JP2007125997A - Vehicular intelligent brake assist system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular intelligent brake assist system capable of reliably reducing the degree of damage to one's own vehicle and a forward obstacle by positively bringing a collision system close to a full-wrap state when a brake assist is operated. <P>SOLUTION: In the vehicular intelligent brake assist system having an intelligent brake assist means for performing deceleration by automatically applying a brake when it is determined that a collision with a forward obstacle cannot be avoided even by the operation of a driver, an offset amount detection means (S1) for detecting an offset amount Loff which is the axial deviation in the vehicle width direction between the center axis Lc' of the forward obstacle and the center axis Lc of the one's own vehicle is provided. The intelligent brake assist means (Fig. 2) is a means for adjusting the distribution of braking forces of right and left wheels of the one's own vehicle so as to reduce the offset amount Loff between the one's own vehicle and the forward obstacle when the brake assist is operated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of an intelligent brake assist system for a vehicle that automatically brakes and decelerates when it is determined that a collision with a forward obstacle cannot be avoided even by a driver's operation.

Conventionally, when it is determined that a collision with a front obstacle is unavoidable even by a driver's operation, a technique is known in which a brake is automatically applied to decelerate and damage at the time of the collision is reduced (for example, patent document) 1 and 2).
JP 2003-175809 A JP 2004-224309 A

  However, in the vehicle brake assist system according to the prior art, only the collision energy is reduced by decelerating the own vehicle and the damage at the time of rear-end collision is reduced. In the case of an offset collision, the overlap area between the vehicle and the front obstacle is reduced. However, there is a problem that the degree of damage is not always reduced by the concentration of collision energy in this small area.

  The present invention has been made paying attention to the above problems, and when the brake assist is activated, the degree of damage to the vehicle and the front obstacle can be surely reduced by actively bringing the collision system closer to the full lap state. An object is to provide an intelligent brake assist system for a vehicle.

To achieve the above object, according to the present invention, an intelligent brake for a vehicle provided with an intelligent brake assist means that automatically brakes and decelerates when it is determined that a collision with a front obstacle is unavoidable even by a driver operation. In the assist system,
An offset amount detecting means for detecting an offset amount which is a vehicle width direction axis shift amount between the center axis of the front obstacle and the center axis of the own vehicle;
The intelligent brake assist means adjusts the braking force distribution of the left and right wheels of the vehicle so as to reduce the offset amount between the vehicle and a front obstacle when the brake assist is operated.

Therefore, in the vehicle intelligent brake assist system according to the present invention, the braking force of the left and right wheels of the vehicle is reduced so that the intelligent brake assist means reduces the offset amount between the vehicle and the front obstacle when the brake assist is activated. Distribution is adjusted.
In other words, when it is determined that a collision with a front obstacle is unavoidable even when the driver operates, the brake assist that automatically applies the brake is activated. When this brake assist is activated, the braking force distribution adjustment of the left and right wheels of the vehicle is adjusted. As a result, the amount of axial displacement between the center axis of the front obstacle and the center axis of the host vehicle is reduced. That is, the behavior of the host vehicle is automatically controlled so as to approach a full lap collision system. Therefore, when an offset collision occurs unless the behavior control of the host vehicle is performed, the overlap area between the host vehicle and the front obstacle is enlarged, and the collision energy is dispersed in the enlarged area. As a result, the degree of damage to the front obstacle (for example, the amount of vehicle body deformation) is reliably reduced.
As a result, when the brake assist is activated, the degree of damage to the vehicle and the front obstacle can be reliably reduced by actively bringing the collision system closer to the full lap state.

  Hereinafter, the best mode for carrying out an intelligent brake assist system for a vehicle according to the present invention will be described based on a first embodiment shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall system diagram showing a hybrid vehicle (an example of a vehicle) to which the intelligent brake assist system of the first embodiment is applied.

  As shown in FIG. 1, the hybrid vehicle according to the first embodiment includes a CPU 101, an auxiliary battery 102, a brake actuator 201, a mechanical brake 202, a high-power battery 301, an inverter 302, a motor 303, and a generator 304. , An engine 305, a power split mechanism 306, an accelerator sensor 401, a brake sensor 402, a DC / DC converter 403, an inter-vehicle sensor 404, and an axle difference detecting means 405.

The CPU 101 monitors the high-power battery 301, calculates the input / output power amount according to the SOC, temperature, and deterioration state, and controls the inverter 302 based on the calculated input / output power amount, thereby generating electric power with the motor 303 (for front drive). The machine 304 is operated and the engine 305 is controlled (including distribution of driving force between the engine and the motor).
Further, the CPU 101 considers the regenerative braking force by the motor 303 and transmits a braking force calculation command value (including front / rear braking force distribution) generated by the mechanical brake 202 to the brake actuator 201.
The CPU 101 collects the distance and size between the host vehicle and the preceding vehicle (obstacle) based on a signal from the inter-vehicle sensor 404, grasps the degree of possibility of collision, and applies the control to avoidance. The vehicle speed is basically determined based on the number of rotations of the motor 303.
Finally, the road surface μ estimation method in the CPU 101 is obtained from the difference between the vehicle body speed estimated by the drive torque instructed to the motor 303 and the engine 305 and the detected value from the wheel speed sensor 404 (general). (There is no need to specify conditions in particular: no special estimation logic is required).

