阅读说明：本技术 行驶控制系统 (Travel control system ) 是由 久保贵嗣 于 2021-03-23 设计创作，主要内容包括：行驶控制系统。一种用于配备有转向装置的车辆的行驶控制系统,所述行驶控制系统包括：成像装置,其用于获取车辆前方的图像；车辆速度传感器；以及控制装置,其被构造成控制所述转向装置,该控制装置包括：行驶车道检测单元,其被构造成从由所述成像装置获取的图像识别出所述车辆当前正在行驶的行驶车道的车道形状；车道保持计划单元,其被构造成设置用于使所述车辆转向的转向时刻以使得所述车辆在识别出的行驶车道上行驶；车道保持执行单元,其被构造成控制所述转向装置在由所述车道保持计划单元设置的转向时刻使所述车辆转向,所述车道保持计划单元被构造成基于识别出的车道形状和检测到的车速来改变转向时刻。(A travel control system. A running control system for a vehicle equipped with a steering device, the running control system comprising: an imaging device for acquiring an image in front of a vehicle; a vehicle speed sensor; and a control device configured to control the steering device, the control device including: a driving lane detection unit configured to recognize a lane shape of a driving lane in which the vehicle is currently driving from the image acquired by the imaging device; a lane keeping planning unit configured to set a steering timing for steering the vehicle so that the vehicle travels on the recognized traveling lane; a lane-keeping performing unit configured to control the steering device to steer the vehicle at a steering timing set by the lane-keeping planning unit, the lane-keeping planning unit being configured to change the steering timing based on the recognized lane shape and the detected vehicle speed.)

1. A running control system for a vehicle equipped with a steering device, the running control system comprising:

an imaging device configured to acquire an image of a front of a body of the vehicle;

a vehicle speed sensor configured to detect a vehicle speed of the vehicle; and

a control device configured to control the steering device,

wherein the control device includes:

a traveling lane detection unit configured to recognize a lane shape of a traveling lane in which the vehicle is currently traveling from the image acquired by the imaging device;

a lane keeping planning unit configured to set a steering timing for steering the vehicle so that the vehicle travels on the recognized traveling lane; and

a lane-keeping execution unit configured to control the steering device to steer the vehicle at the steering timing set by the lane-keeping planning unit,

the lane keeping planning unit is configured to change the steering timing based on the recognized lane shape and the detected vehicle speed.

2. The running control system according to claim 1, wherein the lane keeping planning unit is configured to set the turning timing such that a position in the vehicle where the imaging device is mounted passes through a center of the running lane.

3. The running control system according to claim 1 or 2, wherein the imaging device is located forward of a yaw rotation axis of the vehicle body, and

the lane keeping planning unit delays the steering timing by a predetermined delay time when the vehicle enters a curved portion of the traveling lane, as compared to when the vehicle enters a straight portion of the traveling lane.

4. The running control system according to claim 3, wherein the lane keeping planning unit is configured to increase the delay time when a front-rear distance between a position where the imaging device is mounted and a yaw rotation axis of the vehicle body increases.

5. The running control system according to claim 4, wherein the lane keeping planning unit is configured to set the delay time to a value obtained by dividing a front-rear distance between a position where the imaging device is mounted and the yaw rotation axis by a vehicle speed detected by the vehicle speed sensor.

6. The running control system according to claim 3, wherein the lane keeping planning unit is configured to determine that the vehicle enters the curve portion when an angle formed between a direction of the running lane at a position where the imaging device is mounted and a forward direction of the vehicle is greater than or equal to a threshold value.

Technical Field

The present invention relates to a travel control system configured to control travel of a vehicle, and more particularly, to a travel control system configured to execute lane keeping control to cause a vehicle to travel along a travel lane.

