JP2010069907A - Steering assist device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering assist device that appropriately changes a control mode according to an operating intention of a driver. <P>SOLUTION: The steering assist device for applying a steering force to a steering mechanism 10 so that an own vehicle OV travels along a driving lane includes: an environment recognizing means 110 for recognizing an environment forward from the own vehicle; a target traveling position setting means 120 for setting a target traveling position of the own vehicle; an own vehicle side position recognizing means 130 for recognizing a side position of the own vehicle; a target steering force setting means 150 for setting a target steering force based on a difference between the target traveling position and the own vehicle side position; a steering control means 160 for applying the steering force to the steering mechanism based on the target steering force; a steering operation force detecting means 23 for detecting a steering operation force; and an operating intention determining means 140 for determining the driver's operating intention based on a history of the steering operation force. The target steering force setting means performs a low assist level control, in which an assist level to cause the vehicle to follow the target traveling position is lowered below a normal condition, when a lowered state of the operating intention is detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steering assist device that applies a steering force to a steering mechanism in accordance with a lateral position of a host vehicle with respect to a target travel position set in a travel lane of the host vehicle, and in particular, appropriate control according to a driver's driving intention. About what to do.

The steering assist device recognizes the environment ahead of the host vehicle using a stereo camera, for example, and applies a steering force to the steering mechanism. As such steering assist control, for example, lane keeping assist control for steering the vehicle along the target travel position set in the lane, steering force in the departure prevention direction according to the departure tendency of the vehicle from the lane There are lane departure prevention controls to be given.
Such a steering assist device is positioned as assisting the steering of the driver who performs the driving action actively, and it is not preferable to function as an automatic driving device that performs the driving in place of the driver. For this reason, when the driver's driving intention is low and the driver depends on the steering assist device, the driver needs to prompt the driver to perform a driving operation.

Conventionally, it is known that a steering operation input torque by a driver is monitored, and if this is not detected for a predetermined period or longer, it is determined that the driver does not intend to drive and steering assist control is stopped.
For example, Patent Literature 1 describes a steering control device that determines a decrease in driving intention using a determination time set based on a vehicle speed and a curve curvature, and prohibits steering assist processing.
JP 2007-168720 A

However, as in the above-described prior art, the driver's driving intention is reduced to a control-dependent state that is conscious of the driver but depends on the steering assist control, and a doze state in which the driver's consciousness is reduced. It can be divided roughly. However, if the steering assist control is immediately stopped entirely based on the history of the steering input torque, there is a concern that the behavior of the vehicle, the course will be disturbed, and the lane will be deviated in the dozing state.
The subject of this invention is providing the steering assistance apparatus which changes a control method appropriately according to the driver's driving intention.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is a steering assist device that applies a steering force to the steering mechanism so that the host vehicle travels along the travel lane, and recognizes an environment in front of the host vehicle including the travel lane of the host vehicle. Recognition means; target travel position setting means for setting the target travel position of the host vehicle in the travel lane of the host vehicle using the environment recognition means; host vehicle lateral position recognition means for recognizing the lateral position of the host vehicle; Target steering force setting means for setting a target steering force to be applied to the steering mechanism based on a deviation between the target travel position and the lateral position of the host vehicle, and a steering force applied to the steering mechanism based on the target steering force A steering control means for applying, and a driving intention determination means for determining a driving intention of the driver based on a driving steering state of the driver, wherein the target steering force setting means includes a first target steering force, at least the Area with small deviation The second target steering force is set to a value smaller than the first target steering force, and the steering control means determines that the first control steering force is determined when the driver's driving intention is high. A steering force is applied to the steering mechanism based on a target steering force, and a steering force is applied to the steering mechanism based on the second target steering force when it is determined that the driver's driving intention is in a lowered state. This is a steering assist device.

