Lane deviation prevention device, lane deviation prevention method, and program

Abstract

To provide a lane deviation prevention device which effectively suppresses lane deviation and effectively prevents override operation of a driver from being disturbed.SOLUTION: A lane deviation prevention device includes a controller 100 which performs, when a vehicle SV is deviated from a traveling lane, steering control to change a steering angle of the vehicle SV to prevent the vehicle SV from being deviated from the lane. The controller 100 terminates, after starting the steering control and when the vehicle SV reaches a prescribed first lateral position Δx2 within the lane, the steering control, and configures, when the vehicle SV reaches a prescribed second lateral position Δx1 that is closer to a boundary line LL, LR of the lane relative to the first lateral position Δx2 before the vehicle SV reaches the first lateral position Δx2, a threshold value to determine termination of the steering control through steering operation of a driver of the vehicle SV to be lower relative to the value at the time period before the vehicle SV reaches the second lateral position Δx1.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a lane departure prevention device, a lane departure prevention method, and a program.

Background Art

[0002] For example, in Patent Document 1, when a predetermined condition for the vehicle to deviate from the lane is satisfied, lane departure prevention control is started, and the switching timing of the target turning amount in the lane departure prevention control is determined in consideration of the delay in vehicle response and the detection delay of lane information, so as to optimize the vehicle posture at the end of the control. A technique is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In the technique described in Patent Document 1, the end of the lane departure prevention control is uniformly determined based on a specific lateral position and a duration. For this reason, when the lateral position used for determining the end of the control is far from the departure side boundary line, there is a possibility of interfering with the driver's override operation, and there is a problem that the driver's natural driving is hindered. On the other hand, when the lateral position used for determining the end of the control is too close to the departure side boundary line, the lane departure prevention control may end before the driver returns to the steering operation. In other words, the lane departure prevention control ends in a state where sufficient clearance cannot be ensured between the vehicle and the departure side boundary line, and there is a problem of inducing a re-lane departure or driver anxiety. That is, it is difficult to solve both of these problems by a method of changing the lateral position used for determining the end of the control.

[0005] One object of the present disclosure is to provide a technology that can effectively suppress lane departure and effectively prevent a driver's override operation from being hindered.

[0006] The device of the present disclosure is a lane departure prevention device including a control device that performs steering control to change a steering angle of the vehicle so that the vehicle does not depart from a lane in which the vehicle is traveling when the vehicle is about to depart from the lane. After starting the steering control, the control device terminates the steering control when the vehicle reaches a predetermined first lateral position within the lane, and before the vehicle reaches the first lateral position, when the vehicle reaches a predetermined second lateral position closer to a boundary line of the lane than the first lateral position, sets a threshold value for determining whether to cancel the steering control by a steering operation of a driver of the vehicle to be lower than before the vehicle reaches the second lateral position. It is characterized by this.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0008] Hereinafter, a lane departure prevention device, a lane departure prevention method, and a program according to this embodiment will be described with reference to the drawings.

[0009] [Hardware Configuration] FIG. 1 is a schematic diagram showing the hardware configuration of vehicle SV according to the present embodiment.

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

[0011] The ECU 10 is a central device that performs driving assistance such as lane departure prevention control (Lane Departure Alert Control: hereinafter, LTA control). Driving assistance is a concept that includes autonomous driving. The ECU 10 is communicably connected to a drive device 20, a brake device 21, a steering device 22, an in-vehicle sensor device 30, an external sensor device 40, an HMI (Human Machine Interface) 50, etc.

[0012] The drive device 20 generates a driving force transmitted to the drive wheels of vehicle SV. Examples of the drive device 20 include an electric motor and an engine. In the present embodiment, vehicle SV may be any of a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), a fuel cell vehicle (FCEV), a battery electric vehicle (BEV), and an engine vehicle. The brake device 21 applies a braking force to the wheels of vehicle SV.

[0013] The steering device 22 applies a steering force to the wheels of the vehicle SV. The steering device 22 may be either a rack and pinion type or a steer-by-wire type. The steering device 22 has a steering operation unit 23 including a steering wheel SW or the like. Further, the steering device 22 includes a steering motor 25 that applies a steering torque to the steering shaft 24. The steering motor 25 generates a steering torque in response to a command from the ECU 10. With this steering torque, the left and right steering wheels of the vehicle SV can be steered. Note that the steering operation unit 23 is not limited to the steering wheel SW and may have a shape other than a wheel, such as a steering lever.