  The auxiliary battery 102 serves to provide an operating power source for the CPU 101. In this system, power is supplied by a DC / DC converter 403 that uses a high-power battery 301 as a power source.

  The brake actuator 201 receives a braking amount calculation command value to be generated by the mechanical brake 202 calculated by the CPU 101, and applies a necessary hydraulic pressure to the mechanical brake 202 accordingly.

  The mechanical brake 202 generates a braking force according to the hydraulic pressure generated by the brake actuator 201.

  The high-power battery 301 assists vehicle travel by supplying electric power to the motor 303 via the inverter 302 and also has a function of collecting the electric power generated by the generator 304 via the inverter 302.

  The inverter 302 is directly controlled by the CPU 101. The electric energy of the high-power battery 301 is supplied to the motor 303 according to the generated torque and the rotation speed of the engine 305, and the electric energy generated by operating the generator 304 is returned to the high-power battery 301. Since the motor 303, the generator 304, and the engine 305 are directly connected to the planetary gear mechanism (built in the power split mechanism 306), the vehicle operates normally unless controlled to maintain a balance between torque and rotational speed. I can't.

  The motor 303 alone generates drive torque when the vehicle speed is low. Further, when the vehicle speed is high, the driving torque of the engine 305 is assisted. Further, during deceleration, it has a function of generating electric energy by generating power (regenerative braking) and returning it to the high-power battery 301 via the inverter 302.

  The generator 304 basically has no starter in a hybrid electric vehicle. At the start of the vehicle to which this system is applied, power is supplied from the high-power battery 301 and the engine 305 is started by operating as a motor. During normal travel, electric energy is generated (power generation) by balancing the motor 303 and the engine 305 and is returned to the high-power battery 301. Sometimes, it is possible to cope with rapid acceleration by supplying the motor 303 directly.

  The engine 305 is directly controlled by the CPU 101. Specifically, when the vehicle speed is high, torque is generated for driving the vehicle (when the vehicle speed is low, the motor travels, so no control is required: control that does not start up is applied).

  The power split mechanism 306 has a planetary gear mechanism, and an engine 305 is directly connected to the carrier, a motor 303 is connected to the ring gear, and a generator 304 is directly connected to the sun gear. The transmission equivalent of the conventional system is also configured inside.

  The accelerator sensor 401 transmits to the CPU 101 the amount of accelerator pedal stroke that the driver has depressed during acceleration.

  The brake sensor 402 transmits to the CPU 101 the brake pedal stroke amount that the driver has depressed when decelerating.

  The DC / DC converter 403 converts the energy from the high voltage battery 301 into 12V and supplies it to the auxiliary battery 102. That is, it has the same function as an alternator in a conventional engine vehicle.

  The inter-vehicle sensor 404 collects the distance from the vehicle in front of the host vehicle (or an obstacle) using a radar or the like, and inputs information obtained thereby to the CPU 101.

  The axle difference detection means (laser radar) 405 receives the reflected light, detects a lateral displacement between the front obstacle and the own vehicle, and transmits this to the CPU 101. In response to this, the CPU 101 calculates a necessary offset correction amount.

  FIG. 2 is a flowchart showing the flow of intelligent brake assist control processing executed by the CPU 101 of the first embodiment. Each step will be described below (intelligent brake assist means).

In step S1, on the basis of the detection signal from the axle difference detection means 405, a vehicle width direction misalignment (offset amount Loff) between the center axis Lc of the own vehicle and the center axis Lc ′ of the preceding vehicle (front obstacle) is checked. Then, the process proceeds to step S2 (offset amount detection means).
That is, as shown in FIG. 3, the left-right width L ′ of the front vehicle is grasped by the axle difference detection means 405 set on the center axis Lc of the front surface of the host vehicle, and thereby the center axis Lc ′ of the front vehicle. (Center line) is estimated, and by comparing the vehicle width L, the overlap amount L ", which is the overlap between the two, is grasped. As the offset amount Loff decreases, the overlap amount L The maximum value of “the overlap amount L” is the own vehicle width L or the left / right width L ′ of the preceding vehicle (full wrap state).