Background

A vehicle travel support system that performs vehicle travel support during turning along a curve is known (for example, JP2016-147541 a). The vehicle running support system disclosed in JP2016-147541a generates a steering assist force before entering a curve to assist lane keeping and avoid leaving a lane. The vehicle travel support system disclosed in this prior art document determines a delay of a steering timing (actual steering timing) performed by the driver with respect to a reference steering timing set with reference to the start point of the curve, and advances the timing of starting the steering assist force before entering the curve in accordance with the delay of the actual steering timing.

When the autonomous traveling vehicle enters the curve portion from the straight portion of the lane, steering is started based on the image acquired by the camera. The timing to start turning (hereinafter referred to as turning timing) is set based on the image acquired by the camera. However, since the mounting position of the camera usually does not coincide with the position of the yaw rotation axis of the vehicle, performing steering at the steering timing set based on the image acquired by the camera may shake the vehicle.

Disclosure of Invention

In view of the foregoing background, it is an object of the present invention to provide a running control system for a vehicle equipped with a steering device that can appropriately set a steering timing.

In order to achieve the above object, one embodiment of the present invention provides a running control system 1 for a vehicle 2 equipped with a steering device 3C, the running control system including: an imaging device 4 configured to acquire an image of a front of a body of the vehicle; a vehicle speed sensor 5 configured to detect a vehicle speed of the vehicle; a control device 7 configured to control a steering device, wherein the control device includes: a traveling lane detection unit 7A configured to recognize a lane shape of a traveling lane D on which the vehicle is currently traveling from the image acquired by the imaging device; a lane keeping planning unit 7B configured to set a steering timing for steering the vehicle so that the vehicle travels on the recognized traveling lane; a lane-keeping execution unit 7C configured to control the steering device to steer the vehicle at a steering timing set by the lane-keeping planning unit configured to change the steering timing based on the recognized lane shape and the detected vehicle speed.

According to this configuration, the steering timing is determined according to the lane shape of the traveling lane. Therefore, when the vehicle traveling straight enters the curve portion, the steering timing can be changed. Thus, when the vehicle enters a curve portion, the steering timing can be appropriately set by taking into account the difference between the position where the imaging device is mounted and the position of the yaw rotation axis, so that the vehicle can be prevented from shaking.

In the above configuration, preferably, the lane keeping planning unit is configured to set the turning timing such that a position in the vehicle where the imaging device is mounted passes through a center of the traveling lane.

According to this configuration, setting of the magnitude of the steering angle, the vehicle speed, and the like becomes easy.

In the above configuration, preferably, the imaging device is located forward of a yaw rotation axis X of the vehicle body, and the lane keeping planning unit delays the steering timing by a predetermined delay time τ when the vehicle enters a curved portion of the traveling lane as compared to when the vehicle enters a straight portion of the traveling lane.

According to this configuration, when the vehicle enters a curved portion of the traveling lane, it is possible to set the steering timing to correspond to the position of the yaw rotation axis, which contributes to preventing the vehicle from rolling. On the other hand, when the vehicle enters the straight portion, the responsiveness of the vehicle can be improved.

In the above configuration, preferably, the lane keeping planning unit is configured to increase the delay time as the front-rear distance L between the position where the imaging device is mounted and the yaw rotation axis X of the vehicle body increases.

According to this configuration, it is possible to set the steering timing to correspond to the position of the yaw rotation axis, which contributes to preventing the vehicle from rolling.

In the above configuration, preferably, the lane keeping planning unit is configured to set the delay time to a value obtained by dividing a front-rear distance between a position where the imaging device is mounted and the yaw rotation axis by the vehicle speed detected by the vehicle speed sensor.

According to this configuration, it is possible to set the steering timing to correspond to the position of the yaw rotation axis, which contributes to preventing the vehicle from rolling.

In the above-described configuration, preferably, the lane keeping planning unit is configured to determine that the vehicle enters the curve portion when an angle formed between a direction of the traveling lane at a position where the imaging device is installed and an advancing direction of the vehicle is greater than or equal to a threshold value.

