U.S. patent application number 10/926394 was filed with the patent office on 2005-04-14 for suspension control system and suspension control method for vehicle.
Invention is credited to Ogawa, Fumiharu.
Application Number | 20050077692 10/926394 |
Document ID | / |
Family ID | 34419060 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050077692 |
Kind Code |
A1 |
Ogawa, Fumiharu |
April 14, 2005 |
Suspension control system and suspension control method for
vehicle
Abstract
A suspension control system and a suspension control method for
a vehicle control the suspension based on the condition of the road
surface traveled by the vehicle in addition to information
pertaining to a corner obtained from a navigation device when the
vehicle approaches the corner. A microprocessor controls damping
forces of suspension devices on the basis of a degree of
irregularity of the road surface detected immediately preceding
entry of the automobile into a turn around the corner, and corner
information from the navigation device.
Inventors: |
Ogawa, Fumiharu;
(Okazaki-shi, JP) |
Correspondence
Address: |
LORUSSO, LOUD & KELLY
3137 Mount Vernon Avenue
Alexandria
VA
22305
US
|
Family ID: |
34419060 |
Appl. No.: |
10/926394 |
Filed: |
August 26, 2004 |
Current U.S.
Class: |
280/5.517 |
Current CPC
Class: |
B60G 2400/102 20130101;
B60G 2401/16 20130101; B60G 2800/916 20130101; B60G 2600/184
20130101; B60G 2400/41 20130101; B60G 2800/162 20130101; B60G
2400/824 20130101; B60G 2500/10 20130101; B60G 2400/821 20130101;
B60G 17/08 20130101 |
Class at
Publication: |
280/005.517 |
International
Class: |
B60G 017/01 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2003 |
JP |
2003-336127 |
Claims
What is claimed is:
1. A suspension control system for a vehicle equipped with a
navigational device, said suspension control system comprising: a
plurality of suspension devices, each mounted between a suspension
arm and a body portion of the vehicle, in association with a wheel
of the vehicle, each of said suspension devices expanding and
contracting in accordance with a damping force to damp forces on
the vehicle received from a road surface traveled by the vehicle;
irregularity detecting means for detecting a degree of irregularity
of the road surface; vehicle speed detecting means for detecting
vehicle speed; calculating means for calculating an adjustment
value corresponding to the damping force on the basis of the
detected vehicle speed, the detected degree of irregularity and
information relative to a corner in the road surface received from
the navigation device when the vehicle approaches the corner; and
output means for outputting the adjustment value to a suspension
device so as to control the damping force of the suspension
device.
2. The suspension control system for a vehicle according to claim
1, wherein the suspension control system further comprises: turn
detecting means for detecting turning of the vehicle; and entry
judging means for judging whether or not the vehicle has entered
into a turn around corner on the basis of the turning of the
vehicle detected by said turning detecting means; and wherein said
output means outputs said adjustment value to the suspension
devices so as to control the damping forces in accordance with the
adjustment value responsive to a judgment by said entry judging
means that the vehicle has entered into the turn around the
corner.
3. The suspension control system for a vehicle according to claim
2, wherein said calculating means extracts an irregularity
component corresponding to a predetermined frequency from the
degree of irregularity detected by said irregularity detecting
means, and calculates the adjustment value corresponding to the
damping force of said suspension means on the basis of the
irregularity component.
4. The suspension control system for a vehicle according to claim
2, wherein said calculating means stops the calculation of the
adjustment value in accordance with a judgment by said entry
judging means that the vehicle has entered into a turn around said
corner, and wherein the adjustment value last calculated before
stopping the calculation is used to control the damping force of
said suspension devices in travel of the vehicle around the
corner.
5. The suspension control system for a vehicle according to claim
1, wherein said calculating means extracts an irregularity
component corresponding to a predetermined frequency from the
degree of irregularity detected by said irregularity detecting
means, and calculates the adjustment value corresponding to the
damping force of said suspension means on the basis of the
irregularity component.
6. A suspension control system for a vehicle equipped with a
navigational device, said suspension control system comprising: a
plurality of suspension devices, each mounted between a suspension
arm and a body portion of the vehicle, in association with a wheel
of the vehicle, each of said suspension devices expanding and
contracting in accordance with a damping force to damp forces on
the vehicle received from a road surface traveled by the vehicle;
slip state detecting means for detecting a slip state of the road
surface; vehicle speed detecting means for detecting vehicle speed;
calculating means for calculating an adjustment value corresponding
to the damping force on the basis of said detected vehicle speed,
said detected slip state and information relative to a corner in
the road surface received from the navigation device when the
vehicle approaches the corner; and output means for outputting the
adjustment value to a suspension device so as to control the
damping force of the suspension device.
7. The suspension control system for a vehicle according to claim
6, wherein the suspension control system further comprises: entry
judging means for judging whether or not the vehicle has entered
into a turn around corner on the basis of the turning of the
vehicle detected by said turning detecting means; and wherein said
output means outputs said adjustment value to the suspension
devices so as to control the damping forces in accordance with the
adjustment value, responsive to a judgment by said entry judging
means that the vehicle has entered into the turn around the
corner.
8. The suspension control system for a vehicle according to claim
6, wherein said calculating means stops the calculation of the
adjustment value in accordance with a judgment by said entry
judging means that the vehicle has entered into a turn around said
corner, and wherein the adjustment value last calculated before the
stopping the calculation is used to control the damping force of
said suspension devices in travel of the vehicle around the
corner.
9. A suspension control method for cornering of a vehicle equipped
with a navigation device and with wheel suspension devices, said
suspension control method comprising: detecting present position of
the vehicle; detecting approach of the vehicle to a corner;
detecting road surface condition at the detected present position;
obtaining information for the corner from the navigation device;
calculating an adjustment value corresponding to damping force of
the suspension devices on the basis of both the detected road
surface condition and the information for the corner obtained from
the navigation device; and controlling the damping force of the
suspension devices in accordance with the calculated adjustment
value.
10. A suspension control method for cornering of a vehicle equipped
with a navigation device and with wheel suspension devices, said
suspension control method comprising: detecting present position of
the vehicle; detecting approach of the vehicle to a corner;
obtaining information for the corner from the navigation device;
detecting a degree of irregularity of the road surface at the
detected present position of the vehicle; calculating an adjustment
value corresponding to damping force of the suspension devices on
the basis of the detected vehicle speed, the detected degree of
irregularity of the road surface, and the information for the
corner obtained from the navigation device; and controlling the
damping force of the suspension devices in accordance with the
calculated adjustment value.
11. A suspension control method for cornering of a vehicle equipped
with a navigation device and with wheel suspension devices, said
suspension control method comprising: detecting present position of
the vehicle; detecting approach of the vehicle to a corner;
obtaining information for the corner from the navigation device;
detecting a slip state of the road surface at the detected present
position of the vehicle; calculating an adjustment value
corresponding to damping force of the suspension devices on the
basis of the detected vehicle speed, the detected slip state of the
road surface, and the information for said corner obtained from the
navigation device; and controlling the damping force of the
suspension devices in accordance with the calculated adjustment
value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims, under 35 USC 119, priority of
Japanese Patent Application No.2003-336127 filed on Sep. 26, 2003,
the teachings of which are incorporated by reference herein, in
their entirety, including the specification, drawings and abstract.
Copending application U.S. Ser. No. 10/______ (Attorney Docket No.
AW-C462) in the name of Fumiharu OGAWA as inventor, entitled
"VEHICLE SUSPENSION CONTROL SYSTEM AND SUSPENSION CONTROL METHOD"
and filed on even date herewith discloses and claims related
subject matter.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a suspension control system
and to a suspension control method for a vehicle.