[0014] The in-vehicle sensor device 30 is sensors that detect the state of the vehicle SV. Specifically, the in-vehicle sensor device 30 includes a vehicle speed sensor 31, a steering angle sensor 32, a steering torque sensor 33, a yaw rate sensor 34, an acceleration sensor 35, and the like.

[0015] The vehicle speed sensor 31 detects the traveling speed (vehicle speed V) of the vehicle SV. The steering angle sensor 32 detects the rotation angle of the steering wheel SW or the steering shaft 24 of the vehicle SV, that is, the steering angle σD. The steering torque sensor 33 detects the rotational torque of the steering wheel SW or the steering shaft 24, that is, the steering torque Tq. The yaw rate sensor 34 detects the yaw rate of the vehicle SV. The acceleration sensor 35 detects the acceleration of the vehicle SV. The in-vehicle sensor device 30 transmits the state of the vehicle SV detected by each of the sensors 31 to 35 to the ECU 10 at a predetermined cycle.

[0016] The out-vehicle sensor device 40 is sensors that recognize target information regarding targets around the vehicle SV. Specifically, the out-vehicle sensor device 40 includes a radar sensor 41, a camera sensor 42, and the like. Here, examples of the target information include surrounding vehicles, lane lines such as white lines drawn on the road surface, curbs, guardrails, walls, and the like.

[0017] The radar sensor 41 detects targets existing around the vehicle SV. The radar sensor 41 includes a millimeter-wave radar and / or a lidar. The millimeter-wave radar emits radio waves (millimeter waves) in the millimeter-wave band, and receives the millimeter waves (reflected waves) reflected by the targets existing within the radiation range. The millimeter-wave radar obtains the relative distance between the vehicle SV and the target, the relative speed between the vehicle VH and the target, etc. based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from transmitting the millimeter waves to receiving the reflected waves. The lidar sequentially scans pulsed laser light with a shorter wavelength than millimeter waves in a plurality of directions, and receives the reflected light reflected by the target, thereby obtaining the shape of the target detected in front of the vehicle VH, the relative distance between the vehicle VH and the target, the relative speed between the vehicle VH and the target, etc.

[0018] The camera sensor 42 images the surroundings of the vehicle SV, and obtains target information around the vehicle SV by processing the captured image data. As the camera sensor 42, for example, a digital camera having an imaging element such as a CMOS or a CCD can be used. The target information is information representing the type of the target detected around the vehicle VH, the relative distance between the vehicle SV and the target, the relative speed between the vehicle SV and the target, etc. The type of the target may be recognized by machine learning such as pattern matching.

[0019] The external sensor device 40 repeatedly transmits the acquired target information to the ECU 10 every time a predetermined time elapses. The ECU 10 determines the relative relationship between the vehicle SV and the target by synthesizing the relative relationship between the vehicle SV and the target obtained by the radar sensor 41 and the relative relationship between the vehicle SV and the target obtained by the camera sensor 42. Note that the external sensor device 40 does not necessarily have to include both the radar sensor 41 and the camera sensor 42, and may include only the camera sensor 42, for example.

[0020] The HMI 50 is an interface for inputting and outputting information between the ECU 10 and the driver, and includes an input device and an output device. Examples of the input device include a touch panel, a switch, a voice pickup microphone, etc. Examples of the output device include a display device 51, a speaker 52, etc. The display device 51 is, for example, a center display installed on an instrument panel or the like, a multi-information display, a head-up display, a display of a navigation system, etc. The speaker 52 is, for example, a speaker of an audio system or a navigation system.

[0021] [Software Configuration] FIG. 2A is a schematic diagram showing the software configuration of the ECU 10 according to the present embodiment. As shown in FIG. 2A, the ECU 10 includes, as functional elements, a lane recognition unit 100, an LDA control unit 110, an override control unit 120, etc. Each of these functional elements 100 to 120 is realized by the CPU 11 of the ECU 10 reading out a program stored in the ROM 12 and executing it in the RAM 13. Note that each of the functional elements 100 to 120 is described as being included in the ECU 10 which is an integrated hardware in the present embodiment, but a part of any of these can also be provided in another ECU separate from the ECU 10. Also, all or part of each of the functional elements 100 to 120 of the ECU 10 can be provided in an information processing device of a facility (for example, a management center or the like) capable of communicating with the vehicle SV.

