JP2001047989A - Motion controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent veheicle stability resulting from variation of braking force caused by motion control from being lowered, so as to effectively stabilize motion of a vehicle. SOLUTION: In this controller, target braking force Fbsi of behavior control is computed (S20), target braking force Fbri of roll restraining control is operated (S50), target braking force Fbti of each wheel is computed as a large value out of the target braking forces Fbsi, Fbri, a target slip rate Spti of the each wheel is computed based on the tagrget braking force Fbti (S70-90), a duty ratio Dri of a pressure intensifying and reducing control valve in the each wheel is computed based on the target slip ratio Spti (S110,120), the pressure intensifying and reducing control valve is controlled based on the duty ration Dri, and braking force is controlled to get to the target braking force Fbti (S130). When the possibility that vehicle stability is lowered caused by variation of the braking force by motion control of a vehicle is exists, the duty ratio Dri is reduced to reduce a pressure intensifying and reducing gradient of the braking force (S120).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motion control device for a vehicle such as an automobile, and more particularly to a motion control device for stabilizing the motion of a vehicle by applying a braking force to wheels based on a running state of the vehicle. According to.

[0002]

2. Description of the Related Art As one of motion control devices for vehicles such as automobiles, for example, Japanese Patent Application Laid-Open No. 9-10 / 1998 filed by the present applicant
As described in JP-A-9851, the spin state of a vehicle is detected, and when the spin state of the vehicle is detected, a braking force is applied to wheels to apply a yaw moment in a spin suppression direction to the vehicle to suppress spin. 2. Description of the Related Art There has been conventionally known a behavior control device that is configured to reduce the generation speed of a braking force applied to wheels as the execution time of spin suppression control is longer.

According to such a behavior control device, since the generation speed of the yaw moment in the spin suppression direction decreases as the execution time of the spin suppression control becomes longer, the yaw moment in the excessive spin suppression direction is given to the vehicle. It is possible to reduce the possibility of hunting of the behavior control caused by the hunting.

[0004]

Generally, in a motion control device such as the above-described behavior control device that controls braking force, a target control amount for stabilizing the motion of the vehicle is calculated based on the running state of the vehicle. The target slip ratio of each wheel is calculated based on the target control amount, and the braking force of each wheel is controlled to increase or decrease so that the slip ratio of each wheel becomes the target slip ratio.

[0005] However, since the increasing and decreasing gradient of the braking force in the motion control is uniquely set in advance with respect to the target slip ratio, for example, behavior control for stabilizing the turning behavior of the vehicle and suppression of excessive roll of the vehicle body are performed. Depending on the running conditions of the vehicle, such as when the roll suppression control is executed simultaneously or the actual friction coefficient of the road surface is significantly different from the assumed friction coefficient of the road surface, it is uniquely set in advance to the target slip ratio. The increasing / decreasing gradient of the braking force does not match the actual situation of the vehicle, and therefore the acceleration / deceleration of the vehicle changes rapidly due to the sudden increase / decrease of the braking force due to the motion control, and as a result, the vehicle has a pitching behavior. As a result, the ground contact load of the wheels and the like may change rapidly, and therefore, the motion of the vehicle may not be effectively stabilized.

The present invention has been made in view of the above-mentioned problem in the conventional motion control device in which the increasing / decreasing gradient of the braking force in the motion control is uniquely set in advance with respect to the target slip ratio. A main object of the present invention is to prevent the vehicle acceleration and deceleration from suddenly changing when there is a possibility that the stability of the vehicle may be reduced due to an increase or decrease in the braking force due to the motion control. And stably.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the main object of the present invention is to provide a brake system for stabilizing the motion of a vehicle by applying a braking force to wheels based on the running state of the vehicle. A vehicle motion control device that performs motion control, a determining unit that determines a possibility that the stability of the vehicle is reduced due to an increase or a decrease in a braking force due to the motion control, and a determination unit that determines whether the stability of the vehicle is reduced by the determination unit. Means for reducing the speed at which the braking force is changed by the motion control when the fear is determined, is achieved by a motion control device for a vehicle.

