Vehicle control method and vehicle control device
Patent Information
- Application Number
- PCT/JP2025/014639
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2026-10-22
Smart Images
Figure JP2025014639_22102026_PF_FP_ABST
Abstract
Description
Vehicle control method and vehicle control device
[0001] The present invention relates to a vehicle control method and a vehicle control device.
[0002] A driving assistance device is known that, when a white line defining the own vehicle traveling lane is recognized from image data, estimates the curvature of the own vehicle traveling lane based on the white line, registers a preceding vehicle that meets preset conditions among vehicles ahead of the own vehicle as a preceding vehicle, estimates the travel trajectory of the preceding vehicle based on the image data, and cancels the registration of the preceding vehicle when the deviation between the curvature of the own vehicle traveling lane and the curvature of the travel trajectory of the preceding vehicle is equal to or greater than a set deviation (Patent Document 1).
[0003] Japanese Unexamined Patent Publication No. 2017-47800
[0004] In the above conventional technology, the registration of the preceding vehicle is canceled when the deviation between the curvature of the own lane in which the own vehicle travels and the curvature of the travel trajectory of the preceding vehicle is equal to or greater than the set deviation. Therefore, assuming a driving scene where the own vehicle following the preceding vehicle changes lanes from the currently traveling lane to an adjacent lane, the curvature of the adjacent lane cannot be estimated from the time the own vehicle enters the adjacent lane until the lane boundary line defining the adjacent lane is detected from the image information. For this reason, the above conventional technology has a problem that even when the own vehicle enters the adjacent lane, the registration of the preceding vehicle that is the following target cannot be canceled, and the preceding vehicle traveling in the original lane continues to be registered as the following target.
[0005] Further, in the above conventional technology, the registration of the preceding vehicle is canceled when the deviation between the curvature of the own lane in which the own vehicle travels and the curvature of the travel trajectory of the preceding vehicle is equal to or greater than the set deviation. Therefore, assuming a driving scene where the own vehicle following the preceding vehicle avoids an obstacle present on the currently traveling lane, when the preceding vehicle avoids the obstacle and the deviation between the curvature of the own lane and the curvature of the travel trajectory of the preceding vehicle becomes equal to or greater than the set deviation, the registration of the preceding vehicle is canceled, which causes a problem that the own vehicle can no longer follow the preceding vehicle.
[0006] The problem that the present invention aims to solve is to provide a vehicle control method and a vehicle control device that can appropriately set the target to be followed by the vehicle in at least one of the following situations: when the vehicle changes lanes from its own lane (hereinafter also simply referred to as "the own lane") to an adjacent lane (hereinafter also simply referred to as "the adjacent lane"), and when the vehicle avoids an obstacle in its own lane.
[0007] The present invention solves the above problem by searching for a first preceding vehicle located in the direction of travel of the vehicle estimated from the vehicle's driving state, in at least one of the cases where the vehicle changes lanes from its own lane to an adjacent lane, or when the vehicle avoids an obstacle in its own lane, and setting the first preceding vehicle as the target to follow when a first preceding vehicle exists.
[0008] According to the present invention, the target to be followed by the vehicle can be appropriately set in at least one of the following situations: when the vehicle changes lanes from its own lane to an adjacent lane, and when the vehicle avoids an obstacle in its own lane.
[0009] This is a block diagram showing one embodiment of the vehicle control system according to the present invention. This is a plan view showing an example of a driving scene in which autonomous driving control is performed by the vehicle control system of Figure 1. This is a plan view showing another example of a driving scene in which autonomous driving control is performed by the vehicle control system of Figure 1. This is a plan view showing yet another example of a driving scene in which autonomous driving control is performed by the vehicle control system of Figure 1. This is a flowchart showing an example of a processing procedure performed in the vehicle control system of Figure 1. This is a flowchart showing another example of a processing procedure performed in the vehicle control system of Figure 1. This is a flowchart showing yet another example of a processing procedure performed in the vehicle control system of Figure 1.
[0010] Embodiments of the present invention will be described below with reference to the drawings. In the following description, viewing the vehicle from above in the height direction (i.e., from the top of the vehicle) will be referred to as viewing the vehicle in plan.
[0011] [Configuration of the Vehicle Control System] Figure 1 is a block diagram showing one embodiment of the vehicle control system according to the present invention. The vehicle control system is an in-vehicle system mounted on a vehicle, and uses autonomous driving control to drive the vehicle from its current location to a destination set by the vehicle's occupants (hereinafter also simply referred to as the destination). Autonomous driving control is the autonomous control of the vehicle's driving operations, and these operations include some or all of all driving operations such as acceleration, deceleration, starting, stopping, and steering. The vehicle control system also provides information regarding autonomous driving control to the vehicle's occupants.
[0012] As shown in Figure 1, the vehicle control system 10 of this embodiment includes an imaging device 11, a distance measuring device 12, an on-board sensor 13, an actuator 14, and a vehicle control device 20. The devices constituting the vehicle control system 10 are connected to each other via a CAN (Controller Area Network) or other on-board LAN, and exchange information with each other.
[0013] The imaging device 11 is a camera equipped with an image sensor such as a CCD, which captures images of objects around the vehicle and generates image information of the images including the objects. The imaging device 11 may also be an infrared camera, a stereo camera, or the like. In addition, to suppress the occurrence of blind spots where objects cannot be captured, multiple imaging devices 11 are installed on the vehicle's front grille, side mirrors, rear bumper, etc.
[0014] The rangefinder 12 detects the relative distance and relative speed between the vehicle and the object. The rangefinder 12 includes a laser radar, millimeter-wave radar, and a LiDAR (light detection and ranging) unit. To suppress the occurrence of blind spots where the object cannot be detected, multiple rangefinders 12 are installed on a single vehicle.
[0015] The objects detected by the imaging device 11 and the distance measuring device 12 include objects surrounding the vehicle and objects on the road, such as road lane boundaries, center lines, road markings, median strips, guardrails, curbs, traffic lights, and pedestrian crossings. The objects also include obstacles that may affect the vehicle's movement, such as other vehicles, motorcycles, bicycles, and pedestrians. The term "vehicle" includes both the vehicle itself and other vehicles (including preceding vehicles).