[0004] 2. Description of the Related Art
[0005] JP-A-9-114367 discloses a suspension control system in which
the suspension is adjusted in advance, for example, just before the
vehicle starts to turn a corner in traveling a predetermined route,
on the basis of the speed of the vehicle and corner information
obtained from a navigation device within the vehicle.
[0006] However, in the suspension control system of JP-A-9-114367,
the corner information obtained from the navigation device includes
no information relative to the state of the road surface at the
corner. Accordingly, for example, when the road surface at the
corner is irregular and/or slippery, steering during travel of the
vehicle around the corner may become unstable and the driver may
feel riding discomfort (an unpleasant sensation).
SUMMARY OF THE INVENTION
[0007] Therefore, in order to overcome the above problem, an object
of the present invention is to provide a suspension control system
and a suspension control method for a vehicle in which the
operation of a suspension means in running the vehicle is
controlled by also taking into consideration the state of the road
surface traveled by the vehicle, in addition to the information
relative to the corner from the navigation device when the vehicle
approaches the corner.
[0008] In order to achieve the above objective, in a first aspect,
the present invention provides a suspension control system which
includes:
[0009] suspension means (S1 to S4) interposed and mounted between a
suspension arm (R1, R2) and the body (B) of the vehicle mounting a
navigation device (N), and operated in accordance with a controlled
damping force;
[0010] irregular state detecting means (41a to 41d) for detecting
the degree of irregularity of a road surface on which the vehicle
is running;
[0011] vehicle speed detecting means (30b) for detecting the
running speed of the vehicle as a vehicle speed;
[0012] calculating means (132, 133 to 137, 141, 142, 144, 145) for
calculating an adjustment value corresponding to the damping force
of the suspension means on the basis of the detected vehicle speed
(V), the detected degree of irregularity and information relative
to a corner (T) from the navigation device, when the vehicle
approaches the corner (T) during travel; and
[0013] output means (150, 60a to 60d) for outputting the above
adjustment value to the suspension means so as to control the
damping force of the suspension means in accordance with the
calculated adjustment value.
[0014] Thus, when the vehicle approaches the corner, an adjustment
value corresponding to a desirable damping force of the suspension
means is calculated on the basis of the detected vehicle speed, the
detected irregularity and the information relative to the corner
from the navigation device. The adjustment value is output to the
suspension means so as to control the damping force of the
suspension means by the adjustment value.
[0015] Accordingly, a good ride sensation (riding comfort of the
passengers) and good steering stability during the running of the
vehicle can be maintained even when there are irregularities in the
road surface approaching and/or in the corner.
[0016] In accordance with a second aspect of the invention, the
suspension control system may further include:
[0017] turning detecting means (42) for detecting turning of the
vehicle; and
[0018] entry judging means (146) for judging whether or not the
vehicle has entered into a turn around the corner, on the basis of
the detected turning of the vehicle; and
[0019] wherein the output means outputs the above adjustment value
to the suspension means so as to control its damping force in
accordance with the adjustment value from the calculating means and
in accordance with the judgment of the entry judging means.
[0020] In accordance with a third aspect of the present invention,
the calculating means preferably extracts an irregularity component
corresponding to a predetermined frequency from the degree of
irregularity detected by the irregular state detecting means, and
calculates the adjustment value corresponding to the damping force
of the suspension means on the basis of the irregularity component
extracted in this way. The operating advantages of the invention
previously described can be further improved by calculating the
adjustment value in this manner.
[0021] In accordance with a fourth aspect of the invention, the
calculating means stops the calculation of the adjustment value
responsive to a determination by the entry judging means that the
vehicle has started the turn around the corner, and the calculating
means reports the adjustment value at this point in time (start of
turn) as the adjustment value for the damping force of the
suspension means to be used for turning the corner.
[0022] In accordance with a fifth aspect of the invention, the
suspension control system for a vehicle in the present invention
comprises:
[0023] suspension means (S1 to S4) interposed and mounted between a
suspension arm (R1, R2) and the body (B) of the vehicle mounting a
navigation device (N), and operated in accordance with a controlled
damping force;
[0024] slip state detecting means (43a, 43b) for detecting the slip
state of a road surface at the present location (position) of the
vehicle;
[0025] vehicle speed detecting means (30b) for detecting the
running speed of the vehicle as a vehicle speed;
[0026] calculating means (132a, 133a to 137a, 141, 142, 144, 145a)
for calculating an adjustment value (amount) corresponding to a
preferred level of damping force of the suspension means on the
basis of the detected vehicle speed (V), the detected slip state
and information relative to a corner (T) from the navigation
device, when the vehicle approaches the corner (T) during travel;
and
[0027] output means (150, 60a to 60d) for outputting the adjustment
value to the suspension means so as to control the damping force of
the suspension means in accordance with the calculated adjustment
value.
[0028] Thus, when the vehicle approaches a corner during travel,
the adjustment value corresponding to the damping force of the
suspension means is calculated on the basis of the detected vehicle
speed, the detected slip state and the information relative to the
corner from the navigation device. The above adjustment value is
output to the suspension means so as to control the damping force
of the suspension means in accordance with the calculated
adjustment value.
[0029] Accordingly, riding comfort and stability during travel can
be maintained in a preferred manner even when the road surface
state approaching the corner and the road surface within the corner
are slippery.
[0030] Further, in accordance with a sixth aspect of the invention,
the suspension control system of the fifth aspect further
comprises:
[0031] turning detecting means (42) for detecting turning of the
vehicle;
[0032] entry judging means (146) for determining whether or not the
vehicle has entered into the turn around the corner on the basis of
the determination made by the turning detecting means; and
[0033] wherein the output means outputs the adjustment value to the
suspension means so as to control the damping force of the
suspension means in accordance with adjustment value and in
accordance with the determination of the entry judging means that
the vehicle has entered into the turn around the corner.
[0034] Further, in accordance with another aspect of the invention,
the calculating means determines a predetermined slip state based
on the slip state detected by the slip state detecting means, and
calculates the adjustment value corresponding to the damping force
of the suspension means on the basis of the slip state.
[0035] In another embodiment, the calculating means calculates an
adjustment value corresponding to damping force of the suspension
means on the basis of both the state of the road surface detected
for the present position of the vehicle and information relative to
the corner which is output from the navigation device, and the
damping force of the suspension means during travel of the vehicle
is controlled in accordance with this calculated adjustment
value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a block diagram of a first embodiment of a
suspension control system for an automobile in accordance with the
present invention.
[0037] FIG. 2 is a schematic view showing arrangement of suspension
devices in the automobile.
[0038] FIG. 3 is an enlarged side view of one suspension device of
FIG. 2.
[0039] FIG. 4 is a schematic view of a circuit of the suspension
device.
[0040] FIG. 5 is a flow chart of a navigation control program
executed by a computer of the navigation device of FIG. 1.
[0041] FIG. 6 is a detailed flow chart of the basic navigation
routine (step 100 in FIG. 5).
[0042] FIG. 7 is a flow chart of the running environment
recognition routine (step 110 in FIG. 5).
[0043] FIG. 8 is a flow chart of a suspension control program
executed by the microprocessor of the electronic controller in FIG.
1.
[0044] FIG. 9 is a flowchart of the degree of irregularity setting
routine (step 130 in FIG. 8).
[0045] FIG. 10 is a flow chart of the damping level determination
routine (step 140 in FIG. 8).
