U.S. patent application number 10/264063 was filed with the patent office on 2004-04-08 for method and system for determining an energy-efficient path of a machine.
This patent application is currently assigned to Deere & Company, a Delaware corporation. Invention is credited to Anderson, Noel Wayne.
Application Number | 20040068352 10/264063 |
Document ID | / |
Family ID | 31993576 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040068352 |
Kind Code |
A1 |
Anderson, Noel Wayne |
April 8, 2004 |
METHOD AND SYSTEM FOR DETERMINING AN ENERGY-EFFICIENT PATH OF A
MACHINE
Abstract
A method and system for determining a work path for a machine
determines a path that minimizes energy consumption of the machine
to enhance a usable duration of an electrical charge of an energy
source or to conserve fuel. A work area is defined and is divisible
into a number of cells. Respective geographic factors associated
with corresponding cells within the work area are defined. An
estimator estimates energy levels, associated with a machine moving
in or between adjacent cells, in corresponding proposed directions
based on at least one geographic factor (e.g., any change in
elevation between or within the adjacent cells). Candidate total
energy levels are determined for moving the machine through the
cells along corresponding alternate proposed work paths for the
work area. A selector selects a preferential work path from the
proposed work paths consistent with the determined lowest energy
level of the candidate total energy levels.
Inventors: |
Anderson, Noel Wayne;
(Fargo, ND) |
Correspondence
Address: |
Darin E. Bartholomew
Patent Department
DEERE & COMPANY
One John Deere Place
Moline
IL
61265-8098
US
|
Assignee: |
Deere & Company, a Delaware
corporation
|
Family ID: |
31993576 |
Appl. No.: |
10/264063 |
Filed: |
October 3, 2002 |
Current U.S.
Class: |
701/25 ; 318/587;
701/533 |
Current CPC
Class: |
A01B 69/008 20130101;
G05D 1/0217 20130101; G05D 2201/0208 20130101; G01S 19/14 20130101;
G05D 1/0219 20130101; G05D 1/0274 20130101 |
Class at
Publication: |
701/025 ;
318/587; 701/209 |
International
Class: |
G01C 021/26 |
Claims
1. A method for determining a work path for a machine, the method
comprising the steps of: defining a work area, the work area being
divisible into a number of cells; defining respective geographic
factors of the cells within the work area; estimating energy
levels, associated with a machine moving in or between adjacent
cells, in corresponding proposed directions based on the geographic
factors associated with the cells; determining a lowest total
energy level for moving the machine in the cells along proposed
work paths for the work area, each proposed work path consisting of
a series of generally parallel rows along selected ones of the
proposed directions; and selecting a preferential work path from
the proposed work paths consistent with the determined lowest
energy level.
2. The method according to claim 1 wherein the geographic factors
comprise elevation data of corresponding cells.
3. The method according to claim 1 wherein the geographic factors
comprise a terrain slope associated with one or more cells in a
work area.
4. The method according to claim 1 wherein the geographic factors
comprise surface condition data on the surface of corresponding
cells.
5. The method according to claim 1 wherein the work area is a
generally rectangular region and wherein the work path comprises a
generally boustrophedon pattern of rows parallel to at least one
side of the generally rectangular region.
6. The method according to claim 1 wherein the determining of the
lowest energy level comprises determining total candidate energy
levels for different proposed paths that cover the work area; and
selecting the lowest total energy level among the determined total
candidate energy levels.
7. The method according to claim 1 further comprising altering the
preferential work path to avoid the machine striking an object in
the work area, an altered portion of the work path associated with
additional energy above the lowest total energy level.
8. The method according to claim 1 wherein the change in geographic
factors comprises a change of elevation that varies within a cell
or between adjacent cells, the variation in elevation being
associated with a corresponding energy cost, an increased energy
cost associated with the machine traveling on an upward slope, and
a reduced energy cost associated with the machine traveling on a
downward slope.
9. The method according to claim 1 wherein the lowest energy level
represents a lowest one of candidate total energy levels for
corresponding proposed work paths, each candidate total energy
level comprising a sum of energy costs associated with the machine
traversing the proposed path in the work area in one or more
defined directions.
10. A method for determining a work path for a machine, the method
comprising the steps of: defining a work area, the work area being
divisible into a number of cells; defining respective elevations
associated with corresponding cells within the work area;
estimating a first energy level needed for a machine to traverse at
least one cell in a first direction; estimating a second energy
level needed for the machine to traverse at least one cell in a
second direction opposite the first direction; estimating a third
energy level needed for the machine to traverse at least one cell
in a third direction, the third direction being generally
orthogonal to the first direction; estimating a fourth energy level
needed for the machine to traverse at least one cell in a fourth
direction opposite to the third direction; and determining
candidate total energy levels for corresponding work paths based on
a sum of energy contributions of at least one of the first energy
level, the second energy level, the third energy level and the
fourth energy level.
