U.S. patent application number 09/864010 was filed with the patent office on 2002-08-08 for method and system for adjusting headway in an adaptive speed control system based on road surface coefficient of friction.
This patent application is currently assigned to VISTEON GLOBAL TECHNOLOGIES, INC. Invention is credited to Friedrich, Mark Peter, Rahaim, Sam G., Sielagoski, Gerald L..
Application Number | 20020105297 09/864010 |
Document ID | / |
Family ID | 25117548 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020105297 |
Kind Code |
A1 |
Sielagoski, Gerald L. ; et
al. |
August 8, 2002 |
Method and system for adjusting headway in an adaptive speed
control system based on road surface coefficient of friction
Abstract
In an adaptive speed control system for a vehicle, a method and
system for automatically adjusting a selected following interval
for the vehicle based on driving conditions is provided. The method
includes determining a driving surface coefficient of friction
based on a driven wheel speed of the vehicle, and adjusting the
selected following interval for the vehicle based on the driving
surface coefficient of friction. The system includes a receiver
capable of receiving a signal indicative of a driven wheel speed of
the vehicle, and a controller capable of determining a driving
surface coefficient of friction based on the driven wheel speed,
and capable of adjusting the selected following interval for the
vehicle based on the driving surface coefficient of friction.
Inventors: |
Sielagoski, Gerald L.; (St.
Clair Shores, MI) ; Friedrich, Mark Peter; (Clinton
Township, MI) ; Rahaim, Sam G.; (Ann Arbor,
MI) |
Correspondence
Address: |
Jeffrey M. Szuma
Brooks & Kushman P.C.
22nd Floor
1000 Town Center
Southfield
MI
48075-1351
US
|
Assignee: |
VISTEON GLOBAL TECHNOLOGIES,
INC
Dearborn
MI
|
Family ID: |
25117548 |
Appl. No.: |
09/864010 |
Filed: |
May 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09864010 |
May 23, 2001 |
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09779783 |
Feb 8, 2001 |
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6285153 |
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Current U.S.
Class: |
318/599 |
Current CPC
Class: |
B60T 2210/12 20130101;
B60W 2530/10 20130101; B60W 2520/105 20130101; B60W 2552/40
20200201; B60T 2201/02 20130101; B60K 31/0008 20130101; B60W 30/16
20130101 |
Class at
Publication: |
318/599 |
International
Class: |
G05B 011/28 |
Claims
What is claimed is:
1. In an adaptive speed control system for a vehicle, a method for
automatically adjusting a selected following interval for the
vehicle based on driving conditions, the method comprising:
determining a driving surface coefficient of friction based on a
driven wheel speed of the vehicle; and adjusting the selected
following interval for the vehicle based on the driving surface
coefficient of friction.
2. The method of claim 1 wherein adjusting the selected following
interval comprises: determining a ratio of the driving surface
coefficient of friction and a selected coefficient of friction
value; and scaling the selected following distance based on the
ratio of the driving surface coefficient of friction and a selected
coefficient of friction value.
3. The method of claim 1 wherein adjusting the selected following
interval comprises: comparing the driving surface coefficient of
friction to a coefficient of friction threshold; and when the
driving surface coefficient of friction is less than the
coefficient of friction threshold, adjusting the selected following
interval based on the difference between the coefficient of
friction threshold and the driving surface coefficient of
friction.
4. The method of claim 3 wherein adjusting the selected following
interval based on the difference between the coefficient of
friction threshold and the driving surface coefficient of friction
includes adjusting the selected following interval in direct
relationship to the difference between the coefficient of friction
threshold and the driving surface coefficient of friction.
5. The method of claim 4 wherein adjusting the selected following
interval in direct relationship to the difference between the
coefficient of friction threshold and the driving surface
coefficient of friction includes increasing the selected following
interval when the difference between the coefficient of friction
threshold and the driving surface coefficient of friction
increases.
6. The method of claim 4 wherein adjusting the selected following
interval in direct relationship to the difference between the
coefficient of friction threshold and the driving surface
coefficient of friction includes decreasing the selected following
interval when the difference between the coefficient of friction
threshold and the driving surface coefficient of friction
decreases.
7. The method of claim 3 wherein the selected following interval is
capable of varying continuously.
8. The method of claim 3 wherein the selected following interval is
capable of varying between a plurality of values, each value
corresponding to one of a plurality of ranges of driving surface
coefficients of friction.