[0046] FIG. 11 is a schematic view of a road including a curve
starting point.
[0047] FIG. 12 is a graph of the relationship between damping level
Cn and an estimated transverse acceleration G, as shown by a degree
of irregularity P=Hi in the first embodiment.
[0048] FIG. 13 is a graph of the damping level Cn versus the
estimated transverse acceleration G, as shown by a degree of
irregularity P=Mi in the first embodiment.
[0049] FIG. 14 is a graph of the damping level Cn versus the
estimated transverse acceleration G, as shown by a degree of
irregularity P=Lo in the first embodiment.
[0050] FIG. 15 is a graph showing the relationship between the
diaphragm aperture .beta. of an electromagnetic diaphragm valve and
the damping level Cn.
[0051] FIG. 16 is a block diagram of a second embodiment of the
present invention.
[0052] FIG. 17 is a flow chart of a suspension control program
executed by a microprocessor of the electronic controller in FIG.
16.
[0053] FIG. 18 is a flow chart of the degree of slip setting
routine (step 130a in FIG. 17).
[0054] FIG. 19 is a flow chart of the damping level determination
routine (step 140a in FIG. 17).
[0055] FIG. 20 is a graph showing the relationship between the
damping level Cn and the estimated transverse acceleration G for a
degree of slip SP=Hi in the second embodiment.
[0056] FIG. 21 is a graph of the damping level Cn versus the
estimated transverse acceleration G for a degree of slip SP=Mi in
the second embodiment.
[0057] FIG. 22 is a graph of the damping level Cn versus the
estimated transverse acceleration G for a degree of slip SP=Lo in
the second embodiment.
[0058] FIG. 23 is a graph of detected acceleration G versus time,
showing frequency f and the acceleration component G'.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Preferred embodiments of the present invention will next be
explained with reference to the drawings.
First Embodiment
[0060] FIG. 1 shows a first embodiment of a suspension control
system of the present invention, designed for a sedan type
automobile and including suspension devices S1 to S4 and an
electronic controller E.
[0061] As shown in FIG. 2, the suspension device S1 is interposed
and mounted between a wheel support element R1 supporting the
right-hand side front wheel of the automobile, and the right-hand
side front portion of the vehicle frame B.
[0062] As shown in FIG. 3, this suspension device S1 has a damper
10 and a coil spring 20. The lower end portion of damper 10 is
supported on the wheel support element. The wheel support element,
to which the lower end of the shock absorber attaches, may be
different for front and rear wheels and for different vehicles,
e.g., axle housing, lower suspension arm, steering knuckle, bearing
housing or motor housing. The coil spring 20 is coaxially mounted
on the damper 10, external thereto, between a flange 10a arranged
in an axially intermediate location on the damper 10 and the
vehicle frame B. Thus, the coil spring 20 biases upward the front
right-hand side of the vehicle frame B.
[0063] The construction and function of the damper 10 is
illustrated by the equivalent circuit shown in FIG. 4 which shows
the damper 10 as including a piston 11 and a hydraulic cylinder 12.
The piston 11 is slidably fitted and mounted within the cylinder
12, and partitions the interior of the cylinder 12 into upper and
lower hydraulic compartments 12a, 12b.
[0064] Further, the damper 10 has an electromagnetic diaphragm
valve 13 which provides communication between hydraulic
compartments 12a and 12b through its diaphragm aperture. A piston
rod 14 extends from the piston 11 through the hydraulic compartment
12a and its upper end is connected to the vehicle body B at the
right-hand side front wheel corresponding part.
[0065] As the piston 11 slides upward within the damper 10,
operating oil within the hydraulic compartment 12a flows into the
hydraulic compartment 12b through the electromagnetic diaphragm
valve 13. Likewise, as the piston 11 slides downward, the operating
oil within the hydraulic compartment 12b flows into the hydraulic
compartment 12a through the electromagnetic diaphragm valve 13. In
this embodiment, the electromagnetic diaphragm valve 13 adjusts the
amount of flow of the operating oil between the hydraulic
compartments 12a and 12b, in accordance with its diaphragm aperture
which is reduced (or increased) in accordance with an increase (or
decrease) corresponding to the damping force of the damper 10,
i.e., the damping force of the suspension device S1.
[0066] Likewise, the suspension device S2 is interposed and mounted
between a wheel support element R2, arranged near the right-hand
side rear wheel of the automobile, and the corresponding part
(hereinafter also called the right-hand side rear wheel
corresponding part) of the vehicle frame B. The suspension device
S3 (see FIG. 1) is interposed and mounted between an unillustrated
wheel support element, supporting the left-hand side front wheel of
the automobile and the corresponding part of the vehicle frame B.
Further, the suspension device S4 (see FIG. 1) is interposed and
mounted between an unillustrated wheel support element supporting
the left-hand side rear wheel of the automobile and the
corresponding part of the vehicle frame B.
[0067] Similar to the suspension device S1, each of these
suspension devices S2 to S4 has a damper 10 and coil spring 20 and
each functions in a manner similar to suspension device S1.
[0068] The front wheels of the automobile serve as the drive
wheels.
[0069] The electronic controller E will next be explained in
relation to navigation device N with reference to FIG. 1. The
navigation device N includes a GPS sensor 30a, a vehicle speed
sensor 30b and a gyro sensor 30c. The GPS sensor 30a detects the
present position of the automobile on the basis of respective radio
signals from plural geostationary satellites. The vehicle speed
sensor 30b detects the running speed of the automobile as a vehicle
speed. The gyro sensor 30c detects an angle of rotation of the
automobile around a vertical axis passing through the center of
gravity of the automobile.
[0070] Further, the navigation device N has an input device 30d, a
memory device 30e, a computer 30f and an output device 30g. The
input device 30d is used to input necessary information to the
computer 30f. A series of map data is stored to the memory device
30e as a database so as to be read by the computer 30f.
[0071] The computer 30f executes a navigation control program in
accordance with the flow charts shown in FIGS. 5 to 7. The computer
30f executes routines required for guidance of the automobile
(navigation control program) on the basis of the input from the
input device 30d, the data stored in the memory device 30e and each
of the outputs of the GPS sensor 30a and the vehicle speed sensor
30b. The output device 30g displays data required as information in
the automobile, under control of the computer 30f.
[0072] As shown in FIG. 1, the electronic controller E has
respective acceleration sensors 41a to 41d, a steering sensor 42, a
microprocessor 50 and respective driving circuits 60a to 60d.
[0073] Each of the acceleration sensors 41a to 41d is arranged in
the vehicle body B adjacent respective suspension devices S1 to S4.
Each of these acceleration sensors 41a to 41d detects vertical
acceleration of the automobile. The steering sensor 42 detects a
steering angle relative to a neutral position of the steering wheel
of the automobile.
[0074] The microprocessor 50 executes a suspension control program
in accordance with the respective flow charts shown in FIGS. 8 to
10 to adjust the damping force of each of the suspension devices S1
to S4 on the basis of the output of the computer 30f of the
navigation device N, and the outputs of the vehicle speed sensor
30b, the gyro sensor 41e, the respective acceleration sensors 41a
to 41d and the steering sensor 42.
[0075] The respective driving circuits 60a to 60d operate the
electromagnetic diaphragm valves 13 of the respective suspension
devices S1 to S4 under control of the microprocessor 50.
[0076] In this first embodiment, when the computer 30f of the
navigation device N starts the execution of the navigation control
program in accordance with the flow chart of FIG. 5, basic guidance
is provided by the navigation device N by execution of a basic
navigation routine 100 (see FIG. 6).
