Driving assistance device

Abstract

A driving assistance device includes a driving device configured to change a steering angle that is an angle of a steering wheel of a vehicle by supplying a torque to a steering shaft linked to the steering wheel of the vehicle, and a control unit. The control unit is configured to execute, when a start condition is satisfied, a lane departure avoidance control that is a control of the driving device to change the steering angle in order to avoid a vehicle from departing from a lane. The control unit is configured to execute, at a time point when the start condition is satisfied, the lane departure avoidance control in such a manner that a magnitude of a steering angular velocity that is a change amount per unit time of the steering angle is smaller than a magnitude of the steering angular velocity when a holding position of a steering wheel of a driver satisfies a predetermined specific condition.

Description

Technical Field

[0001] This invention relates to a driving assistance device that performs lane departure avoidance control, which is a control that changes the steering angle of a vehicle to prevent the vehicle from deviating from its driving lane. Background Technology

[0002] Previously, driver assistance devices that perform lane departure avoidance control were known. For example, the driver assistance device described in Japanese Patent Application Publication No. 2010-100120 (hereinafter referred to as "the prior art") performs lane departure avoidance control by providing steering torque to the steering mechanism based on the input torque of the driver's steering operation. As a result, the steering torque can be reduced when the driver intentionally causes the vehicle to deviate from the lane, and the steering torque can be increased when the driver unintentionally causes the vehicle to deviate from the lane. Summary of the Invention

[0003] During lane departure avoidance control, steering torque is supplied to the steering shaft connected to the vehicle's steering wheel in order to change the vehicle's steering angle. Therefore, the steering wheel also rotates during lane departure avoidance control.

[0004] Due to the rotation of the steering wheel, unintentional actions by the driver may occur depending on the position of the steering wheel held by the driver.

[0005] For example, the weight of the driver's hands holding the steering wheel may cause additional rotation of the steering wheel. Furthermore, the driver may be surprised by the rotation of the steering wheel, which is based on lane departure avoidance control, and thus make unintentional movements of the steering wheel.

[0006] This invention was made to address the aforementioned problems. Specifically, one object of this invention is to provide a driving assistance device that reduces the likelihood of unintentional steering wheel manipulation by the driver due to steering wheel rotation based on lane departure avoidance control.

[0007] The driving assistance device of the present invention (hereinafter also referred to as "the device of the present invention") comprises:

[0008] The drive unit (34) is configured to change the steering angle, which is the angle of the steering wheels of the vehicle, by providing torque to the steering shaft (US) connected to the steering wheel (SW) of the vehicle (VA); and

[0009] The control unit (20, 30) is configured to perform lane departure avoidance control when predetermined start conditions are met. The lane departure avoidance control is a control of the drive unit to change the steering angle in order to prevent the vehicle from deviating from the driving lane in which the vehicle is traveling.

[0010] The control unit is configured to perform lane departure avoidance control (MapGytgt(T), steps 660, 665, 1105, 1205 to 1225) in such a way that the magnitude of the steering angular velocity is smaller than the magnitude of the steering angular velocity when the holding position meets the specific condition at the time of establishment (step 710: "No"), where the holding position refers to the position of the driver's hand holding the steering wheel, and the steering angular velocity is the change in the steering angle per unit time.

[0011] Therefore, when the position is not maintained under specific conditions, the rotational speed of the steering wheel based on lane departure avoidance control is smaller compared to when the position is maintained under specific conditions. This reduces the likelihood of additional steering wheel rotation and unintended actions by the driver due to the rotation of the steering wheel based on lane departure avoidance control.

[0012] In one embodiment of the device of the present invention, the control unit is configured to: when the holding position does not meet the specific condition, earlier the timing of the start condition is compared with when the holding position meets the specific condition, thereby increasing the execution time of the lane departure avoidance control (steps 665 and 670).

[0013] According to this technical solution, when the holding position does not meet specific conditions, lane departure avoidance control is initiated at a timing earlier than when the holding position meets specific conditions, thus increasing the execution time of lane departure avoidance control. Therefore, even if the magnitude of the steering angular velocity when the holding position does not meet specific conditions is smaller than when the holding position meets specific conditions, lane departure avoidance control can still be performed.

[0014] In one embodiment of the device of the present invention, the control unit is configured to: determine that the start condition has been met when the width direction distance (Ds) from the predetermined reference point (P) of the vehicle to the avoidance position (PP) set in the width direction of the driving lane is consistent with the necessary distance (Dsn) (step 650: "Yes"). The necessary distance is the distance required to make the lateral speed zero after a predetermined control time (Tc). The lateral speed is the speed of the vehicle in the width direction.

[0015] According to this technical solution, it is possible to prevent the reference point from exceeding the avoidance position during the execution of lane departure avoidance control.

[0016] In the above technical solution, the control unit is configured to: determine that the start condition has been met before the width direction distance is consistent with the necessary distance when the holding position does not meet the specific condition (step 645: "No") (step 665: "Yes")

[0017] According to this technical solution, when the holding position does not meet specific conditions, lane departure avoidance control is initiated at a timing earlier than when the holding position meets specific conditions, thus increasing the execution time of lane departure avoidance control. Therefore, even if the steering angular velocity is smaller when the holding position does not meet specific conditions than when the holding position meets specific conditions, the likelihood of the reference point exceeding the avoidance position during the execution of lane departure avoidance control can be reduced. Furthermore, the likelihood of the lateral vehicle speed becoming zero when the reference point reaches the avoidance position can be increased.

[0018] In the above technical solution, the control unit is configured such that, when the holding position does not meet the specific condition ( Figure 6 In step 645 ("No"), the avoid position is set to a position that is a predetermined distance away in the opposite direction to the direction toward the center of the driving lane in the width direction (step 1105), such that the control time is longer than the control time when the holding position satisfies the specific condition.

[0019] According to this technical solution, when the holding position does not meet certain conditions, the execution time of lane departure avoidance control is lengthened by setting the avoidance position to a position farther away than when the holding position meets the specific conditions. Therefore, even if the magnitude of the steering angular velocity when the holding position does not meet the specific conditions is smaller than when the holding position meets the specific conditions, the possibility that the reference point exceeds the "avoidance position set to be far away" during the execution of lane departure avoidance control can be reduced. Furthermore, the possibility that the lateral vehicle speed becomes zero when the reference point reaches the avoidance position can be increased.