9. The method of claim 1 further comprising: comparing the driving
surface coefficient of friction to a deactivation coefficient of
friction threshold; and deactivating the adaptive speed control
system when the driving surface coefficient of friction is less
than the deactivation coefficient of friction threshold.
10. The method of claim 1 wherein determining a driving surface
coefficient of friction comprises calculating a driving surface
coefficient of friction according to the
equation:.mu.=(T-J.omega.')/mgr cos {sin.sup.-1
[(T-J.omega.'-mx"r)/mgr]}where .mu. is the driving surface
coefficient of friction, T is a driven wheel torque, J is a driven
wheel inertia, .omega.' is a driven wheel acceleration, m is a mass
of the vehicle, g is an acceleration due to gravity, r is a radius
of a driven wheel, and x" is a vehicle acceleration.
11. In an adaptive speed control system for a vehicle, a system for
automatically adjusting a selected following interval for the
vehicle based on driving conditions, the system comprising: a
receiver capable of receiving a signal indicative of a driven wheel
speed of the vehicle; and a controller capable of determining a
driving surface coefficient of friction based on the driven wheel
speed, and adjusting the selected following interval for the
vehicle based on the driving surface coefficient of friction.
12. The system of claim 11 wherein, to adjust the selected
following interval, the controller is capable of determining a
ratio of the driving surface coefficient of friction and a selected
coefficient of friction value, and scaling the selected following
distance based on the ratio of the driving surface coefficient of
friction and a selected coefficient of friction value.
13. The system of claim 11 wherein, to adjust the selected
following interval, the controller is capable of comparing the
driving surface coefficient of friction to a coefficient of
friction threshold and, when the driving surface coefficient of
friction is less than the coefficient of friction threshold,
adjusting the selected following interval based on a difference
between the coefficient of friction threshold and the driving
surface coefficient of friction.
14. The system of claim 13 wherein, to adjust the selected
following interval based on the difference between the coefficient
of friction threshold and the driving surface coefficient of
friction, the controller is capable of adjusting the selected
following interval in direct relationship to the difference between
the coefficient of friction threshold and the driving surface
coefficient of friction.
15. The system of claim 14 wherein, to adjust the selected
following interval in direct relationship to the difference between
the coefficient of friction threshold and the driving surface
coefficient of friction, the controller is capable of increasing
the selected following interval when the difference between the
coefficient of friction threshold and the driving surface
coefficient of friction increases.
16. The system of claim 14 wherein, to adjust the selected
following interval in direct relationship to the difference between
the coefficient of friction threshold and the driving surface
coefficient of friction, the controller is capable of decreasing
the selected following interval when the difference between the
coefficient of friction threshold and the driving surface
coefficient of friction decreases.
17. The system of claim 13 wherein the selected following interval
is capable of varying continuously.
18. The system of claim 13 wherein the selected following interval
is capable of varying between a plurality of values, each value
corresponding to one of a plurality of ranges of driving surface
coefficients of friction.
19. The system of claim 11 wherein the controller is further
capable of comparing the driving surface coefficient of friction to
a deactivation coefficient of friction threshold, and deactivating
the adaptive speed control system when the driving surface
coefficient of friction is less than the deactivation coefficient
of friction threshold.
20. The system of claim 11 wherein, to determine a driving surface
coefficient of friction, the controller is capable of calculating a
driving surface coefficient of friction according to the
equation:.mu.=(T-J.omega.')/mgr cos {sin.sup.-1
[(T-J.omega.'-mx"r)/mgr]}- where .mu. is the driving surface
coefficient of friction, T is a driven wheel torque, J is a driven
wheel inertia, .omega.' is a driven wheel acceleration, m is a mass
of the vehicle, g is an acceleration due to gravity, r is a radius
of a driven wheel, and x" is a vehicle acceleration.
Description
TECHNICAL FIELD
[0001] This invention relates to a method and system for adjusting
the following interval of a vehicle equipped with an adaptive speed
control system based on the driving surface coefficient of
friction.
BACKGROUND ART
[0002] Adaptive Cruise (i.e., speed) Control (ACC) systems operate
much like conventional Cruise Control systems, with the added
capability of being able to sense in-path vehicles and to slow the
ACC equipped vehicle in response. An ACC equipped vehicle thereby
allows its operator to automatically control the vehicle speed, as
with conventional Cruise Control, without the necessity of having
to deactivate and reactivate control whenever slower traffic is
encountered.