[0016] The vehicle control device 20 acquires image information from the imaging device 11 and position information of objects from the distance measuring device 12, thereby recognizing objects and the driving environment around the vehicle. The acquisition of information by the vehicle control device 20 is performed at predetermined time intervals (for example, every 0.1 to 1 millisecond). The vehicle control device 20 may also recognize the driving environment by integrating or combining the information acquired from the imaging device 11 and the distance measuring device 12.
[0017] The on-board sensors 13 detect the vehicle's driving state. The on-board sensors 13 include a speed sensor, an acceleration sensor, a yaw rate sensor, a steering angle sensor, and the like. Any known sensors can be used without any particular limitations, and their arrangement and number can be appropriately set within a range that allows for proper detection of the vehicle's driving state. The vehicle control device 20 acquires the detection results of each sensor at predetermined time intervals (for example, every 0.1 to 1 millisecond).
[0018] The actuator 14 is a device that converts electrical control signals input from the vehicle control device 20 into mechanical work, and includes servo motors, hydraulic motors, hydraulic cylinders, etc. The actuator 14 operates the vehicle's drive system, braking system, steering system, etc.
[0019] The vehicle control device 20 controls and coordinates the devices that constitute the vehicle control system 10 to perform autonomous driving control of the vehicle. The vehicle control device 20 performs autonomous driving control using the devices mounted on the vehicle and controls the driving operation within a predetermined range. Driving operations that are not controlled by the vehicle control device 20 are operated manually by the driver. When the driver operates the vehicle manually, the vehicle control device 20 does not perform autonomous driving control, and the driving operation of the vehicle is controlled by the driver's operation.
[0020] The vehicle control device 20 is, for example, a computer and includes a CPU (Central Processing Unit) which is a processor, a ROM (Read Only Memory) in which the program is stored, and a RAM (Random Access Memory) which functions as an accessible storage device. The CPU is an operating circuit that executes the program stored in the ROM and realizes the functions of the vehicle control device 20. Alternatively, an MPU (Micro Processing Unit), ASIC (Application Specific Integrated Circuit), etc., may be used instead of or in conjunction with the CPU.
[0021] [Functions of the Vehicle Control Device] The ROM of the vehicle control device 20 stores a program for performing autonomous driving control of the vehicle (especially its own vehicle), and the CPU of the vehicle control device 20 executes this program to perform autonomous driving control. Figure 1 shows, for convenience, the determination unit 21, the setting unit 22, and the driving unit 23 as functional blocks for performing autonomous driving control.
[0022] The determination unit 21 performs at least one of the following: acquiring image information from the imaging device 11 and acquiring object position information from the distance measuring device 12. It detects objects around the vehicle and recognizes the driving environment around the vehicle. The driving environment is information used to determine whether the vehicle can maintain its current driving state, and includes information such as the type and location of objects (or obstacles) and road conditions. Object detection uses methods such as pattern matching using algorithms such as brute-force methods, and image processing using trained models such as convolutional neural networks.
[0023] The determination unit 21 determines, based on the recognized driving environment, whether the driving scene of the vehicle is a driving scene in which autonomous driving control according to this embodiment is to be executed. For example, the determination unit 21 determines, based on map information obtained from a database (not shown) (hereinafter also simply referred to as map information), information on the current position of the vehicle obtained from a positioning system (not shown) (hereinafter also referred to as current position information), and information on the driving route to the destination obtained from a navigation device (not shown) (hereinafter also referred to as driving route information), whether the vehicle needs to change lanes from its own lane to an adjacent lane in order to travel along the driving route. If it is determined that the vehicle needs to change lanes from its own lane to an adjacent lane in order to travel along the driving route, the determination unit 21 determines that the driving scene of the vehicle is a driving scene in which a lane change is made from the own lane to an adjacent lane. On the other hand, if it is determined that the vehicle does not need to change lanes from its own lane to an adjacent lane in order to travel along the driving route, the determination unit 21 determines that the driving scene of the vehicle is a driving scene in which a lane change is made.
[0024] As another example, if an obstacle is detected in front of the vehicle in its own lane, the determination unit 21 determines that the vehicle's driving scene is one in which the vehicle is avoiding the obstacle. As yet another example, the determination unit 21 determines, based on map information, current location information, etc., whether or not a curve exists within a predetermined range in front of the vehicle. If it is determined that a curve exists within a predetermined range in front of the vehicle, the determination unit 21 determines that the vehicle's driving scene is one in which the vehicle is entering (or driving on) a curve. On the other hand, if it is determined that there is no curve within a predetermined range in front of the vehicle, the determination unit 21 determines that the vehicle's driving scene is one in which the vehicle is driving straight on the road. The predetermined range is, for example, the range in which an object can be detected from image information and object location information, and is a range from 50 to 200 m in front of the vehicle. Furthermore, if the vehicle's driving scene is determined to fall under both a scene where the vehicle changes lanes from its own lane to an adjacent lane and a scene where the vehicle avoids an obstacle, the determination unit 21 determines that the vehicle's driving scene is a scene where the vehicle avoids an obstacle and prioritizes avoiding the obstacle.
[0025] The determination unit 21 determines whether or not a preceding vehicle exists based on at least one of the image information acquired from the imaging device 11 and the position information of the object acquired from the distance measuring device 12. In this embodiment, the preceding vehicle includes a vehicle traveling in front of the vehicle in its own lane (hereinafter also simply referred to as a vehicle traveling in its own lane) and a vehicle traveling in front of the vehicle in an adjacent lane (hereinafter also simply referred to as a vehicle traveling in an adjacent lane).
[0026] The determination unit 21 determines, based on the driving environment information and the information regarding the vehicle's driving state detected by the on-board sensor 13 (hereinafter also referred to as driving state information), whether the vehicle meets the conditions for following a preceding vehicle (especially a vehicle in the vehicle's lane) (hereinafter also referred to as the conditions for following). If it is determined that the vehicle meets the conditions for following, the driving unit 23 executes autonomous driving control to follow the preceding vehicle. On the other hand, if it is determined that the vehicle does not meet the conditions for following, the vehicle control device 20 executes autonomous driving control to drive the vehicle along its own lane (hereinafter also referred to as lane keeping control).