According to the first aspect of the present invention, when there is a possibility that the stability of the vehicle is reduced due to the increase or decrease of the braking force due to the motion control, the speed at which the braking force is changed by the motion control is reduced. Abrupt changes in the acceleration / deceleration of the vehicle during the motion control are avoided, thereby preventing a decrease in the stability of the vehicle due to an increase or decrease in the braking force due to the motion control.

Further, according to the present invention, in order to effectively achieve the above-mentioned main object, in the configuration of the first aspect, a behavior control means for stabilizing a turning behavior of the vehicle, and an excessively large vehicle body Roll suppression control means for suppressing rolls, and means for calculating a final target control amount for each wheel based on a target control amount for each wheel by the behavior control means and a target control amount for each wheel by the roll suppression control means And means for controlling the braking force of each wheel based on the final target control amount (the configuration of claim 2).

According to the second aspect of the present invention, the final target control amount of each wheel calculated based on the target control amount of each wheel by the behavior control means and the target control amount of each wheel by the roll suppression control means is calculated. Since the braking force of each wheel is controlled on the basis of not only the case where the stability of the vehicle may decrease due to the increase or decrease of the braking force due to the roll suppression control, but also the behavior control and the braking force due to the roll suppression control. Even when the stability of the vehicle may decrease due to the increase or decrease, the speed at which the braking force is changed is surely reduced.

Further, according to the present invention, in order to effectively achieve the above-mentioned main object, in the configuration of the above-mentioned claim 2, the judging means executes the roll suppression control by the roll suppression control means. It is configured to determine that there is a possibility that the stability of the vehicle may be reduced when the vehicle is in the vehicle.

Generally, in a situation where the roll suppression control is being performed by the roll suppression control means, the roll amount of the vehicle body is high, so that if the braking force is rapidly increased or decreased by the roll suppression control, the acceleration / deceleration of the vehicle will increase. Due to the rapid change, the stability of the vehicle tends to decrease.

According to the third aspect of the present invention, it is determined that the stability of the vehicle may be reduced when the roll suppression control is being performed by the roll suppression control means.
The stability of the vehicle is reliably prevented from decreasing due to the increase or decrease in the braking force due to the roll suppression control.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the above-mentioned structure of the first or second aspect, the determining means may be a state quantity indicating a degree of roll of the vehicle body. It is configured to determine that there is a possibility that the stability of the vehicle may be reduced when the value exceeds the reference value (the configuration of claim 4).

According to the configuration of claim 4, when the magnitude of the state quantity indicating the degree of roll of the vehicle body exceeds the reference value, it is determined that the stability of the vehicle may be reduced.
In a situation where the roll of the vehicle body is large, it is possible to reliably prevent the stability of the vehicle from being reduced due to the increase or decrease of the braking force due to the motion control.

[0016]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the means for reducing the change speed of the braking force by the motion control reduces the speed of the reduction of the braking force. (Preferred embodiment 1).

According to another preferred aspect of the present invention, in the configuration of the above-mentioned claim 2, the behavior control means includes a step of controlling the vehicle to be mounted on at least the turning outer front wheel when the value indicating the degree of spin of the vehicle exceeds a reference value. By applying a braking force corresponding to the value indicating the degree of spin, the turning behavior is stabilized (preferred mode 2).

According to another preferred aspect of the present invention, in the configuration of the above-mentioned claim 2, the behavior control means may include at least a turning inside rear wheel when a value indicating the degree of drift-out of the vehicle exceeds a reference value. By applying a braking force in accordance with a value indicating the degree of drift-out of the vehicle, the turning behavior is stabilized (preferred mode 3).

According to another preferred aspect of the present invention, in the configuration according to the second aspect, when the value indicating the degree of the roll of the vehicle body exceeds a reference value, at least the turning outer front wheel is provided. By applying a braking force according to a value indicating the degree of roll of the vehicle body, an excessive roll of the vehicle body is suppressed (preferred mode 4).

According to another preferred aspect of the present invention, in the configuration according to the second aspect, the means for calculating the final target control amount of each wheel is the target control by the behavior control means for each wheel. A larger value of the target control amount by the amount and the roll suppression control means is calculated as a final target control amount (preferred mode 5).

According to another preferred aspect of the present invention, in the configuration of the fourth aspect, the state quantity indicating the degree of roll of the vehicle body is configured to be the lateral acceleration of the vehicle (preferred aspect 6). ).

