U.S. patent application number 09/841511 was filed with the patent office on 2001-09-20 for navigation method and system for autonomous machines with markers defining the working area.
Invention is credited to Abramson, Shai, Dror, Gideon, Peless, Ehud.
Application Number | 20010022506 09/841511 |
Document ID | / |
Family ID | 11067533 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022506 |
Kind Code |
A1 |
Peless, Ehud ; et
al. |
September 20, 2001 |
Navigation method and system for autonomous machines with markers
defining the working area
Abstract
A method for automatically operating a robot, attached to a
lawnmower or other unmanned machine, within an enclosed area is
disclosed. The method includes the steps of: 1) providing the
following elements: a proximity sensor positioned on the robot, a
boundary along the perimeter of the working area and along the
perimeter of each area enclosed in the working area in which the
robot should not operate, the boundaries being detectable by the
proximity sensor, a processing unit connected to the proximity
sensor and receiving an input therefrom, a navigation unit on the
robot to determine the coordinates of the robot relative to an
arbitrary origin, a direction finder, and a memory to store values
generated by the processing unit; and 2) causing the robot to move
along each of the boundaries provided around or within the working
area, to detect the boundaries and to memorize their shape, and to
store in the memory values representative of the coordinates of the
boundaries, thereby to generate a basic map of the working area.
When the robot is to operate within the area, the method includes
the steps of: (a) causing the robot to start from a starting point
having known coordinates within the basic map of the working area;
(b) continuously determining the coordinates of the robot by
analyzing data obtained from the navigation unit and by detecting
the vicinity of a boundary; and (c) correcting the actual position
of the robot on the basic map by comparing the calculated and the
actual coordinates of each detected boundary.
Inventors: |
Peless, Ehud; (Even Yehuda,
IL) ; Abramson, Shai; (Ramat Gan, IL) ; Dror,
Gideon; (Tel Aviv, IL) |
Correspondence
Address: |
SKJERVEN MORRILL MACPHERSON LLP
25 METRO DRIVE
SUITE 700
SAN JOSE
CA
95110
US
|
Family ID: |
11067533 |
Appl. No.: |
09/841511 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09841511 |
Apr 23, 2001 |
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08554691 |
Nov 7, 1995 |
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6255793 |
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Current U.S.
Class: |
318/580 |
Current CPC
Class: |
G05D 1/0234 20130101;
G05D 1/0274 20130101; G05D 1/0265 20130101; A01D 2101/00 20130101;
G01C 22/00 20130101; G05D 1/0219 20130101; A01D 34/008 20130101;
G05D 2201/0208 20130101; G05D 1/0261 20130101; G05D 2201/0216
20130101; G05D 1/0263 20130101; G05D 1/0227 20130101 |
Class at
Publication: |
318/580 |
International
Class: |
G05D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 1995 |
IL |
113913 |
Claims
1. A method for automatically operating a robot within an enclosed
area, comprising the steps of: providing a boundary along the
perimeter of the working area, the said boundary being detectable
by a proximity sensor; providing boundaries along the perimeter of
each area enclosed in the working area, in which it is desired that
the robot should not operate, the said boundaries also being
detectable by a proximity sensor; providing a proximity sensor
positioned on the robot; providing processing means connected to
the said proximity sensor and receiving an input therefrom;
providing location means on the said robot, to determine the
coordinates of the robot relative to an arbitrary origin, at any
specific time; providing direction finding means; providing memory
means to store values generated by the said processing means and,
optionally, by the said location means; causing the robot to move
along each of the boundaries provided around or within the said
working area, to detect the said boundaries and to memorize their
shape, and to store in the memory means values representative of
the coordinates of the said boundaries, relative to an arbitrary
origin, thereby to generate a basic map of the working area; when
the robot is to operate within the said area: (a) causing the robot
to start from a starting point having known coordinates within the
basic map of the working area; (b) continuously determining the
coordinates of the robot by analyzing data obtained from the
location means and by detecting the vicinity of a boundary; and (c)
correcting the actual position of the robot on the basic map by
comparing the calculated and the actual coordinates of each
detected boundary.
2. A method according to claim 1, wherein the boundary comprises a
metallic wire through which electric current flows, and the
proximity sensor comprises a magnetic field detector.
3. A method according to claim 1, wherein the boundary comprises a
guide wire through which an acoustic signal passes, and the
proximity sensor comprises an acoustic detector.
4. A method according to claim 1, wherein the boundary comprises
passive metallic means which is excitable by a magnetic field, and
the proximity sensor comprises an electric field detector.
5. A method according to claim 1, wherein the boundary comprises
passive magnetic means, and the proximity sensor comprises a
magnetic field detector.
6. A method according to claim 3, wherein the acoustic signal is in
the ultra-sound range.
7. A method according to claim 5, wherein said passive magnetic
means comprises a plurality of pins having magnets therein.
8. A method according to claim 5, wherein said passive magnetic
means comprises a multiplicity of magnets each shaped into the form
of pins.
9. A method according to claim 1, wherein the proximity sensor
comprises a high contrast pattern code reader and the boundary
comprises high contrast pattern means.
10. A method according to claim 9, wherein the boundary comprises a
two color guide wire having patterns of a first color at fixed
distances thereon and a second color for the non-patterned portions
of the guide wire.
11. A method according to claim 9, wherein the boundary comprises a
multiplicity of pins each having a high contrast pattern
thereon.
