U.S. patent application number 11/292863 was filed with the patent office on 2006-05-04 for self-propelled mower having enhanced maneuverability.
Invention is credited to David Roy Holm, Kenneth Edward Hunt.
Application Number | 20060090438 11/292863 |
Document ID | / |
Family ID | 34437379 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090438 |
Kind Code |
A1 |
Hunt; Kenneth Edward ; et
al. |
May 4, 2006 |
SELF-PROPELLED MOWER HAVING ENHANCED MANEUVERABILITY
Abstract
A frame of a mower supports wheel assemblies, a propulsion unit,
and a mowing deck. Each wheel assembly is associated with a
corresponding wheel, a corresponding electrical steering motor, and
a corresponding electrical drive motor. A controller controls a
direction of orientation of the corresponding wheel via the
corresponding electrical steering motor. Further, the controller
controls the application of electrical energy to the corresponding
drive motor consistent with maneuverable movement of the mower. The
propulsion unit is capable of rotating at least one cutting blade.
A mowing deck houses the at least one cutting blade. The mowing
deck has indentations to provide a spatial zone for the plurality
of wheel assemblies.
Inventors: |
Hunt; Kenneth Edward; (Rock
Hill, SC) ; Holm; David Roy; (Oconomowoc,
WI) |
Correspondence
Address: |
DEERE & COMPANY
ONE JOHN DEERE PLACE
MOLINE
IL
61265
US
|
Family ID: |
34437379 |
Appl. No.: |
11/292863 |
Filed: |
December 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10808119 |
Mar 23, 2004 |
|
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|
11292863 |
Dec 1, 2005 |
|
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60524143 |
Nov 21, 2003 |
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Current U.S.
Class: |
56/10.2A |
Current CPC
Class: |
A01D 34/66 20130101;
B62D 7/1509 20130101; B62D 7/026 20130101; G05D 1/0272 20130101;
G05D 1/0278 20130101; A01D 34/008 20130101; G05D 1/0282 20130101;
B62D 5/0418 20130101; G05D 1/0238 20130101; G05D 2201/0208
20130101 |
Class at
Publication: |
056/010.20A |
International
Class: |
A01D 34/00 20060101
A01D034/00 |
Claims
1. A mower comprising: a plurality of wheel assemblies, each wheel
assembly associated with a corresponding wheel, a corresponding
electrical steering motor, and a corresponding electrical drive
motor, a controller for controlling a steered direction of the
corresponding wheel via the corresponding electrical steering motor
and application of electrical energy to the corresponding
electrical drive motor consistent with maneuvering the mower in
accordance with a movement mode in any desired direction along the
ground; a propulsion unit for rotating at least one cutting blade;
a mowing deck for housing the at least one cutting blade, the
mowing deck having indentations to provide a spatial zone for the
plurality of wheel assemblies, the mowing deck comprising three
generally semi-circular sections having corresponding centerpoints
that are substantially equidistant to a geometric center point of
the mower; and a frame for supporting the plurality of wheel
assemblies, the propulsion unit, and the mowing deck.
2. The mower according to claim 1 wherein the movement mode is
selected from the group consisting of a linear mode, an arc mode, a
rotating mode, and a trim mode.
3. The mower according to claim 1 wherein the movement mode
comprises a linear mode in which all of the wheels are oriented
parallel to one another with respect to their respective steering
axes.
4. The mower according to claim 1 wherein the movement mode
comprises a rotating mode in which the wheels are oriented
generally tangential to a circular region about the mower.
5. The mower according to claim 1 wherein the movement mode
comprises an arc mode in which each wheel is generally tangential
to a corresponding arc associated with a corresponding radius
extending from a reference point.
6. The mower according to claim 1 wherein the movement mode
comprises a trim mode in which a critical point of the mowing deck
faces a boundary to be trimmed, the critical point associated with
the outermost cutting edge of the at least one cutting blade.
7. The mower according to claim 1 wherein each generally
semi-circular section contains a generally vertical shaft coupled
to a cutting blade, a periphery of the mowing deck having the
indentations as open regions between adjacent semi-circular
sections.
8. The mower according to claim 1 wherein the wheels are free from
mechanical interference to rotate with respect to a steered axis
over a range of at least ninety degrees.
9. The mower according to claim 1 wherein the wheels are oriented
generally tangentially to a circular region about a geometric
center point of the mower to provide a zero turn radius for the
movement of the mower.
10. The mower according to claim 1 wherein the wheels are rotatable
with respect to a steered axis over at least three-hundred and
sixty degrees.
11. The mower according to claim 1 such that the at least one
cutting blade provides a swath that is greater than or equal to a
wheel spacing of the wheels.
12. The mower according to claim 1 such that the at least one
cutting blade provides a swath that is greater than or equal to a
spacing between outer sides of the wheels in at least a rotating
mode and a linear mode.
13. The mower according to claim 1 wherein the propulsion unit
comprises an engine selected from the group consisting of an
internal combustion engine, a diesel engine, a gasoline engine, an
alternating current electrical motor, direct current electrical
motor, an induction motor, and an electrical motor.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a self-propelled mower having
enhanced maneuverability for mowing vegetation.
BACKGROUND OF THE INVENTION
[0002] In the prior art, many mowers for mowing vegetation (e.g.,
grass) have a minimum turn radius of greater than fifteen inches.
The minimum turn radius is generally limited by steering
configurations, such as front-wheel steering, rear-wheel steering,
all wheel steering, and Ackerman steering. A mower with a greater
turning radius may consume more energy than a mower with a lesser
turning radius to mow a given work area. For example, the mower
with the greater turning radius may need to make more passes to
cover the given work area or to shift from one row to the next
adjacent row. Moreover, the mower with the greater turning radius
facilitates completing a mowing task over a greater time period
than a mower with a lesser turning radius of equivalent cutting
width. Accordingly, there is a need to provide a mower with
improved maneuverability and the smallest possible or desired
turning radius.
SUMMARY OF THE INVENTION
[0003] A frame of a mower supports wheel assemblies, a propulsion
unit, and a mowing deck. Each wheel assembly is associated with a
corresponding wheel, a corresponding electrical steering motor, and
a corresponding electrical drive motor. A controller controls a
steering direction of orientation of the corresponding wheel via
the corresponding electrical steering motor. Further, the
controller controls the application of electrical energy to the
corresponding drive motor consistent with maneuverable movement of
the mower. The propulsion unit is capable of rotating at least one
cutting blade. A mowing deck houses the at least one cutting blade.
The mowing deck has indentations to provide a spatial zone for the
plurality of wheel assemblies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a perspective view of a self-propelled
maneuverable mower.
[0005] FIG. 2 is a top view of the self-propelled mower of FIG.
1.
[0006] FIG. 3 is a top view of the self-propelled mower of FIG. 1
with the propulsion unit (e.g., the engine) removed to better
reveal the underlying components.
[0007] FIG. 4 illustrates a front view of a wheel assembly.
[0008] FIG. 5A and FIG. 5B is a block diagram for the electrical
system of the mower.
[0009] FIG. 6 is a diagram that illustrates a top view of an
approximately zero radius trim maneuver.
[0010] FIG. 7 is a method for making an approximately zero radius
trim maneuver.