In step S2, following the check of the degree of shaft misalignment in step S1, the vehicle speed is confirmed by detecting the number of revolutions of the motor 303, and collated with the “braking availability determination correction map (for vehicle speed)” shown in FIG. The correction coefficient K1 is determined, and the process proceeds to step S3.
Here, as shown in FIG. 4, the “braking enable / disable determination correction map (for vehicle speed)” sets the correction coefficient K1 to the maximum value when the vehicle speed is low, and the correction coefficient K1 in proportion to the high vehicle speed. Is set to a low value. This characteristic is set in consideration of the fact that the braking distance increases as the vehicle speed increases. However, the characteristic is not always a linear expression as shown in FIG.

In step S3, following the vehicle speed check in step S2, the latest information on the road surface friction coefficient estimated by the CPU 101 is confirmed and collated with the “braking availability determination correction map (for road surface μ)” shown in FIG. And the process proceeds to step S4.
Here, as shown in FIG. 5, the “braking enable / disable determination correction map (for road surface μ)” sets the correction coefficient K2 to the minimum value (zero) when the road surface μ is low, and becomes a high road surface μ. The correction coefficient K2 is proportionally set to a high value. This characteristic is set in consideration of the fact that the braking distance becomes shorter as the road surface μ is higher, but the characteristic is not always a linear expression as shown in FIG.

  In step S4, following the road surface μ check in step S3, the relative distance (X) to the front obstacle is confirmed by the detection signal from the inter-vehicle sensor 404, and the process proceeds to step S5.

In step S5, following the relative distance (X) check with the front obstacle in step S4, based on the information obtained in steps S2 to S4, it is determined whether or not rear-end collision avoidance due to braking is impossible, If Yes (avoids collision avoidance), the process proceeds to step S6, and if No (a collision avoidance is possible), the process proceeds to step S7.
Here, in the collision avoidance determination by braking, specifically, if (K1 × K2)> 1, it is determined that the collision avoidance by braking is impossible.
Note that the braking is intended to be a combination of “friction braking” using the brake actuator 201 and the mechanical brake 202 and “regenerative braking” using the motor 303.

In step S6, following the determination that the rear-end collision avoidance due to braking in step S5 is impossible, it is determined whether or not the rear-end collision avoidance due to steering is impossible based on the overlap amount L ". If it is No (it is possible to avoid rear-end collision), the process proceeds to step S7.
Here, the determination of avoiding rear-end collision by steering specifically includes a correction coefficient based on vehicle speed (K3: FIG. 6), a correction coefficient based on road surface μ (K4: FIG. 7), and a correction coefficient based on inter-vehicle distance (K5: FIG. 8). If the product of the correction coefficients K3, K4, and K5 is 1 or less, it is determined that rear-end collision avoidance by steering is impossible.
As shown in FIG. 6, in the “steerability determination correction map (for vehicle speed)”, the correction coefficient K3 is set to the maximum value when the vehicle speed is low, and the correction coefficient K3 decreases in proportion to the high vehicle speed. Set to This characteristic is set in consideration of the fact that the degree of avoidance by steering per unit distance decreases as the vehicle speed increases. However, the characteristic is not always a linear expression as shown in FIG.
As shown in FIG. 7, the “steerability determination correction map (for road surface μ)” sets the correction coefficient K4 to the minimum value (zero) when the road surface μ is low, and is proportional to the high road surface μ. The correction coefficient K4 is set to a high value. This characteristic is set considering that the higher the road surface μ is, the greater the degree of avoidance by steering per unit distance is. However, the characteristic is not always a linear expression as shown in FIG. .
As shown in FIG. 8, the “steerability determination correction map (for inter-vehicle distance)” sets the correction coefficient K5 to the minimum value (zero) when the inter-vehicle distance is zero, and is proportional to the increase in the inter-vehicle distance. The correction coefficient K5 is set to a high value. This characteristic is set in consideration of the fact that the longer the distance between the vehicles, the higher the possibility of avoidance by steering per unit distance. However, the characteristic is not always a linear expression as shown in FIG. Absent.

  In step S7, following the determination in step S5 that the rear-end collision can be avoided by braking, or the determination in step S6 that the rear-end collision can be avoided by steering, the brake operation or steering operation by the driver without entering the intelligent brake assist control. Is left to the collision avoidance operation by at least one of the above, and the process returns to step S1.

  In step S8, following the determination that the rear-end collision avoidance by steering in step S6 is impossible, it is determined whether or not there is a person on the side that changes the course of the own vehicle by the braking force distribution control using the inter-vehicle sensor 404, If yes, the process proceeds to step S10, and if no, the process proceeds to step S9.

  In step S9, following the determination that there is a person on the route change side in step S8, the intelligent brake assist control is not applied.

In step S10, following the determination in step S8 that there is no person on the route change side, the yaw is distributed by the braking force distribution of the four wheels so that the vehicle advances in a direction to decrease the offset amount Loff at the time of collision. Although the moment is generated, the number of times of switching (n) for equally dividing the inter-vehicle distance at the start of the brake assist control is determined by the correlation between the vehicle speed and the road surface μ, and the process proceeds to step S11.
Here, the switching number (n) is set to a smaller number as the road surface μ is lower and the vehicle speed is higher as shown in the “braking force distribution switching number setting map” of FIG. . Note that the switching frequency setting policy is “to reliably avoid sudden changes in vehicle behavior whose direction changes greatly at one time”.

