JP2005104345A - Vehicle behavior stabilizing control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely stabilize vehicle behavior. <P>SOLUTION: The vehicle behavior stabilizing control device is equipped with an automatic deceleration control means 34 which automatically decelerates the vehicle by applying the braking force to the wheel to such an extent that the vehicle behavior may not exceed the limit state when the vehicle behavior reaches the limit state. When it is determined that the vehicle is in an under steering state of not less than the predetermined limit during automatic deceleration, the automatic deceleration control means 34 controls the braking of the wheel by the rapid deceleration mode where the vehicle is decelerated most rapidly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle behavior stabilization control device that stabilizes vehicle behavior by suppressing excessive oversteer and excessive understeer of the vehicle.

When the vehicle (hereinafter referred to as a vehicle) is turned at a vehicle speed that exceeds the grip limit of the tire, the vehicle travel route swells outward from the original turn route. Therefore, a technique for controlling the vehicle so as not to deviate from the turning path has been proposed so that this does not occur.
For example, in Patent Document 1, a steering amount of a wheel is detected, a tire grip limit vehicle speed is obtained from this steering amount, and when the actual vehicle speed exceeds the tire grip limit vehicle speed, the wheels of the turning inner wheel and the outer wheel are braked to determine the actual vehicle speed. Has been proposed to control the braking of the turning inner and outer wheels so as to reduce the tire grip to the limit vehicle speed and to generate a limit yaw rate (maximum possible yaw rate) in the vehicle.

Further, in Patent Document 2, when the vehicle exhibits an abnormal behavior (excessive oversteer or excessive understeer), the above vehicle is controlled by controlling the brake pressure to each wheel and the engine torque to the drive wheel. A technique for stabilizing the behavior is disclosed.
Further, in Patent Document 3, in order to generate a vehicle behavior correction moment that corrects an actual vehicle behavior toward a target vehicle behavior, such as an anti-spin moment that suppresses vehicle spin, As a technique for providing a required braking force difference, for example, on a low μ road surface, a technique has been proposed in which a reduction in braking force is given priority and a necessary braking force difference between wheels is obtained. According to this technique, it is possible to obtain a vehicle behavior correction moment while avoiding a decrease in tire grip force and cornering force, and as a result, it is possible to suppress and prevent undesired turning behavior without shifting the travel line, for example.
Japanese Patent Laid-Open No. 3-112754 JP 2001-206107 A Japanese Patent Laid-Open No. 11-208438

By the way, as described above, the control for stabilizing the vehicle behavior (particularly the posture of the vehicle) during turning is efficient by applying braking force to either one of the left and right wheels while suppressing the deceleration of the vehicle as much as possible. By applying the braking force, the yaw moment generated in the vehicle can be controlled to suppress excessive oversteer and excessive understeer.
However, if the vehicle exceeds the turning limit, the vehicle deviates from the predetermined traveling route (turning trajectory) and cannot travel on the predetermined traveling route. In such a case, it is difficult for the vehicle to stabilize the behavior related to the predetermined travel route if a braking force is applied to either one of the left and right wheels, but the braking speed is applied to all wheels to limit the vehicle speed. If it falls in, it becomes possible to hold | maintain a vehicle behavior in a predetermined | prescribed driving | running route. In this case, it is preferable to suppress the braking force applied to the vehicle to a necessary minimum so as not to sacrifice the traveling of the vehicle as much as possible.

  In addition, even when the vehicle is in braking control so that the vehicle does not deviate from the road, the vehicle's understeer tendency may increase. It is desired to control the attitude of the vehicle so as to be properly oriented in the turning direction while allowing the vehicle to travel along a predetermined travel route so that the understeer tendency can be suppressed.

  The present invention has been devised in view of such problems, and an object of the present invention is to provide a vehicle behavior stabilization control device that can reliably stabilize vehicle behavior.

  In order to achieve the above-mentioned goal, the vehicle behavior stabilization control device of the present invention has a vehicle behavior at the time of turning based on a braking mechanism capable of braking each wheel and behavior information on the travel route of the vehicle at the time of turning. Vehicle behavior determination means for determining whether or not the limit state has been reached is provided, and when the vehicle behavior determination means determines that the vehicle behavior has reached the limit state, the vehicle behavior exceeds the limit state. Automatic deceleration control means for automatically decelerating the vehicle by applying braking force to the wheels through the braking mechanism to a certain extent, and based on behavior information regarding the steering characteristics of the vehicle during turning, the vehicle Understeer determination means for determining whether or not the vehicle is in the above-described understeer state is provided, and the automatic deceleration control means is configured so that the vehicle is below a predetermined limit by the understeer determination means during the automatic deceleration. If it is determined that the in understeer state is characterized by controlling the braking of the wheel by sudden deceleration mode in which the vehicle is decelerated the most quickly.

