JPH08142893A - Vehicle control system - Google Patents

Abstract

PURPOSE: To always secure almost the same control performance as the whole vehicle control system by changing control regulation performed by a controller in a vehicle control device in the operating state in the case of at least one of plural vehicle control devices being put in a non-operating state. CONSTITUTION: A vehicle control system in the case of being provided with a rear wheel steering angle control device and a braking force distribution control device as a vehicle control device is provided with a vehicle speed sensor 40, a front wheel steering angle sensor 42, a rear wheel steering angle sensor 44, a yaw rate sensor 40 and a lateral acceleration sensor 48, and the detection signals of these sensors are inputted to a rear wheel steering angle controller 30. Whether or not abnormality is generated to the rear wheel steering angle control device is diagnosed by the self-diagnostic function. At the time of abnormality being generated, rear wheel steering angle control is suspended, and a tire is fixed into the neutral position. At this time, basic control gain used at the time of determining the control quantity by the braking force distribution control device is changed to an abnormality time control gain larger than a normal time control gain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle control system for controlling a turning state of a vehicle, and more particularly to an improvement of a vehicle control system of a type in which a plurality of vehicle control devices comprehensively control the turning state of a vehicle. It is about.

[0002]

2. Description of the Related Art As a vehicle control device for controlling a turning state of a vehicle, a rear wheel steering angle control device, a driving force distribution control device,
A braking force distribution control device and the like are known. In addition, this type of vehicle control device generally includes (a) a sensor that detects a physical quantity related to the turning state of the vehicle, and (b) a turning state control mechanism that controls the turning state of the vehicle based on a signal from the outside. ,
(c) A controller that determines an output signal to the turning state control mechanism based on an input signal from the sensor and outputs the output signal to the turning state control mechanism.

Since these vehicle control devices are common to each other in that the turning state of the vehicle can be controlled, one vehicle control device is usually mounted on one vehicle. But,
It has already been proposed to mount a plurality of vehicle control devices on one vehicle because, for example, a region in which a vehicle control device effectively operates in a turning state of the vehicle is different from other vehicle control devices. However, one conventional example is Japanese Patent Laid-Open No. Hei 6
-32242 gazette.

[0004]

When a plurality of vehicle control devices are mounted on one vehicle, the control characteristics of each vehicle control device are usually based on the assumption that the other vehicle control devices are in operation. Designed. However, other vehicle control devices are not always in operation. For example, if another vehicle control device has failed and it is impossible to enter the operating state, or if it is not out of order but the driver wishes, it is actively prohibited to enter the operating state. This is because there are cases where Therefore, if the control characteristics of each vehicle control device are designed on the assumption that the other vehicle control device is always in the operating state, the desired vehicle turning is performed when the other vehicle control device is in the non-operating state. State control will not be realized.

On the other hand, the present applicant has conducted research on a vehicle control system that comprehensively controls the turning state of the vehicle by a plurality of vehicle control devices, and as a result, the following facts have been found. That is, in order for the vehicle control device in the operating state to sufficiently and quickly and surely compensate for the control amount of the vehicle turning state that is insufficient due to a certain vehicle control device becoming inactive, the controller of each vehicle control device inputs The control rules (eg, control gain, etc.) used to determine the output signal from the signal are more sensitive when the other vehicle controls are inactive (eg, control gain is It turned out that it was desirable to change to the big one).

Therefore, the present invention is based on such a fact, and changes the control rule used by each vehicle control device depending on whether the other vehicle control device is in an operating state or a non-operating state. The task was always to ensure almost the same control performance for the entire control system.

[0007]

In order to solve the problem, the present invention provides a plurality of units each including the above-mentioned (a) sensor, (b) turning state control mechanism, and (c) controller. In a vehicle control system having a vehicle control device, when at least one of the plurality of vehicle control devices is in a non-operational state, the controller in at least one of the plurality of vehicle control devices which is in an operating state receives an input signal. It is characterized in that control rule changing means for changing the control rule used when determining the output signal is provided.

Here, the "sensor" is not limited to, for example, a vehicle speed sensor, a yaw rate sensor, a lateral acceleration sensor, or the like that detects the behavior of the vehicle body, but also a sensor that detects the driver's intention, such as a steering angle sensor, or a wheel. Also included are sensors that detect wheel behavior, such as speed sensors. The "sensor" is
It may be shared among a plurality of vehicle control devices.

