COLLISION PREVENTION DEVICE

Abstract

A collision avoidance device includes a driver assistance ECU configured to determine the risk of a collision between the vehicle and an obstacle when it is determined that the obstacle is in front of the vehicle, based on information acquired by a target object information acquisition device that acquires information about a target object around the vehicle, and to execute countermeasures control that reduces the risk when it is determined that the risk is present.The driver assistance ECU performs at least one of the following actions: changing a condition for determining risk so that it can be more easily determined that the risk exists, or causing a greater effect of countermeasures control when it is determined that the obstacle is a vehicle ahead that is temporarily stopping and the vehicle ahead has started moving.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a collision prevention device that reduces the risk of a collision of an own vehicle with an obstacle. 2. Description of the related art

[0002] As a collision avoidance device for a vehicle such as an automobile, a collision avoidance device is known that determines a risk that the vehicle collides with an obstacle when the obstacle is detected in front of the vehicle, and executes countermeasure control such as autonomous braking that reduces the risk when it is determined that the risk exists.

[0003] For example, Japanese Unexamined Patent Application Laid-Open No. 11-039597 (JP 11-039597 A) described below describes a collision avoidance device that detects a preceding vehicle in front of the own vehicle based on an image taken by an in-vehicle camera, determines the possibility of a collision between the own vehicle and the preceding vehicle, and informs a driver by displaying a determination result on a display.

[0004] According to the collision prevention device, even if there is an obstacle in front of the vehicle and there is a danger of the vehicle colliding with the obstacle, the danger of collision with the obstacle can be reduced because countermeasure control such as autonomous braking and notification of a possible collision is performed. SUMMARY OF THE INVENTION

[0005] For example, if your vehicle is following a vehicle in front, the following will happen: If a traffic light turns red and the vehicle in front and your vehicle temporarily stop before the traffic light, the traffic light then turns green and the vehicle in front starts moving, your vehicle will also start moving afterward. However, if the vehicle in front brakes quickly or stops immediately after starting due to a traffic jam in front of the vehicle in front or something similar, the distance between your vehicle and the vehicle in front will quickly decrease, increasing the risk of your vehicle colliding with the rear of the vehicle in front.

[0006] In the collision avoidance device according to the related art, such as the collision avoidance device described in JP 11-039597 A, a situation in which the distance between the own vehicle and the preceding vehicle decreases rapidly is not taken into account, and therefore it is difficult to reduce the risk of collision of the own vehicle with the preceding vehicle in such a situation.

[0007] The present invention is a collision prevention device which is more likely to be able to reduce the risk of collision of the own vehicle with a preceding vehicle in a situation where the distance between the own vehicle and the preceding vehicle decreases rapidly, compared with the related prior art.

[0008] According to the present invention, there is provided a collision avoidance device (100) comprising: a target object information acquisition device (17) that acquires information about a target object in the vicinity of a host vehicle (102); and a control unit (drive support ECU 10) configured to determine a risk of collision of the host vehicle with an obstacle (S80, S100) when it is determined that the obstacle is present in front of the host vehicle based on the information acquired by the target object information acquisition device (S20), and to execute countermeasure control that reduces the risk (S90, S110) when it is determined that the risk is present.

[0009] The control unit (driver assistance ECU 10) is configured to perform at least one of the following: changing a condition for determining the risk so that the presence of the risk can be more easily determined, or causing a higher effect of the countermeasure control (S70) when it is determined that the obstacle is a preceding vehicle (114) that temporarily stops (S230) and the preceding vehicle has started moving (S250).

[0010] According to the device described above, at least one of the following measures is carried out: changing a condition for determining the risk so that the existence of the risk can be determined more easily, or causing a higher effect of the countermeasure control when it is determined that the obstacle is a preceding vehicle that is temporarily stopped and the preceding vehicle has started moving.

[0011] When the risk determination condition is changed, the existence of the risk is easier to determine, and countermeasure control is therefore initiated earlier. Therefore, the risk of the vehicle colliding with the rear of the vehicle in front can be effectively reduced compared to a case where the risk determination condition is not changed. Countermeasure control is effectively executed when the effect of countermeasure control is higher. Therefore, the risk of the vehicle colliding with the rear of the vehicle in front can be effectively reduced compared to a case where the effect of countermeasure control is not higher.

