example, 1.4 g) is determined.

At the time of execution of steps S8 and S9 at this point, since the ABS control has not been started, the result of these determinations is negative,
Accordingly, in the next step S10, the reference wheel speed VF is set to the reference vehicle speed VREF.

After this, the anti-skid valve device 16
However, in this case, the anti-skid valve device 16 is not actually operated, and only the reference vehicle speed VREF is calculated. It is just done.

Thereafter, in the process in which the above-described steps are repeatedly executed, braking is performed by depressing the brake pedal, and if the determination result of step 1 in FIG. If the wheel speed VW of one of the wheels falls below a predetermined value with respect to the reference vehicle speed VREF, that is, the reference wheel speed VF, then in step S11
Is executed.

In step S11, it is determined whether the driving method is 2WD. The determination here is made based on the signal from the above-described 4WD select switch. If the determination result is positive, the next step S12 is determined, that is, whether the spin flag FS is on is determined.
The determination result is negative because step S2 is still being executed, and the next step S13 is executed.

In this step 13, the wheel speed RVW of the rear wheel which is the driving wheel
Among the lower wheel speed RVW L and the higher wheel speed FVW H among the front wheel speeds FVW of the non-driven wheels.
Is calculated. That is, the deviation D is calculated from the following equation.

D = RVW L−FVW H Then, in the next step S14, it is determined whether or not the calculated deviation D is equal to or larger than a predetermined value D10 (for example, 10 km / h). At this point, it is determined that no spin occurs in the rear wheel 5, and the process proceeds to step S15.

In step S15, the wheel speed V obtained from each wheel speed sensor 19
Among W, the second fastest wheel speed is selected as the selected wheel speed SVW.

On the other hand, if the result of the determination in step S4 is positive, it is determined that spin has occurred in the rear wheel 5, and the next step
In step S16, after the spin flag FS is turned on, the above-described step S3 is executed, whereby the third fastest wheel speed, in this case, the wheel speed FVW H of the front wheel 4 becomes the selected wheel speed SVW Will be selected.

If the result of the determination in step S11 is negative, the process immediately jumps to step S15, and this step is executed. In other words, when the ABS control is executed during 4WD driving, the third highest wheel speed is the selected wheel speed.
It is now selected as SVW.

When the selected wheel speed SVW during the ABS control is selected in this way, the steps after step S4 are executed as described above, but even at this point, the determination results in steps S8 and S9 are negative. In some cases, the execution of step S10 sets the reference wheel speed VF as the reference vehicle speed VREF.

Then, as described above, the determination result in step S14 becomes positive, and the process goes through steps S16 and S3, through the execution of the steps after step S4, that is, through the calculation of the reference vehicle speed VREF and the execution of the drive control routine. Returning to step S1, when the above-described routine is repeated again,
Since the determination result of step S12 is positive, in this case, steps S12 to S17 are executed. In step S17, the deviation D is calculated in the same manner as in step S13 described above, and in the next step S18, it is determined whether or not the deviation D is 0 or less. If the determination here is no, the process proceeds to step S3, and the steps after this step are executed in the same manner.

However, in the process where the calculation of the reference vehicle speed VREF and the drive control routine are repeatedly executed, if the determination result in step S18 becomes positive, in this case, the spin flag FS is turned off in step S19. After the switching, the process proceeds to step S4 and subsequent steps via step S15.

Therefore, in the case of this embodiment, when the result of the determination in step S14 is once positive and the spin flag FS is turned on, that is, when the above-described deviation D is equal to or greater than the predetermined value D10, When it is determined that the wheel 5 is spinning, even if the ABS control is being performed, the same as the case where the non-ABS control is being performed, the step S3 is executed so that the selected wheel speed SVW, That is, as the reference wheel speed VF,
The third wheel speed from the top among the wheel speeds VW is set.

However, during the ABS control, after the spin of the rear wheel 5 is detected as described above, if the determination result in the step S18 becomes positive, the step S15 is performed through the step S19. As in the case of the ABS control, the selected wheel speed SVW, that is, as the reference wheel speed VF,
The second wheel speed from the top of each wheel speed VW is set.

