Driving assistance method and driving assistance device

Abstract

In this driving assistance method, a steering command value for avoiding a first obstacle ahead in a course of a vehicle is calculated (S2), the steering angle of the vehicle is controlled on the basis of the steering command value (S3), whether the state of the vehicle is an avoidance phase in which the vehicle is steered in a direction for avoiding the first obstacle on the basis of the steering command value is determined (S4), a steering direction intended by a driver is detected (S5), an override threshold used when the state of the vehicle is the avoidance phase and the steering direction is a direction approaching the first obstacle is set to a value greater than an override threshold used when the state of the vehicle is the avoidance phase and the steering direction is a direction away from the first obstacle (S7, S8), and, when a steering operation amount by the driver exceeds the override threshold, an override operation by the driver is detected (S11).

Description

Driving assistance method and driving assistance device

[0001] The present invention relates to a driving assistance method and a driving assistance device.

[0002] In the driving assistance device described in Patent Document 1 below, for a certain period of time from the start of collision avoidance assistance operation control that automatically steers steered wheels so as to avoid collision between the host vehicle and an obstacle, cancellation of the collision avoidance assistance operation control by the driver's override is prohibited.

[0003] Japanese Patent No. 7056459

[0004] In the driving assistance device described in Patent Document 1, automatic steering of the steered wheels is not canceled even if the driver performs a steering operation for a certain period of time from the start of collision avoidance assistance operation control, so there occurs a period in which the driver cannot perform intentional override. An object of the present invention is, in control for avoiding a forward obstacle through steering control, to make it less likely to hinder an override that steers the vehicle in a direction away from the obstacle while suppressing the driver's override that steers the vehicle in a direction approaching the obstacle.

[0005] In the driving assistance method according to one aspect of the present invention, a first obstacle existing in front of a traveling path of the vehicle is detected, a steering command value for avoiding the first obstacle is calculated, a steering angle of the vehicle is controlled based on the steering command value, it is determined whether a state of the vehicle is an avoidance phase in which the vehicle is being steered in a direction to avoid the first obstacle based on the steering command value, a steering direction intended by the driver is detected, an override threshold when the state of the vehicle is the avoidance phase and the steering direction is a direction approaching the first obstacle is set to a larger value than an override threshold when the state of the vehicle is the avoidance phase and the steering direction is a direction away from the first obstacle, when the amount of steering operation by the driver exceeds the override threshold, an override operation by the driver is detected, and when the override operation is detected, control of the steering angle based on the steering command value is stopped to allow the driver to operate the steering angle.

[0006] According to the present invention, in control for avoiding obstacles ahead by steering control, it is possible to suppress driver override by steering in the direction of approaching the obstacle, while making it less likely to interfere with override by steering in the direction of moving away from the obstacle. The object and advantages of the present invention are embodied and achieved using the elements and combinations thereof set forth in the claims. Both the above general description and the following detailed description should be understood as merely illustrative and explanatory and not as limiting the present invention in the manner of the claims.

[0007] This is a schematic diagram of an example of a driver assistance device according to the embodiment. This is an explanatory diagram of an example of obstacle avoidance control by the driver assistance device. This is a block diagram of an example of the functional configuration of the controller. (a) to (e) are timing charts explaining the operation of the driver assistance device according to the embodiment. This is a flowchart of an example of a driver assistance method according to the embodiment. (a) and (b) are explanatory diagrams of the first modified example. (a) and (b) are explanatory diagrams of the second modified example. This is an explanatory diagram of the third modified example. This is an explanatory diagram of the fourth modified example.

[0008] (Configuration) Figure 1 is a schematic configuration diagram of an example of the driver assistance device 10 of the embodiment. The vehicle 1 is equipped with a driver assistance device 10 that assists in driving the vehicle 1. The driver assistance control by the driver assistance device 10 includes obstacle avoidance control, which avoids an obstacle by steering control when an obstacle is present in front of the vehicle 1's path and then settles the vehicle's behavior after avoiding the obstacle.

