U.S. patent application number 09/803929 was filed with the patent office on 2001-10-04 for obstacle recognition system for vehicle.
Invention is credited to Morikawa, Katsuhiro, Shirai, Noriaki.
Application Number | 20010026238 09/803929 |
Document ID | / |
Family ID | 18612602 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010026238 |
Kind Code |
A1 |
Shirai, Noriaki ; et
al. |
October 4, 2001 |
Obstacle recognition system for vehicle
Abstract
Height-wise positions of objects are detected on the basis of
distances to the objects from a vehicle, angles of the objects in a
width-wise direction of the vehicle, and angles of the objects in a
height-wise direction of the vehicle. A plurality of objects, which
satisfy conditions predetermined depending on physical
characteristics of delineators, are determined to be objects
composing a delineator group. When the detected height-wise
position of an object in the delineator group which is nearest to
the vehicle corresponds to a predetermined value or less, the
delineator group is determined to be a delineator group on a road
surface. A determination is made as to whether each object in the
on-road-surface delineator group is a non-delineator in response to
conditions of the detected height-wise positions of the objects in
the on-road-surface delineator group.
Inventors: |
Shirai, Noriaki;
(Kariya-shi, JP) ; Morikawa, Katsuhiro; (Nagoya,
JP) |
Correspondence
Address: |
LAW OFFICE OF DAVID G POSZ
2000 L STREET, N.W.
SUITE 200
WASHINGTON
DC
20036
US
|
Family ID: |
18612602 |
Appl. No.: |
09/803929 |
Filed: |
March 13, 2001 |
Current U.S.
Class: |
342/70 ; 342/109;
342/114; 342/115; 342/71 |
Current CPC
Class: |
G01S 17/931 20200101;
G01S 2013/9323 20200101; G01S 7/487 20130101 |
Class at
Publication: |
342/70 ; 342/71;
342/109; 342/114; 342/115 |
International
Class: |
G01S 013/60; G01S
013/93 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2000 |
JP |
2000-98071 |
Claims
What is claimed is:
1. A method of recognizing an obstacle to a vehicle, comprising the
steps of: detecting height-wise positions of objects on the basis
of distances to the objects from the vehicle, angles of the objects
in a width-wise direction of the vehicle, and angles of the objects
in a height-wise direction of the vehicle; determining a plurality
of objects, which satisfy conditions predetermined depending on
physical characteristics of delineators, to be objects composing a
delineator group; when the detected height-wise position of an
object in the delineator group which is nearest to the vehicle
corresponds to a predetermined value or less, determining the
delineator group to be a delineator group on a road surface; and
determining whether or not each object in the on-road-surface
delineator group is a non-delineator in response to conditions of
the detected height-wise positions of the objects in the
on-road-surface delineator group.
2. An apparatus for recognizing an obstacle to a vehicle,
comprising: radar means for applying a transmission wave to a
predetermined angular range in a width-wise direction of the
vehicle and a predetermined angular range in a height-wise
direction of the vehicle, and detecting distances to objects,
angles of the objects in the width-wise direction of the vehicle,
and angles of the objects in the height-wise direction of the
vehicle on the basis of reflected waves which result from
reflections of the transmission wave; and recognizing means for
recognizing obstacles ahead of the vehicle on the basis of the
distances to the objects, the angles of the objects in the
width-wise direction of the vehicle, and the angles of the objects
in the height-wise direction of the vehicle which are detected by
the radar means; wherein the recognizing means comprises: 1) object
recognizing means for detecting height-wise positions of the
objects on the basis of the distances to the objects, the angles of
the objects in the width-wise direction of the vehicle, and the
angles of the objects in the height-wise direction of the vehicle
which are detected by the radar means; 2) delineator-group
determining means for determining ones among the objects, which
satisfy conditions predetermined depending on physical
characteristics of delineators, to be objects composing a
delineator group; 3) on-road-surface delineator-group determining
means for, when the detected height-wise position of an object in
the delineator group which is nearest to the vehicle corresponds to
a predetermined value or less, determining the delineator group to
be a delineator group on a road surface; and 4) non-delineator
determining means for determining whether or not each object in the
on-road-surface delineator group is a non-delineator in response to
conditions of the detected height-wise positions of the objects in
the on-road-surface delineator group.
3. An apparatus as recited in claim 2, wherein the conditions
predetermined depending on the physical characteristics of
delineators are that intervals between the objects are smaller than
a reference value.
4. An apparatus as recited in claim 2, wherein the conditions of
the detected height-wise positions of the objects comprise
conditions of a variation in the detected height-wise positions of
the objects.
5. An apparatus as recited in claim 4, wherein the non-delineator
determining means comprising means for determining whether or not
each object in the on-road-surface delineator group is a
non-delineator in response to a position of occurrence of a change
among an increase, a decrease, and a constancy in a sequence of the
detected height-wise positions of the objects.
6. An apparatus as recited in claim 5, wherein the object
determined to be the non-delineator is at a place immediately
rearward of a position of occurrence of a change from an increase
to a decrease in the sequence of the detected height-wise positions
of the objects as viewed along a direction away from the
vehicle.
7. An apparatus as recited in claim 5, wherein the object
determined to be the non-delineator is at a place immediately
rearward of a position of occurrence of a change from a decrease to
an increase in the sequence of the detected height-wise positions
of the objects as viewed along a direction away from the
vehicle.
8. An apparatus as recited in claim 6, wherein the height-wise
position of the object determined to be the non-delineator
corresponds to a prescribed height or greater.
9. An apparatus as recited in claim 8, wherein the prescribed
height depends on a distance from the present vehicle.
10. An apparatus as recited in claim 2, wherein the object
recognizing means comprises means for recognizing shapes of the
objects, and the delineator-group determining means comprises means
for determining ones among the objects to be objects composing a
delineator group in response to the recognized shapes of the
objects.
11. An apparatus as recited in claim 2, wherein the object
recognizing means comprises means for detecting speeds of the
objects relative to the vehicle, means for detecting a speed of the
vehicle, and means for determining whether the objects are moving
or stationary in response to the detected relative speeds of the
objects and the detected speed of the vehicle, and wherein the
delineator-group determining means comprises means for determining
ones among the stationary objects to be objects composing a
delineator group.
12. An apparatus as recited in claim 2, wherein the detected
height-wise positions of the objects comprise detected height-wise
angles of the objects.