[0003] As is well known in the art, existing ACC methods and
systems use a forward looking range sensor such as radar to sense
an in-path vehicle (which may also be referred to as a sensed
target or primary target). Based on the radar sensor information,
such ACC methods and systems then determine the range and relative
velocity (or range rate) of the sensed in-path vehicle. Using the
range and range rate, the speed of the ACC equipped vehicle is
controlled to maintain a selected following interval between the
ACC equipped vehicle and the sensed in-path vehicle. The speed of
the ACC equipped vehicle is typically controlled by automatic
control of the vehicle throttle actuator. In more advanced ACC
methods and systems, vehicle speed may also be controlled by
automatic control of vehicle brake actuators. Such ACC methods and
systems have the ability to apply a moderate degree of braking to
the vehicle to achieve further vehicle deceleration (i.e., in
addition to vehicle deceleration achieved via throttle control) in
response to an in-path vehicle.
[0004] Existing ACC methods and systems, however, generally do not
take into account driving surface conditions. More particularly,
the time necessary for a vehicle operator is to slow a vehicle to a
selected speed is optimal on those driving surfaces having high
coefficients of friction, such as those provided by dry, concrete
or asphalt pavement. That time generally increases when the driving
surface coefficient of friction deceases, such as when the driving
surface is wet, or is covered by snow or ice. Existing ACC methods
and systems, however, control the vehicle speed to maintain the
following interval selected (either by the vehicle operator or by
default) regardless of the driving surface coefficient of
friction.
[0005] Thus, there exists a need, in an ACC system, for a method
and system for automatically adjusting the following interval of
the ACC equipped vehicle based on the driving surface coefficient
of friction. Such a method and system would determine a driving
surface coefficient of friction based on a driven wheel speed of
the ACC equipped vehicle, and adjust the selected following
interval for the ACC equipped vehicle based on the driving surface
coefficient of friction.
DISCLOSURE OF INVENTION
[0006] Accordingly, it is a principal object of the present
invention to provide, in an adaptive speed control system for a
vehicle, a method and system for automatically adjusting a selected
following interval for the vehicle based on the driving surface
coefficient of friction.
[0007] According to the present invention, then, in an adaptive
speed control system for a vehicle, a method and system are
provided for automatically adjusting a selected following interval
for the vehicle based on driving conditions. The method of the
present invention comprises determining a driving surface
coefficient of friction based on a driven wheel speed of the
vehicle, and adjusting the selected following interval for the
vehicle based on the driving surface coefficient of friction.
[0008] The system of the present invention includes a receiver
capable of receiving a signal indicative of a driven wheel speed of
the vehicle, and a controller capable of determining a driving
surface coefficient of friction based on the driven wheel speed.
The controller is further capable of adjusting the selected
following interval for the vehicle based on the driving surface
coefficient of friction.
[0009] These and other objects, features and advantages of the
present invention will be readily apparent upon consideration of
the following detailed description of the invention in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a simplified block diagram of an adaptive cruise
control system, including the system of the present invention;
[0011] FIG. 2 is a simplified diagram of the forces exerted on a
vehicle on a driving surface; and
[0012] FIG. 3 is a flowchart of the method of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0013] Referring to FIGS. 1-3, the preferred embodiment of the
method and system of the present invention will now be described.
In that regard, FIG. 1 illustrates a simplified block diagram of an
Adaptive Cruise Control (ACC) system, including the system of the
present invention, denoted generally by reference numeral 10.
[0014] In general, as is well known to those of ordinary skill in
the art, ACC system (10) is a closed loop control system intended
to respond to potential targets in front of and in the same lane of
traffic as the vehicle equipped with the ACC system (10). The goal
of ACC system (10) is to partially automate the continuous
longitudinal control of the vehicle, thereby providing the vehicle
operator with improved comfort and convenience. In that regard, ACC
system (10) may operate in either a normal or a following mode. In
normal mode operation, ACC system (10) controls the speed of the
ACC equipped vehicle to the speed set by the vehicle operator as
the control speed. In following mode operation, ACC system (10)
controls the speed of the ACC equipped vehicle to the speed of a
sensed in-path vehicle (which may be referred to as a sensed target
or a primary target).