[0011] FIG. 8 is a diagram that illustrates a top view of near zero
radius trim or greater radius trim maneuver.
[0012] FIG. 9 is a method for making a near zero radius or greater
radius trim maneuver.
[0013] FIG. 10 is an alternate method for making a near zero radius
or greater radius trim maneuver.
[0014] FIG. 11 is a diagram that illustrates a top view of an
approximately zero radius turn.
[0015] FIG. 12 is a method for making a generally zero radius turn
maneuver.
[0016] FIG. 13 is a diagram of a top view of a path segment of a
mower at an end of one row and the start of another row.
[0017] FIG. 14 is a method for mowing a work area with a
self-propelled mower.
[0018] FIG. 15A through FIG. 15C, inclusive, are plan views of the
mower that show illustrative angular orientations of the wheels
with respect to the steering axes for a linear mode.
[0019] FIG. 16 is a plan view of the mower that shows illustrative
angular orientations of the wheels with respect to the steering
axes for an arc mode.
[0020] FIG. 17 is a plan view of the mower that shows illustrative
angular orientations of the wheels with respect to the steering
axes for a rotating mode.
[0021] FIG. 18 is a plan view of the mower that shows illustrative
angular orientations of the wheels with respect to the steering
axes for an interior arc mode.
[0022] FIG. 19 is a plan view of the mower that shows illustrative
angular orientations of the wheels with respect to the steering
axes for a trim mode with approximately zero trim radius or near
zero trim radius.
[0023] FIG. 20 is a plan view of a the mower that shows
illustrative angular orientations of the wheels with respect to the
steering axes for a trim mode with greater than zero trim
radius.
[0024] FIG. 21 represents a chart of an illustrative data structure
for path plan data.
[0025] FIG. 22 is a top view of a path plan consistent with the
illustrative data structure of FIG. 21.
[0026] Like reference numbers indicate like elements throughout the
foregoing drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] In FIG. 1, a mower 10 comprises a frame 14 that supports
wheel assemblies 16, a controller 70, a propulsion unit 12, and a
mowing deck 18. Although the frame 14 is shown as generally
triangular and each wheel assembly 16 is positioned at or near each
apex of sides of the triangle formed by the frame 14, other shapes
of the frame are possible and fall within the scope of the
invention. In one embodiment, each wheel assembly 16 is positioned
approximately equidistant on a radius about a center point of the
mower, as viewed from the top. Each wheel assembly 16 is associated
with a corresponding wheel 51 (FIG. 4), a corresponding electrical
steering motor 44 (FIG. 4), and a corresponding electrical drive
motor 50 (FIG. 4).
[0028] A controller 70 (FIG. 5A and FIG. 5B) controls a direction
of orientation of the corresponding wheel via the corresponding
electrical steering motor 44 and application of electrical energy
to the corresponding drive motor 50 consistent with
omni-maneuverable movement or highly maneuverable movement of the
mower 10. Omni-maneuverable means that the mower 10 can move in any
direction from a starting point to a destination point; even if the
path from the starting point to the destination point requires an
approximately zero radius turn, an approximately zero radius trim,
or a near zero radius trim. For example, the mower 10 can move from
a starting point along the ground or in a generally horizontal
plane (e.g., an x-y plane) to a destination point along the ground
in the generally horizontal plane (e.g., the x-y plane) in any
direction. The controller 70 is capable of individually controlling
the steering rotation of each wheel about a generally vertical
steering axis 13 of each wheel or controlling the steering rotation
of a group of wheels in a coordinated manner. Further, the
controller 70 is capable of individually controlling the propulsion
rotation of each wheel about a wheel axis 113 (FIG. 4) of each
wheel or controlling the propulsion rotation of a group of wheels
in a coordinated manner.
[0029] The mowing deck 18 houses at least one cutting blade. The
cutting blade has an outer edge which is farthest from a geometric
center point of the mower 10. The mowing deck 18 has indentations
19 (FIG. 2) to provide a spatial zone for the plurality of wheel
assemblies 16. For example, the spatial zone may be of sufficient
size and shape to allow the wheels to rotate up to one complete
revolution or more. In one embodiment, the mowing deck 18 comprises
three generally semi-circular sections (e.g., a clover-leaf shape)
having corresponding center points that are substantially
equidistant to a geometric center point of the mower 10. Each
generally semi-circular section contains a generally vertical shaft
24 coupled to a cutting blade. In one embodiment, each vertical
shaft 24 may be equally spaced about the geometric center point of
the mower 10, as viewed from the top. The periphery of the deck 18
has indentations 19 as the open regions between adjacent
semi-circular sections.
[0030] The cutting blades provide a swath or cutting width that is
greater than or equal to a center-line to center-line wheel spacing
of the wheels for one or more movement modes (e.g., linear mode,
arc mode, rotating mode, trim mode, and interior arc mode as
described in later detail in FIG. 15A through FIG. 20, inclusive).
Indentations 19 allow the wheels (including the entire tire width,
wheel width, or track width) to be mounted in board within the
cutting width or swath of the mower 10 as defined by one or more
cutting blades. In one embodiment, the indentations 19 and the
wheel size (e.g., diameter) are selected to balance the cutting
width against traction and propulsion torque considerations such
that the cutting width is greater than or equal to a spacing
between the outer sides of tires on opposite sides of the mower 10
for the rotating mode and the linear mode.
[0031] A guard 20 may be connected to the deck 18 via a guard
mounts 22. The guard mounts 22 may have bushings, elastomer,
springs or another shock absorbing arrangement to absorb, at least
partially, a shock of the vehicle from colliding with another
object. The guard 20 provides a bumper that protects the mowing
deck 18 from damage that otherwise might occur from striking or
contacting objects.
[0032] The propulsion unit 12 comprises an engine, an internal
combustion engine, a diesel engine, a gasoline engine, an
alternating current electrical motor, direct current electrical
motor, an induction motor, and an electrical motor. The propulsion
unit 12 rotates at least one cutting blade to cut or mow vegetation
(e.g., grass, weeds or ground cover), for example. The propulsion
unit 12 may be associated with a belt and a pulley assembly for
simultaneously rotating multiple cutting blades of the mowing deck
18. In an alternate embodiment, one of three cutting blades present
in the mowing deck 18 may be disabled or not rotated to reduce
power consumption of the propulsion unit 12 or a motor for driving
the cutting blades. In yet another alternate embodiment, the
cutting blade may be replaced by a dethatching device (e.g., a
dethatching blade or a rake) for interaction with at least one of
the ground, organic matter lying thereon, and any vegetation
associated therewith.
[0033] Each wheel of the wheel assemblies 16 may rotate angularly
over a desired range with respect to the steering axis to
accommodate omni-maneuverable movement or a lesser freedom of
movement of one or more wheels required to execute a planned,
unplanned, dynamic or on-the-fly path of the mower 10. The
controller 70 controls the wheels or wheel assemblies 16 with
respect to the (a) one or more steering axes 13 and (2) one or more
wheel axes 113 to move the mower 10 in a desired direction or in
accordance with a desired pattern, pattern segment, path segment,
path or maneuver. Although each wheel assembly may have a steering
axis 13 that is generally perpendicular to the wheel axis 113,
other geometric configurations are possible.
