JP3094674B2 - Braking force control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device capable of performing a braking force control for controlling a vehicle behavior and a braking force control for controlling a wheel slip amount.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a braking force control device for controlling the braking force of a vehicle and thereby controlling the behavior of the vehicle (Japanese Patent Application Laid-Open No. 3-112756). Such a braking force control system can perform control (so-called active brake (A / BRK)) that positively uses the braking force, for example, to improve the turning performance of the vehicle during turning braking. In this example, a yaw rate feedback (F / B) type fluid pressure control is performed in which the left and right brake fluid pressures are controlled so as to eliminate the deviation between the actual yaw rate of the vehicle and the target yaw rate. It can contribute to driving stability during braking.

On the other hand, the behavior control of a vehicle is controlled by four-wheel steering (4 W
The technique performed in S) is known. JP-A-60-1612
According to the publication No. 56, the vehicle behavior is controlled by the yaw rate F / B4WS.

[0004] In the yaw rate F / B4WS, the one that controls the left and right brake fluid pressures is disclosed in Japanese Unexamined Patent Publication No. 3-22.
No. 7762 discloses this. In this system, the brake fluid pressure difference control is executed when the front wheels and the rear wheels are fully locked (steering limit).

[0005]

On the other hand, in the braking force control, there is an anti-skid system which aims to prevent wheel lock. In this system, during braking, the brake fluid pressure is reduced to avoid wheel lock. Therefore, for example, when a predetermined difference is generated between the left and right brake fluid pressures for the purpose of controlling the vehicle behavior as described above, the anti-skid system (ABS) -equipped vehicle is required to control the vehicle behavior. In a region where the braking force control and the braking force control by the anti-skid slip amount control are performed simultaneously, mutual control interferes with each other. That is, for example, if the anti-skid control is activated during the vehicle behavior control and the brake fluid pressure is reduced independently for each channel in accordance with the control rule on the ABS control side, the difference between the left and right brake fluid pressures is deviated from the original one. As described above, control interference may occur, and such interference may make it impossible to achieve the difference between the left and right brake fluid pressures (and, therefore, the target vehicle behavior).

In the case where the ABS-equipped vehicle is the yaw rate F / B4WS vehicle mentioned above, regardless of whether braking or non-braking, that is, regardless of whether the ABS is on or off, its 4 W
S controls the yaw rate. Therefore, even if the vehicle is disturbed due to the ABS operation (for example, the ABS operates only on the inner wheel side during turning braking and the one-side wheel is depressurized), the vehicle is disturbed by the ABS. Is just trying to correct with yaw rate F / B4WS as usual. Yaw rate F / B4WS
In this case, since the operation is performed when a difference between the set target value of the yaw rate and the actual yaw rate actually occurs, the above-described correction can be performed only after the disturbance of the vehicle actually occurs. Is executed, and the disturbance at that time is corrected by the yaw rate F / B-type steering angle control, a large deviation tends to occur in the process of controlling the vehicle, and the control is almost delayed.

This point is the same even if the one disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-227762 is applied to an ABS-equipped vehicle. In this case, the braking operation is more effective than the steering angle control. It is necessary to control the behavior of the vehicle by the braking force control (braking force control for vehicle behavior control) and to correct the shortage of the control when the ABS cannot control the braking force sufficiently. A suitable steering angle control amount is calculated in advance using the command values on both braking force control sides, and this is used as a command value to be applied to vehicle control. There is no function of controlling

According to the present invention, in a control in a control region in which the braking force control for controlling the vehicle behavior and the wheel slip amount control are performed simultaneously, even when the interference between the two braking force controls occurs, the feed force is controlled. By performing steering control in words, it is possible to prevent vehicle control delay and the like and control the vehicle behavior so as to appropriately have target characteristics.

[0009]

According to the present invention, in a vehicle capable of independently controlling at least the left and right braking forces of a front wheel and / or a rear wheel, steering means for steering a front wheel and / or a rear wheel, and turning of the vehicle Turning state detecting means for detecting a state; slip physical quantity calculating means for calculating a slip physical quantity used in wheel slip amount control; and a difference in braking force between the left and right wheels of the controlled wheel in response to an output from the turning state detecting means. A first braking force control for controlling the braking force so that the vehicle behavior becomes the target characteristic, and a second braking force control for controlling the wheel slip within a predetermined range based on the output of the slip physical quantity calculating means. In the control means having the functions of the braking force control, when the control interference occurs when the first and second braking force control conditions are satisfied, the braking pressure of each wheel is reduced by the first and second braking forces. The command value of the force control is determined to be the smaller one, and the left-right differential pressure that actually occurs in that case is calculated, and the calculated value and the target left-right braking force in the first braking force control are calculated. A braking force control device includes: a steering amount calculation unit that calculates a steering amount based on a difference from the difference to obtain the target characteristic and instructs the steering unit; and a braking force control unit including a command unit.

