JP7658260B2 - Damage mitigation device in the event of a rear-end collision - Google Patents

Description

The present invention relates to a rear-end collision damage reduction device that reduces damage when a vehicle such as an automobile is rear-ended.

As one type of driving support device for vehicles such as automobiles, a rear-end collision damage mitigation device that reduces damage when the vehicle is rear-ended by another vehicle is known. For example, the following Patent Document 1 describes a rear-end collision damage mitigation device that is configured to execute rear-end collision damage mitigation control that activates automatic brakes when the possibility of a rear-end collision is determined while the vehicle is stopped.

This type of rear-end collision damage mitigation device automatically activates the brakes when it is determined that a rear-end collision is likely to occur while the vehicle is stopped, reducing the risk of the vehicle colliding secondary with an obstacle ahead of the vehicle as a result of the vehicle moving forward in a rear-end collision.

JP 2000-355273 A

[Problem to be solved by the invention]
However, in a vehicle equipped with a rear-end collision damage mitigation device, the rear-end collision damage mitigation control may be executed unnecessarily, causing the automatic brake to be unnecessarily activated. For example, when a vehicle is washed in a self-propelled car wash (a car wash in which the vehicle is automatically moved relative to a fixed car wash device) or when the vehicle is serviced in a maintenance shop, the vehicle may be moved by a conveyor belt or rollers. In such cases, the shift position is set to N range, and braking by the foot brake or the like is not applied.

In such a situation, if it is erroneously determined that an object in the vicinity of the vehicle, such as a car wash or another vehicle, is approaching the vehicle from behind, the automatic brakes will be activated unnecessarily. This may cause the vehicle to derail from a conveyor belt or collide with another vehicle being transported from behind on the conveyor belt.

To prevent unnecessary automatic braking as described above, it is conceivable to prohibit automatic braking as long as the shift position is set to N range, regardless of whether the brakes are applied or not. However, in that case, even if the shift position is set to N range and the vehicle is stationary and another vehicle approaches from behind and there is a possibility of a rear-end collision, the automatic brake cannot be activated, and damage in the event of a rear-end collision cannot be mitigated.

The main objective of the present invention is to provide an improved rear-end collision damage mitigation device that can reduce damage in the event of a rear-end collision and prevent the automatic brakes from being activated unnecessarily during car washing with a self-propelled car wash or maintenance at a repair shop.

[Means for solving the problems and effects of the invention]
According to the present invention, there is provided a rear-end collision damage reduction device (100) including a surrounding information detection device (camera sensor 12, radar sensor 14) that detects information about the surroundings of a vehicle (102), and a control device (such as a vehicle control ECU 10) that activates automatic brakes (S60) when the surrounding information detection device detects an object approaching from behind the vehicle and determines that there is a possibility that the object will rear-end the stopped vehicle (S40).

The control device is configured to prohibit operation of the automatic brake (S250, S50) even if it determines that there is a possibility of an object rear-ending the vehicle (S10 to S40), when the shift position is in N range (S210) and no braking force is being applied by the driver's operation (S220 to S240).

Generally, when the vehicle is temporarily stopped, for example, at a traffic light, the shift position is set to D range and braking force is applied by operating the brake pedal, the shift position is switched to P range, or braking force is applied by the parking brake. Therefore, when the vehicle is temporarily stopped, operation of the automatic brake is not prohibited. Therefore, when another vehicle approaching from behind the stopped vehicle is detected and it is determined that there is a possibility that the other vehicle will collide with the stopped vehicle, the automatic brake is activated, thereby reducing the risk of the vehicle colliding secondary with an obstacle in front of the vehicle due to the vehicle moving forward in the collision.

In addition, when the vehicle is moved by a conveyor belt or rollers during a car wash using a self-propelled car wash or during maintenance at a maintenance shop, the shift position is set to N range and no braking force is applied by the driver's operation. According to the above-mentioned configuration, even if it is determined that there is a possibility that an object will rear-end the vehicle, when the shift position is in N range and no braking force is applied by the driver's operation, the automatic brake is prohibited from operating . Therefore , even if it is erroneously determined that an object or another vehicle in the vicinity of the vehicle is approaching the vehicle from behind, the automatic brake is not activated. Therefore, it is possible to prevent the vehicle from running off the conveyor belt or colliding with another vehicle being transported from behind by the conveyor belt due to unnecessary activation of the automatic brake.

