JP2002337567A - Yaw motion control system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an innovative limit control performance by enabling to provide perfect neutral steering characteristics maintaining vehicle front and rear lateral slip angles roughly same under any traveling conditions. SOLUTION: This system is provided with a rear wheel drive vehicle having tire generating force of a rear wheel set higher than that of a front wheel, yaw moment generating mechanism generating torques roughly same and in opposite directions each other on left and right rear wheel, a vehicle behavior detecting means detecting vehicle behavior, an actual yaw moment detecting means included in the vehicle behavior detecting means and detecting yaw moment actually generated on the vehicle, a target yaw moment calculating means calculating a target yaw moment which is yaw moment required for current vehicle behavior based on input from the vehicle behavior detecting means, and a differential commanding means operating the yaw moment generating mechanism to output yaw moment amount equivalent to differential between the target yaw moment and the actual yaw moment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear-wheel drive vehicle which generates a yaw moment in a vehicle using a yaw moment generating mechanism for generating substantially equal torques in opposite directions to the right and left of the rear wheel. The present invention relates to a vehicle yaw motion control device that optimally controls a yaw momentum of a vehicle during steering.

[0002]

2. Description of the Related Art Conventionally, the steering characteristic of a vehicle is generally set to have a weak under characteristic at the time of steady circular turning or the like. That is, the steering characteristic is ideally a neutral steering characteristic, but in a rear-wheel drive vehicle, when the driving torque increases, the oversteer characteristic increases, and when the oversteering characteristic increases, the vehicle tends to spin. A weak under characteristic is set so that the oversteer characteristic does not become strong even when the driving torque increases. Note that, in a state where the steering wheel is turned so as to turn at a predetermined radius R0, the actual turning radius R becomes R>
The characteristic of R0 is the understeer characteristic, the characteristic of R = R0 is the neutral characteristic, and the characteristic of R <R0 is the oversteer characteristic.

[0003]

As described above, in the prior art, it is difficult for a rear-wheel drive vehicle to always make the steering characteristic of the vehicle neutral. In other words, if the steering characteristic is set so that the neutral characteristic can be obtained when the wheel is still in the grip region, such as during a low-speed turn, the neutral characteristic is obtained when the wheel approaches the limit region, such as in an accelerated turn. Thus, the neutral characteristic cannot be set over the entire region from the grip region of the wheel to the limit region. In particular, when neutral characteristics can be obtained in the limit area of the wheel, even if the vehicle is in the limit state, it will be extremely excellent in controllability, and it will be possible to obtain high sports driving performance and emergency avoidance performance Becomes

[0004] It is an object of the present invention to obtain a completely neutral steering characteristic in which the sideslip angle before and after the vehicle changes substantially equally in all running conditions, and to obtain an innovative limit control performance.

[0005]

In order to achieve the above-mentioned object, the present invention relates to a vehicle which is driven by rear wheels and in which the tire generating force of the rear wheels is set larger than that of the front wheels. A yaw moment generating mechanism for generating substantially equal torques in opposite directions to the left and right, a vehicle behavior detecting means for detecting vehicle behavior, and an actual yaw moment generated in the vehicle included in the vehicle behavior detecting means An actual yaw moment detecting means, a target yaw moment calculating means for obtaining a target yaw moment which is a yaw moment required in the current vehicle behavior based on an input from the vehicle behavior detecting means, Operating command means for operating the yaw moment generating mechanism to output a yaw moment of an amount corresponding to a difference from the moment. It was a means.

[0006] The invention described in claim 2 is the invention according to claim 1.
Wherein the maximum tire generating force of the front turning inner wheel is F1, the maximum tire generating force of the front turning outer wheel is F2, the maximum tire generating force of the rear turning inner wheel is F3, and the rear wheel is F3. The maximum tire generating force of the turning outer wheel is F4, the turning inner wheel side rear wheel driving force is Fx3, the turning outer wheel side rear wheel driving force is Fx4, and the turning inner wheel side rear wheel maximum lateral force is Fy.
3, the maximum lateral force of the rear wheel on the turning outer wheel side is Fy4, the longitudinal distance between the vehicle center of gravity and the front wheel axle is Lf, the longitudinal distance between the vehicle center of gravity and the rear wheel axle is Lr, and the left and right wheel width is Lt. CYM = Lf (F1 + F2) -Lr (Fy3 + Fy4)
+ Lt (−Fx3 + Fx4) / 2 Critical yaw moment CY around the vehicle center of gravity obtained by the equation
The tire generating force of each wheel is set so that M becomes negative when the driving means is in the maximum torque generating turn and the yaw moment generating mechanism is not operated.

[0007] The invention according to claim 3 provides the invention according to claim 1.
Further, in the yaw motion control device for a vehicle described in 2, the tire generating force is set as described above by setting the rear wheels wider than the front wheels.

