U.S. patent application number 09/875125 was filed with the patent office on 2001-12-27 for alarming apparatus and method for automotive vehicle.
This patent application is currently assigned to NISSAN MOTOR CO., LTD.. Invention is credited to Iwasaki, Masahiko, Matsumoto, Shinji.
Application Number | 20010054954 09/875125 |
Document ID | / |
Family ID | 18691282 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054954 |
Kind Code |
A1 |
Matsumoto, Shinji ; et
al. |
December 27, 2001 |
Alarming apparatus and method for automotive vehicle
Abstract
In alarming apparatus and method for an automotive vehicle, a
vehicular running state is detected, a frictional coefficient of a
road surface on which the vehicle is running is detected, a vehicle
using road surface frictional coefficient that corresponds to a
road surface frictional force the presently running vehicle is
using is calculated on the basis of the detected vehicular running
state, a road surface frictional coefficient utilization rate is
calculated which is a rate of the calculated vehicle using road
surface frictional coefficient of the road surface to a maximum
frictional coefficient detected by the road surface frictional
coefficient detector, and an alarm controlling section is
calculated to output an alarm command to an alarm device to issue
an alarm when the calculated road surface frictional coefficient
utilization rate is equal to or larger than a set value.
Inventors: |
Matsumoto, Shinji;
(Yokohama, JP) ; Iwasaki, Masahiko; (Yokohama,
JP) |
Correspondence
Address: |
Richard L. Schwaab
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Assignee: |
NISSAN MOTOR CO., LTD.
|
Family ID: |
18691282 |
Appl. No.: |
09/875125 |
Filed: |
June 7, 2001 |
Current U.S.
Class: |
340/426.1 ;
340/425.5 |
Current CPC
Class: |
B60W 2552/40 20200201;
G08G 1/161 20130101; B60K 31/0008 20130101; B60W 2520/105 20130101;
B60K 31/18 20130101; B60T 2210/12 20130101; B60W 50/0097 20130101;
B60W 2050/143 20130101; B60W 2520/125 20130101; B60T 2201/02
20130101 |
Class at
Publication: |
340/426 ;
340/425.5 |
International
Class: |
B60Q 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2000 |
JP |
2000-192104 |
Claims
What is claimed is:
1. An alarming apparatus for an automotive vehicle, comprising: a
running state detector to detect a vehicular running state; a road
surface frictional coefficient detector to detect a frictional
coefficient of a road surface on which the vehicle is running; a
vehicle using road surface frictional coefficient calculating
section that calculates a vehicle using road surface frictional
coefficient that corresponds to a road surface frictional force the
presently running vehicle is using on the basis of the detected
vehicular running state; a road surface frictional coefficient
utilization rate calculating section that calculates a road surface
frictional coefficient utilization rate which is a rate of the
calculated vehicle using road surface frictional coefficient of the
road surface to a maximum frictional coefficient detected by the
road surface frictional coefficient detector; and an alarm
controlling section that outputs an alarm command to an alarm
device to issue an alarm when the calculated road surface
frictional coefficient utilization rate is equal to or larger than
a set value.
2. An alarming apparatus for an automotive vehicle as claimed in
claim 1, further comprising: an inter-vehicle distance detector to
detect an inter-vehicle distance between the vehicle and a
preceding vehicle which is running ahead of the vehicle; a
vehicular velocity controlling section that controls a vehicular
velocity of the vehicle in accordance with at least the detected
inter-vehicle distance; and a vehicular driving force controlling
section that controls a driving force exerted on the vehicle in
accordance with a vehicular velocity variation command outputted
from the vehicular velocity controlling section, and wherein the
vehicle using road surface frictional coefficient calculating
section calculates a present vehicle using road surface frictional
coefficient or the vehicle using road surface frictional
coefficient after the driving force control is effected in
accordance with the vehicular running state and in response to a
driving force control command outputted from the driving force
controlling section.
3. An alarming apparatus for an automotive vehicle as claimed in
claim 1, wherein the road surface frictional coefficient detector
comprises a detector to detect the road surface frictional
coefficient of a road surface placed in a vehicular forward
direction by obtaining an information of the road surface
frictional coefficient measured by a road surface fiction
coefficient measuring device installed on the road via a wireless
communication.
4. An alarming apparatus for an automotive vehicle as claimed in
claim 1, wherein the road surface frictional coefficient detector
comprises a detector to detect the road surface frictional
coefficient of a road surface placed in a vehicular forwarding
direction from a preceding vehicle which is running ahead of the
vehicle via a wireless communication.
5. An alarming apparatus for an automotive vehicle as claimed in
claim 2, wherein the road surface frictional coefficient detector
comprises an estimator to estimate the road surface frictional
coefficient in accordance with the driving force to be exerted when
a vehicular velocity variation rate occurs during an execution of
the vehicular velocity control and a slip rate of each road wheel
of the vehicle to occur when the vehicular velocity variation rate
occurs during the execution of the vehicular velocity control.
6. An alarming apparatus for an automotive vehicle as claimed in
claim 1, wherein the running state detector comprises a vehicular
longitudinal acceleration detector to detect a vehicular
longitudinal acceleration applied to a vehicle body of the vehicle
and a vehicular lateral acceleration detector to detect a lateral
acceleration thereof and the vehicle using road surface fictional
coefficient calculating section calculates the vehicle using road
surface frictional coefficient on the basis of the detected
vehicular longitudinal acceleration and the detected vehicular
lateral acceleration.
