JP7572289B2 - Lane Keeping Assist Control Device - Google Patents

Description

The present invention relates to a lane keeping assist control device for vehicles such as automobiles.

There is known a lane keeping assist control device for a vehicle such as an automobile that is configured to cancel lane keeping assist control and execute lane change assist control when an operation requesting lane change assist control is performed. It is also known that when a lane change is completed through lane change assist control, the lane change assist control is terminated and lane keeping assist control is resumed.

A lane keeping assist control device configured as described above is described, for example, in the following Patent Document 1. According to this type of lane keeping assist control device, a lane is changed with the assistance of lane change assist control, and when the lane change is completed, the lane keeping assist control can be resumed.

JP 2018-203120 A

[Problem to be solved by the invention]
In the conventional lane keeping assist control device described above, the lane keeping assist control does not resume until the lane change using the lane change assist control is completed, which can cause the driver to feel uneasy due to the delayed resumption of the lane keeping assist control.

In particular, if lane change assist control is not performed, lane keeping assist control may be released when the driver starts to change lanes by steering, and resumed when the lane change is completed. In this type of lane keeping assist control device, if the resumption of lane keeping assist control is delayed, the amount of lateral movement of the vehicle after the lane change may become excessive, resulting in so-called wide-headed driving, which may make the driver feel uneasy.

The main objective of the present invention is to provide an improved lane keeping assist control device that reduces the risk of the vehicle running swerving when a lane change is performed by the driver's steering operation without lane change assist control being performed, compared to conventional devices.
[Means for solving the problems and effects of the invention]

According to the present invention, there is provided a lane keeping assist control device (100) that performs lane keeping assist control (LTA) to assist steering operations so that a vehicle (110) is maintained within a predetermined lateral range within the lane in which the vehicle is currently traveling, and that is configured to cancel the lane keeping assist control when the driver starts to change lanes through steering operations, and to resume the lane keeping assist control when the driver finishes changing lanes through steering operations.

When it is determined (S40) that the vehicle has crossed the boundary between the lane from which the lane is to be changed and the lane to which the lane is to be changed, and it is determined (S50) that the driver intends to change lanes, the lane keeping assist control device (100) is configured to resume lane keeping assist control earlier (S70) when the lane change ends than when it is determined that the driver does not intend to change lanes.

According to the above configuration, when it is determined that the driver intends to change lanes at the time when it is determined that the vehicle has crossed the lane boundary, lane keeping assist control can be resumed sooner when the lane change is completed than when it is determined that the driver does not intend to change lanes.

Therefore, by indicating that the driver intends to change lanes, lane keeping assist control can be resumed sooner when the lane change is completed, thereby reducing the risk of the vehicle moving too far laterally after the lane change, causing the vehicle to run wide, and the resulting anxiety felt by the driver.

The determination of whether the driver intends to change lanes may be made by determining whether the turn signal is activated. Also, even if the turn signal is not activated at the time when it is determined that the vehicle has crossed the lane boundary, if the time from when the turn signal is deactivated to when it is determined that the vehicle has crossed the lane boundary is less than a preset reference time, it may be determined that the driver intends to change lanes.

In the above description, in order to aid in understanding the present invention, the reference numerals used in the embodiments described below are enclosed in parentheses with respect to the configuration of the invention corresponding to the embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the reference numerals enclosed in parentheses. Other objects, other features, and associated advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the drawings.

1 is a schematic configuration diagram showing an embodiment of a lane keeping assist control device according to the present invention; FIG. 2 is a plan view of the vehicle showing the mounting positions of the surrounding sensors and the camera sensor. FIG. 2 is a diagram for explaining lane-related vehicle information. 4 is a flowchart showing a routine of lane keeping assist control in the embodiment. FIG. 13 is a diagram showing a case where a vehicle changes lanes without activating a turn signal. FIG. 13 is a diagram showing a case where a vehicle changes lanes by activating a turn signal. FIG. 13 is a diagram showing a case where a vehicle changes lanes by briefly activating a turn signal. FIG. 13 is a diagram showing a case where a vehicle changes lanes with a turn signal activated for a very short period of time.