13. A recording medium storing a program for controlling a computer
operating as the object recognizing means, the delineator-group
determining means, the on-road-surface delineator-group determining
means, and the non-delineator determining means in the apparatus of
claim 2.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method of recognizing an
obstacle to a vehicle. In addition, this invention relates to an
apparatus for recognizing an obstacle to a vehicle. Furthermore,
this invention relates to a recording medium which stores a
computer program for recognizing an obstacle to a vehicle.
[0003] 2. Description of the Related Art
[0004] A known obstacle recognition apparatus for a vehicle emits a
forward wave beam such as a light beam or a millimeter wave beam
into a given detection area in front of the body of the vehicle. In
the case where an obstacle exists in the detection area, the
forward wave beam encounters the obstacle before being at least
partially reflected thereby. A portion of the reflected wave beam
returns to the apparatus as an echo wave beam. The apparatus
detects the obstacle in response to the echo wave beam.
[0005] The known obstacle recognition apparatus is used in a
warning system for a vehicle which alarms when an obstacle such as
a preceding vehicle exists in a given detection area in front of
the present vehicle. The known obstacle recognition apparatus is
used also in a system for a vehicle which controls the speed of the
vehicle to maintain a proper distance between the vehicle and a
preceding vehicle.
[0006] The known obstacle recognition apparatus additionally has
the function of determining whether or not the detected obstacle is
a preceding vehicle. It is important to discriminate a preceding
vehicle from other objects such as road-side objects or
delineators.
[0007] Japanese patent application publication number 6-59038
discloses a laser radar for a vehicle which detects objects in a
given detection area in front of the vehicle. The laser radar in
Japanese application 6-59038 determines whether or not detected
neighboring objects are road-side reflectors (delineators).
Specifically, detected neighboring objects are recognized as
delineators when the following conditions 1), 2), and 3) are
satisfied. 1) The heights of detected neighboring objects from a
horizontal reference line (for example, the road surface) are
approximately equal to each other. 2) The horizontal intervals
between detected neighboring objects are approximately equal to
each other. 3) The differences between the distances to detected
neighboring objects are approximately equal to each other. In
addition, the laser radar in Japanese application 6-59038
determines whether or not two detected objects correspond to a
vehicle (for example, a preceding vehicle or a stationary vehicle).
This determination is based on the fact that the rear end face of a
vehicle has a pair of reflex reflectors. Specifically, two detected
objects are recognized as corresponding to a vehicle when the
following conditions 4), 5), and 6) are satisfied. 4) The distances
to two detected objects are approximately equal to each other. 5)
The heights of two detected objects from the road surface are
approximately equal to each other, and are in a predetermined
range. 6) The horizontal distance between two detected objects is
equal to or less than about 3 m.
[0008] In the case where the present vehicle is travelling along a
road having a varying slope (for example, the present vehicle
reaches the beginning or the end of a sloping road), the detected
heights of delineators differ from each other so that the
previously-indicated condition 1) is not satisfied. Therefore, in
this case, the laser radar in Japanese application 6-59038 can not
recognize delineators. Furthermore, the laser radar in Japanese
application 6-59038 can not detect delineators on the road surface
which are called cat's-eyes. As previously mentioned, the laser
radar in Japanese application 6-59038 implements the determination
as to a preceding vehicle on the basis of the fact that the rear
end face of a vehicle has a pair of reflex reflectors. Accordingly,
a two-wheeler or a motorcycle having a single reflector at its rear
end can not be recognized as a preceding vehicle.
[0009] U.S. Pat. No. 6,018,308 (corresponding to Japanese patent
application publication number 11-38142) discloses an obstacle
recognition system for an automotive vehicle which is designed to
distinguish preceding vehicles from other objects. The system in
U.S. Pat. No. 6,018,308 includes a radar unit and a preceding
vehicle determining circuit. The radar unit receives a signal
produced by reflection of at least one of transmitted radar signals
from an obstacle present in a given obstacle detectable zone, and
determines a distance to the obstacle and a horizontal and a
vertical angle of the obstacle from a preselected reference
direction. The preceding vehicle determining circuit includes a
two-dimensional shape data producing circuit that produces
two-dimensional shape data of the obstacle on a two-dimensional
plane in a width-wise and a vertical direction of the present
vehicle based on the distance and the horizontal and vertical
angles. The preceding vehicle determining circuit also includes a
non-vehicle determining circuit that determines the obstacle as an
object other than the vehicle when the two-dimensional shape data
of the obstacle lies out of an ordinary vehicle shape range.
[0010] In the system of U.S. Pat. No. 6,018,308, the non-vehicle
determination is responsive to a variation in the height of the
obstacle which occurs for a prescribed time interval. The design
enables the non-vehicle determination to be accurate even in the
case where the present vehicle is traveling along a road having a
varying slope.
[0011] U.S. Pat. No. 5,604,580 (corresponding to Japanese patent
application publication number 7-225276) discloses a vehicular
optical radar apparatus which can identify various types of
obstacles as well as a preceding vehicle, thereby ensuring a
reliable identification of the preceding vehicle running in the
same lane as with a subject vehicle on which the apparatus is
installed. In the apparatus of U.S. Pat. No. 5,604,580, light is
emitted from a light emitting device. A scanner enables an area
ahead of the subject vehicle to be scanned by the emitted light. A
light receiving device receives the light caused by reflection of
the emitted light at an object. A received-light intensity
detection device detects an intensity of the reflected light
received by the light receiving device. An obstacle identifying
device identifies the object according to the distribution pattern
of the received-light intensity detected by the intensity detection
device, such as a pattern being obtained with respect to the
scanning direction.
[0012] Japanese patent application publication number 10-142336
discloses an apparatus for recognizing a lane along which a vehicle
is traveling. The apparatus in Japanese application 10-142336
calculates quantities .DELTA.x, .DELTA.y, and .DELTA..phi. of
movement of the vehicle which occur for every predetermined time
interval on the basis of the speed V and the steering angle
.theta.H of the vehicle. Here, .DELTA.x, .DELTA.y, and .DELTA..phi.
denote the quantity of movement in the lateral direction, the
quantity of movement in the longitudinal direction, and the
quantity of movement in the angular direction with respect to the
vehicle, respectively. The apparatus in Japanese application
10-142336 includes a forward object recognizing section having a
laser radar. The forward object recognizing section feeds a
stationary-object determining section with information representing
the positions of detected objects relative to the vehicle. The
stationary-object determining section detects delineators on the
road sides in response to the calculated vehicle movement
quantities .DELTA.x, .DELTA.y, and .DELTA..phi. and the information
fed from the forward object recognizing section. The
stationary-object determining section feeds a stationary-object-row
recognizing section with information representing the detected
delineators. The stationary-object-row recognizing section
recognizes a row of delineators on the basis of the information fed
from the stationary-object determining section. The
stationary-object-row recognizing section feeds a lane estimating
section with information representing the recognized delineator
row. The lane estimating section estimates a lane along which the
vehicle is traveling on the basis of the information fed from the
stationary-object-row recognizing section. The estimated lane is
used in determining a preceding vehicle. Specifically, a preceding
vehicle to be detected is traveling along the lane same as the
estimated lane.
