JP2001088583A - Behavior control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make high safety compatible with high operability of a vehicle by making the intervention of behavior control appropriate in the case of estimating the traveling state of the vehicle and controlling yaw rate behavior according to the estimated result. SOLUTION: A first target yaw rate ψ (θ) is set on the basis of the steering wheel steering angle and vehicle speed of a vehicle, and a second target yaw rate ψ (G) is set on the basis of the lateral acceleration and vehicle speed of the vehicle. One of these yaw rates is selected as a control target yaw rate Trψ, and the yaw rate behavior of the vehicle is controlled according to the deviation between the control target yaw rate Trψ and an actual yaw rate ψ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a vehicle behavior control device for controlling a yaw rate behavior during turning of a vehicle to avoid a drift-out due to an understeer state and a spin due to an oversteer state. .

[0002]

2. Description of the Related Art Conventionally, as a vehicle behavior control device of this kind, for example, Japanese Patent Application Laid-Open No. 6-183288 and Japanese Patent Application Laid-Open
As shown in each of the publications of Japanese Patent No. 223520, a target yaw rate is set based on a steering angle and a vehicle speed of a vehicle, and an actual yaw rate of the vehicle is detected by a yaw rate sensor. It is known that when the yaw rate has a deviation equal to or more than a predetermined value, each intervention of understeer control for suppressing the understeer state of the vehicle or oversteer control for suppressing the oversteer state is performed.

More specifically, when the target yaw rate is larger than a threshold value obtained by adding a predetermined value to the actual yaw rate, intervention of understeer control is performed, and the target yaw rate is reduced by a predetermined value from the target yaw rate. When the actual yaw rate is large, intervention of oversteer control is performed.

[0004]

However, in the prior art, a target yaw rate is set based on the steering angle and the vehicle speed of the vehicle, and the target yaw rate is a threshold value obtained by adding a predetermined value to the actual yaw rate. If it is larger than that, the understeer control tends to intervene too frequently in order to cause the understeer control to intervene. Even in the so-called drive understeer state that occurs in the case, understeer control may be intervened by determining that the vehicle is in the understeer state that leads to drift out of the vehicle.
The understeer control interferes with the drive understeer state intended by the driver of the vehicle, so that the drive understeer state aimed by the driver cannot be effectively obtained.

[0005] If the threshold value for determining the intervention of the understeer control is increased, the early intervention of the understeer control can be prevented, and the driving understeer state by the driver can be ensured. However, in this case, a delay in the intervention of the understeer control occurs, and it is difficult to quickly suppress the understeer state that causes the vehicle to drift out.

On the other hand, when performing an oversteer control for suppressing the oversteer state of the vehicle, for example, when the vehicle is a front-wheel drive vehicle, the engine output is reduced in a state where the steering angle is reduced by a predetermined angle or more, and so-called tack-in is performed. When a state occurs, or when a so-called counter-steering state occurs in which the driver intentionally turns the steering wheel in the direction opposite to the turning direction of the vehicle to suppress the over-steering state of the vehicle, the tuck-in state or the counter. The present invention has a problem that it is difficult to intervene oversteer control for suppressing the steer state, and the present invention has been made in view of the above-described points, and an object of the present invention is to intervene in the behavior control that is the understeer control or oversteer control. By improving the conditions, the intervention of the behavior control is made appropriate and the safety of the vehicle is increased. It is to achieve both high operability when.

[0007]

In order to achieve the above object, according to the present invention, not only a target yaw rate used for behavior control is set from a component of a steering angle of a vehicle but also a target yaw rate generated when the vehicle turns. Two target yaw rates are provided by also setting the lateral acceleration and the vehicle speed, and these two target yaw rates are selected to be the control target yaw rates.

More specifically, the invention of claim 1 is directed to a vehicle behavior control device for estimating a traveling state of a vehicle and controlling a yaw rate behavior of the vehicle based on the estimation result. A first target yaw rate is set based on the steering angle of the vehicle and the vehicle speed, and a second target yaw rate is set based on the lateral acceleration and the vehicle speed of the vehicle. And the second
There is provided control means for selecting one of the target yaw rates as the control target yaw rate and controlling the yaw rate behavior of the vehicle in accordance with the deviation between the control target yaw rate and the actual yaw rate.

The lateral acceleration of the vehicle changes due to a change in the steering angle during turning of the vehicle. The lateral acceleration is slower than the change in the steering angle, but includes factors such as a road surface friction coefficient in addition to the steering angle. Therefore, when selecting one of the first and second target yaw rates as the control target yaw rate in accordance with the traveling state of the vehicle, if the control target yaw rate is selected as the second target yaw rate having the component of the lateral acceleration of the vehicle, The intervention of the vehicle behavior control is performed smoothly and appropriately.

On the other hand, in the understeer state of the vehicle, the deviation between the second target yaw rate including the lateral acceleration component and the actual yaw rate is small, so that it becomes difficult to intervene in the behavior control. Further, if the second target yaw rate is set as the control target yaw rate, there is no distinction between a drive understeer state in which the driver drives and turns the drive force on the drive wheels and another understeer state. In this case, the first target yaw rate including the steering angle component may be selected as the control target yaw rate. By selecting the two target yaw rates in this manner, the intervention of the vehicle behavior control can be made appropriate.

According to the second aspect of the present invention, the control means sets the control target yaw rate when the first target yaw rate falls below the second target yaw rate in a state where the second target yaw rate is selected as the control target yaw rate. It is configured to switch to the first target yaw rate.

Thus, in a state where the second target yaw rate is selected as the control target yaw rate, for example, in order to suppress the oversteer state of the vehicle, the driver consciously turns the steering wheel in the direction opposite to the turning direction of the vehicle. When a so-called counter-steering state in which the steering wheel is switched back occurs, the first target yaw rate having the steering angle component becomes lower than the second target yaw rate, and the control target yaw rate is switched to the first target yaw rate. In other words, if the second target yaw rate is directly used as the control target yaw rate in the counter steer state, the behavior control of the vehicle slowly yawing is performed, and it becomes difficult to suppress the oversteer state intended by the driver. Second yaw rate
By switching from the target yaw rate to the first target yaw rate, the counter-steering effect by the driver can be satisfactorily enhanced and the oversteer state can be suppressed.

In this case, according to the third aspect of the present invention, a mitigation means for easing the control operation when the control means switches the control target yaw rate from the second target yaw rate to the first target yaw rate is provided. In this way, the control operation at the time of switching the control target yaw rate is relaxed by the mitigation means, and the shock accompanying the switching can be reduced.

According to a fourth aspect of the present invention, the control means in the vehicle behavior control device according to the first aspect of the present invention is configured such that when the control target yaw rate exceeds the intervention threshold value, the first target yaw rate is set as the control target yaw rate. It is assumed that the apparatus is configured to perform an understeer control intervention that controls the output to suppress the understeer state.

According to this configuration, the first target yaw rate having the steering angle component changes faster than the second target yaw rate, and the deviation from the actual yaw rate is large. By using the control for suppressing the understeer state by the control, the understeer control can be interposed earlier than the understeer control by the brake control, etc., and the intervention of the understeer control by controlling the engine output can be appropriately and reliably performed. It can be carried out. It should be noted that lowering the engine output is less likely to cause discomfort to the occupant of the vehicle than applying the brakes.Therefore, lowering the engine output reduces the vehicle speed, secures the lateral force of the tires, and suppresses the understeer condition. it can.

According to a fifth aspect of the present invention, in the vehicle behavior control device of the first aspect, the control means sets a smaller one (a smaller absolute value) of the first and second target yaw rates as a control target yaw rate. When the control target yaw rate exceeds the intervention threshold value, it is configured to perform an intervention of understeer control for controlling the brake of the vehicle to suppress the understeer state.

Thus, when the smaller one of the first and second target yaw rates becomes larger than the intervention threshold value,
Since the intervention of the understeer control by the brake control is performed, the intervention of the understeer control by the brake control can be appropriately and reliably performed.