12. A method according to claim 1, wherein the proximity sensor
comprises a radiometer and the boundary comprises radioactive
means.
13. A method according to claim 12, wherein the boundary comprises
a guide wire having a radioactive unit placed at fixed distances
thereon.
14. A method according to claim 12, wherein the boundary comprises
a multiplicity of pins each having a radioactive unit thereon.
15. A method according to claim 1, wherein the proximity sensor
comprises a resonance tag meter and the boundary comprises a
multiplicity of pins having at least one coil-capacitive circuit
therein.
16. A method according to claim 1, wherein the proximity sensor
comprises a transceiver and the boundary comprises a multiplicity
of pins having at least one transceiver therein.
17. A method according to claim 1, wherein the location means
comprise movement measuring means.
18. A method according to claim 17, wherein the movement measuring
means comprise an odometer.
19. A method according to claim 1, wherein the robot is coupled to
a selected one of the group of: a vacuum cleaner, a floor sweeper
and a floor polisher.
20. A method according to claim 1, wherein the robot is coupled to
a lawn mower.
21. A method according to claim 20 and including the steps of:
providing the lawnmower with at least a plurality of lawn height
sensors; cutting a first swath of lawn in a first direction;
performing a maneuver, under control of said robot and in response
to output of said lawn height sensors, in a second direction
generally opposite of said first direction to bring said lawnmower
to a location parallel to but overlapping said first swath by a
predetermined percentage as indicated by the different output of
said lawn height sensors; cutting a second swath of lawn parallel
to said first swath while continually monitoring the lawn height
output of said lawn height sensors thereby to ensure that the
percentage of overlap is generally maintained; repeating said steps
of performing a maneuver and cutting a second swath for further
swaths of lawn, wherein the previously cut lawn is denoted by said
first swath of lawn and the swath to be cut is denoted by said
second swath of lawn.
22. A method for automatically cutting a lawn, the method
comprising the steps of: providing a lawnmower with a robot and at
least a plurality of lawn height sensors; cutting a first swath of
lawn in a first direction; performing a maneuver, under control of
said robot and in response to output of said lawn height sensors,
in a second direction generally opposite of said first direction to
bring said lawnmower to a location parallel to but overlapping said
first swath by a predetermined percentage as indicated by the
different output of said lawn height sensors; cutting a second
swath of lawn parallel to said first swath while continually
monitoring the lawn height output of said lawn height sensors
thereby to ensure that the percentage of overlap is generally
maintained; repeating said steps of performing a maneuver and
cutting a second swath for further swaths of lawn, wherein the
previously cut lawn is denoted by said first swath of lawn and the
swath to be cut is denoted by said second swath of lawn.
23. A method according to claim 22 and wherein said maneuver is an
S shaped maneuver.
24. A method according to claim 22 and wherein said step of
providing comprises the additional steps of: providing a boundary
along the perimeter of the working area, the said boundary being
detectable by a proximity sensor; providing boundaries along the
perimeter of each area enclosed in the working area, in which it is
desired that the lawnmower should not operate, the said boundaries
also being detectable by a proximity sensor; providing a proximity
sensor positioned on the lawnmower; providing processing means
connected to the said proximity sensor and receiving an input
therefrom; providing location means on the said lawnmower, to
determine the coordinates of the robot relative to an arbitrary
origin, at any specific time; providing direction finding means;
and providing memory means to store values generated by the said
processing means and, optionally, by the said location means.
25. A method according to claim 24 and wherein said steps of
cutting comprise the step of continuously determining the
coordinates of the lawnmower by analyzing data obtained from the
location means and by detecting the vicinity of a boundary.
26. A grass height sensor comprising: a housing; a rotatable wing
against which grass can push, said wing having a pin attached
thereto; a fixed second pin, connected to said housing; a spring
attached around said pin, wherein the ends of said spring press
against opposite sides of said wing and opposite sides of said
fixed pin; and means for measuring the angle of rotation of said
rotatable wing.
27. An automated robot for operation within an enclosed area,
comprising: a proximity sensor positioned on the robot; processing
means connected to the said proximity sensor and receiving an input
therefrom; location means, to determine the coordinates of the
robot relative to an arbitrary origin, at any specific time;
direction finding means; and memory means to store values generated
by the said processing means and, optionally, by the said location
means.
28. A robot according to claim 27, wherein the proximity sensor
comprises a sensor selected from the group of: a magnetic field
detector, an acoustic detector, an electric field detector, a bar
code reader, a radiometer, a resonance tag meter and a
transceiver.
29. A robot according to claim 27, wherein the location means
comprise movement measuring means.
30. A robot according to claim 29, wherein the movement measuring
means comprise an odometer.
31. A robot according to claim 27, which is coupled to a lawn
mower.
32. A robot according to claim 27, which is coupled to a vacuum
cleaner, or floor sweeper, or floor polisher.
33. A system for automatically operating a robot within an enclosed
area, comprising: boundary means suitable for positioning along the
perimeter of the working area, and of each area enclosed in the
working area, in which it is desired the robot not to operate, the
said boundary means being detectable by a proximity sensor; a robot
provided with a proximity sensor; processing means on said robot,
connected to the said proximity sensor and receiving an input
therefrom; location means on the said robot, to determine the
coordinates of the robot relative to an arbitrary origin, at any
specific time; memory means to store values generated by the said
processing means; direction finding means positioned on the said
robot, to determine the direction of travel thereof; and motion
means, to cause the robot to move.