According to a second aspect of the present invention, the first target steering force is set to increase as the deviation increases, and the second target steering force is the first target steering in a region where the deviation is small. 2. The steering assist device according to claim 1, wherein the steering assist device is set to be smaller than a force and is set to increase with an increase in the deviation. 3.
According to a third aspect of the present invention, the driving intention determination means includes a first driving intention reduced state as the driving intention reduced state, and a second driving in which the driving intention is further reduced than the first driving intention reduced state. The intention steering state is determined, and the target steering force setting means sets the steering force only when the deviation is not less than a predetermined value in addition to the first target steering force and the second target steering force. A third target steering force, and the steering control means determines that the second target steering force from the steering control based on the first target steering force when the first drive intention lowering state is determined. When the second drive intention lowering state is determined, the steering control based on the second target steering force is changed to the steering control based on the third target steering force. The operation according to claim 1 or claim 2, wherein It is a support device.
According to a fourth aspect of the present invention, there is provided a steering assist device that applies a steering force to a steering mechanism so that the host vehicle travels along the travel lane, and an environment for recognizing an environment ahead of the host vehicle including the travel lane of the host vehicle. Recognition means; target travel position setting means for setting the target travel position of the host vehicle in the travel lane of the host vehicle using the environment recognition means; host vehicle lateral position recognition means for recognizing the lateral position of the host vehicle; Target steering force setting means for setting a target steering force to be applied to the steering mechanism based on a deviation between the target travel position and the lateral position of the host vehicle, and a steering force applied to the steering mechanism based on the target steering force Steering control means to be applied, and driving intention determination means for determining the driving intention of the driver based on the driving steering state of the driver, wherein the target steering force setting means increases as the deviation increases. First set The steering control means has a second target steering force that is set to a predetermined value only when the deviation is equal to or greater than a predetermined value, and the steering control means is determined to have a high driving intention of the driver. When the steering intention is applied to the steering mechanism based on the first target steering force, and the driving intention of the driver is determined to be in a lowered state, the steering mechanism is based on the second target steering force. The steering assist device is characterized in that a steering force is applied to the steering wheel.

According to the present invention, the following effects can be obtained.
(1) When it is determined that the driver's driving intention is high, the steering force is applied to the steering mechanism based on the first target steering force, and when the driver's driving intention is determined to be in the lowered state, the second is performed. By applying the steering force to the steering mechanism based on the target steering force, the driver's dependence on the steering support control can be resolved and the driver can be encouraged to drive independently when the driving intention is reduced. Further, even if the driving intention is in a lowered state, the lane departure due to the stopping of the control in the lowered driving intention is performed by executing the control based on the second target steering force instead of stopping the support completely. Risk can be reduced.
(2) The first target steering force is set to increase as the deviation increases, and the second target steering force is set smaller than the first target steering force in a region where the deviation is small, and the deviation increases. When the driver's driving intention is determined to be in a reduced state, the driving intention is reduced by applying a steering force to the steering mechanism based on the second target steering force. In this case, it is possible to reduce the support level for causing the host vehicle to travel along the target travel position, and to increase the steering force in a region where the deviation is large, thereby preventing deviation or the like.
(3) The driving intention determination means determines a first driving intention reduced state as a driving intention reduced state and a second driving intention reduced state in which the driving intention is further lowered than the first driving intention reduced state. The steering control means sets the third target steering force in which the steering force is set only when the deviation from the steering control based on the second target steering force is greater than or equal to a predetermined value when the second driving intention lowering state is determined. By changing to the steering control based on the above, in the second driving intention lowering state, only an alarm when there is a tendency to deviate from the driving lane is given, and the driver's voluntary driving operation is promoted and the deviation from the driving lane is avoided. Can be prevented.
(4) The steering control means applies a steering force to the steering mechanism based on a first target steering force that is set to increase in accordance with an increase in deviation when it is determined that the driver's driving intention is high. At the same time, when it is determined that the driver's driving intention is in a lowered state, by applying a steering force to the steering mechanism based on the second target steering force that is set to a predetermined value only when the deviation is greater than or equal to a predetermined value, When the driving intention is in a lowered state, only a warning is given when there is a tendency to deviate from the driving lane, and the driver can be independently driven and prevented from deviating from the driving lane.

  The present invention provides a steering assist device that appropriately changes a control method according to a driver's driving intention, and provides a steering torque proportional to a deviation of the vehicle's lateral position with respect to a target traveling position according to a driver's intention state decrease. This is solved by switching from the primary control that sets the steering torque to the tertiary control that sets the steering torque proportional to the cube of the deviation.

