JP6662188B2 - Driving support method and driving support device - Google Patents

Description

  The present invention relates to a driving support method and a driving support device.

As a technique for running a vehicle employing a steer-by-wire (SBW: Steer-By-Wire) in which a steering wheel and steered wheels are mechanically separated from each other on a target traveling track, for example, a technique described in Patent Document 1 is known. ing.
The vehicle steering control device described in Patent Literature 1 increases the steering reaction force applied to a driver's steering operation in a direction away from the target travel trajectory as the vehicle moves away from the target travel trajectory.

JP 2010-030504 A

If the steering reaction force increases as the vehicle moves away from the target traveling trajectory, the steering reaction force while the vehicle travels on the target traveling trajectory becomes relatively small. For this reason, when the vehicle is traveling on the target traveling trajectory and the driver does not perform the steering operation, if steering unintended by the driver is input to the steering wheel, the vehicle is traveling away from the target traveling trajectory. The steering angle may be more likely to fluctuate than in the case. For this reason, there is a possibility that the steered wheels are steered in accordance with the change in the steering angle, and are likely to deviate from the target traveling trajectory.
The present invention is directed to a vehicle that increases a steering reaction force applied to a steering wheel in a direction to return the vehicle to the target travel trajectory as the vehicle departs from the target travel trajectory. It is an object of the present invention to suppress a change in the turning angle due to unsteering.

  In the driving support method according to one aspect of the present invention, the steering provided to the steering wheel in a direction of returning the vehicle to the target traveling trajectory as the deviation of the vehicle including the steer-by-wire steering mechanism from the target traveling trajectory increases. Increase the reaction force. Then, when the deviation is smaller than when the vehicle deviates from the target traveling trajectory is larger, the responsiveness of turning the steered wheels to the steering of the steering wheel is reduced.

  According to the present invention, in a vehicle that increases the steering reaction force applied to the steering wheel in a direction to return the vehicle to the target traveling trajectory as the vehicle departs from the target traveling trajectory, a driver while the vehicle is traveling on the target traveling trajectory Can suppress a change in the turning angle due to unintended steering.

FIG. 2 is a block diagram illustrating a configuration example of a steering system of a vehicle equipped with the driving support device. FIG. 3 is a block diagram illustrating a configuration example of a steering control unit. FIG. 4 is a block diagram illustrating a configuration example of a differential steer gain setting unit. FIG. 9 is an explanatory diagram of a setting example of a differential steer gain. It is a block diagram showing an example of composition of a lane keep (LK) command turning angle calculation part. It is a block diagram showing the example of a structure of a 1st repulsion calculation part. It is a block diagram showing the example of a structure of a 2nd repulsion calculation part. It is a block diagram showing the example of a structure of a reaction force control part. FIG. 3 is a block diagram illustrating a configuration example of an offset amount calculation unit. FIG. 4 is a block diagram illustrating a configuration example of a reaction torque correction value calculation unit. It is explanatory drawing of an example of the lateral position-reaction map used for calculation of the reaction force N_THW according to a lateral position. It is explanatory drawing of an example of a lane arrival time-reaction map used for calculation of reaction force N_TLC according to a lane arrival time. It is a flowchart showing the whole of an example of a driving assistance method. It is a flowchart showing an example of the setting process of the differential steer gain.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
Please refer to FIG. The vehicle equipped with the driving support device according to the present embodiment includes a steering unit 1, a turning unit 2, a backup clutch 3, and an SBW controller 4. The vehicle includes an SBW-type steering mechanism in which a steering unit 1 that receives a driver's steering input and a steering unit 2 that steers left and right front wheels 5FL and 5FR, which are steered wheels, are mechanically separated.

The steering unit 1 includes a steering wheel 1a, a column shaft 1b, a steering torque sensor 1c, a reaction motor 1d, a reaction motor drive circuit 1e, a steering angle sensor 1f, and a current sensor 1g.
The steering wheel 1a rotates in response to a driver's steering input.
The column shaft 1b rotates integrally with the steering wheel 1a.
The steering torque sensor 1c detects a steering torque transmitted from the steering wheel 1a to the column shaft 1b. This steering torque sensor 1c detects a steering torque by detecting, for example, a torsional angle displacement of a torsion bar with a potentiometer. The steering torque sensor 1c outputs the detected steering torque to the SBW controller 4.

The reaction force motor 1d has an output shaft arranged coaxially with the column shaft 1b. The reaction motor 1d outputs a steering reaction torque to be applied to the steering wheel 1a to the column shaft 1b in accordance with a command current output from the reaction motor driving circuit 1e.
The reaction motor driving circuit 1e is a torque for matching the actual steering reaction torque estimated from the current value of the reaction motor 1d detected by the current sensor 1g with the command steering reaction torque output from the SBW controller 4. The feedback controls the command current output to the reaction motor 1d.
The steering angle sensor 1f detects the rotation angle of the column shaft 1b, that is, the steering angle (handle angle) of the steering wheel 1a. Then, the steering angle sensor 1f outputs the detected steering angle to the SBW controller 4.

The steered unit 2 includes a pinion shaft 2a, a steering gear 2b, a steered motor 2c, a steered motor drive circuit 2d, a steered angle sensor 2e, a rack gear 2f, and a rack 2g.
The steering gear 2b steers the left and right front wheels 5FL and 5FR in accordance with the rotation of the pinion shaft 2a. As the steering gear 2b, for example, a rack and pinion type steering gear or the like may be adopted.

The steering motor 2c has an output shaft connected to the rack gear 2f via a speed reducer. The turning motor 2c outputs a turning torque for turning the left and right front wheels 5FL, 5FR to the rack 2g according to a command current output from the turning motor drive circuit 2d. For example, the steering motor 2c may be a brushless motor or the like.
The turning angle sensor 2e detects the turning angle of the turning motor 2c, and detects the turning angles of the left and right front wheels 5FL and 5FR based on the detected turning angle.
The turning motor drive circuit 2d controls the command current to the turning motor 2c by angle feedback that matches the actual turning angle detected by the turning angle sensor 2e with the command turning angle from the SBW controller 4. I do. The command turning angle output from the SBW controller 4 to the turning motor drive circuit 2d is an example of a target turning angle that is a target turning angle of the steered wheels controlled by the SBW controller 4.

The backup clutch 3 is provided between the column shaft 1b and the pinion shaft 2a. The backup clutch 3 mechanically disconnects the steering unit 1 and the steering unit 2 when the backup clutch 3 is released, and mechanically connects the steering unit 1 and the steering unit 2 when the backup clutch 3 is engaged.
Further, the vehicle includes a camera 6 and a vehicle speed sensor 7.
The camera 6 detects an image of a traveling path ahead of the vehicle. The camera 6 outputs the detected image to the SBW controller 4.
The vehicle speed sensor 7 detects the vehicle speed of the vehicle. The vehicle speed sensor 7 outputs the detected vehicle speed to the SBW controller 4.

The SBW controller 4 includes a steering angle sensor 1f, a steering torque sensor 1c, a current sensor 1g, a steering angle, a steering torque output from the camera 6, and a vehicle speed sensor 7, a current value of a reaction motor 1d, and a current value of a road ahead of the vehicle. Receive images and vehicle speed. For example, the SBW controller 4 is an electronic control unit (ECU: Electronic Control Unit) including a CPU (Central Processing Unit) and CPU peripheral components such as a ROM (Read Only Memory) and a RAM (Random Access Memory). Good.
The SBW controller 4 may receive the steering angle, the steering torque, the current value of the reaction motor 1d, the image of the traveling road, and the vehicle speed via a controller area network (CAN) bus.