[0010]

According to the output from the turning state detecting means for detecting the turning state, the braking force control means makes a difference between the left and right braking forces of the wheels to be controlled, and applies the braking force so that the vehicle behavior becomes the target characteristic. While performing the first braking force control for controlling, the second braking force control for controlling the braking force such that the wheel slip is within a predetermined range based on the output from the slip physical quantity calculating means is performed. In the case of control interference corresponding to a region where the second braking force control is executed simultaneously, the braking pressure of each wheel is determined to be the smaller of the first and second braking force control command values, and the steering amount The calculation and command means calculates the left and right differential pressure that actually occurs in that case, and calculates the difference between the calculated value and the target left and right braking force difference in the first braking force control. The steering amount is calculated from the difference to obtain the target characteristics. It instructs the steering means.

Therefore, during braking, the vehicle behavior can be controlled by the first braking force control which has a large effect, and even when the control interference occurs due to the second braking force control, the braking pressure of each wheel is reduced by the first and second braking forces. While the command value of the second braking force control is determined to be the smaller one, the left-right differential pressure that actually occurs in that case is calculated, and further, the calculated value and the target are determined by the first braking force control. The required steering amount for the steering means is calculated in advance so that the target characteristic is obtained from the difference between the left and right braking forces, and the target turning is performed in a feedforward manner by the steering control using the steering amount. The vehicle can be controlled so as to have the characteristic, and the deviation is not increased unlike the feedback control alone, and the overall control in the above-described region can be appropriately realized with good responsiveness. Further, the first braking force control is not limited to the left and right braking force difference control, but may be a method for controlling the distribution of the braking force between the front and rear wheels as described in claim 2.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. 2 and 3 show the configuration of an embodiment of the apparatus of the present invention. The vehicle to be applied can independently control the left and right braking forces (braking fluid pressure) of the front wheels and / or the rear wheels. In the present embodiment, the left and right braking forces of both the front and rear wheels can be controlled. .

[0013] Regarding the steering angle control system (4WS), the front wheels and / or the rear wheels can be assisted by steering, and here, the rear wheels are steered. FIG. 2 is a configuration diagram of a brake system. In the figure, 1L and 1R denote left and right front wheels, 2L and 2R denote left and right rear wheels, 3 denotes a brake pedal, and 4 denotes a tandem master cylinder (M / C). In addition, 3a is a booster as a booster of a brake, and 4a is a reservoir.
Each of the wheels 1L, 1R, 2L, 2R is provided with wheel cylinders 5L, 5R, 6L, 6R for applying a braking force to each wheel by frictionally holding a brake disk by supplying hydraulic pressure. When the hydraulic pressure is supplied from the master cylinder 4, each wheel is individually braked.

In the present embodiment, the brake fluid pressure (braking fluid pressure) system of the braking device is such that the front wheel brake system 7F from the master cylinder 4 is connected to the pipelines 8F, 9F, 10F and the hydraulic pressure control valve 1
Left and right front wheel cylinders 5L, 5F after 1F, 12F
R, the rear wheel brake system 7R from the master cylinder 4 is connected to the pipelines 8R, 9R, 10R, the hydraulic pressure control valve 11
R, 12R, left and right rear wheel cylinders 6L, 6R
To reach.

The hydraulic pressure control valves 11F, 12F, 11R, 12
R is a wheel cylinder 5L, 5 of the corresponding wheel, respectively.
By individually controlling the brake fluid pressure toward R, 6L, 6R,
This is used for anti-skid and main brake fluid pressure control. When OFF, the brake fluid pressure is increased toward the original pressure at the pressure increasing position shown in the figure, and when the 1st stage is ON, the brake pressure does not increase or decrease. And a pressure reducing position where a part of the second stage ON-time brake fluid pressure is released to the reservoirs 13F and 13R (reservoir tanks) to be reduced. Control of these pressure control valve is performed by the current (control valve drive current) I ₁ ~I ₄ to the solenoid of the corresponding valve from the controller (control unit) to be described later, the current I ₁ ~I ₄
Is 0 A, the pressure increasing position, when the currents I _{1 to} I ₄ are 2 A, the pressure holding position, and when the currents I _{1 to} I ₄ are 5 A, the pressure increasing position. In addition, the reservoirs 13F, 13
The brake fluid in R is returned to the pipelines 8F and 8R by the pumps 14F and 14R which are driven at the time of pressure keeping and pressure reduction, and returned to the accumulators 15F and 15R of these pipelines for reuse.