[0012] In one aspect of the present invention, the control unit (driver assistance ECU 10) may be configured to determine (S40) a distance (Lr) between the host vehicle and the preceding vehicle (114) based on the information acquired by the target object information acquisition device (17) and determine that the risk exists (S80, S100) when the distance is equal to or smaller than a reference distance (Lrc1, Lrc2), and the control unit is further configured to change the condition for determining the risk by correcting the reference distance to be increased (S70) when it is determined that the preceding vehicle has started to move (S250).

[0013] According to the above-described aspect, when it is determined that the preceding vehicle has started moving, the reference distance is corrected to increase it, and it is easier to determine that the distance between the own vehicle and the preceding vehicle is equal to or less than the reference distance. Therefore, the risk determination condition can be changed to make it easier to determine that there is a risk of collision.

[0014] In another aspect of the present invention, the countermeasure control may include autonomous braking (S110) that autonomously brakes the own vehicle, and the control unit (driver assistance ECU 10) may be configured to cause a higher effect of the countermeasure control by increasing a braking degree of the autonomous braking (S70) when it is determined that the preceding vehicle has started moving (S250).

[0015] According to the above-described aspect, when it is determined that the preceding vehicle has started moving, the braking degree of autonomous braking is corrected to increase, and the braking of the own vehicle is effectively performed. Therefore, the effect of countermeasure control that reduces the risk of collision can be enhanced.

[0016] In a further aspect of the present invention, the control unit (driver assistance ECU 10) may be configured to terminate the at least one execution (S300) when a period of time elapsed from a time at which it is determined that the risk exists is equal to or greater than a reference time (Tc).

[0017] According to the aspect described above, the at least one execution is terminated if the time elapsed since the time at which the risk is determined to exist is equal to or greater than the reference time. This can reduce the risk that the at least one execution will last too long.

[0018] In a further aspect of the present invention, the control unit (driver assistance ECU 10) may be configured to terminate the at least one execution (S300) when a travel distance of the own vehicle from a time at which the presence of the risk is determined is equal to or greater than a reference travel distance (Lvc).

[0019] According to the aspect described above, the at least one execution ends when the driving distance of the own vehicle from the time at which the risk is determined to exist is equal to or greater than the reference driving distance. This can reduce the risk that the at least one execution lasts too long.

[0020] In the above description, other objects, other features and attendant advantages of the present invention can be easily understood from the description of the embodiment of the present invention described with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Features, advantages and technical and industrial significance of embodiments of the invention are described below with reference to the accompanying drawings, in which like characters designate like elements and in which: Fig. 1 is a schematic configuration diagram showing a collision prevention device according to an embodiment; Fig. 2 is a flowchart corresponding to a collision prevention control program in this embodiment; Fig. 3 is a flowchart corresponding to a flag control program in this embodiment; Fig. 4 is a view showing a situation in which a traffic light at an intersection is red, a preceding vehicle is stopped, and the own vehicle is stopped behind the preceding vehicle; Fig. 5 is a view showing a situation in which the traffic light at the intersection has turned green, the vehicle in front has started moving, and the own vehicle has stopped; and Fig. 6 is a view showing a situation in which the preceding vehicle has started moving and the own vehicle has started moving immediately thereafter, but the preceding vehicle has quickly decelerated or stopped immediately after starting due to a traffic jam of vehicles in front of the preceding vehicle and the like. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] A collision prevention device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] As in Fig. As shown in Figure 1, a collision avoidance device 100 according to the embodiment of the present invention is applied to a vehicle 102 and includes a driving assistance ECU 10. The vehicle 102 is a vehicle capable of autonomous driving and includes a drive ECU 20, a brake ECU 30, and a meter ECU 50. The term "ECU" refers to an electronic control unit (ECU) that includes a microcomputer as its main component. The vehicle 102 will be referred to as "own vehicle 102" when necessary.