The following describes in detail a lane keeping assist control device (hereinafter also referred to as the present embodiment device) according to an embodiment of the present invention with reference to the drawings. The present embodiment device 100 is applied to a vehicle 110 (hereinafter sometimes referred to as the "own vehicle" to distinguish it from other vehicles), and as shown in FIG. 1, includes a driving assist ECU 10, an electric power steering ECU 20, a meter ECU 30, a steering ECU 40, an engine ECU 50, a brake ECU 60, and a navigation ECU 70.

These ECUs are electric control units that include a microcomputer as a main component, and are connected to each other via a controller area network (CAN) 105 so that they can transmit and receive information. In this specification, the microcomputer includes a CPU, ROM, RAM, non-volatile memory, and an interface. The CPU is configured to realize various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into a single ECU.

Connected to the CAN 105 are multiple types of vehicle state sensors 80 that detect the state of the vehicle 110, and multiple types of driving operation state sensors 90 that detect the driving operation state. The vehicle state sensors 80 include a vehicle speed sensor that detects the vehicle speed V of the vehicle, a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle, a lateral acceleration sensor that detects the lateral acceleration of the vehicle, and a yaw rate sensor that detects the yaw rate of the vehicle.

The driving operation state sensor 90 includes an accelerator operation amount sensor that detects the amount of operation of the accelerator pedal, a brake operation amount sensor that detects the amount of operation of the brake pedal, a brake switch that detects whether the brake pedal is operated or not, a steering angle sensor that detects the steering angle, a steering torque sensor that detects the steering torque, and a shift position sensor that detects the shift position of the transmission.

Information detected by the vehicle condition sensor 80 and the driving operation condition sensor 90 (called sensor information) is transmitted to CAN 105. Each ECU can use the sensor information transmitted to CAN 105 as appropriate. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted from that specific ECU to CAN 105.

The driving assistance ECU 10 is a central control device that provides driving assistance to the driver, and executes lane tracing assist control (LTA). Note that the driving assistance ECU 10 does not perform lane changing assist control, but may also perform other driving assistance, such as adaptive cruise control (ACC).

As shown in FIG. 2, the driving assistance ECU 10 is connected to a central front surroundings sensor 11FC, a right front surroundings sensor 11FR, a left front surroundings sensor 11FL, a right rear surroundings sensor 11RR, and a left rear surroundings sensor 11RL. Each surroundings sensor 11FC, 11FR, 11FL, 11RR, and 11RL is a radar sensor, and basically has the same configuration, except that its detection area is different. Hereinafter, when there is no need to distinguish between each of the surroundings sensors 11FC, 11FR, 11FL, 11RR, and 11RL, they will be referred to as surroundings sensors 11.

The surrounding sensor 11 includes a radar transmitter and receiver and a signal processor (not shown). The radar transmitter and receiver emits millimeter wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by three-dimensional objects (e.g., other vehicles, pedestrians, bicycles, buildings, etc.) within the emission range. The signal processor acquires information (hereinafter referred to as surrounding information) indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object relative to the vehicle, etc., based on the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from transmitting the millimeter wave to receiving the reflected wave, and supplies the information to the driving assistance ECU 10 at predetermined intervals. This surrounding information makes it possible to detect the longitudinal and lateral components of the distance between the vehicle and the three-dimensional object, and the longitudinal and lateral components of the relative speed between the vehicle and the three-dimensional object.

As shown in FIG. 2, the central front surroundings sensor 11FC is provided in the front center of the vehicle 110 and detects three-dimensional objects present in the area in front of the vehicle. The right front surroundings sensor 11FR is provided in the right front corner of the vehicle 110 and mainly detects three-dimensional objects present in the right front area of the vehicle, and the left front surroundings sensor 11FL is provided in the left front corner of the vehicle 110 and mainly detects three-dimensional objects present in the left front area of the vehicle. The right rear surroundings sensor 11RR is provided in the right rear corner of the vehicle 110 and mainly detects three-dimensional objects present in the right rear area of the vehicle, and the left rear surroundings sensor 11RL is provided in the left rear corner of the vehicle body and mainly detects three-dimensional objects present in the left rear area of the vehicle.

