Lane departure prevention device, lane departure prevention method, and program thereof

Abstract

To provide a lane departure prevention device that can reduce the frequency with which the vehicle driver finds the lane departure prevention operation bothersome. [Solution] When a predetermined start condition is met, which is met when there is a possibility that the vehicle HV is traveling in a driving lane, the driver assistance ECU 10 performs a lane departure prevention operation by applying a force to the vehicle to change the direction of travel so that the vehicle does not deviate from the driving lane. When a specific condition is met, which includes as one of the conditions for a first condition that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold, the driver assistance ECU performs at least one of the following: a first process which changes the start condition to a condition that is more likely to be met compared to when the specific condition is not met, and a second process which increases the force that changes the direction of travel applied to the vehicle by the lane departure prevention operation at the moment immediately after the start condition is met compared to when the specific condition is not met.

Description

Technical Field

[0001] The present invention relates to a lane departure prevention device, a lane departure prevention method, and a program thereof that perform a lane departure prevention operation for applying a force to change the traveling direction of a vehicle so that the vehicle does not deviate from the traveling lane on which the vehicle is traveling.

Background Art

[0002] One of the conventional lane departure prevention devices (hereinafter simply referred to as "conventional device") changes a control permission range for determining whether to execute a departure prevention operation according to only the curvature of the traveling lane (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] However, since the conventional device changes the control permission range according to the curvature of the traveling lane regardless of the vehicle speed when the vehicle enters a curved road from a straight road, for example, even when the driver has sufficiently reduced the vehicle speed in preparation for entering a curved road, the lane departure prevention operation may be executed. In this case, there is a problem that the driver of the vehicle feels the lane departure prevention operation troublesome.

[0005] The present invention has been made to address the above-described problems. That is, one of the objects of the present invention is to provide a lane departure prevention device, a lane departure prevention method, and a program thereof that can avoid the vehicle from deviating from the traveling lane of a curved road when the vehicle enters from a straight road to a curved road, and can reduce the frequency with which the driver of the vehicle feels the lane departure prevention operation troublesome.

[0006] One aspect of the lane departure prevention device of the present invention is The system includes a controller (10) that, when a predetermined start condition is met (S520: Yes) which is established when there is a possibility that the vehicle (HV) may deviate from the driving lane (HL) in which it is traveling, performs a lane departure prevention operation (S570, S580) by applying a force to the vehicle to change the direction of travel so that the vehicle does not deviate from the driving lane.

[0007] Furthermore, the controller, When a specific condition is met, which includes as one of the conditions for a first condition that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold (see the "Yes" determination in S420, S425, S450, and 455), the system is configured to perform at least one of the following: a first process (S460, S465, S520) that changes the start condition to a condition that is more likely to be met compared to when the specific condition is not met; and a second process (S610, S615, S570) that increases the force that changes the direction of travel of the vehicle applied to the vehicle by the road departure prevention operation at the time immediately after the start condition is met, compared to when the specific condition is not met.

[0008] According to this, if a specific condition is met, which includes as one of the conditions that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold, then at least one of the first process and the second process is performed.

[0009] If the first process is performed, the lane departure prevention action will be executed at an earlier timing. Therefore, it will be less likely for a vehicle traveling on a curved road to deviate from its lane. If the second process is performed, the lane departure prevention action will change the direction of travel of the vehicle more quickly. Therefore, it will be less likely for a vehicle traveling on a curved road to deviate from its lane.

[0010] In addition, both the first and second processes are performed when the vehicle speed when entering a curved road from a straight road is higher than a predetermined speed threshold. As a result, if the driver has sufficiently reduced the vehicle speed in preparation for entering a curved road, the lane departure prevention action will be less likely to occur, or even if it does occur, the vehicle's direction of travel will not change abruptly, thus reducing the frequency with which the driver finds the lane departure prevention action bothersome.