[0024] The microcomputer of each ECU includes a CPU, a ROM, a RAM, a readable and writable non-volatile memory (N / M), an interface (I / F), and the like. The CPU performs various functions by executing an instruction (a program, a routine) stored in the ROM. These ECUs are interconnected so that data can be exchanged (communicated) via a Controller Area Network (CAN) 104. Therefore, a detection value and the like of a sensor (including a switch) connected to a particular ECU are also transmitted to other ECUs.

[0025] The driving assistance ECU 10 is a central device that performs driving assistance control, such as collision avoidance control, adaptive cruise control, and lane keeping control. In the embodiment described in detail later, the driving assistance ECU 10 executes collision avoidance control for the vehicle 102 by cooperating with other ECUs. The subsequent adaptive cruise control is abbreviated as ACC.

[0026] A camera sensor 12, a radar sensor 14, a sonar device 16, and a setting operator 18 are connected to the driving assistance ECU 10. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices, and the sonar device 16 includes a plurality of sonars. The camera sensor 12, the radar sensor 14, and the sonar device 16 function as a target information acquisition device 17 that acquires target information about the surroundings of the vehicle 102.

[0027] Each device of the camera sensor 12 is not shown in the drawings, but includes a camera unit that photographs the surroundings of the vehicle 102, and a detection unit that detects target objects such as other vehicles and a white line on a road by analyzing the image data captured and obtained by the camera unit. The detection unit provides information about the detected target object to the driver assistance ECU 10 every predetermined period.

[0028] Each radar device of the radar sensor 14 includes a radar transceiver unit and a signal processing unit (not shown). The radar transceiver unit transmits radio waves in the millimeter wave band (hereinafter referred to as "millimeter waves") and receives millimeter waves (in other words, reflected waves) reflected from a three-dimensional object (e.g., another vehicle, a bicycle, and the like) within a transmission range.The signal processing unit provides information including the distance between the host vehicle and the three-dimensional object, the relative speed of the host vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the host vehicle, and the like to the driving assistance ECU 10 at predetermined intervals based on a phase difference between the transmitted millimeter waves and the received reflected waves, an attenuation level of the reflected waves, the time required to receive the reflected waves when the millimeter waves are transmitted, and the like. A LiDAR (Light Detection and Ranging) sensor can be used instead of the radar sensor 14 or in addition to the radar sensor 14.

[0029] The sonar device 16 includes a plurality of sonars, and these sonars are mounted at a plurality of positions in an outer peripheral region of the vehicle 102, for example, at a left front end, a right front end, a left rear end, and a right rear end. Each sonar is configured to transmit ultrasonic waves in a direction separate from the vehicle 102, receive ultrasonic waves transmitted by its own sonar and reflected by an object (in other words, direct waves), and receive ultrasonic waves transmitted by another sonar and reflected by the object (in other words, indirect waves). Each sonar is configured to output a signal to the controller of the sonar device 16 indicating a peak value of the received voltage corresponding to the received ultrasonic waves.

[0030] If the peak value is equal to or greater than a reference value, the controller of the sonar device 16 determines that a corresponding sonar device is currently receiving the ultrasonic waves. The device for controlling the sonar device 16 estimates the distance between the vehicle 102 and the object that reflected the direct waves and the indirect waves, as well as the direction of the object relative to the vehicle, based on the travel time of the direct waves and the indirect waves.

[0031] The adjustment operator 18 is mounted in a position that can be operated by a driver, such as a steering wheel that is in Fig. 1 is not shown and is operated by the driver. Although in Fig. 1, the setting device 18 includes a driving assistance switch. As described in detail later, the driving assistance ECU 10 executes collision avoidance control when the driving assistance switch is turned on.

[0032] A drive device 22 that accelerates the vehicle 102 by applying a driving force to the drive wheels 24 is connected to the drive ECU 20. The drive ECU 20 controls the drive device 22 so that a driving force generated by the drive device 22 changes in accordance with a driving operation by the driver at normal times, and, when a command signal is received from the driving assistance ECU 10, controls the drive device 22 based on the command signal.

[0033] A braking device 32, which decelerates the vehicle 102 by applying braking force to the wheels 34, is connected to the brake ECU 30. The brake ECU 30 performs autonomous braking by controlling the braking device so that a braking force generated by the braking device 32 changes in accordance with a braking operation by the driver at normal times, and, when a command signal is received from the driving support ECU 10, controls the braking device 32 based on the command signal.