The driving assistance ECU 10 is also connected to a camera sensor 12. The camera sensor 12 includes a camera unit and a lane recognition unit that recognizes white lines on the road by analyzing image data captured by the camera unit. The camera sensor 12 (camera unit) captures images of the scenery ahead of the vehicle. The camera sensor 12 (lane recognition unit) repeatedly supplies information about the recognized white lines to the driving assistance ECU 10 every time a predetermined calculation period has elapsed.

The camera sensor 12 recognizes the lane, which represents an area divided by white lines, and is capable of detecting the relative position of the host vehicle with respect to the lane, based on the positional relationship between the white lines and the host vehicle. Here, the position of the host vehicle refers to the position of the center of gravity of the host vehicle, but may also be the center position of the host vehicle in a plan view. The lateral position of the host vehicle, which will be described later, refers to the position of the host vehicle's center of gravity in the lane width direction, the lateral speed of the host vehicle refers to the speed of the host vehicle's center of gravity in the lane width direction, and the lateral acceleration of the host vehicle refers to the acceleration of the host vehicle's center of gravity in the lane width direction. These are determined from the relative positional relationship between the white lines and the host vehicle detected by the camera sensor 12.

As shown in FIG. 3, the camera sensor 12 determines a lane center line (target driving line) CL that is the center position in the width direction of the left and right white lines WL in the lane in which the vehicle 110 is traveling. This lane center line CL is used as the target driving line in the LTA described below. The camera sensor 12 also calculates the curvature Cu of the curve of the lane center line CL. Note that, although the target driving line is the lane center line CL in this embodiment, it may be a line offset in the lane width direction by a predetermined distance from the lane center line CL.

The camera sensor 12 also calculates the position and orientation of the vehicle 110 in the lane defined by the left and right white lines WL. For example, as shown in FIG. 3, the camera sensor 12 calculates the distance Dy [m] in the lane width direction between the center of gravity P of the vehicle 110 and the lane center line CL, that is, the distance Dy that the vehicle 110 is shifted in the lane width direction from the lane center line CL. This distance Dy is called the lateral deviation Dy. The camera sensor 12 also calculates the angle θy [rad] between the direction of the lane center line CL and the front-rear direction of the vehicle 110. This angle θy is called the yaw angle θy. When the lane is curved, the lane center line CL is also curved, so the yaw angle θy represents the angle by which the direction in which the vehicle 110 is facing is shifted based on the curved lane center line CL.

Hereinafter, the information (Cu, Dy, θy) representing the curvature Cu, lateral deviation Dy, and yaw angle θy will be referred to as lane-related vehicle information. Note that for the lateral deviation Dy and yaw angle θy, the left/right direction with respect to the lane center line CL is specified by the sign (positive/negative). For the curvature Cu, the direction of the curve (right or left) is specified by the sign (positive/negative).

In addition, the camera sensor 12 also supplies information about white lines, such as the type of white line detected (solid line, dashed line), the distance between adjacent white lines (lane width), and the shape of the white lines, to the driving assistance ECU 10 every predetermined calculation period, including not only the lane of the vehicle but also adjacent lanes. If the white line is solid, the vehicle is prohibited from crossing the white line to change lanes. On the other hand, if the white line is dashed (a white line formed intermittently at a regular interval), the vehicle is permitted to cross the white line to change lanes. Such lane-related vehicle information (Cu, Dy, θy) and information about white lines are collectively referred to as lane information.

In this embodiment, the camera sensor 12 calculates the lane-related vehicle information (Cu, Dy, θy), but instead, the driving assistance ECU 10 may analyze the image data output by the camera sensor 12 to obtain the lane information.