According to a sixth aspect of the present invention, in the vehicle behavior control apparatus of the first aspect, the control means sets the first target yaw rate to the control target yaw rate when the actual yaw rate fluctuation is equal to or more than a predetermined value. It shall be configured. Also, in the invention according to claim 7, similarly, the control means:
When the actual fluctuation of the yaw rate is equal to or more than a predetermined value, the second
It is assumed that a target yaw rate obtained by adding a correction value corresponding to a difference between the first and second target yaw rates to the target yaw rate is set as a control target yaw rate.

That is, when the vehicle travels on a rough road or the like and the actual yaw rate fluctuates greatly, the second target yaw rate having a lateral acceleration component also fluctuates in accordance with the actual yaw rate. When the control target yaw rate is used, the behavior control is performed in an unstable manner. However, even if the control target yaw rate is the first target yaw rate or the second target yaw rate having the steering wheel angle component as in these inventions. In addition, the target yaw rate in which the element of the first target yaw rate is added (the correction value corresponding to the difference between the first and second target yaw rates is added to the second target yaw rate) is set as the control target yaw rate, and the behavior control is performed. Can be performed stably.

In the invention according to claim 8, in the vehicle behavior control device according to claim 1, the control means, when selecting the second target yaw rate, sets a value between the first and second target yaw rates with respect to the second target yaw rate. It is assumed that the target yaw rate to which the correction value according to the difference is added is set as the control target yaw rate.

Accordingly, when the second target yaw rate having the component of the lateral acceleration is set as the control target yaw rate, the second target yaw rate is not used as it is, but is used as the second target yaw rate.
The control yaw rate is obtained by setting a target yaw rate in which an element of the first target yaw rate is added to the target yaw rate (a correction value corresponding to a difference between the first and second target yaw rates to the second target yaw rate) as a control target yaw rate. The behavior control intervenes only in the understeer state in which the driver has turned the steering wheel. When the driver intentionally enters the drive understeer state, the understeer control is not intervened, so that the intervention of the behavior control can be made appropriate.

In this case, in the invention of claim 9, the control means is configured to obtain a correction value by multiplying a difference between the first and second target yaw rates by a variable that changes according to the lateral acceleration. Shall be In this way, for example, when the lateral acceleration is small and large,
By using a material with a large characteristic when the lateral acceleration is moderate, understeer control is intervened on a snowy surface with a moderate friction coefficient compared to an ice surface with a small friction coefficient or a road surface with a large friction coefficient. This facilitates the intervention of the behavior control, which can be appropriately performed according to the road surface friction coefficient.

[0023]

FIG. 1 shows the overall configuration of a vehicle behavior control device according to an embodiment of the present invention. First, each device on the input side will be described. Reference numeral 11 denotes a wheel speed sensor that detects a wheel speed of each wheel, 12 denotes a steering angle sensor that detects a steering angle of a steering wheel, and 13 denotes a yaw rate generated in the vehicle. A yaw rate sensor that detects
14 is a lateral acceleration sensor (lateral G sensor) for detecting the lateral acceleration of the vehicle, 15 is a throttle opening sensor for detecting the throttle opening, and 16 is a stop lamp for canceling control of an antilock brake system described later. A switch 17 is an engine speed sensor for detecting the engine speed, which is detected for performing feedback control of the engine output. Reference numeral 18 denotes a shift position sensor (AT) for detecting a shift position for detecting an operation state of the engine (power train). The shift position detection sensor 18 cancels the behavior control in the case of reverse. They are also used as switches. Further, reference numeral 19 denotes an MC hydraulic pressure sensor for detecting a hydraulic pressure of a master cylinder (MC) as a first hydraulic pressure generation source. The fluid pressure is corrected to correspond to the pedaling force. In addition, reference numeral 110 is a reservoir level switch for detecting the presence of brake fluid in the reservoir.

Next, each device on the output side will be described. Reference numeral 31 denotes an anti-lock brake system lamp for warning that the anti-lock brake system 21 is operating, and reference numeral 32 denotes a pressurization as a second hydraulic pressure source. A pressurizing motor as a pressurizing / depressurizing means provided in the pump;
Are front solenoid valves and rear solenoid valves as pressurizing and depressurizing means for supplying and discharging brake fluid to brake devices such as disc brakes provided for front wheels and rear wheels, respectively. A TSW solenoid valve as a pressurizing / depressurizing means for shutting off / opening between the brake device side; 36, an ASW solenoid valve as a pressurizing / depressurizing means for shutting off / opening between the master cylinder and the pressurizing pump; An engine controller 38 for controlling the output is an alarm device as alarm means for alarming the driver by sound or display that the behavior control of the vehicle is being performed.

Next, an EC as a control means for receiving a signal from each of the sensors on the input side or switches 11 to 110 and outputting a control signal to each of the devices 31 to 38 on the output side.
U2 will be described.

The ECU 2 includes an anti-lock brake system 21 that controls the braking force to prevent the wheels from being locked when the wheels are likely to lock on the road surface. An electronic braking force distribution device 22 for distributing the braking force applied to the rear wheels, and a phenomenon in which the wheels slip on the road surface while the vehicle is running is suppressed by controlling the driving force or the braking force for each wheel. And a vehicle stability control device 24 that suppresses and avoids yaw rate behavior such as drift-out and spin.

Next, the input and output of signals from each of the above devices will be described. The signal from the wheel speed sensor 11 is used to calculate the wheel speed and the estimated vehicle speed in the wheel speed calculator and the estimated vehicle speed calculator. The signal from the stop lamp switch 16 is input to a stop lamp state determination unit, from which the anti-lock brake system 21,
The signals are input to the electronic braking force distribution device 22, the traction control system 23, and the vehicle stability control device 24, respectively.

The signals from the engine speed sensor 17, the throttle opening sensor 15, and the shift position sensor 18 are input to an engine speed calculating unit, a throttle opening information input unit, and a shift position determining unit, respectively. From there, it is input to the traction control system 23 and the vehicle stability control device 24.

Further, the steering angle sensor 12, the yaw rate sensor 13, the lateral G sensor 14, and the MC hydraulic pressure sensor 19
The steering angle, the yaw rate, the lateral acceleration, and the MC hydraulic pressure are calculated by the steering angle calculation unit, the yaw rate calculation unit, the lateral G calculation unit, and the MC hydraulic pressure calculation unit, respectively. To be entered.

In addition, the signal of the reservoir liquid level switch 110 is input to the traction control system 23 and the vehicle stability control device 24 via a liquid level judgment unit.

The anti-lock brake system 21 calculates a control amount from each signal and outputs signals to the anti-lock brake system lamp 31, the pressurizing motor 32, the front solenoid valve 33 and the rear solenoid valve 34. Control these.

The electronic braking force distribution device 22 controls a rear solenoid valve 34.

The above traction control system 2
Numeral 3 outputs signals to the front solenoid valve 33, the rear solenoid valve 34, the pressurizing motor 32, the TSW solenoid valve 35, and the engine controller 37 to control them.

The vehicle stability control device 24 includes:
Engine controller 37, front and rear solenoid valves 33 and 34, pressurizing motor 32, TSW and AS
Signals are output to the W solenoid valves 35 and 36 and the alarm device 38 to control them.

(Vehicle Stability Control) Next, vehicle stability control (behavior control) in the vehicle stability control device 24 will be described. The vehicle stability control device 24 performs, for example, understeer control that is control for avoiding drift-out and oversteer control that is control for avoiding spin, for example. When the control target yaw rate Trψ is larger than the actual yaw rate ψ, control is performed to apply a braking force to the front wheel in turning or the rear wheel in turning and to reduce the engine output. With such control,
A decrease in centrifugal force due to a decrease in vehicle speed and a vehicle moment due to imbalance of the braking force applied to each wheel occur,
Drift out can be avoided.

On the other hand, in the oversteer control, specifically, when the control target yaw rate Tr # is smaller than the actual yaw rate ψ, a control for applying a braking force to the front wheels outside the turning is performed.
By such control, a moment is generated in which the front portion of the vehicle is turned outside, so that spin can be avoided.

The behavior control by the vehicle stability control device 24 will be described in more detail with reference to the flowchart shown in FIG. First, in step S11, signals from the various sensors 11 to 110 described above are read.

