JP2018203099A - Steering assist device - Google Patents

Abstract

To improve safety and convenience.SOLUTION: When there is detected an approaching vehicle having a probability of abnormally approaching an own vehicle if LCA is continued, a driving assist ECU terminates the LCA and executes yaw angle return control for quickly returning the yaw angle of the own vehicle to zero (S42-S44). Next, the driving assist ECU 10 determines whether or not a lane change is about to be completed (S45). When the lane change is not about to be completed, the driving assist ECU 10 executes steering control so as to return the own vehicle to an original lane (S46). When the lane change is about to be completed, the driving assist ECU 10 executes steering control so that the lateral speed of the own vehicle is maintained at zero (S47).SELECTED DRAWING: Figure 7

Description

  The present invention relates to a steering assist device that assists a steering operation for changing lanes.

  2. Description of the Related Art Conventionally, a steering assist device that performs control (referred to as lane change assist control) for assisting a steering operation so as to change a lane from an original lane in which the host vehicle is currently traveling toward an adjacent lane is known. For example, the vehicle control system proposed in Patent Literature 1 monitors the surroundings of the host vehicle, determines whether there are other vehicles that interfere with the lane change support control, and there are other vehicles that interfere. In such a situation, the lane change support control is not started.

Japanese Patent Laid-Open No. 2006-126360

  However, even if the lane change support control is permitted and started under the periphery monitoring, there may be a case in which another vehicle abnormally approaches the host vehicle thereafter. For example, as shown in FIG. 17, a case where another vehicle C2 suddenly approaches the host vehicle C1 at an unexpected relative speed from the rear of an adjacent lane to be a lane change destination (referred to as a target lane), or further adjacent to the target lane. The other vehicle C3 enters the target lane from the lane (the lane that is two lanes away from the original lane), and the vehicle C1 abnormally approaches. In the system proposed in Patent Document 1, it is not assumed that another vehicle approaches abnormally after the lane change assist control is started, and it is impossible to cope with such a case.

  For example, when it is detected that another vehicle has suddenly approached the host vehicle from the rear side during lane change support control, the lane change support control is stopped and the host vehicle entering the target lane is returned to the original lane. If steering assistance is performed so as to return, abnormal approach to the approaching vehicle can be avoided. However, if the vehicle is returned to the original lane just before the lane change is completed, the driver's original intention is not satisfied, and the driver feels bothered and inconvenient. Therefore, it is not convenient.

  The present invention has been made to solve the above-described problems, and an object thereof is to improve safety and convenience.

In order to achieve the above object, the feature of the steering assist device of the present invention is:
Perimeter monitoring means (11) for monitoring the periphery of the own vehicle;
Lane recognition means (12) for recognizing a lane and acquiring lane information including a relative positional relationship of the host vehicle with respect to the lane;
When no other vehicle that interferes with the vehicle's lane change has been detected by the surrounding monitoring means, the lane change support request is used to determine from the original lane on which the vehicle is currently traveling according to the lane information. A lane change support control means (10, 20) for starting lane change support control for controlling steering so as to change the lane toward a target lane adjacent to the original lane,
A lane that stops the lane change support control when an approaching vehicle that may abnormally approach the host vehicle when the lane change support control is continued is detected by the periphery monitoring unit during the lane change support control. Change support stop means (S17, S19, S30, S40);
Informing means (S42) for notifying the driver of the midway stop of the lane change support control;
When the approaching vehicle is detected and the lane change assist control is stopped while the host vehicle is traveling in the target lane, the steering is performed so that the host vehicle is returned from the target lane to the original lane. Original lane return support control means (S46, S48) for executing the original lane return support control to be controlled;
When the approaching vehicle is detected, progress status determining means (S45) for determining whether or not the lane change by the lane change support control is about to be completed;
When the progress status determining means determines that the lane change is about to be completed, the original lane returning support control by the original lane returning support control means is prohibited, and the speed in the lane width direction of the host vehicle And a lateral velocity zero control means (S47, S48) for performing lateral velocity zero control for controlling the steering so that the lateral velocity is maintained at zero.

  In the present invention, the periphery monitoring means monitors the periphery of the host vehicle. For example, the periphery monitoring unit monitors other vehicles around the own vehicle and determines whether there is another vehicle that may abnormally approach the own vehicle. The lane recognition means recognizes the lane and acquires lane information including the relative positional relationship of the host vehicle with respect to the lane. The lane is an area partitioned by a white line, for example. Therefore, by recognizing the lane, the relative positional relationship of the host vehicle with respect to the lane can be acquired.

  The lane change support control means is configured to cause the host vehicle to currently travel based on the lane information in accordance with the lane change support request when no other vehicle that interferes with the lane change is detected by the surrounding monitoring means. The lane change support control for controlling the steering so as to change the lane from the original lane toward the target lane adjacent to the original lane is started. As a result, the host vehicle changes the lane toward the target lane without requiring the driver to operate the steering wheel.

  Even if the lane change support control is permitted and started under the periphery monitoring, there may be a case where another vehicle abnormally approaches the host vehicle thereafter. Therefore, the steering assist device includes lane change support stop means, notification means, and original lane return support control means.

  The lane change support stop means performs the lane change support control when an approaching vehicle that may abnormally approach the host vehicle is detected by the surrounding monitoring means during the lane change support control. Stop. At this time, the notification means informs the driver that the lane change assist control is stopped halfway. The original lane return support control means returns the own vehicle from the target lane to the original lane when an approaching vehicle is detected and the lane change support control is stopped in a situation where the host vehicle is entering and driving the target lane. The original lane return assist control is performed to control the steering. Thereby, it is possible to support collision avoidance between the host vehicle and the approaching vehicle (support to reduce the possibility of collision).

  However, in that case, the original driver's intention to change lanes is not satisfied. In particular, when the original lane return assist control is performed at a timing when the lane change is completed a little later, the driver feels bothered and inconvenient.

  Therefore, the steering assist device includes a progress status determination unit and a zero lateral speed control unit. When the approaching vehicle is detected, the progress status determination unit determines whether or not the lane change by the lane change support control is about to be completed. The lateral speed zero control means prohibits the original lane return support control by the original lane return support control means when the progress determination means determines that the lane change is about to be completed, and The lateral speed zero control is performed to control the steering so that the lateral speed as the speed is maintained at zero. Accordingly, the host vehicle travels along the formation direction of the target lane. As a result, the host vehicle can be prevented from moving toward the center in the width direction of the target lane, and collision avoidance with an approaching vehicle can be assisted.

  At this time, since the driver recognizes that the lane change support control has been stopped halfway by the notification means, the driver can move the host vehicle to an appropriate position by operating the steering wheel. Since the steering assist device assists the driver's steering operation, a steering force for control is generated so that the driver's steering operation is given priority. Therefore, the driver can move the host vehicle to an appropriate position by operating the steering wheel even during the zero lateral speed control.

  Therefore, according to the present invention, the time until the steering wheel operation is handed over to the driver in a safe state can be secured by the zero lateral speed control. As a result, it is possible to improve the safety and convenience when another vehicle abnormally approaches the host vehicle after the lane change assist control is started.

In the present invention, preferably, the following configuration is further provided.
For example, the steering assist device
The angle formed by the lane formation direction and the direction in which the host vehicle is facing when the approaching vehicle is detected and the lane change assist control is stopped while the host vehicle is traveling in the target lane. A collision avoidance assist control means for performing a collision avoidance assist control for controlling steering so that the yaw angle is reduced at an emergency speed faster than the speed at which the yaw angle changes by the original lane return assist control,
The former lane return assistance control means is configured to implement former lane return assistance control after the collision avoidance assistance control is implemented,
The zero lateral speed control means may be configured to perform zero lateral speed control after the collision avoidance assistance control is performed.

  In this case, the lateral speed zero control means sets the target position in the lane width direction of the host vehicle that performs the zero lateral speed control to the position in the lane width direction of the host vehicle when the approaching vehicle is detected. It is good to be configured as follows.

For example, the steering assist device
When the approaching vehicle is detected and the lane change support control is stopped while the host vehicle is traveling in the original lane, the host vehicle is returned to the center position in the lane width direction of the original lane. It is preferable to provide central return support control means for performing central return support control for controlling steering.

  In the above description, in order to assist the understanding of the invention, the reference numerals used in the embodiments are attached to the constituent elements of the invention corresponding to the embodiments in parentheses. It is not limited to the embodiment defined by.

1 is a schematic configuration diagram of a steering assist device according to an embodiment of the present invention. It is a top view showing the attachment position of a periphery sensor and a camera sensor. It is a figure for demonstrating lane related vehicle information. It is a figure for demonstrating the action | operation of a blinker lever. It is a flowchart showing a steering assistance control routine. It is a flowchart showing a LCA cancellation control routine. It is a flowchart showing a LCA approach warning control routine. It is a figure showing the LTA screen and LCA screen of a display. It is a figure showing a target track. It is a figure showing a target trajectory function. This shows the LCA cancel screen of the display. Represents a graph of target curvature. Represents the LCA approach warning screen on the display. It is a figure showing a target trajectory and a center return target trajectory. It is a figure showing a target track and a former lane return target track. It is a figure showing a target trajectory and a lateral velocity zero target trajectory. It is a figure showing the approach condition of the own vehicle and another vehicle.

  Hereinafter, a steering assist device according to an embodiment of the present invention will be described with reference to the drawings.

  The steering assist device according to the embodiment of the present invention is applied to a vehicle (hereinafter, sometimes referred to as “own vehicle” in order to be distinguished from other vehicles), and as shown in FIG. A driving assistance 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 are provided.

  These ECUs are electric control units (Electric Control Units) each including a microcomputer as a main part, and are connected to each other via a CAN (Controller Area Network) 100 so that information can be transmitted and received. In this specification, the microcomputer includes a CPU, a ROM, a RAM, a nonvolatile memory, an interface I / F, and the like. The CPU implements various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into one ECU.

  Connected to the CAN 100 are a plurality of types of vehicle state sensors 80 that detect a vehicle state, and a plurality of types of driving operation state sensors 90 that detect a driving operation state. The vehicle state sensor 80 is a vehicle speed sensor that detects the traveling speed of the vehicle, a front-rear G sensor that detects the longitudinal acceleration of the vehicle, a lateral G sensor that detects the lateral acceleration of the vehicle, and a yaw rate of the vehicle. Such as a yaw rate sensor.

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

  Information (referred to as sensor information) detected by the vehicle state sensor 80 and the driving operation state sensor 90 is transmitted to the CAN 100. In each ECU, the sensor information transmitted to the CAN 100 can be used as appropriate. The sensor information is information on a sensor connected to a specific ECU, and may be transmitted from the specific ECU to the CAN 100. For example, the accelerator operation amount sensor may be connected to the engine ECU 50. In this case, sensor information representing the accelerator operation amount is transmitted from the engine ECU 50 to the CAN 100. For example, the steering angle sensor may be connected to the steering ECU 40. In this case, sensor information representing the steering angle is transmitted from the steering ECU 40 to the CAN 100. The same applies to other sensors. Further, a configuration in which sensor information is exchanged by direct communication between specific ECUs without interposing the CAN 100 may be employed.

  The driving assistance ECU 10 is a central control device that performs driving assistance of the driver, and performs lane change assistance control, lane keeping assistance control, and following inter-vehicle distance control. As shown in FIG. 2, the driving support ECU 10 is connected to a center front peripheral sensor 11FC, a right front peripheral sensor 11FR, a left front peripheral sensor 11FL, a right rear peripheral sensor 11RR, and a left rear peripheral sensor 11RL. Each of the peripheral sensors 11FC, 11FR, 11FL, 11RR, and 11RL is a radar sensor, and basically has the same configuration as each other only in the detection area. Hereinafter, when it is not necessary to distinguish each of the peripheral sensors 11FC, 11FR, 11FL, 11RR, and 11RL, they are referred to as a peripheral sensor 11.

  The peripheral sensor 11 includes a radar transmission / reception unit and a signal processing unit (not shown). The radar transmission / reception unit radiates a millimeter wave band radio wave (hereinafter referred to as “millimeter wave”), and a radiation range. A millimeter wave (i.e., a reflected wave) reflected by a three-dimensional object (e.g., another vehicle, a pedestrian, a bicycle, or a building) existing inside is received. 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 when the millimeter wave is transmitted until the reflected wave is received, the signal processing unit Information (hereinafter referred to as peripheral information) representing the distance between the vehicle, the relative speed between the host vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the host vehicle, and the like. To supply. Based on this peripheral information, it is possible to detect the front-rear direction component and the lateral component in the distance between the host vehicle and the three-dimensional object, and the front-rear direction component and the lateral component in the relative speed between the host vehicle and the three-dimensional object.

  As shown in FIG. 2, the center front peripheral sensor 11FC is provided at the front center portion of the vehicle body and detects a three-dimensional object existing in the front area of the host vehicle. The right front peripheral sensor 11FR is provided at the right front corner portion of the vehicle body and detects a three-dimensional object mainly present in the right front region of the host vehicle. The left front peripheral sensor 11FL is provided at the left front corner portion of the vehicle body. 3D objects existing in the left front area of the host vehicle are detected. The right rear periphery sensor 11RR is provided at the right rear corner portion of the vehicle body and detects a three-dimensional object mainly present in the right rear region of the host vehicle. The left rear periphery sensor 11RL is provided at the left rear corner portion of the vehicle body. , Detect three-dimensional objects that exist mainly in the left rear area of the vehicle.

  In the present embodiment, the peripheral sensor 11 is a radar sensor, but other sensors such as a clearance sonar and a rider sensor may be employed instead.

  A camera sensor 12 is connected to the driving assistance ECU 10. The camera sensor 12 includes a camera unit and a lane recognizing unit that recognizes a white line on the road by analyzing image data obtained by photographing with the camera unit. The camera sensor 12 (camera unit) captures a landscape in front of the host vehicle. The camera sensor 12 (lane recognition unit) repeatedly supplies information related to the recognized white line to the driving support ECU 10 at a predetermined calculation cycle.