According to a fourth aspect of the present invention, in the vehicle yaw motion control device according to any one of the first to third aspects, the target yaw moment calculating means includes a state quantity of each wheel and a predetermined target yaw moment. A means for calculating a target yaw moment using tire characteristics, wherein the target tire characteristics are set higher for a rear wheel than for a front wheel.

[0009]

In a vehicle which is driven by rear wheels and in which the tire generating force of the rear wheels is set to be larger than that of the front wheels, the basic characteristic that does not operate the yaw moment generating mechanism is that of the front and rear wheels. Understeer characteristics are stronger than the steering characteristics of a vehicle having substantially the same tire generation force. As described above, when the yaw moment generating mechanism is operated in a vehicle having a margin on the understeer side as compared with the neutral steering, the steering characteristic is displaced in the neutral characteristic direction. Therefore, in a vehicle having understeer characteristics over the entire range from the grip region of the wheel to the limit region in the uncontrolled state, the target yaw moment required for the vehicle behavior is obtained, and the yaw moment corresponding to the difference from the actual yaw moment is calculated. By operating the yaw moment generating mechanism so as to obtain the neutral steer characteristic over the entire range from the grip region of the wheel to the limit region. Further, in the present invention, since both the target value and the detected value are obtained by the yaw moment and the two are compared and controlled, there is no delay or vibration in the control result. In the above, the vehicle can be controlled to the neutral steer characteristic without causing a control delay.

[0010] The basic characteristics of the vehicle described above are defined in claim 2.
The maximum tire generating force of the front turning inner wheel is F1 and the maximum tire generating force of the front turning outer wheel is F
2, the maximum tire generating force of the rear turning inner wheel is F3, the maximum tire generating force of the rear turning outer wheel is F4, the rear wheel driving force on the turning inner wheel side is Fx3, and the rear wheel driving force on the turning outer wheel side is Fx.
4. The maximum lateral force of the rear wheel on the turning inner wheel side is Fy3, the maximum lateral force of the rear wheel on the turning outer wheel is Fy4, the longitudinal distance between the vehicle center of gravity and the front wheel axle is Lf, and the longitudinal direction between the vehicle center of gravity and the rear wheel axle. CYM = Lf (F1 + F2) -Lr (Fy3 + Fy4) where Lr is the distance and Lt is the width of the left and right rear wheels.
+ Lt (−Fx3 + Fx4) / 2 Critical yaw moment CY around the vehicle center of gravity obtained by the equation
M, that is, the limit yaw moment CYM is set so that the limit yaw moment CYM becomes negative in the state where the yaw moment generating mechanism is not operated at the time of the maximum torque generation turning of the driving means. Set the tire generation force. This setting can be performed by setting the rear wheel wider than the front wheel, as well as setting the ground friction force of the rear wheel higher than that of the front wheel by the tread shape and the material. It can be implemented by the following.

According to the present invention, the target yaw moment calculating means calculates a target yaw moment by using a state quantity of each wheel and a preset target tire characteristic.
The target tire characteristics are set higher for the rear wheels than for the front wheels.Therefore, the yaw moment generating mechanism can be operated on the rear wheels to greatly change the steering characteristics, and a large margin is provided on the understeer side. Even if it is set, it can be controlled to the neutral steer characteristic.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, before describing the embodiment, a limit yaw moment CYM used in the present invention will be described. As shown in FIG. 1, consider a state in which when the braking / driving force and load of each wheel are applied, the sideslip angle increases under these conditions and the lateral force takes a maximum value. The yaw moment around the vehicle center of gravity due to the tire generation force (the magnitude is equal to the radius of the friction circle) at this time is defined as the limit yaw moment CYM. If the limit yaw moment CYM is a negative value, it means that the vehicle finally has a margin of the restoring moment.

When the rear wheel drive vehicle makes a steady turn or accelerated turn, the limit yaw moment CYM is given by the following equation. CYM = Lf (F1 + F2) -Lr (Fy3 + Fy4) + Lt (-Fx3 + Fx4) / 2 where F1, F2, F3, and F4 are the maximum tire generating force under each wheel load, Fx3 and Fx4 are the driving force of the rear wheels, and Fx
y3 and Fy4 are the rear wheel maximum lateral forces, which have the following relationship. ^{Fy3 = (F3 2 -Fx3 2)} 1/2, Fy4 = (F4
² -Fx4 ^{2) 1/2} Note, Lf denotes a distance between the center of gravity of the vehicle and the front wheel axle, Lr denotes a distance between the center of gravity of the vehicle and the rear wheel axle, the Lt is the distance of the left and right rear wheels.

Next, regarding the yaw moment control of the present embodiment, the relationship among the steering angle δ of the front wheels, the yaw rate △ ψ, the cornering power C, the lateral force F and the like will be described. FIG. 2 shows a two-wheel model of a vehicle generally used.
FW is the front wheel, RW is the rear wheel, WP is the center of gravity of the vehicle, δ is the front wheel steering angle, △ ψ is the yaw rate, △△ Y is the lateral acceleration, β is the slip angle, C1 is the front wheel cornering power (for two wheels), C
2 is rear wheel cornering power (for two wheels), m is vehicle mass, I is vehicle inertia moment, L is wheelbase, V
Indicates the vehicle speed.