[0020] In one embodiment of the device of the present invention, the control unit is configured such that, if the holding position at the establishment time does not satisfy the specific condition, during an initial period from the establishment time until a predetermined time (Td) has elapsed, the magnitude of the steering angular velocity is made smaller than the magnitude of the steering angular velocity assumed to be when the holding position at the establishment time satisfies the specific condition; and after the time point from the establishment time has elapsed through the initial period, the magnitude of the steering angular velocity is increased by an amount corresponding to the amount by which the magnitude of the steering angular velocity was decreased during the initial period. Figure 13 The lateral acceleration map MapGytgt(T) is shown.

[0021] The initial period after lane departure avoidance control begins is the period with the highest probability of additional steering wheel rotation and unintended actions. According to this technical solution, when the position holding condition does not meet certain requirements, the steering wheel rotation speed based on lane departure avoidance control is smaller during the initial period compared to when the position holding condition meets certain requirements. Therefore, the probability of additional steering wheel rotation and unintended actions during the initial period can be reduced.

[0022] In one technical solution of the device of the present invention,

[0023] The control unit is configured as follows:

[0024] In the lane departure avoidance control, the drive unit is controlled so that the magnitude of the steering angular velocity remains greater than a predetermined protection value.

[0025] If the holding position does not meet the specific condition at the establishment time point (step 1205: "No"), the lane departure avoidance control is performed using a smaller protection value than if the holding position met the specific condition at the establishment time point (step 1210) (steps 1220, 1225).

[0026] When the holding position does not meet certain conditions, a smaller protection value is used than when the holding position meets the specific conditions, thus reducing the steering wheel rotation speed. This reduces the likelihood of additional steering wheel rotation and unintentional actions even when the holding position does not meet the specific conditions.

[0027] In one technical solution of the device of the present invention, the control unit is configured to determine that the holding position satisfies the specific condition (step 710: "Yes") when the driver holds the steering wheel with both hands and the position of the driver's hands holding the steering wheel is linearly symmetrical with respect to the imaginary reference line (BL) connecting the point directly above and the point directly below when the steering wheel is in the neutral position.

[0028] Compared to the case where the steering wheel position is linearly symmetrical with respect to the baseline, the likelihood of additional steering wheel rotation and unintended actions is higher when the driver holds the steering wheel with one hand, or when the driver holds the steering wheel with both hands but the position is not linearly symmetrical with respect to the baseline. In this technical solution, in such cases, it is determined that the steering wheel position does not meet specific conditions. Therefore, even when the driver is holding the steering wheel in a manner that greatly increases the likelihood of additional rotation and unintended actions, lane departure avoidance control that reduces the magnitude of the steering angular velocity can be implemented.

[0029] Furthermore, in the foregoing description, to aid in understanding the invention, the names and / or reference numerals used in the embodiments described below are enclosed in parentheses to indicate the components of the invention corresponding to those embodiments. However, the constituent elements of the invention are not limited to the embodiments specified by the names and / or reference numerals. Attached Figure Description

[0030] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

[0031] Figure 1 This is a schematic system configuration diagram of a driving assistance device according to an embodiment of the present invention.

[0032] Figure 2 This is an illustration of lane departure prevention control.

[0033] Figure 3 It is the front view of a steering wheel that is maintained to meet specific conditions.

[0034] Figure 4A This is a front view showing a steering wheel held with one hand.

[0035] Figure 4B This is a front view of the steering wheel when it starts rotating to avoid lane departure control.

[0036] Figure 4C This is a front view of the steering wheel when additional rotation has occurred.

[0037] Figure 5This is an illustration of a working example of lane departure avoidance control when specific conditions are not met.

[0038] Figure 6 It means Figure 1 The flowchart shown is the start determination routine executed by the CPU of the driving assistance ECU.

[0039] Figure 7 It means Figure 1 The flowchart shown is a specific condition determination subroutine executed by the CPU of the driving assistance ECU.

[0040] Figure 8 It means Figure 1 The flowchart shown is of the lane departure avoidance control routine executed by the CPU of the driver assistance ECU.

[0041] Figure 9 It means Figure 1 The flowchart shown is the end determination routine executed by the CPU of the driving assistance ECU.

[0042] Figure 10 This is an explanatory diagram illustrating a working example of lane departure avoidance control according to a first variation of an embodiment of the present invention.

[0043] Figure 11 This is a flowchart illustrating the start determination routine of the first modified example of an embodiment of the present invention.

[0044] Figure 12 This is a flowchart illustrating a lane departure avoidance control routine of a second variation of an embodiment of the present invention.

[0045] Figure 13 This is an explanatory diagram illustrating a working example of lane departure avoidance control according to the third variation of the embodiments of the present invention. Detailed Implementation

[0046] <Composition>

[0047] like Figure 1 As shown, the driving assistance device (hereinafter referred to as "this assistance device") 10 according to the embodiment of the present invention is mounted on a vehicle VA.

[0048] This auxiliary device 10 includes a driver assistance ECU 20 and an electric power steering ECU 30. The driver assistance ECU 20 is referred to as "DSECU 20", and the electric power steering ECU 30 is referred to as "EPSECU 30".

[0049] These ECUs are electronic control units (ECUs) with a microcomputer as their main component, interconnected via a CAN (Controller Area Network) (not shown) to send and receive information. The microcomputer includes a CPU, ROM, RAM, and interfaces (I / F). The CPU executes various functions by processing instructions (programs, routines) stored in ROM. Several or all of these ECUs can be combined into a single ECU. Furthermore, these ECUs are sometimes referred to as "controllers" or "controllers."

[0050] This auxiliary device 10 includes a camera sensor 21, an acceleration sensor 23, a steering angle sensor 24, a steering torque sensor 25, and a touch sensor 26. These are mounted on the vehicle's VA (Vehicle Automation Unit). The DSECU 20 is connected to these sensors and receives detection signals from them. Furthermore, these sensors can also be connected to an ECU other than the DSECU 20. In this case, the DSECU 20 receives the sensor's detection signal from the ECU connected to the sensor via CAN.

[0051] Camera sensor 21 acquires image data by capturing the scenery in front of vehicle VA and sends the image data to DSECU 20. DSECU 20 identifies boundary lines based on the image data. A boundary line is the line that marks the boundary between "the lane in which vehicle VA is currently traveling (hereinafter referred to as the "travel lane")" and "the area outside that travel lane." As an example of a boundary line, it has the left white line LL of the road (see reference). Figure 2 and Figure 3 . ) and the right white line LR (refer to Figure 2 and Figure 3 。).

[0052] Accelerometer 23 detects the acceleration in the longitudinal direction (hereinafter referred to as "forward acceleration") Gx of the vehicle VA and the acceleration in the width direction (hereinafter referred to as "lateral acceleration") Gy of the vehicle VA, and generates detection signals representing the forward acceleration Gx and the lateral acceleration Gy.