Next, in step S12, a first target yaw rate ψ (θ) based on the steering angle and a second target yaw rate ψ (G) based on the lateral acceleration are calculated.

Specifically, the first target yaw rate ψ (θ) is calculated based on the estimated vehicle speed V calculated by the estimated vehicle speed calculating section based on the signal from the wheel speed sensor 11 and the steering angle sensor 1.
2 and the steering angle θ calculated by the steering angle calculation unit, and is calculated by equation (1).

{(Θ) = V × θ / {(1 + K × V ² ) × L} (1) where K is a stability factor, and K is a turning on a high μ (friction coefficient) road. Is a constant obtained from. Also,
L is a wheel base.

On the other hand, the second target yaw rate ψ (G)
Is the lateral acceleration Gy calculated by the lateral G calculating unit based on the estimated vehicle speed V and the signal of the lateral G sensor 14.
And is calculated by equation (2).

Ψ (G) = Gy / V (2) In step S13, is the absolute value of the second target yaw rate ψ (G) smaller than the absolute value of the first target yaw rate ψ (θ)? Determine whether or not. This determination is a step of determining which of the first and second target yaw rates ψ (θ, G) is set as the control target yaw rate Trψ, and the first and second target yaw rates ψ (θ, G). ) Is set as the control target yaw rate Trψ to control the behavior of the vehicle.

Then, in this step S13, NO
In the case of, the process proceeds to step S14, while in the case of YES, the process proceeds to step S15.

In step S14, the first target yaw rate ψ (θ) is set as the control target yaw rate Trψ, and the deviation Δψ between the control target yaw rate Trψ and the actual yaw rate 検 出 detected by the yaw rate sensor 13 and calculated by the yaw rate calculator. (Θ) is calculated.

On the other hand, in step S15, the second target yaw rate ψ (G) is set as the control target yaw rate Trψ. At this time, the control target yaw rate Trψ is given by the following equation (3).
Correction is performed in consideration of the steering angle component. That is, Trψ = ψ (G) + a × k1 (3) Here, a = ψ (θ) -ψ (G). k1
Is a variable.

Then, a deviation Δψ (θ, G) between the corrected control target yaw rate Trψ and the actual yaw rate ψ is calculated.

As described above, by correcting the steering angle component when the second target yaw rate {(G) based on the lateral acceleration is set as the control target yaw rate Tr}, the driver intentionally understeers (driving). In the case of understeer, intervention of behavior control can be suppressed.

That is, for example, when the vehicle is in an understeer state, a driving understeer intentionally performed by the driver to increase the driving force while keeping the steering angle constant;
There are two types of unintentional understeer, in which the behavior of the vehicle does not follow the steering of the driver. Here, for example, when the second target yaw rate {(G) based on the lateral acceleration is set as the control target yaw rate Tr}, the lateral acceleration generated in the vehicle is the same in any of the two types of understeer. Even so, the behavior control is performed. Therefore, when the second target yaw rate ψ (G) is set as the control target yaw rate, the steering angle component is corrected, so that the behavior control is performed only when the driver turns the steering wheel. The behavior control can be performed only when the driver does not intend to understeer without performing the behavior control.

In the above equation, the value of k1 is a value having a characteristic that changes with respect to the lateral acceleration, for example, as shown in FIG. That is, when the lateral acceleration is small (the area of the road surface is low μ such as an ice surface) or the lateral acceleration is large (the area of high μ), the value is set to a small value and the correction ratio of the steering angle component is reduced.

This is because, for example, if the value of k1 is increased in the low μ region, the following inconvenience occurs. That is, since the rudder is hardly effective in the low μ range, the driver normally performs a steering operation with a relatively large rudder angle. In such a case, if the value of k1 is increased to increase the correction ratio of the steering angle component, the deviation between the control target yaw rate Trψ and the actual yaw rate ψ increases, and the control amount of the behavior control, for example, the braking amount increases. turn into. As a result, the vehicle behavior after performing the behavior control may become too large in the reverse direction, and it may be difficult to correct the behavior in the reverse direction.

The reason why the value of k1 is reduced in the high μ region is that, for example, in the high μ region, a sufficient grip force of the tire is obtained, so that the value of k1 is increased to increase the steering angle. This is because if the component is increased, the behavior control starts too early. In other words, in such a high μ region, appropriate control intervention is realized without increasing the correction ratio of the steering angle component. Therefore, in the high μ region, the value of k1 is reduced.

On the other hand, when the lateral acceleration is moderate (medium μ region),
Since the road surface corresponds to the road surface μ in the case of the snow compaction state and the possibility of side slip is high, the correction ratio of the steering angle component is increased by increasing the value of k1 so that the behavior control is performed early. I do.

As described above, by changing the value of k1 depending on the lateral acceleration, the intervention of the behavior control at an appropriate timing can be realized.

In step S14 or S15, the control target yaw rate Tr # and the actual yaw rate Tr #
If the deviation Δψ (θ, G) is calculated, step S1
In step S16, a threshold value (THOS) for determining whether to perform oversteer control, a threshold value (THEUS) for determining whether to perform engine control for understeer control, and a brake control for understeer control are set. The threshold value (THUS) of whether or not to perform is set. Note that THUS> THEUS.

Next, in step S17, it is determined whether or not the THEUS is greater than the deviation Δψ (θ) between the first target yaw rate ψ (θ) and the actual yaw rate ψ. That is, it is determined whether or not to perform the engine control in the understeer control.

In the determination as to whether or not to perform the engine control, even when the second target yaw rate ψ (G) is selected as the target yaw rate in step S13, the value of the first target yaw rate ψ (θ) is determined. A judgment is made as a reference.

This is for the following reason. That is, since the steering angle signal has a fast phase, if the behavior control is performed with the first target yaw rate ψ (θ) as the control target yaw rate Trψ, the behavior control is usually started early. In the present embodiment, the first and second target yaw rates are used to prevent early intervention of the behavior control, but compared to the case where the brake is controlled even when the engine output is reduced. Since there are many cases where the driver does not notice, even if the engine control is started early, there is little adverse effect.

In the understeer control, first, deceleration of the vehicle is effective in avoiding understeer. For this reason, if the vehicle is decelerated by lowering the engine output early, effective understeer is avoided. Will be able to do it.

Further, since the lateral acceleration and the yaw rate are substantially proportional, the difference between the value of the second target yaw rate {G} based on the lateral acceleration and the value of the actual yaw rate ヨ ー is small. Since the value of に な る becomes unstable in the case of understeer, the second target yaw rate ψ (G)
Is set as the control target yaw rate を, it is difficult to perform appropriate control intervention. For the above reasons, the start determination of the engine control is based on the first target yaw rate ψ (θ) as the control target yaw rate Trψ.

Then, in step S17, Y
In the case of ES, the process proceeds to step S18, while in the case of NO, the process proceeds to step S19 to determine the start of oversteer control.

In step S18, it is determined whether the yaw rate acceleration is equal to or less than a predetermined value. This is for the purpose of preventing erroneous intervention of control, and it is determined whether or not the vehicle has actually changed the behavior by a predetermined amount or more. If YES, the process proceeds to step S110, while if NO, the process proceeds to step S113, prohibits engine control, and proceeds to step S19.

In step S110, it is determined whether the vehicle is oversteering. This is because it is conceivable that oversteer and understeer, in which the vehicle moves to the outside of the circuit while rotating in the turning direction, occur simultaneously, and in such a case, first avoid oversteer. It is necessary to correct the attitude of the vehicle.
Therefore, if YES, the process proceeds to step S113 to inhibit the understeer engine control and proceeds to step S19, while if NO, the process proceeds to step S111.

In step S111, it is determined whether the brake is not operated. This means that when the driver is performing the brake operation, no driving force is generated,
This is because not only is the effect less effective even if the engine control is performed, but if the engine control is performed, it becomes impossible to accelerate the next time the accelerator pedal is depressed, so that unnecessary engine control is not performed. If YES, the process proceeds to step S112, and an engine suppression control amount is calculated to perform engine control. Then, the process proceeds to step S114 to output a signal to the engine controller 37 to execute the engine control, that is, reduce the engine output. On the other hand, if NO in step S111, the flow advances to step S113 to prohibit engine control. When step S114 and step S111 are completed, the process proceeds to step S19.