As shown in FIG. 1, a buzzer 13 is connected to the driving assistance ECU 10. The buzzer 13 sounds when it receives a buzzer sounding signal from the driving assistance ECU 10. The driving assistance ECU 10 sounds the buzzer 13 when it needs to notify the driver of the driving assistance situation, when it needs to warn the driver (call his/her attention), etc.

In addition to or in place of the buzzer 13, a vibrator may be provided to transmit a vibration to the driver to warn (call attention). For example, the vibrator may be provided on the steering wheel (not shown) and warn the driver by vibrating the steering wheel.

The driving assistance ECU 10 performs LTA based on surrounding information provided by the surrounding sensor 11, lane information obtained based on white line recognition by the camera sensor 12, the vehicle state detected by the vehicle state sensor 80, and the driving operation state detected by the driving operation state sensor 90.

A setting operation device 14 that is operated by the driver is connected to the driving assistance ECU 10. The setting operation device 14 is an operation device for setting whether or not to perform LTA. The driving assistance ECU 10 inputs a setting signal from the setting operation device 14 to determine whether or not to perform LTA.

The electric power steering ECU 20 is a control device for an electric power steering device. Hereinafter, the electric power steering ECU 20 is referred to as the EPS-ECU (Electric Power Steering ECU) 20. The EPS-ECU 20 is connected to a drive circuit 21. The drive circuit 21 is connected to a steering motor 22. The steering motor 22 is incorporated in a steering mechanism (not shown) of the vehicle 110. The EPS-ECU 20 detects the steering torque input by the driver through the steering wheel using a steering torque sensor provided on the steering shaft of the steering mechanism, and controls the current supply to the drive circuit 21 based on the steering torque and vehicle speed to drive the steering motor 22. When the steering motor 22 is driven, the steering angle of the steered wheels (not shown) of the vehicle 110 is changed (the steered wheels are steered). A steering torque is applied to the steering mechanism by driving the motor 22, assisting the driver's steering operation.

Furthermore, when the EPS ECU 20 receives a steering command from the driving assistance ECU 10 via the CAN 105, it drives the steering motor 22 with a control amount specified by the steering command to generate a steering torque. This steering torque is different from the steering assist torque that is applied to make the driver's steering operation (steering wheel operation) lighter as described above, and represents a torque that is applied to the steering mechanism by a steering command from the driving assistance ECU 10 without the need for steering operation by the driver. This torque changes the steering angle of the steered wheels of the vehicle (the steered wheels are turned).

In addition, even if the EPS ECU 20 receives a steering command from the driving assistance ECU 10, if the EPS ECU 20 detects steering torque due to the driver's steering wheel operation and the steering torque is greater than a threshold value, the EPS ECU 20 prioritizes the driver's steering wheel operation and generates a steering assist torque that makes the operation lighter.

The meter ECU 30 is connected to a display 31 and left and right turn signals 32 (which means turn signal lamps, sometimes called turn lamps). The display 31 is, for example, a multi-information display provided in front of the driver's seat, and displays various information in addition to displaying the measurement values of meters such as the vehicle speed meter. For example, when the meter ECU 30 receives a display command corresponding to the driving assistance state from the driving assistance ECU 10, it causes the display 31 to display a screen specified by the display command. Note that a head-up display (not shown) may be used as the display 31 instead of or in addition to the multi-information display.

The meter ECU 30 also includes a turn signal drive circuit (not shown), and when it receives a turn signal blink command via the CAN 105, it blinks the turn signal 32 in the direction (right, left) specified by the turn signal blink command. While the meter ECU 30 is blinking the turn signal 32, it transmits turn signal blink information indicating that the turn signal 32 is in a blinking state to the CAN 105. Therefore, other ECUs can know the blinking state of the turn signal 32.

The steering ECU 40 is connected to the turn signal lever 41. The turn signal lever 41 is an operating device for activating (flashing) the turn signal 32, and is provided on a steering column (not shown). The turn signal lever 41 is provided so as to be swingable around a support shaft for both the left-handed operating direction and the right-handed operating direction.