[0034] The possible motion and paths of the mower may be described
with reference to a fixed reference point on the mower 10. A
reference point may track a generally linear path, non-linear path,
curved path or non-radius curved path, or any combination of the
foregoing paths on the ground with a generally constant, rotating
or changing vehicle orientation about a central axis associated
with a center point of the mower 10, as viewed from a top view. A
reference point on the mower 10 may rotate about one or more points
on the ground outside the vehicle perimeter or within the vehicle
perimeter of the mower 10; such rotation may be generally constant
or at a variable rate. The mobility of the mower 10 may be combined
with mowing along various paths to efficiently mow closely around
objects, within areas with straight, curved or other boundary
definitions. The controller 70 of the mower 10 may be configured to
track predetermined paths or path segments (e.g., orthogonal
turns),in accordance with program instructions or to follow remote
control commands or automated path segments issued by an operator
via a user interface 74 (FIG. 5A and FIG. 5B).
[0035] In accordance with a first desired maneuver that is referred
to as a zero radius turn, the controller 70 orients the wheels
generally tangentially to a substantially circular zone about
center point of rotation of the mower 10 to provide a zero turn
radius for the movement of the mower 10 about the center point for
a desired degree of angular rotation ranging from a fractional
revolution (e.g., 90 degrees for a substantially right angle turn)
to one or more revolutions. The zero radius turn may be used to
"clean-up" corners or mow interior corners of a work area by making
multiple passes of the cutting blade over the same vegetation. The
zero radius turn is well-suited for orienting the mower in a
certain orientation to prepare for upcoming movement consistent
with a path plan.
[0036] In accordance with a second desired maneuver, which is
referred to as a zero radius trim, a critical point of the mower is
positioned over a reference axis of rotation. The critical point of
the mowing deck may mean one or more of the following (a) an
outermost projecting portion of the mowing deck with respect to a
center point of the mower, (b) an outermost projecting portion of
the mowing other than a discharge region, (c) an outer peripheral
zone of the mowing deck with the edge of the cutting blade most
proximate thereto, and (d) a radially outmost edge of one or more
cutting blades of the mower. In one example, the reference axis of
rotation may lie within an unmowed remnant area of a lawn or
another target area. The wheels are generally oriented tangentially
to an arc or a circular region about the reference axis of rotation
of the mower 10 to produce a zero trim radius of the mower 10 about
the reference axis of rotation. The zero trim radius is well suited
for completing minor remnant or un-mowed areas of a lawn that might
otherwise require multiple passes to mow with a conventional mower
with a greater minimum turning radius.
[0037] In accordance with a third desired maneuver, which is
referred to as a near zero radius trim, a critical point of the
mower is positioned over a reference arc. The reference arc may
coincide with a minimum trim radius of an object (e.g., a tree,
bush, plant, pole, fire hydrant, etc.). In one example, the minimum
trim radius is spaced apart from an object (e.g., the closest outer
extent or outer surface of the object) by a desired degree of
clearance. In another-example, the guard 20 may, but need not, make
contact with the object and may provide an outward force from the
object. The wheels are steered to follow an arc, semi-circular or
generally circular path that is generally concentric with the
reference arc.
[0038] FIG. 2 shows a top view of the mower 10 of FIG. 1. The
indentations 19 of the deck are readily visible in section 19.
Pulleys 26 are associated with the deck 18. The deck 18 generally
has shafts 24 that are rotatably associated with the deck 18 via
one or more bearings (not shown). A cutting blade is mounted at or
near one end of the shaft 24, whereas a pulley 26 is mounted at or
near an opposite end of a shaft 24. The pulleys 26 engage a belt
32. The engine 12 drives-the belt 32 during operation such that the
cutting blades rotate. As best illustrated in FIG. 3, the belt
tension (i.e., tensile force) is controlled by a tensioner 28 that
supports tension pulley 26. The tensioner 28 and the tension pulley
30 may be biased by a spring or a resilient member, for
example.
[0039] FIG. 4 shows a cross-section of a wheel assembly 16. A wheel
assembly 16 comprises a spindle assembly 46 that is affixed to the
frame 14 (FIG. 1) or operably attached to the frame 14 via a
suspension component. The spindle assembly 46 provides a housing
for bearings 45 that receive a shaft 47. One end of the shaft 47 is
associated with a yoke 48 and the opposite end of the shaft 47 is
associated with a steering assembly 41. The yoke 48 provides
mounting for a drive motor 50, a tire 52, and a drive encoder 54.
The steering assembly 41 comprises a steering motor 44, a steering
encoder 40, and a steering gearbox 42.
[0040] The drive encoder 54 comprises a sensor for providing a
feedback signal associated with at least one of the operation,
position, and movement of the drive motor 50. For example, the
drive encoder 54 may provide a feedback signal indicative of the
wheel rotational speed with respect to the wheel axis 113. The
drive encoder 54 acts as an interface between a driver motor 50 and
a master control node 62.
[0041] The steering encoder 40 comprises a sensor for providing a
feedback signal associated with at least one of the operation,
position, and movement of the steering motor 44. For example, the
steering encoder 40 may provide a feedback signal indicative of the
rotational speed of the shaft 47 with respect to the steering axis
13. The steering encoder 40 acts as an interface between the
steering motor 44 and the master control node 62.
[0042] The steering gearbox 42 may provide a gear reduction that
allows the steering motor 44 to turn the wheel with respect to a
steering axis 13 within its operational torque range. In one
embodiment, the steering gearbox 42 may provide gear reduction such
that a lower torque motor (e.g., a lightweight durable motor) than
otherwise possible may be used as the steering motor 44. The
steering motor 44 may be of such a configuration as to allow the
shaft 47 and yoke 48 to pivot freely over a desired range from zero
to three-hundred and sixty degrees when no power or a certain
control signal is applied to the steering motor 44. In an alternate
embodiment, the steering gearbox 42 may permit the steering motor
44 to be disengaged from turning or changing the orientation of the
wheel by a clutch, a gear mechanism or another mechanical or
electromechanical structure.
[0043] In general, the maneuverability of the mower 10 is improved
with increases in the angular range of movement of the wheel 51
about the wheel axis 13. In one embodiment, the minimum angular
range is equal to or greater than ninety (90) degrees of angular
displacement about the steering axis of each wheel. Those skilled
in the art will appreciate that the wheel may achieve the
equivalent of three-hundred and sixty (360) degrees of rotation by
allowing approximately one hundred and eighty (180) degrees of
rotation with slip-lock feature or rotational emulator that
emulates a full three hundred and sixty (360) degrees of
rotation.
[0044] FIG. 5A and FIG. 5B represent a block diagram of the
electrical system 71 for the mower 10. The electrical system 71
comprises a controller 70 for controlling operation of the drive
motors 50 and the steering motors 44. The drive motors 50 and
steering motors 44 may be controlled individually, independently or
collectively as is necessary or required to produce the desired
movement (e.g., omni-maneuverable movement) of the mower 10 from
rest or during movement. The controller 70 may use a feedback
signal from one or more drive encoders 54 and one or more steering
encoders 40 to determine control data or one or more control
signals to be transmitted to the corresponding drive motors 50 and
steering motors 44, respectively.
