JP2789905B2 - Vehicle behavior control device - Google Patents

Abstract

PURPOSE:To provide a vehicle behavior control apparatus capable of securing the continuity of the behavior control and less subjected to failure and having good responsiveness by causing an auxiliary steer control and a right/left-wheel brake force difference control to be always performed in parallel and causing the share proportion between both the controls to be appropriate. CONSTITUTION:An auxiliary steer angle calculation means determines an auxiliary steer angle for obtaining a behaviour target value while, on the other hand, a feedback control quantity calculation means determines an auxiliary steer angle correction quantity and right/left wheel brake force difference for zeroing a deviation between an actual behavior and the target value. An auxiliary steer means auxiliarily steers the vehicle wheels by a sum of the auxiliary steer angle and a correction quantity therefor while a brake force difference control means realizes the right/left wheel brake force difference. Note that suitable upper limit values are set respectively to the auxiliary steer angle correction quantity and the right/left wheel brake force difference in corresponding relation to shared proportions. The feedback control calculation means is determined to have a feedback control gain so that, when the behavior deviation reaches a set value, the auxiliary steer angle correction quantity and the right/left wheel brake force difference may simultaneously become the upper limit values, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a vehicle behavior, in particular, a vehicle plane behavior which can be changed by auxiliary steering of a wheel and control of a braking force difference between left and right wheels.

[0002]

2. Description of the Related Art A device for controlling the behavior of a vehicle by the auxiliary steering of the wheels and the differential control of the braking force between the left and right wheels has a large control capacity and is very useful as compared with a device in which the behavior control is performed only by the auxiliary steering. Conventionally, as this kind of apparatus, Japanese Patent Laid-Open No.
-283555.

If the deviation between the target vehicle behavior, that is, the yaw rate or the lateral acceleration and the actual yaw rate or the lateral acceleration is less than a set value, the main steering wheel or other wheels are controlled. The vehicle behavior is brought to the target value only by auxiliary steering that assists steering the vehicle, and the vehicle behavior is brought to the target value by making full use of the left and right wheel braking force difference control when the deviation is greater than the set value. It was done. This allows
The frequency of using the left and right wheel braking force difference control is reduced by that much,
The effect on braking can be reduced.

[0004]

In the conventional behavior control, when the deviation of the actual vehicle behavior from the target value reaches a set value, the left and right wheel braking force difference control is started. It cannot be denied that the control lacks continuity, giving the driver an uncomfortable feeling. Also, since the difference between the failure rates of the two control systems and the difference in the capacity for the behavior control are not taken into account, the sharing ratio between the two control systems cannot be said to be appropriate, and the number of failures increases. However, the responsiveness may be insufficient. An object of the present invention is to solve the above-mentioned problem by allowing the auxiliary steering and the left and right wheel braking force difference control to be always performed in parallel, and to allow the sharing ratio of the two controls to be appropriate. .

[0005]

For this purpose, the present invention calculates a target value of a vehicle behavior according to a running state including a main steering amount at the time of main steering by a steering wheel as shown in FIG. Target behavior setting means, auxiliary steering angle calculation means for calculating an auxiliary steering angle of at least one of a front wheel and a rear wheel required to achieve the behavior target value, and behavior detection means for detecting an actual behavior of the vehicle, Feedback control amount calculating means for calculating the auxiliary steering angle correction amount and the left and right wheel braking force difference for eliminating the deviation between the actual behavior and the behavior target value calculated by the target behavior setting means; and at least the front wheel and the rear wheel. A vehicle behavior control device comprising: auxiliary steering means for assisting one of them by the sum of the auxiliary steering angle and the auxiliary steering angle correction amount; and left and right wheel braking force difference control means for applying the braking force difference between left and right wheels. smell The husband auxiliary steering angle correction amount and the left and right wheel braking force difference s, sets an upper limit in accordance with the preferred distribution ratio,
The feedback control gain of the feedback control amount calculation means is determined so that the auxiliary steering angle correction amount and the left and right wheel braking force difference each become the upper limit value when the behavior deviation reaches a set magnitude.

