U.S. patent application number 14/323714 was filed with the patent office on 2016-01-07 for dynamic deadband for automatic articulation.
The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Steven C. Budde, Amit Sharma.
Application Number | 20160002885 14/323714 |
Document ID | / |
Family ID | 55016623 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160002885 |
Kind Code |
A1 |
Sharma; Amit ; et
al. |
January 7, 2016 |
DYNAMIC DEADBAND FOR AUTOMATIC ARTICULATION
Abstract
An articulation control system for a machine may include an
actual steering sensor configured to provide a signal indicative of
an actual steering angle, a timer configured to provide a signal
indicative of an elapsed predetermined period of time, and a
controller in communication with the actual steering sensor and the
timer. The controller may be configured to regulate automatic
articulation to zero based on signals received from the actual
steering sensor and the timer.
Inventors: |
Sharma; Amit; (Peoria,
IL) ; Budde; Steven C.; (Dunlap, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Family ID: |
55016623 |
Appl. No.: |
14/323714 |
Filed: |
July 3, 2014 |
Current U.S.
Class: |
701/41 |
Current CPC
Class: |
B62D 12/00 20130101;
B62D 9/00 20130101; E02F 9/225 20130101; E02F 9/0841 20130101; E02F
3/764 20130101 |
International
Class: |
E02F 9/22 20060101
E02F009/22; B62D 12/00 20060101 B62D012/00; E02F 9/08 20060101
E02F009/08 |
Claims
1. An articulation control system for a machine, comprising: an
actual steering sensor configured to provide a signal indicative of
an actual steering angle; a timer configured to provide a signal
indicative of an elapsed predetermined period of time; and a
controller in communication with the actual steering sensor and the
timer, the controller configured to regulate automatic articulation
to zero based on signals received from the actual steering sensor
and the timer, when the machine is in an auto-articulation
mode.
2. The articulation control system of claim 1, wherein the
controller is configured to regulate automatic articulation to zero
within a dead band range of actual steering angles.
3. The articulation control system of claim 2, further comprising a
desired steering sensor in communication with the controller, the
desired steering sensor configured to provide a signal indicative
of a desired steering angle, the controller configured to regulate
automatic articulation to zero within a dead band range of desired
steering angles.
4. The articulation control system of claim 2, wherein the
controller is configured to regulate automatic articulation to zero
when the actual steering angle is within the dead band range of
actual steering angles for a predetermined period of time.
5. The articulation control system of claim 4, further comprising
an actual articulation sensor in communication with the controller,
the actual articulation sensor configured to provide a signal
indicative of an actual articulation angle, the controller
configured to regulate automatic articulation to zero when the
actual articulation angle is within a dead band range of actual
articulation angles proximate to zero.
6. The articulation control system of claim 5, wherein the
controller is configured to regulate automatic articulation to zero
when the actual articulation angle is approaching zero.
7. The articulation control system of claim 6, wherein the
controller is configured to set a target articulation angle to zero
and set a dead band on an articulation error in order to regulate
automatic articulation to zero.
8. The articulation control system of claim 7, wherein the
controller is configured to stop regulating automatic articulation
to zero when the actual steering angle is outside the dead band
range of actual steering angles.
9. The articulation control system of claim 3, wherein the
controller is configured to stop regulating automatic articulation
to zero when the desired steering angle is outside the dead band
range of desired steering angles.
10. The articulation control system of claim 1, wherein the
controller is configured to set a standard dead band on an
articulation error.
11. A method for controlling an articulation of a machine having a
controller, the method comprising: the controller determining the
machine is driving in a straight line direction of travel; and the
controller increasing a standard dead band on articulation error
upon determining the machine is driving in the straight line
direction of travel.
12. The method of claim 11, further comprising the controller
increasing a standard dead band on articulation error in order to
decrease sensitivity to minor steering corrections when the machine
is operating in an automatic articulation mode.
13. The method of claim 11, further comprising the controller
receiving a signal from a timer indicative of an elapsed
predetermined period of time, and the controller determining the
machine is driving in a straight line direction of travel based on
the signal received from the timer.
14. The method of claim 11, further comprising the controller
receiving a signal from an actual steering sensor indicative of an
actual steering angle, and the controller determining the machine
is driving in a straight line direction of travel based on the
signal received from the actual steering sensor.
15. The method of claim 11, further comprising the controller
receiving a signal from an actual articulation sensor indicative of
an actual articulation angle, and the controller determining the
machine is driving in a straight line direction of travel based on
the signal received from the actual articulation sensor.