34. A system according to claim 33, wherein the boundary means
which is detectable by a proximity sensor comprises a metallic wire
through which electric current flows, and the proximity sensor
comprises a magnetic field detector.
35. A system according to claim 33, wherein the boundary which is
detectable by a proximity sensor comprises a guide wire through
which an acoustic signal passes, and the proximity sensor comprises
an acoustic detector.
36. A system according to claim 33, wherein the boundary which is
detectable by a proximity sensor comprises a passive metallic means
which is excitable by a magnetic field, and the proximity sensor
comprises an electric field detector.
37. A system according to claim 33, wherein the boundary which is
detectable by a proximity sensor comprises passive magnetic means,
and the proximity sensor comprises a magnetic field detector.
38. A system according to claim 33, wherein the boundaries are
provided with a plurality of individually recognizable markers.
39. A system according to claim 38, wherein the markers are
substantially located at even distances from one another.
40. A system according to claim 38, wherein the marker comprises an
RF tag or a magnetic tag.
41. A system according to claim 33, wherein the boundary comprises
passive magnetic means, and the proximity sensor comprises a
magnetic field detector.
42. A system according to claim 41, wherein said passive magnetic
means comprises a plurality of pins having magnets therein.
43. A system according to claim 41, wherein said passive magnetic
means comprises a multiplicity of magnets each shaped into the form
of pins.
44. A system according to claim 33, wherein the proximity sensor
comprises a high contrast pattern code reader and the boundary
comprises high contrast pattern means.
45. A system according to claim 44, wherein the boundary comprises
a two color guide wire having patterns of a first color at fixed
distances thereon and a second color for the non-patterned portions
of the guide wire.
46. A system according to claim 44, wherein the boundary comprises
a multiplicity of pins each having a high contrast pattern
thereon.
47. A system according to claim 33, wherein the proximity sensor
comprises a radiometer and the boundary comprises radioactive
means.
48. A system according to claim 47, wherein the boundary comprises
a guide wire having a radioactive unit placed at fixed distances
thereon.
49. A system according to claim 47, wherein the boundary comprises
a multiplicity of pins each having a radioactive unit thereon.
50. A system according to claim 33, wherein the proximity sensor
comprises a resonance tag meter and the boundary comprises a
multiplicity of pins having at least one coil-capacitive circuit
therein.
51. A system according to claim 33, wherein the proximity sensor
comprises a transceiver and the boundary comprises a multiplicity
of pins having at least one transceiver therein.
52. A system according to claim 33, wherein the movement measuring
means comprise an odometer.
53. A system according to claim 33, wherein the robot is coupled to
a lawn mower.
54. A system according to claim 33, wherein the robot is coupled to
a device selected from the group of: a vacuum cleaner, a floor
sweeper and a floor polisher.
55. A system according to claim 53 and additionally including a
plurality of lawn height sensors for measuring the height of the
lawn and means for controlling said lawn mower to cut the lawn
along an already cut swath of grass.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and related
systems for navigation in an enclosed area. More particularly, the
invention relates to method and apparatus which can be used to
cause an automated device to move and to perform predetermined
tasks within an enclosed area.
BACKGROUND OF THE INVENTION
[0002] The use of automated devices is widespread nowadays, and
finds countless applications. For instance, robots perform very
precise and delicate tasks in the construction of electronic
devices, or in medicine and aviation. Robots are also used in uses
which require motion, notably, for automatic warehouses, where
goods are retrieved and stored by means of computer-actuated
robots. Other applications include, e.g., fetching raw materials in
the course of industrial manufacturing, and removing and packaging
finished pieces. In everyday's life, attempts have also been made
to exploit robots for lawn mowing and for vacuum cleaning.
[0003] The major drawback of mobile robots, which the art has so
far been unable to overcome, is the fact that their movements are
limited to well predefined paths, normally requiring that they move
along rails, or that they be provided with expensive navigation
signs, positioned within the area in which they move, which operate
as "stations" which redefine the exact position of the robot, and
from which the program may direct the robot to the next station.
These intermediate signs are expensive, take up space, and are
inconvenient to use, since they must be very precisely positioned
and cannot be easily moved.
[0004] Another approach involves providing an area delimited by
boundaries recognizable by the robot, and permitting the robot to
effect a random walk therein, during which random walk it carries
out its tasks. This approach entails severe drawbacks: first of
all, when the robot moves within a predefined area by random walk,
there is no way to ensure that the whole area will be covered by
the tool which must operate thereon. As a result, even though the
robot may operate for a long period of time, unworked areas may be
left at the end of the operation. Secondly, if the area to be
worked is irregular, or if it presents "islands", viz. areas which
must not be worked, the random walk may lead to imperfect operation
around such islands, as well as at those locations where the
perimeter is of irregular shape. Thirdly, because the operation of
the robot is not programmed to obtain a predetermined coverage, it
is necessary to allow the random walk to go on for a long period of
time, so as to increase the chances of covering a major portion of
the area to be worked. This is not only energy consuming, but also
leads to an increased wear of the equipment, and may also be
environmentally undesirable due, e.g., to noise or other pollution
caused by the operation of the robot. Even if the robot is operated
by sun energy, most of the aforesaid problems are not overcome, and
additional problems exists, connected with such a mode of
operation. For instance, the robot may not work properly in areas
of the world where sun radiation is scarce or low, and may be
inoperative for substantial parts of the day, e.g., on cloudy
weather.