11. The method according to claim 10 further comprising:
determining an optimal or lowest energy level among the candidate
total energy levels.
12. The method according to claim 10 further comprising selecting a
preferential path from between a primary work path and a secondary
work path of the machine, the primary work path arranged such that
the machine primarily travels in the first and second directions in
the work area, and the secondary path arranged such that the
machine primarily travels in the third and fourth directions in the
work area.
13. The method according to claim 10 wherein the determining of the
candidate total energy levels comprises calculating the candidate
total energy levels within a data processor associated with the
machine.
14. The method according to claim 10 wherein the determining of the
candidate total energy levels comprises calculating the candidate
total energy levels within a data processor remotely located from
the machine and communicating a preferential work path to the
machine via an electromagnetic communication.
15. The method according to claim 10 wherein each candidate total
energy level of a corresponding proposed path is determined by the
sum of energy levels for any movement across one or more cells in
at least one of the first direction, the second direction, the
third direction, and the fourth direction.
16. The method according to claim 10 wherein the defining of the
work area is accomplished by defining the work area with respect to
coordinates and corresponding elevations measured via at least one
of a spatial measurement device and location-determining
receiver.
17. The method according to claim 10 wherein the defining of the
corresponding elevation is accomplished by taking a series of
elevational measurements in the work area via a
location-determining receiver.
18. A system for determining a work path for a machine, the system
comprising: a definer for defining a work area divisible into a
number of cells, the definer supporting the definition of at least
one of a geographic factor of a cell and a machine factor; an
estimator estimating energy levels needed for a machine to traverse
at least one cell or cellular dimension in a first direction,
estimating an energy level needed for the machine to traverse at
least one cell or cellular dimension in a second direction opposite
the first direction, estimating an energy level needed for the
machine to traverse at least one cell or cellular boundary in a
third direction, the third direction being generally orthogonal to
the first direction, and estimating an energy level needed for the
machine to traverse at least one cell or cellular dimension in a
fourth direction opposite to the third direction; and a processor
for determining candidate total energy levels for corresponding
proposed work paths of the machine within the work area.
19. The system according to claim 18 further comprising a selector
for selecting an optimal or lowest one of the determined candidate
energy levels.
20. The system according to claim 18 further comprising a selector
for selecting a lowest candidate energy level associated with one
of a primary work path and a secondary work path, the primary work
path arranged such that the machine primarily travels in the first
and second directions in the work area and the secondary work path
arranged such that the machine primarily travels in the third and
fourth directions in the work area.
21. The system according to claim 18 further comprising: a spatial
measurement device for defining a boundary of the work area in
spatial coordinates and for measuring the geographic factors of
corresponding cells within the work area.
22. The system according to claim 18 further comprising: a user
interface for receiving user input on a boundary of the work area
and elevation data as the geographic factors of corresponding cells
within the work area.
23. The system according to claim 18 further comprising: a user
interface for receiving user input on at least one of elevation
data and surface condition data associated with the cells.
24. The system according to claim 18 further comprising: a mapper
for preparing a preferential path for display to a user via a user
interface, the mapper comprising an obstacle avoidance module for
modifying the preferential path to avoid obstacles.
25. The system according to claim 18 further comprising: a guidance
module for guiding the machine along a preferential path and for
modifying the preferential path to comply with a prohibition on
traveling within a cell with a lateral slope exceeding a maximum
lateral slope.
Description
FIELD OF THE INVENTION
[0001] This invention relates at a method and system for
determining an energy-efficient path of a machine.
BACKGROUND OF THE INVENTION
[0002] A self-propelled machine for construction, agricultural, or
domestic applications may be powered by an electric motor, an
internal combustion engine, or a hybrid power plant that includes
an electric motor and an internal combustion engine. For example,
the machine may refer to an electric mower or another work vehicle
for lawn and garden work. An operator of the machine may wish to
cut the grass in a work area, till a garden in a work area, or
accomplish some other task in the work area. If the operator
manually selects a path for the machine without considering the
slope of the terrain of the work area, the machine may consume
greater amounts of fuel or energy that would otherwise be required.
Further, if the machine is driven by an electric motor, the energy
source or battery may be depleted prior to finishing the work over
the entire work area. The disruption to work may cause the operator
to become annoyed with electrically-propelled machines and detract
from the marketability of such machines. Although a manufacturer of
a machine can incorporate batteries or another energy source with
greater capacity, the additional batteries may be too bulky to fit
in the standard housing of the machine or may add too much weight
to the machine. For example, adding too many batteries to a mower
may disrupt a preferential weight distribution among the wheels and
degrade the handling of the mower. Thus, a need exists for a
self-propelled machine that reduces energy consumption by planning
a route that considers any differences in elevation in the work
area.