[0022] The lane recognition unit 100 recognizes the driving lane in which the vehicle SV is traveling based on the detection result of the external sensor device 40. Here, the driving lane refers to not only the dividing lines such as white lines and yellow lines drawn on the road surface, but also the driving area defined by structures such as curbs, guardrails, and walls. In the following, for convenience, the boundary of the driving area defined by these dividing lines and structures or the like is referred to as a "boundary line".

[0023] As shown in FIG. 2B, the lane recognition unit 100 recognizes the left boundary line LL and the right boundary line LR. Further, the lane recognition unit 100 calculates the curve radius R of the center line LC that is the center position between these left and right boundary lines LL and LR, and calculates the deviation angle (hereinafter, yaw angle θy) between the direction of the center line LC and the direction in which the vehicle SV is facing. Furthermore, the lane recognition unit 100 calculates the distance in the road width direction (hereinafter, lateral position Δx) between the vehicle SV (for example, the left front wheel) and the left boundary line LL, and between the vehicle SV (for example, the right front wheel) and the right boundary line LR. FIG. 2B shows only the lateral position Δx between the vehicle SV and the right boundary LR. In this case, there are two lateral positions Δx on the left and right, but in the LDA control described later, the lateral position Δx in the direction indicated by the yaw angle θy, that is, the direction in which the vehicle SV is estimated to deviate from the driving lane, may be used. Hereinafter, the lateral position Δx, the yaw angle θy, and the curve radius R calculated by the lane recognition unit 100 are also collectively referred to as "driving lane information".

[0024] When the vehicle SV is likely to deviate from the driving lane, the LDA control unit 110 executes an alarm by the HMI 50 or a deviation warning by applying vibration to the steering wheel SW, and controls the operation of the steering device 22 and the braking device 21 to execute LDA control for suppressing the deviation of the vehicle SV from the driving lane. The LDA control unit 110 calculates the target steering angle (hereinafter, LDA target steering angle σB) of the LDA control based on the driving lane information (Δx, θY, R) acquired by the lane recognition unit 100. The LDA target steering angle σB is a steering angle set so that the vehicle SV does not deviate outside the boundary lines LL and LR (the right boundary LR in the illustrated example).

[0025] The LDA control unit 110 determines whether or not the LDA start condition is satisfied. Examples of the LDA start condition include a case where the predicted arrival time TR until the vehicle SV reaches the boundary lines LL and LR (the right boundary LR in the illustrated example) becomes shorter than a predetermined threshold time Tv (TR < Tv). The predicted arrival time TR can be obtained based on a well-known mathematical formula or the like assuming, for example, that the vehicle SV moves in a straight line with a constant acceleration until it reaches the boundary lines LL and LR.

[0026] When the LDA start condition is satisfied, the LDA control unit 110 calculates the LDA assist torque Ts based on the steering angle difference Δσ between the LDA target steering angle σB and the actual steering angle σD acquired by the steering angle sensor 32. Further, when the LDA control unit 110 calculates the LDA assist torque Ts, it transmits a command signal including information representing the LDA assist torque Ts to the steering device 22. As a result, the LDA assist torque Ts is transmitted from the steering motor 25 to the steering shaft 24, and the steered wheels of the vehicle SV are steered, thereby suppressing the deviation of the vehicle SV from the travel lane. After starting the LDA control, the LDA control unit 110 ends the LDA control when the lateral position Δx of the vehicle SV acquired by the lane recognition unit 100 becomes equal to or greater than a predetermined end determination lateral position Δx2. The end determination lateral position Δx2 is an example of the "first lateral position" of the present disclosure.

[0027] During the execution of the LDA control by the LDA control unit 110, when the steering torque Tq (absolute value) detected by the steering torque sensor 33 becomes equal to or greater than a predetermined first torque threshold value Tq1, the override control unit 120 executes an override that forcibly ends (i.e., aborts) the LDA control so as to give priority to the driver's steering operation over the LDA control.

[0028] By the way, if the first torque threshold value Tq1, which is the override condition for LDA, is set to a uniform value (fixed value) over the period from the start of the LDA control until the lateral position Δx of the vehicle SV reaches the end determination lateral position Δx2, it may interfere with the driver's override operation and become a factor that hinders the driver's natural driving. On the other hand, if the first torque threshold value Tq1 is changed to a small value early from the start of the LDA control, the LDA control will easily end when the driver has not yet returned to the steering operation, which may induce re-deviation and give the driver a sense of unease. In the present embodiment, the override control unit 120 solves these problems by changing the first torque threshold value Tqv, which is the override condition for LDA, at an optimal timing.

[0029] FIG. 3 is a schematic diagram for explaining the override condition change process by the override control unit 120. When the LDA start condition is satisfied at time t1, the LDA control unit 110 starts LDA control. Time t3 is the timing at which the LDA control unit 110 ends the LDA control when the lateral position Δx of the vehicle SV reaches the end determination lateral position Δx2. When the lateral position Δx of the vehicle SV becomes equal to or greater than a predetermined change determination lateral position Δx1 that is closer to the right boundary line LR than the end determination lateral position Δx2, the override control unit 120 changes the override condition to a second torque threshold value Tq2 (<Tq1) that is smaller than the first torque threshold value Tq1. The change determination lateral position Δx1 is an example of the "second lateral position" of the present disclosure.

[0030] That is, during the period T1 from time t1 when the LDA control is started to time t2 when the lateral position Δx of the vehicle SV reaches the change determination lateral position Δx1 (the period until the vehicle SV returns to the inside of the driving lane from the right boundary line LR), by setting the override condition to the first torque threshold value Tq1, it becomes possible to effectively prevent the induction of re-deviation. Also, during the period T2 from time t2 when the lateral position Δx of the vehicle SV reaches the change determination lateral position Δx1 to time t3 when it reaches the end determination lateral position Δx2, by changing the override condition to the second torque threshold value Tq2 that is smaller than the first torque threshold value Tq1, when the driver performs an override operation, the LDA control can be easily aborted. That is, the driver's steering operation becomes more likely to be prioritized, and it becomes possible to realize the driver's natural driving.

[0031] FIG. 4 is a flowchart for explaining the routine of the override condition change process by the CPU 11 of the ECU 10. This routine is started, for example, by the running of the vehicle SV.

[0032] In step S100, the ECU 10 determines whether the LDA control is being executed. If the LDA control is being executed (Yes), the ECU 10 proceeds to the process of step S110. On the other hand, if the LDA control is not being executed (No), the ECU 10 returns from this routine.

[0033] In step S110, the ECU 10 acquires the lateral position Δx, which is the distance between the vehicle SV and the boundary lines LL and LR, and also acquires the steering torque Tq detected by the steering torque sensor 33. Next, in step S120, the ECU 10 determines whether the steering torque Tq is equal to or greater than the first torque threshold value Tq1. When the steering torque Tq is equal to or greater than the first torque threshold value Tq1 (Yes), the ECU 10 proceeds to the process of step S170, executes an override to cancel the LDA control, and returns from this routine. On the other hand, when the steering torque Tq is not equal to or greater than the first torque threshold value Tq1 (No), that is, when the steering torque Tq is less than the first torque threshold value Tq1, the ECU 10 proceeds to the process of step S130.

[0034] In step S130, the ECU 10 determines whether the lateral position Δx of the vehicle SV has reached the lateral position Δx1 for change determination. When the lateral position Δx of the vehicle SV has not reached the lateral position Δx1 for change determination (No), the ECU 10 returns to the process of step S120. On the other hand, when the lateral position Δx of the vehicle SV has reached the lateral position Δx1 for change determination (Yes), the ECU 10 proceeds to the process of step S140.

[0035] In step S140, the ECU 10 executes a change process to change the override condition to a second torque threshold value Tq2 that is smaller than the first torque threshold value Tq1. Next, in step S150, the ECU 10 determines whether the steering torque Tq is equal to or greater than the second torque threshold value Tq2. When the steering torque Tq is equal to or greater than the second torque threshold value Tq2 (Yes), the ECU 10 proceeds to the process of step S170, executes an override to cancel the LDA control, and returns from this routine. On the other hand, when the steering torque Tq is not equal to or greater than the second torque threshold value Tq2 (No), that is, when the steering torque Tq is less than the second torque threshold value Tq2, the ECU 10 proceeds to the process of step S180.

[0036] In step S180, the ECU 10 determines whether or not the lateral position Δx of the vehicle SV has reached the end determination lateral position Δx2. If the lateral position Δx of the vehicle SV has not reached the end determination lateral position Δx2 (No), the ECU 10 returns to the process of step S150. On the other hand, if the lateral position Δx of the vehicle SV has reached the end determination lateral position Δx2 (Yes), the ECU 10 proceeds to the process of step S190, ends the LDA control, and returns from this routine.

[0037] As described above, the lane departure prevention device, the lane departure prevention method, and the program according to the present embodiment have been described. However, the present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the object of the present disclosure.

[0038] For example, as shown in FIG. 5, a second change determination lateral position Δx3 (the third lateral position of the present disclosure) is set between the change determination lateral position Δx1 and the end determination lateral position Δx2, and the lateral position Δx of the vehicle SV reaches the change determination lateral position Δx1. At the timing (time t2) and the timing (time t2') when the lateral position Δx of the vehicle SV reaches the second change determination lateral position Δx3, it is also possible to configure the override condition to be gradually lowered.

[0039] Specifically, at the timing (time t2) when the lateral position Δx of the vehicle SV reaches the change determination lateral position Δx1, the override condition is changed to a second torque threshold value Tq2 that is smaller than the first torque threshold value Tq1, and the lateral position Δx of the vehicle SV reaches the second change determination lateral position Δx3. At the timing (time t2'), the override condition is changed to a third torque threshold value Tq3 that is smaller than the second torque threshold value Tq2. In this way, it becomes possible to more effectively prevent re-deviation and prevent interference with the driver's override operation.

[0040] Further, the torque threshold value that is the override condition may not be changed stepwise as shown in FIG. 5, but may be decreased linearly or curvilinearly after the timing (time t2) when the lateral position Δx of the vehicle SV reaches the change determination lateral position Δx1.

[0041] Furthermore, the technology of the present disclosure can also be applied to an autonomous vehicle that automatically performs part or all of the driving operations. In this case, after the termination of the LDA control (including override) of the present disclosure, it may be shifted to fully autonomous driving.

Claims

1. A lane departure prevention device comprising a control device that performs steering control to change the steering angle of the vehicle so that the vehicle does not deviate from the lane when the vehicle is about to deviate from the lane in which it is traveling, after starting the steering control, when the vehicle reaches a predetermined first lateral position within the lane, the control device ends the steering control, and before the vehicle reaches the first lateral position, when the vehicle reaches a predetermined second lateral position closer to the boundary line of the lane than the first lateral position, the control device sets a threshold value for determining whether to cancel the steering control by the steering operation of the driver of the vehicle to be lower than before the vehicle reaches the second lateral position A lane departure prevention device characterized by the above.

2. The lane departure prevention device according to Claim 1, wherein a predetermined third lateral position is set between the first lateral position and the second lateral position, and the threshold value is gradually lowered at the timing when the vehicle reaches the second lateral position and at the timing when the vehicle reaches the third lateral position A lane departure prevention device characterized by the above.

3. A lane departure prevention method for performing steering control to change the steering angle of the vehicle so that the vehicle does not deviate from the lane when the vehicle is about to deviate from the lane in which it is traveling, after starting the steering control, when the vehicle reaches a predetermined first lateral position within the lane, the steering control is ended, and before the vehicle reaches the first lateral position, when the vehicle reaches a predetermined second lateral position closer to the boundary line of the lane than the first lateral position, the threshold value for determining whether to cancel the steering control by the steering operation of the driver of the vehicle is set to be lower than before the vehicle reaches the second lateral position A lane departure prevention method characterized by the above.

4. On a computer of a lane departure prevention device that performs steering control to change the steering angle of the vehicle so that the vehicle does not deviate from the lane when the vehicle is about to deviate from the lane in which it is traveling, after starting the steering control, when the vehicle reaches a predetermined first lateral position within the lane, the steering control is ended, and before the vehicle reaches the first lateral position, when the vehicle reaches a predetermined second lateral position closer to the boundary line of the lane than the first lateral position, a process of setting a threshold value for determining whether to cancel the steering control by the steering operation of the driver of the vehicle to be lower than before the vehicle reaches the second lateral position is executed A program characterized by the following.

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