Vehicle braking control device, vehicle braking control method and computer program

Abstract

To provide an improved vehicle braking control device that can stabilize behavior of a vehicle body during anti-skid control.SOLUTION: A vehicle braking control device calculates a proportionality coefficient indicating a relation between friction coefficients and slip ratios of wheels which are determined based on tire force detected with a tire force sensor during anti-skid control; calculates a difference in the proportionality coefficient between respective left and right wheels of a front wheel and a rear wheel; and when a difference in the proportionality coefficients of at least either or both of the front wheel and the rear wheel is more than a predetermined threshold, deteriorates braking force of the wheel in which the proportionality coefficient is high, of the left and right wheels of the front wheel and the rear wheel in which the difference in the proportionality coefficient is more than the predetermined threshold, so as to keep a difference in front and rear force between the left and right wheels in a predetermined range.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle braking control device, a vehicle braking control method, and a computer program. [Background technology]

[0002] Anti-skid brake systems (hereinafter also referred to as "ABS") are known that prevent a vehicle from sliding due to wheel lock when braking. For example, when strong braking is applied under low-friction conditions where the coefficient of friction between the tires and the road surface is low, the ABS reduces braking force when it detects that the vehicle is sliding due to wheel lock, and then increases braking force again when the wheels start to rotate, repeating this process to ensure that each wheel exerts maximum braking force.

[0003] During anti-skid control by ABS, upper and lower limits are set for the tire slip ratio, and braking force is controlled so that the slip ratio falls within the upper and lower limits. Therefore, when the braking force is constant and the road surface changes from a low friction coefficient to a high friction coefficient, the slip ratio decreases, and anti-skid control intervenes, increasing the braking force to increase the slip ratio.

[0004] When braking the vehicle, if only one of the left and right wheels changes from a low friction state to a high friction state, the braking force of that wheel increases, creating a difference in braking force between the left and right wheels and generating a yaw moment on the vehicle. In a low friction state, unless the tire slip angle changes significantly, the force in the width direction of the tire (lateral force) does not increase, which can easily disrupt the behavior of the vehicle.

[0005] In response to this, Patent Document 1 discloses a technology that, when it is detected that one wheel has changed from a low-friction state for both left and right wheels to a high-friction state during braking, limits the increase in brake fluid pressure generated in the wheel cylinder of the wheel with high friction so that the deviation between the detected yaw rate and a set target yaw rate is equal to or less than a predetermined value. Specifically, the brake control device described in Patent Document 1 is configured to increase the wheel cylinder fluid pressure during ABS control pressure increase for the wheel with high friction at the maximum gradient when the yaw rate deviation is less than a predetermined value, and to keep it constant when the yaw rate deviation is equal to or greater than the predetermined value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-171294 Summary of the Invention [Problem to be solved by the invention]

[0007] However, instantaneous and accurate estimation of the road surface friction coefficient is technically difficult and not easy. Even if it were possible to instantaneously and accurately estimate the road surface friction coefficient using, for example, the tire force generated in the only tire that contacts the road surface or a detected value correlated with the tire force, the tire force cannot be reflected in the estimated value of the friction coefficient until after it has actually been generated, resulting in free running time.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide an improved vehicle braking control device, vehicle braking control method, and computer program that are capable of stabilizing the behavior of the vehicle body during anti-skid control. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, according to one aspect of the present disclosure, there is provided a brake control device for a vehicle that performs anti-skid control, comprising one or more processors and one or more memories communicably connected to the one or more processors, wherein the one or more processors perform the following operations: calculate a proportionality coefficient indicating the relationship between the friction coefficient and the slip ratio of each wheel, which is obtained based on tire forces detected by tire force sensors during the anti-skid control; calculate a difference between the proportionality coefficients of the left and right wheels for each of the front wheels and the rear wheels; and, when the difference between the proportionality coefficients of at least one or both of the front wheels and the rear wheels is equal to or greater than a predetermined threshold, reduce the braking force of the wheel with a higher proportionality coefficient of the front wheels and the rear wheels for which the difference between the proportionality coefficients is equal to or greater than the predetermined threshold, thereby keeping the difference in longitudinal forces of the left and right wheels within a predetermined range.

[0010] Furthermore, in order to solve the above-described problems, according to another aspect of the present disclosure, there is provided a vehicle braking control method in which a computer calculates a proportionality coefficient, which is a ratio between the slip rate and the longitudinal force of each wheel, based on the longitudinal force and slip rate of each wheel detected by a tire force sensor during anti-skid control; calculates a difference between the proportionality coefficients of the left and right wheels for each of the front wheels and the rear wheels; and, when the difference between the proportionality coefficients of at least one or both of the front wheels and the rear wheels is equal to or greater than a predetermined threshold, reduces the braking force of the wheel with a higher proportionality coefficient among the left and right wheels of the front wheels and the rear wheels for which the difference between the proportionality coefficients is equal to or greater than the predetermined threshold, thereby keeping the longitudinal forces of the left and right wheels within a predetermined range.

[0011] Furthermore, in order to solve the above-described problems, according to another aspect of the present disclosure, there is provided a computer program that causes a computer to execute the following operations: calculate a proportionality coefficient, which is the ratio between the slip rate and the longitudinal force of each wheel, based on the longitudinal force and slip rate of each wheel detected by a tire force sensor during anti-skid control; calculate a difference in the proportionality coefficient between the left and right wheels for each of the front wheels and the rear wheels; and, when the difference in the proportionality coefficient of at least one or both of the front wheels and the rear wheels is equal to or greater than a predetermined threshold, reduce the braking force of the wheel with the higher proportionality coefficient of the front wheels and the rear wheels for which the difference in the proportionality coefficient is equal to or greater than the predetermined threshold, thereby keeping the longitudinal forces of the left and right wheels within a predetermined range. [Effects of the Invention]

[0012] As described above, according to the present disclosure, the behavior of the vehicle body can be stabilized during anti-skid control. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating an example configuration of a vehicle equipped with a vehicle braking control device according to an embodiment of the present disclosure. [Figure 2] 2 is a block diagram showing an example of the configuration of a braking control device for a vehicle according to the embodiment; FIG. [Figure 3] FIG. 2 is an explanatory diagram showing an example of a friction coefficient curve showing the relationship between the friction coefficient and the slip ratio of a wheel. [Figure 4] 4 is a flowchart showing a routine of a processing operation by the braking control device for a vehicle according to the embodiment; [Figure 5] 4 is a flowchart showing a routine of a processing operation by the braking control device for a vehicle according to the embodiment; [Figure 6] 4 is a flowchart showing a routine of a vehicle body behavior stabilization process performed by the vehicle braking control device according to the embodiment; [Figure 7] 3 is an explanatory diagram showing the operation of the vehicle braking control device according to the embodiment; FIG. [Figure 8]10 is a flowchart showing a routine of a vehicle body behavior stabilization process performed by a braking control device for a vehicle according to another embodiment of the present disclosure. [Figure 9] FIG. 10 is an explanatory diagram showing a vehicle body behavior stabilization process performed by a vehicle braking control device according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0015] <1. Vehicle configuration> First, an example of the overall configuration of a vehicle equipped with a vehicle braking control device according to an embodiment of the present disclosure will be described.

