JP2008308126A - Collision mitigation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a collision by a driver with ease, even when a warning brake is operated by timing for operating a PBA (Predictive Brake Assist), in a collision mitigation device for a vehicle for mitigating damage when the vehicle collides. <P>SOLUTION: A collision mitigation controller is provided with a function as the PBA for increasing braking force when operating the brake by an operation of the driver of one's own vehicle when collision time showing time till the vehicle collides with an object becomes less than normal braking avoidance lower limit time, and a function of an automatic brake 1 for operating the brake for only continuation time when the collision time becomes less than a judging line of the automatic brake 1 in which the collision time is set in advance. The collision mitigation controller changes the continuation time to be longer when the collision time becomes less than the normal braking avoidance lower limit time. Namely, an operation time for the automatic brake 1 is changed to be longer, if it is already operation timing for the PBA when operating the automatic brake 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle collision mitigation device for mitigating damage caused when a vehicle collides.

  Conventionally, as the above-described collision mitigation device, an obstacle on the course of the vehicle is detected, and an automatic brake (warning brake) for warning is activated when the vehicle may collide with the obstacle. Those are known (for example, see Patent Document 1).

Further, in such a collision mitigation device, when the vehicle may collide with this obstacle, a collision prediction brake assist (PBA) that increases the braking force when the braking means is operated by the operation of the driver of the vehicle. : Predictive Brake Assist) is also available.
JP 2004-284422 A

  However, in the above-described collision mitigation device, there is a possibility that which of the warning brake and the PBA is activated first depends on conditions such as relative speed. Here, when the warning brake is activated at the timing when the PBA is activated, there is no allowance until the collision after the driver notices the warning brake, compared with the case where the warning brake is activated at the timing when the PBA is not activated. It seems to be. Therefore, when the warning brake is activated at the timing when the PBA is activated, there is a problem in that a collision cannot be avoided unless the driver performs a fairly rapid deceleration operation.

  Therefore, in view of such a problem, in a vehicle collision mitigation device that mitigates damage caused when a vehicle collides, even if the warning brake is activated at the timing when the PBA is activated, the driver has a margin. It is an object of the present invention to have a collision avoidable.

  The collision mitigation apparatus according to claim 1, wherein the assist control unit is configured to operate the braking unit by an operation of the driver of the vehicle when the collision time is less than a preset assist threshold. Increase braking force when operating. Then, when the collision time becomes less than a preset warning threshold, the warning control means activates the braking means for a preset duration. Further, the time changing means changes the duration longer when the collision time becomes less than the assist threshold.

  That is, when operating the alarm brake by the warning control means, if the operation timing of the assist control means has already been reached, the operation time of the alarm brake by the warning control means is changed to be longer.

  Therefore, according to such a collision mitigation device, when the alarm brake is operated, if the operation timing of the assist control means has already been reached, it is determined that the possibility that the vehicle will collide is higher, and the operation time of the alarm brake Since the vehicle speed can be increased, the speed of the vehicle can be further reduced during alarm braking. Therefore, the driver can avoid the collision with a margin when the alarm brake is activated.

  By the way, in the collision mitigation apparatus according to claim 1, as described in claim 2, the warning control means operates the braking means so that the acceleration of the vehicle changes along a preset acceleration gradient. An acceleration gradient changing unit that changes the gradient of the acceleration gradient when the collision time becomes less than the assist threshold may be provided.

According to such a collision mitigation device, since the gradient of the acceleration (deceleration) gradient when the alarm brake is operated can be increased, the speed of the vehicle can be further reduced during the alarm brake. Therefore, the driver can avoid the collision with a margin when the alarm brake is activated.
According to a third aspect of the present invention, the warning control means is configured to set a target acceleration that is an upper limit of an absolute value of acceleration when the braking means is operated, and the collision time is less than the assist threshold value. Then, an acceleration changing means for changing the target acceleration to be large may be provided.