The control executed by the "controller" includes, for example, front wheel active steering angle control, rear wheel steering angle control, driving force distribution control, braking force distribution control, roll rigidity distribution control and the like. Note that the braking force distribution control includes, for example, a type of controlling the left / right difference of the brake pressure, a type of controlling the left / right difference of the target slip ratio of each wheel, and the like. Further, roll rigidity distribution control includes, for example, a method of controlling the front-back difference of the spring constant of the suspension device, a form of controlling the front-back difference of the damping force,
There is a form that controls the front-back difference of the stabilizer rigidity.

[0010]

In the vehicle control system according to the present invention, when at least one of the plurality of vehicle control devices is in the inoperative state, the control rule changing means includes at least one of the vehicle control devices in the operating state. Change the control rules used by the controller in one to determine the output signal from the input signal.

Therefore, the control rule changing means is, for example,
Changed the control rules used by the operating vehicle control device so that the control amount increases when other vehicle control devices are inactive and the control amount becomes more sensitive than when they are active. Can be
By doing so, even when a certain vehicle control device is in the inoperative state, a control effect sufficiently close to that when it is in the operating state can be obtained.

[0012]

Therefore, according to the present invention, since the vehicle control device in the operating state can complement the vehicle control device in the non-operating state, the vehicle control system as a whole always has substantially the same control performance. It becomes possible to secure.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, some preferred embodiments of the present invention will be listed. (1) The invention according to claim 1, further comprising a rear wheel steering angle control device and a braking force distribution control device which are vehicle control devices, and the rear wheel steering angle control device includes a vehicle speed sensor as the sensor. It has at least one of a front wheel steering angle sensor (a sensor that detects a steering angle of a steering wheel) and a yaw rate sensor, and has a rear wheel steering mechanism as the turning state control mechanism, and the controller controls the sensor from the sensor. The target rear wheel steering angle is determined based on the output signal of the vehicle, and the output signal is determined accordingly, and the braking force distribution control device uses the vehicle speed sensor and the front wheel steering angle sensor (the steering wheel It may be a sensor for detecting a steering angle) and a yaw rate sensor, and has an electromagnetic hydraulic pressure control valve for controlling each brake pressure of the left and right wheels as the turning state control mechanism. The roller determines the target yaw rate based on the input signal from each sensor, and determines the output signal by obtaining the product of the deviation from the actual yaw rate detected by the yaw rate sensor and the control gain, and The vehicle control system, wherein the control rule changing means increases the value of the control gain used by the controller of the braking force distribution control device when the operating state of the rear wheel steering angle control device is abnormal.

The rear wheel steering angle control device can adopt various control methods. For example, a method of controlling the rear wheel steering angle based only on the detected front wheel steering angle, a method of controlling the rear wheel steering angle based on the detected vehicle speed and the front wheel steering angle, or a detected vehicle speed It is possible to adopt a method of controlling the rear wheel steering angle based on the yaw rate and a method of controlling the rear wheel steering angle based on the detected vehicle speed, yaw rate and front wheel steering angle.

(2) In the invention of (1), the controller in the braking force distribution control device further determines, based on a signal from the sensor, whether the tire in the vehicle turning state is in the ground contact state in the vehicle lateral direction. The control rule changing means includes a lateral ground contact state determining means for determining whether a certain lateral ground contact state is in a grip area not exceeding a turning limit or a side slip area exceeding a turning limit; When the direction ground contact state determination means determines that the lateral ground contact state of the tire is in the grip range, the current value of the control gain is increased from a preset basic value, and when it is determined to be in the side slip range. Is a vehicle control system that is a control gain changing unit that reduces the current value of the control gain from the previous value.

(3) In the invention of (2), the controller in the braking force distribution control device further includes a normal time determination rule when the operation state of the rear wheel steering angle control device is normal, In the case of an abnormality, an abnormal condition determination rule, which is more easily determined than the normal condition determination rule to determine that the lateral landing state of the tire is in the side slip area, is used for the lateral direction grounding state determination means. A vehicle control system including a determination rule changing means for determining the lateral ground contact state of the vehicle.

