JP2676726B2 - Anti-skid control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid control device capable of improving braking performance, and particularly capable of coping with a difference in road surface condition between left and right wheels. (Prior Art) When a running vehicle is suddenly braked, a frictional force between a road surface and a tire is limited, so that a wheel is locked and a skid phenomenon occurs. As a means for preventing this skid phenomenon, an anti-skid device is known in which the slip ratio of the wheels with respect to the road surface is controlled to control the braking force so that the slip ratio between the road surface and the wheels always has a predetermined value. In a vehicle equipped with this device, when only one wheel passes through a low μ road such as an icy road surface, if the left and right wheels are controlled to have the same slip ratio, the braking force on the high μ road side becomes larger than that on the low μ road side. As a result, the vehicle may spin. As a means for solving this, for example, a high μ is adjusted in accordance with a braking hydraulic pressure that does not cause a lock on the wheels on the low μ road side.
Some control the braking hydraulic pressure on the road side in the same way. Another known technique is to set the braking force of the left and right wheels to the same low value in the initial stage of slip control, and monotonically increase only the braking hydraulic pressure of the wheels on the high μ road side with the passage of time. (JP-A-58-164460). (Problems to be solved by the invention) However, in the former technique of setting the braking hydraulic pressures of the left and right wheels to be the same, the braking distance is sacrificed in accordance with the braking force on the low μ road so that the braking distance is reduced. There is a problem that it becomes long. On the other hand, in the latter technique of increasing only the braking hydraulic pressure of one wheel, a large difference occurs in the left and right braking forces as the braking hydraulic pressure difference increases, and a yaw moment (rotational force) acts on the vehicle. Therefore, in order to perform straight braking, it is necessary to turn the steering wheel to raise the cornering force, which makes it difficult to operate the steering wheel. The present invention has been made in view of the above problems, and an object of the present invention is to provide an anti-skid control device that can improve braking performance and can cope with a difference in road surface condition between left and right wheels. (Means for Solving Problems) In order to achieve the above object, the first invention detects and detects the rotation speeds of the first and second wheels as shown in FIG. 1 (a). A vehicle speed detecting means for outputting a signal, first and second brake devices to which brake fluid pressures for generating braking forces are supplied to the respective wheels, and brake fluid pressures applied to the respective brake devices are increased. A target for setting a target brake hydraulic pressure in each of the brake devices based on a pressure increase / decrease control means for independently increasing / decreasing pressure control by a predetermined duty control of pressure control and hydraulic pressure control, and a detection signal from the vehicle speed detection means. Brake fluid pressure setting control means, first estimating means for estimating the brake fluid pressure applied to each of the brake devices, and based on the brake fluid pressure estimated by the first estimating means, after a predetermined time, Note Second estimating means for estimating a maximum estimated brake fluid pressure and a minimum estimated brake fluid pressure that can be applied to each brake device, and a maximum estimated brake fluid pressure and a minimum estimated brake fluid pressure in each brake device, The target brake hydraulic pressure is compared, and based on the comparison result, the duty ratio of the pressure increase / decrease control executed by the pressure increase / decrease control means for each of the brake devices is determined, and the first and second brake devices are determined. The gist is an anti-skid control device that includes a determining unit that limits the brake fluid pressure difference according to the above. The second invention, as shown in FIG. 1 (b), detects at least the rotational speeds of the left and right wheels and outputs a detection signal, and the left and right wheels are independently controlled. Brake devices for the left and right wheels to which brake fluid pressure for generating power is supplied, and brake fluid pressures applied to the brake devices for the left and right wheels are respectively controlled by predetermined duty control of pressure increase control and pressure reduction control. A pressure increasing / decreasing control means for independently increasing / decreasing pressure control, and a first target brake hydraulic pressure setting control means for setting a first target brake hydraulic pressure in the brake device for the left wheel based on a detection signal from the vehicle speed detecting means. And second target brake hydraulic pressure setting control means for setting a second target brake hydraulic pressure in the brake device for the right wheel based on a detection signal from the vehicle speed detection means. A correction unit that corrects the first and second target brake hydraulic pressures based on the differential pressure between the first target brake hydraulic pressure and the second target brake hydraulic pressure, and a correction device that is added to the left wheel braking device. First current brake hydraulic pressure estimating means for estimating the brake hydraulic pressure being applied, second current brake hydraulic pressure estimating means for estimating the brake hydraulic pressure applied to the brake device for the right wheel, and the first First maximum / minimum estimating means for