  The camera sensor 12 recognizes a lane representing an area partitioned by white lines, and can detect the relative positional relationship of the host vehicle with respect to the lane based on the positional relationship between the white line and the host vehicle. Here, the position of the host vehicle is the position of the center of gravity of the host vehicle. Further, the lateral position of the host vehicle, which will be described later, represents the position of the center of gravity of the host vehicle in the lane width direction, and the lateral speed of the host vehicle represents the speed of the center of gravity of the host vehicle in the lane width direction. The lateral acceleration represents the acceleration in the lane width direction of the center of gravity position of the host vehicle. These are calculated | required by the relative positional relationship of the white line detected by the camera sensor 12, and the own vehicle. In the present embodiment, the position of the host vehicle is the center of gravity position. However, the position is not necessarily limited to the center of gravity position, and a predetermined specific position (for example, a center position in plan view) may be adopted. it can.

  As shown in FIG. 3, the camera sensor 12 determines a lane center 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 host vehicle is traveling. This lane center line CL is used as a target travel line in lane keeping support control described later. The camera sensor 12 calculates the curvature Cu of the curve of the lane center line CL.

  In addition, the camera sensor 12 calculates the position and orientation of the host vehicle in a lane partitioned by the left and right white lines WL. For example, as shown in FIG. 3, the camera sensor 12 determines that the distance Dy (m) in the lane width direction between the center of gravity P of the host vehicle C and the lane center line CL, that is, the host vehicle C is in the lane center line CL. The distance Dy shifted in the lane width direction is calculated. This distance Dy is called lateral deviation Dy. In addition, the camera sensor 12 is configured such that the angle between the direction of the lane center line CL and the direction of the host vehicle C, that is, the direction of the host vehicle C with respect to the direction of the lane center line CL is horizontal. The deviation angle θy (rad) is calculated. This angle θy is called the yaw angle θy. When the lane is curved, since the lane center line CL is also curved, the yaw angle θy is an angle that is deviated from the direction in which the host vehicle C is facing with respect to the curved lane center line CL. Represents. Hereinafter, information (Cu, Dy, θy) representing the curvature Cu, the lateral deviation Dy, and the yaw angle θy is referred to as lane-related vehicle information. For the lateral deviation Dy and the yaw angle θy, the left-right direction with respect to the lane center line CL is specified by a sign (positive or negative). As for the curvature Cu, the direction (right or left) in which the curve bends is specified by the sign (positive or negative).

  In addition, the camera sensor 12 includes not only the lane of the host vehicle but also the adjacent lanes, the type of detected white line (solid line, broken line), the distance between the left and right white lines (lane width), the shape of the white line, etc. Information regarding the white line is also supplied to the driving support ECU 10 at a predetermined calculation cycle. When the white line is a solid line, the vehicle is prohibited from changing lanes across the white line. On the other hand, when the white line is a broken line (a white line formed intermittently at regular intervals), the vehicle is permitted to change lanes across the white line. Such lane-related vehicle information (Cu, Dy, θy) and information on the white line are collectively referred to as lane information.

  In the present embodiment, the camera sensor 12 calculates lane-related vehicle information (Cu, Dy, θy), but instead, the driving assistance ECU 10 analyzes the image data output from the camera sensor 12, Lane information may be acquired.

  Further, since the camera sensor 12 can also detect a three-dimensional object existing in front of the host vehicle based on the image data, the camera sensor 12 may acquire the surrounding information in front of the vehicle in addition to the lane information. In this case, for example, the peripheral information acquired by the center front peripheral sensor 11FC, the right front peripheral sensor 11FR, and the left front peripheral sensor 11FL and the peripheral information acquired by the camera sensor 12 are combined to detect the detection accuracy. A synthesis processing unit (not shown) that generates high front peripheral information may be provided, and the peripheral information generated by the synthesis processing unit may be supplied to the driving support ECU 10 as the front peripheral information of the host vehicle.

  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 sound signal from the driving support ECU 10. The driving assistance ECU 10 sounds the buzzer 13 when notifying the driver of the driving assistance status and when urging the driver to pay attention.

  The buzzer 13 is connected to the driving support ECU 10 in this embodiment, but is connected to another ECU, for example, a notification ECU (not shown) provided exclusively for notification, and is sounded by the notification ECU. It may be configured as follows. In this case, the driving assistance ECU 10 transmits a buzzer sounding command to the notification ECU.

  Further, instead of or in addition to the buzzer 13, a vibrator that transmits vibrations for alerting the driver may be provided. For example, the vibrator is provided on the steering handle, and alerts the driver by vibrating the steering handle.

  The driving assistance ECU 10 detects the surrounding information supplied from the surrounding sensor 11, the lane information obtained based on the white line recognition of the camera sensor 12, the vehicle state detected by the vehicle state sensor 80, and the driving operation state sensor 90. The lane change assist control, the lane keeping assist control, and the following inter-vehicle distance control are performed based on the driving operation state and the like.

  A setting controller 14 operated by a driver is connected to the driving support ECU 10. The setting operation device 14 is an operation device for setting whether or not to implement each of the lane change support control, the lane keeping support control, and the following inter-vehicle distance control. The driving assistance ECU 10 inputs a setting signal of the setting operation device 14 and determines whether or not each control is performed. In this case, when the execution of the following inter-vehicle distance control is not selected, the lane change assist control and the lane keeping assist control are automatically set so as not to be performed. Further, when the execution of the lane keeping support control is not selected, the lane change support control is automatically set so as not to be executed.

  The setting operator 14 also has a function of inputting a parameter or the like representing the driver's preference when performing the above control.

  The electric power steering ECU 20 is a control device for the electric power steering device. Hereinafter, the electric power steering ECU 20 is referred to as an EPS • ECU (Electric Power Steering ECU) 20. The EPS / ECU 20 is connected to a motor driver 21. The motor driver 21 is connected to the steering motor 22. The steering motor 22 is incorporated in a “steering mechanism including a steering handle, a steering shaft coupled to the steering handle, a steering gear mechanism, and the like” of a vehicle (not shown). The EPS / ECU 20 detects a steering torque input by a driver to a steering handle (not shown) by a steering torque sensor provided on the steering shaft, and controls energization of the motor driver 21 based on the steering torque. The steering motor 22 is driven. By driving the assist motor, a steering torque is applied to the steering mechanism to assist the driver's steering operation.

  When the EPS / ECU 20 receives a steering command from the driving support ECU 10 via the CAN 100, the EPS / ECU 20 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 applied to lighten the driver's steering operation (steering operation) described above, and does not require the driver's steering operation, and the steering mechanism is driven by the steering command from the driving assistance ECU 10. Represents the torque applied to.

  Even if the EPS / ECU 20 receives a steering command from the driving support ECU 10, if the steering torque is detected by the driver's steering operation, the EPS / ECU 20 is in a case where the steering torque is larger than the threshold value. Gives priority to steering of the steering wheel of the driver, and generates a steering assist torque that makes the steering wheel operation light.

  The meter ECU 30 is connected to a display 31 and left and right turn signals 32 (meaning turn signal lamps, sometimes called turn lamps). The indicator 31 is, for example, a multi-information display provided in front of the driver's seat, and displays various types of information in addition to displaying measured values of meters such as vehicle speed. For example, when the meter ECU 30 receives a display command corresponding to the driving support state from the driving support ECU 10, the meter ECU 30 causes the display 31 to display a screen specified by the display command. As the display 31, a head-up display (not shown) can be employed instead of or in addition to the multi-information display. When employing a head-up display, a dedicated ECU for controlling the display of the head-up display may be provided.

  Further, the meter ECU 30 includes a winker drive circuit (not shown). When the winker blinking command is received via the CAN 100, the meter ECU 30 blinks the winker 32 in the direction (right, left) specified by the winker blinking command. Let In addition, while the blinker 32 is blinking, the meter ECU 30 transmits blinker blinking information indicating that the blinker 32 is blinking to the CAN 100. Therefore, other ECUs can grasp the blinking state of the blinker 32.

  The steering ECU 40 is connected to the winker lever 41. The winker lever 41 is an operating device for operating (flashing) the winker 32 and is provided on the steering column. The winker lever 41 is provided so as to be swingable around the support shaft in two stages of operation strokes in each of the counterclockwise operation direction and the clockwise operation direction.

  The winker lever 41 of the present embodiment is also used as an operating device for a driver to request lane change support control. As shown in FIG. 4, the winker lever 41 has a first stroke that is a position rotated by a first angle θW1 from the neutral position PN with respect to each of the counterclockwise operation direction and the clockwise operation direction about the support shaft O. A position P1L (P1R) and a second stroke position P2L (P2R) that is a position rotated by a second angle θW2 (> θW1) from the neutral position PN are configured to be selectively operable. When the winker lever 41 is moved to the first stroke position P1L (P1R) by the driver's lever operation, the winker lever 41 returns to the neutral position PN when the lever operating force of the driver is released. Further, when the winker lever 41 is moved to the second stroke position P2L (P2R) by the lever operation of the driver, even if the lever operating force is released, the winker lever 41 is held at the second stroke position P2L (P2R) by the lock mechanism. It has come to be. Further, the winker lever 41 is held at the second stroke position P2L (P2R), and the steering handle rotates backward to return to the neutral position, or the driver moves the winker lever 41 in the neutral position direction. When a return operation is performed, the lock mechanism is unlocked and returned to the neutral position PN.

  The blinker lever 41 is turned on only when the position is at the first stroke position P1L (P1R) (when an on signal is generated), the first switch 411L (411R), and the position is the second stroke position P2L (P2R). And a second switch 412L (412R) that is turned on only when the switch is on (generates an on signal).

  The steering ECU 40 detects the operating state of the winker lever 41 based on the presence / absence of an ON signal from the first switch 411L (411R) and the second switch 412L (412R). The steering ECU 40 operates in the operating direction (left and right) in a state where the winker lever 41 is tilted to the first stroke position P1L (P1R) and a state where the winker lever 41 is tilted to the second stroke position P2L (P2R). A blinker blinking command including information indicating the is transmitted to the meter ECU 30.

  Further, the steering ECU 40 detects that the winker lever 41 is continuously held at the first stroke position P1L (P1R) for a preset time (lane change request confirmation time: for example, 1 second) or longer. In this case, a lane change support request signal including information indicating the operation direction (left and right) is output to the driving support ECU 10. Therefore, when the driver wants to receive lane change assistance during driving, the driver only has to turn the winker lever 41 to the first stroke position P1L (P1R) in the lane change direction and hold the state for a set time or more. Such an operation is called a lane change support request operation.

  In this embodiment, the winker lever 41 is used as an operating device for a driver to request lane change support. Instead, a dedicated lane change support requesting operating device may be provided on the steering wheel or the like.

  The engine ECU 50 shown in FIG. 1 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. In the present embodiment, the internal combustion engine 52 is a gasoline fuel injection / spark ignition / multi-cylinder engine, and includes a throttle valve for adjusting the intake air amount. The engine actuator 51 includes at least a throttle valve actuator that changes the opening of the throttle valve. The engine ECU 50 can change the torque generated by the internal combustion engine 52 by driving the engine actuator 51. Torque generated by the internal combustion engine 52 is transmitted to drive wheels (not shown) via a transmission (not shown). Therefore, the engine ECU 50 can control the driving force of the host vehicle and change the acceleration state (acceleration) by controlling the engine actuator 51.

  The brake ECU 60 is connected to the brake actuator 61. The brake actuator 61 is provided in a hydraulic circuit between a master cylinder (not shown) that pressurizes hydraulic oil by the depression force of the brake pedal and a friction brake mechanism 62 provided on the left and right front and rear wheels. The friction brake mechanism 62 includes a brake disc 62a fixed to the wheel and a brake caliper 62b fixed to the vehicle body. The brake actuator 61 adjusts the hydraulic pressure supplied to the wheel cylinder built in the brake caliper 62b in accordance with an instruction from the brake ECU 60, and operates the wheel cylinder by the hydraulic pressure to press the brake pad against the brake disc 62a to cause friction. Generate braking force. Therefore, the brake ECU 60 can change the deceleration state (deceleration) by controlling the braking force of the host vehicle by controlling the brake actuator 61.

  The navigation ECU 70 includes a GPS receiver 71 that receives a GPS signal for detecting the current position of the host vehicle, a map database 72 that stores map information, and a touch panel (touch panel display) 73. The navigation ECU 70 specifies the current position of the host vehicle based on the GPS signal, performs various arithmetic processes based on the position of the host vehicle, the map information stored in the map database 72, and the like, and uses the touch panel 73. Route guidance.

  The map information stored in the map database 72 includes road information. The road information includes parameters indicating the position and shape of the road (for example, the curvature radius or curvature of the road, the road lane width, 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 the road is an automobile-only road.

<Control processing performed by the driving support ECU 10>
Next, a control process performed by the driving assistance ECU 10 will be described. The driving support ECU 10 performs the lane change support control when a lane change support request is received in a situation where both the lane keeping support control and the following inter-vehicle distance control are performed. First, the lane keeping support control and the following inter-vehicle distance control will be described.

<Lane maintenance support control (LTA)>
Lane maintenance support control supports the driver's steering operation by applying steering torque to the steering mechanism so that the position of the host vehicle is maintained near the target travel line in the lane in which the host vehicle is traveling It is control to do. In the present embodiment, the target travel line is the lane center line CL, but a line offset in the lane width direction by a predetermined distance from the lane center line CL can also be adopted. Therefore, the lane keeping assist control can be expressed as a control for assisting the steering operation so that the traveling position of the host vehicle is maintained at a constant position in the lane width direction within the lane.

  Hereinafter, the lane keeping assist control is referred to as LTA (lane tracing assist). Although LTA is called by various names, it is known per se (for example, JP 2008-195402 A, JP 2009-190464 A, JP 2010-6279 A, and Patent No. No. 4349210, etc.). Accordingly, a brief description will be given below.

When the LTA is requested by the operation of the setting operation device 14, the driving support ECU 10 executes the LTA. When the LTA is requested, the driving assistance ECU 10 sets the target steering angle θlta * to a predetermined calculation cycle according to the following equation (1) based on the lane-related vehicle information (Cu, Dy, θy) described above. To calculate.

