Lane Departure Prevention Device

Abstract

To provide an improved traffic lane deviation preventing device capable of regulating a traffic lane deviation preventive control even when trying to move a vehicle to a side road that diverges at a small inclination angle from a main line.SOLUTION: A traffic lane deviation preventing device comprises a control unit: which executes a traffic lane deviation preventive control of at least one of automatic steering of a steered wheel and issuing of a warning at S50 when the control unit determines that there is a risk that a vehicle crosses a traffic lane boundary and that a driver does not intend to deviate from the traffic lane at S20 and S30; and which cancels an execution of the traffic lane deviation preventive control at S10 and S40 when the control unit determines that there is the risk that the vehicle crosses the traffic lane boundary and that the driver intends to deviate from the traffic lane. In a situation where the execution of the traffic lane deviation preventive control is canceled, when the control unit determines that there is another traffic lane boundary on an approaching side of the vehicle, but a distance from the vehicle to the other traffic lane boundary is greater than or equal to a reference distance, the control unit continues to cancel the execution of the traffic lane deviation preventive control.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The lane departure prevention device detects the vehicle's position relative to the lane using a vehicle position detection device, and when it determines that there is a risk of the vehicle deviating from the lane based on the detected vehicle position, it executes lane departure prevention control, such as at least one of automatic steering of the steered wheels and issuing an alarm.

[0003] Even if it is determined that the vehicle is at risk of deviating from the lane, if the driver has an intention to depart the lane, such as by changing lanes, it is necessary to limit the lane departure prevention control. The presence or absence of an intention to depart the lane is determined based on the driver's steering operation, the driver's operation of the turn signal lever, the vehicle's inclination angle with respect to the lane, i.e., the skew angle, etc.

[0004] For example, the following Patent Document 1 describes that lane departure prevention control is restricted when a steering speed equal to or greater than a reference value, a steering torque equal to or greater than a reference value, and / or a steering torque change amount equal to or greater than a reference value is detected. This type of lane departure prevention device can reduce the risk that automatic steering of the steered wheels by lane departure prevention control will interfere with the driver's driving operation in a situation where the driver is about to depart from the lane, such as by changing lanes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-177762 A Summary of the Invention

[0006] [Problem to be solved by the invention] Even in conventional lane departure prevention devices such as the lane departure prevention device described in Patent Document 1, depending on the vehicle's driving conditions, the lane departure prevention control may be executed without being restricted. For example, as will be described in detail later, when the vehicle is to be moved to a side road that branches off from the main road at a small inclination angle, it may be determined that the vehicle has an intention to depart from the lane at the lane boundary of the main road, but that the vehicle has no intention to depart from the lane at the lane boundary of the side road. Therefore, even if the driver tries to move the vehicle to the side road, the automatic steering of the steered wheels by the lane departure prevention control interferes with the driver's driving operation, and the driver cannot move the vehicle to the side road smoothly as desired, which may cause the driver to feel uncomfortable.

[0007] The main object of the present invention is to provide an improved lane departure prevention device that can restrict lane departure prevention control even in cases where a vehicle is about to move onto a side road that branches off at a small inclination angle from the main road.

[0008] [Means for solving the problems and effects of the invention] According to the present invention, there is provided a lane departure prevention device (100) including: a vehicle position detection device (camera sensor 12) that detects the position of a vehicle (50) relative to a lane (54); and a control unit (LDA·ECU10) configured to execute at least one of lane departure prevention control of automatically steering the steered wheels (24) and issuing a warning (S50) when it is determined based on the position of the vehicle detected by the vehicle position detection device that the vehicle is in danger of crossing a first lane boundary (56L) and that the driver has no intention of crossing the first lane boundary (S20, S30), and to cancel execution of the lane departure prevention control (S10, S40) until it is determined that a preset control return condition is satisfied (S60).

[0009] The control unit (LDA·ECU10) is configured to continue the suspension of execution of lane departure prevention control when, in a situation where execution of lane departure prevention control has been suspended and a control return condition has not been satisfied, it is determined that a second lane boundary (64) is present on the side to which the vehicle is approaching but the distance from the vehicle to the second lane boundary is equal to or greater than a reference distance (Lsc).

[0010] According to the above configuration, in a situation where the execution of the lane departure prevention control is stopped and the control return condition is not satisfied, when the second lane boundary is present on the side where the vehicle is approaching, but it is determined that the distance from the vehicle to the second lane boundary is equal to or greater than the reference distance, the execution of the lane departure prevention control is continued to be stopped. Therefore, even if the driver attempts to move the vehicle onto a side road that branches off at a small inclination angle from the main road, the lane departure prevention control is not executed. Therefore, the automatic steering of the steered wheels does not interfere with the driver's driving operation or activate an alarm device, so the driver can smoothly move the vehicle onto the side road as desired.

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

[0012] Since the higher the vehicle speed, the faster the vehicle approaches the second lane boundary and the higher the risk of the vehicle crossing the second lane boundary, it is preferable that the reference distance is larger as the vehicle speed is higher. According to the above aspect, the reference distance is variably set according to the vehicle speed so that the reference distance is larger as the vehicle speed is higher. Therefore, compared to the case where the reference distance is constant regardless of the vehicle speed, it is possible to appropriately determine whether or not the vehicle is more likely to cross the second lane boundary and it is necessary to perform lane departure prevention control for the second lane boundary.

