JPH0958444A - Behavior controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a device for accurately computing antiturning moment suited to the spinning state of a vehicle in simple structure on the behavior control device of the vehicle which controls the braking force of each wheel according to the running state to the vehicle to stabilize the behavior of the vehicle. SOLUTION: The change rate dM/dβ of restoring yaw-moment to the slip angle β of a car body is computed on the longitudinal acceleration Gx of a vehicle, lateral acceleration Gy, a yawing rate γ, car speed V and a steering angle δ. (step 100-106). In the case where dM/dβ is smaller in comparison with fixed value, the vehicle is judged to be in the tendency of spinning, and an antiturning moment MVSC for offseting the tendency of spinning is computed on dM/dβ. (step 110). In order to realize MVSC, proper braking force is generated on a front wheel on the side of a turning outer wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle behavior control device, and more particularly to a vehicle behavior control device for stabilizing the vehicle behavior by controlling the braking force of each wheel according to the running state of the vehicle. Regarding

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 62-2535.
As disclosed in Japanese Patent Publication No. 59, there is known a device for stabilizing the vehicle behavior by decelerating the vehicle when it is determined that the grip state of the tire has reached a limit. The above-mentioned conventional device detects a slip angle of a tire (an angle formed by the center plane of the tire and a traveling direction of the tire) and a cornering force, and the increase amount of the cornering force with respect to the increase amount of the slip angle is non-linear. At that point, it is judged that the grip condition of the tire has reached the limit.

In a region where the slip angle is small, the cornering force of the tire has a value substantially proportional to the slip angle. In a region where the slip angle exceeds the limit slip angle determined by the tire performance, etc., the cornering force converges to almost the saturation value, and the linear relationship between the change amount of the slip angle and the change amount of the cornering force is not established. According to the above conventional device, when the slip angle of the wheel is increased due to the steering operation, the tire is in an appropriate grip state in a region where the cornering force increases in proportion to the increase amount. Is judged. On the other hand, in a state where the cornering force does not increase proportionally to the increase amount of the wheel slip angle, that is, in the region where the steering amount and the change amount of the cornering force do not correspond to each other, the tire deviates from the proper grip state. Then, the vehicle is decelerated. According to such control, the grip of the tire is not lost during turning, and stable turning behavior can be obtained.

[0004]

By the way, the slip angle of the wheel is detected by detecting the slip angle β of the vehicle body (the angle formed by the axis of the vehicle body and the traveling direction of the center of gravity C of the vehicle body), and further, the slip angle β of the vehicle body is obtained. , The center of gravity C and the position of the front wheel or the rear wheel are corrected by geometrical correction. The slip angle β of the vehicle body can be obtained by dividing the lateral velocity Vy of the vehicle by the longitudinal velocity Vx of the vehicle. The lateral velocity Vy can be obtained by integrating the translational acceleration acting on the vehicle. Further, the translational acceleration is the longitudinal velocity Vx, the lateral acceleration Gy acting on the vehicle, and the yaw rate γ around the center of gravity C.
Can be expressed as Gy−Vx · γ.

Therefore, the slip angle β of the vehicle body is β = ∫
It can be expressed as {(Gy / Vx) -γ} dt. Gy
And γ can be detected by a lateral acceleration sensor and a yaw rate sensor, respectively. Further, Vx can be approximated by the vehicle speed V. Therefore, the slip angle β of the vehicle body, that is, the slip angle of the wheels can be easily calculated in a vehicle equipped with a lateral acceleration sensor, a yaw rate sensor, and a vehicle speed sensor.

However, as described above, Gy, γ, V
In order to calculate β based on x and the like, it is necessary to perform integral calculation in the calculation process. Therefore, Gy,
When errors are superposed on the detected values of γ, Vx, etc., those errors are accumulated in the calculated value of β. Therefore, in order to accurately detect the vehicle body slip angle β, that is, to accurately detect the wheel slip angle, Gy,
It is necessary to give high accuracy to each sensor that detects γ, Vx, and the like.

Further, as described above, the slip angle β of the vehicle body
Can be obtained by dividing the lateral velocity Vy of the vehicle by the longitudinal velocity Vx of the vehicle. Therefore, for example, if Vy and Vx are accurately detected using a ground speed sensor or the like, the vehicle body slip angle β is directly calculated from the detected values, and the wheel slip angle is accurately obtained based on the calculated value. You can However, a sensor for directly detecting the vehicle body slip angle β, such as a ground speed sensor, is more expensive than a lateral acceleration sensor, a yaw rate sensor, or the like.

As described above, in order to detect the slip angle of the wheel, it is necessary to use an expensive sensor. In this regard,
The above-mentioned conventional device that controls the behavior of the vehicle based on the slip angle of the wheel has a problem that it is difficult to realize it at low cost. The present invention has been made in view of the above points, accurately detects the turning behavior of the vehicle,
An object of the present invention is to realize a vehicle behavior control device that generates an anti-turning moment necessary to realize stable turning behavior without using an expensive sensor.