[0005] A further approach involves preprogramming the robot with a
blueprint of its designated area of operation, such as a floor map
of a building in which a robot is to operate. This approach has two
major drawbacks:
[0006] a) it requires preprogramming by the user, which makes in
unpractical for extensive consumer use; and
[0007] b) it requires that such preprogramming is repeated each
time something changes in the work area.
[0008] It is therefore clear that it would be highly desirable to
be able to provide means by which automated mechanisms may move and
perform their task within a predetermined area, without being
hindered by the need for predefined paths and rails, or by
intermediate navigation signs or preprogramming, and which may
carry out their task in a predetermined manner, without relying on
random occurrences and/or on unstable energy sources.
SUMMARY OF THE PRESENT INVENTION
[0009] It has now been found, and this is an object of the present
invention, that it is possible to free automated mechanisms
operating within an enclosed zone from the need for preprogramming
or predefined paths and rails, and from the need for intermediate
navigation aids, and this to overcome the drawbacks of the prior
art and to provide means by which a robot may perform its tasks
within an enclosed area in a manner free from such limitations,
with high precision and in a minimal period of time.
[0010] It is an object of the present invention to provide a
navigation method which fulfills the aforementioned goals.
[0011] It is another object of the invention to provide means which
can be used in systems utilizing the method of the invention.
[0012] Other objects of the invention will become apparent as the
description proceeds.
[0013] The method for automatically operating a robot within an
enclosed area, according to the invention, comprises the steps
of:
[0014] providing a boundary along the perimeter of the working
area, the said boundary being detectable by a proximity sensor;
[0015] providing boundaries along the perimeter of each area
enclosed in the working area, in which it is desired that the robot
should not operate, the said boundaries also being detectable by a
proximity sensor;
[0016] providing a proximity sensor positioned on the robot;
[0017] providing processing means connected to the said proximity
sensor and receiving an input therefrom;
[0018] providing location means on the said robot, to determine the
coordinates of the robot relative to an arbitrary origin, at any
specific time;
[0019] providing direction finding means;
[0020] providing memory means to store values generated by the said
processing means and, optionally, by the said location means;
[0021] causing the robot to move along each of the boundaries
provided around or within the said working area, to detect the said
boundaries and to memorize their shape, and to store in the memory
means values representative of the coordinates of the said
boundaries, relative to an arbitrary origin, thereby to generate a
basic map of the working area;
[0022] when the robot is to operate within the said area:
[0023] (a) causing the robot to start from a starting point having
known coordinates within the basic map of the working area;
[0024] (b) continuously determining the coordinates of the robot by
analyzing data obtained from the location means and by detecting
the vicinity of a boundary; and
[0025] (c) correcting the actual position of the robot on the basic
map by comparing the calculated and the actual coordinates of each
detected boundary.
[0026] By "robot" it is meant to indicate any autonomously
operating device, which may carry out pre-programmed tasks with one
or more tools, while moving in the process from one location to
another.
[0027] According to a preferred embodiment of the invention, the
location means comprise movement measuring means, such as an
odometer or the like device, to measure the distance traveled by
the robot, e.g., by measuring the number of revolutions of a wheel.
As stated, direction finding means are also provided, so as to
provide information on the direction in which the robot travels at
any given time, which is needed in order to determine the
coordinates of the robot on the map. The direction finding means
can be of any suitable type, e.g., may comprise a compass.
[0028] While, as stated, it is an object of the invention to
utilize relatively inexpensive devices for the operation of the
robot, it is of course possible to employ more expensive and
sophisticated equipment, without exceeding the scope of the
invention. Thus, for instance, it is possible to employ
range-finding means, such as a laser range-finder or RF range
finders, to determine the distance of the robot from one or more
given locations, at any given time, instead of, or in addition to,
using an odometer or the like device to measure the distance
traveled. However, any such modifications will be apparent to the
skilled person, and therefore are not discussed herein in
detail.
[0029] According to a preferred embodiment of the invention, the
boundary which is detectable by a proximity sensor comprises a
metallic wire through which electric current flows, and the
proximity sensor comprises a magnetic field detector. According to
another preferred embodiment of the invention, the boundary which
is detectable by a proximity sensor comprises passive metallic
means which is excitable by a magnetic field, and the proximity
sensor comprises an electric field detector. In still another
preferred embodiment of the invention the boundary which is
detectable by a proximity sensor comprises passive magnetic means,
and the proximity sensor comprises a magnetic field detector. Of
course, the boundary may be marked by continuous or by
discontinuous marking means, or by combinations thereof.
[0030] In still another alternative embodiment of the invention,
the boundary which is detectable by a proximity sensor comprises a
guide wire through which an acoustic signal passes, and the
proximity sensor comprises an acoustic detector.
[0031] A further improvement in the precision of the determination
of the actual coordinates of the robot on the map, at any given
time, can be obtained by further providing on the boundaries a
plurality of individually recognizable markers. Thus, when the
robot reaches the boundaries, it not only identifies them by the
proximity sensor, but may also receive the exact coordinates on the
boundaries assigned to the specific marker it has detected.
According to a preferred embodiment of the invention, when
provided, the markers are substantially located at even distances
from one another. Suitable markers will be easily recognized by the
skilled person, and may comprise, e.g., an RF tag or magnetic
tag.