[0053] Steering angle sensor 24 detects steering angle θ and generates a detection signal representing steering angle θ, which is the rotation angle of the steering wheel SW of vehicle VA relative to the neutral position.

[0054] Steering torque sensor 25 is disposed on steering shaft US, which is connected to steering wheel SW. Steering torque sensor 25 detects the steering torque supplied to steering shaft US and generates a detection signal representing the steering torque.

[0055] Touch sensor 26 detects the position of the driver's hand in contact with the steering wheel SW and generates a detection signal indicating its position.

[0056] EPSECU30 is a well-known control device for electric power steering systems. EPSECU30 is connected to motor driver 32.

[0057] The motor driver 32 is connected to the steering motor 34. The steering motor 34 is sometimes referred to as a "drive unit". The steering motor 34 is assembled into a "steering mechanism including a steering wheel SW, a steering shaft US, and a steering gear mechanism (not shown)".

[0058] The steering motor 34 is an electric motor (electric actuator) that provides torque (force) to the steering shaft US using electricity supplied from the motor driver 32. This torque is used as steering assist torque (steering assist force). With this torque, the left and right steering wheels of the vehicle VA can be steered. That is, the steering motor 34 can change the steering angle (also referred to as "steering angle") of the vehicle VA.

[0059] When lane departure avoidance control described later is not being performed, the EPSECU 30 obtains the steering torque Tra detected by the steering torque sensor 15 as the steering torque input by the driver to the steering wheel SW (hereinafter also referred to as "driver torque TqDr"). The EPSECU 30 assists the driver's operation of the steering wheel SW by providing this driver torque TqDr to the steering shaft US through the steering motor 34.

[0060] Furthermore, while executing the lane departure avoidance control described later, the EPSECU30 receives a steering command from the DSECU20, including the target lateral acceleration Gytgt obtained in the lane departure avoidance control. The EPSECU30 obtains the differential lateral acceleration ΔGy by subtracting the target lateral acceleration Gytgt from the current lateral acceleration Gy, and changes the steering angle by providing a torque to the steering axis US corresponding to the differential lateral acceleration ΔGt. Through the EPSECU30, the larger the absolute value (|ΔGy|) of the differential lateral acceleration ΔGy, the larger the aforementioned torque, and the greater the rotational speed of the steering wheel SW (i.e., the change in steering angle per unit time).

[0061] The greater the inclination of the target lateral acceleration Gytgt in the lateral acceleration mapping MapGytgt(T) described later, the greater the absolute value (|ΔGy|) of the differential lateral acceleration ΔGy.

[0062] The display 40 shows warning messages and the operating status of the lane departure avoidance control during its operation. The display 40 can be a head-up display or a multi-function display. The speaker 50 emits a beeping sound during lane departure avoidance control operation.

[0063] Lane Departure Prevention Control

[0064] Reference Figure 2 The lane departure avoidance control is explained.

[0065] Every predetermined time interval, DSECU20 acquires image data from camera sensor 21 and identifies the boundary lines (e.g., left white line LL and right white line LR) of the driving lane currently being traveled by vehicle VA. DSECU20 obtains an avoidance position (avoidance line) PP by imaginarily moving the boundary line closest to vehicle VA (hereinafter referred to as the "object boundary line") by a predetermined distance Dd. Lane departure avoidance control is performed so that the reference point P of vehicle VA does not extend beyond the avoidance position PP. The reference point P is the center position between the left and right front wheels on the axles of the left and right front wheels of vehicle VA.

[0066] The DSECU20 obtains the distance between the avoidance position PP and the current reference point P (hereinafter referred to as "lateral distance Ds"). Sometimes, the lateral distance Ds is also referred to as "width direction distance". The DSECU20 obtains the lateral vehicle speed Vsy at the current time point as the vehicle speed Vs in the vehicle width direction by integrating the lateral acceleration Gy at the current time point over time.

[0067] Based on the lateral vehicle speed Vsy at the current time point, DSECU20 obtains the lateral acceleration Gy (hereinafter referred to as "necessary lateral acceleration Gyn") required for the lateral vehicle speed Vsy to become zero after a predetermined control time Tc from the current time point. Furthermore, assuming that the vehicle VA moves in the longitudinal direction while maintaining a constant longitudinal speed Vsx (which is the vehicle speed Vs in the longitudinal direction at the current time point), and moves in the width direction with the necessary lateral acceleration Gyn, DSECU20 obtains the distance that the vehicle VA moves in the width direction of the driving lane from the current time point until the control time Tc is passed, as the necessary lateral distance Dsn. In other words, the necessary lateral distance Dsn can also be expressed as the lateral distance Ds required for the lateral vehicle speed Vsy to become zero after a predetermined control time Tc from the current time point.

[0068] When the lateral distance Ds at the current time point is below the necessary lateral distance Dsn, the DSECU20 determines that the predetermined start condition has been met and begins lane departure avoidance control. Figure 2In the example shown, at time point t0, the lateral distance Ds is greater than the necessary lateral distance Dsn, therefore, the starting condition is not met. At time point t1, the lateral distance Ds becomes less than the necessary lateral distance Dsn, and the starting condition is met, thus initiating lane departure avoidance control.

[0069] In lane departure avoidance control, the DSECU20 sends a steering command, including the target lateral acceleration Gytgt, to the EPSECU30 every predetermined time elapsed.

[0070] Upon initiating lane departure avoidance control, DSECU20 generates a lateral acceleration map MapGytgt(T) that defines the relationship between elapsed time and the target lateral acceleration Gytgt from that initiation point (see reference). Figure 2 The graph shown below illustrates this. The DSECU20 obtains the target lateral acceleration Gytgt corresponding to the elapsed time by referring to the lateral acceleration map MapGytgt(T). Furthermore, the target lateral acceleration Gytgt and the lateral acceleration Gy use acceleration in the right direction of the vehicle's VA as positive values ​​and acceleration in the left direction as negative values. Figure 2 In the example shown, the vehicle speed Vsy in the right direction of the vehicle VA at the starting time point (time point t1) is made zero. Therefore, the target lateral acceleration Gytgt becomes the acceleration in the left direction, i.e., a negative value.

[0071] exist Figure 2 In the shown lateral acceleration MapGytgt(T), the target lateral acceleration Gytgt decreases during the period from time point t1 to time point t2, so that the target lateral acceleration Gytgt becomes the predetermined lateral acceleration Ga (Ga < 0) at time point t2. This time point t2 is the time point after which the control time Tc becomes half (Tc / 2). Furthermore, in Figure 2 In the lateral acceleration MapGytgt(T) shown, during the period from time point t2 to time point t3, the lateral acceleration Gy is maintained at a predetermined lateral acceleration Ga.