The hydraulic pressure control valves 11F, 12F, 11R, 12
R is ON / OFF controlled by a controller 16 corresponding to a braking force control means. The controller 16 has a signal from a steering angle sensor 17 for detecting a steering angle of a steering wheel (handle) (see FIG. 3), a brake pedal. Signal from the brake switch 18 which is turned on when the pedal 3 is depressed, the rotational peripheral speed (wheel speed) of the wheels 1L, 1R, 2L and 2R.
Signals from the wheel speed sensors 19 to 22 for detecting V _{w1 to} V _w4 , signals from a yaw rate sensor 23 for detecting a yaw rate (d / dt) φ generated in the vehicle, and the like are respectively input.

Moreover, the wheel cylinders 5L of each wheel to the controller 16, 5R, 6L, fluid pressure sensor 31L for detecting the fluid pressure P ₁ to P ₄ of the 6R, 31R, 32L, with the signal from the 32R is input , signals from the hydraulic sensors 33 _1, 33 ₂ which detects the fluid pressure P _M in the master cylinder 4 (the front wheel system pressure P _M1, the rear wheels based fluid pressure P _M2) is inputted. As for the detection of the master cylinder pressure, for example, the detection may be performed by only the front wheel system and represented. The output of the hydraulic pressure sensor is set so that the actual wheel cylinder hydraulic pressure matches the target value by setting the target value of the wheel cylinder hydraulic pressure (the deviation between the set target value and the actual wheel cylinder hydraulic pressure value is It is used as a control signal for controlling the brake fluid pressure by operating the fluid pressure control valve (to be zero or near zero).

The signal from the steering angle sensor 17 is used as a parameter indicating the turning state of the vehicle by itself or as a part thereof. The signal from the yaw rate sensor 23 is a yaw rate feedback (yaw rate F / B).
It is used as a control parameter in hydraulic pressure control and the like by the system. Further, signals from the wheel speed sensors 19 to 22 can be used as information for estimating a vehicle body speed when the vehicle speed is used as a control parameter, and is used for anti-skid control performed by the controller 9.

In this embodiment, the turning state of the vehicle is detected based on the steering angle, the yaw rate, and the vehicle speed.
The yaw rate sensor 23 and a part of the controller 16 (a vehicle speed estimation calculation processing part to be described later) correspond thereto.

In the anti-skid control according to the four-channel, four-sensor system as in the present embodiment, for example, a wheel speed detection value for each wheel, a target wheel speed, and a deviation between the wheel acceleration and the target wheel acceleration are used. By controlling the braking force and making the slip amount of the corresponding wheel equal to or less than a set value, the maximum braking efficiency is achieved for each wheel, thereby avoiding wheel lock.

The controller 16 includes an input detection circuit, an arithmetic processing circuit, and a braking force control (and a slip amount control, a yaw rate F / B method described later) executed by the arithmetic processing circuit.
Rear wheel steering control) and a microcomputer using a storage circuit for storing the calculation results and the like, an output circuit, and the like. When performing vehicle behavior control by causing a difference in, for example, left and right braking forces of the vehicle according to the turning state,
That is, when the braking force control (first braking force control) is performed so that the vehicle behavior at the time of turning becomes the target characteristic, the arithmetic processing circuit calculates a target yaw rate, a yaw rate difference value, and the like. Using the calculated value, a target wheel cylinder pressure value (command value) as a braking force (braking force) control value for each wheel is calculated, and the output circuit of the controller 16 outputs a signal corresponding thereto.

When performing the slip amount control (second braking force control) based on the skid cycle, the controller 16 calculates a vehicle speed, a target wheel speed, and the like in its arithmetic processing circuit, and, based on the calculated vehicle speed, a target wheel speed, and the like. The target wheel cylinder hydraulic pressure value (command value) is calculated as the braking force control value of the vehicle. When such control is performed alone, similarly to the case where the vehicle behavior control is performed alone, a signal corresponding to the target wheel cylinder hydraulic pressure value by the anti-skid control is output via the output circuit. In the present embodiment, a part of the controller 16 corresponds to the slip physical quantity calculation means for calculating the slip physical quantity used in the wheel slip amount control.

Further, when a control condition is established such that both controls are simultaneously performed, such as when anti-skid control is operated during the vehicle behavior control, the controller 16 performs control based on command values in both controls. Then, a rear wheel steering amount (a target rear wheel steering angle) required to obtain the target turning characteristic is calculated, and a command is issued to the rear wheel steering system.

FIG. 3 is a structural diagram of a steering system used in combination with the brake system of FIG. 2. The steering angle sensor 17 is provided on a steering wheel 30. The rear wheel assist steering system includes a rear wheel steering device 50 and a steering device 51 driven by the rear wheel steering device, and controls the rear wheel steering device 50 by a control signal of a target rear wheel steering angle command value from the controller 16. By driving the steering device 51, the rear wheels 2L, 2L
Turn R. Therefore, in the present embodiment, the steering means for steering the rear wheels corresponds to the rear wheel turning device 50 and the steering device 51, and the steering amount calculation / command for calculating and instructing the above-described steering amount for such steering means. The means corresponds to a part of the controller 16.