[0011] In the above description, to aid in understanding the present invention, the names and / or reference numerals used in the embodiments described later are indicated in parentheses for the components of the invention corresponding to those embodiments. However, the components of the present invention are not limited to the embodiments defined by the above names and / or reference numerals. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a road departure prevention device according to the first embodiment of the present invention. [Figure 2] This is a plan view of the travel lane and vehicle for illustrating the operation of the first embodiment. [Figure 3] This is a plan view of the travel lane and vehicle for illustrating the operation of the first embodiment. [Figure 4] Figure 1 is a flowchart showing the routines executed by the CPU of the driver assistance ECU. [Figure 5] Figure 1 is a flowchart showing the routines executed by the CPU of the driver assistance ECU. [Figure 6] This is a flowchart showing the routine executed by the CPU of the lane departure prevention device according to the second embodiment of the present invention. [Modes for carrying out the invention]

[0013] 1. First Embodiment <Structure> The lane departure prevention device according to the first embodiment of the present invention (hereinafter referred to as "first device DS1") comprises the components shown in Figure 1. The first device DS1 is applied to (mounted on) a vehicle HV. The vehicle HV may be any of the following: a vehicle powered by an internal combustion engine, a vehicle powered by an electric motor (i.e., an electric vehicle), and a hybrid vehicle.

[0014] In this specification, "ECU" refers to an electronic control unit equipped with a microcomputer. The microcomputer includes a CPU (processor), ROM, RAM, data-writable non-volatile memory, and interfaces, etc. An ECU is also referred to as a controller or computer.

[0015] The driver assistance ECU 10 performs lane departure prevention control, which is sometimes referred to as "LDA control." The driver assistance ECU 10 is connected to the components described below and transmits and receives information or signals between them. The driver assistance ECU 10 may be composed of multiple ECUs.

[0016] The camera sensor 21 captures images of the scene in front of the vehicle HV at predetermined intervals and acquires image data. The driver assistance ECU 10 recognizes the "left boundary line LL and right boundary line RL" on the road based on the image data (see Figure 2). The boundary lines are lane markings (e.g., white lines). The area between the left boundary line LL and the right boundary line RL is the driving lane HL.

[0017] Furthermore, the driver assistance ECU 10 acquires the radius of curvature R (see Figure 2), the approach distance Ds, and the yaw angle θy (see Figure 3) based on the image data.

[0018] The radius of curvature R is the radius of curvature of the line (i.e., the center line CL) that passes through the midpoint between the left boundary line LL and the right boundary line RL, located at a predetermined distance forward from the vehicle HV.

[0019] The approach distance Ds is, as shown in FIG. 3, the distance from the reference point P of the vehicle HV to the boundary line on the side where the vehicle HV is about to deviate from the driving lane HL. The reference point P on the vehicle HV is the center point between the left front wheel and the right front wheel of the vehicle HV. The side where the vehicle HV is about to deviate from the driving lane HL is referred to as the "deviation side" for convenience.

[0020] The yaw angle θy is the angle formed by the direction of the center line CL and the longitudinal axis direction of the vehicle HV (i.e., the traveling direction of the vehicle HV).

[0021] Furthermore, the driving support ECU 10 obtains the sum of the approach distance Ds and a predetermined correction distance Df as the "deviation margin distance Dsy (= Ds + Df)". The correction distance Df may be "0", may be a positive value, or may be a negative value.

[0022] The vehicle speed sensor 22 outputs a signal indicating the speed (i.e., vehicle speed) Vh of the vehicle HV. The yaw rate sensor 23 outputs a signal indicating the yaw rate Yr of the vehicle HV. The lateral acceleration sensor 24 outputs a signal indicating the acceleration in the vehicle width direction of the vehicle HV (i.e., lateral acceleration) Gy.

[0023] The brake switch 25 outputs an on signal when the brake pedal of the vehicle HV (not shown) is operated and a braking force is applied to the vehicle HV by a braking device (not shown), and outputs an off signal when the brake pedal is not operated.

[0024] The steering angle sensor 26 outputs a signal indicating the steering angle Sa of the vehicle HV. The steering torque sensor 27 outputs a signal indicating the steering torque Tq input to the steering shaft (not shown) by operating the steering wheel (not shown) of the vehicle HV.