In step S11, following the determination of the left / right braking force distribution switching number n in step S10, the braking force distribution control is applied according to the switching number m, and the process proceeds to step S12.
Here, “braking force distribution control according to the number of times of switching” means that the distance between the vehicle and the front obstacle is equally divided into n at the start of the brake assist operation, for example, when the number of times of switching n is an even number of times, The left and right wheel braking force difference control for reducing the offset amount Loff (= increasing the overlap amount L ") by changing the course of the center axis Lc of the own vehicle in the direction of the preceding vehicle and approaching the preceding vehicle, In the case of an odd number of times, this means that braking force posture control in which the center axis Lc of the own vehicle is returned to the direction matching the center axis Lc ′ of the preceding vehicle while approaching the preceding vehicle while the offset amount is maintained is alternately repeated.
The left and right wheel braking force difference control refers to four-wheel braking force distribution control that generates a yaw moment toward the vehicle ahead. In the left and right wheel braking force difference control, control is performed to increase the braking force distribution difference between the left and right wheels of the host vehicle as the offset amount Loff from the front obstacle is larger and the host vehicle speed is higher.
The braking force attitude control generates a braking force only on the left and right front wheels on the side far from the front vehicle, and is opposite to the yaw moment toward the front vehicle centering on the left and right front wheels on the side far from the front vehicle. Control that generates a yaw moment in the direction.
During this braking force distribution control, the ideal braking force distribution of the front and rear wheels does not break.

In step S12, following the application of the braking force distribution control in accordance with the switching frequency m in step S11, it is determined whether or not the vehicle has traveled the specified distance. If Yes, the process proceeds to step S13. If No, the process proceeds to step S13. Repeat the determination of S12.
Here, the prescribed distance refers to a distance (X / n) obtained by dividing the inter-vehicle distance X at the start of control by the number of switching times n determined at the start of control.

  In step S13, following the travel determination of the specified distance in step S12, the number of switching m in this control is counted up (m = m + 1), and the process proceeds to step S14.

  In step S14, following the count up in step S13, it is determined whether the counted up m is equal to the number of switchings n determined at the start of control. If yes, the counter is cleared and the process proceeds to the end. If No, the process returns to step S11.

Next, the operation will be described.
[Intelligent brake assist]
First, the intelligent brake assist system (IBA) will be described.
The applicant is developing safety technology based on accident analysis, and the core is (1) `` information safety '' to predict danger, (2) `` control safety '' to avoid danger, ( 3) “Impact safety” that minimizes damage from collisions.
The “pre-crash safety system” is a safety technology that evolves these technologies and makes them intelligent (= management functions).

  This "pre-crash safety system" detects the possibility of a collision in advance and informs the driver, and even if a collision is unavoidable, the necessary equipment can be operated in preparation for the collision to reduce occupant damage. Advanced safety technology. The “pre-crash safety system” that is used is the “intelligent brake assist system” and “front-seat emergency brake-sensitive pre-crash seat” that reduce damage during rear-end collisions.

  The “Intelligent Brake Assist System” pays attention to the fact that most of the causes of rear-end collisions are due to delays in discovery by the driver and misjudgment, and the distance from the vehicle following the vehicle is measured by the radar sensor. When there is a possibility of a rear-end collision, if it is determined that an emergency avoidance operation by the driver is necessary immediately, an alarm is sounded, and if it is determined that the rear-end collision cannot be avoided by the driver's operation, the brake is automatically applied. It slows down and avoids rear-end collisions or reduces damage during rear-end collisions.

  In a vehicle equipped with this “intelligent brake assist system”, the only consideration is to reduce the collision energy and reduce the damage during the rear-end collision by decelerating the vehicle. When the intelligent brake assist system is activated at time t1 with the overlap amount L "between the host vehicle and the preceding vehicle being small, as shown in the example when the control is not applied described in the above, the collision time with the preceding vehicle The overlap amount L "is kept small until t2. In other words, an offset collision occurs, and in the case of an offset collision, the overlap area between the host vehicle and the preceding vehicle is narrowed, and the collision energy concentrates on this narrow area, so the degree of damage is not necessarily even if the automatic brake decelerates. It is not necessarily reduced.

  In contrast, the intelligent brake assist system of the first embodiment employs means for adjusting the braking force distribution of the left and right wheels of the vehicle so as to reduce the offset amount Loff between the vehicle and the preceding vehicle when the brake assist is activated. When the brake assist is activated, the collision system is actively brought close to the full lap state, so that the degree of damage to the vehicle and the vehicle ahead can be reliably reduced.