The turn signal lever 41 is equipped with a switch (not shown) that is turned on (generates an on signal) when the switch is in a preset stroke position. The steering ECU 40 detects the operation state of the turn signal lever 41 based on the presence or absence of an on signal from the switch. When the turn signal lever 41 is tilted to the stroke position, the steering ECU 40 transmits a turn signal blinking command including information indicating the operation direction (left or right) to the meter ECU 30.

As shown in FIG. 1, the engine ECU 50 is connected to an engine actuator 51. The engine actuator 51 is an actuator for changing the operating state of the internal combustion engine 52. The engine ECU 50 drives the engine actuator 51 to change the torque generated by the internal combustion engine 52, thereby controlling the driving force of the vehicle and changing the acceleration state (acceleration).

The brake ECU 60 is connected to a brake actuator 61. The brake actuator 61 adjusts the hydraulic pressure supplied to the wheel cylinder built into the brake caliper 62b in response to instructions from the brake ECU 60, and uses the hydraulic pressure to press a brake pad (not shown) against the brake disc 62a to generate a frictional braking force. Therefore, by controlling the brake actuator 61, the brake ECU 60 can control the braking force of the host vehicle 110 and change the deceleration state (deceleration).

The navigation ECU 70 includes a GPS receiver 71 that receives GPS signals to detect the current position of the vehicle, a map database 72 that stores map information, and a touch panel (touch panel display) 73. The navigation ECU 70 identifies the current position of the vehicle 110 based on the GPS signals, and performs various calculations based on the vehicle's position and the map information stored in the map database 72, and provides route guidance using the touch panel 73.

The map information stored in the map database 72 includes road information. The road information includes parameters that indicate the position and shape of the road (e.g., the radius or curvature of the road, the lane width of the road, the number of lanes, the position of the center line of each lane, etc.). The road information also includes road type information that can distinguish whether a road is a motorway or not.

<LTA (Lane Keeping Assist Control)>
LTA is a control that assists the driver's steering operation (lane keeping operation) by applying a steering torque to the steering mechanism to automatically steer the steered wheels so that the position of the vehicle is maintained near a target driving line in the "lane in which the vehicle is traveling". LTA itself is well known, and for details, please refer to, for example, Japanese Patent Application Laid-Open No. 2008-195402, Japanese Patent Application Laid-Open No. 2009-190464, Japanese Patent Application Laid-Open No. 2010-6279, and the specification of Japanese Patent No. 4349210. Therefore, LTA will be briefly described below.

In this embodiment, when a preset LTA start condition is satisfied, the driving assist ECU 10 calculates the target steering angle δltat of the steered wheels every time a predetermined calculation period elapses, based on the above-mentioned lane-related vehicle information (Cu, Dy, θy) in accordance with the following formula (1): In formula (1), K1, K2, K3, K4, and Kr are control gains, each of which is a constant.
δltat=K1・Cu+Kr・(K2・θy+K3・Dy+K4・ΣDy) (1)

In the above formula (1), the first term on the right side is a feedforward control term that changes according to the shape of the target driving line. In addition, in the above formula (1), the second term on the right side is a feedback control term that functions to reduce the various deviations (θy, Dy, and ΣDy) of the host vehicle 110 from the target driving line to zero. In particular, the term K4·ΣDy is an integral control term that functions to eliminate the steady lateral deviation Dy.

The driving assistance ECU 10 also outputs a command signal representing the target steering angle δltat to the EPS ECU 20. The EPS ECU 20 controls the steering motor 22 so that the steering angle δ of the steered wheels follows the target steering angle δltat. If the driving assistance ECU 10 is in a situation where there is a risk that the vehicle 110 will deviate from its lane, it issues a lane departure warning by, for example, sounding the buzzer 13.

<LTA Control Routine>
Next, a control routine for the LTA in this embodiment will be described. When an ignition switch (not shown) is turned on and the LTA switch is turned on, the CPU of the driving assistance ECU 10 executes a control routine corresponding to the flowchart shown in FIG.