[0013] In another aspect of the present invention, when the control unit (LDA·ECU10) determines that there is a risk of the vehicle (50) being in a dangerous situation if the vehicle (50) crosses a second lane boundary (64) while the execution of lane departure prevention control continues to be suspended, the control unit (LDA·ECU10) executes lane departure prevention control for the second lane boundary.

[0014] According to the above aspect, when it is determined that the vehicle may be in a dangerous situation if it crosses the second lane boundary while the execution of the lane departure prevention control is continued, the lane departure prevention control is executed for the second lane boundary. Thus, the lane departure prevention control can reduce the risk of the vehicle crossing the second lane boundary and becoming in a dangerous situation.

[0015] Furthermore, in another aspect of the present invention, when the control unit (LDA·ECU10) determines that the steering torque (Ts) in the direction in which the vehicle (50) approaches the second lane boundary (64) is equal to or less than the reference torque (Tac) while the execution of the lane departure prevention control continues to be suspended, the control unit (LDA·ECU10) executes lane departure prevention control for the second lane boundary.

[0016] When the steering torque in the direction in which the vehicle approaches the second lane boundary exceeds the reference torque, it is considered that the driver wishes to move the vehicle closer to the second lane boundary. On the other hand, when the steering torque in the direction in which the vehicle approaches the second lane boundary is equal to or less than the reference torque, it is considered that the vehicle may approach the second lane boundary due to driver inattention or the like, and may cross the second lane boundary.

[0017] According to the above aspect, when the steering torque in the direction in which the vehicle approaches the second lane boundary is determined to be equal to or less than the reference torque in a situation in which the execution of the lane departure prevention control is continued, the lane departure prevention control is executed for the second lane boundary. Thus, the lane departure prevention control can reduce the risk of the vehicle crossing the second lane boundary.

[0018] Furthermore, in another aspect of the present invention, when the control unit (LDA·ECU10) determines that the speed (Va) at which the vehicle (50) approaches the second lane boundary (64) is equal to or greater than a reference speed (Vac) and the steering torque (Ts) in the direction in which the vehicle approaches the second lane boundary is equal to or less than a reference torque (Tac), the control unit (LDA·ECU10) executes lane departure prevention control for the second lane boundary.

[0019] According to the above aspect, when it is determined that the speed at which the vehicle approaches the second lane boundary is equal to or greater than the reference speed and the steering torque in the direction in which the vehicle approaches the second lane boundary is equal to or less than the reference torque, the lane departure prevention control is executed for the second lane boundary. Therefore, in a situation in which the vehicle approaches the second lane boundary quickly due to driver inattention or the like and there is a high risk of the vehicle crossing the second lane boundary, the lane departure prevention control can reduce the risk of the vehicle crossing the second lane boundary.

[0020] In still another aspect of the present invention, the control unit (LDA·ECU10) variably sets the reference speed in accordance with the vehicle speed (V) so that the reference speed (Vac) becomes smaller as the vehicle speed (V) becomes higher.

[0021] Since the higher the vehicle speed, the faster the vehicle approaches the second lane boundary and the higher the risk of the vehicle crossing the second lane boundary, it is preferable that the reference speed is smaller as the vehicle speed is higher. According to the above aspect, the reference speed is variably set according to the vehicle speed so that the higher the vehicle speed, the lower the reference speed. Therefore, compared to a case where the reference speed is constant regardless of the vehicle speed, it is possible to appropriately determine whether or not the vehicle is more likely to cross the second lane boundary and it is necessary to perform lane departure prevention control for the second lane boundary.

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

[0023] Since the steering resistance when the steered wheels are steered by the driver's steering operation becomes smaller as the vehicle speed increases, it is preferable that the reference torque is smaller as the vehicle speed increases. According to the above aspect, the reference torque is variably set according to the vehicle speed so that the reference torque is smaller as the vehicle speed increases. Therefore, compared to a case where the reference torque is constant regardless of the vehicle speed, it is possible to appropriately determine whether the driver is attempting to move the vehicle in a direction approaching the second lane boundary by the steering operation.

[0024] Furthermore, in another aspect of the present invention, when the control unit (LDA·ECU10) determines that the distance from the vehicle (50) to the second lane boundary (64) is less than the reference distance (Lsc), it executes lane departure prevention control for the second lane boundary, and variably sets the reference distance in accordance with the risk of the vehicle becoming in a dangerous situation if the vehicle crosses the second lane boundary, so that the reference distance is set to a larger value as the risk of the vehicle becoming in a dangerous situation increases.

[0025] According to the above aspect, the reference distance is variably set in accordance with the risk of the vehicle becoming in a dangerous situation such that the reference distance is increased as the risk of the vehicle becoming in a dangerous situation when the vehicle crosses the second lane boundary increases. Therefore, the higher the risk of the vehicle becoming in a dangerous situation when the vehicle crosses the second lane boundary, the more likely it is that the distance from the vehicle to the second lane boundary is determined to be less than the reference distance, and lane departure prevention control can be effectively executed for the second lane boundary.