7. An alarming apparatus for an automotive vehicle as claimed in
claim 2, wherein the running state detector comprises a vehicular
longitudinal acceleration detector to detect a vehicular
longitudinal acceleration applied to a vehicle body and a vehicular
lateral acceleration detector to detect a lateral acceleration
applied to the vehicle body and the vehicle using road surface
fictional coefficient calculating section calculates the vehicle
using road surface frictional coefficient on the basis of the
detected vehicular longitudinal acceleration and the detected
vehicular lateral acceleration and variation rates of the
longitudinal acceleration and the lateral acceleration that would
be predicted in the future and that are estimated from a driving
force control command value to be issued when a vehicular velocity
variation occurs during an execution of the vehicular velocity
control.
8. An alarming apparatus for an automotive vehicle as claimed in
claim 1, wherein the running state detector comprises an estimator
to estimate a longitudinal force and a lateral force of each road
wheel and the road surface frictional coefficient utilization rate
calculating section calculates the road surface frictional
coefficient utilization rate according to a rate of an average
value of the use road surface frictional coefficients of all of the
vehicular road wheels to a maximum frictional coefficient of the
road surface detected by the road surface frictional coefficient
detector.
9. An alarming apparatus for an automotive vehicle as claimed in
claim 1, wherein the running state detector comprises an estimator
to estimate a longitudinal force applied to each road wheel and to
estimate a lateral force applied to each road wheel, wherein the
vehicle using road surface frictional coefficient calculating
section calculates the vehicle using road surface frictional
coefficient for each road wheel according to estimated values of
the longitudinal force and lateral force for each corresponding
road wheel, wherein the road surface frictional coefficient
utilization rate calculating section calculates the road surface
frictional coefficient utilization rates for front road wheels and
for rear road wheels according to rates of a front road wheel
average value of the vehicle using road surface frictional
coefficients to a maximum frictional coefficient detected by the
road surface frictional coefficient detector and of a rear road
wheel average value of the vehicle using road surface frictional
coefficients to the maximum road surface frictional coefficient,
and wherein the alarm controlling section outputs the alarm command
to the alarm device when either the road surface frictional
coefficient utilization rate calculated according to the front road
wheel average value or that calculated according to the rear road
wheel average value is equal to or larger than the set value.
10. An alarming apparatus for an automotive vehicle as claimed in
claim 2, wherein the alarm controlling section outputs the alarm
command to the alarm device when any one of such conditions is
established that a case where the road surface frictional
coefficient utilization rate is equal to or lager than the set
value, a case where the inter-vehicle distance detected by the
inter-vehicle distance detector is equal to or longer than another
set value, and a case where a relative velocity to the preceding
vehicle is equal to or higher than a still another set value.
11. An alarming apparatus for an automotive vehicle as claimed in
claim 3, wherein the road surface frictional coefficient detector
comprises a road-to-vehicle communicating receiver for receiving
the road surface frictional coefficient information and position
information from a plurality of transmitters installed aside the
road surface on which the vehicle is running at a regular interval
of distances.
12. An alarming apparatus for an automotive vehicle as claimed in
claim 11, wherein the road surface frictional coefficient detector
calculates the road surface frictional coefficient .mu.x at the
present position Xcar of the vehicle as follows: Xcar=Xb+.intg.Vdt,
wherein Xb denotes a latest reference position and V denotes the
vehicular velocity, .mu.x0=f(Xcar), and a first-order filter is
applied to f(Xcar).
13. An alarming apparatus for an automotive vehicle as claimed in
claim 6, wherein the vehicle using road surface frictional
coefficient calculating section calculates the vehicle using road
surface frictional coefficient .mu.car as follows: .mu.car={square
root}{square root over ( )}(Xgh.sup.2+Yg.sup.2), wherein
Xgh=Max(.vertline.Xg.vertline., .vertline.Xgs.vertline.), wherein
Max(a, b) denotes a selection of larger one of a and b, Xg denotes
the vehicular longitudinal acceleration and Xgs denotes a target
acceleration, and is expressed as
Xgs=kp.multidot..epsilon.+Ki.multidot..intg..epsilon.dt+Kd.multidot.d.eps-
ilon./dt, .epsilon.=Vs-V, and Vs=Min(Vc,
K1p.multidot.(Lx-Lc)+K1d.multidot- .dLx+V), wherein Vc denotes the
set vehicular velocity, Klp denotes a proportional control gain,
Kld denotes a differential control gain, and Ki denotes an
integration control gain.
14. An alarming apparatus for an automotive vehicle as claimed in
claim 13, wherein the road surface frictional coefficient
calculating section calculates the road surface frictional
coefficient R.mu. as follows: R.mu.=.mu.car/.mu.x
15. An alarming apparatus for an automotive vehicle as claimed in
claim 13, wherein the alarm controlling section comprises a first
comparator to compare Xgs with an acceleration threshold value Xgkl
to determine if Xgkl>Xgs and wherein the alarming controller
outputs the alarm command to the alarm device to issue the alarm
when the first comparator determines that Xgkl>Xgs.
16. An alarming apparatus for an automotive vehicle as claimed in
claim 13, wherein the alarm controlling section comprises a second
comparator to compare the utilization rate R.mu. with the set value
R.mu.k to determine if R.mu.k.ltoreq.R.mu. and wherein the alarm
controlling section outputs the alarm command to the alarm device
to issue the alarm when the second comparator determines that
R.mu.k.ltoreq.R.mu..
17. An alarming method for an automotive vehicle, comprising:
detecting a vehicular running state; detecting a frictional
coefficient of a road surface on which the vehicle is running;
calculating a vehicle using road surface frictional coefficient
that corresponds to a road surface frictional force the presently
running vehicle is using on the basis of the detected vehicular
running state; calculating a road surface frictional coefficient
utilization rate which is a rate of the calculated vehicle using
road surface frictional coefficient of the road surface to a
maximum frictional coefficient detected at the frictional
coefficient detection; and outputting a command to an alarm device
to issue an alarm when the calculated road surface frictional
coefficient utilization rate is equal to or larger than a set
value.