[0006]

In the main steering by the steering wheel, the target behavior setting means calculates a target value of the vehicle behavior according to the traveling state including the main steering amount. Then, the auxiliary steering angle calculation means calculates an auxiliary steering angle of at least one of the front wheels and the rear wheels required to achieve the behavior target value. Further, the feedback control amount calculating means calculates an auxiliary steering angle correction amount and a left and right wheel braking force difference for eliminating a deviation between the actual behavior detected by the behavior detecting means and the behavior target value calculated by the target behavior setting means. Each is calculated. The auxiliary steering means assists at least one of the front wheel and the rear wheel by the sum of the auxiliary steering angle and the auxiliary steering angle correction amount, and the left and right wheel braking force difference control means applies the braking force difference between the left and right wheels. With these controls, the behavior of the vehicle can be constantly maintained at the target value despite changes in control parameters due to braking and disturbances such as crosswinds. By the way, the upper limit of the auxiliary steering angle correction amount and the left and right wheel braking force difference are respectively set according to a suitable sharing ratio, and just when the behavior deviation reaches the set value, the auxiliary steering angle correction amount and the right and left Since the feedback control gain of the feedback control amount calculating means is determined such that the wheel braking force difference becomes the upper limit value, the auxiliary steering and the left and right wheel braking force difference control are always performed in parallel to improve the continuity of the control. As well as realizing, the share ratio of both controls becomes appropriate, for example, by reducing the failure rate by increasing the share ratio of the control with a small failure rate, or by increasing the share ratio of the control with large capacity Control responsiveness can be increased.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic view showing one embodiment of the present invention.
The target yaw rate calculation unit 110 calculates a target yaw rate (d / dt) φm according to the traveling state from the steering wheel steering angle θ and the vehicle speed Vx. In this calculation, the target yaw rate is an instantaneous yaw rate for obtaining a transient characteristic and a steady characteristic of the yaw rate achieved by the target vehicle reference model. The target rear-wheel steering angle calculating unit 120 for feedforward control calculates a rear-wheel auxiliary steering angle δr for realizing the target yaw rate in the own vehicle model expressed by a linear two-degree-of-freedom equation of motion.

On the other hand, the rear wheel steering angle correction amount calculating section 130 for feedback control and the left and right front wheel braking force difference calculating section 140 for feedback control respectively include the actual yaw rate (d / dt) φ of the vehicle 150 and the target yaw rate (d / dt). dt) φm
And the target value ΔPm of the rear wheel steering angle correction amount δr _FB and the left and right front wheel brake fluid pressure difference (braking force difference) for eliminating the deviation from the above. The rear wheel assist steering means 160 is provided with the rear wheel assist steering angle δr.
A rear wheel auxiliary steering angle correction amount [delta] r _FB and the rear wheel auxiliary steering angle target value δrm the sum value of, the rear wheels of a target value by the vehicle 150 to assist steering (rear wheel steer angle indicated by [delta] _R ). Further, the left and right front wheel braking force difference control means 170 gives a difference of ΔPm to the brake fluid pressure of the left and right front wheels as described above to make the braking force different between the left and right of the vehicle 150.

Due to the rear wheel assist steering and the left and right wheel braking force difference control, the vehicle 150 can control the yaw rate (d / dt) φ even if there is a disturbance such as a cross wind or a change in the control parameter due to the braking.
Is constantly maintained at the target yaw rate (d / dt) φm, and the transient characteristics and the steady-state characteristics of the yaw rate targeted by the vehicle reference model can be realized.

FIGS. 3 and 4 show the specific structure of the above embodiment.
FIG. 3 shows a hydraulic brake system used for the behavior control of the present invention, and FIG. 4 shows a rear wheel assist steering system used for the behavior control of the present invention.

First, the brake system shown in FIG. 3 will be described. Reference numerals 1L and 1R denote left and right front wheel cylinders, 2L and 2R denote left and right rear wheel cylinders, and both master cylinders 4 actuated by depressing a brake pedal 3. The hydraulic pressure outlet ports are connected to a front wheel brake hydraulic system relating to the front wheel cylinders 1L, 1R and a rear wheel brake hydraulic system relating to the rear wheel cylinders 2L, 2R, respectively. Then, the following brake fluid pressure control actuator 5, which is also used for a well-known three-channel anti-skid control device, is inserted into these brake fluid pressure systems.

The actuator 5 individually controls the brake fluid pressure of the left and right front wheels, and controls the brake fluid pressure of the left and right rear wheels in common. The pressure control valves 6 _{a and} 6 for the left and right front wheels are used.
comprising a _b, and a pressure control valve 6 _c for 2 rear wheels, further pressure control valve 6 _a, 6 _b common to reservoir 7 _a, and an accumulator 8 _a and a circulation pump 9 _a, the pressure control valve for 6 _c It has a reservoir 7 _b , an accumulator 8 _b and a circulating pump 9 _b , which are connected by piping as shown in the figure.