[0026] In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are added in parentheses to the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols added in parentheses. Other objects, other features, and associated advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the drawings. [Brief description of the drawings]

[0027] [Figure 1]1 is a schematic diagram showing an embodiment of a lane departure prevention device according to the present invention; [Diagram 2] 4 is a flowchart showing a lane departure prevention control routine in the embodiment. [Diagram 3] 11 is a map for calculating a reference value Tc for an elapsed time based on a vehicle speed V. [Figure 4] 11 is a map for calculating a reference distance Lsc based on a vehicle speed V and a risk of danger. [Diagram 5] 2 is a map for calculating a reference speed Vac based on a vehicle speed V. [Figure 6] 2 is a map for calculating a reference torque Tac based on a vehicle speed V. [Figure 7] FIG. 1 is a diagram showing a situation in which a vehicle is traveling at an angle relative to the longitudinal direction of a lane. [Figure 8] A diagram showing a situation in which the driver wishes to deviate from the lane onto a side road so that the vehicle moves from the lane across a first lane boundary onto the side road when the lane departure prevention device is a conventional lane departure prevention device. [Figure 9] This figure shows a situation in which the driver wishes to deviate from the lane to a side road so that the vehicle moves from the lane across a first lane boundary onto the side road when the lane departure prevention device is an embodiment of the lane departure prevention device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lane departure prevention device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. <Configuration>

[0029] 1, 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 (abbreviation of Lane Departure Alert with Control) as necessary, and electric power steering is referred to as EPS (abbreviation of Electric Power Steering) as necessary.

[0030] These ECUs are electronic control units that include a microcomputer as a main component, and are connected to each other via a CAN (Controller Area Network) 52 so that they can transmit and receive information to each other. Each microcomputer includes a CPU, a ROM, a RAM, a non-volatile memory, an interface, and the like. The CPU is adapted to realize various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into one ECU.

[0031] As will be described in detail later, the ROM of the LDA·ECU 10 stores a lane departure prevention control program corresponding to the flowchart shown in Fig. 2, and the CPU executes the lane departure prevention control in accordance with 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).

[0032] The camera sensor 12 includes a camera unit and a lane recognition unit that recognizes white lines on a road by analyzing image data captured by the camera unit. The camera sensor 12 (camera unit) captures images of the scenery ahead 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 predetermined calculation intervals.

[0033] As shown in Fig. 6, the camera sensor 12 is capable of recognizing white lines 56L and 56R, which are boundaries of a lane 54 (called lane boundaries), and detecting the relative positional relationship of the vehicle with respect to the lane 54 based on the relationship between the white lines and the position of the vehicle 50. Here, the position of the vehicle 50 refers to the position of the center of gravity 50A of the vehicle, but may also be the center position of the vehicle in a plan view. The lateral position of the vehicle, which will be described later, refers to the position of the center of gravity of the vehicle in the lane width direction, and the lateral speed of the vehicle refers to the speed of the center of gravity of the vehicle in the lane width direction. These are found based on the relative positional relationship between the white lines detected by the camera sensor 12 and the vehicle.

[0034] The radar sensor 14 includes a radar transmitting / receiving unit and a signal processing unit (not shown), and the radar transmitting / receiving unit emits millimeter-wave band radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by three-dimensional objects (e.g., other vehicles, bicycles, guardrails, roadside structures, etc.) present within the emission range. The signal processing unit acquires information indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, 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, and supplies the information to the LDA·ECU 10 at predetermined time intervals.

[0035] 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 period. The LDA switch is operated by the driver, and supplies a signal indicating whether it is on or off to the LDA·ECU 10. The LDA switch being on means that lane departure prevention control is being executed.

[0036] The warning device 18 is activated when the LDA·ECU 10 determines that the vehicle 50 is at risk of deviating from the lane 54, and issues a warning as one of the lane departure prevention controls, i.e., issues a warning that the vehicle 50 is at risk of deviating from the lane. The warning device 18 may be any of a warning device that issues a visual warning such as a warning lamp, a warning device that issues an auditory warning such as a warning buzzer, a warning device that issues a tactile warning such as seat vibration, or any combination thereof.

[0037] The EPS·ECU 20 can steer the steered wheels 24 as necessary by controlling the EPS device 22. Thus, the EPS·ECU 20 and the EPS device 22 constitute a steering device 26 that automatically steers the steered wheels 24 as necessary. When the LDA·ECU 10 determines that the vehicle 50 is at risk of deviating from its lane, the EPS·ECU 20 performs automatic steering of the steered wheels 24 to prevent the vehicle from deviating from its lane, as another type of lane departure prevention control.

[0038] 1, a steering shaft 30 to which a steering wheel 28 operated by a driver is integrally connected is provided with a torque sensor 32 for detecting steering torque Ts. A signal indicating the steering torque Ts detected by the torque sensor 32 is input to the EPS·ECU 20. The EPS·ECU 22 controls the EPS device 22 in a manner known in the art based on the steering torque Ts and the vehicle speed V detected by the vehicle speed sensor 16, thereby controlling the steering assist torque and reducing the steering burden on the driver. The signal indicating the steering torque Ts is input from the EPS·ECU 20 to the LDA·ECU 10 via the CAN 52.

[0039] The steering ECU 40 is connected to a turn signal lever 42 and turn signal lamps 44L, 44R operated by the driver. When the turn signal lever 42 is tilted in the left turn direction of the vehicle 50, the steering ECU 40 causes the front and rear turn signal lamps 44L on the left side of the vehicle 50 to flash, and when the turn signal lever 42 is tilted in the right turn direction of the vehicle 50, the steering ECU 40 causes the front and rear turn signal lamps 44R on the right side of the vehicle 50 to flash. Tilt information of the turn signal lever 42 is input from the steering ECU 40 to the LDA·ECU 10 via the CAN 52.

[0040] <Lane Departure Prevention Control Routine> Next, a lane departure prevention control routine in this embodiment will be described with reference to the flowchart shown in Fig. 2. The lane departure prevention control according to the flowchart shown in Fig. 2 is repeatedly executed by the CPU of the LDA·ECU 10 at a predetermined control period when an LDA switch, not shown in Fig. 1, is on. In the following description, the lane departure prevention control will be simply referred to as "control".