SUMMARY OF THE INVENTION
[0003] A method and system for determining a work path for a
machine determines a path that minimizes energy consumption of the
machine to enhance a usable duration of an electrical charge of an
energy source or to conserve fuel. A work area is defined and is
divisible into a number of cells. Respective geographic factors
(e.g., elevation data) associated with corresponding cells within
the work area are defined. An estimator estimates energy levels,
associated with a machine moving in or between adjacent cells, in
corresponding proposed directions based on at least one geographic
factor (e.g., any change in elevation between or within the
adjacent cells). Candidate total energy levels are determined for
moving the machine through the cells along corresponding proposed
work paths for the work area. A selector selects a preferential
work path from the proposed work paths consistent with the
determined lowest energy level of the candidate total energy
levels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a block diagram of a system for determining an
energy-efficient path of a machine according to the invention.
[0005] FIG. 2 is a flow chart of one embodiment of a method for
determining an energy-efficient path of a machine in accordance
with the invention.
[0006] FIG. 3 is a flow chart of another embodiment of a method for
determining an energy-efficient path of a machine.
[0007] FIG. 4 shows an illustrative example of a sloped work area
in which a machine might operate.
[0008] FIG. 5 shows the work area of FIG. 4 in the x-y plane and an
illustrative primary path of the machine.
[0009] FIG. 6 shows the work area of FIG. 5 divided into a series
of cells with an energy cost per cell shown based on the path of
the machine depicted in FIG. 5.
[0010] FIG. 7 shows the work area of FIG. 4 in the x-y plane and an
illustrative secondary path of the machine.
[0011] FIG. 8 shows the work area of FIG. 7 divided into a series
of cells with an energy cost per cell shown based on the path of
the machine depicted in FIG. 7.
[0012] FIG. 9 is an alternate embodiment of a system for
determining an energy-efficient path of a machine according to the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] In accordance with the invention, FIG. 1 shows a system 101
for determining an energy-efficient path of a machine. The machine
may be operator-controlled, autonomous, semi-autonomous or any
combination of the foregoing characteristics. An autonomous machine
is self-guided without operator intervention or with minimal
operator intervention. A semi-autonomous machine may provide
guidance instructions to an operator or driver who executes the
guidance instructions and may use independent judgment with respect
to the instructions. The system 101 for determining an
energy-efficient path of the machine includes a user interface 118
coupled to a data processing system 100. The user interface 118
supports user input, output, or both. In one embodiment, the user
interface 118 comprises one or more of the following: a keyboard, a
keypad, a pointing device, and a mouse. The user interface 118 may
allow a user to define or modify a data representation of a work
area by describing points on a perimeter of the work area.
[0014] The data processing system 100 includes a data processor 102
coupled to a data port 104 via a databus 114 or otherwise. The data
port 104 accepts input data from a spatial measurement device 116,
a user interface 118, or both. In one embodiment, the spatial
measurement device 116 comprises a Global Positioning System (GPS)
Receiver. In another embodiment, the spatial measurement device 116
comprises a GPS receiver with differential correction device or
another location-determining receiver. The spatial measurement
device 116 is optional as indicated by the dashed lines of FIG.
1.
[0015] The data processor 102 may include a definer 106, an
estimator 108, a selector 110, and a mapper 112. In one embodiment,
the definer 106, estimator 108, selector 110, and mapper 112 may be
implemented by a digital logic circuit, an arithmetic logic
circuit, at least one software module, or any combination of the
foregoing items.
[0016] The definer 106 uses input data to define a data
representation of a work area of the machine in accordance with one
of several alternate techniques. Under a first technique, a user
manually inputs a boundary of the work area and topographic data on
the work area from a topographic map, a topographic survey, or from
another available source. Under a second technique, the user
defines a boundary of a work area by driving or directing the
vehicle around a perimeter of the work area. Further, the user
defines the interior of the work area by controlling the vehicle
and manually or automatically taking elevation versus position
measurements (e.g., geographic coordinates) via a spatial
measurement device 116 (e.g., a Global Positioning System (GPS)
receiver with differential correction, a GPS receiver without
differential correction or an optical measurement device). Any
differential correction of the location-determining receiver may
be, but does not need to be, in real-time to compile geographic,
topographic, or terrain data on the work area.
[0017] An estimator 108 receives the definition of the work area
from the definer 106. The estimator 108 estimates the projected
energy consumption of the machine based on one or more proposed
paths of the machine through the work area. Each proposed path of
the machine consists of one or more proposed directions of travel
for the machine within the work area to cover the entire work area
or a desired portion of the work area. For example, the desired
portion of the work area may include the work area less any
obstacle, obstruction, unsafe region, and/or excluded zone. In one
embodiment, each proposed work path consists of a series of
generally parallel rows along selected, proposed directions.