[0034] Therefore, the brake control unit 30 and the device 32 function as an autonomous braking device 36 by cooperating with each other. When a braking force is applied to the wheels by the collision prevention control and the like, a Fig. 1 brake light not shown.

[0035] A touchscreen-type display device 52, which displays the control status of the driving assistance ECU 10 and the like, and an alarm device 54, which issues an alarm, are connected to the measurement ECU 50. The display 52 may be a multi-information display on which, for example, measurements and various information are displayed, or a display of a navigation device 80 described later. As described later, the display 52 displays the collision avoidance control status when the display 52 receives a signal from the driving assistance ECU 10.

[0036] The device 54 is activated when it is determined that there is a risk of the vehicle 102 colliding with an obstacle and issues an alarm that serves as one of the collision prevention controls. In other words, it issues an alarm indicating that there is a risk of the vehicle 102 colliding with an obstacle. The alarm device 54 may be any device that issues a visual alarm, such as an alarm lamp, an alarm device that issues an audible alarm, such as an alarm buzzer, an alarm device that issues a sensory alarm, such as the vibration of a seat, or any combination thereof.

[0037] A driving operation sensor 60 and a vehicle condition sensor 70 are also connected to CAN 104. Information (referred to as sensor information) detected by the driving operation sensor 60 and the vehicle condition sensor 70 is transmitted to CAN 104. The sensor information transmitted to CAN 104 can be used in each control unit as needed. The sensor information is information from a sensor connected to a specific control unit, and it can be transmitted from the respective control unit to CAN 104.

[0038] The driving operation sensor 60 includes a driving operation quantity sensor that detects an operation quantity of an accelerator pedal, a braking operation quantity sensor that detects a master cylinder pressure or a pedal force on a brake pedal, and a brake switch that detects whether the brake pedal is being operated. The driving operation sensor 60 includes a steering angle sensor that detects a steering angle, a steering torque sensor that detects a steering torque, and the like.

[0039] The vehicle state sensor 70 includes a vehicle speed sensor that detects a vehicle speed V of the vehicle 102, a front-rear acceleration rate sensor that detects an acceleration rate of the vehicle in the front-rear direction, a lateral acceleration rate sensor that detects an acceleration rate of the vehicle in the lateral direction, a yaw rate sensor that detects a yaw rate of the vehicle, and the like.

[0040] The navigation device 80 is also connected to the CAN 104. The navigation device 80 includes a GPS receiver that detects the position of the vehicle 102, a storage device that stores map information and road information therein, and a communication device that acquires the latest information about the map information and road information from the outside. Specifically, the road information may include information about the position where the vehicle may temporarily stop, such as an intersection, a T-junction, and a pedestrian crossing. The navigation device 80 may not necessarily be mounted.

[0041] In the embodiment, the ROM of the driving assistance ECU 10 stores a collision prevention control program according to the Fig. 2. In the embodiment, the ROM of the driving assistance ECU 10 stores a flag control according to the flow chart shown in Fig. 3 flowchart shown. Collision prevention control (FIG. 2)

[0042] Next, the control for avoiding collisions in the embodiment will be described with reference to the Fig. 2. The control for preventing collisions according to the flow chart shown in Fig. 2 is repeatedly executed every predetermined period of time by the CPU of the driving assistance control device 10 in a situation where the driving assistance switch is turned on.

[0043] First, in step S10, the CPU determines whether the vehicle speed V of the vehicle 102 is equal to or less than a reference value Vc (positive constant) of the low vehicle speed determination. The present control proceeds to step S30 if an affirmative determination is made, and the present control proceeds to step S20 if a negative determination is made, in other words, the vehicle is traveling at a medium and high speed.