The vehicle behavior determining means determines that the vehicle behavior during turning travel reaches the limit state when the lateral acceleration generated in the vehicle during turning exceeds the limit value corresponding to the road surface μ state of the road on which the vehicle travels. It is preferable to determine that it is present.
The vehicle behavior determining means includes a road surface μ estimating means for estimating a road surface μ state of a road on which the vehicle travels, a turning radius estimating means for estimating a turning radius of the vehicle, and a road surface estimated by the road surface μ estimating means. Based on the μ state and the turning radius estimated by the turning radius estimating means, the safety upper limit speed estimating means for estimating the safe upper limit speed at which the vehicle behavior does not exceed the limit state, and the safe upper limit speed estimating means Target deceleration setting means for setting the target deceleration based on the deviation between the safe upper limit speed and the actual vehicle speed, and the target deceleration set by the target deceleration setting means is preset. If it exceeds 1 predetermined value, it is preferable to determine that the vehicle behavior during turning travel has reached the limit state.

The automatic deceleration control means preferably controls the braking force applied to the wheel based on the difference between the target deceleration estimated by the vehicle behavior determination means and the actual deceleration of the vehicle.
The vehicle behavior determination means determines whether or not the magnitude of the target deceleration estimated by the target deceleration setting means is less than a second predetermined value that is preset as a value smaller than the first predetermined value. The automatic deceleration control means preferably ends the automatic deceleration of the vehicle when the magnitude of the target deceleration estimated by the vehicle behavior determining means is less than the second predetermined value.

The understeer determination means compares the difference between the theoretical yaw rate of the vehicle calculated from the vehicle speed and the steering angle and the actual yaw rate of the vehicle detected in real time with a preset threshold value. It is preferable to determine whether the understeer state is equal to or greater than a predetermined limit.
The braking mechanism is configured such that the braking force is controlled by adjusting the working fluid pressure to be increased / decreased, and the automatic deceleration control means has a range in which the deceleration of the vehicle does not become excessive in the rapid deceleration mode. Therefore, it is preferable that the vehicle is decelerated most quickly by maximizing the pressure increase speed of the working fluid pressure.

  According to the vehicle behavior stabilization control device of the present invention, when the vehicle behavior reaches the limit state, the vehicle is automatically applied by applying a braking force to the wheels through the braking mechanism to the extent that the vehicle behavior does not exceed the limit state. Since the vehicle is decelerated, the wheel grip can be secured, the vehicle behavior can be prevented from exceeding the limit state, and the vehicle behavior can be stabilized. Furthermore, during this automatic deceleration control, if the vehicle is in an understeer state exceeding a predetermined limit, the braking of the wheel is controlled by the rapid deceleration mode in which the vehicle decelerates most quickly, so that the wheel grip is quickly secured and excessive The understeer state can be suppressed and the vehicle behavior can be stabilized.

In addition, if the lateral acceleration generated in the vehicle during turning exceeds the limit value corresponding to the road surface μ state of the road on which the vehicle travels, it is determined that the vehicle behavior during turning travel has reached the limit state. Thus, the determination regarding the vehicle behavior can be easily and reliably performed.
Estimate the road surface μ condition of the road on which the vehicle travels, estimate the turning radius of the vehicle, and estimate the safe upper limit speed at which the vehicle behavior does not exceed the limit state based on the estimated road surface μ state and the turning radius Then, a target deceleration is set based on the deviation between the estimated safe upper limit speed and the actual vehicle speed, and if the magnitude of the target deceleration exceeds a preset first predetermined value, the vehicle behavior during turning is determined. By determining that the limit state has been reached, it is possible to accurately and reliably determine the vehicle behavior.

Moreover, the braking force applied to the wheel can be made appropriate by controlling the braking force applied to the wheel based on the difference between the estimated target deceleration and the actual deceleration of the vehicle.
Further, when the estimated target deceleration magnitude is less than a second predetermined value set in advance as a value smaller than the first predetermined value, the vehicle's behavior is stabilized by terminating the automatic deceleration of the vehicle. Unnecessary deceleration can be prevented while aiming.

For the understeer determination, the difference between the theoretical yaw rate of the vehicle calculated from the vehicle speed and the steering angle and the actual yaw rate of the vehicle detected in real time is compared with a preset threshold value. By determining whether or not the vehicle is in an understeer state exceeding a predetermined limit, it is possible to easily and reliably make a determination regarding the understeer of the vehicle.
The braking mechanism is configured so that the braking force is controlled by adjusting the working fluid pressure to be increased or decreased, and in the sudden deceleration mode, the increasing speed of the working fluid pressure is within a range in which the deceleration of the vehicle is not excessive. By controlling to maximize the vehicle behavior, the vehicle behavior can be reliably stabilized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 11 show a vehicle behavior stabilization control device according to an embodiment of the present invention, FIG. 1 is a block diagram showing the configuration of the behavior stabilization control device, and FIG. 2 shows a system according to this device. FIG. 3 is a control block diagram for explaining calculation of yaw rate related to the behavior stabilization control, FIG. 4 is a schematic plan view of a vehicle explaining yaw rate control related to the behavior stabilization control, and FIGS. 8 is a control block diagram for explaining the behavior stabilization control, FIG. 9 is a schematic plan view of the vehicle for explaining the behavior stabilization control, and FIGS. 10 and 11 are flowcharts for explaining the behavior stabilization control.