  According to such a collision mitigation device, the target acceleration when the alarm brake is operated can be increased, so that the speed of the vehicle can be further reduced during the alarm brake. Therefore, the driver can avoid the collision with a margin when the alarm brake is activated.

  Furthermore, in the collision mitigation device according to any one of claims 1 to 3, as described in claim 4, a relative speed detecting means for detecting a relative speed between the vehicle and the obstacle, and a relative speed Assist threshold setting means for setting an assist threshold according to the above.

  According to such a collision mitigation device, the assist threshold value can be set to a different value depending on the relative speed. Therefore, for example, when the warning threshold is set by a function different from the assist threshold, such as when the warning threshold is set to a constant value, the magnitude relationship between the assist threshold and the warning threshold depends on the relative speed. Since it changes, the strength of the warning brake can be changed according to this magnitude relationship.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a pre-crash safety system (hereinafter referred to as PCS; collision mitigation device in the present invention) 1 to which the present invention is applied.

  The PCS 1 is a system that is mounted on, for example, a vehicle such as a passenger car, detects that the vehicle collides, and reduces damage when the vehicle collides. Specifically, as shown in FIG. 1, the PCS 1 includes a collision mitigation controller 10, various sensors 30, and a controlled object 40 (braking means in the present invention).

  As the various sensors 30, for example, a radar sensor 31 (obstacle detection means in the present invention) that detects an object such as a pedestrian, an obstacle on the road, or another vehicle together with its position (relative position with respect to the host vehicle), a vehicle A yaw rate sensor 32 for detecting the turning angular velocity of the vehicle, a wheel speed sensor 33 for detecting the rotational speed of the wheel, and the like. The detection results by these various sensors 30 are acquired by the collision mitigation controller 10.

The radar sensor 31 detects an object located in the traveling direction of the vehicle every predetermined period (for example, 100 ms) set in advance.
The collision mitigation controller 10 is configured as a known microcomputer including a CPU 11, a ROM 12, a RAM 13, and the like. The collision mitigation controller 10 executes various processes such as a collision mitigation process, which will be described later, by executing a program stored in the ROM 12 based on the detection results by the various sensors 30.

  The collision mitigation controller 10 performs such processing, and activates the controlled object 40 according to the processing results of these processing. As a result, damage caused when the vehicle collides can be reduced.

  The controlled object 40 includes, for example, an actuator that drives a brake, a steering, a seat belt, and the like. Hereinafter, in this embodiment, the case where the controlled object 40 is a brake will be described.

  Here, in the PCS 1 of the present embodiment, an alarm brake (automatic brake 1) that warns the driver (driver) that the vehicle and the object may collide, and the vehicle and the object collide with the driver. The damage reduction brake (automatic brake 2) is activated to reduce the damage when

  Since the automatic brake 1 is a brake for the purpose of warning and prompting the driver to perform a collision avoidance operation, when the CPU 11 operates the automatic brake 1, damage is caused so that the driver can easily perform the avoidance operation. Compared with the deceleration of the automatic brake 2 which is the purpose of reducing, braking is performed with a small deceleration. On the other hand, when the CPU 11 operates the automatic brake 2, braking is performed at the maximum deceleration that the host vehicle can exhibit in order to reduce damage.

  As described above, when the CPU 11 operates the function as each automatic brake, the controlled object 40 is operated so as to obtain a preset deceleration according to the detection signal from the wheel speed sensor 33.

  Further, in the PCS 1 of the present embodiment, when there is a possibility that the vehicle may collide with the object, a collision prediction brake assist (PBA) that increases the braking force when the braking means is operated by the operation of the driver of the vehicle. Predictive Brake Assist) function.

  Specifically, PBA means that when the possibility of collision between a vehicle and an object increases, before the driver operates the controlled object 40 (brake), for example, the brake hydraulic pressure is increased or the brake pad is used as a brake disc. For example, when the driver operates the controlled object 40 (brake) by bringing them close to each other, a stronger braking force can be obtained quickly. The specific operation timing will be described in the assist process described later.