The equation of motion between the yaw rate の and the slip angle β of the vehicle traveling at the vehicle speed V as shown in this figure is as shown in the following equations (11) and (12). mV ({β + △ ψ) = − C1 (β + a △ ψ / v−δ) −C2 (β−b △ ψ / V) (11) I △△ ψ = −aC1 (β + a △ ψ / V−δ) + BC2 (β-b △ ψ / V) (12)

FIG. 3 shows a response form of the yaw rate △ ψ and the slip angle β with respect to the steering angle δ. FIG.

FIG. 5 is a diagram for explaining the configuration and operation of the yaw motion control device for a vehicle according to the embodiment.
Is a yaw moment generating mechanism. The details will be described later. Reference numeral 22 denotes a target yaw moment calculating means for obtaining a target yaw moment MM according to the vehicle behavior, and reference numeral 23 denotes an actual yaw moment detecting means for detecting an actual yaw moment M generated in the vehicle. As described above, in the present embodiment, the actual yaw moment M generated in the vehicle detected by the actual yaw moment detection means 23 is compared with the target yaw moment MM calculated by the target yaw moment calculation means 22, and both are compared. (MM-M) is output by the yaw moment generating mechanism 21.

Here, a power distribution device as an example of the yaw moment generating mechanism 21 will be described. FIG. 6 is a cross-sectional view showing the power distribution device, where 1 is a housing. The housing 1 includes a stepped cylindrical input housing portion 2 located on the input side, and a stepped cylinder located on the output side and provided integrally with the input housing portion 2 and extending leftward and rightward, respectively. Output housing part 3
The output housing portion 3 includes a cylindrical body 3A located at the center, and stepped cylindrical covers 3B and 3C provided on both left and right sides of the body 3A.

The output housing 3 has a body 3A.
Between the cover 3C and the stepped cylindrical portion 3D
Is provided, and between the cover portion 3C and the stepped cylindrical portion 3D,
A hydraulic motor 18 described later is rotatably provided. The stepped cylindrical portion 3D extends in the axial direction from the cover portion 3C toward the cover portion 3B, and its distal end is formed so as to avoid interference with an input gear 4A described later.

In FIG. 1, reference numeral 4 denotes a propulsion shaft. The propulsion shaft 4 is rotatably provided inside the input housing portion 2 of the housing 1, and is rotated by an engine (not shown) mounted on the vehicle. Further, the propulsion shaft 4 is provided with an input gear 4A on a tip side extending into the body 3A of the output housing portion 3, and the input gear 4A is meshed with a ring gear 7 described later.

In FIG. 1, reference numeral 5 denotes a differential mechanism, which is located on the side of the cover 3B and is rotatably provided inside the output housing 3. The differential mechanism 5 is constituted by a planetary gear mechanism G, and the ring gear 7 meshed with the input gear 4A is fixed to the outer peripheral side of a differential case 6 forming an outer shell by bolts or the like. Then, the differential case 6 is rotationally driven by the propulsion shaft 4 via the input gear 4A and the ring gear 7,
At this time, the driving force is distributed and transmitted to the left and right wheel shafts 16 and 17 by the sun gear 13 and the carrier 8 described later.

Here, the differential mechanism 5 includes a ring gear 6A of the planetary gear mechanism G formed all around the inner circumference of the differential case 6, and a planet rotatably provided in the differential case 6. A carrier 8 of a gear mechanism G and a plurality of first planetary gears 1 rotatably supported by the carrier 8 and meshed with a ring gear 6A.
And a second planetary gear 12 meshed with the first planetary gear 10 and rotatably supported by the carrier 8.
And a sun gear 13 meshed with the second planetary gear 12 and rotatable relative to the carrier 8. The sun gear 13 is spline-coupled to rotate integrally with the wheel shaft 16. Therefore, the rotation of the differential case 6 is controlled by the first and second planetary gears 1.
The rotation is transmitted to the sun gear 13 via 0 and 12 as rotation in the same direction.

When the vehicle travels straight, the rotational force of the differential case 6 is evenly distributed to the sun gear 13 and the carrier 8 of the planetary gear mechanism G, and the left and right wheel shafts 1
6, 17 rotate at the same rotation speed. Further, when the vehicle turns, the sun gear 13 and the carrier 8 are rotated on the differential case 6 side so that one of the wheel shafts 16 and 17 rotates faster than the other due to a reaction force or the like that a wheel (not shown) receives from the road surface. The forces are transmitted with different rotational ratios. As a result, the wheels on the inside of the turn have a relatively low rotation speed, and the wheels on the outside of the turn have a relatively high rotation speed, thereby exhibiting a differential function of improving the cornering performance and the like of the vehicle.