According to this configuration, it can be easily determined whether the vehicle enters the curve portion.

According to the foregoing configuration, it is possible to provide a running control system for a vehicle equipped with a steering device that can appropriately set the steering timing.

Drawings

Fig. 1 is a functional block diagram of a travel control system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram for explaining the position of a yaw rotation axis and the position of an imaging device in a vehicle; and

fig. 3 is a flowchart showing the setting process.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

< first embodiment >

The running control system 1 is installed in a vehicle 2 (see fig. 2) such as an automobile to enable the vehicle 2 to autonomously run along a running lane D. As shown in fig. 1, the running control system 1 includes a behavior control device 3, an imaging device 4, a vehicle speed sensor 5, a human-machine interface (HMI)6, and a control device 7. The above-described components of the running control system 1 are connected to each other so that signals CAN be transmitted therebetween via a communication device such as a Controller Area Network (CAN).

The behavior control device 3 is a device for controlling the behavior of the vehicle 2 by accelerating, decelerating, and steering the vehicle 2, and includes a powertrain 3A, a brake device 3B, and a steering device 3C. The powertrain 3A is a device configured to apply driving force to the vehicle 2. The powertrain 3A includes a power source and a transmission. The power source includes at least one of an internal combustion engine such as a gasoline engine and a diesel engine and an electric motor. The brake device 3B is a device configured to apply a braking force to the vehicle 2. For example, the braking device 3B includes: a brake caliper configured to press a brake pad toward a brake rotor; and an electric cylinder configured to supply oil pressure to the caliper to control driving of the caliper. The brake device 3B may include an electric parking brake device configured to restrict rotation of the wheel via a cable.

The steering device 3C is a device for changing the steering angle of the wheels. For example, the steering device 3C includes: a rack and pinion device configured to steer (rotate) wheels; and an electric motor configured to drive the rack and pinion device. The power train 3A, the brake device 3B, and the steering device 3C are controlled by the control device 7.

The imaging device 4 functions as an external environment information acquisition device for detecting electromagnetic waves (e.g., visible light), acoustic waves, and the like from the surroundings of the vehicle 2 to acquire an image in front of the body of the vehicle 2. The imaging device 4 includes an external camera 4A, and outputs the acquired image to the control device 7.

The external cameras 4A are devices configured to capture images of the front and the side of the vehicle 2, and include, for example, digital cameras using solid-state imaging elements such as CCDs or CMOSs. The external camera 4A is fixed in the vehicle compartment such that its camera optical axis points in the forward direction of the vehicle body.

Note that the imaging device 4 may include sonar, millimeter wave radar, and/or lidar instead of the external camera 4A or in addition to the external camera 4A. The sonar, the millimeter wave radar, and the laser radar respectively emit ultrasonic waves, millimeter waves, and laser light in the forward direction and the lateral direction of the vehicle 2, and capture the reflected waves to acquire images of the front and the side of the vehicle 2. The imaging device 4 may comprise a plurality of sonars, a plurality of millimeter wave radars and/or a plurality of lidar arranged to collectively acquire images of the front and sides of the vehicle 2.

As shown in fig. 2, the imaging device 4 is arranged at the front on the vehicle center line M of the vehicle 2. In the present embodiment, the imaging device 4 is composed of an external camera 4A and is fixed to the vehicle body so as to be close to the upper portion of the windshield in the vehicle compartment. Since the yaw rotation axis X of the vehicle 2 passes through the center of gravity of the vehicle 2, the imaging device 4 is located forward of the yaw rotation axis X with respect to the vehicle body. In addition, since the imaging device 4 is located on the vehicle center line M, the imaging device 4 and the yaw rotation axis X are arranged in the front-rear direction along the vehicle center line M. However, the arrangement of the imaging device 4 and the yaw rotation axis X is not limited to this, and the imaging device 4 and the yaw rotation axis X may also be disposed at positions offset not only in the front-rear direction but also in the lateral direction of the vehicle body. Note that the yaw rotation axis X here is an axis extending in the vertical direction, and serves as a rotation axis of yaw movement of the vehicle body (see an arrow in fig. 2).