[0041] First, in step S10, the CPU determines whether or not the flag Foff is 1, that is, whether or not 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. The flag Foff is initialized to 0 at the start of the control, and is thereafter set to 0 or 1 according to the flowchart shown in FIG. 2, as described later.

[0042] In step S20, the CPU determines whether or not there is a risk that the vehicle will deviate from the lane in a manner known in the art, based on the relative position of the vehicle 50 with respect to the lane 54 detected by the camera sensor 12. If the CPU determines that the vehicle is likely to deviate from the lane, it temporarily terminates control, and if the CPU determines that the vehicle is likely to deviate from the lane, it advances control to step S30.

[0043] In this case, the determination as to whether or not there is a risk that the vehicle 50 will deviate from the lane may be performed, for example, in the following manner. First, as shown in Fig. 7, an angle (inclination angle) θy between the longitudinal direction 60 of the lane 54 and the traveling direction 62 of the vehicle is estimated based on image information of the front of the vehicle 50. A moving speed Vy of the vehicle 50 in a direction perpendicular to the longitudinal direction 60 of the lane 54 is estimated as Vsinθy based on the angle θy and the vehicle speed V. Note that the angle θy is the same as the inclination angle with respect to the white lines 56L and 56R, and is therefore also the skew angle of the vehicle 50.

[0044] Also, a distance Dy (not shown) in the lane width direction between the white line 56L (first lane boundary) on the side where the vehicle 50 is approaching and the center of gravity 50A of the vehicle is estimated. Furthermore, when Dy-VyΔt is equal to or less than a preset reference value Dyc (a positive constant), where Δt is a preset time, it may be determined that the vehicle 50 is at risk of deviating from the lane.

[0045] In step S30, the CPU determines whether or not the driver intends to depart from the lane. If the CPU determines negative, the control proceeds to step S50, and if the CPU determines positive, the CPU sets flag Foff to 1 in step S40 so that lane departure prevention control is not executed.

[0046] In this case, the CPU determines that the driver intends to depart from the lane beyond the lane boundary when the driver is performing at least one of tilting the turn signal lever 42 in the lane departure direction and steering in the lane departure direction. The steering operation may be determined based on whether the magnitude of the steering torque Ts detected by the torque sensor 32 is equal to or greater than a reference value Tsc or whether the magnitude of the steering angle θ, which is the rotation angle of the steering shaft 30, is equal to or greater than a reference value θsc.

[0047] Note that the reference value Tsc may be a positive constant, but because the steering resistance when the steered wheels are turned by the driver's steering operation becomes smaller as the vehicle speed V increases, the reference value Tsc is set variably according to the vehicle speed so as to become smaller as the vehicle speed V increases. Therefore, it is possible to more appropriately determine whether the driver intends to depart from the lane by crossing the lane boundary, compared to a case in which the reference value Tsc is constant regardless of the vehicle speed.

[0048] Furthermore, for example, when the vehicle 50 is subjected to a lateral force due to a crosswind or a lateral inclination of the road surface, or when the vehicle 50 unnecessarily skews with respect to the lane 54 due to driver inattention or the like, and there is a risk that the vehicle 50 will deviate from the lane 54, the magnitude of the skew angle θy of the vehicle 50 is small. In contrast, when the driver intends to deviate from the lane, the magnitude of the skew angle θy of the vehicle 50 is large. Therefore, even when the magnitude of the skew angle θy of the vehicle 50 is equal to or greater than the reference angle θyc (a positive constant), the CPU determines that the driver intends to deviate from the lane by crossing the lane boundary.

[0049] In step S50, the CPU executes lane departure prevention control. That is, the CPU activates the warning device 18 to issue a warning that the vehicle 50 is at risk of departing from the lane. The CPU also outputs an automatic steering command signal to the EPS·ECU 22, causing the EPS device 22 to automatically steer the steered wheels 24 so that the vehicle 50 does not deviate from the lane.

[0050] In step S60, the CPU calculates a reference value Tc for the elapsed time by referring to the map shown in Fig. 3 based on the vehicle speed V. As shown in Fig. 3, the reference value Tc is variably set according to the vehicle speed so that the higher the vehicle speed V, the shorter the reference value Tc is.

[0051] In step S60, the CPU determines whether or not the lane departure prevention control return condition is satisfied. If the CPU determines that the lane departure prevention control return condition is satisfied, the CPU proceeds to step S80. If the CPU determines that the lane departure prevention control return condition is satisfied, the CPU proceeds to step S70.

[0052] In this case, the CPU determines that the control recovery condition is met at the earlier of the following points in time A and B. Time point A: The time point when the determination in step S30 changes from a negative determination to a positive determination, that is, when it is determined that a time equal to or longer than the reference time Tc has elapsed since the time point when the driver's intention to depart the lane changes from "no" to "yes." 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 entire vehicle 50 has moved into the lane to which the lane change is to be made, based on the relative positional relationship between the vehicle 50 and the white line.

[0053] In step S70, the CPU determines whether the driver has released the intention to depart from the lane. If the CPU determines negative, the control proceeds to step S90, and if the CPU determines positive, the CPU resets the flag Foff to 0 in step S80. The CPU determines that the driver has released the intention to depart from the lane when the driver returns the turn signal lever 42 to the non-tilted position (neutral position) or when the driver performs a steering operation to release the lane change.

[0054] In step S90, the CPU calculates the reference distance Lsc by referring to the map shown by the solid line in Fig. 4 based on the vehicle speed V. As shown in Fig. 4, the reference distance Lsc is variably set according to the vehicle speed so that the reference distance Lsc increases as the vehicle speed V increases.

[0055] Furthermore, in step S90, the CPU determines whether or not a second lane boundary 64 (see FIGS. 8 and 9) is present ahead in the traveling direction 62 of the vehicle 50, and whether or not a distance Ls in the traveling direction 62 from the center of gravity 50A of the vehicle to the second lane boundary is equal to or greater than a reference distance Lsc. If the CPU makes a negative determination, the control proceeds to step S130, and if the CPU makes a positive determination, the control proceeds to step S100.

[0056] In step S100, the CPU calculates an index value Id indicating that the vehicle 50 may be in a dangerous situation if it crosses the second lane boundary. Furthermore, the CPU determines whether the index value Id is equal to or greater than a reference value Idc (a positive constant), that is, whether the vehicle 50 may be in a dangerous situation if it crosses the second lane boundary. If the CPU makes a positive determination, the control proceeds to step S130, and if the CPU makes a negative determination, the control proceeds to step S110.

[0057] In this case, the CPU estimates the second lane boundary and the situation beyond it, and calculates the index value Id so that the higher the damage the vehicle receives when the vehicle 50 crosses the second lane boundary, the larger the index value Id. For example, when the vehicle 50 crosses the second lane boundary and collides with a solid object such as a wall, a guardrail, or a forest, the index value Id is calculated to be a larger value than when the vehicle reaches a non-solid object other than the road, such as grass or gravel. Furthermore, when the vehicle 50 crosses the second lane boundary and reaches a part of the road, such as another lane, a side strip, or a branch road, the index value Id may be calculated to be 0 or a small value. Furthermore, when the solid object is a wall, a guardrail, or a forest, the index value Id may be calculated to be a larger value in this order. Furthermore, the index value Id may be calculated to be a larger value as the vehicle speed V is higher.

[0058] In step S110, the CPU calculates a reference speed Vac by referring to a map shown in Fig. 5 based on the vehicle speed V. As shown in Fig. 5, the reference speed Vac is variably set according to the vehicle speed so that the reference speed Vac decreases as the vehicle speed V increases.

[0059] Furthermore, in step S110, the CPU calculates the approach speed Va of the vehicle 50 with respect to the second lane boundary 64 (for example, the rate of decrease of the extreme 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 approach speed Va is equal to or greater than a reference speed Vac. If the CPU makes a negative determination, it temporarily terminates control, and if the CPU makes a positive determination, it proceeds to step S120.

[0060] In step S120, the CPU calculates a reference torque Tac by referring to the map shown in FIG. 6 based on the vehicle speed V. As shown in FIG. 6, the reference torque Tac is variably set according to the vehicle speed such that it becomes smaller as the vehicle speed V increases.

[0061] Also in step S120, the CPU determines whether the magnitude of the steering torque Ts detected by the torque sensor 32 is less than or equal to the reference torque Tac. When the CPU makes a negative determination, it temporarily ends the control, and when it makes an affirmative determination, it advances the control to step S130.

[0062] In step S130, the CPU executes lane departure prevention control for the second lane boundary 64. That is, the CPU activates the warning device 18 to issue a warning indicating that the vehicle 50 may cross the second lane boundary 64. Further, the CPU outputs a command signal for automatic steering to the EPS·ECU 22, and the EPS device 22 automatically steers the steered wheels 24 so that the vehicle 50 does not cross the second lane boundary 64.

[0063] <Operation of the Embodiment> <C1. When there is no risk of the vehicle 50 deviating from the lane> In steps S10 and S20, a negative determination is made. Therefore, the lane departure prevention control, that is, the activation of the warning device 18 and the automatic steering of the steered wheels 24 are not performed. <C2. When there is a risk of the vehicle 50 deviating from the lane but the driver has no intention of lane departure>

[0064] In step S10, a negative determination is made. In step S20, an affirmative determination is made. In step S30, a negative determination is made. Therefore, in step S50, lane departure prevention control is executed, so that the vehicle 50 can be prevented from deviating from the lane 54 by the operation of the warning device 18 and the automatic steering of the steered wheels 24. For example, even if the vehicle 50 is subjected to a lateral force due to a crosswind, a lateral inclination of the road surface, etc., or if the vehicle 50 obliquely runs unnecessarily with respect to the lane 54 due to driver inattention, etc., and there is a risk of the vehicle 50 deviating from the lane 54, the vehicle 50 can be prevented from deviating from the lane 54.

[0065] <C3. When there is a risk of the vehicle 50 deviating from the lane and the driver intends to deviate from the lane> In step S10, a negative determination is made. In steps S20 and S30, affirmative determinations are made. In step S40, the flag Foff is set to 1. Therefore, when the turn signal lamp 44L or 44R blinks and / or the steering torque Ts is equal to or greater than the reference value Tsc and / or the magnitude of the steering angle θ is equal to or greater than the reference value θsc, the lane departure prevention control is not executed, and thereafter, in step S10, an affirmative determination is made.

[0066] <C3-1. When the return condition of the lane departure prevention control is not satisfied and the intention to deviate from the lane is not canceled> In steps S60 and S70, negative determinations are made. Therefore, since the automatic steering of the steered wheels 24 by the lane departure prevention control is not executed, the driver can execute a lane departure such as a lane change as desired.

[0067] <C3-1-1. When the distance Ls is equal to or greater than the reference distance Lsc and there is a risk of the vehicle 50 being in a dangerous situation> In steps S90 and S100, affirmative determinations are made. In step S130, lane departure prevention control is executed for the second lane boundary 64. Therefore, by operating the warning device 18 and automatically steering the steered wheels 24, the risk of the vehicle 50 deviating from the lane by crossing the second lane boundary 64 is reduced.

[0068] <When the distance Ls is equal to or greater than the reference distance Lsc and there is no risk of the vehicle 50 being in a dangerous situation, but the approach speed Va is equal to or greater than the reference speed Vac and the magnitude of the steering torque Ts is equal to or less than the reference torque Tac> In step S90, an affirmative determination is made, in step S100, a negative determination is made, in steps S110 and S120, affirmative determinations are made, and in step S130, lane departure prevention control is executed for the second lane boundary 64. Therefore, similar to the case of C3-1-1, the warning device 18 is activated and the steered wheels 24 are automatically steered, thereby reducing the risk of the vehicle 50 deviating from the lane by crossing the second lane boundary 64.

[0069] <C3-1-3. When the distance Ls is equal to or greater than the reference distance Lsc and there is no risk of the vehicle 50 being in a dangerous situation, the approach speed Va is equal to or greater than the reference speed Vac, but the magnitude of the steering torque Ts exceeds the reference torque Tac> In step S90, an affirmative determination is made, in step S100, a negative determination is made, in step S110, an affirmative determination is made, but in step S120, a negative determination is made, so lane departure prevention control for the second lane boundary 64 is not executed. It is considered that the reason why the magnitude of the steering torque Ts exceeds the reference torque Tac is that the driver hopes that the vehicle 50 approaches the second lane boundary 64 by crossing the first lane boundary 56L.

[0070] <C3-1-4. When the distance Ls is equal to or greater than the reference distance Lsc and there is no risk of the vehicle 50 being in a dangerous situation, and the approach speed Va is less than the reference speed Vac> In step S90, an affirmative determination is made, and in steps S100 and S110, negative determinations are made, so lane departure prevention control for the second lane boundary 64 is not executed. When the approach speed Va is less than the reference speed Vac, the risk of the vehicle 50 reaching the second lane boundary 64 in a short time is low, so there is little need to execute lane departure prevention control for the second lane boundary 64.

[0071] As can be understood from the above description, when the return condition of the lane departure prevention control is not satisfied, the intention to depart from the lane is not cancelled, and the distance Ls is equal to or greater than the reference distance Lsc, in principle, the lane departure prevention control for the second lane boundary 64 is not executed. However, when there is a risk that the vehicle 50 may be in a dangerous situation, or when the approach speed Va is equal to or greater than the reference speed Vac and the magnitude of the steering torque Ts is equal to or less than the reference torque Tac, the lane departure prevention control for the second lane boundary 64 is executed.

[0072] <C3-1-5. When the distance Ls is less than the reference distance Lsc> In step S90, a negative determination is made, and in step S130, the lane departure prevention control for the second lane boundary 64 is executed. Therefore, similar to the cases of C3-1-1 and C3-1-2, the warning device 18 is activated and the steered wheels 24 are automatically steered, thereby reducing the risk that the vehicle 50 will deviate from the lane beyond the second lane boundary 64.

[0073] <C4. When the return condition of the lane departure prevention control is not satisfied but the intention to depart from the lane is cancelled> In step S60, a negative determination is made, but in step S70, an affirmative determination is made, and in step S80, the flag Foff is reset to 0 so that the lane departure prevention control returns. Therefore, when there is a risk that the vehicle 50 will deviate from the lane 54, similar to the case C2 above, in step S10, a negative determination is made, in step S20, an affirmative determination is made, and in step S30, a negative determination is made. Accordingly, in step S50, the lane departure prevention control is executed, so that the operation of the warning device 18 and the automatic steering of the steered wheels 24 can prevent the vehicle 50 from deviating from the lane 54.

[0074] <C5. When the return condition of the lane departure prevention control is satisfied> In step S60, an affirmative determination is made, and in step S80, the flag Foff is reset to 0 so that the lane departure prevention control is resumed. Therefore, since a negative determination is made in step S10, steps S20 to S50 are executed. <Example of operation>

[0075] Next, a specific example of the operation of a conventional lane departure prevention device and the embodiment will be described with reference to Figures 8 and 9. Figures 8 and 9 show a case where the driver desires to depart from the lane 54 to a side road 66 so that the vehicle 50 crosses the first lane boundary 56L from the lane 54 and moves onto the side road 66. In addition, when the vehicle 50 is in the position shown by the solid line in Figures 8 and 9, the flag Foff is set to 1.

[0076] As shown in Figures 8 and 9, the side road 66 extends at an angle of about 10° with respect to the lane 54. There is a second lane boundary 64 on the side road 66, and a fence 68, which is a three-dimensional object, extends along the second lane boundary outside the second lane boundary. The traveling direction 62 of the vehicle 50 is inclined at angles of about 25° and about 15° with respect to the first lane boundary 56L and the second lane boundary 64, respectively. Therefore, the magnitude of the oblique angle θy of the vehicle 50 with respect to the first lane boundary 56L is equal to or larger than the reference angle θyc, but the magnitude of the oblique angle θy of the vehicle 50 with respect to the second lane boundary 64 is less than the reference angle θyc.