The actuator 5 (pressure control valve 6 _a ,
_6b , _6c and circulation pumps _9a , _9b ) are connected to the controller 1
Controlled by 0, and the signal from the steering angle sensor 11 for detecting a steering wheel steering angle θ in this controller, a signal from a brake switch 12 for turning ON when depression of the brake pedal 3, vehicle speed sensor for detecting a vehicle speed V _x the signal from 13, the signal from the pressure sensor 14 for detecting the pressure P _MC from the master cylinder 4, the left and right front wheel cylinder 1L, the brake fluid pressure P _FL to _1R, P _FR and the rear wheel brake fluid pressure P _RR detecting the pressure sensor 15 _a, 15 _b, 15 a signal from _c, and a signal from a yaw rate sensor 16 for detecting an actual yaw rate (d / dt) φ of the vehicle.

The controller 10 uses these input information to
In addition, a well-known three-channel anti-
In addition to performing skid control, the left and right front wheel cylinders 1
The purpose of the present invention is to individually control the brake fluid pressures of L and 1R.
The following left and right wheel braking force difference control is performed. This left and right wheel braking
To explain the operation of the force difference control, the pressure control valve 6_a, 6_bTo
When turning OFF to bring it to the state shown in the illustration (pressure increase position),
Hydraulic pressure P_MCPassed through these pressure control valves
It is supplied to the left and right front wheel cylinders 1L, 1R as it is,
Left and right front wheel brake fluid pressure P_FL, P_FRTogether with master syringe
Hydraulic pressure P_MCTo the same value as And one side pressure control
Valve 6_a(6_b) Is turned ON and the circulation pump 9_aIs turned on,
Pressure control valve 6_a(6_b) Is the port shown in the center according to the current value.
Port arrangement (pressure holding position) or port arrangement shown below (pressure reduction
), And the corresponding front wheel brake fluid pressure P at the decompression position_FL
(P_FR) And the corresponding front wheel brake at the dwell position
Hydraulic pressure P _FL(P_FR) Is kept at this reduced value. Therefore,
Reduce the brake fluid pressure of the left and right front wheels individually and
Can be set for the vehicle, and
It is possible to give.

The controller 10 also controls the rear wheel auxiliary steering system shown in FIG. 4 in addition to the left and right wheel braking force difference control. In FIG. 4, 21L and 21R denote left and right rear wheels, respectively, and these rear wheels can be steered by a hydraulic cylinder 22. An oil pump 24 driven by an engine 23 is provided as a hydraulic pressure source for the cylinder 22. This pump sucks and discharges hydraulic oil from an oil reservoir 25, regulates the pressure of the discharged oil by an unload valve 26, and accumulates the pressure in an accumulator 27. A pressure servo valve 30 is interposed between the supply passage 28 and the drain passage 29 of the pressure source and the chambers 22L and 22R of the hydraulic cylinder 22, and the servo valve is connected to the stroke of the cylinder 22, that is, the rear wheel assist steering. as the feedback signal from the auxiliary steering angle sensor 31 for detecting angular [delta] _R matches the [delta] _rm calculated value described later (target rear wheel steering angle) is controlled by the controller 10.

When OFF, the pressure control valve 30 has the port arrangement shown in the figure, and shuts off the cylinder chambers 22L and 22R from the supply path 28 and the drain path 29 to inhibit the stroke of the cylinder 22 and maintain the rear wheel steering angle. When the pressure control valve 30 is turned on by a current in one direction, the port arrangement shown in the upper side is provided, the pressure in the supply path 28 is supplied to the cylinder chamber 22L to turn the rear wheel to the left, and the pressure control valve 30 is turned on by the current in the other direction. The port arrangement shown below,
Is supplied to the cylinder chamber 22R to steer the rear wheels to the right.
Such steering, when the wheel steering angle [delta] _R was detected by the sensor 31 coincides with the calculated value [delta] _rm, the controller 10 servo valve 30
To maintain the rear wheel steering angle.

The controller 10 executes the control programs shown in FIGS. 5 to 7 to perform rear wheel auxiliary steering angle control and left and right wheel braking force difference control. Prior to the description, the equation of motion of the vehicle will be discussed with respect to a two-degree-of-freedom model of yawing and lateral motion shown in FIG. 8 (41L and 41R in the figure indicate left and right front wheels that provide a braking force difference in this example). First, it is known that the equation of motion relating to instantaneous (t) yawing and lateral motion is expressed by the following equation.

[0018]

[Equation 1] I _Z · (d ² / dt ² ) φ (t) = 2 (C _f · L _f -C _r · L _r ) ---- (1)

(2) M · V _y (t) = 2 (C _f + C _r ) − M · V _x (t) · (d / dt) φ (t) ---- (2) where C _f , _Cr is the cornering force of the front wheel and the rear wheel, respectively, which can be expressed by the following equations (3) and (4) using the front and rear wheel sideslip angles β _f and β _r .

