Vehicle collision avoidance system

Abstract

The present invention provides an improved collision avoidance device that can avoid a collision through automatic braking even if there is a risk of the vehicle colliding with an obstacle again after the automatic braking has ended. [Solution] A vehicle collision avoidance device 100 includes a driver assistance ECU 10, which is configured as a control unit that, based on the detection results of a target information acquisition device 18 as a target detection device, determines that there is a risk of the vehicle 102 colliding with an obstacle, and performs automatic braking to reduce the risk, wherein the driver assistance ECU 10 determines whether a specific condition is met, such that the accelerator opening due to the driver's driving operation is equal to or greater than a reference opening, when the automatic braking is completed, and when it is determined that the specific condition is met, it is configured to control the driving force of the vehicle so that the vehicle speed does not exceed the upper limit of the vehicle speed range in which automatic braking is performed.

Description

Technical Field

[0001] The present invention relates to a vehicle collision avoidance device for vehicles such as automobiles.

Background Art

[0002] As one of the vehicle collision avoidance devices for vehicles such as automobiles, when there is a risk of the host vehicle colliding with an obstacle, the risk of collision is reduced by automatic braking, and when it is determined that there is no risk of collision, the automatic braking is terminated. There is known a collision avoidance device configured as such.

[0003] For example, in Patent Document 1 below, when there is a risk of collision, the risk of collision is reduced by automatic braking, and when it is determined that the collision has been avoided, the engine driving force is controlled so as not to increase beyond a preset limit driving force. A configured collision avoidance device is described.

[0004] According to this type of collision avoidance device, it is possible to prevent the engine driving force from increasing beyond the preset limit driving force after the collision with the obstacle has been avoided, and thereby prevent the host vehicle from suddenly accelerating after the collision avoidance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] 〔Problems to be Solved by the Invention〕 When there is a risk of the host vehicle colliding with an obstacle, the driver may mistakenly keep pressing the accelerator pedal hard instead of the brake pedal. In that case, the accelerator opening suddenly increases and becomes fully open.

[0007] In conventional collision avoidance systems, such as the device described in Patent Document 1 above, once it is determined that a collision has been avoided, the system is controlled so that the engine drive force does not increase beyond a preset limit. However, when the engine drive force increases, the vehicle speed gradually increases, and the vehicle speed may become high against the driver's will.

[0008] In particular, if automatic braking to avoid a collision is not performed unless the vehicle speed is below a preset upper speed limit, then even if there is a risk of the vehicle colliding with an obstacle again, automatic braking may not be performed because the vehicle speed exceeds the upper speed limit, and the collision may not be avoided.

[0009] The present invention provides an improved collision avoidance device that can avoid a collision by automatically braking even if there is a risk of the vehicle colliding with an obstacle again after the automatic braking, which is performed when the vehicle speed is below the upper limit of the vehicle speed, has finished.

[0010] [Means for solving the problem and the effects of the invention] According to the present invention, a vehicle collision avoidance device (100) is provided, which includes at least a target detection device (target information acquisition device 18) for detecting a target in front of the vehicle (102), and a control unit (driving support ECU 10) configured to reduce the risk of collision by performing automatic braking (S50) when it is determined that the vehicle is likely to collide with an obstacle based on the detection results of the target detection device (S10).

[0011] The control unit (driving support ECU 10) determines whether a specific condition is met, such that the accelerator opening (A) due to the driver's driving operation is equal to or greater than the reference opening (Ac) when automatic braking is completed. If it determines that the specific condition is met (S60-S80), it controls the driving force (Fd) of the vehicle (102) so that the vehicle speed (V) of the vehicle does not exceed the upper limit vehicle speed (Vu) of the vehicle speed range in which automatic braking is performed (S90-S120).

[0012] According to the above-described driving control device, it is determined whether a specific condition is met at the end of automatic braking, namely, that the accelerator opening due to the driver's driving operation is equal to or greater than a standard opening. If it is determined that the specific condition is met, the driving force of the vehicle is controlled so that the vehicle speed does not exceed the upper limit of the vehicle speed range in which automatic braking is performed.

[0013] Therefore, if certain conditions are met when automatic braking ends, the vehicle's speed will not exceed the upper speed limit. Consequently, even if there is a risk of the vehicle colliding with an obstacle again after automatic braking has ended, if it is determined that there is a risk of the vehicle colliding with an obstacle, automatic braking will be executed, allowing the vehicle to slow down and avoid a collision with the obstacle.

[0014] [Aspects of the Invention] In one embodiment of the present invention, the control unit (driving support ECU 10) is configured to control the driving force of its own vehicle so as to limit the amount of temporal increase in the driving force when it determines that certain conditions are not met (S80, S130~S170).

[0015] According to the above embodiment, when it is determined that certain conditions are not met, the driving force of the vehicle is controlled so as to limit the amount of increase in driving force over time. Therefore, in situations where the driver has not mistakenly pressed the accelerator pedal hard instead of the brake pedal, the rate of increase in driving force after automatic braking has ended can be limited, thereby preventing a sudden increase in vehicle speed.

[0016] In another embodiment of the present invention, the control unit (driving support ECU 10) is configured to control the driving force so that the vehicle speed does not exceed the upper limit speed by limiting the amount of increase in the driving force over time (ΔFdl) such that the driving force of the vehicle (Fd) is less than the driving force based on the accelerator opening (A) when the vehicle speed of the vehicle (V) is less than a reference speed (Vre) which is lower than the upper limit speed (Vu), setting the amount of increase in the driving force over time to 0 when the vehicle speed of the vehicle is at the reference speed, and setting the amount of increase in the driving force over time to a negative value when the vehicle speed of the vehicle exceeds the reference speed (S90, S100).

[0017] According to the above embodiment, when the vehicle speed is below the reference speed, which is lower than the upper limit speed, the time increase in the driving force is limited so that the driving force of the vehicle is less than the driving force based on the accelerator opening. When the vehicle speed is at the reference speed, the time increase in the driving force is set to 0, and when the vehicle speed exceeds the reference speed, the time increase in the driving force is set to a negative value.

[0018] Therefore, the amount of increase in driving force over time can be controlled according to the relationship between the vehicle's speed and a reference speed lower than the upper limit speed. Consequently, it is possible to reliably prevent the vehicle's speed from exceeding the upper limit speed.

[0019] In another embodiment of the present invention, the control unit (driving support ECU 10) is configured to terminate automatic braking (S71, S72) when the vehicle remains stopped for a period of time longer than the termination reference time.

[0020] According to the above configuration, automatic braking is terminated when the vehicle remains stopped for a period longer than the termination time. Therefore, compared to the case where automatic braking is terminated when the vehicle is determined to be stopped, without determining the duration of the vehicle's stopped state, automatic braking can be terminated at a point when there is no longer any risk of the vehicle colliding with an obstacle.

[0021] In another aspect of the present invention, the control unit (driving support ECU 10) is configured to determine that a specific condition is satisfied (S90) when a situation where the accelerator opening degree is equal to or greater than the reference opening degree continues for a reference continuous time or longer.

[0022] According to the above aspect, it is determined that a specific condition is satisfied when a situation where the accelerator opening degree is equal to or greater than the reference opening degree continues for a reference continuous time or longer. Therefore, compared with the case where it is determined that a specific condition is satisfied without determining the continuous time of the situation where the accelerator opening degree is equal to or greater than the reference opening degree, it is possible to accurately determine the situation where the accelerator opening degree is equal to or greater than the reference opening degree.

[0023] In the above description, for the purpose of assisting the understanding of the present invention, names and / or symbols used in the embodiments corresponding to the embodiments to be described later are attached in parentheses to the configurations of the invention. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols attached in parentheses. Other objects, other features, and accompanying advantages of the present invention will be easily understood from the description of the embodiments of the present invention described while referring to the following drawings.

Brief Description of the Drawings

[0024] <第 <第 [Figure 1] It is a schematic configuration diagram showing an embodiment of a vehicle collision avoidance device according to the present invention. <第 <第 [Figure 2] It is a flowchart corresponding to a collision avoidance control program in the embodiment. <第0OO0092><第 [Figure 3] It is a graph corresponding to a map for calculating the restricted addition driving force ΔFdl based on the vehicle speed V in a situation where the accelerator opening degree A is equal to or greater than the reference opening degree Ac. <第 <第 [Figure 4] It is a graph corresponding to a map for calculating the restricted addition driving force ΔFdl based on the vehicle speed V in a situation where the accelerator opening degree A is less than the reference opening degree Ac. <第 <第 [Figure 5] It is a time chart showing an example of the operation of the embodiment in a situation where the accelerator opening degree A is equal to or greater than the reference opening degree Ac. [Figure 6] This is a time chart showing an example of the operation of the embodiment when the accelerator opening A is less than the reference opening Ac. [Modes for carrying out the invention]

[0025] A collision avoidance device according to an embodiment of the present invention will be described in detail below with reference to the attached figures.

[0026] As shown in Figure 1, the driving control device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driver assistance ECU 10. The vehicle 102 is a vehicle capable of autonomous driving and is equipped with a drive ECU 20, a brake ECU 30, and a meter ECU 50. ECU stands for Electronic Control Unit, which has a microcomputer as its main component. To distinguish the vehicle 102 from other vehicles, it is sometimes referred to as "our vehicle 102".

[0027] Each ECU's microcomputer includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU implements various functions by executing instructions (programs, routines) stored in ROM. Furthermore, these ECUs are interconnected via CAN (Controller Area Network) 104, enabling data exchange (communication). Therefore, detection values ​​from sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0028] The driver assistance ECU 10 is a central control unit that performs driving control for driver assistance, such as collision avoidance control, following distance control, and lane keeping control. In this embodiment, the driver assistance ECU 10 works in cooperation with other ECUs to perform driving control for the vehicle 102, as will be described in detail later. In the collision avoidance control of this embodiment, if the driver assistance ECU 10 determines that there is a possibility of collision between the vehicle and an obstacle located in front of the vehicle's direction of travel, it issues a warning to alert the vehicle of that possibility. The obstacle is an object that, if it collides with the vehicle, will cause damage to the vehicle and / or the other party, such as a stationary vehicle, a slow-moving preceding vehicle, or a pedestrian crossing the road.

[0029] Furthermore, if the driver assistance ECU 10 determines that the likelihood of collision between the vehicle and an obstacle has increased and there is a risk of collision, it will perform automatic braking to reduce that risk. Automatic braking is performed when the vehicle speed V is less than or equal to the upper limit speed Vu. Therefore, the upper limit speed Vu is the upper limit of the vehicle speed range in which automatic braking is performed.

[0030] The driver assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, and a setting control unit 16. The camera sensor 12 and radar sensor 14 each include multiple camera devices and multiple radar devices, respectively. The camera sensor 12 and radar sensor 14 function as a target information acquisition device 18 that acquires target information in front of the vehicle 102.

[0031] Each camera device of the camera sensor 12, although not shown in the figure, includes a camera unit that photographs the area around the vehicle 102 and a recognition unit that analyzes the image data obtained from the camera unit to recognize road markings, other vehicles, and other objects. The recognition unit supplies information about the recognized objects to the driver assistance ECU 10 at predetermined intervals.

[0032] Each radar device of the radar sensor 14 is equipped with a radar transceiver and a signal processing unit (not shown). The radar transceiver emits millimeter-wave 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, etc.) within the emission range. The signal processing unit supplies information representing the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, and the relative position (direction) of the three-dimensional object to the vehicle at predetermined intervals, based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from the transmission of the millimeter waves to the reception of the reflected waves. LiDAR (Light Detection And Ranging) may be used instead of or in addition to the radar sensor 14.

[0033] The setting control 16 is located in a position accessible to the driver, similar to a steering wheel (not shown in Figure 1), and is operated by the driver. Although not shown in Figure 1, the setting control 16 includes a collision avoidance switch. The driver assistance ECU 10 performs collision avoidance control when the collision avoidance switch is turned on, as will be described in detail later.

[0034] The drive ECU 20 is connected to a drive unit 22 that accelerates the vehicle 102 by applying driving force to the drive wheels 24. Normally, the drive ECU 20 controls the drive unit 22 so that the driving force generated by the drive unit 22 changes in accordance with the driver's driving operation, and when it receives a command signal from the driver assistance ECU 10, it controls the drive unit 22 based on the command signal.

[0035] The braking ECU 30 is connected to a braking device 32 that decelerates the vehicle 102 by applying braking force to the wheels 34. Normally, the braking ECU 30 controls the braking device 32 so that the braking force generated by the braking device 32 changes in accordance with the driver's braking operation. When it receives a command signal from the driver assistance ECU 10, it performs automatic braking by controlling the braking device 32 based on the command signal. As mentioned above, automatic braking to avoid collision with an obstacle is performed when the vehicle speed V is less than or equal to the upper limit vehicle speed Vu.

[0036] Therefore, the braking ECU 30 and the braking device 32 work together to function as an automatic braking device 36. When braking force is applied to the wheels due to driving control or other means, brake lights (not shown in Figure 1) illuminate.

[0037] The meter ECU 50 is connected to a touch-panel display 52 that displays the control status by the driver assistance ECU 10 and a warning device 54 that issues warnings. The display 52 may be, for example, a multi-information display that displays meters and various other information, or it may be a display for a navigation system. As described later, when the display 52 receives a signal from the driver assistance ECU 10, it displays the status of collision avoidance control.

[0038] The warning device 54 is activated when it is determined that vehicle 102 may collide with an obstacle and issues a warning that vehicle 102 may collide with an obstacle. The warning device 54 is also activated when it is determined that there is a risk that vehicle 102 may collide with an obstacle and issues a warning that there is a risk that vehicle 102 may collide with an obstacle. The warning device 54 may be a visual warning device such as a warning lamp, an auditory warning device such as a warning buzzer, or a tactile warning device such as seat vibration, or any combination thereof. The appeal of the warning that vehicle 102 may collide with an obstacle is higher than the appeal of the warning that vehicle may collide with an obstacle.

[0039] The driving operation sensor 60 and the vehicle condition sensor 70 are also connected to CAN 104. Information detected by the driving operation sensor 60 and the vehicle condition sensor 70 (referred to as sensor information) is transmitted to CAN 104. The sensor information transmitted to CAN 104 can be used as appropriate by each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to CAN 104 from that specific ECU.

[0040] The driving operation sensor 60 includes an accelerator opening sensor that detects the accelerator opening A (0 to 100%) as the amount of accelerator pedal operation, a braking operation amount sensor that detects the master cylinder pressure or the pedal force Fbp applied to the brake pedal, and a brake switch that detects whether or not the brake pedal is operated. The driving operation sensor 60 also includes a steering angle sensor that detects the steering angle, a steering torque sensor that detects the steering torque, and the like.

[0041] The vehicle state sensor 70 includes a vehicle speed sensor for detecting the vehicle speed V of the vehicle 102, a longitudinal acceleration sensor for detecting the longitudinal acceleration Gx of the vehicle, a lateral acceleration sensor for detecting the lateral acceleration of the vehicle, and a yaw rate sensor for detecting the yaw rate of the vehicle.

[0042] In this embodiment, the ROM of the driver assistance ECU 10 stores a collision avoidance control program corresponding to the flowchart shown in Figure 2. In this embodiment, the ROM of the driver assistance ECU 10 also stores maps corresponding to the graphs shown in Figures 3 and 4.

[0043] <Collision Avoidance Control> Next, the collision avoidance control routine in the embodiment will be described with reference to the flowchart shown in Figure 2. The control shown in the flowchart in Figure 2 is repeatedly executed at predetermined intervals by the CPU of the driver assistance ECU 10 when the collision avoidance support switch is ON.

[0044] First, in step S10, the CPU acquires information on the relative distance Lr between the vehicle and the obstacle, and the relative speed Vr of the vehicle relative to the obstacle, which are detected, for example, by the camera sensor 12 or the radar sensor 14. Furthermore, the CPU determines whether or not there is a risk of the vehicle colliding with the obstacle based on the relative distance Lr and the relative speed Vr. If a positive determination is made, the control proceeds to step S30; if a negative determination is made, the control proceeds to step S20.

[0045] The predicted collision time TTC, which is the predicted time until the vehicle collides with an obstacle, is calculated by dividing the relative distance Lr by the relative velocity Vr. When TTC is less than or equal to the first reference value TTC1 (a positive constant), it is determined that there is a risk of the vehicle colliding with an obstacle. The predicted collision time TTC is an indicator of the likelihood of the vehicle colliding with the preceding vehicle; the smaller the value, the higher the risk of the vehicle colliding with the preceding vehicle.

[0046] In step S20, the CPU determines whether the vehicle is likely to collide with an obstacle based on the relative distance Lr and the relative velocity Vr. If a negative determination is made, this control process ends; if a positive determination is made, this control process proceeds to step S40. Note that if TTC is less than or equal to the second reference value TTC2 (a positive constant greater than the first reference value TTC1), it is determined that the vehicle is likely to collide with an obstacle.

[0047] In step S30, the CPU determines whether the vehicle speed V detected by the vehicle speed sensor is less than or equal to the upper limit vehicle speed Vu (for example, a positive constant of 15 km / h). If the determination is positive, the control proceeds to step S50; if the determination is negative, the control proceeds to step S40.

[0048] In step S40, the CPU outputs a command signal to the meter ECU 50, which displays a warning on the display unit 52 indicating that the vehicle may collide with the preceding vehicle, and also activates the warning device 54 to issue a warning that the vehicle may collide with the preceding vehicle.

[0049] If a negative determination is made in step S30 and step S40 is executed, a warning indicating that the vehicle may collide with the preceding vehicle will be displayed on the display unit 52, and the warning device 54 will be activated to issue a warning indicating that the vehicle may collide with the preceding vehicle. The intensity of the warning when a negative determination is made in step S30 and step S40 is executed is higher than the intensity of the warning when an affirmative determination is made in step S20 and step S40 is executed.

[0050] In step S50, the CPU calculates a target deceleration Gbt for the vehicle to prevent it from colliding with the obstacle, based on the relative distance Lr between the vehicle 102 and the obstacle and the relative speed Vr of the vehicle with respect to the obstacle. Furthermore, the CPU outputs a command signal to the braking ECU 30 to decelerate the vehicle at the target deceleration Gbt, thereby executing automatic braking by the automatic braking device 36 so that the vehicle's deceleration becomes the target deceleration Gbt.

[0051] In step S60, the CPU determines whether or not to terminate the automatic braking to prevent the vehicle from colliding with an obstacle. If the determination is negative, the control returns to step S50; if the determination is positive, the control proceeds to step S70. The CPU may also determine that the automatic braking should be terminated if it is determined that the vehicle has been stopped for a period of time te (a positive constant) or longer, or if it is determined that there is no possibility of the vehicle colliding with an obstacle.

[0052] In step S70, the CPU determines whether the driver is performing drive operations while the vehicle is stationary. If a negative determination is made, this control process ends; if a positive determination is made, this control process proceeds to step S80. Note that if the accelerator opening A is a positive value other than 0, it may be determined that the driver is performing drive operations.

[0053] In step S80, the CPU determines whether the accelerator opening A remained at or above the reference opening Ac (100% or a positive constant close to 100%) for a reference time tc (a positive constant) or longer before and after the vehicle stopped. If a negative determination is made, the control proceeds to step S130; if an affirmative determination is made, the control proceeds to step S90. An affirmative determination is also made if the accelerator opening A remained at or above the reference opening Ac until the vehicle stopped, and the duration of that period was at or above the reference time tc. Furthermore, an affirmative determination is also made if the accelerator opening A remained at or above the reference opening Ac from the moment the vehicle stopped, and the duration of that period was at or above the reference time tc.

[0054] As can be seen from the above explanation, steps S60 to S80 are steps to determine whether a specific condition is met in which the accelerator opening A due to the driver's driving operation is equal to or greater than the reference opening Ac when automatic braking is terminated.

[0055] In step S90, the CPU calculates the limiting added driving force ΔFdl from the map corresponding to the graph shown in Figure 3, based on the vehicle speed V. As shown in Figure 3, when the vehicle speed V is greater than or equal to 0 and less than V1 (a positive constant), the limiting added driving force ΔFdl decreases from ΔFdl1 (a positive constant) to ΔFdl2 (a positive constant smaller than ΔFdl1) as the vehicle speed increases. When the vehicle speed V is greater than or equal to V1 and less than V2 (a positive constant larger than V1), the limiting added driving force ΔFdl is ΔFdl2 regardless of the vehicle speed, and when the vehicle speed V is greater than or equal to V2 and less than or equal to the reference vehicle speed Vre (a positive constant larger than V2 and smaller than the upper limit vehicle speed Vu), the limiting added driving force ΔFdl decreases from ΔFdl2 to 0 as the vehicle speed increases. Furthermore, the limited added driving force ΔFdl decreases from 0 as the vehicle speed increases (the absolute value increases with negative values) when the vehicle speed V is equal to or greater than the reference vehicle speed Vre.

[0056] In step S100, the CPU calculates the limited driving force Fdl as the sum of the previous value of the driving force Fdf and the limited added driving force ΔFdl, which is Fdf + ΔFdl. Furthermore, the CPU controls the driving force by outputting a command signal to the drive ECU 20 so that the driving force Fd of the vehicle becomes the limited added driving force Fdl.

[0057] In step S110, the CPU determines whether or not the driver is performing a drive operation, similar to step S70. If the determination is positive, the control returns to step S90; if the determination is negative, the control proceeds to step 120.

[0058] In step S120, the CPU terminates the control that limits the vehicle's driving force, that is, the control that limits the vehicle's driving force Fd to a limited driving force Fdl.

[0059] In step S130, the CPU calculates the driving force Fda based on the accelerator opening A in a manner known in the art. The driving force Fda increases as the accelerator opening A increases.

[0060] In step S140, the CPU calculates the limited added driving force ΔFdl from the map corresponding to the graph shown as a solid line in Figure 4, based on the vehicle speed V. As shown by the solid line in Figure 4, when the vehicle speed V is greater than or equal to 0 and less than V3 (a positive constant), the limited added driving force ΔFdl decreases from ΔFdl3 (a positive constant) to ΔFdl4 (a positive constant smaller than ΔFdl3) as the vehicle speed increases. When the vehicle speed V is greater than or equal to V3, the limited added driving force ΔFdl is ΔFdl4 regardless of the vehicle speed. Note that ΔFdl3 and ΔFdl4 may be the same as ΔFdl1 and ΔFdl2, respectively, and V3 may be the same as V1.

[0061] In step S150, the CPU calculates the limiting driving force Fdl as the sum of the previous value of the driving force Fdf and the limiting added driving force ΔFdl, which is Fdf + ΔFdl. Furthermore, the CPU determines whether the driving force Fda based on the accelerator opening A is greater than or equal to the limiting added driving force ΔFdl. If a negative determination is made, the control proceeds to step S170; if a positive determination is made, the control proceeds to step S160.

[0062] In step S160, the CPU outputs a command signal to the drive ECU 20, controlling the driving force so that the vehicle's driving force Fd becomes the limited driving force Fdl. In contrast, in step S170, the CPU outputs a command signal to the drive ECU 20, controlling the driving force so that the vehicle's driving force Fd becomes the driving force Fda based on the accelerator opening A.

[0063] <Example of operation of the embodiment> 1. When a positive judgment is made in step S80 (Figure 5) As shown in Figure 5, at time t1, the judgments in steps S10 and S30 are affirmative, and automatic braking begins. At time t2, the vehicle speed V becomes 0, and at time t3, automatic braking ends. The braking force Fb due to automatic braking increases sharply at time t1, becomes Fba from immediately after time t1 to time 3, becomes 0 immediately after time t3, and remains 0 thereafter. The driving force Fd of vehicle 102 begins to decrease sharply at time t1, and becomes 0 from immediately after time t1 to time 3. The above changes in vehicle speed V, braking force Fb, and driving force Fd are the same in Figure 6, which will be described later.

[0064] Assume that immediately before time t1, the driver mistakenly pressed the accelerator pedal instead of the brake pedal, causing the accelerator opening A to reach 100% before time t2, and that the accelerator opening A remains at 100% thereafter.

[0065] At time t3, the judgments in steps S60 and S70 become affirmative, an affirmative judgment is made in step S80, and steps S90 and S100 are repeatedly executed. Therefore, the increase in the driving force Fd of the vehicle 102 is limited by the limiting sum driving force ΔFdl calculated from the map corresponding to the graph shown in Figure 3. The vehicle speed V gradually increases from time t3 onward.

[0066] At time t4, if the vehicle speed V becomes the reference vehicle speed Vre, the limiting added driving force ΔFdl becomes 0. Immediately after time t4, the limiting added driving force ΔFdl becomes a negative value, and the driving force Fd decreases. Subsequently, as the vehicle speed V fluctuates above and below the reference vehicle speed Vre, the limiting added driving force ΔFdl fluctuates between negative and positive values, so the vehicle speed V is effectively maintained at the reference vehicle speed Vre.

[0067] Therefore, the vehicle speed V does not exceed the upper limit vehicle speed Vu, which is higher than the reference vehicle speed Vre. Consequently, even if an obstacle is again present in front of the vehicle 102, it is possible to prevent a negative judgment from being made in step S30 despite a positive judgment being made in step S10, and to prevent the automatic braking in step S50 from not being executed.

[0068] 2. If a negative determination is made in step S80 (Figure 6) As shown in Figure 6, the accelerator pedal is not pressed suddenly, and the accelerator opening A is assumed to be constant at Ae%. From time t3 onward, the judgments in steps S60 and S70 become affirmative, but a negative judgment is made in step S80. Therefore, steps S160 to S170 are executed, and the increase in the driving force Fd of the vehicle 102 is limited by the limiting sum driving force ΔFdl calculated from the map corresponding to the graph shown in Figure 4.

[0069] The driving force Fd and vehicle speed V of vehicle 102 gradually increase from time t3 onward. The vehicle speed V is assumed to be greater than the reference vehicle speed Vre from time t5 onward and greater than the upper limit vehicle speed Vu from time t6 onward. The limited driving force Fdl, which is the sum of the previous value of the driving force Fdf and the limited added driving force ΔFdl, is assumed to be greater than the driving force Fda based on the accelerator opening A from time t7 onward. The driving force Fd of vehicle 102 is controlled to be the limited driving force Fdl from time t3 onward and before time t7, and to be the driving force Fda based on the accelerator opening A from time t7 onward.

[0070] Therefore, even when the accelerator opening A is a large value, as long as it is smaller than the reference opening Ac, the increase in the vehicle's driving force Fd and vehicle speed V is suppressed, preventing a rapid increase in these values. Consequently, compared to the case where the increase in driving force Fd is not suppressed, the point in time t6 at which the vehicle speed V exceeds the upper limit vehicle speed Vu can be delayed, thereby delaying the point at which the negative determination is made in step S30. Consequently, the point at which the vehicle speed V exceeds the upper limit vehicle speed Vu and automatic braking for collision avoidance is no longer performed can be delayed. Furthermore, it is possible to prevent the driving force Fd from becoming greater than the driving force Fda based on the accelerator opening A.

[0071] In Figure 6, the accelerator opening A is constant, but even if the accelerator opening A fluctuates within a range smaller than the reference opening Ac, a negative determination is made in step S30. Therefore, the vehicle speed V, braking force Fb, and driving force Fd change in the same way as in Figure 6, except that they fluctuate in accordance with the fluctuation of the accelerator opening A.

[0072] <Examples of conventional collision avoidance control> For example, let's explain the operation of a conventional collision avoidance device, such as the one described in Patent Document 1, in the case where the driver mistakenly presses down hard on the accelerator pedal instead of the brake pedal.

[0073] In conventional collision avoidance systems, if a positive determination is made in step S60, steps S70 and S80 are skipped, and the same control as in step S130 and beyond is performed. Therefore, the driving force Fd of the vehicle 102 increases rapidly after time t3 to become the driving force Fda based on the accelerator opening A. As a result, as shown by the dashed line in Figure 5, the vehicle speed V increases rapidly after time t3, and the vehicle speed V at time t8 and beyond, which is earlier than time t4 and time t5 and t6 in Figure 6, becomes higher than the upper limit vehicle speed Vu. Therefore, even if an obstacle is again present in front of the vehicle 102 and a positive determination is made in step S10, a negative determination is made in step S20, and the automatic braking in step S50 is not performed. Consequently, it is not possible to avoid a collision with the obstacle by automatic braking.

[0074] As can be seen from the above explanation, according to the embodiment, when automatic braking is completed, it is determined whether a specific condition is met, namely that the accelerator opening A due to the driver's driving operation is equal to or greater than the reference opening Ac (S60~S80). If it is determined that the specific condition is met, the driving force Fd of the vehicle is controlled so that the vehicle speed V of the vehicle does not exceed the upper limit vehicle speed Vu of the vehicle speed range in which automatic braking is performed (S90~S120).

[0075] Therefore, if certain conditions are met when automatic braking ends, the vehicle's speed V will not exceed the upper limit speed Vu. Consequently, even if there is a risk of the vehicle colliding with an obstacle again after automatic braking has ended, if it is determined that there is a risk of the vehicle colliding with an obstacle, automatic braking will be executed, allowing the vehicle to decelerate and avoid a collision with the obstacle.

[0076] Furthermore, according to the embodiment, when it is determined that certain conditions are not met, the vehicle's driving force Fd is controlled so as to limit the temporal increase in driving force ΔFdl (S80, S130~S170). Therefore, in situations where the driver has not mistakenly pressed the accelerator pedal hard instead of the brake pedal, the rate of increase in driving force after automatic braking is completed is limited, thereby preventing a sudden increase in vehicle speed.

[0077] Furthermore, according to the embodiment, when the vehicle speed V of the vehicle is less than the reference vehicle speed Vre, which is lower than the upper limit vehicle speed Vu, the time increase amount ΔFdl of the driving force is limited so that the driving force Fd of the vehicle is less than the driving force Fda based on the accelerator opening. When the vehicle speed is the reference vehicle speed, the time increase amount of the driving force is set to 0, and when the vehicle speed exceeds the reference vehicle speed, the time increase amount of the driving force is set to a negative value.

[0078] Therefore, the temporal increase in driving force ΔFdl can be controlled according to the relationship between the vehicle speed V of the own vehicle and a reference vehicle speed Vre that is lower than the upper limit vehicle speed Vu. Consequently, it is possible to reliably prevent the vehicle speed V of the own vehicle from exceeding the upper limit vehicle speed Vu.

[0079] Furthermore, according to this embodiment, automatic braking is terminated when the vehicle remains stopped for a period of time te or longer. Therefore, compared to the case where automatic braking is terminated when it is determined that the vehicle has stopped, without determining the duration of the vehicle's stopped state, this embodiment allows for the automatic braking to be terminated at a point where there is no longer any risk of the vehicle colliding with an obstacle.

[0080] Furthermore, according to this embodiment, a specific condition is determined to be met when the situation in which the accelerator opening A is equal to or greater than the reference opening Ac continues for a reference duration tc or longer. Therefore, compared to the case where the situation in which the accelerator opening is equal to or greater than the reference opening is determined without determining the duration of that situation, it is possible to determine with accuracy that the situation in which the accelerator opening is equal to or greater than the reference opening is met.

[0081] Although the present invention has been described in detail above with respect to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described above, and that various other embodiments are possible within the scope of the present invention.

[0082] For example, in the embodiment described above, the limiting added driving force ΔFdl calculated from the map corresponding to the graph shown by the solid line in Figure 4 is a constant value of ΔFdl4 regardless of the vehicle speed when the vehicle speed V is V3 or greater. As shown by the dashed line in Figure 4, when the vehicle speed V is greater than V3 and lower than the reference vehicle speed Vre, and is V4 or greater but less than the reference vehicle speed Vre, the limiting added driving force ΔFdl decreases from ΔFdl4 to 0 as the vehicle speed increases, and may be 0 when the vehicle speed V is equal to or greater than the reference vehicle speed Vre.

[0083] According to this modified example, when the vehicle speed V is V4 or greater and less than the reference vehicle speed Vre, the rate of increase in driving force decreases as the vehicle speed increases, and when the vehicle speed V is greater than or equal to the reference vehicle speed Vre, the driving force does not increase even if the vehicle speed increases. Therefore, the time point t7 at which the limiting driving force Fdl, which is the sum of the previous value of the driving force Fdf and the limiting added driving force ΔFdl, becomes greater than the driving force Fda based on the accelerator opening A, can be made later than in the embodiment.

[0084] Furthermore, in the above-described embodiment, if a negative determination is made in step S80, that is, if it is determined that a specific condition is not met, steps S160 to S170 are executed. However, the limitation of the increase in the driving force Fd of the vehicle 102 when a negative determination is made in step S80 may be carried out in a manner other than steps S160 to S170.

[0085] Furthermore, in the above-described embodiment, when automatic braking is performed, the driving force Fd of the vehicle 102 is reduced to 0. However, the driving force Fd may be reduced to a value higher than 0, or the driving force may not be reduced at all. [Explanation of symbols]

[0086] 10…Driver assistance ECU, 12…Camera sensor, 14…Radar sensor, 18…Target information acquisition device, 22…Drive system, 32…Braking system, 36…Automatic braking system, 100…Collision avoidance system, 102…Vehicle

Claims

1. A collision avoidance device for a vehicle includes, at least, a target detection device that detects a target in front of the vehicle, and a control unit configured to reduce the risk of the vehicle colliding with an obstacle by performing automatic braking when it is determined, based on the detection results of the target detection device, The control unit is configured to determine whether a specific condition is met, such that the accelerator opening angle due to the driver's driving operation is equal to or greater than a reference opening angle, when the automatic braking is terminated, and if it is determined that the specific condition is met, it controls the driving force of the vehicle so that the vehicle speed does not exceed the upper limit of the vehicle speed range in which the automatic braking is performed.

2. A collision avoidance device for a vehicle according to claim 1, wherein the control unit is configured to control the driving force of the vehicle such that the amount of temporal increase in the driving force is limited when it determines that the specific condition is not met.

3. A collision avoidance device for a vehicle according to claim 1, wherein the control unit is configured to control the driving force so that the vehicle speed does not exceed the upper limit speed by limiting the amount of temporal increase of the driving force so that the driving force of the vehicle is less than the driving force based on the accelerator opening when the vehicle speed of the vehicle is less than the reference vehicle speed which is lower than the upper limit vehicle speed, setting the amount of temporal increase of the driving force to 0 when the vehicle speed of the vehicle is the reference vehicle speed, and setting the amount of temporal increase of the driving force to a negative value when the vehicle speed of the vehicle exceeds the reference vehicle speed.

4. A collision avoidance device for a vehicle according to claim 1, wherein the control unit is configured to terminate the automatic braking when the vehicle remains stopped for a period of time longer than the termination reference time.

5. A collision avoidance device for a vehicle according to claim 1, wherein the control unit is configured to determine that the specific condition is met when the situation in which the accelerator opening is equal to or greater than the reference opening continues for a reference duration or longer.

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