16. An articulated machine, comprising: a first frame including a
first traction device and a steering apparatus operable to control
an actual steering angle of the first traction device; a second
frame pivotally coupled to the first frame at an articulation
joint, the second frame including a second traction device; an
actual steering sensor configured to provide a signal indicative of
the actual steering angle of the first traction device; and a
controller in operative communication with the first frame, the
second frame, and the actual steering sensor, the controller
configured to regulate an articulation angle between the first
frame and the second frame to zero when the actual steering angle
of the first traction device is within a dead band range of actual
steering angles.
17. The articulated machine of claim 16, further comprising a timer
in communication with the controller, the controller configured to
regulate the articulation angle to zero when the actual steering
angle is within the dead band range of actual steering angles for a
predetermined period of time.
18. The articulated machine of claim 17, further comprising a
desired steering sensor in communication with the controller, the
desired steering sensor configured to provide a signal indicative
of a desired steering angle from operator input, the controller
configured to regulate the articulation angle to zero when the
desired steering angle is within a dead band range of desired
steering angles.
19. The articulated machine of claim 17, further comprising an
actual articulation sensor in communication with the controller,
the actual articulation sensor configured to provide a signal
indicative of an actual articulation angle between the first frame
and the second frame, the controller configured to regulate the
articulation angle to zero when the actual articulation angle is
within a dead band range of actual articulation angles proximate to
zero.
20. The articulated machine of claim 19, wherein the controller is
configured to regulate the articulation angle to zero when the
actual articulation angle is approaching zero.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates generally to articulated
machines and, more particularly, to articulation control systems
and methods for articulated machines.
BACKGROUND OF THE DISCLOSURE
[0002] Earth-moving machines, such as motor graders, are typically
used for sculpting a surface of a construction site or roadway to a
final shape and contour. Motor graders may be articulated,
including a front frame and a rear frame connected together at an
articulation joint. For example, the front frame may support a
blade for grading the surface of the construction site or roadway,
and the rear frame may support an operator cab and an engine. The
engine may be operatively coupled to a set of rear tires for
primary propulsion of the machine. The set of rear tires may
include two pairs of tires with two axles in tandem, while the
front frame may include one pair of tires on a front axle.
[0003] Generally, steering of the machine is a function of both
front tire steering and articulation of the front frame relative to
the rear frame. Due to the numerous controls currently needed for
steering, controlling articulation, and positioning the blade,
operators may experience difficulty and fatigue during operation.
As a result, there is a need for sophisticated articulation control
systems and methods that help minimize operator input for
articulation control, thereby enabling convenient overall operation
of the machine.
[0004] For example, U.S. Pat. No. 8,548,680, entitled, "Steering
System with Automated Articulation Control," describes a system and
method of improving steering control for an articulated machine
having front wheel steering. The system of the '680 patent receives
steering commands from the operator. Based upon the steering
commands or signals indicative of front wheel steering angle, the
system of the '680 patent automatically commands articulation so
that the rear frame will always be tracking the front frame of the
machine. Thus, a controller of the '680 patent automatically
controls an articulation angle based on a steering angle.
[0005] It should be appreciated that the solution of any particular
problem is not a limitation on the scope of this disclosure or of
the attached claims except to the extent expressly noted.
Additionally, this background section discusses observations made
by the inventors; the inclusion of any observation in this section
is not an indication that the observation represents known prior
art except that the contents of the indicated patent represent a
publication. With respect to the identified patent, the foregoing
summary thereof is not intended to alter or supplement the prior
art document itself; any discrepancy or difference should be
resolved by reference to the document itself.
SUMMARY OF THE DISCLOSURE
[0006] In accordance with one embodiment, an articulation control
system for a machine may include an actual steering sensor
configured to provide a signal indicative of an actual steering
angle, a timer configured to provide a signal indicative of an
elapsed predetermined period of time, and a controller in
communication with the actual steering sensor and the timer. The
controller may be configured to regulate automatic articulation to
zero based on signals received from the actual steering sensor and
the timer.
[0007] In accordance with another embodiment, a method for
controlling an articulation of a machine is disclosed. The machine
may have a controller. The method may comprise the controller
determining the machine is driving in a straight line direction of
travel; and the controller increasing a standard dead band on
articulation error upon determining the machine is driving in the
straight line direction of travel.