Note that "braking force is not applied by driver's operation" means that in the case of a vehicle that does not have brake hold control, braking force is not applied by operating the brake pedal or the parking brake. Also, in the case of a vehicle that has brake hold control, "braking force is not applied by driver's operation" means that braking force is not applied by operating the brake pedal, the parking brake, or the brake hold. Furthermore, in the case of a vehicle that has a manual transmission rather than an automatic transmission, the condition "the shift position is in N range" may be ignored.

In the above description, in order to aid in understanding the present invention, the names and/or symbols used in the embodiments described below are added in parentheses to the configuration of the invention corresponding to the embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and/or symbols added in parentheses. Other objects, other features, and associated advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the drawings.

1 is a schematic diagram showing an embodiment of a rear-end collision damage mitigation control device according to the present invention; 5 is a flowchart showing a rear-end collision damage mitigation control routine in the embodiment. 5 is a flowchart showing a control routine for determining whether or not automatic braking is performed in the embodiment. This shows a situation in which the host vehicle and the preceding vehicle are stopped, and another vehicle is approaching from behind the host vehicle. This shows a situation in which the host vehicle and the preceding vehicle are stopped, and another vehicle approaching the host vehicle from behind stops.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

<Configuration>
As shown in Fig. 1, a collision damage reduction device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a vehicle control ECU 10. The vehicle 102 includes a brake ECU 20, a Shift-by-Wire (SBW) ECU 30, and a meter ECU 40. The ECU stands for an electronic control unit having a microcomputer as a main component. In the following description, the vehicle 102 will be referred to as the host vehicle 102 as necessary in order to distinguish it from other vehicles.

The microcomputer of each ECU includes a CPU, ROM, RAM, a readable/writable non-volatile memory (N/M), and an interface (I/F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are connected to each other via a Controller Area Network (CAN) 50 so that they can exchange data (communicate). Therefore, the detection values of sensors (including switches) connected to a specific ECU are also sent to the other ECUs.

A plurality of camera sensors 12F, 12B, 12R, and 12L and a plurality of radar sensors 14F, 14B, 14R, and 14L are connected to the vehicle control ECU 10. The plurality of camera sensors 12F, 12B, 12R, and 12L are referred to as "camera sensors 12" when there is no need to distinguish between them. Similarly, the plurality of radar sensors 14F, 14B, 14R, and 14L are referred to as "radar sensors 14" when there is no need to distinguish between them. The camera sensors 12 and radar sensors 14 function as surrounding information acquisition devices that acquire information about the surroundings of the vehicle 102.

Although not shown in the figure, the camera sensor 12 includes a camera unit and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and other vehicles. The recognition unit of the camera sensor 12 supplies information about the recognized targets to the vehicle control ECU 10 at predetermined time intervals. Note that a LiDAR (Light Detection And Ranging) may be used instead of the camera sensor 12.

Camera sensor 12F is a front camera sensor that captures an image in front of vehicle 102, and camera sensor 12B is a rear camera that captures an image behind vehicle 102. Camera sensor 12R is a right side camera that captures an image on the right side of vehicle 102, and camera sensor 12L is a left side camera that captures an image on the left side of vehicle 102.

The radar sensor 14 includes a radar transmission/reception unit and a signal processing unit (not shown). The radar transmission/reception unit emits millimeter wave band radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by three-dimensional objects (e.g., other vehicles, bicycles, guardrails, etc.) within the emission range. The signal processing unit acquires information (hereinafter referred to as surrounding information) indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, etc., based on the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from transmitting the millimeter wave to receiving the reflected wave, and supplies this information to the vehicle control ECU 10 at predetermined time intervals.