[0009] The driver assistance system 10 includes an object detection sensor 11, a steering torque sensor 12, a camera 13, a controller 14, and a steering angle control actuator 15. The object detection sensor 11 is a sensor that detects objects around the vehicle 1. For example, the object detection sensor 11 may be a laser radar, a millimeter-wave radar, a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), or an ultrasonic sensor. The object detection sensor 11 may include multiple different types of these sensors. The object detection sensor 11 outputs detection result information to the controller 14.

[0010] The steering torque sensor 12 detects the steering torque, which is the torque input to the steering shaft by the driver, as the amount of steering operation performed by the driver of the vehicle 1. The driver assistance device 10 may also include a steering angle sensor in addition to or instead of the steering torque sensor 12 as a sensor for detecting the amount of steering operation performed by the driver. The steering angle sensor detects the steering angle of the steering wheel. The steering torque sensor 12 and the steering angle sensor output the detection result information to the controller 14.

[0011] Camera 13 captures an image of the area around Vehicle 1, including the area in front of Vehicle 1, generates an image, and outputs the generated image to Controller 14. Controller 14 is an electronic control unit (ECU) that performs driving assistance control of Vehicle 1. For example, Controller 14 performs driving assistance control by driving the steering angle control actuator 15 based on the detection signals of the object detection sensor 11 and the steering torque sensor 12, and the image generated by Camera 13.

[0012] The controller 14 includes a processor 14a and peripheral components such as a storage device 14b. The processor 14a may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device 14b may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The functions of the controller 14 described below are realized, for example, by the processor 14a executing a computer program stored in the storage device 14b.

[0013] The controller 14 may be formed by dedicated hardware for performing the information processing described below. For example, the controller 14 may include functional logic circuits set in a general-purpose semiconductor integrated circuit. For example, the controller 14 may have a programmable logic device (PLD) such as a field-programmable gate array (FPGA). The steering angle control actuator 15 controls the steering direction and steering amount of the steering mechanism of the vehicle 1 in accordance with the control signal from the controller 14.

[0014] Next, obstacle avoidance control by the controller 14 will be described with reference to Figure 2. When the controller 14 detects an obstacle 2 (for example, a parked vehicle) located in front of the vehicle 1's path, and the longitudinal distance between the vehicle 1 and the obstacle 2 falls below a predetermined distance at time t0, the controller 14 starts obstacle avoidance control to avoid the obstacle 2 by steering control. The obstacle 2 is an example of the "first obstacle" described in the claims.

[0015] When obstacle avoidance control is initiated, the controller 14 controls the vehicle to avoid the obstacle by increasing the yaw angle between the direction of travel of the vehicle 1 and the tangential direction of the lane in which the vehicle 1 is traveling, in the direction away from the obstacle 2, through steering control, during the period from time t0 to time t2. In the following description, the stage of obstacle avoidance control from time t0 to time t2 may be referred to as the "avoidance phase".

[0016] In the avoidance phase, the controller 14 increases the steering angle that generates yaw motion away from obstacle 2 during the period from time t0 to time t1, and then decreases the steering angle that generates yaw motion away from obstacle 2 during the period from time t1 to time t2. During the period from time t0 to time t2, the steering angle of vehicle 1 is steered in a direction away from the obstacle from the neutral position. That is, the steering direction during the period from time t0 to time t2 is in the direction away from the obstacle. At time t2, the steering angle that generates yaw motion away from obstacle 2 is the minimum during the period of obstacle avoidance control (for example, the steering angle may be in the neutral position), and the yaw angle between the tangential direction of the lane and the direction of travel of vehicle 1 is the maximum during the period of obstacle avoidance control.

[0017] During the obstacle avoidance control from time t2 to time t4, the controller 14 performs steering control to stabilize the vehicle behavior by reducing the yaw angle between the tangential direction of the lane and the direction of travel of the vehicle 1 after avoiding the obstacle 2. In the following description, the stage of obstacle avoidance control from time t2 to time t4 may be referred to as the "return phase".