According to another preferred embodiment of the present invention, in the configuration of the fourth aspect, the state quantity indicating the degree of roll of the vehicle body is configured to be the yaw rate of the vehicle (preferred embodiment 7). .

According to another preferred embodiment of the present invention, in the configuration according to the fourth aspect, the judging means is such that the magnitude of the lateral acceleration of the vehicle exceeds a corresponding reference value and the yaw rate of the vehicle is adjusted. When the size exceeds the corresponding reference value, it is configured to determine that there is a possibility that the stability of the vehicle is reduced (preferred mode 8).

According to another preferred aspect of the present invention, in the configuration of the fourth aspect, the state quantity indicating the degree of roll of the vehicle body is configured to be the longitudinal acceleration of the vehicle (preferred aspect 9). ).

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic structural view showing one preferred embodiment of a vehicle motion control device according to the present invention.

In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR denote left and right rear wheels which are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steering wheels, are driven by a rack-and-pinion type power steering device 16 driven in response to steering of the steering wheel 14 by the driver via tie rods 18L and 18R. Steered.

The braking force of each wheel is controlled by the hydraulic circuit 22 of the braking device 20 by the wheel cylinders 24FR, 24FL, 24RR,
The control is performed by controlling the braking pressure of 24RL. Although not shown in the figure, the hydraulic circuit 2
Numeral 2 includes various valve devices such as an oil reservoir, an oil pump, and a pressure increasing / decreasing control valve for increasing / decreasing a pressure in a wheel cylinder. The control is performed by controlling the duty ratio of the pressure increasing / decreasing control valve by the electric control device 30 as will be described later in detail, if necessary.

Each of the wheels 10FR to 10RL is provided with a wheel speed sensor 32FR to 32RL for detecting the wheel speed Vwi (i = fr, fl, rr, rl) of the corresponding wheel as a peripheral speed. The steering column is provided with a steering angle sensor 34 for detecting the steering angle θ.

The vehicle 12 has a yaw rate sensor 36 for detecting the yaw rate γ of the vehicle, and a longitudinal acceleration Gx.
And a lateral acceleration sensor 40 for detecting the lateral acceleration Gy. The steering angle sensor 34, the yaw rate sensor 36, and the lateral acceleration sensor 4
0 detects the steering angle, the yaw rate, and the lateral acceleration assuming that the left turning direction of the vehicle is positive.

As shown, wheel speed sensors 32FR-32
A signal indicating the wheel speed Vwi detected by the RL, a signal indicating the steering angle θ detected by the steering angle sensor 34, a signal indicating the yaw rate γ detected by the yaw rate sensor 36, and the longitudinal acceleration detected by the longitudinal acceleration sensor 38 A signal indicating Gx and a signal indicating the lateral acceleration Gy detected by the lateral acceleration sensor 40 are input to the electric control device 30.

Although not shown in detail in the figure, the electric control device 30 has, for example, a CPU, a ROM, a RAM, and an input / output port device, which are generally connected to each other by a bidirectional common bus. Microcomputer with a typical configuration.

The electric control device 30 controls the spin state amount SS indicating the degree of spin of the vehicle based on the running state of the vehicle in accordance with the flowcharts shown in FIGS.
And a drift-out state quantity DS indicating the degree of drift-out of the vehicle is calculated, and a target braking force Fbsi (i = fr, fl, rr, rl) of each wheel of the behavior control is calculated based on the spin state quantity SS and the drift-out state quantity DS. ) Is calculated.

The electric control device 30 calculates a roll evaluation value RV indicating the degree and direction of roll of the vehicle body, and determines whether or not to execute roll suppression control based on the lateral acceleration Gy of the vehicle and the yaw rate γ of the vehicle. When it is determined that the roll suppression control should be executed, the roll suppression control amount B is calculated based on the absolute value of the roll evaluation value RV, and the target braking force Fbri (i) of each wheel of the roll suppression control is calculated based on the roll suppression control amount B.
= Fr, fl, rr, rl).