(4) In the invention of (2) or (3), the lateral ground contact state determining means determines the tire based on at least one of a lateral slip angle around the center of gravity of the vehicle body and a time differential value thereof. Vehicle control system for determining the lateral ground contact state of the vehicle.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the illustrated embodiments. The illustrated embodiment is a vehicle control system including two rear wheel steering angle control devices and a braking force distribution control device as vehicle control devices. This vehicle control system is mounted on a four-wheel vehicle, as shown in FIG. In this vehicle, a steering wheel 10 rotated by a driver is a front wheel steering mechanism 12 with a power assist function.
The left and right front wheels 14 are linked to each other through the steering wheel 10. The steering angle δ _f of the left and right front wheels 14 is mechanically changed according to the steering angle θ of the steering wheel 10. A rear wheel steering mechanism 26 having a step motor 24 as an electric drive source is associated with the left and right rear wheels 22, and a steering angle δ of the left and right rear wheels 22 is associated with the rear wheel steering mechanism 26.
_r can be changed electrically. That is, in the present embodiment, the rear wheel steering mechanism 26 is an example of the turning state control mechanism in the rear wheel steering angle control device.

The step motor 24, as shown in FIG.
It is connected to the output side of the rear wheel steering angle controller 30.
The rear wheel steering angle controller 30 includes a CPU 32 and a ROM 34.
The computer mainly includes a RAM 36 and a RAM 36, and further includes an A / D converter, a driver, and the like (not shown).

On the input side of the rear wheel steering angle controller 30,
Vehicle speed sensor 40, front wheel steering angle sensor 42, rear wheel steering angle sensor 44, yaw rate sensor 46, and lateral acceleration sensor 48
Is connected. The vehicle speed sensor 40 detects a vehicle speed V which is a traveling speed of the vehicle. Front wheel steering angle sensor 42
Is for detecting the front wheel steering angle δ _f . The rear wheel steering angle sensor 44 detects the rear wheel steering angle δ _r . The yaw rate sensor 46 detects the yaw rate γ of the vehicle. The lateral acceleration sensor 48 detects the lateral acceleration Gy at the center of gravity of the vehicle. The front wheel steering angle sensor 42
Is the operating angle θ of the steering wheel 10 by the driver
It is possible to replace the steering angle sensor for detecting

The rear wheel steering angle controller 30 includes a ROM 34.
The rear wheel steering angle control is executed by executing a rear wheel steering angle control routine (represented by a flowchart in FIG. 3) stored in advance. In this rear wheel steering angle control, the target rear wheel steering angle δ _r ^* is determined using the formula δ _r = K ₁ δ _f + K ₂ γ, and the step motor 24 is controlled so that it is realized. It is a front wheel steering angle proportional type and a yaw rate feedback type.

In this equation, K ₁ is always a negative control gain whose absolute value increases as the vehicle speed V increases. On the other hand, K ₂ is a positive control gain whose absolute value increases as the vehicle speed V increases. However, those control gains K
Even if the vehicle speed V is the same, ₁ and K ₂ are in the grip range when the lateral ground contact state (hereinafter, simply referred to as the ground contact state) of one of the tires of the wheels 14 and 22 in the vehicle turning state is in the grip range or the side slip range. It is a different value depending on whether it is in or in the intermediate range.

Specifically, each control gain K₁, K₂Base of
Basic control gain K that is this value_Ten, K ₂₀And the relationship with vehicle speed V
Is stored in the ROM 34 in advance, and the ground contact state of the tire
Are in the grip range, those basic control gains K
_Ten, K₂₀The value obtained by multiplying
Control gain K_{1 (i)}, K_{2 (i)}Used as a target rear wheel rudder
Angle δ_r ^*The current value of is decided. And the ground contact of the tire
If the state is in the intermediate range, the previous control gain K_{1 (i
-1)}, K_{2 (i-1)}As it is this time control gain
K_{1 (i)}, K_{2 (i)}Target rear wheel steering angle δ_r ^*of
This time the value is determined and the actual rear wheel steering angle δ_rSuppress the change of. This
As a result, changes in vehicle behavior are suppressed and tire ground contact
The state should not shift to the sideslip area. Also tires
If the ground contact state of the
In K_{1 (i-1)}, K_{2 (i-1)}Preset decrement from
The value obtained by subtracting ΔK is the control gain K of this time._{1 (i)},
K_{2 (i)}Target rear wheel steering angle δ_r ^*This time the value of
Then, the steering position of the rear wheel 22 is brought close to the neutral position. This
As a result, the ground contact state of the tire escapes from the skid area.
Try to recover to the grip area.