estimating a maximum estimated brake hydraulic pressure and a minimum estimated brake hydraulic pressure applied to the brake device for the left wheel after a predetermined time, based on the brake hydraulic pressure estimated by the present brake hydraulic pressure estimating means. Based on the brake fluid pressure estimated by the second current brake fluid pressure estimating means, the maximum estimated brake fluid pressure and the minimum estimated brake fluid pressure applied to the right wheel braking device after a predetermined time. Second maximum / minimum estimating means for estimating the brake hydraulic pressure; maximum estimated brake hydraulic pressure and minimum estimated brake hydraulic pressure estimated by the first maximum / minimum estimating means; and the first target brake hydraulic pressure. Based on the comparison result, and is estimated by the first determination means for determining the duty ratio of the pressure increase / decrease control executed by the pressure increase / decrease control means for the left wheel and the second maximum / minimum estimation means. The maximum estimated brake fluid pressure and the minimum estimated brake fluid pressure are compared with the second target brake fluid pressure, and based on the comparison result, the pressure increase / decrease control means executes the pressure increase / decrease control for the right wheel. The gist is an anti-skid control device provided with a second determining means for determining the duty ratio of. (Operation) In the first invention, the determination of the duty ratio of the brake hydraulic pressure for the first and second brake devices is performed for a predetermined time with respect to the brake hydraulic pressure estimated from the past control state of the brake hydraulic pressure. The maximum brake fluid pressure (maximum estimated brake fluid pressure) that can be adjusted by the pressure increase control of the pressure increase / decrease control later (for example, after the processing of one routine) and the minimum brake that can be adjusted by the pressure decrease control of the pressure increase / decrease control after a predetermined time. Since the hydraulic pressure (minimum estimated brake hydraulic pressure) and the target brake hydraulic pressure are used, the brake hydraulic pressure should be adjusted early in accordance with the target brake hydraulic pressure by comparing with a constant duty ratio. You can Further, by determining the duty ratio in this way and limiting the difference between the brake fluid pressures applied to the first and second brake devices, a pressure increase gradient (amount of pressure increase per unit time) and a pressure increase gradient of the brake fluid pressure can be obtained. (Amount of pressure increase per unit time)
Since the value can be set according to the target brake fluid pressure,
It is possible to suppress an increase in pressure that tends to cause the wheels to slip excessively. As a result, the brake fluid pressure control can be executed in accordance with the μ peak, so that the braking performance can be improved. In the second aspect of the invention, even if the road surface conditions of the left and right wheels are different, the target hydraulic pressure is corrected based on the target brake hydraulic pressure difference between the left and right wheels, so that the brake hydraulic pressure can be controlled in consideration of the cornering force and the like. Therefore, suitable yaw control can be realized. Then, at this time, the target brake fluid pressures of the left and right wheels are compared with the maximum and minimum estimated brake fluid pressures after a predetermined time to determine the duty ratio of the pressure increase / decrease control. In the brake control according to the above, the brake fluid pressure can be controlled only by the pressure increase control and the pressure decrease control. Further, by executing the duty ratio control based on the target brake hydraulic pressure and the maximum and minimum estimated brake hydraulic pressures, the actual brake hydraulic pressure that changes exponentially can be brought closer to the target brake hydraulic pressure. be able to. Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a configuration diagram schematically showing the overall configuration of an anti-skid control device equipped in a front-wheel drive vehicle. In FIG. 2, 1 to 4 represent wheels of the vehicle,
1 is a right front wheel, 2 is a left front wheel, 3 is a right rear wheel, and 4 is a left rear wheel. 5 to 8 respectively detect wheel speeds and detect signals
An electromagnetic pickup type or photoelectric conversion type wheel speed sensor that outputs 5a to 8a, of which 5 is a right front wheel speed sensor that is mounted near the right front wheel 1 and that generates a signal in response to the rotation of the right front wheel 1. , 6 are left front wheel speed sensors that are mounted near the left front wheel 2 and generate a signal in response to the rotation of the left front wheel 2, and 7 and 8 are wheel speeds that are mounted on the right rear wheel 3 and the left rear wheel, which are idler wheels. It is a sensor. Reference numerals 9 to 12 are wheel cylinders constituting a hydraulic brake device. The wheel cylinder 9 is on the right front wheel 1, the wheel cylinder 1 is on the left front wheel 2, the wheel cylinder 11 is on the right rear wheel 3, and the wheel cylinder 12 is on the left rear. Each is provided on the wheel 4. 13 is a brake pedal, 14 is a stop switch for detecting braking or non-braking according to the state of the brake pedal 13, 15 is a master cylinder that generates brake hydraulic pressure when the brake pedal 13 is depressed, and 17 is a master cylinder. Cylinder
It is an actuator that adjusts the hydraulic pressure from 15 according to the output from an electronic control circuit 18 described later and sends the braking hydraulic pressure to the wheel cylinders 9 to 12. The actuator 17 is configured as shown in FIG.