Further, the electric control device 30 calculates the target braking force Fbti (i = fr, fl, rr, r) of each wheel based on the target braking force Fbsi of the behavior control and the target braking force Fbri of the roll suppression control.
l) is calculated, the target slip ratio Rsti (i = fr, fl, rr, rl) of each wheel is calculated based on the target braking force Fbti, and the pressure increase / decrease control valve of each wheel is controlled based on the target slip ratio Rsti. Thus, the braking force is controlled so that the slip ratio of each wheel becomes the target slip ratio, and thereby the motion control for stabilizing the motion of the vehicle is performed.

Further, the electric control device 30 determines whether there is a possibility that the stability of the vehicle is reduced due to the increase or decrease of the braking force due to the motion control, and there is a possibility that the stability of the vehicle is reduced. When there is no (normal time), the braking pressure of each wheel is controlled to increase or decrease with a relatively large increasing / decreasing gradient so that the braking force of each wheel can be increased / decreased with good responsiveness. However, there is a possibility that the stability of the vehicle may decrease. In some cases, the brake pressure of each wheel is controlled to increase or decrease with a pressure increasing / decreasing gradient smaller than usual.

Next, the main routine of the motion control in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 10, the wheel speed Vwi
Is read. At the start of the control according to the flowchart shown in FIG.
Prior to the roll angular velocity estimated value Rr, the roll angle estimated value R,
The roll evaluation value RV is reset to 0 as an initial value at the start of control.

In step 20, according to the routine shown in FIG. 3, the target braking force Fbsi of each wheel of the behavior control is performed.
(I = fr, fl, rr, rl) are calculated, and in step 50, the target braking force Fbri (i = fr, fl, rr, rl) of each wheel of the roll suppression control in accordance with the routine shown in FIG. ) Is calculated.

In step 70, the target braking force Fbti (i = fr, fl, rr, rl) of each wheel is calculated in accordance with the following equation 1 with MAX () being the larger value in parentheses, In step 80, based on the target braking force Fbti, a target slip ratio Rsti (i = fr, fl, rr, i) of each wheel for achieving the target braking force Fbti from the map corresponding to the graph shown in FIG. rl) is calculated. Fbti = MAX (Fbsi, Fbri) (1)

In step 90, the vehicle speed Vb is calculated based on the wheel speed Vwi of each wheel in a manner known in the art, and the wheel speed corresponding to the target slip ratio Rsti is calculated according to the following equation (2). The target wheel speed Vwti is calculated, and the target slip ratio Spti of each wheel for achieving the target wheel speed Vwti is calculated according to the following equation (3). Vwti = Vb (1-Rsti) (2) Spti = (Vwi-Vwti) / Vwti (3)

The wheel speed of the front inside wheel may be substituted for the vehicle speed Vb in the above equation (2). The target slip ratio Spti is expressed as Vwdi (i = fr, f
l, rr, rl) may be calculated according to the following equation 4 as the rate of change of the wheel speed Vwi. Spti = {Vwi−Vwti + Ks (Vwdi−Gx)} / Vwti (4)

In step 100, it is determined whether or not there is a possibility that the stability of the vehicle may be reduced due to an increase or decrease in the braking force due to the motion control. If a negative determination is made, the process proceeds to step 110. From the map corresponding to the graph shown by the solid line in FIG. 6 based on the target slip ratio Rsti, the increasing / decreasing gradient of the braking force of each wheel, that is, the duty ratio Dri of the increasing / decreasing control valve (i = fr, fl , Rr, rl), and when an affirmative determination is made, in step 120, based on the target slip ratio Rsti, the pressure increase / decrease control of each wheel is performed based on the map corresponding to the graph shown by the broken line in FIG. The valve duty ratio Dri is calculated.

Whether the stability of the vehicle is likely to be reduced due to the increase or decrease of the braking force due to the motion control is determined by whether the roll suppression control amount B is present, that is, the roll suppression control. The determination may be the same as the determination in steps 58 and 60 of the target braking force Fbri calculation routine of the roll suppression control described later, that is, in a situation where the roll amount of the vehicle body becomes excessive. It may be performed by determining whether or not there is.

In step 130, the pressure increase / decrease control valve of each wheel is controlled based on the duty ratio Dri calculated in step 110 or 120 so that the braking force of each wheel becomes the target braking force Fbti. Controlled, and then returns to step 10.