Here, the content of the rear wheel steering angle control will be specifically described based on the rear wheel steering angle control routine shown in FIG. First, in step S1 (hereinafter, simply referred to as S1; the same applies to other steps), the content of the flag F representing the grounded state is read from the RAM 36. The flag F
The content of is controlled by the execution of a grounding state determination routine described later. Further, it is determined whether or not the read flag F is 1, that is, whether or not the grounded state is in the intermediate range.

Assuming that the value of the flag F is not 1 this time, the determination is NO and the flag F is set to 0 in S2.
Or not, that is, whether or not the ground contact state is the grip state. Assuming 0 this time,
The determination is YES, the vehicle speed V is read from the vehicle speed sensor 40 in S3, and the ROM 34 is read according to the vehicle speed V.
The basic control gains K ₁₀ and K ₂₀ for controlling the rear wheel steering angle are read from this and multiplied by a value larger than 1, for example, 1.5 to obtain the control gains K _{1 (i)} and K _{2 (i )} Is calculated. In the figure, K ₁ and K ₂ are collectively represented by K. Since the ground contact state is in the grip range this time, the control gains K _{1 (i)} and K _{2 (i)} this time are increased from the basic values K ₁₀ and K ₂₀ , and the actual rear wheel steering angle δ _r is the input signal. It is made to respond sensitively to changes. However, the control gains K _{1 (i)} and K _{2 (i )} at this time cannot be increased at once, and are set to prevent a sudden change in the vehicle body behavior due to a sudden change in the actual rear wheel steering angle δ _r . The gradient is gradually increased, and the product of each basic value K ₁₀ , K ₂₀ and 1.5 is set as the upper limit value.

Then, in S4, the yaw rate γ and the front wheel steering angle δ _f are read from the respective sensors, and based on them and the control gains K _{1 (i)} and K _{2 (i)} calculated above,
The present value of the target rear wheel steering angle δ _r ^* is calculated by using the above equation. Subsequently, in S5, an output signal for realizing the target rear wheel steering angle δ _r ^* is output to the step motor 24. Further, the actual operating state of the step motor 24 based on the output signal is the rear wheel steering angle sensor 4
4, the target value and the actual value of the control amount of the step motor 24 are made to coincide with each other. Thus, one execution of this routine is completed.

On the other hand, assuming that the flag F is 1 this time, that is, if the grounded state is in the intermediate range, the determination in S1 is YES, and in S6, each control gain K of this time is determined.
_{1 (i )} and K _{2 (i)} are the previous control gains K _{1 (i-1)} and K
_{2 (i-1)} , so that each control gain K ₁ ,
K ₂ is retained. After that, the process proceeds to S4 and subsequent steps.

Further, this time, if the flag F is 2, that is, assuming that the ground contact state is in the side slip area, the determination of S1 is NO, the determination of S2 is NO, and whether the flag F is 2 is determined in S7. Is determined. This time flag F is 2
Therefore, the determination is YES, and in S8, the preset decrease amount ΔK is subtracted from the previous control gains K _{1 (i-1)} and K _{2 (i-1)} to obtain each control gain K this time.
_{1 (i)} and K _{2 (i)} are calculated. Each control gain K ₁ , K
₂ is reduced so that the actual rear wheel steering angle δ _r becomes insensitive to changes in the input signal. However,
As in the case of increasing the control gain, each control gain K this time
_{1 (i)} and K _{2 (i)} are not reduced at a time, and are gradually increased at a set gradient to prevent a sudden change in vehicle body behavior due to a sudden change in the actual rear wheel steering angle δ _r . When this S8 is continuously executed a plurality of times, the lower limit value is the value obtained by subtracting the decrease amount ΔK from each control gain K _{1 (i-1)} , K _{2 (i-1)} before the first execution. It

If the read flag F is neither 0, 1 nor 2, it is determined that the self-diagnosis device itself described later has some abnormality, and the determination in S1 is N.
The determination of O and S2 is NO, the determination of S7 is NO, and S6
At, the control gain K is held.