θlta * = Klta1, Cu + Klta2, θy + Klta3, Dy + Klta4, ΣDy
... (1)

  Here, Klta1, Klta2, Klta3, and Klta4 are control gains. The first term on the right side is a steering angle component that works in a feed-forward manner determined according to the curvature Cu of the road. The second term on the right side is a steering angle component that acts as a feedback so as to reduce the yaw angle θy (so as to reduce the deviation of the direction of the host vehicle from the lane center line CL). That is, the steering angle component is calculated by feedback control in which the target value of the yaw angle θy is zero. The third term on the right side is a steering angle component that works in a feedback manner so as to reduce the lateral deviation Dy, which is a deviation (position deviation) in the lane width direction position of the host vehicle with respect to the lane center line CL. That is, the steering angle component is calculated by feedback control in which the target value of the lateral deviation Dy is zero. The fourth term on the right side is a steering angle component that works in a feedback manner so as to reduce the integral value ΣDy of the lateral deviation Dy. That is, the steering angle component is calculated by feedback control in which the target value of the integral value ΣDy is zero.

  For example, when the lane center line CL is curved to the left, when the own vehicle is laterally shifted to the right with respect to the lane center line CL, and when the own vehicle is right to the lane center line CL. When the vehicle is facing in the direction, the target rudder angle θlta * is set such that the target rudder angle θlta * becomes the left rudder angle. Further, when the lane center line CL is curved in the right direction, when the own vehicle has a lateral shift in the left direction with respect to the lane center line CL, and when the own vehicle is left with respect to the lane center line CL. When the vehicle is facing in the direction, the target rudder angle θlta * is set so that the target rudder angle θlta * becomes the right rudder angle. Therefore, the driving assistance ECU 10 performs the calculation based on the above formula (1) using codes corresponding to the left direction and the right direction, respectively.

  The driving assistance ECU 10 outputs a command signal representing the target rudder angle θlta * as a calculation result to the EPS • ECU 20. The EPS / ECU 20 drives and controls the steering motor 22 so that the steering angle follows the target steering angle θlta *. In the present embodiment, the driving assistance ECU 10 outputs a command signal indicating the target steering angle θlta * to the EPS • ECU 20, and calculates a target torque for obtaining the target steering angle θlta *, which is a calculation result. A command signal representing the target torque may be output to the EPS / ECU 20.

In addition, the driving assistance ECU 10 issues a lane departure warning by, for example, sounding the buzzer 13 when the host vehicle is in a state where it may depart from the lane.
The above is the outline of LTA.

<Following inter-vehicle distance control (ACC)>
Follow-up inter-vehicle distance control is based on the surrounding information, and when there is a preceding vehicle traveling in front of the host vehicle, the distance between the preceding vehicle and the host vehicle is maintained at a predetermined distance while In this control, the vehicle is caused to follow the preceding vehicle, and when the preceding vehicle does not exist, the host vehicle travels at a constant speed at the set vehicle speed. Hereinafter, the following inter-vehicle distance control is referred to as ACC (adaptive cruise control). ACC itself is well known (see, for example, Japanese Patent Application Laid-Open No. 2014-148293, Japanese Patent Application Laid-Open No. 2006-315491, Japanese Patent No. 4172434, and Japanese Patent No. 4929777). Accordingly, a brief description will be given below.

  When the ACC is requested by the operation of the setting operation device 14, the driving assistance ECU 10 executes the ACC. When the ACC is requested, the driving assistance ECU 10 selects the tracking target vehicle based on the surrounding information supplied from the surrounding sensor 11. For example, the driving assistance ECU 10 determines whether or not another vehicle exists in a predetermined tracking target vehicle area.

  When the other vehicle exists in the tracking target vehicle area for a predetermined time or more, the driving assistance ECU 10 selects the other vehicle as the tracking target vehicle, and the own vehicle maintains a predetermined inter-vehicle distance with respect to the tracking target vehicle. Set the target acceleration to follow. When there is no other vehicle in the tracking target vehicle area, the driving assistance ECU 10 sets the target based on the set vehicle speed and the detected vehicle speed (the vehicle speed detected by the vehicle speed sensor) so that the vehicle speed of the host vehicle matches the set vehicle speed. Set the acceleration.

The driving support ECU 10 controls the engine actuator 51 using the engine ECU 50 and the brake actuator 61 using the brake ECU 60 as necessary so that the acceleration of the host vehicle matches the target acceleration.
When an accelerator operation is performed by the driver during the ACC, the accelerator operation is given priority, and automatic deceleration control for maintaining the inter-vehicle distance between the preceding vehicle and the host vehicle is not performed.
The above is the outline of ACC.

<Lane change support control (LCA)>
Lane change support control monitors the surroundings of the host vehicle and determines that it is possible to change the lanes safely, then monitors the surroundings of the host vehicle and lanes adjacent to the lane in which the host vehicle is currently traveling. In this control, a steering torque is applied to the steering mechanism so as to move the vehicle to assist the driver's steering operation (lane change operation). Therefore, according to the lane change support control, it is possible to change the lane in which the host vehicle travels without requiring the driver's steering operation (handle operation). Hereinafter, the lane change assist control is referred to as LCA (lane change assist).

  The LCA is a control of the lateral position of the host vehicle in the same manner as the LTA, and is performed in place of the LTA when a lane change support request is accepted during the implementation of the LTA and the ACC. Hereinafter, LTA and LCA are collectively referred to as steering support control, and the state of steering support control is referred to as a steering support control state.

  The steering assist device is control that assists the driver's steering operation. Therefore, the driving assistance ECU 10 generates a steering force for steering assistance control so that the steering operation of the driver is prioritized when the steering assistance control (LTA, LCA) is performed. Therefore, even during the steering assist control, the driver can advance the host vehicle in the intended direction by operating the steering wheel of the driver.

  FIG. 5 shows a steering assistance control routine executed by the driving assistance ECU 10. The steering assist control routine is executed when the LTA execution permission condition is satisfied. The LTA execution permission condition is that the LTA execution is selected by the setting operation device 14, that the ACC is executed, the white line can be recognized by the camera sensor 12, and the like.

  When starting the steering support control routine, the driving support ECU 10 sets the steering support control state to the LTA / ON state in step S11. The LTA / ON state represents a control state in which LTA is performed.

  Subsequently, in step S12, the driving assistance ECU 10 determines whether or not the LCA start condition is satisfied.

The LCA start condition is satisfied, for example, when all of the following conditions are satisfied.
1. A lane change support request operation (lane change support request signal) is detected.
2. Implementation of LCA is selected by the setting controller 14.
3. The white line in the turn signal operating direction (white line serving as a boundary between the original lane and the target lane) is a broken line.
4). The surrounding monitoring LCA execution result can be judged (the obstacle information (other vehicles, etc.) that obstructs the lane change is not detected by the surrounding information obtained by the surrounding sensor 11, and the lane change can be performed safely. Is determined).
5. The road is an automobile-only road (the road type information acquired from the navigation ECU 70 represents an automobile-only road).
6). The vehicle speed of the vehicle is within the LCA-permitted vehicle speed range permitted by the LCA.
For example, the condition 4 is satisfied when it is estimated that the distance between the two vehicles after the lane change is properly secured based on the relative speed between the host vehicle and another vehicle traveling in the target lane.
The LCA start condition is not limited to such a condition, and can be arbitrarily set.

  If the LCA start condition is not satisfied, the driving assistance ECU 10 returns the process to step S11 and continues the LTA.

  If the LCA start condition is satisfied while the LTA is being performed (S12: Yes), the driving assistance ECU 10 performs the LCA instead of the LTA in step S13. In this case, the driving assistance ECU 10 sets the steering assistance control state to the LCA first half state. The steering assist control state for the LCA is divided into an LCA first half state and an LCA second half state, and is set to the LCA first half state at the start of the LCA. When the steering assist control state is set to the first half of the LCA, the driving assist ECU 10 transmits an LCA execution display command to the meter ECU 30. As a result, the implementation status of the LCA is displayed on the display 31.

  FIG. 8 shows an example of a screen 31a (referred to as LTA screen 31a) displayed on the display 31 during the implementation of LTA and a screen 31b (referred to as LCA screen 31b) displayed during the implementation of LCA. In any of the LTA screen 31a and the LCA screen 31b, an image of the host vehicle traveling between the left and right white lines is shown. On the LTA screen 31a, a virtual wall GW is displayed outside the left and right white line display GWL. The driver can recognize that the vehicle is controlled to travel in the lane by the wall GW.

  On the other hand, on the LCA screen 31b, the display of the wall GW is erased, and the track Z of the LCA is displayed instead. The driving assistance ECU 10 switches the screen displayed on the display 31 between the LTA screen 31a and the LCA screen 31b in accordance with the steering assistance control state. As a result, the driver can easily determine whether the implementation status of the steering assist control is LTA or LCA.

  The LCA is control that supports a driver's steering operation for changing lanes, and the driver is obliged to monitor the surroundings. Therefore, a message GM for causing the driver to monitor the surroundings is displayed on the LCA screen 31b.

  When starting the LCA, the driving assistance ECU 10 first calculates a target trajectory in step S14 of the routine shown in FIG. Here, the target trajectory of the LCA will be described.

  The driving assistance ECU 10 calculates a target trajectory function that determines a target trajectory of the host vehicle when performing LCA. The target track is the width of the lane (referred to as the target lane) in the lane change support request direction adjacent to the original lane from the lane where the vehicle is currently traveling (referred to as the original lane) over the target lane change time. The trajectory is moved to the center position in the direction (referred to as the final target lateral position), and has a shape as shown in FIG. 9, for example.

  As will be described later, the target trajectory function corresponds to the elapsed time t with the elapsed time t from the LCA start time (that is, the time when the LCA start condition is satisfied) as a variable with reference to the lane center line CL of the original lane. This is a function for calculating the target value of the lateral position of the host vehicle (that is, the target lateral position). Here, the lateral position of the host vehicle represents the position of the center of gravity of the host vehicle in the lane width direction (sometimes referred to as a lateral direction) with reference to the lane center line CL.

  The target lane change time is a distance (hereinafter referred to as a required lateral distance) for moving the vehicle from the initial position, which is the LCA start position (the lateral position of the vehicle at the start of LCA), to the final target lateral position. It is variably set proportionally. As an example, when the lane width is generally 3.5 m, the target lane change time is set to, for example, 8.0 seconds. In this example, the host vehicle at the start of the LCA is located on the lane center line CL of the original lane. The target lane change time is adjusted in proportion to the width of the lane width. Therefore, the target lane change time is set to a larger value as the lane width is wider, and conversely, the target lane change time is set to a smaller value as the lane width is narrower.

  Further, when the lateral position of the host vehicle at the start of LCA is shifted to the lane change side from the lane center line CL of the original lane, the target lane change time increases as the shift amount (lateral deviation Dy) increases. Set to decrease. Conversely, when the lateral position of the host vehicle at the start of LCA is shifted to the opposite lane change side from the lane center line CL of the original lane, the shift amount (lateral deviation Dy) is the target lane change time. It is set to increase as the number increases. For example, if the deviation is 0.5 m, the increase / decrease adjustment amount for the target lane change time may be 1.14 seconds (= 8.0 × 0.5 / 3.5). Note that the value for setting the target lane change time shown here is merely an example, and an arbitrarily set value can be adopted.

In the present embodiment, the target lateral position y is calculated by a target trajectory function y (t) shown in the following equation (2). This target trajectory function y (t) is a quintic function with the elapsed time t as a variable.

y (t) = c ₀ + c ₁ · t + c ₂ · t ² + c ₃ · t ³ + c ₄ · t ⁴ + c ₅ · t ⁵
... (2)
This target track function y (t) is set to a function that smoothly moves the host vehicle to the final target lateral position.

Here, the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ are the state of the host vehicle at the start of LCA (initial lateral state amount) and the target state of the host vehicle at the end of LCA (final Target lateral state quantity).

  For example, as shown in FIG. 10, the target trajectory function y (t) is determined based on the lane center line CL of the lane (original lane) in which the host vehicle C is traveling at the current time point (the target trajectory of the target trajectory). This is a function for calculating the target lateral position y (t) of the host vehicle C corresponding to the elapsed time t (sometimes referred to as the current time t) from the (calculation time point). In FIG. 10, the lane is formed in a straight line, but when the lane is formed in a curve, the target track function y (t) is the lane center with respect to the lane center line CL formed in the curve. This is a function for calculating the target lateral position of the host vehicle with respect to the line CL.

The driving assistance ECU 10 sets target trajectory calculation parameters as follows in order to determine the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of the target trajectory function y (t). The target trajectory calculation parameters are the following seven (P1 to P7).
P1. The lateral position of the host vehicle with respect to the lane center line of the original lane at the start of LCA (referred to as the initial lateral position).
P2. The lateral speed of the host vehicle at the start of LCA (referred to as initial lateral speed).
P3. Lateral acceleration of the host vehicle at the start of LCA (referred to as initial lateral acceleration).
P4. The target lateral position of the host vehicle (referred to as the final target lateral position) with respect to the lane center line of the original lane at the time when the LCA is completed (referred to as LCA completion).
P5. The target speed in the lateral direction of the host vehicle when the LCA is completed (referred to as the final target lateral speed).
P6. The target acceleration in the lateral direction of the host vehicle when the LCA is completed (referred to as final target lateral acceleration).
P7. A target time (referred to as a target lane change time) that is a target value of the time for performing LCA (the time from the start of LCA to the end of LCA itself).
As described above, the lateral direction is the lane width direction. Accordingly, the lateral speed represents the speed of the host vehicle in the lane width direction, and the lateral acceleration represents the acceleration of the host vehicle in the lane width direction.

  The process of setting these seven target trajectory calculation parameters is called an initialization process. In this initialization process, target trajectory calculation parameters are set as follows. That is, the initial lateral position is set to a value equal to the lateral deviation Dy detected by the camera sensor 12 at the start of LCA. The initial lateral speed is a value obtained by multiplying the vehicle speed v detected by the vehicle speed sensor at the start of LCA by the sine value (sin (θy)) of the yaw angle θy detected by the camera sensor 12 (v · sin (θy)). Set to The initial lateral acceleration is set to a value (v · γ) obtained by multiplying the yaw rate γ (rad / s) detected by the yaw rate sensor at the start of LCA by the vehicle speed v. However, the initial lateral acceleration may be set to a differential value of the initial lateral velocity. The initial lateral position, initial lateral velocity, and initial lateral acceleration are collectively referred to as initial lateral state quantity.

  In addition, the driving assistance ECU 10 of the present embodiment regards the lane width of the target lane as the same as the lane width of the original lane detected by the camera sensor 12. Accordingly, the final target lateral position is set to the same value as the lane width of the original lane (final target lateral position = the lane width of the original lane). Further, the driving support ECU 10 sets both the final target lateral speed and the final target lateral acceleration to zero. The final target lateral position, the final target lateral velocity, and the final target lateral acceleration are collectively referred to as a final target lateral state quantity.

As described above, the target lane change time is calculated based on the lane width (which may be the lane width of the original lane) and the lateral displacement of the host vehicle at the start of LCA.
For example, the target lane change time tlen is calculated by the following equation (3).
tlen = Dini · A (3)
Here, Dini is a necessary distance for moving the host vehicle in the lateral direction from the LCA start position (initial lateral position) to the LCA completion position (final target lateral position). Therefore, if the host vehicle is located in the lane center line CL of the original lane at the start of LCA, Dini is set to a value equal to the lane width, and the host vehicle is deviated from the lane center line CL of the original lane. Is a value obtained by adjusting the deviation amount to the lane width. A is a constant (referred to as a target time setting constant) that represents a target time that the host vehicle spends moving laterally by a unit distance, and is, for example, (8 sec / 3.5 m = 2.29 sec / m). Is set. In this example, for example, when the necessary distance Dini for moving the host vehicle in the lateral direction is 3.5 m, the target lane change time tlen is set to 8 seconds.

  The target time setting constant A is not limited to the above value, and can be set arbitrarily. Further, for example, the setting operation device 14 may be used so that the target time setting constant A can be selected in a plurality of ways according to the preference of the driver. Alternatively, the target lane change time may be a fixed value.

Based on the initial lateral state quantity, the final target lateral state quantity, and the target lane change time obtained by the initialization process of the target trajectory calculation parameter, the driving assistance ECU 10 calculates the target trajectory function y expressed by Expression (2). Coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of (t) are calculated to determine the target trajectory function y (t).

From the target trajectory function y (t) expressed by the above equation (2), the lateral velocity y ′ (t) of the host vehicle can be expressed by the following equation (4), and the lateral acceleration y ″ ( t) can be expressed by the following equation (5).
y ′ (t) = c ₁ + 2c ₂ · t + 3c ₃ · t ² + 4c ₄ · t ³ + 5c ₅ · t ⁴
... (4)
y ″ (t) = 2c ₂ + 6c ₃ · t + 12c ₄ · t ² + 20c ₅ · t ³
... (5)

Here, the initial lateral position is y0, the initial lateral speed is vy0, the initial lateral acceleration is ay0, the final target lateral position is y1, the final target lateral speed is vy1, the final target lateral speed is ay1, and the lane width of the original lane is W. Then, the following relational expression is obtained based on the target trajectory calculation parameter.
y (0) = c ₀ = y0 (6)
y ′ (0) = c ₁ = by0 (7)
y ″ (0) = 2c ₂ = ay0 (8)
y (tlen) = c ₀ + c ₁ · tlen + c ₂ · tlen ² + c ₃ · tlen ³
+ C ₄ · t len ⁴ + c ₅ · t len ⁵ = y1 = W (9)
y ′ (tlen) = c ₁ + 2c ₂ · tlen + 3c ₃ · tlen ²
+ 4c ₄ · t len ³ + 5c ₅ · t len ⁴ = vy1 = 0 (10)
y ″ (tlen) = 2c ₂ + 6c ₃ · tlen + 12c ₄ · tlen ²
+ 20c ₅ · tlen ³ = ay1 = 0 (11)

Therefore, the values of the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of the target trajectory function y (t) can be calculated from these six expressions (6) to (11). Then, the target trajectory function y (t) is calculated by substituting the values of the calculated coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ into the equation (2). The driving assistance ECU 10 stores and maintains the target trajectory function y (t) until the LCA is terminated. Further, simultaneously with the calculation of the target trajectory function y (t), the driving support ECU 10 activates a timer (initial value: zero) and starts counting up the elapsed time t from the start of LCA.

  When the target trajectory function is calculated in this way, the driving support ECU 10 performs steering control based on the target trajectory function in the subsequent step S15. This steering control will be specifically described.

  First, the driving assistance ECU 10 calculates the target lateral state amount of the host vehicle at the current time. The target lateral state quantity includes a target lateral position that is a target value of the lateral position of the host vehicle in the lane width direction, a target lateral speed that is a target value of the speed (lateral speed) of the host vehicle in the lane width direction, And a target lateral acceleration that is a target value of acceleration (lateral acceleration) in the lane width direction. The lateral velocity and the lateral acceleration may be collectively referred to as a lateral motion state quantity, and the target lateral velocity and the target lateral acceleration may be collectively referred to as a target lateral motion state quantity.

  In this case, the driving assistance ECU 10 calculates the target lateral position, the target lateral speed, and the target lateral acceleration at the current time based on the target trajectory function y (t) determined in step S14 and the current time t. . The current time t is the elapsed time after the target trajectory function y (t) is determined in step S14, and is equivalent to the elapsed time from the start of LCA. When the driving assistance ECU 10 calculates the target trajectory function y (t) in step S14, the driving assistance ECU 10 resets the clock timer and starts counting up the elapsed time t (= current time t) from the start of the LCA. The target lateral position is calculated by substituting the current time t into the target trajectory function y (t), and the target lateral speed is calculated by subtracting the target trajectory function y (t) from the current time t. And the target lateral acceleration is calculated by substituting the current time t into a function y ″ (t) obtained by second-order differentiation of the target trajectory function y (t). The driving assistance ECU 10 reads the elapsed time t measured by the timer, and calculates the target lateral state quantity based on the measured time t and the function.

  Hereinafter, the target lateral position at the current time is represented as y *, the target lateral velocity at the current time is represented as vy *, and the target lateral acceleration at the current time is represented as ay *.

  Subsequently, the driving assistance ECU 10 calculates a target yaw state amount that is a target value related to an exercise that changes the direction of the host vehicle. The target yaw state quantity represents the target yaw angle θy * of the host vehicle, the target yaw rate γ * of the host vehicle, and the target curvature Cu * at the present time. The target curvature Cu * is the curvature of the track that changes the lane of the host vehicle, that is, the curvature of the curve component related to the lane change that does not include the curve curvature of the lane.

  The driving assistance ECU 10 reads the current vehicle speed v (current vehicle speed detected by the vehicle speed sensor), and based on the vehicle speed v, the target lateral speed vy *, and the target lateral acceleration ay *, the following formula ( 12), (13), and (14) are used to calculate the current target yaw angle θy *, target yaw rate γ *, and target curvature Cu *.

θy * = sin ⁻¹ (vy * / v) (12)
γ * = ay * / v (13)
Cu * = ay * / v ² (14)
That is, the target yaw angle θy * is calculated by substituting a value obtained by dividing the target lateral speed vy * by the vehicle speed v into the inverse sine function. The target yaw rate γ * is calculated by dividing the target lateral acceleration ay * by the vehicle speed v. The target curvature Cu * is calculated by dividing the target lateral acceleration ay * by the square value of the vehicle speed v.

Subsequently, the driving assistance ECU 10 calculates the target control amount of the LCA. In the present embodiment, the target rudder angle θlca * is calculated as the target control amount. The target rudder angle θlca * is calculated by the following equation (15) based on the target lateral position y *, the target yaw angle θy *, the target yaw rate γ *, the target curvature Cu *, and the curvature Cu calculated as described above. Calculated.

θlca * = Klca1 · (Cu * + Cu) + Klca2 · (θy * −θy) + Klca3 · (y * −y)
+ Klca4 ・ (γ * −γ) + Klca5 ・ Σ (y * −y) (15)

  Here, Klca1, Klca2, Klca3, Klca4, Klca5 are control gains. Cu is a curvature at the present time (at the time of calculation) detected by the camera sensor 12. y corresponds to the horizontal position at the present time (at the time of calculation) detected by the camera sensor 12, that is, Dy. θy is a yaw angle at the present time (at the time of calculation) detected by the camera sensor 12. Γ represents the current yaw rate of the host vehicle detected by the yaw rate sensor. Note that γ may be a differential value of the yaw angle θy.

The first term on the right side is a feedforward control amount that is determined according to an addition value of the target curvature Cu * and the curvature Cu (lane curve). Klca1 · Cu * is a feedforward control amount for changing the lane, and Klca1 · Cu is a feedforward control amount for causing the host vehicle to travel along the lane curve. Therefore, the control amount represented by the first term on the right side is basically set to a value that allows the host vehicle to travel along the target course if the steering angle is controlled by the control amount. . In this case, the control gain Klca1 is set to a value corresponding to the vehicle speed v. For example, the control gain Klca1 may be set as in the following equation (16) according to the wheel base L and the stability factor Ksf (a fixed value determined for each vehicle). Here, K is a fixed control gain.
Klca1 = K · L · (1 + Ksf · v ² ) (16)

  The second term to the fifth term on the right side are feedback control amounts. The second term on the right side is a steering angle component that works in a feedback manner so as to reduce the deviation between the target yaw angle θy * and the actual yaw angle θy. The third term on the right side is a steering angle component that works in a feedback manner so as to reduce the deviation between the target lateral position y * and the actual lateral position y. The fourth term on the right side is a steering angle component that works in a feedback manner so as to reduce the deviation between the target yaw rate γ * and the actual yaw rate γ. The fifth term on the right side is a steering angle component that acts as a feedback so as to reduce the integral value Σ (y * −y) of the deviation between the target lateral position y * and the actual lateral position y.

  The target rudder angle θlca * is not limited to the one calculated with the five rudder angle components described above, and may be calculated using only one of these rudder angle components, or other rudder angle components It may be calculated by adding. For example, regarding the feedback control amount related to the yaw motion, either one of the deviation of the yaw angle or the deviation of the yaw rate may be used. Further, the feedback control amount using the integral value Σ (y * −y) of the deviation between the target lateral position y * and the actual lateral position y can be omitted.

When calculating the target control amount, the driving assistance ECU 10 transmits a steering command representing the target control amount to the EPS / ECU 20. In the present embodiment, the driving assistance ECU 10 calculates the target rudder angle θlca * as the target control amount, but calculates the target torque for obtaining the target rudder angle θlca * and outputs a steering command representing the target torque to the EPS · You may transmit to ECU20.
The above is the process of step S15.

  When the EPS / ECU 20 receives a steering command from the driving support ECU 10 via the CAN 100, the EPS / ECU 20 drives and controls the steering motor 22 so that the steering angle follows the target steering angle θlca *.

  Subsequently, in step S16, the driving assistance ECU 10 determines whether or not the progress of the lane change is in the second half.

  Here, the determination in the first half of the progress of the lane change will be described. The driving assistance ECU 10 determines the first half of the progress of the lane change by comparing the position of the reference point of the host vehicle (the center of gravity of the vehicle in the present embodiment) with a predetermined determination position. If the position of the reference point of the own vehicle (hereinafter, also simply referred to as the position of the own vehicle or the lateral position) is the side opposite to the determination position (that is, the original lane side), It is determined that the progress status of the lane change is the first half, and if the lateral position of the host vehicle is the lane change side with respect to the determination position, it is determined that the progress status of the lane change is the second half.

  As will be described later, during the LCA, the surrounding vehicles are monitored based on the surrounding information obtained by the surrounding sensor 11. Then, if the LCA is continued, the LCA is stopped when another vehicle that may abnormally approach the host vehicle in the target lane (sometimes referred to as an approaching vehicle) is detected. If the host vehicle can be prevented from protruding from the original lane, the approaching vehicle will not collide with the host vehicle. On the other hand, when the host vehicle enters the target lane, it is necessary to avoid a collision between the host vehicle and the approaching vehicle.

  Therefore, the driving assistance ECU 10 of the present embodiment grasps the progress of the lane change, and switches processing when an approaching vehicle is detected in the first half and the second half of the lane change. Therefore, the first half of the progress of the lane change is determined. Determination of the progress status of the lane change is performed based on lane information detected by the camera sensor 12.

<Example 1 of the first half determination method>
For example, when it is estimated that the entire vehicle body of the host vehicle is located in the original lane, the driving assistance ECU 10 determines that the progress of the lane change is in the first half, and at least a part of the vehicle body of the host vehicle is When it is estimated that the target lane protrudes from the original lane, it is determined that the progress of the lane change is in the second half. In this case, based on the lane information (particularly the lane width and lateral deviation Dy) detected by the camera sensor 12 and the vehicle body dimensions (particularly the vehicle body width), the side surface in the lane change direction of the host vehicle is the original lane and the target lane. It may be determined whether or not the boundary white line that becomes the boundary with the vehicle has exceeded the target lane side (for example, whether or not the tire in the lane change direction has passed the boundary white line).

<Example 2 of the first half of the determination method>
As will be described later, when an approaching vehicle is detected in the first half of the lane change, the LCA is stopped halfway, and steering control is performed to return the host vehicle to the center position in the lane width direction of the original lane. This steering control is called LCA cancellation control. Even if an approaching vehicle is detected and LCA cancellation control is performed, the host vehicle may enter the target lane due to control response delay, white line recognition delay, peripheral monitoring recognition delay, calculation delay, and the like. Therefore, the overshoot (the lateral distance moving in the lane change direction) due to the delay due to these factors (the delay time from the time when the approaching vehicle is detected to the time when the lateral speed of the host vehicle switches to the anti-lane change direction) In consideration, the front and rear half of the progress of the lane change may be switched at an early timing before the side surface (tire) of the host vehicle passes the boundary white line.

In this case, it is only necessary to determine whether or not the side surface of the host vehicle has exceeded the boundary white line toward the target lane, based on the look-ahead lateral position Dyf considering overshoot. Overshoot increases as the lateral speed of the host vehicle increases. Therefore, the prefetch lateral position Dyf is calculated by the following equation (17), and it is only necessary to determine whether the side surface of the host vehicle has exceeded the boundary white line toward the target lane based on the prefetch lateral position Dyf.
Dyf = Dy + vy · Tre (17)
Here, Dy represents the current lateral deviation, vy represents the current lateral velocity, and Tre is a preset time (referred to as a look-ahead time) for compensating for the response delay.

  In this case, with respect to the lateral position of the host vehicle detected by the camera sensor 12, a predetermined distance (vy · Tre) set in accordance with the lateral speed vy is laterally set (to the target lane with reference to the lane center of the original lane). The position offset in the approaching direction) is regarded as the lateral position (prefetch position) of the host vehicle. Then, it is determined whether or not the side surface of the host vehicle at the prefetch position exceeds the boundary white line.

<Example 3 of the determination method in the first and second half>
For example, a specific position estimated that the host vehicle does not enter the target lane may be determined in advance as a determination position by LCA cancellation control. For example, as an example, the determination position is Dy = 0.5 m (fixed value). This determination position represents a position on the lane change side with respect to the lane center line CL. In this case, if the position of the center of gravity of the vehicle does not exceed 0.5 m from the lane center line CL to the lane change side, that is, if the lateral deviation Dy on the lane change side is 0.5 m or less, the lane change is the first half. If the lateral deviation Dy on the lane change side exceeds 0.5 m, it is determined that the lane change is in the second half. In this example, for example, when the lane width is 3.5 m and the vehicle width of the host vehicle is 1.8 m, when the lateral deviation Dy is 0.5 m, the distance between the center of gravity position of the host vehicle and the boundary white line is 1 Since the distance is .25 m (= (3.5 / 2) −0.5), the distance between the side surface of the vehicle on the lane change side and the boundary white line is 0.35 m (= 1.25− (1.8 / 2)). Therefore, in this example, if the overshoot is 0.35 m or less, the own vehicle can be prevented from entering the target lane by the LCA cancellation control. In the case of using this first / second half determination method, the determination position may be determined in consideration of the lane width and the overshoot amount.

  In other words, for the second and third examples of the first and second half determination methods, the driving support ECU 10 determines that the host vehicle is at a position closer to the center of the original lane than the boundary between the original lane and the target lane. When the specific position that is on the border side of the center position in the lane width direction is used as the determination position, it is determined that the progress is in the first half when it is estimated that the vehicle is positioned in the direction opposite to the lane change direction from the determination position. When the host vehicle is estimated to be located in the lane change direction from the determination position, the progress status is determined to be the second half.

  In the following description, the driving assistance ECU 10 determines the progress status of the lane change using the second or second determination method example 2 or example 3.

  Returning to the description of the steering assist control routine of FIG. Since the progress at the beginning of the LCA is the first half, the determination in step S16 is “No”. In this case, in step S17, the driving assistance ECU 10 determines that another vehicle (collision) that abnormally approaches the host vehicle when the host vehicle changes lanes along the target track based on the surrounding information obtained by the surrounding sensor 11. It is determined whether or not there is another vehicle that is likely to perform.

  For example, the driving assistance ECU 10 determines whether the other vehicle is currently running based on the relative speed between the own vehicle and the “original lane and another vehicle existing in the lane adjacent to the original lane” and the distance between the own vehicle and the other vehicle. A predicted time (collision time TTC: Time to Collision) until the vehicle collides is calculated. The driving assistance ECU 10 determines whether or not the collision time TTC is equal to or greater than the first half threshold value TTC1, and outputs a periphery monitoring result that is the determination result. The peripheral monitoring result is “no approaching vehicle” if the collision time TTC is equal to or greater than the first half threshold value TTC1, and “has approaching vehicle” if the collision time TTC is less than the first half threshold value TTC1. For example, the first half threshold value TTC1 is set to 4 seconds.

  In step S17, the driving assistance ECU 10 further determines whether there is another vehicle in the lateral direction of the host vehicle, and determines that there is an approaching vehicle if there is another vehicle in the lateral direction of the host vehicle. May be. In addition, in step S17, the driving support ECU 10 determines whether or not the own vehicle does not abnormally approach another vehicle existing in the target lane when the vehicle changes lanes by LCA, and the distance and relative speed with the other vehicle. It is possible to determine that there is an approaching vehicle when abnormally approaching another vehicle.

  In step S17, the driving support ECU 10 returns the process to step S15 when the surrounding monitoring result is “no approaching vehicle” (S17: Yes), and when the surrounding monitoring result is “with approaching vehicle” (S17: No), the process proceeds to step S30. Here, the case where the periphery monitoring result is “no approaching vehicle” will be described.

  The driving assistance ECU 10 repeats the processes of steps S15 to S17 described above at a predetermined calculation cycle while the surrounding monitoring result is “no approaching vehicle”. Thereby, LCA is continued and the own vehicle moves toward the target lane.

  If such processing is repeated and it is determined that the progress of the lane change is in the second half (S16: Yes), the driving assistance ECU 10 sets the steering assistance control state to the LCA latter half state in step S18. The LCA control content itself does not differ between the LCA first half state and the LCA second half state unless an approaching vehicle is detected and the LCA is stopped. In other words, when an approaching vehicle is detected and the LCA is stopped, the subsequent processing depends on whether the progress state of the lane change at the time when the LCA is stopped is the first half of the LCA or the second half of the LCA. Is different.

  Subsequently, in step S19, the driving support ECU 10 determines that another vehicle (collision) that abnormally approaches the host vehicle when the host vehicle changes lanes along the target track based on the surrounding information obtained by the surrounding sensor 11. It is determined whether or not there is another vehicle that is likely to perform. In this case, the driving assistance ECU 10 calculates the collision time TTC to determine the presence or absence of a vehicle that is abnormally approaching, as in step S17, and uses the second-half threshold value TTC2 as the determination threshold value. That is, if the collision time TTC is equal to or greater than the second half threshold value TTC2, the driving assistance ECU 10 determines “no approaching vehicle”, and if the collision time TTC is less than the second half threshold value TTC2, the surrounding monitoring result is “There is an approaching vehicle present”. Is determined.

  The second half threshold value TTC2 is set to a smaller value than the first half threshold value TTC1. For example, the second half threshold value TTC2 is set to 2 seconds. Therefore, in the latter half of the LCA state, it is determined that there is an approaching vehicle when another vehicle that has reached a higher level of approach than the first half of the LCA is detected.

  If the surrounding monitoring result is “no approaching vehicle” in step S19, the driving assistance ECU 10 advances the process to step S20 and determines whether or not the LCA completion condition is satisfied. In the present embodiment, the LCA completion condition is satisfied when the lateral position y of the host vehicle reaches the final target lateral position y *. If the LCA completion condition is not satisfied, the driving assistance ECU 10 returns the process to step S15, and repeatedly performs the processes of steps S15 to S20 described above at a predetermined calculation cycle. Thus, LCA is continued.

  During the execution of LCA, the target lateral state quantity (y *, vy *, ay *) corresponding to the elapsed time t is calculated. Further, the target yaw state quantity (θy *, γ *, Cu *) is calculated based on the calculated target lateral state quantity (y *, vy *, ay *) and the vehicle speed v, and the calculated target A target control amount (θlca *) is calculated based on the yaw state amount (θy *, γ *, Cu *). Each time the target control amount (θlca *) is calculated, a steering command representing the target control amount (θlca *) is transmitted to the EPS / ECU 20. Thus, the host vehicle travels along the target track.

  Note that if the travel position of the host vehicle is switched from the original lane to the target lane during the LCA, the lane related vehicle information (Cu, Dy, θy) supplied from the camera sensor 12 to the driving assistance ECU 10 is changed to the original lane. The lane related vehicle information is switched from the lane related vehicle information to the lane related vehicle information related to the target lane. For this reason, the target trajectory function y (t) calculated at the beginning of LCA cannot be used as it is. When the lane where the host vehicle is located is switched, the sign of the lateral deviation Dy is reversed. Accordingly, when the driving assistance ECU 10 detects that the sign (positive / negative) of the lateral deviation Dy output from the camera sensor 12 has been switched, the driving assistance ECU 10 offsets the target track function y (t) by the lane width W of the original lane. Thereby, the target track function y (t) calculated with the lane center line CL of the original lane as the origin can be converted into a target track function y (t) with the lane center line CL of the target lane as the origin.

  If the driving assistance ECU 10 determines in step S20 that the LCA completion condition has been established, the driving assistance ECU 10 sets the steering assistance control state to the LTA / ON state in step S21. That is, the LCA is terminated and the LTA is resumed. Thus, steering control is performed so that the host vehicle travels along the lane center line CL in the target lane. When the steering assistance control state is set to the LTA / ON state in step S21, the driving assistance ECU 10 returns the process to step S11 and continues the above-described steering assistance control routine as it is.

  When the LCA is completed and the steering assist control state is set to the LTA / ON state, the screen displayed on the display 31 is switched from the LCA screen 31b to the LTA screen 31a as shown in FIG.

  The driving support ECU 10 transmits a blinking command of the winker 32 in the winker operating direction to the meter ECU 30 during a period from the start of LCA to the end of the steering support control routine. The blinker 32 blinks according to the blink command transmitted from the steering ECU 40 in accordance with the operation of the blinker lever 41 to the first stroke position P1L (P1R) before the LCA is started. Even if the blink command transmitted from the steering ECU 40 is stopped, the meter ECU 30 continues to blink the blinker 32 while the blink command is transmitted from the driving support ECU 10.

  Next, the case where the surrounding monitoring result in step S17 is “with approaching vehicle” in the first half of the LCA will be described. In the first half of the LCA state, when the surrounding monitoring result is “with approaching vehicle”, the driving assistance ECU 10 advances the process to step S30 and performs LCA cancellation control. FIG. 6 is a flowchart showing an LCA cancel control routine which is the process of step S30.

  In the first half of the LCA, the host vehicle is in the original lane. For this reason, unless the own vehicle enters the target lane, the vehicle does not abnormally approach another vehicle (an approaching vehicle). Therefore, in the LCA cancellation control routine, the following processing is performed so that the host vehicle does not enter the target lane.

  First, in step S31, the driving assistance ECU 10 sets the steering assistance control state to the LCA cancellation control state. When the steering assist control state is set to the LCA cancel control state, the LCA is terminated.

Subsequently, in step S32, the driving assistance ECU 10 moves the host vehicle from the current position (the position of the host vehicle at the moment when the LCA cancellation control state is set) to the center position in the lane width direction of the original lane (hereinafter simply referred to as the center position). To calculate the target trajectory. Hereinafter, this target trajectory is referred to as a center return target trajectory. For this center return target trajectory, the function y (t) shown in Expression (2) is used. A function representing the center return target trajectory is called a center return target trajectory function y (t). In calculating the center return target trajectory function y (t), in order to determine the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of the function y (t) shown in Equation (2). The center return target trajectory calculation parameters are set as follows. The center return target trajectory calculation parameters are the following seven (P11 to P17).
P11. Horizontal position of own vehicle at present (when set to LCA cancellation control state) P12. Lateral speed of own vehicle at present (when set to LCA cancellation control state) P13. Lateral acceleration of own vehicle at present (when set to LCA cancellation control state) P14. Target lateral position that is the target value of the lateral position to move the host vehicle (in this example, the center position of the original lane, hereinafter referred to as center return completion target lateral position)
P15. Target lateral speed of the host vehicle when the host vehicle is moved to the center return completion target lateral position (referred to as center return completion target lateral speed)
P16. Target lateral acceleration of the host vehicle when the host vehicle is moved to the center return completion target lateral position (referred to as center return completion target lateral acceleration)
P17. Target time that is the target value of the time required to move the host vehicle from the current position to the center return completion target lateral position (referred to as center return target time)

  Here, the lateral position of the host vehicle at the present time (when set to the LCA cancellation control state) is ycancel, the lateral speed is vycancel, the lateral acceleration is aycancel, and the time when the steering assist control state is set to the LCA cancellation control state A new t = 0 is set, and the center return target time is tcancel. The center return target trajectory calculation parameters are y (0) = ycancel, y ′ (0) = vycancel, y ″ (0) = aycancel, y (tcancel) = 0, y ′ (tcancel) = 0, y ″. (Tcancel) = 0 is set.

  The lateral position ycancel, the lateral velocity vycancel, and the lateral acceleration aycancel are detected values at the present time, and can be calculated by a method similar to the method for obtaining the initial lateral state quantity described above. That is, the lateral position ycancel is the current lateral deviation Dy. The lateral speed vycancel is obtained from the current vehicle speed v and the current yaw angle θy (vycancel = v · sin (θy)). The lateral acceleration aycancel is a value (v · γ) obtained by multiplying the current yaw rate γ by the current vehicle speed v. Further, y (tcancel) is the center return completion target lateral position and is set to the center position of the original lane. y ′ (tcancel) represents the center return completion target lateral velocity, and y ″ (tcancel) represents the center return completion target lateral acceleration, both of which are set to zero.

Further, the center return target time tcancel is expressed by the following equation using the target time setting constant Acancel set to the same value as the target time setting constant A used when the target lane change time tlen is calculated at the start of LCA. Calculated by (18).
tcancel = Dcancel / Acancel (18)
Here, Dcancel moves the host vehicle in the lateral direction from the lateral position of the host vehicle when the steering assist control state is set to the LCA cancel control state to the center return completion target lateral position (center position of the original lane). Required distance. In the LCA cancellation control state, the host vehicle is present in the original lane, and thus has no urgency. Therefore, the speed at which the host vehicle is moved in the lateral direction may be approximately the same as that of LCA. Therefore, the target time setting constant Acancel is set to a value that is approximately the same as the target time setting constant A when LCA is performed.

Based on the set value of the center return target trajectory calculation parameter, the driving assistance ECU 10 uses the same method as in step S14 to calculate the coefficients c ₀ , c ₁ , c ₂ , c of the function y (t) shown in Expression (2). _3, calculates the value of c _4, c _5. Then, the central return target trajectory function y (t) is calculated by substituting the values of the calculated coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ into the equation (2).

  In step S32, the driving assistance ECU 10 calculates the center return target trajectory function and simultaneously notifies the driver that the LCA has been canceled (finished halfway). For example, the driving support ECU 10 drives the buzzer 13 to generate a notification sound (for example, a “beep” sound) and transmits an LCA cancellation notification command to the meter ECU 30. When the meter ECU 30 receives the LCA cancel notification command, the meter ECU 30 displays an LCA cancel screen 31c on the display 31 as shown in FIG. On the LCA cancellation screen 31c, the trajectory Z (see FIG. 8) that has been brightly displayed until then becomes dark or disappears. As a result, the driver recognizes that the LCA has ended. The LCA cancel screen 31c is displayed until the LCA cancel control state ends.

  Subsequently, in step S33, the driving assistance ECU 10 performs steering control based on the center return target trajectory function y (t) calculated in the previous step S32. In this case, the driving assistance ECU 10 resets the clock timer t (starts after clearing to zero), the elapsed time t after the steering assistance control state is set to the LCA cancellation control state, and the center return target trajectory function y (t). As in step S15, the calculation of the target lateral motion state quantity (y *, vy *, ay *) and the target yaw state quantity (θy *, γ *, Cu *) are performed. The target steering angle θcancel * is calculated. The target rudder angle θcancel * can be calculated in the same manner as θlca *, for example, by replacing the left side of Equation (15) with θcancel *.