[0008] In accordance with yet another embodiment, an articulated
machine may include a first frame, a second frame, and actual
steering sensor, and a controller. The first frame may include a
first traction device and a steering apparatus operable to control
an actual steering angle of the first traction device. The second
frame may be pivotally coupled to the first frame at an
articulation joint and may include a second traction device. The
actual steering sensor may be configured to provide a signal
indicative of the actual steering angle of the first traction
device. The controller may be in operative communication with the
first frame, the second frame, and the actual steering sensor. The
controller may be configured to regulate an articulation angle
between the first frame and the second frame to zero when the
actual steering angle of the first traction device is within a dead
band range of actual steering angles.
[0009] These and other aspects and features will become more
readily apparent upon reading the following detailed description
when taken in conjunction with the accompanying drawings. In
addition, although various features are disclosed in relation to
specific exemplary embodiments, it is understood that the various
features may be combined with each other, or used alone, with any
of the various exemplary embodiments without departing from the
scope of the disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a side view of a machine constructed in accordance
with one embodiment of the present disclosure;
[0011] FIG. 2 is a diagrammatic top view of the machine of FIG.
1;
[0012] FIG. 3 is a perspective view of a joystick of the machine of
FIG. 1;
[0013] FIG. 4 is a block diagram of an articulation control system
for the machine of FIG. 1; and
[0014] FIG. 5 is a flowchart illustrating a process for controlling
an articulation of a machine according to another embodiment.
[0015] While the present disclosure is susceptible to various
modifications and alternative constructions, certain illustrative
embodiments thereof will be shown and described below in detail.
The disclosure is not limited to the specific embodiments
disclosed, but instead includes all modifications, alternative
constructions, and equivalents thereof.
DETAILED DESCRIPTION
[0016] The present disclosure provides a system and method for
controlling an articulation of a machine. The system and method
provide an automatic articulation control with a dynamic dead band
in order to eliminate oversensitivity to minor steering corrections
around center. For example, when an operator is steering the
machine in a straight line direction of travel (e.g., over an
uneven surface), instead of automatic articulation following a
steering angle of the machine, an articulation angle may be
regulated to zero within a dead band range for steering angles. As
a result, undesired articulation or wiggling of the machine during
an automatic articulation mode may be reduced. In addition, the
system and method may require certain conditions to be met before
applying the dead band in order to ensure articulation to zero is
appropriate.
[0017] Reference will now be made in detail to specific embodiments
or features, examples of which are illustrated in the accompanying
drawings. Generally, corresponding reference numbers will be used
throughout the drawings to refer to the same or corresponding
parts.
[0018] FIG. 1 illustrates a machine 20 consistent with certain
embodiments of the present disclosure. It is to be understood that
although the machine 20 is illustrated as a motor grader, the
machine may be of any other articulated type. As used herein, the
term "machine" refers to a mobile machine that performs a driven
operation involving physical movement associated with a particular
industry, such as, without limitation, landscaping, construction,
mining, agriculture, transportation, forestry, etc.
[0019] Non-limiting examples of machines include commercial and
industrial machines, such as, motor graders, trucks, earth-moving
vehicles, mining vehicles, backhoes, material handling equipment,
agricultural equipment, marine vessels, on-highway vehicles, or
other types of machines that operate in a work environment. It is
also to be understood that the machine 20 is shown primarily for
illustrative purposes to assist in disclosing features of various
embodiments, and that FIG. 1 does not depict all of the components
of a machine.
[0020] As shown in FIGS. 1-2, machine 20 may include a front frame
22, a rear frame 24, and an articulation joint 26 pivotally
connecting the front frame 22 and the rear frame 24. The machine
may further include a blade assembly 28 (and/or other work
implement), which may be used to move a blade 30 for grading a
surface of a construction site or roadway. The front frame 22 may
support the blade assembly 28 and a front axle 32 with a pair of
front wheels 34 (or other traction devices). The rear frame 24 may
support an operator cab 36, an engine 38 (or other power source),
and rear axles 40 with two pairs of rear wheels 42 (or other
traction devices) in tandem. It is to be understood that other
configurations are certainly possible.
[0021] Steering of the machine 20 may be accomplished through a
combination of both front wheel steering and machine articulation.
A steering apparatus 44, which may include a linkage and a
hydraulic cylinder (not shown), may be used for steering the front
wheels 34 about front wheel pivot points 46. For example, as shown
in FIG. 2, an actual steering angle .theta. may be defined between
a longitudinal axis 48 parallel to a longitudinal axis 50 of the
front frame 22 and a longitudinal axis 52 of the front wheels 34.