Next, the relationship between the differential mechanism 5 and the wheel shafts 16 and 17 will be described. The sun gear 13 is connected to the wheel shaft 16 via a spline connecting portion.
Rotates integrally with the sun gear 13. Further, the wheel shaft 16 has a spline shaft portion 16A inserted into the output housing portion 3, and the spline shaft portion 16A is connected to the cylinder block 25 in a detented state.

On the other hand, the carrier 8 is connected via a sleeve 14 to a motor case 19 formed so as to surround the wheel shaft 16 and the cylinder block 25.

The hydraulic motor 18 is provided side by side in the left-right direction with the differential mechanism 5 inside the output housing portion 3. The hydraulic motor 18 is, for example, a radial piston type hydraulic motor, and includes a motor case 19, a cylinder block 25, a piston 27, and a passage block 32.
And the cylinder 2 formed in the cylinder block 25
By supplying and discharging hydraulic oil to and from the hydraulic pump 40 from the hydraulic pump 40 to the piston 27, a relative rotational force is applied between the motor case 19 and the cylinder block 25,
This imparts a relative rotational force to the left and right wheel shafts 16 and 17.

The hydraulic pump 40 is connected to the hydraulic motor 18.
The direction of the pressure oil supplied to and discharged from the directional control valve 42 is switched by the direction control valve 42, and the relative rotation direction of the left and right wheel shafts 16 and 17 can be switched based on the switching position of the direction control valve 42. The supply / discharge can be stopped. Further, the discharge pressure of the hydraulic pump 40 is variably controlled by a variable pressure relief valve 43, whereby the driving force of the hydraulic motor 18 can be arbitrarily changed.

Next, the target yaw moment calculating means 22 will be described in detail. FIG. 7 shows target yaw moment calculating means 2
FIG. 2 is an explanatory diagram of a target yaw moment calculating means 22;
Are each wheel braking / driving force calculating section 22a and each wheel load calculating section 22a.
b, each wheel slip angle calculator 22d and target lateral force calculator 2
2g and a target yaw moment calculating unit 22i, and are connected to input means such as a sensor described later as a vehicle behavior detecting means. These input means are usually OFF
A brake switch 231 that is turned on when the driver performs a braking operation in the vehicle, and a longitudinal acceleration of the vehicle (hereinafter, longitudinal G).
Front and rear G sensor 232 for detecting the lateral acceleration (hereinafter referred to as lateral G) of the vehicle.
33, a steering angle sensor 23 for detecting a driver's steering angle
4 and a yaw rate sensor 2 for detecting the yaw rate of the vehicle
35, a vehicle speed sensor 236 for detecting a vehicle speed, and a slip angle detecting means 237 for detecting a slip angle β of the vehicle.

The wheel braking / driving force calculating section 22a calculates a braking / driving force T which is a braking force and a driving force acting on each of the four wheels.
1, T2, T3, T4 (where T1 is the braking / driving force of the front left wheel, T2 is the braking / driving force of the front right wheel, T3 is the braking / driving force of the rear left wheel, and T4 is the braking / driving force of the rear right wheel). When the brake switch 231 is ON, the front and rear G
Is applied to the four wheels at a predetermined ratio in the front and rear, and when the brake switch 231 is OFF, the driving force corresponding to the front and rear G at that time is applied to the rear wheels which are the driving wheels. , The braking / driving force of each wheel is determined. Specifically, when the signal from the brake switch 231 is Bsig, the front and rear G is ΔX, and the vehicle weight is m, it is obtained based on the following equation. Bsig = 0
When (brake OFF), T1 = T2 = 0 T3 = T4 = m △△ X / 2 When Bsig = 1 (brake ON), T1 = T2 = m △△ X · (0.7 / 2) T3 = T4 = m △△ X · (0.3 / 2)

Each wheel load calculating section 22b calculates each wheel load W1, W2, W3, according to front and rear G 前後 X and lateral G △△ Y.
W4 (W1 is the wheel load of the front left wheel, W2 is the wheel load of the front right wheel, W3 is the wheel load of the rear left wheel, and W4 is the wheel load of the rear right wheel) is calculated based on the following equation. . In addition,
L is the wheelbase, a is the distance from the front axle to the center of gravity, b is the distance from the rear axle to the center of gravity, and h is the height of the center of gravity. W1 = m (b / 2L) −0.5m △△ X (h / L) −
0.6m △△ Yh / t W2 = m (b / 2L) −0.5m △△ X (h / L) +
0.6m △△ Yh / t W3 = m (a / 2L) + 0.5m △△ X (h / L)-
0.4m △△ Yh / t W4 = m (a / 2L) + 0.5m △△ X (h / L) +
0.4m △△ Yh / t