In step S19, it is determined whether or not to perform oversteer control. The determination of the oversteer control is performed by determining whether or not the yaw rate deviation Δψ (θ, G) calculated in step S14 or S15 is larger than the oversteer threshold THOS. If YES, step S11
In step 5, the amount of braking to be applied to the outer front wheels, that is, the outer front wheels with respect to the rotation direction of the yaw rate, is set in accordance with the yaw rate deviation Δψ (θ, G) in order to avoid oversteer.

When the braking amount has been set, step S117 is performed.
To execute the braking force control. This is the pressure motor 3
2. Front and rear solenoid valves 33, 34, T
This is performed by controlling the SW and ASW solenoid valves 35 and 36, respectively. Next, step S118
Then, it is determined that the oversteer control has been completed, and the process returns.

On the other hand, if NO is determined in the step S19, the process proceeds to a step S116. In this step S116, it is determined whether or not to start the understeer control. If YES to start, the process proceeds to step S119, while if NO to start, the process returns.

In step S119, it is determined whether the understeer is small. If smaller, the process proceeds to step S120, while if larger, the process proceeds to step S120.
Go to 121.

In step S120, the braking amount of the inner front wheel is calculated. On the other hand, in step S121, the braking amount of the inner rear wheel is calculated. This is considered to be a state where the front wheel has a grip force when the understeer is small, and applying braking force to the front wheel has better braking efficiency than applying braking force to the rear wheel, That is, the vehicle can be decelerated more efficiently. For this reason, when understeer is small, braking is performed on the inner front wheel, whereby it is possible to perform reliable and quick understeer control.

On the other hand, when the understeer is large, it is considered that there is no grip force on the front wheels, so that a braking force is applied to the inner rear wheels.

When the braking amount has been calculated in this manner, the process proceeds to step S122, where braking force control is executed.

Then, in step S123, it is determined whether the understeer control has been completed. This is performed by determining whether or not the yaw rate deviation Δψ (θ, G) has become smaller than the threshold value THUS. Then, in the case of YES, the process proceeds to step S124 to end the control and return. On the other hand, in the case of NO, the routine returns without terminating the control.

(Determination of Start of Understeer Brake Control) Next, the determination of the start of brake control in the understeer control in step S116 will be described with reference to FIG.
This will be described according to the flowchart shown in FIG. In this control start determination, the control is started not only when the yaw rate deviation Δψ (θ, G) exceeds the threshold value THUS, but also when another condition is satisfied. I have.

First, in step S21, the yaw rate deviation Δψ (θ, G) is set to the understeer threshold value THU.
It is determined whether it is larger than S. In the case of YES, the process proceeds to step S22, whereas in the case of NO, the process proceeds to step S23.

In step S22, it is determined whether the acceleration of the actual yaw rate ψ is equal to or less than a predetermined value. This is intended to prevent erroneous control intervention as in step S18 (see FIG. 2).

Then, in the above step S23,
It is determined whether or not the steering speed of the steering wheel is equal to or more than a predetermined value in the increasing turning direction. If the determination is YES, the process proceeds to step S25. If the determination is NO, the process proceeds to step S27. In step S25, as shown in FIG. 5, the value of the first target yaw rate ψ (θ) is larger than twice the value of the actual yaw rate ψ, and the first target yaw rate ψ (θ) -actual Value of yaw rate ψ Δψ
It is determined whether (θ) is equal to or greater than a predetermined value. If step S25 is NO, the process proceeds to step S26, where the acceleration of the actual yaw rate ψ is equal to or less than the predetermined value, and Δψ
It is determined whether (θ) is equal to or greater than a predetermined value. If NO, the process proceeds to step S27, where control is not performed and control is returned.

Step S25 determines whether the deviation between the first target yaw rate {(θ) and the actual yaw rate} is large.
The step S26 determines whether or not the speed of the spread of the deviation between the first target yaw rate ψ (θ) and the actual yaw rate 速 い is high. If YES in the step S25 or the step S26, the step S24 is performed. To start the understeer brake control.

That is, the yaw rate deviation Δψ (θ, G)
If the behavior control is started only based on whether or not is greater than the threshold value THUS, the control is started even when the driver intentionally enters the understeer state as in the case of driving understeer. Despite operating, there is no increase in yaw rate following it,
The control is performed only when the vehicle does not behave as intended by the driver and the vehicle is understeer.

(Judgment of Start of Oversteer Control) Next, the judgment of oversteer will be described. As described above, the start determination of the oversteer control is performed by setting the first and second target yaw rates ψ (θ, G) as the control target yaw rates.
Of the control target yaw rate Trψ
And the control target yaw rate Trψ and the actual yaw rate ψ
(Θ, G) is the oversteer threshold T
This is performed depending on whether or not it is larger than HOS.

For example, as shown in FIG. 7, the absolute value of the second target yaw rate ψ (G) is equal to the first target yaw rate ψ
When the absolute value of (θ) is smaller than the absolute value, oversteer control is performed using the second target yaw rate {(G) as the control target yaw rate Tr} (see T1 in the same figure).

For example, when the driver performs counter-steering to avoid such over-steering, the value of the first target yaw rate ψ (θ) becomes equal to the second target yaw rate ヨ ー (θ).
The target yaw rate may be smaller than the target yaw rate ψ (G).
At this time, the control target yaw rate Tr # is changed from the second target yaw rate ψ (G) to the first target yaw rate ψ (θ) (see T2 in the same figure).

When counter-steering is performed as described above, the value of the actual yaw rate ψ becomes smaller than the value of the second target yaw rate ψ (G) with the change of the first target yaw rate ψ (θ). Here, for example, the second target yaw rate ψ
If (G) is kept at the control target yaw rate Tr #, the oversteer control is changed to the understeer control. If understeer control is performed in this way, the vehicle behavior is still oversteer, and even though the driver is performing countersteer, the effect of the countersteer does not occur, that is, oversteer. Control that promotes However, the first and second target yaw rates ψ (θ,
If the smaller one of G) is set as the control target yaw rate Tr #, the oversteer control is continuously performed even when the counter steer is performed, and the above-described disadvantage is solved.

The value of the first target yaw rate ψ (θ) passes through the neutral point, and the first target yaw rate ψ (θ)
Is different from the sign of the value of the second target yaw rate ψ (G), the value of the control target yaw rate Trψ is made constant at a predetermined value (see T3 in FIG. 3), and thereafter, the first and second target yaw rates are set. If the values of ψ (θ, G) have the same sign,
The smaller of the absolute values of the first and second target yaw rates ψ (θ, G), in FIG. 7, the second target yaw rate ψ
The value of (G) is set to the control target yaw rate Tr # (see T4 in the figure).

As described above, maintaining the value of the control target yaw rate Tr # at a constant value avoids an increase in control gain during a state transition in which the steering angle exceeds the neutral point. That's why. Also, for example, the first
If the value of the target yaw rate ψ (θ) is directly used as the control target yaw rate Trψ, the control amount becomes large, and the vehicle may spin in the opposite direction.
Thus, when the vehicle spins in the opposite direction,
Since it is difficult to avoid the reverse spin, when the values of the first and second target yaw rates ψ (θ, G) have different signs, the control target yaw rate Trψ is held at a predetermined value.

If the predetermined value is set to, for example, a neutral point, the vehicle will not cause yaw behavior thereafter. Therefore, the predetermined value is a value offset to the neutral point.

(Counter Convergence Control) As described above, in the case of oversteering, the driver may perform countersteering. Even in such a case, control is performed to properly avoid oversteering. However, by performing brake control by behavior control,
The behavior of the vehicle becomes larger than steering with the steering wheel. As a result, for example, oversteering in the reverse direction may occur due to a delay in returning the steering wheel after the driver performs countersteering. As a result, the yaw rate behavior of the vehicle may not converge.