Radar sensor 14F is provided at the front end of vehicle 102 and acquires surrounding information in front of the vehicle. Radar sensor 14B is provided at the rear end of vehicle 102 and acquires surrounding information behind the vehicle. Radar sensor 14R is provided on the right side of vehicle 102 and acquires surrounding information on the right side of the vehicle. Radar sensor 14L is provided on the left side of vehicle 102 and acquires surrounding information on the left side of the vehicle.

Furthermore, a vehicle speed sensor 16 is connected to the vehicle control ECU 10. The vehicle speed sensor 16 detects the vehicle speed V by detecting the wheel speed of each wheel, and supplies a signal indicating the vehicle speed V to the vehicle control ECU 10.

The brake ECU 20 is connected to a braking device 22, a parking brake device 24, a pressure sensor 26 that detects the master cylinder pressure Pm, and a brake hold switch 28. In FIG. 1, the parking brake device is indicated as a PB device, and the brake hold switch is indicated as a BH switch. Although not shown in detail in FIG. 1, the braking device 22 includes a brake actuator and a braking force generating mechanism.

Under normal circumstances, the brake ECU 20 generates a braking force according to the amount of braking operation by the driver by controlling the braking force generating mechanism via the brake actuator based on the master cylinder pressure Pm, and therefore based on the driver's operation of the brake pedal (not shown). In addition, the brake ECU 20 can execute automatic braking that generates a braking force without the driver's braking operation by controlling the braking force generating mechanism in response to instructions from the vehicle control CU 10.

The parking brake device 24 may be a mechanical parking brake device that is activated by operating a foot pedal or a parking lever, or may be an electric parking brake device that is activated by operating a parking brake switch. When activated, the parking brake device 24 applies a braking force to the wheels to keep the vehicle 102 stationary. When the parking brake device 24 is activated, a display 42 (described below) indicates that the parking brake device 24 is activated.

Furthermore, when the brake hold switch 28 is on and the vehicle 102 is stopped by braking, the brake ECU 20 controls the braking force generating mechanism to execute brake hold control that maintains the braking force even if the driver releases the braking operation. Also, when the brake hold control is being executed, the brake ECU 20 releases the brake hold control if the driver performs a predetermined release operation, such as a drive operation. Note that while the brake hold control is being executed, a display 42, described below, displays that fact.

As can be seen from the above explanation, when the driver operates the brake pedal, foot pedal, parking lever, etc., a braking force is applied, and when the vehicle 102 is stopped, the stopped state is maintained so that the vehicle does not move. Conversely, when the driver does not operate the brake pedal, foot pedal, parking lever, etc., no braking force is applied.

The SBW-ECU 30 is connected to a shift position sensor 32 and an automatic transmission 34, and in FIG. 1, the shift position sensor is indicated as an SP sensor. The shift position sensor 32 detects the position (shift position) of a shift lever not shown in FIG. 1. The positions of the shift lever include N range (neutral position), P range (parking position), D range (forward position), and R range (reverse position). The SBW-ECU 30 receives information on the position of the shift lever from the shift position sensor 32, and controls the gear ratio and shift range of the automatic transmission 34 based on that position (i.e., performs shift control). The automatic transmission 34 may be either a gear-type automatic transmission or a continuously variable transmission.

The meter ECU 40 is connected to a display 42 and brake lights 44. The meter ECU 40 displays information related to various vehicle controls, including collision damage mitigation control, on the display 42 in accordance with a display command from the vehicle control ECU 10. The display 42 is, for example, a head-up display or a multi-information display that displays meters and various information. In addition, the meter ECU 40 turns on the brake lights 44 when a brake switch provided on a brake pedal (not shown in FIG. 1) is on, i.e., when the driver is applying the brakes.

In this embodiment, the ROM of the vehicle control ECU 10 stores a program for rear-end collision damage mitigation control corresponding to the flowchart shown in FIG. 2, and the CPU executes rear-end collision damage mitigation control in accordance with the program. The ROM of the vehicle control ECU 10 also stores a program for automatic braking feasibility control corresponding to the flowchart shown in FIG. 3, and the CPU executes automatic braking feasibility control in accordance with the program. The vehicle control ECU 10 may also perform various driving assistance controls known in the art, such as lane departure prevention control and constant speed driving control, when the vehicle 102 is traveling.