[0027] Conditions for follow-the-lead driving include, but are not limited to, the detection of lane boundary lines on the right and left sides of the vehicle, the driver holding (or gripping) the steering wheel, the vehicle traveling near the center of the lane in the width direction (hereinafter also simply referred to as the width direction), the turn signals (e.g., indicator lights) not being activated, high-precision map information being available for the road the vehicle is traveling on, the speed of the vehicle and the preceding vehicle being below the road's speed limit, the speed difference between the vehicle and the preceding vehicle being below a predetermined threshold, and the distance between the vehicle and the preceding vehicle being below a predetermined distance. The predetermined threshold can be set to an appropriate value within the range in which the vehicle can follow the preceding vehicle, for example, 5 to 20 km / h. The predetermined distance can be set to an appropriate value within the range in which contact between the vehicle and the preceding vehicle can be avoided, for example, 5 to 50 m.
[0028] The setting unit 22 searches for (or selects) a preceding vehicle to follow when the vehicle is following a preceding vehicle, and sets it as the vehicle to follow. Based on information regarding the center position in the width direction of the vehicle's lane (hereinafter also simply referred to as the center position) and information regarding the direction of travel of the vehicle, the setting unit 22 sets an appropriate preceding vehicle as the vehicle to follow, according to the driving scene.
[0029] The center position of the vehicle's lane is obtained from the image captured by the imaging device 11. For example, the setting unit 22 detects the lane boundary line that defines the vehicle's lane from the image captured by the imaging device 11 and calculates the center position at a certain interval in front of the vehicle. A lane boundary line is a boundary line that divides (or defines) the lanes of a road, and is a type of road marking. The lane boundary line may be a solid line or a dashed line. Also, the color of the lane boundary line is not limited to white, but may be yellow, orange, green, blue, etc. The center position of the vehicle's lane corresponds to, for example, the midpoint between the position of the lane boundary line on the left side of the vehicle and the position of the lane boundary line on the right side of the vehicle at a certain point on the vehicle's lane. The direction of travel of the vehicle is estimated from the vehicle's driving state. For example, the setting unit 22 estimates the direction of travel of the vehicle from information such as the yaw rate obtained from the yaw rate sensor and the steering angle obtained from the steering angle sensor.
[0030] The driving unit 23 drives its own vehicle using autonomous driving control. For example, the driving unit 23 drives its own vehicle following a target vehicle set by the setting unit 22. The driving unit 23 obtains the relative distance and relative speed between its own vehicle and the preceding vehicle from the distance measuring device 12 and sets a target vehicle speed (hereinafter also simply referred to as target vehicle speed) for its own vehicle to drive in accordance with the preceding vehicle. The target vehicle speed is, for example, the vehicle speed that maintains a predetermined distance between its own vehicle and the preceding vehicle. The driving unit 23 may also drive its own vehicle along its own lane using lane keeping control.
[0031] The driving unit 23 generates a control signal corresponding to the target vehicle speed and outputs it to the actuator 14. For example, the driving unit 23 generates a control signal to output to the actuator 14 of the drive unit and brake unit, and uses the control signal to control the drive unit and brake unit so that the vehicle's speed reaches the target vehicle speed. The driving unit 23 also generates a control signal to output to the actuator 14 of the steering unit, and uses the control signal to control the steering unit so that the vehicle follows the preceding vehicle (or travels along its own lane).
[0032] The functions of the determination unit 21, the setting unit 22, and the driving unit 23 will be explained in detail below using Figures 2 to 6.
[0033] Figure 2 is a plan view showing an example of a driving scene in which autonomous driving control is performed by the vehicle control system 10 of this embodiment. In the driving scene shown in Figure 2, a road with two lanes extends in the left-right direction of the drawing, and the vehicle is assumed to be traveling on the road shown in Figure 2 from left to right in the drawing.
[0034] In the driving scene shown in Figure 2, vehicle V1 is traveling in its own lane L1, with vehicle V2 ahead of vehicle V1 in lane L1, and vehicle V3 ahead of vehicle V1 in the adjacent lane L2. Vehicle V1 in Figure 2 is following vehicle V2 and will change lanes from its own lane L1 to the adjacent lane L2 along the driving trajectory T1 in order to travel along the set driving path. In the driving scene shown in Figure 2, the conditions for vehicle V1 to follow vehicle V2 are assumed to be met.
[0035] In the driving scene shown in Figure 2, the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2 in order to travel along the driving path. Therefore, the determination unit 21 determines that the driving scene of the vehicle V1 is a driving scene in which the vehicle changes lanes from its own lane L1 to the adjacent lane L2. The determination unit 21 also detects the preceding vehicle V3 in the adjacent lane from the image information acquired from the imaging device 11. Furthermore, the determination unit 21 determines whether the conditions for the vehicle V1, which has entered the adjacent lane L2 due to the lane change, to follow the preceding vehicle V3 in the adjacent lane are met. In the driving scene shown in Figure 2, it is assumed that the conditions for the vehicle V1, which has entered the adjacent lane L2, to follow the preceding vehicle V3 in the adjacent lane are met.
[0036] After the vehicle V1 completes a lane change, the setting unit 22 selects a preceding vehicle to follow based on at least one of information regarding the center position of the vehicle's lane L1 and information regarding the direction of travel of the vehicle V1, and sets it as the target vehicle to follow. This is done so that the driving unit 23 can smoothly transition to the next autonomous driving control in the adjacent lane L2 (or the driving unit 23 can smoothly continue autonomous driving control before and after the vehicle V1 changes lanes). In the driving scene shown in Figure 2, the setting unit 22 obtains the center position A1 shown in Figure 2 from the image captured by the imaging device 11, and obtains, for example, the direction of travel A2 shown in Figure 2 from the yaw rate detected by the yaw rate sensor (onboard sensor 13).
[0037] In the driving scene shown in Figure 2 (i.e., a driving scene in which the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2), if the preceding vehicle V2 in the vehicle's own lane, which is located on the center position A1 of the vehicle's own lane L1, is set as the target to follow based on the information regarding the center position A1 of the vehicle's own lane L1, then even after the lane change is completed and the vehicle V1 enters the adjacent lane L2, the preceding vehicle V2 in the vehicle's own lane will remain set as the target to follow the vehicle V1. In this case, the setting unit 22 cannot set the preceding vehicle V3 in the adjacent lane as the target to follow until it has acquired information regarding the center position of the adjacent lane L2, and therefore the driving unit 23 cannot smoothly continue autonomous driving control before and after the lane change.