Here, a collision mitigation process, which is a process when the automatic brakes 1 and 2 are executed, will be described with reference to FIGS. 2 to 4 and FIG. 6.
FIG. 2 is a flowchart showing a collision mitigation process executed by the CPU 11 of the collision mitigation controller 10, and FIG. 3 is a flowchart showing an operation determination process in the collision mitigation process. FIG. 4 is a flowchart showing threshold calculation processing (FIG. 4A) and duration calculation processing (FIG. 4B) in the operation determination processing, and FIG. 6 shows operation control processing in the collision mitigation processing. It is a flowchart to show.

  The collision mitigation process is a process that is activated every predetermined period (for example, about 50 ms) set in advance. Specifically, as shown in FIG. 2, in the collision mitigation process, the object selection process (S110: relative speed detection means), the driver operation determination process (S120), the operation determination process (S130), and the arbitration process (S140). The operation control process (S150) is performed in order.

In the object selection process (S110), other vehicles that enter the lane (own lane) on which the host vehicle (the vehicle on which the PCS 1 is mounted) run, pedestrians and road obstacles that are on the course of the host vehicle. The object such as is detected. In this object selection process, a process of estimating the course of the object, a process of calculating a relative speed with the object using a detection result by the radar sensor 31, and the like are performed. Based on these processes, Select an object that may collide with your vehicle.

  In the driver operation determination process (S120), it is determined whether or not the driver of the host vehicle has performed an operation (a collision avoiding operation) for avoiding a collision with the object. In this process, for example, it is detected whether or not the brake is operated, and when it is detected that the brake is operated, the collision avoiding operation is performed and the result is recorded in the RAM 13.

  In the operation determination process (S130), it is determined whether it is time to operate the controlled object 40 based on the path of the object estimated by the object selection process, the relative speed with the object, and the like. An operation instruction is generated and recorded in the RAM 13 at the timing for operating the control target 40.

  In the arbitration process (S140), it is finally determined whether or not the controlled object 40 is actually operated. Subsequently, in the operation control process (S150), on the basis of the generated operation instruction, an operation command corresponding to the controlled object 40 is sent to the controlled object 40 (if there are a plurality of controlled objects 40, each of the controlled commands 40). To the controlled object 40).

Next, details of the operation determination process will be described. Details of the arbitration process and the operation control process will be described later.
In the operation determination process, as shown in FIG. 3, a collision time that represents the time until the vehicle collides with the object is calculated based on the behavior and relative speed of the object detected in the object selection process. (S210: collision time calculation means). Then, a threshold value calculation process for calculating a threshold value that is a criterion for determining whether or not to operate the automatic brake (braking means) is performed (S220).

  In this threshold value calculation process, as shown in FIG. 4A, first, a braking avoidance limit time is calculated (S310). Here, the braking avoidance limit time represents a limit time during which a collision between the object and the vehicle can be avoided by operating the braking means. Therefore, even if the driver operates the brake after the collision time becomes less than the braking avoidance limit time, the collision with the object cannot be avoided only by operating the brake.

  The accurate braking avoidance limit time becomes a large value approximately in proportion to the relative speed with the object, and a specific numerical value is experimentally obtained for each vehicle. However, when this braking avoidance limit time is calculated by the PCS 1, it is approximated as a function having the relative speed as a variable.

  That is, the function is expressed by, for example, an expression that multiplies the relative speed with the object by a constant (for example, a value of about 0.016) set in advance according to the deceleration that the brake of the vehicle can exert. . In addition, you may enable it to change a constant here according to vehicle environments, such as a friction coefficient of a road surface.

  Subsequently, a steering avoidance limit time is calculated (S320). Here, the steering avoidance limit time represents a limit time during which the collision between the object and the vehicle can be avoided by the driver steering. Therefore, even if the driver operates the steering after the collision time becomes less than the steering avoidance limit time, the collision with the object cannot be avoided only by the steering.