<Routine for reducing damage caused by rear-end collision>
Next, a rear-end collision damage mitigation control routine in this embodiment will be described with reference to the flowchart shown in Figure 2. The rear-end collision damage mitigation control according to the flowchart shown in Figure 2 is started by the CPU of the vehicle control ECU 10 when the vehicle speed V detected by the vehicle speed sensor 16 becomes 0 with the ignition switch (not shown) on, and is repeatedly executed at a predetermined control period. In the following description, the rear-end collision damage mitigation control will be simply referred to as "control". Note that flags Fa and Fb, which will be described later, are each reset to 0 when the control is started.

First, in step S10, the CPU determines whether or not there is another vehicle following behind the host vehicle 102 and whether or not the other vehicle is approaching the host vehicle. If the CPU determines that the other vehicle is not following the host vehicle, the control proceeds to step S80. If the CPU determines that the other vehicle is following the host vehicle, the control proceeds to step S20.

In step S20, the CPU calculates a collision prediction time TTC, which is a predicted time until another vehicle will collide with the host vehicle 102. The collision prediction time TTC is calculated according to the following formula (1) based on the distance Dr between the host vehicle and the other vehicle and the relative speed Vr of the other vehicle with respect to the host vehicle (= the vehicle speed of the other vehicle). The collision prediction time TTC is an index that indicates the likelihood that another vehicle will collide with the host vehicle 102, and the smaller the value, the higher the likelihood (risk) of the other vehicle colliding with the host vehicle.
TTC=Dr/Vr...(1)

In step S30, the CPU determines whether flag Fa is 1, that is, by executing step S60 described below, determines whether automatic braking has already started. If the CPU makes a positive determination, it advances control to step S90, and if the CPU makes a negative determination, it advances control to step S40.

In step S40, the CPU determines whether the collision prediction time TTC is equal to or less than the automatic brake start threshold TTCs (a positive constant), i.e., whether there is a high possibility that another vehicle will collide with the host vehicle 102. If the CPU makes a negative determination, it temporarily ends control, and if the CPU makes a positive determination, it advances control to step S50.

In step S50, the CPU judges whether or not the flag Fb is 1 , that is, whether or not automatic braking for mitigating damage from a rear-end collision is prohibited. If the CPU judges yes , the CPU temporarily ends the control, and if the CPU judges no , the control proceeds to step S60. The flag Fb is set to 0 or 1 by the automatic braking permission/prohibition judgment control executed according to the flowchart shown in FIG.

In step S60, the CPU outputs an automatic braking start command to the brake ECU 20 to start automatic braking, which generates a braking force without the driver's braking operation, and in step S70, sets flag Fa to 1. When automatic braking has started and is being executed, the display 42 displays that fact.

In step S80, the CPU determines whether flag Fa is 1, in the same way as in step S30, that is, whether automatic braking has already started. If the CPU determines that the flag is 1, it advances control to step S100, and if the CPU determines that the flag is 1, it temporarily terminates control.

In step S90, the CPU determines whether or not the automatic braking termination condition is satisfied. If the CPU determines that the automatic braking termination condition is satisfied, the CPU temporarily terminates the control. If the CPU determines that the automatic braking termination condition is satisfied, the CPU advances the control to step S100. In this case, if any of the following E1 to E4 is satisfied, the automatic braking termination condition is determined to be satisfied.
E1: Flag Fb is 1 (automatic braking is prohibited).
E2: The collision prediction time TTC is equal to or greater than the end threshold TTCe of the automatic brake (a positive constant greater than the start threshold TTCs).
E3: The shift position has been switched to D range.
E4: The vehicle speed V is equal to or greater than a reference value Ve (a positive constant).

In step S100, the CPU outputs an automatic braking end command to the brake ECU 20 to end the automatic braking, and in step S110, resets the flag Fa to 0. This causes the display 42 to erase the indication that automatic braking is being performed.