[0077] First, if request for display of a map is made by operation
of the input device 30d, the judgement is YES in step 101 of FIG.
6. Next, in step 102, map data for the requested map is read from
the memory device 30e. Thereafter, in step 103, a routine for
display of the requested map is executed, whereby the output device
30g displays the requested map on the basis of the road map
data.
[0078] Next, a route search is executed in step 104 on the basis of
the outputs of the GPS sensor 30a and the gyro sensor 41e and an
input destination (input using the input device 30d). In step 105,
route guidance is provided on the basis of the results of the route
search. In accordance with this guidance processing, the automobile
driver is assisted in following the route determined by the route
search.
[0079] When the execution of the basic navigation routine 100 is
completed, a travel environment recognition routine 110 (see FIGS.
5 and 7) is executed as follows. First, as shown in FIG. 11, it is
assumed that plural nodes N show a starting point K of a curve
around a corner T, as a transition from a road extending in a
straight line in the direction of advance of the automobile. The
nodes N, included in the read map data, serve as positions for
calculating a radius of curvature Ra for the corner T.
[0080] The curve starting point K is judged as follows in step 111
of FIG. 7. First, as shown in FIG. 11, the angle formed by straight
lines Ya and Yb is calculated as a turning angle .theta. at each of
the nodes N in advance of the automobile. Here, the straight line
Ya is a straight line passing through a pair of nodes adjacent to
and preceding and following a point a predetermined distance La
backward from an object node K. Further, the straight line Yb is a
straight line passing through nodes adjacent to and preceding and
following a position a predetermined distance Lb forward from the
object node K.
[0081] When the turning angle .theta. is calculated for every node
N as mentioned above, the first node for which the calculated
turning angle .theta. is greater than a predetermined angle is
judged to be the curve starting point K.
[0082] Next, in step 112, the radius of curvature Ra of the corner
T is calculated for every node N as the radius of a circle passing
through nodes at three points in total, including nodes at two
points located before and after a node N at the corner T. Here, a
minimum value among the radii of curvature calculated in this way
is set as radius of curvature Ra of the corner.
[0083] When step 112 is completed, a running environment
information transmission routine is executed (step 120 in FIG. 5).
In this routine, information relative to the curve starting point K
determined in the running environment recognition routine 110 and
the radius of curvature Ra of the corner T are output to the
electronic controller E.
[0084] In execution of the degree of irregularity setting routine
130 (see FIG. 9) by the microprocessor 50 of the electronic
controller E, in the first routine in the suspension control
program shown in FIG. 8, an acceleration signal from each of the
acceleration sensors 41a to 41d is input to the microprocessor 50
in a step 131.
[0085] The filter processing routine 132 involves sampling of the
acceleration signal of each of the acceleration sensors 41a to 41d
input in the step 131, and extraction of an acceleration component
G' at a predetermined frequency and its averaging, which are
performed as follows.
[0086] Namely, in the sampling, the acceleration signal G of each
of the acceleration sensors 41a to 41d is sequentially sampled with
the passage of time, e.g., every tenth acceleration signal from
each of the acceleration sensors 41a-41d as shown in FIG. 23. On
the basis of the data sampled in this way, the acceleration
component G' corresponding to a predetermined frequency within the
range of 10 (Hz) to 20 (Hz) is sequentially extracted from the
sampling data for each of the acceleration sensors 41a-41d. All the
acceleration components extracted in this way are then averaged to
obtain an average acceleration component as the arithmetic
mean.
[0087] In this embodiment, the above acceleration component
determined at a frequency within the range of 10 (Hz) to 20 (Hz)
because such a frequency corresponds to irregularity of a road
surface which is irregular approximately to the extent of that
creating discomfort for a passenger. The averaged acceleration
component is a component common to the respective suspension
devices S1 to S4 of the automobile.
[0088] Next, it is judged in step 133 whether or not the above
averaged acceleration component is equal to or greater than a first
predetermined acceleration. Here, this first predetermined
acceleration corresponds to that from a road surface having a worst
case irregularity. In this embodiment, the first predetermined
acceleration is set to, e.g., 2.0 G.
[0089] When the averaged acceleration component is greater than the
first predetermined acceleration, the judgement in step 133 is YES
and the degree of irregularity P=Hi is set in step 134. Here, the
degree of irregularity P represents the degree of irregularity of
the road surface traveled by the automobile, and a degree of
irregularity P=Hi indicates that the road surface traveled by the
automobile is a worst case degree of irregularity.
[0090] When the judgment in step 133 is NO, it is then determined
in step 135 whether or not the averaged acceleration component is
equal to or greater than a second predetermined acceleration. Here,
this second predetermined acceleration corresponds to a state less
irregular than the worst case irregularity corresponding to the
first predetermined acceleration, and is set to e.g., 1.0 G in this
embodiment.
[0091] When the averaged acceleration component is equal to or
greater than the second predetermined acceleration, the judgement
in step 135 is YES. Next, a degree of irregularity P=Mi is set in
step 136. Here, degree of irregularity P=Mi indicates that the
degree of irregularity of the road surface traveled by the
automobile is a degree gentler than the worst case degree of
irregularity corresponding to P=Hi.
[0092] When the judgment in step 135 is NO, a degree of
irregularity P=Lo is set in step 137. Here, the degree of
irregularity P=Lo indicates that the degree of irregularity of the
road surface traveled by the automobile is the gentlest degree,
e.g., approximately corresponding to a flat road surface. Further,
steering instability and riding discomfort are stepwise less with
changing of the degree of irregularity P to P=Hi, P=Mi and
P=Lo.
[0093] When the degree of irregularity setting routine 130 is
finished, a damping level determination routine 140 (see FIGS. 8
and 10) is next executed. In execution of this damping level
determination routine 140, it is judged in step 141 whether or not
a flag F is F=1. Here, F=1 shows that the automobile is in running
under corner control. F=0 shows that the automobile is not in the
course of execution of the corner control program.
[0094] If the flag F is F=0 in step 141, the corner control program
is not being executed so that the judgment is NO. In the next step
142, the present position X of the automobile is detected on the
basis of the output of the GPS sensor 30a from the computer 30f of
the navigation device N. The distance L from this detected present
position X of the automobile to the curve starting point K is then
calculated. It is then judged whether or not this calculated
distance L is less than a predetermined distance. When the distance
L is not less than this predetermined distance, the judgement is NO
in step 142.
[0095] Thereafter, a damping level Cn is determined as Cn=2 as a
damping level for normal running of the automobile in step 143.
Here, the damping level Cn is a level common for the diaphragm
aperture (corresponding to an adjusting amount) of each
electromagnetic diaphragm valve 13, i.e., a level corresponding to
a common damping force for each of the suspension devices S1 to
S4.
[0096] When the judgment in step 142 is YES, the flag F is set to
F=1 in step 144 since the distance L is determined to be less than
the predetermined distance. After step 144, determination of the
damping level Cn common for the diaphragm aperture of each
electromagnetic diaphragm valve 13 (corresponding to the damping
force of each of the suspension devices S1 to S4) is performed as
follows in step 145.
[0097] First, an estimated transverse acceleration G is calculated
on the basis of the vehicle speed V of the automobile and the
radius of curvature Ra of the corner T by using the following
formula I. The estimated transverse acceleration G is an estimated
transverse acceleration applied to the automobile in travel of the
automobile in a turn around the corner T.
[0098] Estimated transverse acceleration:
G={(V.times.Vr)2}/Ra I.