[0018] In the return phase, the controller 14 increases the steering angle that generates yaw motion in the direction of approaching the obstacle 2 during the period from time t2 to time t3, and then decreases the steering angle that generates yaw motion in the direction of approaching the obstacle 2 during the period from time t3 to time t4. At time t4, the steering angle that generates yaw motion in the direction of approaching the obstacle 2 is the minimum during the obstacle avoidance control period (for example, the steering angle may be in the neutral position), and the yaw angle between the tangential direction of the lane and the direction of travel of the vehicle 1 is the minimum during the obstacle avoidance control period. The trajectory of the vehicle 1 when steered by the above obstacle avoidance control is, for example, as shown by the dashed line Ta.

[0019] On the other hand, the driver of vehicle 1 may want to drive vehicle 1 along a different trajectory than the trajectory Ta realized by obstacle avoidance control. For example, if there is another obstacle 3 (such as an oncoming vehicle) in the direction away from obstacle 2 by obstacle avoidance control, the driver may want to drive vehicle 1 along a trajectory Td that is as close to obstacle 2 as possible. Obstacle 3 is an example of the "second obstacle" described in the claims. In the driver assistance device of Patent Document 1, even if the driver performs steering operations in such a situation, the driver's override operation is not effective for a certain period of time from the start of collision avoidance support operation control, which presents a problem in that the driver cannot drive vehicle 1 along the desired trajectory Td.

[0020] Therefore, in the driving assistance method of this embodiment, during the execution of obstacle avoidance control, it is determined whether the state of vehicle 1 is in the avoidance phase and the steering direction intended by the driver is detected. If the state of vehicle 1 is in the avoidance phase and the steering direction is toward approaching obstacle 2, the override threshold that allows the driver to override is set to a larger value than when the state of vehicle 1 is in the avoidance phase and the steering direction is toward moving away from obstacle 2.

[0021] When the amount of steering input by the driver exceeds the override threshold, the system detects the driver's override operation. Upon detection of the override operation, the control of the steering angle based on the steering command value is stopped, allowing the driver to control the steering angle. As a result, after the state of vehicle 1 transitions from the avoidance phase to the return phase, the override threshold becomes smaller than in the avoidance phase, making it easier to detect the driver's override operation. This makes it easier for the driver to drive vehicle 1 along the desired travel trajectory Td. Furthermore, override operations are not uniformly prohibited even in the avoidance phase; if the amount of steering input exceeds the override threshold, the override operation is detected, making it easier for the driver to drive vehicle 1 along the desired travel trajectory Td.

[0022] Next, the functional configuration of the controller 14 will be described with reference to Figure 3. The controller 14 includes a steering command value calculation unit 20, a steering control unit 21, a steering direction determination unit 22, an override prediction unit 23, a phase determination unit 24, a threshold setting unit 25, and an override determination unit 26. The steering command value calculation unit 20 recognizes an obstacle 2 located in front of the vehicle 1's path based on at least one of the detection result from the object detection sensor 11 and the captured image generated by the camera 13.

[0023] The steering command value calculation unit 20 calculates steering command values ​​to avoid the recognized obstacle 2. For example, the steering command value calculation unit 20 may calculate a steering command value that increases the yaw angle in the direction away from the obstacle 2 during the avoidance phase, and a steering command value that reduces the yaw angle between the tangential direction of the lane and the direction of travel of the vehicle 1 during the return phase to stabilize the vehicle behavior. The steering command value calculated by the steering command value calculation unit 20 may be a steering angle command value that specifies a target steering angle, or it may be a steering torque command value for controlling the steering angle by torque feedback control.

[0024] The steering control unit 21 controls the steering angle of the vehicle 1 based on the steering command value. The steering direction determination unit 22 determines whether the steering direction intended by the driver is towards an obstacle or away from an obstacle. For example, the steering direction determination unit 22 may determine the steering direction intended by the driver based on the direction in which the steering angle of the steering wheel operated by the driver is rotating from the neutral position.

[0025] For example, if the steering angle of the steering wheel operated by the driver is such that it increases the yaw angle in the direction of approaching obstacle 2, it can be determined that the steering direction intended by the driver is in the direction of approaching the obstacle. Conversely, if the steering angle of the steering wheel operated by the driver is such that it increases the yaw angle in the direction of moving away from obstacle 2, it can be determined that the steering direction intended by the driver is in the direction of moving away from the obstacle.