FIGS. 4 and 5 are flowcharts showing an example of a braking force control program including the above-described vehicle behavior control and the rear wheel steering control in the anti-skid control execution area executed by the controller 16. This program is executed at regular intervals. First, in step 101, based on the signals from the sensors, the steering angle δ, the wheel cylinder pressure P _j (j = 1 to 4) of each wheel, the master cylinder pressure P _M , and the actual yaw rate (d / dt) φ, wheel speed V _{wj of} each wheel
(J = 1 to 4) are read respectively.

In the following step 102, the speed of the vehicle body is estimated, and the wheel acceleration (d / dt) V _wj (j =
1) to 4) are obtained. That is, the vehicle speed is obtained by calculation from V _wj , for example, in the case of an FR vehicle, using the wheel speeds V _w1 and V _w2 of the two front wheels that are non-driving wheels,

## EQU1 ## The V value is obtained by setting V = (V _w1 + V _w2 ) / 2, and this is set as the vehicle speed value. The wheel acceleration (d / dt) V _wj is obtained from the differential coefficient of V _wj .

The vehicle speed value and wheel acceleration value calculated above are calculated based on the following yaw rate feedback (yaw rate F /
B) Target yaw rate calculation processing in vehicle behavior control by control (step 103), and anti-skid (AB
S) This is applied to the slip amount calculation process in the control (step 106) and the like, and the latter is the process of calculating the deviation of the wheel acceleration of each wheel from the target value in the anti-skid control (step 10).
Applies to 7).

Next, for the yaw rate feedback control at the time of control, here, at step 103, the target yaw rate (target yaw angular velocity) (d /
dt) Calculate _φref . In the present embodiment, the calculation of the target yaw rate is determined according to the following equation.

(D / dt) φ _ref = (δ × V) / {A (1 + K ₂ × V ² )} (1) where (d / dt) φ _ref in the expression (1) is arbitrary Rudder angle,
It is obtained in relation to the target turning radius _Rref when the vehicle speed is given, and _Rref is obtained according to the following equation (2).

R _ref = A × (1 + K ₂ × V ² ) / δ (2) where A is a constant determined by the wheelbase and the steering gear ratio of the vehicle, and K ₂ is a constant representing the steering characteristic of the vehicle. is there.

Generally, the steer characteristic considered to be easy to drive is called a so-called weak understeer characteristic.
This is because K ₂ in the equation (2) is K ₂ > 0 and K ₂ ≒ 0, that is, the steering characteristic that the turning radius does not increase so much even when the vehicle speed V is increased while the steering angle δ is fixed. Can be expressed. Therefore, in order to obtain this preferable steering characteristic,
R _ref is given when given δ and V are given.
in relation to the _{ref (d / dt) φ ref} = V / R ref) (d
/ Dt) φ _ref value is determined.

Next, in step 104, the above-mentioned step 10
Yaw rate difference value is a difference between the calculated target yaw rate (d / dt) φ _ref and the actual yaw rate (d / dt) φ (the detected actual yaw rate) at 3 delta a (d / dt) phi computed according to the following equation.

Δ (d / dt) φ = (d / dt) φ _ref− (d / dt) φ (3) As described above, the target yaw rate (d / dt)
Once φ _ref and yaw rate difference value Δ (d / dt) φ have been calculated, then in step 105, target wheel cylinder pressure P _jA (S) for each wheel for vehicle behavior control
(J = 1 to 4) is calculated.

First, based on Δ (d / dt) φ, a target differential pressure ΔP _A (S) to be generated in the left and right wheel cylinders of the wheel to be controlled is calculated according to the following equation.

ΔP _A (S) = H × Δ (d / dt) φ (4) where H is a constant determined by vehicle specifications.

ΔP _A obtained by the above formulas 1, 2, and 3
The (S) value, including its magnitude and polarity, can be determined and calculated according to the turning direction, the state at the time of turning, and the like. In the case of the above four equations, the yaw rate difference value Δ (d /
dt) As a feedback control method for φ, a so-called proportional control method is used. However, the present invention is not limited to this, and a control method including one or both of the differential operations may be used. In this manner, the responsiveness and stability of the actual yaw rate of the vehicle with respect to the target yaw rate can be improved.

Next, based on the target difference ΔP _A (S) and the master cylinder pressure P _M , the target wheel cylinder pressure P _jA (S) is _calculated.
(J = 1 to 4) is calculated. In the present embodiment, the difference in control hydraulic pressure between the left and right wheels for controlling vehicle control during turning to have target characteristics is given on the front wheel side, and a target value is calculated according to the following equation. .