The SBW controller 4 includes an image processing unit 11, a vehicle state setting unit 12, a control state setting unit 13, a turning control unit 14, and a reaction force control unit 15. The CPU of the SBW controller 4 executes a computer program stored in a storage medium to execute an image processing unit 11, a vehicle state setting unit 12, a control state setting unit 13, a steering control unit 14, and a reaction force control unit. Then, the following processing performed by step 15 is executed.
The image processing unit 11, the vehicle state setting unit 12, the control state setting unit 13, the turning control unit 14, and the reaction force control unit 15 may be independent circuits or devices.

The image processing unit 11 performs image processing such as edge extraction on the image of the traveling road ahead of the vehicle acquired from the camera 6, so that the left and right traveling lane dividing lines of the traveling lane on which the vehicle travels, that is, the road white line, To detect. In practice, the road segmentation line may be a yellow line or a broken line.
In addition, when there is no road white line or it is difficult to detect it, road shoulders, curbs, gutters, guard rails, protective fences, soundproof walls, retaining walls, median strips, etc. are detected as travel road division lines instead of road white lines. You may make it.
The image processing unit 11 outputs the detection results of the left and right lane markings of the traveling lane to the vehicle state setting unit 12 and the reaction force control unit 15. Hereinafter, the detection results of the lane markings on the left and right of the traveling lane may be referred to as “white line information”.
In addition, the image processing unit 11 outputs a determination result as to whether or not to detect the lane marking to the control state setting unit 13.

The vehicle state setting unit 12 receives a steering torque, a vehicle speed, and a turn signal operation signal via a CAN bus. Further, the vehicle state setting unit 12 receives white line information from the image processing unit 11.
The vehicle state setting unit 12 controls the steering control by the steering control unit 14, the steering reaction force control by the reaction force control unit 15, the lane keeping (lane keeping (LK: LK)) based on the steering torque, the vehicle speed, the blinker operation signal, and the white line information. Lane Keep)) Calculate the following variables used for support control.

In the steering control, the steering angle is controlled according to the steering angle and the steering angular speed of the steering wheel 1a that is steered by the driver.
In the steering reaction force control, the steering reaction force applied to the steering wheel 1a is controlled according to the steering angle or the turning angle.
In the LK support control, the steering control unit 14 controls the steering angle in accordance with the lateral position and the yaw angle of the vehicle in addition to the steering angle and the steering angular speed of the steering wheel 1a that is steered by the driver. The steered wheels are steered in a direction to return the vehicle to the target traveling trajectory. The target traveling trajectory may be, for example, the center of the traveling lane in which the vehicle travels, or a trajectory separated from the center by a predetermined distance.

Here, as the lateral position of the vehicle, a lateral distance between a planned position to be reached when the vehicle travels forward from the current position for a predetermined delay time (for example, 0.5 seconds) and the target traveling trajectory is used. Good. Further, as the yaw angle, a yaw angle between the white line of the road and the traveling direction of the vehicle when a predetermined delay time has elapsed is used.
In the following description, the travel distance when the vehicle travels forward by a predetermined delay time may be referred to as “scheduled travel distance”. In addition, a scheduled position reached when the vehicle travels forward from the current position by a predetermined delay time, that is, when the vehicle travels from the current position for a predetermined travel distance, may be referred to as a “scheduled arrival position”. The lateral distance between the scheduled arrival position and the target traveling trajectory is simply referred to as “lateral position”.

  In the LK support control, when the vehicle deviates from the target traveling trajectory, the reaction force control unit 15 applies a steering reaction force in a direction of returning the vehicle to the target traveling trajectory to the steering wheel 1a. The reaction force control unit 15 increases the steering reaction force in accordance with at least one of the lateral position of the vehicle and the lane arrival time as the amount of deviation of the vehicle from the target traveling trajectory increases. Here, the lane arrival time is the time required for the vehicle to reach the road white line.

In the following description, the steering reaction force applied by the reaction force control unit 15 in the LK support control, that is, the steering reaction force in the direction of returning the vehicle to the target traveling trajectory may be referred to as “LK steering reaction force”. .
When the vehicle is traveling on the target traveling track and there is no steering operation by the driver, the LK steering reaction force is small. For this reason, the vehicle body shakes, for example, when the vehicle travels on unevenness of the road surface or on pebbles, and the steering angle fluctuates when steering unintended by the driver is input to the steering wheel 1a due to a change in the posture of the driver. May be easier. For this reason, there is a possibility that the left and right front wheels 5FL and 5FR are steered in accordance with the change in the steering angle, so that the left and right front wheels 5FL and 5FR are easily deviated from the target traveling trajectory.

Therefore, in the LK support control, when the deviation amount is smaller than when the vehicle deviates from the target traveling trajectory is larger, the turning control unit 14 determines that the steering response of the left and right front wheels 5FL and 5FR to the steering of the steering wheel 1a. To reduce the nature.
As described above, when the deviation from the target travel trajectory is small, the response of the steering to the steering is reduced, so that the vehicle travels near the target travel trajectory and the LK steering reaction force is small, and the driver does not intend to perform steering. Even if the operation is performed, the change in the turning angle can be suppressed.

The vehicle state setting unit 12 includes a gain calculation unit 12a, a yaw angle calculation unit 12b, a lateral position calculation unit 12c, a lane arrival time calculation unit 12d, a steering intention determination unit 12e, and a differential steer gain setting unit 12f. .
The gain calculator 12a includes a first vehicle speed sensitive gain, a second vehicle speed sensitive gain, a third vehicle speed sensitive gain, a fourth vehicle speed sensitive gain, a gain according to a turn signal operation, a first vehicle speed sensitive rate limiter, and a second vehicle speed sensitive rate. Calculate the limiter.
The first vehicle speed sensitive gain is a gain that increases or decreases the amount of change in the turning angle that changes according to the lateral position of the vehicle in the LK support control according to the vehicle speed.

The second vehicle speed sensitive gain is a gain that increases or decreases the amount of change in the steering angle that changes according to the yaw angle when a predetermined delay time has elapsed in the LK support control according to the vehicle speed.
The third vehicle speed sensitive gain is a gain that increases or decreases the amount of change in the turning angle that changes according to the steering angular speed of the steering wheel 1a according to the vehicle speed.
The fourth vehicle speed sensitive gain is a gain that increases or decreases the steering reaction force applied to the steering wheel 1a according to at least one of the lateral position of the vehicle and the lane arrival time in the LK support control according to the vehicle speed.
The gain calculation unit 12a calculates the first to fourth vehicle speed-sensitive gains based on a vehicle speed-sensitive gain map that determines a relationship between a predetermined vehicle speed and the first to fourth vehicle speed-sensitive gains, respectively. For example, in the vehicle speed sensitive gain map, the gain becomes the maximum value between the vehicle speed of zero and the first vehicle speed threshold, decreases as the vehicle speed increases from the first vehicle speed threshold to the second vehicle speed threshold, and the vehicle speed becomes the minimum at the second vehicle speed threshold. The map may be a value (for example, 0).

The gain according to the turn signal operation is given according to the lateral position of the vehicle and the amount of change given to the steering angle in accordance with the yaw angle when a predetermined delay time has elapsed in the LK support control, and according to the lateral position of the vehicle and the lane arrival time. This is a gain that suppresses the steering reaction force during the turn signal operation.
The gain according to the turn signal operation becomes 0, for example, after a lapse of a fixed time (for example, 3 seconds) from the start of the turn signal operation.