The above-described switching of the selected wheel speed SVW becomes more apparent with reference to FIG. FIG. 6 shows the front wheel 4
Respectively shows the time change of the wheel speed FVW of the rear wheel 5 and the wheel speed RVW of the rear wheel 5, in this case, the non-ABS before the start of the braking.
During control, as is clear by comparing the wheel speeds FVW and RVW,
For example, the rear wheel 5 is spinning due to running on a low μ road or the like. In such a situation, the selected wheel speed SVW, that is, the reference wheel speed VF,
Since the third wheel speed from the top of VW is set, in this case, the reference wheel speed VF is the faster wheel speed FVW H of the front wheel speed FVW.

Thereafter, when the ABS control is started along with the start of the braking, in the conventional normal ABS control, each wheel speed V
In the case where the second wheel speed from the top of W, that is, the rear wheel 5 is spinning, the lower wheel speed RVWL of the wheel speeds of the rear wheel 5 is set as the reference wheel speed VF. Therefore, as indicated by the broken line in FIG. 6, when the control is shifted from the non-ABS control to the ABS control, the reference wheel speed VF sharply increases.

However, in this embodiment, when the rear wheel 5 is spinning, the wheel speed FVW H of the front wheel 4 is reduced by performing the same ABS control of the spin compensation as during the non-ABS control. Since the selected wheel speed SVW is used as the selected wheel speed SVW and the selected wheel speed SVW is used as the reference wheel speed VF, it is possible to prevent a rapid increase in the reference wheel speed VF as shown by a broken line in FIG. The reference vehicle speed VREF determined based on the wheel speed VF is close to the actual vehicle speed VA indicated by a dashed line in FIG.

Thereafter, by executing the drive control routine in the ABS control, when the spin of the rear wheel 5 is eliminated and the deviation D becomes 0 or less, the selected wheel speed SVW becomes the same as that in the normal ABS control. Similarly, the third wheel speed from the top among the respective wheel speeds VW is set, and the selected wheel speed SVW becomes the reference wheel speed VF.

Therefore, according to the embodiment of the present invention, the reference wheel speed VF can be appropriately obtained even when the ABS control is started in a situation where the rear wheel 5 as the driving wheel is spinning. , The reference vehicle speed V obtained from the reference wheel speed VF
The REF will also be accurate. As a result, for example, even if the front wheels 4 tend to lock, the brake pressure control for the front wheels 4 that tend to lock, that is, the anti-skid control can be appropriately performed. The brake pressure of No. 4 does not undesirably remain reduced. Therefore, in the case of this embodiment, the anti-skid valve device 1 based on the reference wheel speed VREF
By properly executing the drive control routine of 6,
By applying a sufficient braking force to the front wheels 4, the braking distance can be effectively reduced.

After the spin of the rear wheel 5 is eliminated, the reference vehicle speed VREF is obtained in the same manner as in the case of the normal ABS control. Therefore, it is not desirable to switch the selected wheel speed SVW due to the occurrence of the spin. Normal AB without continuing
It will surely return to S control.

In the above description, although the flowcharts shown in FIGS. 3 to 5 are not described in detail, this flowchart is particularly applicable to a case where a slip occurs in four wheels at the same time while the vehicle is running in 4WD. The procedure for calculating the reference wheel speed VREF in this case will be described below.

If all four wheels are in the slip state after the start of the ABS control, the calculated deceleration G1 obtained from the reference wheel speed VF is equal to the allowable deceleration of the vehicle body, even if the determination result in step S8 is negative. The value becomes larger than CG
The determination at S9 is positive, and the next step S20 is executed.
The flag F1 turns off and the flag Fa turns on, and the process proceeds to step S21 in FIG.

In step S21, the reference vehicle speed VREF is changed to the reference wheel speed VF.
It is determined whether or not the following is true. Here, as is apparent from the determination result in the previous step S8 in FIG. 3, in this case, the reference vehicle set in the previous control cycle is used. Since the reference wheel speed VF is much lower than the speed VREF, the determination result is negative, and the next step
S22 is performed.

In step S22, it is determined whether or not a predetermined time T2 (for example, 80 msec) has elapsed since the determination in step S9 became positive. At this point, the determination result in step S22 is still negative. Then, the next step S23 is executed.

In step S23, the reference vehicle speed VREF is calculated by assuming that the reference vehicle speed VREF decelerates at a deceleration gradient of a constant value CG without considering the reference wheel speed VF.

Therefore, in the subsequent drive control routine of the anti-skid valve device 16, the reference vehicle speed VR calculated in step S23 is used.
ABS control will be performed based on EF.

Then, in the subsequent control cycle, since the flag Fa has already been turned on in step S20, the determination result in step S6 is positive, and therefore, immediately after step S6, steps S21 and after in FIG. Steps are executed. In this case, as long as the determination result of step S22 is not positive, step S23 is continuously performed, and reference vehicle speed VREF is calculated.

However, when the determination result of step S22 becomes positive, step S24 is performed. In this step, the reference vehicle body speed REF is calculated assuming that the vehicle body decelerates at a deceleration gradient obtained by adding a predetermined value β (for example, β = 0.13 g) to the detected deceleration MUG. In such a step S24, the reference vehicle speed VREF
Is continued until the result of the determination in step S21 becomes positive. That is, when the reference wheel speed VF rises to the reference vehicle speed VREF and recovers by the execution of the ABS control, the determination in step S21 becomes positive, and step S25 is executed.
Here, while the flag Fa is reset to off,
The reference vehicle speed VREF is again set to the reference wheel speed VF.

FIG. 7 shows the relationship between the reference vehicle speed VREF and the reference wheel speed VF. That is, as apparent from FIG. 7, during the ABS control, before the slip of the reference wheel speed VF occurs, the reference vehicle speed VREF follows the reference wheel speed VF. At the time when the calculated speed G1 becomes larger than the constant value CG, that is, from the first separation point, the reference vehicle speed VRE
F does not follow the reference wheel speed VF, and during a predetermined time T2 from the first separation point, the reference vehicle speed VREF is calculated on the assumption that the vehicle decelerates at a deceleration gradient of CG which is a constant value. In this case, the reference vehicle speed VREF is calculated by decelerating at a deceleration gradient of MUG + β until the reference wheel speed VF recovers to the reference vehicle speed VREF.

After the reference wheel speed VF is recovered, when the reference vehicle speed VREF is again set to the reference wheel speed VF, in the next control cycle, the steps S5, S6, and S7 in FIG. Since all the determinations are negative, step S26 is performed next. In this step, it is determined whether or not the calculated deceleration G1 is greater than MUG + α. If this determination result is negative, in step S10, the reference vehicle speed VREF is set to the reference vehicle speed VF.

However, if the determination result in step S26 is positive, the flag Fb is turned on in step S27,
Thereafter, steps after step S28 in FIG. 5 are executed.

That is, in step S28, similarly to step S21 described above, it is determined whether the reference wheel speed VF is equal to or higher than the reference vehicle speed VREF, but since the determination here is negative, the next step S29 is performed. Be executed. In this step, similarly to step S24 in FIG. 4 described above, the detected deceleration MUG is
The reference vehicle speed REF is calculated assuming that the vehicle decelerates at the deceleration gradient to which the vehicle speed is added.

In the next control cycle, the flag F has already been set in step S27.
Since b is on, the steps after step S28 are immediately repeated from step S5.
Until the result of the determination becomes positive, that is, until the reference wheel speed VF recovers to the reference vehicle speed VREF, the reference vehicle speed VREF is calculated in step S29.

When the result of the determination in step S28 becomes positive, the flag Fb is turned off in step S30, and the reference vehicle speed VREF
Is again set to the reference wheel speed VF.

The steps after step S28 in FIG. 5 described above are executed after the slip has occurred in the reference wheel speed VF again. As shown in FIG.
After G1 becomes larger than MUG + α, that is, the second
After the separation point, and the reference wheel speed VF is equal to the reference vehicle speed VREF
Until the vehicle speed recovers, the reference vehicle speed VREF is maintained at the reference wheel speed VF
Instead, it is calculated based on the detected deceleration MUG.

When the reference wheel speed VF is restored to the reference vehicle speed VREF,
In step S30, the flag Fb is turned off.In the subsequent control cycle, the determination results in steps S6 and S7 are always negative as long as the determination result in step S1 is maintained positive. If the result of the determination in step S28 is NO again, that is, if the reference wheel again slips, the steps after the slip S28 in FIG. 5 are repeated to calculate the reference vehicle speed VREF. Become.