When ΔP _A (S)> 0, the following is performed.

## _EQU6 ## P _1A (S) = P _M (5)

P _2A (S) = P _M −ΔP _A (S) (6)

## _EQU8 ## P _3A (S) = P _M (7)

## _EQU9 ## P _4A (S) = P _M (8)

When ΔP _A (S) <0, the following is performed.

P _1A (S) = P _M + ΔP _A (S) (9)

P _2A (S) = P _M (10)

## _EQU12 ## P _3A (S) = P _M (11)

P _4A (S) = P _M (12) The P _jA (S) value obtained in step 105 is a hydraulic pressure command value determined by the vehicle behavior control as described above.

Next, in this embodiment, in steps 106 to 109 following step 105, the target wheel cylinder hydraulic pressure _values P _jB (for each of the front and rear wheels and left and right wheels) as the hydraulic pressure command values in the anti-skid control. S) The calculation processing of (j = 1 to 4) is performed. First, in step 106, the slip amount S _j (j
= 1 to 4), the vehicle speed V value and the wheel speed V _Wj value are used to obtain the values according to the following equation.

S _j = V−V _Wj (13) Further, in step 107, a difference Δ (d / dt) V _j (j = 1 to 4) of the wheel acceleration of each wheel is calculated according to the following equation.

Δ (d / dt) V _j = (d / dt) V _ref − (d / dt) V _Wj (14) where (d / dt) V _ref is a target wheel acceleration. And a preset constant value (for example, -1.3G)
May be.

In the next step 108, the operation is performed as described above.
Slip amount S calculated_jAnd the difference Δ (d /
dt) V_jFrom the wheel cylinder pressure reduction of each wheel
ΔP _j(J = 1 to 4) is calculated and determined according to the following equation.

ΔP _j = K ₄ × S _j + K ₅ × Δ (d / dt) V _j (15) where K ₄ and K ₅ are the slip amount S _j and the difference Δ (d of the wheel acceleration, respectively. / Dt) is a constant representing the weight for V _j .

After the execution of steps 106 to 108, a target wheel cylinder hydraulic pressure _PjB (S) for each wheel in the case of anti-skid control is calculated in step 109. This is performed as follows. That is, the hydraulic pressure sensor 31
P _jB (S) is obtained by subtracting the pressure reduction amount ΔP _j calculated in step 108 from each wheel cylinder hydraulic pressure P _j detected in L to 32R according to the following equation.

P _jB (S) = P _j −ΔP _j (16) The P _jB (S) value is determined by the above calculation, and these are hydraulic pressure command values determined by the anti-skid control. When the anti-skid control is executed independently, the wheel cylinder hydraulic pressure of each wheel is controlled depending on the target value.

Now, after step 109, in the program example, it is checked in next step 110 whether or not it is timing to simultaneously perform both the braking force control by the vehicle behavior control and the braking force control by the anti-skid control. If the answer is YES, the process proceeds to step 112 and the following steps.
_j (CMD) (j = 1 to 4) is set to the corresponding control target value. For example, if the yaw rate feedback control alone is used, the target wheel cylinder hydraulic pressure value P _jA (S) calculated by the above formulas 5 to 8 or 9 to 12 is used as the final command value P _j (CM
D), and the following steps 114 to 116 are executed to terminate the program.

Although FIG. 8 will be referred to later, for example, the braking force control during the time t _{0 to} t ₁ in the figure shows the state of the hydraulic pressure of the left and right front wheel cylinders (W / C) in such a case. In this period, only the yaw rate feedback control is executed according to the target differential pressure ΔP _A (S). Also, in the case of anti-skid control alone, the P _j (CMD) value setting process is performed according to the above.

On the other hand, steps 110 to 11
When proceeding to 2 or less, for example, at time t in FIG._Two Or t₆
During the yaw rate feedback control,
When the skid control is in the operating range (time
Time t_Three~ T_Four Or time t ₇~ T₈) Contains step 11
2 Normally, vehicle behavior control and
The command value for chip skid control, ie, the target wheel
By selecting the smaller one of the cylinder fluid pressure values,
Effect and start anti-skid control
Accompanying, for example, can no longer occur (occur
Left and right of vehicle behavior control
The differential pressure (t in FIG. 8)_Three~ T_Four Complements the example in this case)
In order to steer the rear wheels.
You.

That is, in the braking force control in a control region in which the vehicle behavior control and the anti-skid control (wheel slip amount control) are performed simultaneously, when the control interference occurs, for example, the target brake fluid is caused by the interference. In order to control the vehicle behavior by compensating for the pressure difference that cannot be properly realized by steering the rear wheels, in such a case, based on the command values in both controls, It is performed on a feed-forward (F / F) basis.