An origin of the actual steering angle .theta. may be at the front
wheel pivot point 46.
[0022] In one example, the actual steering angle .theta. may range
from -50.degree. to 50.degree., with 0.degree. being attributed to
an alignment of the longitudinal axis 52 of the front wheels 34 to
the longitudinal axis 48, a positive .theta. associated with right
steering, and a negative .theta. associated with left steering.
However, other numerical ranges and references may certainly be
possible. Although only shown in connection with a right front
wheel of the front wheels 34, it is to be understood that the
actual steering angle .theta. applies equally to a left front wheel
of the front wheels 34 as well.
[0023] Connected between the front frame 22 and the rear frame 24,
articulation cylinders 54 may be used to pivot the front frame 22
relative to the rear frame 24 about the articulation joint 26. For
example, as shown in FIG. 2, an actual articulation angle .alpha.
may be defined between the longitudinal axis 50 of front frame 22
and a longitudinal axis 56 of rear frame 24. An origin of the
actual articulation angle .alpha. may be at the articulation joint
26. In one example, the actual articulation angle .alpha. may range
from -20.degree. to 20.degree., with 0.degree. being attributed to
an alignment of the longitudinal axes 50, 56 of the front and rear
frames 22, 24, a positive angle .alpha. associated with a right
articulation, and a negative angle .alpha. associated with a left
articulation in this particular example. However, other numerical
ranges and references may certainly be possible.
[0024] An operator of the machine 20 may manually control steering
and articulation via an operator interface. As shown in FIG. 3, the
operator may manipulate a joystick 58 and/or other type of operator
control in order to input a desired steering angle .beta. and a
desired articulation angle .omega. (or a desired rate of change of
the articulation angle .alpha.). For example, the operator may tilt
the joystick 58 in a right direction 60 or a left direction 62
relative to a neutral axis 64 in order to steer the machine 20
right or left, respectively.
[0025] A position of the joystick 58 relative to the neutral axis
64 may represent the desired steering angle .beta., or an angular
amount by which the operator wishes to steer the machine 20 in
order to control front wheel steering and the actual steering angle
.theta.. For example, a positive .beta. may be associated with the
joystick 58 tilted in the right direction 60, a negative .beta. may
be associated with the joystick 58 tilted in the left direction 62,
and 0.degree. may be associated with the joystick 58 in alignment
with the neutral axis 64. However, other numerical ranges and
references may certainly be possible.
[0026] In order to manually control articulation, the operator may
twist the joystick 58 in a clockwise direction 66 or a
counter-clockwise direction 68 about the neutral axis 64 in order
to articulate the machine 20 right or left, respectively. An amount
of rotation of the joystick 58 about the neutral axis 64 may
represent the desired articulation angle .omega., or an angular
rate of change of articulation by which the operator wishes to
articulate the machine 20 in order to control the front and rear
frames 22, 24 and the actual articulation angle .alpha.. Although
other configurations are possible, a positive .omega. may be
associated with the joystick 58 rotated in the clockwise direction
66, a negative .omega. may be associated with the joystick 58
rotated in the counter-clockwise direction 68, and 0.degree. may be
associated with no rotation of the joystick 58.
[0027] It is to be understood that other types of operator controls
than the joystick 58, described herein, may be used to control
steering and articulation. For example, push button controls,
steering wheels, etc. may be used in place of or in addition to the
joystick 58. Furthermore, steering and articulation may be
controlled independent of each other, e.g., two separate joysticks,
one for steering and one for articulation, and other configurations
are certainly possible.
[0028] FIG. 3 may illustrate the joystick 58 in a neutral position.
However, it is to be understood that the joystick 58 may be moved
in a wide variety of positions for manual steering and articulation
of the machine 20.
[0029] Referring now to FIG. 4, with continued reference to FIGS.
1-3, the machine 20 may include an articulation control system 70.
The articulation control system 70 may comprise a controller 72 in
communication with a hydraulic system 74, a plurality of sensors
76, 78, and 80, and a timer 82. The controller 72 may comprise a
processor (e.g., "computer processor") or processor-based device
that may include or be associated with a non-transitory computer
readable storage medium having stored thereon computer-executable
instructions. It is understood that the articulation control system
70 and controller 72 may include other hardware, software,
firmware, or combinations thereof.
