U.S. patent application number 15/869938 was filed with the patent office on 2018-07-19 for lane keeping traveling support apparatus.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Kazuma HASHIMOTO, Hiroaki KATAOKA.
Application Number | 20180201318 15/869938 |
Document ID | / |
Family ID | 62838993 |
Filed Date | 2018-07-19 |
United States Patent
Application |
20180201318 |
Kind Code |
A1 |
KATAOKA; Hiroaki ; et
al. |
July 19, 2018 |
LANE KEEPING TRAVELING SUPPORT APPARATUS
Abstract
A lane keeping traveling support apparatus includes a driving
support ECU. The driving support ECU is configured to determine a
lane departure prevention torque in such a manner that a magnitude
of the lane departure prevention torque becomes smaller or to stop
performing a lane departure prevention control, when the lane
departure prevention control is performed in place of a lane
keeping assist control and a specific operation of a steering wheel
is performed by a driver so as to have a direction of an own
vehicle head to a lane departure direction.
Inventors: |
KATAOKA; Hiroaki;
(Toyota-shi, JP) ; HASHIMOTO; Kazuma; (Nukata-gun,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
62838993 |
Appl. No.: |
15/869938 |
Filed: |
January 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62D 15/025 20130101;
B62D 5/0463 20130101; G06T 7/60 20130101; G06K 9/00798 20130101;
G06K 9/209 20130101; G06T 2207/30256 20130101; G06T 2207/30204
20130101; B62D 6/08 20130101; G08G 1/167 20130101 |
International
Class: |
B62D 15/02 20060101
B62D015/02; B62D 5/04 20060101 B62D005/04; B62D 6/08 20060101
B62D006/08; G06K 9/00 20060101 G06K009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2017 |
JP |
2017-005970 |
Claims
1. A lane keeping traveling support apparatus comprising: an
electric motor for applying a steering assist torque to a steering
mechanism for changing a turning angle of steered wheels of an own
vehicle; a lane recognition section: for recognizing a pair of lane
markers that defines a traveling lane in which said own vehicle is
traveling; for setting a target traveling line based on said lane
markers; and for obtaining lane information including a position
and a direction of said own vehicle with respect to said lane
markers and said target traveling line; and a control unit for
selectively performing one of: a lane keeping assist control: for
determining a lane keeping support torque which is said steering
assist torque to keep a traveling position of said own vehicle in
the vicinity of said target traveling line based on said lane
information; and for applying said determined lane keeping support
torque to said steering mechanism by using said electric motor; and
a lane departure prevention control: for determining, based on said
lane information, a lane departure prevention torque which is said
steering assist torque to change a direction of said own vehicle to
a direction opposite to a lane departure direction which is a
direction of said own vehicle when deviating from said traveling
lane so as to prevent said own vehicle from deviating from said
traveling lane, when a specific traveling situation occurs in which
said own vehicle is likely to deviate from said traveling lane to
outside of said traveling lane, said lane departure prevention
torque having a magnitude larger than a magnitude of said lane
keeping support torque determined when it is assumed that said lane
keeping support control is being performed under said specific
traveling situation; and for applying said determined lane
departure prevention torque to said steering mechanism by using
said electric motor, the control unit configured to perform said
lane departure prevention control instead of said lane keeping
assist control, when said specific driving situation occurs while
said lane keeping support control is being performed by said
control unit, wherein, the control unit is configured to: determine
said lane departure prevention torque, when said specific driving
situation occurs and a specific operation of a steering wheel is
performed by said driver so as to have said direction of said own
vehicle head to said lane departure direction, in such a manner
that a magnitude of said lane departure prevention torque becomes
smaller than a magnitude of said lane departure prevention torque
when said specific operation of said steering wheel is not
performed by said driver; or stop performing said lane departure
prevention control, when said specific driving situation occurs and
said specific operation of said steering wheel is performed by said
driver.
2. The lane keeping traveling support apparatus according to claim
1, wherein, said control unit is configured, when performing said
lane departure prevention control: to determine a reference LDA
target torque which is a basic value of said lane departure
prevention torque based on said lane information; to calculate a
corrected LDA target torque by multiplying said reference LDA
target torque by an LDA control gain larger than 0 and smaller than
1, when said specific driving situation occurs and said specific
operation of said steering wheel is performed by said driver; and
to set said reference LDA target torque as said corrected LDA
target torque, when said specific driving situation occurs and said
specific operation of said steering wheel is not performed by said
driver; and to use said corrected LDA target torque as said lane
departure prevention torque.
3. The lane keeping traveling support apparatus according to claim
1, wherein, said control unit is configured, when said specific
driving situation occurs and said specific operation of said
steering wheel is performed by said driver: to stop performing said
lane departure prevention control; and to perform said lane keeping
assist control instead of said stopped lane departure prevention
control.
4. The lane keeping traveling support apparatus according to claim
1, wherein, said control unit is configured, when performing said
lane keeping assist control: to calculate a reference LKA target
torque which is a basic value of said lane keeping support torque
based on said lane information; to calculate a corrected LKA target
torque by multiplying said reference LKA target torque by a LKA
control gain which becomes smaller within a range from 0 to 1 as a
magnitude of a driver torque which is a torque applied to said
steering wheel by said driver increases; and to use said corrected
LKA target torque as said lane keeping support torque.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a lane keeping traveling
support apparatus which controls a steering assist torque in such a
manner that a vehicle (own vehicle) does not deviate from a lane
where the own vehicle is traveling.
2. Description of the Related Art
[0002] A lane keeping traveling support apparatus, which has been
conventionally known, recognizes lane markers such as a white line
or a yellow line on a road by using a camera sensor mounted on an
own vehicle to control a steering assist torque in such a manner
that the own vehicle travels at an appropriate position within a
"traveling lane (lane) specified by the recognized lane markers"
(for example, refer to WO 2011/064825). Hereinafter, the
conventional lane keeping traveling support apparatus is also
referred to as a "conventional apparatus". A lane keeping assist
control and a lane departure prevention control are known as a
control to realize a typical lane keeping traveling support (lane
keeping assist) performed by the conventional apparatus.
[0003] When the conventional apparatus performs the lane keeping
assist control, for example, the conventional apparatus detects the
left and right white lines by the camera sensor and sets/determines
a center line which is positioned at a central position between the
left white line and the right white line as a target traveling
line. Further, the conventional apparatus supports a steering
operation of a driver by applying the steering assist torque to a
steering mechanism in such a manner that a position of the own
vehicle is kept in the vicinity of the target traveling line. It
should be noted that such a lane keeping assist control is referred
to as an "LKA (Lane Keeping Assist) control".
[0004] On the other hand, while the conventional apparatus performs
the lane departure prevention control, the conventional apparatus
generates a warning to the driver when the own vehicle is likely to
deviate from the traveling lane, and supports the steering
operation of the driver by applying the steering assist torque to
the steering mechanism so as to prevent the own vehicle from
deviating from the traveling lane.
[0005] It should be noted that such a lane departure prevention
control is also referred to as an "LDA (Lane Departure Alert)
control with a steering control" or simply as an "LDA control".
SUMMARY OF THE INVENTION
[0006] The lane keeping assist control is a control to have a
vehicle smoothly travel along the target traveling line. Therefore,
while the lane keeping assist control is performed, for example, an
upper limit value is set for limiting the steering assist torque
(that is, a control amount changed by the lane keeping assist
control) in such a manner that a lateral acceleration and/or a yaw
rate change rate of the vehicle do/does not become excessive.
Therefore, for example, in a situation where the speed of the
vehicle traveling in a curve section is excessively high, and/or in
a situation where a disturbance (a cross/side wind, a road surface
inclination, and the like) is excessively serious, a case may arise
where the steering assist torque by the lane keeping assist control
reaches the upper limit value.
[0007] When the steering assist torque reaches the upper limit
value, the conventional apparatus can not keep a traveling position
of the own vehicle close to the target traveling line by the lane
keeping assist control. As a result, a case arises where the own
vehicle deviates from the traveling lane. In view of this, in such
a case, the conventional apparatus starts the lane departure
prevention control to generate a "relatively large steering assist
torque" which exceeds the upper limit value in the lane keeping
assist control so that the own vehicle does not deviate from the
traveling lane, when the own vehicle excessively approaches an end
of the traveling lane (for example, one of a pair of the left and
right white lines).
[0008] On the other hand, when the own vehicle excessively
approaches the end of the traveling lane due to an intentional
steering operation (steering wheel operation) by the driver to
change lanes while the lane keeping assist control is being
performed, the conventional apparatus also starts the lane
departure prevention control to generate the relatively large
steering assist torque similar to the above.
[0009] However, since a steering direction of the steering assist
torque is opposite to a steering direction of the driver's
intentional steering operation to cause the own vehicle to deviate
from the traveling lane, the lane departure prevention control does
not follow (is not along with) the driver's intention.
[0010] When the lane departure prevention control is performed in a
manner that the lane departure prevention control is not along with
the intention of the driver as described above, the driver is
highly likely to feel discomfort. In other words, it can be said
that it is difficult for the conventional apparatus to work along
with the intention of the steering operation performed by the
driver to change the traveling direction of the own vehicle (that
is, the conventional apparatus is an apparatus having a low
acceptability for intentional steering operation by the
driver).