  The vehicle behavior stabilization control device is installed in a vehicle braking system as shown in FIG. That is, as shown in FIG. 2, the vehicle braking system includes a brake pedal 1, a master cylinder 2 that operates in conjunction with the depression of the brake pedal 1, and the state of the master cylinder 2 or a braking controller ( The brake brakes (front brake left and right wheels and rear left and right wheels) 5FL, 5FR, 5RL, and 5RR wheel brakes (hereinafter referred to as brakes) from the master cylinder 2 or the brake fluid reservoir 4 according to commands from the brake ECU) 3. A hydraulic unit 6 for controlling the brake fluid pressure supplied to the 10 wheel cylinders is provided. Here, it is assumed that a braking mechanism is constituted by the hydraulic pressure adjusting system such as the master cylinder 2 and the hydraulic unit 6 and the wheel brake 10 of each braking wheel.

As shown in FIG. 2 (FIG. 2 shows only the left and right front brakes of the front wheels), the hydraulic unit 6 has a predetermined pressure difference between the upstream and downstream of the differential pressure valve 68 in the vehicle behavior control mode. Then, the differential pressure valve 68 is activated.
When the brake pedal 1 is not depressed in the vehicle behavior control mode, the in-line intake valve 61 is closed and the outline intake valve 62 is opened, so that the brake fluid in the brake fluid reservoir 4 is out of the outline 64 and outline intake valve. 62 and the pump 65, the pressure is increased by the pump 65, the pressure is adjusted by the hydraulic pressure holding valve 66 and the pressure reducing valve 67, and the pressure is supplied to the brake 10 of each wheel.

  When the brake pedal 1 is depressed in the vehicle behavior control mode, the inline intake valve 61 is opened and the outline intake valve 62 is closed, so that the brake fluid in the master cylinder 2 is inline 63 and the inline intake valve 61. The pressure is adjusted by the hydraulic pressure holding valve 66 and the pressure reducing valve 67 and supplied to the brake 10 of each wheel.

The inline 63 and the outline 64 are merged downstream of the inline intake valve 61 and the outline intake valve 62. A pump 65 is disposed downstream of the merged portion, and the brake wheels 5FL, A hydraulic pressure holding valve 66 and a pressure reducing valve 67 are provided for each of 5FR, 5RL, and 5RR.
During normal braking, the in-line intake valve 61 and the outline intake valve 62 are closed, the differential pressure valve 68 and the hydraulic pressure holding valve 66 are opened, and the pressure reducing valve 67 is closed. As a result, the brake fluid pressure corresponding to the pressure in the master cylinder 2 (that is, the brake depression force) is supplied to the brakes 10 of the respective wheels through the in-line 63, the differential pressure valve 68, and the fluid pressure holding valve 66. Further, when the ABS (anti-lock brake system or anti-skid brake system) is operated, the brake hydraulic pressure corresponding to the brake pedaling force is appropriately adjusted through the hydraulic pressure holding valve 66 and the pressure reducing valve 67 so as not to lock the wheel.

The in-line intake valve 61, the outline intake valve 62, the pump 65, the hydraulic pressure holding valve 66, the pressure reducing valve 67, and the differential pressure valve 68 of each brake wheel of the hydraulic unit 6 are controlled by the brake ECU 3.
The brake ECU 3 receives a handle angle signal from a handle angle sensor 11 attached to a steering wheel (handle), a yaw rate signal from a yaw rate sensor 12 installed on the vehicle body, and a master cylinder hydraulic pressure from a master cylinder hydraulic pressure sensor 14. A wheel speed signal is input from the wheel speed sensor 15 of each wheel, a brake pedal depression signal is input from the brake switch 16, and a longitudinal acceleration signal and a lateral acceleration signal are input from the longitudinal / lateral acceleration sensor 17 installed on the vehicle body. It has become so.

  The brake ECU 3 is input with various functional elements as shown in FIG. 1, that is, various information relating to the driving state of the driver, and appropriately processes and outputs the input information, and the vehicle motion. A vehicle motion state input unit 32 that inputs various information related to the state (behavior) and processes and outputs the input information as appropriate, a yaw moment control means (steer characteristic control means) 33, an automatic deceleration control means 34, Integrated control means 35 is provided.

The driver operation state input unit 31 determines whether braking is being performed based on a brake pedal depression signal from the brake switch 16.
The vehicle motion state input unit 32 recognizes the actual yaw rate generated in the vehicle body by the yaw rate signal from the yaw rate sensor 12, and further calculates the vehicle body speed, the target yaw rate, and the yaw rate deviation. The vehicle body speed (vehicle speed) is normally calculated based on the wheel speed signal from the wheel speed sensor 15, but when the wheel slips, the vehicle body speed based on the wheel speed signal obtained so far is added to the longitudinal acceleration sensor 17. Is calculated by adding the time integral value of the longitudinal acceleration obtained from (in this case, the estimated vehicle speed).

The target yaw rate Yaw _tgt is originally a yaw rate that should be generated in the vehicle. As shown in FIG. 3, the target yaw rate Yaw _tgt is obtained from the vehicle body speed V _body obtained as described above and the handle angle signal from the handle angle sensor 11. The calculated actual steering angle (steering wheel angle) δ is calculated by the following equation (1), and the calculated value is obtained by low-pass filter processing to remove noise.