[0045] A base station 72 comprises a user interface 74 and a
mission planner 76. The user interface 74 supports a user's entry,
selection or input of input data for the mission planner 76 or
otherwise. The input data for the mission planner 76 may include
one or more of the following items: (1) the approximate dimensions
of the work area or portions thereof to be mowed, (2) a description
of the work area or portions thereof to be mowed, (3) location data
or geographic coordinates of points defining a perimeter or
boundary of the work area, (4) location data or geographic
coordinates of points defining fixed obstacles, mobile obstacles,
or both within or around the work area, and (5) historical or
empirical data on minimization of cost of mowing or mowing time.
The mission planner 76 may comprise a path planner. In one
embodiment, the path planner supports generation of a path plan or
selection of pre-programmed path plan for movement of the mower 10.
The path plan data or other input data may be communicated from the
base station 72 to the controller 70. The path plan may be subject
to suspension, interruption or cancellation for safety or other
reasons.
[0046] In an alternate embodiment, the user interface 74 supports
tele-operation or remote control of the mower by an individual.
Accordingly, the user interface may be equipped with controls,
buttons, switches or other electromechanical interfaces for
steering, stopping, starting, controlling, and safeguarding the
mower 10.
[0047] The controller 70 and a base station 72 communicate with
each other via a wireless communications device 68, a wireless
modem 60 or both. The wireless communications device 68 may
comprise a transceiver that modulates an electromagnetic signal
with an analog or digital modulation (e.g., phase-shift keying,
code division multiple access, time division multiple access,
spread spectrum, frequency hopping spread spectrum or otherwise).
The wireless modem 60 generally comprises a wireless modem 60.
[0048] In one configuration, the presence of both the wireless
modem 60 and the wireless communications devices 68 supports
redundancy in communications with a user at a base station 72.
Accordingly, if either the wireless modem 60 or the wireless
communications device 68 fails, becomes jammed, subject to
interference or otherwise inoperable, communications may be routed
to the other functioning communication device (between the wireless
modem 60 and wireless communications device 60) with due
consideration of transmission rate or bandwidth constraints.
[0049] In another configuration, the wireless modem 60 may comprise
a wireless transceiver that operates over a lesser bandwidth than
the high-bandwidth wireless communications device 68. Accordingly,
the wireless communications device 68 may transmit and/or receive
data at a higher transmission rate (e.g., bits per second) than the
wireless modem 60. The higher transmission rate may be suitable for
transmission of one or more of the following between the controller
70 and the base station 72: real-time video signals from the
controller 70 to the base station 72, real-time mission plan or
path planning data from the base station 72 to the controller 70,
field optical guidance data (FOG data), and location data from the
location-determining receiver 66 to the base station 72.
[0050] The controller 70 receives input data from a wireless modem
60 and a wireless communications device 68. The controller 70
includes a master control node 62 that receives input data from a
location-determining receiver 66 (e.g., Global Positioning Receiver
66), a field optical guidance 64 (FOG) system, a wireless modem 60,
and a high-bandwidth wireless communications device 68. The master
control node 62 provides output data to one or more steering motor
amplifiers 86 and drive motor amplifiers 88. As shown in FIG. 5B,
the steering motor amplifiers 86 includes a first steering motor
amplifier 200, a second steering motor amplifier 201, and a third
steering motor amplifier 202. The drive motor amplifiers 88
includes a first drive motor amplifier 209, a second drive motor
amplifier 210, and a third drive motor amplifier 211.
[0051] The steering motor amplifiers 86 provide suitable power
signals for the steering motors 44. The driver motor amplifiers 88
provide suitable power signals or the absence thereof for
controlling the rotation of the shafts associated with the drive
motors 50. The steering encoders 40 provide feedback signals or
feedback data for the corresponding steering motors 44 to control
the angular position of each steering motor 44 at any corresponding
point in time. The drive encoders 54 provide feedback signals for
the corresponding drive motors 50 to provide status information to
one or more drive motors 50. The status information may include one
or more of the following: angular position of a motor shaft versus
time, speed, torque, velocity, acceleration, and revolutions per
unit time for steering motor 44, a drive motor 50, or both.
[0052] In one embodiment, the direction of travel of the vehicle
may be controlled by the angular position or steered direction of
orientation of each wheel. In another embodiment, the application
of electrical energy to one or more drive motors 50 may allow the
vehicle to be steered under certain conditions, regardless of
whether the steered direction of the wheels is changed. For
example, the mower 10 may be permitted to torque steer, "spin
steer," or "skid steer" by providing differential torque to
different wheels of the mower 10, without changing the steered
direction or angular position of the wheels with respect to any
reference point on the frame or another fixed part of the mower 10.
The controller 70 may energize a drive motor 50 (a) to apply more
revolutions to one wheel per unit time than one wheel than to
another wheel of the mower 10 to turn the mower or (b) to apply
rotation in opposite directions to different wheels on the vehicle
to turn or spin the mower.
[0053] The steering motor amplifiers 86, the steering motors 44,
and steering encoders 40 are mounted on and/or housed within the
wheel assemblies 16. The drive motor amplifiers 88, the drive
motors 50, and the drive encoders 54 are mounted on/or housed
within the wheel assemblies 16. The first wheel assembly comprises
(a) a first steering motor amplifier 200 and a first steering
encoder 206 coupled to the corresponding first steering motor 203
and (b) the first drive motor amplifier 209 and the first drive
encoder 215 coupled to the first drive motor 212. The second wheel
assembly comprises (a) the second steering motor amplifier 201 and
a second steering encoder 207 coupled to the second steering motor
204 and (b) the second drive motor amplifier 210 and the second
drive encoder 216 coupled to the second drive motor 213. The third
wheel assembly comprises (a) the third steering motor amplifier 202
and the third steering encoder 208 coupled to the third steering
motor 205 and (b) the third drive motor amplifier 211 and the third
drive encoder 217 coupled to the third drive motor 214. In this
paragraph, "coupled" refers to an electrical or electromagnetic
connection.
[0054] An electrical supply system 78 may include batteries 80 and
an electrical charging system 82. The batteries 80 may be charged
by an alternator, a generator, or a magneto driven by the
mechanical power of the propulsion unit 12 (e.g., engine), for
example. The electrical supply system 78 may be associated with a
power distribution board 84 that routes electrical energy from the
electrical supply system to various components of the controller 70
and the electrical system 71. For example, the electrical supply
system 78 may provide electrical energy to the steering motor
amplifiers 86 and the drive motor amplifiers 88.
[0055] In an alternate embodiment, the controller 70 may further
control hydraulic, mechanical, cable or electromechanical brakes
that stop the rotation of one or more wheels of the mower. In
another alternate embodiment, one or more drive motors are selected
to resist rotation of their shafts if electrical energy or voltage
potential is not applied to such drive motors and the controller 70
is configured to withdraw such electrical energy to brake (e.g.,
stop or slow) the mower 10 as required.