[0011] The present invention has been made in order to solve the
above-described problem. That is, one of objects of the present
invention is to provide a lane keeping traveling support apparatus
which has a high acceptability for the intentional steering
operation of the driver. Hereinafter, the lane keeping traveling
support apparatus according to the present invention is also
referred to as a "present invention apparatus".
[0012] The present invention apparatus comprises:
[0013] an electric motor for (21) applying a steering assist torque
to a steering mechanism for changing a turning angle of steered
wheels of an own vehicle;
[0014] a lane recognition section (11): [0015] for recognizing a
pair of lane markers that defines a traveling lane in which the own
vehicle is traveling; [0016] for setting a target traveling line
based on the lane markers; and [0017] for obtaining lane
information including a position and a direction of the own vehicle
with respect to the lane markers and the target traveling line;
and
[0018] a control unit (10) for selectively performing one of:
[0019] a lane keeping assist control and a lane departure
prevention control.
[0020] The lane keeping assist control is a control: [0021] for
determining a lane keeping support torque which is the steering
assist torque to keep a traveling position of the own vehicle in
the vicinity of the target traveling line based on the lane
information; and [0022] for applying the determined lane keeping
support torque to the steering mechanism by using the electric
motor.
[0023] The lane departure prevention control: [0024] for
determining, based on said lane information, a lane departure
prevention torque which is the steering assist torque to change a
direction of the own vehicle to a direction opposite to a lane
departure direction which is a direction of the own vehicle when
deviating from the traveling lane so as to prevent the own vehicle
from deviating from the traveling lane, when a specific traveling
situation occurs in which the own vehicle is likely to deviate from
the traveling lane to outside of the traveling lane, the lane
departure prevention torque having a magnitude larger than a
magnitude of the lane keeping support torque determined when it is
assumed that the lane keeping support control is being performed
under the specific traveling situation; and [0025] for applying the
determined lane departure prevention torque to the steering
mechanism by using the electric motor.
[0026] The control unit is configured to perform the lane departure
prevention control instead of the lane keeping assist control (step
770 shown in FIG. 7), when the specific driving situation occurs
while the lane keeping support control is being performed by the
control unit (refer to a "Yes" determination at step 840 shown in
FIG. 8).
[0027] The control unit is configured to: [0028] determine the lane
departure prevention torque (step 760 shown in FIG. 7), when the
specific driving situation occurs and a specific operation of a
steering wheel (SW) is performed by the driver so as to have the
direction of the own vehicle head to the lane departure direction
(refer to a "Yes" determination at step 745 shown in FIG. 7), in
such a manner that a magnitude of the lane departure prevention
torque becomes smaller than a magnitude of the lane departure
prevention torque when the specific operation of the steering wheel
is not performed by the driver; or [0029] stop performing the lane
departure prevention control, when the specific driving situation
occurs and the specific operation of the steering wheel is
performed by the driver.
[0030] When the specific traveling situation occurs in which the
own vehicle is likely to deviate from the traveling lane to the
outside of the traveling lane and the specific operation of the
steering wheel is performed by the driver so as to have the own
vehicle head/direct to the lane departure direction, the present
invention apparatus determines the lane departure prevention torque
in such a manner that the magnitude of the lane deviation
prevention torque becomes smaller than a magnitude of the lane
departure prevention torque when the specific operation of the
steering wheel is not performed by the driver, or stops performing
the lane departure prevention control. Thereby, it is possible to
reduce the possibility that the LDA control causes the driver to
feel uncomfortable. As a result, the present invention apparatus
can increase acceptability for the intentional steering operation
of the driver.
[0031] In one of aspects of the present invention apparatus, the
control unit is configured, when performing the lane departure
prevention control: [0032] to determine a reference LDA target
torque which is a basic value of the lane departure prevention
torque based on the lane information (step 740 shown in FIG. 7);
[0033] to calculate a corrected LDA target torque by multiplying
the reference LDA target torque by an LDA control gain larger than
0 and smaller than 1 (step 760 shown in FIG. 7), when the specific
driving situation occurs and the specific operation of the steering
wheel is performed by the driver (refer to a "Yes" determination at
step 745 shown in FIG. 7); and [0034] to set the reference LDA
target torque as the corrected LDA target torque (steps 765 and 760
shown in FIG. 7), when the specific driving situation occurs and
the specific operation of the steering wheel is not performed by
the driver (refer to a "No" determination at step 745 shown in FIG.
7); and [0035] to use the corrected LDA target torque as the lane
departure prevention torque (step 775 shown in FIG. 7).
[0036] According to the above aspect, when the above specific
driving situation occurs, and when the specific operation of the
steering wheel is performed by the driver, the control amount of
the lane departure prevention is decreased (or an effect of the
lane departure prevention is weakened). Thereby, the possibility
that the lane departure prevention control causes the driver to
feel uncomfortable can be reduced. Therefore, the above aspect can
increase the acceptability for the intentional steering operation
of the driver.
[0037] In one of aspects of the present invention apparatus,
[0038] the control unit is configured, when the specific driving
situation occurs and the specific operation of the steering wheel
is performed by the driver (refer to a "Yes" determination at step
745 shown in FIG. 7): [0039] to stop performing the lane departure
prevention control; and [0040] to perform the lane keeping assist
control instead of the stopped lane departure prevention
control.
[0041] According to the above aspect, when the above specific
driving situation occurs, and when the specific operation of the
steering wheel is performed by the driver, the lane departure
prevention control is stopped. Thereby, the possibility that the
lane departure prevention control causes the driver to feel
uncomfortable can be reduced. Therefore, it can increase the
acceptability for the intentional steering operation of the
driver.
[0042] In one of aspects of the present invention apparatus,
[0043] the control unit is configured, when performing the lane
keeping assist control: [0044] to calculate a reference LKA target
torque which is a basic value of the lane keeping support torque
based on the lane information (step 710 shown in FIG. 7); [0045] to
calculate a corrected LKA target torque by multiplying the
reference LKA target torque by a LKA control gain which becomes
smaller within a range from 0 to 1 as a magnitude of a driver
torque which is a torque applied to the steering wheel by the
driver increases (step 720 shown in FIG. 7); and [0046] to use the
corrected LKA target torque as the lane keeping support torque
(step 780 shown in FIG. 7).
[0047] According to the above aspect, the lane keeping assist
control decreases the magnitude of the steering assist torque for
causing the own vehicle to travel along the target traveling line
by the lane keeping assist control. That is, the control effect of
the lane keeping assist control is weakened. As a result, when the
driver is performing the specific steering operation with the
intention to change lanes, the specific steering wheel operation to
have the own vehicle turn/head to the lane departure direction can
be performed with a light force. Therefore, the possibility that
the lane keeping assist control causes the driver to feel
uncomfortable can be reduced.
[0048] In the above description, references used in the following
descriptions regarding embodiments are added with parentheses to
the elements of the present invention, in order to assist in
understanding the present invention. However, those references
should not be used to limit the scope of the invention. Other
objects, other features, and accompanying advantages of the present
invention will be readily understood from the description of
embodiments of the present invention to be given referring to the
following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a schematic system configuration diagram of a lane
keeping traveling support apparatus according to an embodiment of
the present invention.
[0050] FIG. 2 is a plan view showing left and right white lines LL
and LR, a target traveling line Ld, and a curve radius R.
[0051] FIG. 3 is a plan view showing, a center distance Dc, and a
yaw angle .theta.y, serving as lane information for a lane keeping
assist control.
[0052] FIG. 4A is a plan view showing a side distance Ds and a yaw
angle .theta.y, serving as lane information for a lane departure
prevention control is performed.
[0053] FIG. 4B is a graph showing relationship between a deviation
indicator distance Ds' and the side distance Ds.
[0054] FIG. 5 is a graph showing relationship between a traveling
position of an own vehicle and target torques.
[0055] FIG. 6A is a plan view showing relationship between a
traveling position of the own vehicle and a control state when a
driving support ECU 10 is operating in a lane keeping traveling
support mode.
[0056] FIG. 6B is a graph showing relationship between a driver
torque TqDr and a gain GLKA.
[0057] FIG. 7 is a flowchart showing a lane keeping traveling
support mode routine executed by a CPU of the driving support
ECU.
[0058] FIG. 8 is a flowchart showing an LDA operation execution
flag setting routine executed by the CPU of the driving support
ECU.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0059] A lane keeping traveling support apparatus (hereinafter,
referred to as a "present apparatus") according to an embodiment of
the present invention will be described below, referring to
figures.
(Construction)
[0060] The present apparatus is applied to a vehicle (not shown).
In the present specification, in order to distinguish the vehicle
to which the present apparatus is applied from other vehicles, the
vehicle to which the present apparatus is applied may be referred
to as an "own vehicle". As shown in FIG. 1, the present apparatus
comprises a driving support ECU 10, an electric power steering ECU
20, a camera 30, vehicle state sensors 40, an operation switch 50,
a steering torque sensor 51, a buzzer 60, and a display unit
(indicator) 70. Hereinafter, the electric power steering ECU 20 is
referred to as an "EPS ECU (Electric Power Steering ECU) 20".