In order to prevent such oversteering in the reverse direction, control is performed to apply a braking force to the front wheels in turning. That is, FIG. 8 shows a flowchart of the convergence control after the counter steer. In this control, first,
In step S31, it is determined whether the oversteer control is being performed or within a predetermined time after the control. If YES, the process proceeds to step S32, and if NO, the process returns.

In step S32, a counter determination is made as to whether or not countersteering has been performed. This may be determined using, for example, the fact that the value of the first target yaw rate 基 づ く based on the value of the actual yaw rate ψ and the steering angle is inverted or that the steering angular velocity is inverted. And YES
If so, the process proceeds to step S33, while if NO, the process returns.

In step S33, it is determined whether the counter value is large. This may be determined based on, for example, whether the oversteer state before performing countersteering is large, or whether the steering angular velocity of the steering wheel during performing countersteering is large. If YES, the process proceeds to step S34 and N
If O, return.

In step S34, it is determined whether the steering angular speed has been reversed. That is, it is determined whether or not the steering wheel is returned after the counter steer is performed. If YES, the process proceeds to step S35, and if NO, the process returns.

In step S35, it is determined whether or not the actual yaw rate ψ follows the change in the steering angle.
That is, if the actual yaw rate ψ follows the change in the steering angle,
Since it is considered that the yaw rate behavior is heading in the direction of convergence, the braking force is not applied to the front inner wheel. Even if the braking force is applied, the application of the braking force may be stopped when the actual yaw rate follows the change in the steering angle.

If the determination is NO, the process proceeds to step S36, and the braking force is applied to the front wheel in turning, while if the determination is YES, the process returns.

By such control, it is possible to prevent the vehicle from oversteering in the reverse direction after performing countersteering.

(Setting of Understeer Threshold)
The setting of the understeer threshold value THUS in step S16 (see FIG. 2) will be described. The understeer threshold value THUS is set by determining a basic threshold value and correcting the basic threshold value.

First, as shown in FIG. 9, step S41
In, a basic threshold is set. This basic threshold value may be a predetermined constant.

Next, in step S42, if the steering wheel is turned back, the threshold value is increased as the steering speed increases, and the intervention of the behavior control is suppressed, that is, the intervention of the behavior control is made difficult. This is because the steering wheel is turned back in spite of the understeer, it is considered that the driver is intentionally operating, and such a driver is driving intentionally. In this case, the intervention of the behavior control is suppressed and the operation of the driver is left to the driver. As a result, it is possible to prevent the behavior control intervention and the driver's operation from interfering with each other.

Then, in step S43, the larger the fluctuation of the actual yaw rate (change of the actual yaw rate), the higher the threshold value is set to suppress the control intervention. This is because understeer is avoided if the yaw rate is increasing. Conversely, if control is intervened early in such a case, the yaw rate will change further, possibly resulting in oversteer. Therefore, in order to avoid erroneous control intervention in such a case, the threshold value is increased.

In step S44, when the steering wheel is in the vicinity of the neutral position, the threshold is raised to suppress the control intervention. This is because understeering usually occurs when the steering wheel is turned, and it is not necessary to control the understeering when the steering wheel is near neutral. This is to avoid erroneous intervention.

In step S45, when the lateral acceleration is small (in the low μ range), the threshold value is lowered and the control intervention is advanced. This is for example the low μ
This is because the behavior control is started early in such a case because understeer is likely to occur sometimes.

In step S46, during the turning, the second
When the target yaw rate ψ (G) decreases by a predetermined value or more, the threshold value is lowered to speed up the control intervention. this is,
For example, when the road surface μ is suddenly reduced, such as when the road surface is partially frozen, and the vehicle is skidding, the control intervention is expedited. That is, when the road surface μ changes suddenly, the driver cannot operate the steering wheel, or it takes a long time to operate the steering wheel.
Here, for example, when the behavior control is performed using only the first target yaw rate ψ (θ), the behavior control cannot be started because the first target yaw rate ψ (θ) does not change. . On the other hand, in the present embodiment, since the behavior control is also performed using the second target yaw rate ψ (G) based on the lateral acceleration, accurate control can be performed early even for such a change in the road surface μ. become able to.

In this manner, the threshold value THUS for understeer brake control is set.

(Setting of Oversteer Control Threshold) Next, the setting of the oversteer threshold THOS in step S16 (see FIG. 2) will be described. The oversteer threshold THOS is also determined by determining a basic threshold and correcting the basic threshold.

First, as shown in FIG. 10, step S5
At 1, a basic threshold is set. As shown in FIG. 11, the basic threshold value is set to a larger value as the vehicle speed V is lower. At a very low speed, the basic threshold value is set to a higher value.

Then, in step S52, FIG.
As shown in FIG. 2, the higher the lateral acceleration is, the higher the threshold is, and the higher the vehicle speed is, the larger the correction is. This is because, for example, in a region where the lateral acceleration is low, that is, in a low μ region, oversteering is likely to occur, so that the threshold value is lowered and control is performed early. In addition, when the lateral acceleration is high (high μ region) and the vehicle is traveling at high speed, the behavior changes quickly. For example, when the threshold value is lowered, erroneous intervention of the behavior control is likely to occur. Furthermore, a driver who can drive in a high μ region at a high vehicle speed is considered to be a driver who can sufficiently cope with a slight change in the behavior of the vehicle. In order to prevent this, the threshold value is increased in a high lateral acceleration and high speed region.

In step S53, the smaller the steering wheel angle is, the higher the threshold value is set to suppress the intervention of the control. For example, even when the steering angle is small, the direction of the vehicle and the direction of the steering angle may be reversed due to disturbance or the like, particularly on a snowy road. In such a case, since the vehicle naturally runs stably without performing the behavior control, control intervention is suppressed.

In step S54, the lower the steering wheel speed is at the time of turning back the steering wheel, the higher the threshold value is, and the intervention of the control is suppressed. This is because the driver slowly returns the steering wheel, and thus it is considered that the driver can sufficiently avoid oversteer by his own operation without performing control intervention. Therefore, the threshold is increased to suppress the control intervention.

In step S55, when the yaw rate overshoots, the threshold value is raised to suppress the control intervention. When the yaw rate overshoots, as shown in FIG. 13, when the steering wheel is turned from a turned state to a neutral point, the actual yaw rate ψ overshoots even though the vehicle is not in an unstable state. In such a case, it is determined that the vehicle is oversteering. Therefore, the threshold value is increased to suppress control intervention.

In step S56, when the fluctuation of the yaw rate is large, the threshold value is increased to suppress the control intervention. This is to prevent erroneous control intervention.

In step S57, when the tuck-in or counter-steer of the front wheel drive vehicle whose front wheel is the drive wheel is determined, the threshold value is lowered to speed up the control intervention. Here, as the determination of tack-in,
For example, if it is determined that the vehicle is tack-in when the condition that the steering angle is constant in a cut state, the shift speed is a low speed such as the second speed or the third speed, and the throttle opening is reduced by returning the accelerator pedal is satisfied. Good. On the other hand, the counter steer is determined from the steering angle of the steering wheel.

In step S58, if correction is performed to increase the basic threshold value in each of the above steps, the value may become too large.
Set an upper limit. In this way, the threshold value THOS for the oversteer control is set.

(End determination of oversteer control)
The end determination of the oversteer control (see step S118 in FIG. 2) will be described with reference to the flowchart shown in FIG. This is a control for the purpose of avoiding the interference between the operation of the driver and the behavior control while terminating the behavior control in a state where the behavior of the vehicle is stabilized.

First, in step S61, it is determined whether or not the steering wheel is stable in the straight running state, that is, whether or not the steering angle is stable in the substantially neutral position. If NO, the process proceeds to step S62.

In step S62, it is determined whether or not the steering wheel has been turned further. If NO, the process proceeds to step S63.

In step S63, it is determined whether the difference between the second target yaw rate ψ (G) and the actual yaw rate ψ is stable at a predetermined value or less. That is, it is determined whether or not both values are sufficiently small and substantially coincide with each other. If NO, the process proceeds to step S65.