[0099] wherein Vr is a deceleration correction coefficient. This
deceleration correction coefficient Vr is a correction coefficient
for estimating and correcting the deceleration from the vehicle
speed V in the present position X of the automobile to the vehicle
speed during travel of the automobile around the corner. In this
embodiment, for example, Vr=0.8 to 0.9 is set.
[0100] The above formula I is stored in a ROM of the microprocessor
50 in advance.
[0101] The damping level Cn is determined as follows by using the
estimated transverse G and the above degree of irregularity P, on
the basis of map shape data given in the following Table 1.
1 TABLE 1 Degree of irregularity estimated transverse G P = Hi P =
Mi P = Lo G3 < G Cn = 5 Cn = 6 Cn = 7 G2 < G.English Pound.G3
Cn = 4 Cn = 5 Cn = 6 G1 < G.English Pound.G2 Cn = 3 Cn = 4 Cn =
5 G.English Pound.G1 Cn = 2 Cn = 3 Cn = 4
[0102] In the map shape data of the above Table 1, the damping
level Cn represents the relationship between the degree of
irregularity P and the estimated transverse acceleration G. In this
case, the estimated transverse acceleration G is set so as to be
increased in the order of G=G1, G=G2 and G=G3.
[0103] When the degree of irregularity P=Hi is set as mentioned
above and the estimated transverse acceleration G is greater than
G1 and is G2 or less, the damping level is determined to be Cn=3 on
the basis of the data of Table 1. Further, when the degree of
irregularity P=Mi is set and the estimated transverse acceleration
G is greater than G1 and is G2 or less, the damping level is
determined to be Cn=4 on the basis of the data of Table 1. Further,
when the degree of irregularity P=Lo is set and the estimated
transverse acceleration G is greater than G1 and is G2 or less, the
damping level is determined to be Cn=5 on the basis of the data of
Table 1.
[0104] The relationship between the damping level Cn, the estimated
transverse acceleration G and the degree of irregularity P in the
data of Table 1 will now be explained with reference to FIGS. 12 to
14. In the relationship between the damping level Cn and the
estimated transverse acceleration G, as shown by FIGS. 12 to 14,
the damping level Cn is increased as the estimated transverse
acceleration G increases. The estimated transverse acceleration G
is increased as the vehicle speed of the automobile during running
of the corner is increased or the radius of curvature Ra of the
corner is less.
[0105] Conversely, in the relationship between the damping level Cn
and the degree of irregularity P, as shown in FIGS. 12 to 14, the
damping level Cn is reduced as the degree of irregularity P becomes
worse in the order of P=Lo, P=Mi and P=Hi. Namely, as the averaged
acceleration component increases, the degree of irregularity
becomes worse and the damping level Cn is reduced.
[0106] If the flag F is F=1, when the execution of the damping
level determination routine 140 has proceeded to step 141 as
mentioned above, the corner control is in effect so that the
judgment is YES. Next, when the output of the steering sensor 42
indicates approximately the neutral position, the automobile has
not started turning the corner. Accordingly, the judgement is NO in
step 146. In accordance with this judgment, similar to the above
case, the determination of the damping level Cn common to the
diaphragm aperture of each electromagnetic diaphragm valve 13 is
made in step 145.
[0107] However, when the automobile is found to have started
turning the corner in step 146, the judgement is YES, based on the
output of the steering sensor 42. Next, it is judged in step 147
whether or not the automobile has passed through the corner T,
i.e., completed the turn. At the present stage, just after the
judgement YES in step 146, the judgement is NO in step 147, on the
basis of the output of the gyro sensor 41e from the computer
30f.
[0108] In accordance with this judgment, the suspension control
program proceeds to complete the damping level determination
routine 140 without making a new determination of the damping level
Cn in step 145. This means that the damping level Cn already
determined in step 145 is held, in consideration of the degree of
irregularity of the road surface just before the automobile enters
the turn. This holding of the damping level Cn is maintained and
the judgement becomes YES in step 147.
[0109] Thereafter, when the judgement is YES in step 147 on the
basis of the output of the gyro sensor 41e from the computer 30f
indicating that the automobile has completed turning the corner T
in step 147, F=0 is set in step 148. Next, similar to step 143, the
damping level Cn is determined as Cn=2 as a damping level for the
normal running of the automobile in step 149.
[0110] When the damping level determination routine 140 (see FIGS.
8 and 10) is terminated, the diaphragm aperture of each
electromagnetic diaphragm valve 13 of the respective suspension
devices S1 to S4 is determined as follows in the next step 150 (see
FIG. 8) in accordance with the result in one of the above steps
143, 145, 147 and 149.
[0111] When the damping level Cn is determined as Cn=2 in step 143,
the diaphragm aperture .beta. for the electromagnetic diaphragm
valve 13 of each of the suspension devices S1 to S4 is determined
as .beta.=5 on the basis of the damping level Cn=2 from the graph
of the relationship between the diaphragm aperture .beta. and the
damping level Cn (.beta.-Cn characteristics) shown in FIG. 15. In
this embodiment, as shown in FIG. 15, the diaphragm aperture .beta.
is set so as to be increased (or decreased) in accordance with a
reduction (or increase) in the damping level Cn.
[0112] When the diaphragm aperture .beta. is determined as
.beta.=5, the diaphragm aperture .beta. is output to respective
driving circuits 60a to 60d as data showing .beta.=5 in step 150.
Thus, each of the driving circuits 60a to 60d operates an
electromagnetic diaphragm valve 13 on the basis of this output
data. This operation is performed such that all the diaphragm
apertures of the respective electromagnetic diaphragm valves 13 are
adjusted to the diaphragm aperture .beta.=5.
[0113] When the diaphragm aperture is adjusted in this way, each
electromagnetic diaphragm valve 13 greatly increases the flow of
operating oil between the hydraulic compartments 12a and 12b and
greatly reduces the resistance to circulation of the operating oil,
since the diaphragm apertures .beta. have been enlarged to .beta.=5
as mentioned above. Thus, the damping force of each of the
suspension devices S1 to S4 is controlled so as to be reduced
during straight running of the automobile just before the entry
into the turn around the corner T, and riding comfort (ride
sensation) during travel along the straight road can be optimized,
irrespective of the degree of irregularity of the road surface.
[0114] When the damping level Cn is determined in step 145 after
the judgement YES in step 142, the diaphragm aperture .beta. is
determined as follows from the .beta.-Cn characteristics shown in
FIG. 15 on the basis of the damping level Cn in step 150.
[0115] For example, when the degree of irregularity (see step 134
in FIG. 9) is set as P=Hi and the damping level is determined as
Cn=3, since the estimated transverse G is greater than G1 and is G2
or less, the diaphragm aperture .beta. of each electromagnetic
diaphragm valve 13 is determined as .beta.=4 on the basis of the
damping level Cn=3 from the .beta.-Cn graph shown in FIG. 15. Such
a determination corresponds to that for a road surface having the
worst case degree of irregularity.
[0116] When the degree of irregularity is judged to be P=Lo (see
step 137 in FIG. 9) and the damping level is determined as Cn=6,
since the estimated transverse G is greater than G2 and is G3 or
less, the diaphragm aperture .beta. for each electromagnetic
diaphragm valve 13 is determined as .beta.=1 on the basis of the
damping level Cn=6 from the .beta.-Cn graph shown in FIG. 15. Such
a determination corresponds to that for the lowest degree of
irregularity of the road surface.
[0117] Next, the diaphragm aperture .beta. (e.g., .beta.=4 or 1)
determined in this way is output to each of the driving circuits
60a to 60d in step 150 and each of the suspension devices S1 to S4
is controlled responsive to this output.