[0061] It should be noted that the ECU is an abbreviation of an
Electric Control Unit, and is an electronic control circuit having
a microcomputer including a CPU, a ROM, a RAM, an interface, and
the like as its main components. The CPU realizes various functions
by executing instructions (routines) stored in a memory (ROM).
[0062] Focusing on functions of the microcomputer, the driving
support ECU 10 is roughly divided into a lane recognition section
11, a lane departure prevention control section 12, a lane keeping
assist control section 13, and a switching control section 14. The
driving support ECU 10 calculates a target torque (a control
amount) for a lane keeping traveling support by using these
functions. The driving support ECU 10 transmits a steering command
including a signal representing the target torque to the EPS ECU
20.
[0063] The EPS ECU 20 is a control apparatus of an electric power
steering apparatus, and mainly includes a microcomputer and a motor
drive circuit. The EPS ECU 20 obtains a steering torque
(hereinafter, also referred to as a "driver torque TqDr") applied
to a steering wheel SW by a driver, using the steering torque
sensor 51 provided on a steering shaft US, when a lane keeping
traveling support which will be described later is not being
performed. Further, the EPS ECU 20 drives an assist motor 21 which
is an electric motor based on the obtained driver torque TqDr,
thereby applying a steering assist torque to a steering mechanism
to assist a steering wheel operation of the driver. In the
embodiment, it should be noted that the driver torque TqDr is a
positive value when the driver torque TqDr is a torque in a
direction in which the own vehicle generates a yaw rate in a left
turning direction. The driver torque TqDr is a negative value when
the driver torque TqDr is a torque in a direction in which the own
vehicle generates a yaw rate in a right turning direction.
[0064] The EPS ECU 20 is connected with the driving support ECU 10.
When the EPS ECU 20 receives the steering command from the driving
support ECU 10, the EPS ECU 20 drives the assist motor 21 based on
the target torque specified by the steering command, thereby
generating the steering assist torque equal to the target torque.
This steering assist torque is different from the steering assist
torque applied for assisting the steering wheel operation of the
driver. This steering assist torque is the assist torque applied to
the steering mechanism based on the steering command transmitted
from the driving support ECU 10.
[0065] The vehicle state sensors 40 include a vehicle speed sensor
for detecting the vehicle speed of the own vehicle, a yaw rate
sensor for detecting a yaw rate of the own vehicle, a lateral
acceleration sensor for detecting a lateral acceleration of the own
vehicle, and the like. The vehicle state sensors 40 are used to
acquire information necessary for calculating the target torque for
the lane keeping assist.
[0066] The lane recognition section 11 is connected with the camera
30 which is a stereo camera. The camera 30 photographs (takes an
image of) an area ahead of the own vehicle and transmits an image
data acquired by photographing to the lane recognition section 11.
The lane recognition section 11 recognizes (detects) lane markers
such as left and right white lines (each of which includes a
continuous line and a dashed line), left and right yellow lines, or
the like, on a road by analyzing the image data transmitted from
the camera 30. Hereinafter, the lane marker is referred to as a
"white line" for convenience.
[0067] As shown in FIG. 2, the lane recognition section 11
recognizes a left white line LL and a right white line LR and
sets/determines a center line which is positioned at the center
between the left white line LL and the right white line LR as a
target traveling line Ld. Further, the lane recognition section 11
calculates a curve radius R of the target traveling line Ld. It
should be noted that the target traveling line Ld is not
necessarily set at the central position of the left and right white
lines. The target traveling line Ld may be set at a position
shifted from the center position in the left or the right direction
by a "predetermined distance which is sufficiently short as
compared with a lane width".
[0068] The lane recognition section 11 calculates a position and a
direction of the own vehicle C in the traveling lane defined by the
left white line LL and the right white line LR. More specifically,
the lane recognition section 11 calculates "a center distance Dc
and a yaw angle .theta.y" defined below and shown in FIG. 3. It
should be noted that a reference point P of the own vehicle C is
the central position between the left and right front wheels on an
axle of the left and right front wheels of the own vehicle C.
[0069] The center distance Dc: the center distance Dc is a distance
Dc in a road width direction (lateral direction) between the
reference point P and the target traveling line Ld. In the present
embodiment, the center distance Dc is "0" when the reference point
P is on the target traveling line Ld. The center distance Dc is a
positive value when the reference point P is in the right side of
the target traveling line Ld. The center distance Dc is a negative
value when the reference point P is in the left side of the target
traveling line Ld.
[0070] The yaw angle .theta.y: the yaw angle .theta.y is an angle
(deviation angle) formed between the direction of the target
traveling line Ld and a direction Cd in which the own vehicle C
heads, and is an acute angle from -90.degree. to +90.degree.. In
the present embodiment, the yaw angle .theta.y is "0" when the
direction Cd (the own vehicle C heading direction) coincides with
the direction of the target traveling line Ld. The yaw angle
.theta.y is a positive value when the direction Cd of the own
vehicle C inclines in the clockwise direction (the direction shown
in FIG. 3) with respect to the direction of the target traveling
line Ld. The yaw angle .theta.y is a negative value when the
direction Cd of the own vehicle C inclines in the counterclockwise
direction (the direction shown in FIG. 4A) with respect to the
direction of the target traveling line Ld.
[0071] Further, the lane recognition section 11 calculates a side
distance Ds defined below and shown in FIG. 4A.
[0072] The side distance Ds: the side distance Ds is a distance in
the road width direction between the "reference point P" and a
"white line to which the reference point P of the own vehicle C is
closer among the right white line LR and the left white line LL".
Hereinafter, the white line to which the reference point P of the
own vehicle C is closer is referred to as an "objective (or target)
white line" for convenience. In the example shown in FIG. 4A, the
objective white line is the left white line LL. In the present
embodiment, the side distance Ds is "0" when the reference point P
is on the objective white line. The side distance Ds is a positive
value when the reference point P is inside the traveling lane with
respect to the objective white line (at a position in the center
side of the road). The side distance Ds is a negative value when
the reference point P is outside the traveling lane with respect to
the objective white line (at a position in the side departing from
the road).
[0073] The values (Dc, Ds, .theta.y, R) calculated by the lane
recognition section 11 are referred to as lane information.
[0074] The lane departure prevention control section 12 performs
the lane departure prevention control. The lane departure
prevention control is a control for applying the steering assist
torque to the steering mechanism in such a manner that the own
vehicle does not deviate from the traveling lane when the own
vehicle is about to deviate from the traveling lane to the outside
of the traveling lane, so as to support a steering operation of the
driver (steering operation) with alerting the driver. Hereinafter,
the lane departure prevention control section 12 is referred to as
an "LDA control section 12" and the lane departure prevention
control is referred to as an "LDA control".
[0075] The LDA control section 12 receives the lane information
(Ds, .theta.y, R) calculated by the lane recognition section 11 to
calculate a target torque for preventing the own vehicle from
deviating from the traveling lane to the outside of the traveling
lane. Hereinafter, the calculated target torque is also referred to
as an "LDA target torque". As will be described later, the LDA
target torque includes a reference LDA target torque TLDAs and a
corrected LDA target torque TLDAf. In the embodiment, the LDA
target torque TLDA is a positive value when the LDA target torque
TLDA is a torque in a direction in which the own vehicle generates
a yaw rate in a left turning direction. The LDA target torque TLDA
is a negative value when the LDA target torque TLDA is a torque in
a direction in which the own vehicle generates a yaw rate in a
right turning direction. In this regard, the same applies not only
to "the reference LDA target torque TLDAs and the corrected LDA
target torque TLDAf" but also to "a reference LKA target torque
TLKAs and a corrected LKA target torque TLKAf" both of which will
be described later.
[0076] When and after an LDA calculation start condition described
below is satisfied, the LDA control section 12 calculates the
reference LDA target torque TLDAs using a following formula (1)
until an LDA calculation termination condition is satisfied. When
the LDA control section 12 does not calculate the LDA target torque
TLDAs using the formula (1), the LDA control section 12
provisionally sets the reference LDA target torque TLDAs to "0".
[0077] The LDA calculation start condition: the LDA calculation
start condition is a condition which is satisfied when the side
distance Ds becomes equal to or shorter/smaller than a reference
side distance Dsref and when an operating condition of an lane
keeping traveling support mode is satisfied. [0078] The LDA
calculation termination condition: the LDA calculation termination
condition is a condition which is satisfied when both of following
conditions (a) and (b) are satisfied.
[0079] (a) The side distance Ds is longer/greater than the
reference side distance Dsref.
[0080] (b) The yaw angle .theta.y is equal to or greater than a
"negative switching determination threshold value .theta.yrefF"
when the objective white line is the left white line LL, or the yaw
angle .theta.y is smaller than or equal to a "positive switching
determination threshold value .theta.yrefS" when the objective
white line is the right white line LR.
[0081] Each of the switching determination threshold value
.theta.yrefF and the switching determination threshold value
.theta.yrefS is set to an angle which allows the direction of the
own vehicle C to be regarded as being roughly parallel
(substantially parallel) to the target traveling line Ld.
TLDAs=K1 (V.sup.2/R)+K2 Ds'+K3 .theta.y (1)
[0082] Here, each of K1, K2, and K3 is a control gain.
[0083] K1 is set to a positive value (k1>0) when the traveling
lane curves to the left, and is set to a negative value (-k1) when
the traveling lane curves to the right.