[0056] FIG. 6 shows a top view of the mower 10 completing an
approximately zero radius trim maneuver. Each cluster of three
non-concentric circles is suggestive of a top view of a deck of the
mower 10. A first position of the mower 10 at a first time is shown
by the cluster of three non-concentric circles in dashed lines 303,
whereas the second position of the mower 10 at a second time is
illustrated by the solid lines 304. The second time may be later
than the first time. The arrow 300 shows that the mower 10 is
rotating in a clockwise direction about a reference axis 301 of
rotation from a first position to a second position. Although the
mower 10 has rotated approximately one-hundred and eighty degrees
302 as illustrated, the approximately zero radius trim maneuver may
be made from greater than zero degrees to approximately
three-hundred and sixty degrees.
[0057] Alternatively, the mower 10 may make multiple revolutions
about the reference axis 301 during which the cutting blade is
successively lowered to trim high grass or vegetation, for
instance.
[0058] In order to complete the zero trim circle of FIG. 6, each
wheel of the mower 10 is oriented generally orthogonal to a
corresponding radius about the reference axis 301. In other words,
each wheel of the mower is oriented generally tangential to a
corresponding arc (e.g., a portion of circle 305 or circle 307)
formed by the radii about the reference axis 301. The mower 10
orients the wheels by energizing or de-energizing the steering
motors 44 associated with the wheel assemblies. In one embodiment,
each wheel may be locked in position when it reaches a generally
tangential position to the arcs formed by the radii about the
reference axis 301. Energy may be applied to the drive motors 50 of
one or more of the outer wheels to drive the mower 10 on the ground
to achieve the desired degree of rotation of the mower 10 from
greater than zero to three-hundred and sixty degrees or more.
[0059] FIG. 7 is a method for executing an approximately zero
radius trim maneuver of a mower 10. FIG. 6 provides an illustrative
example of an approximately zero radius trim maneuver executed in
accordance with the method of FIG. 7. The method of FIG. 6 begins
in step S100.
[0060] In step S100, a target area is identified for application of
the approximately zero radius trim maneuver. The target area may be
designated as a portion of a work area to be serviced by the mower
10. With respect to a zero radius trim, the target area may
represent a remnant unmowed region of a lawn or another work area.
The remnant unmowed region may comprise one or more remaining uncut
central portions of a lawn, which results from a perimeter tracking
path plan in which the mower follows an outer perimeter of the
uncut vegetation (e.g., grass) of the work area for one or more
successively inward passes to generate a mowed outer region and one
or more unmowed central regions. Multiple unmowed central regions
may be present where an obstacle, such as a building, covers a
portion of the work area.
[0061] In step S101, the controller 70 positions a critical point
of the mowing deck or an outer periphery (e.g., bumper) over a
reference axis or substantially adjacent thereto a reference axis
301.
[0062] In step S102, the controller 70 orients each wheel generally
tangentially to a corresponding arc about the reference axis 301 of
rotation. The corresponding arc may define at least a portion of
the first circle 305 and a second circle 307 (of lesser radius than
the first circle), for example. Up to two wheels of the mower 10
may overlie or track at least a portion of the second circle 307
depending upon the relative position and geometry of the wheel
assemblies, whereas one wheel overlies the first circle 305. In
alternate configurations, each wheel may overlie or track a
corresponding arc, circle or semi-circle.
[0063] In step S104, the controller 70 controls the application of
rotational mechanical energy to one or more of the wheels to rotate
the mower 10 about the reference axis 301 of rotation by a desired
revolutional amount (e.g., fraction and/or number of
revolutions).
[0064] FIG. 8 shows a top view of the mower 10 completing a near
zero radius trim maneuver or a greater than zero radius trim
maneuver. Each cluster of three non-concentric circles is
suggestive of a top view of a deck of the mower 10. A first
position of the mower 10 at a first time is shown by the cluster of
three non-concentric circles in dashed lines 503, whereas the
second position of the mower 10 at a second time is illustrated by
the solid lines 504. The second time may be later than the first
time.
[0065] A minimum radius 552 is selected around the object 550. If
the minimum radius 552 were rotated about a center point associated
with the object, it would form an reference arc 554. The reference
arc 554 may have a traversed portion 556 (indicated by the solid
curved line) that is traversed by a critical point of the mower 10
and an un-traversed portion 558 (indicated by the dashed line) that
is not traversed by the critical point of the mower 10. The
critical point of the mowing deck may mean one or more of the
following (a) an outermost projecting portion of the mowing deck
with respect to a center point of the mower, (b) an outermost
projecting portion of the mowing other than a discharge region, (c)
an outer peripheral zone of the mowing deck with the edge of the
cutting blade most proximate thereto, and (d) a radially outmost
edge of one or more cutting blades of the mower.
[0066] The wheels of the mower are aligned tangentially to
respective arcs about the object 550. In one embodiment, the
minimum radius 552 is selected such that an edge or periphery or
critical point of the mowing deck is generally tangential to the
object 550 or generally tangential to the object 550 with a minimal
clearance zone to avoid abrading or bumping into the object.
[0067] The arrow 300 shows that the mower 10 is rotating in a
clockwise direction about an object 550 from a first position to a
second position. Although the mower 10 has rotated approximately
one-hundred and eighty degrees as illustrated, the approximately
zero radius trim maneuver may be made from greater than zero
degrees to approximately three-hundred and sixty degrees.
[0068] FIG. 9 is a method for executing a near zero radius trim or
greater than zero radius trim maneuver of a mower. FIG. 8 provides
an illustrative example of a greater than zero radius trim maneuver
executed pursuant to the method of FIG. 9. The method of FIG. 9
begins in step S500.
[0069] In step S500, a target area is identified for application of
the near zero radius trim or greater than zero radius trim
maneuver. The target area may be designated as a portion of a work
area to be serviced by the mower 10. With respect to a near zero
radius trim or greater than zero radius trim maneuver, the target
area may represent an unmowed region of vegetation around an object
550 (e.g., a pole, tree, fire hydrant, a stake, bush, a plant or
otherwise). A minimum radius 552 is selected around the object that
provides sufficient clearance (one no clearance if desired) between
the object 550 and the mower 10. For example, the sufficient
clearance may depend upon one or more of the following factors: (a)
maintaining adequate physical clearance between a periphery (e.g.,
guard 20) of the mower 10 and the object 550 to avoid bumping,
scuffing, abrading or other contact with the object, (b)
maintaining a sufficiently close cut to the object as influenced by
the placement and configuration of the cutting blades with respect
to the deck and the outer periphery of the mower 10, (c) aligning
an edge or periphery of the mowing deck to be generally tangential
or otherwise adjacent to the object 550 without contacting or
abrading the object 550, and (d) contacting the object 550 with the
guard 20 or with rollers, elastomeric bumpers, or other
non-destructive means.
[0070] In step S501, the controller 70 positions a critical point
of the mowing deck or an outer periphery of the mower over the
reference arc 554 or substantially adjacent to the reference arc
554. For example, the critical point of the mowing deck overlies or
tracks the traversed portion 556 of the reference arc 554.
[0071] In step S502, the controller 70 aligns the steered direction
of the wheel to be generally tangential to two or more respective
arcs that are generally concentric with respect to the reference
arc 554. The steered direction means the angular orientation of a
respective wheel with respect to a corresponding steering axis of
the wheel assembly. FIG. 8 illustrates the reference arc 554 as a
traversed portion 556 (indicated by the solid line) and an
untraversed portion 558 (indicated by a dotted line). The traversed
portion 556 may extend any desired amount (e.g., angular or
rotational displacement) necessary to trim the vegetation around
the object 550, while avoiding obstacles. For example, the
traversed portion 556 may be semi-circular or generally
circular.