[0009]

The above-mentioned object is defined in claim 1.
In the vehicle behavior control device for stabilizing the vehicle behavior by controlling the braking force of each wheel when the vehicle is running, the yaw moment change rate detecting means for detecting the yaw moment change rate with respect to the vehicle body slip angle. And an anti-turning moment calculating means for calculating an anti-turning moment to be applied to the vehicle based on the detection result of the yaw moment change ratio detecting means, and a braking force of each wheel so that the anti-turning moment is generated. And a braking force control means for controlling the vehicle.

In the present invention, the yaw moment change rate detecting means detects the rate of change of the yaw moment due to the change of the vehicle body slip angle. If the grip condition of the tire is proper, as the slip angle of the car body increases,
The yaw moment in the direction in which the vehicle body goes straight (hereinafter, referred to as the restored yaw moment) becomes large. On the other hand, when the grip state of the tire exceeds the limit, the restored yaw moment becomes smaller as the slip angle of the vehicle body increases.

The anti-turning moment calculation means calculates the anti-turning moment to be applied to the vehicle based on the change rate of the yaw moment. In the region where the restored yaw moment has a negative inclination with respect to the vehicle body slip angle, the moment the vehicle body is directed straight ahead decreases as the vehicle body slip angle increases, and the vehicle tends to spin. The anti-turning moment calculation means calculates a moment to be applied in the anti-turning direction, that is, an anti-turning moment, in order to bring the vehicle into a stable turning state under such a situation.

The braking force control means controls the braking force of each wheel so that the anti-turning moment calculated as described above is generated. When the braking force control means controls the braking force of each wheel, the resultant force of the moment in the direction of straightening the vehicle becomes an appropriate value even in the region where the restored yaw moment of the tire shows a negative inclination, and the vehicle spin The tendency is suppressed.

[0013]

FIG. 1 shows a system configuration diagram of an embodiment of the present invention. The system of this embodiment is controlled by an electronic control unit (ECU) 10 described later. In FIG. 1, 12FL, 12FR, 12RL, 12
RR indicates the left front wheel, right front wheel, left rear wheel, and right rear wheel of the vehicle, respectively. Four wheels 12FL, 12FR, 12RL,
A wheel cylinder (not shown) is incorporated in each of the 12RRs. When the hydraulic pressure is supplied, each wheel cylinder generates a braking force according to the hydraulic pressure.

Wheels 12FL, 12FR, 12RL, 12
Each wheel cylinder of RR has a hydraulic control valve 14F.
L, 14FR, 14RL, and 14RR (hereinafter, when these are collectively referred to by the reference numeral 14) are connected. A reservoir tank 18 communicates with the hydraulic control valve 14 via a hydraulic passage 16 and a path shown by a chain line in FIG. The hydraulic control valve 14 is a two-position valve that operates in response to a signal supplied from the outside, and has a pressure increasing position that communicates the wheel cylinder with the hydraulic passage 16, and a pressure reducing position that communicates the wheel cylinder with the reservoir tank 18. And realize.

A hydraulic source switching valve 20 is provided in the hydraulic passage 16.
Are in communication. The hydraulic source switching valve 20 is also in communication with a high pressure source including a hydraulic pump 22 and an accumulator 24 and a master cylinder 26. The hydraulic power source switching valve 20 is a two-position valve that operates in response to a signal supplied from the outside, and connects the hydraulic passage 16 and the master cylinder 26 to a control execution position that connects the hydraulic passage 16 and the hydraulic pump 22. To achieve the normal position.

The hydraulic pump 22 pumps up the brake fluid from the reservoir tank 18 and pumps it to the accumulator 24 side under the condition that the hydraulic pressure switching valve 20 is in the control execution position. The accumulator 24 stores the hydraulic pressure generated at that time and supplies a stable hydraulic pressure with little pulsation to the hydraulic pressure switching valve 20. Therefore, when the hydraulic pressure switching valve 20 is at the control execution position, the hydraulic pump 2 is provided in the hydraulic passage 16.
A predetermined hydraulic pressure corresponding to the discharge capacity of 2 is introduced. The master cylinder 26 generates a hydraulic pressure according to the brake pedal force applied to the brake pedal 28. Therefore, when the hydraulic pressure switching valve 20 is in the normal position, the hydraulic pressure according to the brake pedal force is guided to the hydraulic passage 16.