[0030] The hydraulic system 74 may be configured to operate
articulation cylinders 54, thereby controlling the actual
articulation angle .alpha. between the front and rear frames 22,
24, based on signals received from the controller 72. For example,
the hydraulic system 74 may include one or more pumps, motors,
valves, cylinders, controllers, hydraulic drives, electric drives,
combinations thereof, etc. Furthermore, the signals from the
controller 72 may be, for example, electro-hydraulic signals that
control operation of the hydraulic system 74.
[0031] The plurality of sensors may include a desired steering
sensor 76, an actual steering sensor 78, and an actual articulation
sensor 80. The desired steering sensor 76 may be configured to
provide a signal indicative of a desired steering angle to the
controller 72. For example, the desired steering sensor 76 may
detect the desired steering angle .beta. (FIG. 3) of the joystick
58 based on operator input. More specifically, the desired steering
sensor 76 may be used to measure a position of the joystick, which
may be transformed into a desired steering angle of the operator.
However, other types of sensors and configurations may be used to
provide a signal indicative of the desired steering angle.
[0032] The actual steering sensor 78 may be configured to provide a
signal indicative of an actual steering angle to the controller 72.
More specifically, the actual steering sensor 78 may directly or
indirectly detect the actual steering angle .theta. (FIG. 2) and/or
a position of the front wheels 34 (FIG. 2). For example, the actual
steering sensor 78 may comprise an angular sensor used to directly
measure an angular position of the front wheels 34.
[0033] In another example, the actual steering sensor 78 may
comprise a cylinder displacement sensor which may measure a linear
position of steering cylinders of the front wheels 34. Measurements
gathered by the cylinder displacement sensor may then be used by
the controller 72 to calculate the actual steering angle .theta..
However, it is to be understood that other types of sensors and
configurations may also be used to provide a signal indicative of
the actual steering angle.
[0034] The actual articulation sensor 80 may be configured to
provide a signal indicative of an actual articulation angle to the
controller 72. More specifically, the actual articulation sensor 80
may directly or indirectly detect the actual articulation angle
.alpha. (FIG. 2). For example, the actual articulation sensor 80
may comprise an angular sensor that directly detects the actual
articulation angle .alpha. (FIG. 2) at the articulation joint 26
between the front and rear frames 22, 24.
[0035] In another example, the actual articulation sensor 80 may
comprise a linear cylinder position sensor, which may measure a
length of the articulation cylinder 54. Measurements gathered by
the linear cylinder position sensor may then be used by the
controller 72 to calculate the actual articulation angle .alpha. or
to determine the actual articulation angle .alpha. based on known
corresponding cylinder lengths. However, it is to be understood
that other types of sensors and configurations may also be used to
provide a signal indicative of the actual articulation angle.
[0036] The timer 82 may be configured to provide a signal
indicative of an elapsed predetermined period of time. Separate
from or integral to the controller 72, the timer 82 may be
configured to measure an amount of time that has passed. For
example, the timer 82 may receive a command from the controller 72
to start tracking a period of time. Once the period of time has
elapsed, the timer 82 may send a signal to the controller 72
indicating the period of time has elapsed.
[0037] Furthermore, the articulation control system 70 may provide
automatic articulation control of the machine 20. For example, the
operator may select (e.g., via the operator interface) to operate
the machine 20 in an auto-articulation mode. In auto-articulation
mode, the control system 70 may automatically control the actual
articulation angle .alpha. of the machine 20 to follow the actual
steering angle .theta.. More specifically, based on the actual
steering angle .theta. detected by the actual steering sensor 78,
the controller 72 may calculate a target articulation angle
depending on parameters and formulae programmed into a memory
associated with the controller 72.
[0038] In one example, with the actual steering angle .theta. range
from -50.degree. to 50.degree. and the actual articulation angle
.alpha. range from -20.degree. to 20.degree., the controller 72 may
calculate the target articulation angle based on a preprogrammed
relationship with the actual steering angle .theta.. For instance,
when the actual steering angle .theta. is within -10.degree. to
10.degree., articulation may have a linear relationship. Therefore,
the target articulation angle set by the controller 72 may be the
same as the actual steering angle .theta.. However, it is to be
understood other correlations between the actual steering angle
.theta. and target articulation angle are certainly possible.