[0032] As stated, according to another preferred embodiment of the
invention, the distance-measuring means comprise an odometer or the
like device, coupled to the wheels of the robot.
[0033] As stated, the robot, when initialized, moves along the
boundaries and memorizes their shape. Such memorization may be
carried out in a number of ways. For instance, the shape can be
memorized by taking continuous or discontinuous readings of the
compass and the odometer, and any such readings are then
continuously integrated, to give the full coordinates of the
boundaries.
[0034] The method of the invention can be exploited in a variety of
uses, and is not limited to any particular field of application.
One particularly interesting use, however, to which reference will
be made also hereinafter for the purpose of exemplification, is
when the robot is coupled to a lawn mower. Such robot permits to
mow the lawn in the absence of the owner, and at any suitable time,
or to vacuum clean any predetermined premises.
[0035] Of course, safety means should preferably be provided to
ensure safe operation of the robot. for instance, automatic
shut-off of the robot should be provided, coupled to logic
circuitry, to ensure that the operation of the robot is
discontinued if one of a number of contemplated possibilities takes
place. for instance, if the measured distance traveled without
encountering a boundary exceeds by a threshold value the maximal
linear distance within the bounded area, as calculated from the map
of the boundaries, this may mean that the robot has exited the
boundaries due, for instance, to a malfunctioning of the system due
to which the proximity sensor has failed to identify the boundary.
Other required safety means will be easily recognized by the
skilled person, according to the type of robot and the intended use
thereof.
[0036] The invention is further directed to an automated robot for
operation within an enclosed area, comprising:
[0037] a proximity sensor positioned on the robot;
[0038] processing means connected to the said proximity sensor and
receiving an input therefrom;
[0039] location means, to determine the coordinates of the robot
relative to an arbitrary origin, at any specific time;
[0040] direction finding means; and
[0041] memory means to store values generated by the said
processing means and, optionally, by the said location means.
[0042] The term "proximity sensor", as used herein, indicates any
device which is capable of detecting that the boundary of the
working area is near. This may include, e.g., magnetic field
detectors, acoustic signal detectors, bar code readers, resonance
tag meters, transceivers, etc.
[0043] The invention also encompasses a system for automatically
operating a robot within an enclosed area, comprising:
[0044] boundary means suitable for positioning along the perimeter
of the working area, and of each area enclosed in the working area,
in which it is desired the robot not to operate, the said boundary
means being detectable by a proximity sensor;
[0045] a robot provided with a proximity sensor;
[0046] processing means on said robot, connected to the said
proximity sensor and receiving an input therefrom;
[0047] distance-measuring means on the said robot, to measure the
distance of the robot from a given starting point, at any specific
time;
[0048] direction finding means;
[0049] memory means to store values generated by the said
processing means and, optionally, by the said distance measuring
means and/or direction finding means; and
[0050] motion means, to cause the robot to move.
[0051] In accordance with a further embodiment of the invention, a
method for automatically cutting a lawn is provided. The method
includes the steps of:
[0052] providing a lawnmower with a robot and at least a plurality
of lawn height sensors;
[0053] cutting a first swath of lawn in a first direction;
[0054] performing a maneuver, under control of the robot and in
response to output of the lawn height sensors, in a second
direction generally opposite of the first direction to bring said
lawnmower to a location parallel to but overlapping the first swath
by a predetermined percentage as indicated by the different output
of the lawn height sensors;
[0055] cutting a second swath of lawn parallel to the first swath
while continually monitoring the lawn height output of said lawn
height sensors thereby to ensure that the percentage of overlap is
generally maintained;
[0056] repeating the steps of performing a maneuver and cutting a
second swath for further swaths of lawn, wherein the previously cut
lawn is denoted by said first swath of lawn and the swath to be cut
is denoted by the second swath of lawn.
[0057] The maneuver can be an S-shaped maneuver and the grass
height sensor can include the following elements:
[0058] a housing;
[0059] a rotatable wing against which grass can push, the wing
having a pin attached thereto;
[0060] a fixed second pin, connected to the housing;
[0061] a spring attached around said pin, wherein the ends of the
spring press against opposite sides of the wing and opposite sides
of the fixed pin; and
[0062] means for measuring the angle of rotation of the rotatable
wing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] The present invention will be understood and appreciated
more fully from the following detailed description taken in
conjunction with the drawings in which:
[0064] FIG. 1 schematically shows an enclosed area within which a
robot must operate, the shaded areas representing "islands" in
which the robot must not enter;
[0065] FIG. 2 shows, in cross-section, a boundary of FIG. 1,
according to a particular embodiment of the invention;
[0066] FIGS. 3(A and B) illustrates the method of the invention,
using polar coordinates;
[0067] FIG. 4 illustrates the method of the invention, using
Cartesian coordinates;
[0068] FIGS. 5(A and B) is a flow-sheet of an example of a location
correction process, according to one preferred embodiment of the
invention;
[0069] FIG. 6 is a flow chart of the operation of a system,
according to one preferred embodiment of the invention;
[0070] FIG. 7 is a pictorial illustration of a lawnmower following
the line of cut grass, constructed and operative in accordance with
a further preferred embodiment of the present invention;
[0071] FIG. 8 is a flow chart illustration of a method of operating
the lawnmower of FIG. 7;
[0072] FIG. 9 is a pictorial illustration useful in understanding
the method of FIG. 8;
[0073] FIG. 10 is a schematic illustration of a lawn height sensor,
useful in the method of FIG. 8;
[0074] FIGS. 11A and 11B are schematic illustrations of a
lawnmower, a sensor and two types of boundary markings, forming
further embodiments of the present invention; and
[0075] FIGS. 12A, 12B, 13A, 13B, 14A, 14B, 15 and 16 are schematic
illustrations of various types of boundary markings useful in the
embodiments of FIGS. 11A and 11B.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0076] The present invention will be better understood through the
following illustrative and non-limitative description of preferred
embodiments.