[0016] FIG. 1 is a schematic diagram showing an example of the configuration of a vehicle 1. As shown in FIG. The vehicle 1 is configured as a four-wheel drive automobile in which drive torque output from a drive force source 2 that generates drive torque is transmitted to a left front wheel 5LF, a right front wheel 5RF, a left rear wheel 5LR, and a right rear wheel 5RR (hereinafter collectively referred to as "wheels 5" unless a distinction is required. The left front wheel 5LF and the right front wheel 5RF may be referred to as "front wheels 5F," and the left rear wheel 5LR and the right rear wheel 5RR may be referred to as "rear wheels 5R"). The drive force source 2 may be an internal combustion engine such as a gasoline engine or a diesel engine, a drive motor, or may be equipped with both an internal combustion engine and a drive motor.

[0017] The driving force source control device 21 includes a processor such as a CPU (Central Processing Unit) and controls the driving of the driving force source 2. The driving torque output from the driving force source 2 is distributed to the left and right front wheels 5F via the front wheel differential 3F and the left and right axles 4LF, 4RF. The driving torque is also distributed to the left and right front wheels 5F via a propeller shaft (not shown). The driving torque output from the driving force source 2 is also distributed to the left and right rear wheels 5R via a propeller shaft (not shown), the rear wheel differential 3R, and the left and right axles 4LR, 4RR.

[0018] Vehicle 1 may be a two-wheel drive vehicle that transmits drive torque to either the front or rear wheels. Vehicle 1 may also be an electric vehicle equipped with two drive motors, for example, a front-wheel drive motor and a rear-wheel drive motor, or an electric vehicle equipped with drive motors corresponding to each of the wheels 5. If vehicle 1 is an electric vehicle or hybrid electric vehicle, vehicle 1 is equipped with a secondary battery that stores power supplied to the drive motors, and a generator that generates power to charge the secondary battery.

[0019] The vehicle 1 also includes a hydraulic brake system that generates braking force on each wheel 5. The hydraulic brake system includes a master cylinder 6, wheel cylinders 7LF, 7RF, 7LR, and 7RR (hereinafter collectively referred to as "wheel cylinders 7" unless a distinction is required) provided on each wheel 5, and a hydraulic control unit 20. Brake fluid supplied from the master cylinder 6 in accordance with the amount of brake pedal operation by the driver is supplied to the wheel cylinders 7 of each wheel 5 via the hydraulic control unit 20, generating braking pressure on each wheel 5.

[0020] The hydraulic control unit 20 includes a motor pump and a plurality of control valves. The hydraulic control unit 20 is controlled by the brake control device 50 to increase and decrease the brake pressure for each wheel 5. If the vehicle 1 is an electric vehicle or a hybrid electric vehicle, the hydraulic brake system may be used in combination with regenerative braking using a drive motor.

[0021] Each wheel 5 is provided with a tire force sensor 8LF, 8RF, 8LR, 8RR (hereinafter collectively referred to as "tire force sensor 8" unless a distinction is particularly required) and a wheel speed sensor 9LF, 9RF, 9LR, 9RR (hereinafter collectively referred to as "wheel speed sensor 9" unless a distinction is particularly required).

[0022] The tire force sensor 8LF is provided, for example, on the left front axle 4LF at the connection between the left front axle 4LF and the left front wheel 5LF. The tire force sensor 8RF is provided, for example, on the right front axle 4RF at the connection between the right front axle 4RF and the right front wheel 5RF. The tire force sensor 8LR is provided, for example, on the left rear axle 4LR at the connection between the left rear axle 4LR and the left rear wheel 5LR. The tire force sensor 8RR is provided, for example, on the right rear axle 4RR at the connection between the right rear axle 4RR and the right rear wheel 5RR. The tire force sensors 8 are load sensors that detect the load applied to each wheel 5.

[0023] For example, the tire force sensor 8 may be a six-component force detector that detects loads (Fx, Fy, Fz) generated in each of the three axial directions of the wheel 5, namely the fore-and-aft direction (x-axis), width direction (y-axis), and height direction (z-axis), as well as moments (Mx, My, Mz) generated around each of the three axes. In this embodiment, the load generated in the fore-and-aft direction (x-axis direction) of the contact surface of the wheel 5 is referred to as the fore-and-aft force Fx, the load generated in the width direction (y-axis direction) is referred to as the lateral force Fy, and the load generated in the height direction (z-axis direction) is referred to as the ground reaction force Fz.

[0024] The wheel speed sensor 9 is provided on the axle 4 of each wheel 5 (front left axle 4LF, front right axle 4RF, rear left axle 4LR, and rear right axle 4RR) to detect the rotation speed of each wheel 5.

[0025] The vehicle 1 also includes a steering angle sensor 11, a brake sensor 13, and a yaw rate sensor 15. The steering angle sensor 11 is provided, for example, on a steering column and detects the rotation angle of the steering wheel. The brake sensor 13 is provided on a brake pedal or brake rod and detects the amount of brake pedal operation. The yaw rate sensor 15 is provided, for example, near the center of gravity of the vehicle body and detects the rotation angular velocity of the vehicle 1 around the z-axis.

[0026] The braking control device 50 includes one or more electronic control devices that control the braking of the vehicle 1. The braking control device 50 acquires detection information output from various sensors and executes control to stabilize vehicle behavior, including anti-skid control.

[0027] <2. Vehicle Braking Control Device> Next, the vehicle braking control device 50 according to this embodiment will be described in detail.

[0028] (2-1. Overall configuration of braking control device) The braking control device 50 functions as a device that controls the braking of the vehicle body by having one or more processors such as CPUs execute a computer program. The computer program is a computer program that causes the processor to execute the operations described below that should be performed by the braking control device 50. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 53 provided in the braking control device 50, or may be recorded on a recording medium built into the braking control device 50 or any recording medium that can be externally attached to the braking control device 50.