In this embodiment, the hydraulic control valve 1 described above is used.
4 and the hydraulic pressure source switching valve 20 are controlled by the ECU 10. The ECU 10 has wheels 12FL, 12
Wheel speed V _WFL, V of FR, 12RL, 12RR respectively
_WFR, V _WRL, V _WRR (Hereinafter, when these are collectively referred to,
A wheel speed sensor 30FL for detecting the wheel speed V _W ),
30FR, 30RL, 30RR (hereinafter, these are collectively denoted by reference numeral 30), a steering angle sensor 34 for detecting a steering angle δ of the steering wheel 32, a longitudinal acceleration Gx acting on the vehicle, and a lateral direction. Directional acceleration G
A G sensor 36 for detecting y and a yaw rate sensor 38 for detecting a turning angular velocity generated around the center of gravity of the vehicle, that is, a yaw rate γ of the vehicle are connected.

Next, the content of the braking force control for stabilizing the vehicle behavior, which is executed in the system of this embodiment, will be described with reference to FIGS. FIG.
The figure which showed the vehicle in the left turn in planar view is shown. In FIG. 2, “C” represents the center of gravity of the vehicle. As shown in the figure, when the vehicle is making a left turn, a yaw rate γ is generated around the center of gravity C of the vehicle in the counterclockwise direction. Wheels 12FL,
When the vehicle is traveling while maintaining the proper grip state of the 12FR, 12RL, and 12RR, an appropriate yaw rate γ according to the vehicle speed V and the steering angle δ is generated in the vehicle. On the other hand, when the front wheels 12FL and 12FR lose their grip, the vehicle tends to drift because the turning moment acting in the direction of turning the vehicle is insufficient, while the rear wheels 12RL and 12RR lose their grip. Then, since the anti-turning moment acting in the direction to prevent the turning of the vehicle is insufficient, the vehicle tends to spin.

By the way, when the front wheel (the front right wheel FR in FIG. 2) located on the outer side of the turning wheel generates the braking force F _BRK as shown by the solid arrow in FIG. 2 while the vehicle is turning, the braking force F _BRK is generated. _{The BRK} acts on the center of gravity C as a moment in a direction that prevents the vehicle from turning. Therefore, if a braking force is generated on the front wheels FL or FR located on the outer side of the turning wheel while the vehicle is turning, the tendency of the vehicle to spin can be suppressed.

On the other hand, when the rear wheels 12RL, 12RR generate the braking force F _BRK as shown by the broken line arrow in FIG. 2 during turning of the vehicle, the load of the vehicle shifts to the front wheels 12FL, 12FR side and the front wheels 12FL, 12FR. Grip is restored. As a result, the centripetal force of the vehicle is increased and the turning moment is increased. Therefore, the braking force F is applied to the rear wheels 12RL and 12RR during turning of the vehicle.
_{If BRK} is generated, the drift tendency of the vehicle can be suppressed.

Therefore, in the system of the present embodiment, the vehicle behavior is estimated while the vehicle is turning, and when the vehicle tends to spin according to the estimation result, the front wheel 12FL or 12FR on the outer turning wheel side is detected. By supplying an appropriate hydraulic pressure to the wheel cylinders, or, if it is determined that the vehicle is in a drift tendency, by supplying an appropriate hydraulic pressure to the wheel cylinders of the front front wheels 12FL or 12FR on the turning inner wheel side, It is intended to stabilize the behavior.

In order to realize the above-mentioned function, the behavior of the vehicle is accurately estimated, and the turning moment or anti-turning moment necessary for maintaining the vehicle in a stable state is detected, and those moments are detected. It is necessary to control the braking force of each wheel so that In the system of the present embodiment, when the vehicle has a spin tendency, the anti-turning moment necessary for canceling the spin tendency and realizing a stable turning state can be accurately realized with a simple configuration. It has features.

By the way, whether or not the vehicle has a tendency to spin is determined by the slip angle (hereinafter referred to as the rear wheel slip angle) βr of the rear wheels 12RL and 12RR and the corner rig force (hereinafter referred to as the rear wheel slip force) of the rear wheels 12RL and 12RR. It can be determined from the relationship with CFr (which is called wheel cornering force). That is, the rear wheel cornering force CFr is generated by the rear wheel slip angle βr. CFr shows a linear relationship with βr in a region where βr is small, and shows a nonlinear relationship with βr in a region where the tire grip state exceeds the limit. Therefore, by determining whether the relationship between CFr and βr is linear, the rear wheel 12R
It is possible to determine whether the L and 12RR are in the proper grip state.

However, in order to obtain the slip angle βr, it is necessary to integrate the output values of various sensors as shown below. Hereinafter, a method of calculating the rear wheel slip angle βr will be described with reference to FIG. FIG. 3 shows an equivalent two-wheel vehicle model of a four-wheel vehicle used to estimate the behavior of the vehicle during turning. 3, C is the center of gravity of the vehicle, V is the vehicle body speed, β is the vehicle body slip angle (the counterclockwise direction is positive in FIG. 3), 2CFf is the front wheel 12
The resultant force of cornering force CFf of FL and 12FR,
2CFr is the resultant force of the cornering forces of the rear wheels 12RL and 12RR, and δ is the steering angle (the counterclockwise direction is positive in FIG. 3).