That is, the master cylinder 15 is connected to the wheel cylinders 9 to 12 via the check valves 19a to 19d and the conduits 20a to 20d, respectively. Two-position electromagnetic switching valves 24a, 24b are provided in the conduits 22a, 22b between the master cylinder 15 and the wheel cylinders 9-12. Further, the wheel cylinders 9 to 12 have hydraulic pumps 31a,
The hydraulic pressure from 31b is applied to the check valves 35a to 35d, the 2-position solenoid switching valve 38a to
It is configured to be supplied via 38d. In order to make the operation of the following configuration easy to understand, description will be made with reference to the schematic configuration diagram of FIG. 4 and the operation diagram of FIG. Now, when the driver depresses the brake 13, the braking hydraulic pressure of the master cylinder 15 increases. In this case, since it is before the anti-skid control, the two-position electromagnetic switching valves 24a, 38a,
The drive signals 18a to 18d to the 38d and the motor 30 are logic 0, that is, the electromagnetic switching valves 24a, 38a, 38d are held in the state of FIG. 4, and the motor 30 is also in the stopped state to drive the hydraulic pump 31b. do not do. Therefore, master cylinder 1
The braking hydraulic pressure of 5 is directly applied to the wheel cylinders 9 and 12 to generate braking torque. At this time, the hydraulic pressure of the master cylinder 15 does not reversely flow through the solenoid valves 38a and 38d and is applied to the hydraulic pump 31b. Then, when the anti-skid control is started by the judgment of the electronic control circuit 18 based on the detection signals from the vehicle speed sensors 5-8, the drive signals 18a-18d are output from the electronic control circuit 18 to the logic 1, that is, the electromagnetic signals. While switching the valves 24a, 38a, 38d, the motor 30 is driven to supply the braking hydraulic pressure from the hydraulic pump 31b. That is, by switching the solenoid valve 24a, the master cylinder 15 and the wheel cylinders 9, 12 are shut off, and by switching the solenoid valves 38a, 38d,
The braking hydraulic pressure is controlled by reducing or increasing the hydraulic pressure of the wheel cylinders 9 and 12. Then, the increase / decrease control of the braking hydraulic pressure is performed by the duty control, so that the hydraulic pressure changes as shown in FIG. Here, the characteristic line A in FIG. 5 shows the actual braking hydraulic pressure value of the wheel cylinder, and the characteristic line B shows the calculated braking hydraulic pressure value inside the computer. In the figure, the duty control is performed at a constant time T (for example, 32 msec) by variably controlling the time d0, d1, ... For increasing the hydraulic pressure. Therefore, if the time d1, d2, ... Is set to be long, the pressure can be increased, and if it is set to be short, the pressure can be decreased. In this control, the pressure increase shows a substantially constant gradient due to the characteristics of the hydraulic pump, while the pressure reduction is determined by the squeezing and oil viscosity, and exhibits an exponential function of the pressure reduction. As can be seen from the figure, the difference between the braking hydraulic pressure value Px0 inside the computer, which is set to the maximum hydraulic pressure value of the hydraulic pump as an initial value, and the actual braking hydraulic pressure value Px0 ′ gradually decreases, and the braking pressure inside the computer decreases. Since the hydraulic pressure converges to almost the same value as the actual braking hydraulic pressure value, it is possible to detect the braking hydraulic pressure value without providing a sensor on the wheel cylinder. This is for the following reason. That is, if both pressure reduction characteristics are linear and decrease at the same rate, the pressure difference between the two is constant, the error between the two is not narrowed, and the hydraulic pressure value in the computer does not approach the actual braking hydraulic pressure value. However, due to the characteristic of the exponential function, the rate of decrease of the hydraulic pressure value increases as the hydraulic pressure value increases, so even if the calculated hydraulic pressure inside the computer is set to a large value, it decreases exponentially and both This is because the hydraulic pressure values of 1 and 2 will approach each other in a short time. The hydraulic pressures of the left and right wheel cylinders are controlled by the above hydraulic device.Furthermore, the braking hydraulic pressures of the left and right wheels are based on the following principle in order to prevent the vehicle from skidding when the road surface condition μ is different. Braking hydraulic pressure is controlled. That is, as shown in FIG. 6, when the braking forces of the left and right front wheels and the left and right rear wheels are FXFL, FXFR, FXRL, and FXRR, respectively, and the angle with respect to the center of gravity G is θ, the rotational moment Mx due to the braking force is MX = { FXFL-FXFR) l1 + (FXRL-FXRR) l2} SINθ (1) On the other hand, if the cornering forces of the left and right front wheels are FYFL, FYFR, FXRL, FXRR, the rotational moment MY due to the cornering force is expressed by MY = {FYFL-FYFR) l1 + (FXRL + FXRR) l2} COSθ (2) . Therefore, the yaw moment M, which is a force for rotating the vehicle, is obtained from the difference between the rotation moment MX caused by the braking force and the rotation moment MY caused by the cornering force MY.