<Automatic braking feasibility determination control routine>
Next, an automatic braking feasibility determination control routine in this embodiment will be described with reference to the flowchart shown in Figure 3. The automatic braking feasibility determination control according to the flowchart shown in Figure 3 is also started by the CPU of the vehicle control ECU 10 when the vehicle speed V detected by the vehicle speed sensor 16 becomes 0 with the ignition switch (not shown) on, and is repeatedly executed at a predetermined control period. In the following description, the automatic braking feasibility determination control will be simply referred to as "feasibility determination control."

First, in step S210, the CPU determines whether the position of the shift lever detected by the shift position sensor 32 is in the N range. If the CPU determines that the shift lever is in the N range, the CPU advances the feasibility determination control to step S260, and if the CPU determines that the shift lever is in the N range, the CPU advances the feasibility determination control to step S220.

In step S220, the CPU determines whether the brake lamps 44 are on. If the CPU makes a positive determination, it advances the feasibility determination control to step S260, and if the CPU makes a negative determination, it advances the feasibility determination control to step S230.

In step S230, the CPU determines whether the parking brake device 24 is activated. If the CPU determines that the parking brake device 24 is activated, the CPU advances the determination control to step S260. If the CPU determines that the parking brake device 24 is activated, the CPU advances the determination control to step S240.

In step S240, the CPU determines whether brake hold control is being executed. If the CPU determines that the brake hold control is being executed, the CPU advances the execution control to step S260. If the CPU determines that the brake hold control is being executed, the CPU advances the execution control to step S250.

In step S250, the CPU sets flag Fb to 1 to prohibit automatic braking control to mitigate the damage caused by a rear-end collision, and in step S260, sets flag Fb to 0 to permit automatic braking.

<Example of operation of the embodiment>
Next, the operation of the embodiment will be described with reference to FIG. 4 and FIG. 5 in the case where another vehicle 106 approaches from behind the host vehicle 102 while the host vehicle 102 and the leading vehicle 104 are stopped.

Figure 4 shows a situation in which another vehicle 106 is approaching from behind the vehicle 102 at a relative speed Vr (= the speed of the other vehicle) and the collision prediction time TTC calculated according to the above formula (1) is equal to or less than the automatic brake initiation threshold TTCs. It is assumed that the shift lever is in the N range and braking force is being applied by the driver's operation, i.e., braking force is being applied by operating the brake pedal, braking force is being applied by operating the parking brake device, or braking force is being applied by brake hold control.

In this situation, a positive determination is made in step S210, and a positive determination is made in any of steps S220 to S240, so flag Fb is set to 0 in step S260. Note that flag Fb is also set to 0 if the position of the shift lever is in a range other than N range, and no braking force is being applied by operating the brake pedal, by operating the parking brake device, or by brake hold control.

Therefore, positive and negative determinations are made in steps S10 and S30 , respectively , positive and negative determinations are made in steps S40 and S50, respectively , and automatic braking is started in step S60, thereby executing automatic braking. Therefore, even if the following vehicle 106 collides into the host vehicle 102 from behind and the host vehicle moves forward, the risk of the host vehicle causing a secondary collision with the leading vehicle 104 in front of the host vehicle can be reduced.

Figure 5 shows a case where the following vehicle 106 stops behind the host vehicle 102 without colliding with it. In this case, the vehicle speed of the other vehicle 106 decreases, so that the relative speed Vr becomes very small, and the collision prediction time TTC becomes equal to or greater than the automatic braking termination threshold TTCe. Therefore, positive determinations are made in steps S10, S30, and S90, and the automatic braking is terminated in step S100. Therefore, once the leading vehicle 104 starts moving, the host vehicle 102 can also start moving without any problems.

Next, although not shown in the figure, the operation of the embodiment will be described for a case in which the vehicle 102 is moved by a conveyor belt or rollers during a car wash using a self-propelled car wash or during maintenance at a maintenance shop.

When washing the car in a self-propelled car wash or when maintenance is being done at a repair shop, the shift position is set to N range, and braking force is not applied by the driver's operation, i.e., by operating the brake pedal, by operating the parking brake device, or by brake hold control.

