U.S. patent application number 11/691735 was filed with the patent office on 2007-12-20 for robot confinement.
This patent application is currently assigned to IROBOT CORPORATION. Invention is credited to Joseph L. Jones, Philip R. Mass.
Application Number | 20070290649 11/691735 |
Document ID | / |
Family ID | 30772382 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070290649 |
Kind Code |
A1 |
Jones; Joseph L. ; et
al. |
December 20, 2007 |
ROBOT CONFINEMENT
Abstract
The present invention discloses a system and method for
confining a robot to a particular space. The system includes a
portable barrier signal transmitter that produces a barrier signal
primarily along an axis, and a mobile robot capable of avoiding the
barrier signal upon detection of the barrier signal. In the
preferred embodiment the barrier signal is emitted in an infrared
frequency and the robot includes an omni-directional signal
detector. Upon detection of the signal, the robot turns in a
direction signal is no longer detected.
Inventors: |
Jones; Joseph L.; (Acton,
MA) ; Mass; Philip R.; (Denver, CO) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
IROBOT CORPORATION
63 South Ave.
Burlington
MA
01803
|
Family ID: |
30772382 |
Appl. No.: |
11/691735 |
Filed: |
March 27, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11221392 |
Sep 8, 2005 |
7196487 |
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11691735 |
Mar 27, 2007 |
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10921775 |
Aug 19, 2004 |
6965209 |
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11221392 |
Sep 8, 2005 |
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10696456 |
Oct 29, 2003 |
6781338 |
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10921775 |
Aug 19, 2004 |
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10056804 |
Jan 24, 2002 |
6690134 |
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10696456 |
Oct 29, 2003 |
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60263692 |
Jan 24, 2001 |
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Current U.S.
Class: |
318/568.12 ;
901/1 |
Current CPC
Class: |
G05D 1/0272 20130101;
G05D 1/0238 20130101; G05D 1/0242 20130101; G05D 1/0225 20130101;
G05D 1/0234 20130101; G05D 1/0214 20130101; A47L 9/009 20130101;
G05D 1/0227 20130101; A47L 2201/04 20130101; G05D 2201/0215
20130101; G05D 1/028 20130101 |
Class at
Publication: |
318/568.12 ;
901/001 |
International
Class: |
B25J 5/00 20060101
B25J005/00 |
Claims
1. A robot confinement system, comprising: a. a portable barrier
signal transmitting device that includes at least a primary
emitter, said primary emitter being operative to emit a confinement
beam primarily along an axis, said axis of said emitted confinement
beam defining a directed barrier; b. a mobile robot; c. said mobile
robot comprising: means for turning in a least one direction; a
detector operative to detect said directed barrier formed by said
emitted confinement beam; and a control unit controlling said means
for turning; d. whereby the control unit runs an algorithm for
avoiding said directed barrier formed by said emitted confinement
beam upon detection of said directed barrier formed by said emitted
confinement beam, said algorithm being operative to turn the robot
in a chosen direction until said directed barrier formed by said
emitted confinement beam is no longer detected.
2.-19. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/263,692, filed Jan. 24, 2001.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a method and system for robot
localization and confinement.
[0003] There have been many systems proposed in the prior art for
confining a robot to specific physical space for the purpose of
performing work. These systems are typically designed for any
number of robotic applications such as lawn care, floor cleaning,
inspection, transportation, and entertainment, where it is desired
to have a robot operate in a confined area for performing work over
time.
[0004] By way of example, a vacuuming robot working in one room may
unintentionally wander from one room to another room before
satisfactorily completing the vacuuming of the first room by
closing all doors and physically preventing the robot from leaving
the first room. In may houses, however, open passageways often
separate rooms, and doors or other physical barriers cannot easily
be placed in the robot's exit path. Likewise, a user may desire to
only have the robot operate in a portion of a single open space
and, therefore, letting the robot work in the entire room decreases
efficiency.
[0005] It is therefore advantageous to have a means for confining
the area in which a robot works.
[0006] One approach in the prior art is to provide sophisticated
systems for navigation and orientation for the robot such that the
robot either travels along a predetermined path and/or monitors its
current location against a map stored in memory. These systems
require significant computer memory and computational power, and
typically do not adapt well to changes in the area in which the
robot is working. Likewise the robot cannot simply be taken from
one building to another building, or even from room-to room,
without significant reprogramming or training.
[0007] For example, the method disclosed in U.S. Pat. No. 4,700,427
(Knepper) requires a means for generating a path for the robot to
travel, which can be either a manually-controlled teaching of the
path or automatic mapping function. If "the place of use is
frequently changed" or the "rooms are modified", large amounts of
data memory is required in order to store information related to
each location. Similarly, the method and system disclosed in U.S.