[0026] The override prediction unit 23 predicts whether the current situation around the vehicle 1 is such that the driver is likely to perform an override operation on the steering wheel. For example, the override prediction unit 23 may determine whether there is another obstacle 3 in the direction away from obstacle 2 by the steering control in the obstacle avoidance control by the controller 14, and predict that an override operation is likely to occur if obstacle 3 is present. If the override prediction unit 23 predicts that an override operation is likely to occur, it sets the value of the override prediction flag to "True", and if it does not predict that an override operation is likely to occur, it sets the value of the override prediction flag to "False".

[0027] The phase determination unit 24 determines whether the state of vehicle 1 is the avoidance phase, the return phase, or any other state (phase). The threshold setting unit 25 sets an override threshold Th that allows the driver to override the steering operation against the obstacle avoidance control. For example, the threshold setting unit 25 may set the override threshold Th value when the state of vehicle 1 is the avoidance phase and the steering direction is toward the obstacle 2 to a value ThH that is greater than the override threshold Th value ThL when the state of vehicle 1 is the avoidance phase and the steering direction is toward the obstacle 2 (for example, the override threshold Th may be set to value ThH when the state of vehicle 1 is the avoidance phase and the steering direction is toward the obstacle 2, and the override threshold Th may be set to value ThL when the state of vehicle 1 is not the avoidance phase or the steering direction is toward the obstacle 2).

[0028] For example, the threshold setting unit 25 may set the override threshold Th to a value ThH that is greater than the override threshold ThL that is greater than the override threshold ThL that is greater than the override threshold ThL that is greater than the override threshold ThH

[0029] The override determination unit 26 detects an override operation by the driver when the amount of steering operation by the driver (for example, the steering torque Ts detected by the steering torque sensor 12 or the steering angle detected by a steering angle sensor not shown) exceeds the override threshold Th, and does not detect an override operation by the driver when the amount of steering operation by the driver is less than or equal to the override threshold Th. When the override determination unit 26 detects an override operation, the steering control unit 21 stops the control of the steering angle based on the steering command value by the obstacle avoidance control and allows the driver to control the steering angle through an override operation. On the other hand, when the override determination unit 26 does not detect an override operation, the steering control unit 21 continues the control of the steering angle based on the steering command value by the obstacle avoidance control until the return phase is completed, and then terminates the obstacle avoidance control after the return phase is completed.

[0030] Figures 4(a) to 4(e) are timing charts illustrating examples of changes in the state of vehicle 1, steering direction, override determination flag, steering torque Ts, and override threshold Th in the obstacle avoidance control of the embodiment. At time t1, the override prediction unit 23 predicts that the current situation around vehicle 1 is likely to result in an override operation (for example, the steering control in obstacle avoidance control detects another obstacle 3 in the direction away from obstacle 2). As a result, the value of the override prediction flag changes from "False" to "True" (Figure 4(c)).

[0031] At this point t1, the phase determination unit 24 has not yet determined that the state of vehicle 1 is the avoidance phase (Figure 4(a)), and because the steering angle is relatively small, the steering direction determination unit 22 has not detected the steering direction (Figure 4(b)). As a result, the override threshold Th is set to a relatively small value ThL (Figure 4(e)). At the subsequent point t2, the phase determination unit 24 determines that the state of vehicle 1 is the avoidance phase (Figure 4(a)). However, because the steering direction is away from obstacle 2 (Figure 4(b)), the override threshold Th is set to a relatively small value ThL (Figure 4(e)). Thus, when the steering direction is away from obstacle 2, the override threshold Th is set to a relatively small value ThL. For this reason, override operations that steer away from obstacle 2 during the avoidance phase are easily detected and are less likely to be interfered with even during obstacle avoidance control.

[0032] If, at a subsequent time point t3, the driver operates the steering wheel in a direction that approaches the obstacle 2 (Figure 4(d)), the steering direction determination unit 22 detects the steering direction as one that approaches the obstacle 2 (Figure 4(b)). As a result, the override threshold Th is set to a relatively large value ThH (Figure 4(e)). This makes it more difficult to detect override operations in the direction that approaches the obstacle 2 during the avoidance phase, thereby suppressing overrides by drivers who steer in the direction that approaches the obstacle.