[0072] In an alternate procedure, step S502 may be replaced by the
controller 70 aligning the steered direction of orientation of the
wheels with respect to a reference axis associated with the object
550 or lying within the object 550.
[0073] In step S504, the controller 70 controls the application of
rotational mechanical energy to one or more of the wheels to rotate
the mower 10 about the object by a desired fraction and/or number
of revolutions.
[0074] The method of FIG. 10 represents one illustrative technique
for executing a near zero radius trim maneuver or other close
trimming around an object 550. The method FIG. 10 illustrates an
alternative technique to FIG. 9 for executing a near zero radius
trim maneuver. The method of FIG. 10 begins in step S700.
[0075] In step S700, an edge or periphery of the mowing deck (e.g.,
including guard 20) is positioned generally tangentially to an
object 550 for mowing or trimming vegetation (e.g., grass) near or
around the object 550. In one example, the mower 10 is moving along
a global path plan and reaches a proximate point of the path plan
that is closest to the object, where the controller 70 deviates
from the global path plan to orient the wheels of the mower 10 in
any possible (e.g., the most efficient) steering orientation to
bring the mowing deck in proper alignment with the object 550
(e.g., over the shortest possible time or traversed distance of the
mower 10).
[0076] In step S702, after the mowing deck is aligned with the
object 550 or a clearance zone about the object 550, the controller
70 orients an angular direction (e.g., the steering orientation) of
the wheels (e.g., all of the wheels) in preparation for traversing
a generally tangential arc about the object 550. The generally
tangential arc may comprise a substantially curved portion or the
entire portion of an ellipsoid, an ellipse, a semi-ellipse, a
semi-circle, an ovoid, and a circle.
[0077] In an alternate technique for carrying out step S702, if it
is not desired for the mower 10 to track a generally circular or
elliptical shape around the object 550, the controller 70 may
dynamically change a steering orientation of the wheels to track a
substantially curved or substantially linear segment of a desired
contour around the object. The desired contour around the object
550 may be defined by a combination of generally linear segments,
non-linear segments, curved segments, or other contours.
[0078] In step S704, the controller 70 applies propulsion or
rotational force to one or more of the wheels to move the mower 10
about the object 550 by the desired amount, consistent with
selected wheel orientation of step S702. Following step S704, the
controller 70 may realign the position of the mower to be
coincident with or to otherwise merge with the global path plan.
For instance, the mower 10 may return to the global path plan at
the proximate point to continue mowing from the proximate point to
provide an efficient transition between the near zero radius trim
maneuver and the global path plan.
[0079] FIG. 11 illustrates the mower 10 moving in an approximately
zero radius turn, in which the mower 10 spins on a reference axis
301 at a desired point within the work area. The mower 10 is
represented by the cluster three non-concentric circles shown at
two discrete time instants during its revolution about the axis
301. At a first time the mower is at a first position as indicated
by the dashed lines 311 and at a second time the mower is at a
second position as indicated by the solid lines 309. The
displacement between the first and second positions represents a
generally orthogonal left (counterclockwise) turn, as illustrated
by right angle 399, although other types and directions of turns
are possible and fall within the scope of the invention. The mower
10 may make a factional revolution or any number of revolutions
about the axis 301. To carry out the zero radius turn of FIG. 11,
three of the wheels are oriented in a generally tangential manner
with respect to a circular zone 305 about the axis 301. Energy is
applied to one or more of the drive motors 50 to spin the mower 10
by the desired angular amount 22.
[0080] FIG. 12 is a method for making an approximately zero radius
turn maneuver. FIG. 11 is one illustrative example of carrying out
the method of FIG. 12. The method of FIG. 12 begins in step
S108.
[0081] In step S108, a controller 70, a mission planner 76 or both
define a reference axis 301 of rotation at a desired point along a
path segment of the mower 10. The desired point may represent a
point where the mower 10 could service the work area or extending
beyond the work area without the mower or one or more of its
cutting blades extending beyond a boundary (e.g., outer perimeter)
of the work area by more than an allowable tolerance.
[0082] In step S110, the wheels are oriented generally tangentially
to a circular region 305 about the reference axis 301 of
rotation.
[0083] In step S112, rotational mechanical energy is applied to one
or more of the wheels to rotate the mower by a desired angular
amount (e.g., 90 degrees for a generally orthogonal turn, to the
left (counterclockwise) or the right (clockwise)). For example,
drive motors 50 may apply rotational energy to the wheels.
[0084] In step S114, the controller 70 stops the application of
rotational energy to one or more of the wheels before or upon
completion of rotation to achieve rotation of a fixed reference
point on the mower 10 by the desired angular amount.
[0085] In step S116, the wheels 51 of the mower 10 are reoriented
toward the steered direction of a next desired path segment.
[0086] FIG. 13 illustrates the mower 10 traversing over at least a
fraction of a work area. The mower 10 travels in a direction
indicated by the arrow heads 406. The work area includes a first
row 400 traveled in a first direction that is spaced apart from a
second row 402 traveled in a second direction, that is generally
opposite the first direction. The rows (400, 402) may be spaced
apart by an amount less than one mower width or one cutting swath
of the mower 10 to allow for cutting overlap between adjacent rows
(400, 402). The first row 400 and the second row 402 are connected
by a transverse section 404 or transition section, which is
generally transverse with respect to the first row 400 and second
row 402. The first row 400 forms a generally right angle with the
traverse section 404 and the second row 402 forms a generally right
angle with the transverse section 404.
[0087] The mower 10 may track the first row 400, followed by
execution of a first zero radius turn of approximately ninety
degrees at the end of the first row 400 at a first axis 408. The
first axis 408 is located at the intersection of the first row 400
and the transverse section 404. The mower 10 moves in a generally
linear direction along the traverse section 404 of length 411 until
it reaches a termination point of the traverse section 404 and
makes a second zero degree radius turn of approximately ninety
degrees at a second axis 410. The mower 10 is aligned with the
second row 402 and moves in a generally linear direction along the
second row 402, and so forth, until the desired portion of the work
area is covered.
[0088] FIG. 14 illustrates the mower 10 following a path plan to
traverse or cover a work area. FIG. 13 provides an illustrative
example of the mower following a path in accordance with the method
of FIG. 14. The path plan of FIG. 14 may represent back and forth
movement of the mower 10 along generally parallel rows within a
generally polygonal (e.g., rectangular) work area, where adjacent
rows are interconnected by one or more generally orthogonal turns
of the mower. The method of FIG.14 begins in step S200.
[0089] In step S200, the mower 10 moves along a first row 400 of a
path plan in a first direction (e.g., indicated by the direction of
arrowhead 406). For example, the mower moves along a first
generally linear row as the first row 400.
[0090] In step S202, the mission planner or controller 70 defines
an end point of the first row 400 as a first axis 408 of rotation.
For example, the end point of the first row may be selected such
that an outer cutting edge of a cutting blade of the mower, an
outer edge of a mowing deck, or guard 20 is generally coextensive
with a boundary or perimeter of the work area.
