U.S. patent application number 09/736901 was filed with the patent office on 2002-06-13 for method for determining a position and heading of a work machine.
Invention is credited to Alig, Jeffrey S., Kalafut, James J..
Application Number | 20020072840 09/736901 |
Document ID | / |
Family ID | 24961787 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020072840 |
Kind Code |
A1 |
Kalafut, James J. ; et
al. |
June 13, 2002 |
METHOD FOR DETERMINING A POSITION AND HEADING OF A WORK MACHINE
Abstract
A method for determining a position and a heading of a work
machine having a work implement controllably attached. The method
includes the steps of positioning the work machine at a desired
work location, determining an initial position and heading of the
work machine in site coordinates, determining a position of the
work implement relative to the work machine, positioning the work
implement at a desired reference point, determining the position of
the work implement at the reference point in site coordinates,
periodically positioning the work implement at the reference point
during work operations, and determining a new position and heading
of the work machine as a function of the position of the work
implement relative to the work machine.
Inventors: |
Kalafut, James J.; (Peoria,
IL) ; Alig, Jeffrey S.; (Morton, IL) |
Correspondence
Address: |
Steve D. Lundquist
Caterpillar Inc.
Intellectual Property Department, AB6490
100 N.E. Adams Street
Peoria
IL
61629-6490
US
|
Family ID: |
24961787 |
Appl. No.: |
09/736901 |
Filed: |
December 13, 2000 |
Current U.S.
Class: |
701/50 ; 340/992;
701/469 |
Current CPC
Class: |
G01C 21/00 20130101 |
Class at
Publication: |
701/50 ; 701/210;
340/992 |
International
Class: |
G01C 021/32 |
Claims
1. A method for determining a position and a heading of a work
machine having a work implement controllably attached, including
the steps of: positioning the work machine at a desired work
location; determining an initial position and heading of the work
machine in site coordinates; determining a position of the work
implement relative to the work machine; positioning the work
implement at a desired reference point; determining the position of
the work implement at the reference point in site coordinates;
periodically positioning the work implement at the reference point
during work operations; and determining a new position and heading
of the work machine as a function of the position of the work
implement relative to the work machine.
2. A method, as set forth in claim 1, wherein determining an
initial position and heading of the work machine includes the steps
of: determining a plurality of positions of the work machine in
site coordinates as the work machine approaches the desired work
location; and determining the initial position and heading of the
work machine at the desired work location as a function of the
plurality of determined positions.
3. A method, as set forth in claim 1, wherein determining a
position of the work implement relative to the work machine
includes the step of sensing an angular position of at least one
linkage connecting the work implement to the work machine.
4. A method, as set forth in claim 1, wherein positioning the work
implement at a desired reference point includes the step of moving
the work implement to a point near the work location that provides
a reference in fixed site coordinates, the desired reference point
being adapted to remain fixed and accessible during work
operations.
5. A method, as set forth in claim 1, wherein periodically
positioning the work implement at the reference point includes the
step of positioning the work implement at the reference point in
response to the work machine moving from the initial position and
heading.
6. A method, as set forth in claim 1, wherein periodically
positioning the work implement at the reference point is performed
by an operator of the work machine to periodically calibrate the
position and heading of the work machine.
7. A method, as set forth in claim 2, wherein determining an
initial position and heading further includes determining an angle
of inclination of the work machine.
Description
TECHNICAL FIELD
[0001] This invention relates generally to a method for determining
a position and heading of a work machine at a work location and,
more particularly, to a method for periodically checking the
position and heading of the work machine by comparing with a known
reference point.
BACKGROUND ART
[0002] Work operations which require the use of work machines, for
example, earthworking operations requiring earthworking machines,
must be performed with some degree of accuracy. However, the power
required to perform the work, and the inherent harshness of the
work environment, often make accuracy difficult to achieve. For
example, it is often desired to dig trenches and the like using a
work machine such as a backhoe loader. The backhoe loader must
frequently be moved as the trench is created. If the heading of the
backhoe loader shifts during excavation, as is often the case
during digging, the operator must be careful not to drift off the
intended course and dig the trench along the wrong boundaries.
[0003] Furthermore, work machines are becoming increasingly
dependent on advances in technology. For example, electro-hydraulic
work machines, such as the backhoe loader exemplified above, are
increasingly automating many of the work functions that typically
were performed by skilled operators. As an example, position and
heading determining systems may be used to guide a work machine
along an intended path. However, the harshness of the work
environment, e.g., rocks, clay, and other obstructions in the soil,
may shift the work machine off its determined heading, for example
during trenching operations. Therefore, as the work machine moves
to follow the trench line being created, the work machine may drift
off its intended course, thus introducing errors in the
excavation.