The accurate steering avoidance limit time is a substantially constant value regardless of the relative speed with respect to the object, and a specific numerical value is experimentally obtained for each vehicle. However, in PCS1, the steering avoidance limit time is approximated as a constant value. That is, a fixed value (for example, 0.6 seconds) set in advance based on the steering performance of the vehicle (responsiveness of the steering device, turning radius of the vehicle, etc.) is adopted.

  Next, a collision determination line is calculated (S330). The collision determination line represents a limit line where a collision can be avoided by braking or steering. Specifically, the smaller one of the braking avoidance limit time and the steering avoidance limit time is adopted as the collision determination line. .

Therefore, when the collision time is shorter than the collision determination line, the collision with the object cannot be avoided.
Subsequently, a normal steering avoidance lower limit time is calculated (S340). Here, the normal steering avoidance lower limit time represents a time necessary for avoiding a collision with an object by a driver's normal steering operation, and adopts a preset fixed value (for example, 1.4 seconds). Shall.

  Next, the normal braking avoidance lower limit time is calculated (S350: assist threshold setting means). Here, the normal braking avoidance lower limit time corresponds to the assist threshold in the present invention, and represents the time required for the driver to avoid the collision with the object by operating the braking means. Further, the normal braking avoidance lower limit time becomes a large value according to the relative speed with the object, and in this embodiment, a value obtained by adding 1 second to the braking avoidance limit time is adopted.

  Then, an automatic brake 1 determination line (set time) serving as a determination criterion for determining whether or not to operate the automatic brake 1 is calculated (S360). Here, the automatic brake 1 determination line corresponds to the warning threshold in the present invention, and is set by adopting a time obtained by adding a time (for example, 0.8 seconds) to react to the driver warning to the normal steering avoidance lower limit time. Is done. That is, the automatic brake 1 determination line has a constant value regardless of the relative speed.

  Subsequently, an automatic brake 2 determination line (a set time) serving as a determination criterion for determining whether or not to operate the automatic brake 2 is calculated (S370). Here, the automatic brake 2 determination line is set by adopting the collision determination line as it is.

  As described above, when each value such as the determination line is set, the relationship between the normal braking avoidance lower limit time, the normal steering avoidance lower limit time, and the set time in the automatic brake 1 determination line is as shown in FIG. FIG. 5 is a graph showing the relationship between the relative speed [km / h] between the host vehicle and the object and the set time [s].

  As shown in FIG. 5, the set time in the normal steering avoidance lower limit time (solid line in (2) of FIG. 5) and the automatic brake 1 determination line (solid line in (3) of FIG. 5) is constant regardless of the relative speed. Although set, the set time of the normal braking avoidance lower limit time (the solid line in FIG. 5 (1)) increases as the relative speed increases. For this reason, the set time of the normal braking avoidance lower limit time and the set time of the automatic brake 1 determination line depend on the relative speed (in the example of FIG. 5, the relative speed is about 72 [km / h] as a boundary), Change.

  That is, the normal braking avoidance lower limit time is used as a threshold value when operating the PBA, and the automatic brake 1 determination line is used as a threshold value when operating the automatic brake 1, so that the magnitude relationship between these is switched. This means that the operation timings of the PBA and the automatic brake 1 are switched. Here, when the automatic brake 1 is operated after the collision time is less than the normal steering avoidance lower limit time (the set time), since the time until the collision is approaching, the vehicle speed is reduced as much as possible by the operation of the automatic brake 1. It is preferable to slow down.

  Therefore, in the continuing time calculation process (S380: time changing means), the operation continuation time of the automatic brake 1 is changed according to the magnitude relationship between the normal braking avoidance lower limit time and the automatic brake 1 determination line.