[0029] Recording media for recording computer programs include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs (Compact Disc Read Only Memory), DVDs (Digital Versatile Discs), and Blu-ray (registered trademark), magneto-optical media such as floptical disks, memory elements such as RAMs (Random Access Memory) and ROMs (Read Only Memory), flash memories such as USB (Universal Serial Bus) memories and SSDs (Solid State Drives), and other media capable of storing programs.

[0030] FIG. 2 is a block diagram showing an example of the configuration of the braking control device 50. As shown in FIG. The braking control device 50 is connected to a tire force sensor 8, a wheel speed sensor 9, a steering angle sensor 11, a brake sensor 13, and a yaw rate sensor 15 via a dedicated line or communication means such as a CAN (Controller Area Network) or a LIN (Local Inter Net). In addition, the braking control device 50 is connected to a hydraulic pressure control unit 20 and a driving force source control device 21 so as to be able to communicate with each other.

[0031] The braking control device 50 includes a processing unit 51 and a storage unit 53. The processing unit 51 is configured with one or more processors such as CPUs and various peripheral components. Part or all of the processing unit 51 may be configured with updatable firmware or the like, or may be a program module or the like that is executed by commands from the CPU or the like.

[0032] The storage unit 53 is configured with one or more storage elements such as RAM or ROM connected to the processing unit 51 so as to be able to communicate with it. However, the type and number of storage units 53 are not particularly limited. The storage unit 53 stores information such as computer programs executed by the processing unit 51, various parameters used in arithmetic processing, detection data, and arithmetic results. A part of the storage unit 53 is used as a work area for the processing unit 51.

[0033] (2-2. Functional configuration of the processing unit) Next, the configuration of the processing unit 51 of the braking control device 50 will be described. The processing unit 51 includes an acquisition unit 61, a running state calculation unit 63, an anti-skid control unit 65, a proportionality coefficient calculation unit 67, a target running state calculation unit 69, and a vehicle body behavior stabilization control unit 71. Each of these units is a function realized by the execution of a computer program by one or more processors. However, part of the acquisition unit 61, the running state calculation unit 63, the anti-skid control unit 65, the proportionality coefficient calculation unit 67, the target running state calculation unit 69, and the vehicle body behavior stabilization control unit 71 may be configured by hardware such as an analog circuit.

[0034] Below, the function of each part of the processing unit 51 will be briefly explained, and then the specific processing content of each part will be explained.

[0035] (Acquisition Department) The acquisition unit 61 acquires detection information output from various sensors. For example, the acquisition unit 61 acquires sensor signals output from the tire force sensor 8, the wheel speed sensor 9, the steering angle sensor 11, the brake sensor 13, and the yaw rate sensor 15 at a predetermined sampling period, and detects the six-component forces generated in each wheel 5, the rotational speed of each wheel 5, the steering angle, the amount of brake pedal operation, and the yaw rate (actual yaw rate) of the vehicle body.

[0036] (Driving condition calculation unit) The running condition calculation unit 63 calculates information about the running condition of the vehicle 1. For example, the running condition calculation unit 63 calculates a differential value of the rotational speed of each wheel 5 to calculate the rotational acceleration of each wheel 5 (hereinafter also referred to as "wheel acceleration"). The running condition calculation unit 63 also calculates the vehicle body speed based on the rotational speed of each wheel 5. The running condition calculation unit 63 also calculates the yaw moment of the vehicle body based on the longitudinal force Fx and lateral force Fy generated on each wheel 5, the toe angle θ of each wheel 5, the tread length, and the shortest distance from the center of gravity of the vehicle body to the axle, and calculates the angular acceleration of the vehicle body (hereinafter also referred to as "vehicle body angular acceleration") by dividing the yaw moment by the inertia of the vehicle body. The running condition calculation unit 63 also calculates the slip ratio of each wheel 5 based on the vehicle body speed and the wheel speed. The slip ratio of the wheel 5 is a state quantity that represents the degree of grip of the wheel 5 with respect to the road surface on which the vehicle is traveling.

[0037] Furthermore, the running condition calculation unit 63 estimates the road surface condition based on the friction coefficient of each wheel 5 determined based on the tire force detected by the tire force sensor 8 and the slip ratio calculated by the running condition calculation unit 63. The friction coefficient μ can be defined as a value (Fx / Fz) obtained by normalizing the longitudinal force Fx of each wheel 5 by the ground reaction force Fz.

[0038] Fig. 3 shows examples of friction coefficient curves for each road surface condition, which show the relationship between the friction coefficient μ of the wheel 5 and the slip ratio Sw. Fig. 3 shows friction coefficient curves for a dry paved road, a wet paved road, a dry gravel road, and a snowy road, but in addition to the road surface conditions shown, friction coefficient curves for other road surface conditions such as a dry concrete road surface, a wet concrete road surface, and an icy road surface may also be included. The friction coefficient μ of the wheel 5 for each road surface condition increases as the slip ratio Sw increases from zero, reaches a maximum value at a predetermined slip ratio Sw, and then decreases as the slip ratio Sw increases.

[0039] (Anti-skid control unit) The anti-skid control unit 65 executes a process to prevent each wheel 5 from locking when the brake pedal is depressed strongly. For example, the anti-skid control unit 65 executes anti-skid control based on the wheel acceleration, the slip ratio of the wheel 5, the amount of brake pedal operation, the required deceleration, the vehicle speed, the yaw rate, the steering angle, and the vehicle lateral acceleration. Note that the process of anti-skid control is a conventionally known method and is not limited to the above example.

[0040] (Proportional coefficient calculation section) The proportionality coefficient calculation unit 67 calculates a proportionality coefficient K that indicates the relationship between the friction coefficient of each wheel 5 determined based on the tire force detected by the tire force sensor 8 and the slip ratio calculated by the running condition calculation unit 63. As described above, the friction coefficient μ can be defined as a value (Fx / Fz) obtained by normalizing the longitudinal force Fx of each wheel 5 with the ground reaction force Fz. Therefore, the relationship between the friction coefficient μ of each wheel 5 and the slip ratio Sw is expressed as Fx / Fz=K×Sw. The proportionality coefficient calculation unit 67 calculates the proportionality coefficient K [=(Fx / Fz) / Sw] of each wheel 5 based on the longitudinal force Fx and the ground reaction force Fz detected based on the sensor signal of the tire force sensor 8 and the slip ratio Sw calculated by the running condition calculation unit 63.

