Vehicle control device and control method

Abstract

This reduces secondary collision damage in the event that your vehicle is rear-ended while stopped. [Solution] A vehicle control device that acquires the relative relationship between the vehicle and an object target located within a predetermined range in the direction of travel of the vehicle, and performs automatic brake control to automatically stop the vehicle when it is determined that the risk of collision between the vehicle and the object target is at or above a predetermined level based on the acquired relative relationship, and when it is determined that the risk of a rear-end collision by a following vehicle approaching from behind is at or above a predetermined level while the vehicle is stopped due to the execution of automatic brake control, it performs automatic steering control to steer the wheels of the vehicle in order to change the direction of travel of the vehicle in the event of a rear-end collision with the following vehicle, based on first information of whether or not there is an obstacle in front of the vehicle, second information of whether or not there is an obstacle diagonally in front of the vehicle, and third information including the curvature of the road on which the vehicle is stopped.

Description

Technical Field

[0001] The present disclosure relates to a vehicle control device and a control method.

Background Art

[0002] For example, in Patent Document 1, when it is determined that the host vehicle will be rear-ended by a following vehicle in a situation where the host vehicle has stopped due to automatic braking, it is determined whether there is an obstacle in the diagonally forward direction. When it is determined that there is no obstacle, a technique is disclosed in which the wheels of the host vehicle are automatically steered in the diagonally forward direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The technique described in Patent Document 1 does not consider the shape of the road (straight road, curved road, etc.) on which the host vehicle has stopped due to automatic braking. Therefore, in the technique described in Patent Document 1, for example, when the host vehicle has stopped at the entrance of a curved road or on a curved road due to automatic braking, if the host vehicle is automatically steered in the diagonally forward direction where it is determined that there is no obstacle, when the host vehicle is rear-ended by a following vehicle, there is a risk that the host vehicle will deviate off the road or deviate from its own lane and collide with a preceding vehicle in the same direction.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to effectively suppress secondary collision damage when the host vehicle is rear-ended while it is stopped. <9000028> The technique of the present disclosure is A vehicle control device and control method that acquire the relative relationship between the vehicle and an object target located within a predetermined range in the vehicle's direction of travel, and, based on the acquired relative relationship, determines that the risk of collision between the vehicle and the object target is at or above a predetermined level, and then automatically stops the vehicle using automatic braking control. When the vehicle is stopped due to the execution of the automatic braking control, and it is determined that the risk of a following vehicle approaching from behind colliding with the vehicle is at or above a predetermined level, the system is characterized by executing automatic steering control to steer the wheels of the vehicle in order to change the direction of travel of the vehicle in the event of a collision with the following vehicle, based on first information of whether or not there is an obstacle in front of the vehicle, second information of whether or not there is an obstacle diagonally in front of the vehicle, and third information including the curvature of the road on which the vehicle is stopped. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing the hardware configuration of the vehicle according to this embodiment. [Figure 2] This is a schematic diagram showing the software configuration of the control device according to this embodiment. [Figure 3] This is a flowchart illustrating the routine for abnormality detection processing according to this embodiment. [Figure 4] This flowchart illustrates the routine for determining a rear-end collision with a following vehicle according to this embodiment. [Figure 5] This is a flowchart illustrating the routine for detecting obstacles ahead according to this embodiment. [Figure 6] This flowchart illustrates the routine for detecting surrounding obstacles according to this embodiment. [Figure 7] This is a schematic diagram illustrating an example of automatic steering control according to this embodiment. [Figure 8] This flowchart illustrates the various determinations and automatic steering control routines according to this embodiment. [Modes for carrying out the invention]

[0008] The control device and control method of the vehicle according to this embodiment will be described below with reference to the drawings.

[0009] [Hardware configuration] Figure 1 is a schematic diagram showing the hardware configuration of the vehicle SV according to this embodiment. Hereafter, the vehicle SV may be referred to as "the vehicle itself" when it is necessary to distinguish it from other vehicles, etc.

[0010] The vehicle SV has an ECU (Electronic Control Unit) 10. The ECU 10 includes a CPU (Central Processing Unit) 11, ROM (Read Only Memory) 12, RAM (Random Access Memory) 13, and an interface device 14, etc. The CPU 11 is a processor that executes various programs stored in the ROM 12. The ROM 12 is a non-volatile memory that stores data necessary for the CPU 11 to execute various programs. The RAM 13 is a volatile memory that provides a work area that is expanded when various programs are executed by the CPU 11. The interface device 14 is a communication device for communicating with external devices.

[0011] The ECU10 is a central device that provides driver assistance, such as pre-crash safety control (PCS control). Driver assistance is a concept that includes autonomous driving. The ECU10 is connected to various devices such as an internal sensor device 20, an external sensor device 30, a drive device 40, a steering device 41, a brake device 50, a driver monitor device 60, a position information detection device 70, a map database 80, and an HMI (Human Machine Interface) 90, all of which are able to communicate with each other.

[0012] The internal sensor device 20 consists of sensors that acquire the status of the vehicle SV. The internal sensor device 20 includes a vehicle speed sensor 21, an accelerator sensor 22, a brake sensor 23, a steering angle sensor 24, a steering torque sensor 25, a yaw rate sensor 26, and the like.

[0013] The vehicle speed sensor 21 detects the vehicle speed (vehicle speed V) of the vehicle SV. The accelerator sensor 22 detects the amount of accelerator pedal operation by the driver (not shown). The brake sensor 23 detects the amount of brake pedal operation by the driver (not shown). The steering angle sensor 24 detects the rotation angle (steering angle) of the steering wheel or steering shaft (not shown). The steering torque sensor 25 detects the rotation torque (steering torque) of the steering wheel or steering shaft (not shown). The yaw rate sensor 26 detects the yaw rate of the vehicle SV. The internal sensor device 20 transmits the state of the vehicle SV detected by each sensor 21 to 26 to the ECU 10 at a predetermined interval.

[0014] The external sensor device 30 consists of sensors that recognize object information relating to objects around the vehicle SV. The external sensor device 30 includes a radar sensor 31, a camera sensor 32, etc. Here, object information can be, for example, surrounding vehicles, road markings, signs, etc.

[0015] The radar sensor 31 detects targets present around the vehicle SV. The radar sensor 31 includes a millimeter-wave radar and / or a lidar. The millimeter-wave radar emits radio waves in the millimeter-wave band and receives millimeter waves reflected by targets within its radiation range. The millimeter-wave radar acquires the relative distance and relative speed between the vehicle SV and the target 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. The lidar sequentially scans pulsed laser light with a wavelength shorter than millimeter waves in multiple directions and receives the reflected light reflected by targets to acquire the shape of targets detected in front of the vehicle SV, the relative distance and relative speed between the vehicle SV and the targets.

[0016] The camera sensor 32 captures the surroundings of the vehicle SV and obtains target information around the vehicle SV by processing the captured image data. As the camera sensor 32, for example, a digital camera having an image pickup device such as a CMOS or a CCD can be used. The target information is information representing the type of the target detected around the vehicle SV, the relative distance between the vehicle SV and the target, the relative speed, and the like. The type of the target may be recognized by machine learning such as pattern matching, for example.

[0017] The external sensor device 30 repeatedly transmits the obtained target information to the ECU 10 every time a predetermined time elapses. Note that the external sensor device 30 does not necessarily have to include both the radar sensor 31 and the camera sensor 32, and may include, for example, only the radar sensor 31 or only the camera sensor 32.

[0018] The drive device 40 generates a driving force transmitted to the drive wheels of the vehicle SV. Examples of the drive device 40 include an electric motor and an engine. The steering device 41 applies a steering force to the wheels of the vehicle SV.

[0019] The brake device 50 is, for example, a disc-type brake device that applies a braking force to the wheels of the vehicle SV. The brake device 50 includes a brake actuator 51, a brake mechanism 52, and the like. The brake actuator 51 is provided in a hydraulic circuit between a master cylinder (not shown) that pressurizes hydraulic oil by the stepping force of the brake pedal and the brake mechanism 52. The brake mechanism 52 includes a brake disk 53 fixed to the wheel and a brake caliper 54 fixed to the vehicle body. The brake actuator 51 adjusts the hydraulic pressure supplied to a wheel cylinder built in the brake caliper 54 according to an instruction from the ECU 10 and operates the wheel cylinder by the hydraulic pressure. Thereby, the brake actuator 51 presses the brake pad against the brake disk 53 to generate a frictional braking force. Note that the brake device 50 may be a drum-type brake device or the like.

[0020] The driver monitoring device 60 is a device that acquires the state of the driver of the vehicle SV, and for example, includes a driver camera 61. The driver camera 61 mainly photographs the driver's face, and detects the orientation of the driver's face, the line-of-sight direction, the eye-opening state, etc. from the photographed face image. The driver monitoring device 60 transmits the driver's state information (hereinafter, driver monitoring information) acquired based on the detection result of the driver camera 61 to the ECU 10 at a predetermined cycle. Note that the driver monitoring device 60 is not limited to only the driver camera 61, and may include other sensors capable of acquiring the state of the driver, such as a physiological measurement device that detects the driver's heart rate and pulse rate.

[0021] The position information detection device 70 detects the current position information of the vehicle SV. As the position information detection device 70, for example, GPS (Global Positioning System), GNSS (Global Navigation Satellite System), etc. provided in a navigation system not shown can be used. The position information detection device 70 transmits the detected current position information of the vehicle SV to the ECU 10 at a predetermined cycle.

[0022] The map database 80 is, for example, a database of map information provided in a navigation system, and is stored in a storage device (hard disk, flash memory, etc.) of the vehicle SV. The map information includes, for example, information representing the shape of a road such as a curved road or a straight road. Note that the map database 80 may be stored in an external server that can communicate with the vehicle SV. In this case, the vehicle SV may acquire the map information from the external server through a communication device not shown.

[0023] The HMI90 is an interface for inputting and outputting information between the ECU10 and the driver, and includes input and output devices. Examples of input devices include a touch panel, switches, and a voice-gathering microphone. Examples of output devices include a display device 91 and a speaker 92. The display device 91 is, for example, a center display, a multi-information display, or a head-up display. The speaker 92 is, for example, a speaker in an audio system or a navigation system.

[0024] [Software Configuration] Figure 2 is a schematic diagram showing the software configuration of the control device according to this embodiment.

[0025] As shown in Figure 2, the ECU 10 includes functional elements such as a PCS control unit 100, a stop-hold control unit 110, a driver state determination unit 120, a rear-end collision determination unit 130, a forward obstacle determination unit 140, a curved road determination unit 150, a surrounding obstacle determination unit 160, a road type determination unit 170, and a steering control unit 180. Each of these functional elements 100 to 180 is realized by the CPU 11 of the ECU 10 reading a program stored in the ROM 12 into the RAM 13 and executing it. Note that all or part of each of the functional elements 100 to 180 may also be provided in another ECU separate from the ECU 10, or in an information processing device of a facility (such as a management center) that can communicate with the vehicle SV.

[0026] The PCS control unit 100 performs PCS control to avoid collisions between the vehicle SV and targets ahead or to mitigate the damage from such collisions. Based on target information transmitted from the external sensor device 30, the PCS control unit 100 acquires coordinate information of objects located in front of the vehicle SV. The PCS control unit 100 also calculates the turning radius of the vehicle SV based on the detection results of the vehicle speed sensor 21, steering angle sensor 24, and yaw rate sensor 26, and calculates the trajectory of the vehicle SV based on this turning radius. The PCS control unit 100 determines whether moving and stationary objects in front of the vehicle SV are obstacles that could potentially collide with the vehicle SV. If the object is moving, the PCS control unit 100 calculates the trajectory of the moving object based on the coordinate information of the moving object, and determines the moving object to be an obstacle if its trajectory intersects with the trajectory of the vehicle SV. If the object is stationary, the PCS control unit 100 determines the stationary object to be an obstacle if the trajectory of the vehicle SV intersects with the stationary object's current position.

[0027] When the PCS control unit 100 determines that an object is an obstacle, it calculates the predicted collision time (TTC) until the vehicle SV collides with the obstacle, based on the distance L from the vehicle SV to the obstacle and the relative velocity Vr of the vehicle SV with respect to the obstacle. TTC is an index value indicating the probability that the vehicle SV will collide with the obstacle. TTC can be obtained by dividing the distance L from the vehicle SV to the obstacle by the relative velocity Vr (TTC = L / Vr). If the TTC is below a predetermined TTC threshold, the PCS control unit 100 determines that there is a high probability that the vehicle SV will collide with the obstacle, i.e., that the collision risk is above a predetermined level. When the PCS control unit 100 determines that the collision risk is above a predetermined level, it executes a warning via the speaker 92 and / or the display device 91, and also executes automatic brake control. Automatic brake control is a control that decelerates the vehicle SV by controlling the operation of the brake actuator 51 so that the deceleration of the vehicle SV matches a predetermined target deceleration. This allows the vehicle SV to be forcibly decelerated without requiring the driver to operate the brake pedal.

[0028] When the vehicle SV is stopped by the automatic brake control by the PCS control unit 100, the stop-hold control unit 110 controls the operation of the brake actuator 51 so that the vehicle SV is held in a stopped state. When the stop-hold control unit 110 confirms that the vehicle SV has stopped by the automatic brake control, it controls the operation of the brake actuator 51 to supply the hydraulic pressure set for stop-holding to the wheel cylinder of the brake mechanism 52. This maintains the stopped state of the vehicle SV. Hereinafter, maintaining the stopped state of the vehicle SV will be referred to as stop-holding, and the braking force control that maintains the stopped state of the vehicle SV will be referred to as stop-holding control. For example, when the duration of the stop-holding control reaches a predetermined set time, the stop-hold control unit 110 terminates the stop-holding control, thereby releasing the stop-holding of the vehicle SV.

[0029] The driver state determination unit 120 determines whether the driver is in an abnormal state where they cannot operate the vehicle SV normally while the stop-hold control unit 110 is performing stop-hold control. Figure 3 is a flowchart illustrating the routine for abnormality determination processing by the driver state determination unit 120. This routine is started, for example, when the stop-hold control unit 110 performs stop-hold control.

[0030] In step S100, the driver state determination unit 120 determines, based on the driver monitor information transmitted from the driver monitor device 60, whether the driver is in an abnormal state where they cannot drive the vehicle SV normally due to distraction, drowsiness, etc. Hereinafter, the determination result based on the driver monitor information will be referred to as the driver monitor determination result. Based on the driver monitor information transmitted from the driver monitor device 60, the driver state determination unit 120 acquires, for example, the driver's gaze direction and eye open state. The driver state determination unit 120 determines the driver monitor determination result to be abnormal if the driver's gaze direction is outside a predetermined range including the front of the vehicle SV, or if the driver's eyes are closed for a predetermined period of time. If the driver state determination unit 120 determines the driver monitor determination result to be abnormal (No), it proceeds to the process in step S140 and determines that the driver is in an abnormal state. On the other hand, if the driver monitor determination result is normal (Yes), the driver state determination unit 120 proceeds to the process in step S110.

[0031] In step S110, the driver state determination unit 120 determines whether the number of times the vehicle SV swayed during a predetermined period immediately before PCS control was executed was less than or equal to a predetermined first threshold T1. The number of times the vehicle SV swayed can be obtained based on the detection results of the internal sensor device 20 and / or the external sensor device 30. If the number of swaying was not less than or equal to the first threshold T1 (No), the driver state determination unit 120 proceeds to the process in step S140 and determines that the driver is in an abnormal state. On the other hand, if the number of swaying was less than or equal to the first threshold T1 (Yes), the driver state determination unit 120 proceeds to the process in step S120.

[0032] In step S120, the driver state determination unit 120 determines whether the duration of the driver's hands-off state (not gripping the steering wheel) during a predetermined period immediately before PCS control is executed was less than or equal to a predetermined second threshold T2. The driver's hands-off state can be obtained, for example, based on the detection result of the steering torque sensor 25. If the duration of the driver's hands-off state was not less than or equal to the second threshold T2 (No), the driver state determination unit 120 proceeds to step S140 and determines that the driver is in an abnormal state. On the other hand, if the duration of the driver's hands-off state was less than or equal to the second threshold T2 (Yes), the ECU 10 proceeds to step S130 and determines that the driver is in a normal state.

[0033] The following vehicle collision detection unit 130 determines whether a following vehicle approaching from behind the vehicle SV may collide with the vehicle SV while the stop-hold control unit 110 is performing stop-hold control. Figure 4 is a flowchart illustrating the routine for collision detection processing by the following vehicle collision detection unit 130. This routine is started, for example, when the stop-hold control unit 110 performs stop-hold control.

[0034] In step S200, the following vehicle collision determination unit 130 determines whether or not there is a following vehicle behind the vehicle SV based on the detection results of the external sensor device 30. If there is no following vehicle (No), the following vehicle collision determination unit 130 proceeds to step S270 and determines that there is no possibility of the following vehicle rear-ending the vehicle SV. On the other hand, if there is a following vehicle (Yes), the following vehicle collision determination unit 130 proceeds to step S210.

[0035] In step S210, the following vehicle collision determination unit 130 acquires the relative speed and distance of the following vehicle to the vehicle SV based on the detection results of the external sensor device 30. Next, in step S220, the following vehicle collision determination unit 130 calculates the TTC, which is the predicted time until the following vehicle rear-ends (collides) with the vehicle SV, based on the relative speed and distance acquired in step S210.

[0036] In step S230, the following vehicle collision determination unit 130 determines whether the TTC calculated in step S220 is less than or equal to a predetermined third threshold T3. If the TTC is not less than or equal to the third threshold T3 (No), that is, if the TTC is greater than the third threshold T3, the following vehicle collision determination unit 130 proceeds to step S270 and determines that there is no possibility of the following vehicle rear-ending the vehicle SV. On the other hand, if the TTC is less than or equal to the third threshold T3 (Yes), the following vehicle collision determination unit 130 proceeds to step S250.

[0037] In step S250, the rear-end collision detection unit 130 calculates the lateral overlap ratio Rr between the own vehicle SV and the following vehicle. The overlap ratio Rr can be calculated by obtaining the lateral positions of the own vehicle SV and the following vehicle based on the detection results of the external sensor device 30. Here, lateral position refers to the positions of the own vehicle SV and the following vehicle in the lane width direction relative to the road.

[0038] In step S255, the following vehicle collision determination unit 130 determines whether the lap rate Rr calculated in step S250 is equal to or greater than a predetermined fourth threshold T4. If the lap rate Rr is less than the fourth threshold T4 (No), the following vehicle collision determination unit 130 proceeds to step S270 and determines that there is no possibility of the following vehicle rear-ending the vehicle SV. On the other hand, if the lap rate Rr is equal to or greater than the fourth threshold T4 (Yes), the following vehicle collision determination unit 130 proceeds to step S260 and determines that there is a possibility of the following vehicle rear-ending the vehicle SV (i.e., the collision risk is above a predetermined level).

[0039] The forward obstacle detection unit 140 determines whether or not an obstacle exists in front of the vehicle SV while the stop-hold control unit 110 is performing stop-hold control. Figure 5 is a flowchart illustrating the routine for forward obstacle detection processing by the forward obstacle detection unit 140. This routine is started, for example, when the stop-hold control unit 110 performs stop-hold control.

[0040] In step S300, the forward obstacle determination unit 140 determines whether the object in front of the vehicle SV (hereinafter referred to as the forward object) is stationary or not, based on the detection results of the external sensor device 30. If the forward object is stationary (Yes), the forward obstacle determination unit 140 proceeds to the process in step S360. On the other hand, if the forward object is not stationary (No), that is, if it is something other than a stationary object, the forward obstacle determination unit 140 proceeds to the process in step S310.

[0041] In step S310, the forward obstacle determination unit 140 determines whether the object in front is a stationary vehicle or not based on the detection result of the external sensor device 30. If the object in front is a stationary vehicle (Yes), the forward obstacle determination unit 140 proceeds to the process in step S360. On the other hand, if the object in front is not a stationary vehicle (No), the forward obstacle determination unit 140 proceeds to the process in step S320.

[0042] In step S320, the forward obstacle detection unit 140 obtains the distance of the object in front of the vehicle SV based on the detection results of the external sensor device 30. Next, in step S330, the forward obstacle detection unit 140 determines, based on the distance obtained in step S320, whether the object in front is moving forward in the same direction as the vehicle SV's direction of travel. If the object in front is moving forward (Yes), the forward obstacle detection unit 140 proceeds to step S340 and determines that there is no obstacle in front. On the other hand, if the object in front is not moving forward (No), the forward obstacle detection unit 140 proceeds to step S360.

[0043] In step S360, the forward obstacle detection unit 140 calculates the lateral overlap ratio Rr between the vehicle SV and the object in front based on the lateral position of the object in front obtained based on the detection result of the external sensor device 30. Next, in step S370, the forward obstacle detection unit 140 determines whether the overlap ratio Rr calculated in step S360 is 0 (zero) or greater. If the overlap ratio Rr is not 0 or greater (No), that is, if the vehicle SV and the object in front do not overlap laterally, the forward obstacle detection unit 140 proceeds to the process of step S340 and determines that there is no obstacle in front. On the other hand, if the overlap ratio Rr is 0 or greater (Yes), the forward obstacle detection unit 140 proceeds to the process of step S380 and determines that there is an obstacle in front.

[0044] The curved road determination unit 150 determines whether the vehicle SV is stopped at the entrance to a curved road or on the curved road while the stop-hold control unit 110 is performing stop-hold control. Whether the vehicle SV is stopped at the entrance to a curved road or on the curved road may be determined based on the detection results of the external sensor device 30, or based on the current position of the vehicle SV detected by the position information detection device 70 and the map information of the map database 80. Furthermore, if the curved road determination unit 150 determines that the vehicle SV is stopped at the entrance to a curved road or on the curved road, it obtains the curvature of the curved road (i.e., the curvature in the direction of travel). The curvature of the curved road may be calculated based on the detection results of the external sensor device 30, or obtained from the map information of the map database 80.

[0045] The surrounding obstacle detection unit 160 determines whether or not there are obstacles around the vehicle SV while the stop-hold control unit 110 is performing stop-hold control. Figure 6 is a flowchart illustrating the routine for the surrounding obstacle detection process performed by the surrounding obstacle detection unit 160. This routine is started, for example, when the stop-hold control unit 110 performs stop-hold control.

[0046] In step S400, the surrounding obstacle determination unit 160 determines, based on the detection results of the external sensor device 30, whether or not there is a space to avoid obstacles diagonally in front of the vehicle SV. If there is no space to avoid obstacles diagonally in front of the vehicle SV (No), the surrounding obstacle determination unit 160 proceeds to step S460 and determines that there is a surrounding obstacle. On the other hand, if there is space to avoid obstacles diagonally in front of the vehicle SV (Yes), the surrounding obstacle determination unit 160 proceeds to step S410.

[0047] In step S410, the surrounding obstacle determination unit 160 determines, based on the detection results from the external sensor device 30 or the map database 80, whether the avoidance space diagonally in front of the vehicle SV is an oncoming lane. If the avoidance space is an oncoming lane (Yes), the surrounding obstacle determination unit 160 proceeds to step S460 and determines that there is an obstacle in the surrounding area. On the other hand, if the avoidance space is not an oncoming lane (No), the surrounding obstacle determination unit 160 proceeds to step S420.

[0048] In step S420, the surrounding obstacle determination unit 160 determines, based on the detection results of the external sensor device 30, whether or not there is an object approaching the vehicle SV from diagonally behind the vehicle SV (hereinafter referred to as a diagonally rear object). If a diagonally rear object exists (Yes), the surrounding obstacle determination unit 160 proceeds to step S460 and determines that there is a surrounding obstacle. On the other hand, if there is no diagonally rear object (No), the surrounding obstacle determination unit 160 proceeds to step S440 and determines that there is no surrounding obstacle.

[0049] The road type determination unit 170 determines whether the road on which the vehicle SV is stopped is an expressway while the stop-hold control unit 110 is performing stop-hold control. Whether the road is an expressway can be determined based on the current position of the vehicle SV detected by the position information detection device 70 and the map information in the map database 80. Alternatively, it may be determined based on road signs, etc., recognized from the detection results of the external sensor device 30.

[0050] The steering control unit 180 performs automatic steering control that changes the steering angle of the vehicle SV according to the determination results of each functional element 120 to 170 while the stop-hold control unit 110 is performing stop-hold control. Specifically, while the stop-hold control is being performed, the steering control unit 180 determines whether a first specific condition is met, in which the driver state determination unit 120 determines the driver is in an abnormal state, the road type determination unit 170 determines the road type is an expressway, and the following vehicle collision determination unit 130 determines that there is a possibility of a following vehicle rear-ending the vehicle SV. If the first specific condition is met, the steering control unit 180 further determines whether a second specific condition is met, in which the forward obstacle determination unit 140 determines that there is no obstacle ahead, and the curved road determination unit 150 determines that the vehicle SV is stopped at the entrance of a curved road or on a curved road.

[0051] When the first and second specific conditions are met, the steering control unit 180 performs automatic steering control to steer the wheels of the vehicle SV so that the direction of travel of the vehicle SV follows the curvature of the curved road. As a result, for example, as shown by the solid arrows in Figures 7(A) and (B), if the vehicle SV is stopped at the entrance or on the curved road due to stop-hold control and is hit from behind by a following vehicle (not shown), the vehicle SV will move forward along the curved road. In other words, as shown by the dashed arrow in Figure 7(A), if the wheels of the vehicle SV are in a straight-ahead state (steering angle is approximately zero) and are hit from behind by a following vehicle, it becomes possible to effectively suppress secondary collision damage caused by the vehicle VH entering an adjacent lane and colliding with another vehicle OV (a preceding vehicle in the same direction or an oncoming vehicle in the opposing lane). Furthermore, as shown by the dashed arrow in Figure 7(B), if the wheels of the vehicle SV are in a straight-ahead position (steering angle is approximately zero) and are rear-ended by a following vehicle, it becomes possible to effectively suppress accidents caused by the vehicle VH deviating from its lane and going off the road.

[0052] If the first specific condition is met but the second specific condition is not met, the steering control unit 180 determines whether the third specific condition is met, which is that the forward obstacle determination unit 140 determines that there is an obstacle ahead, the overlap ratio Rr between the vehicle SV and the forward obstacle is greater than or equal to a predetermined value, and the surrounding obstacle determination unit 160 determines that there are no surrounding obstacles. If the first and third specific conditions are met, the steering control unit 180 performs automatic steering control to steer the wheels of the vehicle SV so that the direction of travel of the vehicle SV is diagonally forward. This makes it possible to effectively suppress secondary collision damage, which occurs when the vehicle SV collides with a forward obstacle in the event of a rear-end collision with a following vehicle.

[0053] Figure 8 is a flowchart illustrating the various decision-making processes and automatic steering control routines executed by the CPU 11 of the ECU 10. The routines shown in Figure 8 are started when stop-hold control is executed.

[0054] In step S500, the ECU10 determines whether the driver is in an abnormal state based on the abnormality detection routine shown in Figure 3. If the driver is in an abnormal state (Yes), the ECU10 proceeds to step S510. On the other hand, if the driver is not in an abnormal state (No), i.e., normal, the ECU10 returns from this routine.

[0055] In step S510, the ECU10 determines whether the road on which its vehicle SV is stopped by stop-hold control is an expressway. If the road is an expressway (Yes), the ECU10 proceeds to step S520. On the other hand, if the road is not an expressway (No), the ECU10 returns to this routine.

[0056] In step S520, the ECU 10 determines whether a following vehicle is likely to rear-end its own vehicle SV, based on the collision detection routine shown in Figure 4. If there is a possibility of a following vehicle rear-ending its own vehicle SV (Yes), the ECU 10 proceeds to step S530. On the other hand, if there is no possibility of a following vehicle rear-ending its own vehicle SV (No), the ECU 10 returns from this routine. Note that the processes in steps S500 to S520 can be performed in any order.

[0057] In step S530, the ECU 10 determines whether or not there is an obstacle in front of the vehicle SV based on the forward obstacle detection routine shown in Figure 5. If there is an obstacle in front of the vehicle SV (Yes), the ECU 10 proceeds to step S570. On the other hand, if there is no obstacle in front of the vehicle SV (No), the ECU 10 proceeds to step S540.

[0058] In step S540, the ECU 10 determines whether the vehicle SV is stopped at the entrance to the curved road or on the curved road. If the vehicle SV is stopped at the entrance to the curved road or on the curved road (Yes), the ECU 10 proceeds to step S550. On the other hand, if the vehicle SV is not stopped at the entrance to the curved road or on the curved road (No), the ECU 10 returns to this routine.

[0059] In step S550, the ECU10 calculates the curvature of the curved road. Then, in step S560, the ECU10 performs automatic steering control to steer the wheels of the vehicle SV so that the direction of travel of the vehicle SV follows the curvature of the curved road, and then returns to this routine.

[0060] When the process proceeds from step S530 to step S570, the ECU 10 calculates the overlap ratio Rr between the vehicle SV and the obstacle in front based on the detection results of the external sensor device 30. Next, in step S575, the ECU 10 determines whether the overlap ratio Rr calculated in step S570 is greater than or equal to a predetermined value. If the overlap ratio Rr is greater than or equal to the predetermined value (Yes), the ECU 10 proceeds to the process in step S580. On the other hand, if the overlap ratio Rr is less than the predetermined value (No), the ECU 10 returns to this routine.

[0061] In step S580, the ECU 10 determines whether or not there are surrounding obstacles based on the surrounding obstacle detection routine shown in Figure 6. If there are no surrounding obstacles (No), the ECU 10 proceeds to step S590 and executes automatic steering control to steer the wheels of the vehicle SV so that the direction of travel of the vehicle SV is diagonally forward. After that, the ECU 10 returns from this routine. On the other hand, if the determination in step S580 indicates that there are surrounding obstacles (Yes), the ECU 10 returns from this routine. Even if there are surrounding obstacles, the ECU 10 may also perform a steering feasibility determination based on the detection results of the external sensor device 30, and if it is determined that steering is possible, it may execute the automatic steering control in step S590.

[0062] Although the vehicle control device and control method according to this embodiment have been described above, this disclosure is not limited to the above embodiment, and various modifications are possible as long as they do not depart from the purpose of this disclosure. For example, in the above embodiment, the first specific condition is met when the driver is in an abnormal state and there is a possibility that a following vehicle will rear-end the vehicle SV, but the first specific condition may be met even if the driver is normal, if there is a possibility that a following vehicle will rear-end the vehicle SV. Also, in the above embodiment, automatic brake control of PCS control was described as an example, but the technology of this disclosure can also be applied when the vehicle SV is stopped by automatic brake control other than PCS control. Furthermore, the technology of this disclosure can also be applied to autonomous vehicles that perform some or all of the driving operations automatically.

Claims

1. A vehicle control device that acquires the relative relationship between the vehicle and an object target located within a predetermined range in the direction of travel of the vehicle, and, based on the acquired relative relationship, determines that the risk of collision between the vehicle and the object target is at or above a predetermined level, and performs automatic braking control to automatically stop the vehicle, When the vehicle is stopped due to the execution of the automatic braking control, and it is determined that the risk of a following vehicle approaching from behind colliding with the vehicle is above a predetermined level, the automatic steering control is executed to steer the vehicle's wheels in order to change the direction of travel of the vehicle in the event of a collision with the following vehicle, based on first information whether or not there is an obstacle in front of the vehicle, second information whether or not there is an obstacle diagonally in front of the vehicle, and third information including the curvature of the road on which the vehicle is stopped. A vehicle control device characterized by the following features.

2. A vehicle control device according to claim 1, If, based on the first information, it is determined that there is no obstacle in front of the vehicle, and the vehicle is stopped on a curved road or at the entrance to a curved road, the automatic steering control is executed by steering the wheels so that the direction of travel of the vehicle follows the curvature of the curved road, based on the third information. A vehicle control device characterized by the following features.

3. A vehicle control device according to claim 2, If, based on the first information, it is determined that there is an obstacle in front of the vehicle, and based on the second information, it is determined that there is no obstacle diagonally in front of the vehicle, the automatic steering control is executed by turning the wheels so that the direction of travel of the vehicle is diagonally forward. A vehicle control device characterized by the following features.

4. A vehicle control method that acquires the relative relationship between the vehicle and an object target located within a predetermined range in the direction of travel of the vehicle, and, based on the acquired relative relationship, determines that the risk of collision between the vehicle and the object target is at or above a predetermined level, and then performs automatic braking control to automatically stop the vehicle, When the vehicle is stopped due to the execution of the automatic braking control, and it is determined that the risk of a following vehicle approaching from behind colliding with the vehicle is above a predetermined level, the automatic steering control is executed to steer the vehicle's wheels in order to change the direction of travel of the vehicle in the event of a collision with the following vehicle, based on first information whether or not there is an obstacle in front of the vehicle, second information whether or not there is an obstacle diagonally in front of the vehicle, and third information including the curvature of the road on which the vehicle is stopped. A vehicle control method characterized by the following features.

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