  Specifically, as shown in FIG. 4B, first, it is determined whether or not the normal braking avoidance lower limit time is longer than the automatic brake 1 determination line (S410). If the normal braking avoidance lower limit time is equal to or shorter than the automatic brake 1 determination line (S410: NO), the operation duration of the automatic brake 1 is set to 0.3 seconds (S420), and the duration calculation process is terminated.

  On the other hand, if the normal braking avoidance lower limit time is larger than the automatic brake 1 determination line (S410: YES), the operation duration time of the automatic brake 1 is set to 0.8 seconds (S430), and the duration calculation process is terminated. That is, when the normal braking avoidance lower limit time is longer than the automatic brake 1 determination line (when the automatic brake 1 operates in a state where the brake assist operation condition is satisfied), the normal braking avoidance lower limit time is equal to or shorter than the automatic brake 1 determination line. Compared with the case where it is, the operation continuation time of the automatic brake 1 is set longer.

  Each calculation result in the threshold calculation process is recorded in the RAM 13. When such threshold value calculation processing is completed, it is determined whether or not the collision time calculated in S210 is less than the automatic brake 2 determination line (S230). If the collision time is less than the automatic brake 2 determination line (S230: YES), an automatic brake 2 operation command is generated (S240), and the operation determination process is terminated.

  If the collision time is equal to or longer than the automatic brake 2 determination line (S230: NO), it is determined whether the collision time calculated in S210 is less than the automatic brake 1 determination line (S250). If the collision time is less than the automatic brake 1 determination line (S250: YES), an automatic brake 1 operation command is generated (S260: warning control means), and the operation determination process ends.

If the collision time is equal to or longer than the automatic brake 1 determination line (S230: NO), the operation determination process is immediately terminated.
Next, in the arbitration process (S140) performed following the operation determination process, even if an operation instruction for operating the controlled object 40 is recorded in the RAM 13 in the operation determination process, collision avoidance is performed by the driver in S120. If the operation is recorded in the RAM 13, the arbitration process (S140) may prevent the controlled object 40 from being operated in the collision mitigation process.

  Specifically, in the operation determination process, if the operation instruction for the automatic brake 1 is recorded in the RAM 13 and the fact that the collision avoidance operation is performed by the driver is recorded in the RAM 13, the driver itself performs the collision avoidance. As a result, operating the controlled object 40 (brake) as the automatic brake 1 is prohibited. On the other hand, even if the operation instruction for the automatic brake 2 is recorded in the RAM 13 and the collision avoidance operation by the driver is recorded in the RAM 13, the collision cannot be avoided already. The controlled object 40 (brake) is operated.

  In other words, in the arbitration process, the operation of the automatic brake 1 may be canceled, but the process of continuing the operation of the automatic brake 2 is performed. As a result, in the operation control process (S150), when the collision can be avoided, the driver's operation is prioritized, and when the collision cannot be avoided, the controlled object 40 can be appropriately operated so as to reduce the damage of the collision. It becomes like this.

  Next, the operation control process will be described with reference to FIG. In the operation control process, first, in the operation determination process and the arbitration process, it is determined whether or not a request for operating the automatic brake 1 is set (S510). If this request is set (S510: YES), an acceleration gradient for decelerating the vehicle is set (acceleration gradient changing means) in the processing of S520 to S540.

That is, it is determined whether the normal braking avoidance lower limit time is longer than the automatic brake 1 determination line (S520). If the normal braking avoidance lower limit time is equal to or shorter than the automatic brake 1 determination line (S520: NO), the acceleration gradient is set to −10 [m / s ³ ] (S530), and the process proceeds to S550. If the normal braking avoidance lower limit time is larger than the automatic brake 1 determination line (S520: YES), the acceleration gradient is set to −20 [m / s ³ ] (S540), and the process proceeds to S550.