Each wheel slip angle calculating section 22d calculates a steering angle δ, a yaw rate ψ, a yaw rate ψ, based on the slip angle β at the center of gravity of the vehicle.
Using the vehicle speed V, a calculation (the following equation) for obtaining the front wheel slip angle βf and the rear wheel slip angle βr is performed. βf = β− (△ ψ / V) Lf + δ βr = β + (△ ψ / V) Lr

The slip angle detecting means 237 estimates the vehicle slip angle β based on the yaw rate △ ψ, the lateral G △△ Y, and the vehicle speed V. Describing this estimation method, first, an estimated cornering power value PC2 is calculated by the following equation (21). PC ₂ = (V / L) (ma △△ Y-I △ ψs) s / [△ ψ (bs + V)-△△ Y] + f (△△ Y) (21) (where s is a Laplace operator , M is the vehicle mass, a is the longitudinal distance from the vehicle center of gravity to the front axle, b is the longitudinal distance from the vehicle center of gravity to the rear axle, L is the wheelbase, I is the moment of inertia of the vehicle, and the first term on the right side. Is the cornering power of the rear wheel analytically obtained from the two-wheel model of the vehicle, and the second term f (△△ Y) is a correction term by the lateral G)

Using the estimated cornering power value PC2 of the rear wheels and the yaw rate signal △ ψ, the slip angle is calculated by the following equation (22), which is a relational expression between the yaw rate and the slip angle analytically obtained from a two-wheel model of the vehicle. (Estimate)
Calculate β. _{β = -K br [(T b} s + 1) / (T r s + 1)] △ ψ ... (12) [ _{wherein, K br = (1- (ma} / (LbPC 2))
V ² ) (b / V), T _b = IV / (LbPC ₂ −m)
aV ² ), _Tr = [ma / (LPC ₂ )] V]. The correction term f (△△ Y) is calculated by the following equation (23).
It is also possible to use a linear expression of | △△ Y | f (△△ Y) = C ^* ₂ | △△ Y | /9.8 (23) (C ^* ₂ indicates the point where the side force is substantially saturated and the origin on the side force and slip angle diagram of the rear tire. The slope of the connecting line)

Alternatively, instead of the yaw rate 横, the horizontal G
Using Δ △ Y, analytically from the two-wheel model of the vehicle
The following equation (2), which is a relational equation between the obtained lateral G and the slip angle β,
It is also possible to calculate the slip angle (estimated value) β using 4)
it can. β = -K_bg[(T_bs + 1) / (T_g2s²+ T_g1s + 1)] △△ Y (24) [where K_bg= (1- (ma / (LbPC)₂)) V²) (B / V ² ), T_b= IV / (LbPC₂-MaV²), T_g2= [I / (LPC₂)], T_g1= B / V]

Also, instead of the above (21), the following equation (3)
Thereby calculating the cornering power estimate PC ₂ of the rear wheel by 1), the following equation in place of the equation (22) (3
The slip angle β can be calculated according to 2). PC ₂ = [(V / L) (ma △△ Y-I △ ψs) s] / [△ ψ (bs + V)-△△ Y] (31) (where s is a Laplace operator and m is a vehicle mass, a is longitudinal distance from the center of gravity of the vehicle position to the front wheel axle, b is longitudinal distance to the rear wheel axle from the vehicle center of gravity position, L is wheel base, I is a vehicle moment of inertia,) β = -K _{br [(T b s + 1)} / (T r s + 1)] △ ψ ... (32) [ _{wherein, K br = (1- (ma} / (LbPC 2))
V ² ) (b / V), T _b = IV / (LbPC ₂ −m)
aV ² ), _Tr = [ma / (LPC ₂ )] V]

The target lateral force calculating section 22g calculates target lateral forces Fy1, Fy2 acting on each wheel based on the wheel loads W1 to W4 and the wheel slip angles βf, βr based on the target tire characteristic map shown in FIG. , Fy3, Fy4. In FIG. 8, a solid line indicates a target tire characteristic, which is set to an ideal tire characteristic. That is, the actual tire characteristics are such that when the slip angles βf and βr become large, the lateral force F cannot be obtained to a certain extent and the vehicle reaches a plateau state, whereas the ideally set target tire characteristics are The lateral force F is set to increase as the angles βf and βr increase, that is, a high cornering force is obtained. In FIG. 8, (a) shows the characteristics of the front wheels,
(B) shows the characteristics of the rear wheels. In the present embodiment, the actual limit lateral force is set higher for the rear wheels than for the front wheels, and accordingly, the target tire characteristics are also higher for the rear wheels than for the front wheels. The ring is set higher. The difference between the characteristics of the front wheel and the rear wheel is that the material and tread shape of the tire are different between the front wheel and the rear wheel (the material of the rear wheel is made more flexible than the front wheel, and the tread has higher lateral force than the front wheel). Or by selecting a shape) or setting the tire width of the rear wheels wider than that of the front wheels.