  In other words, when it is determined that a collision with a front obstacle is unavoidable due to the driver's brake operation or steering operation, the brake assist that automatically applies the brake is activated. By adjusting the braking force distribution, the amount of axial displacement (= offset amount Loff) between the center axis Lc ′ of the front obstacle and the center axis Lc of the host vehicle is reduced. That is, the behavior of the host vehicle is automatically controlled so as to approach a full lap collision system. Therefore, when an offset collision occurs unless the behavior control of the host vehicle is performed, the overlap area between the host vehicle and the front obstacle is enlarged, and the collision energy is dispersed in the enlarged area. As a result, the degree of damage to the front obstacle (for example, the amount of vehicle body deformation) is reliably reduced.

  As a result, when the brake assist is activated, the degree of damage to the vehicle and the front obstacle can be reliably reduced by actively bringing the collision system closer to the full lap state.

[Intelligent brake assist control action]
If it is determined that the rear-end collision with the front obstacle can be avoided by the driver's brake operation, step S1, step S2, step S3, step S4, step S5, step S7 in the flowchart of FIG. The flow to go to is repeated.
If it is determined that the rear-end collision with the front obstacle can be avoided by the driver's steering operation, it is impossible to avoid the rear-end collision by the driver's brake operation, but step S1 → step S2 in the flowchart of FIG. Step S3 → Step S4 → Step S5 → Step S6 → Step S7 is repeated.
That is, if it is determined that the collision with the front obstacle can be avoided by the brake operation or the steering operation by the driver, the intelligent brake assist control is not performed and the process proceeds to step S7 and is left to the driver operation.

This is a case where it is determined that it is impossible to avoid the rear-end collision by the driver's brake operation or the steering operation. However, if there is a person on the route change side of the vehicle, step S1 → step S2 in the flowchart of FIG. -> Step S3-> Step S4-> Step S5-> Step S6-> Step S8-> Step S9 It becomes a flow which progresses, and in step S9, intelligent brake assist control is not applied.
Therefore, when there is a person on the route change side of the own vehicle, the safety control is executed with the highest priority given to respecting human life, abandoning the effect of reducing the degree of damage by intelligent brake assist control.

Next, when it is determined that the rear-end collision cannot be avoided by the driver's brake operation or the steering operation, and when there is no person on the route change side of the own vehicle, in the flowchart of FIG. Step S1 → Step S2 → Step S3 → Step S4 → Step S5 → Step S6 → Step S8 → Step S10 → Step S11 → Step S12 → Step S13 → Step S14 and the switching number m becomes the initial switching number n. Until it becomes, the flow which progresses to step S11-> step S12-> step S13-> step S14 is repeated.
That is, in step S10, the left / right braking force distribution switching number n is determined, and in step S11, either left / right wheel braking force difference control or braking force attitude control is applied according to the switching number m at that time. The left and right wheel braking force difference control and the braking force attitude control are alternately repeated until m reaches the default number n of switching. For example, when the switching number n is an even number, left and right wheel braking force difference control is performed to reduce the offset amount by changing the course of the center axis Lc of the host vehicle in the direction of the preceding vehicle and approaching the preceding vehicle. When the number of times is an odd number, the braking force attitude control is performed such that the center axis Lc of the own vehicle is returned to the direction matching the center axis Lc ′ of the preceding vehicle while the offset amount is maintained, and approaches the preceding vehicle.

  The brake assist operation in the intelligent brake assist system will be described with reference to a time chart showing an example when the present control is applied in FIG. FIG. 10 shows characteristics of the overlap amount L ", braking force, vehicle speed, and inter-vehicle distance before and after the start of the brake assist operation.

From time t0 to time t1 when the IBA operation starts, the overlap amount L ″ fluctuates, the braking force is maintained at zero, the vehicle speed is maintained at a constant vehicle speed, and the inter-vehicle distance is also maintained at a constant inter-vehicle distance.
When the IBA operation starts at time t1, braking is automatically applied, and the braking force distribution that distributes the total braking force unevenly between the left and right wheels so as to reduce the offset amount Loff with the front obstacle. As the control is executed, the overlap amount L ″ gradually increases from the start of the IBA operation.
Then, at the collision time t2 when the vehicle speed becomes zero and the inter-vehicle distance becomes zero, the own vehicle and the front obstacle collide with each other with the maximum overlap amount L ". The difference in the lap amount L "is the effect cost of this proposal. At the time of an offset collision, the overlap area between the vehicle and the front obstacle is expanded, and the collision energy is dispersed in this expanded area. And the damage degree of the front obstacle can be reduced surely.

As described above, in the intelligent brake assist system according to the first embodiment, the intelligent brake assist means increases the braking force distribution difference between the left and right wheels of the vehicle as the offset amount Loff from the front obstacle increases. To do.
For example, regardless of the magnitude of the offset with the front obstacle, if the braking force distribution difference between the left and right wheels of the vehicle is given by a certain difference, if the offset with the front obstacle is small, the full lap state is exceeded. In contrast, if the amount of offset with the front obstacle is large, the relative position correction amount of the vehicle will be insufficient and a large offset amount will remain. turn into.
On the other hand, by increasing the braking force distribution difference between the left and right wheels of the vehicle as the offset amount Loff with the front obstacle increases, the collision system can be brought closer to a full lap state regardless of the offset amount Loff. it can.