Subsequently, the acceleration (deceleration) of the automatic brake 1 is set based on the set acceleration gradient (S550: warning control means). When setting the acceleration (deceleration) in this process, for example, the target acceleration that is the upper limit of the absolute value of the acceleration when the controlled object 40 is operated is set to -2.45 [m / s ² ]. To do.

  The target acceleration may be changed according to the relationship between the normal braking avoidance lower limit time and the automatic brake 1 determination line, similarly to the acceleration gradient. Specifically, for example, when the normal braking avoidance lower limit time is longer than the automatic brake 1 determination line, the absolute value of the target acceleration is set larger than when the normal braking avoidance lower limit time is equal to or shorter than the automatic brake 1 determination line. You may make it do.

Then, the target set acceleration in the current process is set along the acceleration gradient −10 [m / s ³ ] or −20 [m / s ³ ].
That is, when the operation control process is started every 50 ms and the acceleration gradient is set to −10 [m / s ³ ], the set acceleration set in S550 is used every time the operation control process is performed. By −0.05 [m / s ² ]. When the operation control process is started every 50 ms and the acceleration gradient is set to −20 [m / s ³ ], the set acceleration set in S550 is used every time the operation control process is performed. Increase by -0.1 [m / s ² ].

  When the set acceleration reaches the target acceleration, it is fixed thereafter. In addition, the automatic brake 1 is released after the operation continuation time set in S420 or S430 has elapsed since the start of operation. That is, when the operation duration time elapses, the set acceleration is set to 0 thereafter.

  On the other hand, if the request for operating the automatic brake 1 is not set in S510 (S510: NO), it is determined whether or not the request for operating the automatic brake 2 is set (S560). If this request is set (S560: YES), the acceleration (deceleration) of the automatic brake 2 is set (S570).

When setting the acceleration (deceleration) in this process, for example, the target acceleration is set to −8 [m / s ² ] and the set acceleration is set along the acceleration gradient −20 [m / s ³ ]. Set. That is, when the operation control process is started every 50 ms, the set acceleration set in S570 is increased by −0.1 [m / s ² ] every time the operation control process is performed, and the setting is performed. When the acceleration reaches the target acceleration, it is fixed thereafter.

When the processing of S550 or S570 is thus completed, the brake is operated with the set acceleration (S580: warning control means), and the operation control processing is ended.
If the request for operating the automatic brake 2 is not set (S560: NO), the operation control process is immediately terminated.

  Next, the operation timing of PBA will be described with reference to FIG. FIG. 7 is a flowchart showing assist processing executed by the CPU 11 of the collision mitigation controller 10. The assist process corresponds to the assist control means in the present invention.

  The assist process is a process that is activated at a preset predetermined cycle (for example, every 50 ms), and is performed in parallel with the above-described collision mitigation process. In this assist process, first, the collision time and the normal braking avoidance lower limit time are acquired from the RAM 13 (S610, S620), and it is determined whether or not the collision time is less than the normal braking avoidance lower limit time (S630).

  If the collision time is less than the normal braking avoidance lower limit time (S630: YES), preparation for brake assist (operation for increasing the brake hydraulic pressure or bringing the brake pad close to the brake disc as described above) is performed (S640). ), The assist process ends. On the other hand, if the collision time is equal to or longer than the normal braking avoidance lower limit time (S630: NO), the assist process is terminated as it is.

  In the PCS 1 described in detail above, the CPU 11 of the collision mitigation controller 10 determines that when the collision time indicating the time until the host vehicle collides with the target object is less than the preset normal braking avoidance lower limit time. The braking force when operating the controlled object 40 by the driver's operation is increased. Then, when the collision time is less than the preset automatic brake 1 determination line, the CPU 11 operates the controlled object 40 for a preset duration. Further, when the collision time becomes less than the normal braking avoidance lower limit time, the CPU 11 changes the duration time longer.