For this reason, in the present embodiment, specifically, the command values of the braking force control in both these controls are compared, and the smaller command value is selected as the braking force control command value of the wheel to be controlled. command value to be selected, the vehicle if the behavior control by not the command value (the as between t ₃ ~t ₄ in FIG. 8, a case such as antiskid control side command value per opposite wheels are selected, t ₇ to as between ~t _8, in a case, etc.), as also the anti-skid control side command value per ipsilateral wheels is selected is to be controlled (controlled by the command value by the vehicle behavior control have not been selected Estimate the shortage or excess of the differential pressure between the left and right wheels, and for that shortage or excess,
In order to compensate for this, it is possible to steer the rear wheels, and when anti-skid control makes it impossible to sufficiently control the vehicle behavior braking force, or when it becomes excessive, It is possible to calculate in advance for a part that cannot be controlled, etc., and at the same time compensate for it by rear wheel steering in F / F control.

First, proceeding to step 112,
A target wheel cylinder pressure P _jA (S) values of the respective wheels by the yaw rate feedback control, among by anti-skid control of the target wheel cylinder pressure P _jB of each wheel (S), the target wheel cylinder that outputs a smaller value It is selected as a hydraulic pressure value, that is, a hydraulic pressure command value P _j (CMD). Normally, thus smaller target wheel cylinder pressure P _jB (S) according to the target wheel cylinder pressure P _jA (S) and the anti-skid control by yaw rate feedback control is selected,
Thereby, both control effects are ensured.

Next, at step 113, processing for steering the rear wheels is performed. FIG. 6 is an example of a subroutine of such rear wheel steering control. Here, first, in step 201,
When the control is executed by the hydraulic pressure command value finally selected from the hydraulic pressure command values of both the yaw rate feedback control and the anti-skid control, the left / right differential pressure ΔP _O generated in the vehicle (the actual left / right difference, For example, at time t _{3 in} FIG.
If during ~t _4, it calculates the difference between the left and right value) denoted by the arrow by the following equation.

The final command value for both controls is already
It has been calculated and determined by the processing up to 112, and therefore, using the calculation command value at that time, the left-right difference to be actually generated can be calculated in advance in advance,
In addition, in the present embodiment, since the left and right differences are provided by the front two wheels, the value ΔP
_O is as follows.

ΔP _O = P ₁ (CMD) −P ₂ (CMD) (17)

Next, in step 202, the left / right difference Δ to be generated by the yaw rate feedback control is calculated.
P _A (S) (see FIG. 8), i.e. compares the target differential pressure of the equation 4, the left and right differential pressure actually occurs [Delta] P _O (calculated value of the formula 17), their differential pressure value E _P ( 8) is obtained by the following equation.

Equation 19 calculates the steering amount of the rear wheels _{E P = ΔP A (S)} -ΔP O ... (18) followed by step 203. Rear-wheel steering amount [delta] _r is determined by the following equation.

Δ _r = k × E _P (19) Here, k is a constant determined by vehicle specifications.

That is, an attempt is made to generate due to the difference between the left and right hydraulic pressures.
However, for example, at time t in FIG._Three~ T_FourAnne like
Yaw that cannot be generated due to the operation of the chiskid control
To compensate for the wing moment by steering the rear wheels.
is there. Moreover, the steering amount δ _rThe setting is just
Yaw that actually occurred as in the case of 4WS
Check the late deviation and determine the control amount to eliminate it.
Vehicle behavior braking force control, not feedback control
And anti-skid control based on command values
Steering amount δ necessary to obtain the target turning characteristics_rIs the above equation
The calculation is performed at 19.

[0049] Thus, in this embodiment, based on such steering amount [delta] _r, actually the rear wheel 2L in the next step 204, so as to steer the 2R, control the rear wheel steering device 50 for the rear wheel steering angle control A signal is output (see FIG. 8).

Returning to FIG. 5, in steps 114 and 115, a process for setting the value of P _j (CMD) to 0 is executed. That is, the final command value P _j (CMD) that has been set may be negative, but in that case, P _j (CMD)
Value, that is, the target wheel cylinder fluid pressure may be set to 0,
In the next step 116, a brake fluid pressure control process is executed, and this program ends.