[0091] In step S204, the drive motors 50, the drive encoder 54, and
the controller 70 cooperate to rotate the mower by approximately
ninety degrees with respect to the first axis 408 of rotation. The
method of FIG. 14 may be used to execute the generally right angle
turn of the mower in step S204.
[0092] In an alternative procedure for executing step S204 that is
referred to as "crabbing over" or a modified turn, the drive motors
50, the drive encoder 54, and the controller do not rotate the
mower by approximately ninety degrees, but merely change the
orientation of the wheels by approximately ninety degrees. For
example, at the end point of the first row 400, the controller
stops or pauses the mower, while simultaneously rotating the wheels
by approximately ninety degrees, prior to proceeding along in a new
direction in step S206 that is generally orthogonal to the first
row 400.
[0093] In step S206, the mower 10 moves along a transverse section
404 that is substantially orthogonal to the first row 400. The
length 411 of the transverse section may be selected to provide a
proper generally parallel spacing between the first row 400 and the
second row 402, in which the swath or cut width of the mower is
permitted to overlap. Accordingly, the centerline of each row is
generally spaced apart by less than one-half of the swath or cut
width of the mower to minimize overlap and reduce energy
consumption of the mower.
[0094] In step S208, the mower 10 defines an end point of the
transverse section as a second axis 410 of rotation. In one
embodiment, the end point lies at the end of the length of the
transverse section 404.
[0095] In step S210, one or more drive motors 50 rotate the mower
10 by approximately ninety degrees with respect to the second axis
410 of rotation. The method of FIG. 12 may be used to execute the
generally right angle turn of step S210.
[0096] In an alternative procedure for executing step S210 that is
referred to as "crabbing over" or a modified turn, the drive motors
50, the drive encoder 54, and the controller 70 do not rotate the
mower by approximately ninety degrees, but merely change the
orientation of the wheels by approximately ninety degrees. For
example, at the end point of the transverse section 404, the
controller stops or pauses the mower, while simultaneously rotating
the wheels by approximately ninety degrees, prior to proceeding
along in a new direction in step S212 that is generally orthogonal
to the transverse section 400.
[0097] In step 212, one or more drive motors 50 move the mower 10
along a second generally linear row 402 in a generally opposite
direction (e.g., indicated by arrowhead 406) with respect to the
first direction.
[0098] FIG. 15A through 15C, inclusive, illustrate the steered
direction of the wheels 51 of the mower 10 oriented in a linear
mode. In a linear mode, the mower 10 travels in a generally linear
path and the directions of the wheels 51 are generally parallel to
each other. FIG. 15A illustrates a linear mode in which the mower
10 moves forward or backwards. FIG. 15B illustrates a linear mode
in which the mower 10 moves sideways. FIG. 15C illustrates a linear
mode in which the mower 10 moves diagonally.
[0099] FIG. 16 illustrates an arc mode in which the mower 10 turns
with reference to a reference point 161 or reference axis that is
spaced apart from the mower 10. Here, in FIG. 16 the reference
point 161 or reference axis does not lie beneath the mowing deck
18. In an arc mode, the mower follows a path or path segment 167 of
an arc, a semi-circle, a semi-ellipse, an ellipse, or a circle with
reference to the reference point 161. The path segment 167 is
indicated by dotted curved line. The arc mode may be accomplished
with a constant radius (from each wheel 51 to the reference point
161) over time to produce a circle or semi-circular figure.
[0100] Referring to FIG. 16, a first radius 163 has a first length
between a first wheel 151 and the reference point 161; a second
radius 164 has a second length between a second wheel 251 and the
reference point 161; a third radius 165 has a third length between
a third wheel 351 and the reference point 161, where the at least
two of the first length, the second length, and the third length
are different from one another. The first wheel 151 may track a
first arc 168 having the first radius 163; the second wheel 251 may
track a second arc 170 having the second radius 164; the third
wheel 351 may track a third arc 169 having a third radius 165. If
the first radius 163, the second radius 164 and the third radius
165 (collectively radii) are kept constant, the mower 10 follows a
generally semi-circular path or generally circular path. The wheels
51 (including the first wheel 151, the second wheel 251, and the
third wheel 351) may be aligned generally perpendicular to their
corresponding radii, which is equivalent to tangential alignment
with their corresponding arcs.
[0101] In an alternate embodiment, one or more of the radii from
the reference point are varied over time to produce an elliptical
path or a spiral path or other curved paths of the mower.
[0102] FIG. 17 illustrates a rotating mode in which the mower 10
rotates about a center point 166 (of the mower 10) that overlies or
coincides with a reference point 161. The first radius 172 is
located between the reference point 161 and the first wheel 151,
the second radius 173 is located between the reference point and
the second wheel 251, the third radius 174 is located between the
reference point and the third wheel 351. As illustrated in FIG. 17,
the first radius 172 is generally orthogonal to the second radius
173; the second radius 173 is generally orthogonal to the third
radius 174. The wheels 51 (including the first wheel 151, the
second wheel 251, and the third wheel 351) may be aligned generally
perpendicular to their corresponding radii, which is equivalent to
tangential alignment with their corresponding arcs. Accordingly,
the wheels cover or scribe a generally circular or semi-circular
shape 175 about the reference point 161. The semi-circular shape
175 is indicated by the dashed lines.
[0103] The rotating mode may be combined with the linear mode or
the arc mode to produce a linear-rotating mode or an arc-rotating
mode. In the linear-rotating mode, the mower moves along a linear
progression and the mower pauses or coasts to rotate with respect
to at least one stationary or mobile reference point along the
linear progression by an angular displacement over time. The
angular displacement may be selected to prepare the mower for an
upcoming or next maneuver. In the arc-rotating mode, the mower
moves along a curved progression and the mower pauses or coasts to
rotate with respect to at least one stationary or mobile reference
point along the linear progression by an angular displacement over
time. The angular displacement may be selected to prepare the mower
for an upcoming or next maneuver. For instance, the rotating mode,
the linear-rotating mode, or the curved-rotating mode may be used
to align a critical point of the mowing deck with a reference point
or axis for a subsequent or planned trimming operation.
[0104] FIG. 18 illustrates an interior arc mode in which the
reference point 180 lies within or underneath a perimeter of the
mower 10. The wheels 51 are aligned perpendicularly to radii 181
about the reference point 180. The radii 181 are indicated by the
solid lines extending between the reference point 180 and the
wheels 51. The mower 10 follows an arc or curved path 182 indicated
by the dotted line. Each wheel 51 follows or tracks the arc or
curved path indicated by the dashed lines 183.
[0105] The trim mode of FIG. 19 is similar to the interior arc mode
of FIG. 18, except reference point 191 of FIG. 19 is located
differently than reference point 180 of FIG. 18. Like numbers
indicate like elements in FIG. 18 and FIG. 19.
[0106] FIG. 19 illustrates a zero radius trim mode or near zero
radius trim mode in which the reference point 191 is coextensive
with or adjacent to a critical point 190 on the outer periphery of
the mower. A critical point (e.g., 190 or 191) of the mowing deck
may mean one or more of the following (a) an outermost projecting
portion of the mowing deck with respect to a center point of the
mower, (b) an outermost projecting portion of the mowing other than
a discharge region, (c) an outer peripheral zone of the mowing deck
with the edge of the cutting blade most proximate thereto, and (d)
a radially outmost edge of one or more cutting blades of the mower.