[0077] Furthermore, before the center of gravity 50A of the vehicle 50 crosses the first lane boundary 56L relative to the second lane boundary 64, a negative judgment is made in step S10, positive judgments are made in steps S20 and S30, and flag Foff is set to 1 in step S40.

[0078] In the conventional lane departure prevention device, instead of step S70 and steps S90 to S120 in FIG. 2, steps similar to 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 the second lane boundary 64 is in front of the vehicle 50, the magnitude of the skew angle θy of the vehicle 50 with respect to the second lane boundary 64 is less than the reference angle θyc, so that it is determined that the driver has no intention of departing from the lane. Therefore, lane departure prevention control is executed for the second lane boundary 64, and the steered wheels 24 are automatically steered so that the center of gravity 50A of the vehicle 50 does not approach the second lane boundary 64, as shown by the imaginary line in FIG. 8. Therefore, it is inevitable that the lane departure prevention control will have a counterproductive effect on smoothly moving the vehicle 50 to the side road 66 as the driver desires.

[0079] 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. Therefore, lane departure prevention control is not executed for the second lane boundary 64, and the vehicle 50 can move smoothly onto the side road 66 as desired by the driver, as shown by the phantom line in FIG.

[0080] In the above example, the side road 66 and the second lane boundary 64 extend linearly and inclined with respect to the first lane boundary 56L. However, as shown by the dashed lines in Figures 8 and 9, the side road 66 and the second lane boundary 64 may extend in a curved manner so as to gradually move away from the first lane boundary 56L. In addition, although not shown in Figures 8 and 9, the lane 54 and the lane boundaries 56L, 56R may extend in a curved manner so as to gradually move away from the second lane boundary 64.

[0081] 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 onto the side road 66. Therefore, the automatic steering of the steered wheels 24 does not interfere with the driver's driving operation and the warning device 18 does not activate, so the driver can smoothly move the vehicle onto the side road as desired.

[0082] According to the embodiment, the reference distance Lsc is variably set according to the vehicle speed (FIG. 4) so ​​that the reference distance Lsc increases as the vehicle speed V increases. Therefore, compared to a case where the reference distance is constant regardless of the vehicle speed, it is possible to appropriately determine whether or not there is a high possibility that the vehicle will cross the second lane boundary and therefore whether or not it is necessary to execute lane departure prevention control for the second lane boundary.

[0083] Furthermore, according to the embodiment, in a situation where the suspension of the execution of the lane departure prevention control continues, when it is determined that there is a risk that the vehicle 50 will be in a dangerous situation if it crosses the second lane boundary 64, the lane departure prevention control is executed for the second lane boundary. Thus, the lane departure prevention control can reduce the risk that the vehicle will cross the second lane boundary and be in a dangerous situation.

[0084] Furthermore, according to the embodiment, in a situation where the suspension of the execution of the lane departure prevention control continues, when it is determined that the steering torque Ts in the direction in which the vehicle 50 approaches the second lane boundary 64 is equal to or less than the reference torque Tac, the lane departure prevention control is executed for the second lane boundary. Therefore, in a situation where the vehicle approaches the second lane boundary due to driver inattention or the like and there is a risk that the vehicle will cross the second lane boundary, the lane departure prevention control can reduce the risk that the vehicle will cross the second lane boundary.

[0085] In particular, according to the embodiment, when it is determined that the speed Va at which the vehicle 50 approaches the second lane boundary 64 is equal to or greater than the reference speed Vac and the steering torque Ts in the direction in which the vehicle 50 approaches the second lane boundary 64 is equal to or less than the reference torque Tac, lane departure prevention control is executed for the second lane boundary. Thus, in a situation in which the vehicle approaches the second lane boundary quickly due to driver inattention or the like and there is a high risk of the vehicle crossing the second lane boundary, the lane departure prevention control can reduce the risk of the vehicle crossing the second lane boundary.

[0086] Furthermore, according to the embodiment, the reference speed is variably set according to the vehicle speed so that the reference speed Vac decreases as the vehicle speed V increases (FIG. 5). Therefore, compared to a case where the reference speed is constant regardless of the vehicle speed, it is possible to appropriately determine whether or not there is a high possibility that the vehicle will cross the second lane boundary and therefore whether or not it is necessary to execute lane departure prevention control for the second lane boundary.

[0087] Furthermore, according to the embodiment, the reference torque Tac is variably set according to the vehicle speed (FIG. 6) so that the reference torque Tac decreases as the vehicle speed V increases. Therefore, it is possible to appropriately determine whether the driver is attempting to move the vehicle in a direction approaching the second lane boundary by a steering operation, as compared to a case in which the reference torque is constant regardless of the vehicle speed.

[0088] Furthermore, according to the embodiment, when it is determined that the distance of the vehicle 50 to the second lane boundary 64 is less than the reference distance Lsc, lane departure prevention control is executed for the second lane boundary. Also, the reference distance is variably set according to the risk of the vehicle becoming in a dangerous situation such that the reference distance increases as the risk of the vehicle becoming in a dangerous situation increases when the vehicle crosses the second lane boundary. Thus, the higher the risk of the vehicle becoming in a dangerous situation when the vehicle crosses the second lane boundary, the more likely it is that the distance of the vehicle to the second lane boundary is less than the reference distance, and lane departure prevention control can be effectively executed for the second lane boundary.

[0089] Furthermore, according to the embodiment, the reference time Tc is variably set according to the vehicle speed so that the reference time Tc is shorter as the vehicle speed V is higher (FIG. 3). Therefore, it is possible to appropriately determine whether the control recovery condition is satisfied, compared to a case where the reference time Tc is constant regardless of the vehicle speed.

[0090] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0091] For example, in the above-described embodiment, lane departure prevention control involves issuance of a warning by activation of the warning device 18 and automatic steering of the steered wheels 24 by the EPS device 22. However, one of the issuance of a warning and the automatic steering of the steered wheels 24 may be omitted.

[0092] In the above-described embodiment, the reference value Tc for the elapsed time, the reference distance Lsc, the reference speed Vac, and the reference torque Tac are variably set according to the vehicle speed, as shown in Fig. 3 to Fig. 6. However, at least one of the reference value Tc, the reference distance Lsc, the reference speed Vac, and the reference torque Tac may be constant regardless of the vehicle speed V.

[0093] In the above embodiment, in step S110, it is determined whether the approach speed Va of the vehicle 50 with respect to the second lane boundary 64 is equal to or greater than the reference speed Vac, and when a positive determination is made, step S120 is executed. However, step S110 may be omitted, and step S120 may be executed when a negative determination is made in step S100.

[0094] Furthermore, in the above-described embodiment, the reference distance Lsc is the distance in the vehicle traveling direction 62 from the center of gravity 50A of the vehicle 50 to the second lane boundary 64, but it may be, for example, the distance in the vehicle traveling direction 62 from the front end of the vehicle 50 to the second lane boundary 64. In addition, the reference distance Lsc may be the extreme distance from a reference position such as the center of gravity 50A of the vehicle 50 to the second lane boundary 64.

[0095] Furthermore, in the above-described embodiment, the reference distance Lsc is calculated by referring to the map shown by the solid line in FIG. 4. As shown by the solid line, the dashed line, and the dashed double-dot line in FIG. 4, the reference distance Lsc may be variably set according to the degree of danger to which the vehicle 50 is exposed when the vehicle 50 crosses the second lane boundary. In this case, when the vehicle 50 crosses the second lane boundary and reaches a non-solid object such as grass or gravel other than the road, it may be determined that the degree of danger to the vehicle is high compared to when the vehicle reaches a part of the road such as another lane, a side strip, or a branch road. Also, when the vehicle 50 crosses the second lane boundary and collides with a solid object such as a fence, a guardrail, or a forest, it may be determined that the degree of danger to the vehicle is high compared to when the vehicle reaches a non-solid object such as grass or gravel other than the road. [Explanation of symbols]

[0096] 10...Lane departure prevention ECU (LDA·ECU), 12...Camera sensor, 14...Radar sensor, 16...Vehicle speed sensor, 18...Warning device, 20...Electric power steering ECU (EPS·ECU), 22...EPS device, 24...Steering wheel, 28...Steering wheel, 32...Torque sensor, 40...Steering ECU, 42...Torque sensor, 44L, 44R...Blinker lamp, 54...Lane, 56L, 56R...White line, 64...Second lane boundary, 66...Side road, 68...Fence, 100...Lane departure prevention device

Claims

1. a vehicle position detection device that detects a position of a vehicle relative to a lane; and a control unit configured to execute at least one of lane departure prevention control of automatic steering of steered wheels and issuing a warning when it is determined based on the position of the vehicle detected by the vehicle position detection device that the vehicle is in danger of crossing a first lane boundary and that the driver has no intention of crossing the first lane boundary, and to suspend execution of the lane departure prevention control until it is determined that a preset control return condition is satisfied, A lane departure prevention device configured to continue suspending the execution of the lane departure prevention control when the control unit determines, in a situation where the execution of the lane departure prevention control has been suspended and the control return condition has not been satisfied, that there is a second lane boundary on the side to which the vehicle is approaching but the distance from the vehicle to the second lane boundary is equal to or greater than a reference distance.

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

3. 3. The lane departure prevention device according to claim 1 or 2, wherein the control unit is configured to execute the lane departure prevention control for the second lane boundary when it determines that the vehicle is at risk of being in a dangerous situation if the vehicle crosses the second lane boundary while the execution of the lane departure prevention control is continued to be suspended.

4. 4. A lane departure prevention device according to claim 1, wherein the control unit is configured to execute the lane departure prevention control for the second lane boundary when the control unit determines that the steering torque in the direction in which the vehicle approaches the second lane boundary is equal to or less than a reference torque while the execution of the lane departure prevention control is continued to be suspended.

5. 5. The lane departure prevention device according to claim 4, wherein the control unit is configured to execute the lane departure prevention control for the second lane boundary when it determines that the speed at which the vehicle approaches the second lane boundary is equal to or greater than a reference speed and that the steering torque in the direction in which the vehicle approaches the second lane boundary is equal to or less than a reference torque.

6. 6. The lane departure prevention device according to claim 5, wherein the control unit is configured to variably set the reference speed in accordance with the vehicle speed so that the higher the vehicle speed is, the smaller the reference speed becomes.

7. 6. The lane departure prevention device according to claim 4, wherein the control unit is configured to variably set the reference torque in accordance with the vehicle speed so that the reference torque decreases as the vehicle speed increases.

8. 8. A lane departure prevention device according to any one of claims 1 to 7, wherein the control unit, when determining that the distance from the vehicle to the second lane boundary is less than a reference distance, executes the lane departure prevention control for the second lane boundary, and is configured to variably set the reference distance in accordance with the risk of the vehicle becoming in a dangerous situation if the vehicle crosses the second lane boundary, so that the reference distance becomes larger the higher the risk of the vehicle becoming in a dangerous situation.

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