[0084] K2 is set to a positive value (k2>0) when the objective
white line is the right white line LR, and is set to a negative
value (-k2) when the objective white line is the left white line
LL.
[0085] K3 is set to a positive value.
[0086] V is the vehicle speed of the own vehicle detected by the
vehicle speed sensor.
[0087] R is the curve radius (R>0) of the target traveling line
Ld calculated by the lane recognition section 11.
[0088] .theta.y is the above-described yaw angle.
[0089] Ds' is a departure indicator distance Ds' which is a value
(Ds'=Dsref-Ds) obtained by subtracting the side distance Ds from
the preset reference side distance Dsref. The departure indicator
distance Ds' has relationship shown in a graph of FIG. 4B with
respect to the side distance Ds.
[0090] The first term on the right side of the formula (1) is a
torque component (feedforward control amount with respect to the
curve radius R) determined according to the curve radius R of the
road (target traveling line Ld) and the vehicle speed V. The torque
component acts in a feedforward control manner with respect to the
curve radius R. That is, the first term on the right side of the
formula (1) is the torque component to have the own vehicle C
travel according to a curvature of the target traveling line
Ld.
[0091] The second term on the right side of the formula (1) is a
torque component which acts in a feedback control manner so that
the own vehicle C does not excessively approach the white line (in
particular, the objective white line) in the road width direction,
or so that the own vehicle C travels at the inner side (road center
side) with respect to the objective white line after the own
vehicle C has deviated from the traveling lane. The second term is
a feedback control amount with respect to the side distance Ds or
with respect to the departure indicator distance Ds'.
[0092] The third term on the right side of the formula (1) is a
torque component (feedback control amount with respect to the yaw
angle .theta.y) which acts in a feedback control manner so as to
reduce a magnitude |.theta.y| of the yaw angle .theta.y (i.e., so
as to reduce a deviation of the direction of the own vehicle with
respect to the target traveling line Ld).
[0093] It should be noted that the LDA control section 12 may
obtain/acquire the reference LDA target torque TLDAs by adding a
value K4 (.gamma.*-.gamma.) to the right side of the above formula
(1) (i.e., TLDAs=K1 (V.sup.2/R)+K2 Ds'+K3 .theta.y+K4
(.gamma.*-.gamma.)).
[0094] K4 is a positive gain (control gain).
[0095] .gamma.* is the target yaw rate, and is the yaw rate to be
achieved/realized based on the sum of the first term of the right
side, the second term of the right side, and the third term of the
right side.
[0096] .gamma. is an actual yaw rate of the own vehicle C detected
by the yaw rate sensor.
[0097] Therefore, the value K4 (.gamma.*-.gamma.) is a torque
component (feedback amount with respect to the yaw rate) which acts
in a feedback control manner so as to reduce a deviation between
the target yaw rate .gamma.* and the actual yaw rate .gamma..
[0098] Here, the following situation is considered, where the own
vehicle C is about to deviate from the right white line LR of the
traveling lane (in other words, the side distance Ds has become
equal to or smaller than the reference side distance Dsref) when
the own own vehicle C is traveling at a constant speed V along the
target traveling line Ld curving to the left and having a constant
curve radius R which is excessively small with respect to the
vehicle speed V. In this case, since the control gain K2 is set to
the positive value k2 and the departure indicator distance Ds'
becomes a positive value, the second term (K2Ds') on the right side
of the formula (1) becomes a positive value. Further, the control
gain K3 is set to the positive value and the yaw angle .theta.y
becomes a positive value because the own vehicle is about to depart
from the right white line LR. Thus, the third term
(K3.about..theta.y) on the right side of the formula (1) also
becomes a positive value. In addition, at the beginning of the
tendency of the own vehicle C (that is, the departure tendency)
when deviating from the right white line LR, the deviation
indicator distance Ds' and the yaw angle .theta.y increase. That
is, the deviation indicator distance Ds' and the yaw angle .theta.y
can be said to be parameters whose absolute values increase as the
possibility that the own vehicle C deviates from the traveling lane
increases.
[0099] Meanwhile, the LDA control section 12 calculates the
reference LDA target torque TLDAs each time a predetermined time
elapses. The control gain K2 and the control gain K3 are control
gains each of which is multiplied by the parameter whose absolute
value becomes larger as the possibility that the own vehicle C
deviates from the traveling lane increases. Therefore, a change
amount of the reference LDA target torque TLDAs per unit time
becomes larger as the absolute value of each of these control gains
is larger. That is, the responsiveness of the LDA control can be
more enhanced as the absolute values of these control gains are
larger.
[0100] Further, as will be described later, the LDA control section
12 calculates the corrected LDA target torque TLDAf by multiplying
the reference LDA target torque TLDAs calculated according to the
formula (1) by the LDA control gain GLDA. This point will be
described in detail later. As shown in FIG. 1, the LDA control
section 12 supplies the corrected LDA target torque TLDAf to the
switching control section 14.
[0101] The lane keeping assist control section 13 performs the lane
keeping assist control. The lane keeping assist is a control for
applying the steering assist torque to the steering mechanism in
such a manner that a traveling position of the own vehicle C is
kept in the vicinity of the target traveling line Ld, so as to
support the steering operation of the driver. Hereinafter, the lane
keeping assist control section 13 is referred to as an LKA control
section 13, and the lane keeping assist control is referred to as
LKA control.
[0102] The LKA control section 13 receives the lane information
(Dc, .theta.y, R) calculated by the lane recognition section 11 to
calculate a target torque TLKA (hereinafter referred to as an "LKA
target torque TLKA") to have the own vehicle C travel along the
target traveling line Ld each time a predetermined time elapses. As
will be described later, the LKA target torque includes a reference
LKA target torque TLKAs and a corrected LKA target torque
TLKAf.
[0103] When the LKA control section 13 determines that an operating
condition of a lane keeping traveling support mode which will be
described later is satisfied, the LKA control section 13 calculates
the LKA target torque TLKA using a following formula (2) each time
the predetermined time elapses.
TLKAs=K11 (V.sup.2/R)+K12 Dc+K13 .theta.y (2)
[0104] Each of K11, K12, and K13 is control gain.
[0105] K11 is set to a positive value (k11>0) when the traveling
lane curves to the left, and is set to a negative value (-k11) when
the traveling lane curves to the right.
[0106] K12 is set to a positive value.
[0107] K13 is set to a positive value.
[0108] The first term on the right side of formula (2) is a torque
component (feedforward control amount with respect to the curve
radius R) determined according to the curve radius R of the road
(target traveling line Ld) and the vehicle speed V. The torque
component acts in a feedforward control manner with respect to the
curve radius R. That is, the first term on the right side is a
torque component to have the own vehicle C travel according to the
curvature of the target traveling line Ld.
[0109] The second term on the right side of the formula (2) is a
torque component (feedback control amount with respect to the
center distance Dc) which acts in a feedback control manner so as
to reduce a magnitude of the center distance Dc which is a
deviation (position deviation) of the position of the own vehicle
in the road width direction from the target traveling line Ld.
[0110] The third term on the right side of the formula (2) is a
torque component (feedback control amount with respect to the yaw
angle .theta.y) which acts in a feedback control manner so as to
reduce the magnitude |.theta.y| of the yaw angle .theta.y (that is,
so as to reduce the deviation of the direction of the own vehicle
with respect to the target traveling line Ld).
[0111] Further, the LKA control section 13 calculates the corrected
LKA target torque TLKAf by multiplying the reference LKA target
torque TLKAs by the LKA control gain GLKA. This point will be
described in detail later.
[0112] The LKA control section 13 supplies the corrected LKA target
torque TLKAf to the switching control section 14.
[0113] Here, as described above, the LKA control is the control for
supporting the steering operation of the driver so that the own
vehicle C travels along the target traveling line Ld. Therefore, it
is required that the steering feel when the LKA control is being
performed is good and comfortable. For this reason, the steering
assist torque (the reference LKA target torque TLKAs) is set to a
value which causes a slow/moderate steering. On the other hand, the
LDA control is a control to support/assist the steering operation
of the driver by applying the steering assist torque to the
steering mechanism so as to prevent the own vehicle C from
deviating from the traveling lane when the own vehicle C is about
to deviate from the traveling lane (to the outside of the objective
white line). Therefore, the steering assist torque (the reference
LDA target torque TLDAs) is set to a value which causes (allows) a
relatively steep/rapid steering.
[0114] For these reasons, a change rate of the target value (the
target torque) of the steering assist torque (i.e., a change amount
in the target torque per unit time) in the LDA control is set to be
larger than that in the LKA control. That is, the absolute value of
the control gain used in the LDA control is set to be larger than
the control gain used in the LKA control. In particular, with
respect to the control gains K2 and K12 of the feedback control
term of the positional deviation are set to have a relationship of
K2>K12, and the control gains K3 and K13 of the feedback control
term of the direction deviation are set to have a relationship of
K3>K13.
[0115] Further, when the LDA control or the LKA control is
performed, the lateral acceleration is generated in the own vehicle
C. In the present apparatus, the LDA control or the LKA control is
performed in such a manner that the magnitude of the lateral
acceleration Gy does not exceed a predetermined upper limit
value.