[0025] The LDA switch 28 outputs an ON signal when the driver of the HV vehicle requests the execution of lane departure prevention control while it is generating an OFF signal. The LDA switch 28 outputs an OFF signal when the driver of the HV vehicle requests the deactivation of lane departure prevention control while it is generating an ON signal.

[0026] The driving mode selection switch 29 is operated by the driver of the vehicle HV. When the driver performs a predetermined operation on the driving mode selection switch 29 to set the driving mode of the vehicle HV to normal mode, the driving mode selection switch 29 outputs a signal indicating that normal mode has been selected. When the driver performs a predetermined operation on the driving mode selection switch 29 to set the driving mode of the vehicle HV to sport mode, the driving mode selection switch 29 outputs a signal indicating that sport mode has been selected.

[0027] The driver assistance ECU 10 is connected to the steering motor 30. The steering motor 30 drives the steering mechanism (not shown) of the vehicle HV in response to instructions from the driver assistance ECU 10 to change the steering angle of the vehicle HV (i.e., the steering angle of the steering wheels).

[0028] (Summary of operation) As shown in Figure 3, the first device DS1 determines the left departure restriction line LD as a line obtained by moving the left boundary line LL by a correction distance Df to the outside (left side) of the driving lane HL. The first device DS1 determines the right departure restriction line RD as a line obtained by moving the right boundary line RL by a correction distance Df to the outside (right side) of the driving lane HL. If the first device DS1 anticipates that the vehicle HV will deviate from the driving lane HL through the left departure restriction line LD, it changes the steering angle of the vehicle HV so that the vehicle HV moves to the right. If the first device DS1 anticipates that the vehicle HV will deviate from the driving lane HL through the right departure restriction line RD, it changes the steering angle of the vehicle HV so that the vehicle HV moves to the left. This operation to change the steering angle is called the "driving lane departure prevention operation" and is described as "an operation that applies a force to the vehicle HV to change the direction of travel" to prevent the vehicle HV from deviating from the driving lane HL. The conditions for starting the driving lane departure prevention operation are met when the vehicle HV is expected to deviate from the driving lane HL. The control system that prevents a vehicle hybrid from deviating from its driving lane (HL) through lane departure prevention measures is called "lane departure prevention control."

[0029] Incidentally, as shown in Figure 2, when a vehicle HV enters a curved road from a straight road, if the vehicle speed Vh is higher than the vehicle speed threshold Vhth, the vehicle HV is more likely to deviate from the driving lane HL due to strong centrifugal force while traveling on the curved road.

[0030] Therefore, when a specific condition is met, which includes the first condition that the vehicle speed Vh when the vehicle HV enters a curved road from a straight road is higher than the vehicle speed threshold Vhth, the first device DS1 changes the conditions for starting the road departure prevention operation to conditions that are more likely to be met compared to when the specific condition is not met.

[0031] Therefore, with the first device DS1, if a vehicle HV enters a curved road at a high speed and specific conditions are met, the lane departure prevention operation is initiated at a relatively earlier timing, thereby reducing the possibility of the vehicle HV deviating from its lane on the curved road. Furthermore, if the first device DS1 does not meet the specific conditions, it initiates the lane departure prevention operation at the normal timing. Therefore, with the first device DS1, if the driver guides the vehicle HV into a curved road at an appropriate speed, there is a high probability that the lane departure prevention operation will not be initiated. Thus, the first device DS1 can reduce the frequency with which the driver finds the lane departure prevention operation bothersome.

[0032] (Specific operation) The CPU of the driver assistance ECU 10 executes the routines shown in Figures 4 and 5 at predetermined intervals. Note that "step" may be abbreviated as "S" below. The values ​​of each flag described below are set to "0" in an initialization routine (not shown) executed by the CPU when the vehicle HV is started.

[0033] When the predetermined timing arrives, the CPU starts processing from S400 in Figure 4 and proceeds to S405, where it determines whether the value of the precondition fulfillment flag XZ is "0".