Although the operator may define the desired portion of the work
area, the data processing system 100 may cooperate with an
obstruction avoidance system or a safety system to define or modify
the desired portion of the work area.
[0018] The candidate total energy levels may be affected by
variation in the geographic factors (e.g., elevation data or
topographic data) associated with different cells in the work area.
If the topographic data reveals that the work area is generally
flat or planar, the energy consumption of the machine may vary
insignificantly from one proposed direction of travel to another.
If the topographic data reveals that the work area is generally
sloped, the energy consumption of the machine may vary
significantly from one proposed direction of travel to another
through cells within the work area.
[0019] In one embodiment, the estimator 108 determines candidate
total energy levels for corresponding proposed paths within the
work area. The sum of energy levels associated with movement of the
machine through the cells along each alternate proposed path
provides a total candidate energy level for a path of the machine.
In one embodiment, the estimator 108 stores a list or look-up table
of candidate path identifiers and associated candidate total energy
levels in a data storage device 103 associated with the data
processing system 100.
[0020] The selector 110 selects a preferential path associated with
a preferential one of the candidate total energy levels. For
example, the selector 110 may search for the lowest value for the
candidate total energy levels in the list or look-up table in the
storage device 103 to find the corresponding path identifier. If no
single path provides a lowest total energy consumption, (1) the
selector 110 may randomly select from among two or more of the
candidate paths having the lowest candidate total energy level or
consumption or (2) the selector 110 may apply a secondary selection
criteria (e.g., shortest time to complete the work in the work
area) to two or more candidate paths having the lowest candidate
total energy.
[0021] The mapper 112 may provide a map or guidance instructions to
the user or the machine (e.g., an electric drive controller). For
example, the mapper 112 may output guidance instructions via a
display on the user interface 118 to facilitate a user following
the selected preferential path for operation of the machine in the
work area. In one embodiment, the mapper 112 may display real-time
target bearings along with the actual position of the machine to an
operator via user interface 118 or otherwise to foster tracking of
the preferential path.
[0022] FIG. 2 shows a method for determining an energy-efficient
path for a machine. The method of FIG. 2 begins in step S10.
[0023] In step S10, a work area is defined. For example, a user
defines a work area in accordance with several or cumulative
alternate techniques. Under a first technique, the user enters a
boundary of the work area into a user interface 118 and geographic
data (e.g., elevation data versus position data; or surface
condition data versus position data) into the user interface 118
from a source. Under a second technique, the operator or machine
uses the spatial measurement device 116 to define the boundary
and/or to take geographical measurements (e.g., elevation data
versus position data) of the work area. Under a third technique,
the user may enter a surface condition and a corresponding location
(e.g., cell identifier) into the user interface 118 prior to
beginning a task with the machine. In one embodiment, the work area
may be a generally rectangular region that allows a work path
(e.g., a proposed work path) to generally follow a series of
substantially parallel rows that are parallel to at least one side
of the work area.
[0024] The work area is divisible into a number of cells or nodes.
In one embodiment, the dimensions of each cell are approximately
the same. The dimensions of each cell are generally proportional to
the size of the machine. Although a cell may have any size that is
consistent with practicing the invention, for explanatory purposes,
one cell may be a generally rectangular or polygonal shape with an
area of one square meter.
[0025] In step S12, geographic factors (e.g., respective elevations
or altitudes) of the cells are defined within the work area.
Geographic factors may comprise elevation data of corresponding
cells, a terrain slope associated with one or more cells, surface
condition data on one or more cells, topographic data, or other
data associated with the physical attributes of a cell within the
work area. In one embodiment, each cell is defined by a cell
identifier and a corresponding geographic factor datum (e.g.,
elevation datum). The cell identifier may represent any of the
following: a row and column description of the placement of a cell
within a grid of cells that define the work area, absolute
geographic coordinates of a cell, and relative geographic
coordinates of a cell within the work area. An elevation datum or
data may be expressed in terms of relative elevation with respect
to a reference elevation (e.g., a reference elevation of a
reference cell) or a mean elevation above sea level, for
example.
[0026] In step S14, an estimator 108 determines or references an
energy level (e.g., an energy level per cell) associated with a
machine moving across at least one cell or a replacement of the
machine by a cellular dimension or between adjacent cells in a
particular direction consistent with a proposed path of the
machine. The energy level may be based upon a geographic factor,
(e.g., any variation in elevation between adjacent cells), and a
machine factor. In data storage 103 or a database, the data
processing system 100 may store an energy level per cell associated
with a corresponding cell identifier and a corresponding direction
of proposed travel of the machine across the cell. The energy level
per cell may be based at least partially on the size of the cell
and any change in elevation within a cell or between adjacent
cells. The energy requirement may vary depending upon the direction
of travel across one or more cells where the work area is sloped or
hilly.