SUMMARY OF THE INVENTION
[0013] It is a first object of this invention to provide a method
of recognizing an obstacle to a vehicle which can discriminate a
delineator group on the road surface and a nearby two-wheeler from
each other at an early stage.
[0014] It is a second object of this invention to provide an
apparatus for recognizing an obstacle to a vehicle which can
discriminate a delineator group on the road surface and a nearby
two-wheeler from each other at an early stage.
[0015] It is a third object of this invention to provide a
recording medium which stores a computer program for recognizing an
obstacle to a vehicle which can discriminate a delineator group on
the road surface and a nearby two-wheeler from each other at an
early stage.
[0016] A first aspect of this invention provides a method of
recognizing an obstacle to a vehicle. The method comprises the
steps of detecting height-wise positions of objects on the basis of
distances to the objects from the vehicle, angles of the objects in
a width-wise direction of the vehicle, and angles of the objects in
a height-wise direction of the vehicle; determining a plurality of
objects, which satisfy conditions predetermined depending on
physical characteristics of delineators, to be objects composing a
delineator group; when the detected height-wise position of an
object in the delineator group which is nearest to the vehicle
corresponds to a predetermined value or less, determining the
delineator group to be a delineator group on a road surface; and
determining whether or not each object in the on-road-surface
delineator group is a non-delineator in response to conditions of
the detected height-wise positions of the objects in the
on-road-surface delineator group.
[0017] A second aspect of this invention provides an apparatus for
recognizing an obstacle to a vehicle. The apparatus comprises radar
means for applying a transmission wave to a predetermined angular
range in a width-wise direction of the vehicle and a predetermined
angular range in a height-wise direction of the vehicle, and
detecting distances to objects, angles of the objects in the
width-wise direction of the vehicle, and angles of the objects in
the height-wise direction of the vehicle on the basis of reflected
waves which result from reflections of the transmission wave; and
recognizing means for recognizing obstacles ahead of the vehicle on
the basis of the distances to the objects, the angles of the
objects in the width-wise direction of the vehicle, and the angles
of the objects in the height-wise direction of the vehicle which
are detected by the radar means. The recognizing means comprises 1)
object recognizing means for detecting height-wise positions of the
objects on the basis of the distances to the objects, the angles of
the objects in the width-wise direction of the vehicle, and the
angles of the objects in the height-wise direction of the vehicle
which are detected by the radar means; 2) delineator-group
determining means for determining ones among the objects, which
satisfy conditions predetermined depending on physical
characteristics of delineators, to be objects composing a
delineator group; 3) on-road surface delineator-group determining
means for, when the detected height-wise position of an object in
the delineator group which is nearest to the vehicle corresponds to
a predetermined value or less, determining the delineator group to
be a delineator group on a road surface; and 4) non-delineator
determining means for determining whether or not each object in the
on-road-surface delineator group is a non-delineator in response to
conditions of the detected height-wise positions of the objects in
the on-road-surface delineator group.
[0018] A third aspect of this invention is based on the second
aspect thereof, and provides an apparatus wherein the conditions
predetermined depending on the physical characteristics of
delineators are that intervals between the objects are smaller than
a reference value.
[0019] A fourth aspect of this invention is based on the second
aspect thereof, and provides an apparatus wherein the conditions of
the detected height-wise positions of the objects comprise
conditions of a variation in the detected height-wise positions of
the objects.
[0020] A fifth aspect of this invention is based on the fourth
aspect thereof, and provides an apparatus wherein the
non-delineator determining means comprising means for determining
whether or not each object in the on-road-surface delineator group
is a non-delineator in response to a position of occurrence of a
change among an increase, a decrease, and a constancy in a sequence
of the detected height-wise positions of the objects.
[0021] A sixth aspect of this invention is based on the fifth
aspect thereof, and provides an apparatus wherein the object
determined to be the non-delineator is at a place immediately
rearward of a position of occurrence of a change from an increase
to a decrease in the sequence of the detected height-wise positions
of the objects as viewed along a direction away from the
vehicle.
[0022] A seventh aspect of this invention is based on the fifth
aspect thereof, and provides an apparatus wherein the object
determined to be the non-delineator is at a place immediately
rearward of a position of occurrence of a change from a decrease to
an increase in the sequence of the detected height-wise positions
of the objects as viewed along a direction away from the
vehicle.
[0023] An eighth aspect of this invention is based on the sixth
aspect thereof, and provides an apparatus wherein the height-wise
position of the object determined to be the non-delineator
corresponds to a prescribed height or greater.
[0024] A ninth aspect of this invention is based on the eighth
aspect thereof, and provides an apparatus wherein the prescribed
height depends on a distance from the present vehicle.
[0025] A tenth aspect of this invention is based on the second
aspect thereof, and provides an apparatus wherein the object
recognizing means comprises means for recognizing shapes of the
objects, and the delineator-group determining means comprises means
for determining ones among the objects to be objects composing a
delineator group in response to the recognized shapes of the
objects.
[0026] An eleventh aspect of this invention is based on the second
aspect thereof, and provides an apparatus wherein the object
recognizing means comprises means for detecting speeds of the
objects relative to the vehicle, means for detecting a speed of the
vehicle, and means for determining whether the objects are moving
or stationary in response to the detected relative speeds of the
objects and the detected speed of the vehicle, and wherein the
delineator-group determining means comprises means for determining
ones among the stationary objects to be objects composing a
delineator group.
[0027] A twelfth aspect of this invention is based on the second
aspect thereof, and provides an apparatus wherein the detected
height-wise positions of the objects comprise detected height-wise
angles of the objects.
[0028] A thirteenth aspect of this invention provides a recording
medium storing a program for controlling a computer operating as
the object recognizing means, the delineator-group determining
means, the on-road-surface delineator-group determining means, and
the non-delineator determining means in the apparatus of the second
aspect of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a block diagram of a vehicle control apparatus
according to an embodiment of this invention.