[0034] If the value of the prerequisite fulfillment flag XZ is "0", the CPU proceeds from S405 to S410 to determine whether the LDA switch 28 is outputting an ON signal. That is, the CPU determines whether the driver is requesting the execution of lane departure prevention control.

[0035] If the LDA switch 28 outputs an ON signal, the CPU proceeds from S410 to S415 and determines whether normal mode is selected as the driving mode based on the output signal of the driving mode selection switch 29. In other words, the CPU determines whether the driver has selected sport mode.

[0036] If normal mode is selected as the driving mode, the CPU proceeds from S415 to S420 to determine whether the current time is "immediately after the point in time when the radius of curvature R changed from being greater than or equal to the radius threshold Rth to being less than the radius threshold Rth". In other words, in S420, the CPU determines whether the vehicle HV has entered a curved road from a straight road. The radius threshold Rth is set to a value that allows the driving lane HL to be considered a curved road when the radius of curvature R is less than the radius threshold Rth.

[0037] When a hybrid vehicle (HV) enters a curved road from a straight road, the CPU proceeds from S420 to S425 to determine whether the vehicle speed Vh is equal to or greater than the vehicle speed threshold Vhth. The condition that the vehicle speed Vh is equal to or greater than the vehicle speed threshold Vhth when a hybrid vehicle enters a curved road from a straight road is sometimes referred to as the "first condition" for convenience.

[0038] If the vehicle speed Vh is greater than or equal to the vehicle speed threshold Vhth, the CPU determines that the precondition has been met and proceeds from S425 to S430, setting the value of the precondition fulfillment flag XZ to "1". After that, the CPU proceeds to S445.

[0039] If the CPU determines "No" in any of steps S410 through S425, it proceeds from that step to S445. Therefore, in these cases, the value of the precondition fulfillment flag XZ remains "0".

[0040] In contrast, when the CPU proceeds to S405, if the value of the precondition fulfillment flag XZ is "1", the CPU proceeds from S405 to S435 to determine whether the vehicle HV has entered a straight section from a curved section. In other words, the CPU determines whether the vehicle HV has left the curved section. Specifically, the CPU determines whether the current time is "immediately after the point in time when the radius of curvature R changed from less than the radius threshold Rth to greater than or equal to the radius threshold Rth".

[0041] If the vehicle HV has not exited the curved track, the CPU proceeds directly from S435 to S445. In this case, the value of the precondition fulfillment flag XZ is maintained at "1". On the other hand, if the vehicle HV has exited the curved track, the CPU proceeds from S435 to S440 and sets the value of the precondition fulfillment flag XZ to "0". After that, the CPU proceeds to S445.

[0042] In S445, the CPU determines whether the value of the precondition fulfillment flag XZ is "1". A value of "1" for the precondition fulfillment flag XZ means that when vehicle HV enters the curved road, vehicle Vh is higher than the vehicle speed threshold Vhth. In other words, when the value of the precondition fulfillment flag XZ is "1", there is a high probability that vehicle HV will deviate from the driving lane HL toward the outside of the curved road upon entering the curved road.

[0043] If the value of the precondition fulfillment flag XZ is "1", the CPU proceeds from S445 to S450 and determines whether braking force is being applied to the vehicle HV by checking whether the brake switch 25 is outputting an ON signal. That is, in S450, the CPU determines whether the driver of the vehicle HV has indicated an intention to decelerate the vehicle HV by performing a braking operation. The condition that is fulfilled when the driver of the vehicle HV performs a braking operation is sometimes referred to as the "second condition" for convenience.

[0044] If the brake switch 25 outputs an ON signal, the CPU proceeds from S450 to S455 and determines whether the magnitude of the lateral acceleration Gy (|Gy|) detected by the lateral acceleration sensor 24 is greater than or equal to the lateral acceleration threshold Gyth. That is, the CPU determines whether the vehicle VH is actually being affected by centrifugal force and has begun to move rapidly toward the outside of the curved road. The condition that is met when the magnitude of the lateral acceleration Gy (|Gy|) is greater than or equal to the lateral acceleration threshold Gyth is sometimes referred to as the "third condition" for convenience.