[0004] The present invention is directed to overcoming one or more
of the problems as set forth above.
DISCLOSURE OF THE INVENTION
[0005] In one aspect of the present invention a method for
determining a position and a heading of a work machine having a
work implement controllably attached is disclosed. The method
includes the steps of positioning the work machine at a desired
work location, determining an initial position and heading of the
work machine in site coordinates, determining a position of the
work implement relative to the work machine, positioning the work
implement at a desired reference point, determining the position of
the work implement at the reference point in site coordinates,
periodically positioning the work implement at the reference point
during work operations, and determining a new position and heading
of the work machine as a function of the position of the work
implement relative to the work machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a diagrammatic illustration of a work machine at a
work location;
[0007] FIG. 2 is a diagrammatic illustration of a work machine
traveling to a work location;
[0008] FIG. 3 is a block diagram illustrated a preferred embodiment
of the present invention; and
[0009] FIG. 4 is a flow diagram illustrating a preferred method of
the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0010] Referring to the drawings, and with particular reference to
FIG. 1, a work machine 102 at a work location 106 is shown.
Preferably, the work machine 102 has a work implement 104
controllably attached.
[0011] The work machine 102 in FIG. 1 is shown as an earthworking
machine 110, in this example a backhoe loader. However, other types
of work machines may be used in the present invention, for example,
excavators, front shovels, trenchers, and the like.
[0012] In the preferred embodiment, the work implement 104 is a
bucket 116. However, other types of work implements, e.g., blades,
boring tools, rippers, and the like, may be used as well.
Preferably, the bucket 116 is attached to the work machine 102 by
at least one linkage, for example, a boom 112 and a stick 114, as
is commonly used with earthworking machines of the type depicted in
FIG. 1.
[0013] A reference point 108, shown in FIG. 1, is used to provide a
reference for a position and a heading of the work machine 102, as
is discussed in more detail below. In the preferred embodiment, the
reference point 108 is a point that is easily recognizable by an
operator of the work machine 102, is not likely to be moved from
its present position at the work location 106, and may readily be
referred to by the operator at periodic intervals. Examples of
suitable reference points include, but are not limited to, rocks,
flags, markers, trees, and the like.
[0014] Referring to FIG. 3, a block diagram illustrating a
preferred embodiment of the present invention is shown. A
controller 302, preferably located on the work machine 102, is
adapted to receive information from various sensors and systems,
and responsively determine a position and heading of the work
machine 102.
[0015] A machine position determining system 304, located on the
work machine 102, is adapted to determine the position of the work
machine 102, preferably in site coordinates, i.e., with reference
to a coordinate system relative to the work location 106. A
suitable example of a coordinate system is a Cartesian coordinate
system having x,y,z coordinates. However, other types of coordinate
systems, e.g., latitude and longitude with respect to a fixed
point, polar coordinates, and the like may be used as well. In the
preferred embodiment, the machine position determining system 304
includes a global position satellite (GPS) system. However, other
types of positioning systems, e.g., laser referencing, dead
reckoning, and the like, may be used.
[0016] With reference to FIG. 2, an example of a technique for
determining an initial position and heading of a work machine 102
is shown. The technique requires a plurality of position
determinations of the work machine 102, for example, at position A
and position B. The position of the work machine 102 at each
position is determined. From the plurality of position
determinations, a line 202 indicating a direction of travel is
determined. The line 202 provides an indication of an initial
heading of the work machine 102. It is understood that, although
only two positions A and B are shown, the plurality of positions
may be of any number desired to determine the initial position and
heading of the work machine 102 as the work machine 102 approaches
the desired work location 106.
[0017] The initial heading determination must be made as the work
machine 102 travels to the desired work location 106. A heading
cannot be obtained by this method when the work machine 102 is not
moving, e.g., when the work machine 102 stops and is positioned to
perform work operations. A system to allow the determination of
heading when a work machine 102 is not moving would require more
elaborate, and thus more costly, sensors and systems. For example,
the use of two GPS antennas would allow heading determination while
the work machine 102 is not moving, but would be more costly. The
present invention, therefore, as described more fully below, is
advantageous with work machines that use one machine position
determining system 304 of the type described above.
[0018] An inclination sensor 306, located on the work machine 102,
is used to determine an angle of inclination of the work machine
102, for example, pitch (fore and aft inclination) and roll (side
to side inclination). The inclination sensor 306 is preferably of a
type that is well known in the art, such as a gyro.