[0072] DSECU20 obtains the value (integral value) by integrating the target lateral acceleration Gytgt over the period from time t1 to time t3 (i.e., in...). Figure 2 The lateral acceleration Ga is calculated in the same way as the area of ​​the filled part in the curve shown in the figure, and the value obtained by multiplying the control time Tc by the necessary lateral acceleration Gyn.

[0073] At time t3, vehicle VA reaches the avoidance position PP, and the lateral speed Vsy becomes zero. In lane departure avoidance control after time t3, DSECU20 sends a steering command including a target lateral acceleration Gytgt for vehicle VA to move towards the center of the driving lane in the width direction. Furthermore, after time t3, DSECU20 terminates lane departure avoidance control when the end-side distance Des, which is the distance between the predetermined end position and the reference point P, becomes below a threshold distance Dth. The end position is obtained by imaginarily moving the boundary line (object boundary line) closest to vehicle VA towards the center of the driving lane by a predetermined end distance De.

[0074] (Job Summary)

[0075] The DSECU20 performs lane departure avoidance control in a manner that minimizes the change in the target lateral acceleration Gytgt per unit time when the holding position does not meet predetermined specific conditions, compared to the change when the holding position meets the specific conditions. The holding position is the position of the driver's hands holding the steering wheel SW. This reduces the change in the steering angle per unit time (i.e., the magnitude of the rotational speed of the steering wheel SW), thereby decreasing the likelihood of additional and unintentional steering wheel rotation by the driver during lane departure avoidance control.

[0076] Reference Figure 3 The specific conditions mentioned above will be explained.

[0077] When the driver's hands are symmetrical about the reference line BL of the steering wheel SW, the DSECU20 determines that the holding position meets a specific condition (i.e., the specific condition is met). Furthermore, the reference line BL is an imaginary line connecting the point Pu directly above and the point Pb directly below when the steering wheel SW is in the neutral position.

[0078] exist Figure 3 In the example shown, the driver holds the steering wheel SW at the so-called "9:15" position, keeping the position linearly symmetrical with respect to the baseline BL, satisfying specific conditions.

[0079] like Figure 4A As shown, the specific condition described above does not apply when the driver holds the upper part of the steering wheel (SW) with one hand. When lane departure avoidance control is executed under such conditions, as... Figure 4B As shown, the steering wheel SW is rotated. At this time, due to the centrifugal force generated by the rotation of the steering wheel SW, the hand holding the steering wheel SW may rotate additionally.

[0080] In this embodiment, when the specific conditions are not met, the change in steering angle is reduced compared to when the specific conditions are met, thus reducing the rotational speed of the steering wheel SW. This reduces the centrifugal force and lowers the likelihood of additional rotation of the steering wheel SW. Furthermore, according to this embodiment, the likelihood of the driver being surprised by the rotation of the steering wheel SW is reduced, thus reducing the possibility of the driver performing unintentional operations on the steering wheel.

[0081] (Work Example)

[0082] exist Figure 2 The document describes the typical (i.e., under the specific conditions described above) lane departure avoidance control. (See reference...) Figure 5 This section explains how to prevent lane departure when the specific conditions mentioned above are not met.

[0083] If a specific condition is not met, the DSECU20 determines that the starting condition has been met and begins lane departure avoidance control when the lateral distance Ds is below "the distance Dsn' obtained by adding the predetermined distance Dp1 to the necessary lateral distance Dsn". Figure 5 In the example shown, it is assumed that at time point t0, a specific condition is not met, and the lateral distance Ds becomes less than or equal to the distance Dsn'. Based on this assumption, at time point t0, the starting condition is met, and lane departure avoidance control begins.

[0084] At time t0, DSECU20 generates the lateral acceleration map MapGytgt(T).

[0085] The necessary acceleration Gyn' required for the vehicle speed Vsy (Vsy0) in the width direction at time point t0 to become zero after a necessary time Tn from time point t0 can be expressed using the aforementioned necessary time Tn (refer to Equation 1).

[0086] Gyn'=-Vsy0 / Tn···Equation 1

[0087] Under the assumption that the vehicle VA maintains a constant speed Vsx0 in the longitudinal direction at time t0 and moves with the necessary acceleration Gyn' in the width direction, DSECU20 calculates the time (necessary time Tn) required for the distance "the vehicle VA moves in the width direction of the driving lane" to match the distance Dsn'.

[0088] The necessary time Tn is longer than the control time Tc mentioned above.

[0089] Furthermore, DSECU20 obtains the integral value (in the case of integrating the target lateral acceleration Gytgt corresponding to the elapsed time from the start time point to the elapsed necessary time Tn) by integrating the time. Figure 5 The lateral acceleration Ga' is calculated in the same way as the product of the necessary lateral acceleration Gyn and the control time Tc, using the area of ​​the shaded region in the graph shown. Based on this lateral acceleration Ga', DSECU20 generates a lateral acceleration map MapGytgt(T) (refer to...). Figure 5 (The curve graph.)

[0090] According to Figure 5 As can be understood from the curve, the execution time (Tn) of lane departure avoidance control when the specific conditions are not met is longer than the execution time (Tc) of lane departure avoidance control when the specific conditions are met. The magnitude of the tilt angle gr of the target lateral acceleration Gytgt at time points t0 to t2 in lane departure avoidance control when the specific conditions are not met is smaller than the magnitude of the tilt angle gr at time points t1 to t2 in lane departure avoidance control when the specific conditions are met. Therefore, the magnitude of the steering wheel rotation speed (i.e., the magnitude of the steering angular velocity, which is the change in steering wheel angle per unit time) based on lane departure avoidance control when the specific conditions are not met can be smaller than the magnitude of the steering wheel rotation speed (steering angular velocity) of the steering wheel SW when the specific conditions are met.

[0091] (Specific tasks)

[0092] <Start the decision routine>

[0093] The CPU of DSECU20 (hereinafter, unless otherwise stated, "CPU" refers to the CPU of DSECU20) executes the following functions every predetermined time interval: Figure 6 The start decision routine is represented by a flowchart.

[0094] Therefore, when the scheduled time is reached, the CPU starts from... Figure 6 The process begins at step 600 and proceeds to step 605. In step 605, the CPU determines whether the value of the execution flag Xexe is "0".