[0045] If the magnitude of the lateral acceleration Gy (|Gy|) is greater than or equal to the lateral acceleration threshold Gyth, the CPU proceeds from S455 to S460 and sets the threshold Dref for the start distance of the lane departure prevention operation to "DLarge, which is greater than the standard value DStd". After that, the CPU proceeds to S595 and tentatively terminates this routine.

[0046] As described later, when the deviation margin distance Dsy (=Ds+Df) becomes less than or equal to the starting distance threshold Dref, the lane departure prevention operation (i.e., the operation to change the steering angle of the steering wheels) is initiated (S520, S530, S560 to S580 in Figure 5). Therefore, when the starting distance threshold Dref for the lane departure prevention operation is set to the value DLarge, the lane departure prevention operation is initiated earlier than when the starting distance threshold Dref for the lane departure prevention operation is set to the standard value DStd. Note that the process in S460 is sometimes referred to as the "first process" or "starting condition change process," which changes the starting condition to a condition that is more likely to be met.

[0047] In response, if the CPU determines "No" in any of steps S445, S450, or S455, the CPU proceeds from that step to S465. In S465, the CPU sets the starting distance threshold Dref for the lane departure prevention operation to the standard value DStd. After that, the CPU proceeds to S495 and provisionally terminates this routine.

[0048] At a predetermined timing, the CPU starts processing from S500 in Figure 5 and proceeds to S510, where it determines whether the value of the LDA operation execution flag XLDA is "0". As will be described later, the value of the LDA operation execution flag XLDA is set to "1" when the start condition for the lane departure prevention operation is met, and is set to "0" when the end condition for the lane departure prevention operation is met.

[0049] If the value of the LDA operation execution flag XLDA is "0", the CPU proceeds from S510 to S520 to determine whether the conditions for starting the lane departure prevention operation have been met. These conditions are met, for example, when both of the following conditions C1 and C2 are met.

[0050] <<Conditions for initiating lane departure prevention operation>> (Condition C1) The deviation margin distance Dsy is less than or equal to the starting distance threshold Dref, which is a positive predetermined value. (Condition C2) The direction of travel of the vehicle HV, indicated by the yaw angle θy, is towards the deviation control line on the side of the deviation.

[0051] The CPU may also determine that the conditions for starting the lane departure prevention operation have been met when the time required for the deviation margin distance Dsy to reach the starting distance threshold Dref (i.e., arrival time) TTD is less than or equal to the arrival time threshold TTDth. In this case, the CPU calculates the arrival time TTD based on the current deviation margin distance Dsy, the current lateral velocity Vy, the current lateral acceleration Gy, and the starting distance threshold Dref. The CPU calculates the change in approach distance Ds per unit time as the current lateral velocity Vy.

[0052] If the conditions for starting the lane departure prevention operation are met, the CPU proceeds from S520 to S530 and sets the value of the LDA operation execution flag XLDA to "1". After that, the CPU proceeds to S560, which will be described later. On the other hand, if the conditions for starting the lane departure prevention operation are not met, the CPU proceeds directly from S520 to S560.

[0053] When the CPU proceeds to S510, if the value of the LDA operation execution flag XLDA is "1", the CPU proceeds from S510 to S540 to determine whether the conditions for terminating the lane departure prevention operation have been met. The conditions for terminating the lane departure prevention operation are met, for example, when both of the following conditions D1 and D2 are met.

[0054] <<Conditions for ending lane departure prevention operation>> (Condition D1) The deviation margin distance Dsy is greater than the starting distance threshold Dref plus a small positive value d (=Dref+d). Note that the value d may be "0". (Condition D2) The direction of travel of the vehicle HV, indicated by the yaw angle θy, is not towards the deviation control line on the side of the deviation. In other words, the direction of travel of the vehicle HV, indicated by the yaw angle θy, is towards the deviation control line on the opposite side of the deviation control line at the time it was determined that the conditions for starting the road departure prevention operation were met.