[0019] An implement position determining system 308, located on the
work machine 102, is adapted to determine the position of the work
implement 104 relative to the work machine 102. For example, the
boom 112, stick 114, and bucket 116 of FIG. 1 may have a plurality
of angular sensors, at least one located at each connecting joint,
to sense an angular position of each linkage with respect to each
adjacent linkage. For example, the angle of the boom 112 with
respect to the work machine 102 may be sensed, the angle of the
stick 114 with respect to the boom 112 may be sensed, and the angle
of the bucket 116 with respect to the stick 114 may be sensed.
These sensed angles are then delivered to the controller 302 to
determine the position of the bucket 116 with respect to a known
fixed point on the work machine 102. The above described technique
for determining the position of a work implement 104 with respect
to a work machine 102 is well known in the art and will not be
discussed further.
[0020] Referring to FIG. 4, a flow diagram illustrating a preferred
method of the present invention is shown.
[0021] In a first control block 402, the work machine 102 is
positioned at the desired work location 106. For example, an
earthworking machine 110, such as the backhoe loader depicted in
FIG. 1, is driven to the work location 106, and positioned there to
perform excavating operations. Typically, an earthworking machine
110 is prepared for excavating by stabilizing the excavating
machine 110 using stabilizers (not shown) which help to hold the
earthworking machine 110 in a fixed position as excavation takes
place. However, the loading placed upon the work implement 104
tends to cause the earthworking machine 110 to shift about its
position, thus creating a need for the present invention, as
discussed below.
[0022] In a second control block 404, the initial position and
heading of the work machine 102 is determined, preferably by a
method comparable to the one described above with reference to FIG.
2.
[0023] In a third control block 406, the position of the work
implement 104 relative to the work machine 102 is determined.
Preferably, the position of the work implement 104 is determined by
a method such as or similar to the above-described use of the
implement position determining system 308. Alternatively, the use
of cylinder position sensors (not shown) to sense the position of a
plurality of hydraulic cylinders 118a,b,c may be used, the
hydraulic cylinders 118a,b,c being used to control the positions of
the boom 112, stick 114, and bucket 116. The use of cylinder
position sensors to sense the position of hydraulic cylinders is
well known in the art and will not be discussed further.
[0024] In a fourth control block 408, the work implement 104 is
positioned at the desired reference point 108, preferably by the
operator of the work machine 102 moving the work implement 104 to
the reference point 108 until the work implement 104 touches the
reference point 108.
[0025] The position of the work implement 104 in site coordinates
at the reference point 108 is then determined in a fifth control
block 410. The site coordinates of the reference point 108 then
become a calibration point for future use, since the reference
point 108 is fixed, and therefore, the site coordinates of the
reference point 108 do not change.
[0026] In a sixth control block 412, the work implement 104 is
periodically positioned at the reference point 108 during work
operations, and a new position and heading of the work machine 102
is determined, in a seventh control block 414, as a function of the
position of the work implement 104 relative to the work machine
102. Alternatively, the new position of the work machine 102 may be
determined by the machine position determining system 304 and the
new heading of the work machine 102 may be determined as a function
of the position of the work implement 104 relative to the work
machine 102.
[0027] In one embodiment, the work implement 104 is positioned at
the reference point 108 in response to the work machine 102
knowingly moving from the initial position and heading, for
example, by shifting during a heavily loaded work cycle. In another
embodiment, the operator of the work machine 102 periodically
positions the work implement 104 at the reference point 108 to
calibrate the position and heading of the work machine 102 as a
routine part of the work procedure. In yet another embodiment, the
work implement 104 is positioned at the reference point 108 for
calibration of position and heading prior to moving the work
machine 102 from its fixed position to a next work position. A
combination of the above embodiments may be employed for use in the
present invention.
[0028] Industrial Applicability
[0029] As an example of the present invention in use, a backhoe
loader is commonly used to dig trenches and holes for various
purposes. A backhoe loader is a relatively lightweight machine, and
thus is subject to shifting about from its initial position and
heading as the bucket of the loader encounters heavy loads, such as
boulders, clay deposits, tree roots, and the like.
[0030] In modern electro-hydraulic systems used by an increasing
number of backhoe loaders, it is desired to automate some of the
features that previously were performed by skilled operators,
although with some difficulty at times. For example, when digging a
trench, the backhoe loader is stabilized at a first position and
heading, and is then moved slightly as the trenching progresses.
Automating this process, using modern position determining
technology, helps to maintain trenching operations along a desired
path. However, as the heading of the backhoe loader is changed due
to undesired shifts in position, movement of the backhoe loader
tends to drift off course. With the present invention, however,
undesired changes in position and heading are accounted for by
periodic calibration, and the backhoe loader stays on the desired
path.
[0031] Other aspects, objects, and features of the present
invention can be obtained from a study of the drawings, the
disclosure, and the appended claims.
* * * * *