[Equation 3] C _f = K _f · β _f ---- (3)

[Equation 4] C _r = K _r · β _r ---- (4)

The front and rear wheel sideslip angles β _f and β _r are given by
This is the quantity defined by equations (5) and (6).

Equation 5 β _f = θ (t) / N- ｛V _y + L _f · (d / dt) φ (t)｝ / V _x (t) ---- (5)

(6) β _r = δ _r (t)-｛V _y -L _r · (d / dt) φ (t)｝ / V _x (t) ---- (6)

The meaning of each symbol in the above formula is partially as shown in FIG. (d / dt) φ (t): yaw rate θ (t): steering angle δ _r (t): rear wheel steering angle V _x (t): vehicle longitudinal direction velocity V _y (t): vehicle lateral velocity T _f : Front wheel tread I _Z : Vehicle yaw inertia moment L _f : Vehicle center of gravity to front axle distance L _r : Vehicle center of gravity to rear axle distance M: Vehicle weight N: Steering gear ratio Equation (3), (6) ) And (2), the yawing motion and the lateral motion are the yaw rate (d / dt) φ (t) and the lateral velocity V _y (t), respectively.
Considering the differential equation with respect to, it can be expressed as the following equations (7) and (8).

[0021]

(D ² / dt ² ) φ (t) = a ₁₁・ (d / dt) φ (t) + a ₁₂・ V _y (t) + b _f1θ (t) + _{br 1}・ δ _r (t) ----- (7)

(D / dt) V _y (t) = a ₂₁ · (d / dt) φ (t) + a ₂₂ · V _y (t) + b _f2 · θ (t) + b _r2 · δ _r (t) ----- (8) where

A ₁₁ = −2 (K _f · L _f ² + K _r · L _r ² ) / (I _z · V _x ) ---- (9.1)

A ₁₂ = −2 (K _f · L _f −K _r · L _r ) / (I _z · V _x ) ----- (9.2)

[Equation 11] a ₂₁ = −2 (K _f · L _f −K _r · L _r ) / (M · V _x ) −V _x ----- (9.3)

A ₂₂ = −2 (K _f + K _r ) / (M · V _x ) ----- (9.4)

[Expression 13] b _f1 = 2 · K _f · L _f / (I _z · N) ----- (9.5)

[ _Formula 14] b _f2 = 2 · K _f / (M · N) ----- (9.6)

[ _Equation 15] b _r1 = −2 · K _r · L _r / I _z ----- (9.7)

## _EQU16 ## b _r2 = 2 · K _r / M ----- (9.8)

From equations (7) and (8), the relation of the generated yaw rate (d / dt) φ (t) to the steering angle input θ (t) is expressed by the differential operator S
And can be expressed as in equation (10).

(D / dt) φ (S) / θ (S) = ｛b _f1 · S + (a ₁₂ · b _f2 -a ₂₂ · b ₁ )｝ / ｛S ^2- (a ₁₁ + a ₂₂ ) S + (a ₁₁・ a ₂₂ -a ₁₂・ a ₂₁ )｝ ----- (10)

Similarly, the relation between the generated lateral velocity V _y (t) and the steering angle input θ (t) is calculated by using the differential operator S as shown in (11)
It can be expressed like an expression.

V _y (S) / θ (S) = ｛b _f2 · S + (a ₂₁ · b _f1 -a ₁₁ · b _f2 )｝ / ｛S ^2- (a ₁₁ + a ₂₂ ) S + (a ₁₁ · A ₂₂ -a ₁₂ · a ₂₁ )｝ ----- (11) The transfer functions in equations (17) and (18) are (primary) / (2
In the form of the next), generating a yaw rate with respect to the general vehicles without steering assist steering angle input as V _x increases (d / dt)
φ (t) and lateral velocity V _y (t) are high response but oscillating,
It can be seen that vehicle maneuverability and stability deteriorate. Therefore, as in the conventional example, it has been proposed to assist the rear wheels so that the generated yaw rate of the vehicle coincides with a desired yaw rate (d / dt) φ _r (t) desired by the driver.

For example, the target yaw rate (d / dt) φ _r (t) is a first-order lag system having no overshoot / undershoot with respect to the steering angle input θ (t), and the steady-state value is a base vehicle when no braking is performed. (Vehicles that do not perform rear wheel steering), (d / dt) φ _r (t) can be expressed as in equation (12).