In the two-wheeled vehicle model shown in FIG. 3, when the vehicle weight is m, the following equation of motion is established on the Y axis passing through the center of gravity C. mV (dβ / dt + γ) = 2C _Ff + 2C _Fr (1) The first term (mV · dβ / dt) in the left side of the above equation (1) is the translational acceleration dVy / acting on the center of gravity C of the vehicle. It is a product of the approximate value of dt (V · dβ / dt) and the vehicle weight (m). Further, the second term (mVγ) on the left side of the equation (1) is a centrifugal force acting on the vehicle. The total value of them is the total value of the lateral force acting on the vehicle, and is 2CFf + 2C shown on the right side.
Balance with Fr.

The total value of the lateral force acting on the vehicle is 2CFf +
With 2CFr, the lateral acceleration Gy acting on the vehicle can be expressed by the following equation. Gy = (2CFf + 2CFr) / m (2) When the above formulas (1) and (2) are arranged, translational acceleration
dVy / dt = (V · dβ / dt) can be expressed by the following equation.

DVy / dt = V · dβ / dt = Gy−V · γ (3) Therefore, the rate of change dβ / dt of the slip angle β of the vehicle and the slip angle β are respectively expressed as follows. You can dβ / dt = (Gy / V) −γ (4) β = ∫ {(Gy / V) −γ)} dt (5) As shown in the above equation (5), the vehicle body slip angle β Is the lateral acceleration Gy acting on the vehicle, the vehicle speed V, and the yaw rate γ.
Is calculated by substituting into the integral formula. Also, the center of gravity C
And the distance between the rear wheel axis and the rear wheel axis is a, the velocity vector Vr of the rear wheel when the vehicle is turning while generating the yaw rate γ around the center of gravity C is the magnitude a ·
It can be grasped as a composite vector of the vector of γ and the vector of the vehicle speed V.

In this case, the angle formed by the direction of the vehicle speed V and the traveling direction of the rear wheels can be expressed as "b.γ / V". Therefore, the slip angle β _f of the rear wheel can be expressed by the following equation using the vehicle body slip angle β. βr = β−b · γ / V (6) Thus, the rear wheel slip angle βr is the vehicle body slip angle β
Is calculated by performing geometrical correction due to the distance between the center of gravity C and the rear wheel axle. Body slip angle β
Is calculated by substituting the lateral acceleration Gy, the vehicle speed V, and the yaw rate γ into the integral equation shown in the above equation (5). Therefore, in order to calculate the rear wheel slip angle βr,
As described above, it is necessary to perform integral calculation.

The output value of the sensor is accumulated in the function value calculated by the integral calculation. Therefore, as described above, the rear wheel slip angle β obtained by the arithmetic expression including the integration process
In order to obtain r with high accuracy, it is necessary to impart high calculation accuracy to the sensor that detects the lateral acceleration Gy, the sensor that detects the vehicle speed V, and the sensor that calculates the yaw rate γ. Therefore, a system that obtains the behavior of the vehicle based on the rear wheel slip angle βr and the rear wheel cornering force CFr cannot be realized at low cost.

Next, referring to FIG. 4, a method executed by the system according to the present embodiment to detect the degree of the tendency of spin of the vehicle will be described. FIG. 4 is a characteristic diagram showing the relationship between the restoration yaw moment M acting around the center of gravity C of the vehicle and the vehicle body slip angle β with the steering angle δ as a parameter. The restored yaw moment M is a yaw moment generated around the center of gravity C of the vehicle due to the front wheel cornering force CFf and the rear wheel cornering force CFr. In this embodiment, the clockwise direction is the positive direction of the restored yaw moment M. As described above, the yaw rate γ and the vehicle body slip angle β are positive in the counterclockwise direction in this embodiment.

When the vehicle is turning left at the yaw rate γ (> 0) and the vehicle approaches a straight traveling state, the yaw rate γ
The differential value of (yaw angular acceleration) dγ / dt is a negative value. At this time, when the vehicle turns to the right, the size | I ・ dγ / dt |
The restored yaw moment M of M must be acting, and its sign is positive. In addition, the vehicle has a yaw rate γ (<0)
If the vehicle approaches straight when the vehicle is turning right at
dγ / dt is a positive value. At this time, the restoring yaw moment M of magnitude | I · dγ / dt | should act on the vehicle in the left turning direction, and the sign thereof is negative. Therefore, the restored yaw moment M can be expressed by the following equation using the yaw moment of inertia I of the vehicle and the yaw angular acceleration dγ / dt.