The vehicle speed sensor 5 is a sensor configured to detect the speed of the vehicle 2. The vehicle speed sensor 5 may be any known speed sensor. For example, the vehicle speed sensor 5 may be of a type using a magnetic sensor including a magnet provided on a wheel of the vehicle and a magnetic sensor (hall sensor) for detecting a change in magnetic field due to rotation of the wheel.

The HMI 6 is an input/output device for receiving an input operation of an occupant and notifying the occupant of various information by display and/or voice. The HMI 6 includes, for example, a touch panel 6A, and the touch panel 6A includes a display screen such as a liquid crystal display or an organic EL display and is configured to receive an input operation of an occupant. The HMI 6 also includes various switches configured to receive input operations of the occupant.

The control device 7 is composed of an Electronic Control Unit (ECU) including a CPU, a nonvolatile memory such as a ROM, a volatile memory such as a RAM, and the like. The CPU executes operation processing according to the program, so that the control device 7 performs various types of vehicle control. The control device 7 may be composed of one piece of hardware, or may be composed of a unit including a plurality of pieces of hardware. Further, as a result of executing a program by hardware (e.g., LSI, ASIC, or FPGA) constituting the control device 7, various functional units each performing a predetermined function are configured in the control device 7.

The control device 7 determines a travel lane D on which the vehicle 2 should travel based on the image acquired by the imaging device 4, and controls the powertrain 3A, the braking device 3B, and the steering device 3C based on the vehicle speed acquired by the vehicle speed sensor 5 and the image acquired by the imaging device 4 so that the vehicle 2 autonomously travels along the travel lane D. To execute such control, the control device 7 includes, as its functional units, a traveling lane detection unit 7A, a lane keeping planning unit 7B, and a lane keeping execution unit 7C as shown in fig. 1.

The traveling lane detection unit 7A extracts road marks (such as white lines), road boundaries, and the like in the image acquired by the imaging device 4, and detects the shape of the traveling lane D on the side and in front of the vehicle body. The traveling lane detection unit 7A is preferably configured to detect the traveling lane D in a range having a semicircular shape and covering at least an area within a radius range of 5 meters from the front end of the vehicle 2 in a plan view, wherein the position where the imaging device 4 is installed is the center of the semicircle.

When there is a predetermined input to the HMI, the lane keeping plan unit 7B performs a setting process to calculate the delay time τ and a driving parameter for performing a lane keeping process for causing the vehicle 2 to travel to keep near the center of the traveling lane D. In the setting process, the lane keeping planning unit 7B calculates a target point through which the vehicle 2 travels in the center of the travel lane D and driving parameters necessary for the vehicle 2 to travel to the target point, based on the shape of the travel lane D detected by the travel lane detection unit 7A. The driving parameters include information such as the magnitude of the steering angle to be set and the vehicle speed. Note that the lane keeping plan unit 7B calculates driving parameters including a steering angle and a vehicle speed so that the position where the imaging device 4 is installed passes through the target point. In the present embodiment, the target point is set at a position at a distance of about two meters from the center of the front end of the vehicle body. The lane keeping plan unit 7B performs a setting process to calculate the delay time τ and the driving parameters, and outputs the driving parameters to the lane keeping performing unit 7C immediately after the delay time τ from the calculation.

When the driving parameters are input from the lane keeping plan unit 7B, the lane keeping execution unit 7C promptly controls the steering device 3C, the powertrain 3A, and the brake device 3B according to the driving parameters. That is, steering is performed at a time after the delay time τ, based on the calculation of the delay time τ and the drive parameter. Therefore, in the present embodiment, the steering timing is delayed by the delay time τ based on the calculation of the delay time τ and the driving parameters.