(D / dt) φ _r (t) = _HO / θ (t) / (1 + τS) ---- (12) where τ is a time constant, H _O is a steady yaw rate gain,
H _O is defined by the following equation (13.1) using the stability factor A defined by the following equation (13.1).

[Equation 20] H _O = V _x / ｛(1+ AV _x ² ) LN｝ ---- (13.1)

A = -M (L _f K _f -L _r K _r ) / (2L ² L _f K _r ) ---- (13.2)

A control method for realizing the target yaw rate of equation (12) by rear wheel steering angle control will be described below. By transforming equation (12), the differential value of the target yaw rate (d ² / dt ² ) φ
_r (t) is obtained by the following equation (14).

(D ² / dt ² ) φ _r (t) = _HO · θ (t) / τ− (d / dt) φ _r (t) / τ ---- (14)

Assuming that the yaw rate (d / dt) φ (t) generated by the steering input θ (t) and the rear wheel steering angle input δ _r (t) coincides with (d / dt) φ _r (t). , Each derivative (d ² / dt ² ) φ (t),
(d ² / dt ² ) φ _r (t) also match. Therefore, (d / dt) φ _r (t)
= (D / dt) φ (t), (d ² / dt ² ) φ _r (t) = (d ² / dt ² ) φ (t), and V _y ( t) to V _yr
(t) and substituting these into equations (7) and (8) gives
Equations (15) and (16) are obtained.

(D ² / dt ² ) φ _r (t) = a ₁₁・ (d / dt) φ _r (t) + a ₁₂・ V _yr (t) + b _f1θ (t) + b _r1・ Δ _r (t) ---- (15)

(D / dt) V _yr (t) = a ₂₁ · (d / dt) φ _r (t) + a ₂₂ · V _yr (t) + b _f2 · θ (t) + b _r2 · δ _r (t) ---- (16) From equations (15) and (16), δ _r (t) is obtained by the following equation (17).

Δ _r (t) = ｛(d ² / dt ² ) φ _r (t)-a ₁₁・ (d / dt) φ _r (t)-a ₁₂・ V _yr (t) + b _f1・θ (t)｝ / b _r1 ---- (17) By performing the rear wheel steering angle control shown in equation (17), the yaw rate generated by the vehicle matches the target yaw rate, and the vibration of the lateral speed is also reduced. Can be eliminated.

However, if the rear wheel steering angle control is performed only by the above-described method, the target yaw rate and the generated yaw rate are not affected by disturbances such as crosswind, modeling errors of the vehicle, and parameter fluctuations of the vehicle in the braking / driving state. Will not match. Therefore, the generated yaw rate is detected, and feedback control for eliminating the deviation is performed by correcting the rear wheel steering angle according to the deviation between the detected yaw rate and the target yaw rate and controlling the difference between the left and right wheel braking forces.

Hereinafter, the feedback control amounts of both will be described. First, the absolute value of the maximum value of the target rear wheel steering angle correction amount is δ
_rmax (t), and the maximum value of the target left and right wheel braking force difference is ΔP _max
(t). δ _rmax (t) is set by equation (18), and ΔP
_max (t) is set by equation (19).

_{数 rmax} (t) = ｛δ _max -δ _r (t)｝ · K _fs1 ----- (18)

ΔP _max (t) = P _MC (t) · K _fs2 ----- (19) where δ _max is the maximum rear wheel steering angle due to mechanical limitation of the rear wheel steering mechanism, P _MC ( t) is the master cylinder pressure shown in FIG.
K _fs1 and K _fs2 are safety factors in consideration of the fail-safe property at the time of failure, and are arbitrarily set in the range of 0 to 1.

Next, the amounts of δ _rmax and ΔP _max that affect the yaw rate (d / dt) φ of the vehicle are calculated by the equations (20) and (21).

(D / dt) φ _FB δ _rmax (t) = G _FB δ _r・ δ _rmax (t) ---- (20)

[Number 29] _{(d / dt) φ FB ΔP} max (t) = G FB ΔP · ΔP max (t) ---- (21) However, G _FB δ _r a steady gain the rear wheel steering angle is on the yaw rate Same as H _O. G _FB ΔP is a steady gain that the left and right wheel cylinder differential pressure exerts on the yaw rate, and is calculated by the following equation (21.1).

[0030]

Equation 30] _{G FB ΔP = V x · K} p · T f (K f + K r) / {4 · K f · K r (L f + L r) 2 + 2 · M · V x 2 (L _r・ K _r -L _f・ K _f )｝ ---- (21.1) Correction amount δ due to feedback control of target rear wheel steering angle
_rFB (t) is calculated by the following equation (22).