The rear wheel steering angle controller 30 has a self-diagnosis device for diagnosing whether or not an abnormality has occurred in the rear wheel steering angle controller. The self-diagnosis device determines, for example, the presence or absence of a failure (for example, disconnection or short circuit) of the sensor 40 or the like, or the presence or absence of a failure of the step motor 24. Diagnose that an abnormality has occurred. The rear-wheel steering angle controller 30 suspends the rear-wheel steering angle control and fixes the tire to the neutral position while diagnosing that an abnormality has occurred in the rear-wheel steering angle control device. The rear wheel steering angle controller 30 also sends the self-diagnosis result to the RAM of the computer of the brake controller described later.

This vehicle is also equipped with an electric control-manual dual system braking device. As shown in FIG. 4, a master cylinder 64 and an electrically controlled hydraulic pressure source 66 are connected to a brake cylinder 60 of each wheel 14, 22 via a two-position valve 62 as a switching device. The electric control hydraulic pressure source 66 is provided with a linear hydraulic pressure control valve 68 as an electromagnetic hydraulic pressure control valve, a pump 70 as a high pressure source, an accumulator 72, and a reservoir 74 as a low pressure source for each wheel 14, 22. It is composed by.

Although the two-position valve 62 is an electromagnetic type switching device, it may be a mechanical type that mechanically switches using the hydraulic pressure of the master cylinder 64, for example. The linear hydraulic pressure control valve 68 is an electromagnetic hydraulic pressure control valve that linearly changes the hydraulic pressure with respect to the exciting current.
It is possible to use two or more two-position valves or three-position valves.

The two-position valve 62 and the linear hydraulic pressure control valve 68 are connected to the output side of the brake controller 80, as shown in FIG. This brake controller 80 is
The computer mainly includes a CPU 82, a ROM 84, and a RAM 86, and further includes an A / D converter, a driver, and the like (not shown).

On the input side of the brake controller 80,
The vehicle speed sensor 40, the yaw rate sensor 46, the steering angle sensor 88, and the pedaling force sensor 92 are connected. The steering angle sensor 88 detects the steering angle θ of the steering wheel 10. The pedal force sensor 92 detects the pedal force of the brake pedal 90 based on the driver's operation. Both the vehicle speed sensor 40 and the yaw rate sensor 46 are sensors shared by the rear wheel steering angle control device.

The brake controller 80 executes normal brake control by executing a normal brake control routine stored in the ROM 84 in advance. In particular,
Hydraulic pressure of the brake cylinder 60 of each wheel 14, 22 (hereinafter,
A brake pressure) is electrically controlled to a height corresponding to the pedaling force of the brake pedal 90.

The brake controller 80 further includes an RO
A braking force distribution control routine previously stored in M84 (see FIG. 6).
(Represented by a flow chart in)
Execute force distribution control. Specifically, the vehicle speed V and the steering angle θ
And the target yaw rate γ of the vehicle based on the lateral acceleration Gy.
^*And the actual yaw rate γ is calculated as the target yaw rate γ ^*
Target that is the right and left difference of the brake pressure suitable to match
Left-right difference ΔB^*Each linearity so that it is realized.
The liquid pressure control valve 68 is controlled. Target left-right difference ΔB ^*Is the real
Target yaw rate γ of yaw rate γ^*Deviation from Δγ
If expressed, ΔB^*= K · Δγ. The left-right difference ΔB is
It is also possible to generate only the braking force,
It is possible to generate only the braking force,
To generate braking force for both the left and right rear wheels 22
You can also

In this equation, K is a control gain, but is not a fixed value, but is a different value depending on whether the ground contact state of the tire is in the grip range, the side slip range, or the middle range thereof. . The method of changing the control gain K in accordance with the ground contact state of the tire is the same as in the preceding rear wheel steering angle control device.