[0041] (Target driving state calculation unit) The target driving state calculation unit 69 sets a target yaw rate and a target vehicle body angular acceleration while anti-skid control is being executed. For example, the target driving state calculation unit 69 calculates the target yaw rate using a predetermined stabilization coefficient based on the steering angle and vehicle body speed. The target yaw rate represents a target value for the yaw rate of the vehicle body determined from the driving operation state of the driver of the vehicle 1. In addition, the target driving state calculation unit 69 calculates the target vehicle body angular velocity based on the steering angle, vehicle body weight, cornering stiffness, and the shortest distance from the center of gravity of the vehicle body to the axle.

[0042] (Vehicle behavior stabilization control unit) The vehicle body behavior stabilization control unit 71 adjusts the braking force generated in each wheel 5 and executes processing to stabilize the traveling state of the vehicle 1. For example, the vehicle body behavior stabilization control unit 71 calculates the differences ΔK_f, ΔK_r in the proportionality coefficients K of the left and right wheels 5 for each of the front wheels 5F and the rear wheels 5R. Furthermore, when the difference ΔK (ΔK_f, ΔK_r) in the proportionality coefficients K of at least one or both of the front wheels 5F and the rear wheels 5R is equal to or greater than a predetermined threshold ΔK_thr, the vehicle body behavior stabilization control unit 71 reduces the braking force of the wheel 5 on the side with a higher proportionality coefficient K for the front wheels 5F and the rear wheels 5R whose difference ΔK in the proportionality coefficients K is equal to or greater than the predetermined threshold, thereby keeping the difference ΔFx in the longitudinal forces Fx of the left and right wheels 5 within a predetermined range.

[0043] <3. Operation of braking control device> Next, an example of the processing operation by the processing unit 51 of the braking control device 50 according to this embodiment will be specifically described with reference to a flowchart. To facilitate understanding of the description, the description will be given taking an example in which the vehicle is traveling straight ahead.

[0044] 4 and 5 show a main routine of the processing operation by the braking control device 50. FIG. When the processing unit 51 detects that the ignition switch of the vehicle 1 has been turned on (step S11), the acquisition unit 61 of the processing unit 51 starts a process of acquiring various detection information based on sensor signals output from the various sensors (step S13). For example, the acquisition unit 61 acquires sensor signals output from the tire force sensor 8, the wheel speed sensor 9, the steering angle sensor 11, the brake sensor 13, and the yaw rate sensor 15 at a predetermined sampling period, and detects the six-component forces (Fx, Fy, Fz, Mx, My, Mz) generated in each wheel 5, the rotational speed Vw (Vw_LF, Vw_RF, Vw_LR, Vw_RR) of each wheel 5, the steering angle θs, the brake pedal operation amount Ba, and the yaw rate (actual yaw rate) Yr of the vehicle body.

[0045] Next, the running condition calculation unit 63 of the processing unit 51 calculates the wheel acceleration dVw (dVw_LF, dVw_RF, dVw_LR, dVw_RR) of each wheel 5 based on the rotational speed Vw of each wheel 5 (step S15). For example, the running condition calculation unit 63 differentiates the rotational speed Vw of each wheel 5 to calculate the wheel acceleration dVw of each wheel 5.

[0046] Next, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the rotational speed Vw of each wheel 5 (step S17). For example, when no braking force is being applied to each wheel 5, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the slowest rotational speed among the rotational speeds Vw of each wheel 5. Furthermore, when a braking force is being applied to each wheel 5, the traveling condition calculation unit 63 calculates the vehicle body speed Vx based on the fastest rotational speed among the rotational speeds Vw of each wheel 5. When calculating the vehicle body speed Vx, a limit may be placed on the amount of change over time in the vehicle body speed Vx. For example, an upper limit value for the increase gradient of the vehicle body speed Vx and a lower limit value for the decrease gradient of the vehicle body speed Vx may be set, and the change in the vehicle body speed Vx may be restricted by the upper and lower limit values.

[0047] The method for calculating the vehicle speed Vx is not limited to the above example, and any calculation method, including conventionally known methods, may be used.

[0048] Next, the running condition calculation unit 63 calculates a slip ratio that indicates the degree of grip of the wheels 5 with respect to the road surface based on the vehicle body speed Vx and the wheel rotation speed Vw (step S19). For example, the running condition calculation unit 63 calculates a deceleration slip speed hV (hV=Vx-Vw), which is the deviation between the vehicle body speed Vx and the rotation speed Vw of each wheel 5, and calculates a slip ratio Sw (Sw=hV / Vx) by non-dimensionalizing the calculated deceleration slip speed hV using the vehicle body speed Vx.

[0049] Next, the anti-skid control unit 65 determines whether or not to execute anti-skid control based on information about the traveling state of the vehicle 1 (step S21). For example, the anti-skid control unit 65 determines whether or not the vehicle 1 is braking based on at least one of the brake pedal operation amount Ba and the required deceleration Gr. The required deceleration Gr is a deceleration command value from automatic driving control or other driving assistance functions, and is obtained from the control device that manages each function. Furthermore, when at least one of the following conditions is met and it is determined that the vehicle 1 is braking: the brake pedal operation amount Ba is equal to or greater than a predetermined value, the operation signal St is in an ON state, and the required deceleration Gr is equal to or greater than a predetermined value, the anti-skid control unit 65 permits the execution of anti-skid control for each wheel 5.

[0050] If the anti-skid control unit 65 does not determine to execute anti-skid control (S21 / No), the process returns to step S15, and calculation of the running state of the vehicle 1 and determination of whether or not to execute anti-skid control are repeated.

[0051] On the other hand, when the anti-skid control unit 65 determines that anti-skid control is to be performed (S21 / Yes), it repeats the process of reducing the brake pressure when the rotation speed Vw of the wheel 5 for which anti-skid control is to be performed falls to a predetermined lower limit, and increasing the brake pressure when the rotation speed Vw of the wheel 5 rises to a predetermined upper limit, thereby controlling the brake pressure within the range between the upper limit and the lower limit.