Then, the above steps S61 to S
If YES in step 63, the process proceeds to step S64 to end the control and return. This is performed in step S61.
In the determination of the above, it is considered that the driver is operating the steering wheel calmly, so there is no need to perform the behavior control, and if the behavior control is performed, there is a possibility that the operation of the driver and the behavior control may interfere with each other. Because there is. In addition, in the determination of step S62, since the driver operates the steering wheel in a direction that promotes oversteering, the driver intentionally oversteers and turns, or the vehicle is intentionally spun to cause an accident. This is because it is conceivable that an attempt is made to avoid it. In such a case, by ending the behavior control promptly, it is possible to prevent interference between the behavior control and the driver's operation. Further, in the determination of step S63, since the second target yaw rate {(G)} and the actual yaw rate 略 substantially match and are in a stable state,
Since the behavior of the vehicle is in a stable state and there is no need to perform behavior control, the control is terminated.

Then, in step S65,
It is determined whether or not the estimated brake fluid pressure estimated from the braking amount in the behavior control is substantially equal to the master cylinder pressure. That is, it is determined whether the control of the braking force is not substantially performed and it is considered that the behavior control may be terminated. If YES, the process proceeds to step S66, while if NO, the process proceeds to step S69.

In step S66, it is determined whether the slip angle β is small. That is, it is determined whether or not side slip has occurred. If YES, the process proceeds to step S67, while if NO, the process returns without ending the control.

In step S67, the value of the second target yaw rate ψ (G) and the value of the first target yaw rate ψ (θ)
And the value of the actual yaw rate ψ are all less than or equal to a predetermined value. That is, it is determined whether or not the three values are smaller than the predetermined value and approximate to each other.
This determination is made to determine whether the vehicle is in a substantially straight-ahead state and the steering operation is not performed, and whether the behavior control is not required.
Since the condition of 63 may not be satisfied in some cases, the determination is made to end the behavior control even if the condition is looser than the condition of step S63. If YES, the process proceeds to step S68, and it is determined whether or not the condition in which the above condition is satisfied has elapsed for a predetermined time T1. That is, since it is possible that the above condition is satisfied by chance, it is determined whether a predetermined time has elapsed. If YES, the process proceeds to step S612, ends the behavior control, and returns. If NO, return.

Then, in step S69,
It is determined whether the slip angle β is small. If YES, the process proceeds to step S610.

In step S610, the second target yaw rate ψ (G), the first target yaw rate ψ (θ),
It is determined whether two of the actual yaw rate ψ and the actual yaw rate で are equal to or smaller than a predetermined value, and the remaining one is not a value that is far from the predetermined value. This is a looser condition than the condition in step S67. If YES, the process proceeds to step S611, and it is determined whether or not a predetermined time T2 has elapsed while the condition of step S610 is satisfied. Here, the predetermined time T2 is a condition that is looser than the condition of step S67, and is therefore set to a value larger than the predetermined time T1 in step S68. And YE
If S, the control is terminated and the routine returns.

On the other hand, the above steps S69 and S6
10, and if NO in step S611, control is continued and the routine returns.

By continuing the control until the vehicle enters a stable running state, for example, when the control end is determined based only on the deviation between the control target yaw rate Trψ and the actual yaw rate ψ, It is possible to prevent the behavior control from ending early.

It is effective to determine the end of the behavior control in a case where the behavior control is required once after the behavior control is performed, for example, for avoiding an obstacle. In addition, it is possible to prevent the end of the control from being repeated and the start of the operation being repeated in a short time to cause a change in the behavior accompanying the end of the behavior control, and to prevent the stability of the driving operation from becoming unstable.

On the other hand, in a situation where the driver does not need the control, by ending the behavior control early,
The behavior control and the driver's operation can be prevented from interfering with each other.

(Brake Hydraulic Pressure Control) Next, brake hydraulic (hydraulic) control in the behavior control will be described with reference to the flowchart shown in FIG. The brake fluid pressure control in the present embodiment does not perform pressure feedback control, but performs a first phase in which the brake fluid is pressurized at a predetermined pressurization (boosting) speed. If the behavior of the vehicle changes due to the application of the brake pressure, the process shifts to a second phase (pressure adjustment state) for adjusting the brake fluid pressure.

First, in step S71, it is determined whether behavior control has been started. Next, step S7
In 2, it is determined whether or not the control is oversteer control. If YES (oversteer), step S7
Proceed to 3 and if NO (understeer), step S
Proceed to 74.

In step S73, the brake fluid pressure is increased at a mechanical limit pressurizing speed (oil pressure MAX). That is, the pressurizing pump 32 is operated at the mechanical limit, and A
Pressurization is performed by fully opening the SW solenoid valve 36 and the front or rear solenoid valves 33 and 34 provided in the supply path for the wheels that apply the braking force.

Then, in a step S77, it is determined whether or not the slip ratio is equal to or more than a predetermined value. here,
The slip ratio may be calculated based on the estimated vehicle speed and the wheel speed obtained from the detection signal of the wheel speed sensor 11. This determination is performed for the purpose of preventing the excessive brake fluid pressure since the brake fluid pressure becomes excessive when the brake fluid is further pressurized. If NO, the process proceeds to step S78.

In step S78, it is determined whether or not the peak of the change acceleration of the slip angle β has passed.
If the determination is YES, the process proceeds to step S79. If the determination is NO, the process proceeds to step S710.

In step S79, it is determined whether the rate of change (rate of change) of the yaw rate deviation Δψ (θ, G) or the rate of change of the yaw rate deviation Δψ (θ, G) is decreasing, that is, the direction of convergence. Determine whether or not.

In step S710, even if the peak of the slip angle has not passed, whether the change rate of the slip angle β or the change acceleration of the slip angle β is in a decreasing direction, that is, whether or not it is in the convergence direction. Is determined.

Steps S78 to S710
Determines whether or not the behavior of the vehicle has changed due to the application of the braking force by increasing the brake fluid pressure, that is, whether or not the effect of the behavior control has appeared.

Then, the above steps S77, S
If 79 or YES is determined in the step S710, the process proceeds to a step S711 to determine whether or not the pressurizing time of the brake fluid pressure has passed a predetermined time T4. This predetermined time T4
May be set in consideration of the start threshold value of the behavior control, the characteristics of the brake fluid pressure control system such as the pressure pump 32, and the like. In other words, the time may be set as a minimum necessary time until the pressure is increased to the required brake fluid pressure from the characteristics of the brake fluid pressure system and the like. Then, if YES, the process proceeds to step S712, where the pressure adjustment state as the second phase,
That is, the state shifts to a state in which the brake fluid pressure is maintained or increased or decreased according to the state. If NO, return and continue pressurization.

On the other hand, if it is determined that the understeer control is performed and the process proceeds to step S74, first, in step S74, the brake fluid pressure is increased at a mechanically-applied pressurizing speed. Then, the process proceeds to a step S75, and it is determined whether or not the pressurizing time has passed a predetermined time T3. If the determination is YES, the process proceeds to step S76. If the determination is NO, the pressurization at the pressurization speed of the mechanical limit is continued until the pressurization time elapses a predetermined time T3. On the other hand, step S76
In, the brake fluid pressure is pressurized at a speed of, for example, the pressurizing speed of the mechanical limit × 0.8.

This is to avoid locking the wheels because there is no grip on the tires during understeer. In other words, first, the brake fluid pressure is increased at the mechanical limit pressurization speed, so that, for example, after the delay of the brake fluid pressure for the behavior control such that the brake pad is brought into close contact with the disk rotor is recovered, the pressurization speed is slightly reduced. And continue to pressurize. As a result, the wheel is prevented from being locked by applying an excessive brake fluid pressure.

Then, in step S713, it is determined whether or not the slip ratio is equal to or more than a predetermined value. If NO, the process proceeds to step S714 to determine whether or not the actual yaw rate ψ changes following the steering operation of the steering wheel. If NO, the effect of the behavior control is not exhibited, so the routine returns and pressurization is continued.

On the other hand, in the case of YES in step S713 or step S714, step S71
Proceeding to 5, it is determined whether the pressurization time has passed a predetermined time T5. If YES, the process proceeds to step S716 and shifts to the pressure regulation state. If NO, return to continue pressurization.