Therefore, if the reference wheel speed VF first slips during the ABS control, the reference vehicle speed VREF is calculated as shown in FIG. 7, and thereafter, the reference wheel speed VF is calculated. If slip occurs repeatedly in VF,
As shown in FIG. 8, the reference vehicle speed VREF is calculated.

Also, if a slip occurs first in the reference wheel speed VF during the ABS control, the steps after step S21 in FIG. 4 will be performed based on the determination result in step S9 in FIG. However, in this embodiment, since the determination in step S8 is performed before the determination in step S9, if the determination result in this step is positive, the process proceeds from step S8 to step S31. And the flag F
After the flag 1 is turned off and the flag Fb is turned on, the steps after step S28 in FIG. 5 are immediately performed. That is, in this case, the reference vehicle speed VREF is calculated as shown in FIG. 8 from the time when the reference wheel speed VF first slips.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in one embodiment, the rear wheels are described as the drive wheels. However, it is needless to say that the present invention can be applied to a 2WD vehicle in which the front wheels are the drive wheels. Further, the anti-skid brake device shown in FIG. 1 is also merely shown as an example, and the present invention can be applied to the specific configuration even if the configuration is appropriately changed.

(Effects of the Invention) As described above, according to the anti-skid control method of the present invention, when the anti-skid control is started,
Since the deviation between the wheel speed on the lower side of the drive wheels and the wheel speed on the higher side of the non-drive wheels is determined, it is determined from the magnitude of this deviation whether or not the drive wheels are spinning. be able to. Then, when spin occurs in the driving wheels, the reference vehicle speed is calculated based on the third or fourth wheel speed from the high-speed side among the wheel speeds, and under normal circumstances, based on the wheel speed of the non-driving wheels. Since the anti-skid control is performed, the reference vehicle speed is close to the actual vehicle speed. As a result, even if spin occurs in the driving wheels, the execution of the anti-skid brake control is appropriate, and the braking force can be sufficiently applied to the non-driving wheels, and the braking distance can be reduced. This will greatly contribute to shortening. Further, in the present invention, when the deviation is eliminated, the reference vehicle body is determined based on the first or second wheel speed from the high speed side of each wheel speed, as in the case of the normal anti-skid control. Since the speed is determined, there is an excellent effect that switching of the selection of the wheel speed when determining the reference vehicle speed does not adversely affect the execution of the normal anti-skid control.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of an anti-skid brake device. FIGS. 2 to 5 are flowcharts showing a routine for calculating a reference vehicle speed. FIG. 6 is a graph for explaining the setting of the reference wheel speed before and after the ABS control in a situation where the rear wheel is spinning. FIG. 7 is a diagram in which a slip first occurs at the reference wheel speed during the ABS control. FIG. 8 is a graph showing a relationship between the reference wheel speed and the reference vehicle speed in the case, and FIG. 8 is a graph showing a relationship between the reference wheel speed and the reference vehicle speed when the second or subsequent slip occurs in the reference wheel speed. It is. 4 Front wheel 5 Rear wheel 9 Wheel brake 12
…… Master cylinder, 16 …… Anti-skid valve device, 20
... Controller, 21... Deceleration sensor, VREF... Reference vehicle speed, VF.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-213552 (JP, A) JP-A-53-100382 (JP, A) JP-A-1-306353 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B60T 8/58 B60T 8/66

Claims (2)

(57) [Claims] During normal driving, a reference vehicle speed is determined based on a third or fourth low-speed wheel speed from the high-speed side of each wheel speed. Occurs, the reference vehicle speed is determined based on the first or second high-speed wheel speed from the high-speed side of the wheel speeds. Thereafter, anti-skid control is performed in accordance with the reference vehicle speed. In the anti-skid brake control method for controlling the increase and decrease of the brake pressure in the wheels, thereby preventing the lock of the wheels, when the anti-skid control is started, the wheel speed of the drive wheels and the non-drive wheels A deviation from the wheel speed is obtained, and when the deviation is equal to or greater than a predetermined value, an anti-skid control is performed by obtaining a reference vehicle speed based on the low-speed wheel speed. Ddobureki control method. 2. The anti-skid control according to claim 1, wherein when the reference vehicle speed is determined based on the low-speed wheel speed, the reference vehicle speed is determined based on the high-speed wheel speed when the deviation is eliminated. The anti-skid brake control method according to claim 1.