Embodiments of a steering assist device to which the present invention is applied will be described below.
The steering assist device of the embodiment is provided in, for example, a four-wheeled vehicle such as a passenger car that steers the two front wheels.
FIG. 1 is a diagram illustrating a system configuration of a vehicle including a steering assist device according to an embodiment. This steering assist device applies a steering torque (steering force) to the steering mechanism 10.
The steering mechanism 10 performs steering by rotating the housing H that supports the front wheel FW about a predetermined steering axis (king pin).

The steering mechanism 10 includes a steering wheel 11, a steering shaft 12, a steering gear box 13, a tie rod 14, and the like.
The steering wheel 11 is an annular operation member through which a driver inputs a steering operation.
The steering shaft 12 is a rotating shaft that transmits the rotation of the steering wheel 11 to the steering gear box 13.
The steering gear box 13 includes a rack and pinion mechanism that converts the rotational movement of the steering shaft 12 into a straight movement in the vehicle width direction.
The tie rod 14 is a shaft-like member having one end connected to the rack of the steering gear box 13 and the other end connected to the knuckle arm of the housing H. The tie rod 14 steers by rotating the housing H by pushing and pulling the knuckle arm of the housing H.

  The vehicle also includes an electric power steering (EPS) control unit 20, a steering control unit 30, an engine control unit 40, a transmission control unit 50, a vehicle integration unit 60, and the like.

The EPS control unit 20 comprehensively controls an electric power steering device that generates a steering assist force in accordance with a driver's steering operation. The EPS control unit 20 is connected to an electric actuator 21, a steering angle sensor 22, a torque sensor 23, and the like.
The electric actuator 21 is, for example, an electric motor that is provided in the middle of the steering shaft 12 and applies a steering torque (steering force) to the steering mechanism 10 via a speed reduction mechanism.
The steering angle sensor 22 includes an encoder that detects the angular position of the steering shaft 12 (substantially equal to the angular position of the steering wheel 11).
The torque sensor 23 is inserted into the steering shaft 12 between the electric actuator 21 and the steering wheel 11 and detects torque acting on the steering shaft 12. Normally, the torque detected by the torque sensor 23 is substantially equal to the steering torque input to the steering wheel 11 by the driver. The torque sensor 23 functions as a steering operation force detecting means according to the present invention.

The steering control unit 30 performs vehicle steering control and ABS control for individually controlling the braking force of each wheel brake. In vehicle stability control, when understeer or oversteer occurs, the braking force on the turning inner wheel side and the outer wheel side is made different to generate a yaw moment in the restoring direction. ABS control (anti-lock brake control) is for reducing and recovering the braking force of a wheel when the tendency of the wheel to lock is detected.
The steering control unit 30 is connected to a hydraulic control unit (HCU) 31, a vehicle speed sensor 32, a yaw rate sensor 33, a lateral acceleration (lateral G) sensor 34, and the like.

The HCU 31 is a device that individually controls the brake fluid hydraulic pressure applied to the hydraulic service brake of each wheel. The HCU 31 includes a motor pump that pressurizes the brake fluid, a solenoid valve that adjusts the pressure applied to the caliper cylinder of each wheel, and the like.
The vehicle speed sensor 32 is provided in a housing that holds the hub bearing of each wheel, and outputs a vehicle speed pulse signal corresponding to the wheel speed. The vehicle speed pulse signal is subjected to predetermined processing, whereby the traveling speed of the vehicle can be obtained.
The yaw rate sensor 33 and the lateral G sensor 34 include a MEMS sensor that detects a rotational speed around the vertical axis of the vehicle body and a lateral acceleration, respectively.

The engine control unit 40 controls the engine, which is a driving power source for the vehicle, and its auxiliary equipment.
The transmission control unit 50 controls the automatic transmission that changes the output of the engine and transmits it to the differential gear of the drive shaft.
The vehicle integration unit 60 controls the electrical components of the vehicle other than those related to each unit.

Further, the steering assist device of the embodiment includes a steering assist control unit 100 described below.
The steering assist control unit 100 is connected to the above-described EPS control unit 20, the operation control unit 30, the engine control unit 40, the transmission control unit 50, and the vehicle integration unit 60 via an in-vehicle LAN such as a CAN communication system, for example. Various information and signals can be acquired.

  The steering assist control unit 100 includes an environment recognition unit 110, a target travel position setting unit 120, a host vehicle traveling path estimation unit 130, a driving intention determination unit 140, a target steering force setting unit 150, a steering force control unit 160, and the like. ing. Each of these means may be configured as independent hardware, or a part or all of them may be configured as common hardware.

The environment recognition unit 110 recognizes the shape of the traveling lane of the host vehicle based on image information obtained by capturing the front of the host vehicle.
FIG. 2 is a diagram illustrating an example of a planar arrangement of the host vehicle and the lane in the embodiment.
The environment recognition unit 110 is connected to a stereo camera 111, an image processing unit 112, and the like.
The stereo camera 111 includes, for example, a pair of main cameras and sub-cameras provided near the room mirror base at the upper end of the front window of the vehicle. Each of the main camera and the sub camera has a CCD camera. The main camera and the sub camera are installed apart from each other in the vehicle width direction. The main camera and the sub camera capture a reference image and a comparative image, respectively, and output image data related to these images to the image processing unit 112.
The image processing unit 112 performs A / D conversion on the image data of the reference image and the comparison image output from the stereo camera 111, performs predetermined image processing, and outputs the result to the environment recognition unit 110. This image processing includes, for example, correction of an attachment position error of each camera, noise removal, gradation optimization, and the like. The digitized image has, for example, a plurality of pixels arranged in a matrix in the vertical direction and the horizontal direction. Each of these pixels has a luminance value corresponding to the brightness of the subject.

  The environment recognition unit 110 detects the parallax of a pixel group that is a block composed of an arbitrary pixel or a plurality of pixels on the reference image based on the data of the reference image and the comparison image. This parallax is the amount of deviation between the position on the reference image and the position on the comparison image of a certain pixel or pixel group. Using this parallax, the distance from the vehicle to the subject corresponding to the pixel can be calculated based on the principle of triangulation.

Moreover, the environment recognition means 110 recognizes the shape of the white line etc. which are arrange | positioned at the lane both ends ahead of the own vehicle. In this specification, claims, etc., a white line means a continuous line or a broken line drawn at the end in the width direction of the lane, and the actual color is other than white (for example, amber) Includes lines.
The environment recognition unit 110 detects a pixel group in the white line WL portion based on the luminance data of the pixel from the reference image data. The orientation of the pixel group of the white line WL portion with respect to the host vehicle is detected based on the pixel position on the image data. Specifically, an area corresponding to the pixel position in the vertical direction on the road surface is scanned in the horizontal direction, and a portion where the brightness value changes suddenly is recognized as the outline of the white line WL. Then, the position of the white line WL is detected by calculating the distance of the pixel group in the white line WL portion.
The environment recognition means 110 can continuously detect the position of the white line to set a plurality of lane candidate points in the traveling direction of the vehicle, ignore the lane candidate points that cannot be matched, and set the lane candidate points. The area that does not exist is subjected to a predetermined complement process to recognize the lane shape ahead of the host vehicle.

  The target travel position setting unit 120 sets the target travel position Xc at the center in the width direction of the travel lane of the host vehicle OV set by the environment recognition unit 110.

The own vehicle traveling path estimation means 130 is based on information from the environment recognition means 110, the running state of the vehicle detected by the steering angle sensor 22, the vehicle speed sensor 32, the yaw rate sensor 33, etc., and known vehicle specifications. The vehicle traveling path is estimated. The own vehicle traveling path estimating means 130 functions as the own vehicle lateral position recognizing means according to the present invention.
The own vehicle traveling path is estimated by, for example, calculating the lateral position Xe of the own vehicle OV at the gaze distance Z in front of the vehicle.
This will be described below using a coordinate system having an X-axis extending in the vehicle width direction and a Z-axis extending forward of the vehicle body with the center of gravity of the host vehicle OV as the origin.
The estimated lateral position Xe of the host vehicle's center of gravity at the gaze distance Z is obtained by the following equation 1 using the handle angle α.

In addition, the vehicle traveling path estimation unit 130 may estimate the lateral position using the yaw rate detected by the yaw rate sensor 33 as shown in the following equation 2, instead of estimating the lateral position using the steering wheel angle. it can.

Xe = Z ² γ / 2V (Formula 2)
Z: Gaze distance [m]
γ: vehicle yaw rate [rad / sec]

The driving intention determination unit 140 determines a driving intention lowering state of the driver based on the history of the steering operation torque of the driver detected using the torque sensor 23.
The driving intention determination means 140 detects a driver steering torque Td that is an input torque from the driver based on the output of the torque sensor 23, and based on the elapsed time in a state where the driver steering torque Td is less than a predetermined threshold value Tth. To determine a decline in intention. The driving intention determination unit 140 includes a driver input determination timer that measures the elapsed time. The operation of this driver input determination timer will be described in detail later.

In addition, the driving intention determination unit 140 sets the driving intention state of the driver to a normal state where no intention decrease is recognized, the first driving intention decreased state, and the first driving intention decreased state. It is determined that the driving intention is in a reduced state.
The first driving intention lowering state corresponds to, for example, a state in which the driver is conscious but depends on the steering assist control.
The second driving intention reduced state corresponds to, for example, a state in which the driver's consciousness is reduced due to falling asleep.

The target steering force setting unit 150 sets a target steering torque in the steering assist control and provides it to the steering force control unit 160.
The target steering force setting unit 150 includes a primary control steering force setting unit 151, a tertiary control steering force setting unit 152, an alarm pulse steering force setting unit 153, and the like. The target steering force setting means 150 selects one of the steering forces set by each of these steering force setting means based on the driving intention state of the driver determined by the driving intention determination means 140, and serves as a steering assist device. Set as the target steering torque. This switching of the steering force (control) will be described in detail later.

FIG. 3 shows the deviation Δe and the steering torques Tc1, Tc3, and Tp in the support control 1 to 3 performed by the primary control steering force setting unit 151, the tertiary control steering force setting unit 152, and the warning pulse steering force setting unit 153, respectively. It is a graph which shows correlation with.
The primary control steering force setting means 151 includes the target travel position Xc at the gaze distance Z set by the target travel position setting means 120 and the lateral position Xe of the host vehicle at the gaze distance Z estimated by the own vehicle traveling path estimation means 130. The first steering torque Tc1 by the assist control 1 (primary control) is set by multiplying the deviation Δe (= Xc−Xe) by a predetermined primary control gain. The primary control steering force setting means 151 calculates the first target steering force according to the present invention.
As shown in FIG. 3, the steering torque Tc1 is set to 0 when the deviation Δe is 0. The steering torque Tc1 increases linearly in proportion to the absolute value of the deviation Δe in a region where the absolute value of the deviation Δe is less than half of the lane width Xw. The steering torque Tc1 is set to a constant value T_lim in a region where the absolute value of the deviation Δe is more than half of the lane width Xw.

The tertiary control steering force setting means 152 sets the second steering torque Tc3 by the assist control 2 (tertiary control) by increasing the above-mentioned deviation Δe to the cube and multiplying it by a predetermined tertiary control gain. To do. The tertiary control steering force setting means 152 calculates the second target steering force according to the present invention.
As shown in FIG. 3, the steering torque Tc3 is set to 0 when the deviation Δe is 0. The steering torque Tc3 increases linearly in proportion to the absolute value of the cube of the deviation Δe in a region where the absolute value of the deviation Δe is less than half of the lane width Xw. Further, the steering torque Tc3 is set to a constant value T_lim in a region where the absolute value of the deviation Δe is more than half of the lane width Xw.

The warning pulse steering force setting means 153 has a rectangular pulse-like steering torque Tp (support control 3 / third by alarm pulse control) only in a region where the absolute value of the deviation Δe exceeds half of the lane width Xw (at the time of lane departure). (Steering torque) is set periodically, and the steering torque is set to 0 in the region where the absolute value of the deviation Δe is less than half of the lane width Xw. This pulse-shaped steering torque Tp is mainly intended to urge the driver to recover driving intention and to drive the driving operation mainly by vibrating the steering wheel 11. The alarm pulse steering force setting means 153 calculates the third target steering force according to the present invention.
In each control described above, the support level (strength of restraint or the like) for driving the host vehicle OV along the target travel position Xc is support control 1 (primary control), support control 2 (tertiary control), It becomes higher in order of support control 3 (alarm pulse control). That is, the support control 2 functions as the low support level control according to the present invention with respect to the support control 1.

Based on the target steering torque set by the target steering force setting means 150, the steering force control means 160 calculates the target instruction current i _ind using the following equation (3). The steering force control means 160 controls the electric actuator 21 via the EPS control unit 20 to apply a steering torque to the steering mechanism 10.

Next, the change of the assistance level in the steering assistance apparatus of a present Example is demonstrated.
FIG. 4 is a flowchart showing the operation when the support level is changed. Hereinafter, the steps will be described step by step.
<Step S01: Environmental State Detection / Vehicle State Detection / Deviation Δe and Lane width Xw>
The target steering force setting means 150 uses the environment recognition means 110, the target travel position setting means 120, the own vehicle traveling path estimation means 130, etc., and the lane shape in front of the host vehicle, the lane width Xw, and the target travel position Xc in the lane. The information about the estimated lateral position Xe of the own vehicle is acquired.
Thereafter, the process proceeds to step S02.

<Step S02: Driver Steering Torque Td Detection>
The driving intention determination unit 140 detects the driver steering torque Td based on the output value of the torque sensor 23 via the EPS control unit 20.
Thereafter, the process proceeds to step S03.

<Step S03: Driver Input Determination>
The driving intention determination means 140 determines whether or not the driver steering torque Td detected in step S02 is equal to or greater than a predetermined determination threshold value Tth. If Td ≧ Tth, it is determined that the driver's driving intention has not decreased and proceeds to step S04. If Td <Tth, the process proceeds to step S05.

<Step S04: Clear Driver Input Determination Timer>
The driving intention determination unit 140 clears the driver input determination timer and sets the timer value t to zero.
Thereafter, the process proceeds to step S06.

<Step S05: Increment driver input determination timer>
The driving intention determination unit 140 increments the timer value t of the driver input determination timer.
Thereafter, the process proceeds to step S07.

<Step S06: Select Support Control 1>
The target steering force setting means 150 sets the steering torque Tc1 by the assist control 1 (primary control) set by the primary control steering force setting means 151 as the target steering torque.
Thereafter, the process returns, the process returns to step S01, and the subsequent processing is repeated.

<Step S07: Driver Input Determination Timer Determination 1>
The driving intention determination means 140 compares the timer value t of the driver input determination timer with a predetermined threshold value t_th1, and when t ≧ t_th1, it is determined that the intention lowering state is either the first or the second step S08. If t <t_th1, the process proceeds to step S06 on the assumption that no intention has been lowered.

<Step S08: Driver Input Determination Timer Determination 2>
The driving intention determination means 140 compares the timer value t of the driver input determination timer with a predetermined threshold value t_th2 that is larger than the above-described t_th1, and when t ≧ t_th2, it is assumed that the second driving intention lowering state is present. The process proceeds to step S10, and when t <t_th2, the process proceeds to step S09 assuming that the first drive intention lowering state is present.

<Step S09: Select Support Control 2>
The target steering force setting unit 150 sets the steering torque Tc3 by the assist control 2 (third control) set by the tertiary control steering force setting unit 152 as the target steering torque.
Thereafter, the process returns, the process returns to step S01, and the subsequent processing is repeated.

<Step S10: Control stop>
The target steering force setting means 150 sets the target steering torque to 0 and stops the steering assist control.
Then, it progresses to step S11.

<Step S11: Lane departure determination>
The target steering force setting means 150 determines whether the absolute value of the deviation Δe of the host vehicle lateral position Xe with respect to the target travel position Xc is smaller than half the lane width (Xw / 2), and Xw / 2 ≧ | Δe |. In this case, it is determined that the host vehicle OV tends to deviate from the lane, and the process proceeds to step S12. If Xw / 2 <| Δe |, the process proceeds to step S13.

<Step S12: Select support control 3>
The target steering force setting means 150 sets the steering torque Tp by the assist control 3 (alarm pulse control) set by the alarm pulse steering force setting means 153 as the target steering torque.
Thereafter, the process returns, the process returns to step S01, and the subsequent processing is repeated.

<Step S13: Continue control stop>
The target steering force setting means 150 continues to stop the steering assist control.
Thereafter, the process returns, the process returns to step S01, and the subsequent processing is repeated.

FIG. 5 is a timing chart showing an example of the transition of the support level in the present embodiment.
The steering assist device executes assist control 1 (primary control) in a normal state where it is not determined that the driving intention is lowered. When the state where the driver input torque Td is less than Tth continues for T_th1 or more, the first driving intention lowering state is determined, and the control is switched to support control 2 (tertiary control). Furthermore, when the state where the driver input torque Td is less than Tth continues for T_th2 or more, the second driving intention lowering state is determined, and the steering assist control is stopped. Thereafter, the support control 3 (alarm pulse control) is executed only when the host vehicle has a tendency to deviate from the lane. Further, when the driver input torque Td that is equal to or greater than the threshold value Tth is detected, the assist control 1 is immediately resumed.

According to the present embodiment described above, when it is determined that the driver's intention to drive is in a lowered state, the support level that causes the host vehicle to follow the target travel position is reduced from the primary control during normal time. By setting the target steering torque based on the next control, the driver's dependence on the steering assist control can be eliminated and the main driving operation can be promoted. Further, even in the low intention state, in the first driving intention low state where the degree of intention reduction is relatively slight, the support is not completely stopped, but based on the tertiary control with a relatively low support level. By setting the target steering torque, it is possible to reduce the risk of lane departure or the like due to stopping the control while the driving intention is lowered.
Further, the first driving intention lowering state and the second driving intention lowering state are determined. In the first driving intention lowering state, the target steering torque is set by the tertiary control, and in the second driving intention lowering state. By executing the alarm pulse control, even when the tertiary control is stopped, the driver can be alerted at the time of departure from the lane, and the driver's intention can be improved. Can be executed.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) In the above-described embodiment, the first target steering force based on the primary control is used in the normal state, and the second target steering force based on the tertiary control is used when the intention is lowered. At least one of the force and the second target steering force is a combination of the target steering force by primary control and the target steering force by high-order control such as tertiary control (primary control + high-order control), The second target steering force may be configured such that the ratio (weight) of the target steering force based on the higher-order control is larger than the first target steering force. For example, both the first target steering force and the second target steering force are set by primary control + tertiary control, and the weight of the tertiary control is increased with respect to the second target steering force over the first target steering force. You may do it. Further, the first target steering force may be primary control, and the second target steering force may be primary control + tertiary control (however, the gain of the primary control is lower than the first target steering force). . Alternatively, the first target steering force may be primary control + tertiary control, and the second target steering force may be tertiary control.
(2) In the embodiment, the environment recognizing means detects the lane shape using a stereo camera. However, the present invention is not limited to this. For example, the map data prepared for the navigation device etc. The lane shape may be detected based on the positioning information. Further, the method for detecting the lateral position of the own vehicle and the yaw angle is not particularly limited.
(3) The configuration of the actuator that applies the steering torque to the steering mechanism is not limited to the column assist type as in the embodiment. For example, the pinion assist type that drives the pinion shaft connected to the steering shaft, the steering shaft A double pinion type that drives a pinion that is independent of the connected pinion, a rack direct-acting type that drives the steering rack itself in a straight direction, or the like may be used.
(4) In the embodiment, the driving intention determination means determines the driver's driving intention based on the history of the steering input torque, but the present invention is not limited to this, and the driver's driving intention is determined by other methods. Also good. For example, the driver's driving intention may be determined based on the steering wheel steering angle history.