In the intelligent brake assist system of the first embodiment, the intelligent brake assist means increases the braking force distribution difference between the left and right wheels of the host vehicle as the host vehicle speed increases at the time of brake assist operation.
For example, if the braking force distribution difference between the left and right wheels of the own vehicle is given by a certain difference regardless of the level of the own vehicle speed, if the own vehicle speed is low, an excessive relative vehicle On the contrary, when the host vehicle speed is high, the relative position correction amount of the host vehicle is insufficient and an offset collision in which a large offset amount remains.
On the other hand, by increasing the braking force distribution difference between the left and right wheels of the host vehicle as the host vehicle speed is higher, the collision system can be brought closer to a full lap state regardless of the level of the host vehicle speed.

In the intelligent brake assist system of the first embodiment, the intelligent brake assist means divides the distance between the vehicle and the front obstacle into n equal parts at the start of the brake assist operation, and gradually increases the braking force of the left and right wheels of the vehicle. Adjust the distribution.
For example, if the braking force distribution of the left and right wheels of the vehicle is adjusted at a time when the brake assist is activated, the vehicle behavior may change abruptly and may cause anxiety to the occupant.
On the other hand, by adjusting the braking force distribution of the left and right wheels of the host vehicle in a stepwise manner, there is no sharp change in the vehicle behavior, and the possibility of anxiety to the occupant can be reduced.

In the intelligent brake assist system according to the first embodiment, the intelligent brake assist means divides the distance between the host vehicle and the front obstacle into n equal parts at the start of the brake assist operation, and the center axis Lc of the host vehicle is defined as the front obstacle. The left and right wheel braking force difference control that reduces the offset amount Loff by approaching the front obstacle by changing the course in the direction of, and the central axis Lc ′ of the front obstacle while maintaining the offset amount Loff And the braking force posture control approaching the front obstacle by returning to the direction corresponding to.
For example, if only the left and right wheel braking force difference control that reduces the offset Loff between the vehicle and the front obstacle is executed when the brake assist is activated, the yaw moment is continuously applied only in one direction, and the collision with the front obstacle , The vehicle will be in a collision system with the vehicle obstructing the front obstacle. Therefore, the contact area between the vehicle and the front obstacle gradually increases from a very narrow contact area, and the collision energy concentrates on the narrow part at the start of the collision, resulting in a degree of damage. In some cases, reduction cannot be expected.
In contrast, the left and right wheel braking force difference control for reducing the offset amount Loff and the braking force attitude control for facing the front obstacle are alternately repeated so that the vehicle faces the front obstacle. As a result of the collision, a wide contact area is ensured from the start of the collision, and the collision energy is distributed over a wide contact area, so that the degree of damage can be reduced as a result.

In the intelligent brake assist system according to the first embodiment, the intelligent brake assist unit is configured such that n, which is an equal number of times of the inter-vehicle distance, is set such that the road surface friction coefficient is a low friction coefficient road and the vehicle speed is high. Set to a low number of times.
For example, if the equal number of inter-vehicle distances is given as a fixed value based on a high μ road, the braking force adjustment limit may be exceeded on a low μ road, and the vehicle balance may be disrupted, causing a sudden change in vehicle behavior. There is. Similarly, if the number of equal divisions of the inter-vehicle distance is given as a fixed value based on the average vehicle speed range, the braking force adjustment limit may be exceeded at high vehicle speeds, and the vehicle balance may be disrupted, causing a sudden change in vehicle behavior. There is.
On the other hand, by setting n, which is an equal number of times of the inter-vehicle distance, to a smaller number as the road surface friction coefficient is a lower friction coefficient road and the vehicle speed is higher, the road surface friction coefficient and the vehicle speed are reduced. Regardless of the height, it is possible to reliably avoid the possibility that the vehicle balance will be lost and the vehicle behavior will be suddenly changed when the braking force distribution control to the left and right wheels is executed.

In the intelligent brake assist system of the first embodiment, the intelligent brake assist means adjusts the braking force distribution of the left and right wheels of the vehicle without breaking the ideal braking force distribution of the front and rear wheels during the brake assist operation.
For example, when braking by intelligent brake assist operation on a low μ road, if you try to cover the total braking force (regenerative braking force + friction braking force) only on the front wheel side, when turning, a lateral force is generated, between the tire and road surface of the front wheel The braking force limit level allowed in step 1 is exceeded (a state where the limit of the friction circle is exceeded), and the front wheels are in a braking locked state, resulting in an understeer characteristic as a turning characteristic.
In contrast, by adjusting the braking force distribution of the left and right wheels of the vehicle without breaking the ideal braking force distribution of the front and rear wheels when the brake assist is activated, the braking lock of the front wheels can be prevented even when turning on a low μ road. As a result, it is possible to avoid the occurrence of understeer while not reducing the total braking force for ensuring deceleration.