[0044] In step S20, the CPU executes pre-crash safety control (hereinafter referred to as PCS control) in a manner known in the current technical field. In PCS control, a collision risk of the own vehicle with the preceding vehicle is determined based on the distance between the own vehicle and the preceding vehicle and the relative speed of the own vehicle with respect to the preceding vehicle, which is detected, for example, by the camera sensor 12 or the radar sensor 14. If it is determined that there is a collision risk, the collision is prevented by issuing an alarm from the alarm device 54 and decelerating the own vehicle through autonomous braking by the autonomous braking device 36.

[0045] In step S30, the CPU determines whether an obstacle is present in front of the vehicle 102 based on the information about a target object in front of the vehicle 102 detected by the sonar device 16 or the radar sensor 14 of the target object information detecting device 17. The present control temporarily ends when a negative determination is made, and the present control proceeds to step S40 when an affirmative determination is made.

[0046] In step S40, the CPU calculates a distance Lr between the vehicle 102 and the obstacle and a relative speed Vr of the vehicle 102 with respect to the obstacle based on the information about the target object in front of the vehicle 102 detected by the sonar device 16 or the radar sensor 14.

[0047] In step S50, the CPU calculates a target stopping distance Lst such that the target stopping distance Lst becomes larger as, for example, a ratio Lr / Vr of the distance Lr to the relative speed Vr becomes smaller. The target stopping distance Lst is a target value of a stopping distance Ls, where the distance Lr between the vehicle 102 and the obstacle when the vehicle 102 has stopped by autonomous braking is the stopping distance Ls. The CPU calculates a target braking degree Gbt of the vehicle 102 to cause the stopping distance Ls to be the target stopping distance Lst based on the current distance Lr, the target stopping distance Lst, and the current vehicle speed V. The target braking degree Gbt is calculated such that it becomes larger as the relative speed Vr becomes higher and larger as a difference Lr-Lst between the distance Lr and the target stopping distance Lst becomes smaller.

[0048] In step S60, the CPU determines whether a flag Fa set according to a Fig. 3 and described later, is 1, in other words, it is determined that the preceding vehicle, which was temporarily stopped, has started moving. The present control proceeds to step S80 when a negative determination is made, and the present control proceeds to step S70 when an affirmative determination is made.

[0049] In step S70, the CPU corrects the target braking rate Gbt to be increased by correcting the target stopping distance Lst to be increased. The CPU corrects the first and second reference distances Lrc1 and Lrc2, respectively, used in the determination in step S80 and the determination in step S100 described later, to increase them. The first reference distance Lrc1 is greater than the second reference distance Lrc2. Therefore, the risk determination conditions in steps S80 and S100 are changed so that it is easier to determine that there is a risk of the host vehicle colliding with an obstacle.

[0050] The increase correction can be performed by multiplying by a correction coefficient greater than 1 or by adding corresponding correction amounts (positive constants). The increase correction of the target braking rate Gbt can be performed without correcting the target stopping distance Lst to be increased. A notification indicating that the alarm issuance and autonomous braking are initiated earlier can be made by issuing a command signal to the ECU of the meter 50 and activating the display 52.

[0051] In step S80, the CPU determines whether the distance Lr between the vehicle 102 and the obstacle is equal to or less than the first reference distance Lrc1, in other words, whether there is a risk of the vehicle 102 colliding with the obstacle. The present control temporarily ends when a negative determination is made, and the present control proceeds to step S90 when a positive determination is made.

[0052] In step S90, the CPU issues an alarm indicating that there is a risk of the vehicle 102 colliding with an obstacle by outputting a command signal to the meter ECU 50 and activating the alarm device 54. The CPU issues a notification indicating that there is a risk of the vehicle 102 colliding with an obstacle by outputting a command signal to the counter ECU 50 and activating the display device 52.

[0053] In step S100, the CPU determines whether the distance Lr between the vehicle 102 and the obstacle is equal to or less than the second reference distance Lrc2. The present control temporarily ends when a negative determination is made, and the present control proceeds to step S110 when a positive determination is made.

[0054] In step S110, the CPU executes autonomous braking so that the braking degree of the vehicle reaches the target braking degree Gbt by activating the autonomous braking device 36 and applying a braking force to the vehicle 102 and by reducing the driving force of the driving device 22 by outputting command signals to the driving ECU 20 and the braking ECU 30.