Next, details of the setting processing will be described with reference to the flowchart of fig. 3. Here, it is assumed that the setting process is started when the vehicle 2 travels on the straight traveling lane D. In addition, the setting process is performed in a sufficiently short period of time, and therefore, the movement of the vehicle 2 during the setting process is negligible.

In the first step ST1 of the setting process, the lane keeping planning unit 7B acquires the shape of the traveling lane D in which the vehicle 2 is traveling from the traveling lane detection unit 7A, which detects the shape of the traveling lane D based on the image acquired by the imaging device 4. Thereafter, the lane keeping planning unit 7B determines whether the vehicle 2 enters the curve portion. More specifically, the lane keeping planning unit 7B first acquires the direction of the traveling lane D at the position where the imaging device 4 (the external camera 4A) is installed, based on the shape of the traveling lane D detected by the traveling lane detection unit 7A. Here, the direction of the travel lane D at the position where the imaging device 4 (the external camera 4A) is mounted refers to the direction (extending direction) of the tangent line to the center of the travel lane D at the position where the imaging device 4 (the external camera 4A) is mounted. Subsequently, the lane keeping planning unit 7B calculates an angle Δ θ formed between the direction of the acquired traveling lane D and the advancing direction of the vehicle body (see fig. 2). In the case where the calculated angle Δ θ has increased to be equal to or larger than the predetermined threshold value, the lane keeping planning unit 7B determines that the vehicle 2 is entering or has entered the curve portion, and executes step ST 2. Otherwise, the lane keeping planning unit 7B executes step ST 3.

In step ST2, the lane keeping plan unit 7B acquires the vehicle speed v from the vehicle speed sensor 5. Subsequently, the lane keeping planning unit 7B calculates the delay time τ (delay time τ L/v) by dividing the distance L (see fig. 2) between the imaging device 4 and the yaw rotation axis X in the front-rear direction of the vehicle body by the vehicle speed v. Thus, the delay time τ is set to a positive value according to the vehicle speed v. After the calculation of the delay time τ is completed, the lane keeping planning unit 7B executes step ST 4.

In step ST3, the lane keeping planning unit 7B sets the delay time τ to zero. When the setting of the delay time τ is completed, the lane keeping planning unit 7B executes step ST 4.

In step ST4, the lane keeping plan unit 7B calculates driving parameters including a vehicle speed and a steering angle set to move the position where the imaging device 4 is installed toward the target point, based on the shape of the traveling lane D acquired in step ST 1. When the calculation of the driving parameters is completed, the lane keeping planning unit 7B ends the setting process, and outputs the driving parameters to the lane keeping performing unit 7C after the delay time τ.

Next, the advantages of the running control system 1 configured as above will be described. The imaging device 4 is installed more forward than the yaw rotation axis X. Therefore, the steering timing calculated at the position of the imaging device 4 (i.e., the steering timing calculated based on the image acquired by the imaging device 4) is earlier than the steering timing calculated at the position of the yaw rotation axis X by the time obtained by dividing the distance L between the imaging device 4 and the yaw rotation axis X in the front-rear direction of the vehicle body by the vehicle speed v.

In the present embodiment, when the vehicle 2 is traveling in the straight traveling lane D and it is determined that the vehicle 2 is about to enter the curve portion (ST 1: YES), the lane keeping planning unit 7B sets the delay time τ to a positive value (step ST 2). Thus, the turning timing calculated at the position of the imaging device 4 can be delayed.

As shown in fig. 2, when the vehicle 2 enters the curve portion of the traveling lane D from the straight portion of the traveling lane D, the imaging device 4 enters the curve portion earlier than the yaw rotation axis X. In the case where the delay time τ is zero, the steering of the vehicle 2 is started immediately after the imaging device 4 has entered the curve portion. In contrast, by setting the positive delay time τ, the timing to start steering can be delayed, so that the timing to start steering can be made close to the timing at which the yaw rotation axis X enters the curve portion. Thus, the movement locus of the yaw rotation axis X can be brought closer to the center of the travel lane D.