[0027] In an alternate embodiment, the energy level for at least
one cell is based upon both the topography of the work area and the
surface conditions of the work area. More energy is needed to move
the machine uphill than downhill than along a contour of generally
constant elevation. Surface conditions include the identity of the
materials, level of moisture in the materials, the geometry of the
materials, and other physical characteristics. For example, the
machine may expend a higher energy level in traveling through or
over mud or sand, than over a hard, dry surface. The estimator 108
may determine or reference an energy penalty or de-rating factor on
a per cell basis for surface conditions within the cell.
Accordingly, in data storage 103, the data processing system 100
may store an energy level per cell associated with a cell
identifier, a corresponding direction of travel, and a surface
condition descriptor.
[0028] In step S14, the estimator 108 determines a candidate energy
level needed to move to a machine from one cell to another along a
proposed path or a portion of the proposed path in the work area.
For example, the estimator 108 may determine a candidate total
energy level for corresponding alternate proposed paths within the
work area that cover a desired portion of the work area. In one
embodiment, each proposed work path consists of a series of
generally parallel rows along selected, proposed directions. The
desired portion of the work area refers to any portion of the work
area or the entire work area that is selected for processing. The
work area or the desired portion may be limited by obstacles,
hazards, safety precautions, time constraints, a work assignment
definition, or otherwise as previously described herein.
[0029] In step S16, a lowest total energy level is identified from
among the determined candidate total energy levels of step S14.
Each proposed work path is associated with a total candidate energy
level for the work area. The preferential work path is identified
as the proposed path having the lowest total energy level among or
between the candidate total energy herein. The lowest total energy
level or optimal energy level is generally associated with a
preferential path (through the cells) in the work area for moving
the machine.
[0030] In step S18, a selector 110 selects a preferential work path
from the proposed work paths consistent with the determined lowest
energy level or optimal energy level. The selector 110 outputs the
preferential work path. The preferential work path may be defined
by a series of cell identifiers or geographic coordinates that
define points on the preferential path. In one embodiment, after
step S18, a mapper 112 provides guidance data (e.g., a graphical
display) to the operator or the machine to direct or steer the
machine consistent with the preferential work path.
[0031] In an alternate procedure for executing the method of FIG.
2, the selector 110 may select a preferential path based on
additional factors besides the determined lowest energy level or
power consumption of the machine. The additional factors for
selection of a preferential path may include one or more of the
following: (1) obstacle avoidance; (2) avoidance of zones with
predefined surface conditions (e, g., muddy cells that do not
provide a suitable travel surface for the wheels or tread of the
machine); (3) avoidance of an unsafe travel path (e.g., traveling
substantially perpendicular to grade or slope that exceeds a
maximum threshold); (4) limitation on the maximum available energy
consumption for a work area and a machine; (5) time constraints for
completion of a task within a given energy budget; and (6)
heuristic data on proposed work paths or paths analogous thereto
the selector 110 may override the path with the lowest energy level
to foster compliance with one or more of the above additional
factors and to establish a modified preferential path. If the
preferential path is altered to avoid the machine striking an
object in the work area or around the work area, an altered portion
of the work path is associated with an additional energy
consumption above the lowest total energy level (e.g., absolute
lowest energy level) among the candidate total energy levels.
[0032] FIG. 3 is a flow chart of another method for determining an
energy efficient path for a machine. Steps S10 and S12 of FIG. 3
were previously described in conjunction with FIG. 2. Like elements
in FIG. 2 and FIG. 3 indicate like elements.
[0033] Any of steps S22, S24, S26 and S28 may determine the energy
level in a similar manner to step S14. The estimated energy level
per cell or per a group of cells may be based upon one or more of
the following geographic factors: the elevation of a cell or cells,
the elevation of surrounding cells, the difference in height or
elevation of adjacent cells, the direction of proposed travel of
the machine across the cell or cells, the surface conditions within
the cell or cells, obstacle avoidance within the cell or cells, and
safety deviation from a proposed course within the cell or cells.
The estimated energy level per cell or per group of cells may be
based on the following machine factors: (1) weight of the machine,
(2) electrical power consumption or fuel consumption of the machine
under full load, partial load, or at rest, (3) electrical power
consumption or fuel consumption of the machine at a corresponding
estimated revolution per minute of the motor, drive train, or
transmission, (4) target speed of the machine and (5) electrical
power consumption of electrical and electronic accessories (e.g.,
radio, navigation system, windshield wipers) of the machine, (6)
electrical power consumption or mechanical power consumption of
processing equipment (e.g., mower, thresher, cutter, or harvester)
associated with the machine.
[0034] In step S22, an estimator 108 estimates a first energy level
needed for a machine to traverse a cell or a group of cells in a
first direction. The first energy level of the machine is
determined with reference to a move across a cell in the first
direction or a group of adjacent cells in the first direction,
subject to at least the above geographic factors and machine
factors.