Next, the effect will be described.
In the intelligent brake assist system for the hybrid vehicle of the first embodiment, the effects listed below can be obtained.

  (1) In an intelligent brake assist system for a vehicle provided with an intelligent brake assist means that automatically brakes and decelerates when it is determined that a collision with a forward obstacle is unavoidable even by a driver's operation, the forward obstacle Is provided with an offset amount detecting means (step S1) for detecting an offset amount Loff, which is a vehicle width direction axis deviation amount between the center axis Lc ′ of the vehicle and the center axis Lc of the host vehicle. In order to adjust the braking force distribution of the left and right wheels of the vehicle so as to reduce the offset amount Loff between the vehicle and the front obstacle, when the brake assist is activated, the collision system is actively brought close to a full wrap state. The degree of damage to the vehicle and obstacles ahead can be reduced reliably.

  (2) When the brake assist operation is performed, the intelligent brake assist means increases the braking force distribution difference between the left and right wheels of the host vehicle as the offset amount Loff with the front obstacle increases, regardless of the offset amount Loff. , The collision system can be brought close to a full lap.

  (3) When the brake assist is activated, the intelligent brake assist means increases the difference in braking force distribution between the left and right wheels of the vehicle as the vehicle speed increases, so the collision system is fully wrapped regardless of the vehicle speed. Can be close to the state.

  (4) When the brake assist operation is started, the intelligent brake assist means divides the distance between the vehicle and the front obstacle into n equal parts, and adjusts the braking force distribution of the left and right wheels of the vehicle in stages. There is no steep change in behavior, and the possibility of raising anxiety for the passenger can be reduced.

  (5) At the start of the brake assist operation, the intelligent brake assist means divides the distance between the host vehicle and the front obstacle into n equal parts, and changes the direction of the center axis Lc of the host vehicle in the direction of the front obstacle. Left and right wheel braking force difference control that reduces the offset amount Loff by approaching the front obstacle, and while maintaining the offset amount Loff, return the center axis Lc of the host vehicle to the direction that matches the center axis Lc ′ of the front obstacle. Since the braking force posture control approaching the front obstacle is repeated alternately, the vehicle collides with the front obstacle, and a wide contact area is secured from the beginning of the collision, and the collision energy is wide. As a result, the extent of damage can be reduced.

  (6) The intelligent brake assist means sets n, which is an equal number of times of the inter-vehicle distance, to a smaller number as the road surface friction coefficient is a lower friction coefficient road and the vehicle speed is higher. Regardless of the road surface friction coefficient or the vehicle speed, when the braking force distribution control to the left and right wheels is executed, it is possible to reliably avoid the possibility that the vehicle balance will be lost and the vehicle behavior will be suddenly changed.

  (7) When the brake assist is activated, the intelligent brake assist means adjusts the braking force distribution of the left and right wheels of the vehicle without breaking the ideal braking force distribution of the front and rear wheels. Is prevented, and the total braking force for ensuring deceleration as a vehicle is not reduced, and the occurrence of understeer can be avoided.

  As described above, the intelligent brake assist system for a vehicle according to the present invention has been described based on the first embodiment. However, the specific configuration is not limited to the first embodiment, and the claims relate to each claim. Design changes and additions are allowed without departing from the scope of the invention.

  In Example 1, as the intelligent brake assist means, braking force distribution control for reducing the offset amount between the host vehicle and the front obstacle and braking force distribution control for controlling the posture of the host vehicle are alternately performed when the brake assist is operated. In this example, the braking force distribution adjustment of the left and right wheels of the vehicle is stepwise, but when the possibility of collision is judged, the offset amount between the vehicle and the obstacle ahead when the brake assist is activated. It is good also as control which performs braking force distribution control which reduces the above in a stepless manner. In short, the intelligent brake assist means is limited to the first embodiment as long as the brake force distribution of the left and right wheels of the own vehicle is adjusted so as to reduce the offset amount between the own vehicle and the front obstacle during the brake assist operation. I can't.

  In the first embodiment, the offset amount is detected by using the laser radar as the offset amount detection unit. However, for example, the image pickup unit in front of the vehicle is used, or the offset is detected by using the image pickup unit and the laser radar in combination. The amount may be detected.

  In the first embodiment, the vehicle intelligent brake assist system based on the front wheel drive base is shown, but the present invention can also be applied to a hybrid vehicle and a hybrid four wheel drive vehicle based on the rear wheel drive base. Of course, the present invention can also be applied to gasoline engine vehicles, diesel engine vehicles, electric vehicles, fuel cell vehicles, and the like. In short, the present invention can be applied to a vehicle equipped with intelligent brake assist means that automatically brakes and decelerates when it is determined that a collision with a front obstacle is unavoidable even by a driver's operation.