[0015] More specifically, as seen in FIG. 1, the ACC system (10)
includes a vehicle controller (12) provided in communication with a
range sensor (14), a vehicle speed sensor (16), a driven wheel
speed sensor (17), a yaw rate sensor (18), a user interface (20), a
throttle actuator (22), and a brake actuator (24). As previously
described, the system (10) extends the function of conventional
speed control systems. In that regard, based on range and relative
velocity information obtained and/or derived from forward looking
range sensor (14) and speed sensor (16), vehicle controller (12)
uses throttle and brake actuators (22, 24) to control the speed of
the ACC equipped vehicle in order to maintain a selected following
interval (in seconds) between the ACC equipped vehicle and a sensed
target in the forward path of travel of the ACC equipped vehicle
(i.e., a lead vehicle).
[0016] The following interval between the ACC equipped vehicle and
the sensed target is initially set at a default value (typically
two seconds) upon activation of the system (10), but may be
modified by the vehicle operator to any of a number of other
selectable values via user interface (20). The default following
interval is typically the maximum following interval allowed, and
modification of the following interval by the vehicle operator is
permitted between that maximum and a defined minimum following
interval. The following interval is referred to as headway, and is
defined as the range to the sensed target (in meters), divided by
the speed of the ACC equipped vehicle (in meters per second). User
interface (20) is also used by the vehicle operator to set the
desired vehicle control speed.
[0017] As previously noted, ACC systems and methods are well known
in the art. As a result, a detailed description of the general
operation of ACC system (10), including such functions as
acquisition, discrimination, differentiation, selection and
tracking of targets, range and relative velocity (including range
rate) determinations, sensor operations, and throttle and brake
control is unnecessary and, for the sake of brevity, is not set
forth herein. In connection with the method and system of the
present invention, such functions of ACC system (10) may be
undertaken in any fashion known to those of ordinary skill.
[0018] As also previously noted, existing ACC methods and systems,
however, generally do not take into account driving surface
conditions. More particularly, the time necessary for a vehicle
operator is to slow a vehicle to a selected speed is optimal on
those driving surfaces having high coefficients of friction, such
as those provided by dry, concrete or asphalt pavement. That time
generally increases when the driving surface coefficient of
friction deceases, such as when the driving surface is wet, or is
covered by snow or ice. Existing ACC methods and systems, however,
control the vehicle speed to maintain the following interval
selected (either by the vehicle operator or by default) regardless
of the driving surface coefficient of friction.
[0019] In contrast, the present invention provides, in the ACC
system (10) of FIG. 1, a method and system for automatically
adjusting the following interval of the ACC equipped vehicle based
on the driving surface coefficient of friction. In general, the
present invention increases the following interval as the driving
surface coefficient of friction decreases, such as on wet, or snow
or ice covered pavement. Still further, if the driving surface
coefficient of friction becomes too low, the present invention
deactivates the ACC system.
[0020] More specifically, still referring to FIG. 1, the system of
the present invention is preferably included in vehicle controller
(12). In that regard, vehicle controller (12) includes a receiver
(not shown) capable of receiving an input signal from driven wheel
speed sensor (17) indicative of the speed of a driven wheel of the
ACC equipped vehicle. Vehicle controller (12) also includes a
controller (not shown) capable of determining a driving surface
coefficient of friction based on a driven wheel speed of the ACC
equipped vehicle, and adjusting the selected following interval for
the ACC equipped vehicle based on the driving surface coefficient
of friction determined. It should be noted here that the controller
(as well as vehicle controller (12) of ACC system (10)) may take
the form of an appropriately programmed microprocessor, or any
equivalent thereof.
[0021] According to the present invention, the controller of the
system preferably determines the driving surface coefficient of
friction as follows, although other techniques for determining such
a coefficient may also be employed. In that regard, it is known
that the dynamics equation for a vehicle may be expressed as
J.omega.'=T-.mu.mgr cos .alpha.,
[0022] where J is a driven wheel inertia, .omega.' is a driven
wheel acceleration, T is a driven wheel torque, .mu. is the driving
surface coefficient of friction, m is the mass of the vehicle, g is
gravitational acceleration, r is a driven wheel radius, and .alpha.