[0033] At the time point t4, once the avoidance phase is completed (Figure 4(a)), the override threshold Th is set to a relatively small value ThL (Figure 4(e)). This makes override operations easier to detect and less likely to be interfered with, even in the case of obstacle avoidance control. At the time point t5, the steering direction changes to move away from the obstacle (Figure 4(b)), at time t6 the value of the override prediction flag changes from "True" to "False" (Figure 4(c)), and at time t7 the steering angle becomes small and the steering direction determination unit 22 no longer detects the steering direction (Figure 4(b)).

[0034] (Operation) Figure 5 is a flowchart of an example of the driving assistance method of the embodiment. In step S1, the steering command value calculation unit 20 determines whether or not it has detected an obstacle 2 located ahead of the path. If no obstacle 2 is detected (step S1:N), the process returns to step S1. If obstacle 2 is detected (step S1:Y), the process proceeds to step S2. In step S2, the steering command value calculation unit 20 calculates a steering command value to avoid the recognized obstacle 2. In step S3, the steering control unit 21 controls the steering angle of the vehicle 1 based on the steering command value.

[0035] In step S4, the phase determination unit 24 determines whether the state of vehicle 1 is in the avoidance phase. If it is not in the avoidance phase (step S4:N), the process proceeds to step S7. If it is in the avoidance phase (step S4:Y), the process proceeds to step S5. In step S5, the steering direction determination unit 22 determines whether the steering direction intended by the driver is the direction of approaching (approaching) the obstacle. If the steering direction is not the direction of approaching the obstacle (step S5:N), the process proceeds to step S7. If the steering direction is the direction of approaching the obstacle (step S5:Y), the process proceeds to step S6.

[0036] In step S6, the override prediction unit 23 determines whether or not to set the value of the override prediction flag to "True". If the value of the override prediction flag is not set to "True" (step S6: N), the process proceeds to step S7. If the value of the override prediction flag is set to "True" (step S6: Y), the process proceeds to step S8. In step S7, the threshold setting unit 25 sets the override threshold Th to a relatively small value ThL. The process then proceeds to step S9. In step S8, the threshold setting unit 25 sets the override threshold Th to a relatively large value ThH. The process then proceeds to step S9.

[0037] In step S9, the steering torque sensor 12 detects the amount of steering operation Ts performed by the driver of the vehicle 1. In step S10, the override determination unit 26 determines whether the amount of steering operation Ts is greater than the override threshold Th. If the amount of steering operation Ts is not greater than the override threshold Th (step S10: N), the override determination unit 26 does not detect an override operation, and the process proceeds to step S12. If the amount of steering operation Ts is greater than the override threshold Th (step S10: Y), the override determination unit 26 detects an override operation, and the process proceeds to step S11.

[0038] In step S11, the steering control unit 21 stops controlling the steering angle based on the steering command value from the obstacle avoidance control and enables the driver to control the steering angle by override operation. In step S12, the steering control unit 21 continues controlling the steering angle based on the steering command value from the obstacle avoidance control until the return phase is completed, and terminates the obstacle avoidance control after the return phase is completed.

[0039] (Effects of the Embodiment) (1) In the driving assistance method of the embodiment, a first obstacle 2 located in front of the path of the vehicle 1 is detected, a steering command value for avoiding the first obstacle 2 is calculated, the steering angle of the vehicle 1 is controlled based on the steering command value, it is determined whether the state of the vehicle 1 is in the avoidance phase, where it is being steered in the direction to avoid the first obstacle 2 based on the steering command value, the steering direction intended by the driver is detected, the override threshold when the state of the vehicle 1 is in the avoidance phase and the steering direction is moving towards the first obstacle 2 is set to a value greater than the override threshold when the state of the vehicle 1 is in the avoidance phase and the steering direction is moving away from the first obstacle 2, the amount of steering operation by the driver exceeds the override threshold, the override operation by the driver is detected, and when an override operation is detected, the control of the steering angle based on the steering command value is stopped, allowing the driver to operate the steering angle.