The target braking force Fbs for the behavior control shown in FIG.
In step 22 of the i calculation routine, the wheel speed Vw
The vehicle speed V is calculated based on i, and the deviation of the lateral acceleration, that is, the vehicle slip acceleration Vyd is calculated as the deviation Gy-γV between the lateral acceleration Gy and the product γV of the vehicle speed V and the yaw rate γ. As a result, the vehicle body slip speed Vy is calculated, and the ratio V of the vehicle body slip speed Vy to the vehicle body front-rear speed Vx (= vehicle speed V) is obtained.
The slip angle β of the vehicle body is calculated as y / Vx.

In step 24, the spin amount SV is calculated as the linear sum K1β + K2Vyd of the vehicle slip angle β and the skid acceleration Vyd, using K1 and K2 as positive constants, respectively. In step 26, the sign of the yaw rate γ is calculated. The turning direction of the vehicle is determined based on the spin state amount SS.
Is calculated as SV when the vehicle turns to the left and -SV when the vehicle turns to the right. When the calculation result is a negative value, the spin state amount is set to 0. The spin amount SV may be calculated as a linear sum of the slip angle β of the vehicle body and its differential value βd.

In step 28, the actual steering angle δ of the front wheels is calculated based on the steering angle θ, and H
The target yaw rate γe is calculated according to the following equation 5 using h as a stability factor, and the estimated yaw rate γt of the vehicle based on the vehicle speed V and the steering angle θ according to the following equation 6 using T as a time constant and s as a Laplace operator. Is calculated. The target yaw rate γe may be calculated in consideration of the dynamic yaw rate by taking into account the lateral acceleration Gy of the vehicle. γe = Vδ / (1 + KhV ² ) H (5) γt = γe / (1 + Ts) (6)

In step 30, the drift value DV is calculated according to the following equation (7). The drift value DV may be calculated according to the following equation (8). DV = (γt−γ) (7) DV = H (γt−γ) / V (8)

In step 32, the turning direction of the vehicle is determined based on the sign of the yaw rate γ, and the drift-out state amount DS is calculated as DV when the vehicle is turning left, and as -DV when the vehicle is turning right. When the result is a negative value, the drift-out state amount is set to zero.

In step 34, the spin state amount SS
From the map corresponding to the graph shown in FIG. 7, the target braking force Fssfo of the turning outer front wheel is calculated based on
In 6, the target braking force Fsall of the entire vehicle is calculated from the map corresponding to the graph shown in FIG. 8 based on the drift-out state amount DS.

In step 38, Ksri is changed to the distribution ratio of the rear inner wheel (generally, a positive constant larger than 50).
The target braking force Fsfo of the turning outer front wheel, the turning inner front wheel, the turning outer rear wheel, and the turning inner rear wheel according to Equation 9 below,
Fsfi, Fsro, and Fsri are calculated. Fsfo = Fssfo Fsfi = 0 Fsro = (Fsall−Fssfo) (100−Ksri) / 100 Fsri = (Fsall−Fssfo) Ksri / 100 (9)

In step 40, the turning inner and outer wheels are specified by determining the turning direction of the vehicle based on the sign of the yaw rate γ, and the target braking force Fbsi (i = fr, fl, rr, rl) are calculated. That is, when the target braking force Fbsi is a left turn and a right turn of the vehicle, respectively,
It is determined according to 1.

Fbsfr = Fsfo Fbsfl = Fsfi Fbsrr = Fsro Fbsrl = Fsri (10) Fbsfr = Fsfi Fbsfl = Fsfo Fbsrr = Fsri Fbsrl = Fsro (11)

In step 52 of the target braking force Fbri calculation routine of the roll suppression control shown in FIG.
Is the previous value of the roll angular velocity estimated value Rr, ωo is the natural frequency of the vehicle body, φo is the steady roll angle per unit gravity acceleration, ξ is the roll damping coefficient, and ΔT is the cycle of the flowchart shown in FIG. Formula 1
2, the roll angular velocity estimated value Rr is calculated. Rr = Rrf + ｛(ωo ² (Gyφo−R) −2ωoξRrf｝ ΔT (12)

In step 54, the roll angle estimation value R is calculated according to the following equation 13 using Rf as the previous value of the roll angle estimation value R. R = Rf + RrΔT (13)

In step 56, the roll evaluation value RV is calculated on the basis of the lateral acceleration Gy of the vehicle in accordance with the following equation 14 using Gylim as the allowable limit value of the lateral acceleration and Rrlim as the allowable limit value of the roll angular velocity. The allowable limit value Gylim
And Rrlim may be positive constants, but may be variably set based on, for example, the vehicle speed V or the like. RV = Gy / Gylim + Rr / Rrlim (14)

In step 58, the lateral acceleration G of the vehicle
It is determined whether or not the absolute value of y exceeds a reference value Gyo (positive constant). If a negative determination is made, the process proceeds to step 62; if an affirmative determination is made, step 6 is performed.
Go to 0.