The first vehicle speed-sensitive rate limiter is an upper limit value for limiting the change speed of the turning angle changed in the LK support control, and the second vehicle speed-sensitive rate limiter limits the change speed of the steering reaction force changed in the LK support control. Is the upper limit. The vehicle state setting unit 12 sets these upper limits smaller when the vehicle speed is higher than when the vehicle speed is lower.
The gain calculating unit 12a outputs the first to third vehicle speed sensitive gains, the gain according to the turn signal operation, and the first vehicle speed sensitive rate limiter to the turning control unit 14.
The gain calculation unit 12a outputs the fourth vehicle speed sensitive gain, the gain according to the turn signal operation, and the second vehicle speed sensitive rate limiter to the reaction force control unit 15.

The yaw angle calculation unit 12b calculates a yaw angle between the road white line and the traveling direction of the vehicle based on the white line information output by the image processing unit 11. The yaw angle calculation unit 12b calculates a yaw angle when a predetermined delay time has elapsed based on the white line information and the yaw rate generated in the vehicle. The yaw angle calculator 12b outputs the calculated yaw angle to the lateral position calculator 12c and the lane arrival time calculator 12d. In addition, the yaw angle calculation unit 12b outputs the yaw angle when a predetermined delay time has elapsed to the steering control unit 14.
The lateral position calculator 12c calculates the lateral position of the vehicle. The lateral position calculation unit 12c calculates the expected travel distance by multiplying the predetermined delay time by the vehicle speed. The lateral position calculator 12c calculates the lateral position by multiplying the planned traveling distance by the yaw angle and adding the result to the distance from the target traveling trajectory. The lateral position calculation unit 12c outputs the calculated lateral position to the steering control unit 14 and the reaction force control unit 15.

The lane arrival time calculator 12d calculates the lane arrival time. The lane arrival time calculator 12d calculates the lateral speed by multiplying the vehicle speed by the yaw angle. The lane arrival time calculation unit 12d calculates the lane arrival time by dividing the distance to the road white line by the lateral speed. The lateral position calculation unit 12c outputs the calculated lane arrival time to the reaction force control unit 15.
The steering intention determination unit 12e determines the presence or absence of the driver's steering intention according to the steering torque detected by the steering torque sensor 1c. For example, the steering intention determination unit 12e determines that there is a steering intention when the steering torque is equal to or greater than the threshold, and determines that there is no steering intention when the steering torque is less than the threshold. The steering intention determining unit 12e outputs the result of determining the steering intention to the control state setting unit 13.

  The differential steer gain setting section 12f sets a differential steer gain used for differential steering control. Differential steering control adds a steering amount corresponding to the steering angular velocity to a steering angle determined according to the steering angle, thereby compensating for a delay in the driver's steering operation and increasing the responsiveness of the vehicle yaw motion. Control. The differential steer gain setting unit 12f outputs the differential steer gain to the steering control unit 14. Details of the differential steer gain setting unit 12f will be described later.

  The control state setting unit 13 receives a vehicle speed, a blinker operation signal, a lateral acceleration detection signal, an SBW system abnormality detection signal, a brake lamp lighting signal, and an on / off signal of a lane keep switch via a CAN bus. In addition, the control state setting unit 13 receives a vehicle dynamics control (VDC) activation signal and an antilock brake system (ABS) activation signal via a CAN bus.

Further, the control state setting unit 13 receives from the image processing unit 11 the white line information and the determination result as to whether or not the lane marking can be detected. Further, the control state setting unit 13 receives a determination result of the driver's steering intention from the steering intention determination unit 12e.
The control state setting unit 13 sets the LK support control flag to ON when all of the following LK support control permission conditions (A1) to (A10) are satisfied. The control state setting unit 13 turns off the LK support control flag when any of the following LK support control permission conditions (A1) to (A10) is not satisfied.

(A1) The lane keep switch is on.
(A2) The left and right traveling lane markings of the traveling lane are detected.
(A3) The vehicle speed is equal to or higher than the threshold.
(A4) The turn signal is not operating.
(A5) No abnormality of the SBW system is detected.
(A6) The road curvature is smaller than the threshold.
(A7) The lateral acceleration is smaller than the threshold.
(A8) Neither VDC nor ABS is operating.
(A9) The brake lamp is not lit.
(A10) There is a driver's steering intention.
The control state setting unit 13 outputs an LK support control flag to the steering control unit 14 and the reaction force control unit 15.

  The turning control unit 14 receives a steering angle and a vehicle speed via a CAN bus. Further, the turning control unit 14 receives the first to third vehicle speed sensitive gains, the gain according to the turn signal operation, and the first vehicle speed sensitive rate limiter from the gain calculating unit 12a. Further, the steering control unit 14 receives the lateral position of the vehicle and the yaw angle when a predetermined delay time has elapsed from the lateral position calculation unit 12c and the yaw angle calculation unit 12b, respectively. The turning control unit 14 receives the differential steer gain from the differential steer gain setting unit 12f.

The turning control unit 14 calculates a command for controlling the turning angles of the left and right front wheels 5FL, 5FR based on the received information.
When the LK support control flag is off, the turning control unit 14 outputs the basic command turning angle calculated based on the steering angle and the steering angular velocity to the turning motor drive circuit 2d as the command turning angle. That is, the steering control unit 14 steers the left and right front wheels 5FL and 5FR, which are steered wheels, in accordance with the steering operation of the steering wheel 1a by the driver. Further, the turning control unit 14 performs differential steering control based on the steering angular velocity.

When the LK support control flag is on, the turning control unit 14 turns the LK command to turn the vehicle in the direction to return the vehicle to the target traveling trajectory in accordance with the lateral position of the vehicle and the yaw angle when a predetermined delay time has elapsed. Calculate the steering angle. The turning control unit 14 outputs a command turning angle obtained by adding the LK command turning angle to the basic command turning angle to the turning motor drive circuit 2d.
That is, the turning control unit 14 turns the left and right front wheels 5FL and 5FR in accordance with the steering operation of the steering wheel 1a by the driver, and turns the left and right front wheels 5FL and 5FR in a direction to return the vehicle to the target traveling path. .

  The reaction force control unit 15 receives a steering angle and a vehicle speed via a CAN bus. Further, the reaction force control unit 15 receives the fourth vehicle speed sensitive gain, the gain according to the turn signal operation, and the second vehicle speed sensitive rate limiter from the gain calculating unit 12a. Further, the turning control unit 14 receives the white line information, the lateral position, and the lane arrival time from the image processing unit 11, the lateral position calculation unit 12c, and the lane arrival time calculation unit 12d, respectively.

The reaction force control unit 15 calculates a command steering reaction torque for controlling the steering reaction torque applied to the column shaft 1b based on the received information.
When the LK support control flag is OFF, the reaction force control unit 15 calculates the rack axial force according to the steering angle or the turning angle, and outputs the target reaction torque calculated based on the rack axial force to the command steering reaction force. The torque is output to the reaction motor drive circuit 1e.

When the LK support control flag is ON, the reaction force control unit 15 offsets the rack axial force calculated in accordance with the steering angle or the turning angle in accordance with the vehicle speed and the road curvature, and thereby adjusts the rack axial force in accordance with the road curvature. To generate a reaction force for maintaining the steering angle. The reaction force control unit 15 calculates a target reaction force torque based on the rack axial force after the offset.
When the LK support control flag is on, the reaction force control unit 15 corrects the target reaction torque according to the lateral position and the lane arrival time, and thereby the LK steering reaction in the direction of returning the vehicle to the target traveling trajectory. Generate force.

The reaction force control unit 15 outputs the corrected target reaction torque to the reaction motor drive circuit 1e as a command steering reaction torque.
Here, the reaction control unit 15 increases the steering reaction according to at least one of the lateral position of the vehicle and the lane arrival time as the deviation of the vehicle from the target traveling trajectory increases. Therefore, when the vehicle is traveling on the target traveling path and there is no steering operation by the driver, the LK steering reaction force is small.
For this reason, the vehicle body shakes, for example, when the vehicle travels on unevenness of the road surface or on pebbles, and the steering angle fluctuates when steering unintended by the driver is input to the steering wheel 1a due to a change in the posture of the driver. May be easier.

Here, the responsiveness of the vehicle yaw motion is improved by the steering control unit 14 performing the differential steering control, and thus the straightness is reduced in response to such a steering input unintended by the driver. There is a fear.
For this reason, when the LK support control flag is ON, when the deviation amount is smaller than when the deviation amount is large, the steering amount added by the differential steering control is also reduced, so that the steering angle can be reduced. Suppress fluctuations. That is, when the deviation amount is smaller than when the deviation amount is large, the steering amount calculated for the same steering angular velocity is reduced. In other words, the steering amount calculated for the steering angular velocity when the deviation amount is small is smaller than the steering amount calculated for the same steering angular velocity as the steering angular velocity when the deviation amount is large.

Please refer to FIG. The turning control section 14 includes a gain multiplying section 20, a steering angular velocity calculating section 21, a differential steer gain multiplying section 22, an LK command turning angle calculating section 23, a multiplier 24, and an adder 25.
The gain multiplication unit 20 multiplies the steering angle detected by the steering angle sensor 1f by a gain and outputs the result to the adder 25.
The steering angular velocity calculator 21 calculates the steering angular velocity of the steering wheel 1a based on the steering angle detected by the steering angle sensor 1f, and outputs the result to the differential steer gain multiplier 22. The differential steer gain multiplying unit 22 multiplies the steering angular velocity by the differential steer gain set by the differential steer gain setting unit 12f and outputs the result to the multiplier 24.

When the LK support control flag is off, the differential steer gain setting unit 12f sets the differential steer gain to a constant value regardless of the lateral position. For example, the differential steer gain setting unit 12f sets the differential steer gain to the maximum value Kmax.
On the other hand, when the LK support control flag is on, the differential steer gain setting unit 12f sets the differential steer gain to a value corresponding to the lateral position.
Please refer to FIG. The differential steer gain setting unit 12f receives the lateral position output by the lateral position calculation unit 12c and the steering angle output by the steering angle sensor 1f. The differential steer gain setting unit 12f includes a differential steer gain calculation unit 30, a steering angular velocity calculation unit 31, and a gain update unit 32.

  The differential steer gain calculator 30 calculates a differential steer gain according to the lateral position. The differential steer gain calculator 30 sets the differential steer gain so that the differential steer gain when the horizontal position is smaller than when the horizontal position is larger is smaller. As a result, the steering amount added by the differential steering control when the lateral position is small is smaller than when the lateral position is large.

Please refer to FIG. Reference numeral 33 indicates a lateral position of the vehicle, an alternate long and short dash line 34 indicates a target traveling trajectory, that is, a position where the lateral position is zero, and a solid line 35 indicates a setting example of the differential steer gain. Assuming that the sign of the lateral position on the right side of the vehicle is plus and the sign of the lateral position on the left side is minus, for example, the value of the differential steer gain may be the minimum value Kmin within the range of d1 to (−d2). . d1 and d2 are non-zero values. d1 and d2 may be the same or different.
Further, for example, the minimum value Kmin may be zero. When the differential steer gain becomes zero, the steering amount added by the differential steering control becomes zero. That is, when the lateral position is in the range of d1 to (−d2), the steering amount added by the differential steering control becomes zero.

Further, the value of the differential steer gain may be the maximum value Kmax in the range where the horizontal position is d3 or more and (−d4) or less. Note that d3 is larger than d1 and d4 is larger than d2. d3 and d4 may be the same or different. For example, the maximum value Kmax may be one.
In the horizontal position range d1 to d3 and the horizontal position range (−d2) to (−d3), the differential steer gain gradually increases as the absolute value of the horizontal position increases. For example, the differential steer gain may increase in proportion to the absolute value of the lateral position.
Please refer to FIG. The differential steer gain calculator 30 outputs the calculated differential steer gain to the gain updater 32.

The steering angular velocity calculator 31 sequentially calculates the steering angular velocity of the steering wheel 1a based on the steering angle detected by the steering angle sensor 1f, and outputs the calculated steering angular velocity to the gain updater 32.
When the steering angular velocity is equal to or less than a predetermined value or when the sign of the steering angular velocity received last time is different from the sign of the steering angular velocity received this time, the gain update unit 32 calculates the differential steer gain to be output to the differential steer gain multiplying unit 22 by the differential steer gain. The value is updated to the value received from the against calculation unit 30. For example, when the steering angular velocity is 0 or when the sign of the steering angular velocity received previously and the sign of the steering angular velocity received this time are different, the gain updating unit 32 updates the differential steer gain output to the differential steer gain multiplying unit 22. Is also good.

On the other hand, when the steering angular velocity is larger than the predetermined value and the sign of the previously received steering angular velocity and the sign of the currently received steering angular velocity are the same, the gain updating unit 32 holds the value of the differential steer gain output to the differential steer gain multiplying unit 22. I do. That is, the gain updating unit 32 does not update the value of the differential steer gain output to the differential steer gain multiplying unit 22.
Here, when the steering angular velocity is 0, the turning amount added by the differential steering control is 0. When the sign of the steering angular velocity changes, the steering angular velocity is small, and the steering amount added by the differential steering control is also small. By updating the differential steer gain only during a period in which the steering amount added by the differential steering control is small, it is possible to prevent the steering angle from being changed due to a change in the differential steer gain, thereby preventing the driver from feeling uncomfortable.

Please refer to FIG. The multiplier 24 multiplies the operation result of the differential steer gain multiplying unit 22 by the third vehicle speed sensitive gain and outputs the result to the adder 25.
The LK command steering angle calculation unit 23 includes a vehicle speed, a lateral position of the vehicle, a yaw angle when a predetermined delay time has elapsed, a gain according to a turn signal operation, first and second vehicle speed-sensitive gains, and a first vehicle speed-sensitive rate limiter. To receive. The LK command turning angle calculation unit 23 calculates an LK command turning angle for turning the vehicle in the direction of returning to the target traveling trajectory based on the received information. The LK command turning angle calculation unit 23 outputs the LK command turning angle to the adder 25.

When the LK support control flag is off, the adder 25 calculates the basic command turning angle by adding the calculation result of the gain multiplying unit 20 and the calculation result of the multiplier 24, and gives the calculated basic command turning angle to the command. The steering angle is output to the steering motor drive circuit 2d as a steering angle.
When the LK support control flag is on, the adder 25 calculates the command turning angle by adding the calculation result of the gain multiplying unit 20, the calculation result of the multiplier 24, and the LK command turning angle, and Output to the circuit 2d.

Please refer to FIG. The LK command turning angle calculator 23 includes a first repulsive force calculator 40, a second repulsive force calculator, an adder 42, a target yaw moment calculator 43, a target yaw acceleration calculator 44, and a target yaw rate. An operation unit 45, a command turning angle operation unit 46, and a limiter processing unit 47 are provided.
The first repulsive force calculation unit 40 receives a lateral position of the vehicle, a first vehicle speed sensitive gain, and a gain according to the turn signal operation. The first repulsive force calculator 40 performs the lateral position feedback control based on the received information.