M = −I · dγ / dt (7) First and fourth quadrants (β> 0) of β-M coordinates shown in FIG.
Region) indicates a case where the vehicle is traveling in the left turning direction. Further, the second quadrant and the third quadrant (region of β <0) represent the case where the vehicle is traveling in the right turning direction. Further, the area (β = 0) on the M-axis represents the case where the vehicle is in a straight traveling state.

When the vehicle is traveling straight ahead (β = 0), the steering angle δ is steered counterclockwise (δ>
0), the resultant force of the front wheel cornering force CFf and the rear wheel cornering force CFr generates a yaw moment that turns the vehicle counterclockwise. On the other hand, when the vehicle is traveling straight ahead and the steering angle δ is steered clockwise (δ <0), the front wheel cornering force CF
The resultant force of f and the rear wheel cornering force CFr generates a yaw moment that turns the vehicle clockwise. Therefore, in the vicinity of β = 0, the restored yaw moment M
Is a negative value when δ> 0, and a positive value when δ <0, as shown in FIG.

When the steering angle δ is fixed to a positive (δ> 0) predetermined value, a yaw moment that rotates the vehicle counterclockwise is generated around the center of gravity C of the vehicle. This yaw moment becomes smaller as the vehicle shifts to the left and the vehicle body slip angle β increases. Then, under the situation where the yaw moment is "0", the vehicle is in a steady circular turning state. Also, for example, when the steering wheel is turned back, if a situation occurs in which the vehicle body slip angle β exceeds the vehicle body slip angle β ₀ that realizes a steady circular turning state, a yaw moment in the clockwise direction acts on the vehicle. , The vehicle is approaching straight. Therefore, when the vehicle is turning counterclockwise and δ> 0, the fourth number in FIG.
As shown in the quadrant and the first quadrant, with respect to the vehicle body slip angle β, the restoring yaw moment M tends to increase while maintaining a substantially linear relationship in a region where β is small, and it is non-increasing in a region where β is large. It tends to increase according to a linear relationship.

Next, a case where the steering angle δ is steered in the clockwise direction (when δ <0) under the condition where the vehicle is turning in the counterclockwise direction will be described. Under such circumstances, when the tire maintains an appropriate grip state, the larger the vehicle body slip angle β is, the larger yaw moment acts on the vehicle in the right rotation direction. In this case, β and the yaw moment acting on the vehicle have a substantially linear relationship. However, in a region where the vehicle body slip angle β exceeds the limit value at which the tire can maintain an appropriate grip state, the relationship between β and the yaw moment acting on the vehicle becomes non-linear. Under such circumstances, the larger β is, the smaller yaw moment acts on the vehicle in the rightward rotation direction. Therefore, the vehicle is turning counterclockwise, and
When δ <0, as shown in the first quadrant in FIG. 4, the restoration yaw moment M is increased with respect to the vehicle body slip angle β.
However, in a region where β is small, it changes while maintaining a substantially linear relationship with a positive slope, and in a region where β is large, it changes with a negative slope without maintaining a linear relationship.

As described above, the restored yaw moment M has a small vehicle body slip angle β regardless of the direction of the steering angle δ,
In a region where the tire can maintain a proper grip state, it shows a linear relationship with the vehicle body slip angle β, and in a region where the vehicle body slip angle β is large and the tire cannot maintain a proper grip state, the vehicle body slip angle β It shows a non-linear relationship with β. In a region where the restored yaw moment M has a linear relationship with the vehicle body slip angle β, when the turning state of the vehicle changes so that the vehicle body slip angle β increases, the restored yaw moment M corresponds to the change of β. Also increases. Therefore, in such a situation, the vehicle exhibits stable turning behavior. On the other hand, in the region where the restored yaw moment M has a non-linear relationship with the vehicle body slip angle β, the vehicle body slip angle β
When the turning state of the vehicle changes so as to increase .beta., A restoring yaw moment M that can balance the increased .beta. Cannot be obtained, and .beta. Is more likely to increase. Therefore, in such a situation, the vehicle tends to spin.

Similarly, the relationship between the vehicle body slip angle β and the restored yaw moment M in the left turning region (first quadrant and fourth quadrant shown in FIG. 4) is similar to the right turning region (first quadrant shown in FIG. 4).
It also holds in the quadrant and the fourth quadrant. That is, as shown in FIG. 4, the restoration yaw moment M when the vehicle is traveling in the right turning direction (when β <0) has a small absolute value | β | of β, and the tire is in a proper grip state. In a region where the tire can be maintained, it tends to increase in a linear relationship with the vehicle body slip angle β, and in a region where | β | is large and the tire cannot maintain a proper grip state, the vehicle body slip angle β Shows a tendency to increase or decrease in a non-linear relationship.