Is calculated from (1)-(2), and is rearranged into the moment between the front wheel side and the rear wheel side, the following equation (3) is obtained. M = MX-MY = {(FXFL-FXFR) l1 SINθ- {FYFL-FYFR) l1}
COSθ + {FXRL-FXRR) l2 SINθ- (FYRL + FYRR) l2 COS
θ} (3) From this equation (3), in order to prevent the vehicle from rotating, the yaw moment due to the braking force is expressed by the following equation so that it becomes the maximum cornering force at the steering angle that enables straight-ahead braking. It suffices to set the braking force on the front wheel side in (4) and on the rear wheel side in equation (5). FXFL-FXFR = (FYFL + FYFR) l1 COSθ / SINθ (4) FXRL-FXRR = (FYRL + FYRR) l2 COSθ / SINθ (5) Here, the front and rear wheels are separated by steering on the front wheel side. This is because it was taken into consideration that the cornering force is increased by cutting. The concrete control using the equations (4) and (5) is that the braking force, the braking torque, and the braking oil pressure value increase substantially proportionally up to the slip ratio Sa as shown in FIG. have. Further, as shown in FIG. 8, considering that the cornering force varies depending on the steering angle, the slip angle, the road surface condition μ and the braking force FX, the differential pressures K1 and K2 of the left and right braking hydraulic pressures are shown in FIG. Can be set to a value as shown in, for example, the following equations (7) and (8). | PFR-PFL | <K1 ( = 40kg / cm 2) ... (7) | PRR-PRL | <K2 (= 5kg / cm 2) ... (8) Next, the flowchart of FIG. 10 for executing the control described above Will be explained. This flow chart is performed at regular intervals, for example, every 32 ms. The processing operation for one cycle will be sequentially described below. First, in step 100, the wheel speed VW is read from each wheel sensor 5-9, the vehicle speed VB and the wheel acceleration dVW are calculated in step 110 based on the wheel speed VW, and each wheel is calculated by the following equation. Parameter WP is calculated. WP = K1 * (VW-K2 * VB) + K3 (dVW-dVB) (9) (K1, K2, K3 are constants) Next, at step 120, this wheel parameter WP and the following equation (11) are shown. Using the hydraulic parameter PM, the following equation (1
The target oil pressure Py is calculated for each of the four wheels by 2). PM = PM + K4 * WP (11) Py = PM + K5 * WP (12) (K1 and K2 are constants) Next, in step 130, the left front wheel and the right front wheel, and the left rear wheel and the right rear wheel are wheeled. After calculating the difference between the target hydraulic pressures to be applied, it is determined in step 140 whether the difference between the target hydraulic pressures is within a predetermined value. If it is determined in step 140 that the pressure is within the predetermined range, the process proceeds to step 150, and the respective target hydraulic pressures are set as they are. On the other hand, if it is determined that the target oil pressure is not within the predetermined value, that is, because the road surface μs of the left and right wheels are different, the target hydraulic pressure obtained by the calculation becomes equal to or higher than the predetermined value. Set the calculated value as the hydraulic pressure as it is, and proceed to Step 17
At 0, the target hydraulic pressure on the high μ road side is set to a value obtained by adding a predetermined value to the target hydraulic pressure on the low μ road side. That is, the target hydraulic pressure on the high μ side is limited by the guard. The target hydraulic pressure set in step 150 or steps 160 and 170 is duty controlled in step 190 and below. That is, in step 190, PMAX is obtained from the current estimated hydraulic pressure value Px. PMAX is 100% duty, that is,
The estimated hydraulic pressure value that is expected to be reached at the end point of the cycle when a command signal consisting only of the pressure increase command portion is output to the two-position solenoid valve, and PMIN is a duty ratio 0%, that is, a command signal consisting only of the pressure reduction command portion. 2 position solenoid switching valves 38a-3
This is the estimated hydraulic pressure value that is expected to be reached at the end of the cycle when output to 8d. Next, at step 200, the target hydraulic pressure values PMAX, PMIN
Are compared. If Py ≦ PMIN, in step 210 the duty ratio D
Is set to 0%, that is, the duty ratio D for creating a command signal consisting only of the pressure reduction command part, and PMIN is set to Px,
That is, the next target Py is set (step 220). On the other hand, when Py ≧ PMAX, in step 230, the duty D is set to 100%, that is, the duty ratio for creating the command signal consisting of only the pressure increase command component, and PMAX is set to PMAX.