FIG. 7 shows such a brake fluid pressure control routine.
An example is shown below. The subroutine is for each wheel cylinder
Determine the pressure increase, hold pressure, and pressure reduction of the hydraulic pressure, and
Outputs drive current required for control valves 11F, 12F, 11R, 12R
Processing. That is, in FIG.
Is the target wheel cylinder hydraulic pressure obtained in step 112.
P_j(CMD) and actual wheel cylinder pressure P_j(J
= 1 to 4) (read value of step 101)
Absolute value of difference | P_j(CMD) -P _jWhere | is set in advance
It is checked whether it is equal to or smaller than the fixed value Δα. As a result of the determination,
If the absolute value is less than the value Δα, the actual wheel cylinder
Hydraulic pressure P_jIs almost the target wheel cylinder hydraulic pressure P_j(CM
Considering that it is in the state controlled in D),
Proceeds to the pressure-holding process in step 122 to maintain this hydraulic state.
Control the hydraulic pressure control valve to

On the other hand, if the result of the determination is that the absolute value is larger than the value Δα, the target wheel cylinder hydraulic pressure P _j (CMD) is compared with the actual wheel cylinder hydraulic pressure P _j in step 123 to determine the target wheel cylinder hydraulic pressure P _j (CMD). Wheel cylinder pressure P
_{If j} (CMD) is larger, the process proceeds to the pressure increasing process in step 124, and the hydraulic pressure control valve is controlled so as to increase the wheel cylinder hydraulic pressure. Conversely, if the actual wheel cylinder hydraulic pressure is greater, the process proceeds to step 125 where the hydraulic pressure control valve is controlled to reduce the wheel cylinder hydraulic pressure. In this way, the pressure holding, pressure increase, and pressure reduction of the wheel cylinder fluid pressure are determined, and a current value to be output to the fluid pressure control valve is set according to the determination, and is output in this routine.

In this embodiment, by the above control,
As shown in FIG. 8 showing an example of a time chart when this control is operated, the rear wheel steering can be executed.
As already mentioned, in the case of the time t ₀ ~t _1, anti-skid is when only the yaw rate F / B control operation to the braking force is operating in a non actuated, making the steering of the rear wheels according to the control in this state There is no.

On the other hand, at timings t _{3 to} t ₄ and t _{7 to} t ₈ , both controls are operated, and the former case (t _{3 to} t 8) in which the anti-skid is operated on the opposite wheel.
In _4), it can be seen that the rear wheels are steered in accordance with the difference between the left and right pressure E _P that have not been generated by the anti-skid operation. Moreover, even the latter case the anti-skid on the same side wheel is actuated (t ₇ ~t _8), but similarly the rear wheel steering is performed, in such a case, E _P is calculated as being as shown, Based on this, it can be seen that the rear wheels are being steered. Although the anti-skid control is shown in the time chart of FIG. 2 as an example in which only one of the left and right wheels is operated, the control is also performed in accordance with the control content according to the above when the anti-skid control is operated on both wheels. It goes without saying that it is executed.

In any case, the shortage and the excess due to the anti-skid operation of the vehicle behavior control by the left and right braking force difference control can be estimated, and at the same time, can be appropriately compensated for. The effectiveness of the vehicle behavior control can be further enhanced even in comparison with the combination of the yaw rate feedback (F / B) 4WS and the braking force control.

In the case of the yaw rate F / B4WS, if FIG.
The case of the anti-skid operation as shown by (t _{3 to} t
_{If the} vehicle is disturbed due to ₄ ), the disturbance will be corrected by the 4WS, which is corrected by the 4WS by the F / B control. When correcting the vehicle behavior with the braking force control that is more effective (basically, the yaw rate control effect by 4WS tends to be weaker at the time of braking) and the braking force control cannot be performed sufficiently by the anti-skid, Calculate in advance the loss of control, and at the same time,
It is also effective in controlling the vehicle by performing a supplementary steering (here, rear wheel steering) control to compensate for it. Therefore, the complementary assist steering control performed in both control execution regions as the target of the present control is not controlled by the F / B, but is performed by using the target value and the actual value as in the F / B control. A large deviation does not occur and the response delay is small (the F / F control is also excellent in response). It is easy and effective to use the auxiliary steering more effectively before such deviation actually occurs. is there.

When the rear wheels are steered as the steering control, the rear wheel steering device (50) does not only control the above-mentioned right and left differential pressure compensation, but usually performs the normal four-wheel steering control. When the system of the present control is operated, the rear wheels may be steered in a manner that is added to the normal control. Further, the present invention is not limited to steering the rear wheels, and may be implemented in a mode in which the front wheels are steered or in a mode in which the front wheels and the rear wheels are steered.

Further, the steering control may be such that the other left and right braking force difference control of the braking force control is stopped by the anti-skid operation (ABSON) of one of the wheels and the steering control is started. Operation (ABSO
N), the left and right braking force difference control may be continued as in the embodiment, and the missing portion may be compensated for by the steering control. That is, it is sufficient to calculate how to control the steering control system from the state of both command values of the braking force control, and to enter the front wheel and / or rear wheel steering control by the F / F control method.