The target yaw moment calculating section 22i includes:
The target yaw moment MM is calculated by the following equation based on the target lateral forces Fy1 to Fy4. MM = (Fy1 + Fy2) a- (Fy3 + Fy4) b

FIG. 9 shows another example of the target yaw moment calculating means 22. In this example, each wheel load calculating means 22c is used.
Calculates the load shift based on the lateral G, and calculates the load shift and each wheel slip angle β determined by each wheel slip angle calculation unit 22d.
The target lateral forces F1 to F4 based on the target tire characteristics preset in the target lateral force calculation unit 22g according to f and βr.
This is an example of a configuration configured to obtain The lateral force taking this load movement into consideration is configured to be obtained from the slip angles βf and βr and the wheel load W, for example, as in a first lateral force calculator 23f of the actual yaw moment detecting means 23 described later.

The target yaw moment can be calculated as follows. MM = I (d △ ψ1 / dt) = (I / L) (△ δV +
δ △ V) (where △ ψ1 is the target yaw rate, I is the vehicle moment of inertia, L is the wheelbase, δ is the steering angle, and △ δ is the steering speed)

Next, the actual yaw moment detecting means 23
Will be described. This vehicle yaw moment detecting means 2
3 is, as shown in FIG.
, Each wheel load calculating unit 22b, and each wheel slip angle calculating unit 2
2d, the lateral force reduction rate calculator 23e, and the first lateral force calculator 2
3f, a second lateral force calculator 23h, and an actual yaw moment calculator 23i. Here, the respective wheel braking / driving force calculators 22a, the respective wheel load calculators 22b, and the respective wheel slip angle calculators 22d are the same as those described in the above-described target yaw moment calculator 22, and will not be described. Omitted.

The lateral force reduction rate calculating section 22e calculates braking / driving forces T1 to T of each wheel calculated by the wheel braking force calculating section 22a.
4 and each wheel load W1 calculated by each wheel load calculation unit 22b.
-W4, the lateral force reduction rate k for each wheel by the following formula
1, k2, k3, k4 (where k1 is the front left wheel lateral force reduction rate, k2 is the front right wheel lateral force reduction rate, k3 is the rear left wheel lateral force reduction rate, and k4 is the rear right wheel lateral force reduction rate) Is what you do.
That is, as the braking / driving force T increases, the lateral force Fy decreases, and the reduction rate of the lateral force Fy according to the braking / driving force T is calculated. ^{k1 = (W1 2 -T1 2)} 1/2 / W1 k2 = (W2 2 -T2 2) 1/2 / W2 k3 = (W3 2 -T3 2) 1/2 / W3 k4 = (W4 2 -T4 2 ) ^1/2 / W4

The first lateral force calculating section 23f calculates the lateral force F in consideration of the load movement, and calculates the lateral force F acting on each wheel based on the wheel load W and the slip angles βf, βr in a map shown in FIG. Ask based on. In addition, when the wheel load W is arbitrary, the value complemented between the map data is determined.

The second lateral force calculating section 23h calculates the lateral force Fy1, Fy2, Fy3, Fy4 (Fy4) of each wheel from the lateral force reduction rate k of each wheel and the lateral force F in consideration of the load movement.
1 is the front left wheel lateral force, Fy2 is the front right wheel lateral force, Fy3 is the rear left wheel lateral force, and Fy4 is the rear right wheel lateral force. Fy1 = k1 · F1 Fy2 = k2 · F2 Fy3 = k3 · F3 Fy4 = k4 · F4

The actual yaw moment calculating section 23i calculates the actual yaw moment M generated in the vehicle from the lateral forces Fy1 to Fy4 acting on each wheel by the following equation. M = (Fy1 + Fy2) a- (Fy3 + Fy4) b

FIG. 11 is a diagram showing characteristics of the vehicle to which the present embodiment is applied when the transmission is turned at a fixed second speed, and FIG. It is a figure which shows the characteristic at the time of the similar turning in the vehicle which does not make a lateral force differ. In both figures, (b) shows the characteristic at the time of steady turning, and (c) shows the characteristic at the time of accelerating turning. At the time of steady turning, the throttle is slowly depressed from a very low-speed turning with a radius of 15 m while the rudder is fixed. This is the case. Accelerated turning is a case where the vehicle is depressed from a very low speed turning with a radius of 15 m to a full throttle with the rudder fixed.
In FIGS. 11 and 12, MP indicates the output from the yaw moment generating mechanism 21, and MP = r (Fx4-F
x3) / 2 holds. Here, r is the tire radius.

As shown in FIG. 11, the vehicle of the present embodiment has a limit yaw moment CY even at the second speed full throttle.
M is set so that an understeer moment of less than 0 (minus) can be maintained. On the other hand,
As shown in FIG. 12, in a normal vehicle, the limit yaw moment CYM shifts to an oversteer side larger than 0 irrespective of the value of MP with an increase in the driving force (T) during the acceleration turning.