[0055] As apparent from the above description, the countermeasure control for reducing the risk of the vehicle colliding with an obstacle in the present embodiment is autonomous braking, which is performed by issuing an alarm by activating the alarm device 54, reducing the driving force of the driving device 22, and applying the braking force of the autonomous braking device 36. However, the countermeasure control may be omitted. Flag control (FIG. 3)

[0056] Next, the flag control in the embodiment will be explained with reference to the Fig. 3 is described. The flag control according to the flow chart shown in Fig. The flowchart shown in Figure 3 is repeatedly executed by the CPU of the drive assistance ECU 10 every predetermined period of time when the drive assistance switch is turned on. The flags Fa and Fb are reset to 0 at the start of flag control.

[0057] First, in step S210, the CPU determines whether the flag Fa is 1, that is, it determines whether the preceding vehicle, which was temporarily stopped, has started moving. The present control proceeds to step S280 if an affirmative determination is made, and the present control proceeds to step S220 if a negative determination is made.

[0058] In step S220, the CPU determines whether a flag Fb is 1, in other words, whether it has already been determined that there is a preceding vehicle temporarily stopped in front of the own vehicle in step S230 described later. The present control proceeds to step S250 when an affirmative determination is made, and the present control proceeds to step S230 when a negative determination is made.

[0059] In step S230, the CPU determines, based on information acquired by the target object information acquisition device 17 and the like, whether the vehicle speed V of the host vehicle is equal to or lower than the vehicle speed reference value Vs and whether there is a preceding vehicle temporarily stopped in front of the host vehicle. The present control temporarily ends when a negative determination is made, and the flag Fb is set to 1 in step S240, and the present control then proceeds to step S250 when the positive determination is made.

[0060] The vehicle speed reference value Vs is a reference value for determining an extremely low vehicle speed and is a positive constant smaller than the low vehicle speed determination reference value Vc used in the determination in step S10. The determination in step S230 may be the determination of whether the subject vehicle is temporarily stopped and whether there is a preceding vehicle that is temporarily stopped in front of the subject vehicle.

[0061] In step S250, the CPU determines whether the preceding vehicle that was temporarily stopped has started moving. The present control temporarily ends if a negative determination is made, and the present control proceeds to step S260 if a positive determination is made.

[0062] In step S260, the CPU variably sets a reference time period Tc and a reference travel distance Lvc, which are used in the determination of step S280 and the determination of step S290 described later, respectively, in accordance with at least one of the type of the road ahead, the positions at which the host vehicle and the preceding vehicle are temporarily stopped, and the congestion degree of the vehicles.

[0063] When the road ahead is an intersection or a T-junction, the reference time Tc and the reference travel distance Lvc can be set longer because the road intersecting the road on which the own vehicle is traveling has a wider width and a larger number of lanes. When the road ahead is a road with a crosswalk or a stop line, the reference time Tc and the reference travel distance Lvc can be set to smaller values ​​than in a case where the road ahead has an intersection or a T-junction. The reference time Tc and the reference travel distance Lvc can be set to a longer value as the degree of congestion of the vehicles ahead of the own vehicle increases.

[0064] In step S270, the CPU sets the flag Fa to 1 and resets the flag Fb to 0.

[0065] In step S280, the CPU determines whether the time period elapsed from the time at which it is determined in step S80 that there is a risk of collision of the vehicle 102 with an obstacle is equal to or greater than the reference time Tc. The present control proceeds to step S300 if an affirmative determination is made, and the present control proceeds to step S290 if a negative determination is made. The elapsed time period may be the time period elapsed from the time at which it is determined in step S100 that there is a risk of collision of the vehicle 102 with an obstacle.