[0095] The value of the execution flag Xexe is set to "1" when lane departure avoidance control begins and to "0" when lane departure avoidance control ends. Furthermore, the value of the execution flag Xexe is also set to "0" in the initial routine. The initial routine is executed by the CPU when the ignition switch (not shown) of the vehicle's VA changes from the off position to the on position.

[0096] If the value of the execution flag Xexe is “0”, the CPU determines “yes” in step 605 and executes steps 615 to 645 in sequence.

[0097] Step 615: The CPU obtains image data from the camera sensor 21 and identifies the boundary line based on the image data.

[0098] Step 620: The CPU obtains the lateral distance Ds between the reference point P and the avoidance position PP.

[0099] Step 625: Based on the detection signal from the acceleration sensor 23, the CPU determines the longitudinal acceleration Gx of the vehicle VA, integrates the longitudinal acceleration Gx over time, and thus obtains the longitudinal vehicle speed Vsx, which is the vehicle speed in the longitudinal direction of the vehicle VA. Further, based on the detection signal from the acceleration sensor 23, the CPU determines the lateral acceleration Gy of the vehicle VA, integrates the lateral acceleration Gy over time, and thus obtains the lateral vehicle speed Vsy.

[0100] Step 630: The CPU obtains the necessary lateral acceleration Gyn based on the lateral vehicle speed Vsy and the control time Tc.

[0101] Step 635: Under the assumption that the vehicle VA moves in the longitudinal direction while maintaining a constant longitudinal speed Vsx and moves in the width direction with a necessary lateral acceleration Gyn, the CPU obtains the necessary lateral distance Dsn, which is the distance that the vehicle VA moves in the width direction of the driving lane from the current time point until the control time Tc has elapsed.

[0102] Step 640: The CPU executes a specific condition-determining subroutine. In fact, when the CPU enters step 640, it executes... Figure 7 The subroutine is represented by a flowchart. In this subroutine, if the CPU holds the position and meets a specific condition, it sets the value of the specific flag Xsp to "0"; if the holding position does not meet the specific condition, it sets the value of the specific flag Xsp to "1". Furthermore, the value of the specific flag Xsp is set to "1" in the initial routine.

[0103] Step 645: The CPU determines whether the value of a specific flag Xsp is "0".

[0104] If the value of the specific flag Xsp is "0", the CPU determines "yes" in step 645 and proceeds to step 650.

[0105] In step 650, the CPU determines whether the side distance Ds is below the necessary side distance Dsn.

[0106] If the lateral distance Ds is greater than the necessary lateral distance Dsn, the CPU determines "no" in step 650, proceeds to step 695, and temporarily ends this routine.

[0107] On the other hand, if the lateral distance Ds is less than or equal to the necessary lateral distance Dsn, the CPU determines "yes" in step 650 and executes steps 655 and 660 in sequence.

[0108] Step 655: The CPU sets the value of the execution flag Xexe to "1" and the value of the execution timer Texe to "0". The execution timer Texe is a timer used to count the elapsed time since the start of the lane departure avoidance control.

[0109] Step 660: The CPU generates the lateral acceleration map MapGytgt(T).

[0110] Then, the CPU proceeds to step 695, temporarily ending this routine.

[0111] On the other hand, when the CPU enters step 645 and the value of the specific flag Xsp is "1", the CPU determines "no" in step 645 and enters step 665.

[0112] In step 665, the CPU determines whether the side distance Ds is below the distance Dsn'.

[0113] If the lateral distance Ds is greater than the distance Dsn', the CPU determines "no" in step 665, proceeds to step 695, and temporarily ends this routine.

[0114] On the other hand, if the lateral distance Ds is less than or equal to the distance Dsn', the CPU determines "yes" in step 665 and proceeds to step 670. In step 670, the CPU obtains the necessary acceleration Gyn' and the necessary time Tn. Then, the CPU proceeds to step 655, generates the lateral acceleration map MapGytgt(T), proceeds to step 695, and temporarily ends this routine.

[0115] When the CPU enters step 605, if the value of the execution flag Xexe is "1", the CPU determines "no" in step 605, enters step 695, and temporarily ends this routine.

[0116] <Specific Condition Decision Subroutine>

[0117] When the CPU enters Figure 6 In step 640 as shown, from Figure 7 The process begins at step 700, followed by steps 705 and 710.

[0118] Step 705: The CPU determines the position (holding position) of the driver's hands holding the steering wheel SW based on the detection signal from the touch sensor 26.

[0119] Step 710: The CPU determines whether the holding position meets specific conditions.

[0120] If the position meets specific conditions, the CPU determines "yes" in step 710 and proceeds to step 715. In step 715, the CPU sets the value of the specific flag Xsp to "0". Then, the CPU proceeds to step 795, temporarily ending this routine and entering... Figure 6 Step 645 is shown.

[0121] On the other hand, if the position does not meet a specific condition, the CPU determines "No" in step 710 and proceeds to step 720. In step 720, the CPU sets the value of the specific flag Xsp to "1". Then, the CPU proceeds to step 795, temporarily ending this routine and entering... Figure 6 Step 645 is shown.

[0122] <Lane Departure Prevention Control Routine>

[0123] The CPU executes the program at predetermined intervals. Figure 8 The flowchart illustrates the lane departure avoidance control routine.

[0124] Therefore, when the scheduled time is reached, the CPU starts from... Figure 8 The process begins at step 800 and proceeds to step 805. In step 805, the CPU determines whether the value of the execution flag Xexe is "1".

[0125] If the value of the execution flag Xexe is "0", the CPU determines "No" in step 805, proceeds to step 895, and temporarily ends this routine.

[0126] On the other hand, if the value of the execution flag Xexe is "1", the CPU determines "yes" in step 805 and executes steps 810 and 815 in sequence.

[0127] Step 810: The CPU increments the execution timer Texe by "1".

[0128] Step 815: The CPU determines whether the value of the specific flag Xsp is "0".

[0129] If the value of the specific flag Xsp is "0", the CPU determines "yes" in step 815 and proceeds to step 820. In step 820, the CPU determines whether the value of the execution timer Texe is below the first time threshold T1th.

[0130] The first time threshold T1th is set such that when the execution timer Texe becomes the first time threshold T1th, the elapsed time from the start time of the lane departure avoidance control becomes the value of the control time Tc.

[0131] If the value of the execution timer Texe is below the first time threshold T1th, the CPU determines "yes" in step 820 and executes steps 825 and 830 in sequence.

[0132] Step 825: The CPU obtains the target lateral acceleration Gytgt by applying the value of the execution timer Texe to the lateral acceleration map MapGytgt(T).