[0052] Next, the proportionality coefficient calculation unit 67 calculates a proportionality coefficient K that indicates the relationship between the friction coefficient of each wheel 5 and the slip ratio Sw, based on the longitudinal force Fx generated on each wheel 5 and the slip ratio Sw of each wheel 5 (step S23). In this embodiment, the proportionality coefficient calculation unit 67 calculates the proportionality coefficient K using the following equation (1), based on the longitudinal force Fx generated on each wheel 5, the ground reaction force Fz, and the slip ratio Sw. Proportional coefficient K = (Fx / Fz) / Sw …(1)

[0053] Next, the vehicle body behavior stabilization control unit 71 calculates the difference ΔK in the proportionality coefficients K of the left and right wheels for each of the front wheels and rear wheels (step S25). The vehicle body behavior stabilization control unit 71 calculates the difference ΔK_f in the proportionality coefficients of the left and right front wheels 5LF, 5RF and the difference ΔK_r in the proportionality coefficients of the left and right rear wheels 5LR, 5RR. The difference ΔK in the proportionality coefficients indicates the absolute value of the difference in the proportionality coefficients K of the left and right wheels.

[0054] Next, the vehicle body behavior stabilization control unit 71 determines whether the difference ΔK between the left and right proportionality coefficients K for at least one of the front wheels 5F and the rear wheels 5R is equal to or greater than a predetermined threshold ΔK_thr (step S27). The predetermined threshold ΔK_thr is set in advance as a value based on deceleration in order to prevent the vehicle 1 from spinning or otherwise becoming unstable in vehicle body behavior. When the tire force is close to its limit, the longitudinal force Fx becomes dominant and the amount of lateral force Fy that can be generated decreases. Therefore, for example, by making the threshold ΔK_thr smaller as the deceleration increases, the difference between the left and right longitudinal forces Fx decreases, and the amount of lateral force Fy that can be generated can be suppressed. The predetermined threshold ΔK_thr may be a variable value that varies depending on the vehicle body speed Vx.

[0055] If the vehicle body behavior stabilization control unit 71 does not determine that the difference ΔK in the proportionality coefficients K between the left and right wheels for at least one of the front wheels 5F and the rear wheels 5R is greater than or equal to a predetermined threshold value ΔK_thr (S27 / No), it proceeds to step S37 without performing vehicle body behavior stabilization processing.

[0056] On the other hand, if the vehicle body behavior stabilization control unit 71 determines that the difference ΔK between the left and right proportional coefficients K for at least one of the front wheels 5F and the rear wheels 5R is greater than or equal to a predetermined threshold value ΔK_thr (S27 / Yes), it executes vehicle body behavior stabilization processing to stabilize the driving state (step S29).

[0057] FIG. 6 shows a flowchart of the vehicle body behavior stabilization process according to this embodiment. First, the vehicle body behavior stabilization control unit 71 determines whether the difference ΔK between the left and right proportionality coefficients K for either the front wheels 5F or the rear wheels 5R is equal to or greater than a predetermined threshold value ΔK_thr (step S41). If the vehicle body behavior stabilization control unit 71 determines that the difference ΔK between the left and right proportionality coefficients K for either the front wheels 5F or the rear wheels 5R is equal to or greater than the predetermined threshold value ΔK_thr (S41 / Yes), the vehicle body behavior stabilization control unit 71 determines whether there is a margin of error in the braking force of the front wheels 5F or the rear wheels 5R for which the difference ΔK between the left and right proportionality coefficients K is less than the predetermined threshold value ΔK_thr (step S43). For example, if the vehicle body behavior stabilization control unit 71 determines that the difference ΔK between the left and right proportionality coefficients K for the front wheels 5F is equal to or greater than the predetermined threshold value K_thr, the vehicle body behavior stabilization control unit 71 determines whether there is a margin of error in the braking force of the rear wheels 5R.

[0058] A state in which there is a margin of braking force refers to a state in which the slip ratio Sw of the front wheels 5F or the rear wheels 5R, for which the difference ΔK between the left and right proportionality coefficients K is less than a predetermined threshold ΔK_thr, is smaller than the slip ratio Sw_max at which the friction coefficient μ reaches its maximum value on the friction coefficient curve ( FIG. 3 ) corresponding to the road surface conditions during travel. The proportion of braking force to be generated on the front wheels 5F and the rear wheels 5R when decelerating the vehicle 1 is determined based on a preset map. To stabilize vehicle behavior, not all of the longitudinal force Fx that can be generated when generating braking force on the wheels 5 is used, but a margin is provided to leave enough space for the lateral force Fy to be generated. Therefore, the vehicle behavior stabilization control unit 71 determines whether the slip ratio Sw of the front wheels 5F or the rear wheels 5R, for which the difference ΔK between the left and right proportionality coefficients K is less than a predetermined threshold ΔK_thr, is smaller than the slip ratio Sw_max at which the friction coefficient μ reaches its maximum value on the friction coefficient curve corresponding to the road surface conditions estimated by the traveling condition calculation unit 63.

[0059] When the vehicle body behavior stabilization control unit 71 determines that there is a margin of braking force on the front wheels 5F or the rear wheels 5R where the difference ΔK between the left and right proportionality coefficients K is less than a predetermined threshold ΔK_thr (S43 / Yes), it shifts the allocation of braking force to the front wheels 5F or the rear wheels 5R where the difference ΔK between the left and right proportionality coefficients K is less than the predetermined threshold ΔK_thr (step S45). For example, when the vehicle body behavior stabilization control unit 71 determines that the difference ΔK between the left and right proportionality coefficients K on the front wheels 5F is equal to or greater than the predetermined threshold K_thr and there is a margin of braking force on the rear wheels 5R side, it shifts part of the braking force allocated to the front wheels 5F to the rear wheels 5R. At this time, the braking force is shifted within a range where the slip ratio Sw of the rear wheels 5R does not exceed the slip ratio Sw_max at which the friction coefficient μ becomes maximum.

[0060] Next, the vehicle body behavior stabilization control unit 71 reduces the braking force of the wheel with the higher proportionality coefficient K of the left and right wheels, for the front wheels 5F or rear wheels 5R, whose difference ΔK in proportionality coefficient K is equal to or greater than the threshold ΔK_thr, so that the difference in longitudinal force between the left and right wheels falls within a predetermined range (step S47). For example, the vehicle body behavior stabilization control unit 71 reduces the braking force of the wheel with the higher proportionality coefficient K of the left and right wheels so that the yaw moment of the vehicle body calculated by the running state calculation unit 63 based on the tire forces detected by the tire force sensors 8 becomes zero or equal to or less than a predetermined standard. At this time, the vehicle body behavior stabilization control unit 71 reduces the braking force with the braking force of the wheel with the lower proportionality coefficient K as the lower limit.