is the angle of inclination of the driving surface. Solving this
equation for the driving surface coefficient of friction, .mu., it
can be seen that
.mu.=(T-J.omega.')/mgr cos .alpha.. (1)
[0023] Referring now to FIG. 2, a simplified diagram of the forces
exerted on a vehicle on a driving surface is shown. As seen
therein, on a driving surface (30) having an angle of inclination,
a, a vehicle experiences a gravitational force equal to the mass of
the vehicle, m, multiplied by the acceleration of gravity, g. That
gravitational force is also equal to the sum of a normal force,
F.sub.n, and a force due to torque on the vehicle, F.sub.T. From
the diagram, it can thus be seen that
F.sub.N=mg cos .alpha. (2)
[0024] and that
F.sub.T=mg sin .alpha.. (3)
[0025] It is known that the force experienced by a moving vehicle
is equal to the mass of the vehicle, m, multiplied by the
acceleration of the vehicle, x". That same force is also equal to
the difference between the force exerted on the vehicle due to
friction, F.sub.frict, and the force due to torque, F.sub.T. That
is,
mx"=F.sub.frict-F.sub.T. (4)
[0026] It is also known that the frictional force, F.sub.frict, is
equal to the normal force, F.sub.N, multiplied by the driving
surface coefficient of friction, .mu.. Thus,
F.sub.frict=.mu.F.sub.N. (5)
[0027] Using equations (1), (2), (3) and (5), it can be seen that
equation (4) may be re-written as
mx"=[(T-J.omega.')/r]-mg sin .alpha. (6)
[0028] From equation (6), .alpha., the angle of inclination of the
driving surface, may be expressed as
.alpha.=sin.sup.-1 [(T-J.omega.'-mx"r)/mgr]. (7)
[0029] Using equation (7), it can be seen that equation (1) may be
rewritten so that the driving surface coefficient of friction,
.mu., may be finally expressed as
.mu.=(T-J.omega.')/mgr cos {sin.sup.-1 [(T-J.omega.'-mx"r)/mgr]}.
(8)
[0030] Thus, referring again to FIG. 1, as previously noted, the
controller of the system of the present invention is preferably
included in vehicle controller (12), and is capable of determining
a driving surface coefficient of friction. To do so, the controller
of the system is preferably capable of calculating a driving
surface coefficient of friction according to equation (8), above.
In that regard, each of the variables in equation (8) are either
known, or measured or derived in conventional fashion. For example,
vehicle speed sensor (16) measures a vehicle speed (at a non-driven
wheel), from which vehicle acceleration, x", is derived. Driven
wheel speed sensor (17) measures a driven wheel speed, from which
driven wheel acceleration, .omega.', is derived. A measured
throttle position and engine RPM have an associated engine torque.
Engine torque and known transmission axle gear ratios may be used
to determine wheel torque, T.
[0031] As also previously noted, the controller of the system of
the present invention is capable of adjusting the selected
following interval for the vehicle based on the driving surface of
coefficient determined. To do so, the controller may be capable of
determining a ratio of the driving surface coefficient of friction
and a selected coefficient of friction value, and scaling the
selected following distance based on the ratio of the driving
surface coefficient of friction and a selected coefficient of
friction value.
[0032] Alternatively, to adjust the selected following interval for
the vehicle based on the driving surface of coefficient determined,
the controller may be capable of comparing the driving surface
coefficient of friction to a coefficient of friction threshold and,
when the driving surface coefficient of friction is less than the
coefficient of friction threshold, adjusting the selected following
interval based on the difference between the coefficient of
friction threshold and the driving surface coefficient of friction.
In that regard, adjusting the selected following interval based on
such a difference may include adjusting the selected following
interval in direct relationship to that difference. That is, when
the driving surface coefficient of friction is less than the
coefficient of friction threshold, adjusting the selected following
interval includes both increasing the selected following interval
when the difference between the coefficient of friction threshold
and the driving surface of coefficient of friction increases, as
well as decreasing the selected following interval when that
difference decreases.
[0033] The selected following interval is preferably adjusted
proportionally to the difference between the coefficient of
friction threshold and the driving surface coefficient of friction.
As used herein, proportional adjustment is intended to include
linear, as well as other functions. In that regard, according to
the present invention, the selected following interval may be
capable of varying continuously as the difference between the
coefficient of friction threshold and the driving surface of
coefficient of friction continuously varies. Alternatively, the
selected following interval may be capable of varying between a
plurality of values in a step-like fashion, wherein each one of
those values corresponds to one of a plurality of ranges of driving
surface coefficient of friction values. That is, when the driving
surface coefficient of friction is less than the coefficient of
friction threshold, the selected following interval may be adjusted
to a first value when the value of the driving surface coefficient
of friction falls within a first range, and adjusted to a second
value when the value of the driving surface coefficient of friction
transitions to a second range.