In the present embodiment, as described above, a vehicle having tire characteristics set so that the limit yaw moment CYM can maintain an understeer moment of less than 0 (minus) even at the second speed full throttle is used. The command value MP of the yaw moment generating mechanism 21 based on the yaw moment so that the limit yaw moment CYM always becomes zero.
To achieve a completely neutral steer characteristic.

FIGS. 13A and 13B show the control results. FIG. 13A shows experimental data of a steady turning with a fixed rudder and slow acceleration with a second gear from a very low speed turning with a radius of 15 m, and FIG. 13B shows a yaw moment. It is experiment (simulation) data to which feedback control was applied. As shown in this figure,
When the yaw moment feedback control is applied, the steering characteristic hardly changes up to the turning limit region, and it can be seen that almost the neutral characteristic can be realized. Further, the reason why the maximum value of the turning lateral acceleration is increased in FIG. 13B can be explained as follows. In the vehicle model of FIG. 1 which simplifies and considers the case where the front and rear weight distribution is equal,
Without control, the maximum lateral acceleration is 2 (F1 + F2) / m
It is represented by Here, when the control works, the maximum lateral acceleration becomes (F
1 + F2 + Fy3 + Fy4) / m. Further, since the increase ΔAy of the maximum lateral acceleration is the difference between these two accelerations, ΔAy = (Fy3 + Fy4-F1-F2) /
m. Further, as a result of the moment balance, the following equation is established. Fy3 + Fy4-F1-F2 = (Fx4-Fx3) Lt
/ (Lf + Lr) Therefore, ΔAy = (Fx4-Fx3) Lt / (Lf + L
r) / m, and it can be seen that ΔAy is proportional to the yaw moment applied in the control. The range in which this equation holds depends on the size of the tire friction circle. By the way, Figure 1
3 (b), when the value of the maximum lateral acceleration Ay increases, the steering characteristic slightly deviates from the neutral characteristic to the understeer characteristic, but this is because the output of the yaw moment generating mechanism 21 has reached the limit. If the output of the yaw moment generating mechanism 21 is set to be large, it is possible to obtain a completely neutral characteristic.

Next, FIG. 14A shows experimental data of the sideslip angle of the front and rear wheels in the embodiment, and FIG. 14B shows experimental (simulation) data when the yaw moment feedback control is applied. As shown in this figure, in the vehicle in the embodiment, in the uncontrolled state, the front wheels drift at the turning limit and exhibit a sharp understeer characteristic, but when the yaw moment feedback control is performed, the front and rear wheels drift almost simultaneously. Neutral steer characteristics maintained.

As described above, in the steady turning, the realization of the complete neutral steering was confirmed, but the vehicle behavior with respect to the throttle change at points A and B in FIG. 13 is further confirmed. As shown in FIG. 15, A and B reach the turning limit.
At this point, the behavior of the vehicle when the throttle was depressed and a substantially stepped torque was applied was evaluated by parallel loop simulation. FIG. 16 shows rear wheel left and right wheel speeds V4 indicates an outer wheel, and V3 indicates an inner wheel. In FIG. 16, (a) is a case where no control is performed, and (b) is a case where the yaw moment feedback control is executed. The torque Ta indicates experimental data, and the torques Tb, Tc, and Td indicate parallel loop simulations. In the case without the control of (a), the differential ratio of transfer ratio 2.0 is set, but the tendency of inner wheel idling starts to appear at the full throttle Td. On the other hand, when controlled, even at full throttle, inner wheel idling is firmly suppressed.

FIG. 17 shows the sideslip angles of the front and rear wheels. FIG. 11A shows the result at the time of non-control, and FIG. 10B shows the result at the time of yaw moment feedback control. Even at full acceleration, the behavior is gentler at control than at non-control. I understand.

FIG. 18 shows output data of the left-right axis torque command value MP. At point A of the turning limit, the left and right axis torques reach 600 Nm in opposite directions, respectively, which causes the vehicle to generate a yaw moment on the oversteer side. When the throttle is depressed at point A, the lateral force on the rear wheels decreases due to the increase in driving force, and the yaw moment required for neutral steering decreases. Therefore, after point A, the torque of the left and right shafts in the order of Tb, Tc, and Td The command value MP has decreased.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a limit yaw moment CYM of a vehicle in an embodiment.

FIG. 2 is a two-wheel model diagram.

FIG. 3 shows a front wheel steering angle δ, a slip angle β, and a yaw rate △ ψ
FIG. 4 is a model diagram of an equation of motion showing the relationship with.

FIG. 4 is a model diagram in which the above equation of motion is simplified.

FIG. 5 is an explanatory diagram showing an embodiment.

FIG. 6 is an overall view showing a brake control device which is an example of a yaw moment generating mechanism according to the embodiment.

FIG. 7 is a block diagram showing a target yaw moment calculating means of the embodiment.