Although the invention may be practiced with a mowing deck with
only one critical point 190, the mowing deck may have other
critical points 191 besides the critical point 190. The mowing deck
of FIG. 19 has three critical points (190, 191), for example.
[0107] The trim mode of FIG. 20 is similar to the trim mode of FIG.
19 and the interior arc mode of FIG. 20, except the critical point
190 of FIG. 20 is spaced apart from the reference point 195 by a
radial clearance 196. Like reference numbers in FIG. 18 through
FIG. 20 indicate like elements.
[0108] FIG.20 represents a greater than zero radius trim mode in
which the reference point 195 lies outside of the mower 10 by a
radial clearance 196 to avoid striking or damaging an object 197
(or to contact the object in a controlled manner). The reference
point 195 may be coincident with or adjacent to an object 197 such
that a suitable clearance radius is established between an outer
periphery of the object 197 and the outer periphery of the mower
10.
[0109] FIG. 21 shows an illustrative data structure for path plan
data. In accordance with FIG. 21 the path plan data has two
hierarchical levels: (1) path segments identifiers and (2) path
segment data. The path segment data depends upon a corresponding
path segment identifier. In one embodiment, the path segment
identifier represents a parent data type with respect to path
segment data; the path segment data represents a child data type to
the path segment identifier.
[0110] In the illustrative data structure of FIG. 21, the first
path segment identifier is associated with a first starting
coordinate (X.sub.1, Y.sub.1), a destination coordinate (X.sub.2,
Y.sub.2), a mode (e.g., linear, arc, spiral, rotating, trim, or
combination)(M.sub.1), and reference point coordinates (where
applicable to the relevant mode, e.g., for arcs or trim
modes)(R.sub.1).
[0111] The second path segment identifier is associated with a
first starting coordinate (X.sub.2, Y.sub.2), a destination
coordinate (X.sub.3, Y.sub.3), a mode (e.g., linear, arc, spiral,
rotating, turn, crab-turn, or combination)(M.sub.2), and reference
point coordinate (where applicable)(R.sub.3). It should be noted
that the ending coordinate of the first path segment identifier is
the same as the starting coordinate of the second path segment
identifier, such that the first path segment and the second path
segment can form part of a continuous path plan for the mower.
[0112] In the example, the Nth path segment identifier is
associated with a first starting coordinate (X.sub.N, Y.sub.N): a
destination coordinate (X.sub.N+1, Y.sub.N+1), a mode (e.g.,
linear, arc, spiral, rotating, or combination)(M.sub.N), and
reference point coordinate (where applicable)(R.sub.N). Although N
may equal any whole number or positive natural number that is
greater than two in the example of FIG. 21, it is possible to
execute the invention with other values of N. It should be noted
that the ending coordinate of the previous path segment identifier
(e.g., the N-1 path segment identifier) is the same as the starting
coordinate of the Nth path segment identifier, such that the
previous path segment and the Nth path segment can form part of a
continuous path plan for the mower.
[0113] FIG. 22 represents an illustrative path plan consistent with
the path plan data structure presented in FIG. 23. The path plan
follows is executed in a work area 421 with one or more
obstructions. Here, for illustrative purposes, the obstructions
include a building 419 and an object 420. In practice, the path
plan may differ from the illustrative example of FIG. 22 to
accommodate a myriad of possible work areas and an assortment of
obstructions of various quantities, size, and scope.
[0114] The mower 10 follows a first path segment 407, which extends
from X.sub.1, Y.sub.1 to X.sub.2, Y.sub.2, in a linear mode. The
second path segment 408 may have the same starting and destination
point of X.sub.2, Y.sub.2. The second path segment 408 is conducted
in a rotating mode in which an approximately ninety (90) degree
clockwise turn is made. The mower 10 follows the third path segment
409, which extends from X.sub.2, Y.sub.2 to X.sub.3, Y.sub.3, in a
generally linear mode. The fourth path segment 410 has the same
starting and destination point of X.sub.3, Y.sub.3. The fourth path
segment 410 is conducted in a rotating mode in which the mower 10
makes an approximately ninety (90) degrees clockwise turn. The
mower 10 follows a fifth path segment 411, which extends from
X.sub.3, Y.sub.3 to X.sub.4, Y.sub.4 in a linear mode. For the
sixth path segment 413, the mower 10 changes to a trim mode or arc
mode in which the mower trims in an arc about a reference point 417
(associated with object 420). The sixth path segment 413 may start
at X.sub.4, Y.sub.4 and end at X.sub.4, Y.sub.4 to define the sixth
path segment 413 as an intervening arc, or circle executed between
the starting and the end coordinates.
[0115] The mower follows a seventh path segment 414 from X.sub.4,
Y.sub.4 to X.sub.5,Y.sub.5 in a linear mode. In an eighth path
segment 415, the mower 10 follows an arc path of a constant or
variable radius with respect to reference point 418 from a starting
point X.sub.5, Y.sub.5 to destination point X.sub.6, Y.sub.6. The
critical point of the mower (e.g., mowing deck) faces the area to
be trimmed and is aligned with a curved border (e.g., which
stretches along one side of the building 419), regardless of
whether the border is convex or concave. Accordingly, in one
illustrative example, the mower may reorient the critical point of
the mower 10 by altering the mode of the seventh or eight path
segment to a rotating-linear mode or a rotating curved mode,
respectively. After the eight path segment 415, the mower follows a
ninth path segment 416, which extends from at X.sub.6, Y.sub.6 to
X.sub.7, Y.sub.7.
[0116] Advantageously, the mower of the invention is highly
maneuverable and has a lower center of gravity than many other
mowers of comparable cutting width (e.g., riding mowers that
accommodate an on-board operator). In one configuration, the
mounting of the engine, drive motors 50, the steering motors 44,
and the lack of a human operator on-board the mower 10 facilitate a
generally low center of gravity of the mower to reduce the
possibility of tipping when mowing sloped terrain.
[0117] The maneuverability of the mower 10 supports flexible path
definition, which can be,used to vary paths to reduce soil
compaction, vegetation compaction or turf compaction. The
controller provides accurate steering angles and wheel speed for
minimizing tire scuffing and turf damage.
[0118] 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. For example, two of the three wheels of the mower may be
steered and driven to reduce costs of the mower. The remaining
wheel could be unsteered, not driven or both. In another example, a
high velocity air blower may be attached to the mower for blowing
grass clippings, leaves or other debris from the ground or paved
areas.
Assignment
[0119] The entire right, title and interest in and to this
application and all subject matter disclosed and/or claimed
therein, including any and all divisions, continuations, reissues,
etc., thereof are, effective as of the date of execution of this
application, assigned, transferred, sold and set over by the
applicant(s) named herein to Deere & Company, a Delaware
corporation having offices at Moline, Ill. 61265, U.S.A., together
with all rights to file, and to claim priorities in connection
with, corresponding patent applications in any and all foreign
countries in the name of Deere & Company or otherwise.
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