[0118] For example, when the diaphragm aperture .beta. which is
output to each of the driving circuits 60a to 60d is .beta.=4 (step
150), the driving circuits 60a to 60d adjust the diaphragm
apertures .beta. of the respective electromagnetic diaphragm valves
13 to .beta.=4. This adjustment of the electromagnetic diaphragm
valves 13 to .beta.=4 greatly increases the amount of flow of the
operating oil between the hydraulic compartments 12a and 12b, and
greatly reduces resistance to circulation of the operating oil.
Thus, the respective electromagnetic diaphragm valves 13 greatly
reduce the damping forces of the suspension devices S1 to S4.
[0119] On the other hand, when the diaphragm aperture data for
.beta.=1 is output to each of the driving circuits 60a to 60d (step
150), the respective driving circuits 60a to 60d adjust the
diaphragm apertures .beta. of the electromagnetic diaphragm valves
13 to .beta.=1. When the diaphragm aperture .beta. is adjusted to
.beta.=1, each electromagnetic diaphragm valve 13 greatly decreases
the amount of flow of the operating oil between the hydraulic
compartments 12a and 12b by increasing the resistance to
circulation of the operating oil. Thus, each electromagnetic
diaphragm valve 13 greatly increases the damping force of the
respective suspension devices S1 to S4.
[0120] The damping force of each of the suspension devices S1 to S4
is controlled by also taking into consideration the degree of
irregularity of the road surface in straight travel of the
automobile before entering the curve at starting point K, i.e.,
just before initiation of the corner control by controlling the
damping force as described above. For example, when the diaphragm
aperture is determined as .beta.=4, the road surface has the worst
degree of irregularity. Therefore, the damping force of each of the
suspension devices S1 to S4 is controlled so as to be greatly
reduced just before the entry of the automobile into the turn
around corner T. Accordingly, it is possible to set the ride
sensation for straight travel just before the entry of the
automobile into the curve, even though the road surface has the
worst degree of irregularity.
[0121] The diaphragm aperture is determined as .beta.=1 for the
lowest degree of irregularity. Accordingly, the damping force of
each of the suspension devices S1 to S4 is set higher. Thus,
steering stability in turning the corner T can be set as
preferred.
[0122] Further, when the damping level Cn is determined in step 145
after a NO determination in step 146, execution of the corner
control is started. Thereafter, in straight travel, up to just
before entry of the automobile into the turn at corner T, the
damping force of each of the suspension devices S1 to S4 is
controlled in a manner similar to the case in which the damping
force is controlled by adjusting the diaphragm aperture .beta. in
step 150, after the determination YES in step 142.
[0123] Further, when the judgement is NO in step 147 after a YES
determination in step 146, the damping level Cn already determined
in step 145, just before the YES determination in step 146 is
maintained. This means that the damping force of each of the
suspension devices S1 to S4 is controlled taking into consideration
the degree of irregularity of the road surface just before the
entry of the automobile into the curve around corner T and set in
advance to be held and utilized as the damping force after entry of
the automobile into the curve around corner T. Accordingly, when
the automobile enters into the turn (curve) around corner T, the
operations of the respective suspension devices S1 to S4 are
estimated and controlled so as to maintain the damping force
already set in advance just before entry of the automobile into the
turn around the corner T. As a result, the steering stability and
the ride sensation during travel of the automobile in turning the
corner T can be preferably maintained even when there are
irregularities in the road surface around the corner T.
[0124] Further, when the damping level Cn is determined as Cn=2 in
step 149 after a judgement YES in step 147, the diaphragm aperture
.beta. of each electromagnetic diaphragm valve 13 is set to
.beta.=5, by application of the damping level Cn=2 to the graph of
FIG. 15.
[0125] When the diaphragm aperture .beta. is set to be .beta.=5,
data for the diaphragm aperture .beta.=5 is output to each of the
driving circuits 60a to 60d in step 150. Thus, the respective
driving circuits 60a to 60d operate the respective electromagnetic
diaphragm valves 13 on the basis of this output data. When the
diaphragm aperture is enlarged to .beta.=5 in this way, each
electromagnetic diaphragm valve 13 greatly increases the flow of
the operating oil between the hydraulic compartments 12a and 12b by
reducing resistance to circulation of the operating oil. Thus, in
straight line travel of the automobile after passage around the
corner, the damping force of each of the suspension devices S1 to
S4 is reduced to provide a comfortable ride in straight line
travel.
Second Embodiment
[0126] FIG. 16 shows a second embodiment of the present invention
in which rotational speed sensors 43a, 43b are used instead of the
acceleration sensors 41a to 41d in the electronic controller E of
the above first embodiment. Each of these rotational speed sensors
43a, 43b is arranged near a drive wheel of an axle of the
automobile. Each of these rotational speed sensors 43a, 43b detects
the rotational speed of a drive wheel.
[0127] Further, this second embodiment is operated in accordance
with the flow chart of FIG. 17, instead of the flow chart of FIG. 8
as in the first embodiment. Further, this second embodiment employs
the slip degree setting routine 130a of FIG. 18 and the damping
level determination routine 140a of FIG. 19, instead of the degree
of irregularity setting routine 130 of FIG. 9 and the damping level
determination routine 140 of FIG. 10 in the suspension control
program of the first embodiment. Other features are similar to
those of the first embodiment.
[0128] In this second embodiment, similar to the processing in the
first embodiment, the microprocessor 50 of the electronic
controller E begins to execute the above suspension control program
in accordance with the flow chart of FIG. 17 when execution of the
navigation basic routine 100 of FIG. 5 through step 120 has been
terminated.
[0129] However, when the suspension control program proceeds to the
slip degree setting routine 130a (see FIG. 18), signals from the
respective rotational speed sensors 43a, 43b are input to the
microprocessor 50 in step 131a. Thus, the microprocessor 50
calculates an average value (hereinafter referred to as average
rotational speed .alpha.) of the rotational speeds of the
respective drive wheels on the basis of these signals.
[0130] Next, in step 132a, a slip ratio is calculated in a manner
which differs depending on whether the automobile is in a driving
state or in a braking state. Here, "driving state" means that the
automobile is traveling with positive acceleration in its direction
of advance. In contrast "braking state" means that the automobile
is running with negative acceleration with respect to its direction
of advance.
[0131] When the automobile is in the driving state, the slip ratio
is calculated on the basis of the average rotational speed .alpha.
and the vehicle speed V of the automobile by using the following
formula II:
Slip ratio={(.pi..times.D.times.a)-V)}/(.pi..times.D.times.a)
II.
[0132] wherein, .pi. is the ratio of the circumference of a circle
to its diameter and D is the diameter of the drive wheel.
[0133] Further, when the automobile is in the braking state, the
slip ratio is calculated on the basis of the above average
rotational speed .alpha. and the vehicle speed V of the automobile
by using the following formula III:
Slip ratio={V-(.pi..times.D.times.a)}/V III.
[0134] The above formulas II and III are stored in the ROM of the
microprocessor 50 in advance.
[0135] After step 132a, a judgement is made in step 133a whether or
not the slip ratio calculated in the step 132a is equal to or
greater than a first predetermined slip ratio. Here, this first
predetermined slip ratio corresponds to that for a road surface
having a worst case slip state. In this embodiment, the first
predetermined slip ratio is set to, e.g., 40%.