[0038] Specifically, the control gain basic control gain K ₀ is a base value of K is stored in advance in ROM 84, when the contact state of the tire is in a gripping zone, on the basic control gain K ₀ The value obtained by multiplying the value larger than 1 is set as the current control gain K _(i) , and the target left-right difference ΔB ^*
The current value of is decided. Then, when the tire ground contact state is in the intermediate range, the previous control gain K _{(i-1 )} is used as it is as the current control gain K _(i) to determine the current value of the target left-right difference ΔB ^* , and the actual left-right difference is determined. The change in the difference ΔB is suppressed. This suppresses a change in the behavior of the vehicle and prevents the ground contact state of the tire from advancing to the sideslip area. In addition, when the ground contact state of the tire is in the side slip area, a value obtained by subtracting a preset decrease amount ΔK from the previous control gain K _{(i -1) is} set as the current control gain K _{(i ).} Target left-right difference ΔB ^*
The current value of is determined and the braking force difference between the left and right wheels is approached to zero. As a result, the ground contact state of the tire escapes from the side slip area and is restored to the grip area.

However, in the preceding rear wheel steering angle control, one basic value for each control gain K ₁ and K ₂ is prepared, but in this braking force distribution control, the basic value for the control gain K is set. Two are prepared. A normal time control gain K _NOR selected when the rear wheel steering angle control device is normal,
Abnormal control gain K _{AB N} used when there is an abnormality
That is, a control gain larger than the normal-time control gain K _NOR is prepared. As a result, the braking force distribution control quickly and surely compensates for the shortage of the control effect due to the rear wheel steering angle control device having an abnormality and the rear wheel steering angle control being stopped. The normal-time control gain K _NOR and the abnormal-time control gain K _ABN are stored in the ROM 8 in advance.
It is stored in 4.

That is, in this embodiment, the vehicle speed sensor 40, the steering angle sensor 88, and the yaw rate sensor 46 as sensors, the linear hydraulic pressure control valve 68 as a turning state control mechanism, and the brake controller 80 as a controller. The part that executes the braking force distribution control constitutes a braking force distribution control device.

Like the rear wheel steering angle controller 30, the brake controller 80 also has a self-diagnosis device for diagnosing whether or not an abnormality has occurred in the braking force distribution control device, and it is diagnosed that an abnormality has occurred. While the braking force is being distributed, the braking force distribution control is stopped. However, in the following description, it is assumed that the braking force distribution control device is always normal for convenience of description.

Here, the content of the braking force distribution control will be concretely described based on the braking force distribution control routine shown in FIG. First, in S101, the vehicle speed V, the steering angle θ, and the actual yaw rate γ are input from the respective sensors. Next, in S102, the target yaw rate γ ^* is calculated based on the vehicle speed V and the steering angle θ. The yaw rate expected to occur when the vehicle makes a steady circular turn under the vehicle speed V and the steering angle θ is calculated as the target yaw rate γ ^* . Subsequently, in S103, the yaw rate deviation Δγ is calculated by subtracting the actual yaw rate γ from the target yaw rate γ ^* thus calculated.

Thereafter, in S104, it is determined whether or not the rear wheel steering angle control device is abnormal based on the information from the RAM 86. Assuming that there is no abnormality this time, the determination is NO, and in step S105, the normal-time control gain K _NOR is read from the ROM 84 and set as the current basic control gain K ₀ . On the other hand, if the rear wheel steering angle control device is abnormal, the determination is YES and S1
In 06, the control gain K for abnormal time is read from the ROM 84.
_{The ABN} is read and used as the basic control gain K _{0 of} this time.

In any case, after that, the process proceeds to steps S107 and thereafter, but since these steps are based on those in FIG. 5 described above, they will be briefly described. First, in S107, the flag F is read from the RAM 86.
Is read and it is determined whether it is 1. This time, assuming that it is not 1, the determination is NO,
In S108, it is determined whether the flag F is 0. This time, if it is assumed that 0, that is, the ground contact state is in the grip area, the determination is YES, and in S109, the current basic control gain K ₀ is multiplied by a value larger than 1, for example, 1.5, The control gain K _(i) is calculated and the control gain K is increased. This increase will also be moderate.