Where A: Stability factor of the vehicle
L: The wheel base yaw rate deviation ΔYaw of the vehicle is calculated by the following equation (2) as a difference between the target yaw rate Yaw _tgt and the actual yaw rate Yaw _body recognized by the vehicle motion state input unit 32.
ΔYaw = Yaw _tgt −Yaw _body (2)
For example, if the right direction is set to be positive with respect to the yaw rate direction so that the yaw rate deviation ΔYaw is positive at the time of understeer (US) and negative at the time of oversteer (OS), the sign of the left direction is converted (multiplied by −1). And perform the above calculation.

The yaw moment control means (steer characteristic control means) 33 performs yaw moment control (steer characteristic control) according to the yaw rate deviation ΔYaw when a predetermined start condition is satisfied. The start conditions are (i) the vehicle body speed V _body is equal to or higher than a reference value (a preset low speed value) V ₁ , and (ii) the yaw rate deviation ΔYaw is an understeer (US) start determination threshold value ΔYaw _us1 or oversteer ( it exceeds the start determination threshold ΔYaw _as1 OS), a, that each of these conditions are all satisfied, starts the yaw moment control. The determination function (ii) in the steering characteristic control means 33 is referred to as a steering characteristic determination means (understeer determination means) 33a.

  In yaw moment control, during understeering, the flaking force of the inner turning wheel is increased and the flaking force of the outer turning wheel is reduced. In this case, if a braking force is applied only to the rear wheels among the turning inner wheels, understeer can be suppressed smoothly and efficiently without excessive deceleration of the vehicle. That is, if the brake is not being operated, as shown in FIG. 4 (a1), the braking force is applied to the rear wheel 5RL or 5RR among the turning inner wheels, and if the brake is being operated, the brake is being operated as shown in FIG. 4 (a2). In addition, the braking force applied amount (specifically, the brake fluid pressure to be applied) is increased so that the braking force of the rear wheel 5RL or 5RR of the turning inner wheel is increased and the braking force of the front wheel 5FR or 5FL of the turning outer wheel is decreased. ) Or a braking force increase amount and a decrease amount (specifically, brake fluid pressure to be increased or decreased). Further, the braking force application amount or the braking force increase amount and the decrease amount are set to increase as the magnitude of the yaw rate deviation ΔYaw increases corresponding to the yaw rate deviation ΔYaw.

  In the yaw moment control, during oversteering, the flaking force of the outer turning wheel is increased and the flaking force of the inner turning wheel is reduced. In this case, if a braking force is applied only to the front wheels of the turning outer wheels, oversteer can be suppressed smoothly and efficiently without excessive deceleration of the vehicle. That is, if the brake is not being operated, as shown in FIG. 4 (b1), a braking force is applied to the front wheel 5FL or 5FR among the turning outer wheels, and if the brake is being operated, as shown in FIG. 4 (b2). The amount of braking force applied (specifically, the brake fluid pressure to be applied) so as to increase the braking force of the front wheel 5FL or 5FR of the outer turning wheel and decrease the braking force of the rear wheel 5RR or 5RL of the inner turning wheel Alternatively, the brake force increase amount and the decrease amount (specifically, the brake fluid pressure to be increased or decreased) are set. Further, the braking force application amount or the braking force increase amount and the decrease amount are set to increase as the magnitude of the yaw rate deviation ΔYaw increases corresponding to the yaw rate deviation ΔYaw.

Further, when a predetermined end condition is satisfied during the yaw moment control, the yaw moment control (steer characteristic control) is ended. The end conditions are (i) the vehicle body speed V _body is equal to or less than a reference value (a preset low speed value) V ₂ (where V ₂ <V ₁ ), and (ii) the yaw rate deviation ΔYaw is understeer (US). If it is within the hour end determination threshold value or the oversteer (OS) end determination threshold value, and at least one of these conditions is satisfied, the yaw moment control is ended.

  The automatic deceleration control means 34 decelerates the vehicle when the wheel (tire) of the vehicle that is turning reaches the grip limit and the vehicle's travel route deviates from the originally intended turn route. This is a control to be prevented. In this automatic deceleration control, the braking force is applied to all four wheels because the purpose is to decelerate the vehicle. In addition, the automatic deceleration control means 34 starts predetermined control relating to vehicle behavior, such as when the lateral acceleration of the vehicle reaches a limit state corresponding to the road surface μ on which the vehicle travels, on the precondition that the yaw moment control is being performed. When the condition is satisfied, the automatic deceleration control is started, and when a predetermined control termination condition relating to the vehicle behavior is satisfied, such as the yaw moment control being terminated, the automatic deceleration control is terminated.

During this automatic deceleration control, the braking force applied to the wheels is adjusted so that the vehicle has a predetermined deceleration at normal times (when the understeer tendency is not excessive), but the understeer tendency is excessive. Then, the control amount is set so that the braking force applied to the wheels is increased at the maximum speed so that the vehicle decelerates as quickly as possible.
Therefore, the automatic deceleration control means 34 includes a start / end determination means (vehicle behavior determination means) 36 for determining the start and end of automatic deceleration control, and a control amount for setting a control amount related to braking when the automatic deceleration control is performed. Setting means 37 is provided.