In the lateral position feedback control, a repulsive force of the vehicle for reducing a change in the lateral position of the vehicle caused by a disturbance is calculated. Hereinafter, this repulsive force may be referred to as “repulsive force according to the lateral position”. Thus, in the lateral position feedback control, the turning angle of the left and right front wheels 5FL and 5FR is controlled in the center direction of the traveling lane, that is, in the direction in which the lateral position decreases, based on the lateral position of the vehicle. Then, the first repulsive force calculator 40 outputs the calculation result to the adder 42.
Please refer to FIG. The first repulsive force calculation unit 40 includes a gain multiplication unit 40a and a multiplier 40b. The gain multiplication unit 40a multiplies the lateral position of the vehicle by the basic gain and outputs a calculation result to the multiplier 40b.
The multiplier 40b multiplies the calculation result of the gain multiplication unit 40a, the first vehicle speed sensitive gain, and the gain according to the turn signal operation to calculate the repulsive force according to the lateral position.

  Please refer to FIG. The second repulsive force calculator 41 receives the yaw angle at the time when a predetermined delay time has elapsed, the second vehicle speed sensitive gain, and the gain according to the turn signal operation. The second repulsive force calculator 41 performs yaw angle feedback control based on the received information. In the yaw angle feedback control, a repulsive force of the vehicle for reducing the yaw angle generated by the disturbance is calculated. Hereinafter, this repulsion may be referred to as “repulsion according to the yaw angle”. Thus, in the yaw angle feedback control, the turning angles of the left and right front wheels 5FL and 5FR are controlled in the direction in which the yaw angle decreases based on the yaw angle of the vehicle. Then, the second repulsive force calculation unit 41 outputs the calculation result to the adder 42.

Please refer to FIG. The second repulsion calculation unit 41 includes a gain multiplication unit 41a and a multiplier 41b. The gain multiplication unit 41a multiplies the yaw angle when a predetermined delay time has elapsed by the basic gain, and outputs a calculation result to the multiplier 41b.
The multiplier 41b multiplies the calculation result of the gain multiplication unit 41a, the second vehicle speed-sensitive gain, and a gain according to the turn signal operation to calculate a repulsive force according to the yaw angle.

Please refer to FIG. The adder 42 calculates a lateral repulsion, which is the sum of the repulsion according to the lateral position and the repulsion according to the yaw angle. The adder 42 outputs the lateral repulsion to the target yaw moment calculation unit 43.
The target yaw moment calculator 43 calculates a target yaw moment based on the lateral repulsion output from the adder 42. Specifically, the target yaw moment calculating unit 43 calculates a target yaw moment M * according to the following equation (1) based on the lateral repulsion, the wheelbase WHEELBASE, the rear wheel axle weight, and the front wheel axle weight. Then, the target yaw moment calculator 43 outputs the calculation result to the target yaw acceleration calculator 44.
M * = lateral repulsion × (rear wheel axle load / (front wheel axle load + rear wheel axle load)) × WHEELBASE (1)

The target yaw acceleration calculator 44 calculates a target yaw acceleration based on the target yaw moment M * output from the target yaw moment calculator 43. Specifically, the target yaw acceleration calculating section 44 multiplies the target yaw moment by a predetermined yaw inertia moment coefficient. Then, the target yaw acceleration calculator 44 outputs the multiplication result to the target yaw rate calculator 45 as the target yaw acceleration.
The target yaw rate calculator 45 calculates a target yaw rate, which is a change speed of the yaw angle, based on the target yaw acceleration output from the target yaw acceleration calculator 44. Specifically, the target yaw rate calculator 45 multiplies the target yaw acceleration by a predetermined delay time. Then, the target yaw rate calculator 45 outputs the multiplication result to the command steering angle calculator 46 as a target yaw rate.

The command steering angle calculation unit 46 calculates the LK command steering angle based on the target yaw rate and the vehicle speed output by the target yaw rate calculation unit 45. Specifically, the command turning angle calculation unit 46 calculates the LK command turning angle δst * according to the following equation (2) based on the target yaw rate φ *, the vehicle speed V, the wheel base WHEELBASE, and the characteristic speed Vch of the vehicle. calculate. Here, the characteristic speed Vch may be, for example, a parameter representing a self-steering characteristic of the vehicle in a known Ackerman equation. Then, the command turning angle calculation unit 46 outputs the calculation result to the limiter processing unit 47.
δst * = (φ * × WHEELBASE × (1+ (V / Vch) 2) × 180) / (V × MPI) (2)
MPI is a predetermined coefficient.

  The limiter processing unit 47 limits the upper limit of the change speed of the LK command turning angle δst * by the first vehicle speed sensitive rate limiter. In addition, the limiter 47 limits the maximum value of the LK command steering angle δst *. The maximum value of the LK command steering angle δst * is within a play range when the steering angle of the steering wheel 1a is near the neutral position in a conventional steering device in which the steering unit and the steering unit are mechanically connected. The steering angle ranges of the corresponding left and right front wheels 5FL, 5FR may be used. Then, limiter processing section 47 outputs the LK command steering angle δst * after the restriction to adder 25 (see FIG. 2).

Referring to FIG. The reaction force control unit 15 includes a rack axial force calculation unit 60, an offset amount calculation unit 61, a subtractor 62, a target reaction force torque calculation unit 63, a reaction force torque correction value calculation unit 64, and an adder 65. Prepare.
The rack axial force calculating unit 60 estimates the rack axial force based on the steering angle and the vehicle speed with reference to a steering angle-axial force conversion map (MAP). That is, the rack axial force calculation unit 60 estimates the rack axial force based on the steering angle and the vehicle speed and the steering angle-axial force conversion map.
For example, the steering angle-axial force conversion map is a map representing the relationship between the steering angle for each vehicle speed and the rack axial force in a conventional steering device calculated in advance through experiments or the like. The rack axial force calculator 60 outputs the calculation result to the subtractor 62.

The offset calculating unit 61 calculates a road curvature based on the white line information, calculates an axial force offset based on the vehicle speed and the road curvature, and outputs the calculated axial force offset to the subtractor 62.
The axial force offset amount is an offset amount for offsetting the rack axial force calculated by the rack axial force calculating unit 60 so that a steering reaction force for maintaining a steering angle according to the road curvature is generated. By offsetting the rack axial force, a steering reaction force characteristic curve indicating the relationship between the steering angle of the steering wheel 1a and the steering reaction force to be applied to the steering wheel 1a in accordance with the steering angle is offset.
The offset amount calculation unit 61 offsets the steering reaction force characteristic curve in the same direction as the direction of the turning angle at which the road turns, and increases the absolute value of the axial force offset amount as the curvature of the road white line increases. .

Please refer to FIG. The offset amount calculator 61 includes an upper / lower limiter 61a, a self-aligning torque (SAT) gain calculator 61b, a curvature calculator 61c, a multiplier 61d, and a limiter processor 61e.
The upper / lower limiter 61a performs an upper / lower limiter process on the vehicle speed output from the vehicle speed sensor 7. In the upper / lower limiter processing, for example, the vehicle speed increases as the vehicle speed increases in a range of 0 to V (> 0), and reaches a maximum value in a range of V or higher. Then, the upper / lower limiter 61a outputs the vehicle speed after the upper / lower limiter processing to the SAT gain calculator 61b.

The SAT gain calculation unit 61b calculates an SAT gain according to the vehicle speed based on the vehicle speed after the limiter output from the upper and lower limiter 61a. The SAT gain according to the vehicle speed increases, for example, as the vehicle speed increases in a range of 0 to 70 km / h, and reaches a maximum value in a range of 70 km / h or more. Further, when the vehicle speed is high, the change amount of the SAT gain with respect to the vehicle speed change amount is larger than when the vehicle speed is low. Then, the SAT gain calculator 61b outputs the calculation result to the multiplier 61d.
Based on the white line information output by the image processing unit 11, the curvature calculation unit 61c calculates the curvature of the road white line at the scheduled arrival position (the curvature of the road white line at the position of the vehicle after a predetermined delay time (0.5 seconds) has elapsed). ) Is calculated. Then, the curvature calculator 61c outputs the calculation result to the multiplier 61d.

The multiplier 61d multiplies the curvature output by the curvature calculator 61c by the SAT gain output by the SAT gain calculator 61b. Then, the multiplier 61d outputs the multiplication result to the limiter 61e as an axial force offset amount. Thereby, the multiplier 61d increases the axial force offset amount as the curvature of the road white line at the scheduled arrival position increases, that is, as the road curvature increases.
The limiter processing unit 61e limits the maximum value of the axial force offset amount output from the multiplier 61d and the upper limit of the rate of change. The maximum value of the axial force offset amount is 1000N. In addition, the upper limit of the rate of change of the axial force offset amount is set to 600 N / s. Then, the limiter processing unit 61 e outputs the limited axial force offset amount to the subtractor 62.

Referring to FIG. The subtracter 62 outputs to the target reaction force torque calculation unit 63 a difference obtained by subtracting the axial force offset amount output from the offset amount calculation unit 61 from the rack axial force output from the rack axial force calculation unit 60.
The target reaction torque calculation unit 63 calculates a steering reaction torque generated by the rack axial force after the offset with reference to the axial force-steering reaction force conversion map based on the calculation result output by the subtractor 62. That is, the target reaction torque calculator 63 calculates the steering reaction torque generated by the offset rack axial force based on the offset rack axial force and the axial force-steering reaction force conversion map.

For example, the axial force-steering reaction force conversion map is a map representing the relationship between the rack axial force and the steering reaction force torque in a conventional steering device calculated in advance through experiments or the like. That is, the axial force-steering reaction force conversion map may be a map that simulates a steering reaction force characteristic representing a steering reaction torque corresponding to a self-aligning torque generated by a rack axial force in a conventional steering device. In the axial force-steering reaction force conversion map, the larger the rack axial force, the larger the steering reaction torque. In the axial force-steering reaction force conversion map, the change amount of the steering reaction force torque with respect to the change amount of the rack axial force is larger when the absolute value of the rack axial force is smaller than when it is larger. Further, in the axial force-steering reaction force conversion map, the higher the vehicle speed, the smaller the steering reaction torque.
The target reaction torque calculator 63 outputs the steering reaction torque to the adder 65.

The reaction torque correction value calculation unit 64 calculates the reaction torque correction value based on the lateral position, the lane arrival time, the fourth vehicle speed sensitive gain, the gain according to the turn signal operation, and the second vehicle speed sensitive rate limiter, and adds the values. Output to the container 65.
The reaction torque correction value is a correction value for generating an LK steering reaction force applied to return the vehicle to the target traveling trajectory.
Please refer to FIG. The reaction torque correction value calculation unit 64 includes a first reaction force calculation unit 64a, a second reaction force calculation unit 64b, a selection unit 64c, a multiplier 64d, and a limiter processing unit 64e.

The first reaction force calculation unit 64a calculates a reaction force N_THW according to the lateral position with reference to the lateral position-reaction force map 64i based on the lateral position output by the lateral position computation unit 12c. That is, the first reaction force calculation unit 64a calculates the reaction force N_THW according to the lateral position based on the lateral position output by the lateral position computation unit 12c and the lateral position-reaction force map 64i.
FIG. 11 shows an example of the lateral position-reaction force map 64i. Here, the sign of the lateral position Δx is determined such that the sign of the lateral position Δx becomes positive when the vehicle deviates to the right side of the target traveling trajectory and becomes negative when the vehicle deviates to the left side. Also, the sign of the reaction force applied in the direction of turning to the left (ie, in the counterclockwise direction) is determined to be positive, and the sign of the reaction force applied in the direction of turning to the right (ie, in the clockwise direction) becomes negative. Stipulated.
As illustrated, the sign of the reaction force N_THW according to the lateral position becomes positive when the sign of the lateral position Δx is positive, and becomes negative when the sign of the lateral position Δx is negative.

In addition, the absolute value of the reaction force N_THW according to the lateral position when the absolute value of the lateral position Δx, which is the difference between the planned arrival position and the target traveling trajectory, is larger than when the absolute value is smaller.
Further, when the absolute value of the lateral position Δx is large, the change amount of the reaction force N_THW according to the lateral position with respect to the change amount of the lateral position Δx is made larger than when the absolute value is small.
Therefore, the reaction force N_THW corresponding to the lateral position increases as the amount of deviation of the vehicle from the target traveling trajectory increases, and is an example of the LK steering reaction force applied in a direction to return the vehicle to the target traveling trajectory.
Please refer to FIG. The first reaction force calculator 64a outputs a reaction force N_THW corresponding to the lateral position to the selector 64c.

The second reaction force calculation unit 64b calculates a reaction force N_TLC according to the lane arrival time by referring to the lane arrival time-reaction force map 64j based on the lane arrival time output by the lane arrival time calculation unit 12d. That is, the second reaction force calculation unit 64b calculates the reaction force N_TLC according to the lane arrival time based on the lane arrival time and the lane arrival time-reaction force map 64j output by the lane arrival time calculation unit 12d.
FIG. 12 shows an example of the lane arrival time-reaction force map 64j. Here, the sign of the lane arrival time TLC is determined such that the sign of the lane arrival time TLC becomes positive when the vehicle deviates to the right side of the target traveling trajectory and becomes negative when the vehicle deviates to the left side. Also, the sign of the reaction force applied in the direction of turning to the left (ie, in the counterclockwise direction) is determined to be positive, and the sign of the reaction force applied in the direction of turning to the right (ie, in the clockwise direction) becomes negative. Stipulated.
As shown in the drawing, the reaction force N_TLC according to the lane arrival time according to the lateral position becomes positive when the sign of the lane arrival time TLC is positive, and becomes negative when the sign of the lane arrival time TLC is negative. Become.

Also, the absolute value of the reaction force N_TLC according to the lane arrival time when the absolute value of the lane arrival time TLC is smaller than when the deviation amount from the target traveling trajectory is smaller and the absolute value of the lane arrival time TLC is larger. large.
When the absolute value of the lane arrival time TLC is small, the change amount of the reaction force N_TLC according to the lane arrival time with respect to the change amount of the lane arrival time TLC is larger than when the absolute value is large.
Therefore, the reaction force N_TLC according to the lane arrival time increases as the amount of deviation of the vehicle from the target traveling trajectory increases, and is an example of the LK steering reaction force applied in a direction to return the vehicle to the target traveling trajectory. .
Please refer to FIG. The second reaction force calculation unit 64b outputs the reaction force N_TLC according to the lane arrival time to the selection unit 64c.

When the reaction force N_THW according to the lateral position and the reaction force N_TLC according to the lane arrival time have the same sign, the selection unit 64c selects the one having a larger absolute value among these reaction forces, and It outputs to the multiplier 64d as a force command value. When the reaction force N_THW according to the lateral position and the reaction force N_TLC according to the lane arrival time have different signs, the sum of these reaction forces is output to the multiplier 64d as a reaction force command value.
The multiplier 64d calculates the reaction force command value by multiplying the reaction force command value by a fourth vehicle speed sensitive gain and a gain according to the turn signal operation, and outputs the reaction force command value to the limiter processing unit 64e.