[0038] Therefore, in a driving scene where the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2, the setting unit 22 sets the target vehicle for the vehicle V1 to follow based on information regarding the direction of travel A2 of the vehicle V1. That is, when the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2, the setting unit 22 searches for a first preceding vehicle that is in the direction of travel A2 of the vehicle V1. If a first preceding vehicle exists, the setting unit 22 sets the first preceding vehicle as the target vehicle for following, and the driving unit 23 makes the vehicle V1 follow the first preceding vehicle after the lane change to the adjacent lane L2 is completed. On the other hand, if a first preceding vehicle does not exist, the setting unit 22 does not set a target vehicle for following, and the driving unit 23 executes autonomous driving control (lane keeping control) to make the vehicle V1 drive along the adjacent lane L2, for example, after the lane change to the adjacent lane L2 is completed.
[0039] In the driving scene shown in Figure 2, the setting unit 22 searches for a first preceding vehicle located in the direction of travel A2 of the vehicle V1. In the driving scene shown in Figure 2, there is a preceding vehicle V3 in the adjacent lane in the direction of travel A2 of the vehicle V1. Therefore, the setting unit 22 detects the preceding vehicle V3 in the adjacent lane located in the direction of travel A2 from the image information acquired from the imaging device 11 and the position information of the target object acquired from the distance measuring device 12, and sets it as the target to be followed after the lane change is completed. In other words, in the driving scene shown in Figure 2, the preceding vehicle V3 in the adjacent lane becomes the first preceding vehicle. After the lane change to the adjacent lane L2 is completed, the driving unit 23 makes the vehicle V1 follow the preceding vehicle V3 in the adjacent lane. This allows the driving unit 23 to smoothly transition to lane keeping control after the lane change of the vehicle V1 is completed.
[0040] Note that the direction of travel A2 shown in Figure 2 is the direction of travel when the vehicle V1 turns to the right in order to travel along the travel trajectory T1. In the travel scene shown in Figure 2, the direction of travel acquired by the setting unit 22 is not always the direction of travel A2 shown in Figure 2, but changes according to the direction of travel of the vehicle V1 while the vehicle V1 is traveling along the travel trajectory T1.
[0041] Figure 3 is a plan view showing another example of a driving scene in which autonomous driving control is performed by the vehicle control system 10 of this embodiment. In the driving scene shown in Figure 3, a road with two lanes extends in the left-right direction of the drawing, and the vehicle is assumed to be traveling on the road shown in Figure 3 from left to right in the drawing.
[0042] In the driving scene shown in Figure 3, vehicle V1 is traveling in its own lane L1, and there is a preceding vehicle V2 traveling ahead of vehicle V1 in lane L1. An obstacle X is present in front of both vehicle V1 and the preceding vehicle V2. In Figure 3, vehicle V1 is following the preceding vehicle V2, and the preceding vehicle V2 turns to the right to avoid obstacle X. It should be assumed that in the driving scene shown in Figure 3, the conditions for vehicle V1 to follow the preceding vehicle V2 are met.
[0043] In the driving scene shown in FIG. 3, the determination unit 21 detects an obstacle X present ahead of the host vehicle V1 in the host lane L1 from the position information of the object acquired from the distance measuring device 12. In this case, the determination unit 21 determines that the driving scene of the host vehicle V1 is a driving scene for avoiding the obstacle X.
[0044] The setting unit 22 sets a tracking target to be followed by the host vehicle V1, based on at least one of information related to the center position A1 of the host lane L1 and information related to the traveling direction A2 of the host vehicle V1, so as to avoid the obstacle X while continuing the autonomous driving control in which the host vehicle V1 travels following the preceding vehicle V2 in the host lane. In the driving scene shown in FIG. 3, the setting unit 22 acquires the center position A1 shown in FIG. 3 from the image captured by the imaging device 11, and acquires the traveling direction A2 shown in FIG. 3 from the yaw rate detected by the yaw rate sensor.
[0045] In the driving scene shown in FIG. 3 (that is, the driving scene in which the host vehicle V1 avoids the obstacle X ahead), if the tracking target of the host vehicle V1 is set based on the information related to the center position A1 of the host lane L1, the preceding vehicle V2 in the host lane that has turned to the right side in the traveling direction to avoid the obstacle X cannot be set as the tracking target, and the autonomous driving control in which the host vehicle V1 travels following the preceding vehicle V2 in the host lane cannot be continued.
[0046] Accordingly, in the driving scene where the host vehicle V1 avoids the obstacle X ahead, the setting unit 22 sets the tracking target of the host vehicle V1 based on the information related to the traveling direction A2 of the host vehicle V1. That is, when the host vehicle V1 avoids the obstacle X on the host lane L1, the setting unit 22 searches for a first preceding vehicle present in the traveling direction A2 of the host vehicle V1. When the first preceding vehicle is present, the setting unit 22 sets the first preceding vehicle as the tracking target, and the traveling unit 23 causes the host vehicle V1 to travel following the first preceding vehicle. On the other hand, when the first preceding vehicle is not present, the setting unit 22 does not set the tracking target, and the traveling unit 23 executes, for example, autonomous driving control for avoiding the obstacle X.
[0047] In the driving scene shown in FIG. 3, the setting unit 22 searches for a first preceding vehicle present in the traveling direction A2 of the host vehicle V1. In the driving scene shown in FIG. 3, since the host lane preceding vehicle V2 is present on the traveling direction A2 of the host vehicle V1, the setting unit 22 detects the host lane preceding vehicle V2 present in the traveling direction A2 from the image information acquired from the imaging device 11 and the position information of the object acquired from the distance measuring device 12, and sets it as a tracking target. That is, in the driving scene shown in FIG. 3, the host lane preceding vehicle V2 serves as the first preceding vehicle. The traveling unit 23 causes the host vehicle V1 to travel while following the host lane preceding vehicle V2. Accordingly, the traveling unit 23 can avoid the obstacle X on the host lane L1 while continuing the autonomous driving control in which the host vehicle V1 travels following the host lane preceding vehicle V2.
[0048] The traveling direction A2 shown in FIG. 3 is the traveling direction when the host vehicle V1 turns right to avoid the obstacle X. The traveling direction acquired by the setting unit 22 in the driving scene shown in FIG. 3 is not always the traveling direction A2 shown in FIG. 3, and varies according to the traveling direction of the host vehicle V1 until the autonomous driving control for avoiding the obstacle X is completed.