Then, in S110, the target left-right difference ΔB ^* is calculated as the product of the control gain K _(i) thus calculated and the yaw rate deviation Δγ, and then S1
At 11, an output signal for realizing the target left-right difference ΔB ^* is output to the linear hydraulic pressure control valve 68. The braking force generated on each wheel is made to differ from each other on the left and right, so that a yaw moment is generated around the center of gravity of the vehicle, and the actual yaw rate γ matches the target yaw rate γ ^* . Thus, one execution of this routine is completed.

On the other hand, assuming that the flag F is 1 this time, that is, if the grounded state is in the intermediate range, the determination in S107 is YES, and in S6, the control gain K _{(i )} of this time is the previous control. It is made equal to the gain K _(i-1) , so that the control gain K is held. Then, the process proceeds to S110 and subsequent steps.

Further, this time, if the flag F is 2, that is, assuming that the ground contact state is in the side slip area, the determination in S107 is NO, the determination in S108 is NO, and in S113, whether the flag F is 2 or not. Is determined. Since the flag F is 2 this time, the determination is YES and S11
In 4, the control gain K _(i) is calculated by subtracting a preset decrease amount ΔK from the previous control gain K _(i-1) , and the control gain K is decreased. This decrease is also gradual. Then, the process proceeds to S110 and subsequent steps.

In the normal state in which the electrically controlled hydraulic pressure source 66 is selected, the brake controller 80 opens the electromagnetic opening / closing valve 94 to allow the brake fluid to be discharged from the master cylinder 64, and discharge the brake fluid. By storing the brake fluid in the stroke simulator 96 under pressure, the rigidity of the brake pedal 90 is appropriately softened.

Further, the brake controller 80 selects the master cylinder 64 by the two-position valve 62 in the abnormal state in which the electric control hydraulic pressure source 66 has failed, and the pressure of each brake cylinder 60 corresponds to the depression force of the brake pedal 90. It is in a manual state that is mechanically controlled.

In both the rear wheel steering angle control device and the braking force distribution control device described above, the determination of the ground contact state is made by determining the side slip angle β around the center of gravity of the vehicle body and the side slip angular velocity β'which is a time differential value thereof. And both. Specifically, as shown in the graph in FIG. 7, the first quadrant of the coordinate plane in which the horizontal slip angle β is plotted on the horizontal axis and the horizontal slip angular velocity β ′ is plotted on the vertical axis is divided into three regions A, B, and C. It is determined which of the areas A, B and C the intersection of the actual side slip angle β and the side slip angular velocity β ′ belongs to, the grip area when the area A belongs, and the intermediate area when the area B belongs. If it belongs to the region C, it is determined to be in the side slip region.

Region A is a region below the first straight line which is a straight line connecting the point where the sideslip angle β is a ₁ and the point where the sideslip angular velocity β'is b ₁ . Region B has the first straight line, the point where the side slip angle β is a ₂ and the side slip angular velocity β ′.
Is a region sandwiched by a second straight line which is a straight line connecting the point b ₂ with. Region C is a region above the second straight line.

However, regarding the braking force distribution control device,
When an abnormality occurs in the rear wheel steering angle control device, the ground contact state is determined based on a determination value different from the above case. That is, as shown in the graph in FIG. 8, in the area A, the side slip angle β is a ₁ and the side slip angular velocity β ′ is b ₁ ′.
It is a region below the third straight line which is a straight line connecting the point (<b ₁ ). Region B has a third straight line, a point where the side slip angle β is a ₂ and a side slip angular velocity β ′ of b ₂ ′ (<b
It is a region sandwiched by a fourth straight line which is a straight line connecting the point ₂ ). Region C is a region above the fourth straight line. Therefore, in the braking force distribution control device, when the rear wheel steering angle control device is abnormal, it is more easily determined that the ground contact state of the tire is in the side slip range, and thus the rear wheel steering angle control device It is possible to prevent the vehicle from truly falling into the turning limit regardless of the abnormality of the wheel steering angle control device, or it is possible to quickly recover from it even if it truly falls into the turning limit. Becomes

That is, regarding the braking force distribution control device
The rule for determining the ground contact state of the tire is the rear wheel steering angle.
It depends on whether the control device is normal or abnormal
As you can see, there are two rules, one for normal times and one for abnormal times.
Since it is prepared, the judgment rule for normal time is
a₁, B₁, A₂And b₂The ground contact state of the tire using
On the other hand, the abnormality determination rule is
a₁, B₁’, A₂And b ₂Grounding the tire using '
It is a rule that determines the state and is easier than the normal rule
The rules that determine that the tire is in the skid area
It is a rule.