The conditions for starting the automatic deceleration control are: (i) the target deceleration gx _tgt is less than the control start threshold (first predetermined value) gx _trcs , (ii) the vehicle speed V _body is equal to or higher than the constant speed V1, (iii) ) All of the conditions that the driver is not operating the brake are satisfied.
Among these conditions, the condition (i) corresponds to the fact that the vehicle speed V _body is excessive and the vehicle needs to be decelerated more than a certain level. That is, here, since the acceleration value is positive and the deceleration value is negative, the fact that the target deceleration gx _tgt is less than the control start threshold gx _{trcs indicates} the magnitude of the target deceleration | gx _tgt This corresponds to that | is larger than the predetermined value | gx _trcs |. Therefore, the condition (i) corresponds to the necessity of decelerating the vehicle more than a predetermined value.

Here, the target deceleration gx _tgt used for the condition (i) will be described. As shown in FIGS. 5 and 6, the start / end determination means 36 has a function for estimating the turning radius of the vehicle (turning radius estimation). Means) 36a, a function (road surface μ estimation means) 36b for estimating the road surface μ on which the vehicle is traveling, a turning radius estimated by each of the estimation means 36a and 36b, and a road surface μ to calculate the safe traveling vehicle speed V _sfty . Functions (safe traveling vehicle speed calculating means as safe upper limit speed estimating means) 36c, safe traveling vehicle speed V _sfty calculated by safe traveling vehicle speed calculating means 36c, and actual vehicle speed (body speed) calculated by vehicle motion state input unit 32 function of calculating a target deceleration gx _tgt from the deviation between V _body and (target deceleration setting means) 36d, function of determining the start and end of the automatic deceleration control based on the target deceleration gx _tgt like (judging means And 36e are provided.

In the turning radius estimation means 36a, the average lateral acceleration gy _ave obtained by processing the lateral acceleration detected by the longitudinal / lateral acceleration sensor 17 with a low-pass filter, and the actual vehicle speed V _body calculated by the vehicle motion state input unit 32, and From this, the turning radius: r _est is calculated by the following equation (3).
r _est = V _body ² / gy _ave (3)
In the road surface μ estimation means 36b, from the average longitudinal acceleration gx _ave and average lateral acceleration gy _ave obtained by processing the longitudinal acceleration and lateral acceleration detected by the longitudinal / lateral acceleration sensor 17 with a low-pass filter, the following equation (4) To calculate the road surface μ: μ _est .

μ _est = (1 / G) · √ (gx _ave ² + gy _ave ² ) (4)
Here, G is the gravitational acceleration.
The calculation of the road surface μ is performed on the condition that the vehicle is running at the limit (running at the grip limit of the tire). While the vehicle is running at the limit, the yaw moment control, which is a precondition for automatic deceleration control, is equivalent to this, but in addition, the four-wheel ABS is operating, or the yaw rate deviation ΔYaw is excessive (a predetermined value or more). This is also the case.

In safe driving speed calculating unit 36c, the turning was estimated as described above radius: r _est and the road surface mu: mu _est and, from a preset safety factor mu _SFTY, safe running speed V by the following equation (5) _{Calculate sfty} .
V _sfty = √ (μ _sfty · μ _est · r _est ) (5)
In the target deceleration setting means 36d, as shown in the following equation (6), the difference ΔV (= V _sfty −V _body ) between the safe traveling vehicle speed V _sfty and the actual vehicle speed V _body is multiplied by the feedback gain K _trc. The target deceleration is gx _tgt .

gx _tgt = K _trc · (V _sfty −V _body ) (6)
However, the target deceleration gx _tgt is subjected to a limiter process within a predetermined range.
Accordingly, the target deceleration gx _tgt calculated in this way being less than the threshold means that the current vehicle speed is excessive with respect to the turning radius of curvature and the road surface μ of the running road, that is, during running. This means that the lateral acceleration is excessive with respect to the road surface μ of this road, which corresponds to the need for deceleration of the vehicle.

In addition, the automatic deceleration control start condition (ii) is that when the vehicle speed is very low, it is easy to stabilize the vehicle behavior by the driver's operation, and the automatic deceleration control is not particularly required. Is set.
In addition, the automatic deceleration control start condition (iii) considers the case where the driver performs a deceleration operation in the limit running state of the vehicle. When the driver performs the deceleration operation, the vehicle performs deceleration according to the deceleration operation instead of automatic deceleration. However, the vehicle behavior can be controlled in a stable direction, and if the vehicle is decelerated by a response different from the driver's deceleration operation, the driver feels uncomfortable.

As shown in FIG. 6, the determination means 36e determines the start of automatic deceleration control based on these control start conditions (i) to (iii) during yaw moment control.
The conditions for termination of automatic deceleration control are (i) that the target deceleration gx _tgt is greater than the control termination threshold (second predetermined value) gx _trce for a predetermined period of time, and (ii) vehicle speed V _body Is any one of the following conditions: (iii) the yaw moment control is completed.