Let x (step 240). In the case of PMIN <Py <PMAX, the duty ratio D is obtained from the map of FIG. 11 showing the relationship between Px and Py (addition of interpolation calculation if necessary) in step 250, and step 260. Let Py be the Py set in. Note that, here, the arithmetic expression is represented by the following expression instead of the map. Py = (Px + 0.344) * 0.5EXP [-0.0021 (32-d)] (12) In this equation, d is a parameter representing the pressure increasing time in one cycle of 32 ms. An exciting current pulse based on the duty ratio D set in steps 220, 240, and 260 is output to the two-position electromagnetic switching valve (step 270). By repeating this process, anti-skid control is performed, which is shown in a time chart in FIG. In the figure, after the brake is applied (t0) and the pressure is reduced (t1), the left and right wheels are independently duty controlled so that the braking hydraulic pressure does not differ by more than a predetermined hydraulic pressure. It can be seen that the hydraulic pressure parameter of is different at the initial stage of braking, but shows a value that coincides with the actual braking hydraulic pressure over time. As described above, in this embodiment, the braking performance can be improved by performing the above-described processing, and
In particular, it is possible to preferably deal with the difference in road surface condition between the left and right wheels. In other words, even if the road surface conditions on the left and right are different, the yaw moment generated by the difference between the braking force by the brake on the low-friction road surface and the braking force by the brake on the high-friction road surface is smaller than the value that can be taken by the cornering force. Therefore, the straight braking of the vehicle becomes possible with a large braking force. In the above embodiment, the control is performed in the region where the braking force is 20% or less of the slip ratio and the braking force is proportional to the slip ratio, but it is possible to perform the following processing as a means for accurately controlling the non-proportional region as well. Is. That is, if the braking force is μN and PB is the brake oil pressure, then μN = K1PB + KdVw is expressed. By correcting the difference, the slip control can be performed in a wide range. In addition, in the above-described embodiment, the calculation processing is executed at a cycle of 32 msec, but high-speed calculation and slip ratio calculation are performed.
It may be executed at a cycle of 8 msec, and the calculation of the duty drive control of the actuator may be executed at a cycle of 32 mesc. (Effects of the Invention) As described above, according to the first invention, the brake fluid pressure can be adjusted earlier according to the target brake fluid pressure, as compared with the case where the duty ratio is constant. Also,
By thus determining the duty ratio and limiting the brake fluid pressure difference applied to the first and second brake devices, the pressure increase gradient and the pressure reduction gradient of the brake fluid pressure can be set to values according to the target brake fluid pressure. Therefore, the braking performance can be improved. Further, according to the second aspect of the invention, even if the road surface conditions of the left and right wheels are different, it is possible to control the brake fluid pressure in consideration of the cornering force and the like, so that suitable yaw control can be realized. Further, at this time, in the brake control applied to the brake devices for the left and right wheels, the brake fluid pressure can be controlled only by the pressure increase control and the pressure decrease control. Further, the actual brake fluid pressure that changes exponentially can be brought closer to the target brake fluid pressure more quickly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a configuration of the present invention, (a) is a configuration diagram of the first invention, (b) is a configuration diagram of the second invention, and FIG. FIG. 3 is a configuration diagram of a vehicle equipped with an anti-skid control device according to an embodiment, FIG. 3 is a hydraulic circuit diagram of the anti-skid control device, FIG. 4 is a circuit diagram showing a main part of FIG. 3, and FIG. 6 is an explanatory view for explaining the state of the yaw moment applied to the vehicle, FIG. 7 is a graph showing the relationship between the slip ratio and the road surface friction coefficient, and FIG. 8 is for the cornering force and the braking force. Fig. 9 is a graph showing the relationship with the power, Fig. 9 is a graph showing the braking hydraulic pressure difference between the left and right wheels, Fig. 10 is a flowchart according to the same embodiment, Fig. 11 is a graph for performing duty control, and Fig. 12 is antiskid. It is a time chart which shows the state of control. 1-4 Wheels 5-8 Wheel speed sensors 9-12 Wheel cylinders 13 Brake pedals 15 Master cylinders 17 Actuators 18 Electronic control circuits 24a, 24b, 38a to 38d 2-position switching valve 30 …… Motor 31a, 31b …… Hydraulic pump