[0031]

Δ _rFB (t) = [(d / dt) φ _FB δ _rmax (t) / ｛(d / dt) φ _FB δ _rmax (t) + (d / dt) φ _FB ΔP _max (t) ｝] ・ ｛1 / (G _FB δ _r )｝ ・ K ・ (d / dt) φ _err (t) ----- (22) However, δ _rFB (t)> δ _rmax (t) Δ _rFB
(t) = _δrmax (t). K: feedback control gain (d / dt) φ _err (t): deviation between target yaw rate and generated yaw rate

The control input δ _rm (t), which is the final target rear wheel steering angle to the rear wheel steering angle controller (pressure servo valve 30) shown in FIG. 4, is expressed by the following equation (23). Is done.

Δ _rm (t) = δ _r (t) −δ _rFB (t) ---- (23) Also, the target left and right wheel braking differential pressure (wheel cylinder differential pressure) ΔP
_m (t) is calculated by the following equation (24).

(33) ΔP _m (t) = [(d / dt) φ _FB ΔP _max (t) / ｛(d / dt) φ _FB δ _rmax (t) + (d / dt) φ _FB ΔP _max (t) ｝] ・ ｛1 / (G _FB ΔP)｝ ・ K ・ (d / dt) φ _err (t) ----- (24) However, if ΔP _m (t)> ΔP _max (t) Is ΔP
Let _m (t) = ΔP _max (t). Where K is the same feedback control gain as in equation (22).

By obtaining the target rear wheel steering angle δ _rm and the target left and right wheel braking differential pressure ΔP _m in this way, the feedback control amounts of both according to the yaw rate deviation can be simultaneously determined.
It is possible to reach the upper limit set as in the equations (18) and (19). Further, by setting these upper limit values to correspond to a preferable sharing ratio of the two controls that can be determined according to the failure rate and the behavior control capacity of the two controls, for example, the sharing ratio of the control with a small failure occurrence rate is increased. As a result, the responsiveness of the control can be increased by lowering the failure rate or increasing the share of the control with a large capacity.

The target wheel cylinder pressures P _mFL (t) for the left and right front wheels to achieve ΔP _m (t) obtained by the equation (24),
P _mFR (t) is calculated by the following equations (25) and (26) based on the master cylinder pressure P _MC (t).

[Number 34] _{P mFL (t) = P MC} (t) (ΔP m (t) ≧ 0 _{o'clock) = P MC (t) +} ΔP m (t) (ΔP m (t) <0 and P _MC (t )>-ΔP _m (t)) = 0 (when ΔP _m (t) <0 and _PMC (t) ≤-ΔP _m (t)) ----- (25)

[Number 35] _{P mFR (t) = P MC} (t) (ΔP m (t) <0 _{o'clock) = P MC (t) -ΔP} m (t) (ΔP m (t) ≧ 0 and P _MC (t )> ΔP _m (t)) = 0 (when ΔP _m (t) ≥ 0 and _PMC (t) ≤ ΔP _m (t)) ----- (26)

The above rear wheel steering angle control and left and right braking force difference control are performed by the controller 10 shown in FIGS. 3 and 4 by executing the control programs shown in FIGS. In these figures, in order to correspond to the processing by the microcomputer, a symbol with (n) indicating a discrete value system is used instead of the continuous system with (t). 5 and 6 show a rear wheel steering angle calculation and control program and a left and right front wheel cylinder differential pressure calculation program which are continuously executed at regular time intervals ΔT, and FIG. 7 shows a program for generating this differential pressure. 4 shows a program for output processing of left and right front wheel cylinder pressures.

First, the control program shown in FIGS.
In step 50, the vehicle speed V _x(n), steering angle θ
(n), generated yaw rate (d / dt) φ (n), master cylinder
Pressure P_MC(n) and wheel cylinder pressure P of each wheel_FR(n)
 , P_FL(n), P_RRRead (n). In the next step 51
Is the differential process of the above equations (7) and (8) by the calculation of the above equation (9).
Calculate each coefficient used in the equation. In the next step 52, the previous
Calculate Equations (12) and (14) to calculate the target yaw angular acceleration (d^Two/ dt
^Two) φ_r(n) and target yaw rate (d / dt) φ_rCalculate (n)
You. The target yaw rate is obtained by integrating the target yaw angular acceleration.
Here, the rectangular product of the discrete value system
The integration operation is performed by the minute. Step 53
Then, by the calculation of the above equations (16) and (17), the lateral acceleration target value (d
/ dt) V_yr(n) is obtained, and its integral is used to calculate the lateral velocity V_yr(n)
And calculate the target rear wheel steering angle for feedforward control.
δ_rFind (n). In steps 54 to 61, the steps (18) to (2
4) is calculated and the final target rear wheel steering angle δ, which is the control input
_rm(n) and target wheel cylinder differential pressure ΔP_mCalculate (n)
I do. In steps 62 to 70, the master cylinder pressure P
_MC(n) and the left and right front wheel cylinder pressure difference ΔP_m(n)
Is used to calculate the above equations (25) and (26), and ΔP_m(n)
Target wheel cylinder pressure P on the left and right front wheels to achieve
_mFR(n), P_mFLCalculate (n).