Pat. No. 4,119,900 (Kremnitz) requires powerful computation and
sensors to constantly ascertain the orientation of the robot in a
given space. Other examples of robotic systems requiring inputted
information about the space in which the robot is working include
methods and systems shown in U.S. Pat. Nos. 5,109,566 (Kobayashi et
al.) and 5,284,522 (Kobayashi et al.).
[0008] Similarly, certain prior art systems not only require the
training or programming of the robot to the specifics of a
particular space, but also require some preparation or alteration
to the space in which the robot is to work. For example, U.S. Pat.
No. 5,341,540 (Soupert et al.) discloses a system in which in a
preferred embodiment requires the robot to include a positioning
system and that the area for the robot be set up with "marking
beacons . . . placed at fixed reference points". While this system
can avoid an unknown obstacle and return to its preprogrammed path
through signals from the beacons, the system requires both
significant user set-up and on-board computational power.
[0009] Similar systems and methods containing one or more of the
above-described disadvantages are disclosed in U.S. Pat. Nos.
5,353,244 (Lee et al.), 5,537,017 (Feiten et al.), 5,548,511
(Bancroft), and 5,634,237 (Paranjpe).
[0010] Yet another approach for confining a robot to a specified
area involves providing a device defining the entire boundary of
the area. For example, U.S. Pat. No. 6,300,737 (Bergvall et al.)
discloses an electronic bordering system in which a cable is placed
on or under the ground to separate the inner area from the outer
area. Likewise, the system disclosed in U.S. Pat. No. 6,255,793
(Peless et al.) requires installation of a metallic wire through
which electricity flows to define a boarder. While these systems
provide an effective means for confinement, they are difficult to
install, are not portable from room-to-room, and can be unsightly
or a tripping hazard if not placed under ground or beneath
carpeting. Equally important, such systems can be difficult to
repair if the wire or other confinement device breaks as the
location of such breaks can be difficult to determine when the
system is placed underground or under carpet.
[0011] The present invention provides a modified and improved
system for confining a robot to a given space without the drawbacks
of the prior art.
SUMMARY OF THE INVENTION
[0012] In accordance with the present invention a robot confinement
system is disclosed comprising: a portable barrier signal
transmitter, wherein said barrier signal is transmitted primarily
along an axis, said axis defining a barrier; a mobile robot, where
said mobile robot comprises means for turning in at least one
direction, a barrier signal detector, and a control unit
controlling said means for turning; whereby the control unit runs
an algorithm for avoiding said barrier signal upon detection of
said barrier signal, said algorithm comprising the step of turning
the robot until said barrier signal is no longer detected.
[0013] Accordingly, the present invention has several objects and
advantages.
[0014] It is an object of the invention to provide a simplified and
portable system and method for confining a robot to a given
area.
[0015] It is an object of the invention to provide a confinement
system that does not require installation.
[0016] It is an object of the invention to provide a barrier system
that can be set up intuitively and includes a means for visually
indicating the barrier.
[0017] It is an additional object of the invention to provide a
system such that a robot approaching the barrier from either side
of the barrier will turn in such a way as to avoid crossing the
barrier.
[0018] It is an object of the invention to provide a robot
confinement system that operates regardless of the angle at which
the robot approaches the barrier.
[0019] It is an additional object of a preferred embodiment of the
invention to provide a system that is substantially impervious to
the effects of sunlight, will not cause interference with other
devices, and will not be interfered by other devices.
[0020] The preferred embodiment of the present invention is for a
robotic, indoor cleaning device similar to the types disclosed in
U.S. Pat. Nos. 4,306,329 (Yokoi), 5,293,955 (Lee), 5,369,347 (Yoo),
5,440,216 (Kim), 5,613,261 (Kawakami et al.), 5,787,545 (Colens),
5,815,880 (Nakanishi), 6,076,226 (Reed). One of skill in the art
will recognize that the present invention can be used in any number
of robotic applications where confinement is desired. In addition,
while the preferred embodiments described herein are for a robot
without a navigation system, one of skill in the art will recognize
the utility of the invention in applications using more
sophisticated robots.