[0055] If the conditions for terminating the lane departure prevention operation are not met, the CPU proceeds directly from S540 to S560. Conversely, if the conditions for terminating the lane departure prevention operation are met, the CPU proceeds from S540 to S550 and sets the value of the LDA operation execution flag XLDA to "0". After that, the CPU proceeds to S560, which will be described later.

[0056] In S560, the CPU determines whether the value of the LDA operation execution flag XLDA is "1". If the value of the LDA operation execution flag XLDA is not "1", the CPU proceeds directly from S560 to S595 and terminates this routine. In this case, the lane departure prevention operation is not performed.

[0057] In contrast, if the value of the LDA operation execution flag XLDA is "1", the CPU proceeds from S560 to S570 and calculates the target torque Tqtgt as the target steering control amount based on the vehicle speed Vh, radius of curvature R, approach distance Ds, and yaw angle θy.

[0058] For example, the CPU calculates the target torque Tqtgt according to equation (1) below. Tqtgt=K·f(Vh,R,Ds,θy) =K·(K1·(Vh 2 / R)+K2·(Dref-Dsy)+K3·θy) …(1)

[0059] In equation (1), K, K1, K2, and K3 are control gains. Gain K is a predetermined positive value, which is "1" in the first embodiment. The signs (positive and negative) of the control gains K1, K2, and K3 change depending on whether the driving lane HL is a right curve, a left curve, or a straight road, and whether the deviation restriction line on the deviation side is a left deviation restriction line LD or a right deviation restriction line RD, etc. That is, when a torque equal to the target torque Tqtgt is generated by the steering motor 30, the signs of these control gains K1, K2, and K3 are determined so that "the steering angle of the vehicle HV is a value that directs the vehicle HV toward the center line CL".

[0060] Note that the function f in equation (1) may also have the term K4·(Yr*-Yr) added to it. Yr* is the target yaw rate, and Yr is the actual yaw rate of the vehicle detected by the yaw rate sensor 23. The "value obtained by subtracting the deviation margin distance Dsy from the starting distance threshold Dref (Dref-Dsy)" in equation (1) is sometimes called the side distance Ds'.

[0061] Thus, the target torque Tqtgt is calculated such that its absolute value |Tqtgt| increases as the deviation margin distance Dsy decreases (i.e., as the side distance Ds' increases). Furthermore, the target torque Tqtgt is calculated such that its absolute value |Tqtgt| increases as the direction of travel of the vehicle HV, indicated by the yaw angle θy, is towards the deviation side and the magnitude of the yaw angle θy |θy| increases. This method for calculating the target torque Tqtgt is well known and is disclosed, for example, in Japanese Patent Publication No. 2018-79835 and Japanese Patent Publication No. 2020-11562.

[0062] Next, the CPU proceeds to S580, where it drives the steering motor 30 so that it generates a torque equal to the target torque Tqtgt. After that, the CPU proceeds to S595.

[0063] As explained above, the first device DS1 initiates lane departure prevention operation early when the vehicle HV enters a curved road at a vehicle speed Vh that is equal to or greater than the threshold vehicle speed Vhth, which increases the likelihood of the vehicle deviating from the curved road. Therefore, the first device DS1 can reduce the likelihood of the vehicle HV deviating from the driving lane HL on a curved road. Conversely, when the vehicle HV enters a curved road at a vehicle speed Vh that is less than the threshold vehicle speed Vhth, the lane departure prevention operation is not initiated early. Therefore, the frequency with which the driver finds the lane departure prevention operation bothersome is reduced.

[0064] 2. Second Embodiment The lane departure prevention device according to the second embodiment of the present invention (hereinafter referred to as "second device DS2") differs from the first device DS1 in that, when the above-mentioned specific conditions are met, the amount of steering control (i.e., steering torque or steering angle for preventing lane departure) immediately after the start condition is met is increased compared to when the specific conditions are not met, even if the degree of lane departure tendency of the vehicle HV is the same. The degree of lane departure tendency is represented, for example, by a combination of the departure margin distance Dsy and the yaw angle θy, or by a combination of the departure margin distance Dsy, the lateral acceleration Gy and the yaw angle θy.