In step S10, the CPU of the driving assistance ECU 10 determines whether or not the flag Flc is 1, i.e., whether or not the vehicle 110 is changing lanes. When the CPU determines that the flag Flc is 1, the control proceeds to step 40. In contrast, when the CPU determines that the flag Flc is 0, the control proceeds to step 20. The CPU initializes the flag Flc to 0 when control starts.

In step S20, the CPU determines whether the vehicle 110 has started to change lanes due to the driver's steering operation (without receiving assistance from the lane change assist control). If the CPU determines that the vehicle 110 has not started to change lanes, the CPU advances control to step 90. In contrast, if the CPU determines that the vehicle 110 has started to change lanes, the CPU advances control to step 30.

The determination of whether the vehicle 110 has started to change lanes may be performed in any manner known in the art. For example, it may be determined that the vehicle 110 has started to change lanes when the steering angle θs is equal to or greater than a reference value θso and the steering torque Ts is equal to or greater than a reference value Tso. The reference values θso and Tso may be constants, but are preferably variably set according to the vehicle speed V so that they become smaller as the vehicle speed V increases.

In step S30, the CPU cancels the LTA and sets flag Flc to 1. As described above, flag Flc being 1 means that vehicle 110 is changing lanes.

In step S40, the CPU determines whether the vehicle 110 has crossed the boundary between the lane from which the lane change is to be made and the lane to which the lane change is to be made. If the CPU determines that the vehicle 110 has not crossed the lane boundary, the CPU advances control to step 60. In contrast, if the CPU determines that the vehicle 110 has crossed the lane boundary, the CPU advances control to step 50.

In step S50, the CPU determines whether the turn signal 32 is on or whether it is within Δt time since the turn signal 32 was deactivated, i.e., whether the driver intends to change lanes. If the CPU makes a positive determination, it advances control to step 70. In contrast, if the CPU makes a negative determination, it advances control to step 60. Note that Δt may be a constant, but it is preferable that it be variably set according to the vehicle speed V so that it is smaller as the vehicle speed V increases.

In step S60, the CPU sets the reference value Dyo for LTA restart determination to the standard value Dyon, and in step S70, sets the reference value Dyo for LTA restart determination to a relaxed standard value Dyog that is greater than the standard value Dyon. Note that the standard value Dyon and the relaxed standard value Dyog may each be constants, but it is preferable that they are variably set according to the angle θy between the direction of the lane center line CL of the lane to be changed to and the longitudinal direction of the vehicle 110 so that the angle θy becomes smaller as the angle θy becomes larger. Furthermore, the standard value Dyon and the relaxed standard value Dyog may be variably set according to the width of the lane to be changed to so that the angle becomes larger as the width of the lane to be changed to is larger.

In step S80, the CPU determines whether the LTA restart condition is met by determining whether the distance Dy in the lane width direction between the center of gravity P of the vehicle 110 and the lane center line CL of the lane to which the lane is to be changed is equal to or less than a reference value Dyo. If the CPU determines that the LTA restart condition is not met, the CPU temporarily ends the control. In contrast, if the CPU determines that the LTA restart condition is met, the CPU advances the control to step 90.

In step S90, the CPU executes LTA. That is, the CPU calculates the target steering angle δltat of the steered wheels according to the above formula (1) and outputs a command signal representing the target steering angle δltat to the EPS-ECU 20. The EPS-ECU 20 drives and controls the steering motor 22 so that the steering angle δ of the steered wheels follows the target steering angle δltat, and automatically steers the steered wheels.

In step S100, the CPU determines whether the vehicle 110 is traveling along the lane in the lane to which the lane is to be changed. If the CPU makes a negative determination, the control is temporarily terminated. In contrast, if the CPU makes a positive determination, the CPU resets the flag Flc to 0 in step S110. Note that if the flag Flc is 0, the control may be temporarily terminated without executing steps S100 and S110.