18. An alarming apparatus for an automotive vehicle, comprising:
running state detecting means for detecting a vehicular running
state; road surface frictional coefficient detecting means for
detecting a frictional coefficient of a road surface on which the
vehicle is running; vehicle using road surface frictional
coefficient calculating means for calculating a vehicle using road
surface frictional coefficient that corresponds to a road surface
frictional force the presently running vehicle is using on the
basis of the detected vehicular running state; road surface
frictional coefficient utilization rate calculating means for
calculating a road surface frictional coefficient utilization rate
which is a rate of the calculated vehicle using road surface
frictional coefficient of the road surface to a maximum frictional
coefficient detected by the road surface frictional coefficient
detecting means; and alarm controlling means for outputting a
command to an alarm device to issue an alarm when the calculated
road surface frictional coefficient utilization rate is equal to or
larger than a set value.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to alarming apparatus and
method for an automotive vehicle.
[0003] 2. Description of the Related Art
[0004] Japanese Patent Application First Publications No. Heisei
11-34696 published on Feb. 9, 1999 and Heisei 10-119673 published
on May 12, 1998 exemplify first and second previously proposed
alarming apparatuses applied to automotive vehicles.
[0005] In the former above-described Japanese Patent Application
First Publication (JP1134696), the vehicle is too approaching to
the preceding vehicle in a case where another vehicle is
interrupted into a space as a new preceding vehicle between the
vehicle and the old preceding vehicle. At this time, a blink of an
alarm lamp or a sound of an alarm buzzer is activated to inform the
driver of such an abrupt approach to the other vehicle as described
above so that the driver is forcefully pressed to manipulate a
brake system of the vehicle.
[0006] The latter above-described Japanese Patent Application First
publication (JP10119673) discloses a technique in which a predicted
arrival time duration for the vehicle to arrive at an obstacle on
the basis of an obstacle information and vehicular information is
calculated and an alarm device is activated on the basis of a
relationship between an alarm timing and the predicted arrival time
in terms of a time concept.
SUMMARY OF THE INVENTION
[0007] However, in the previously proposed alarming apparatus
disclosed in the former Japanese Patent Application Publication, a
determination of whether the vehicle is about to collide against a
rear portion of the preceding vehicle is set in accordance with
such a deceleration as would be developed by means of a preceding
vehicle following adaptive vehicular velocity control
apparatus.
[0008] For example, in a case where the inter-vehicle distance from
the vehicle to the preceding vehicle indicates such an
inter-vehicle distance as requiring the deceleration equal to or
larger than 0.2 G, the previously proposed alarming apparatus
issues an alarm to the vehicle driver.
[0009] In other words, no consideration of a road surface
frictional coefficient of a road surface on which the vehicle is
running is taken but only the alarm in accordance with the
inter-vehicle distance to the preceding vehicle and the relative
velocity is issued. Even if the vehicle is running on a road
surface having a low road surface frictional coefficient, the alarm
is issued at the same timing as the vehicular run on a high
frictional coefficient.
[0010] The alarm at this timing is effective in terms of avoidance
of the vehicle from a possible collision against the preceding
vehicle.
[0011] However, for example, in cases where the deceleration of
0.15 G is developed during the vehicular run on the road surface
having the road surface frictional coefficient of 1.0 and where the
same deceleration of 0.15 G is developed during the vehicular run
on the road surface having the road surface frictional coefficient
of 0.3, the same deceleration of 0.15 G can be developed and the
alarm is not issued since 0.15 G is smaller than 0.2 G.
[0012] Actually, however, a safety margin of the vehicle is
different in such a way as the margin becomes smaller, as the
frictional coefficient of the road surface on which the vehicle is
running becomes lower. It is difficult for the vehicle driver to
recognize this state when the vehicle is running on the road
surface having the low frictional coefficient.
[0013] On the other hand, in the vehicular alarming apparatus
disclosed in the latter Japanese Patent Application first
Publication, no consideration of the frictional coefficient of the
road surface on which the vehicle is running is taken but only the
alarm is issued in accordance with a predicted arrival time
duration toward an obstacle placed in the forward direction.
[0014] For example, in a case where the inter-vehicle distance
between the vehicle and the preceding vehicle and the relative
velocity of the vehicle to the preceding vehicle are the same, the
same predicted arrival time durations are resulted where the
vehicle is running on the road surface having the low road surface
frictional coefficient and having the high road surface frictional
coefficient and the alarm is issued at the same timing.
[0015] Hence, the timing at which the alarm is issued becomes
delayed when the vehicle is running on the road surface of the low
frictional coefficient having the small vehicular safety margin. It
is difficult for the vehicle driver to recognize such a situation
as described above when the vehicle is running on the low
frictional road surface.
[0016] It is an object of the present invention to provide alarming
apparatus and method for an automotive vehicle which can have the
vehicle driver recognize that a vehicular safety margin is reduced
at an appropriate timing irrespective of a magnitude of the road
surface frictional coefficient.