[0039] When the actual steering angle .theta. is outside of
-10.degree. to 10.degree., then a ratio of the actual steering
angle .theta. to the target articulation angle may be four-to-one
(4:1). Therefore, if the actual steering angle .theta. is between
-50.degree. to -10.degree. or between 10.degree. to 50.degree.,
then the controller 72 may calculate the target articulation angle
by dividing the actual steering angle .theta. by four (4). However,
other correlations between the actual steering angle .theta. are
certainly possible.
[0040] Based on the target articulation angle and the actual
articulation angle .alpha. detected by the actual articulation
sensor 80, the controller may determine an articulation error. The
articulation error may correspond to a difference between the
actual articulation angle .alpha. and the target articulation
angle. For example, to determine the articulation error, the actual
articulation angle .alpha. may be subtracted from the target
articulation angle. After determining the articulation error, the
controller 72 may send a corresponding signal to the hydraulic
system 74 in order to adjust the actual articulation angle .alpha.
to achieve the target articulation angle.
[0041] Turning now to FIG. 5, with continued reference to FIGS.
1-4, a flowchart illustrating a process 90 for controlling
articulation of the machine 20 is shown. In the auto-articulation
mode, the articulation control system 70 may provide a wider dead
band in order to decrease sensitivity to small steering
corrections, such as, when the operator is steering the machine in
a straight line direction of travel. More specifically, the
controller 72 of the articulation control system 70 may be
programmed according to the process 90 illustrated in FIG. 5.
[0042] At block 92, the controller 72 may be configured to apply a
standard dead band on the articulation error in order to filter
noise on the signal for the articulation error. A small amount of
articulation error may correspond to the noise on the actual
steering angle .theta.. Therefore, instead of commanding
articulation to follow steering, the controller 72 may not change
the actual articulation angle .alpha., thereby reducing an effect
of the noise on the steering signal.
[0043] For example, the standard dead band may have a total range
of 0.5.degree. on the articulation error, such as, from
-0.25.degree. to 0.25.degree., although other ranges are certainly
possible. When the articulation error is within the standard dead
band, the controller 72 may set the articulation error to zero such
that articulation is not moved. In so doing, vibration of the
machine 20 due to the articulation tracking the noise on the
steering is eliminated when the machine 20 in the auto-articulation
mode.
[0044] The controller 72 may be configured to increase the standard
dead band to a larger dead band range in order to eliminate
oversensitivity to minor steering corrections. For example, when an
operator is steering the machine in a straight line direction of
travel, such as, over an uneven surface, the machine 20 may
experience undesired articulation or wiggling when articulation is
commanded to follow steering in the auto-articulation mode. To
address this, the controller 72 may be configured to regulate
articulation to zero within a dead band range of steering
angles.
[0045] At block 94, the controller 72 may be configured to
determine whether the actual steering angle .theta. is within a
dead band range of actual steering angles. For example, the dead
band range of actual steering angles may be from -6.5.degree. to
6.5.degree., although other ranges are certainly possible. The dead
band range of actual steering angles may be programmed into the
memory associated with the controller 72. The controller 72 may
determine whether the actual steering angle .theta. is within the
dead band range of actual steering angles based on signals
indicative of the actual steering angle .theta. received from the
actual steering sensor 78.
[0046] If the actual steering angle .theta. is outside of the dead
band range of actual steering angles, this may signify that the
operator is not steering the machine in a straight line direction
of travel. Therefore, the process 90 may proceed to block 92, and
the standard dead band does not change. If the actual steering
angle .theta. is within the dead band range of actual steering
angles, this may signify that the operator is steering the machine
in a straight line direction of travel. Therefore, the process 90
may proceed to block 96.
[0047] The controller 72 may be configured to check that certain
conditions are met before increasing the standard dead band. For
example, when the operator performs a full steering sweep from one
side to another, the actual steering angle .theta. may be within
the dead band range of actual steering angles. However, because the
operator is performing a full steering sweep, it may be undesirable
for articulation to be regulated to zero in the auto-articulation
mode. To address this, at block 96, the controller 72 may be
configured to wait for a predetermined period of time.
[0048] For example, the predetermined period of time may be three
seconds (3 s), although other time periods are certainly possible.
The predetermined period of time may be programmed into the memory
associated with the controller 72. Based on signals received from
the timer 82, the controller 72 may determine when the
predetermined period of time has elapsed. By waiting the
predetermined period of time to elapse, the articulation control
system 70 may recognize whether the operator is steering the
machine from one side to another, such as, in a full sweep, or the
operator is keeping the machine at center (within the dead band
range of actual steering angles) in a straight line direction of
travel.