In this way, by setting the delay time τ to a positive value, the steering timing can be appropriately set by taking into account that the position where the imaging device 4 is mounted is different from the position of the yaw rotation axis X. Therefore, deviation of the vehicle 2 from the center of the running lane D and shaking of the vehicle posture can be prevented or reduced.

Further, in the above-described embodiment, the delay time τ is preferably set to a value obtained by dividing the distance L between the imaging device 4 and the yaw rotation axis X in the front-rear direction of the vehicle body by the vehicle speed v. Thus, by delaying the steering timing by the delay time τ, the steering timing can be made to correspond to the position of the yaw rotation axis X.

The lane keeping planning unit 7B sets the driving parameters based on the image acquired by the imaging device 4 so that the position where the imaging device 4 is installed moves toward the target point (ST 4). By thus determining the driving parameters, the driving parameters can be set easily as compared with the case where the driving parameters are determined to move another portion of the vehicle body to the target point, because in the present embodiment, correction based on the positional relationship between the imaging device 4 and another portion of the vehicle body is not required.

In the lane keeping process, when it is determined in step ST1 that the vehicle 2 traveling on the straight lane is about to enter the curve portion, the lane keeping planning unit 7B sets the delay time τ to a positive value in step ST 2. Thus, the steering timing can be set by taking into account the difference in the position where the imaging device 4 is mounted and the position of the yaw rotation axis X, whereby the wobble of the vehicle 2 can be prevented.

On the other hand, when the vehicle 2 is traveling straight along the straight lane and the lane-keeping control is performed to keep traveling straight, the delay time τ is set to zero, so that the driving parameters are output to the lane-keeping performing unit 7C immediately after the calculation. This can improve the responsiveness of the vehicle 2.

When an angle Δ θ formed between the direction of the traveling lane D at the position where the imaging device 4 (the external camera 4A) is installed and the advancing direction of the vehicle body of the vehicle 2 is greater than or equal to a threshold value (ST1), the lane keeping planning unit 7B determines that the vehicle 2 enters the curve portion. By thus using the angle Δ θ formed between the direction of the traveling lane D at the position where the imaging device 4 (the external camera 4A) is mounted and the advancing direction of the vehicle body, it is possible to easily determine whether the vehicle 2 enters the curve portion of the lane without calculating the curvature or the like based on the shape of the traveling lane D.

The specific embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and may be modified or changed in various ways.

For example, in the above-described embodiment, the control device 7 controls the powertrain 3A, the brake device 3B, and the steering device 3C so that the vehicle 2 autonomously travels along the travel lane D, but the present invention is not limited to this embodiment. For example, the control device 7 may control only the steering device 3C to autonomously run the vehicle 2 along the running lane D.

In the above embodiment, the case where the vehicle 2 enters the curved portion of the traveling lane D from the straight portion of the traveling lane D has been described, but the above embodiment is effective in other cases. For example, when the vehicle 2 travels along a gently curved lane, the adjustment (delay) of the steering timing corresponding to the position of the yaw rotation axis X contributes to stabilizing the attitude of the vehicle 2. Further, the above embodiment is also applicable when the vehicle 2 is controlled to turn left or right at the intersection along the target route. At this time, the lane keeping plan unit 7B sets the timing (steering timing) at which steering of the vehicle 2 to the left or right is performed such that the steering timing is delayed compared to when the vehicle 2 travels straight.

In the above-described embodiment, in step ST2, the delay time τ is set to a time obtained by dividing the distance L between the imaging device 4 and the yaw rotation axis X in the front-rear direction of the vehicle body by the vehicle speed v, but the delay time τ is not limited to this embodiment. The delay time τ needs to be increased only when the distance L in the front-rear direction of the vehicle body from the position where the imaging device 4 is mounted to the yaw rotation axis X of the vehicle body increases. Thus, the steering timing can be set to correspond to the position of the yaw rotation axis X, so that the wobble of the vehicle 2 can be prevented.