[0035] In step S24, the estimator 108 estimates a second energy
level needed for the machine to traverse a cell or a group of
adjacent cells in a second direction opposite the first direction.
The second energy level of the machine is determined with reference
to a move across a cell in the second direction or across a
boundary between adjacent cells in the second direction, subject to
at least the above geographic factors and machine factors.
[0036] In step S26, the estimator 108 estimates a third energy
level needed for the machine to traverse a cell or a group of
adjacent cells in a third direction. The third direction is
generally orthogonal to the first direction. The third energy level
of the machine is determined with reference to a move across a cell
in the third direction or across a boundary between adjacent cells
in the third direction, subject to at least the above geographic
factors and machine factors.
[0037] In step S28, the estimator 108 estimates a fourth energy
level needed for the machine to traverse a cell or a group of
adjacent cells in a fourth direction opposite to the third
direction. The fourth energy level of the machine is determined
with reference to a move across a cell in the fourth direction or
across a group of adjacent cells in the fourth direction, subject
to at least the above geographic factors and machine factors.
[0038] In step S29, the data processor 102 or the estimator 108
determines a candidate total energy level for respective proposed
work parts. Each candidate total energy level may be defined by the
sum of energy contributors for travel of the machine in the first,
second, third, and fourth directions to cover a desired portion of
the work area.
[0039] In step S30, a selector 110 determines a preferential work
path having a lowest total energy level from among the determined
candidate energy levels of step S29. The lowest energy level for
the work area may be based upon at least a sum of one of the first
energy level, the second energy level, the third energy level, and
the fourth energy level. The preferential work path may include
path segments or contributions in one or more of the following
directions: the first direction, the second direction, the third
direction, and the fourth direction.
[0040] In one embodiment, the preferential work path is selected
from at least a primary work path and a secondary work path of a
machine. The primary work path is arranged such that the machine
primarily travels in the first and second directions in the work
area to cover a desired portion of the work area. The secondary
work path is arranged such that the machine primarily travels in
the third and fourth directions in the work area to cover a desired
portion of the work area. The preferential work path may continue
in a single direction until a boundary of the work is reached and a
turn is required. The preferential work path may be determined in
part by the conservation of momentum of the machine to maintain an
orderly travel of the machine along adjacent rows.
[0041] FIG. 4 shows a terrain profile of a work area. The work area
may be described in with reference to a Cartesian coordinate
system. The x, y, and z axes (200), of the Cartesian coordinate
system, are perpendicular to one another. The work area has a
perimeter that may be defined in an x-y plane. The profile or
contour 202 of the work area may be defined in an x-z plane, a y-z
plane, or both. As shown in FIG. 4, the profile slopes upward from
the left to right. Although the work area may also be sloped in a
y-z plane in FIG. 4, the work area is generally planar or flat in
the y-z plane. The machine (e.g., tractor 204) is heading in the y
direction along a contour of generally uniform height with respect
to the z axis.
[0042] FIG. 5 is a top view of the work area 500 that illustrates a
primary path of the machine. Although an x-y plane representation
of the work area may have almost any shape and dimension, as shown
in FIG. 5, the work area 500 is a generally rectangular region with
A displacement units in the x direction and B displacement units in
the y direction, where A and B are any positive numbers. A primary
path 504 of the machine is shown over the work area 500, such that
the machine covers a desired portion of the work area 500 or the
entire work area. The primary path 504 begins in the lower right
corner of FIG. 5, which is designated the starting cell 502. The
primary path consists of a series of substantially parallel rows
506 in the y direction. The machine makes turns 508 between the
parallel rows to move from one row to the next in the x direction.
The primary path terminates on the lower left corner, which is
designated a terminating cell 510.
[0043] In the illustrative example of FIG. 5 and FIG. 6, assume
that A equals 8 length units and B equals 16 length units. For
illustrative purposes, the y axis may be generally aligned in the
north-south direction, whereas the x axis may be generally aligned
in the east-west direction. In practice, the x and y axes are not
limited to any particular orientation with respect to north, south,
east, or west. If the yard were mowed in a generally row-like or
boustrophedon north-south pattern, there would be 4 north-to-south
passes at a cost of 16 energy units, 4 south-to-north passes at a
cost of 16 energy units, and 8 east-to-west transitions at a cost
of 0.75 energy units per transition from one end of a cell to
another end of the cell. Boustrophedon refers to a movement pattern
in which the machine moves in opposite directions in adjacent rows
that are generally parallel to one another. The energy to return to
start requires 8 west-to-east transitions at 1.5 energy units per
transition. The return to start is indicated by the dashed line 512
in FIG. 5. Here, the first direction refers to the north-to-south
pass; the second direction refers to the south-to-north pass; the
third direction refers to the east-to-west transition; and the
fourth direction refers to the west-to-east transition. The sum of
the energy levels in each direction or directions of travel of the
machine may be used to determine the total candidate energy level
for the proposed path (e.g., primary path 504). Accordingly, total
energy cost for the area coverage path plan of FIG. 5 and FIG. 6 is
4*16+4*16+8*0.75+8*1.5=146 energy units.