[0066] In step S290, the CPU determines whether a travel distance of the vehicle from the time point at which it was determined in step S80 that there is a danger of collision of the vehicle 102 with an obstacle is equal to or greater than the reference travel distance Lvc. The present control is temporarily terminated when a negative determination is made. If the affirmative determination is made, the flag Fa is reset to 0 in step S300, and the present control is then temporarily terminated. The travel distance may be the travel distance from a time point at which it is determined in step S100 that there is a danger of collision of the vehicle 102 with an obstacle. Activation and effects of the embodimentWhen the vehicle in front and the own vehicle are stopped (FIG. 4)

[0067] Fig. For example, Fig. 4 is a view showing a situation in which a traffic light 112 at an intersection 110 is red, a preceding vehicle 114 is stationary, and the own vehicle 102 is behind the preceding vehicle. In the case of the Fig. In the situation shown in Figure 4, a negative determination is made in steps S210 and S220 and an affirmative determination is made in step S230, and therefore the flag Fb is set to 1 in step S240. A negative determination is made in step S250, and therefore steps S260 and S270 are not executed.

[0068] Therefore, the flag Fa is still 0. Therefore, a negative determination is made in step S60, and step S70 is not executed. Therefore, the first and second reference distances Lrc1 and Lrc2 are not corrected to increase, and the target braking rate Gbt is also not corrected to increase. The determination in steps S80 and S100 is made by maintaining both the first and second reference distances Lrc1 and Lrc2 at a standard value. When the vehicle in front starts moving (FIG. 5)

[0069] Fig. Figure 5 shows a situation in which the traffic light 112 of the intersection 110 turns green, the preceding vehicle 114 has started moving and the own vehicle 102 has stopped. In the case of the Fig. The situation shown in Figure 5 is as in the case of Fig. 4, first, a negative determination is made in steps S210 and S220, and an affirmative determination is made in step S230, and therefore, the flag Fb is set to 1 in step S240. If an affirmative determination is made in step S250, the reference time Tc and the reference travel distance Lvc are set according to the type of the road ahead in step S260, the flag Fa is set to 1 in step S270, and the flag Fb is reset to 0.

[0070] Therefore, in step S60, an affirmative determination is made, and step S70 is executed. As a result, the first and second reference distances Lrc1 and Lrc2 are corrected to be increased. In other words, the conditions for determining the risk in steps S80 and S100 are changed so that it is easier to determine that there is a risk of the host vehicle colliding with an obstacle. As a result, the determination in step S80 and the determination in step S100 are respectively performed using the first and second reference distances Lrc1 and Lrc2 that have been corrected to be increased, and therefore the affirmative determination is made earlier compared to the case where the first and second reference distances are standard values. If the vehicle in front brakes or stops quickly immediately after starting (FIG. 6)

[0071] Fig. 6 shows a situation in which the preceding vehicle 114 has started moving and the own vehicle 102 has started moving immediately thereafter, but the preceding vehicle 114 cannot move due to a traffic jam of vehicles in front of the preceding vehicle and the like. braked or stopped quickly immediately after starting. In a situation such as that described in Fig. 6, the distance between the host vehicle 102 and the preceding vehicle 114 decreases rapidly, and thus the risk of the host vehicle colliding with the rear of the preceding vehicle increases.

[0072] However, according to the embodiment, as described above, the determination in steps S80 and S100 becomes an affirmative determination earlier compared to a case where the first and second reference distances are standard values, and therefore, the issuance of an alarm in step S90 and the autonomous braking in step S110 are started earlier. Therefore, the risk of the own vehicle colliding with the rear of the preceding vehicle can be effectively reduced compared to a related art in which the first and second reference distances Lrc1 and Lrc2 are not corrected to be increased.

[0073] According to the embodiment, not only are the first and second reference distances Lrc1 and Lrc2 increased, but the target braking degree Gbt is also increased, so that the host vehicle can be decelerated with a high braking degree. Therefore, the risk of the host vehicle colliding with the rear of the preceding vehicle can be effectively reduced compared to a related art in which the target braking degree Gbt is not increased.

[0074] According to the embodiment, the execution of the countermeasure control (S80 and S100) for reducing the risk of the vehicle colliding with a preceding vehicle as an obstacle (S300) ends when the time period elapsed from the time it is determined that there is a risk of the vehicle 102 colliding with an obstacle is equal to or greater than the reference time Tc (S280). Thus, the risk of the countermeasure control being executed for an excessively long period of time can be reduced.

[0075] According to the embodiment, the execution of the countermeasure control for reducing the risk of the vehicle colliding with a preceding vehicle as an obstacle (S300) ends when the vehicle's travel distance from the time it is determined that the vehicle 102 is at risk of colliding with an obstacle is equal to or greater than the reference travel distance Lvc (S290). Thus, the risk of the countermeasure control being executed for an excessively long period of time can also be reduced by the above-mentioned measures.

[0076] According to the embodiment, in step S260, the period of the reference time Tc and the reference travel distance Lvc are variably set depending on the type of road ahead of the positions where the vehicle and the preceding vehicle were temporarily stopped and / or the degree of vehicle congestion. Therefore, the risk that the countermeasure control is executed for too long a period of time and the risk that the period for which the countermeasure control is executed is insufficient can be reduced compared to a case where the reference time Tc and the reference travel distance Lvc are constant. Step S260 may be omitted. In other words, the period of the reference time Tc and the reference travel distance Lvc may be constant.

[0077] The present invention has been described in detail above for a specific embodiment, but the present invention is not limited to the embodiment described above, and it will be obvious to those skilled in the art that other various embodiments are possible within the scope of the present invention.

[0078] For example, in the above-described embodiment, the target braking rate Gbt and the first and second reference distances Lrc1 and Lrc2 are corrected to increase in step S70. However, it is also possible to perform the increase correction only for the target braking rate Gbt or only for the first and second reference distances Lrc1 and Lrc2.

[0079] In the above-described embodiment, in step S280, it is determined whether the elapsed time is equal to or greater than the reference time Tc, and in step S290, it is determined whether the vehicle travel distance is equal to or greater than the reference travel distance Lvc. However, step S280 or S290 may be omitted. In this case, the setting (step S260) of the reference time Tc or the reference travel distance Lvc according to the omitted determination is omitted.

[0080] In the above-described embodiment, the effect of the alarm, which is one of the countermeasure controls, is not increased even when the flag Fa is 1. However, when the flag Fa is 1, the responsive effect of the alarm can be increased. For example, if the alarm is triggered by an intermittent sound of a buzzer, the buzzer sound can be changed from an intermittent sound to a continuous sound.

[0081] In the embodiment described above, the countermeasure control is implemented by issuing an alarm and autonomous braking of the vehicle. However, the countermeasure control may also be either issuing an alarm or autonomous braking of the vehicle. In this case, the effect of the countermeasure control can be set higher than in the case where the countermeasure control consists of issuing an alarm and autonomous braking of the vehicle. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 11-039597

[0003] JP 11-039597 A [0003, 0006]

Claims

[1] Collision prevention device comprising: a target object information acquisition device that acquires information about a target object around a self-vehicle; and a control unit configured to determine, on the basis of the information acquired by the target object information acquisition device, a risk that the host vehicle will collide with an obstacle when it is determined that the obstacle exists in front of the host vehicle, and to execute countermeasure control that reduces the risk when it is determined that the risk exists, wherein the control unit is arranged to carry out at least one of the following actions: changing a condition for determining the risk so that it can be more easily determined that the risk exists, or causing an effect of the countermeasure control to be higher if it is determined that the obstacle is a preceding vehicle that is temporarily stopped and the preceding vehicle has started moving. [2] A collision prevention device according to claim 1, wherein: the control unit is configured to obtain a distance between the host vehicle and the preceding vehicle on the basis of the information acquired by the target object information acquisition device and to determine that the risk exists when the distance is equal to or less than a reference distance; and the control unit is further configured to change the condition for determining the risk by correcting it by increasing the reference distance when it is detected that the vehicle in front has started moving. [3] A collision prevention device according to claim 1, wherein: the countermeasure control includes autonomous braking, which brakes the own vehicle autonomously; and the control unit is configured to effect a higher countermeasure control effect by correcting by increasing a braking degree of the autonomous braking when it is determined that the preceding vehicle has started moving. [4] The collision avoidance device according to claim 1, wherein the control unit is configured to terminate the at least one execution when a time period elapsed from a time point at which it was determined that the risk exists is equal to or greater than a reference time period. [5] The collision avoidance device according to claim 1, wherein the control unit is configured to terminate the at least one execution when a travel distance of the own vehicle from a time point at which it is determined that the risk exists is equal to or greater than a reference travel distance.

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