In step 60, it is determined whether or not the absolute value of the yaw rate γ of the vehicle exceeds a reference value γo (positive constant). If a negative determination is made, the roll is determined in step 62. Target braking force Fbri of suppression control is 0
Then, the routine proceeds to step 70, and when an affirmative determination is made, the routine proceeds to step 64.

As understood from the above description, in steps 58 and 60, it is determined whether or not the roll suppression control should be executed by determining whether or not the vehicle is in a situation where the roll amount of the vehicle body is excessive. Done. In step 60, it may be determined whether or not the product of the yaw rate γ of the vehicle and the vehicle speed V, that is, whether or not the estimated lateral acceleration of the vehicle exceeds a reference value (a positive constant).

In step 64, the roll evaluation value RV
The roll restraining control amount B is calculated from the map corresponding to the graph shown in FIG. 9 on the basis of the absolute value of the roll angle, and in step 66, the turning direction of the vehicle is determined based on the roll evaluation value RV or the sign of the lateral acceleration Gy of the vehicle body. Is determined, and Kfou
Assuming that t, Krin, and Krout are positive constant coefficients, when the vehicle is turning left, the target braking force Fbri of the roll suppression control of each wheel is calculated according to the following equation 15.
When the vehicle is turning right, the target braking force Fbri of the roll suppression control of each wheel is calculated according to the following equation (16).

Fbrfr = KfoutB Fbrfl = 0 Fbrrr = KroutB Fbrrl = KrinB (15) Fbrfr = 0 Fbrfl = KfoutB Fbrrr = KrinB Fbrrl = KroutB (16)

Thus, according to the illustrated embodiment, the spin state amount SS indicating the degree of spin of the vehicle is calculated in steps 22 to 26, and the drift state indicating the degree of drift out of the vehicle is calculated in steps 28 to 32. The out state amount DS is calculated, and in step 34, the spin state amount S
Based on S, a target braking force Fssfo of the turning outer front wheel for spin suppression is calculated, and in step 36, a target braking force Fsall of the entire vehicle for suppressing driftout is calculated based on the driftout state amount DS. Step 3
Target braking force Fss for spin suppression at 8 and 40
target braking force Fsa for suppressing fo and drift-out
The target braking force Fbsi of each wheel of the behavior control is calculated based on ll.

In steps 52 to 56, a roll evaluation value RV indicating the degree and direction of roll of the vehicle body is calculated. In steps 58 and 60, the absolute value of the lateral acceleration Gy of the vehicle and the yaw rate γ of the vehicle are calculated in steps 58 and 60, respectively. It is determined whether or not the roll suppression control should be executed based on the absolute value. When it is determined that the roll suppression control should be executed, in step 64, the roll suppression is performed based on the absolute value of the roll evaluation value RV. The control amount B is calculated, and step 66
Then, the target braking force Fbri of each wheel of the roll suppression control is calculated based on the roll suppression control amount B.

In step 70, the target braking force Fbti of each wheel is calculated as the larger of the target braking force Fbsi of the behavior control and the target braking force Fbri of the roll suppression control. The target slip ratio Rsti of each wheel is calculated based on Fbti, and step 90
The target wheel speed Vwti of each wheel corresponding to the target slip ratio Rsti is calculated at the same time, and the target wheel speed Vwti is calculated.
The target slip ratio Spti of each wheel for achieving the above is calculated, and in step 110 or 120, the increasing / decreasing gradient of each wheel braking pressure based on the target slip ratio Spti, that is, the duty ratio Dri of the increasing / decreasing control valve of each wheel. Is calculated, and in step 130, the pressure increase / decrease control valve of each wheel is controlled based on the duty ratio Dri, so that the braking force of each wheel is controlled to the target braking force Fbti.