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor, Taichi Taiko               1-1 1-1 Showacho, Kariya City Nippondenso Co., Ltd.               In the formula company                (56) References JP-A-60-143169 (JP, A)                 JP 60-213550 (JP, A)                 JP 60-213554 (JP, A)

Claims (1)

(57) [Claims] Vehicle speed detecting means for detecting the rotation speeds of the first and second wheels and outputting a detection signal, and first and second brakes to which brake fluid pressures for generating braking forces are supplied to the respective wheels. A device, a brake fluid pressure applied to each of the brake devices, a pressure increase / decrease control means for independently increasing / decreasing pressure control by a predetermined duty control of pressure increase control and pressure decrease control, based on a detection signal from the vehicle speed detection means. , Target brake hydraulic pressure setting control means for setting a target brake hydraulic pressure in each of the brake devices, first estimating means for estimating the brake hydraulic pressure applied to each of the brake devices, and the first estimating means Based on the brake fluid pressure estimated by, the maximum estimated brake fluid pressure and the minimum estimated brake fluid pressure that can be applied to each of the braking devices after a predetermined time are estimated. The second estimating means compares the maximum estimated brake hydraulic pressure and the minimum estimated brake hydraulic pressure in each of the brake devices with the target brake hydraulic pressure, and increases or decreases with respect to each of the brake devices based on the comparison result. An anti-skid control device comprising: a determination unit that determines the duty ratio of the pressure increase / decrease control executed by the pressure control unit and limits the brake fluid pressure difference applied to the first and second brake devices. 2. Vehicle speed detection means for detecting at least the rotational speeds of the left and right wheels and outputting detection signals, and brakes for the left and right wheels to which brake fluid pressures are independently supplied to the left and right wheels to generate braking force. Device, the brake fluid pressure applied to the brake device for the left wheel and the right wheel, the pressure increase / decrease control means for independently increasing / decreasing pressure control by a predetermined duty control of pressure increase control and hydraulic pressure control, and from the vehicle speed detection means A first target brake fluid pressure setting control means for setting a first target brake fluid pressure in the left wheel braking device based on the detection signal; and a detection signal from the vehicle speed detection means for the right wheel. Second target brake hydraulic pressure setting control means for setting a second target brake hydraulic pressure in the braking device, and the first target brake hydraulic pressure and the second target brake hydraulic pressure. A correction unit that corrects the first and second target brake hydraulic pressures based on the differential pressure from the hydraulic pressure, and a first current brake that estimates the brake hydraulic pressure applied to the brake device for the left wheel. Hydraulic pressure estimating means, second current brake hydraulic pressure estimating means for estimating the brake hydraulic pressure applied to the brake device for the right wheel, and brake hydraulic fluid estimated by the first current brake hydraulic pressure estimating means Based on the pressure, a first maximum / minimum estimating means for estimating a maximum estimated brake fluid pressure and a minimum estimated brake fluid pressure applied to the left wheel braking device after a predetermined time, and estimated by the second current brake fluid pressure estimating means. Second maximum / minimum estimating means for estimating a maximum estimated brake fluid pressure and a minimum estimated brake fluid pressure applied to the braking device for the right wheel after a predetermined time based on the brake fluid pressure thus obtained; The maximum estimated brake fluid pressure and the minimum estimated brake fluid pressure estimated by the first maximum / minimum estimation means are compared with the first target brake fluid pressure, and the pressure increase / decrease control means is based on the comparison result. A first determining means for determining the duty ratio of the pressure increasing / decreasing control to be performed on the left wheel; a maximum estimated brake fluid pressure and a minimum estimated brake fluid pressure estimated by the second maximum / minimum estimating means; Second target brake fluid pressure, and based on the comparison result, second determining means for determining the duty ratio of the pressure increasing / decreasing control executed by the pressure increasing / decreasing control means for the right wheel. Anti-skid control device.