[0136] When the calculated current slip ratio is equal to or
greater than the first predetermined slip ratio, the result is YES
in step 133a. Next, a slip degree SP=Hi is set in step 134a. Here,
the slip degree SP shows the degree of slip on the road surface as
currently traveled by the automobile. The slip degree SP=Hi shows
that the road surface has a worst case degree of slip.
[0137] In contrast, when the judgment in step 133a is NO, in step
135a a determination is made as to whether or not the slip ratio is
equal to or greater than a second predetermined slip ratio. This
second predetermined slip ratio corresponds to an un-slippery state
as compared with the worst case slip state represented by the first
predetermined slip ratio. In this embodiment, the second
predetermined slip ratio is set to, e.g., 20%.
[0138] When the slip ratio is equal to or greater than the second
predetermined slip ratio, the determination is YES in step 135a.
Next, a slip degree SP=Mi is set in step 136a. The slip degree
SP=Mi indicates that the degree of slip of the road surface
traveled by the automobile is less slippery than the worst case
degree of slip represented by the slip degree SP=Hi.
[0139] When the judgment in the above step 135a is NO, a slip
degree SP=Lo is set in step 137a. Here, the degree of slip SP=Lo
shows that the road surface currently run by the automobile is a
best case degree, i.e., not slippery. Further, stability of the
automobile while running the road surface and the influence on the
riding comfort (ride sensation) are stepwise reduced as the slip
degree SP changes from SP=Hi, to SP=Mi and to SP=Lo.
[0140] When the slip degree setting routine 130a is terminated, the
damping level determination routine 140a (see FIG. 19) is executed.
In the execution of this damping level determination routine 140a,
it is judged in step 141 whether or not the flag F is F=1. If the
flag F is F=0 corner control is not being executed. Therefore, the
determination (judgement) is NO in step 141. In the next step 142,
it is judged whether or not the distance L, calculated as in step
142 (see FIG. 10) described in connection with the first
embodiment, is less than the above predetermined distance.
[0141] If this distance L is not less than the above predetermined
distance, the determination is NO in step 142. In step 143a, the
damping level Cn=2 is determined for normal running of the
automobile. On the other hand, when the judgment in step 142 is
YES, the distance L is less than the predetermined distance,
accordingly, as in the first embodiment, the flag F is set to F=1
in step 144.
[0142] After step 144, a determination of a damping level Cn,
common to the respective suspension devices S1 to S4, is made in
step 145a.
[0143] First, the estimated transverse acceleration G is calculated
by using formula I, on the basis of the vehicle speed V and the
radius of curvature Ra of the corner T.
[0144] Next, the damping level Cn is determined as follows, using
the estimated transverse acceleration G and the slip degree SP on
the basis of map shape data of the following Table 2.
2 TABLE 2 slip degree SP estimated transverse acceleration G SP =
Hi SP = Mi SP = Lo G3 < G Cn = 5 Cn = 6 Cn = 7 G2 < G.English
Pound.G3 Cn = 4 Cn = 5 Cn = 6 G1 < G.English Pound.G2 Cn = 3 Cn
= 4 Cn = 5 G.English Pound.G1 Cn = 2 Cn = 3 Cn = 4
[0145] Here, in the map shape data of this Table 2, the damping
level Cn is specified by the relationship between the slip degree
SP and the estimated transverse acceleration G. However, when the
slip degree is set as SP=Hi, the damping level is determined as
Cn=3 on the basis of the data of Table 2 when the estimated
transverse acceleration G is greater than G1 and is G2 or less.
Further, when the set degree of slip is SP=Mi, the damping level is
determined as Cn=4 on the basis of the data of Table 2 when the
estimated transverse acceleration G is greater than G1 and is G2 or
less. Further, when the degree of slip SP=Lo is set, the damping
level is determined to be Cn=5 when the estimated transverse
acceleration G is greater than G1 and is G2 or less.
[0146] The relationship between the damping level Cn, the estimated
transverse acceleration G and the degree of slip SP in the data of
Table 2 will now be explained with reference to FIGS. 20 to 22. In
the relationship between the damping level Cn and the estimated
transverse acceleration G, as shown in FIGS. 20 to 22, the damping
level Cn increases as the estimated transverse acceleration G
increases.
[0147] Further, in the relationship between of the damping level Cn
and the degree of slip SP, as shown in FIGS. 20 to 22, the damping
level Cn is reduced as the slip degree SP becomes worse in the
order of SP=Lo, SP=Mi and SP=Hi. Namely, as the slip degree becomes
worse, the damping level Cn is reduced.
[0148] When the damping level determination processing routine 140a
proceeds to step 141, corner control is being executed if the flag
F is F=1. Therefore, the judgment in step 141 is YES. Next, when
the automobile has not started turning a corner, when the
determination is NO in step 146, on the basis of the output of the
steering sensor 42 as in the first embodiment, the determination of
a damping level Cn common to the diaphragm apertures of all
electromagnetic diaphragm valves 13 is made in step 145a as in the
above case.
[0149] On the other hand, when the automobile has started turning a
corner in step 146, the determination is YES. Next, a judgement is
made in step 147 whether or not the automobile has completed
turning the corner T as described in connection with the first
embodiment, just after a judgement YES in step 146. Accordingly,
similar to the first embodiment, the judgement is NO in the step
147.
[0150] In accordance with this judgment, the suspension control
program proceeds to the last step of the damping level
determination routine 140a without newly determining the damping
level Cn in step 145a. This means that the damping level Cn already
determined in the step 145a is held by also taking into
consideration the degree of slip for the road surface immediately
preceding the point (K) where the automobile starts turning the
corner. This holding of the damping level Cn is maintained until
the judgement becomes YES in step 147.
[0151] Thereafter, similar to the first embodiment, when the
judgement becomes YES in step 147, i.e., when the automobile has
completed turning the corner T, F=0 is set in step 148 similar to
the case described in connection with the first embodiment. Next,
similar to step 143a, the damping level Cn is determined as Cn=2 as
a damping level for the normal running of the automobile in step
149a.
[0152] When the damping level determination routine 140a (see FIGS.
17 and 19) is terminated, the diaphragm aperture of each
electromagnetic diaphragm valve 13 is set in the next step 150 (see
FIG. 17), in accordance with the results of one of the steps 143a,
145a, 147, 149a.
[0153] As mentioned above, when the damping level Cn is determined
as Cn=2 in step 143a, the diaphragm aperture .beta. for each
electromagnetic diaphragm valve 13 is set to .beta.=5 on the basis
of the damping level Cn=2 from the .beta.-Cn characteristic graph
of FIG. 15.
[0154] When the diaphragm aperture is determined as .beta.=5 in
this manner, data for .beta.=5 is output to each of the driving
circuits 60a to 60d in step 150 and the driving circuits 60a to 60d
operate the respective electromagnetic diaphragm valves 13 on the
basis of this data output to adjust the diaphragm apertures of all
the electromagnetic diaphragm valves 13 to .beta.=5.
[0155] When the diaphragm aperture is adjusted to .beta.=5, the
diaphragm aperture is a relatively large value, i.e., on a scale of
.beta.=1 to .beta.=5. Therefore, in travel of the automobile in a
straight line just before the entry into the turn around the corner
T, the damping force of each of the suspension devices S1 to S4 is
reduced, and riding comfort in straight running of the automobile
can be maximized irrespective of the degree of slip of the road
surface.
[0156] Further, when the damping level Cn is determined in step
145a after a judgement YES in step 142, the diaphragm aperture
.beta. is determined in step 150 on the basis of the damping level
Cn from the .beta.-Cn characteristic graph of FIG. 15.