[0116] That is, the corrected LDA target torque TLDAf finally
determined in the LDA control is determined (set) in such a manner
that the magnitude of the actual lateral acceleration Gy does not
exceed a maximum lateral acceleration GyLDAmax. In other words, the
maximum lateral acceleration GyLDAmax is the maximum value of "the
magnitude of the actual lateral acceleration Gy that is allowed to
be generated" by the LDA control. Hereinafter, an upper limit value
of the LDA target torque TLDA restricted by the maximum lateral
acceleration GyLDAmax is referred to as an "upper limit torque
TLDAmax".
[0117] Similarly, the corrected LKA target torque TLKAf finally
determined in the LKA control is determined (set) in such a manner
that the magnitude of the actual lateral acceleration Gy does not
exceed the maximum lateral acceleration GyLKAmax. In other words,
the maximum lateral acceleration GyLKAmax is the maximum value of
"the magnitude the actual lateral acceleration Gy that is allowed
to be generated" by the LKA control. The maximum lateral
acceleration GyLKAmax is set to a value smaller than the maximum
lateral acceleration GyLDAmax. Hereinafter, the upper limit value
of the corrected LKA target torque TLKAf restricted by the maximum
lateral acceleration GyLKAmax is referred to as an "upper limit
torque TLKAmax".
[0118] The switching control section 14 receives the corrected LDA
target torque TLDAf and the corrected LKA target torque TLKAf from
the LDA control section 12 and the LKA control section 13,
respectively, every time the predetermined time elapses. Further,
the switching control section 14 selects the target torque having a
larger magnitude (absolute value) among the corrected LDA target
torque TLDAf and the corrected LKA target torque TLKAf to transmit
the steering command which can specify the selected target torque
to the EPS ECU 20. Therefore, the LDA control and the LKA control
are not performed at the same time. In other words, the switching
control section 14 switches controls for realizing the lane keeping
traveling support between the LDA control and the LKA control.
[0119] The operation switch 50 is provided on a steering column of
the own vehicle. The operation switch 50 moves to an ON position
when it is pushed downward by the driver, and remains at the ON
position unless the driver operates it thereafter. Further, the
operation switch 50 moves to an OFF position when it is pushed
upward by the driver from the ON position, and remains at the OFF
position unless the driver operates it thereafter. The operation
switch 50 is an operation device for selecting whether or not the
driver accepts the lane keeping traveling support. The driving
support ECU 10 recognizes that the state of the operation switch 50
is in an ON state when the operation switch 50 is at the ON
position and recognizes that the state of the operation switch 50
is at an OFF state when the operation switch 50 is at the OFF
position.
[0120] Although illustration and detailed description are omitted,
the driving support ECU 10 is capable of performing the well-known
trailing inter-vehicle (distance) control (hereinafter referred to
as an "ACC (Adaptive Cruise Control)"). The own vehicle includes an
ACC operation switch (not shown) for enabling the driver to select
whether or not to perform the ACC, and a radar sensor (not shown).
When the ACC operation switch is set to an ON position, the ACC
control is performed by the driving support ECU 10. When the ACC
operation switch is set to an OFF position, the ACC control is not
performed. It should be noted that the ACC is a control for
performing a follow-up/trailing control for maintaining the
inter-vehicle distance with other vehicle at a predetermined
distance when the ACC determines that there is other vehicle which
is ahead of the own vehicle and which the own vehicle should
follow. Further, the ACC is a control for performing a constant
speed control for causing the own vehicle to travel at a
predetermined speed when it is determined that there is no other
vehicle that the own vehicle should follow ahead of the own vehicle
based on the target information detected by the radar sensor. The
ACC itself is well known (for example, refer to Japanese Unexamined
Patent Publication No. 2014-148293, Japanese Patent No. 4172434,
and Japanese Patent No. 4929777).
[0121] The buzzer 60 and the display unit 70 are connected to the
driving support ECU 10. The driving support ECU 10 sounds the
buzzer 60 by transmitting a command to the buzzer 60, thereby
alerting the driver. Further, the driving support ECU 10 has the
display unit 70 display a operation status of the lane keeping
traveling support by transmitting a command to the display unit
70.
<Outline of Operation>
[0122] When the following operating condition (hereinafter also
referred to as a "specific operation condition") of a lane keeping
traveling support mode is satisfied, the driving support ECU 10
performs one of the LDA control and the LKA control, thereby
performing the lane keeping traveling support.
[0123] The Specific Operation Condition
[0124] The ACC is being performed, the state of the operation
switch 50 is in the ON state, and the vehicle speed of the own
vehicle is equal to or higher than the predetermined threshold
vehicle speed.
[0125] It should be noted that the predetermined threshold vehicle
speed in the specific operation condition can be set to an
arbitrary vehicle speed. However, when the ACC is configured in
such a manner that it can be performed only when the vehicle speed
is equal to or higher than an ACC allowable vehicle speed, the
predetermined threshold vehicle speed in the specific operation
condition is set to the vehicle speed equal to or higher than the
ACC allowable vehicle speed. Further, the specific operation
condition is not limited to the above-described conditions. For
example, the specific operation condition may be a condition which
is satisfied when the vehicle speed of the own vehicle is equal to
or higher than the predetermined threshold vehicle speed,
regardless of whether ACC is being performed or not.
[0126] Hereinafter, an operation when the driving support ECU 10
performs the lane keeping traveling support will be described.
Here, a situation (situation1) where there is no operation (the
steering operation) of the steering wheel SW by the driver will be
described firstly, and then, a situation (situation2) where there
is the steering operation by the driver will be described.
<The Situation1: When there is No the Steering Operation>
[0127] In the situation1, the driving support ECU 10 sets each of
"the LKA control gain GLKA and the LDA control gain GLDA" to "1".
Therefore, the reference LKA target torque TLKAs is equal to the
corrected LKA target torque TLKAf, and the reference LDA target
torque TLDAs is equal to the corrected LDA target torque TLDAf.
FIG. 5 shows the traveling position of the own vehicle C and each
of the target torques in the lane keeping traveling support in one
example belonging to the situation 1. In FIG. 5, a torque waveform
of an upper section (A) shows "the corrected LKA target torque
TLKAf equal to the reference LKA target torque TLKAs", and a torque
waveform of an middle section (B) shows "the corrected LDA target
Torque TLDAf equal to the reference LDA target torque TLDAs".
Further, a torque waveform of a lower section (C) shows the final
target torque (that is, the torque selected by the switching
control section 14) specified by the steering command transmitted
from the driving support ECU 10 to the EPS ECU 20. Therefore, the
actual steering assist torque changes along the torque waveform of
the lower section (C).
[0128] In this example, it is assumed that the traveling lane of
the own vehicle C includes a curve section curving to the right,
and the specific operation condition described above is satisfied
at time t0. During a period (the period from time t0 to time t4) in
which the own vehicle C travels on the road section including the
curve section, the driving support ECU 10 selects one of the LKA
control and the LDA control according to the traveling situation of
the own vehicle C to perform either one of the LKA control and the
LDA control, as will be described below.
[0129] In the situation1, the LKA control section 13 calculates the
reference LKA target torque TLKAs based on the formula (2) every
time the predetermined time elapses, and supplies the corrected LKA
target torque TLKAf obtained by multiplying the reference LKA
target torque TLKAs by the LKA control gain GLKA set to "1" to the
switching control section 14. Therefore, a target torque equal to
the reference LKA target torque TLKAs is supplied to the switching
control section 14 during the period from time t0 to time t4.
[0130] Meanwhile, the LDA control section 12 calculates the
reference LDA target torque TLDAs based on the above formula (1)
during a period (hereinafter referred to as an "LDA calculation
period") from the "time t1 at which the LDA calculation start
condition described above is satisfied" to the "time t3 at which
the LDA calculation termination condition described above is
satisfied" out of the period from time t0 to time t4. Further, the
LDA control section 12 supplies the corrected LDA target torque
TLDAf obtained by multiplying the reference LDA target torque TLDAs
by the LDA control gain GLDA set to "1" to the switching control
section 14. Therefore, a target torque equal to the reference LDA
target torque TLDAs is supplied to the switching control section 14
during the LDA calculation period. Further, the LDA control section
12 supplies "0" as the corrected LDA target torque TLDAf to the
switching control section 14 during a period other than the LDA
calculation period.
[0131] More specifically, in the example shown in FIG. 5, the own
vehicle C is traveling in the vicinity of the center of the
traveling lane (the vicinity of the target traveling line Ld which
is positioned at a central position between the left white line LL
and the right white line LR) during a period from time t0 to a time
point immediately before time t1. Therefore, the side distance Ds
is larger than the reference side distance Dsref. Accordingly,
since the LDA calculation start condition is not satisfied during
the period from time t0 to the time point just before time t1, the
LDA control section 12 provisionally sets the corrected LDA target
torque TLDAf to "0". As a result, the magnitude of the corrected
LKA target torque TLKAf is equal to or larger than the corrected
LDA target torque TLDAf. Therefore, the switching control section
14 selects the "corrected LKA target torque TLKAf equal to the
reference LKA target torque TLKAs" supplied from the LKA control
section 13, and transmits the steering command which can specify
the corrected LKA target torque TLKAf to the EPS ECU 20. That is,
the driving support ECU 10 selects and performs the LKA control
during the period from time t0 to the time point immediately before
time t1.
[0132] Further, the own vehicle C enters the curve section at the
time point immediately before time t1. In this case, since a
curvature of the curve section is excessive with respect to the
vehicle speed of the own vehicle C, the position of the own vehicle
C approaches the left white line LL. Thereafter, the side distance
Ds becomes equal to or less than the reference side distance Dsref
at time t1. As a result, since the LDA calculation start condition
is satisfied at time t1, the LDA control section 12 calculates the
reference LDA target torque TLDAs based on the above formula (1)
and supplies the corrected LDA target torque TLDAf equal to the
reference LDA target torque TLDAs to the switching control section
14 after time t1. In the meantime, as described above, the LKA
control section 13 calculates the reference LKA target torque TLKAs
based on the above formula (2), and supplies the corrected LKA
target torque TLKAf equal to the reference LKA target torque TLKAs
to the switching control section 14.
[0133] In the example shown in FIG. 5, the corrected LKA target
torque TLKAf is equal to or larger than the corrected LDA target
torque TLDAf during the period from time t1 to the time point
immediately before time t2. Therefore, the switching control
section 14 selects the corrected LKA target torque TLKAf and
transmits the steering command which can specify the corrected LKA
target torque TLKAf to the EPS ECU 20. That is, the driving support
ECU 10 continues the LKA control during the period from time t1 to
the time point immediately before time t2. It should be noted that
in this example, the corrected LKA target torque TLKAf reaches the
upper limit torque TLKAmax at a time point immediately before time
t2. As a result, the corrected LKA target torque TLKAf is
maintained at the upper limit torque TLKAmax after time t2.
[0134] Further, in this example, the magnitude of the corrected LDA
target torque TLDAf coincides with the magnitude of the upper limit
torque TLKAmax at time t2 and continues to increase thereafter. As
a result, the magnitude of the corrected LDA target torque TLDAf is
equal to or larger than the magnitude of the corrected LKA target
torque TLKAf after time t2. Therefore, the switching control
section 14 selects the corrected LDA target torque TLDAf and
transmits the steering command that can specify the corrected LDA
target torque TLDAf to the EPS ECU 20 after time t2. That is, the
driving support ECU 10 switches the controls from the LKA control
to the LDA control to realize the lane keeping traveling support at
time t2, and performs the LDA control after time t2.
[0135] In addition, in this example, at time t3, the own vehicle C
approaches the end point of the curve section, and further
approaches the target traveling line Ld by the yaw rate in the
direction to avoid/prevent deviation of the traveling lane
generated by the LDA control. As a result, the side distance Ds
becomes larger than the reference side distance Dsref at time t3.
Therefore, since the above-described LDA calculation termination
condition is satisfied at time t3, the LDA control section 12 sets
the corrected LDA target torque TLDAf to "0". As a result, the
magnitude of the corrected LKA target torque TLKAf is equal to or
larger than the magnitude of the corrected LDA target torque TLDAf.
Therefore, the switching control section 14 selects the corrected
LKA target torque TLKAf supplied from the LKA control section 13,
and transmits the steering command that can specify the corrected
LKA target torque TLKAf to the EPS ECU 20. That is, the driving
support ECU 10 switches the controls from the LDA control to the
LKA control to realize the lane keeping traveling support at time
t3, and performs the LKA control after time t3.
<The Situation 2: When there is the Steering Operation>
[0136] Next, an outline of the operation of the driving support ECU
10 in the situation (situation2) where there is the steering
operation by the driver will be described, referring to FIGS. 6A
and 6B.
[0137] FIG. 6A is a plan view showing relationship between the
traveling position of the own vehicle C and the respective states
of LDA control and LKA control when the driving support ECU 10 is
performing the lane keeping traveling support. FIG. 69 is a graph
showing relationship between the magnitude (absolute value) |TqDr|
of the "driver torque TqDr detected by the steering torque sensor
51" and the LKA control gain GLKA.
[0138] Here, in a state in which the driving support ECU 10 is
performing the LKA control in order to perform the lane keeping
traveling support, a case arises where the driver intentionally
performs the steering operation with the aim of causing the own
vehicle C to deviate from the current traveling lane in an attempt
to change lanes. In this case, the steering operation is performed
against the steering assist torque by the LKA control.
[0139] Therefore, the driver may feel uncomfortable due to the
steering assist torque acting in the opposite direction to the
driver torque TqDr which the driver is giving by himself/herself.
In view of this, the LKA control section 13 reduces the magnitude
of the steering assist torque by the LKA control in such a case. It
should be noted that, as will be described later, when the LDA
control is performed in a case where such a steering operation is
occurring, the magnitude of the steering assist torque by the LDA
control is also reduced.
[0140] More specifically, when the steering operation by the driver
is performed while the LKA control is being performed (that is,
when the magnitude |TqDr| of the driver torque TqDr is larger than
"0"), the LKA control section 13 determines/obtains the LKA control
gain GLKA by applying the magnitude |TqDr| of the actual driver
torque TqDr to a "lookup table MapGLKA (|TqDr|) shown in FIG. 6B".
Further, the LKA control section 14 calculates the final corrected
LKA target torque TLKAf by multiplying the reference LKA target
torque TLKAs by the determined LKA control gain GLKA.
[0141] According to the lookup table MapGLKA (|TqDr|) shown in FIG.
6B, the LKA control gain GLKA is determined as described below.
[0142] When the magnitude |TqDr| of the actual driver torque TqDr
is less than the first threshold value (for example, 1 [Nm]), the
LKA control gain GLKA is set to 1 (100%) (referring to the region
A). [0143] When the magnitude |TqDr| of the actual driver torque
TqDr is equal to or larger than the first threshold value and less
than the second threshold value (for example, 2 [Nm]), the LKA
control gain GLKA is set to a value which decreases from 1 to
"value .beta. between 0 and 1" as the magnitude |TqDr| increases
from the first threshold value (referring to the region B). In this
case, the magnitude of the corrected LKA target torque TLKAf
becomes smaller than the magnitude of the reference LKA target
torque TLKAs. Therefore, the magnitude of the steering assist
torque for making the own vehicle C travel along the traveling line
Ld by the LKA control becomes small. That is, the control effect of
the LKA control is weakened. [0144] When the magnitude |TqDr| of
the actual driver torque TqDr is equal to or larger than the second
threshold value, the LKA control gain GLKA is set to "0". As a
result, the corrected LKA target torque TLKAf becomes "0". In other
words, when the magnitude of the driver torque TqDr is equal to or
larger than the second threshold value, the driving support ECU 10
stops the LKA control.
[0145] The above mentioned LKA control will be described based on
the example shown in FIG. 6A. The steering operation is not
performed at time t0, and the steering operation starts to be
performed from immediately after time to. However, the magnitude
|TqDr| of the driver torque TqDr applied to the steering wheel SW
is less than the first threshold value during a period from time t0
to the time point immediately before time t1. Therefore, the LKA
control gain GLKA is set to 1. Further, since the own vehicle C has
not excessively approached the objective white line (the target
white line) (in this case, the left white line LR) during this
period, the side distance Ds is larger than the reference side
distance Dsref. Therefore, the LDA calculation start condition is
not satisfied. Therefore, the corrected LDA target torque TLDAf is
maintained at "0". In other words, the LDA control is maintained in
a non-operating state (state before starting operation). As a
result, the switching control section 14 selects the "corrected LKA
target torque TLKAf equal to the reference LKA target torque TLKAs"
supplied from the LKA control section 13 during the period from
time t0 to the time point immediately before time t1, and transmits
the steering command which can specify the corrected LKA target
torque TLKAf to the EPS ECU 20. That is, the driving support ECU 10
performs the normal LKA control based on the "corrected LKA target
torque TLKAf equal to the reference LKA target torque TLKAs" during
this period.
[0146] In this example, the driver torque TqDr having a magnitude
equal to or larger than the first threshold and less than the
second threshold is applied to the steering wheel SW during a
period from time t1 to the time point immediately before time t2.
In this case, according to the conventional LKA control, in order
to return the position of the own vehicle C to the vicinity of the
target traveling line Ld, a steering assist torque is generated
based on the "reference LKA target torque TLKAs having a relatively
large magnitude" calculated according to the above formula (2).
[0147] In contrast, as described above, the LKA control gain GLKA
becomes between "1" and ".beta." during the period from time t1 to
the time point immediately before time t2. Therefore, the LKA
control section 13 obtains the corrected LKA target torque TLKAf
(smaller than the reference LKA target torque TLKAs) by multiplying
the reference LKA target torque TLKAs by the LKA control gain GLKA,
and supplies the corrected LKA target torque TLKAf to the switching
control section 14. Further, the side distance Ds is still larger
than the reference side distance Dsref during the period from time
t1 to the time point immediately before time t2. Therefore, the LDA
calculation start condition is not satisfied. Therefore, the
corrected LDA target torque TLDAf is maintained at "0". In other
words, the LDA control is maintained in the non-operating state
(state before starting operation). As a result, the switching
control section 14 selects "the corrected LKA target torque having
a magnitude smaller than a magnitude of the reference LKA target
torque TLKAs" supplied from the LKA control section 13, and
transmits to the EPS ECU 20 the steering command which can specify
the corrected LKA target torque TLKAf during the period from time
t1 to the time point immediately before time t2. That is, the
driving support ECU 10 generates the steering assist torque based
on "the corrected LKA target torque TLKAf having the magnitude
which is smaller than the magnitude of the reference LKA target
torque TLKAs" during this period. Thus, the driving support ECU 10
performs the LKA control whose control effect has been weakened. As
a result, when the driver is performing the steering operation with
the intention to change lanes, the steering wheel operation in the
lane departing direction can be performed with a light force, and
therefore, the driver is unlikely to feel uncomfortable.
[0148] Here, in the example shown in FIG. 6A, the driver torque
TqDr having a magnitude larger than the magnitude of the steering
assist torque by the LKA control is continuously applied to the
steering wheel SW after time t1. As a result, the own vehicle C
continues to move toward the end of the traveling lane (in this
case, the left white line LL), and the side distance Ds becomes
equal to or less than the reference side distance Dsref at time t2.
In this case, since the above-described LDA calculation start
condition is satisfied, the LDA control section 12 starts
calculating the reference LDA target torque TLDAs. On the other
hand, the LKA control section 13 sets the value of the corrected
LKA target torque TLKAf to "0" when the LDA calculation start
condition is satisfied in a state where the driver torque TqDr is
not "0".
[0149] In this case, if the conventional steering assist torque
(that is, the reference LDA target torque TLDAs calculated based on
the above formula (1)) is generated, a steering assist torque in a
direction opposite to the driver torque TqDr by the driver's
steering operation and having a large magnitude is applied to the
steering mechanism. Therefore, the driver is likely to feel
uncomfortable. That is, there is a high possibility that the driver
is likely to feel that the own vehicle C is being controlled so as
to resist his/her intention.
[0150] In view of the above, according to the present apparatus,
when the LDA calculation start condition is satisfied, the LDA
control section 12 determines whether or not the steering operation
is being performed (that is, whether or not the driver torque TqDr
is generated). When the LDA control section 12 determines that the
steering operation is being performed in a case where the LDA
calculation start condition is satisfied, the LDA control section
12 adjusts/varies the steering assist torque in such a manner that
the magnitude of the "steering assist torque by the LDA control" is
smaller than the steering assist torque by the conventional LDA
control.
[0151] More specifically, the LDA control section 12 calculates the
corrected LDA target torque TLDAf by multiplying the reference LDA
target torque TLDAs calculated according to the formula (1) by the
LDA control gain GLDA having a predetermined value .alpha. (for
example, .alpha.=0.3 (30%)), and transmits the corrected LDA target
torque TLDAf to the switching control section 14. It should be
noted that the value .alpha. is set to a suitable value within a
range larger than 0 and smaller than 1.
[0152] Also in this case, the switching control section 14 selects
the target torque having a larger magnitude among the corrected LDA
target torque TLDAf supplied from the LDA control section 12 and
the corrected LKA target torque TLKAf supplied from the LKA control
section 13, to transmit the steering command representing the
selected target torque to the EPS ECU 20. As described above, the
corrected LKA target torque TLKAf is set to "0" under this
situation. Therefore, the switching control section 14 selects the
corrected LDA target torque TLDAf, and transmits the steering
command which can specify the corrected LDA target torque TLDAf to
the EPS ECU 20. As a result, the LKA control is
effectively/substantially prohibited (stopped) and the LDA control
is performed. That is, the driving support ECU 10 switches the
control for realizing the lane keeping traveling support from the
LKA control to the LDA control at time t2 and performs the LDA
control with weakening the control effect of the LDA control. As a
result, when the driver is performing the steering operation with
the intention to change lanes, the steering wheel operation in the
lane departing direction can be performed with a light force, and
thus, the driver is unlikely to feel uncomfortable.
[0153] In this manner, the present apparatus weakens the control
effect of the LDA control when an intentional steering wheel
operation by the driver who is attempting to depart from the
traveling lane is performed. That is, the present apparatus reduces
the magnitude of the steering assist torque in the direction
opposite to the direction of the steering torque provided by such a
driver's steering wheel operation. As a result, the present
apparatus can reduce the possibility that the LDA control causes
the driver to feel uncomfortable. Therefore, the present apparatus
can perform the lane keeping traveling support which allows the
intention of the steering operation by the driver to be easily
reflected in changing the traveling direction of the own vehicle
(that is, the present apparatus can perform the lane keeping
traveling support having a high receptivity for the driver's
intentional steering operation). Further, as a result, the present
apparatus can reduce the possibility that the driver's
acceptability for the lane keeping traveling support provided by
the present system will be reduced.
<Specific Operation>
[0154] Next, a specific operation of the present apparatus will be
described. The CPU of the driving support ECU 10 (hereinafter
simply referred to as the "CPU") executes a lane keeping traveling
support routine shown by a flowchart in FIG. 7 every time a
predetermined time elapses.
[0155] Therefore, when an appropriate time point arrives, the CPU
starts processing from step 700 in FIG. 7 and proceeds to step 705
to determine whether or not the above-described operating condition
(i.e., the specific operating condition) of the lane keeping
traveling support mode is satisfied.
[0156] When the operating condition of the lane keeping traveling
support mode is satisfied, the CPU makes a "Yes" determination at
step 705 and proceeds to step 710 to calculate the reference LKA
target torque TLKAs according to the above formula (2).
[0157] Next, the CPU proceeds to step 715 to determine whether or
not the direction of the "driver torque TqDr detected by the
steering torque sensor 51" (that is, the steering direction by the
steering wheel SW) is the same as the displacement direction of the
reference point P of the own vehicle with respect to the target
traveling line Ld. That is, for example, the determination
condition at step 715 is satisfied, when the steering direction of
the steering wheel SW is the direction to have the own vehicle turn
to the left and the reference point P is displaced/positioned in
the left side area with respect to the target traveling line Ld
(that is, the center distance Dc is negative). Similarly, the
determination condition at step 715 is satisfied, when the steering
direction of the steering wheel SW is the direction to have the own
vehicle turn to the right and the reference point P is
displaced/positioned in the right side area with respect to the
target traveling line Ld (that is, the center distance Dc is
positive).
[0158] When the determination condition at step 715 is satisfied,
the CPU makes a "Yes" determination at step 715 and proceeds to
step 720 to calculate the LKA control gain GLKA by applying the
driver torque TqDr detected by the steering torque sensor 51 to the
lookup table MapGLKA (|TqDr|) shown in FIG. 6B. Thereafter, the CPU
proceeds to step 730.
[0159] In contrast, when the determination condition at step 715 is
not satisfied (this case includes the case where the driver torque
TqDr detected by the steering torque sensor 51 is "0"), the CPU
makes a "No" determination at step 715. In this case, the CPU
proceeds to step 725 and sets the LKA control gain GLKA to "1" at
step 725 to proceed to step 730.
[0160] The CPU calculates the product of the LKA control gain GLKA
and the reference LKA target torque TLKAs so as to obtain the
corrected LKA target torque TLKAf at step 730. Next, the CPU
proceeds to step 735 to determine whether or not the value of the
LDA calculation execution flag XLDA is "1". The value of the LDA
calculation execution flag XLDA is set by the LDA calculation
execution flag setting routine shown in FIG. 8 which will be
described later. Briefly, the value of the LDA calculation
execution flag XLDA is set to "1" when the LDA calculation start
condition is satisfied and to "0" when the LDA calculation
termination condition is satisfied. Further, the value of the LDA
calculation execution flag XLDA is set to "0" in an initialization
routine (not shown) executed by the CPU when the ignition key
switch (not shown) of the own vehicle is changed from the OFF
position to the ON position.
[0161] When the value of the LDA calculation execution flag XLDA is
"1", the CPU makes a "Yes" determination at step 735 and proceeds
to step 740 to calculate the reference LDA target torque TLDAs
according to the above formula (1).
[0162] Next, the CPU proceeds to step 745, and determines whether
or not the "driver torque TqDr detected by the steering torque
sensor 51" is not "0" and the direction of the driver torque TqD
(that is, the steering direction by the steering wheel SW) is the
same as the lane departure direction. That is, for example, the
determination condition at step 745 is satisfied, when the steering
direction of the steering wheel SW is the direction to have the own
vehicle turn to the left and the objective white line is the left
white line LL. Similarly, the determination condition at step 745
is satisfied, when the steering direction of the steering wheel SW
is the direction to have the own vehicle turn to the right and the
objective white line is the right white line LR.
[0163] When the determination condition at step 745 is satisfied,
the CPU makes a "Yes" determination at step 745 and proceeds to
step 750 to set the LDA control gain GLDA to the predetermined
value .alpha. (in the example, the predetermined value .alpha. is
0.3) larger than 0 and smaller than 1. Next, the CPU proceeds to
step 752 to set the corrected LKA target torque TLKAf to "0".
Thereby, the LKA control is effectively/substantially prohibited
(stopped). Thereafter, the CPU proceeds to step 760.
[0164] In contrast, when the determination condition of step 745 is
not satisfied (this case includes the case where the driver torque
TqDr detected by the steering torque sensor 51 is "0"), the CPU
makes a "No" determination at step 745. In this case, the CPU
proceeds to step 755 to set the LDA control gain GLDA to "1" at
step 755 and proceeds to step 760.
[0165] The CPU calculates the product of the LDA control gain GLDA
and the reference LDA target torque TLDAs so as to obtain the
corrected LDA target torque TLDAf at step 760 and proceeds to step
770.
[0166] In contrast, when the value of the LDA calculation execution
flag XLDA is "0" at the time point at which the CPU executes the
process of step 735, the CPU makes a "No" determination at step 735
and proceeds to step 765 to set the corrected LDA target torque
TLDAf to "0". Thereby, the LDA control is effectively/substantially
prohibited (stopped). Thereafter, the CPU proceeds to step 770.
[0167] The CPU determines whether or not the magnitude |TLDAf| of
the corrected LDA target torque TLDAf is larger than the magnitude
|TLKAf| of the corrected LKA target torque TLKAf at step 770.
[0168] When the magnitude |TLDAf| of the corrected LDA target
torque TLDAf is larger than the magnitude |TLKAf| of the corrected
LKA target torque TLKAf, the CPU makes a "Yes" determination at
step 770 and proceeds to step 775 to perform the LDA control based
on the corrected LDA target torque TLDAf. That is, the CPU
transmits the steering command which can specify the corrected LDA
target torque TLDAf to the EPS ECU 20, thereby generating a
steering assist torque equal to the corrected LDA target torque
TLDAf. Thereafter, the CPU proceeds to step 795 to tentatively
terminate the present routine.
[0169] In contrast, when the magnitude |TLDAf| of the corrected LDA
target torque TLDAf is equal to or smaller than the magnitude
|TLKAf| of the corrected LKA target torque TLKAf, the CPU makes a
"No" determination at step 770 and proceeds to step 780 to perform
the LKA control based on the target torque TLKAf. That is, the CPU
transmits the steering command which can specify the corrected LKA
target torque TLKAf to the EPS ECU 20, thereby generating a
steering assist torque equal to the corrected LKA target torque
TLKAf. Thereafter, the CPU proceeds to step 795 to tentatively
terminate the present routine.
[0170] When the operating condition of the lane keeping traveling
support mode is not satisfied at the time point at which the CPU
executes the process of step 705, the CPU makes a "No"
determination at step 705, and executes the processes of steps 785
and 790 described below to proceed to step 795 to tentatively
terminate the present routine.
[0171] Step 785: the CPU stops the LKA control.
[0172] In this case, the CPU sets the corrected LKA target torque
TLKAf to "0".
[0173] Step 790: the CPU stops the LDA control.
[0174] In this case, the CPU sets the corrected LDA target torque
TLDAf to "0".
[0175] Further, the CPU executes the "LDA calculation execution
flag setting routine" shown by a flowchart in FIG. 8 every time the
predetermined time elapses. Therefore, when an appropriate timing
arrives, the CPU starts processing from step 800 in FIG. 8 and
proceeds to step 810 to determine whether or not the
above-described operating condition of the lane keeping traveling
support mode (that is, the specific operating condition) is
satisfied.
[0176] When the specific operating condition is not satisfied, the
CPU makes a "No" determination at step 810 and proceeds to step 820
to set the value of the LDA calculation execution flag XLDA to "0".
Thereafter, the CPU proceeds to step 895 to tentatively terminate
the present routine.
[0177] In contrast, when the specific operating condition is
satisfied, the CPU makes a "Yes" determination at step 810 and
proceeds to step 830 to determine whether or not the value of the
LDA calculation execution flag XLDA is "0" at the present time.
[0178] When the value of the LDA calculation execution flag XLDA is
"0", the CPU makes a "Yes" determination at step 830 and proceeds
to step 840 to determine whether or not the LDA calculation start
condition described above is satisfied. When the LDA calculation
start condition is not satisfied, the CPU makes a "No"
determination at step 840 and proceeds directly to step 895 to
tentatively terminate the present routine.
[0179] In contrast, when the LDA calculation start condition is
satisfied at the time point at which the CPU executes the process
of step 840, the CPU makes a "Yes" determination at step 840 and
proceeds to step 850 to set the value of the LDA calculation
execution flag XLDA to "1". Thereafter, the CPU proceeds to step
895 to tentatively terminate the present routine.
[0180] In contrast, when the value of the LDA calculation execution
flag XLDA is not "0" (that is, "1") at the time point at which the
CPU executes the process of step 830, the CPU makes a "No"
determination at step 830 and proceeds to step 860 to determine
whether or not the LDA calculation termination condition described
above is satisfied.
[0181] When the LDA calculation termination condition is not
satisfied, the CPU makes a "No" determination at step 860 and
proceeds to step 895 to tentatively terminate the present routine.
In contrast, the LDA calculation termination condition is
satisfied, the CPU makes a "Yes" determination at step 860 and
proceeds to step 820 to set the value of the LDA calculation
execution flag XLDA to "0". Thereafter, the CPU proceeds to step
895 to tentatively terminate the present routine.
[0182] As described above, the present apparatus weakens the
control effect of the LDA control when the driver performs an
intentional steering wheel operation which causes the own vehicle
to deviate from the traveling lane. That is, the present apparatus
decreases the magnitude of the steering assist torque in the
direction which obstructs the driver's intentional steering wheel
operation. Thereby, the present apparatus can reduce the
possibility that the LDA control causes the driver to feel
uncomfortable. Therefore, the present apparatus can perform the
lane keeping traveling support which allows the intention of the
steering operation by the driver to be easily reflected in changing
the traveling direction of the own vehicle (that is, the present
apparatus can perform the lane keeping traveling support having a
high receptivity for the driver's intentional steering operation).
Further, as a result, the present apparatus can reduce the
possibility that the driver's acceptability for the lane keeping
traveling support provided by the present system is reduced.
Modified Examples
[0183] Although the embodiment of the present invention has been
specifically described above, the present invention is not limited
to the above embodiment, and various modified examples based on the
technical idea within the scope of the present invention can be
adopted.
[0184] The above-described present apparatus is said to be
configured as follows, when the specific driving situation arises
where the own vehicle is likely to deviate from the traveling lane
(i.e., when the LDA calculation start condition is satisfied), and
when it is determined that the steering of the steering wheel SW is
performed by the driver of the own vehicle in such a manner that
the own vehicle faces (heads to) the lane departing direction. That
is, in such a case, the above-described present apparatus
calculates the corrected LDA target torque TLDAf by multiplying the
reference LDA target torque TLDAs calculated using the formula (2)
by the LDA control gain GLDA set to the value .alpha. larger than
"0" and smaller than "1", and generates the steering assist torque
equal to the corrected LDA target torque TLDAf so as to weaken the
LDA control which interferes with the operation of the steering
wheel by the driver.
[0185] In contrast, a first modified example of the present
apparatus is configured to prohibit the LDA control (or is
configured not to perform the LDA control) which interferes with
the operation of the steering wheel by the driver (or which
generates an assist torque acting in the direction opposite to the
steering direction of the operation of the steering wheel SW), when
the specific driving situation occurs where the own vehicle is
likely to deviate from the traveling lane, and when it is
determined that the steering of the steering wheel SW is performed
by the driver of the own vehicle in such a manner that the own
vehicle faces (heads to) the lane departing direction.
[0186] In this first modified example, the LDA control section 12
is configured to terminate the calculation of "the reference LDA
target torque TLDAs and the corrected LDA target torque TLDAf" and
stop supplying the reference LDA target torque TLDAs and the
corrected LDA target torque TLDAf to the switching control section
14, so as to prohibit the LDA control. It should be noted that the
first modified example of the present apparatus may continue
performing the LKA control when it prohibits the LDA control as
described above.
[0187] Further, a second modified example of the present apparatus
is configured to set the LDA control gain GLDA to "0", and to
calculate the corrected LDA target torque TLDAf to be "0" by
multiplying the reference LDA target torque TLDAs calculated using
the formula (2) by the LDA control gain GLDA set to "0", to supply
the corrected LDA target torque TLDAf (that is, "0") to the
switching control section 14, when the specific driving situation
arises where the own vehicle is likely to deviate from the
traveling lane and when it is determined that the steering of the
steering wheel SW is performed by the driver of the own vehicle in
such a manner that the own vehicle faces (heads to) the lane
departing direction. According to this second modified example, the
LDA control is substantially prohibited (stopped). It should be
noted that the second modification may continue performing the LKA
control when the LDA control is substantially prohibited.
[0188] Each of the first and second modified examples of the
present apparatus prohibits the LDA control which interferes with
the operation of the steering wheel by the driver (or which acts in
the direction opposite to the steering direction of the steering
wheel operation of the driver), when the steering of the steering
wheel SW is performed by the driver of the own vehicle in such a
manner that the own vehicle faces (heads to) the lane departing
direction. Thereby, since the LDA control that acts in the
direction opposite to the steering direction of the operation of
the steering wheel is not performed, each of the first and second
modified examples of the present apparatus can reduce the
possibility that the LDA control causes the driver to feel
uncomfortable. In other words, each of the first and second
modified examples of the present apparatus can perform the lane
keeping traveling support with high acceptability for the driver's
intentional steering operation. Further, as a result, each of the
first and second modified examples of the present apparatus can
reduce the possibility that the driver's acceptability for the lane
keeping traveling support provided by each of the first and second
modified examples is reduced.
* * * * *