[0044] FIG. 6 shows the work area of FIG. 5 divided up into a group
of cells. The cells may be generally rectangular, polygonal,
circular, or shaped other ways. Each cell is assigned a
corresponding energy cost or relative energy cost per cell based on
the direction of travel of the machine in the work area consistent
with the primary path of FIG. 5. The energy levels per cell are
consistent with the exemplary calculation described in conjunction
with FIG. 5. The candidate total energy level (e.g., 146 energy
units) of the machine for the proposed path (e.g., primary path
504) can be determined by adding the energy level contribution from
each cell. Although the energy contribution is calculated with
respect to movement from one end (e.g., side) of the cell to
another, the energy could also be calculated based on the
transition energy to move between two cells or a central region
therein.
[0045] FIG. 7 is a top view of the work area 500 that illustrates a
secondary path 600 of the machine. Although an x-y plane
representation of the work area may have almost any shape and
dimension, as shown in FIG. 5, the work area is a generally
rectangular region with A displacement units in the x direction and
B displacement units in the y direction, where A and B are any
positive numbers. A secondary path 600 of the machine is shown over
the work area, such that the machine covers a desired portion of
the work area 500 or the entire work area 500. The secondary path
600 starts in the cell 502 in the lower right-hand corner of the
work area of FIG. 7. The secondary path 600 consists of a series of
substantially parallel rows 602 in the x direction. The machine
makes turns 604 between the parallel rows in the y direction. The
secondary path terminates in the end cell 606 in the upper
right-hand corner of the work area. The dashed line 608 indicates
the return path of the machine from the end cell to the beginning
cell 502 of FIG. 7.
[0046] FIG. 8 shows the work area of FIG. 5 divided up into a group
of cells. The cells may be generally rectangular, polygonal,
circular, or shaped other ways. Each cell is assigned a
corresponding energy cost or relative energy cost based on the
direction of travel of the machine in the work area consistent with
the secondary path of FIG. 7. The total candidate energy level of
the machine for the proposed path (e.g., the secondary path 600)
can be determined by adding the energy level contribution from each
cell.
[0047] Here, the work area 500 (e.g., field or yard) is represented
by a grid 16 cells by 8 cells, although other representations of
the work area fall under the scope of the claims. In FIG. 8, for
exemplary purposes, the y direction may be generally aligned with a
north-south axis and the x direction may be generally aligned with
the east-west axis. The machine uses an energy cost of 1 energy
unit per cell going north or south along a row, an energy cost of
1.5 energy units per cell going uphill west to east, and an energy
cost of 0.75 energy units per cell going downhill east to west.
Here, in the illustrative example, the first, second, third, and
fourth directions refer to the north-to-south direction, the
south-to-north direction, the east-to-west direction, and the
west-to-east direction, respectively. The machine may start from a
starting cell 502 in the southeast corner of the work area 500
(e.g. yard or field) to which the machine returns. If the machine
were operated (e.g., mowed) predominately in a generally row-like
or a boustrophedon east-west pattern, there would be 8 east-to-west
passes at a cost of 6 energy units, 8 west-to-east passes or rows
at a cost of 12 energy units, 16 south-to-north intervals at a cost
of one energy unit per cell, and a return to start of 16
north-to-south steps at one energy level per cell. In accordance
with FIG. 8, the total energy cost for the machine covering the
work area is 8*6+8*12+16*1+16*1=176 energy units. Therefore,
primary path 504 of FIG. 5 and FIG. 6 uses approximately 83% of the
energy needed for the secondary path 600 of FIG. 7 and FIG. 8. The
method of FIG. 2, FIG. 3 or a variation thereof may be used to
determine and select the primary path 504 as a preferential path,
for example. The energy savings could be used to extend the range
of the machine, reduce the operating cost of the machine, or reduce
the size of an energy source (e.g., battery or fuel cell) of the
machine.
[0048] Although the data processing system 100 may be mounted on
the machine as shown in FIG. 1, in an alternate embodiment, the
data processing system 100 may be located remotely from the machine
at a data processing site as illustrated in FIG. 9. Like reference
numbers in FIG. 1 and FIG. 9 indicate like elements.
[0049] In the embodiment of FIG. 9, machine electronics 130 are
mounted on the machine. The machine electronics 130 includes a
spatial measurement device 116 in communication with a wireless
unit 120, a user interface 118, or both. The machine electronics
130 further includes a processor 126 coupled to the wireless unit
120 and the user interface 118. The processor 126 is associated
with a guidance module 128 which may comprise software instructions
for directing the machine or an operator of the machine in a work
area.