The controller 10 commands the target rear wheel steering angle δ _rm determined in step 58 to the pressure servo valve 30 in FIG.
Wheel actual steering angle [delta] _R after the detection by 31 performs wheel auxiliary steering After that coincides with the target value [delta] _rm. On the other hand, the controller 10
And right front wheel target wheel cylinder pressure P _MFR obtained in step 65, 66 or 67, and a left front wheel target wheel cylinder pressure P _MFL obtained in step 63, 69 or 70 to the output processing by the control program as shown in FIG. 7, The left and right front wheel braking force difference control is performed. However, FIG. 7 shows the target left front wheel cylinder pressure P _mFL
The output processing of FIG. 5 is exemplified, and is repeatedly executed at regular time intervals ΔT similar to FIGS. The output processing of the target front right wheel cylinder pressure _PmFR is the same as that described above, and therefore, the details are omitted here.

Referring to FIG. 7, first, at step 71, FIG.
Is not braking depending on whether or not the brake switch 12 is OFF
Check if braking is in progress, and in step 72, the left front wheel brake fluid
Pressure command P_mFLIs the master cylinder pressure P_MCSame or not
Check. P during braking _mFL≠ P_MCThen step
Counter m is set to m by 73, 76, 83_oIs set to 0
Every time, that is, m_o× ΔT Processing of steps 74 and 75 every time
I do. In step 74, the command value P of the left front wheel brake fluid pressure
_mFLAnd measured value P_FLDeviation from P_errAnd in step 75
Is the brake fluid pressure compensation amount P per stroke_oDeviation P from
_errRatio, that is, the deviation P_errIs gone
(P_FL= P_mFLCorrection value request value T that indicates_pTo
Find (however, INT means take a rounded integer value)
Do).

The command value left front wheel brake fluid pressure P _FL and outputs the pressure increase and decrease instruction of the original predetermined number of management by step 77-82 T _p to the pressure control valve 6a in FIG. 3 P _MFL ungated, then coercive Output pressure command to valve 6a to maintain P _FL = P _mFL .

The right front wheel brake fluid pressure P _FR also by pressure regulating in the same manner as described above, by forming the command value P _{mF R,} of the operation as between the left and right front wheel cylinder pressure difference [Delta] P _m
(n) can be given.

[0041] In FIG. 6 in step 71, 72 or determines that during non-braking, when determining to as P _MFL = P _MC in braking, since the brake fluid pressure control described above is not required, step 84, 8
The loop passing through 5, 77, 78, 80, 83 keeps the pressure control valve 6a at the pressure increasing position, makes the left front wheel cylinder pressure equal to the master cylinder hydraulic pressure, and allows the brake pedal 3 to be operated.

The control of the yaw rate of the vehicle between the left and right front wheel braking force difference control and the rear wheel assist steering can be performed by using the target value aimed at by the equation (12) even if there is a disturbance such as a cross wind or a modeling error. Behavior control. Then, at this time, the rear wheel steering angle correction amount and the left and right wheel braking force difference, which are the feedback control amounts, are determined as in Equations (22) and (24), respectively.
An upper limit is set according to the sharing ratio of the two controls expressed by the equations (18) and (19), and the feedback control gain is set so that when the yaw rate deviation φ _err reaches the set value, both control amounts simultaneously reach the upper limit. Since K has been determined, the rear wheel steering angle control and the left and right front wheel braking force difference control are always performed in parallel, so that continuity of control can be ensured, and the sharing ratio of both controls is arbitrarily and appropriately determined. As a result, the failure rate can be reduced and the control responsiveness can be increased.

In the above example, the auxiliary steering is performed on the rear wheels. However, the idea of the present invention can be similarly applied to the case where the front wheels are auxiliary-steered or the front and rear wheels are both assisted. Of course. When a difference in braking force is applied between the left and right front wheels, a wheel cylinder pressure difference may be applied between the other left and right wheels. Needless to say, this may be done. Further, the vehicle behavior to be controlled is not limited to the yaw rate, but may be other planar behavior such as lateral acceleration.