[0040] This makes it possible to suppress driver overrides that steer towards obstacles while making it less likely to interfere with driver overrides that steer away from obstacles, in control that avoids obstacles ahead through steering control.

[0041] (2) Determine whether a second obstacle 3 exists in a direction away from the first obstacle 2. If a second obstacle 3 exists, the override threshold when the state of vehicle 1 is in the avoidance phase and the steering direction is towards the first obstacle 2 may be set to a value greater than the override threshold when the state of vehicle 1 is in the avoidance phase and the steering direction is away from the first obstacle 2. This makes it possible to change the override threshold only in scenes where an override operation that moves towards the first obstacle 2 is likely to occur.

[0042] (Modification) (1) When the steering direction intended by the driver is a direction approaching the obstacle 2, the threshold setting unit 25 may gradually decrease the override threshold Th when decreasing the override threshold Th with the end of the avoidance phase. For example, as shown in FIG. 6(a), if the override threshold Th (the dashed-dotted line) is abruptly switched from a relatively high value ThH to a relatively low value ThL at the time of transition from the avoidance phase to the return phase, the steering operation amount Ts (the solid line) exceeds the override threshold Th at the end of the avoidance phase, which enables the driver's override operation and may cause a sudden change in vehicle behavior.

[0043] Therefore, when decreasing the override threshold Th along with the transition from the avoidance phase to the return phase as shown in FIG. 6(b), gradually decreasing the override threshold Th can prevent the override operation from becoming abruptly enabled at the end of the avoidance phase. The override threshold Th may also be gradually decreased when decreasing the override threshold Th along with the switching of the override prediction flag from "True" to "False".

[0044] (2) When the steering direction intended by the driver is a direction approaching the obstacle 2, the threshold setting unit 25 may decrease the override threshold Th during a period in which the steering operation amount Ts by the driver decreases, when decreasing the override threshold Th with the end of the avoidance phase. For example, when the override threshold Th (the dashed-dotted line) is gradually decreased along with the transition from the avoidance phase to the return phase as shown in FIG. 7(a) or the switching of the override prediction flag from "True" to "False", immediately after the time point t1 when the steering operation amount Ts (the solid line) by the driver changes from decreasing to increasing (time point t2), the override operation is suddenly enabled, which may give the driver a sense of discomfort.

[0045] Therefore, as shown in FIG. 7(b), by decreasing the override threshold Th only during the period in which the steering operation amount Ts by the driver decreases, and enabling the override operation after the steering operation amount Ts increases to a certain extent from the time point t1 when the steering operation amount Ts (the solid line) by the driver changes from decreasing to increasing to the time point t3, it becomes possible to detect an override operation with less sense of discomfort.

[0046] (3) FIG. 8 is an explanatory diagram of a third modification. Since the override threshold Th decreases with the end of the avoidance phase or the switching of the override prediction flag from "True" to "False", the override operation does not need to be detected from time t1 when the steering operation amount Ts by the driver exceeds the override threshold Th to time t2 when the steering operation amount Ts by the driver increases.

[0047] When the override determination threshold decreases at the end of the avoidance phase or when the override prediction flag is switched, if an override operation is detected regardless of whether the steering operation amount Ts by the driver is constant or decreasing, the driver may feel a sense of discomfort. Such discomfort can be prevented by not detecting an override operation while the steering operation amount Ts by the driver is not increasing.

[0048] (4) FIG. 9 is an explanatory diagram of a fourth modification. When the lateral distance ΔD between the trajectory Ta passing through the lateral center of the vehicle 1 and the obstacle 2 is equal to or less than a threshold value, the threshold setting unit 25 does not need to set the override threshold Th for the case where the vehicle 1 is in the avoidance phase and the steering direction is a direction approaching the obstacle 2 to a value larger than the override threshold ThL for the case where the vehicle 1 is in the avoidance phase and the steering direction is a direction moving away from the obstacle 2.

[0049] In such a situation, both left and right are conceivable as directions for the vehicle 1 to avoid the obstacle 2. Therefore, by not increasing the override threshold Th, it is possible to suppress obstruction of an override operation in a direction opposite to the avoidance direction by the obstacle avoidance control.