The determination unit 36e determines the end of automatic deceleration control based on these control end conditions (i) to (iii).
As shown in FIG. 6, the control amount setting means 37 sets an increasing / decreasing gradient of the brake fluid pressure (an increasing / decreasing amount per control cycle) according to the deviation between the target deceleration gx _tgt and the actual deceleration gx _body. Then, the brake fluid pressure control for the four wheels is performed based on this increasing / decreasing pressure gradient. That is, in the control amount setting means 37, if the target deceleration _gxtgt is larger than the actual deceleration gx _body on the deceleration side, the brake fluid pressure increasing gradient rate _trc is set according to this deviation, and the target deceleration is set. If gx _tgt is smaller than the actual deceleration gx _body on the deceleration side, a brake fluid pressure reduction rate rate _trc is set according to this deviation.

The setting of the increasing / _decreasing gradient rate _trc will be described more specifically. The control amount setting means 37 sets the control amount as shown in FIG. That is, the target deceleration gx _tgt, the difference between the actual deceleration gx _body value cornering drag drag is subtracted from (= gx _body -drag) - calculates _{(= gx tgt (gx body -drag} )), the value the averaged by the low-pass filter, the value was positive or negative code conversion processing, and calculates the deceleration deviation gx _err, which in a decreasing pressure gradient rate _trc of multiplying the automatic deceleration proportional gain P _trc and the brake fluid pressure Set.

Further, the control amount setting means 37 employs a rapid deceleration mode in which the brake fluid pressure of the four wheels is fully increased when the yaw rate deviation ΔYaw becomes larger than the threshold Yaw _s1 during automatic deceleration. In the rapid deceleration mode, the control amount (pressure increase gradient) rate _{trc is set} to the full pressure increase pressure increase rate rate _trc4 so as to maximize the pressure increase speed of the brake fluid pressure (working fluid pressure).
The full pressure increase control ends when the automatic deceleration ends or when the yaw rate deviation ΔYaw decreases below a predetermined threshold Yaw _s2 (Yaw _s2 <Yaw _s1 ).

However, in this full pressure increase control, the pressure increase rate of the brake fluid pressure (working fluid pressure) is maximized within a range where the vehicle deceleration does not become excessive, that is, the actual deceleration gx _body exceeds the limit. When it is, the value of the full pressure increasing pressure increasing rate rate _trc4 is suppressed.
That is, the deceleration limit value gx _limit is set in advance. The deceleration limit value gx _limit is a theoretical limit value of the longitudinal acceleration that can be generated by the vehicle based on the grip characteristics of the wheel or the like, or a value corresponding to this. Then, the difference (= gx _limit −gx _body ) between the deceleration limit value gx _limit and the actual deceleration gx _body is calculated, and when this difference Δgx is positive, that is, the actual deceleration gx _body is the deceleration limit. When the value is larger than the value gx _limit on the deceleration side, the value _obtained by multiplying the difference Δgx by the proportional gain P _gxlimit and the value _obtained by multiplying the differential value of the difference Δgx by the proportional gain D _gxlimit are used. The value of the gradient rate _trc4 is subtracted and corrected.

  This is because when the actual deceleration of the vehicle is smaller than the theoretical limit deceleration (the actual deceleration is larger than the deceleration limit), the brake fluid pressure is fully increased. It is considered that the vehicle is decelerating excessively and may cause the vehicle behavior to become unstable.Therefore, the increase in brake fluid pressure should be suppressed according to the difference between the actual deceleration and the deceleration limit value. -ing

In the integrated control means 35, when control by the automatic deceleration control means 34 is added during the yaw moment control by the steering characteristic control means 33, a control amount (increase / decrease gradient of brake fluid pressure) is set so as to be integrated. Basically, as shown in FIG. 9, the increase / decrease gradient of the brake fluid pressure of each wheel is determined by the steer characteristic control means 33 for the yaw moment control and the control of the automatic deceleration control means 34. This is an added value with the increasing / decreasing pressure gradient set by the amount setting means 37. However, the same applies when full pressure increase control is performed in the automatic deceleration control means 34. In this case, when the actual deceleration gx _body is larger than the deceleration limit value gx _limit on the deceleration side, the above correction is applied to the value of the full pressure increase pressure increase rate rate _trc4 .

The vehicle behavior stabilization control device according to one embodiment of the present invention is configured as described above, and the vehicle behavior stabilization control according to the present embodiment is performed as shown in the flowcharts of FIGS. 10 and 11, for example. The Note that the flowcharts shown in FIGS. 10 and 11 are executed in a preset control cycle (calculation cycle).
That is, as shown in FIG. 10, it is determined by the flag F1 whether or not the yaw moment control is currently being performed (step a10). The flag F1 is set to 1 during yaw moment control, and set to 0 otherwise. If the yaw moment control is not currently being performed (flag F1 = 0), the process proceeds to step a20 to determine whether or not the above-described yaw moment control start condition is satisfied. If the yaw moment control start condition is satisfied, the flag F1 is set to 1 (step a30), and the braking control amount (increase / decrease gradient) of each wheel for yaw moment control is set (step a40). That is, if the oversteer tendency is strong, a braking control amount (increase / decrease gradient) corresponding to the yaw rate deviation is set to the target wheel so that the front wheel of the turning outer wheel is braked. If the understeer tendency is strong, the rear wheel of the turning inner wheel is set. A braking control amount (increase / decrease gradient) corresponding to the yaw rate deviation is set to the target wheel so as to brake.