[0061] On the other hand, when the vehicle body behavior stabilization control unit 71 does not determine that there is a margin of error in the braking force of the front wheels 5F or the rear wheels 5R where the difference ΔK in the proportionality coefficients K between the left and right is less than the predetermined threshold ΔK_thr (S43 / No), the vehicle body behavior stabilization control unit 71 proceeds to step S47 without changing the distribution of braking force. Even in this case, the vehicle body behavior stabilization control unit 71 reduces the braking force of the wheel with the higher proportionality coefficient K of the left and right wheels for the front wheels 5F or the rear wheels 5R where the difference ΔK in the proportionality coefficients K is equal to or greater than the threshold ΔK_thr, thereby bringing the difference in the longitudinal forces of the left and right wheels within a predetermined range (step S47).

[0062] In the above step S41, if the vehicle body behavior stabilization control unit 71 does not determine that the difference ΔK between the left and right proportional coefficients K for either the front wheels 5F or the rear wheels 5R is greater than or equal to the predetermined threshold value ΔK_thr (S41 / No), that is, if the difference ΔK between the left and right proportional coefficients K for both the front wheels 5F and the rear wheels 5R is greater than or equal to the predetermined threshold value ΔK_thr, it proceeds to step S49.

[0063] In this case, the vehicle body behavior stabilization control unit 71 prioritizes the front wheels 5F over the rear wheels 5R, and reduces the braking force of the wheel having the higher proportionality coefficient K of the left and right front wheels 5F so that the difference between the longitudinal forces of the left and right front wheels 5F falls within a predetermined range (step S49). After the difference between the longitudinal forces of the left and right front wheels 5F falls within the predetermined range, the vehicle body behavior stabilization control unit 71 further reduces the braking force of the wheel having the higher proportionality coefficient K of the left and right rear wheels 5R so that the difference between the longitudinal forces of the left and right rear wheels 5R falls within the predetermined range (step S51). The reason for prioritizing the front wheels 5F over the rear wheels 5R is that it is known that the tire reserve of the rear wheels 5R is related to the stability of vehicle body behavior, and by prioritizing the front wheels 5F over the rear wheels 5R, it is possible to ensure the tire reserve of the rear wheels 5R.

[0064] Returning to Figure 5, after the vehicle body behavior stabilization control unit 71 has brought the difference in longitudinal force between the left and right wheels of each of the front wheels 5F and the rear wheels 5R within a predetermined range by processing step S29, it determines whether the tire force (lateral force Fy) of the wheel on the side with a lower proportionality coefficient K for the front wheels 5F and the rear wheels 5R, where the difference ΔK in the proportionality coefficient K was equal to or greater than the predetermined threshold ΔK_thr, has stopped increasing (step S31).

[0065] If the vehicle body behavior stabilization control unit 71 does not determine that the tire force of the wheel on the side with the lower proportionality coefficient K has stopped increasing (S31 / No), it returns to step S29 and continues the vehicle body behavior stabilization process. On the other hand, if the vehicle body behavior stabilization control unit 71 determines that the tire force of the wheel on the side with the lower proportionality coefficient K has stopped increasing (S31 / Yes), it holds the slip ratio Sw of each wheel 5 at that time (step S33). As a result, the longitudinal force Fx of the wheel on the side with the lower friction coefficient μ is held at its maximum.

[0066] Thereafter, the processing unit 51 determines whether the ignition switch is turned off (step S35), and if the ignition switch is not turned off (S35 / No), the processing returns to step S15 and repeats the processing of each step described above. On the other hand, if the processing unit 51 determines that the ignition switch is turned off (S35 / Yes), the processing unit 51 ends the series of processes.

[0067] <4. Effect> Next, the operation when the vehicle body behavior stabilization process according to this embodiment is executed will be described.

[0068] Figure 7 shows a schematic diagram of the longitudinal forces Fx (Fx_L, Fx_R) of the left and right front wheels 5LF, 5RF, the lateral forces Fy (Fy_L, Fy_R), the friction coefficients μ (μ_L, μ_R) between the left and right front wheels 5LF, 5RF and the road surface, the slip ratios Sw (Sw_L, Sw_R) of the left and right front wheels 5LF, 5RF, the yaw rate deviation ΔYr of the vehicle body, and the angular acceleration deviation Δα of the vehicle body over time when anti-skid control is being performed.

[0069] The example shown in FIG. 7 is a case where the left wheel enters a high friction state while the vehicle 1 is traveling straight and the driver applies the brakes hard, causing anti-skid control to be executed, and is an example where it is assumed that the steering angle θs is zero.

[0070] At time t0, anti-skid control begins. Between time t0 and time t1, the friction coefficients μ_L and μ_R of the left and right front wheels 5LF and 5RF are equal. During this time, the anti-skid control unit 65 adjusts the braking force so that the slip ratios Sw_L and Sw_R of the left and right front wheels 5LF and 5RF fall within a predetermined range. Accordingly, the longitudinal forces Fx_L and Fx_R of the left and right front wheels 5LF and 5RF repeatedly increase and decrease. While the friction coefficients μ_L and μ_R of the left and right front wheels 5LF and 5RF are equal, the difference ΔK between the proportionality coefficient K, which indicates the relationship between the friction coefficients μ_L and μ_R of the left and right front wheels 5LF and 5RF and the slip ratios Sw_L and Sw_R, is maintained below a predetermined threshold ΔK_thr. During this time, the lateral forces Fy_L and Fy_R of the left and right front wheels 5LF and 5RF are equal.

[0071] At time t1, when the friction coefficient μ_L of the left front wheel 5LF increases, the longitudinal force Fx_L of the left front wheel 5LF begins to increase. At this time, with conventional anti-skid control, the braking force is adjusted so that the slip ratio Sw_L of the left front wheel 5LF continues to fall within a predetermined range, and the longitudinal force Fx_L of the left front wheel 5LF repeatedly increases and decreases while remaining greater than the longitudinal force Fx_R of the right front wheel 5RF. In addition, the lateral forces Fy_L and Fy_R generated at the left and right front wheels 5LF and 5RF decrease. At this time, the lateral force Fy_L of the left front wheel 5LF, which has a larger friction coefficient μ_L, becomes greater than the lateral force Fy_R of the right front wheel 5RF. In conventional anti-skid control, the difference ΔK_f between the proportionality coefficients K_f of the left and right front wheels 5LF, 5RF exceeds a predetermined threshold ΔK_thr, and the vehicle body yaw rate deviation ΔYr, which is the difference between the target yaw rate Yr_tgt (zero in the example shown in FIG. 7) and the actual yaw rate Yr, increases. Also, a vehicle body angular acceleration deviation Δα, which is the difference between the target outboard angular acceleration α_tgt (zero in the example shown in FIG. 7) and the actual vehicle body angular acceleration α, occurs.