[0133] Step 830: The CPU determines whether the absolute value (|ΔGy|) of the differential lateral acceleration ΔGy is below the predetermined protection value grd. The differential lateral acceleration ΔGy is obtained by subtracting the target lateral acceleration Gytgt from the lateral acceleration Gy at the current time point.

[0134] If the absolute value (|ΔGy|) is below the protection value grd, the CPU determines "yes" in step 830 and proceeds to step 835. In step 835, the CPU sends a steering command including the target lateral acceleration Gytgt to the EPSECU30. Then, the CPU proceeds to step 895, temporarily ending this routine.

[0135] On the other hand, if the absolute value (|ΔGy|) is greater than the protection value grd, the CPU determines "No" in step 830 and proceeds to step 840. In step 840, the CPU sets the target lateral acceleration Gytgt so that the absolute value (|ΔGy|) becomes less than or equal to the protection value grd.

[0136] When the differential lateral acceleration ΔGy is positive, the CPU will set the value obtained by subtracting the protection value grd from the lateral acceleration Gy as the target lateral acceleration Gytgt.

[0137] When the differential lateral acceleration ΔGy is negative, the CPU sets the value obtained by adding the lateral acceleration Gy and the protection value grd as the target lateral acceleration Gytgt.

[0138] Then, in step 835, the CPU sends a steering command to the EPSECU30, proceeds to step 895, and temporarily ends this routine.

[0139] When the CPU enters step 820, if the value of the execution timer Texe is greater than the first time threshold T1th, the CPU determines "no" in step 820 and executes steps 845 and 850 in sequence.

[0140] Step 845: The CPU identifies the boundary line based on the image data from the camera sensor 21.

[0141] Step 850: The CPU determines the driving lane based on the boundary line and obtains the target lateral acceleration Gytgt for driving the vehicle VA towards the center of the driving lane in the width direction.

[0142] Then, the CPU proceeds to step 830.

[0143] If the CPU enters step 815 and the value of the specific flag Xsp is "1", the CPU determines "No" in step 815 and proceeds to step 855. In step 855, the CPU determines whether the value of the execution timer Texe is below the second time threshold T2th.

[0144] The second time threshold T2th is set such that when the execution timer Texe becomes the second time threshold T2th, the elapsed time from the start time of lane departure avoidance control becomes the value of the necessary time Tn.

[0145] If the value of the execution timer Texe is below the second time threshold T2th, the CPU determines "yes" in step 855, proceeds to step 825, and obtains the target lateral acceleration Gytgt corresponding to the value of the execution timer Texe. Then, the CPU proceeds to step 830.

[0146] On the other hand, if the value of the execution timer Texe is greater than the second time threshold T2th, the CPU determines "no" in step 855 and proceeds to step 845.

[0147] <End of decision routine>

[0148] The CPU executes the program at predetermined intervals. Figure 9 The termination determination routine is represented by a flowchart.

[0149] Therefore, when the scheduled time is reached, the CPU starts from... Figure 9 The process begins at step 900 and proceeds to step 905. In step 905, the CPU determines whether the value of the execution flag Xexe is "1".

[0150] If the value of the execution flag Xexe is "0", the CPU determines "No" in step 905, proceeds to step 995, and temporarily ends this routine.

[0151] On the other hand, if the value of the execution flag Xexe is "1", the CPU determines "yes" in step 905 and proceeds to step 910. In step 910, the CPU determines whether the value of the specific flag Xsp is "0".

[0152] If the value of the specific flag Xsp is "0", the CPU determines "yes" in step 910 and proceeds to step 915. In step 915, the CPU determines whether the value of the execution timer Texe is greater than the first time threshold T1th.

[0153] If the value of the execution timer Texe is below the first time threshold T1th, the CPU determines "No" in step 915, proceeds to step 995, and temporarily ends this routine.

[0154] On the other hand, if the value of the execution timer Texe is greater than the first time threshold T1th, the CPU determines "yes" in step 915 and executes steps 920 to 930 in sequence.

[0155] Step 920: The CPU identifies the boundary lines based on image data from camera sensor 21.

[0156] Step 925: The CPU determines the end-side distance Des based on the boundary line.

[0157] Step 930: The CPU determines whether the end-side distance Des is below the threshold distance Dth.

[0158] If the distance Des at the end is greater than the threshold distance Dth, the CPU determines "No" in step 930, proceeds to step 995, and temporarily ends this routine.

[0159] On the other hand, if the distance Des at the end is less than the threshold distance Dth, the CPU determines "yes" in step 930 and executes steps 935 and 940 in sequence.

[0160] Step 935: The CPU sets the values ​​of the execution flag Xexe and the execution timer Texe to "0".

[0161] Step 940: The CPU deletes the lateral acceleration map MapGytgt(T).

[0162] Then, the CPU proceeds to step 995, temporarily ending this routine.

[0163] When specific conditions are not met, this auxiliary device 10 increases the execution time of lane departure avoidance control by starting it at a timing earlier than when the specific conditions are met. This results in a smaller change (tilt angle) in the target lateral acceleration Gytgt per unit time when the specific conditions are not met compared to the change (tilt angle) when the specific conditions are met. Consequently, the magnitude of the steering wheel SW rotation speed (steering angular velocity) when the specific conditions are not met is smaller than the magnitude of the steering wheel SW rotation speed (steering angular velocity) when the specific conditions are met. Therefore, the possibility of additional steering wheel SW rotation is reduced, as is the possibility of unintentional steering wheel manipulation by the driver.

[0164] This invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of this invention.

[0165] (First variation)

[0166] Reference Figure 10 A summary of this variation is provided.

[0167] DSECU20 initiates lane departure avoidance control when the lateral distance Ds becomes the necessary lateral distance Dsn (refer to time point t1). If the specific conditions are not met in this case, DSECU20 obtains a new avoidance position PP' by imaginarily moving the avoidance position PP a predetermined distance Dp2 in the direction opposite to the direction toward the center of the driving lane (the direction below the paper).

[0168] The DSECU20 calculates the necessary time Tn in the same manner as described in the above embodiment's working example. This necessary time Tn is longer than the control time Tc. Next, the DSECU20 calculates the lateral acceleration Ga' in the same manner as described in the above embodiment's working example, and generates a lateral acceleration map MapGytgt(T) based on this lateral acceleration Ga' (see...). Figure 10 (The curve graph.)

[0169] In addition, Figure 10 In the lateral acceleration mapping MapGytgt(T) shown, during the period from the start time point t1 until the predetermined time (Tn-Tc / 2) has elapsed, the target acceleration Gytgt decreases to the lateral acceleration Ga'. During the period from the time point after the predetermined time (Tn-Tc / 2) has elapsed until time point t4, the target acceleration Gytgt is maintained at the lateral acceleration Ga'.