[0049] It is to be understood that other methods may be used to
determine if the machine is driving in a straight line direction of
travel. For example, the controller 72 may calculate a derivative
of the actual steering angle and/or the desired steering angle.
Using the derivative of the actual and/or desired steering angle,
the controller 72 may then determine whether the wheels are
sweeping through center or slowing down to a stop.
[0050] After the predetermined period of time has elapsed (or the
controller 72 has determined whether the machine 20 is driving
straight), the process 90 may proceed to block 98. At block 98, the
controller may be configured to determine if the actual steering
angle .theta. is still within the dead band range for actual
steering angles. If the actual steering angle .theta. is outside
the dead band range for actual steering angles after the
predetermined period of time has elapsed, this may indicate that
the operator is steering the machine from one side to the other,
such as, in a full sweep. Therefore, the process 90 may proceed to
block 92, and the standard dead band does not change.
[0051] If the actual steering angle .theta. is within the dead band
range for actual steering angles after the predetermined period of
time has elapsed, this may further indicate that the operator is
keeping the machine at center and trying to steer in a straight
line direction of travel. However, there may be instances when the
actual steering angle .theta. is within the dead band range for
actual steering angles for the predetermined period of time but it
is undesirable for articulation to be regulated to zero. For
example, the operator may have unintentionally stopped steering
while on a turn (e.g., when operating the blade 30 or other
implements), and automatically regulating articulation to zero is
undesired. To address this, at block 98, the controller may also be
configured to determine if the actual articulation angle .alpha. is
within a dead band range of actual articulation angles.
[0052] In one example, the dead band range of actual articulation
angles may be near zero, e.g., from -0.5.degree. to 0.5.degree.,
although other ranges are certainly possible. The dead band range
of actual articulation angles may be programmed into the memory
associated with the controller 72. Based on signals received from
the actual articulation sensor 80, the controller 72 may determine
whether the actual articulation angle .alpha. is within the dead
band range of actual articulation angles.
[0053] If the actual articulation angle .alpha. is outside the dead
band range of actual articulation angles, this may indicate that
the operator stopped steering while on a turn. Therefore, the
process 90 may proceed to block 92, and the standard dead band does
not change. If the actual articulation angle .alpha. is within the
dead band range of actual articulation angles, this may further
indicate that the operator is keeping the machine at center without
much articulation and trying to steer in a straight line direction
of travel. Therefore, the process 90 may proceed to block 100.
[0054] At block 100, a last condition the controller 72 may check
before increasing the standard dead band is whether articulation is
coming towards center. In order to determine whether the actual
articulation angle .alpha. is approaching zero, the controller 72
may compare a sign (or polarity) of the actual articulation angle
.alpha. to a sign (or polarity) of the articulation error. If the
actual articulation angle .alpha. and the articulation error have
the same sign, then articulation may be approaching zero. If the
actual articulation angle .alpha. and the articulation error have
opposite signs, then articulation may be moving away from zero.
[0055] In addition, if the target articulation angle is zero and
the actual articulation angle .alpha. is non-zero, articulation may
be approaching zero. If the target articulation angle is non-zero
and the actual articulation angle .alpha. is zero, articulation may
be moving away from zero. If the target articulation angle is zero
and the actual articulation angle .alpha. is zero, articulation may
be at zero. However, other methods may be used to detect whether
articulation is coming towards center (e.g., articulation angle is
zero). For example, the actual articulation angle .alpha. may be
captured at different moments of time and subtracted from each
other in order to determine a direction of movement.
[0056] When the actual articulation angle .alpha. is moving away
from zero, it may undesirable to force machine articulation to
zero. Therefore, the process 90 may proceed to block 92, and the
standard dead band does not change. When the actual articulation
angle .alpha. is approaching zero (or at zero), this may further
indicate that the operator is trying to steer in a straight line
direction of travel. Therefore, the process 90 may proceed to block
102.
[0057] At block 102, the controller 72 may be configured to
regulate automatic articulation of the machine 20 to zero. After
determining that the actual steering angle .theta. is within the
dead band range of actual steering angles for the predetermined
period of time and the actual articulation angle .alpha. proximate
to and approaching zero, the controller 72 may move the actual
articulation angle .alpha. to zero and may increase the standard
dead band on articulation error.