That is, when the automatic brake 1 is operated, if the PBA operation timing has already been reached, the operation time of the automatic brake 1 is changed to be longer.
Therefore, according to such PCS1, when the automatic brake 1 is operated, if the operation timing of the CPU 11 of the collision mitigation controller 10 has already been reached, it is assumed that the possibility that the vehicle will collide is higher. Since the operation time of the vehicle can be lengthened, the speed of the vehicle can be further reduced during the automatic braking 1. Therefore, when the automatic brake 1 is operated, the driver can avoid the collision with a margin.

  Further, the CPU 11 is configured to operate the controlled object 40 so that the acceleration of the vehicle changes along a preset acceleration gradient. When the collision time is less than the normal braking avoidance lower limit time, the acceleration gradient is increased. Change to increase the slope.

  Therefore, according to such PCS1, since the inclination of the acceleration (deceleration) gradient when operating the automatic brake 1 can be increased, the speed of the vehicle can be further reduced during the automatic brake 1. . Therefore, when the automatic brake 1 is operated, the driver can avoid the collision with a margin.

Further, the CPU 11 detects the relative speed between the vehicle and the obstacle, and sets the normal braking avoidance lower limit time according to the relative speed.
Therefore, according to such PCS1, the normal braking avoidance lower limit time can be set to a different value depending on the relative speed. Therefore, when the alarm threshold is set by a function different from the normal braking avoidance lower limit time, such as when the automatic brake 1 determination line is set to a constant value as in the present embodiment, it depends on the relative speed. Since the magnitude relationship between the normal braking avoidance lower limit time and the automatic brake 1 determination line changes, the strength of the warning brake can be changed according to this magnitude relationship.

The embodiment of the present invention is not limited to the above-described embodiment, and can take various forms as long as it belongs to the technical scope of the present invention.
For example, in the above embodiment, in the assist process, the collision time and the normal steering avoidance lower limit time are acquired from the RAM 13, but each time may be obtained by calculation.

It is a block diagram which shows schematic structure of PCS1. It is a flowchart which shows a collision mitigation process. It is a flowchart which shows an operation | movement determination process. It is a flowchart which shows a threshold value calculation process (a) and a duration calculation process (b). It is a graph which shows the relationship between the relative speed [km / h] of the own vehicle and a target object, and setting time [s]. It is a flowchart which shows an operation control process. It is a flowchart which shows an assist process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... PCS, 10 ... Collision mitigation controller, 11 ... CPU, 12 ... ROM, 13 ... RAM, 31 ... Radar sensor, 32 ... Yaw rate sensor, 33 ... Wheel speed sensor, 40 ... Controlled object.

Claims (4)

A collision mitigation device for a vehicle, which is mounted on a vehicle and alleviates damage when the vehicle collides by operating a braking means for braking the vehicle,
Obstacle detection means for detecting obstacles located around the vehicle;
A collision time calculating means for calculating a collision time which is an expected time until the obstacle collides with the obstacle detected by the obstacle detecting means;
An assist control means for increasing a braking force when the braking means is operated by an operation of a driver of the vehicle when the collision time is less than a preset assist threshold;
Warning control means for operating the braking means for a preset duration when the collision time is less than a preset warning threshold;
When the collision time becomes less than the assist threshold, time changing means for changing the duration longer,
A collision mitigation device comprising: The warning control means is configured to operate the braking means so that the acceleration of the vehicle changes along a preset acceleration gradient,
The collision mitigation device according to claim 1, further comprising an acceleration gradient changing unit configured to change the gradient of the acceleration gradient so as to increase when the collision time becomes less than the assist threshold value. The warning control means is configured to set a target acceleration that is an upper limit of an absolute value of acceleration when the braking means is operated,
The collision mitigation device according to claim 1, further comprising an acceleration changing unit that changes the target acceleration so as to increase when the collision time becomes less than the assist threshold. A relative speed detecting means for detecting a relative speed between the vehicle and the obstacle;
Assist threshold setting means for setting the assist threshold according to the relative speed;
The collision mitigation device according to any one of claims 1 to 3, further comprising:

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