The determination of whether the vehicle is traveling in and along the lane of the lane to which the lane is to be changed may be made by determining whether the distance Dy in the lane width direction between the center of gravity P of the vehicle and the center line CL of the lane to which the lane is to be changed is equal to or less than the control reference value Dyc (a constant smaller than Dyon). As can be seen from the above explanation, there is a relationship of Dyog>Dyon>Dyc among the reference values Dyon, Dyog, and Dyc.

According to this embodiment, when it is determined that the vehicle 110 has started to change lanes as a result of the driver performing a steering operation for lane change (step S20), the LTA is released (step S30). When it is determined that the vehicle 110 has crossed the boundary of the lane and the turn signal 32 is in operation or within Δt time since it was released, that is, when it is determined that the driver intends to change lanes (steps S40, 50), the reference value Dyo for determining whether to resume LTA is set to the reference value Dyog (step S70).

The reference value Dyog is a relaxed value that is greater than the standard value Dyon. Therefore, compared to when the reference value Dyog is set to the standard value Dyon (step S60), it is determined earlier that the distance Dy in the lane width direction between the center of gravity P of the vehicle 110 and the center line CL of the lane to which the lane is to be changed is equal to or less than the reference value Dyo (step S80). Therefore, LTA can be resumed earlier (step S90).

<Operation of the embodiment>
Next, the operation of the embodiment will be described with reference to FIGS. 5 to 8 for the following cases C1 to C4 in which the vehicle 110 changes lanes due to a steering operation by the driver while the LTA is being performed.

<C1. Changing lanes without turning on the turn signal (Figure 5)>
Assume that at time t2, the vehicle 110 starts to change lanes, and at time t3, it is determined that the vehicle 110 has crossed the boundary of the lanes. Furthermore, at time t5, it is determined that the condition for resuming LTA is satisfied, and the LTA is resumed, and at time t6, the vehicle 110 is traveling in and along the lane after the lane change.

At time t3, the determination in step S40 is positive, but a negative determination is made in step S50, so the reference value Dyog is set to the standard value Dyon in step S60. Therefore, until the distance Dy in the lane width direction between the center of gravity P of the vehicle 110 and the center line CL of the lane to which the lane is to be changed becomes equal to or less than Dyon (time t5), a negative determination is made in step S80 and LTA is not resumed (step S90). Therefore, as shown by the phantom line trajectory in FIG. 5, there is a risk that the lateral movement of the vehicle 110 will be excessive (the vehicle will run with a bulging edge).

<C2. When changing lanes with the turn signal activated (Figure 6)>
Assume that at time t1, the turn signal 32 is activated, at time t2, the vehicle 110 starts changing lanes, and at time t3, the vehicle 110 crosses the boundary of a lane while the turn signal is activated. Furthermore, at time t4, the turn signal 32 is deactivated, at time t5', the condition for resuming LTA is satisfied and LTA is resumed, and at time t6', the vehicle 110 is traveling in and along the lane after the lane change. Note that time t4 is later than time t3, and times t5' and t6' are earlier than times t5 and t6, respectively.

In this case, immediately after time t3, the determination in step S50 becomes positive, and the reference value Dyog is set to the relaxed reference value Dyog in step S70. Therefore, at time t5', which is earlier than time t5, the determination in step S80 becomes positive, and LTA is resumed (step S90). Therefore, the action of LTA can effectively prevent the vehicle 110 from traveling with a bulging lateral direction.

<C3. When changing lanes by briefly activating the turn signal (Fig. 7)>
Assume that the operation of the turn signal 32 is started at time t1, the vehicle 110 starts changing lanes at time t2, the vehicle 110 crosses the boundary of the lane at time t3, and the operation of the turn signal is deactivated at time t4' which is earlier than time t3. If the elapsed time from time t4' to time t3 is equal to or less than Δt, a positive determination is made in step S50, and the condition for resuming LTA is satisfied at time t5', and LTA is resumed.