[0050] All examples and conditional terms set forth herein are intended for educational purposes to help the reader understand the concepts given by the inventors for the advancement of the invention and the art, and should be interpreted without limitation to the examples and conditions specifically described herein, as well as the configuration of examples relating to demonstrating the superiority and inferiority of the invention. Although embodiments of the invention are described in detail, it should be understood that various changes, substitutions, and modifications are possible without departing from the spirit and scope of the invention.

[0051] 1...Vehicle, 2...First obstacle, 3...Second obstacle, 10...Driving support device, 11...Object detection sensor, 12...Steering torque sensor, 13...Camera, 14...Controller, 14a...Processor, 14b...Storage device, 15...Steering angle control actuator, 20...Steering command value calculation unit, 21...Steering control unit, 22...Steering direction determination unit, 23...Override prediction unit, 24...Phase determination unit, 25...Threshold setting unit, 26...Override determination unit

Claims

1. A driving assistance method characterized by: detecting a first obstacle located in front of the vehicle's path; calculating a steering command value to avoid the first obstacle; controlling the steering angle of the vehicle based on the steering command value; determining whether the vehicle's state is in an avoidance phase where it is being steered in a direction to avoid the first obstacle based on the steering command value; detecting the steering direction intended by the vehicle's driver; setting an override threshold greater than the override threshold when the vehicle's state is in the avoidance phase and the steering direction is moving away from the first obstacle; detecting an override operation by the driver when the amount of steering operation by the driver exceeds the override threshold; and stopping the control of the steering angle based on the steering command value and enabling the driver to operate the steering angle when an override operation is detected.

2. The driving assistance method according to claim 1, characterized in that when the steering direction is in the direction of approaching the first obstacle, the override threshold is gradually reduced when the override threshold is reduced upon the end of the avoidance phase.

3. The driving assistance method according to claim 2, characterized in that when the steering direction is in the direction of approaching the first obstacle, the override threshold is reduced at the end of the avoidance phase, and the amount of steering operation by the driver is reduced during the period in which the override threshold is reduced.

4. The driving assistance method according to claim 2 or 3, characterized in that the override operation is not detected from the point in time when the amount of steering operation by the driver exceeds the override threshold due to the decrease in the override threshold upon the end of the avoidance phase, until the point in time when the amount of steering operation by the driver increases.

5. The driving assistance method according to claim 1, characterized in that, if the lateral distance between the trajectory through which the lateral center of the vehicle passes and the first obstacle is less than or equal to a threshold, the override threshold when the state of the vehicle is in the avoidance phase and the steering direction is toward approaching the first obstacle is not set to a value greater than the override threshold when the state of the vehicle is in the avoidance phase and the steering direction is toward moving away from the first obstacle.

6. The driving assistance method according to claim 1, characterized in that it determines whether a second obstacle exists in a direction away from the first obstacle, and when the second obstacle exists, the override threshold when the vehicle is in the avoidance phase and the steering direction is toward the first obstacle is set to a value greater than the override threshold when the vehicle is in the avoidance phase and the steering direction is toward the first obstacle.

7. A sensor for detecting a first obstacle located in front of the vehicle's path; a steering actuator for controlling the steering angle of the vehicle; a controller that performs the following: a process for calculating a steering command value to avoid the first obstacle; a process for driving the steering actuator based on the steering command value to control the steering angle of the vehicle; a process for determining whether the state of the vehicle is in the avoidance phase, where it is being steered in a direction to avoid the first obstacle based on the steering command value; a process for detecting the steering direction intended by the driver; a process for setting an override threshold when the state of the vehicle is in the avoidance phase and the steering direction is moving towards the first obstacle to a value greater than the override threshold when the state of the vehicle is in the avoidance phase and the steering direction is moving away from the first obstacle; a process for detecting an override operation by the driver when the amount of steering operation by the driver exceeds the override threshold; and a process for stopping the control of the steering angle based on the steering command value and enabling the driver to operate the steering angle when an override operation is detected. A driver assistance device characterized by being equipped with the following features.

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