It is a figure which shows the system configuration | structure of the vehicle provided with the Example of the steering assistance device to which this invention is applied. It is a figure which shows an example of the planar arrangement | positioning of the own vehicle and lane in the steering assistance apparatus of an Example. The graph which shows the correlation with the deviation and steering torque in assistance control 1-3 which the primary control steering force setting means, the tertiary control steering force setting means, and the warning pulse steering force setting means in the steering assistance device of an Example perform, respectively. It is. It is a flowchart which shows the operation | movement at the time of the assistance level change in the steering assistance apparatus of an Example. It is a timing chart which shows an example of transition of the assistance level in the steering assistance device of an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Steering mechanism 11 Steering wheel 12 Steering shaft 13 Steering gear box 14 Tie rod FW Front wheel H Housing 20 Electric power steering (EPS) control unit 21 Electric actuator 22 Steering angle sensor 23 Torque sensor 30 Steering control unit 31 Hydraulic control unit (HCU) )
32 Vehicle speed sensor 33 Yaw rate sensor 34 Lateral acceleration (lateral G) sensor 40 Engine control unit 50 Transmission control unit 60 Vehicle integrated unit
DESCRIPTION OF SYMBOLS 100 Steering assistance control unit 110 Environment recognition means 111 Stereo camera 112 Image processing part 120 Target travel position setting means 130 Own vehicle travel path estimation means 140 Driving intention judgment means 150 Target steering force setting means 151 Primary control steering force setting means 152 3 Next control steering force setting means 153 Warning pulse steering force setting means 160 Steering force control means OV Own vehicle WL White line Xc Target travel position Xe Own vehicle lateral position

Claims (4)

A steering assist device that applies a steering force to a steering mechanism so that the host vehicle travels along a traveling lane,
Environment recognition means for recognizing the environment ahead of the host vehicle including the traveling lane of the host vehicle;
Target travel position setting means for setting a target travel position of the host vehicle in the travel lane of the host vehicle using the environment recognition unit;
Own vehicle lateral position recognition means for recognizing the lateral position of the own vehicle;
Target steering force setting means for setting a target steering force applied to the steering mechanism based on a deviation between the target travel position and a lateral position of the host vehicle;
Steering control means for applying a steering force to the steering mechanism based on the target steering force;
Driving intention determining means for determining the driver's driving intention based on the driving steering state of the driver,
The target steering force setting means has a first target steering force and a second target steering force that is set to a value smaller than the first target steering force at least in a region where the deviation is small.
The steering control means applies a steering force to the steering mechanism based on the first target steering force when it is determined that the driver's driving intention is high, and the driver's driving intention is reduced. When it is determined, the steering assist device is configured to apply a steering force to the steering mechanism based on the second target steering force. The first target steering force is set to increase as the deviation increases, and the second target steering force is set to be smaller than the first target steering force in a region where the deviation is small. The steering assist device according to claim 1, wherein an increase rate is set to increase as the deviation increases. The driving intention determination means determines a first driving intention reduced state as the driving intention reduced state and a second driving intention reduced state in which the driving intention is further reduced than the first driving intention reduced state. ,
The target steering force setting means includes, in addition to the first target steering force and the second target steering force, a third target steering force that sets a steering force only when the deviation is equal to or greater than a predetermined value. Have
The steering control means changes from the steering control based on the first target steering force to the steering control based on the second target steering force when the first driving intention lowering state is determined, The steering control based on the second target steering force is changed to the steering control based on the third target steering force when the driving intention lowering state is determined. The steering assist device described. A steering assist device that applies a steering force to a steering mechanism so that the host vehicle travels along a traveling lane,
Environment recognition means for recognizing the environment ahead of the host vehicle including the traveling lane of the host vehicle;
Target travel position setting means for setting a target travel position of the host vehicle in the travel lane of the host vehicle using the environment recognition unit;
Own vehicle lateral position recognition means for recognizing the lateral position of the own vehicle;
Target steering force setting means for setting a target steering force applied to the steering mechanism based on a deviation between the target travel position and a lateral position of the host vehicle;
Steering control means for applying a steering force to the steering mechanism based on the target steering force;
Driving intention determining means for determining the driver's driving intention based on the driving steering state of the driver,
The target steering force setting means includes a first target steering force that is set to increase as the deviation increases, and a second target steering that is set to a predetermined value only when the deviation is greater than or equal to a predetermined value. Power and
The steering control means applies a steering force to the steering mechanism based on the first target steering force when it is determined that the driver's driving intention is high, and the driver's driving intention is reduced. When it is determined, the steering assist device is configured to apply a steering force to the steering mechanism based on the second target steering force.

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