[0058] More specifically, the controller 72 may set the target
articulation angle to zero. Therefore, the actual articulation
angle .alpha. is forced to zero. In addition, the controller 72 may
set an increased dead band range on articulation error. For
example, the increased dead band range on articulation error may be
from -6.5.degree. to 6.5.degree., although other ranges are
certainly possible. In so doing, the dead band may be increased
from the standard dead band (e.g., from -0.25.degree. to
0.25.degree. increased to -6.5.degree. to 6.5.degree.).
[0059] When the articulation error is within the dead band, the
controller 72 may set the desired articulation angle to zero,
thereby keeping the actual articulation angle .alpha. at zero.
Therefore, within the dead band on articulation error, articulation
does not follow steering. In so doing, undesired articulation or
wiggling due to oversensitivity to minor steering corrections is
eliminated when the operator is trying to steer the machine 20 in a
straight line direction of travel in the auto-articulation
mode.
[0060] At block 104, the controller 72 may be configured to
determine whether the actual steering angle .theta. is staying
within the dead band range of actual steering angles. As discussed
above in reference to block 94, the dead band range of actual
steering angles may be from -6.5.degree. to 6.5.degree., although
other ranges are certainly possible. Based on signals received from
the actual steering sensor 78, the controller 72 may determine
whether the actual steering angle .theta. is within the dead band
range of actual steering angles.
[0061] At block 104, the controller 72 may also be configured to
determine whether the desired steering angle .beta. is staying
within a dead band range of desired steering angles. The dead band
range of desired steering angles may be from -10.degree. to
10.degree., although other ranges are certainly possible. The dead
band range of desired steering angles may be programmed into the
memory associated with the controller 72. Based on signals received
from the desired steering sensor 76, the controller 72 may
determine whether the desired steering angle .beta. is within the
dead band range of desired steering angles.
[0062] If the actual steering angle .theta. is outside the dead
band range of actual steering angles or the desired steering angle
.beta. is outside the dead band range of desired steering angles,
the controller 72 may stop regulating automatic articulation to
zero, and articulation may follow steering in the auto-articulation
mode. For example, the process 90 may proceed to block 92, and the
dead band on articulation error may be re-set or shrink down to the
standard dead band (e.g., from -6.5.degree. to 6.5.degree.
decreased to -0.25.degree. to 0.25.degree.). If the actual steering
angle .theta. is within the dead band range of actual steering
angles and the desired steering angle .beta. is within the dead
band range of desired steering angles, the process 90 may proceed
to block 102, and articulation stays at zero (instead of tracking
steering).
[0063] Automatic articulation of the machine 20 may end when the
operator selects (e.g., via the operator interface) to exit the
auto-articulation mode. It will be understood that the flowchart in
FIG. 5 is shown and described as an example only to assist in
disclosing the features of the system and that more or fewer steps
than shown, in a same or different order, may be included in the
method corresponding to the various features described above for
the disclosed system without departing from the scope of the
present disclosure.
INDUSTRIAL APPLICABILITY
[0064] In general, the foregoing disclosure finds utility in
various industrial applications, such as in earthmoving,
construction, industrial, agricultural, and forestry machines. In
particular, the disclosed operator coaching system and method may
be applied to motor graders, trucks, earth-moving vehicles, mining
vehicles, backhoes, material handling equipment, agricultural
equipment, marine vessels, on-highway vehicles, and the like.
[0065] By applying the disclosed articulation control system to a
machine, sophisticated and advanced automatic articulation may be
provided. In particular, a controller may be configured to apply a
dynamic dead band that changes according to sensed parameters and
preset conditions, thereby adding enhanced intelligence to an
auto-articulation mode. The disclosed articulation control system
may determine whether an operator is steering the machine in a
straight line direction of travel, and thus, regulate automatic
articulation to zero instead of responding to steering commands. In
so doing, undesired articulation or wiggling due to oversensitivity
to minor steering corrections in the auto-articulation mode may be
eliminated. As a result, the disclosed system minimizes operator
input for articulation control and enables a convenient overall
operation of the machine.
[0066] While the foregoing detailed description has been given and
provided with respect to certain specific embodiments, it is to be
understood that the scope of the disclosure should not be limited
to such embodiments, but that the same are provided simply for
enablement and best mode purposes. The breadth and spirit of the
present disclosure is broader than the embodiments specifically
disclosed and encompassed within the claims appended hereto.
Moreover, while some features are described in conjunction with
certain specific embodiments, these features are not limited to use
with only the embodiment with which they are described, but instead
may be used together with or separate from, other features
disclosed in conjunction with alternate embodiments.
* * * * *