[0034] Still further, the controller of the system of the present
invention is also capable of comparing the driving surface
coefficient of friction to a deactivation coefficient of friction
threshold, and deactivating the adaptive speed control system when
the driving surface coefficient of friction is less than the
deactivation coefficient of friction threshold. In such a fashion,
the present invention deactivates ACC system (10) in the event the
driving surface coefficient of friction becomes too low. In that
regard, the deactivation coefficient of friction threshold is a
value less than the coefficient of friction threshold previously
described. Moreover, both such thresholds may be predefined, and
determined empirically.
[0035] Referring now to FIG. 3, a flowchart of the method of the
present invention is shown, denoted generally by reference numeral
40. As seen therein, the method (40) of the present invention
comprises, in an ACC system, determining (42) a driving surface
coefficient of friction based on a driven wheel speed of the
vehicle, and adjusting (44) the selected following interval for the
vehicle based on the driving surface coefficient of friction. As
noted above in connection with the description of the system of the
present invention, determining (42) a driving surface coefficient
of friction preferably comprises calculating a driving surface
coefficient of friction according to the equation
.mu.=(T-J.omega.')/mgr cos {sin.sup.-1 [(T-J.omega.'-mx"r)/mgr]},
(8)
[0036] where .mu. is the driving surface coefficient of friction, T
is a driven wheel torque, J is a driven wheel inertia, .omega.' is
a driven wheel acceleration, m is a mass of the vehicle, g is an
acceleration due to gravity, r is a radius of a driven wheel, and
x" is a vehicle acceleration.
[0037] As also noted above, adjusting (44) the selected following
interval may comprise determining a ratio of the driving surface
coefficient of friction and a selected coefficient of friction
value, and scaling the selected following distance based on the
ratio of the driving surface coefficient of friction and a selected
coefficient of friction value. Alternatively, adjusting (44) the
selected following interval may comprise comparing the driving
surface coefficient of friction to a coefficient of friction
threshold and, when the driving surface coefficient of friction is
less than the coefficient of friction threshold, adjusting the
selected following interval based on the difference between the
coefficient of friction threshold and the driving surface
coefficient of friction. In that regard, adjusting the selected
following interval based on such a difference may include adjusting
the selected following interval in direct relationship to that
difference. That is, when the driving surface coefficient of
friction is less than the coefficient of friction threshold,
adjusting the selected following interval includes both increasing
the selected following interval when the difference between the
coefficient of friction threshold and the driving surface of
coefficient of friction increases, as well as decreasing the
selected following interval when that difference decreases.
[0038] Once again, the selected following interval is preferably
adjusted proportionally to the difference between the coefficient
of friction threshold and the driving surface coefficient of
friction. In that regard, the selected following interval may be
capable of varying continuously as the difference between the
coefficient of friction threshold and the driving surface of
coefficient of friction continuously varies. Alternatively, the
selected following interval may be capable of varying between a
plurality of values in a step-like fashion, wherein each one of
those values corresponds to one of a plurality of ranges of driving
surface coefficient of friction values.
[0039] The method of the present invention may further comprise
comparing the driving surface coefficient of friction to a
deactivation coefficient of friction threshold, and deactivating
the adaptive speed control system when the driving surface
coefficient of friction is less than the deactivation coefficient
of friction threshold. In such a fashion, the method of the present
invention deactivates ACC system (10) in the event the driving
surface coefficient of friction becomes too low.
[0040] From the foregoing description, it can be seen that the
present invention provides, in an ACC system, a method and system
for adjusting the following interval of an ACC equipped vehicle
based on the coefficient of friction of the driving surface. More
particularly, the present invention generally increases the
following interval as the driving surface coefficient of friction
decreases, such as on wet, or snow or ice covered pavement. Still
further, if the driving surface coefficient of friction becomes too
low, the present invention deactivates the ACC system.
[0041] While various embodiments of the invention have been
illustrated and described, it is not intended that these
embodiments illustrate and describe all possible forms of the
invention. Rather, the words used in the specification are words of
description rather than limitation, and it is understood that
various changes may be made without departing from the spirit and
scope of the invention.
* * * * *