  Then, it is determined by the flag F2 whether or not automatic deceleration control is currently being performed (step a50). The flag F2 is set to 1 during automatic deceleration control and is set to 0 when automatic deceleration control is not being performed. If automatic deceleration control is not currently being performed (flag F2 = 0), the process proceeds to step a60 to determine whether or not the above-described automatic deceleration control start condition is satisfied. If the automatic deceleration control start condition is satisfied, the flag F2 is set to 1 (step a70), and the braking control amount (increase / decrease gradient) of each wheel for automatic deceleration control is set (step a80).

On the other hand, if the automatic deceleration control is currently being performed (flag F2 = 1), the process proceeds from step a50 to step a90, and it is determined whether or not the above-described automatic deceleration control termination condition is satisfied. If the automatic deceleration control end condition is satisfied, the flag F2 is set to 0 (step a100).
Thus, when the braking control amount (increase / decrease gradient) of each wheel is appropriately set (steps a40 and a80), the braking control amount of each wheel is integrated (step a110). That is, when the braking control amount for each wheel for automatic deceleration control is set in step a80, the braking control for each wheel for automatic deceleration control is added to the braking control amount for each wheel for yaw moment control. The amount is added to set the final braking control amount (increase / decrease gradient) for each wheel.

  On the other hand, if the yaw moment control is currently being performed (flag F1 = 1), the process proceeds to step a130, and it is determined whether or not the above-described yaw moment control end condition is satisfied. If the yaw moment control end condition is not satisfied, the process proceeds to step a40. If the yaw moment control end condition is satisfied, the flag F1 is set to 0 (step a140). In step a150, whether F2 = 1 or not. If F2 = 1, the flag F2 is reset to 0.

Incidentally, the braking control amount of each wheel for automatic deceleration control is set as shown in FIG. That is, as described above, it is determined whether or not the understeer tendency is larger than a predetermined limit (step b10). If the understeer tendency is not larger than the predetermined limit, the actual deceleration gx _body and the target deceleration gx _tgt are determined. A braking control amount for each wheel is set according to the deceleration deviation gx _err (step b50).

On the other hand, if the understeer tendency is larger than a predetermined limit, the rapid deceleration mode is adopted. In this sudden deceleration mode, basically, the braking control amount of each wheel is set to the maximum increase so as to fully increase the brake fluid pressure of the four wheels (step b20), but the actual deceleration gx _body is large. Is determined whether or not the value exceeds the deceleration limit value gx _limit (step b30). If the actual deceleration gx _body exceeds the deceleration limit value gx _limit , the actual decrease Based on the deviation Δgx between the speed gx _body and the deceleration limit value gx _limit and the differential value of the deviation Δgx, the control amount (four-wheel full pressure increase) set in step b20 is subtracted and corrected so that the deceleration does not become excessive. Like that.

  Thus, according to the present apparatus, the automatic deceleration control can reliably prevent the vehicle from exceeding the turning limit and the vehicle travel route from deviating from the travel route originally intended to travel. If the understeer tendency becomes excessive during the deceleration control, the vehicle is rapidly decelerated (rapid deceleration mode), so that the understeer tendency can be suppressed and the vehicle behavior can be reliably stabilized.

In the rapid deceleration mode, if the deceleration becomes excessive (the actual deceleration gx _body is larger than the deceleration limit value gx _limit ), the vehicle behavior may become unstable. In such a case, the control amount (four-wheel full pressure increase) is subtracted and corrected based on the deviation between the actual deceleration and the deceleration limit value and the differential value of this deviation. Lateral force loss can be prevented, and rear wheel lateral force decrease due to rear wheel load loss can be prevented, so that the vehicle behavior can be reliably stabilized.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the subtraction correction of the control amount (four-wheel full pressure increase) is performed based on the deviation between the actual deceleration and the deceleration limit value and the differential value of this deviation. Although correction accuracy is improved by adding control, in the simplest case, only proportional control (subtraction correction is performed based only on the deviation between the actual deceleration and the deceleration limit value) may be performed.

  In this embodiment, the automatic deceleration control is performed only when the yaw moment control is performed. However, the automatic deceleration control may be performed independently of the yaw moment control.

  The behavior at the time of turning of the automobile can be stabilized, which contributes to further improvement of the safety of the automobile and reduction of the driving burden on the driver, and can be applied to various automobiles.