[0030] FIG. 2 is a perspective diagram of a distance and
two-direction measurement device in the apparatus of FIG. 1, and a
two-dimensional measurement area periodically scanned by a laser
beam emitted from the distance and two-direction measurement
device.
[0031] FIG. 3 is an operation flow diagram of a computer in FIG.
1.
[0032] FIG. 4 is a diagram of a detected object, and top and bottom
edge angle numbers Ntop and Nbottom for the detected object.
[0033] FIG. 5 is a flowchart of a portion of a program for the
computer in FIG. 1.
[0034] FIG. 6 is a diagram of a detected delineator group.
[0035] FIG. 7 is a diagram of conditions where the present vehicle
is traveling along a flat road, and there are delineators on the
surface of the road.
[0036] FIG. 8 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by a downward
slope, and there are delineators on the surface of the road.
[0037] FIG. 9 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by an upward slope,
and there are delineators on the surface of the road.
[0038] FIG. 10 is a diagram of conditions where the present vehicle
is traveling along a flat road, and there are delineators on the
surface of the road while a two-wheeler exists near two of the
delineators.
[0039] FIG. 11 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by a downward
slope, and there are delineators on the surface of the road while a
two-wheeler exists near two of the delineators.
[0040] FIG. 12 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by an upward slope,
and there are delineators on the surface of the road while a
two-wheeler exists near two of the delineators.
[0041] FIG. 13 is a diagram of conditions where the present vehicle
is traveling along a flat road, and there are delineators on the
surface of the road while a two-wheeler exists near two of the
delineators.
[0042] FIG. 14 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by a downward
slope, and there are delineators on the surface of the road while a
two-wheeler exists near two of the delineators.
[0043] FIG. 15 is a diagram of conditions where the present vehicle
is traveling along a flat road portion preceded by an upward slope,
and there are delineators on the surface of the road while a
two-wheeler exists near two of the delineators.
DETAILED DESCRIPTION OF THE INVENTION
[0044] FIG. 1 shows a vehicle control apparatus according to an
embodiment of this invention. The vehicle control apparatus is
mounted on a vehicle. The vehicle control apparatus alarms when an
obstacle in a specified condition exists in a given detection area
in front of the present vehicle. The vehicle control apparatus
adjusts the speed of the present vehicle in accordance with the
speed of a preceding vehicle.
[0045] As shown in FIG. 1, the vehicle control apparatus includes a
computer (for example, a microcomputer) 3. The computer 3 has a
combination of an input/output (I/O) interface, a CPU, a ROM, and a
RAM. The computer 3 operates in accordance with a program stored in
the ROM. The program may be stored in the RAM. In this case, the
RAM is provided with a backup device.
[0046] Alternatively, the program may be stored in a recording
medium such as a floppy disk, a magneto-optical disk, a CD-ROM, or
a hard disk. In this case, the computer 3 is connected with a drive
for the recording medium, and the program is downloaded into the
computer 3 through the drive.
[0047] The vehicle control apparatus includes a distance and
two-direction measurement device 5, a vehicle speed sensor 7, a
brake switch 9, and a throttle opening degree sensor (a throttle
position sensor) 11 which are connected to the computer 3. The
output signals of the devices 5, 7, 9, and 11 are inputted into the
computer 3.
[0048] The distance and two-direction measurement device 5 acts as
an obstacle detection device for the present vehicle. The distance
and two-direction measurement device 5 has a transmitting and
receiving portion 5a, and a distance and two-direction calculating
portion 5b. The transmitting and receiving portion 5a emits a
forward laser beam ahead of the present vehicle, and controls the
forward laser beam to periodically scan a given detection area in
front of the present vehicle. The given detection area is monitored
by the transmitting and receiving portion 5a. The given detection
area has a predetermined angular dimension in the width-wise
direction of the present vehicle and also a predetermined angular
dimension in the height-wise direction of the present vehicle. In
the case where an object exists in the given detection area, the
forward laser beam encounters the object before being at least
partially reflected thereby. A portion of the reflected laser beam
returns to the transmitting and receiving portion 5a as an echo
laser beam. The transmitting and receiving portion 5a receives the
echo laser beam, and converts the echo laser beam into a
corresponding electric signal. The transmitting and receiving
portion 5a outputs the electric signal to the distance and
two-direction calculating portion 5b. The distance and
two-direction calculating portion 5b detects the angular direction
of the object relative to the present vehicle in the coordinates of
the two angular directions (the widthwise and height-wise angular
directions) on the basis of the output signal of the transmitting
and receiving portion 5a. The distance and two-direction
calculating portion 5b measures the time interval between the
moment of the transmission of a forward laser beam and the moment
of the reception of a related echo laser beam in response to the
output signal from the transmitting and receiving portion 5a. The
distance and two-direction calculating portion 5b detects the
distance "r" to the object from the present vehicle on the basis of
the measured time interval. The distance and two-direction
calculating portion 5b informs the computer 3 of the angular
direction of the object and the distance "r" thereto. In general,
since the object is smaller than the cross-sectional area of the
forward laser beam and is scanned thereby, the distance and
direction information notified from the distance and two-direction
calculating portion 5b to the computer 3 relates to a partial
object or a point-like part of an object. Objects detected by the
distance and two-direction measurement device 5 include obstacles
with respect to the present vehicle.
[0049] As shown in FIG. 2, a two-dimensional measurement area 81
corresponding to the given detection area is periodically scanned
by the laser beam 82 emitted from the distance and two-direction
measurement device 5. The scanning is of a line-by-line format. The
laser beam 82 has an approximately circular cross-section. The
cross section of the laser beam 82 may be elliptical or
rectangular. The laser beam 82 may be replaced by a radio wave
beam, a millimeter wave beam, or an ultrasonic beam. The scanning
may be implemented by controlling the echo beam reception by the
transmitting and receiving portion 5a.
[0050] With reference to FIG. 2, the central direction in the
measurement area 81 is defined as the Z axis. The measurement area
81 corresponds to a given detection area in a two-dimensional X-Y
plane perpendicular to the Z axis. The given detection area is
scanned by the forward laser beam. The height-wise direction of the
present vehicle is defined as corresponding to the Y axis. The Y
axis is equal to a reference direction or a sub scanning direction.
The width-wise direction of the present vehicle is defined as
corresponding to the X axis. The X axis is equal to a main scanning
direction. The given detection area has an angular dimension of 16
degrees (0.15 degree multiplied by 105 points or pixels) in the
X-axis direction, and an angular dimension of 4 degrees (0.7 degree
multiplied by 6 lines) in the Y direction. The X-axis scanning
direction (the main scanning direction) starts from the left-hand
edge of the measurement area 81 toward the right-hand edge thereof.
The Y-axis scanning direction (the sub scanning direction) starts
from the upper edge of the measurement area 81 toward the lower
edge thereof. The measurement area 81 is covered by first, second,
third, fourth, fifth, and sixth scanning lines extending parallel
to the X axis. The first, second, third, fourth, fifth, and sixth
scanning lines are sequentially arranged as viewed in the direction
from the upper edge of the measurement area 81 to the lower edge
thereof. During every period of the scanning, the uppermost linear
zone in the measurement area 81 is scanned along the first scanning
line. Subsequently, the second uppermost linear zone in the
measurement area 81 is scanned along the second scanning line.
Then, the following linear zones in the measurement area 81 are
sequentially scanned along the third, fourth, fifth, and sixth
scanning lines. Therefore, measurement-result data of 630 (105
points multiplied by 6 lines) points or pixels are available for
every period of the scanning.
[0051] The fourth scanning line is defined as being horizontal.
Thus, the direction of the forward laser beam in the fourth
scanning line coincides with the horizontal axis. The direction of
the forward laser beam in the first scanning line deviates upward
from the horizontal axis by an angle of 3 multiplied by 0.7
degrees. The direction of the forward laser beam in the second
scanning line deviates upward from the horizontal axis by an angle
of 2 multiplied by 0.7 degrees. The direction of the forward laser
beam in the third scanning line deviates upward from the horizontal
axis by an angle of 0.7 degrees. The direction of the forward laser
beam in the fifth scanning line deviates downward from the
horizontal axis by an angle of 0.7 degrees. The direction of the
forward laser beam in the sixth scanning line deviates downward
from the horizontal axis by an angle of 2 multiplied by 0.7
degrees.
[0052] As previously mentioned, the information (the data)
generated by the distance and two-direction calculating portion 5b
represents the angular direction of a detected object and the
distance "r" thereto. Specifically, the angular direction of the
object is given by a set of the horizontal angle (the horizontal
scan angle) .theta.x and the vertical angle (the vertical scan
angle) .theta.y. The angle between the forward laser beam related
to the object and the X-Z plane is defined as the vertical angle
(the vertical scan angle) .theta.y. The angle between the Z axis
and the line resulting from projecting the forward laser beam on
the X-Z plane is defined as the horizontal angle (the horizontal
scan angle) .theta.x.
[0053] With reference back to FIG. 1, the vehicle control apparatus
includes an alarm sound generator 13, a distance indicator 15, a
sensor failure indicator 17, a brake drive device 19, a throttle
drive device 21, and an automotive automatic transmission control
device 23 which are connected to the computer 3. The computer 3
outputs drive signals to the devices 13, 15, 17, 19, 21, and
23.
[0054] The vehicle control apparatus includes an alarm sound volume
setting device 24, an alarm sensitivity setting device 25, a cruise
control switch 26, a steering sensor 27, and a yaw rate sensor 28
which are connected to the computer 3. The output signals of the
devices 24, 25, 26, 27, and 28 are inputted into the computer 3.
The alarm sound volume setting device 24 acts to set the volume of
alarm sound. The alarm sensitivity setting device 25 acts to set
the sensitivity in a warning determination process mentioned later.
The steering sensor 27 detects the degree of operation of a vehicle
steering wheel (not shown), that is, the steering angle in the
present vehicle.
[0055] The vehicle control apparatus includes a power supply switch
29 connected to the computer 3. When the power supply switch 29 is
changed to its on position, the computer 3 is powered and starts
predetermined processes.
[0056] The computer 3 executes a warning determination process
designed to generate an alarm in the case where an obstacle remains
in a specified area during longer than a prescribed time interval.
The obstacle corresponds to, for example, a preceding vehicle, a
stationary vehicle, a guardrail on a road side, or a prop on a road
side. Simultaneously with the execution of the warning
determination process, the computer 3 operates to control the
distance between the present vehicle and a preceding vehicle.
Specifically, during the inter-vehicle distance control (the
vehicle-to-vehicle distance control), the computer 3 controls the
brake drive device 19, the throttle drive device 21, and the
automatic transmission control device 23 and thereby adjusts the
speed of the present vehicle in accordance with conditions of the
preceding vehicle.
[0057] FIG. 3 shows the flow of operation of the computer 3 rather
than the hardware structure thereof. With reference to FIG. 3, an
object recognition block 43 receives, from the distance and angle
calculating portion 5b in the distance and two-direction
measurement device 5, measurement data representing a distance "r",
a horizontal scan angle .theta.x, and a vertical scan angle
.theta.y concerning each detected object (each detected partial
object or each detected point-like object part). The object
recognition block 43 converts the polar-coordinate data of the
distance "r" and the horizontal scan angle .theta.x into
measurement data of X-Z orthogonal coordinates designed so that the
origin (0, 0) coincides with the center of a laser radar formed by
the distance and angle measurement device 5, and the X axis and the
Z axis coincide with the width-wise direction and the longitudinal
forward direction of the present vehicle respectively. The object
recognition block 43 calculates the central position (X, Z) and
size (W, D) of each detected object on the basis of the
orthogonal-coordinate measurement data. Here, W denotes a
transverse width, and D denotes a depth. The object recognition
block 43 calculates the speed (Vx, Vz) of the object relative to
the present vehicle from time-domain change in the central position
(X, Z) thereof.
[0058] With reference to FIGS. 3 and 4, the object recognition
block 43 recognizes the top and bottom edges of each detected
object by referring to the data of the vertical scan angle .theta.y
concerning the detected object. For each detected object, the
object recognition block 43 uses the .theta.y data as an indication
of (Ntop, Nbottom) where Ntop denotes a number representative of
the vertical scan angle of the top edge of the detected object and
Nbottom denotes a number representative of the vertical scan angle
of the bottom edge of the detected object. Each of the top and
bottom edge angle numbers Ntop and Nbottom assumes one among values
of "1", "2", "3", "4", "5", and "6" which correspond to the first,
second, third, fourth, fifth, and sixth scanning lines (see FIG.
2), respectively. As previously mentioned, the fourth scanning line
is defined as being horizontal. Thus, an Ntop value of "1", "2", or
"3" indicates that the top edge of the related target is above the
horizontal axis. On the other hand, an Ntop value of "5" or "6"
indicates that the top edge of the related target is below the
horizontal axis.
[0059] A vehicle speed calculation block 47 computes the speed V of
the present vehicle on the basis of the output signal from the
vehicle speed sensor 7. The object recognition block 43 is informed
of the speed V of the present vehicle by the vehicle speed
calculation block 47. The object recognition block 43 determines
whether or not each detected object is stationary or moving on the
basis of the vehicle speed V and the relative speed (Vx, Vz). One
or more which may affect the travel of the present vehicle are
selected from among detected objects on the basis of the
stationary-moving determination results and the central positions
of the detected objects. Information of the distance to each
selected object is transferred to the distance indicator 15 so that
the distance to the selected object is indicated by the distance
indicator 15. A model of an object which is represented by central
position data, size data, relative-speed data, stationary-moving
determination result data (recognition type data), and top and
bottom edge angle data will be called a target model.
[0060] A sensor failure detection block 44 receives the output data
(the object-recognition result data) from the object recognition
block 43 which represent the object parameters calculated thereby.
The sensor failure detection block 44 determines whether the output
data from the object recognition block 43 are in a normal range or
an abnormal range. When the output data from the object recognition
block 43 are in the abnormal range, the sensor failure detection
block 44 activates the sensor failure indicator 17 to indicate a
failure.
[0061] A steering angle calculation block 49 computes the steering
angle regarding the present vehicle on the basis of the output
signal from the steering sensor 27. A yaw rate calculation block 51
computes the yaw rate of the present vehicle on the basis of the
output signal from the yaw rate sensor 28.
[0062] A curvature-radius calculation block 63 is informed of the
vehicle speed V by the vehicle speed calculation block 47. The
curvature-radius calculation block 63 is informed of the computed
steering angle by the steering angle calculation block 49. The
curvature-radius calculation block 63 is informed of the computed
yaw rate by the yaw rate calculation block 51. The curvature-radius
calculation block 63 computes the radius R of curvature of the road
on the basis of the vehicle speed V, the steering angle, and the
yaw rate.
[0063] A preceding-vehicle determination block 53 is informed of
the computed curvature radius R by the curvature-radius calculation
block 63. The preceding-vehicle determination block 53 is informed
of the stationary-moving determination results, the object central
positions (X, Z), the object sizes (W, D), the relative speeds (Vx,
Vz), and the top and bottom edge angle numbers (Ntop, Nbottom) by
the object recognition block 43. The preceding vehicle
determination block 53 determines or selects a preceding vehicle
from among the detected objects on the basis of the curvature
radius R, the stationary-moving determination results, the object
central positions (X, Z), the object sizes (W, D), the relative
speeds (Vx, Vz), and the top and bottom edge angle numbers (Ntop,
Nbottom). The preceding-vehicle determination block 53 calculates
the distance Z to the preceding vehicle from the present vehicle,
and the speed Vz of the preceding vehicle relative to the present
vehicle.
[0064] An inter-vehicle distance control and warning determination
block 55 is informed of the distance Z to the preceding vehicle and
the relative speed Vz by the preceding-vehicle determination block
53. The inter-vehicle distance control and warning determination
block 55 is informed of the vehicle speed V by the vehicle speed
calculation block 47. The inter-vehicle distance control and
warning determination block 55 computes the acceleration of the
preceding vehicle from the relative speed Vz and the vehicle speed
V. The inter-vehicle distance control and warning determination
block 55 is informed of the object central positions (X, Z), the
object widths D, and the stationary-moving determination results by
the object recognition block 43. The inter-vehicle distance control
and warning determination block 55 detects setting conditions of
the cruise control switch 26 from the output signal thereof. The
inter-vehicle distance control and warning determination block 55
detects the state of the brake switch 9 from the output signal
thereof. The state of the brake switch 9 represents whether or not
a vehicle brake pedal is depressed. The inter-vehicle distance
control and warning determination block 55 is informed of the
degree of opening through a vehicular engine throttle valve by the
throttle opening degree sensor 11. The inter-vehicle distance
control and warning determination block 55 is informed of the alarm
sensitivity setting value by the alarm sensitivity setting device
25. The inter-vehicle distance control and warning determination
block 55 implements a warning determination and a cruise
determination in response to the distance Z to the preceding
vehicle, the relative speed Vz, the vehicle speed V, the
preceding-vehicle acceleration, the object central positions (X,
Z), the object widths D, the stationary-moving determination
results, the setting conditions of the cruise control switch 26,
the state of the brake switch 9, the throttle opening degree, and
the alarm sensitivity setting value. During the warning
determination, the inter-vehicle distance control and warning
determination block 55 determines whether or not an alarm should be
generated. During the cruise determination, the inter-vehicle
distance control and warning determination block 55 determines the
contents of vehicle speed control. When it is determined that an
alarm should be generated, the inter-vehicle distance control and
warning determination block 55 outputs an alarm generation signal
to the alarm sound generator 13. In this case, the alarm sound
generator 13 produces alarm sound. The inter-vehicle distance
control and warning determination block 55 adjusts the level of the
alarm sound in accordance with the sound volume set by the alarm
sound volume setting device 24. In the case where the cruise
determination corresponds to the execution of cruise control, the
inter-vehicle distance control and warning determination block 55
outputs suitable control signals to the automotive automatic
transmission control device 23, the brake drive device 19, and the
throttle drive device 21. During the execution of warning control
and cruise control, the inter-vehicle distance control and warning
determination block 55 outputs an indication signal to the distance
indicator 15 to inform the vehicle's driver of distance-related
conditions.
[0065] As previously mentioned, the computer 3 operates in
accordance with a program stored in its internal ROM or RAM. FIG. 5
is a flowchart of a portion of the program for the computer 3 which
relates to the recognition of an obstacle to the present vehicle.
The program portion in FIG. 5 is repetitively executed at a period
corresponding to the period of the scanning implemented by the
distance and two-direction measurement device 5.
[0066] As shown in FIG. 5, a first step S1000 of the program
portion receives distance and two-direction angle measurement data
from the distance and two-direction measurement device 5 for one
period of the scanning. In other words, the step S1000 receives
distance and two-direction angle measurement data corresponding to
one frame. The scanning period is equal to, for example, 100
msec.
[0067] A step S2000 following the step S1000 corresponds to the
object recognition block 43. The step S2000 implements the
previously-mentioned object recognition on the basis of the
distance and two-direction angle measurement data. Each object
recognized or detected by the step S2000 will be called a target or
a target model.
[0068] A step S3000 subsequent to the step S2000 groups the targets
detected by the step S2000 to recognizes a delineator group.
[0069] The targets detected by the step S2000 correspond to
delineators, signboards, vehicles, two-wheelers, and other objects.
The step S3000 excludes non-delineator targets (for example,
targets corresponding to signboards and vehicles), and selects
targets corresponding to delineators. To this end, the step S3000
searches the targets detected by the step S2000 for ones which
satisfy both the following conditions {circle over (1)} and {circle
over (2)}.
[0070] {circle over (1)} The transverse width W of a target is
smaller than 1.0 m.
[0071] {circle over (2)} The absolute value of the X-axis-direction
distance .DELTA.X between the centers of targets is smaller than 1
m, and the absolute value of the Z-axis-direction distance .DELTA.Z
therebetween is smaller than 20 m.
[0072] In other words, .vertline..DELTA.X.vertline.<1 m and
.vertline..DELTA.Z.vertline.<20 m.
[0073] The step S3000 places the targets which satisfy both the
above-indicated conditions {circle over (1)} and {circle over (2)}
in a common candidate group. There can be a plurality of candidate
groups. The step S3000 uses one or more of candidate groups as a
delineator group or groups. Each selected candidate group, that is,
each delineator group, is required to have three or more targets.
FIG. 6 shows an example of a delineator group recognized or
detected by the step S3000.
[0074] With reference back to FIG. 5, a step S4000 following the
step S3000 determines whether or not each delineator group detected
by the step S3000 corresponds to a group of delineators
(cat's-eyes) on the road surface. Specifically, the step S4000
selects one from among targets in the delineator group which is the
nearest to the present vehicle (that is, which is the smallest in
distance value Z). The step S4000 compares the top edge angle
number Ntop of the nearest target with a value of "5". When the top
edge angle number Ntop is equal to or greater than a value of "5",
the step S4000 determines that the delineator group corresponds to
an on-road-surface delineator group. In this case, the program
advances from the step S4000 to a step S5000. When the top edge
angle number Ntop is smaller than a value of "5", the step S4000
determines that the delineator group does not correspond to an
on-road-surface delineator group. In this case, the program exits
from the step S4000, and then the current execution cycle of the
program portion ends.
[0075] When the present vehicle is travelling on the beginning or
the end of a sloping road, the detected heights of far targets in
the delineator group tend to be greatly offset from their actual
heights. On the other hand, the detected height of the nearest
target in the delineator group is less offset from its actual
height. Accordingly, the use of the nearest target by the step
S4000 enhances the accuracy of the determination as to whether or
not the delineator group corresponds to an on-road-surface
delineator group.
[0076] There is a chance that the on-road-surface delineator group
determined by the step S4000 contains a non-delineator target, for
example, a target corresponding to a two-wheeler near
on-road-surface delineators. The step S5000 detects such a
non-delineator target.
[0077] Specifically, the step S5000 searches the targets in the
on-road-surface delineator group for one which satisfies both the
following conditions (a) and (b).
[0078] (a) In the case where the distance Z to a subject target is
smaller than 40 m, the top edge angle number Ntop of the target is
equal to "1", "2", or "3". In the case where the distance Z to a
subject target is equal to or greater than 40 m, the top edge angle
number Ntop of the target is equal to "1", "2", "3", or "4".
[0079] (b) In the case where the targets of the on-road-surface
delineator group are sequentially arranged in the order of distance
Z from the smallest to the greatest, a subject target is at a place
immediately rearward of a point of the occurrence of a change from
a monotonically decrease or a constancy to an increase in top edge
angle number Ntop.
[0080] The step S5000 determines that the target which satisfies
both the conditions (a) and (b) corresponds to a non-delineator.
The non-delineator target detected by the step S5000 can be used as
candidates for a preceding vehicle to be determined. After the step
S5000, the current execution cycle of the program portion ends.
[0081] FIG. 7 shows the case where the present vehicle is traveling
along a flat road, and there are delineators on the surface of the
road. In this case, the heights of the delineators relative to the
present vehicle are equal to each other. FIG. 8 shows the case
where the present vehicle is traveling along a flat road portion
preceded by a downward slope, and there are delineators on the
surface of the road. In this case, the height of a delineator
relative to the present vehicle monotonically decreases as the
delineator is farther from the present vehicle. FIG. 9 shows the
case where the present vehicle is traveling along a flat road
portion preceded by an upward slope, and there are delineators on
the surface of the road. In this case, the height of a delineator
relative to the present vehicle monotonically increases as the
delineator is farther from the present vehicle.
[0082] FIG. 10 shows the case where the present vehicle is
traveling along a flat road, and is preceded by a two-wheeler.
There are delineators on the surface of the road. The two-wheeler
is located near two of the delineators. The delineators and the
two-wheeler are now defined as targets. In the case of FIG. 10, the
height of a target relative to the present vehicle remains constant
for a certain range and then increases and decreases as the target
is farther from the present vehicle. FIG. 11 shows the case where
the present vehicle is traveling along a flat road portion preceded
by a downward slope, and a two-wheeler is moving along the downward
slope. There are delineators on the surface of the road. The
two-wheeler is located near two of the delineators. The delineators
and the two-wheeler are now defined as targets. In the case of FIG.
11, the height of a target relative to the present vehicle remains
constant for a certain range and then increases and decreases as
the target is farther from the present vehicle. FIG. 12 shows the
case where the present vehicle is traveling along a flat road
portion preceded by an upward slope, and a two-wheeler is moving
along the downward slope. There are delineators on the surface of
the road. The two-wheeler is located near two of the delineators.
The delineators and the two-wheeler are now defined as targets. In
the case of FIG. 12, the height of a target relative to the present
vehicle increases and then decreases as the target is farther from
the present vehicle.
[0083] In view of the target height changes mentioned with
reference to FIGS. 10, 11, and 12, the step S5000 of FIG. 5
discriminates a non-delineator target (for example, a two-wheeler
target) from on-road-surface delineator targets. The discrimination
between a non-delineator target and on-road-surface delineator
targets will be described below in more detail.
[0084] FIG. 13 shows the case where the present vehicle is
traveling along a flat road, and is preceded by a two-wheeler. FIG.
14 shows the case where the present vehicle is traveling along a
flat road portion preceded by a downward slope, and a two-wheeler
is moving along the downward slope. In this case, the height of a
target as viewed from the present vehicle decreases in accordance
with an increase in the distance to the target. In view of the case
of FIG. 14, the previously-mentioned conditions (a) are designed to
depend on whether or not the distance Z to a subject target is
smaller than 40 m. FIG. 15 shows the case where the present vehicle
is traveling along a flat road portion preceded by an upward slope,
and a two-wheeler is moving along the upward slope. In this case,
the height of a target as viewed from the present vehicle increases
in accordance with an increase in the distance to the target. The
previously-mentioned conditions (b) are introduced to prevent an
actual on-road-surface delineator from being recognized as a
non-delineator in the case of FIG. 15.
[0085] A further description will be given below with reference to
FIGS. 13, 14, and 15. In FIG. 13, there are delineators on the
surface of the flat road, and the two-wheeler is located near two
of the on-road-surface delineators. The top edge angle number Ntop
of the two-wheeler target is equal to "4", while the top edge angle
number Ntop of the on-road-surface delineator target immediately
rearward of the two-wheeler target is equal to "5". The top edge
angle number Ntop of the on-road-surface delineator target
immediately ahead of the two-wheeler target is equal to "5". The
top edge angle number Ntop of the nearest on-road-surface
delineator is equal to "6". These targets compose an
on-road-surface delineator group detected or recognized by the step
S4000 (see FIG. 5). According to the previously-mentioned
conditions (b), the targets are sequentially arranged in the order
of distance Z from the smallest to the greatest. In this case, the
top edge angle number Ntop changes as 6.fwdarw.5>4.fwdarw.5. The
two-wheeler target is at a place immediately rearward of a point of
the occurrence of a change from a monotonically decrease to an
increase in top edge angle number Ntop. Accordingly, the
two-wheeler target satisfies the previously-mentioned conditions
(b). Thus, the two-wheeler target is recognized by the step S5000
(see FIG. 5) as a non-delineator.
[0086] In FIG. 14, there are delineators on the surface of the
road, and the two-wheeler is located near two of the
on-road-surface delineators. The top edge angle number Ntop of the
two-wheeler target is equal to "4", while the top edge angle number
Ntop of the on-road-surface delineator target immediately ahead of
the two-wheeler target is equal to "5". The top edge angle number
Ntop of the on-road-surface delineator target immediately rearward
of the two-wheeler target is equal to "5". The top edge angle
number Ntop of the nearest on-road-surface delineator is equal to
"6". These targets compose an on-road-surface delineator group
detected or recognized by the step S4000 (see FIG. 5). According to
the previously-mentioned conditions (b), the targets are
sequentially arranged in the order of distance Z from the smallest
to the greatest. In this case, the top edge angle number Ntop
changes as 6.fwdarw.5.fwdarw.4.fwdarw.5. The two-wheeler target is
at a place immediately rearward of a point of the occurrence of a
change from a monotonically decrease to an increase in top edge
angle number Ntop. Accordingly, the two-wheeler target satisfies
the previously-mentioned conditions (b). Thus, the two-wheeler
target is recognized by the step S5000 (see FIG. 5) as a
non-delineator.
[0087] In FIG. 15, there are delineators on the surface of the
road, and the two-wheeler is located near two of the
on-road-surface delineators. The top edge angle number Ntop of the
two-wheeler target is equal to "3", while the top edge angle number
Ntop of the on-road-surface delineator target immediately rearward
of the two-wheeler target is equal to "4". The top edge angle
number Ntop of the on-road-surface delineator target immediately
ahead of the two-wheeler target is equal to "4". The top edge angle
number Ntop of the nearest on-road-surface delineator is equal to
"6". These targets compose an on-road-surface delineator group
detected or recognized by the step S4000 (see FIG. 5). According to
the previously-mentioned conditions (b), the targets are
sequentially arranged in the order of distance Z from the smallest
to the greatest. In this case, the top edge angle number Ntop
changes as 6.fwdarw.4.fwdarw.3.fwdarw.4. The two-wheeler target is
at a place immediately rearward of a point of the occurrence of a
change from a monotonically decrease to an increase in top edge
angle number Ntop. Accordingly, the two-wheeler target satisfies
the previously-mentioned conditions (b). Thus, the two-wheeler
target is recognized by the step S5000 (see FIG. 5) as a
non-delineator.
[0088] In the embodiment of this invention, the distance and
two-direction measurement device 5 corresponds to radar means while
the object recognition block 43 and the preceding-vehicle
determination block 53 provided by the computer 3 correspond to
recognizing means. Specifically, the object recognizing block 43
corresponds to object recognizing means. The preceding-vehicle
determination block 53 corresponds to delineator-group determining
means, on-road-surface delineator-group determining means, and
non-delineator determining means.
[0089] The embodiment of this invention has advantages as follows.
Object recognition (obstacle recognition) includes a determination
concerning a delineator group on the surface of a road which is
designed to use object-height information. Accordingly, it is
possible to discriminate an on-road-surface delineator group from
vehicles except two-wheelers (the steps S3000 and S4000 in FIG. 5).
Furthermore, it is possible to discriminate a non-delineator or a
two-wheeler from an on-road-surface delineator group (the step
S5000 in FIG. 5). Thus, an on-road-surface delineator group and a
nearby two-wheeler can be recognized while being discriminated from
each other. This recognition is based on instantaneously-available
information of the heights of targets in the on-road-surface
delineator group rather than information of a time-domain change of
a condition of one target. Thus, the result of the recognition can
be provided at an early stage.
[0090] As previously mentioned, a non-delineator is discriminated
from an on-road-surface delineator group. Therefore, a
non-delineator corresponding to a two-wheeler can be added to
candidate targets for a preceding vehicle to be detected.
Accordingly, a preceding vehicle can be more suitably selected from
among candidate targets. In addition, the inter-vehicle distance
control and the warning determination can be more properly
executed.
[0091] The embodiment of this invention may be modified as follows.
The total number of scanning lines may differ from six. In the
case, each of the top and bottom edge angle numbers Ntop and
Nbottom assumes one among different values, the number of which is
equal to the total number of scanning lines.
[0092] In the embodiment of this invention, the distance and
two-direction measurement device 5 which employs the laser beam is
used as radar means. The distance and two-direction measurement
device 5 may be modified to use a millimeter wave beam. In the case
where the radar means uses a Doppler radar or an FMCW radar
employing a millimeter wave beam, information of a distance to a
preceding vehicle and information of a relative speed of the
preceding vehicle are simultaneously derived from an echo wave beam
(a return wave beam). Thus, in this case, it is unnecessary to
execute a step of calculating a relative speed from distance
information.
* * * * *