[0170] In lane departure avoidance control under specific conditions, at time point t4 after a necessary time Tn has elapsed from the start time point t1, the reference point P of vehicle VA reaches the avoidance position PP', and the lateral vehicle speed Vsy becomes zero.

[0171] According to this variation, when the specific condition is not met, by using the avoidance position PP' instead of the avoidance position PP, the execution time (necessary time Tn) of the lane departure avoidance control becomes longer than the execution time when the specific condition is met. Therefore, the magnitude of the steering wheel rotation speed (steering angular velocity) based on lane departure avoidance control when the specific condition is not met can be smaller than the magnitude of the steering wheel rotation speed (steering angular velocity) of the steering wheel SW when the specific condition is met.

[0172] In this variant, the CPU of DSECU20 executes [the command] every predetermined time elapsed. Figure 11 The start decision routine shown is used instead Figure 6 The start-determining routine shown executes every time a predetermined time has elapsed. Figures 7-9 The example shown. In Figure 11 In the middle, to conduct with Figure 6 The steps shown are the same as the steps in the process of assigning to the same processing steps. Figure 6 The same labels used in the text are omitted from the description.

[0173] When the CPU reaches its scheduled time, from Figure 11 The process begins at step 1100, as shown. Figure 11 Step 605 is shown. With the execution flag Xexe set to "0", the CPU... Figure 11 If the condition in step 605 is "yes", then execute the following steps sequentially. Figure 11 Steps 615 to 635 as shown indicate the entry point. Figure 11 Step 650 is shown. When the lateral distance Ds is larger than the necessary lateral distance Dsn, the CPU... Figure 11 If step 650 is determined to be "No", proceed to step 1195 and temporarily end this routine. When the lateral distance Ds is less than the necessary lateral distance Dsn, the CPU... Figure 11 If the condition in step 650 is "yes", then execute the following steps sequentially. Figure 11 Steps 640 and 645 are shown.

[0174] When the value of the specific flag Xsp is "0", the CPU... Figure 11 If the condition in step 645 is "yes", then execute the following steps sequentially. Figure 11 Steps 655 and 660 shown lead to step 1195, temporarily ending this routine.

[0175] When the value of the specific flag Xsp is "1", the CPU in Figure 11 If step 645 is determined to be "No", proceed to step 1105. In step 1105, the CPU obtains the avoidance position PP' and proceeds to... Figure 11 As shown in step 670, the necessary time Tn is obtained. Then, the CPU executes sequentially. Figure 11 Steps 655 and 660 shown lead to step 1195, temporarily ending this routine.

[0176] (Second variation)

[0177] In this modified example, the DSECU20 uses a second protection value, grd2, which is smaller than the first protection value grd1 used in lane departure avoidance control when the specific condition is not met, at the start time of lane departure avoidance control. Therefore, in lane departure avoidance control when the specific condition is not met, the absolute value of the differential lateral acceleration ΔGy (|ΔGy|) remains larger than the second protection value grd2. Thus, it is possible to make the magnitude of the steering wheel rotation speed (steering angular velocity) in lane departure avoidance control when the specific condition is not met smaller than the magnitude of the steering wheel rotation speed (steering angular velocity) in lane departure avoidance control when the specific condition is met.

[0178] In this variant, the CPU of DSECU20 executes "from" every predetermined time interval. Figure 11 The start determination routine shown has removed the start determination routines for steps 645, 1105, and 670.

[0179] Furthermore, the CPU executes every predetermined time interval. Figure 12 The lane departure avoidance control routine shown is shown. Figure 12 In the middle, to conduct with Figure 8 The steps shown are the same as the steps of the process given in Figure 8 The same labels used in the text are omitted from the description.

[0180] In addition, the CPU executes every predetermined time interval. Figure 7 and Figure 9 The example shown.

[0181] When the CPU reaches its scheduled time, from Figure 12 The process begins at step 1200, as shown. Figure 12 Step 805 is shown. With the execution flag Xexe set to "0", the CPU... Figure 12 If the result in step 805 is "No", proceed to step 1295 and temporarily end this routine.

[0182] With the execution flag Xexe set to "1", the CPU... Figure 12 In step 805 shown, if the determination is "yes", then execute. Figure 12 Steps 810 and 815 are shown. When the value of the specific flag Xsp is "0", the CPU... Figure 12 If the condition in step 815 is "yes", proceed to... Figure 12 Step 820 is shown.

[0183] When the value of the execution timer Texe is below the first time threshold T1th, the CPU... Figure 12 If the determination in step 820 is "yes", then execute. Figure 12 Step 825 is shown, proceed to step 1205.

[0184] In step 1205, the CPU determines whether the value of a specific flag Xsp is "0".

[0185] If the value of the specific flag Xsp is "0", the CPU determines "yes" in step 1205 and proceeds to step 1210. In step 1210, the CPU determines whether the absolute value (|ΔGy|) of the differential lateral acceleration ΔGy is below the predetermined first protection value grd1.

[0186] If the absolute value (|ΔGy|) is below the first protection value grd1, the CPU determines "yes" in step 1210 and proceeds to... Figure 12 As shown in step 835, a redirection command is sent. Then, the CPU proceeds to step 1295, temporarily ending this routine.

[0187] On the other hand, if the absolute value (|ΔGy|) is greater than the first protection value grd1, the CPU determines "No" in step 1210 and proceeds to step 1215. In step 1215, the CPU sets the target lateral acceleration Gytgt so that the aforementioned absolute value (|ΔGy|) becomes less than or equal to the first protection value grd1, and proceeds to... Figure 12 Step 835 is shown. Furthermore, the details of setting the target lateral acceleration Gytgt are as follows: Figure 8 Step 840 shown is the same, therefore, the explanation is omitted.

[0188] If the value of the specific flag Xsp is "1" when the CPU enters step 1205, the CPU determines "No" in step 1205 and proceeds to step 1220. In step 1220, the CPU determines whether the absolute value (|ΔGy|) is below the predetermined second protection value grd2. Furthermore, the second protection value grd2 is preset to be a value smaller than the first protection value grd1.

[0189] If the absolute value (|ΔGy|) is below the second protection value grd2, the CPU determines "yes" in step 1220 and proceeds to... Figure 12 Step 835 is shown. On the other hand, if the absolute value (|ΔGy|) is greater than the second protection value grd2, the CPU determines "No" in step 1220 and proceeds to step 1225. In step 1225, the CPU sets the target lateral acceleration Gytgt so that the absolute value (|ΔGy|) becomes less than or equal to the second protection value grd2, and proceeds to... Figure 12 Step 835 is shown.