Therefore, whether or not the vehicle has a tendency to spin depends on whether or not the restored yaw moment M maintains a linear relationship with the vehicle body slip angle β regardless of the turning direction of the vehicle. The determination can be made based on whether or not the change rate dM / dβ of M with respect to the amount of change of β maintains a predetermined slope. The hatched area shown in FIG. 4 represents an area determined to be a spin area from this viewpoint.

The restored yaw moment M is M as described above.
= −I · dγ / dt. Therefore, the differential value dM / dt of the restored yaw moment M can be expressed by the following equation. dM / dt = −I · d ² γ / dt ² (8) The vehicle body slip angle β is the ratio of the longitudinal velocity Vx of the vehicle to the lateral velocity Vy. Therefore, the differential value dβ / dt of the vehicle body slip angle β can be expressed by the following equation.

Dβ / dt = d (Vy / Vx) / dt = {(dVy / dt) / Vx}-{Vy · (dVx / dt) / Vx ² } (9) In the above equation (9), The dVy / dt used can be approximated by “Gy−V · γ” as shown in the equation (3). The lateral velocity Vy of the vehicle is the longitudinal velocity Vx of the vehicle and the longitudinal acceleration G detected by the G sensor 36.
It can be expressed as follows using x and.

Vy = (1 / γ) · (dVx / dt −Gx) (10) Further, the vehicle front-rear direction speed Vx can be approximated by the vehicle speed V. Therefore, the relationship shown in the equation (9) can be rewritten as the following equation. dβ / dt = {(Gy−V · γ) / V} + {(dV / dt) / (V ² · γ)} · (Gx−dV / dt) (11) The above equation (8) and From the equation (11), the change rate of M with respect to the change amount of β, dM / dβ, can be expressed by the following equation.

DM / dβ = − (I · d ² γ / dt ² ) · V ² · γ / {V · (Gy−dV / dt) + V · γ · (Gx−dV / dt)} ( 12) In the system of the present embodiment, the yaw rate γ, the vehicle speed V, the lateral acceleration Gy, and the longitudinal acceleration Gx shown in the equation (12) are calculated using the yaw rate sensor 38, the wheel speed sensor 30, and the G sensor 36, respectively. Can be detected. Therefore, according to the system of the present embodiment, the above (1
It is possible to perform the calculation of the expression 2). Also, (12) above
The equation does not include the integral term as shown in the equation (5). Therefore, the calculation of the above formula (12) can be performed accurately without being affected by the error of various sensors.

Therefore, in the system of this embodiment, the calculation of the above formula (12) is performed based on the detected values of various sensors, and when the calculated value dM / dβ is smaller than the predetermined value, the vehicle tends to spin. It is judged that there is, and the calculated value dM
Based on / dβ, the magnitude of the anti-turning moment required to cancel the spin tendency is determined.

FIG. 5 shows a control routine executed by the ECU 10 to generate the anti-turning moment by calculating the anti-turning moment by using the above method and controlling the braking force of the left and right front wheels 12FL and 12FR. 3 shows an example flowchart. It should be noted that this routine is a regular interrupt routine that is activated at regular time intervals.

When the routine shown in FIG. 5 is started, first, at step 100, various parameters required for executing this routine are read. Specifically, the longitudinal acceleration Gx, the lateral acceleration Gy, the yaw rate γ, the wheel speed Vw, and the steering angle δ are read.

Next, at step 102, the estimated vehicle speed V
Is calculated. In this embodiment, the wheel speed Vw of the four wheels is
The average value of _FL , Vw _FR , Vw _RL , and Vw _RR is used as the estimated vehicle speed. The method of calculating the estimated vehicle speed V is not limited to this, and for example, a method of actually measuring using a ground speed sensor can be used.

In step 104, the differential value dV / dt of the estimated vehicle body speed V is calculated based on the estimated vehicle body speed V calculated in the previous processing and the estimated vehicle body speed calculated this time, and the processing of the previous two times is performed. The two-time differential value d ² γ / dt ^{2 of} the yaw rate γ is calculated based on the yaw rate γ detected from time to this processing.

Then, in step 106, the various parameters read in step 100 and the various parameters calculated in steps 102 and 104 are substituted into the equation (12) to calculate dM / dβ.
When the above processing is completed, next, at step 108, the anti-turning moment MVSC required to cancel the spin tendency of the vehicle is calculated. As mentioned above, the degree of spin tendency of the vehicle (hereinafter referred to as the spin degree) is dM / d
It can be judged based on β. Specifically, dM
If / dβ is an appropriate positive value, it can be determined that the vehicle is traveling with stable behavior, and it can be determined that the smaller the M / dβ, the greater the spin degree of the vehicle.