By controlling the brake fluid pressure without performing the feedback control in this manner, a brake fluid pressure control system can be simply configured.

In addition, first, the brake fluid is pressurized at the pressurizing speed at the mechanical limit or at a pressurizing speed slower than the mechanical limit (first phase), whereby the braking force is applied earlier. Rapid behavior control can be realized. At the same time, if the behavior of the vehicle is in the convergence direction, the control is shifted to the brake fluid pressure control (second phase), so that accurate behavior control can be realized without an excessive control amount. become.

In particular, when the intervention of the behavior control is delayed as much as possible as in the present embodiment, the driver or the like rarely feels uncomfortable even with such control of the brake fluid pressure. This is an extremely effective control of the brake fluid pressure in that quick behavior control becomes possible.

(Control of Alarm Device) Next, control of the alarm device 38 will be described with reference to the flowchart shown in FIG. The alarm device 38 delays the start of the operation from the start of the behavior control and delays the end of the operation from the end of the behavior control.

First, in step S81, the flag F
Is 1 or not. This is set to 1 when the vehicle stability control is being performed, as described later. If YES, step S87
On the other hand, in the case of NO, the process proceeds to step S82 in order to control the start of operation of the alarm device.

In step S82, it is determined whether the behavior control is being performed. If YES, step S
Proceed to 83, and return if NO.

In step S83, it is determined whether or not the estimated brake fluid pressure is equal to or higher than a predetermined value. And YE
If S, the process proceeds to step S84. On the other hand, if NO, the process proceeds to step S85.

In step S85, it is determined whether a predetermined time has elapsed since the start of the behavior control.
If YES, the process proceeds to step S84, while if NO, the process returns.

In step S84, the flag F
Is set to 1 and the process proceeds to step S86, the alarm device is operated (alarm ON), and the process returns.

As described above, the operation start of the alarm device is delayed from the control start of the behavior control by, for example, until the estimated brake pressure becomes equal to or more than a predetermined value or until the behavior control device operates for a predetermined time or more. This makes it possible to prevent the driver from feeling uncomfortable, for example, giving an alarm without noticing the behavior control, or an operation error caused by the uncomfortable feeling.

Then, the above steps S82 to S
Reference numeral 86 denotes control related to the start of the operation of the alarm device 38. The control performed in the case of YES in step S81 is control related to the end of the operation of the alarm device 38.

That is, first, in step S87, it is determined whether or not the vehicle is straight and stable. If NO, the process proceeds to step S88.

In step S88, it is determined whether a predetermined time has elapsed since the end of the behavior control.
If NO, the process proceeds to step S89.

In step S89, it is determined whether or not the brake fluid pressure (braking pressure) is substantially equal to the master cylinder pressure, that is, whether or not the brake fluid pressure is atmospheric pressure when the driver does not depress the brake pedal. On the other hand, when the driver is stepping on the brake pedal, it is determined whether or not the brake fluid pressure is the master cylinder pressure corresponding to the amount of depression of the brake pedal. If NO, the process returns.

Then, the above-mentioned steps S83, S
88 and YES in step S89, the process proceeds to step S810, where the flag F is set to 0, and
At 11, the operation of the alarm device 38 is terminated and the routine returns.

As described above, by ending the operation of the alarm device 38 after the elapse of a predetermined time from the end of the behavior control,
For example, when behavior control such as obstacle avoidance is performed intermittently, the end and start of the alarm are continuously performed without repeating. Therefore, it is possible to prevent the driver from feeling uncomfortable.

Further, the operation of the alarm device 38 is continued until the running environment of the vehicle changes after the behavior control is completed such that the vehicle is stabilized in a straight running state or the brake fluid pressure substantially matches the master cylinder pressure. By doing so, it is possible to prevent the end / start of the alarm from being repeated. As a result, an appropriate warning is realized so that the driver does not feel uncomfortable.

(Other Embodiments) The present invention is not limited to the above embodiments, but includes various other embodiments. That is, in the above-described embodiment, when the threshold value THUS of the understeer control is set (see FIG. 9), if the second target yaw rate ψ (G) falls below a predetermined value during turning, the threshold value is decreased. (See step S46 in the figure)
Instead of correcting the HUS, when the above condition is met, the brake control itself of the understeer control may be forcibly intervened and the control may be started.

In the above embodiment, when setting the oversteer control threshold value THOS (see FIG. 10),
In the case of tack-in, the threshold value is lowered (see step S57 in the figure), but in the case of tack-in, the oversteer control itself is forcibly intervened and the control is started. Good. That is, in step S19 shown in FIG. 2, it may be determined whether the yaw rate deviation Δψ (θ, G) has exceeded the threshold value or whether the yaw rate deviation is tack-in.

Further, in the above embodiment, the threshold value THOS is lowered in the case of the counter steer (see step S57 in the figure). However, as in the case of the tack-in, the counter steer is performed. For example, the oversteer control itself may be forcibly intervened and the control may be started.

In addition, as in the case where the driver performs counter-steering during over-steering (see FIG. 7),
The first target yaw rate {(θ) is the second target yaw rate}
In the above embodiment, when it becomes smaller than (G),
The first target yaw rate {(θ) is the second target yaw rate}
(G), the control target yaw rate Tr # is changed from the second target yaw rate to the first target yaw rate. However, the present invention is not limited to this. For example, the following control may be performed.

That is, the control target yaw rate Tr is changed from the second target yaw rate ψ (G) to the first target yaw rate ψ (θ).
If the position is changed, there is a possibility that the brake pressure or the like may change rapidly. For this reason, when it is predicted that the absolute value of the first target yaw rate ψ (θ) will be smaller than the second target yaw rate ψ (G) based on the fact that the steering angle has been reversed, the control target yaw rate Trψ sharply increases. The control amount may be reduced so as not to change. That is, the control target yaw rate Trψ is changed to the second target yaw rate ψ (G).
Therefore, a mitigation means is provided to alleviate the control operation when switching from the first yaw rate to the first target yaw rate ψ (θ).

As the mitigation means, for example, an upper limit value of the brake fluid pressure is set in advance, and the control target yaw rate Trψ is changed from the second target yaw rate ψ (G) to the first target yaw rate ψ (θ). Even in such a case, if the brake fluid pressure is not caused to exceed the upper limit value, or if the first target yaw rate ψ (θ) is predicted to be smaller than the second target yaw rate ψ (G), the control is performed. As a correction formula for the target yaw rate Trψ, the value of the first derivative of the first target yaw rate ψ (θ) is calculated as the second target yaw rate ψ
(G) to set the control target yaw rate Trψ. Thus, the control operation at the time of switching the control target yaw rate Tr # is relaxed, and the shock accompanying the switching can be reduced.

In the above embodiment, the smaller of the first and second target yaw rates ψ (θ, G) is set as the control target yaw rate Trψ. When the yaw rate fluctuation is extremely large, such as during running, the second target yaw rate ψ (G)
Is smaller than the absolute value of the first target yaw rate ψ (θ), the first target yaw rate ψ (θ)
May be set as the control target yaw rate Tr #. That is, when the yaw rate fluctuation is extremely large, the fluctuation of the lateral acceleration becomes large, and the value of the second target yaw rate ψ (G) may not be suitable as the value of the control target yaw rate Trψ. Therefore, the first target yaw rate ψ (θ) based on the steering angle having a stable value may be set as the control target yaw rate Tr レ ー ト.

When the yaw rate fluctuation is extremely large, the following equation may be used in place of equation (3) as a correction equation for control target yaw rate Tr #.

Trψ = (1−k2) × ψ (G) + k2 × ψ (θ) (4) That is, for the second target yaw rate ψ (G), the first and second target yaw rates ψ (θ),を Control the target yaw rate to which a correction value corresponding to the difference between (G) is added.
ψ Here, if the value of k2 is increased, the correction ratio of the first target yaw rate ψ (θ) increases, and appropriate behavior control can be performed even when the yaw rate fluctuation is extremely large.