[0190] As can be understood from the above, in lane departure avoidance control when specific conditions are not met, a second protection value, grd2, which is smaller than the first protection value, grd1, is used. This prevents the magnitude of the steering wheel rotation speed (steering angular velocity) from becoming greater than the value corresponding to the second protection value, grd2. Therefore, it is possible to ensure that the magnitude of the steering wheel rotation speed (steering angular velocity) in lane departure avoidance control when specific conditions are not met is smaller than the magnitude of the steering wheel rotation speed (steering angular velocity) in lane departure avoidance control when specific conditions are met.

[0191] (3rd variation)

[0192] Reference Figure 13 The third variation will be explained.

[0193] In this variation, the DSECU20, when the specific condition for lane departure avoidance control at the start time (time point t1) is not met, during the initial period from the start time until the predetermined time Td (<Tc / 2), causes the tilt angle of the target lateral acceleration Gytgt to be greater than that assumed to be "when the specific condition is met at the start time (time point t1)". Figure 13 The magnitude of the tilt of the target lateral acceleration Gytgt, represented by the dashed line, is small. Therefore, during the initial period, it is possible to make the magnitude of the steering wheel rotation speed (steering angular velocity) for lane departure avoidance control when the specific conditions are not met smaller than that when the specific conditions are met.

[0194] DSECU20 is used to obtain the integral value obtained by integrating the target lateral acceleration Gytgt over the control time Tc when the specific conditions are not met. Figure 13The predetermined lateral acceleration Ga' after time point t2 is calculated in the same way as the area of ​​the filled part in the curve shown, which is the integral value obtained by integrating the target lateral acceleration Gytgt under the assumption that specific conditions are met over the control time Tc. During the initial period, the magnitude of the lateral acceleration Ga' increases accordingly, corresponding to the amount by which the tilt of the target lateral acceleration Gytgt is reduced. The magnitude of the lateral acceleration Ga' naturally becomes larger than the lateral acceleration Ga under the assumption that specific conditions are met.

[0195] When lane departure avoidance control begins, the steering wheel SW starts to rotate. Therefore, the likelihood of the aforementioned additional rotation and unintentional operation occurring immediately after lane departure avoidance control has begun is high. According to this variation, the magnitude of the tilt angle of the target lateral acceleration Gytgt during the initial period when the specific condition is not met is smaller than the magnitude of the tilt angle of the target lateral acceleration Gytgt when the specific condition is assumed to be met. Therefore, it is possible to make the magnitude of the rotational speed of the steering wheel SW during the initial period when the specific condition is not met smaller than the magnitude of the rotational speed of the steering wheel SW when the specific condition is met.

[0196] As described above, the lateral acceleration Ga' is determined in such a way that the integral value under the condition that the specific condition is not met is consistent with the integral value under the condition that the specific condition is met. Therefore, at time point t3, after a control time Tc has elapsed from the start time point (time point t1), the lateral vehicle speed Vsy is indeed zero.

[0197] (4th variation)

[0198] In the above embodiment, the holding position of the driver's steering wheel SW is detected by the touch sensor 26, but the detection of the holding position is not limited to this. For example, if the vehicle VA is equipped with a driver's seat camera that captures images of the driver's seat, the DSECU 20 can also detect the holding position based on the images captured by the driver's seat camera.

[0199] (5th variation)

[0200] This auxiliary device 10 can be applied not only to the aforementioned engine vehicles, but also to hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), fuel cell electric vehicles (FCEV), and battery electric vehicles (BEV).

Claims

1. A driving assistance device, comprising: A drive unit configured to change the steering angle, which is the angle of the steering wheels of the vehicle, by providing torque to a steering shaft connected to a steering wheel of the vehicle; and The control unit is configured to perform lane departure avoidance control when predetermined starting conditions are met. This lane departure avoidance control is the control of the drive unit to change the steering angle to prevent the vehicle from deviating from its driving lane. The control unit is configured to perform lane departure avoidance control in such a manner that the magnitude of the steering angular velocity is smaller when the holding position does not meet a predetermined specific condition at the time of the initial condition than when the holding position meets the specific condition at the time of the initial condition, where the holding position refers to the position of the driver's hands holding the steering wheel, and the steering angular velocity is the change in the steering angle per unit time. The control unit is configured to determine that the holding position satisfies the specific condition when the driver holds the steering wheel with both hands and the position of the driver's hands holding the steering wheel is linearly symmetrical with respect to an imaginary reference line connecting the point directly above and the point directly below when the steering wheel is in a neutral position.

2. The driving assistance device according to claim 1, The control unit is configured to extend the execution time of the lane departure avoidance control by advancing the timing of the start condition when the holding position does not meet the specific condition, compared to when the holding position meets the specific condition.

3. The driving assistance device according to claim 1, The control unit is configured to determine that the start condition is met when the distance in the width direction of the driving lane from a predetermined reference point of the vehicle to an avoidance position set in the width direction of the driving lane is consistent with a necessary distance. The necessary distance is the distance required to make the lateral speed zero after a predetermined control time has elapsed. The lateral speed is the speed of the vehicle in the width direction.

4. The driving assistance device according to claim 3, The control unit is configured to determine that the start condition is met before the distance in the width direction is consistent with the necessary distance, if the holding position does not meet the specific condition.

5. The driving assistance device according to claim 3, The control unit is configured such that, if the holding position does not meet the specific condition, the avoidance position is set to a position that has moved a predetermined distance away in a direction opposite to the direction toward the center of the driving lane in the width direction, such that the control time is longer than the control time if the holding position meets the specific condition.

6. The driving assistance device according to claim 1, The control unit is configured such that, if the holding position does not meet the specific condition at the establishment time point, during the initial period from the establishment time point until a predetermined time has elapsed, the magnitude of the steering angular velocity is smaller than the magnitude of the steering angular velocity assumed to be when the holding position meets the specific condition at the establishment time point; and after the time point from the establishment time point has elapsed through the initial period, the magnitude of the steering angular velocity is increased by an amount equivalent to the amount by which the magnitude of the steering angular velocity was decreased during the initial period.

7. The driving assistance device according to claim 1, The control unit is configured as follows: In the lane departure avoidance control, the drive unit is controlled so that the magnitude of the steering angular velocity does not exceed a predetermined protection value. If the holding position does not meet the specific condition at the established time point, the lane departure avoidance control is performed using a smaller protection value than if the holding position met the specific condition at the established time point.

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