Therefore, in the present embodiment, FIG.
The ECU 10 stores a map as shown in (1) and searches the map with dM / dβ to obtain the necessary anti-turning moment MVSC. Incidentally, MV
As shown in FIG. 6, the SC map shows that dM / dβ is set so that MVSC becomes “0” in the region where dM / dβ exceeds the threshold value α (region where the vehicle behavior can be determined to be stable). In the area below the threshold value α, M decreases as dM / dβ decreases.
The VSC is set to be large.

By the way, as shown in FIG. 4, the value of dM / dβ at the boundary point between the slip region and the stable region varies depending on the steering angle δ. Therefore, the ECU 10
A plurality of MVSC maps are stored with the steering angle δ as a parameter. The ECU 10 reads out a map corresponding to δ from the maps based on the steering angle δ read in step 100, and executes the step 108.
Execute the processing of

When the vehicle has a tendency to spin, it is advantageous to cancel the spin tendency by increasing the possible anti-turning moment. Therefore, in the configuration in which the anti-turning moment is generated by utilizing the braking force difference between the wheels as in the system of the present embodiment, it is easier to suppress the spin tendency as the road surface μ is higher. In other words, on a road with a small road surface μ, it is preferable to set the spin area to a relatively large value and generate an anti-turning moment early.
For roads with a large road surface μ, it is preferable to set the spin area to a relatively small value to suppress unnecessary anti-turning moment. Therefore, in a system having a function of estimating the road surface μ, it is possible to realize more excellent vehicle behavior control by correcting the MVSC according to the road surface μ. The MVSC correction can be realized by, for example, increasing the threshold value α shown in FIG. 6 when the road surface μ is large, and increasing the threshold value α shown in FIG. 6 when the road surface μ is small. You can

After the above processing is completed, next step 1
At 10, the turning direction of the vehicle is specified. As described above, the yaw rate sensor 38 outputs a yaw rate signal having a different sign depending on the turning direction of the vehicle. In this step, the turning direction of the vehicle is specified based on the code, and based on the result, the left and right front wheels 12FL, 12F are determined.
One of the Rs is the turning outer wheel fout and the other is the turning inner wheel fin.
Specified as.

In the system of this embodiment, as described above, the anti-turning moment is generated by generating the braking force on the front wheel 12FL or 12FR on the turning outer wheel side. Here, a braking force is generated on each wheel according to the slip ratio generated on the wheel by the braking operation. That is, the braking force of the wheel is generated when a brake torque acts on the wheel and slip occurs between the tire and the road surface. Then, the braking force exhibits a maximum value at a predetermined slip ratio (hereinafter referred to as a limit slip ratio) according to the characteristics of the tire, and becomes a value substantially proportional to the slip ratio in a region below the limit slip ratio. Therefore, when the braking force control is performed, by controlling the brake hydraulic pressure so that the slip ratio does not exceed the limit slip ratio, the grip state of the wheels can always be properly maintained. Further, in a region where the slip ratio does not exceed the limit slip ratio, by controlling the brake hydraulic pressure so that the slip ratio becomes the target value, it is possible to accurately control the braking force generated between the tire and the road surface. .

Therefore, in the present embodiment, the braking force control is executed based on the slip ratio of the wheels. For the above reason, in step 112, the target slip ratio S ₀ fout to be realized in the front wheel 12FL or 12FR on the outer wheel turning side is calculated in order to generate the anti-turning moment MVSC obtained in step 108.
In step 112, specifically, the target slip ratio S ₀ fout is calculated by searching the map shown in FIG. 7 with the MVSC.
Is calculated. Specifically, in the region of MVSC> 0, the slip ratio S ₀ fL of the left front wheel is set to a value set in the map (a positive value), and the slip ratio S ₀ fR of the right front wheel is “0”.
Is set to each. As shown in FIG. 7, the map of the target slip ratio is S ₀ f in the region of MVSC> M ₁ so that S ₀ fout does not exceed the limit slip ratio of the tire.
out is set to saturate to a specified value. Also,
In the region of MVSC ≦ M _1, the braking force F _BRK generated at the front wheel on the outer wheel side of the turning with respect to the target slip ratio S ₀ fout,
The product of the center of gravity C of the vehicle and the distance b between the front wheel axles and the value "aF
_BRK "is set to be equal to MVSC.

When the above processing is completed, next step 1
In FIG. 14, the front wheel 12FL or 12FR on the turning outer wheel side
It is determined whether or not S ₀ fout> 0 holds for the target slip ratio S ₀ fout of. As described above, the condition of this step is satisfied when dM / dβ is smaller than the threshold value α and it is determined that the vehicle is in the spin state. If the above conditions are met, then proceed to step 116,
A process for generating MVSC is executed. on the other hand,
If the above conditions are not satisfied, it is determined that the vehicle behavior is stable, and the routine of this time is ended.