In addition, in the above embodiment, the alarm device 38
As an operation start condition, the estimated brake fluid pressure is equal to or higher than a predetermined value (step S83 in FIG. 16). In addition to this condition, if the reduction amount of the engine output becomes equal to or higher than the predetermined value, the alarm device 38 is activated. You may make it do.

[0164]

As described above, according to the first aspect of the present invention, the first target yaw rate is determined based on the steering angle of the vehicle and the vehicle speed, and the second target yaw rate is determined based on the lateral acceleration and the vehicle speed of the vehicle. Respectively, and one of them is selected as the control target yaw rate, and the yaw rate behavior of the vehicle is controlled in accordance with the deviation between the control target yaw rate and the actual yaw rate. Can be performed smoothly and properly.

According to the second aspect of the invention, when the first target yaw rate is lower than the second target yaw rate, the control target yaw rate is switched from the second target yaw rate to the first target yaw rate. The counter-steering effect by the driver can be satisfactorily enhanced to suppress the over-steer state.

According to the third aspect of the invention, the control operation when the control target yaw rate is switched from the second target yaw rate to the first target yaw rate is relaxed, so that the shock accompanying the switching of the control target yaw rate is reduced. Can be reduced.

According to the fourth aspect of the present invention, the first target yaw rate is set as a control target yaw rate, and when the control target yaw rate exceeds an intervention threshold, the understeer control is intervened by controlling the engine output. Thus, the understeer control by controlling the engine output can be intervened earlier than the understeer control by the brake control, and the understeer control can be appropriately and reliably performed.

According to the fifth aspect of the present invention, the smaller one of the first and second target yaw rates is set as the control target yaw rate, and when the control target yaw rate exceeds the intervention threshold value, the intervention of the understeer control by the brake control is performed. Is performed, the intervention of the understeer control by the brake control of the vehicle can be appropriately and reliably performed.

According to the sixth aspect of the present invention, the first target yaw rate is set to the control target yaw rate when the actual fluctuation of the yaw rate is equal to or more than a predetermined value. According to the seventh aspect of the present invention, at the same time, the target yaw rate obtained by adding the correction value corresponding to the difference between the first and second target yaw rates to the second target yaw rate is set as the control target yaw rate.
According to these inventions, even when the vehicle travels on a bad road or the like and the actual fluctuation of the yaw rate is large, the behavior control of the vehicle can be stably performed.

According to the present invention, when the second target yaw rate is selected, the target yaw rate obtained by adding a correction value corresponding to the difference between the first and second target yaw rates to the second target yaw rate is controlled. By doing so, the intervention of the understeer control when the driver intentionally enters the drive understeer state can be eliminated, and the intervention of the behavior control can be made appropriate.

According to the ninth aspect of the present invention, the difference between the first and second target yaw rates is multiplied by a variable that changes in accordance with the lateral acceleration to obtain a correction value. It can be performed appropriately according to the road surface friction coefficient.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a behavior control device of a vehicle.

FIG. 2 is a flowchart of behavior control.

FIG. 3 is a diagram illustrating characteristics of a correction coefficient k with respect to a lateral acceleration.

FIG. 4 is a flowchart illustrating a start determination of brake control in understeer control.

FIG. 5 is an explanatory diagram showing a relationship between an actual yaw rate indicating an understeer control start condition and a first target yaw rate.

FIG. 6 is an explanatory diagram showing a relationship between an actual yaw rate and a first target yaw rate indicating understeer control start conditions different from those in FIG. 5;

FIG. 7 is an explanatory diagram showing an example of changes in a first target yaw rate, a second target yaw rate, a control target yaw rate, and an actual yaw rate.

FIG. 8 is a flowchart illustrating convergence control after countersteering.

FIG. 9 is a flowchart for setting a threshold value for brake control in understeer control.

FIG. 10 is a flowchart for setting a threshold value for oversteer control.

FIG. 11 is a diagram illustrating a relationship between a basic threshold value of oversteer control and a vehicle speed.

FIG. 12 is a diagram illustrating a correction amount according to a lateral acceleration and a vehicle speed with respect to a threshold value of oversteer control.

FIG. 13 is a diagram showing an overshoot state of the actual yaw rate.

FIG. 14 is a flowchart illustrating a termination determination of oversteer control.

FIG. 15 is a flowchart illustrating hydraulic control in stability control.

FIG. 16 is a flowchart illustrating control of the alarm device.

[Explanation of symbols]

 2 ECU (control means) 11 Wheel speed sensor 12 Steering angle sensor 13 Yaw rate sensor 14 Lateral G sensor 32 Pressure motor 33 Front solenoid valve 34 Rear solenoid valve 35 TSW solenoid valve 36 ASW solenoid valve 38 Alarm device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshio Katayama 1-1-1, Koyokita, Itami-shi, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Kazuhiro Kato 1-chome, Koyo-Kita, Itami-shi, Hyogo No. 1-1 Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Yoshihiro Watanabe 3-1 Fuchu-cho, Anaka-gun, Hiroshima Pref. Mazda Co., Ltd. F-term (reference) 3D041 AA40 AA47 AA80 AB01 AC15 AD00 AD02 AD04 AD31 AD41 AD51 AE03 AE41 AE43 AF09 3D045 BB40 CC01 EE21 GG00 GG01 GG25 GG26 GG28 3G093 AA05 BA01 BA02 BA15 CB09 DA01 DA06 DB00 DB05 DB11 DB15 EA01 EB03 EB04 FA07 FB01 FB02

Claims (9)

[Claims] 1. A vehicle behavior control device for estimating a running state of a vehicle and controlling a yaw rate behavior of the vehicle based on a result of the estimation, wherein a yaw rate behavior of the vehicle is controlled based on a steering angle of the vehicle and a vehicle speed. A first target yaw rate is set, and a second target yaw rate is set based on the lateral acceleration and the vehicle speed of the vehicle, and one of the first and second target yaw rates is selected as a control target yaw rate according to the running state of the vehicle. And a control means for controlling yaw rate behavior according to a deviation between the control target yaw rate and an actual yaw rate. 2. The vehicle behavior control device according to claim 1, wherein the control means selects the second target yaw rate as the control target yaw rate and sets the first target yaw rate to the second target yaw rate.
A behavior control device for a vehicle, wherein the control target yaw rate is switched to the first target yaw rate when the target yaw rate becomes lower than the target yaw rate. 3. The vehicle behavior control device according to claim 2, further comprising a mitigation means for easing a control operation when the control means switches the control target yaw rate from the second target yaw rate to the first target yaw rate. Vehicle behavior control device. 4. The vehicle behavior control device according to claim 1, wherein the control means controls the engine output when the first target yaw rate is a control target yaw rate and the control target yaw rate exceeds an intervention threshold value. A vehicle behavior control device configured to perform an intervention of understeer control for suppressing an understeer state. 5. The vehicle behavior control device according to claim 1, wherein the control means sets a smaller one of the first and second target yaw rates as a control target yaw rate, and the control target yaw rate exceeds an intervention threshold value. A vehicle behavior control device characterized in that the vehicle behavior control device is configured to intervene understeer control for controlling a vehicle brake to suppress an understeer state. 6. The vehicle behavior control device according to claim 1, wherein the control means is configured to set the first target yaw rate to a control target yaw rate when an actual yaw rate change is equal to or greater than a predetermined value. A behavior control device for a vehicle, comprising: 7. The vehicle behavior control device according to claim 1, wherein the control means determines a difference between the first and second target yaw rates with respect to the second target yaw rate when a fluctuation of the actual yaw rate is equal to or more than a predetermined value. A vehicle behavior control device characterized in that a target yaw rate to which a corresponding correction value is added is set as a control target yaw rate. 8. The vehicle behavior control device according to claim 1, wherein the control means corrects the second target yaw rate according to a difference between the first and second target yaw rates when selecting the second target yaw rate. A vehicle behavior control device characterized in that a target yaw rate to which a value is added is set as a control target yaw rate. 9. The vehicle behavior control device according to claim 8, wherein the control means obtains a correction value by multiplying a difference between the first and second target yaw rates by a variable that changes according to a lateral acceleration. A behavior control device for a vehicle, comprising: