Lane departure prevention device

Abstract

The present disclosure relates to a lane departure prevention device. The lane departure prevention device includes a control unit that, when determining that a vehicle is likely to cross a lane boundary and the driver has not intentionally left the lane, performs lane departure prevention control, including at least one of automatic steering of the steering wheel and the issuance of an alarm. If the control unit determines that the vehicle is likely to cross a lane boundary and the driver has intentionally left the lane, the control unit suspends execution of the lane departure prevention control. If, after suspending execution of the lane departure prevention control, the control unit determines that there is another lane boundary on the side the vehicle is approaching but the distance from the vehicle to the other lane boundary is greater than a reference distance, the control unit continues to suspend execution of the lane departure prevention control.

Description

Technical Field

[0001] The present invention relates to a lane departure prevention device for a vehicle such as an automobile. Background Art

[0002] The lane departure prevention device detects the position of the vehicle relative to the lane by a vehicle position detection device, and when it is determined that the vehicle is likely to deviate from the lane (dangerous, possible) based on the detected vehicle position, it performs lane departure prevention control of at least one of automatic steering of the steering wheel and issuance of an alarm.

[0003] Even if it is determined that the vehicle is at risk of lane departure, if the driver intentionally (or deliberately) attempts to depart from the lane, such as by changing lanes, lane departure prevention control may be limited. Whether the driver intends to depart from the lane is determined based on the driver's steering operation, the driver's operation of the turn signal lever, and the vehicle's inclination angle relative to the lane, i.e., the angle of the vehicle's diagonal travel.

[0004] For example, Japanese Patent Application Laid-Open No. 2019-177762 describes limiting lane departure prevention control when a steering speed, steering torque, and / or steering torque change exceeding a reference value are detected. This lane departure prevention system reduces the likelihood that automatic steering of the steering wheel, which is implemented by lane departure prevention control, will interfere with the driver's driving operation when the driver intends to depart the lane, such as by changing lanes. Summary of the Invention

[0005] Even in previous lane departure prevention devices such as the lane departure prevention device described in Japanese Patent Application Laid-Open No. 2019-177762, there are cases where lane departure prevention control is performed without restriction depending on the driving conditions of the vehicle. For example, as will be described in detail later, when the vehicle is intended to move to a side road (fork road) that branches off at a small inclination angle relative to the main road, sometimes even if the lane boundary of the main road is determined to be intentional lane departure, the lane boundary of the side road may be determined to be unintentional lane departure. Therefore, even if the driver intends to move the vehicle to the side road, since the automatic steering of the steering wheel based on the lane departure prevention control will interfere with the driver's driving operation, the driver will not be able to move the vehicle to the side road smoothly as desired, and sometimes there will be a sense of incongruity.

[0006] A main object of the present invention is to provide a lane departure prevention device that is improved so as to be able to restrict lane departure prevention control even in a situation where a vehicle intends to move to a side road that branches off at a small inclination angle with respect to a main road.

[0007] According to the present invention, a lane departure prevention device (100) is provided, which includes a vehicle position detection device (camera sensor 12) and a control unit (LDA ECU 10), wherein the vehicle position detection device detects the position of a vehicle (50) relative to a lane (54), and the control unit is configured to, when it is determined based on the position of the vehicle detected by the vehicle position detection device that the vehicle is likely to cross a first lane boundary (56L) and the driver of the vehicle that will cross the first lane boundary does not intend to deviate from the lane (S20, S30), execute lane departure prevention control (S50) of at least one of automatic steering of a steering wheel (24) and issuance of an alarm, and when it is determined that the vehicle is likely to cross the first lane boundary and the driver of the vehicle that will cross the first lane boundary intends to deviate from the lane, suspend execution of the lane departure prevention control (S10, S40) until it is determined that a predetermined control recovery condition is met (S60).

[0008] The control unit (LDA ECU 10) is configured to continue suspending the lane departure prevention control when it is determined that there is a second lane boundary (64) on the side to which the vehicle is approaching but the distance from the vehicle to the second lane boundary is greater than a reference distance (Lsc) under a condition in which the lane departure prevention control is suspended and a control recovery condition is not satisfied.

[0009] According to the above configuration, if lane departure prevention control is suspended and the control resumption condition is not met, and if it is determined that there is a second lane boundary on the side the vehicle is approaching but the distance from the vehicle to the second lane boundary is greater than the reference distance, lane departure prevention control continues to be suspended. Consequently, even if the driver intends to move the vehicle to a side road that branches off at a small inclination angle from the main road, lane departure prevention control is not executed. Consequently, there is no automatic steering of the steering wheel to interfere with the driver's driving operation, and the warning device is not activated, allowing the driver to smoothly move the vehicle to the side road as desired.

[0010] [Technical solution of the invention]

[0011] In one aspect of the present invention, the control unit (LDA ECU 10 ) variably sets the reference distance according to the vehicle speed so that the higher the vehicle speed (V), the larger the reference distance (Lsc).

[0012] As vehicle speed increases, the vehicle approaches the second lane boundary more quickly, increasing the likelihood that the vehicle will cross the second lane boundary. Therefore, the reference distance is preferably set to increase as vehicle speed increases. According to the above technical solution, the reference distance is variably set according to vehicle speed, increasing as vehicle speed increases. This increases the likelihood that the vehicle will cross the second lane boundary compared to a case where the reference distance is constant regardless of vehicle speed, making it possible to appropriately determine whether lane departure prevention control should be executed with respect to the second lane boundary.

[0013] In another technical solution of the present invention, the control unit (LDA ECU 10) performs lane departure prevention control on the second lane boundary when it determines that the vehicle (50) is likely to become dangerous if it crosses the second lane boundary (64) while continuing to suspend the execution of lane departure prevention control.

[0014] According to the above technical solution, while lane departure prevention control is still suspended, if it is determined that the vehicle is at risk of becoming dangerous if it crosses the second lane boundary, lane departure prevention control is executed at the second lane boundary. This reduces the possibility of the vehicle crossing the second lane boundary and becoming dangerous due to lane departure prevention control.

[0015] Furthermore, in another technical solution of the present invention, the control unit (LDA ECU 10) performs lane departure prevention control on the second lane boundary when it is determined that the steering torque (Ts) of the vehicle (50) in the direction approaching the second lane boundary (64) is less than the reference torque (Tac) while the execution of the lane departure prevention control is continuously suspended.

[0016] When the steering torque of the vehicle in the direction approaching the second lane boundary exceeds the reference torque, it can be assumed that the driver intends to move the vehicle toward the second lane boundary. In contrast, when the steering torque of the vehicle in the direction approaching the second lane boundary is less than the reference torque, it can be assumed that the vehicle is approaching the second lane boundary due to driver negligence or the like and is in danger of crossing the second lane boundary.

[0017] According to the above technical solution, while lane departure prevention control is still suspended, if the steering torque of the vehicle in the direction approaching the second lane boundary is determined to be less than the reference torque, lane departure prevention control is executed toward the second lane boundary. This reduces the likelihood of the vehicle crossing the second lane boundary through lane departure prevention control.

[0018] Furthermore, in another technical solution of the present invention, the control unit (LDA ECU 10) performs lane departure prevention control on the second lane boundary when it is determined that the speed (Va) of the vehicle (50) approaching the second lane boundary (64) is greater than the reference speed (Vac) and the steering torque (Ts) of the vehicle in the direction approaching the second lane boundary is less than the reference torque (Tac).

[0019] According to the above technical solution, lane departure prevention control is executed with respect to the second lane boundary when it is determined that the vehicle's speed approaching the second lane boundary is greater than or equal to a reference speed and the vehicle's steering torque in the direction of approaching the second lane boundary is less than or equal to a reference torque. This reduces the likelihood of the vehicle crossing the second lane boundary when the vehicle rapidly approaches the second lane boundary due to driver negligence or other factors, and the likelihood of the vehicle crossing the second lane boundary is high.

[0020] Furthermore, in another aspect of the present invention, the control unit (LDA ECU 10 ) variably sets the reference speed according to the vehicle speed such that the higher the vehicle speed (V), the lower the reference speed (Vac).

[0021] As vehicle speed increases, the vehicle approaches the second lane boundary more quickly, increasing the likelihood that the vehicle will cross the second lane boundary. Therefore, the reference speed is preferably set to decrease as vehicle speed increases. According to the above technical solution, the reference speed is variably set according to vehicle speed, decreasing as vehicle speed increases. This increases the likelihood that the vehicle will cross the second lane boundary compared to a case where the reference speed is constant regardless of vehicle speed, enabling appropriate determination of whether lane departure prevention control should be executed with respect to the second lane boundary.

[0022] Furthermore, in another aspect of the present invention, the control unit (LDA ECU 10 ) variably sets the reference torque according to the vehicle speed so that the higher the vehicle speed (V), the smaller the reference torque (Tac).

[0023] As vehicle speed increases, the steering resistance experienced by the steering wheel decreases in response to the driver's steering operation. Therefore, the reference torque preferably decreases as vehicle speed increases. According to the above technical solution, the reference torque is variably set according to vehicle speed, such that the reference torque decreases as vehicle speed increases. This makes it possible to more accurately determine whether the driver intends to move the vehicle toward the second lane boundary through steering operation, compared to a scenario where the reference torque is constant regardless of vehicle speed.

[0024] Furthermore, in another technical solution of the present invention, when the control unit (LDA ECU 10) determines that the distance from the vehicle (50) to the second lane boundary (64) is less than the reference distance (Lsc), the lane departure prevention control is performed on the second lane boundary, and the reference distance is variably set according to the risk that the vehicle will become dangerous if the vehicle crosses the second lane boundary, so that the higher the risk that the vehicle will become dangerous, the larger the reference distance.

[0025] According to the above technical solution, the reference distance is variably set according to the likelihood that the vehicle will become dangerous if the vehicle crosses the second lane boundary. The greater the likelihood that the vehicle will become dangerous if the vehicle crosses the second lane boundary, the greater the reference distance. As a result, the greater the likelihood that the vehicle will become dangerous if the vehicle crosses the second lane boundary, the more likely it is that the distance from the vehicle to the second lane boundary is less than the reference distance, enabling effective lane departure prevention control at the second lane boundary.

[0026] In the above description, to facilitate understanding of the present invention, the names and / or reference numerals used in the embodiments are enclosed in parentheses for the inventive components corresponding to the embodiments described later. However, the various constituent elements of the invention are not limited to the constituent elements of the embodiments corresponding to the names and / or reference numerals enclosed in parentheses. Other objects, other features, and attendant advantages of the present invention should be readily understood from the following description of the embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals represent like elements, and wherein:

[0028] Figure 1 This is a schematic diagram showing the configuration of an embodiment of a lane departure prevention device according to the present invention.

[0029] Figure 2 This is a flowchart showing a lane departure prevention control routine in the embodiment.

[0030] Figure 3 This is a map for calculating a reference value Tc for the elapsed time based on the vehicle speed V.

[0031] Figure 4 This is a map used to calculate the reference distance Lsc based on the vehicle speed V and the risk of danger.

[0032] Figure 5 This is a map for calculating the reference speed Vac based on the vehicle speed V.

[0033] Figure 6This is a map for calculating the reference torque Tac based on the vehicle speed V.

[0034] Figure 7 This is a diagram showing a situation in which a vehicle is traveling obliquely with respect to the longitudinal direction of a lane.

[0035] Figure 8 This diagram shows a situation in which, when the lane departure prevention device is a conventional lane departure prevention device, the driver desires to perform lane departure from the lane to the side road so that the vehicle moves from the lane across the first lane boundary to the side road.

[0036] Figure 9 This diagram shows a situation in which the driver wishes to perform lane departure from a lane to a side road so that the vehicle moves from the lane across a first lane boundary to the side road when the lane departure prevention device is the lane departure prevention device of the embodiment. DETAILED DESCRIPTION

[0037] Hereinafter, a lane departure prevention device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0038] <Composition>

[0039] like Figure 1 As shown, a lane departure prevention device 100 according to an embodiment is applied to a vehicle 50 and includes a lane departure prevention ECU 10, an electric power steering ECU 20, and a steering ECU 40. In this specification, lane departure prevention is referred to as LDA (Lane Departure Alert with Control), and electric power steering is referred to as EPS (Electric Power Steering), as needed.

[0040] These ECUs are electronic control units (ECUs) with microcomputers as their primary components. They are connected via CAN (Controller Area Network) 52 to enable communication between them. Each microcomputer includes a CPU, ROM, RAM, non-volatile memory, and interfaces. The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Several or all of these ECUs can be integrated into a single ECU.

[0041] As will be described in detail later, the ROM of the LDA ECU 10 stores Figure 2The flowchart shown corresponds to a lane departure prevention control program, and the CPU executes the lane departure prevention control according to the program. The LDA ECU 10 is connected to a camera sensor 12, a radar sensor 14, a vehicle speed sensor 16, an alarm device 18, and an LDA switch (not shown).

[0042] The camera sensor 12 includes a camera unit and a lane recognition unit. The lane recognition unit analyzes image data captured by the camera unit to recognize white lines on the road. The camera sensor 12 (camera unit) captures the scenery in front of the vehicle 50. The camera sensor 12 (lane recognition unit) repeatedly supplies information about the recognized white lines to the LDA ECU 10 at every predetermined computation cycle.

[0043] like Figure 7 As shown, the camera sensor 12 can identify the boundaries of lane 54 (referred to as lane boundaries), namely white lines 56L and 56R, and detect the relative position of the vehicle with respect to lane 54 based on the relationship between the white lines and the position of vehicle 50. The position of vehicle 50 here refers to the position of the vehicle's center of gravity 50A, but it may also be the center position of the vehicle in a top-down view. The vehicle's lateral position, described later, indicates the position of the vehicle's center of gravity in the lane width direction, and the vehicle's lateral speed indicates the speed of the vehicle's center of gravity in the lane width direction. These are determined based on the relative positional relationship between the white lines detected by the camera sensor 12 and the vehicle.

[0044] The radar sensor 14 includes a radar transceiver and a signal processing unit (not shown). The radar transceiver transmits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves reflected by three-dimensional objects (e.g., other vehicles, bicycles, guardrails, roadside structures, etc.) within the transmission range (i.e., reflected waves). The signal processing unit obtains information indicating the distance between the vehicle 50 and the three-dimensional object, the relative speed between the vehicle 50 and the three-dimensional object, and the relative position (orientation) of the three-dimensional object relative to the vehicle 50, based on the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from the transmission of the millimeter wave to the reception of the reflected wave, and supplies the information to the LDA ECU 10.

[0045] The vehicle speed sensor 16 detects the vehicle speed V of the vehicle 50 and repeatedly supplies a signal indicating the vehicle speed V to the LDA ECU 10 at a predetermined control cycle. The LDA switch is operated by the driver and supplies a signal indicating whether it is on to the LDA ECU 10. When the LDA switch is on, lane departure prevention control is executed.

[0046] When the LDA ECU 10 determines that the vehicle 50 is likely to depart from the lane 54, the warning device 18 is activated to issue a warning as part of the lane departure prevention control, specifically, to indicate that the vehicle 50 is likely to depart from the lane. The warning device 18 may be any one of a visual warning device such as a warning light, an auditory warning device such as a warning buzzer, and a sensory warning device such as seat vibration, or any combination thereof.

[0047] The EPS ECU 20 controls the EPS device 22 to steer the steered wheels 24 as needed. Thus, the EPS ECU 20 and the EPS device 22 constitute a steering system 26 that automatically steers the steered wheels 24 as needed. When the LDA ECU 10 determines that the vehicle 50 is at risk of departing from its lane, the EPS ECU 20 automatically steers the steered wheels 24 as another lane departure prevention control to prevent the vehicle from departing from its lane.

[0048] like Figure 1 As shown, a torque sensor 32 for detecting steering torque Ts is provided on a steering shaft 30 integrally connected to a steering wheel 28 operated by the driver. A signal representing the steering torque Ts detected by the torque sensor 32 is input to the EPS ECU 20. Based on the steering torque Ts and the vehicle speed V detected by the vehicle speed sensor 16, the EPS ECU 20 controls the EPS device 22 in a manner known in the art, thereby controlling the steering assist torque and reducing the steering burden on the driver. A signal representing the steering torque Ts is input from the EPS ECU 20 to the LDA ECU 10 via the CAN 52.

[0049] The steering ECU 40 is connected to a turn signal lever 42 and turn signal lamps 44L and 44R, which are operated by the driver. When the turn signal lever 42 is tilted toward the left turn of the vehicle 50, the steering ECU 40 flashes the front and rear turn signal lamps 44L on the left side of the vehicle 50. When the turn signal lever 42 is tilted toward the right turn of the vehicle 50, the steering ECU 40 flashes the front and rear turn signal lamps 44R on the right side of the vehicle 50. Information on the tilt of the turn signal lever 42 is input from the steering ECU 40 to the LDA ECU 10 via the CAN 52.

[0050] Lane Departure Prevention Control Routine

[0051] Next, refer to Figure 2 The flowchart shown in FIG. 1 illustrates the lane departure prevention control routine in the embodiment. Figure 1 When the LDA switch (not shown) is turned on, the Figure 2The lane departure prevention control shown in the flowchart is repeatedly executed in a predetermined control cycle by the CPU of the LDAECU 10. In the following description, the lane departure prevention control is simply referred to as "control."

[0052] First, in step S10, the CPU determines whether the flag Foff is 1, that is, whether the lane departure prevention control is not being executed. If the CPU makes a positive determination, the control proceeds to step S60, and if the CPU makes a negative determination, the control proceeds to step S20. In addition, the flag Foff is initialized to 0 at the start of the control, and thereafter, as described later, the flag Foff is initialized to 0. Figure 2 The flow chart shown is set to 0 or 1.

[0053] In step S20, the CPU determines whether the vehicle is at risk of leaving the lane based on the relative position of the vehicle 50 relative to the lane 54 detected by the camera sensor 12, using a method known in the art. If the CPU determines negatively, it temporarily terminates control. If the CPU determines positively, it advances control to step S30.

[0054] In this case, the determination of whether the vehicle 50 is likely to deviate from the lane can be performed, for example, as follows. Figure 7 As shown, based on image information in front of vehicle 50, the angle (inclination angle) θy formed by vehicle's traveling direction 62 with respect to the longitudinal direction 60 of lane 54 is estimated. The moving speed Vy of vehicle 50 in a direction perpendicular to the longitudinal direction 60 of lane 54 is estimated as Vsinθy based on angle θy and vehicle speed V. Furthermore, angle θy is the same as the inclination angle with respect to white lines 56L and 56R, and therefore also represents the oblique angle of vehicle 50.

[0055] In addition, a distance Dy (not shown) in the lane width direction between the white line 56L (first lane boundary) on the side that the vehicle 50 is approaching and the center of gravity 50A of the vehicle is estimated. Furthermore, Δt can be a predetermined time, and when Dy-VyΔt is equal to or less than a predetermined reference value Dyc (a positive constant), it is determined that the vehicle 50 is likely to depart from the lane.

[0056] In step S30, the CPU determines whether the driver intentionally departs the lane. If a negative determination is made, the CPU advances control to step S50. If a positive determination is made, the CPU sets a flag Foff to 1 in step S40 to disable lane departure prevention control.

[0057] In this case, if the driver performs at least one of a tilting operation on the turn signal lever 42 in the lane departure direction or a steering operation in the lane departure direction, the CPU determines that the driver intends to depart across the lane boundary. The steering operation can be determined based on whether the magnitude of the steering torque Ts detected by the torque sensor 32 is greater than or equal to a reference value Tsc or whether the magnitude of the steering angle θ, the rotation angle of the steering shaft 30, is greater than or equal to a reference value θsc.

[0058] Furthermore, while reference value Tsc can be a positive constant, it is variably set according to vehicle speed, decreasing as vehicle speed V increases, since the steering resistance to the steered wheel decreases when the driver's steering operation is performed. Therefore, compared to a case where reference value Tsc is constant and independent of vehicle speed, it is possible to more accurately determine whether the driver intentionally intends to depart from a lane boundary.

[0059] Furthermore, if, for example, vehicle 50 is unnecessarily inclined relative to lane 54 due to a lateral force applied to it by a side wind or a lateral inclination of the road, or due to driver negligence, the magnitude of vehicle 50's inclined angle θy is relatively small, creating a risk of vehicle 50 departing from lane 54. In contrast, if the driver intends to depart from the lane, the magnitude of vehicle 50's inclined angle θy is relatively large. Therefore, the CPU also determines that the driver intends to depart across the lane boundary even when the magnitude of vehicle 50's inclined angle θy is greater than or equal to a reference angle θyc (a positive constant).

[0060] In step S50, the CPU executes lane departure prevention control. Specifically, the CPU activates the alarm device 18 to issue an alarm indicating that the vehicle 50 is in danger of departing from its lane. Furthermore, the CPU outputs an automatic steering command signal to the EPS ECU 20, causing the EPS device 22 to automatically steer the steering wheels 24 to prevent the vehicle 50 from departing from its lane.

[0061] In step S60, the CPU performs the following operations based on the vehicle speed V reference. Figure 3 The mapping diagram shown in FIG. 1 calculates the reference value Tc for the elapsed time. Figure 3 As shown, the reference value Tc is variably set according to the vehicle speed so as to be shorter as the vehicle speed V increases.

[0062] In step S60, the CPU determines whether the lane departure prevention control return condition is satisfied. If the CPU makes an affirmative determination, the control proceeds to step S80, and if the CPU makes a negative determination, the control proceeds to step S70.

[0063] In this case, the CPU determines that the control restoration condition is satisfied at the earlier of the following time points A and B.

[0064] Time point A: when it is determined that a time period equal to or longer than the reference time Tc has elapsed since the time point at which the determination in step S30 changes from a negative determination to a positive determination, that is, the time point at which the driver's lane departure intention changes from "no" to "yes"

[0065] Time point B: when it is determined that the vehicle 50 has crossed the lane boundary and completed the lane change, that is, when it is determined that the vehicle 50 has moved as a whole to the lane of the lane change target based on the relative positional relationship between the vehicle 50 and the white line

[0066] In step S70, the CPU determines whether the driver has canceled their lane departure intention. If the CPU makes a negative determination, the control proceeds to step S90. If the CPU makes an affirmative determination, the CPU resets the flag Foff to 0 in step S80. Furthermore, the CPU determines that the driver has canceled their lane departure intention when the driver returns the turn signal lever 42 to the non-deflected position (neutral position) or performs a steering operation to cancel a lane change.

[0067] In step S90, the CPU refers to the vehicle speed V. Figure 4 The mapping diagram shown by the solid line in FIG is used to calculate the reference distance Lsc. Figure 4 As shown, the reference distance Lsc is variably set according to the vehicle speed so as to increase as the vehicle speed V increases.

[0068] In step S90, the CPU determines whether there is a second lane boundary 64 (see FIG. Figure 8 and Figure 9 ) and whether the distance Ls from the center of gravity 50A of the vehicle to the second lane boundary in the travel direction 62 is greater than or equal to the reference distance Lsc. If the CPU makes a negative determination, the control proceeds to step S130; if the CPU makes an affirmative determination, the control proceeds to step S100.

[0069] In step S100, the CPU calculates an index value Id indicating the likelihood that vehicle 50 will become dangerous if it crosses the second lane boundary. The CPU then determines whether index value Id is greater than a reference value Idc (a positive constant), specifically, whether there is a risk that vehicle 50 will become dangerous if it crosses the second lane boundary. If the CPU determines this is positive, control proceeds to step S130; if it determines this is negative, control proceeds to step S110.

[0070] In this case, the CPU estimates the conditions at the second lane boundary and the area immediately ahead, and calculates the index value Id so that the greater the damage to the vehicle 50 when crossing the second lane boundary, the greater the damage to the vehicle. For example, if the vehicle 50 is likely to collide with a three-dimensional object such as a wall, guardrail, or tree line when crossing the second lane boundary, the index value Id is calculated to be a larger value than if the vehicle is likely to reach a non-three-dimensional object such as grass or gravel outside the road. Alternatively, if the vehicle 50 is likely to reach a portion of the road such as another lane, a roadside strip, or a branch road when crossing the second lane boundary, the index value Id may be calculated to be zero or a smaller value. Furthermore, if the three-dimensional object is a wall, guardrail, or tree line, the index value Id may be calculated in ascending order. Furthermore, the index value Id may be calculated to be a larger value as the vehicle speed V increases.

[0071] In step S110, the CPU performs the following operations based on the vehicle speed V reference. Figure 5 The mapping diagram shown in the figure is used to calculate the reference speed Vac. Figure 5 As shown, the reference speed Vac is variably set according to the vehicle speed so as to decrease as the vehicle speed V increases.

[0072] Furthermore, in step S110, the CPU calculates the closing velocity Va of the vehicle 50 relative to the second lane boundary 64 (e.g., the rate of decrease in the shortest distance between the center of gravity 50A and the second lane boundary 64) based on the detection results of the camera sensor 12 and / or the radar sensor 14. Furthermore, the CPU determines whether the closing velocity Va is greater than or equal to the reference velocity Vac. If the CPU determines negatively, it temporarily terminates control. If the CPU determines positively, it proceeds to step S120.

[0073] In step S120, the CPU performs the following operations based on the vehicle speed V reference. Figure 6 The base torque Tac is calculated using the mapping diagram shown. Figure 6 As shown, the base torque Tac is variably set according to the vehicle speed so as to decrease as the vehicle speed V increases.

[0074] In step S120, the CPU determines whether the magnitude of the steering torque Ts detected by the torque sensor 32 is equal to or less than the reference torque Tac. If the CPU makes a negative determination, the control is temporarily terminated, and if the CPU makes an affirmative determination, the control proceeds to step S130.

[0075] In step S130, the CPU executes lane departure prevention control for the second lane boundary 64. Specifically, the CPU activates the warning device 18 to issue a warning indicating that the vehicle 50 is in danger of crossing the second lane boundary 64. Furthermore, the CPU outputs an automatic steering command signal to the EPS ECU 20, causing the EPS device 22 to automatically steer the steering wheels 24 so that the vehicle 50 does not cross the second lane boundary 64.

[0076] <Implementation Plan>

[0077] <C1. Case where the vehicle 50 is not likely to depart from the lane>

[0078] Negative determinations are made in steps S10 and S20 . Therefore, the lane departure prevention control, that is, the operation of the warning device 18 and the automatic steering of the steered wheels 24 are not performed.

[0079] <C2. Case where the vehicle 50 may deviate from the lane but the driver does not intend to do so>

[0080] A negative determination is made in step S10, an affirmative determination is made in step S20, and a negative determination is made in step S30. Thus, lane departure prevention control is executed in step S50, and the operation of warning device 18 and automatic steering of steering wheel 24 can prevent vehicle 50 from deviating from lane 54. For example, even if vehicle 50 is subjected to lateral forces due to crosswind, lateral inclination of the road surface, or the driver's negligence, causing vehicle 50 to unnecessarily travel at an angle relative to lane 54, creating a risk of vehicle 50 deviating from lane 54, vehicle 50 can be prevented from deviating from lane 54.

[0081] <C3. Case where the vehicle 50 is likely to deviate from the lane and the driver intentionally deviates from the lane>

[0082] A negative determination is made in step S10, and an affirmative determination is made in steps S20 and S30. In step S40, the flag Foff is set to 1. Thus, when the turn signal lamp 44L or 44R is flashing and / or the steering torque Ts is greater than or equal to the reference value Tsc and / or the magnitude of the steering angle θ is greater than or equal to the reference value θsc, the lane departure prevention control is not executed, and an affirmative determination is then made in step S10.

[0083] <C3-1. When the lane departure prevention control recovery conditions are not met and the lane departure intention has not been cancelled>

[0084] Negative determinations are made in steps S60 and S70 . Thus, automatic steering of the steerable wheels 24 by the lane departure prevention control is not performed, and the driver can perform lane departure such as lane change as desired.

[0085] <C3-1-1. Case where the distance Ls is greater than or equal to the reference distance Lsc and the vehicle 50 may be in a dangerous situation>

[0086] Affirmative determinations are made in steps S90 and S100, and in step S130, lane departure prevention control is executed for the second lane boundary 64. Thus, the risk of the vehicle 50 crossing the second lane boundary 64 and departing from the lane is reduced by the activation of the warning device 18 and the automatic steering of the steering wheel 24.

[0087] <C3-1-2. Case where the distance Ls is greater than the reference distance Lsc and the vehicle 50 is not in a dangerous situation, but the approaching speed Va is greater than the reference speed Vac and the magnitude of the steering torque Ts is less than the reference torque Tac>

[0088] A positive determination is made in step S90, a negative determination is made in step S100, and positive determinations are made in steps S110 and S120. In step S130, lane departure prevention control is executed for the second lane boundary 64. Thus, similar to the case of C3-1-1, the risk of the vehicle 50 crossing the second lane boundary 64 and departing from the lane is reduced by the activation of the warning device 18 and the automatic steering of the steering wheel 24.

[0089] <C3-1-3. Case where the distance Ls is greater than the reference distance Lsc, the vehicle 50 is not likely to become dangerous, the closing speed Va is greater than the reference speed Vac, but the magnitude of the steering torque Ts exceeds the reference torque Tac>

[0090] A positive determination is made in step S90, a negative determination is made in step S100, and a positive determination is made in step S110, but a negative determination is made in step S120. Therefore, lane departure prevention control is not executed for the second lane boundary 64. Furthermore, it is considered that the magnitude of the steering torque Ts exceeds the reference torque Tac because the driver intends that the vehicle 50 cross the first lane boundary 56L and approach the second lane boundary 64.

[0091] <C3-1-4. Case where the distance Ls is greater than or equal to the reference distance Lsc, the vehicle 50 is not in a dangerous situation, and the closing speed Va is less than the reference speed Vac>

[0092] Since a positive determination is made in step S90 and negative determinations are made in steps S100 and S110, lane departure prevention control is not executed for the second lane boundary 64. Furthermore, when the approaching speed Va is less than the reference speed Vac, the possibility that the vehicle 50 will reach the second lane boundary 64 in a short time is low, and therefore, the necessity for executing lane departure prevention control for the second lane boundary 64 is low.

[0093] As can be seen from the above description, in principle, lane departure prevention control is not executed for the second lane boundary 64 if the lane departure prevention control recovery conditions are not met, the lane departure intention has not been cancelled, and the distance Ls is greater than the reference distance Lsc. However, if the vehicle 50 is in a dangerous situation or if the closing speed Va is greater than the reference speed Vac and the steering torque Ts is less than the reference torque Tac, lane departure prevention control is executed for the second lane boundary 64.

[0094] <C3-1-5. When the distance Ls is smaller than the reference distance Lsc>

[0095] A negative determination is made in step S90, and in step S130, lane departure prevention control is executed for the second lane boundary 64. Thus, as in the cases of C3-1-1 and C3-1-2, the risk of the vehicle 50 crossing the second lane boundary 64 and departing from the lane is reduced by the activation of the warning device 18 and the automatic steering of the steering wheel 24.

[0096] <C4. When lane departure prevention control return conditions are not met but the lane departure intention is canceled>

[0097] A negative determination is made in step S60, but an affirmative determination is made in step S70. In step S80, flag Foff is reset to 0, resuming lane departure prevention control. Thus, when vehicle 50 is in danger of departing from lane 54, similar to the above-described case C2, a negative determination is made in step S10, an affirmative determination is made in step S20, and a negative determination is made in step S30. Therefore, lane departure prevention control is executed in step S50, and the activation of warning device 18 and automatic steering of steering wheel 24 prevent vehicle 50 from departing from lane 54.

[0098] <C5. When lane departure prevention control recovery conditions are met>

[0099] A positive determination is made in step S60 , and in step S80 , the flag Foff is reset to 0 to resume lane departure prevention control. Therefore, a negative determination is made in step S10 , so steps S20 to S50 are executed.

[0100] <Specific examples of work>

[0101] Next, refer to Figure 8 and Figure 9 , respectively describe the specific examples of the operation of the conventional lane departure prevention device and the implementation method. Figure 8 and Figure 9The driver intends to make a lane departure from the lane 54 to the side road 66 so that the vehicle 50 moves from the lane 54 across the first lane boundary 56L to the side road 66. Figure 8 and Figure 9 When the position is shown by the solid line, the flag Foff is 1.

[0102] like Figure 8 and Figure 9 As shown, bypass 66 extends at an angle of approximately 10° relative to lane 54. Side road 66 has a second lane boundary 64, and a three-dimensional wall 68 extends along the outside of the second lane boundary. Vehicle 50's travel direction 62 is inclined at angles of approximately 25° and 15° relative to first lane boundary 56L and second lane boundary 64, respectively. Consequently, the vehicle 50's oblique travel angle θy relative to first lane boundary 56L is greater than a reference angle θyc, but the vehicle 50's oblique travel angle θy relative to second lane boundary 64 is less than the reference angle θyc.

[0103] Furthermore, before the center of gravity 50A of the vehicle 50 crosses the first lane boundary 56L with respect to the second lane boundary 64 , a negative determination is made in step S10 , and affirmative determinations are made in steps S20 and S30 , and the flag Foff is set to 1 in step S40 .

[0104] In the conventional lane departure prevention device, it is assumed that instead of Figure 2 In steps S70 and S90 to S120, the same steps as steps S20 and S30 are executed for the second lane boundary 64. In the case of the conventional lane departure prevention device, even if it is determined that there is a second lane boundary 64 in front of the vehicle 50, since the magnitude of the oblique angle θy of the vehicle 50 relative to the second lane boundary 64 is smaller than the reference angle θyc, it is determined that the driver has not intended to leave the lane. Therefore, the lane departure prevention control is executed for the second lane boundary 64. Therefore, as in Figure 8 As shown by the virtual line in FIG, the steering wheel 24 is automatically steered so that the center of gravity 50A of the vehicle 50 does not approach the second lane boundary 64. Therefore, it is inevitable that the lane departure prevention control has the opposite effect of smoothly moving the vehicle 50 to the side road 66 as the driver desires.

[0105] In contrast, according to the embodiment, a positive determination is made in step S90 and a negative determination is made in step S100. Furthermore, a negative determination is made in step S110, or a positive determination and a negative determination are made in steps S110 and S120, respectively. As a result, the lane departure prevention control is not executed for the second lane boundary 64. Therefore, as in Figure 9As shown by the virtual line in FIG. 5 , the vehicle 50 can smoothly move to the bypass 66 as the driver wishes.

[0106] Furthermore, in the above example, the bypass 66 and the second lane boundary 64 extend straight and obliquely relative to the first lane boundary 56L. Figure 8 and Figure 9 As shown by the dotted line in FIG, the bypass 66 and the second lane boundary 64 may also extend in a curved manner so as to gradually move away from the first lane boundary 56L. Figure 8 and Figure 9 Although not shown, lane 54 and lane boundaries 56L, 56R may also extend in a curved manner so as to gradually move away from second lane boundary 64 .

[0107] As can be seen from the above description, according to the embodiment, lane departure prevention control is not executed when the driver intends to move the vehicle 50 to the side road 66. Therefore, the automatic steering of the steering wheel 24 does not interfere with the driver's driving operation, and the warning device 18 does not operate, so the driver can smoothly move the vehicle to the side road as desired.

[0108] According to the embodiment, the reference distance Lsc is variably set according to the vehicle speed so that the higher the vehicle speed V, the larger the reference distance Lsc is. Figure 4 ). As a result, compared to a case where the reference distance is constant and has nothing to do with the vehicle speed, the possibility of the vehicle crossing the second lane boundary is higher, and it is possible to appropriately determine whether lane departure prevention control needs to be executed for the second lane boundary.

[0109] Furthermore, according to the embodiment, while lane departure prevention control is still suspended, if it is determined that the vehicle 50 is at risk of becoming dangerous if it crosses the second lane boundary 64, lane departure prevention control is executed for the second lane boundary. This reduces the possibility of the vehicle crossing the second lane boundary and becoming dangerous due to lane departure prevention control.

[0110] Furthermore, according to the embodiment, while lane departure prevention control is still suspended, if it is determined that the steering torque Ts of the vehicle 50 in the direction of approaching the second lane boundary 64 is less than or equal to the reference torque Tac, the lane departure prevention control is executed with respect to the second lane boundary. Thus, in situations where the vehicle approaches the second lane boundary and is in danger of crossing the second lane boundary due to driver negligence, the lane departure prevention control can be used to reduce the likelihood of the vehicle crossing the second lane boundary.

[0111] In particular, according to the embodiment, lane departure prevention control is executed with respect to the second lane boundary when it is determined that the speed Va of the vehicle 50 approaching the second lane boundary 64 is greater than or equal to the reference speed Vac and the steering torque Ts of the vehicle 50 in the direction of approaching the second lane boundary 64 is less than or equal to the reference torque Tac. Thus, in situations where the vehicle is rapidly approaching the second lane boundary due to driver negligence or the like and there is a high probability that the vehicle will cross the second lane boundary, lane departure prevention control can be used to reduce the likelihood of the vehicle crossing the second lane boundary.

[0112] Furthermore, according to the embodiment, the reference speed ( Vac ) is variably set according to the vehicle speed so that the higher the vehicle speed V, the lower the reference speed Vac. Figure 5 ). As a result, compared to a case where the reference speed is constant and independent of the vehicle speed, the possibility of the vehicle crossing the second lane boundary is higher, and it is possible to appropriately determine whether lane departure prevention control needs to be executed for the second lane boundary.

[0113] Furthermore, according to the embodiment, the reference torque ( Tac ) is variably set according to the vehicle speed so that the higher the vehicle speed V, the smaller the reference torque Tac. Figure 6 ) Thus, compared to a case where the reference torque is constant and has no relation to the vehicle speed, it is possible to appropriately determine whether the driver intends to move the vehicle in a direction approaching the second lane boundary through the steering operation.

[0114] Furthermore, according to the embodiment, when the distance between the vehicle 50 and the second lane boundary 64 is determined to be less than the reference distance Lsc, lane departure prevention control is executed for the second lane boundary. Furthermore, the reference distance is variably set according to the likelihood of the vehicle becoming dangerous, such that the greater the likelihood of the vehicle crossing the second lane boundary, the greater the reference distance. Consequently, as the likelihood of the vehicle crossing the second lane boundary increases, the greater the likelihood of the vehicle becoming dangerous, the more likely it is to be determined that the distance between the vehicle and the second lane boundary is less than the reference distance, effectively enabling lane departure prevention control to be executed for the second lane boundary.

[0115] Furthermore, according to the embodiment, the reference time ( Tc ) is variably set according to the vehicle speed so that the higher the vehicle speed V, the shorter the reference time Tc. Figure 3 ) Thus, compared with the case where the reference time Tc is constant and has no relation to the vehicle speed, it is possible to appropriately determine whether the control restoration condition is satisfied.

[0116] While the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments. It will be apparent to those skilled in the art that various other embodiments can be implemented within the scope of the present invention.

[0117] For example, in the above embodiment, lane departure prevention control includes the issuance of an alarm by the alarm device 18 and the automatic steering of the steering wheels 24 by the EPS device 22. However, either the issuance of an alarm or the automatic steering of the steering wheels 24 may be omitted.

[0118] In addition, in the above-mentioned embodiment, Figures 3 to 6 As shown, the reference value Tc, reference distance Lsc, reference speed Vac, and reference torque Tac for the elapsed time are variably set according to the vehicle speed. However, at least one of the reference value Tc, reference distance Lsc, reference speed Vac, and reference torque Tac may be constant regardless of the vehicle speed V.

[0119] In the above embodiment, step S110 determines whether the closing speed Va of the vehicle 50 relative to the second lane boundary 64 is greater than or equal to the reference speed Vac. If the determination is affirmative, step S120 is executed. However, step S110 may be omitted, and step S120 may be executed if the determination is negative in step S100.

[0120] Furthermore, in the above-described embodiment, the reference distance Lsc is the distance from the center of gravity 50A of the vehicle 50 to the second lane boundary 64 in the vehicle's traveling direction 62. For example, it may also be the distance from the front end of the vehicle 50 to the second lane boundary 64 in the vehicle's traveling direction 62. Alternatively, the reference distance Lsc may be the shortest distance from a reference position such as the center of gravity 50A of the vehicle 50 to the second lane boundary 64.

[0121] Furthermore, in the above embodiment, the reference distance Lsc is obtained by referring to Figure 4 The calculation is performed based on the mapping diagram shown by the solid line. Figure 4 As indicated by the solid lines, dashed lines, and double-dashed lines, the reference distance Lsc may also be variably set based on the degree of danger posed to the vehicle 50 when crossing the second lane boundary. In this case, when the vehicle 50 crosses the second lane boundary, if the vehicle is likely to reach a non-three-dimensional object such as grass or gravel outside the road, the degree of danger to the vehicle may be determined to be higher than when the vehicle is likely to reach a portion of the road such as another lane, a roadside strip, or a branch road. Furthermore, when the vehicle 50 crosses the second lane boundary, if the vehicle is likely to collide with a three-dimensional object such as a wall, guardrail, or tree, the degree of danger to the vehicle may be determined to be higher than when the vehicle is likely to reach a non-three-dimensional object such as grass or gravel outside the road.

Claims

1. A lane departure prevention device comprising a vehicle position detection device and a control unit, wherein the vehicle position detection device detects a position of a vehicle relative to a lane, the control unit being configured to execute lane departure prevention control of at least one of automatic steering of a steering wheel and issuance of an alarm when it is determined based on the vehicle position detected by the vehicle position detection device that the vehicle is likely to cross a first lane boundary and that the driver of the vehicle that is likely to cross the first lane boundary has not intentionally left the lane, and when it is determined that the vehicle is likely to cross a first lane boundary and that the driver of the vehicle that is likely to cross the first lane boundary has intentionally left the lane, suspend execution of the lane departure prevention control until it is determined that a predetermined control resumption condition is satisfied. The control unit is configured to, in a situation where the lane departure prevention control is suspended and the control resumption condition is not satisfied, continue to suspend the lane departure prevention control if it is determined that there is a second lane boundary on the side the vehicle is approaching but the distance from the vehicle to the second lane boundary is greater than a reference distance; The control unit is configured to execute the lane departure prevention control on the second lane boundary when it is determined that the vehicle is likely to be in a dangerous state if the vehicle crosses the second lane boundary while execution of the lane departure prevention control is continuously suspended.

2. The lane departure prevention device according to claim 1, The control unit is configured to variably set the reference distance according to the vehicle speed so that the reference distance increases as the vehicle speed increases.

3. The lane departure prevention device according to claim 1, The control unit is configured to execute the lane departure prevention control on the second lane boundary when it is determined that the steering torque of the vehicle in a direction approaching the second lane boundary is equal to or less than a reference torque while execution of the lane departure prevention control is continuously suspended.

4. The lane departure prevention device according to claim 3, The control unit is configured to execute the lane departure prevention control on the second lane boundary when it is determined that the speed of the vehicle approaching the second lane boundary is greater than or equal to a reference speed and the steering torque of the vehicle in a direction approaching the second lane boundary is less than or equal to a reference torque.

5. The lane departure prevention device according to claim 4, The control unit is configured to variably set the reference speed according to the vehicle speed so that the reference speed decreases as the vehicle speed increases.

6. The lane departure prevention device according to claim 3, The control unit is configured to variably set the reference torque according to the vehicle speed so that the reference torque decreases as the vehicle speed increases.

7. The lane departure prevention device according to any one of claims 1 to 6, The control unit is configured to perform the lane departure prevention control on the second lane boundary when it is determined that the distance from the vehicle to the second lane boundary is less than a reference distance, and to variably set the reference distance according to the risk that the vehicle will become in a dangerous situation if the vehicle crosses the second lane boundary, such that the reference distance becomes larger as the risk that the vehicle will become in a dangerous situation becomes higher.

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