[0065] More specifically, the CPU of the driver assistance ECU 10 of the second device DS2 executes the routine shown in Figure 6 at predetermined intervals, instead of the routine shown in Figure 4. The routine shown in Figure 6 differs from the routine shown in Figure 4 only in that steps S460 and S465 are replaced with steps S610 and S615, respectively. These differences will be explained below.

[0066] That is, if the CPU determines "Yes" in all steps S445 to S455 shown in Figure 6, it proceeds to S610 and sets the value of gain K in equation (1) to the value KLarge. The value KLarge is a value greater than the standard value KStd described later (for example, "1.2", which is greater than "1"). After that, the CPU proceeds to S695 and provisionally terminates this routine.

[0067] In response, if the CPU determines "No" in any of the steps S445 to S455 shown in Figure 6, it proceeds from that step to S615. In S615, the CPU sets the value of gain K in equation (1) to the standard value KStd (for example, "1"). After that, the CPU proceeds to S695 and provisionally terminates this routine.

[0068] As a result, when the above specific conditions are met, the magnitude of the target torque Tqtgt immediately after the start condition is met, calculated in step 570 of Figure 5, is larger than when the specific conditions are not met. Therefore, when the above specific conditions are met, the force that changes the direction of travel of the vehicle HV due to the lane departure prevention operation is larger immediately after the start condition is met compared to when the specific conditions are not met, so the vehicle HV is quickly returned to the center line CL side. The process in S610 is sometimes referred to as the "second process" or "action enhancement process" because it increases the force that changes the direction of travel of the vehicle HV due to the lane departure prevention operation immediately after the start condition is met, compared to when the specific conditions are not met.

[0069] Therefore, when the second device DS2 enters a curved road at a vehicle speed Vh that is equal to or greater than the threshold vehicle speed Vhth, the vehicle HV performs a lane departure prevention operation that applies a greater force to the vehicle HV to change its direction of travel towards the center line CL. Thus, the possibility of the vehicle HV deviating from the driving lane HL on a curved road can be further reduced. In contrast, when the vehicle HV enters a curved road at a vehicle speed Vh that is less than the threshold vehicle speed Vhth, the normal lane departure prevention operation is performed. Thus, the frequency with which the driver finds the lane departure prevention operation bothersome is reduced.

[0070] The present invention is not limited to the embodiments described above, and various modifications described below can be adopted within the scope of the present invention.

[0071] For example, while the first device DS1 and the second device DS2 each perform an action to change the steering angle of the steering wheels as a lane departure prevention action, another action to generate a yaw moment in the vehicle may also be performed as a lane departure prevention action. For example, this other action may be an action to create a difference between the driving force of the left drive wheel and the driving force of the right drive wheel, or an action to create a difference between the braking force applied to the left wheel and the braking force applied to the right wheel.

[0072] For example, the first device DS1 and the second device DS2 may each calculate a target steering angle θtgt as the "target control amount in the lane departure prevention control" calculated in S570 of Figure 5, instead of the target torque Tqtgt. In this case, the first device DS1 and the second device DS2 each drive the steering motor 30 so that the actual steering angle is equal to the target steering angle θtgt.

[0073] For example, the first device DS1 and the second device DS2 can be used in combination. Furthermore, each of the first device DS1 and the second device DS2 may perform a first process (operation enhancement process) that sets the correction distance Df when the above specific condition is met to a value smaller than the correction distance Df when the above specific condition is not met. This also allows the start condition for the lane departure prevention operation to be met earlier when the specific condition is met. Furthermore, the magnitude of the second term (K2·(Dref-Dsy)) on the right side of equation (1) above can be increased, so the force that changes the direction of travel of the vehicle HV immediately after the start condition is met can be increased.