It is a block diagram which shows the structure of the vehicle behavior stabilization control apparatus concerning one Embodiment of this invention. It is a lineblock diagram of the brake system of vehicles concerning one embodiment of the present invention. It is a control block diagram explaining calculation of the target yaw rate concerning behavior stabilization control (yaw moment control) of one embodiment of the present invention. It is a typical top view of vehicles explaining yaw moment control concerning one embodiment of the present invention. It is a control block explaining vehicle behavior stabilization control concerning one embodiment of the present invention. It is a control block explaining vehicle behavior stabilization control concerning one embodiment of the present invention. It is a control block explaining vehicle behavior stabilization control concerning one embodiment of the present invention. It is a control block explaining vehicle behavior stabilization control concerning one embodiment of the present invention. It is a typical top view of vehicles explaining vehicle behavior stabilization control concerning one embodiment of the present invention. It is a flowchart explaining the vehicle behavior stabilization control concerning one Embodiment of this invention. It is a flowchart explaining the vehicle behavior stabilization control concerning one Embodiment of this invention.

Explanation of symbols

1 Brake pedal 2 Master cylinder 3 Brake controller (brake ECU)
4 Brake Fluid Reservoir 5FL, 5FR, 5RL, 5RR Braking Wheel 6 Hydraulic Unit 10 Wheel Brake 11 Handle Angle Sensor 12 Yaw Rate Sensor 14 Master Cylinder Fluid Pressure Sensor 15 Wheel Speed Sensor 16 Brake Switch 17 Longitudinal / Lateral Acceleration Sensor 31 Operating State Input Unit 32 Vehicle motion state input unit 33 Yaw moment control means (steer characteristic control means)
33a Steer characteristic determining means (understeer determining means)
34 Automatic deceleration control means 35 Integrated control means 36 Start / end determination means (vehicle behavior determination means)
36a Turning radius estimating means 36b Road surface μ estimating means 36c Safe traveling vehicle speed calculating means (safety upper limit speed estimating means)
36d Target deceleration setting means 36e Determination means 37 Control amount setting means

Claims (7)

A braking mechanism capable of braking each wheel;
Vehicle behavior determining means is provided for determining whether or not the vehicle behavior at the time of turning travel has reached a limit state based on behavior information relating to the travel route of the vehicle at the time of turning travel. When it is determined that the limit state has been reached, automatic deceleration control means for automatically decelerating the vehicle by applying braking force to the wheels through the braking mechanism to the extent that the vehicle behavior does not exceed the limit state is provided. ,
Understeer determination means for determining whether or not the vehicle is in an understeer state exceeding a predetermined limit based on behavior information relating to the steer characteristic of the vehicle during turning,
When the vehicle is in an understeer state exceeding a predetermined limit by the understeer determination unit during the automatic deceleration, the automatic deceleration control unit brakes the wheels in a rapid deceleration mode in which the vehicle decelerates most quickly. A vehicle behavior stabilization control device that controls the vehicle behavior. The vehicle behavior determining means determines that the vehicle behavior during turning travel reaches the limit state when the lateral acceleration generated in the vehicle during turning exceeds the limit value corresponding to the road surface μ state of the road on which the vehicle travels. The vehicle behavior stabilization control device according to claim 1, wherein it is determined that the vehicle behavior is present. The vehicle behavior determination means includes
Road surface μ estimation means for estimating the road surface μ state of the road on which the vehicle travels;
A turning radius estimating means for estimating a turning radius of the vehicle;
A safe upper limit speed estimating means for estimating a safe upper limit speed at which the vehicle behavior does not exceed a limit state based on the road surface μ state estimated by the road surface μ estimating means and the turning radius estimated by the turning radius estimating means; ,
A target deceleration setting means for setting a target deceleration based on a deviation between the safe upper limit speed estimated by the safe upper limit speed estimation means and the actual vehicle speed;
When the target deceleration set by the target deceleration setting means exceeds a preset first predetermined value, it is determined that the vehicle behavior during turning travel has reached the limit state. The vehicle behavior stabilization control device according to claim 2. The automatic deceleration control means controls the braking force applied to the wheel based on the difference between the target deceleration estimated by the vehicle behavior determination means and the actual deceleration of the vehicle. Vehicle behavior stabilization control device. The vehicle behavior determination means determines whether or not the magnitude of the target deceleration estimated by the target deceleration setting means is less than a second predetermined value that is preset as a value smaller than the first predetermined value. And
The automatic deceleration control means ends the automatic deceleration of the vehicle when the magnitude of the target deceleration estimated by the vehicle behavior determination means becomes less than the second predetermined value. 4. The vehicle behavior stabilization control device according to 4. The understeer determination means compares the difference between the theoretical yaw rate of the vehicle calculated from the vehicle speed and the steering angle and the actual yaw rate of the vehicle detected in real time with a preset threshold value. The vehicle behavior stabilization control device according to any one of claims 1 to 5, wherein it is determined whether or not an understeer state is equal to or greater than a predetermined limit. The braking mechanism is configured to control the braking force by increasing and decreasing the working fluid pressure.
The automatic deceleration control means is characterized in that, in the rapid deceleration mode, the vehicle decelerates most rapidly by maximizing the pressure increase rate of the working fluid pressure within a range where the deceleration of the vehicle does not become excessive. The vehicle behavior stabilization control device according to any one of claims 1 to 6.

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