[0157] For example, when the slip degree is SP=Hi (see step 134a of
FIG. 18) and the damping level is determined as Cn=3, since the
estimated transverse G is greater than G1 and is G2 or less, the
diaphragm aperture .beta. for each electromagnetic diaphragm valve
13 is determined as .beta.=4, on the basis of the damping level
Cn=3 from the .beta.-Cn characteristic graph of FIG. 15, which
corresponds to a worst case slip degree.
[0158] Further, when the slip degree is SP=Lo (see the step 137a of
FIG. 18) and the damping level is determined as Cn=6 since the
estimated transverse G is greater than G2 and is G3 or less, the
diaphragm aperture .beta. of each electromagnetic diaphragm valve
13 is set as .beta.=1, by applying the damping level Cn=6 to the
.beta.-Cn characteristic graph of FIG. 15, which corresponds to a
least slippery road surface.
[0159] Next, data for the diaphragm aperture .beta. determined in
this way is output to each of the driving circuits 60a to 60d in
step 150 and the damping force of each of the suspension devices S1
to S4 is controlled on the basis of this output.
[0160] For example, when for the diaphragm aperture .beta.=4 is
output to each of the driving circuits 60a to 60d in step 150, the
driving circuits 60a to 60d operate the respective electromagnetic
diaphragm valves 13 so as to adjust the diaphragm apertures to
.beta.=4. When the diaphragm aperture .beta. is adjusted to
.beta.=4, the electromagnetic diaphragm valves 13 greatly reduce
the damping force for each of the suspension devices S1 to S4.
[0161] Further, when data for a diaphragm aperture .beta.=1 is
output to each of the driving circuits 60a to 60d in step 150 as
mentioned above, the driving circuits 60a to 60d operate the
respective electromagnetic diaphragm valves 13 so as to adjust the
diaphragm apertures to .beta.=1. When the diaphragm aperture is
adjusted to .beta.=1 in this manner, the electromagnetic diaphragm
valves 13 greatly increase the damping force of each of the
suspension devices S1 to S4, similar to the above first
embodiment.
[0162] In the straight running of the automobile until just before
start of execution of the corner control, the damping force of each
of the suspension devices S1 to S4 is controlled in consideration
of the slip degree of the road surface.
[0163] When the diaphragm aperture is determined as .beta.=4 as
mentioned above, the damping force of each of the suspension
devices S1 to S4 is reduced just before the automobile enters the
turn around the corner T since the road surface has a high degree
of slip, but ride comfort in straight running of the automobile can
be maintained.
[0164] Further, when the diaphragm aperture is .beta.=1, the
damping force of each of the suspension devices S1 to S4 is greatly
increased since the road surface is at the least slippery state.
Thus, steering stability in turning the automobile at the corner T
can be maximized.
[0165] Further, when the damping level Cn is determined in step
145a after a judgement NO in step 146, execution of corner control
is started. Thereafter, in straight running, until just before the
automobile enters into the turn around the corner T, the damping
force of each of the suspension devices S1 to S4 is controlled by
adjusting the diaphragm aperture .beta. in step 150 after a
determination of YES in step 142.
[0166] Further, when the judgement is NO in step 147, after a
judgement YES in step 146, the damping level Cn already determined
in step 145a, just before the judgement YES in step 146 is
maintained. This means that the damping force of each of the
suspension devices S1 to S4 is controlled taking into consideration
the slip degree of the road surface just before entry of the
automobile into the turn around the corner T and is held and
utilized as the damping force after the entry of the automobile
into the turn around the corner T, similar to the first
embodiment.
[0167] Accordingly, when the automobile enters into the turn around
the corner T, the operation of each of the suspension devices S1 to
S4 is estimated and controlled so as to maintain the damping force
already set, just before the entry of the automobile into the turn
around the corner T. As a result, the stability and the riding
comfort in the turning of the automobile around the corner T can be
maximized even when the road surface at the corner T is
slippery.
[0168] Further, when the damping level is Cn=2 in step 149, after
ajudgement YES in step 147, the diaphragm aperture of each
electromagnetic diaphragm valve 13 is set to .beta.=5 on the basis
of application of the damping level Cn=2 to the .beta.-Cn
characteristic graph of FIG. 15, similar to the first
embodiment.
[0169] When data for the diaphragm aperture .beta.=5 is output to
each of the driving circuits 60a to 60d, on the basis of this
output data, the driving circuits 60a to 60d adjust all the
diaphragm apertures of the respective electromagnetic diaphragm
valves 13 to .beta.=5.
[0170] When the diaphragm aperture is adjusted to .beta.=5, the
damping force of each of the suspension devices S1 to S4 is reduced
for straight running of the automobile after having turned the
corner T, similar to the above first embodiment, since the
diaphragm aperture .beta. is a large value. Thus, the riding
comfort in straight running of the automobile can be maximized.
[0171] The present invention is not limited to the above
embodiments; rather, various modifications may be made as
follows:
[0172] (1) In judging the degree of irregularity of the road
surface, a single acceleration sensor may be utilized instead of
acceleration sensors 41a to 41d described in connection with the
first embodiment. Further, in judging degree of irregularity of the
road surface, a vehicle height sensor for detecting the height of
the automobile and a stroke sensor for detecting the length of
expansion of each suspension device may be utilized instead of the
acceleration sensors 41a to 41d.
[0173] (2) Calculation of the estimated transverse acceleration G
is not limited to use of Formula I, the deceleration correction
coefficient Vr and the radius of curvature Ra. For example, an
estimated transverse acceleration G may be obtained by subtracting
a predetermined value from the vehicle speed V of the automobile
(minus-correcting), squaring the remainder and dividing by the
radius of curvature Ra.
[0174] (3) Judgment of the degree of slip of the road surface on
which the automobile is traveling, is not limited to the
calculation of the slip ratio from the rotational speed of a drive
wheel of the automobile and the vehicle speed V, using the above
formulas II and III. For example, the slip degree may be also
judged by imaging of the road surface and/or by output of an
ultrasonic sensor.
[0175] (4) Air suspension devices may be substituted for the
suspension devices S1 to S4. Further, an active suspension device
having the capability of adjusting the vehicle height may be
adopted to control the posture of the automobile during the turning
of the corner T.
[0176] (5) Determination of the radius of curvature Ra of the
corner T, is not limited to the adoption of a minimum value of the
curvature radii of all nodes N included in the corner. Instead, an
average value at a number of points of smaller values for the
radius of curvature may be adopted as the radius of curvature Ra of
the corner.
[0177] (6) The present invention is not limited to a sedan type
automobile, but may be applied in general to any vehicle. For
example, the present invention may also be applied to a station
wagon, a minivan or an electric railcar.
[0178] (7) The diaphragm aperture of each electromagnetic diaphragm
valve 13 may also be adjusted on the basis of mutually independent
damping levels instead of making the adjustment on the basis of a
common damping level.
[0179] (8) The damping force of the suspension device estimated in
advance before entry of the automobile into the turn around the
corner T may also be controlled responsive to a combination of
determination of the degree of irregularity and a determination of
the degree of slip, instead of being limited to one determination
or the other.
[0180] (9) The judgment in step 146, need not be based on output of
the steering sensor 42. The output of a gyro sensor 41e may be
utilized instead.
[0181] (10) The estimated transverse acceleration G may be also
calculated by using node angle (corresponding to a turning angle
.theta.) instead of the radius of curvature Ra.
[0182] (11) The present invention is not limited to a suspension
control system for an automobile, but also includes a suspension
control method for an automobile.
[0183] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
* * * * *