[0074] The first device DS1 and the second device DS2 may each omit S415. In this case, if the CPU determines "Yes" in S410, it proceeds to S420.

[0075] In S420, the first device DS1 and the second device DS2 may each acquire the current position of the vehicle HV and map information from a navigation system (not shown), and based on these, determine whether or not the vehicle HV has entered a curved road from a straight road.

[0076] The first device DS1 and the second device DS2 may each omit S450. In this case, if the CPU determines "Yes" at S445, it proceeds from S445 to S455. Furthermore, the first device DS1 and the second device DS2 may each omit S455. In this case, if the CPU determines "Yes" at S450, it proceeds from S450 to S460 or SS610. The first device DS1 and the second device DS2 may each omit both S450 and S455.

[0077] For example, the first device DS1 and the second device DS2 can be applied to an autonomous vehicle when the driving mode has transitioned from autonomous driving to driver-operated driving. [Explanation of symbols]

[0078] 10...Driver assistance ECU, 21...Camera sensor, 22...Vehicle speed sensor, 30...Steering motor.

Claims

1. A lane departure prevention device equipped with a controller that performs a lane departure prevention operation, which applies a force to the vehicle to change the direction of travel so that the vehicle does not deviate from the lane when a predetermined starting condition is met that is met when there is a possibility that the vehicle will deviate from the lane in which it is traveling, The aforementioned controller, When a specific condition is met, which includes as one of the conditions for a first condition that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold, the system is configured to perform at least one of the following: a first process of changing the start condition to a condition that is more likely to be met compared to when the specific condition is not met; and a second process of increasing the force that changes the direction of travel of the vehicle applied to the vehicle by the road departure prevention operation at the time immediately after the start condition is met, compared to when the specific condition is not met. Lane departure prevention device.

2. In the lane departure prevention device according to claim 1, The aforementioned controller, The system is configured to determine that the specific condition has been met when the second condition, which is met when the driver of the vehicle performs a braking operation after the first condition has been met, is met. Lane departure prevention device.

3. In the lane departure prevention device according to claim 1, The aforementioned controller, The system is configured to determine that the specific condition has been met when, after the first condition has been met, the third condition, which is met when the magnitude of the vehicle's lateral acceleration is equal to or greater than a predetermined lateral acceleration threshold, is met. Lane departure prevention device.

4. A method for preventing a vehicle from deviating from its lane, which, when a predetermined starting condition is met that occurs when there is a possibility that the vehicle may deviate from the lane it is traveling in, performs a lane departure prevention operation by applying a force to the vehicle to change the direction of travel so that the vehicle does not deviate from the lane, The step of determining whether a specific condition has been met, which includes as one of the conditions that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold, If it is determined that the aforementioned specific condition has been met, the process includes at least one of the following steps: a first process of changing the start condition to a condition that is more likely to be met compared to when the aforementioned specific condition has not been met; and a second process of increasing the force that changes the direction of travel of the vehicle, applied to the vehicle by the lane departure prevention operation, at the time immediately after the start condition has been met, compared to when the aforementioned specific condition has not been met. A method for preventing lane departure, including the above.

5. A program to be executed by the computer installed in the vehicle, The program is sent to the computer, When a predetermined starting condition is met, which is established when there is a possibility that the vehicle will deviate from the driving lane in which it is traveling, the vehicle performs a lane departure prevention operation which involves applying a force to the vehicle to change the direction of travel so that the vehicle does not deviate from the driving lane. The step of determining whether a specific condition has been met, which includes as one of the conditions that the vehicle speed when the vehicle enters a curved road from a straight road is higher than a predetermined vehicle speed threshold, If it is determined that the aforementioned specific condition has been met, the process includes at least one of the following steps: a first process of changing the start condition to a condition that is more likely to be met compared to when the aforementioned specific condition has not been met; and a second process of increasing the force that changes the direction of travel of the vehicle, applied to the vehicle by the lane departure prevention operation, at the time immediately after the start condition has been met, compared to when the aforementioned specific condition has not been met. A program that executes the command.

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