Both the sideslip angle β and the sideslip angular velocity β'of the vehicle body can be directly detected by a dedicated sensor, but in this embodiment, the vehicle body is calculated by using the formula Gy / V-γ. The sideslip angular velocity β'is acquired,
By integrating it over time, the sideslip angle β
Is obtained.

The routine executed by the computer to determine the grounding state is the grounding state determination routine shown in the flow chart of FIG. In the present embodiment, the ground contact state determination routine is stored in advance in the ROM 34 of the rear wheel steering angle controller 30 and is executed by the CPU 32 to determine the ground contact state.
The result is transmitted to the RAM 86 of the brake controller 80.

Here, the content of the grounding state determination routine will be specifically described with reference to FIG. First, in S201, the vehicle speed V, the yaw rate γ, and the lateral acceleration Gy are input from each sensor. Next, in S202, the side slip angular velocity β'and the side slip angle β of the vehicle body are calculated based on these input values as described above. afterwards,
In S203, it is determined based on the information from the RAM 86 whether the rear wheel steering angle control device is abnormal. Assuming that there is no abnormality this time, the determination is NO, and S2
At 04, the normal time determination rule is selected as the grounding state determination rule. On the other hand, if it is assumed that the abnormality is present this time, the determination becomes YES, and in S205, the abnormality determination rule is selected as the ground state determination rule.

In any case, after that, S206 to S2
At 11, the ground contact state of the tire is determined according to the selected determination rule. When the ground contact state is in the grip area, the determination in S206 is YES, and the flag F is set to 0 in S207. If the grounded state is in the intermediate range, the determination in S206 is NO and the determination in S208 is YE.
S is set, and the flag F is set to 1 in S209.
When the ground contact state is in the side slip area, the determination in S206 is NO, the determination in S208 is NO, and the determination in S210 is YE.
In S211, the flag F is set to 2.
Thus, one execution of this routine is completed.

As is clear from the above description, in this embodiment, the brake controller 80 of FIG.
The part that executes 104 to S106 constitutes the control rule changing means.

Although one embodiment of the present invention has been described in detail with reference to the drawings, various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the claims. The present invention can be implemented in such a manner.

[Brief description of drawings]

FIG. 1 is a plan view showing a four-wheel steering mechanism in a four-wheel vehicle equipped with a vehicle control system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a rear wheel steering angle control device in the vehicle control system.

3 is a flowchart showing a rear wheel steering angle control routine stored in a ROM of FIG.

FIG. 4 is a system diagram showing an electric control-manual two-system braking system mounted on the four-wheel vehicle.

FIG. 5 is a block diagram showing an electrical configuration of a brake control device for controlling the brake system.

FIG. 6 is a flowchart showing a braking force distribution control routine for executing a braking force distribution control in the brake control device.

FIG. 7 is a graph for explaining a determination rule used by the vehicle control system for determining a lateral ground contact state of a tire.

FIG. 8 is a graph for explaining another determination rule used by the vehicle control system to determine a lateral ground contact state of a tire.

FIG. 9 is a flowchart showing a ground contact state determination routine used by the vehicle control system to determine a lateral ground contact state of a tire.

[Explanation of symbols]

 14 left and right front wheels 22 left and right rear wheels 24 step motor 26 rear wheel steering mechanism 60 brake cylinder 68 linear hydraulic pressure control valve

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Claims (1)

[Claims] 1. A sensor for detecting a physical quantity related to a turning state of a vehicle, a turning state control mechanism for controlling a turning state of the vehicle based on a signal from the outside, and a input signal from the sensor. And a controller that determines an output signal to the turning state control mechanism and outputs the output signal to the turning state control mechanism. At least one of the plurality of vehicle control devices is provided. Control rule changing means for changing the control rule used when the controller in at least one of the vehicle control devices in the operating state determines the output signal from the input signal when the one becomes inactive A vehicle control system comprising: