U.S. patent application number 10/954997 was filed with the patent office on 2005-05-12 for roll-over suppressing control apparatus for a vehicle.
Invention is credited to Sakata, Kunio.
Application Number | 20050102084 10/954997 |
Document ID | / |
Family ID | 34536089 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050102084 |
Kind Code |
A1 |
Sakata, Kunio |
May 12, 2005 |
Roll-over suppressing control apparatus for a vehicle
Abstract
The invention provides a roll-over suppressing control apparatus
for a vehicle which can suppress roll-over of the vehicle
sufficiently also upon steering back turning wherein the turning
direction of the vehicle changes over halfway. The roll-over
suppressing control apparatus includes a roll-over suppressing
control section for controlling, if a roll rate sensor detects
that, upon turning of the vehicle, the vehicle is in an excessive
rolling state, a braking mechanism so as to apply or increase
braking force to a turning outer wheel to perform roll-over
suppressing control. If a decision section decides during the
roll-over suppressing control that all of the left and right wheels
of the vehicle remain in contact with the road, then the roll-over
suppressing control section carries out all wheel braking control
of controlling the braking mechanism so as to apply the braking
force to all of the left and right wheels of the vehicle.
Inventors: |
Sakata, Kunio; (Tokyo,
JP) |
Correspondence
Address: |
ROSSI & ASSOCIATES
P.O. Box 826
Ashburn
VA
20146-0826
US
|
Family ID: |
34536089 |
Appl. No.: |
10/954997 |
Filed: |
September 30, 2004 |
Current U.S.
Class: |
701/70 ;
340/440 |
Current CPC
Class: |
B60T 2230/03 20130101;
B60T 8/17554 20130101 |
Class at
Publication: |
701/070 ;
340/440 |
International
Class: |
G06F 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2003 |
JP |
2003-341501 |
Claims
What is claimed is:
1. A roll-over suppressing control apparatus for a vehicle,
comprising: a braking mechanism capable of braking left and right
wheels of said vehicle separately from each other; rolling state
detection means for detecting a rolling state of said vehicle;
roll-over suppressing control means for controlling, if it is
detected by said rolling state detection means that, upon turning
of said vehicle, said vehicle is in an excessive rolling state,
said braking mechanism so as to apply or increase braking force to
a turning outer wheel to perform roll-over suppressing control; and
decision means for deciding whether or not all of said left and
right wheels of said vehicle remain in contact with a road during
the roll-over suppressing control; said roll-over suppressing
control means performing, when it is decided by said decision means
that all of said left and right wheels of said vehicle remain in
contact with the road, all wheel braking control of controlling
said braking mechanism so as to apply the braking force to all of
said left and right wheels of said vehicle.
2. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 1, wherein said decision means decides, where a
rolling angle of said vehicle can be estimated to be substantially
zero when turning of said vehicle during the roll-over suppressing
control is steering back turning wherein the direction of the
turning of said vehicle is changed over halfway, that all of said
left and right wheels of said vehicle remain in contact with the
road.
3. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 2, wherein said decision means estimates that,
when turning of said vehicle during the roll-over suppressing
control is steering back turning wherein the direction of the
turning of said vehicle is changed over halfway, if the magnitude
of a roll rate of said vehicle becomes equal to or higher than a
predetermined value set in advance, the rolling angle of said
vehicle is approximately zero and decides that all of said left and
right wheels of said vehicle remain in contact with the road.
4. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 2, wherein said decision means estimates that,
when turning of said vehicle during the roll-over suppressing
control is steering back turning wherein the direction of the
turning of said vehicle is changed over halfway, if the magnitude
of a lateral acceleration of said vehicle becomes lower than a
predetermined value around zero set in advance, the rolling angle
of said vehicle is approximately zero and decides that all of said
left and right wheels of said vehicle remain in contact with the
road.
5. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 1, wherein said roll-over suppressing control
means ends the all wheel braking control after the roll-over
suppressing control is carried out for a predetermined period of
time set in advance.
6. A roll-over suppressing control apparatus for a vehicle,
comprising: a braking mechanism capable of braking left and right
wheels of said vehicle separately from each other; a rolling state
sensor for detecting a rolling state of said vehicle; and a braking
controller for controlling, if it is detected by said rolling state
sensor that, upon turning of said vehicle, said vehicle is in an
excessive rolling state, said braking mechanism so as to apply or
increase braking force to a turning outer wheel to perform
roll-over suppressing control; said braking controller deciding
whether or not all of said left and right wheels of said vehicle
remain in contact with a road during the roll-over suppressing
control, said braking controller performing, when it is decided
that all of said left and right wheels of said vehicle remain in
contact with the road during the roll-over suppressing control, all
wheel braking control of controlling said braking mechanism so as
to apply the braking force to all of said left and right wheels of
said vehicle.
7. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 6, wherein said braking controller decides, where
a rolling angle of said vehicle can be estimated to be
substantially zero when turning of said vehicle during the
roll-over suppressing control is steering back turning wherein the
direction of the turning of said vehicle is changed over halfway,
that all of said left and right wheels of said vehicle remain in
contact with the road.
8. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 7, wherein said braking controller estimates that,
when turning of said vehicle during the roll-over suppressing
control is steering back turning wherein the direction of the
turning of said vehicle is changed over halfway, if the magnitude
of a roll rate of said vehicle becomes equal to or higher than a
predetermined value set in advance, the rolling angle of said
vehicle is approximately zero and decides that all of said left and
right wheels of said vehicle remain in contact with the road.
9. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 7, wherein said braking controller estimates that,
when turning of said vehicle during the roll-over suppressing
control is steering back turning wherein the direction of the
turning of said vehicle is changed over halfway, if the magnitude
of a lateral acceleration of said vehicle becomes lower than a
predetermined value around zero set in advance, the rolling angle
of said vehicle is approximately zero and decides that all of said
left and right wheels of said vehicle remain in contact with the
road.
10. The roll-over suppressing control apparatus for a vehicle as
claimed in claim 6, wherein said braking controller ends the all
wheel braking control after the roll-over suppressing control is
carried out for a predetermined period of time set in advance.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a roll-over suppressing control
apparatus for a vehicle which causes, when the vehicle is placed
into an excessive rolling state upon turning thereof, braking force
to be applied to turning outer wheels to carry out roll-over
suppressing control.
[0003] 2. Description of the Related Art
[0004] As a technique for controlling the posture of a vehicle upon
turning, a technique has been develop wherein a rolling state of
the vehicle body is detected and, when the rolling of the vehicle
body is excessively great, braking force is applied to particular
wheels to suppress rolling of the vehicle thereby to suppress
roll-over (turning over on its side) of the vehicle (refer to, for
example, Japanese Patent Laid-Open No. Hei 11-11272).
[0005] According to the technique, when a roll rate (rolling
angular velocity) of the vehicle body is detected and the detected
roll rate is equal to or higher than a predetermined value or when
a steering angular velocity is arithmetically operated based on a
steering angle detected by a steering angle sensor and the value of
the arithmetically operated steering angular velocity is equal to
or higher than a predetermined value, the brake system of the
vehicle is controlled to suppress rolling of the vehicle body.
[0006] In order to suppress rolling of a vehicle, it is effective
to lower the speed of the vehicle and suppress turning of the
vehicle, and it is effective to apply braking force, for example,
to front and rear wheels on the turning outer wheel side.
[0007] Incidentally, turning which gives rise to roll-over of a
vehicle has not only an ordinary type of one-directional turning
but also turning wherein the turning direction of a vehicle changes
over halfway of turning as a result of a steering back operation of
a steering wheel as upon lane change or upon S-shaped curve
traveling (the turning is hereinafter referred to as steering back
turning). In such steering back turning, a great reactive movement
is generated in the rolling direction of the vehicle. In this
instance, only if braking force is applied to turning outer wheels
of the vehicle described above, there is the possibility that the
roll-over may be suppressed sufficiently.
[0008] Further, in such steering back turning as described above,
since the turning direction changes over halfway, where roll-over
suppressing control is being carried out, the turning outer wheels
to be controlled change over halfway. However, since response time
is required for changeover of braking force, considerable time is
required until the braking state to the turning outer wheels to be
controlled changes over completely, and consequently, there is the
possibility that the roll-over may not be suppressed sufficiently
also in this regard.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
roll-over suppressing control apparatus for a vehicle which can
suppress roll-over of the vehicle sufficiently also upon steering
back turning wherein the turning direction of the vehicle changes
over halfway.
[0010] In order to attain the object described above, according to
the present invention, there is provided a roll-over suppressing
control apparatus for a vehicle, comprising a braking mechanism
capable of braking left and right wheels of the vehicle separately
from each other, rolling state detection means for detecting a
rolling state of the vehicle, roll-over suppressing control means
for controlling, if it is detected by the rolling state detection
means that, upon turning of the vehicle, the vehicle is in an
excessive rolling state, the braking mechanism so as to apply or
increase braking force to a turning outer wheel to perform
roll-over suppressing control, and decision means for deciding
whether or not all of the left and right wheels of the vehicle
remain in contact with a road during the roll-over suppressing
control, the roll-over suppressing control means performing, when
it is decided by the decision means that all of the left and right
wheels of the vehicle remain in contact with the road, all wheel
braking control of controlling the braking mechanism so as to apply
the braking force to all of the left and right wheels of the
vehicle.
[0011] It is to be noted that the state wherein all of the left and
right wheels of the vehicle remain in contact with a road signifies
a state wherein all of the left and right wheels contact with a
sufficient load with the road.
[0012] Upon steering back turning wherein the turning direction of
a vehicle changes over halfway upon steering back of the steering
wheel as in the case of lane change or S-shaped curve traveling, a
great reactive movement occurs in the rolling direction of the
vehicle, and therefore, only if braking force is applied to turning
outer wheels as described above, there is the possibility that
roll-over may not be suppressed sufficiently. However, with the
roll-over suppressing control apparatus for a vehicle according to
the present invention, while the vehicle is in a four-wheel ground
contacting state (a state wherein the four wheels contact with a
sufficient load with the road) which occurs upon steering back
turning, braking force is applied to the four wheels, and
consequently, the speed of the vehicle is suppressed, which
contributes much to roll-over suppression.
[0013] Further, such a four-wheel ground contacting state as
described above occurs when the turning outer wheels to which
braking force is to be applied change over from one to the other of
the left and right wheels halfway during steering back turning, and
while the four wheels remain in contact with the road, braking
force is applied to all of the four wheels, whereupon a state
transition occurs from a state wherein braking force is applied to
one of the left and right wheels to another state wherein braking
force is applied to the other of the left and right wheels through
an intermediate state wherein braking force is applied to all of
the four wheels. Consequently, changeover of the braking wheels
from one to the other of the left and right wheels can be performed
smoothly. Also in this regard, roll-over can be suppressed
sufficiently.
[0014] Preferably, the decision means decides, where a rolling
angle of the vehicle can be estimated to be substantially zero when
turning of the vehicle during the roll-over suppressing control is
steering back turning wherein the direction of the turning of the
vehicle is changed over halfway, that all of the left and right
wheels of the vehicle remain in contact with the road.
[0015] Preferably, the decision means estimates that, when turning
of the vehicle during the roll-over suppressing control is steering
back turning wherein the direction of the turning of the vehicle is
changed over halfway, if the magnitude of a roll rate of the
vehicle becomes equal to or higher than a predetermined value set
in advance, the rolling angle of the vehicle is approximately zero
and decides that all of the left and right wheels of the vehicle
remain in contact with the road.
[0016] Preferably, the decision means estimates that, when turning
of the vehicle during the roll-over suppressing control is steering
back turning wherein the direction of the turning of the vehicle is
changed over halfway, if the magnitude of a lateral acceleration of
the vehicle becomes lower than a predetermined value around zero
set in advance, the rolling angle of the vehicle is approximately
zero and decides that all of the left and right wheels of the
vehicle remain in contact with the road.
[0017] Preferably, the roll-over suppressing control means ends the
all wheel braking control after the roll-over suppressing control
is carried out for a predetermined period of time set in
advance.
[0018] The above and other objects, features and advantages of the
present invention will become apparent from the following
description and the appended claims, taken in conjunction with the
accompanying drawings in which like parts or elements denoted by
like reference symbols.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a control block diagram of a roll-over suppressing
control apparatus for a vehicle according to an embodiment of the
present invention;
[0020] FIG. 2 is a system diagram of the roll-over suppressing
control apparatus for a vehicle;
[0021] FIGS. 3(a) and 3(b) are schematic views illustrating a
relationship between a turning direction of a vehicle which
includes the roll-over suppressing control apparatus for a vehicle
and braking wheels upon ordinary roll-over suppression control;
[0022] FIGS. 4(a), 4(b), 4(c) and 4(d) are diagrammatic views
illustrating different control starting conditions by different
types of turning by the roll-over suppressing control apparatus for
a vehicle; and
[0023] FIGS. 5 and 6 are flow charts illustrating roll-over
suppressing control by the roll-over suppressing control apparatus
for a vehicle.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] A roll-over suppressing control apparatus for a vehicle
according to an embodiment of the present invention is equipped in
such a braking system for a vehicle as shown in FIG. 2. Referring
to FIG. 2, the braking system for a vehicle includes a brake pedal
1, a master cylinder 2 which operates in an interlocking
relationship with an operation of the brake pedal 1, and a
hydraulic unit 6 for controlling the brake fluid pressure to be
supplied from the master cylinder 2 or a brake fluid reservoir 4 to
wheel cylinders of wheel brakes (hereinafter referred to as brakes)
10 for braking wheels (front left and right wheels and rear left
and right wheels) 5FL, 5FR, 5RL, 5RR in response to the state of
the master cylinder 2 or an instruction from a braking controller
(brake ECU) 3. It is to be noted here that a braking mechanism is
formed from a liquid pressure adjusting system including the master
cylinder 2, hydraulic unit 6 and so forth and the brakes 10 for the
braking wheels and so forth.
[0025] As seen in FIG. 2 (in FIG. 2, only the left and right wheel
brakes for the front wheels are shown), when the vehicle is in a
behavior control mode, a differential pressure regulating valve 68
in the hydraulic unit 6 operates so that a predetermined pressure
difference may appear between the upstream and the downstream of
the differential pressure regulating valve 68.
[0026] When the vehicle is in the behavior control mode and the
brake pedal 1 is not operated, an in-line intake valve 61 is closed
while an out-line intake valve 62 is opened. Consequently, the
brake fluid in the brake fluid reservoir 4 is introduced through an
out-line 64, the out-line intake valve 62 and a pump 65 and is
pressurized by the pump 65, and the pressure of the brake liquid is
adjusted by a liquid pressure holding valve 66 and a pressure
reducing valve 67 and the brake liquid of the adjusted pressure is
supplied to the brakes 10 for the wheels.
[0027] When the vehicle is in the behavior control mode and the
brake pedal 1 is operated, since the in-line intake valve 61 is
opened and the out-line intake valve 62 is closed, the brake fluid
in the master cylinder 2 is introduced through an in-line 63, the
in-line intake valve 61 and the pump 65 and pressurized by the pump
65. Then, the pressure of the brake fluid is adjusted by the liquid
pressure holding valve 66 and the pressure reducing valve 67, and
the brake fluid of the adjusted pressure is supplied to the brakes
10 for the wheels.
[0028] It is to be noted that the in-line 63 and the out-line 64
join together on the downstream of the in-line intake valve 61 and
the out-line intake valve 62, and the pump 65 is disposed on the
downstream of the joining location. The liquid pressure holding
valve 66 and the pressure reducing valve 67 are provided for each
of the braking wheels 5FL, 5FR, 5RL, 5RR on the downstream of the
pump 65.
[0029] Upon normal braking, the in-line intake valve 61 and the
out-line intake valve 62 are closed, and the differential pressure
regulating valve 68 and the liquid pressure holding valve 66 are
opened while the pressure reducing valve 67 is closed.
Consequently, a brake fluid pressure corresponding to the pressure
(that is, braking operation force) in the master cylinder 2 is
supplied to the brake 10 for each of the wheels through the in-line
63, differential pressure regulating valve 68 and liquid pressure
holding valve 66. On the other hand, when an ABS (antilock brake
system or antiskid brake system) operates, a brake fluid pressure
corresponding to the braking operation force is suitably adjusted
through the liquid pressure holding valve 66 and the pressure
reducing valve 67 so that each wheel may not be locked.
[0030] The in-line intake valve 61, out-line intake valve 62, pump
65, liquid pressure holding valves 66, pressure reducing valves 67
and differential pressure regulating valve 68 of the hydraulic unit
6 having such a configuration as described above are controlled by
the brake ECU 3.
[0031] Various signals are inputted to the brake ECU 3. In
particular, a steering wheel angle signal is inputted from a
steering wheel angle sensor 11 provided for a steering wheel, and a
yaw rate signal of the vehicle body is inputted from a yaw rate
sensor 12 provided on the vehicle body. Further, a roll rate signal
of the vehicle body is inputted from a roll rate sensor (rolling
state detection means) 13 provided on the vehicle body, and a brake
pedal operation signal is inputted from a brake switch 16.
Furthermore, a forward-backward acceleration signal and a lateral
acceleration signal are inputted from a forward-backward and
lateral acceleration sensor 17 provided on the vehicle body, and
vehicle speed (wheel speed) signals are inputted from wheel speed
sensors 15.
[0032] The brake ECU 3 includes such various functional elements as
seen in FIG. 1. Referring to FIG. 1, the brake ECU 3 includes a
driver operation state inputting section 31 for receiving various
information relating to an operation state of the driver as an
input thereto, suitably processing the input information and
outputting resulting information, a vehicle motion state inputting
section 32 for receiving various information relating to a motion
state (behavior) of the vehicle, suitably processing the input
information and outputting resulting information, and a roll-over
suppressing control section 33.
[0033] The driver operation state inputting section 31 decides
whether or not the brake pedal is operated from a brake pedal
operation signal from the brake switch 16 and time differentiates a
steering wheel angle based on a steering wheel angle signal from
the-steering wheel angle sensor 11 to calculate a steering wheel
angular velocity (steering angular velocity).
[0034] The vehicle motion state inputting section 32 calculates a
vehicle body speed, a roll rate deviation and a lateral
acceleration. Although the vehicle body speed is normally
calculated based on the wheel speed signals from the wheel speed
sensors 15, if a slip occurs with a wheel, then the vehicle motion
state arithmetic operation section 32 adds a time integrated value
of a forward-backward acceleration obtained from the
forward-backward and lateral acceleration sensor 17 to the vehicle
body speed obtained till then based on the wheel speed signal to
calculate the vehicle body speed (in this instance, the calculated
vehicle body speed is an estimated vehicle body speed).
[0035] The roll-over suppressing control section 33 includes a
turning decision section 34 for deciding a start and an end of
turning of the vehicle, a control decision section 35 for deciding
a start and an end of roll-over suppressing control, a four-wheel
ground contact decision section 36 for deciding whether or not all
of the four wheels remain in contact with the ground upon roll-over
suppressing control, and a control amount setting section 37 for
setting a control amount (roll-over suppressing control braking
force) to each braking wheel upon roll-over suppressing
control.
[0036] The roll-over suppressing control section 33 starts
roll-over suppressing control if it is decided by the control
decision section 35 that roll-over suppressing control should be
started, and ends the roll-over suppressing control if it is
decided by the control decision section 35 that the roll-over
suppressing control should be ended. Upon such roll-over
suppressing control, if all of the four wheels remain in contact
with the road, then the roll-over suppressing control section 33
carries out control (all wheel braking control) of applying braking
force to all of the four wheels, but if all of the four wheels are
not in contact with the road, then the roll-over suppressing
control section 33 carries out control of applying braking force to
turning outer wheels which remain in contact with the road. The
roll-over suppressing control section 33 performs such braking
control as just described with a control amount (braking force) set
by the control amount setting section 37.
[0037] It is to be noted that, in ordinary roll-over suppressing
control, braking force is applied to the front and rear wheels
which are turning outer wheels as seen in FIG. 3(a) or 3 (b). The
magnitude of the braking force applied at this instance is set as a
value commensurate with the magnitude of the roll rate R.sub.r by
the control amount setting section 37. It is to be noted that,
while, in order to suppress rolling, it is effective to suppress
the yaw rate of the vehicle and suppress the vehicle speed, braking
force to the front wheel which is a turning outer wheel contributes
much to suppression of the yaw rate of the vehicle while braking
force to the rear wheel which is a turning outer wheel contributes
much to suppression of the vehicle speed.
[0038] The turning decision section 34 decides that turning of the
vehicle has been started if both of conditions (i) that the vehicle
body speed V.sub.b is equal to or higher than a reference value
(low speed value set in advance) V.sub.1 and that (ii) the
magnitude of the lateral acceleration G.sub.y of the vehicle body
is equal to or higher than a reference value (fixed value set in
advance) G.sub.y1. Further, if any one of two conditions (iii) that
the vehicle body speed V.sub.b is lower than a reference value (low
speed value determined in advance) V.sub.2 (where
V.sub.2<V.sub.1) and (iv) that the magnitude of the lateral
acceleration G.sub.y of the vehicle body is lower than a reference
value (predetermined acceleration set in advance) G.sub.y2 (where
G.sub.y2<G.sub.y1) is satisfied, then the turning decision
section 34 decides that the vehicle has ended the turning.
[0039] The control decision section 35 performs roll-over
suppressing control in response to the detected roll rate R.sub.r
when a predetermined control start condition is satisfied. Here,
the control start condition resides in satisfaction of a condition
that it is decided by the turning decision section 34 that the
vehicle is turning and another condition that the magnitude of the
roll rate R.sub.r which is a value of a parameter corresponding to
a rolling state of the vehicle is equal to or higher than a control
start threshold value R.sub.rs1 set in advance.
[0040] Further, the control decision section 35 ends the roll-over
suppressing control when a predetermined control end condition is
satisfied during the roll-over suppressing control. Here, the
control end condition resides in satisfaction of any one of a
condition that it is decided by the turning decision section 34
that the vehicle is not turning and another condition that the
magnitude of the roll rate R.sub.r is lower than a control end
threshold value R.sub.rs2 set in advance
(R.sub.rs2<R.sub.rs1).
[0041] The four-wheel ground contact decision section 36 decides,
upon steering back turning (for example, upon lane change or upon
S-shaped curve traveling) wherein a steering back operation of the
steering wheel is performed during roll-over suppressing control,
whether or not all of the four wheels remain in contact with the
road under sufficient loads. Here, the four-wheel ground contact
decision section 36 makes the decision based on the roll rate. The
decision of steering back turning can be made depending upon
whether or not the steering wheel angular velocity X has been
reversed (the direction has been reversed).
[0042] Here, a four-wheel ground contact situation is
described.
[0043] In particular, if the steering wheel operation and the
vehicle speed operation are carried out appropriately, then the
magnitude of the roll rate or the magnitude of the roll angle does
not become excessive and does not cause turning over of the vehicle
on its side as seen, for example, in FIG. 4(c) or 4(d). However, if
the steering wheel operation and the vehicle speed operation are
not carried out appropriately, then the magnitude of the roll rate
or the magnitude of the roll angle becomes excessive and sometimes
causes turning over of the vehicle on its side as seen, for
example, in FIG. 4(a) or 4(b).
[0044] For example, in ordinary turning (one-directional turning)
which does not involve a steering back operation of the steering
wheel, the steering wheel angle .alpha. increases in one direction
as indicated by a solid line curve LH1 in FIG. 4(a). At this time,
the roll rate R.sub.r increases suddenly to the turning outer side
as the steering wheel angle a increases (that is, upon turning of
the steering wheel) as indicated by another curve LR1. If the
magnitude of the roll rate R.sub.r exceeds a limit, then the
magnitude of the roll angle increases as indicated by a curve LA1
and may cause turning over of the vehicle on its side as indicated
by a reference character A [refer to FIGS. 4(a) and 4(b)].
[0045] On the other hand, in steering back turning wherein turning
back of the steering wheel is performed (for example, upon lane
change or upon S-shaped curve traveling), the steering wheel angle
a is directed in the reverse direction halfway as indicated by a
curve LH2. At this time, the roll rate R.sub.r increases suddenly
to the outer side of the steering back turning as the steering
wheel angle .alpha. increases in the reverse direction (that is,
upon starting of steering back turning) as indicated by a curve LA2
and sometimes causes turning over of the vehicle on its side as
indicated by a reference character B [refer to FIGS. 4(a) and
4(b)].
[0046] In such steering back turning as described above, since the
turning direction changes halfway, also the turning outer wheels
changeover. For example, if steering back of the steering wheel is
performed to change the turning direction from left turning to
right turning, then upon the left turning in the beginning, the
vehicle weight is biased to the right wheels which are turning
outer wheels, but when the right turning is performed later as a
result of the steering back, the vehicle weight is biased to the
left wheels which now are turning outer wheels. When the bias of
the vehicle weight changes over from the right wheel side to the
left wheel side or reversely from the left wheel side to the right
wheel side, naturally a state wherein the four wheels contact with
a sufficient load with the road (the state is hereinafter referred
to as "four-wheel ground contacting state") occurs halfway during
the changeover.
[0047] The four-wheel ground contact decision section 36 decides
whether or not the wheel is in such a four-wheel ground contacting
state.
[0048] The four-wheel ground contacting state wherein the four
wheels contact with a sufficient load with the road corresponds to
a state wherein the magnitude of the steering wheel angle is small
or a state wherein the magnitude of the rolling angle is small, and
corresponds, if attention is paid to the roll rate, to a state
wherein the magnitude of the roll rate increases to some degree
after the steering back of the steering wheel.
[0049] Therefore, the four-wheel ground contact decision section 36
determines that "the vehicle is in the four-wheel ground contacting
state wherein the four wheels contact with a sufficient load with
the road" when the magnitude of the detected roll rate R.sub.r is
equal to or greater than a four-wheel ground contact decision roll
rate threshold value R.sub.rs3 set in advance. It is to be noted
that, although the four-wheel ground contact decision roll rate
threshold value R.sub.rs3 is generally higher than the control
start threshold value R.sub.rs1 (R.sub.rs1<R.sub.rs3), in order
to hasten the start of four-wheel ground contact control, the
four-wheel ground contact decision roll rate threshold value
R.sub.rs3 and the control start threshold value R.sub.rs1 may be
set otherwise so as to satisfy R.sub.rs3<R.sub.rs1.
[0050] Upon roll-over suppressing control, the control amount
setting section 37 normally sets, that is, unless it is decided by
the four-wheel ground contact decision section 36 that the vehicle
is in a four-wheel ground contacting state, the control amount
setting section 37 sets the control amount (roll-over suppressing
control braking force) to each of turning outer wheels in response
to the roll rate and so forth so that braking force may be applied
to the turning outer wheels. On the other hand, if it is decided by
the four-wheel ground contact decision section 36 that the vehicle
is in the four-wheel ground contacting state, then the control
amount setting section 37 sets the control amount (roll-over
suppressing control braking force) to each of the four wheels in
response to the roll rate and so forth so that braking force may be
applied to all of the four wheels. Naturally, the control amount
need not necessarily correspond to the roll rate but may be a
predetermined value set in advance. Further, the state wherein
braking force is applied to all of the four wheels continues only
for a predetermined period of time (very short time period) set in
advance, and thereafter, until the roll-over suppressing control in
the current control cycle comes to an end, the decision of the
four-wheel ground contact decision section 36 is not performed and
ordinary roll-over suppressing control, that is, control of
applying braking force to turning outer wheels, is carried out.
[0051] Since the roll-over suppressing control apparatus for a
vehicle according to the embodiment of the present invention is
configured in such a manner as described above, it carries out its
control, for example, in such a manner as illustrated in FIGS. 5
and 6.
[0052] Referring first to FIG. 5, a parameter necessary to start or
end roll-over suppressing control is inputted at step A5. Then at
step A10, it is decided based on a flag F1 whether or not roll-over
suppressing control is being carried out. The flag F1 used for the
decision is a flag (roll-over suppressing control carrying out
flag) indicative of whether or not roll-over suppressing control is
being carried out and initially has a value set to zero. Here, if
F1=0, then since roll-over suppressing control is not being carried
out, the processing advances to step A20, at which a starting
condition of roll-over suppressing control is decided. On the other
hand, if F1=1, then since roll-over suppressing control has been
started already, the processing advances to step A50, at which an
ending condition of the roll-over suppressing control is
decided.
[0053] At step A20, it is decided from the decision condition
described above based on the parameter inputted at step A5 whether
or not the starting condition of roll-over suppressing control is
satisfied. If this condition is satisfied, then the processing
advances to A30, at which the flag F1 is set to 1 (on). Then at
step A40, roll-over suppressing control is started, and then the
flow is ended. However, if the condition is not satisfied, then the
flow is ended without changing the flags and the control.
[0054] On the other hand, if the decision at step A10 is F1=1, then
it is decided at step A50 from the decision condition described
above based on the parameter inputted at step A5 whether or not the
ending condition of the roll-over suppressing control is satisfied.
If this condition is satisfied, then the processing advances to
step A60, at which the flag F1 is set to 0. Then at step A70, the
roll-over suppressing control is ended, and the flow is ended
thereby. However, if the condition described above is not
satisfied, then the flow is ended without changing the flags and
the control.
[0055] The roll-over suppressing control is illustrated in FIG. 6.
Referring to FIG. 6, first at step B10, a parameter necessary to
decide a start or an end of roll-over suppressing control is
inputted. Then at next step B20, it is decided whether or not the
roll-over suppressing control carrying out flag F1 is 1. If the
flag F1 is 1, then the processing advances to step B30, at which it
is decided whether or not another flag F2 is 1.
[0056] The flag F2 used for the decision is a flag (four-wheel
ground contact control carrying out flag) indicative of whether or
not four-wheel ground contacting control, that is, braking force
application control to the four wheels for roll-over suppression,
is being carried out and whether or not the four-wheel ground
contacting control has been carried out already. The flag F2
initially has a value 0 set thereto, but when four-wheel ground
contacting control is carried out, the flag F2 is set to a value of
1, and if four-wheel ground contacting control is carried out once
and then completed while the roll-over suppressing control is
continuing, then the flag F2 is set to another value of 2.
[0057] If the flag F2 is not 1 at step B30, then the processing
advances to step B40, at which it is decided whether or not the
current turning is lane change (steering back turning) depending,
for example, upon whether or not the steering wheel angular
velocity X has been reversed (whether or not the direction has been
reversed).
[0058] Here, if the current turning is not lane change (steering
back turning), then the processing advances to step B120, at which
a control amount (braking force to be applied) for ordinary
roll-over suppressing control, that is, for control for applying
braking force to turning outer wheels, is set in response to the
roll rate, and braking control is carried out based on the control
amount (step B130).
[0059] If it is decided at step B40 that the current turning is
lane change (steering back turning), then the processing advances
to step B45, at which it is decided whether or not the flag F2 is
0. If it is decided at step B45 that the flag F2 is not 0, then the
processing successively advances to B120 and to step B130 so that
ordinary roll-over suppressing control is carried out similarly as
described above. If it is decided at step B45 that the flag F2 is
0, then the processing advances to step B50, at which it is decided
whether or not the vehicle is in a four-wheel ground contacting
state. In this decision, if the roll rate R.sub.r detected is equal
to or higher than the four-wheel ground contact decision roll rate
threshold value R.sub.rs3 set in advance, then it is determined
that "the vehicle is in the four-wheel ground contacting state
wherein the four wheels contact with a sufficient load with the
road".
[0060] If it is decided at step B50 that the vehicle is not in a
four-wheel ground contacting state, then the processing
successively advances to step B120 and to B130 so that ordinary
roll-over suppressing control is carried out similarly as described
above.
[0061] On the other hand, if it is decided at step B50 that the
vehicle is in a four-wheel ground contacting state, then the
processing advances to step B60, at which the flag F2 is set to 1,
and then to step B70, at which counting of a timer is started. Then
at step B80, it is decided whether or not the thus counted timer
value is lower than a predetermined value set in advance.
[0062] If the timer value is lower than the predetermined value,
then the processing advances to step B90, at which a control amount
(braking force to be applied) is set in response to the roll rate
in order to apply braking force to the four wheels in conformity
with the four-wheel ground contacting state and braking control is
carried out based on the control amount (step B130).
[0063] If the timer value is equal to or higher than the
predetermined value, then the processing advances from step B80 to
step B100, at which the flag F2 is set to 2, and then to step B110,
at which the counting of the timer is stopped and the timer is
reset to 0. Then, the processing successively advances to step B120
and to step B130 so that ordinary roll-over suppressing control is
carried out similarly as described above.
[0064] It is to be noted that, when the roll-over control is ended
(when the flag F1 is set to 0), also the flag F2 is reset to 0
(step B140).
[0065] In this manner, when lane change (steering back turning) is
carried out during roll-over suppressing control or when roll-over
suppressing control is carried out as a result of lane change
(steering back turning), the four-wheel ground contacting state
wherein the four wheels contact with a sufficient load with the
road occurs halfway. Thus, this four-wheel ground contacting state
is detected, and thereafter, braking force is applied to the four
wheels to reduce the vehicle speed to suppress occurrence of
rolling for a predetermined period of time. Thereafter, at or
around a timing at which the wheels to which the vehicle weight is
applied are biased to the turning outer wheel side, if the
roll-over suppressing control is required further, then normal
control wherein braking force is applied only to the turning outer
wheels is restored.
[0066] Accordingly, while the road ground contacting load is taken
into consideration, roll-over can be suppressed by suppressing the
vehicle speed sufficiently through four-wheel braking when the four
wheels remain in contact with the road with a sufficient load.
However, when only the turning outer wheels contact with a
sufficient load with the road, suppression of the yaw moment and
suppression of the vehicle speed can be performed efficiently to
suppress roll-over by applying braking force only to the turning
outer wheels.
[0067] Further, since the four-wheel ground contacting state occurs
when the turning outer wheels to which braking force is to be
applied halfway of steering back turning change over from one to
the other of the left and right wheels, by applying braking force
to all of the four wheels while the four wheels remain in contact
with the road, the state transition occurs from a state wherein
braking force is applied to one of the left and right wheels to
another state wherein braking force is applied to the other of the
left and right wheels through an intermediate state wherein braking
force is applied to all of the four wheels. Consequently,
changeover of the braking wheels from one to the other of the left
and right wheels can be performed smoothly. Also in this regard,
roll-over can be suppressed sufficiently.
[0068] While a predetermined embodiment of the present invention is
described above, the present invention is not limited to the
embodiment specifically described above, and variations and
modifications can be made without departing from the scope of the
present invention.
[0069] For example, while, in the embodiment described above, the
four-wheel ground contact decision is performed based on the roll
rate upon steering back turning, the four-wheel ground contact
decision is not limited to this but may be performed based on, for
example, the lateral acceleration or the rolling angle of the
vehicle. In short, since the four-wheel ground contacting state is
established when the lateral acceleration or the rolling angle is
small, if the lateral acceleration or the rolling angle is smaller
than a threshold value set in advance, then it may be decided that
the vehicle is in the four-wheel ground contacting state.
[0070] Further, while, in the embodiment described above,
four-wheel ground contacting control wherein braking force is
applied to all of the four wheels is carried out for a
predetermined period of time set in advance after the four-wheel
ground contact decision is made, alternatively such logic may be
employed that four-wheel ground contacting control wherein braking
force is applied to all of the four wheels is started after the
four-wheel ground contact decision is made and, when a state
wherein the four-wheel ground contacting state is lost, that is, a
state wherein the vehicle weight is applied principally to turning
outer wheels, is entered thereafter, the four-wheel ground
contacting control is ended. In this instance, whether or not the
state wherein the vehicle weight is applied principally to turning
outer wheels is entered may be decided based on such a parameter as
the roll rate, lateral acceleration or rolling angle.
* * * * *