[0049] FIG. 4 is a plan view illustrating still another example of a driving scene in which autonomous driving control is executed by the vehicle control system 10 of the present embodiment. In the driving scene shown in FIG. 4, a road having two lanes extends in the left-right direction of the drawing, and on the road shown in FIG. 4, vehicles are assumed to travel from the left side to the right side of the drawing.
[0050] In the driving scene shown in FIG. 4, the host vehicle V1 travels in the host lane L1, and there is a host lane preceding vehicle V2 that travels ahead of the host vehicle V1 in the host lane L1. The host vehicle V1 shown in FIG. 4 is assumed to be traveling following the host lane preceding vehicle V2. In the driving scene shown in FIG. 4, it is assumed that the condition for the host vehicle V1 to travel following the host lane preceding vehicle V2 is satisfied.
[0051] In the driving scene shown in Figure 4, the determination unit 21 detects a curve in front of the vehicle V1 from the map information, current location information, and driving route information. If the detected curve is included within a predetermined range in front of the vehicle V1, the determination unit 21 determines that the driving scene of the vehicle V1 is a driving scene in which the vehicle is entering a curve.
[0052] The setting unit 22 sets the target vehicle that the vehicle V1 will follow, based on at least one of the information regarding the center position A1 of the vehicle's lane L1 and the information regarding the direction of travel A2 of the vehicle V1, in order to continue autonomous driving control in which the vehicle V1 follows the preceding vehicle V2 in its lane. In the driving scene shown in Figure 4, the setting unit 22 obtains the center position A1 shown in Figure 4 from the image captured by the imaging device 11, and obtains the direction of travel A2 shown in Figure 4 from the yaw rate detected by the yaw rate sensor.
[0053] In the driving scene shown in Figure 4 (i.e., the driving scene in which the vehicle V1 enters a curve), if the target to follow for the vehicle V1 is set based on information regarding the direction of travel A2 of the vehicle V1 traveling straight in its own lane L1, it will not be possible to set the preceding vehicle V2 in the same lane, which has entered the curve ahead and turned to the right, as the target to follow. As a result, autonomous driving control in which the vehicle V1 follows the preceding vehicle V2 in its own lane will not be able to continue.
[0054] Therefore, in a driving scene where the vehicle V1 enters a curve, the setting unit 22 sets the target vehicle for the vehicle V1 to follow based on information regarding the center position A1 of the vehicle's lane L1. That is, if there is a curve in front of the vehicle V1, the setting unit 22 searches for a second preceding vehicle that is within a first predetermined distance in the width direction from the center position A1 of the vehicle's lane L1. If a second preceding vehicle exists, the setting unit 22 sets the second preceding vehicle as the target vehicle for following, and the driving unit 23 makes the vehicle V1 follow the second preceding vehicle. On the other hand, if there is no second preceding vehicle, the setting unit 22 does not set a target vehicle for following, and the driving unit 23 performs, for example, lane keeping control.
[0055] In the driving scene shown in Figure 4, the setting unit 22 searches for a second preceding vehicle that is located within a first predetermined distance in the width direction from the center position A1 of the current lane L1. The first predetermined distance can be set to an appropriate value within the range in which the preceding vehicle V2 traveling in the current lane L1 can be accurately detected, for example, 0.5 to 1.5 m. In the driving scene shown in Figure 4, since the preceding vehicle V2 is located on the center position A1 of the current lane L1, the setting unit 22 detects the preceding vehicle V2 located on the center position A1 of the current lane L1 from the image information acquired from the imaging device 11 and the position information of the target object acquired from the distance measuring device 12, and sets it as the target to follow. In other words, in the driving scene shown in Figure 4, the preceding vehicle V2 in the current lane becomes the second preceding vehicle. The driving unit 23 makes the current vehicle V1 drive in pursuit of the preceding vehicle V2 in the current lane. As a result, the driving unit 23 can continue autonomous driving control in which its own vehicle V1 follows the preceding vehicle V2 in its own lane that has entered a curve ahead.
[0056] When determining the driving scene of the vehicle V1, the determination unit 21 may obtain information regarding the center position A1 of the vehicle's lane L1 from the image captured by the vehicle's imaging device 11, and may estimate information regarding the vehicle's direction of travel A2 from information such as the yaw rate obtained from the yaw rate sensor. The determination unit 21 may also determine whether the vehicle V1 is at least a second predetermined distance away in the width direction from the center position A1 of the vehicle's lane L1, whether the angle between the vehicle V1's direction of travel A2 and the direction along the center position A1 of the vehicle's lane L1 (hereinafter also referred to as the determination angle) is greater than or equal to a predetermined angle, and whether autonomous driving control (i.e., lane keeping control) that drives the vehicle V1 along the vehicle's lane L1 is not being performed.
[0057] If all three conditions are met, the determination unit 21 determines that the driving scene of the vehicle V1 is either a driving scene in which the vehicle V1 changes lanes from its own lane L1 to an adjacent lane L2, or a driving scene in which the vehicle V1 avoids an obstacle X on its own lane L1. In other words, if all three conditions are met, the setting unit 22 sets the target to follow based on information regarding the direction of travel A2 of the vehicle V1. On the other hand, if at least one of the above three conditions is not met, the determination unit 21 further uses other information such as driving environment information and driving state information to determine the driving scene of the vehicle V1.
[0058] The second predetermined distance can be set to an appropriate value within a range that allows for accurate determination of whether the vehicle V1 has deviated from its own lane L1, for example, between 0.5 and 1.5 m. The direction along the center position A1 of the own lane L1 is the tangential direction at the position of the vehicle V1 of the line along the center position A1 of the own lane L1. The line along the center position A1 of the own lane L1 is, for example, the line that passes through all the calculated center positions A1 if the center position A1 has been calculated at multiple positions on the own lane L1. The determination angle is, for example, the angle formed by the direction of travel A2 of the vehicle V1 and the direction along the center position A1 of the own lane L1 when the vehicle V1 is viewed from above. The predetermined angle can be set to an appropriate value within a range that allows for accurate determination of whether the vehicle V1 has deviated from its own lane L1, for example, between 5 and 30°.
[0059] The determination unit 21 may acquire information regarding the center position A1 of the vehicle's lane L1 from the image captured by the imaging device 11 of the vehicle V1. The determination unit 21 may also determine whether at least one of the following conditions is met when the vehicle V1 is following a preceding vehicle V2 in its lane: the determination angle is less than a predetermined angle, and autonomous driving control (i.e., lane keeping control) that causes the vehicle V1 to travel along its lane L1 is being performed. If the determination angle is greater than or equal to the predetermined angle and it is determined that lane keeping control is not being performed, the determination unit 21 determines, for example, that the vehicle V1 is in a driving scene where it is deviating from its lane L1. On the other hand, if it is determined that at least one of the following conditions is met: the determination angle is less than a predetermined angle, and lane keeping control is being performed, the determination unit 21 further determines whether the preceding vehicle V2 in its lane is at least a third predetermined distance in the width direction from the center position A1 of the vehicle's lane L1.
[0060] If the driving unit 23 determines that the vehicle V2 ahead in the same lane is less than a third predetermined distance in the width direction from the center position A1 of the same lane L1, the driving unit 23 continues autonomous driving control, for example, to make the vehicle V1 follow the vehicle V2 ahead in the same lane. On the other hand, if the driving unit 21 determines that the vehicle V2 ahead in the same lane is more than a third predetermined distance away in the width direction from the center position A1 of the same lane L1, the determination unit 21 determines that the vehicle V2 ahead in the same lane has deviated from the same lane L1 (or the vehicle V2 ahead in the same lane has changed lanes to the adjacent lane L2). In this case, the driving unit 23 terminates the autonomous driving control that makes the vehicle V1 follow the vehicle V2 ahead in the same lane and switches to lane keeping control, for example. The third predetermined distance can be set to an appropriate value within a range in which it is possible to accurately determine that the vehicle V2 ahead in the same lane has deviated from the same lane L1, for example, 0.5 to 1.5 m.
[0061] The determination unit 21 may acquire information regarding the center position A1 of the vehicle's lane L1 from the image captured by the imaging device 11 of the vehicle V1. The determination unit 21 may also determine, if there is a preceding vehicle V3 in an adjacent lane, whether the preceding vehicle V3 has entered a range of a fourth predetermined distance in the width direction from the center position A1 of the vehicle's lane L1 (hereinafter also referred to as the determination range). If it is determined that the preceding vehicle V3 in the adjacent lane has not entered the determination range, the determination unit 21 determines that the preceding vehicle V3 has not entered the vehicle's lane L1, and the driving unit 23 continues the autonomous driving control that is currently being executed. On the other hand, if it is determined that the preceding vehicle V3 in the adjacent lane has entered the determination range, the determination unit 21 determines that the preceding vehicle V3 has changed lanes from the adjacent lane L2 to the vehicle's lane L1. In this case, the driving unit 23 executes (or starts) autonomous driving control to make its own vehicle V1 follow the preceding vehicle V3 in the adjacent lane. The fourth predetermined distance can be set to an appropriate value within a range in which it is possible to accurately determine that the preceding vehicle V3 in the adjacent lane has entered its own lane L1, for example, 0.5 to 1.5 m.
[0062] [Processing in the Vehicle Control System] Referring to Figures 5 to 7, the procedure for information processing by the vehicle control device 20 will be explained below. The processing described below is executed by the processor (CPU) of the vehicle control device 20 at predetermined time intervals (for example, every 0.1 to 1 millisecond).
[0063] Figure 5 is a flowchart showing an example of the processing procedure executed in the vehicle control system 10 when setting a target vehicle to follow for the vehicle V1.
[0064] First, in step S1, the vehicle control device 20 acquires image information from the imaging device 11 and object position information from the distance measuring device 12, detects objects around the vehicle V1, and determines whether or not there is a vehicle preceding the vehicle V1 (i.e., at least one of the vehicle preceding in the current lane V2 and the vehicle preceding in the adjacent lane V3). If it is determined that there is no vehicle preceding the vehicle V1 (step S1: No), the vehicle control device 20 terminates the processing of this embodiment and performs normal autonomous driving control. On the other hand, if it is determined that there is a vehicle preceding the vehicle V1 (step S1: Yes), the process proceeds to step S2.
[0065] In step S2, the vehicle control device 20 determines whether the angle formed by the direction of travel A2 of the vehicle V1 and the direction along the center position A1 in the width direction of the vehicle lane (i.e., the determination angle) is less than a predetermined angle. If it is determined that the determination angle is less than the predetermined angle (step S2: Yes), the process proceeds to step S9. On the other hand, if it is determined that the determination angle is greater than or equal to the predetermined angle (step S2: No), the process proceeds to step S3.
[0066] In step S3, the vehicle control device 20 determines whether the position of the vehicle V1 is at least a first predetermined distance away from the center position A1 in the width direction of the lane. If it is determined that the position of the vehicle V1 is less than the first predetermined distance away from the center position A1 in the width direction of the lane (step S3: No), the process proceeds to step S9. On the other hand, if it is determined that the position of the vehicle V1 is at least a first predetermined distance away from the center position A1 in the width direction of the lane (step S3: Yes), the process proceeds to step S4.
[0067] In step S4, the vehicle control device 20 determines whether the conditions for executing lane keeping control are met and whether lane keeping control is currently being executed. If it is determined that lane keeping control is currently being executed (step S4: Yes), the process proceeds to step S9. On the other hand, if it is determined that lane keeping control is not currently being executed (step S4: No), the process proceeds to step S5.
[0068] In step S5, the vehicle control device 20 determines whether the turn signal of its own vehicle V1 is activated. If it is determined that the turn signal of its own vehicle V1 is activated (step S5: Yes), the process proceeds to step S6. In step S6, the vehicle control device 20 sets the preceding vehicle to be followed based on information regarding the direction of travel A2 of its own vehicle V1. After that, the vehicle control device 20 terminates the processing of this embodiment. On the other hand, if it is determined that the turn signal of its own vehicle V1 is not activated (step S5: No), the process proceeds to step S7.
[0069] In step S7, the vehicle control device 20 determines whether or not there is another lane in the direction A2 of travel of the vehicle V1. If it is determined that there is another lane in the direction A2 of travel of the vehicle V1 (step S7: Yes), the process proceeds to step S6. On the other hand, if it is determined that there is no other lane in the direction A2 of travel of the vehicle V1 (step S7: No), the process proceeds to step S8.
[0070] In step S8, the vehicle control device 20 determines whether the driving scene of its own vehicle V1 is a driving scene in which the vehicle V1 avoids an obstacle X in its own lane. If it is determined that the driving scene of the vehicle V1 is a driving scene in which the vehicle V1 avoids an obstacle X in its own lane (step S8: Yes), the process proceeds to step S6. On the other hand, if it is determined that the driving scene of the vehicle V1 is not a driving scene in which the vehicle V1 avoids an obstacle X in its own lane (step S8: No), the process proceeds to step S9. In step S9, the vehicle control device 20 sets the preceding vehicle to be followed based on information regarding the center position A1 in the width direction of its own lane. After that, the vehicle control device 20 terminates the processing of this embodiment.
[0071] Next, Figure 6 is a flowchart showing an example of a processing procedure executed by the vehicle control system 10 when a preceding vehicle V2 in its own lane changes lanes from its own lane L1 to the adjacent lane L2.
[0072] First, in step S11, the vehicle control device 20 determines whether the vehicle V1 is following the preceding vehicle V2 in its lane. If it is determined that the vehicle V1 is not following the preceding vehicle V2 in its lane (step S11: No), the vehicle control device 20 terminates the processing of this embodiment and performs normal autonomous driving control. On the other hand, if it is determined that the vehicle V1 is following the preceding vehicle V2 in its lane (step S11: Yes), the process proceeds to step S12.
[0073] In step S12, the vehicle control device 20 determines whether the turn signal of the preceding vehicle V2 in the same lane is activated. If it is determined that the turn signal of the preceding vehicle V2 in the same lane is not activated (step S12: No), the process proceeds to step S15. On the other hand, if it is determined that the turn signal of the preceding vehicle V2 in the same lane is activated (step S12: Yes), the process proceeds to step S13.
[0074] In step S13, the vehicle control device 20 determines whether the preceding vehicle V2 in its lane is at least a third predetermined distance from the center position A1 in the width direction of the lane L1. If it is determined that the preceding vehicle V2 is at least a third predetermined distance from the center position A1 in the width direction of the lane L1 (step S13: Yes), the process proceeds to step S14. In step S14, the vehicle control device 20 terminates the autonomous driving control that follows the preceding vehicle V2 in its lane and then performs normal autonomous driving control. On the other hand, if it is determined that the preceding vehicle V2 is at least a third predetermined distance from the center position A1 in the width direction of the lane L1 (step S13: No), the process proceeds to step S15. In step S15, the vehicle control device 20 continues the autonomous driving control that follows the preceding vehicle V2 in its lane.
[0075] Next, Figure 7 is a flowchart showing an example of a processing procedure executed by the vehicle control system 10 when a preceding vehicle V3 in an adjacent lane changes lanes from the adjacent lane L2 to its own lane L1.
[0076] First, in step S21, the vehicle control device 20 determines whether the vehicle V1 is following the preceding vehicle V2 in its lane. If it is determined that the vehicle V1 is not following the preceding vehicle V2 in its lane (step S21: No), the vehicle control device 20 terminates the processing of this embodiment and performs normal autonomous driving control. On the other hand, if it is determined that the vehicle V1 is following the preceding vehicle V2 in its lane (step S21: Yes), the process proceeds to step S22.
[0077] In step S22, the vehicle control device 20 acquires image information from the imaging device 11 and position information of the target object from the distance measuring device 12, and determines whether or not there is a preceding vehicle V3 in the adjacent lane. If it is determined that there is no preceding vehicle V3 in the adjacent lane (step S22: No), the process proceeds to step S26. On the other hand, if it is determined that there is a preceding vehicle V3 in the adjacent lane (step S22: Yes), the process proceeds to step S23.
[0078] In step S23, the vehicle control device 20 determines whether the turn signal on the side of the vehicle in its own lane L1 of the vehicle preceding in the adjacent lane V3 is activated. If it is determined that the turn signal on the side of the vehicle in its own lane L1 of the vehicle preceding in the adjacent lane V3 is not activated (step S23: No), the process proceeds to step S26. On the other hand, if it is determined that the turn signal on the side of the vehicle in its own lane L1 of the vehicle preceding in the adjacent lane V3 is activated (step S23: Yes), the process proceeds to step S24.
[0079] In step S24, the vehicle control device 20 determines whether the preceding vehicle V3 in the adjacent lane has entered a range of four predetermined distances from the center position A1 in the width direction of the current lane L1. If it is determined that the preceding vehicle V3 in the adjacent lane has entered a range of four predetermined distances from the center position A1 in the width direction of the current lane L1 (step S24: Yes), the process proceeds to step S25. In step S25, the vehicle control device 20 starts autonomous driving control to follow the preceding vehicle V3 in the adjacent lane. Conversely, if it is determined that the preceding vehicle V3 in the adjacent lane has not entered a range of four predetermined distances from the center position A1 in the width direction of the current lane L1 (step S24: No), the process proceeds to step S26. In step S26, the vehicle control device 20 continues autonomous driving control to follow the preceding vehicle V2 in the current lane.
[0080] [Embodiments of the present invention] According to this embodiment, a vehicle control device 20 is provided for driving a vehicle V1 by autonomous driving control, and includes a setting unit 22 that searches for a first preceding vehicle located in the direction of travel A2 of the vehicle V1 estimated from the driving state of the vehicle V1 in at least one of the cases in which the vehicle V1 changes lanes from its own lane L1 to an adjacent lane L2 of the same lane L1, or when the vehicle V1 avoids an obstacle X on the same lane L1, and sets the first preceding vehicle as the target to follow when the first preceding vehicle exists; and a driving unit 23 that, when the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2, causes the vehicle V1 to follow the first preceding vehicle after the lane change to the adjacent lane L2 is completed, and when the vehicle V1 avoids the obstacle X, causes the vehicle V1 to follow the first preceding vehicle. A vehicle control method is also provided that is executed by the vehicle control device 20. This allows the target of the vehicle V1 to be followed to be appropriately set in at least one of the following cases: when the vehicle V1 changes lanes from its own lane L1 to the adjacent lane L2, and when the vehicle V1 avoids an obstacle X in its own lane L1.
[0081] In the vehicle control method and vehicle control device 20 of this embodiment, information regarding the center position A1 in the width direction of the vehicle's lane L1 is obtained from the image captured by the imaging device 11 of the vehicle V1. If a curve exists in front of the vehicle V1, a second preceding vehicle located within a first predetermined distance range in the width direction from the center position A1 is searched for. If the second preceding vehicle exists, the second preceding vehicle is set as the target to follow, and the vehicle V1 is made to follow the second preceding vehicle. This makes it possible to set a vehicle V2 in the vehicle's lane that has entered a curve ahead as the target to follow.
[0082] In the vehicle control method and vehicle control device 20 of this embodiment, information regarding the center position A1 in the width direction of the vehicle's lane L1 is obtained from the image captured by the imaging device 11 of the vehicle V1. If the conditions are met that the vehicle V1 is at least a second predetermined distance away from the center position A1 in the width direction, that the angle between the direction of travel A2 and the direction along the center position A1 is at least a predetermined angle, and that the autonomous driving control that drives the vehicle V1 along the vehicle's lane L1 is not being performed, then it is determined that the driving scene of the vehicle V1 is either a driving scene in which the vehicle V1 changes lanes from the vehicle's lane L1 to the adjacent lane L2 or a driving scene in which the vehicle V1 avoids the obstacle X. This allows for accurate determination of the driving scene of the vehicle V1.
[0083] In the vehicle control method and vehicle control device 20 of this embodiment, information regarding the center position A1 in the width direction of the vehicle lane L1 is obtained from the image captured by the imaging device 11 of the vehicle V1. When the vehicle V1 is traveling in the vehicle lane L1 following a preceding vehicle V2 traveling in front of the vehicle V1, at least one of the following conditions is met: the angle between the direction of travel A2 and the direction along the center position A1 is less than a predetermined angle, and the autonomous driving control that causes the vehicle V1 to travel along the vehicle lane L1 is being performed. Furthermore, when the preceding vehicle V2 moves more than a third predetermined distance in the width direction from the center position A1, the autonomous driving control that causes the vehicle V1 to follow the preceding vehicle V2 is terminated. This allows the autonomous driving control to continue smoothly even if the preceding vehicle V2 deviates from the vehicle lane L1.
[0084] In the vehicle control method and vehicle control device 20 of this embodiment, information regarding the center position A1 in the width direction of the vehicle's lane L1 is obtained from the image captured by the imaging device 11 of the vehicle V1. If there is a vehicle V3 traveling ahead of the vehicle V1 in the adjacent lane L2, and the vehicle V3 enters a range of a fourth predetermined distance in the width direction from the center position A1, the vehicle V1 is made to follow the vehicle V3. This allows autonomous driving control to continue smoothly even when the vehicle V3 enters the vehicle's lane L1 from the adjacent lane L2.
[0085] 10...Vehicle control system, 11...Imaging device, 12...Distance measuring device, 13...On-board sensor, 14...Actuator, 20...Vehicle control device, 21...Determination unit, 22...Setting unit, 23...Driving unit, A1...Center position, A2...Direction of travel, L1...Own lane, L2...Adjacent lane, T1, T2, T3...Driving trajectory, V1...Own vehicle, V2...Vehicle preceding in the current lane, V3...Vehicle preceding in the adjacent lane, X...Obstacle
Claims
1. A vehicle control method performed by a vehicle control device that drives the vehicle by autonomous driving control, wherein the vehicle control device searches for a first preceding vehicle located in the direction of travel of the vehicle estimated from the driving state of the vehicle, in at least one of the cases in which the vehicle changes lanes from its own lane to an adjacent lane, or when the vehicle avoids an obstacle in its own lane, if a first preceding vehicle exists, sets the first preceding vehicle as the target to follow, if the vehicle changes lanes from its own lane to the adjacent lane, after the lane change to the adjacent lane is completed, drives the vehicle following the first preceding vehicle, and if the vehicle avoids an obstacle, drives the vehicle following the first preceding vehicle.
2. The vehicle control method according to claim 1, wherein the vehicle control device obtains information regarding the center position in the width direction of the vehicle's lane from an image captured by the vehicle's imaging device, searches for a second preceding vehicle that is within a first predetermined distance range from the center position in the width direction if a curve exists in front of the vehicle, sets the second preceding vehicle as the target to follow if a second preceding vehicle exists, and causes the vehicle to drive following the second preceding vehicle.
3. The vehicle control device obtains information regarding the center position in the width direction of the vehicle's lane from an image captured by the vehicle's imaging device, and determines that the vehicle's driving scene is a driving scene in which the vehicle changes lanes from its own lane to an adjacent lane or a driving scene in which the vehicle avoids an obstacle, if the vehicle control device satisfies the following conditions: the vehicle is at least a second predetermined distance from the center position in the width direction, the angle between the direction of travel and the direction along the center position is at least a predetermined angle, and the autonomous driving control that causes the vehicle to drive along its own lane is not being performed.
4. The vehicle control device obtains information regarding the center position in the width direction of the vehicle's lane from an image captured by the vehicle's imaging device, and when the vehicle is traveling in the lane following a vehicle traveling ahead of it, at least one of the following conditions is met: the angle between the direction of travel and the direction along the center position is less than a predetermined angle, and the autonomous driving control that causes the vehicle to travel along the lane is being performed, and when the vehicle is traveling in the lane following a vehicle traveling ahead of it, the autonomous driving control that causes the vehicle to follow the vehicle is terminated. This is the vehicle control method according to any one of claims 1 to 3.
5. The vehicle control method according to any one of claims 1 to 4, wherein the vehicle control device obtains information regarding the center position in the width direction of the vehicle's lane from an image captured by the vehicle's imaging device, and if there is a vehicle traveling ahead of the vehicle in the adjacent lane, and the vehicle enters a range of a fourth predetermined distance in the width direction from the center position, the vehicle control device causes the vehicle to follow the vehicle in the adjacent lane.
6. A vehicle control device for driving a vehicle by autonomous driving control, comprising: a setting unit that searches for a first preceding vehicle located in the direction of travel of the vehicle estimated from the driving state of the vehicle in at least one of the following cases: when the vehicle changes lanes from its own lane to an adjacent lane, or when the vehicle avoids an obstacle in its own lane, and sets the first preceding vehicle as the target to follow when the first preceding vehicle is present; and a driving unit that, when the vehicle changes lanes from its own lane to an adjacent lane, causes the vehicle to drive following the first preceding vehicle after the lane change to the adjacent lane is completed, and when the vehicle avoids an obstacle, causes the vehicle to drive following the first preceding vehicle.