At step 116, the front wheel 1 on the turning outer wheel side is
Ideal wheel speed V of 2FL or 12FR ₀fout is calculated
You. Ideal wheel speed V₀In fout, the vehicle turns at the estimated vehicle speed V
When traveling, front wheel 12FL or 1 on the outer side of the turning wheel
A car obtained when 2FR rotates at a slip ratio of "0"
It is a wheel speed. Ideal wheel speed V₀fout is the estimated vehicle speed V,
By performing geometric correction according to the position of the turning outer wheel
Is calculated.

At step 118, the front wheel 1 on the outer wheel turning side
A process for controlling the braking force of 2FL or 12FR is executed. Specifically, first, the front wheel 12FL on the turning outer wheel side
Alternatively, based on the ideal wheel speed V ₀ fout of 12FR and the actual wheel speed Vfout, the slip ratio Sfout of the front wheel 12FL or 12FR on the outer turning wheel side Sfout = (1−V ₀ fout / Vfout) × 100
Is calculated. Then, the slip ratio Sfout is to match the target slip rate S ₀ fout, brake hydraulic pressure is controlled to be supplied to the turning outer side of the front wheel 12FL or 12FR wheel cylinder. When such control is executed,
In the front wheel 12FL or 12FR on the turning outer wheel side, the braking state with the target slip ratio S ₀ fout is realized. When the above process ends, the current process of this routine ends.

When this routine is executed by the ECU 10, the restored yaw moment M with respect to the vehicle body slip angle β
The spin degree of the vehicle is accurately detected on the basis of the change ratio, and the anti-turning moment for canceling the spin tendency of the vehicle can be generated by the braking force difference between the left and right front wheels 12FL and 12FR. Therefore, according to the system of the present embodiment, stable turning behavior can be obtained even in a region where the tire grip state exceeds the limit.

By the way, in the above-described embodiment, the braking force is generated in one of the left and right front wheels 12FL and 12FR,
Moreover, the necessary anti-turning moment is generated by not generating the braking force on the other side, but the present invention is not limited to this, and the left and right rear wheels 12RL, 12RR are not limited to this.
In addition, the vehicle behavior may be stabilized by giving a sufficient braking force difference to generate a necessary anti-turning moment.

In the above embodiment, the ECU 10
However, the yaw moment change ratio detecting means described above by executing the processing of steps 100 to 106, the anti-turning moment calculating means described above by executing the processing of step 108, and the step 11
By executing the processing of 0 to 118, the braking force control means described above is realized.

[0061]

As described above, according to the vehicle behavior control device of the present invention, the braking force of each wheel is controlled by controlling the braking force of each wheel based on the change rate of the yaw moment associated with the change of the vehicle body slip angle. Even in a region where the restored yaw moment shows a negative inclination, an appropriate anti-turn yaw moment can be applied to the vehicle in a direction in which the vehicle is in a straight traveling state. Therefore, according to the vehicle behavior control device of the present invention, the vehicle behavior during turning can be stably maintained. Further, unlike the vehicle body slip angle, the rate of change of the yaw moment due to each change of the vehicle body slip can be detected easily and highly accurately without using an expensive sensor. Therefore, according to the present invention, a behavior control device capable of controlling the vehicle behavior with high accuracy can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a plan view of a vehicle turning left.

FIG. 3 is a diagram showing a two-wheel model used for vehicle behavior analysis.

FIG. 4 is a characteristic diagram showing a relationship between a vehicle body slip angle β and a restored yaw moment M using a steering angle δ as a parameter.

FIG. 5 is a flowchart of an example of a braking force control routine executed in an embodiment of the present invention.

FIG. 6 is an example of a map used in a braking force control routine executed in an embodiment of the present invention.

FIG. 7 is another example of the map used in the braking force control routine executed in the embodiment of the present invention.

[Explanation of symbols]

10 electronic control unit (ECU) 12FL, 12FR, 12RL, 12RR wheels 14 (14FL, 14FR, 14RL, 14RR) hydraulic control valve 20 hydraulic source switching valve 30 (30FL, 30FR, 30RL, 30RR) wheel speed sensor 32 steering wheel 34 Steering angle sensor 36 G sensor 38 Yaw rate sensor

Claims (1)

[Claims] 1. A yaw moment change ratio detecting means for detecting a yaw moment change ratio with respect to a vehicle body slip angle in a vehicle behavior control device for stabilizing a vehicle behavior by controlling a braking force of each wheel while the vehicle is traveling. And an anti-turning moment calculating means for calculating an anti-turning moment to be applied to the vehicle based on the detection result of the yaw moment change ratio detecting means, and a braking force of each wheel so that the anti-turning moment is generated. A vehicle behavior control device, comprising: a braking force control means for controlling the vehicle.