[0077] Looking now at FIG. 1, the working area in which the robot
must operate, indicated at "A", is enclosed by a boundary 1. Within
the working area there are "islands" in which the robot must not
penetrate, which are shadowed and enclosed by boundaries 2 and 3.
According to one embodiment of the invention, the robot is an
automated lawn mower, and the area A is a lawn. Islands 2 and 3 may
be, e.g., trees and their vicinities or flower beds. Thus, we wish
the mower to operate only in areas in which grass grows, and to
avoid other areas. Alternatively, the robot can be coupled to a
floor sweeper or a floor polisher or any other device which has to
scan a flat surface.
[0078] As stated, according to one particular embodiment of the
invention, the boundaries 1, 2 and 3 may comprise a conducting
wire. This type of boundary is shown in cross-section in FIG. 2,
which shows a wire 4, comprising a metallic core 5 and a plastic
outer layer 6. A current "i" is caused to flow through the wire,
thus generating a magnetic field along the wire. The intensity of
the current may be very low, since it is not necessary that the
magnetic field be sensed at a great distance from the boundary, and
it is sufficient that it be felt in the close vicinity of the wire.
The magnetic field is sensed, according to this particular
embodiment of the invention, by a magnetic field sensor provided on
the lawn mower. The magnetic field and the sensor to sense it are
conventional and well known in the art, and therefore are not
described here in detail, for the sake of brevity.
[0079] Taking the lawn mower as an example, but it being understood
that the invention is in no way limited to its use with a lawn
mower, or with any other particular device, the invention operates
as follows. A coordinates system is defined, as well as a starting
point. FIG. 3A shows a lawn mower L relative to the starting point
"S" within the lawn, the lawn mower L being at a point (.THETA.,r)
viz. at a distance r, which is measured by measuring the movement
of the mower, and at an angle .THETA. from starting point S, which
is measured by means of a compass. Thus, as shown in FIG. 2B, any
point within the enclosed area S will have a unique polar
coordinate.
[0080] When it is desired to teach the robot the boundaries of its
task, the lawn mower is caused first to move around the boundary 1
of FIG. 1. The memory means of the robot memorize the coordinates
of the boundary 1, relative to starting point S. Throughout this
teaching movement, the boundary sensor positioned on the robot (not
shown) senses the boundary 1. Similarly, the boundaries 2 and 3 are
sensed for the first time by the robot, and memorized for future
use. The robot now has an initial map of the area, similar to what
is shown in FIG. 3B, each point having been assigned a coordinate.
The set of coordinates so created will be termed "the map" of the
working area.
[0081] When it is desired to mow the lawn, the robot is brought to
starting point S, and it is started according to a set of
instructions which has been preprogrammed, and which may be
different for each different task. For instance, a circular lawn
may be better looking if mowed in circles, while a soccer field
requires back-and-forth mowing. An automated lawn mower according
to the invention may further be provided with a number of pre-set
programs, from which the user can choose.
[0082] The robot, as said, is further provided with
distance-measuring means, such as an odometer or the like device.
However, these devices are not fully accurate, and may provide only
approximate distance values for any given position. The error in
the measurement of the distance may derive from a variety of
reasons, e.g., the slipping of wheels on a moist lawn, uneven
ground, etc., and the error may build up to quite a substantial
extent, impairing the ability of the robot to complete its task
with a high degree of precision. While, of course, precise
measuring means exist, such as laser distance measurements, these
are expensive and/or require calibration targets located in or
around the working area. It is a purpose of the invention to avoid
the use of such expensive and complicated distance-measuring
means.
[0083] According to the invention, therefore, the robot starting a
task continuously compares the distance measured by the odometer or
other distance measuring device, with the distance from an earlier
position to the boundaries in the angular coordinate it is
following. If the boundary is detected earlier than anticipated
according to this comparison (or, in other words, if the difference
between the distance according to the map and the measured distance
is negative), the robot continues to move until the boundary is
detected. If the difference between the distance according to the
map and the measured distance is positive, or in other words, if
the boundaries are encountered earlier than expected, actual value
of the coordinate is corrected to be that of the map.
[0084] The starting point will initially be the point "S", and
correction of distance errors will be effected relative to this
point. As work proceeds, of course, the starting point may be
updated to be another point within the area, e.g., a meeting point
with the boundaries, for comparison purposes with the map of the
area.
[0085] Similarly, the robot has been pre-programmed to avoid
"islands", but will detect an island according to the actual
position of the boundary detected, and will correct its present
working map based on the detection of the boundary and the original
map. As will be understood by the skilled person, the larger the
number of bounded areas, the higher the precision of the correction
of the actual working map., Therefore, the islands actually help in
keeping precision and correcting the actual working map. therefore,
if the working area is particularly large, it may be desirable to
provide artificial islands for the purposes of map correction.