  When the driving assist ECU 10 calculates the target control amount (target steering angle θcancel *), the driving support ECU 10 transmits a steering command representing the target control amount to the EPS / ECU 20. In the present embodiment, the driving assistance ECU 10 calculates the target steering angle θcancel * as the target control amount, calculates the target torque for obtaining the target steering angle θcancel *, and outputs a steering command representing this target torque to the EPS · You may transmit to ECU20.

  Subsequently, in step S34, the driving assistance ECU 10 determines whether an end condition for the LCA cancellation control state is satisfied. In this case, when the driving support ECU 10 detects that the lateral position of the host vehicle has reached the center return completion target lateral position (the central position of the original lane) by the steering control described above, the end condition of the LCA cancellation control state is It is determined that it has been established. Alternatively, when the driving assistance ECU 10 detects that the LCA cancellation control state has continued for a predetermined time (for example, a center return target time tcancel and a time longer than the center return target time tcancel by a predetermined time), the driving support ECU 10 It may be determined that the termination condition for the cancel control state is satisfied.

  If the driving assistance ECU 10 determines that the termination condition for the LCA cancellation control state is not satisfied (S34: No), the process returns to step S33. Therefore, the steering control is performed until the end condition of the LCA cancellation control state is satisfied. Thereby, the own vehicle travels toward the center position of the original lane.

  When these processes are repeated and the end condition for the LCA cancel control state is satisfied, the driving support ECU 10 ends the LCA cancel control routine and advances the process to step S21 of the main routine (steering support control routine). As a result, the steering assist control state is switched from the LCA cancel control state to the LTA / ON state. The functional part of the driving assistance ECU 10 that executes this LCA cancellation control routine corresponds to the central return assistance control means of the present invention.

  FIG. 14 shows a center return target track when the host vehicle C1 and another vehicle C2 traveling in the target lane approach each other in the first half of the LCA.

  Next, the case where the vicinity monitoring result in step S19 is “with approaching vehicle” in the latter half of the LCA state (S19: No) will be described. In the second half of the LCA state, when the surrounding monitoring result is “there is an approaching vehicle”, the driving support ECU 10 advances the process to step S40 and performs LCA approach warning control. FIG. 7 is a flowchart showing an LCA approach warning control routine which is the process of step S40.

  If the peripheral monitoring result in the first half of the LCA is “no approaching vehicle”, no approaching vehicle is normally detected even in the second half of the LCA. However, during the LCA, as shown in FIG. 17, the other vehicle C2 suddenly approaches the host vehicle C1 from the rear of the target lane at an unexpected relative speed, or a lane (original lane) further adjacent to the target lane. For example, a case where another vehicle C3 enters the target lane and abnormally approaches the host vehicle C1 from a lane that is two lanes away from the vehicle). Moreover, the case where the own vehicle which was in the blind spot range of the periphery sensor 11 approaches abnormally of the own vehicle is also considered.

  Therefore, in the LCA approach warning control in step S40, a warning is given to the driver, and the movement of the own vehicle is changed in a short time so that the own vehicle does not move to the center side in the width direction of the target lane. A process for supporting collision avoidance is performed.

  When the LCA approach warning control routine in step S40 is started, the driving assistance ECU 10 sets the steering assistance control state to the LCA approach warning control state in step S41. When the steering assist control state is set to the LCA approach warning control state, the LCA is terminated.

  Subsequently, in step S42, the driving support ECU 10 calculates a yaw angle return target trajectory for returning the yaw angle of the host vehicle to a state immediately before the start of the LCA.

  Here, the yaw angle return target trajectory will be described. The yaw angle return target track is a target track (in other words, a change in the lane of the host vehicle) that makes the yaw angle of the host vehicle zero in as short a time as possible within a range that does not hinder the running stability of the vehicle. This represents a target trajectory for making the lateral speed in the direction zero in the shortest possible time within a range that does not hinder the running stability of the vehicle. Immediately before the start of LCA, LTA is performed. Therefore, when the LCA is started, the yaw angle is estimated to be a value close to zero. Therefore, the driving assistance ECU 10 returns the yaw angle generated by the LCA to the state immediately before the start of the LCA, so that the target lateral speed vy * calculated from the target trajectory function of the LCA is canceled (the target lateral speed vy * is Calculate yaw angle return target trajectory (which will be zero).

  The target trajectory in the LCA described above represents the target lateral position with respect to the elapsed time from the start of the LCA. The yaw angle return target trajectory represents the target curvature with respect to the elapsed time from the time when the approaching vehicle is detected in the latter half of the LCA. Represent. The target control amount finally output to the EPS / ECU 20 is a control gain (the curvature is converted into a steering angle) to a value obtained by adding the target curvature and the curvature (curve curvature of the lane) detected by the camera sensor 12. The coefficient is set to a value obtained by multiplying the above-mentioned control gain Klca1.

  Here, a method for returning the yaw angle to the state immediately before the start of the LCA will be described. The target control amount in the LCA is represented by the target steering angle θlca *. This target rudder angle θlca * includes a feedforward control term (Klca1 · Cu *) calculated from the target curvature Cu *, as expressed by the above equation (15).

  The change in the target curvature corresponds to the change in the steering angle and can be grasped as a change in the yaw angle. Accordingly, when an approaching vehicle is detected in the latter half of the LCA state, the integral value of the target curvature Cu * in the period from the start of LCA to the detection of the approaching vehicle is calculated, and the integrated value of the target curvature Cu * is calculated. The yaw angle can be returned to the state immediately before the start of LCA by inverting the sign and outputting the corresponding control amount to the EPS • ECU 20.

  For example, as shown in FIG. 12, when an approaching vehicle is detected at time t1, the integrated value of the target curvature Cu * from time t0 when the LCA is started to time t1 is painted in gray in the figure. It corresponds to the area of the part. Therefore, if the feed-forward control amount corresponding to this area is inverted (inverted in the left-right direction) and commanded to the EPS • ECU 20, the yaw angle is set just before the start of LCA when the output of the feed-forward control amount is completed. It can be returned to the state. A value obtained by inverting the sign (positive / negative) of the integral value of the target curvature Cu * from time t0 to time t1 is referred to as an inverted integral value. By adding this inverted integral value to the integral value of the target curvature Cu * from time t0 to time t1, the integral value of the target curvature Cu * from the start of LCA can be made zero.

  If an approaching vehicle (another vehicle that may abnormally approach the host vehicle in the target lane) is detected in the latter half of the LCA state, it is highly likely that a part of the host vehicle has entered the target lane. It is. Therefore, it is necessary to return the yaw angle to zero for as short a time as possible so that the host vehicle is parallel to the lane formation direction. On the other hand, the control system in the steering assist device can change the upper limit value of the lateral acceleration of the vehicle (the lateral acceleration acting on the vehicle and different from the lateral acceleration in the lane width direction) and the lateral acceleration. The upper limit of the rate of change that can be performed (the amount of change in lateral acceleration per unit time) is determined.

Therefore, the driving assistance ECU 10 calculates a target curvature Cuemergency * after the time t1, as indicated by a thick line in FIG. The target curvature Cuemergency * is calculated using the maximum value (Cumax) and the maximum change gradient (Cu′max). This maximum value (Cumax) is set to the upper limit value of the lateral acceleration of the vehicle allowed in the control system in the steering assist device. The maximum change gradient (Cu′max) represents a change gradient that increases the target curvature Cuemergency * toward the maximum value Cumax and a change gradient that decreases the maximum value Cumax toward zero. In the steering assist control system, It is set to an allowable upper limit. For example, the maximum value Cumax is set to a value at which the lateral acceleration of the vehicle is 0.2 G (G: gravitational acceleration). The lateral acceleration YG acting on the vehicle can be calculated as a value obtained by multiplying the square value (v ² ) of the vehicle speed by the curvature (Cu) (YG = v ² · Cu). Therefore, the maximum value Cumax can be obtained from this relational expression. The sign of the maximum value Cumax and the maximum change gradient Cu′max is determined by the sign of the inverted integral value.

  The driving assistance ECU 10 starts from the time when the approaching vehicle is detected (time t1 in FIG. 12) based on the magnitude of the inversion integral value, the maximum value Cumax of the target curvature, and the maximum change gradient Cu′max of the target curvature. A target curvature Cuemergency * with respect to the elapsed time t is calculated. Hereinafter, the target curvature Cuemergency * with respect to the elapsed time t may be referred to as a target curvature function Cuemergency * (t). The target curvature function Cuemergency * (t) determines the target track of the host vehicle. Therefore, this target curvature function Cuemergency * (t) corresponds to the yaw angle return target trajectory.

  The inversion integral value can be calculated by integrating the value every time the target curvature Cu * is calculated during the LCA and inverting the sign of the integration value. Is calculated as follows.

The target curvature Cu * in the LCA can be expressed by the following equation (19) using the target lateral acceleration ay * and the vehicle speed v.
Cu * = ay * / v ² (19)
Therefore, the value obtained by integrating the target curvature Cu * from time t0 (ie, elapsed time t = 0) to time t1 (ie, elapsed time t = t1) is calculated using the vehicle speed v and the target lateral speed vy *. It can be expressed as in equation (20). Note that Expression (20) is based on the assumption that the vehicle speed v can be considered constant during the LCA.

従って、反転積分値は、式（２０）によって得られた積分値の符号を反転することによって算出される。反転積分値が算出されれば、上述したように、反転積分値の大きさと、目標曲率の最大値Ｃｕmaxと、目標曲率の最大変化勾配Ｃｕ’maxとに基づいて、接近車両が検出された時点からの経過時間ｔに対する目標曲率Ｃｕemergency*を演算することができる。このように運転支援ＥＣＵ１０は、最大値Ｃｕmaxと最大変化勾配Ｃｕ’maxとの制限下において、最短時間で、ＬＣＡの開始からの目標曲率Ｃｕ*の積分値をゼロに戻す目標曲率Ｃｕemergency*を演算する。

Therefore, the inverted integral value is calculated by inverting the sign of the integral value obtained by Expression (20). When the reverse integral value is calculated, as described above, the time point when the approaching vehicle is detected based on the magnitude of the reverse integral value, the maximum value Cumax of the target curvature, and the maximum change gradient Cu′max of the target curvature. The target curvature Cuemergency * with respect to the elapsed time t from can be calculated. In this way, the driving assistance ECU 10 calculates the target curvature Cuemergency * for returning the integrated value of the target curvature Cu * from the start of the LCA to zero in the shortest time under the limitation of the maximum value Cumax and the maximum change gradient Cu′max. To do.

  The above is the description of the calculation of the yaw angle return target trajectory (target curvature Cuemergency * (t)).

  In step S42, the driving assistance ECU 10 calculates a yaw angle return target trajectory, and at the same time, issues a warning to notify the driver that LCA has been terminated halfway and that an approaching vehicle has been detected. For example, the driving assistance ECU 10 drives the buzzer 13 to generate an alarm sound (for example, a “beep” sound) and transmits an LCA approach alarm command to the meter ECU 30. This alarm sound is emitted in a mode with the highest alert level.

  When the meter ECU 30 receives the LCA approach warning command, the meter ECU 30 displays an LCA approach warning screen 31d on the display 31 as shown in FIG. In the LCA approach warning screen 31d, the track Z (see FIG. 8) displayed so far is erased, and a warning is given next to the white line display GWL on the lane change direction side (right side in this example) in parallel with the white line display GWL. The mark GA is displayed blinking. The driver recognizes that the LCA has been terminated halfway and that the other vehicle is abnormally approaching the host vehicle in the target lane based on the sound of the buzzer 13 and the LCA approach warning screen 31d displayed on the display 31. can do. In this case, an alarm message may be generated by voice announcement. Moreover, you may make it issue a warning to a driver by vibrating a vibrator (not shown). The LCA approach warning screen 31d is continued until the end condition for the LCA approach warning control state is satisfied.

Subsequently, in step S43 of the routine shown in FIG. 7, the driving assistance ECU 10 performs steering control based on the target curvature function Cuemergency * (t) calculated in the previous step S42. In this case, the driving assistance ECU 10 resets the clock timer t (starts after clearing to zero), and based on the elapsed time t from when the approaching vehicle is detected in the latter half of the LCA and the target curvature function Cuemergency * (t), The target curvature Cuemergency * is calculated. The driving assistance ECU 10 calculates the current target steering angle θemergency * from the target curvature Cuemergency * and the curvature Cu detected by the current camera sensor 12. The target rudder angle θemergency * is calculated by multiplying the added value of the current target curvature Cuemergency * and the curvature Cu detected by the camera sensor 12 by the control gain Klca1, as shown in the following equation (21). .
θemergency * = Klca1 ・ (Cuemergency * + Cu) (21)

  The driving assistance ECU 10 transmits a steering command representing the target steering angle θemergency * to the EPS / ECU 20 every time the target steering angle θemergency * is calculated. When the EPS / ECU 20 receives the steering command, the EPS / ECU 20 drives and controls the steering motor 22 so that the steering angle follows the target steering angle θemergency *. In this embodiment, the driving assistance ECU 10 calculates the target rudder angle θemergency * as the target control amount, calculates the target torque for obtaining the target rudder angle θemergency *, and outputs a steering command representing the target torque to the EPS · You may transmit to ECU20.

  Hereinafter, the steering control using the target rudder angle θemergency * is referred to as yaw angle return control. In the yaw angle return control, the steering angle is controlled only by the feedforward control term using the added value of the target curvature Cuemergency * and the curvature Cu detected by the camera sensor 12. That is, feedback control using the yaw angle θy detected by the camera sensor 12 is not performed.

  Note that the driving assistance ECU 10 holds the value of the feedback control amount (the second term on the right side of the equation (15), calculated in the right side of the equation (15)) just before the time when the approaching vehicle is detected (time t1). (Fixed value) may be added to the right side of Equation (21) as part of the feedforward control amount during yaw angle return control.

  Subsequently, in step S44, the driving assistance ECU 10 determines whether the yaw angle return control has been completed. Completion of yaw angle return control is the timing (time t2 in FIG. 12) when the target curvature Cuemergency * becomes zero. If the yaw angle return control is not completed, the driving assistance ECU 10 returns the process to step S43 and performs the same process. By repeating such a process at a predetermined calculation cycle, the yaw angle is reduced at a high speed.

  The yaw angle also changes when the host vehicle is returned to the center position of the original lane by the LCA cancellation control, but in the case of the yaw angle angle return control, the maximum value Cumax and the maximum change gradient Cu ′ of the target curvature described above. By setting max, the speed decreases at a higher speed (that is, an emergency speed) than the change speed during the LCA cancellation control.

  When these processes are repeated and the yaw angle return control is completed (S44: Yes), the driving assistance ECU 10 advances the process to step S45. At this point, the yaw angle has been reduced to almost zero. That is, the lateral speed of the host vehicle is almost zero. Accordingly, the host vehicle can be prevented from moving toward the center in the width direction of the target lane, and collision avoidance with an approaching vehicle can be supported.

  In step S45, the driving assistance ECU 10 determines whether or not the progress of the lane change is about to be completed. In this case, based on the peripheral information obtained by the peripheral sensor 11, the driving assistance ECU 10 determines that the LCA remaining distance, which is the distance between the lateral position of the host vehicle and the final target lateral position (the center position in the width direction of the target lane), It is determined whether or not the threshold value is less than a preset completion threshold. The LCA remaining distance is represented by the absolute value of the lateral deviation Dy in the target lane of the host vehicle. For example, when the near-completion determination threshold is 0.5 m, the driving assistance ECU 10 detects that the absolute value of the lateral deviation Dy in the target lane of the host vehicle is 0.5 m or less, and the progress status of the lane change Is determined to be near completion.

  If the driving assistance ECU 10 determines that the progress status of the lane change is not close to completion (S45: No), the process proceeds to step 46, and if the progress status of the lane change is determined to be close to completion (S45: Yes). The process proceeds to step 47.

  First, the case where it is determined that the progress status of the lane change is not close to completion will be described.

In step S46, the driving assistance ECU 10 calculates a target track for moving the host vehicle from the current position (position of the host vehicle at the moment when the yaw angle return control is completed) to the center position of the original lane. Hereinafter, this target track is referred to as the original lane return target track. The function y (t) shown in Expression (2) is also used for the original lane return target track. A function representing the original lane return target trajectory is called an original lane return target trajectory function y (t). In calculating the original lane return target trajectory function y (t), the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of the function y (t) shown in Equation (2) are determined. In addition, the original lane return target trajectory calculation parameters are set as follows. The original lane return target track calculation parameters are the following seven (P21 to P27).
P21. Horizontal position of own vehicle at present time (when yaw angle return control is completed) P22. Lateral speed of own vehicle at present time (when yaw angle return control is completed) P23. Lateral acceleration of own vehicle at present time (when yaw angle return control is completed) P24. The target lateral position that is the target value of the lateral position to move the host vehicle (in this example, the center position of the original lane, hereinafter referred to as the original lane return completion target lateral position)
P25. The target lateral speed of the host vehicle when the host vehicle is moved to the original lane return complete target lateral position (referred to as the original lane return complete target lateral speed)
P26. Target lateral acceleration of the host vehicle when the host vehicle is moved to the original lane return complete target lateral position (referred to as the original lane return complete target lateral acceleration)
P27. Target time (referred to as original lane return target time) that is the target value of the time required to move the host vehicle from the current position to the original lane return complete target lateral position

  Here, the lateral position of the host vehicle at the present time (when the yaw angle return control is completed) is yreturn, the lateral speed is byyreturn, the lateral acceleration is ayreturn, and the time when the yaw angle return control is completed is newly set to t = 0, Let the original lane return target time be treturn. The original lane return target trajectory calculation parameters are y (0) = yreturn, y ′ (0) = byreturn, y ″ (0) = ayreturn, y (return) = W (signs are set according to the lane change direction) Y ′ (treturn) = 0 and y ″ (treturn) = 0.

  The lateral position yreturn, the lateral velocity vyreturn, and the lateral acceleration ayreturn are detected values at the present time, and can be calculated by a method similar to the method for obtaining the initial lateral state quantity described above. That is, the lateral position yreturn is the current lateral deviation Dy. The lateral speed vyreturn is obtained from the current vehicle speed v and the current yaw angle θy (byreturn = v · sin (θy)). The lateral acceleration ayreturn is a value (v · γ) obtained by multiplying the current yaw rate γ by the current vehicle speed v. Further, y (treturn) is the original lane return completion target lateral position and is set to the center position of the original lane. In this case, when the camera sensor 12 outputs the lane information of the original lane at the time when the yaw angle return control is completed, y (treturn) = 0. y ′ (treturn) represents the original lane return completion target lateral velocity, and y ″ (treturn) represents the original lane return completion target lateral acceleration, both of which are set to zero.

In addition, the original lane return target time treturn is calculated using the target time setting constant Areturn that is the same value as the target time setting constant A used when the target lane change time tlen is calculated at the start of LCA. 22).
treturn = Dreturn ・ Areturn (22)
Here, Dreturn is a necessary distance to move the host vehicle in the horizontal direction from the lateral position of the host vehicle at the time when the yaw angle return control is completed to the original lane return complete target lateral position (the center position of the original lane). When the yaw angle return control is completed, a collision with another vehicle is avoided. Therefore, since the speed at which the position of the host vehicle is moved to the side may be approximately the same as that of LCA, the target time setting constant Areturn is set to a value that is approximately the same as the target time setting constant A when performing LCA. .

Based on the set value of the original lane return target trajectory calculation parameter, the driving support ECU 10 uses the same method as in step S14 to calculate the coefficients c ₀ , c ₁ , c ₂ , c of the function y (t) shown in the equation (2). The values of c ₃ , c ₄ , and c ₅ are calculated. Then, by substituting the calculated coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ into equation (2), the original lane return target trajectory function y (t) is calculated.

  When the driving assistance ECU 10 calculates the original lane return target trajectory function in step S46, the process proceeds to step S48. In step S48, the driving assistance ECU 10 performs steering control based on the original lane return target trajectory function calculated in the previous step S46. In this case, the driving assistance ECU 10 resets the clock timer t (starts after clearing to zero), and from the elapsed time t after the yaw angle return control is completed and the original lane return target trajectory function y (t), the step Similar to S15, the target lateral motion state quantity (y *, vy *, ay *) and the target yaw state quantity (θy *, γ *, Cu *) are calculated to obtain the final target steering angle θreturn. Calculate *. The target rudder angle θreturn * can be calculated, for example, by replacing the left side of Equation (15) with θreturn *.

  When calculating the target control amount (target steering angle θreturn *), the driving assistance ECU 10 transmits a steering command representing the target control amount to the EPS / ECU 20. In the present embodiment, the driving assistance ECU 10 calculates the target rudder angle θreturn * as the target control amount, calculates the target torque for obtaining the target rudder angle θreturn *, and outputs a steering command representing the target torque to the EPS · You may transmit to ECU20.

  Subsequently, in step S49, the driving assistance ECU 10 determines whether or not a condition for ending the LCA approach warning control state is satisfied. In this case, when the driving support ECU 10 detects that the lateral position of the host vehicle has reached the original lane return completion target lateral position (the center position of the original lane) by the steering control in step S48, It is determined that the end condition is satisfied. Alternatively, the driving assistance ECU 10 may determine that the condition for ending the LCA approach warning control state is satisfied when it detects that the LCA approach warning control state has continued for a predetermined time.

  If the driving assistance ECU 10 determines that the termination condition for the LCA approach warning control state is not satisfied (S49: No), the process returns to step S48. Therefore, the steering control in step S48 is performed until the end condition for the LCA approach warning control state is satisfied. As a result, the host vehicle travels to the center position of the original lane.

  When such processing is repeated and the end condition of the LCA approach warning control state is satisfied, the driving assistance ECU 10 ends the LCA approach warning control routine. In this case, the main routine (steering support control routine) is also terminated. The functional part of the driving assistance ECU 10 that performs the processes of steps S46, S48, and S49 corresponds to the original lane return assistance control means of the present invention. The control process in which the host vehicle is returned to the original lane through steps S46, S48, and S49 is referred to as original lane return control. The former lane return control corresponds to the former lane return assist control in the present invention. When the original lane return control is finished, the driving assistance ECU 10 may advance the process to step S21 of the main routine and set the steering assistance control state to the LTA / ON state.

  FIG. 15 shows the original lane return target track when the host vehicle C1 and the other vehicle C3 approach each other in the latter half of the LCA state.

  Next, the case where it is determined in step S45 that the lane change is about to be completed (S45: Yes) will be described.

  In this case, the driving assistance ECU 10 advances the process to step S47. In step S47, the driving assistance ECU 10 calculates a target trajectory for maintaining the lateral speed of the host vehicle at zero. This target trajectory is called zero lateral velocity target trajectory. In this case, the target lateral position of the host vehicle that maintains the lateral speed at zero may be the actual lateral position at the present time (when the yaw angle return control is completed), but in the present embodiment, the peripheral monitoring result in step S19 Is set to the lateral position of the host vehicle when the steering assist control state is set to the LCA approach warning control state. This is to eliminate the influence of the overshoot that causes the host vehicle to move in the lane change direction due to the control response delay while the yaw angle return control is being performed. Accordingly, the target lateral position of the host vehicle is set to a position that is returned in the opposite lane change direction by the amount of overshoot from the lateral position when the yaw angle return control is completed.

The function y (t) shown in Equation (2) is also used for this zero lateral velocity target trajectory. A function representing a zero lateral velocity target trajectory is referred to as a zero lateral velocity target trajectory function y (t). In calculating the lateral velocity zero target trajectory function y (t), the coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ of the function y (t) shown in the equation (2) are determined. In addition, the zero lateral velocity target trajectory calculation parameter is set as follows. Zero lateral velocity target trajectory calculation parameters are the following seven (P31 to P37).
P31. Target lateral position of the vehicle at the present time (when the yaw angle return control is completed) (referred to as zero-keep starting target lateral position)
P32. Target lateral speed of the vehicle at the present time (when the yaw angle return control is completed) (referred to as zero keep start target lateral speed)
P33. Target lateral acceleration of the vehicle at the present time (when the yaw angle return control is completed) (referred to as zero-keep start target lateral acceleration)
P34. The target lateral position that is the target value of the lateral position to move the host vehicle (referred to as the zero-keep completion target position)
P35. Target lateral speed of the host vehicle when the host vehicle is moved to the zero keep completion target position (referred to as zero keep completion target lateral speed)
P36. Target lateral acceleration of the host vehicle when the host vehicle is moved to the zero-keep completion target position (referred to as zero-keep completion target lateral acceleration)
P37. Target time for moving the host vehicle from the zero-keep start target lateral position to the zero-keep completion target position (referred to as zero-keep target time)

  Here, the lateral position (detected value) of the host vehicle at the time when the steering assist control state is set to the LCA approach warning control state is set to yalert, and the time (current time) at which the yaw angle return control is completed is newly set to t = 0. And the zero keep target time is tzero. Hereinafter, yalert is referred to as a lateral position at the time of approach detection.

Both the zero-keep start target lateral position and the zero-keep completion target position are set to the lateral position yalert at the time of approach detection. Further, the zero keep start target lateral speed, the zero keep start target lateral acceleration, the zero keep completion target lateral speed, and the zero keep completion target lateral acceleration are all set to zero. Therefore, the lateral velocity zero target trajectory calculation parameter is set as follows.
y (0) = yalert
y ′ (0) = 0
y '' (0) = 0
y (tzero) = yalert
y ′ (tzero) = 0
y '' (tzero) = 0

The driving assistance ECU 10 uses the coefficients c ₀ , c ₁ , c ₂ , c2 of the function y (t) shown in Expression (2) in the same manner as in step S14 based on the set value of the zero-speed lateral trajectory calculation parameter. The values of c ₃ , c ₄ , and c ₅ are calculated. Then, by substituting the values of the calculated coefficients c ₀ , c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ into the equation (2), the zero lateral velocity target trajectory function y (t) is calculated. In this case, the lateral velocity zero target trajectory function y (t) is y (t) = yalert (constant value).

  For example, the zero keep target time tzero is set to 5 seconds. Accordingly, a zero lateral velocity target trajectory function y (t) that sets the target lateral position at yalert is set for 5 seconds.

  When the driving assistance ECU 10 calculates the zero lateral velocity target trajectory function in step S47, the process proceeds to step S48. In step S48, the driving assistance ECU 10 performs the steering control based on the zero lateral velocity target trajectory function calculated in the previous step S47. In this case, the driving assistance ECU 10 resets the clock timer t (starts after clearing to zero), and from the elapsed time t after the yaw angle return control is completed and the zero lateral velocity target trajectory function (t), step S15, Similarly, the target lateral motion state quantity (y *, vy *, ay *) is calculated and the target yaw state quantity (θy *, γ *, Cu *) is calculated to obtain the final target steering angle θzero *. Calculate. The target rudder angle θzero * can be calculated, for example, by replacing the left side of Equation (15) with θzero *.

  When calculating the target control amount (target steering angle θzero *), the driving assistance ECU 10 transmits a steering command representing the target control amount to the EPS / ECU 20. In the present embodiment, the driving assistance ECU 10 calculates the target rudder angle θzero * as the target control amount, calculates the target torque for obtaining the target rudder angle θzero *, and outputs a steering command representing the target torque to the EPS · You may transmit to ECU20.

  Subsequently, in step S49, the driving assistance ECU 10 determines whether or not a condition for ending the LCA approach warning control state is satisfied. In this case, the driving assistance ECU 10 determines whether or not the duration of the steering control in step S48 has reached the zero keep target time tzero. Alternatively, the driving support ECU 10 may determine that the termination condition for the LCA approach warning control state is satisfied when the abnormal approach state with the other vehicle is canceled based on the peripheral information. Alternatively, when the driver's steering operation is detected (for example, when the steering torque detected by the steering torque sensor exceeds the steering operation determination threshold), the driving assistance ECU 10 satisfies the LCA approach warning control termination condition. You may make it determine with having carried out.

  If the driving assistance ECU 10 determines that the termination condition for the LCA approach warning control state is not satisfied (S49: No), the process returns to step S48. Therefore, the steering control in step S48 is performed until the end condition for the LCA approach warning control state is satisfied. As a result, the host vehicle travels along the zero lateral speed target track. Accordingly, the yaw angle of the host vehicle is kept at zero, and the direction of the host vehicle (the longitudinal axis) is parallel to the lane formation direction. That is, it is possible to keep the state where the host vehicle is traveling in parallel with the lane.

  Accordingly, it is possible to secure time for handing over the steering wheel operation to the driver while assisting in avoiding a collision between the host vehicle and the other vehicle. The driver recognizes the necessity of steering operation by an approach warning. Therefore, while the host vehicle is traveling in parallel with the lane, it is possible to grasp the situation of other surrounding vehicles and start the steering operation.

  Here, the reason why the target lateral position (constant) in the lateral velocity zero target trajectory is set to the lateral position yalert at the time of approach detection will be described. When an approaching vehicle is detected in the latter half of the LCA state, yaw angle return control is performed. However, even if the yaw angle return control is performed, the host vehicle may travel in the lane change direction to some extent due to a response delay in the control. Therefore, in calculating the zero lateral speed target trajectory, the host vehicle at the time when the surrounding monitoring result in step S19 is determined to be “with approaching vehicle”, that is, when the steering assist control state is set to the LCA approach warning control state. Is set as the target lateral position.

  Therefore, when the steering control in step S48 is started, the host vehicle once returns to the lateral position yalert at the time of approach detection, and then parallel to the lane formation direction so as to maintain the lateral position yalert at the time of approach detection. Drive to. Thereby, safety can be further improved.

  When such processing is repeated and the end condition of the LCA approach warning control state is satisfied, the driving assistance ECU 10 ends the LCA approach warning control routine. In this case, the main routine (steering support control routine) is also terminated. The functional part of the driving support ECU 10 that performs the processes of steps S47, S48, and S49 corresponds to the lateral velocity zero control means of the present invention. Hereinafter, the control process in which the lateral position of the host vehicle is maintained at zero by steps S47, S48, and S49 is referred to as lateral speed zero control.

  FIG. 16 shows a zero lateral velocity target trajectory when the host vehicle C1 and another vehicle C3 approach in the latter half of the LCA state.

  According to the steering assist device of the present embodiment described above, the periphery monitoring is continued even after the LCA is started under the periphery monitoring, and the LCA is terminated halfway when an approaching vehicle is detected. Then, depending on the progress of the lane change at that time, the mode of steering assist control thereafter is switched. When an approaching vehicle is detected in the first half of the lane change, the steering operation is assisted to return the host vehicle to the center position in the lane width direction of the original lane. As a result, the host vehicle is returned to a preferred position for the driver while ensuring safety. Therefore, convenience can be improved.

  When an approaching vehicle is detected in the second half of the lane change, an approach warning is issued to the driver, and the steering angle is controlled so that the yaw angle of the host vehicle is quickly returned to the state immediately before the start of the LCA. Immediately before the start of LCA, LTA is performed. For this reason, the yaw angle is reduced to almost zero. Moreover, in the yaw angle return control, the steering angle is controlled only by feedforward control using the target steering angle θemergency * calculated based on the integral value of the target curvature Cu *.

  The yaw angle return control needs to be performed in as short a time as possible. For example, when the detected value of the camera sensor 12 is used to quickly change the rudder angle, if there is an error in the detected value of the camera sensor 12, the rudder angle changes quickly in the wrong direction. End up making the driver feel uncomfortable. Further, when feedback control is performed using the yaw angle θy detected by the camera sensor 12, a target control amount is set by detecting a change in the behavior of the vehicle, so that a control delay occurs. Therefore, in this embodiment, the yaw angle can be quickly reduced toward zero by returning the yaw angle to the state immediately before the start of the LCA by feedforward control based on the integral value of the target curvature Cu *. . Thereby, the lateral speed of the own vehicle can be reduced in a short time. Accordingly, the host vehicle can be quickly prevented from moving to the center side in the width direction of the target lane, and the collision avoidance with the approaching vehicle can be supported (support for reducing the possibility of the collision). it can. The feedforward control amount includes a component of curvature Cu (Klca1 · Cu) representing the curve shape of the road. This component is a control amount that causes the host vehicle to travel along the road shape, and its change is Since it is extremely gradual, it does not adversely affect yaw angle return control.

  When the yaw angle return control is completed, it is determined whether or not the lane change is about to be completed. The driver performs a lane change support request operation with the intention of changing the lane. Therefore, steering assistance that meets the demands of the driver as much as possible is required. Therefore, in this embodiment, when the yaw angle return control is completed, the original lane return control is performed if the lane change is not completed, and the lateral speed zero control is performed if the lane change is just completed. .

  When the original lane return control is performed, the original lane return target track for returning the host vehicle to the center position of the original lane is calculated, and the steering angle is controlled so that the host vehicle moves along the original lane return target track. The Therefore, the host vehicle can be returned to a safer position and a preferable position for the driver.

  In addition, when the original lane return control is performed at a timing when the lane change is completed in a short time, the driver feels bothered and inconvenient. Therefore, when the lane change is about to be completed at the time when the yaw angle return control is completed, the lateral speed zero control is performed. Thereby, the own vehicle is maintained in the lateral position when the approach is detected. Accordingly, it is possible to secure time for handing over the steering wheel operation to the driver while assisting in avoiding a collision between the host vehicle and the other vehicle. Therefore, the driver can move the host vehicle to an appropriate position by operating his / her steering wheel while the host vehicle is traveling in parallel with the lane.

  Further, the target lateral position in the zero lateral velocity target trajectory is set to the lateral position (actual lateral position) of the own vehicle at the time when the peripheral monitoring result is determined to be “with approaching vehicle” in the latter half of the LCA state, so the yaw angle Even if a response delay of the return control occurs, the host vehicle can be maintained in an appropriate lateral position.

  The lateral velocity zero control is started when the yaw angle is reduced to zero by the yaw angle return control. Therefore, the switching from the yaw angle return control to the lateral speed zero control can be performed smoothly.

  Thus, according to the present embodiment, safety and convenience can be improved even when an approaching vehicle is detected in the second half of the lane change.

  In addition, as for the threshold value of the collision time TTC used for determining whether there is an approaching vehicle, the second half threshold value TTC2 is set to a smaller value than the first half threshold value TTC1. For this reason, in the first half of the LCA, when another vehicle that may abnormally approach the host vehicle is detected, the LCA can be completed with a margin in a state where safety is ensured. On the other hand, in the latter half of the LCA state, it is possible to prevent emergency operation support for collision avoidance more than necessary. Therefore, it is possible to prevent the LCA from being stopped halfway more than necessary, and the convenience can be improved.

  In addition, not only when the LCA is completed, but also when the LCA cancellation control state ends and when the original lane return control ends, the target lateral speed and target lateral acceleration of the host vehicle are set to zero. Can travel stably along the lane center line CL.

<Modification 1>
In the present embodiment, the target lateral position in the zero lateral velocity target trajectory is set to the lateral position (actual lateral position) of the host vehicle at the time when the peripheral monitoring result is determined as “with approaching vehicle” in the latter half of the LCA state. . For this reason, when the lateral speed zero control is performed, the host vehicle travels in parallel with the lane at a position returned in the opposite lane change direction from the lateral position at the time when the yaw angle return control is completed. In this case, if the return amount in the anti-lane change direction is large, the driver may feel uncomfortable. In addition, the driver's request (change lane) cannot be met.

  Therefore, in the first modification, the deviation between the lateral position of the host vehicle at the time when the surrounding monitoring result is determined to be “with approaching vehicle” and the lateral position when the yaw angle return control is completed is the upper limit value in the latter half of the LCA state. The zero keep completion target position is set to be as follows. This deviation is called zero-keep deviation. The zero-keep deviation corresponds to the amount of overshoot that the host vehicle has moved in the lane change direction during yaw angle return control. If the zero-keep deviation is equal to or less than the upper limit value, the driving assistance ECU 10 sets the zero-keep completion target position to the lateral position at the completion of the yaw angle return control. On the other hand, when the zero-keep deviation exceeds the upper limit value, the driving assistance ECU 10 sets the zero-keep completion target position that is moved in the opposite lane change direction by the upper limit value from the lateral position at the completion of the yaw angle return control. .

  According to this modification, the convenience is further improved.

<Modification 2>
Regarding the yaw angle return control, in this embodiment, control is performed to return the yaw angle to the state immediately before the start of LCA using the inverted integral value. However, it is not always necessary to use the inverted integral value. For example, in step S42 of the routine shown in FIG. 7, the driving assistance ECU 10 calculates a target steering angle in a direction in which the yaw angle (absolute value) is reduced using the maximum steering angle allowed in the steering assistance device. In this case, the driving assistance ECU 10 may calculate the target steering angle based on the maximum value Cumax of the target curvature and the maximum change gradient Cu′max of the target curvature, as in the above embodiment. In step S43, the driving assistance ECU 10 transmits a steering command representing the target steering angle to the EPS / ECU 20.

  In step S44, the driving assistance ECU 10 determines whether the yaw angle θy detected by the camera sensor 12 has become zero or whether the sign (positive / negative) of the yaw angle θy has been reversed. The driving assistance ECU 10 determines that the yaw angle return is completed when the yaw angle θy becomes zero or when the sign of the yaw angle θy is reversed (S44: Yes). This modification 2 is preferably applied when the high-precision camera sensor 12 is mounted.

<Modification 3>
In the LCA approach warning control routine (S40) of the present embodiment, when the steering assist control state is set to the LCA approach warning control state, the yaw angle return control is first performed and the yaw angle return control is completed. Based on the remaining LCA distance, a determination is made as to whether or not the progress of the lane change is about to be completed. Instead, whether or not the progress of the lane change is about to be completed when the steering assist control state is set to the LCA approach warning control state (that is, when an approaching vehicle is detected in the latter half of the LCA state). A configuration in which the determination is performed may be used.

  For example, in the third modification, steps S42 to S44 are omitted in the LCA approach warning control routine (S40). Therefore, yaw angle return control is omitted. However, the warning process for the driver in step S42 is performed.

  In this case, for the set values of the parameters P21, P22, and P23 set in the calculation of the original lane return target track (S46), the host vehicle at the present time (when the steering assist control state is set to the LCA approach warning control state) The detected values of the lateral position, lateral velocity, and lateral acceleration are set in the same manner as in the embodiment. Further, the original lane return target time treturn of the parameter P27 is set to a short time for emergency collision avoidance. That is, the target time setting constant Areturn is set to a value smaller than the value of the embodiment. Therefore, when the original lane return control is performed, the steering angle is controlled so that the host vehicle is quickly returned to the original lane.

  The set values of the parameters P31 to P37 set in the calculation of the zero lateral velocity target trajectory (S47) are the same as in the embodiment.

  Even if the original lane return control or the lateral speed zero control is performed, at the beginning of the start, the host vehicle moves (overshoots) in the lane change direction due to the response delay of the control. Therefore, in step S45, the driving support ECU 10 considers this overshoot amount (the distance that the host vehicle moves in the lane change direction due to the control response delay), and determines whether or not the progress of the lane change is about to be completed. Judge about. That is, the driving assistance ECU 10 calculates a position (overshoot-considered lateral position) in which the lateral position of the host vehicle is moved in the lane change direction by the overshoot amount (estimated value) at the current position of the host vehicle (the time of determination in step S45). The remaining LCA distance, which is the distance between the overshoot-considered lateral position and the final target lateral position, is calculated.

  If the LCA remaining distance is equal to or less than the near completion threshold, the driving support ECU 10 determines that the progress of the lane change is just before completion. For example, the estimated value of the overshoot amount may be set to a value proportional to the lateral speed vy based on the lateral speed vy of the host vehicle.

  The steering assist device according to this embodiment and the modification has been described above, but the present invention is not limited to the above-described embodiment and modification, and various modifications can be made without departing from the object of the present invention. is there.

  For example, in the above-described embodiment, in the LCA approach warning control state, the final target lateral position is set to the center position of the original lane, but it is not always necessary to set the position in the original lane. Any lateral position may be used.

  Moreover, in the said embodiment, although it is a premise for implementing LCA that steering assistance control state is a LTA * ON state (state in which LTA is implemented), such a premise is not necessarily do not need. Further, there may be no assumption that ACC is being implemented. In the present embodiment, the LCA is performed on the condition that the road on which the host vehicle is traveling is an automobile-only road, but such a condition is not necessarily provided.

  Moreover, in the said embodiment, although comprised so that a lane may be recognized by the camera sensor 12, you may detect the relative positional relationship of the own vehicle with respect to a lane by navigation ECU70, for example.

  DESCRIPTION OF SYMBOLS 10 ... Driving assistance ECU, 11 ... Peripheral sensor, 12 ... Camera sensor, 20 ... EPS / ECU, 21 ... Motor driver, 22 ... Steering motor, 40 ... Steering ECU, 41 ... Turn signal lever, 80 ... Vehicle state sensor, 90: Driving operation state sensor, CL: Lane center line, WL: White line, Cu: Curvature, Dy: Lateral deviation, θy: Yaw angle, y (t): Target trajectory function.

Claims (1)

Perimeter monitoring means for monitoring the surroundings of the own vehicle;
Lane recognition means for recognizing a lane and acquiring lane information including a relative positional relationship of the host vehicle with respect to the lane;
When no other vehicle that interferes with the vehicle's lane change has been detected by the surrounding monitoring means, the lane change support request is used to determine from the original lane on which the vehicle is currently traveling according to the lane information. A lane change support control means for starting lane change support control for controlling the steering so as to change the lane toward the target lane adjacent to the original lane,
A lane that stops the lane change support control when an approaching vehicle that may abnormally approach the host vehicle when the lane change support control is continued is detected by the periphery monitoring unit during the lane change support control. Change support stop means,
Informing means for informing the driver of the midway stop of the lane change support control;
When the approaching vehicle is detected and the lane change assist control is stopped while the host vehicle is traveling in the target lane, the steering is performed so that the host vehicle is returned from the target lane to the original lane. Original lane return assistance control means for performing original lane return assistance control to be controlled;
When the approaching vehicle is detected, progress status determining means for determining whether or not the lane change by the lane change support control is about to be completed,
When the progress status determining means determines that the lane change is about to be completed, the original lane returning support control by the original lane returning support control means is prohibited, and the speed in the lane width direction of the host vehicle A steering assist device comprising: zero lateral velocity control means for performing lateral velocity zero control for controlling steering so that the lateral velocity is maintained at zero.

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