The braking force control is not limited to the left and right braking force difference control, but may be a method for controlling the braking force distribution between the front and rear wheels, or performs both the left and right braking force difference control and the braking force front and rear distribution control. It may be something. Further, in the embodiment, as shown in FIG. 2, a configuration using the same actuator as a normal anti-skid actuator has been described. However, if a proportional pressure control valve or the like is used, the wheel cylinder hydraulic pressure is increased to the master cylinder pressure or more. It is also possible. This control can be applied also when such a control valve is used. Further, the braking force control is not limited to the feedback control, and may be F / F control as disclosed in, for example, JP-A-3-281467.

[0060]

According to the present invention, as described in claim 1,
In a control region where the first braking force control for the vehicle behavior control and the second braking force control of the wheel slip amount control interfere with each other, the braking pressure of each wheel is equal to the command value of the first and second braking force control. The smaller of the two, the left and right differential pressure that would actually occur in that case is calculated, and the difference between the calculated value and the target left and right braking force difference in the first braking force control is determined. A steering amount is calculated from the difference thus obtained so as to attain the target characteristic, and the steering amount is commanded to the steering means to execute the steering control in a feedforward manner. Can be controlled such that the target characteristic is obtained even in such a control region. Further, the first braking force control may be implemented as the braking force control for controlling the distribution of the braking force between the front and rear wheels.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the device of the present invention.

FIG. 2 is a system diagram showing one embodiment of the present invention, showing an example of a configuration of a braking force control system.

FIG. 3 is a diagram showing an example of the configuration of a steering control system.

FIG. 4 is a flowchart illustrating an example of a control program of a controller in the same example, and is a diagram illustrating a part of the flowchart.

FIG. 5 is a view showing another part in the same manner.

FIG. 6 is a flowchart showing an example of a rear wheel steering control routine of the same program.

FIG. 7 is a flowchart showing an example of a brake fluid pressure control routine.

FIG. 8 is a diagram showing an example of a time chart for explaining control contents.

[Explanation of symbols]

 1L, 1R Left and right front wheels 2L, 2R Left and right rear wheels 3 Brake pedal 4 Master cylinder 5L, 5R, 6L, 6R Wheel cylinders 11L, 12R, 11L, 12R Hydraulic pressure control valve 16 Controller 17 Steering angle sensor 19-22 Wheel speed sensor 23 Yaw rate sensor 30 Steering wheel 50 Rear wheel steering Steering 51 Steering device

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naoki Maruko 2 Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-4-185562 (JP, A) JP-A-1 -172070 (JP, A) JP-A-62-173372 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/00-8/96 B62D 7/14

Claims (2)

(57) [Claims] 1. A least a front wheel and / or rear wheels of the left and right of the controllable vehicles the braking force independently and steering means for steering the front wheels and / or rear wheel, the turning state detection for detecting a turning state of the vehicle means and causes a slip physical quantity calculation means for calculating a slip physical quantity used in the wheel slip quantity control, the difference in the braking force of the left and right controlled wheel in accordance with an output from said turning state detecting means, target vehicle both behavior Functions of the first braking force control for controlling the braking force so as to achieve the characteristic described above, and the second braking force control for controlling the braking force so that the wheel slip is within a predetermined range based on the output of the slip physical quantity calculating means. Control means having the first and second
When you Keru control interference when the condition of the braking force control is established
In the meantime, the braking pressure of each wheel is the finger of the first and second braking force control.
Decide on the smaller of the quotes, and in that case the actual
A left-right differential pressure that will occur is calculated, and the calculated value and the second
From the difference between the target left and right braking force difference in braking force control 1
A braking force control device comprising: a steering amount calculation unit that calculates a steering amount so as to achieve the target characteristic and instructs the steering unit, and a braking force control unit that includes a command unit. 2. A vehicle capable of controlling at least the distribution of braking force between front and rear wheels, a steering means for steering front wheels and / or rear wheels, a turning state detecting means for detecting a turning state of the vehicle, and a wheel slip amount control. A slip physical quantity calculating means for calculating a slip physical quantity to be used, and a braking force control for controlling a braking force distribution between the front and rear wheels in accordance with an output from the turning state detecting means to control the braking force so that the vehicle behavior becomes a target characteristic. Control means having the functions of braking force control and second braking force control for controlling the braking force so that the wheel slip is within a predetermined range based on the output of the slip physical quantity calculating means; at the time of your Keru control interference when the condition of the braking force control is established, control of each wheel
The dynamic pressure is the smaller of the first and second braking force control command values.
And in that case it will actually occur.
The braking force before and after the first braking is calculated.
The difference from the braking force distribution of the front and rear wheels targeted by force control
A braking force control device, comprising: a steering amount calculation unit that calculates a steering amount so as to have a target characteristic and instructs the steering unit, and a braking force control unit including a command unit.