[0086] As will be appreciated by the skilled person, operating
according to the preferred embodiment of the invention described
above is very convenient also in respect of the boundaries, since
the wire or coil may be embedded in the soil, thus avoiding any
actual or even aesthetic disturbance to the working area, and the
power requirements to generate a localized magnetic field are very
small.
[0087] FIG. 4 shows an alternative embodiment of the invention, in
which the location of each point is measured in Cartesian
coordinates. As will be appreciated by the skilled person, it is
not essential to the invention that any specific coordinates system
be chosen, but it may be more convenient to select a particular set
of coordinates, depending on the map correction process
employed.
[0088] One particular process, employing Cartesian coordinates,
will be described hereinafter by way of example, with reference to
the flow-sheet of FIG. 5.
[0089] In FIG. 5A the correction of an error on one axis (Y in the
example shown in the flow-sheet of FIG. 5A) is shown, according to
one possible embodiment of the invention, while the error in the
other axis is not dealt with. FIG. 5B, on the other hand, shows a
method according to another possible embodiment of the invention,
in which both the X and the Y errors are corrected in one step. It
should be noted that, although only the error on one axis can be
corrected at a time in the embodiment of FIG. 5A, the error on the
other axis can be corrected by moving in a direction perpendicular
to the axis being corrected. The movement of the robot can be
programmed such that both the X and Y location coordinates are
updated at a suitable rate of correction.
[0090] In FIG. 5B another preferred embodiment of the invention is
shown, in which the boundaries are marked with markers (4 in FIG.
5B), which have a unique identity. The markers will typically be
conveniently evenly spaced, although any spacing scheme is
possible. The markers can be of any suitable type, e.g., and RF
tag, magnetic tag or the like marker, which emits a signal
identifiable by a sensor. In such a case, of course, a suitable
sensor, capable of identifying unique identity signals must also be
provided on the robot.
[0091] During the initiation process the robot performs a complete
loop around the edge and memorizes the shape of the boundary as
well as the position of each marker (X,Y coordinates of each
individual marker). This procedure allows for the correction of
both the X and the Y coordinates error, each time an edge is
detected, according to the method shown in the flow-sheet of FIG.
5B.
[0092] Schematically speaking, the robot will operate according to
the flow-sheet of FIG. 6.
[0093] Reference is now made to FIGS. 7, 8 and 9 which illustrate a
further embodiment of the robotic lawnmower of the present
invention. In this embodiment, the robot sweeps the space with
overlapping straight lines by determining the location of the edge
between uncut and cut grass.
[0094] In the present embodiment, the lawnmower, labeled 20 in FIG.
7, additionally includes a plurality of sensors 22, each one
measuring the height of the grass in its general vicinity. FIG. 7
shows two areas, one 24 of cut grass and one 26 of uncut grass.
Thus, sensors 22a and 22b will provide a high height output and
sensors 22c and 22d will provide a low height output.
[0095] By comparing the height output of the sensors 22, the
control system of the lawnmower can determine generally where the
edge between cut and uncut grass is. One embodiment of a sensor 22
is illustrated in FIG. 10 and described in detail hereinbelow.
[0096] FIG. 8 details the operations performed by the control
system of lawnmower 20 and FIG. 9 illustrates the movements of the
lawnmower 20 at the edge of the lawn. While the lawnmower 20 is
cutting a swath 25 indicated by dotted arrows in FIG. 9, the
sensors 22 continually measure the height of the lawn nearby (step
30). The control system, with the navigation system (compass and
odometer), steers the lawnmower 20 in the desired direction, as
described hereinabove, while additionally ensuring that the edge of
the lawn is maintained in a desired location vis-a-vis the sensors
22. For example, it may be desired to cut a swath which is only
three-quarters the width of the lawnmower. For this situation, the
edge between cut and uncut grass should be maintained between
sensors 22a and 22b or between sensors 22c and 22d.
[0097] The control system maintains the desired direction until the
edge of the lawn is detected, as described hereinabove. At this
point, the lawnmower 20 must change direction of movement while
keeping the proper percentage of uncut grass under the lawnmower
20. It is noted that the lawnmower can move both forward and
backward.
[0098] FIG. 9 illustrates the change in direction. Initially, the
lawnmower 20 moves in the forward direction along swath 25 (step
30). Upon reaching the edge, the lawnmower 20 performs an `S`
shaped backwards maneuver, labeled 40, using the navigation system,
until the edge between cut and uncut lawn is sensed between the
desired two sensors 22. This step is indicated in step 32 of FIG. 8
and produces an `S` shaped cut in the lawn. As shown by line A in
FIG. 9, the edge of the cut grass is maintained between the desired
two sensors 22.
[0099] In step 34, the lawnmower 20 moves forward along the edge of
the cut grass until the edge of the lawn is sensed once again. This
movement is indicated by the short arrows 42 of FIG. 9. Finally,
the lawnmower 20 backtracks along the new swath 44. Initially and
until reaching the location of the line A, the lawnmower 20
utilizes only the compass information. Once the edge of cut grass
is found again (at the location of line A), the control system
utilizes both the compass and the sensor output to create the new
swath 44. This is indicated at step 36 of FIG. 8.
[0100] As discussed with respect to the previous embodiments, the
lawnmower 20 has to return to locations of unfinished scanning,
such as locations on the opposite side of a flower bed or tree. To
do so, the lawnmower 20 utilizes the navigation system to head
towards the desired location and, when it is close to the desired
location, it additionally senses for the edge between cut and uncut
grass.