The running control system 1 is not limited to the above-described embodiment, and may have any configuration as long as it is configured as follows: when the vehicle 2 has entered a curve portion (a portion where the curvature is greater than or equal to a predetermined threshold value) of the traveling lane D, the travel control system 1 delays the steering timing, as compared to when the vehicle 2 travels on a straight portion.

More specifically, in another embodiment of the invention, the running control system 51 for the vehicle 2 equipped with the steering device 3C may include: an imaging device 4 mounted in front of the yaw rotation axis X of the vehicle 2 and configured to acquire an image in the forward direction of the vehicle body; and a control device 7 configured to recognize a traveling lane D in which the vehicle 2 is currently traveling from the acquired image, calculate an angle Δ θ formed between a direction of the traveling lane D at a portion of the vehicle where the imaging device 4 is installed and a forward direction of the vehicle body (see fig. 2), acquire an angle Δ θ 'formed between the direction of the traveling lane D at the yaw rotation axis X of the vehicle and the forward direction of the vehicle body by correcting the angle Δ θ, and feedback-control the steering device 3C so as to make the angle Δ θ' (i.e., the deviation) zero.

For the above correction, the running control system 51 may include a yaw rate sensor 52 (see fig. 1) configured to acquire a yaw rate of the vehicle body, and the lane-keeping planning unit 7B may estimate the shape of the running lane D to be detected after a predetermined time using the vehicle speed and the yaw rate, and compare the estimation result with the shape of the running lane D detected based on the image acquired by the imaging device 4 to estimate a true value of the inclination of the vehicle body to the running lane D (an angle Δ θ' formed between the direction of the running lane D at the yaw rotation axis X and the advancing direction of the vehicle body). The amount of lateral deviation of the vehicle 2 from the traveling lane D or the like may also be estimated. At this time, in estimating the shape of the traveling lane D, a known state estimation method using an observer, a kalman filter, or the like may be used.

With the above configuration, the steering angle is determined based on the angle Δ θ' formed between the direction of the traveling lane D at the portion where the yaw rotation axis X is located and the advancing direction of the vehicle body. Therefore, when the vehicle 2 has entered the curve portion from the straight line portion, the steering angle is not set to the angle at which it travels along the curve portion during the period in which the imaging device 4 is in the curve portion while the yaw rotation axis X is in the straight line portion, but is set to the angle once the yaw rotation axis X enters the curve portion. Therefore, the steering timing is delayed to correspond better to the position of the yaw rotation axis X, as compared with the case where the steering device 3C is controlled based on the angle Δ θ formed between the direction of the traveling lane D at the position where the imaging device 4 is installed and the advancing direction of the vehicle body.

In the above embodiment, the lane keeping planning unit 7B calculates the delay time τ by the formula τ ═ L/v, but the present invention is not limited to this embodiment. The lane keeping plan unit 7B may determine in step ST2 whether the vehicle 2 is in a high vehicle speed range (i.e., L/v is smaller than a predetermined time threshold τ 0) such that if the determination result is yes, the lane keeping plan unit 7B sets the delay time τ to zero in step ST3, and if the determination result is no, the lane keeping plan unit 7B calculates the delay time τ by the formula τ -L/v. In this case, the time threshold τ 0 may be determined based on the operation time τ 1 from the start of steering to the completion of steering. With this configuration, it is possible to prevent the steering from being unduly delayed in the high vehicle speed range.

In addition, in another embodiment, the lane keeping planning unit 7B may calculate the delay time τ by the formula τ L/v- τ 1 in step ST 2; that is, in the present embodiment, τ is smaller than the above-described embodiment by the operation time τ 1. Here, when L/v- τ 1 is less than zero, the lane keeping planning unit 7B should set the delay time τ to zero in step ST 2.