Therefore, although a positive determination is made in step S210, a negative determination is made in all of steps S220 to S240, so that in step S250, flag Fb is set to 1 and operation of the automatic brake is prohibited. Therefore, even if it is erroneously determined in step S10 that an object or another vehicle in the vicinity of the vehicle 102 is approaching the vehicle from behind and a positive determination is made in step S40, a positive determination is made in step S50 and step S60 is not executed, so that the automatic brake is not operated. Therefore, it is possible to prevent the vehicle 102 from running off a belt conveyor or colliding with another vehicle being carried from behind by a belt conveyor due to unnecessary operation of the automatic brake.

Although the present invention has been described in detail above with respect to a specific embodiment, the present invention is not limited to the above-described embodiment, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present invention.

For example, in the above embodiment, the vehicle 102 is equipped with a brake hold switch 28, and when the vehicle 102 is stopped by braking, brake hold control is executed to maintain the braking force even if the driver releases the braking operation. However, the rear-end collision damage reduction device 100 of the present invention may be applied to a vehicle in which brake hold control is not executed. In that case, step S240 in the flowchart shown in FIG. 3 is omitted. Therefore, the requirement for prohibiting the operation of the automatic brake, "no braking force is applied by the driver's operation", means that braking force is not applied by operating the brake pedal and braking force is not applied by operating the parking brake.

In the above embodiment, when it is determined in step S40 of the flowchart shown in FIG. 2 that the collision prediction time TTC is equal to or less than the automatic braking start threshold TTCs, it is determined that there is a high possibility that another vehicle will collide with the vehicle 102 from the rear. However, when it becomes equal to or less than TTCw (a positive constant) that is greater than the automatic braking start threshold TTCs, an alarm may be issued by activating an alarm device (not shown in the figure).

In addition, in the above embodiment, the surrounding information detection device that detects information about the surroundings of the vehicle 102 is the camera sensor 12 and the radar sensor 14, but one of the camera sensor 12 and the radar sensor 14 may be omitted.

In addition, in the above embodiment, the control for determining whether or not to apply automatic braking according to the flowchart shown in FIG. 3 is executed as a separate control from the control for mitigating damage caused by a rear-end collision according to the flowchart shown in FIG. 2. However, the control for determining whether or not to apply automatic braking may be modified so that it is executed as part of the control for mitigating damage caused by a rear-end collision, for example, at a stage prior to step S50.

Furthermore, in the above embodiment, the vehicle 102 is equipped with the SBW ECU 30 and the shift position sensor 32 and automatic transmission 34 connected thereto. However, the rear-end collision damage mitigation device 100 of the present invention may be applied to a vehicle whose transmission is a manual transmission. In that case, step S210 in the flowchart shown in FIG. 3 is omitted. Therefore, the requirement for prohibiting the operation of the automatic brake, "the shift position is in N range and," is omitted.

10...vehicle control ECU, 12...camera sensor, 14...radar sensor, 16...vehicle speed sensor, 20...brake ECU, 22...braking device, 24...parking brake device, 26...pressure sensor, 28...brake hold switch, 30...SBW ECU, 32...shift position sensor, 34...automatic transmission, 40...meter ECU, 42...display, 44...brake lamp, 100...rear-end collision damage reduction device, 102...vehicle, 104...preceding vehicle, 106...other following vehicle

Claims (1)

A rear-end collision damage mitigation device including a surrounding information detection device that detects information about the surroundings of a vehicle, and a control device that activates an automatic brake when the surrounding information detection device detects an object approaching the vehicle from behind and determines that the object may rear-end the vehicle that is stopped,
The control device is configured to prohibit the operation of the automatic brake when it determines that an object may rear-end the vehicle, but when the shift position is in N range and braking force is not applied by the driver's operation, the control device is configured to prohibit the operation of the automatic brake when the object determines that the vehicle may rear-end the vehicle, and when the shift position is in N range and braking force is not applied by the driver's operation, the rear-end collision damage mitigation device is configured.

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