[0050] The machine electronics 130 at a machine location
communicates to the data processing system 100 at the data
processing site via wireless units 120 that transmit and receive
electromagnetic signals. In one embodiment, each wireless unit 120
includes a receiver 122 and a transmitter 124. The transmit and
receive signal paths of each wireless unit 120 may be combined or
duplexed onto one antenna. In an alternate embodiment, a wireless
unit 120 may comprise a transceiver (e.g., a cellular phone,
wireless Ethernet, or Bluetooth) rather than a transmitter and a
receiver.
[0051] The spatial measurement device 116 outputs spatial
measurements (e.g., positional data versus elevation data)
associated with the work area to the wireless unit 120, the user
interface 118, or both. The wireless unit 120 at the data
processing system 100 may receive the transmitted spatial
measurements. The data processing system 100 may use the received
spatial measurements in determining a preferential path remotely
from the machine. For example, the data processing system 100 of
FIG. 9 may be used to execute the method described in FIG. 2, FIG.
3, or some variation of the foregoing methods that fall within the
scope of the claims. The selector 110 may select a preferential
path and the mapper 112 may plan a route or preferential path data
for executing the preferential path. The data processing system 100
may transmit preferential path data to the machine via a
communications link formed by the wireless units 120.
[0052] The wireless unit 120 of the machine electronics 130
receives the preferential path data. The wireless unit 120 of the
machine electronics 130 sends the preferential path data to the
processor 126. The processor 126 may include a guidance module 128
for executing one or more of the following processing functions:
(1) interpreting preferential path data; (2) avoiding obstacles in
or outside of the work area; (3) complying with safety criteria
associated with the preferential path data; (4) facilitating
display of preferential path data in a suitable or desired format
for an operator of the machine; and (5) forwarding the preferential
path to a controller of an autonomous vehicle as the machine. The
user interface 118 may display the preferential data in a desired
format for action and/or interpretation by an operator of the
machine. In one embodiment, the guidance module is arranged to
guide the machine along the preferential path and to modify the
preferential path to comply with a prohibition on traveling within
a cell with a slope (e.g., a lateral slope relative to the machine)
exceeding a maximum slope. The maximum slope may depend upon
whether the machine is manned, unmanned, or fully autonomous, among
other safety factors.
[0053] The remote location of the data processing system 100 at the
data processing site supports reduced electrical power consumption
of the machine by removing the electrical load of the data
processing system 100 from the machine electrical system. The data
processing system 100 may offer more reliable performance in an
environmentally controlled place (e.g., an air-conditioned
building) or the data processing system 100 may be economically
configured to meet less rigid environmental specifications (e.g.,
vibration, heat, and reliability standards) than might otherwise be
required for vehicular mounting of the data processing system
100.
[0054] The method and system may be applied to a vehicle, a mower,
a tractor, an agricultural machine, a construction machine, an
industrial machine, an autonomous machine, a semi-autonomous
machine, or some other machine that is partially or completely
propelled by an electric motor or an electric drive system. For
example, the machine may comprise an electric lawn tractor, a
hybrid lawn tractor, a self-propelled lawn mower, a hybrid electric
lawn mower or another machine that may need to minimize the energy
used to maximize the area that may be mowed on a single charge of
an energy source (e.g., a battery). If an electrically-propelled
machine does not have enough power to simultaneously process
vegetation (e.g., mow) and go up a steep hill, the path of the
machine may be determined to avoid an energy cost per cell that is
greater than some threshold amount to accommodate power constraints
and promote energy source longevity.
[0055] In another example, the machine may comprise a material
transport vehicle. A material transport vehicle such as a log
forwarder, agricultural bulk material mover (e.g., a grain cart),
or construction bulk material mover (e.g., a dump truck) may reduce
fuel energy consumption or fuel costs by taking energy costs for
various alternative paths into account.
[0056] The method and system of the invention may be used to
determine a preferential path for a machine to plan the route of a
machine prior to engaging in a task. In one embodiment, the
preferential path represents a lowest total energy level required
for completing a task such as mowing, snow pushing, sweeping, or
other work. The preferential path may be expressed as a path
defined by a series of consecutive nodes or cells. The consecutive
nodes or cells may be identified by cell identifiers or geographic
coordinates, for example.
[0057] Although specific embodiments have been illustrated and
described herein, those of ordinary skill in the art will
appreciate that other arrangements of the invention may be
substituted for the specific embodiments. Various adaptations and
variations of the invention may become apparent to those of
ordinary skill in the art. Accordingly, this document is intended
to cover any adaptations, modifications or variations of the
invention consistent with this document. It is intended that this
invention be limited only by the following claims and equivalents
thereof.
[0058] Having described the preferred embodiment, it will become
apparent that various modifications can be made without departing
from the scope of the invention as defined in the accompanying
claims.
* * * * *