Therefore, as in the case of C2 above, immediately after time t3, the judgment in step S50 becomes positive, and the reference value Dyog is set to the relaxed reference value Dyog in step S70, so that LTA is resumed at time t5', which is earlier than time t5. Therefore, the action of LTA can effectively prevent the vehicle 110 from traveling with a lateral bulge. In addition, at time t6', which is earlier than time t6, the vehicle 110 travels in and along the lane to which it is about to change lanes.

<C4. When changing lanes by activating the turn signal for a very short time (Fig. 8)>
Assume that at time t1, operation of the turn signal 32 is started, at time t2, the vehicle 110 starts changing lanes, at time t3, the vehicle 110 crosses the lane boundary, and at time t4'', which is earlier than time t4', the turn signal is deactivated. The turn signal is not activated after time t4'', the elapsed time from time t4'' to time t3 is greater than Δt, and a negative determination is made in step S50.

As a result, as in the case of C1 above, the reference value Dyog is set to the standard value Dyon in step S60, and a negative determination is made in step S80 until the distance Dy becomes equal to or less than Dyon (time t5). Even if the driver mistakenly activates the turn signal without wishing to change lanes and the vehicle crosses lanes, LTA is not resumed early, so that the vehicle is controlled by LTA to run along the lane to which it is about to change lanes, i.e., it is possible to prevent the vehicle from being forced to change lanes.

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

For example, in the above embodiment, in step S50, it is determined whether the turn signal 32 is in operation or whether it has been within Δt time since the turn signal 32 was deactivated. However, step S50 may be modified to determine whether the turn signal 32 is in operation or has been activated. According to this modified example, if the turn signal 32 is activated even for a short time, the determination in step S50 is a positive determination, so that the reference value Dyo for determining whether to resume LTA can be set to a relaxed reference value Dyog that is greater than the standard value Dyon, and LTA can be resumed early.

In the above embodiment, when it is determined in step S20 that the vehicle 110 has started to change lanes, the flag Flc is set to 1 in step S30. When the flag Flc is 1, a positive determination is made in step S10, and step S40 is executed. However, when a positive determination is made in step S10, a determination is made as to whether the lane change has been cancelled, and when a positive determination is made, the control is temporarily terminated, and when a negative determination is made, step S40 is executed.

Furthermore, in the above embodiment, the control gain Kr in equation (1) for calculating the target steering angle δltat of the steered wheels is a constant. However, the control gain Kr may be modified so as to be gradually increased each time the calculation of the target steering angle δltat is repeated in step S90. In that case, the control amount of the second term on the right side of the above equation (1), i.e., the feedback control term, can be gradually increased. Therefore, the control effect of the LTA can be gradually increased while avoiding excessive steering control of the steered wheels when the LTA is resumed.

Furthermore, in the above embodiment, in step S40, it is determined whether the vehicle 110 has crossed the boundary between the lane from which the lane change is to be made and the lane to which the lane change is to be made. However, the determination in step S40 may be replaced with a determination of whether the vehicle 110 has crossed the boundary between the lane from which the lane change is to be made and the lane to which the lane change is to be made when the yaw angle θy is equal to or greater than a preset reference value θyo.

10: driving assistance ECU, 11: surrounding sensor, 12: camera sensor, 22: steering motor, 32: turn signal, 80: vehicle state sensor, 90: driving operation state sensor, 100: lane keeping assistance control device, 110: vehicle

Claims (1)

A lane keeping assist control device that performs lane keeping assist control to assist steering operation so that a vehicle is kept within a predetermined lateral range in a lane in which the vehicle is currently traveling, the lane keeping assist control being released when a lane change caused by a driver's steering operation is started, and the lane keeping assist control being resumed when the lane change caused by the driver's steering operation is completed,
The lane keeping assist control device is configured to, when it is determined that the driver has an intention to change lanes at the time when it is determined that the vehicle has crossed the boundary between the lane from which the lane is to be changed and the lane to which the lane is to be changed, make the timing of resuming the lane keeping assist control earlier when the lane change is completed, compared to when it is determined that the driver has no intention to change lanes.

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