FIG. 8 is a characteristic diagram showing a map for obtaining a target lateral force according to the embodiment.

FIG. 9 is a block diagram showing another example of the target yaw moment calculating means.

FIG. 10 is a block diagram showing actual yaw moment detecting means of the embodiment.

FIG. 11 is a characteristic diagram illustrating vehicle characteristics of the embodiment.

FIG. 12 is a characteristic diagram showing comparative vehicle characteristics with the embodiment.

FIG. 13 is a steering characteristic diagram of the embodiment.

FIG. 14 is a slip angle characteristic diagram of the embodiment.

FIG. 15 is a torque characteristic diagram showing an operation example of the embodiment.

FIG. 16 is a time chart showing a difference between left and right wheel speeds in an operation example of the embodiment.

FIG. 17 is a slip angle characteristic diagram in an operation example of the embodiment.

FIG. 18 is an output characteristic diagram showing an output example of a command value MP in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Input housing part 3 Output housing part 3A body part 3B cover part 3C cover part 3D stepped cylinder part 4 Propulsion shaft 4A input gear 5 Differential mechanism 6 Differential case 6A Ring gear 7 Ring gear 8 Carrier 10 Planetary gear 12 Planetary gear 13 Sun gear 14 Sleeve 16 Wheel shaft 16A Spline shaft 17 Wheel shaft 18 Hydraulic motor 19 Motor case 21 Yaw moment generating mechanism 22 Yaw moment generating mechanism 22 Target yaw moment calculating means 22a Wheel control driving force calculating section 22b Wheel load calculating section 22c Wheel load calculation 22d Each wheel slip angle calculation unit 23e Lateral force reduction rate calculation unit 22g Target lateral force calculation unit 22i Target yaw moment calculation unit 23 Actual yaw moment detection means 23f Side force calculation unit 23h Lateral force calculation unit 2 i Actual yaw moment calculation unit 25 Cylinder block 26 Cylinder 27 Piston 32 Passage block 40 Hydraulic pump 42 Direction control valve 43 Relief valve G Planetary gear mechanism 231 Brake switch 232 Front and rear G sensor 233 Lateral G sensor 234 Steering angle sensor 235 Yaw rate sensor 236 Vehicle speed Sensor 237 Slip angle detection means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D036 GA04 GA35 GB08 GB09 GC05 GD02 GD04 GE04 GF06 GF10 GG33 GG35 GG42 GG43 GG44 GG53 GG60 GH12 GH17 GH18 GH20 GH23 GJ01 3D042 AA01 AB01 CA06 CA09 CB

Claims (4)

[Claims] 1. A vehicle that is driven by rear wheels and has a larger tire generation force on the rear wheels than on the front wheels, and a yaw moment that generates substantially equal torques in opposite directions to the left and right sides of the rear wheels. Generating mechanism; vehicle behavior detecting means for detecting vehicle behavior; real yaw moment detecting means included in the vehicle behavior detecting means for detecting an actual yaw moment occurring in the vehicle; and input from the vehicle behavior detecting means. Target yaw moment calculating means for obtaining a target yaw moment, which is a yaw moment required in the current vehicle behavior, based on the vehicle yaw moment, and outputting a yaw moment of an amount corresponding to a difference between the target yaw moment and the actual yaw moment. A yaw motion control device for a vehicle, comprising: operation command means for operating a yaw moment generating mechanism. 2. The maximum tire generation force of the front turning inner wheel is F
1, the maximum tire generating force of the front turning outer wheel is F2, the maximum tire generating force of the rear turning inner wheel is F3, and the maximum tire generating force of the rear turning outer wheel is F4, and the rear inner wheel side rear wheel driving force is Fx3, the rear wheel driving force on the turning outer wheel side is Fx4, the maximum rear wheel lateral force on the turning inner wheel side is Fy3, the maximum rear wheel lateral force on the turning outer wheel side is Fy4, and the longitudinal distance between the vehicle center of gravity and the front wheel axle is Lf. CYM = Lf (F1 + F2) -Lr (Fy3 + Fy4), where Lr is the distance between the center of gravity of the vehicle and the rear wheel axle in the front-rear direction and Lt is the width of the left and right wheels.
+ Lt (−Fx3 + Fx4) / 2 Critical yaw moment CY around the vehicle center of gravity obtained by the equation
The tire generating force of each wheel is set so that M becomes negative when the driving means does not operate the yaw moment generating mechanism at the time of maximum torque generating turning of the driving means. A yaw motion control device for a vehicle according to the claim. 3. The yaw motion control device for a vehicle according to claim 1, wherein the tire generation force is set as described above by setting the rear wheels wider than the front wheels. 4. The target yaw moment calculating means is means for calculating a target yaw moment using a state quantity of each wheel and a preset target tire characteristic. The yaw motion control device for a vehicle according to any one of claims 1 to 3, wherein is set higher than the front wheels.