[0044]

As described above, according to the vehicle behavior control device of the present invention, the auxiliary steering angle correction amount (rear wheel steering angle correction amount in the illustrated example), which is a feedback control amount, and the left and right wheel braking force difference ( In the illustrated example, the upper and lower front wheel cylinder pressures are respectively set with an upper limit corresponding to a suitable sharing ratio, and when the behavior deviation (the yaw rate deviation in the illustrated example) reaches the set magnitude, the auxiliary steering angle correction amount is just adjusted. And the feedback control gain used in the calculation of the feedback control amount is determined so that the left and right wheel braking force differences each become the upper limit value. Therefore, the auxiliary steering and the left and right wheel braking force difference control are always performed in parallel and the control is performed. The continuity can be realized, and the sharing ratio of both controls becomes appropriate.For example, by increasing the sharing ratio of the control with a small failure rate, the failure rate can be reduced, or the control with a large capacity can be shared. It is possible to enhance the responsiveness of the control by increasing the rate.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a vehicle behavior control device according to the present invention.

FIG. 2 is a schematic diagram showing one embodiment of the vehicle behavior control device of the present invention.

FIG. 3 is a system diagram showing a left-right braking force difference control system of the same example.

FIG. 4 is a system diagram showing a rear wheel assist steering system of the same example.

FIG. 5 is a flowchart showing a program for calculating a target rear wheel steering angle and a target left and right wheel cylinder differential pressure executed by the controller of the example.

FIG. 6 is a flowchart showing a calculation program for a target rear wheel steering angle and a target left and right wheel cylinder differential pressure executed by the controller of the example.

FIG. 7 is a flowchart showing an output processing program of target left and right front wheel cylinder pressures of the example.

FIG. 8 is a diagram of a two-degree-of-freedom model of a vehicle used to derive an equation of motion of the vehicle.

[Explanation of symbols]

 1L Left front wheel cylinder 1R Right front wheel cylinder 2L Left rear wheel cylinder 2R Right rear wheel cylinder 3 Brake pedal 5 Brake fluid pressure control actuator 6a Pressure control valve 6b Pressure control valve 6c Pressure control valve 9a Circulation pump 9b Circulation pump 10 Controller 11 Steering angle sensor 12 Brake switch 13 Vehicle speed sensor 14 Pressure sensor 15a Pressure sensor 15b Pressure sensor 15c Pressure sensor 16 Yaw rate sensor 21L Left rear wheel 21R Right rear wheel 22 Auxiliary steering hydraulic cylinder 24 Oil pump 30 Servo valve 31 Auxiliary steering angle sensor 41L Left front wheel 41R Right front wheel 110 Target yaw rate calculation unit 120 Target rear wheel steering angle calculation unit for feedforward control 130 Rear wheel steering angle correction amount calculation unit for feedback control 140 Left and right front wheel braking force difference calculation unit for feedback control 150 Vehicle 160 rear Wheel assist steering means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B62D 101: 00 109: 00 113: 00 137: 00 (56) References JP-A-3-239673 (JP, A) JP-A-2-283555 (JP, A) JP-A-3-157268 (JP, A) JP-A-3-276857 (JP, A) JP-A-2-175466 (JP, A) (58) Int.Cl. ⁶ , DB name) B62D 6/00

Claims (1)

(57) [Claims] 1. A target behavior setting means for calculating a target value of a vehicle behavior according to a traveling state including a main steering amount at the time of main steering by a steering wheel, and a front wheel and a rear wheel required to achieve the behavior target value. Auxiliary steering angle calculating means for calculating at least one auxiliary steering angle of the wheel; behavior detecting means for detecting actual behavior of the vehicle; and eliminating deviation between the actual behavior and the behavior target value computed by the target behavior setting means. Control amount calculating means for calculating the auxiliary steering angle correction amount and the left and right wheel braking force difference, respectively, and assisting auxiliary steering of at least one of the front wheels and the rear wheels by the sum of the auxiliary steering angle and the auxiliary steering angle correction amount. In a vehicle behavior control device provided with a steering means and a left and right wheel braking force difference control means for providing the braking force difference between the left and right wheels, it is preferable that the auxiliary steering angle correction amount and the left and right wheel braking force difference be respectively shared. Percent The feedback control of the feedback control amount calculating means is set so that the auxiliary steering angle correction amount and the left and right wheel braking force difference each become the upper limit value when the behavior deviation reaches the set value. A behavior control device for a vehicle, wherein a gain is determined.