[0072] On the other hand, the brake control device 50 according to this embodiment reduces the braking force of the left front wheel 5LF, which has a higher proportionality coefficient K, when the difference ΔK_f between the proportionality coefficients K_f of the left and right front wheels 5LF, 5RF becomes equal to or greater than a predetermined threshold ΔK_thr after the friction coefficient μ_L of the left front wheel 5LF increases at time t1 and the longitudinal force Fx_L_rev of the left front wheel 5LF begins to increase. As a result, the slip ratio Sw_L_rev of the left front wheel 5LF falls below the range of slip ratios maintained by anti-skid control, the increase in the longitudinal force Fx_L_rev of the left front wheel 5LF is suppressed, and the slip ratio Sw_L_rev changes to match the longitudinal force Fx_R of the right front wheel 5RF. As a result, the increases in the vehicle body yaw rate deviation ΔYr and the vehicle body angular acceleration deviation Δα are suppressed, and the lateral forces Fy_L, Fy_R of the left and right front wheels 5LF, 5RF increase.

[0073] In this way, when the left front wheel 5LF is in a high friction state during execution of anti-skid control and the difference ΔK_f in the proportionality coefficients K between the left and right front wheels 5F becomes equal to or greater than a predetermined threshold ΔK_thr, the braking control device 50 of the vehicle according to this embodiment suppresses the braking force of the wheel with the higher proportionality coefficient K. As a result, even if the friction states of the left and right wheels are different, the longitudinal forces of the left and right wheels are brought closer together, thereby stabilizing the behavior of the vehicle body.

[0074] <5. Effects> As described above, the vehicle braking control device 50 according to this embodiment includes one or more processors and one or more memories communicably connected to the one or more processors. The one or more processors are configured to calculate a proportionality coefficient K that indicates the relationship between the slip ratio Sw and the friction coefficient μ of each wheel 5, which is determined based on the tire force detected by the tire force sensor 8 during anti-skid control; calculate the difference ΔK in the proportionality coefficients K of the left and right wheels for each of the front wheels 5F and the rear wheels 5R; and, when the difference ΔK in the proportionality coefficients K of at least one of the front wheels 5F and the rear wheels 5R is equal to or greater than a predetermined threshold ΔK_thr, reduce the braking force of the wheel with the higher proportionality coefficient K of the front wheels 5F and the rear wheels 5R whose difference ΔK in the proportionality coefficients K is equal to or greater than the predetermined threshold ΔK_thr, thereby bringing the difference in the longitudinal forces Fx of the left and right wheels within a predetermined range.

[0075] Therefore, the braking control device 50 directly detects the longitudinal force difference ΔFx between the left and right wheels 5 measured using the tire force sensors 8 provided on each wheel 5, and suppresses the braking force of the wheel in a high friction state, thereby directly controlling the amount of yaw moment generated in the vehicle body. This makes it possible to quickly approximate the slip ratios of the left and right wheels and shorten the free-running time after the longitudinal force difference ΔFx between the left and right wheels occurs. Therefore, it is possible to reduce the risk of the vehicle body's behavior becoming unstable.

[0076] Furthermore, in the braking control device 50 of the vehicle according to this embodiment, one or more processors reduce the braking force of the wheel with the higher proportionality coefficient K to bring the longitudinal force Fx of the left and right wheels within a predetermined range, and maintain the slip ratio at that time when the tire force (lateral force Fy) of the wheel with the lower proportionality coefficient K stops increasing. Therefore, the braking control device 50 can directly control the amount of yaw moment generated in the vehicle body until the behavior of the vehicle body is reliably stabilized, while directly monitoring the lateral force Fy of the rear wheel 5R using the tire force sensor 8R.

[0077] Furthermore, in the vehicle braking control device 50 according to this embodiment, when the difference ΔK in the proportionality coefficients K of either one of the front wheels 5F or the rear wheels 5R is equal to or greater than a predetermined threshold ΔK_thr, one or more processors determine whether there is a margin of braking force on the other front wheel 5F or rear wheel 5R where the difference ΔK in the proportionality coefficients K is less than the predetermined threshold ΔK_thr, and if there is a margin of braking force, shift the allocation of braking force from one front wheel 5F or rear wheel 5R to the other front wheel 5F or rear wheel 5R where there is a margin of braking force. This increases the braking force generated on the front wheel 5F or rear wheel 5R where the difference ΔK in the proportionality coefficients K is small, making it possible to decelerate the vehicle while stabilizing vehicle behavior.

[0078] Furthermore, in the vehicle braking control device 50 according to this embodiment, when the difference ΔK between the proportionality coefficients K of the front wheels 5F and the rear wheels 5R is equal to or greater than a predetermined threshold ΔK_thr, the one or more processors are configured to set the difference between the longitudinal forces Fx of the left and right wheels on the front wheels 5F side within a predetermined range, and then set the difference between the longitudinal forces Fx of the left and right wheels on the rear wheels 5R side within a predetermined range. This makes it possible to ensure the tire reserve force of the rear wheels 5R.

[0079] <6. Other embodiments> In the above embodiment, the braking control device 50 is configured to adjust the braking force so as to guide the vehicle 1 to an evacuation area or a drivable area when an obstacle is present in front of the vehicle 1 during anti-skid control.

[0080] A braking control device 50 according to another embodiment has a configuration capable of acquiring signals or information output from a sensor (hereinafter also referred to as an "ambient environment sensor") mounted on the vehicle 1 that recognizes the environment surrounding the vehicle 1. The ambient environment sensor may be, for example, a camera that performs object recognition processing based on a captured image, or a distance measurement sensor such as LiDAR or radar that emits electromagnetic waves or optical waves and performs object recognition processing based on a group of reflected points, or both. These object recognition processes are well-known technologies, and therefore detailed explanations thereof will be omitted.

[0081] 8 is a flowchart of a vehicle body behavior stabilization process according to another embodiment. The flowchart shown in FIG. 8 is executed following the process of step S47 or step S51 in the flowchart shown in FIG.

[0082] After the vehicle body behavior stabilization control unit 71 sets the longitudinal forces Fx of the left and right wheels, the front wheels 5F and the rear wheels 5R, within a predetermined range in step S47 or step S51, it calculates a drivable area ahead based on information about the environment around the vehicle 1 (step S53). For example, as shown in Fig. 9, the vehicle body behavior stabilization control unit 71 sets a drivable area in which the vehicle 1 can retreat or travel, based on information about road boundaries 91, 93 of the road on which the vehicle 1 is traveling and the positions and velocities of dynamic objects and static objects 90. The vehicle body behavior stabilization control unit 71 also calculates the aspect ratio (Ys / Ls) of the set drivable area.

[0083] Next, the vehicle body behavior stabilization control unit 71 calculates the target yaw moment based on the aspect ratio of the travelable area (step S55). For example, the vehicle body behavior stabilization control unit 71 calculates the target yaw rate Yr_tgt using the following equation (2), and performs PID calculation on the calculated target yaw rate Yr_tgt to calculate the target yaw moment Myr_tgt. Target yaw moment γ_tgt=(2Vx / Ls 2 ) × Ys …(2) However, the method for calculating the target yaw moment Myr_tgt is not limited to the above example.

[0084] Next, the vehicle body behavior stabilization control unit 71 adjusts the braking force of the wheel with the higher proportionality coefficient K out of the left and right wheels, the front wheels 5F and the rear wheels 5R, for which the difference ΔK in the proportionality coefficient K is equal to or greater than a predetermined threshold ΔK_thr, based on the calculated target yaw moment Myr_tgt (step S57). As a result, a yaw moment is generated in the vehicle body so that the vehicle 1 travels within a drivable area. In this way, the vehicle braking control device 50 according to the other embodiment can stabilize the vehicle body behavior in the same way as the above embodiment, and can also guide the vehicle 1 into a drivable area where a collision between the vehicle 1 and an obstacle can be avoided.

[0085] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art to which the present disclosure pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0086] In addition, the technology disclosed herein can also be realized as a vehicle equipped with the braking control device described in the above embodiments, a braking control method using the braking control device, a program that causes a computer to function as the above-mentioned braking control device, and a non-temporary tangible recording medium on which the program is recorded. [Explanation of symbols]

[0087] 1: Vehicle 4: Axle 5: Wheels 8: Tire force sensor 9: Wheel speed sensor 11: Steering angle sensor 13: Brake sensor 15: Yaw rate sensor 20: Hydraulic control unit 50: Braking control device 51: Processing section 53: Storage section 61: Acquisition part 63: Driving state calculation unit 65: Anti-skid control unit 67: Proportional coefficient calculation section 69: Target driving state calculation unit 71: Vehicle behavior stabilization control unit

Claims

1. In a vehicle braking control device that performs anti-skid control, one or more processors; and one or more memories communicatively coupled to the one or more processors; the one or more processors: calculating a proportionality coefficient indicating a relationship between the friction coefficient and the slip ratio of each wheel, which is obtained based on the tire force detected by the tire force sensor during the anti-skid control; calculating a difference between the proportionality coefficients of the left and right wheels for each of the front and rear wheels; When the difference in the proportionality coefficient of at least one of the front wheels and the rear wheels is equal to or greater than a predetermined threshold, the braking force of the wheel with the higher proportionality coefficient out of the left and right wheels of the front wheels and the rear wheels whose difference in the proportionality coefficient is equal to or greater than the predetermined threshold is reduced, so that the difference in the longitudinal forces of the left and right wheels is kept within a predetermined range; A vehicle braking control device that performs the above.

2. the one or more processors: reducing the braking force of the wheel on the side with the higher proportionality coefficient to bring the longitudinal forces of the left and right wheels within a predetermined range, and maintaining the slip ratio when the tire force of the wheel on the side with the lower proportionality coefficient no longer increases; The vehicle braking control device according to claim 1.

3. the one or more processors: When the difference in the proportionality coefficient of one of the front wheels and the rear wheels is equal to or greater than a predetermined threshold, it is determined whether or not there is a margin of braking force for the other of the front wheels or the rear wheels, the difference in the proportionality coefficient of which is less than the predetermined threshold; If there is a margin, a distribution of braking force is shifted from the one of the front wheels or the rear wheels to the other of the front wheels or the rear wheels having the margin. The vehicle braking control device according to claim 1.

4. the one or more processors: When the difference between the proportionality coefficients of both the front wheels and the rear wheels is equal to or greater than a predetermined threshold value, the braking force of the front wheel with the higher proportionality coefficient is reduced to bring the difference between the longitudinal forces of the left and right wheels within a predetermined range, and then the braking force of the rear wheel with the higher proportionality coefficient is reduced to bring the difference between the longitudinal forces of the left and right wheels within the predetermined range. The vehicle brake control device according to claim 1.

5. the one or more processors: determining a travelable area ahead of the vehicle, and calculating a target yaw moment based on an aspect ratio of the travelable area; reducing the braking force of the wheel with the higher proportionality coefficient to bring the difference between the longitudinal forces of the left and right wheels within a predetermined range, and then adjusting the braking force of the wheel with the higher proportionality coefficient based on the target yaw moment; The vehicle brake control device according to claim 1.

6. The computer Calculating a proportionality coefficient, which is a ratio between the slip rate and the longitudinal force of each wheel, based on the longitudinal force and slip rate of each wheel detected by the tire force sensor during anti-skid control; calculating a difference between the proportionality coefficients of the left and right wheels for each of the front and rear wheels; When the difference in the proportionality coefficients of at least one of the front wheels and the rear wheels is equal to or greater than a predetermined threshold value, reducing the braking force of the wheel with a higher proportionality coefficient out of the left and right wheels of the front wheels and the rear wheels whose difference in the proportionality coefficients is equal to or greater than the predetermined threshold value, thereby keeping the longitudinal forces of the left and right wheels within a predetermined range; A vehicle braking control method for performing the above.

7. On the computer, Calculating a proportionality coefficient, which is a ratio between the slip rate and the longitudinal force of each wheel, based on the longitudinal force and slip rate of each wheel detected by the tire force sensor during anti-skid control; calculating a difference between the proportionality coefficients of the left and right wheels for each of the front and rear wheels; When the difference in the proportionality coefficients of at least one of the front wheels and the rear wheels is equal to or greater than a predetermined threshold value, reducing the braking force of the wheel with a higher proportionality coefficient out of the left and right wheels of the front wheels and the rear wheels whose difference in the proportionality coefficients is equal to or greater than the predetermined threshold value, thereby keeping the longitudinal forces of the left and right wheels within a predetermined range; A computer program that executes

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