For example, when the vehicle is in a spin state,
The braking force is applied to the turning outer front wheel, and the spin is suppressed by applying the yaw moment in the spin suppression direction to the vehicle. When the vehicle is in a drift-out state, the braking force is applied to the left and right rear wheels to decelerate the vehicle. In addition, drift-out is suppressed by applying a yaw moment in the turning assist direction to the vehicle. Further, when the roll of the vehicle body is excessive, a braking force is applied to the turning outer front wheel and the left and right rear wheels, so that the vehicle is decelerated and the turning radius of the vehicle is increased, whereby the centrifugal force acting on the vehicle is reduced. As a result, the roll of the vehicle body is suppressed.

In particular, according to the illustrated embodiment, step 1
At 00, it is determined whether or not there is a risk that the stability of the vehicle may be reduced due to an increase or decrease in the braking force due to the motion control of the vehicle. If there is a risk of reduction, in step 120, the duty ratio Dri of the pressure increase / decrease control valve of each wheel is calculated from the map corresponding to the graph shown by the broken line in FIG.
As a result, the pressure reduction gradient of the braking pressure is reduced as compared with the normal case, so that the roll suppression control executed when the roll amount of the vehicle body is excessively large or the behavior control and the roll suppression control are simultaneously executed. As a result, the braking force of the wheels is sharply reduced, whereby it is possible to reliably prevent the stability of the vehicle from being reduced due to the pitching of the vehicle due to the sudden load movement.

According to the illustrated embodiment, when there is a possibility that the stability of the vehicle is reduced due to the increase or decrease of the braking force due to the motion control of the vehicle, the pressure reduction gradient of the braking pressure is reduced as compared with the normal case. In addition to this, the pressure increase gradient of the braking pressure is also reduced to some extent compared to the normal time, so the braking pressure is rapidly increased by the roll suppression control without suddenly sacrificing the effect of the roll suppression control, causing a sudden load transfer. Therefore, it is possible to reliably prevent the stability of the vehicle from being reduced due to the pitching of the vehicle due to the above.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments may be included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the illustrated embodiment, the determination as to whether or not there is a risk of pitching of the vehicle executed in step 100 is made by determining whether or not there is a roll suppression control amount B or by determining whether or not there is a roll suppression control amount B. The determination is performed in the same manner as the determination in steps 58 and 60 of the target braking force Fbri calculation routine of the suppression control. However, it is determined whether or not the absolute value of the longitudinal acceleration Gx exceeds the reference value, that is, the vehicle. May be determined by determining the actual pitching degree.

In the illustrated embodiment, when it is determined that there is a possibility that the stability of the vehicle may be reduced,
Although the pressure increase gradient of the braking pressure is also reduced to some extent in step 120, there is a possibility that the stability of the vehicle may be reduced due to the sudden increase in the braking pressure. Therefore, the reduction in the pressure increase gradient of the braking pressure in step 120 may be omitted, since the vehicle stability is lower than the possibility that the vehicle stability will decrease due to the reduction in the vehicle speed.

In the illustrated embodiment, when the increasing / decreasing gradient of the braking pressure is reduced, the target slip ratio Spt is reduced.
When the value of i becomes equal to or larger than the reference value, the duty ratio Dri of the pressure increasing / decreasing control valve of each wheel is maintained at a constant value, but as shown by a dashed line in FIG.
As the magnitude of the target slip ratio Spti becomes larger than the reference value, the duty ratio D becomes smaller at a rate smaller than the normal state.
The magnitude of ri may be modified to increase gradually.

In the illustrated embodiment, the spin state amount SS and the drift-out state amount DS are calculated, and the target braking force Fbsi for behavior control is calculated based on the spin state amount SS and the drift-out state amount DS. The spin state amount SS and the drift-out state amount D
S is calculated, and the target braking force Fbs for the behavior control is calculated based on the spin state amount SS or the drift-out state amount DS.
i may be corrected to be calculated, and the target braking force based on the drift-out state amount DS is calculated for the right and left rear wheels, but is calculated for three wheels except the turning outer front wheel, or The calculation may be modified so as to be performed only for the turning inner rear wheel.