[0017] According to one aspect of the present invention, there is
provided an alarming apparatus for an automotive vehicle,
comprising: a running state detector to detect a vehicular running
state; a road surface frictional coefficient detector to detect a
frictional coefficient of a road surface on which the vehicle is
running; a vehicle using road surface frictional coefficient
calculating section that calculates a vehicle using road surface
frictional coefficient that corresponds to a road surface
frictional force the presently running vehicle is using on the
basis of the detected vehicular running state; a road surface
frictional coefficient utilization rate calculating section that
calculates a road surface frictional coefficient utilization rate
which is a rate of the calculated vehicle using road surface
frictional coefficient of the road surface to a maximum frictional
coefficient detected by the road surface frictional coefficient
detector; and an alarm controlling section that outputs an alarm
command to an alarm device to issue an alarm when the calculated
road surface frictional coefficient utilization rate is equal to or
larger than a set value.
[0018] According to another aspect of the present invention, there
is provided an alarming method for an automotive vehicle,
comprising: detecting a vehicular running state; detecting a
frictional coefficient of a road surface on which the vehicle is
running; calculating a vehicle using road surface frictional
coefficient that corresponds to a road surface frictional force the
presently running vehicle is using on the basis of the detected
vehicular running state; calculating a road surface frictional
coefficient utilization rate which is a rate of the calculated
vehicle using road surface frictional coefficient of the road
surface to a maximum frictional coefficient detected at the
frictional coefficient detection; and outputting a command to an
alarm device to issue an alarm when the calculated road surface
frictional coefficient utilization rate is equal to or larger than
a set value.
[0019] According to a still another aspect of the present
invention, there is provided an alarming apparatus for an
automotive vehicle, comprising: running state detecting means for
detecting a vehicular running state; road surface frictional
coefficient detecting means for detecting a frictional coefficient
of a road surface on which the vehicle is running; vehicle using
road surface frictional coefficient calculating means for
calculating a vehicle using road surface frictional coefficient
that corresponds to a road surface frictional force the presently
running vehicle is using on the basis of the detected vehicular
running state; road surface frictional coefficient utilization rate
calculating means for calculating a road surface frictional
coefficient utilization rate which is a rate of the calculated
vehicle using road surface frictional coefficient of the road
surface to a maximum frictional coefficient detected by the road
surface frictional coefficient detecting means; and alarm
controlling means for outputting a command to an alarm device to
issue an alarm when the calculated road surface frictional
coefficient utilization rate is equal to or larger than a set
value.
[0020] This summary of the invention does not necessarily describe
all necessary features so that the invention may also be a
sub-combination of these described features.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic circuit block diagram of an alarming
apparatus for an automotive vehicle in a preferred embodiment
according to the present invention.
[0022] FIG. 2 is an operational flowchart representing an example
of a control program executed in a drive force related controller
shown in FIG. 1.
[0023] FIG. 3A and 3B are explanatory views for explaining alarm
operations during a vehicular run on a high frictional coefficient
road surface and a low frictional coefficient road surface on which
the vehicle in which the alarming apparatus shown in FIG. 1 is
mounted is running to follow a preceding vehicle.
[0024] FIG. 4A is an explanatory view for explaining an example of
positional information of the vehicle and road surface frictional
coefficient information which are obtained from an infrastructure
used in the preferred embodiment of the alarming apparatus shown in
FIG. 1.
[0025] FIG. 4B is an explanatory view for explaining an example of
positional information and road surface frictional coefficient
information as an alternative of FIG. 4A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Reference will hereinafter be made to the drawings in order
to facilitate a better understanding of the present invention.
[0027] FIG. 1 shows a whole system configuration of a rear-wheel
drive vehicle (an automatic transmission mounted and a conventional
differential mounted vehicle) to which an alarming apparatus in the
preferred embodiment according to the present invention is
applicable. A brake system of the vehicle shown in FIG. 1 can
control left road wheel and right road wheel braking forces (brake
liquid pressures) independently of each other on rear and front
road wheels independently of each other.
[0028] In FIG. 1, a brake pedal 1, a booster 2, a master cylinder
3, and a reservoir 4 are disposed in the brake system. Left and
right front road wheels 10 and 20 and left and right rear road
wheels 30 and 40 are disposed in the vehicle. Each of the four road
wheels 10, 20, 30, and 40 is provided with a brake disc 11, 21, 31,
and 41, a wheel cylinder 12, 22, 32, and 42 for frictionally
grasping the brake disc 11, 21, 31, and 41 to give a braking force
for each road wheel by a supply of a liquid pressure. When the
liquid pressure is supplied to each wheel cylinder 12, 22, 32, and
42 of the brake system from a pressure control unit 5, each road
wheel 10, 20, 30, and 40 is individually controlled. Pressure
control unit 5 is constituted by an actuator included in an
individual liquid pressure supply system (each channel) at front
and rear left and right road wheels. A proportional solenoid valve
is used to enable a control over a brake liquid pressure in each
wheel cylinder to an arbitrary braking liquid pressure as the
actuator.
[0029] Pressure control unit 5 adjusts a hydraulic pressure from
master cylinder 3 in response to an input signal from the drive
force controller 50 and controls the braking liquid pressure
supplied to the wheel cylinders 12, 22, 32, and 42 of respective
road wheels. In addition, drive force controller 50 performs the
engine control such as to control a fuel injection quantity of an
engine 6, a throttle valve control such as to control an opening
angle of an engine throttle valve through a throttle controller 7,
and performs an automatic transmission control such as to control a
gear ratio of an automatic transmission 8 so as to perform a drive
torque control via a drive torque related controller 60 which
controls the drive torque of the drive torque of the driven
wheels.
[0030] Drive force controller 50 receives signals a signal from an
accelerator sensor 52 detecting a vehicular longitudinal
acceleration Xg and a vehicular lateral acceleration Yg, signals
from wheel velocity sensors 13, 23, 33, and 43 installed on the
respectively corresponding road wheels to detect respectively
corresponding road wheel velocities Vwi, and a signal indicating a
set position of a switch 53 to set a set vehicular velocity Vc
manually by the vehicle driver. Drive force controller 50 receives
signals from a master cylinder liquid pressure sensor 55 to detect
a master cylinder liquid pressure Pm in order to detect a
manipulated variable of brake pedal 1, a signal from an accelerator
opening angle sensor 56 to detect an opening angle Acc of
accelerator in order to detect a manipulated variable of an
accelerator pedal, and a signal indicating a drive torque Tw on a
wheel axle from drive torque related controller 60.
[0031] After a road surface frictional coefficient .mu. is received
from a receiver 57 and is outputted into drive force controller 50.
It is noted that road surface frictional coefficient .mu.
transmitted from the infrastructure is a data in a unit of 0.1 and
ranges from 0.1 to 1.0. In addition, as shown in FIG. 4, a
reference position Xb (from a lane marker such as to enable
obtaining of a positional information) is simultaneously obtained
with the present position Xcar of the vehicle as an estimation
enabled information. In addition, an alarm buzzer 54 to have the
vehicle driver recognize that there is a possibility of collision
of the vehicle against the preceding vehicle and that the safety
margin of the vehicle becomes small is disposed within a passenger
compartment and the alarm is issued in accordance with the output
from the drive force controller 50.
[0032] Next, an operation of the alarming apparatus shown in FIG. 1
will be described below.
[0033] [Alarming process]
[0034] FIG. 2 shows a flowchart representing a control procedure
executed by drive force controller 50. It is noted that the term
drive force used in the specification includes the brake force as
well as the drive force.
[0035] This procedure shown in FIG. 2 is executed as a regular time
interrupt routine whenever a predetermined time duration has passed
by monitoring a time duration through an operating system of drive
force controller 50. It is noted that drive force controller 50
generally includes a microcomputer having a CPU (Central Processing
Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an
Input Port, an Output Port, an interrupt routine controller, a DMA
(Direct Memory Access) controller, and a common bus.
[0036] At a step S100, drive force controller 50 reads various data
from respective sensors 13, 23, 33, 43, 51, 52, 53, 55, 56, and 57
and drive torque controller 60.
[0037] In details, controller 50 stores into a memory such as RAM
respective road wheel velocities Vwi(i=1 through 4) from road wheel
velocity sensors 13, 23, 33, and 43, vehicular longitudinal
acceleration Xg and lateral acceleration Yg from acceleration
sensor 52 (corresponds to a vehicular running state detector), an
accelerator opening angle Acc from accelerator opening angle sensor
56, master cylinder liquid pressure Pm from master cylinder liquid
pressure sensor 55, the set vehicular velocity from switch 53, and
the road surface frictional coefficient .mu.i, the position Xmi,
and reference position Xb from the road-and-vehicle communicating
receiver 57. It is noted that i denotes a plural number and the
road surface frictional coefficient .mu.i is stored into the memory
as a function of position Xm: That is to say,
.mu.i=f(Xmi) (1).
[0038] In addition, drive force controller 50 reads drive torque Tw
and inter-vehicle distance Lx to the preceding vehicle from a drive
torque controller 60.
[0039] At a step S101, drive force controller 50 calculates a
vehicular velocity V of the vehicle. In this embodiment, drive
force controller 50 calculates a vehicular velocity V from an
average value of the front road wheel velocities in accordance with
road wheel velocities Vwi during a normal run.
V=(Vw1+Vw2)/2 (2).
[0040] In addition, in a case where an ABS (Anti-Lock Brake System)
control is activated, drive force controller 50 may calculate the
vehicular velocity from a pseudo vehicular velocity estimated in
ABS controller.
[0041] At a step S102, drive force controller 50 estimates the
relative velocity dLx to the preceding vehicle. In the embodiment,
drive force controller 50 calculates the relative velocity dLx in
accordance with the following equation (3) according to the
inter-vehicle distance Lx to the preceding vehicle. That is to
say,
dLx=k1.multidot.(Lx(n)-Lx(n-1))/.DELTA.T (3).
[0042] It is noted that, in the equation (3), .DELTA.T denotes a
calculation period, k1 denotes a conversion constant, and n denotes
a calculation timing.
[0043] At a step S103, drive force controller 50 calculates a
target inter-vehicle distance Lc to the preceding vehicle. In this
embodiment, target inter-vehicle distance Lc is calculated from
vehicular velocity V in accordance with the following equation (4).
That is to say,
Lc=Kv1.multidot.V+Kv2 (4).
[0044] In the equation (4), Kv1 and kv2 denote control
constants.
[0045] In this embodiment, drive force controller 50 calculates
target inter-vehicle distance Lc merely in accordance with the
vehicular velocity V. A manual setting of the inter-vehicle
distance by the driver may be used to set the target inter-vehicle
distance.
[0046] For example, if the driver sets the target inter-vehicle
distance from three stages of long, middle, and short, control
constants in the equation (4) may be modified, and target
inter-vehicle distance Lc may be modified.
[0047] At a step S104, drive force controller 50 calculates a road
surface frictional coefficient .mu.x at the present position of the
vehicle (corresponds to a road surface frictional coefficient
detector).
[0048] In this embodiment, the road surface frictional coefficient
.mu.x at the present position of the vehicle on the basis of
.mu.i=f(Xmi) in equation (1) which is the function of the road
surface frictional coefficient .mu.i and the position Xmi received
from the road-and-vehicle communications with the
infrastructure.
[0049] First, drive force controller 50 calculates the present
position Xcar of the vehicle according to an integration of a
latest reference position Xb and vehicular velocity V of the
vehicle.
Xcar=Xb+.intg.Vdt (integration from a time at which the vehicle has
passed reference position to the present time) (5).
[0050] Next, a reference road surface frictional coefficient
.mu.x0=f(Xcar) (6)
[0051] It is noted that since the road surface functional
coefficient .mu.i is varied in accordance with an internal of
distance installed in the infrastructure, the road surface
frictional coefficient is discontinuous with respect to the
position Xcar of the vehicle. Hence, a first order filter is
supplied to the reference road surface frictional coefficient
.mu.x0 to smooth .mu.x0 to derive the road surface frictional
coefficient .mu.x.
[0052] At a subsequent step S105, drive force controller 50
calculates a target vehicular velocity Vs according to the set
vehicular velocity Vc set manually by the vehicular driver, the
inter-vehicle distance Lx, target inter-vehicle distance Lc, and
relative velocity dLx. In this embodiment, target vehicular
velocity Vs is calculated in accordance with the following
equation: That is to say,
Vs=Min (Vc, k1p.multidot.(Lx-Lc)+k1d.multidot.dLx+V) (7).
[0053] It is noted that k1p and k1d denote control gains, Min (a,
b) denotes a function to select a minimum value from a and b.
[0054] It is noted that (Lx-Lc)<0 denotes a narrowed
inter-vehicle distance and dLx indicates minus when the vehicle is
approaching to the preceding vehicle.
[0055] At a step S106, drive force controller 50 calculates a
target acceleration Xgs. In this embodiment, target acceleration
Xgs is calculated according to vehicular velocity V and target
vehicular velocity Vs in accordance with the following equation (it
is noted that the acceleration indicates positive and the
deceleration indicates negative). That is to say,
Xgs=kp.multidot..epsilon.+ki.multidot..intg..epsilon.dt+Kd.multidot.d.epsi-
lon./dt (8).
.epsilon.=Vs-V (9).
[0056] It is noted that, in the equations (8) and (9), kp, ki, and
kd denote control gains (proportional control gain, integration
control gain, and differential control gain). The contents of steps
S105 and S106 correspond to a vehicular velocity controlling
section (vehicular velocity controlling means).
[0057] At a step S107, drive force controller 50 calculates a
target braking liquid pressure Pwsi. In this embodiment, target
braking liquid pressure Pwsi is modified in accordance with the
following equation according to target acceleration Xgs, master
cylinder liquid pressure Pm, and brake requirements.
[0058] 1) Xgs<0
Pwsi=Max(Kxi*Xgs, kb*Pm) (10).
[0059] 2) Xgs>0
Pwsi=Max(0, kb*Pm) (11).
[0060] In equations (10) and (11), kxi and kb denote coefficients
(pad .mu. of each road wheel, w/c area, an effective radius of a
rotor, and a tire effective radius).
[0061] At a step S108, drive force controller 50 calculates a
target drive force torque Tes in accordance with the following
equations (12 and 13) according to a drive train
specifications.
1) Xgs<0; Tgs=Max(0, ka*Acc) (12)
[0062] and
2) Xgs.gtoreq.0 Tes=Max[kt*Xgs, Ka*Acc] (13)
[0063] It is noted that ka and kt denote variables determined
according to drive system requirements (gear inertia, gear ratio,
transmission efficiency, engine characteristic, and so forth). It
is also noted that in this case no consideration of an engine brake
is paid. Steps S107 and S108 correspond to drive force controlling
section.
[0064] At a step S109, drive force controller 50 calculates a
vehicle using frictional coefficient .mu.car which is a road
surface fictional force (a resultant force between the longitudinal
force and lateral force developed on whole road wheels) that the
vehicle is presently using during the vehicular run (corresponds to
a vehicle using road surface frictional coefficient calculating
section). In this embodiment, the vehicle using road surface
frictional coefficient .mu.car is calculated in accordance with the
following equation according to the vehicular longitudinal
acceleration kg, the lateral acceleration kg, and target
acceleration kgs.
.mu.car={square root}{square root over ( )}(Xgh.sup.2+Yg.sup.2)
(14).
[0065] In this equation, Xgh denotes a vehicular longitudinal
acceleration correction value and is expressed as follows: That is
to say,
Xgh=Max(.vertline.Xg.vertline., .vertline.Xgs.vertline.) (15).
[0066] In this way, by using one of the values of actually
developing longitudinal acceleration Xg and target acceleration Xgs
which is larger than the other, such a merit that the fact is
previously known how the safety margin is varied immediately before
the acceleration or deceleration is actually developed by means of
the control can be exhibited.
[0067] At a step S110, drive force controller 50 calculates a
utilization rate R.mu. of road surface frictional coefficient
according to the road surface frictional coefficient calculated at
S104 and vehicle using road surface frictional coefficient .mu.car
calculated at step S109 (corresponds to a vehicle using road
surface coefficient utilization rate calculating section). In the
embodiment, the utilization rate is calculated in accordance with
the following equation: That is to say,
R.mu.=.mu.car/.mu.x (16).
[0068] At a step S111, drive force controller 50 determines whether
the alarm should be issued. In this embodiment, drive force
controller 50 determines whether the alarm should be issued on the
basis of two kinds of information. The first one is a possibility
of a future collision of vehicle against the preceding vehicle. An
acceleration threshold value Xgk1 (for example, -0.2 G) set with a
capacity of brake force controlling system and an influence on the
vehicular driver during the deceleration in mind is compared with
target acceleration Xgs.
If Xgk1>Xgs (17),
[0069] an alarm issuance flag F.sub.ON is turned to ON ("1").
Second, drive force controller 50 turns alarm issuance flag
F.sub.ON to "1" in a case where
R.mu.k.ltoreq.R.mu. (18),
[0070] wherein R.mu. denotes the road surface frictional
coefficient, R.mu.k denotes a threshold value (for example, 0.5)
when utilization rate is high and, in this case, safety margin of
the vehicle is determined to be small.
[0071] On the other hand, if neither equation (17) nor equation
(18) is established, the alarm issuance flag F.sub.ON is turned to
OFF ("0").
[0072] At a step S112, drive force controller 50 outputs drive
signals to pressure control unit 5 and drive torque related
controller 60, respectively, in accordance with target braking
liquid pressure Pwsi and target drive torque Tes. In addition, if
the alarm issuance flag F.sub.ON determined at step S111 is turned
to ON, drive force controller 50 issues a buzzer sound in order to
make the vehicle driver recognize that there is a possibility of
the collision of the vehicle against the preceding vehicle and the
safety margin of vehicle becomes decreased. Steps S111 and S112
correspond to alarming control section.
[0073] [Alarming Operation]
[0074] For example, a following control to follow the preceding
vehicle on the high frictional coefficient road surface will be
described below.
[0075] If both of the vehicle (host vehicle) and the preceding
vehicle are running at a cruise speed of each vehicular velocity V1
as shown in {circle over (1)} of FIG. 3A and, thereafter, are
slowed down at reduced vehicular velocities as shown in {circle
over (2)} and {circle over (3)} of FIG. 3A, the road surface
frictional coefficient utilization rates R.mu. of both vehicles are
smaller than threshold value of R.mu.k.
[0076] Then, in a case of {circle over (2)} of FIG. 3A wherein a
deceleration-oriented target acceleration (hereinafter, referred to
as a target deceleration) Xgs is equal to or larger than a
deceleration-oriented acceleration threshold value (hereinafter,
referred to as a deceleration threshold value) Xgk, alarm issuance
flag F.sub.ON is turned to "0" (OFF) at step S111. No issuance of
alarm occurs in this case.
[0077] However, in a case of {circle over (3)} of FIG. 3A wherein
target deceleration Xgs is smaller than deceleration threshold
value Xgk1 (Xgk1>Xgs), alarm issuance flag F.sub.ON is turned to
"1" (ON) and the alarm is issued.
[0078] Next, the following control to follow the preceding vehicle
on the low frictional coefficient road surface shown in FIG. 3B
will be described below.
[0079] First, if both of the vehicle (host vehicle) and the
preceding vehicle are running at the cruise speed of V1 as shown in
{circle over (1)}' of FIG. 3B and, thereafter, are decelerated as
shown in {circle over (2)}' and {circle over (3)}' of FIG. 3B,
target deceleration Xgs of the vehicle is equal to or larger than
deceleration threshold value Xgk1 since the vehicle is running on a
low frictional road surface. In a case of {circle over (2)}' where
utilization rate R.mu. of road surface frictional coefficient is
smaller than threshold value (set value) R.mu.k, the alarm issuance
flag F.sub.ON at step S111 of FIG. 2 is turned to "1" (off). Thus,
the alarm issuance does not occur. However, in a case of {circle
over (3)}' wherein the utilization rate R.mu. of the road surface
frictional coefficient is equal to or larger than the threshold
value R.mu.k, the alarm issuance flag F.sub.ON is turned to "1"
(ON) at step S111 of FIG. 2 and, thus, the alarm is issued.
[0080] That is to say, in a case where the forward road surface
frictional coefficient is small, the alarm is issued in accordance
with the road surface frictional coefficient R.mu.. Thus, in a case
where the deceleration is not so large that is decelerated
according to the following control, the driver can recognize that
the safety margin of the vehicle is reduced.
[0081] Since the alarm in accordance with the possibility of
collision against the preceding vehicle is directly used, for
example, the vehicle is running using the preceding vehicle
following control on the high frictional coefficient road surface
as shown in FIG. 3A. There is quite few that the utilization rate
of road surface coefficient R.mu. becomes large. Hence, the alarm
due to the deceleration is a mainly implemented alarm process.
[0082] (Other Embodiments and Alternatives)
[0083] In the preferred embodiment, the control equations described
in the equations (7) through (13) are used in the vehicular
velocity control portion based on the inter-vehicle distance to the
preceding vehicle. A feed-forward control plus a feedback control
may be used as described in Automotive Engineering Society Journal,
November, 1999 (pages 98 through 103, titled as "Development of
Adaptive Cruise Control with Brake Actuation" authored by Tetsuya
Iijima et al). A European Patent Application Publication No. EP 0
982 172 A2 published on Mar. 1, 2000 describes the feed-forward
control and the feedback control system in the vehicular velocity
control apparatus.
[0084] In details, since the present invention relates to the alarm
occurrence in accordance with the utilization rate of the road
surface frictional coefficients, various control rules are
applicable to the control portion of the inter-vehicle
distance.
[0085] In the preferred embodiment, the alarm is issued in
accordance with the utilization rate of the road surface frictional
coefficient with the vehicular velocity control having the
inter-vehicle distance maintenance control as a prerequisite.
[0086] However, the present invention is applicable not only to an
automotive vehicle in which such a chassis control system as
described above is not installed but also to another automotive
vehicle in which no such a chassis control system as described
above is installed. That is to say, the vehicle using road surface
frictional coefficient is calculated according to the vehicular run
state, the road surface frictional coefficient utilization rate is
determined according to the detected road surface frictional
coefficient, and the alarm is issued in accordance with the
utilization rate.
[0087] In this case, the chassis control is especially specified.
For example, in a case where the system in which the target value
is set in the longitudinal acceleration and lateral acceleration,
target acceleration Xgs (or Ygs) is used in a portion corresponding
to step S109 of the flowchart shown in FIG. 2. In a case where the
system in which no target value is set in the longitudinal
acceleration and lateral acceleration, target acceleration Xgs is
not present but only the vehicular longitudinal acceleration Xg is
always used.
[0088] In this embodiment, the vehicular forwarding road surface
frictional coefficient is detected on the basis of the obtained
information which is received from the measured information by the
infrastructure installed on the road via a wireless communication.
However, the vehicular forwarding road surface frictional
coefficient may be derived from the vehicular running state as
disclosed in a Japanese Patent Application First Publication No.
Heisei 11-334555 published on Dec. 7, 1999 or may be estimated in
accordance with the drive/brake force applied at the time of
acceleration/deceleration during the vehicular control and the slip
rates of the respective road wheels. The method of estimating the
slip rate is also exemplified by a U.S. Pat. No. 6,015,192 issued
on Jan. 18, 2000 (the disclosure of which is herein incorporated by
reference).
[0089] The above-described Japanese Patent Application First
Publication (JP11334555) describes the road surface frictional
coefficient estimating apparatus comprising: road wheel velocity
detecting means for detecting road wheel velocities; vehicular body
velocity detecting means for detecting a vehicular body velocity;
driving/braking force detecting means for detecting a braking force
or braking force exerted on each road wheel; slip rate calculating
means for receiving one of the detected road wheel velocities which
corresponds to the road wheel and the detected vehicular body
velocity and calculating a slip rate for the corresponding road
wheel; a pseudo .mu.--s function generating means for receiving the
slip rate for each road wheel and generating a pseudo .mu.--s
function which is analogous function to a .mu.--s function
representing a functional coefficient developed between a road
surface and a road wheel; a road wheel velocity estimation error
calculating means for receiving the road wheel velocities, a
driving/braking force, and the estimated value of the road surface
frictional coefficient, and calculating an estimated value of the
road wheel velocity which accords with the estimated value of the
road surface frictional coefficient, and subtracting the road wheel
velocity estimated value from the road wheel velocities to derive
an estimation error of the corresponding road wheel velocity; a
calibration parameter calculating means for receiving the pseudo
.mu.--s function and calculating a calibration parameter to
calibrate the pseudo .mu.--s function; and calibrating means for
receiving the pseudo .mu.--s function and calibration parameter,
calibrating the pseudo .mu.--s function by the calibration
parameter, and outputting the calibration value as the road surface
frictional coefficient estimated value. The pseudo function is
expressed as follows: .lambda.=(Xw-Xv)/Xv(.thrfore.Xw>Xv) or
(Xw-Xv)/Xw(.thrfore.Xw.ltoreq.X- v), wherein .lambda. denotes a
slip rate between the road surface and the corresponding road
wheel, Xw denotes the corresponding road wheel velocity, and Xv
denotes the vehicular body velocity.
[0090] Furthermore, as shown in FIG. 4B, the vehicular forwarding
road wheel surface frictional coefficient may be determined on the
basis of the obtained information on the road frictional
coefficient by a wireless communication from the preceding vehicle
which is running ahead of the vehicle (host vehicle). The vehicular
forwarding road surface frictional coefficient may be detected on
the basis of the obtained information.
[0091] In this embodiment, the vehicle using road surface
frictional coefficient .mu.car is calculated according to the
vehicular longitudinal and lateral accelerations Xg and Yg.
However,the vehicular run state detect or may estimate the
longitudinal force mXg and lateral force mYg of each road wheel and
may calculate the vehicle using road surface frictional coefficient
.mu.car.sub.(10, 20, 30, 40) for each road wheel 10, 20, 30, and 40
according to estimated values thereof mXg and mYg.
[0092] In this case, the utilization rate for the road surface
frictional coefficient may be calculated according to a rate of an
average value .mu.car.sub.avg of the vehicle using road surface
frictional coefficient of the whole road wheels to a maximum
frictional coefficient of the road surface or according to a rate
of a rear wheel average value .mu.car.sub.R of the vehicle using
road surface frictional coefficient and a front wheel average value
thereof .mu.car.sub.F to the maximum frictional coefficient of the
road surface on which the vehicle runs.
[0093] In this embodiment, the issuance condition of the alarm is
exemplified in a case where the utilization rate R.mu. for the road
surface frictional coefficient .mu.car is equal to or larger than
the threshold value R.mu.k and in a case where the target
acceleration Xgs is less than the acceleration threshold value
Xgk1. Otherwise, in a case where the inter-vehicle distance Lx is
equal to or shorter than a set value Lx1 or in a case where the
relative velocity dLx to the preceding vehicle is equal to or
larger than the set value dLx1 may be used. If any one of these
(four) conditions is established, the alarm may be issued.
[0094] It is noted that a drive force defined in the claims
includes a brake force since the drive force is positive and the
brake force is negative, the target acceleration Xgs also includes
a target deceleration, and the maximum road surface coefficient may
be deemed to be equal to the first-order filtered road surface
frictional coefficient .mu.x.
[0095] The entire contents of a Japanese Patent Application No.
2000-192104 (filed in Japan on Jun. 27, 2000) are herein
incorporated by reference. Although the invention has been
described above by reference to certain embodiment of the
invention, the invention is not limited to the embodiments
described above. Modifications and variations of the embodiments
described above will occur to those skilled in the art in the light
of the above teachings. The scope of the invention is defined with
reference to the following claims.
* * * * *