[0101] Reference is now made to FIG. 10 which illustrates an
exemplary lawn height sensor. The lawn sensor comprises a rotatable
wing 50 connected to a potentiometer 52 via a pin 54 and a flexible
joint 56. A weak spring 58 is attached around pin 54 and extensions
60 of spring 58 extend on either side of wing 50 and of a fixed pin
62. A cam 64 is connected also to pin 54 and a microswitch 66
measures the movement of cam 64.
[0102] The grass presses against the wing 50, which, since it is
not heavy, will rotate. In turn, the wing 50 pushes against the
relevant one of extensions 60. Since the other extension 60 is
maintained in place by fixed pin 62, the spring 58 is tightened,
thereby providing a returning force against the force of the
grass.
[0103] The rotation of the wing causes the cam 64 and flexible
joint 56 to rotate, which rotation is measured by the potentiometer
52. Furthermore, if the wing 50 rotates too far, protrusions 68 of
cam 64 will press against a rod 70 connected to microswitch 66
which will indicate maximum travel of wing 50.
[0104] Reference is now made to FIGS. 11A and 11B which illustrate
two alternative embodiments of boundary markers and a sensor for
detecting the boundary markers located on the lawnmower. Reference
is also made to FIGS. 12A, 12B, 13A, 13B, 14A, 14B, 15 and 16 which
illustrate additional types of boundary markers.
[0105] FIGS. 11A and 11B illustrate the lawnmower 10 with a
boundary sensor 80 attached thereto. In FIG. 11A, the boundary is
marked by a series of markers 82 placed into the ground on the edge
of the lawn. Typically, the markers are placed at set distances one
from the next. Alternatively, they can be placed close together
along portions of the edge which are very curvy and further apart
along straighter portions of the edge. In FIG. 11B, the boundary is
marked by a wire 84 which is marked in some suitable and detectable
manner. The type of marking matches the type of sensor attached to
the lawnmower 10.
[0106] In one embodiment, shown in FIGS. 12A and 12B, the boundary
markers 82 have a magnet therein. In the embodiment of FIG. 12A,
the boundary marker 82 is formed of a plastic pin 90, a magnet 92
placed within pin 90 and a plastic cover 94 covering the magnet-pin
unit. In the embodiment of FIG. 12B, the boundary marker 82 is a
metallic pin which is magnetized, as shown.
[0107] The corresponding sensor 80, for both embodiments, is a
gauss meter, such as the model 4048 manufactured by F.W. Bell Inc.
of the USA, or any other magnetometer which senses the magnetism in
the combined unit. The distances between the boundary markers 82
are defined by the strength of the magnet 92 in such a way that at
any point along the marked perimeter, at least two markers are
detectable by the sensor on the robot.
[0108] In a further embodiment, shown in FIGS. 13A and 13B, the
sensor 82 is a bar code reader, such as the model 1516 from
Intermek Inc. of Seattle, Wash., USA. The corresponding boundary
markers are, in FIG. 13A, a white cable 96 with black bar code
markings 98 thereon. The bar code markings 98 are located at fixed
distances from each other. In FIG. 13B, the boundary markers are
pins (typically of white plastic) with black markings 100
thereon.
[0109] FIGS. 14A and 14B illustrate a further embodiment which
utilizes a Geiger counter, or other suitable radiometer, to detect
the boundary markers. FIG. 14A illustrates a cable 102 having a
piece of a radioactive mineral 104, such as Americium, located
thereon and FIG. 14B illustrates an individual pin 106 (typically
of plastic) having a radioactive mineral 104 thereon. A suitable
Geiger counter for use with lawnmower 10 is the SURVIVOR 200,
manufactured by Bicron Inc. of the USA.
[0110] FIG. 15 illustrates a coil-capacitor circuit 110
incorporated into a plastic or ceramic substance 112. Such a
circuit 110 is then placed into a pin unit such as pin 90 and cover
94 of FIG. 12A. The corresponding sensor 80 is a resonance tag
reader such as the ones manufactured by Checkpoint Inc. of
Thorofare, N.J., USA, for anti-theft protection in stores, such as
clothing stores. The coil-capacitor unit 110 can be similar to
those manufactured by Checkpoint or any other suitable
coil-capacitor unit.
[0111] FIG. 16 illustrates a further embodiment utilizing
transceiver units 120. The transceiver unit 120 can be any suitable
narrow band transmitting and receiving unit and is typically placed
into a pin unit such as pin 90 and cover 94 of FIG. 12A. The
corresponding sensor is a similar transceiver. Each transceiver,
within each pin, operates at the same frequency and the sensor
transceiver continually determines how close it is to the nearest
transceiver unit 120. When the sensor transceiver comes to within a
predetermined distance, the sensor transceiver determines that it
has reached the boundary.
[0112] For all of the above embodiments, the sensor 80 determines
that the lawnmower 10 has reached the boundary when the signal
sensor 80 receives is at or above a threshold level which is
calculated as the expected reading five to ten inches from the
marker or cable.
[0113] It will be appreciated that other types of markers and their
corresponding detectors are incorporated within the present
invention.
[0114] All the above description and examples have been provided
for the purpose of illustration, and are not intended to limit the
invention in any way. Many modifications can be effected in the
method and devices of the invention, without departing from its
spirit.
* * * * *