In the illustrated embodiment, the target braking force of the roll suppression control is calculated for the three wheels except the front wheel on the inside of the turn. However, the target braking force of the roll suppression control is calculated for the front wheel on the outside of the turn. Only the operation may be modified.

[0075]

As is apparent from the above description, according to the first aspect of the present invention, it is possible to prevent a sudden change in the acceleration / deceleration of the vehicle during the motion control, and thereby to control the braking force by the motion control. Therefore, it is possible to reliably prevent the stability of the vehicle from being reduced due to the increase and decrease of the vehicle speed, and to effectively and reliably stabilize the motion of the vehicle.

According to the second aspect of the present invention, the behavior control and the roll suppression control are performed simultaneously, not only when there is a possibility that the stability of the vehicle may be reduced due to the increase or decrease of the braking force due to the roll suppression control. Thus, even when the stability of the vehicle is likely to be reduced due to the increase or decrease in the braking force, the speed at which the braking force is changed can be reliably reduced.

According to the third aspect of the invention, it is possible to reliably prevent the stability of the vehicle from being reduced due to the increase or decrease of the braking force due to the roll suppression control. In addition, it is possible to reliably prevent the stability of the vehicle from being reduced due to an increase or decrease in the braking force due to the motion control in a situation where the roll of the vehicle body is large.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one preferred embodiment of a vehicle motion control device according to the present invention.

FIG. 2 is a flowchart showing a main routine of motion control in the illustrated embodiment.

FIG. 3 is a step 20 of the flowchart shown in FIG. 2;
Is a flowchart showing a target braking force Fbsi calculation routine for behavior control in the embodiment.

FIG. 4 is a step 50 of the flowchart shown in FIG. 2;
Is a flowchart showing a target braking force Fbri calculation routine of roll suppression control in the embodiment.

FIG. 5 is a graph showing a relationship between a target braking force Fbti of each wheel and a target slip ratio Rsti of each wheel.

FIG. 6 is a graph showing a relationship between a target slip ratio Spti of each wheel and a duty ratio Dri of the pressure increasing / decreasing control valve of each wheel.

FIG. 7 is a graph showing a relationship between a spin state amount SS and a target braking force Fssfo of a turning outer front wheel.

FIG. 8 is a graph showing a relationship between a drift-out state quantity DS and a target braking force Fsall of the entire vehicle.

FIG. 9 is a graph showing a relationship between a roll evaluation value RV and a roll suppression control amount B.

[Explanation of symbols]

 10FR-10RL ... Wheels 20 ... Brake device 28 ... Master cylinder 30 ... Electrical control device 32FR-32RL ... Wheel speed sensor 34 ... Steering angle sensor 36 ... Yaw rate sensor 38 ... Longitudinal acceleration sensor 40 ... Lateral acceleration sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D045 BB40 GG00 GG05 GG25 GG26 GG28 3D046 BB21 HH08 HH21 HH25 HH26 HH36 JJ02 JJ06 JJ14 JJ19

Claims (4)

[Claims] 1. A vehicle motion control device for performing a motion control for stabilizing the motion of a vehicle by applying a braking force to wheels based on a running state of the vehicle. Determining means for determining a possibility that the stability of the vehicle will decrease, and means for reducing the change speed of the braking force by the motion control when the determining means determines that the stability of the vehicle may decrease. Characteristic vehicle motion control device. 2. A behavior control means for stabilizing the turning behavior of the vehicle, a roll suppression control means for suppressing an excessive roll of the vehicle body, a target control amount of each wheel by the behavior control means, and a roll suppression control means. A means for calculating a final target control amount for each wheel based on the target control amount for each wheel; and a means for controlling the braking force of each wheel based on the final target control amount. The vehicle motion control device according to claim 1. 3. A vehicle according to claim 2, wherein said judging means judges that there is a possibility that the stability of the vehicle is reduced when the roll suppression control is being executed by said roll suppression control means. Vehicle motion control device. 4. The apparatus according to claim 1, wherein said determining means determines that there is a possibility that the stability of the vehicle is reduced when the magnitude of the state quantity indicating the degree of roll of the vehicle body exceeds a reference value. Item 3. The vehicle motion control device according to item 1 or 2.