1 is an overall system diagram showing a hybrid vehicle to which an intelligent brake assist system of Example 1 is applied. It is a flowchart which shows the flow of the intelligent brake assist control process performed with CPU of Example 1. FIG. It is a figure which shows the image of the vehicle axis shift | offset | difference confirmation by the intelligent brake assist control of Example 1. FIG. It is a figure which shows an example of the brake avoidance possibility determination correction map (for vehicle speed) used by the intelligent brake assist control of Example 1. FIG. It is a figure which shows an example of the brake avoidance possibility determination correction map (for road surface μ) used in the intelligent brake assist control of the first embodiment. It is a figure which shows an example of the steering avoidance possibility determination correction map (for vehicle speed) used by the intelligent brake assist control of Example 1. It is a figure which shows an example of the steering avoidance possibility determination correction map (for road surface μ) used in the intelligent brake assist control of the first embodiment. It is a figure which shows an example of the steering avoidance possibility determination correction map (for the distance between vehicles) used by the intelligent brake assist control of Example 1. FIG. It is a figure which shows an example of the braking force distribution switching frequency setting map used by the intelligent brake assist control of Example 1. FIG. Example of each characteristic of overlap amount L ", braking force, vehicle speed, and inter-vehicle distance when the control of Example 1 is applied before and after the start of the brake assist operation, and the over time when this control is not applied before and after the start of the brake assist operation 6 is a time chart showing an example of each characteristic of a lap amount L ", a braking force, a vehicle speed, and an inter-vehicle distance.

Explanation of symbols

101 CPU
102 Auxiliary battery
201 Brake actuator
202 Mechanical brake
301 Heavy battery
302 inverter
303 motor
304 generator
305 engine
306 Power split mechanism
401 Accelerator sensor
402 Brake sensor
403 DC / DC converter
404 Inter-vehicle sensor
405 Axle difference detection means

Claims (8)

In an intelligent brake assist system for vehicles with intelligent brake assist means that automatically brakes and decelerates when it is determined that a collision with a front obstacle is unavoidable even by driver operation,
An offset amount detecting means for detecting an offset amount which is a vehicle width direction axis shift amount between the center axis of the front obstacle and the center axis of the own vehicle;
The intelligent brake assist means adjusts the braking force distribution of the left and right wheels of the vehicle so as to reduce the offset amount between the vehicle and a front obstacle when the brake assist is operated. system. The vehicle intelligent brake assist system according to claim 1,
The intelligent brake assist system according to claim 1, wherein the intelligent brake assist means increases the difference in braking force distribution between the left and right wheels of the host vehicle as the offset amount with respect to a front obstacle increases during brake assist operation. In the intelligent brake assist system for a vehicle according to claim 1 or 2,
The intelligent brake assist system according to claim 1, wherein the intelligent brake assist means increases the braking force distribution difference between the left and right wheels of the vehicle when the vehicle speed is higher when the brake assist is activated. In the vehicle intelligent brake assist system according to any one of claims 1 to 3,
The vehicle is characterized in that the intelligent brake assist means divides the distance between the vehicle and the front obstacle into n equal parts at the start of the brake assist operation, and adjusts the braking force distribution of the left and right wheels of the vehicle in stages. Intelligent brake assist system. The intelligent brake assist system for a vehicle according to claim 4,
The intelligent brake assist means divides the distance between the host vehicle and the front obstacle into n equal parts at the start of the brake assist operation, changes the center axis of the host vehicle in the direction of the front obstacle, Left and right wheel braking force difference control that reduces the offset amount by approaching, and braking force attitude control that approaches the front obstacle by returning the center axis of the host vehicle to the direction matching the center axis of the front obstacle while maintaining the offset amount And an intelligent brake assist system for vehicles characterized by alternately repeating the above. The vehicle intelligent brake assist system according to claim 4 or 5,
The intelligent brake assist means sets n, which is an equal number of times of the inter-vehicle distance, to a smaller number as the road surface friction coefficient is a low friction coefficient road and the vehicle speed is higher. Intelligent brake assist system for vehicles. The intelligent brake assist system for a vehicle according to any one of claims 1 to 6,
An intelligent brake assist system for a vehicle, wherein the intelligent brake assist means adjusts the braking force distribution between the left and right wheels of the vehicle without breaking the ideal braking force distribution of the front and rear wheels when the brake assist is operated. In an intelligent brake assist system for vehicles with intelligent brake assist means that automatically brakes and decelerates when it is determined that a collision with a front obstacle is unavoidable even by driver operation,
An intelligent brake assist system for a vehicle that adjusts the braking force distribution of the left and right wheels of the vehicle so as to reduce an offset amount between the vehicle and a front obstacle when the brake assist is activated.

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