The limiter processing section 64e limits the upper limit of the changing speed of the reaction torque command value by the second vehicle speed sensitive rate limiter. In addition, the limiter processing unit 64e limits the maximum value of the reaction torque command value. The limiter processing unit 64e outputs the restricted reaction torque command value to the adder 65 (see FIG. 8) as a reaction torque correction value.
Referring to FIG. The adder 65 calculates the command steering reaction torque by adding the reaction torque correction value calculated by the reaction torque correction value calculation unit 64 to the steering reaction torque calculated by the target reaction torque calculation unit 63, Output to the motor drive circuit 1e.

  The camera 6 is an example of a traveling state sensor that detects an amount of deviation of the vehicle from a target traveling trajectory. The lateral position and the lane arrival time of the vehicle are examples of the amount of deviation of the vehicle from the target traveling trajectory. The LK steering reaction force is an example of a steering reaction force applied to the steering wheel 1a in a direction to return the vehicle to the target traveling trajectory. The differential steer gain is an example of a variable gain that is multiplied by the steering angular velocity to calculate a steering amount added to the steering angle calculated according to the steering angle.

(motion)
Next, the operation of the driving support device according to the present embodiment will be described. Please refer to FIG.
In step S1, the SBW controller 4 sends the steering angle, steering torque, reaction force motor 1d output from the steering angle sensor 1f, the steering torque sensor 1c, the current sensor 1g, the camera 6, and the vehicle speed sensor 7 via the CAN bus. , The image of the traveling road ahead of the vehicle, and the vehicle speed.
In step S2, the vehicle state setting unit 12 reads a map for determining various gain constants and gains from the storage device of the SBW controller 4.

In step S3, the vehicle state setting unit 12 calculates the yaw angle, the yaw angle when a predetermined delay time has elapsed, the lateral position, and the lane arrival time.
Further, the vehicle state setting unit 12 includes a first vehicle speed sensitive gain, a second vehicle speed sensitive gain, a third vehicle speed sensitive gain, a fourth vehicle speed sensitive gain, a gain according to a turn signal operation, a first vehicle speed sensitive rate limiter, and a second vehicle speed. Calculate the sensitive rate limiter.
In step S4, the control state setting unit 13 sets the LK support control flag to ON when all the LK support control permission conditions (A1) to (A10) are satisfied. The control state setting unit 13 turns off the LK support control flag when any of the LK support control permission conditions (A1) to (A10) is not satisfied.

  In step S5, the turning control unit 14 calculates a command turning angle for controlling the turning angles of the left and right front wheels 5FL, 5FR. When the LK support control flag is off, the turning control unit 14 calculates the basic command turning angle calculated based on the steering angle and the steering angular velocity as the command turning angle. When the LK support control flag is on, the turning control unit 14 turns the LK command to turn the vehicle in the direction to return the vehicle to the target traveling trajectory in accordance with the lateral position of the vehicle and the yaw angle when a predetermined delay time has elapsed. Calculate the steering angle. The turning control unit 14 calculates a command turning angle obtained by adding the LK command turning angle to the basic command turning angle.

  Here, when the LK support control flag is off, the differential steer gain setting unit 12f sets the differential steer gain to a constant value regardless of the lateral position. On the other hand, when the LK support control flag is on, the differential steer gain setting unit 12f reduces the differential steer gain when the lateral position is small compared to when the lateral position is large. Accordingly, the turning control unit 14 reduces the responsiveness of turning the steered wheels to the steering of the steering wheel 1a when the amount of deviation of the vehicle from the target traveling trajectory is small as compared with the case where the amount of deviation is large. .

In step S6, when the LK support control flag is on, the reaction torque correction value calculation unit 64 calculates a reaction torque correction value. A reaction force N_THW corresponding to the lateral position and a reaction force N_TLC corresponding to the lane arrival time are calculated, and a reaction torque correction value is calculated based on these reaction forces.
When the LK support control flag is off, the reaction torque correction value calculation unit 64 does not calculate the reaction torque correction value.

In step S7, when the LK support control flag is ON, the offset amount calculation unit 61 calculates the axial force offset amount based on the vehicle speed and the road curvature. When the LK support control flag is off, the offset amount calculation unit 61 does not calculate the axial force offset amount.
In step S8, the reaction force control unit 15 calculates a command steering reaction torque for controlling the steering reaction torque applied to the column shaft 1b. When the LK support control flag is OFF, the reaction force control unit 15 calculates the rack axial force according to the steering angle or the turning angle, and outputs the target reaction torque calculated based on the rack axial force to the command steering reaction force. Calculate as torque.

When the LK support control flag is ON, the reaction force control unit 15 calculates the target reaction force torque by correcting the rack axial force based on the axial force offset amount. The reaction force control unit 15 corrects the target reaction force torque with the reaction force torque correction value to calculate a command steering reaction force torque.
In step S9, the turning control unit 14 outputs the command turning angle to the turning motor drive circuit 2d to perform turning control. Further, the reaction force control unit 15 outputs the command steering reaction force torque to the reaction force motor drive circuit 1e to perform the reaction force control. Thereafter, the process ends.

A method for setting the differential steer gain used in the steering angle command value calculation in step S5 will be described. Please refer to FIG.
In step S20, the differential steer gain calculator 30 calculates a new differential steer gain according to the lateral position, that is, the deviation amount from the target traveling trajectory.
In step S21, the steering angular velocity calculator 31 calculates the steering angular velocity of the steering wheel 1a. The gain updating unit 32 determines whether the sign of the steering angular velocity has changed.

If the sign of the steering angular velocity has changed (step S21: Y), the process proceeds to step S23. When the sign of the steering angular velocity has changed (step S21: N), the process proceeds to step S22.
In step S22, the gain update unit 32 determines whether the steering angular velocity is equal to or less than a predetermined value. When the steering angular velocity is equal to or less than the predetermined value (step S22: Y), the process proceeds to step S23.
In step S23, the gain updating unit 32 updates the differential steer gain output to the differential steer gain multiplying unit 22 to the calculation result of step S20. Thereafter, the process ends. If the steering angular velocity is not lower than the predetermined value (step S22: N), the process ends without executing step S23. Therefore, the gain updating unit 32 does not update the differential steer gain output to the differential steer gain multiplying unit 22, but retains the previously output value.

(Effects of the embodiment)
(1) In a vehicle provided with an SBW-type steering mechanism, the steering control unit 14 steers the steered wheels in accordance with the steering operation of the steering wheel 1a by the driver. The lateral position calculation unit 12c and the lane arrival time calculation unit 12d detect the amount of deviation of the vehicle from the target traveling trajectory. The first reaction force calculation unit 64a, the second reaction force calculation unit 64b, the selection unit 64c, the multiplier 64d, and the limiter processing unit 64e move the vehicle toward the target traveling trajectory as the deviation amount of the vehicle from the target traveling trajectory increases. The LK steering reaction force applied to the steering wheel in the direction to return to is increased.
The differential steer gain setting unit 12f and the steering control unit 14 reduce the responsiveness of turning the steered wheels to the steering of the steering wheel 1a when the deviation amount is smaller than when the deviation amount is large.
In this manner, when the deviation from the target traveling trajectory is small, the response of the steering to the steering is reduced, so that the steering operation not intended by the driver is performed in a state where the LK steering reaction force is small without the driver's steering operation. Even if it is performed, the fluctuation of the steering angle can be suppressed.

For example, it is assumed that a vehicle is traveling on a target traveling trajectory on a highway or the like by lane keeping support control, and the driver is relaxing and not performing a steering operation. In such a case, if the vehicle body shakes due to unevenness of the road surface or running on a pebble, the posture of the driver changes due to the shake, and steering unintended by the driver is input to the steering wheel 1a. .
At this time, if the vehicle is traveling on the target traveling trajectory, the LK steering reaction force applied to the steering wheel 1a in the direction of returning the vehicle to the target traveling trajectory is small, so that the steering wheel 1a due to steering unintended by the driver is generated. The steering angle is likely to fluctuate, and the left and right front wheels 5FL and 5FR may be steered to reduce the straightness.
For this reason, when it is determined that there is no steering operation by the driver, it is assumed that the subsequent steering operation may be an operation not intended by the driver, and the steering wheel for this steering operation is Responsiveness of turning of the vehicle is reduced. As a result, it is possible to suppress a change in the turning angle due to a steering operation not intended by the driver.

(2) The turning control unit 14 calculates a command turning angle obtained by adding a turning amount calculated according to the steering angular velocity to a turning angle calculated according to the steering angle of the steering wheel 1a. The steered wheels are steered according to the angle. When the deviation amount is smaller than when the deviation amount is large, the differential steer gain setting unit 12f and the steering control unit 14 reduce the steering amount calculated for the same steering angular velocity. That is, the differential steer gain setting unit 12f and the steering control unit 14 reduce the steering amount calculated for the same steering angular velocity when the deviation amount is smaller than when the deviation amount is large.
For example, the turning control unit 14 may calculate the turning amount by multiplying the steering angular velocity by the differential steer gain. The differential steer gain setting unit 12f may reduce the differential steer gain when the deviation amount is smaller than when the deviation amount is large.
As described above, the steering amount calculated for the steering angular velocity when the deviation amount is small is made smaller than that when the deviation amount is large, so that the differential steering control for the steering unintended by the driver can be suppressed. it can. As a result, it is possible to prevent the steering angle from being sensitively responded to steering unintended by the driver, thereby reducing the straightness of the vehicle.

  (3) The gain updating unit 32 holds the value of the differential steer gain when the steering angular velocity is equal to or more than the predetermined value and the sign of the steering angular velocity does not change. The gain updating unit 32 updates the value of the differential steer gain when the steering angular velocity is smaller than a predetermined value or when the sign of the steering angular velocity changes. By updating the differential steer gain only during a period in which the steering amount added by the differential steering control is small, it is possible to prevent the steering angle from being changed due to a change in the differential steer gain, thereby preventing the driver from feeling uncomfortable.

(Modification)
(1) The differential steer gain setting unit 12f may calculate the differential steer gain using the lane arrival time instead of or in addition to the lateral position. For example, the differential steer gain setting unit 12f may set the differential steer gain so that the differential steer gain when the lane arrival time is longer than when the lane arrival time is shorter is smaller.
(2) Instead of multiplying by the differential steer gain, the relationship between the steering angular velocity and the steering amount is referred to a predetermined calculation formula or map, and the steering amount added by the differential steering control, that is, the rotation determined according to the steering angle. The steering amount to be added to the steering angle may be determined. In this case, by switching a calculation formula or a map in which the relationship between the steering angular velocity and the steering amount is determined in advance, the steering amount calculated for the same steering angular velocity is smaller than the case where the deviation amount is large. If it is small, it may be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Steering part, 1a ... Steering wheel, 1b ... Column shaft, 1c ... Steering torque sensor, 1d ... Reaction force motor, 1e ... Reaction force motor drive circuit, 1f ... Steering angle sensor, 1g ... Current sensor, 2 ... Steering Parts, 2a: pinion shaft, 2b: steering gear, 2c: steering motor, 2d: steering motor drive circuit, 2e: steering angle sensor, 2f: rack gear, 2g: rack, 3: backup clutch, 4: SBW controller 5FL: front left wheel, 5FR: front right wheel, 6: camera, 7: vehicle speed sensor, 11: image processing unit, 12: vehicle state setting unit, 12a: gain calculation unit, 12b: yaw angle calculation unit, 12c: lateral position Computing unit, 12d: Lane arrival time computing unit, 12e: Steering intention determination unit, 12f: Differential steer gain setting unit, 13: Control state setting unit, 14: Steering control unit, 1 ... Reaction force controller, 20 ... Gain multiplier, 21 ... Steering angular velocity calculator, 22 ... Derived steer gain multiplier, 23 ... LK command steering angle calculator, 24 ... Multiplier, 25 ... Adder, 30 ... Derivative Steer gain calculator, 31: steering angular velocity calculator, 32: gain updater, 40: first repulsive force calculator, 40a: gain multiplier, 40b: multiplier, 41: second repulsive force calculator, 41a: gain Multiplier, 41b Multiplier, 42 Adder, 43 Target yaw moment calculator, 44 Target yaw acceleration calculator, 45 Target yaw rate calculator, 46 Command steering angle calculator, 47 Limiter processor , 60: Rack axial force calculator, 61: Offset amount calculator, 61a: Upper / lower limiter, 61b: SAT gain calculator, 61c: Curvature calculator, 61d: Multiplier, 61e: Limiter processor, 62: Subtractor 63: target reaction torque calculation unit, 64: reaction torque correction value calculation unit, 64a: first reaction force calculation unit, 64b: second reaction force calculation unit, 64c: selection unit, 64d: multiplier, 64e: limiter Processing unit, 64i lateral position-reaction map, 64j lane arrival time-reaction map 64j, 65 adder

Claims (5)

A driving support method for a vehicle including a steer-by-wire steering mechanism,
The steered wheels are steered according to the steering operation of the steering wheel,
The vehicle detects a deviation amount deviating from a target traveling trajectory,
As the deviation increases, the steering reaction force applied to the steering wheel in a direction to return the vehicle to the target traveling trajectory is increased,
When the deviation amount is smaller than the case where the deviation amount is large, the responsiveness of turning the steered wheels to the steering of the steering wheel is reduced.
A driving support method characterized by the above-mentioned. The steered wheels are steered according to a target steering angle obtained by adding a steering angle calculated according to the steering angular velocity of the steering wheel to a steering angle calculated according to the steering angle of the steering wheel. ,
When the deviation amount is smaller than the case where the deviation amount is large, the steering amount calculated for the same steering angular velocity is reduced,
The driving support method according to claim 1, wherein: Multiplying the steering angular velocity by a variable gain to calculate the steering amount;
The driving support method according to claim 2, wherein the variable gain is reduced when the deviation amount is smaller than when the deviation amount is large. When the steering angular velocity is equal to or more than a predetermined value and the sign of the steering angular velocity does not change, the variable gain value is held,
The method according to claim 3, wherein the variable gain value is updated when the steering angular velocity is smaller than a predetermined value or when the sign of the steering angular velocity changes. A driving assistance device for a vehicle including a steer-by-wire steering mechanism,
A traveling state sensor for detecting an amount of deviation of the vehicle from a target traveling trajectory;
Steering the steered wheels in response to the steering operation of the steering wheel, and increasing the deviation increases the steering reaction force applied to the steering wheel in a direction to return the vehicle to the target traveling trajectory as the deviation increases. And a controller that reduces responsiveness of turning the steered wheels to steering of the steering wheel when the deviation amount is smaller than when the deviation is larger.

Images