[0021] Other features and advantages of the invention will be
apparent from the following detailed description, including the
associated drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1A shows an embodiment of the robot confinement system
according to the invention with the barrier signal transmitter in
an unpowered state;
[0023] FIG. 1B shows an embodiment of the robot confinement system
according to the invention with the barrier signal transmitter in a
powered state;
[0024] FIG. 2A shows a schematic representation of a preferred
embodiment of the barrier signal transmitter;
[0025] FIG. 2B shows a circuit diagram of a specific embodiment of
the barrier signal transmitter;
[0026] FIG. 3A shows a side-view schematic representation of a
mobile robot used in a preferred embodiment of the invention;
[0027] FIG. 3B shows a top-view schematic representation of a
mobile robot used in a preferred embodiment of the invention;
[0028] FIG. 4 shows a side-view of a preferred embodiment of an
omni-directional barrier signal detector;
[0029] FIG. 5 demonstrates a hardware block diagram of the robot
shown in FIGS. 3A & 3B;
[0030] FIG. 6 shows a schematic representation of an alternative
embodiment of the robot employing multiple barrier signal
detectors;
[0031] FIGS. 7A & 7B are flow-chart illustrations of the
barrier avoidance algorithm of a preferred embodiment of the
invention;
[0032] FIGS. 8A-C are schematic illustrations of the system and
method a preferred embodiment of the present invention;
[0033] FIG. 9A-B are schematic illustrations of the system and
method of an alternative embodiment of the present invention.
DETAILED DESCRIPTION
[0034] Referring to FIGS. 1A & 1B, living room 10 is shown
separated from dining room 12 by interior walls 14 & 15. The
living room and/or dining room may contain various furnishings, for
example, couch 16, television 17, buffet 18 and table and chairs
19.
[0035] The rooms also contain a mobile robot 20 and a barrier
signal transmitting device 30, which for purposes of this
specification is also called a robot confinement (or RCON)
transmitter 30. In FIGs. 1A & 1B, the robot is placed in the
living room 10, and the RCON transmitter 30 is placed in the area
dividing the living room 10 from the dining room 12, against
interior wall 14 and pointing toward interior wall 15.
[0036] As described in more detail herein, FIG. 1B shows the same
configuration of rooms with the RCON transmitter 30 in a powered
state emitting, e.g., an infrared beam 42 from the RCON transmitter
30 toward interior wall 15. The beam 42 is directed primarily along
an axis to create a boundary or barrier between living room 10 and
dining room 12.
[0037] The system and method described herein each rely on a
portable RCON transmitting unit 30 and a mobile robot 20. Each of
these elements is first described independently, then the operation
of a preferred embodiment of the invention is discussed.
[0038] RCON Transmitter
[0039] FIG. 2A illustrates a preferred embodiment of the RCON
transmitter 30. The RCON transmitter 30 includes a first infrared
emitter 32, a second infrared emitter 34, a power switch 36, and
variable power-setting know 38. The RCON transmitter enclosure 31
also houses the batteries (not shown) and necessary electronics for
the various components. FIG. 2B shows a circuit diagram for the
necessary electronics for an embodiment of the RCON transmitter 30.
Other embodiments may use other conventional power sources.
[0040] In the embodiment shown in FIG. 2A, a user would turn on the
RCON transmitter 30 using power switch 36 at the same time as the
robot 20 begins operation. The user can also select a variable
power using knob 38. In other embodiments, any number of known
input devices can be used to turn on the unit and/or select a power
setting, such as keypads, toggle switches, etc. A higher power can
be used to provide a longer barrier useful for dividing a single
room, while a lower power setting can be used to provide a barrier
for a single doorway. Because of the reflective properties of
various materials such as walls painted white, it is preferable to
limit the power of the RCON transmitter 30 to the minimum necessary
to provide the desired barrier.
[0041] In alternative embodiments, the RCON transmitter's power may
be automatically turned off after a predetermined amount of time in
order to preserve battery life.
[0042] In alternative embodiments, a control system can be used to
turn on and turn off one or more RCON transmitters and/or robots in
order to allow automatic cleaning of multiple rooms or spaces in a
controlled manner. For example, a "smart house" control system
might communicate directly with one or more RCON transmitters
allowing a cycling of work spaces. In the alternative, the robot 20
might send a signal to the RCON to turn it on.
[0043] In the preferred embodiment, two infrared emitters 32 &
34 are used. The first IR emitter 32--the primary emitter--is
powered to provide a directed barrier 42 of a given length from the
RCON transmitter 30. In this embodiment, the beam 42 is a
modulated, narrow IR beam. In the preferred embodiment, a
collimated IR emitter is used such as Waitrony p/n IE-320H. The
specifics of the emitter(s) are left to one of skill in the art;
however, as explained in detail below, the beam 42 must have
sufficient width. It is preferred that the minimum beam width be
greater than the turning radius of the detector on a particular
robot.
[0044] The second IR emitter 34--the secondary emitter--is powered
to provide a diffuse region 44 near the RCON transmitter 30 to
prevent robot 20 from crossing the beam 42 in its most narrow
region closest to the RCON transmitter 30 and, in addition,
prevents robot 20 from coming into direct contact with the RCON
transmitter 30. In the preferred embodiment, a lens identical to
the lens portion of the RCON detector, described below, is used for
the secondary emitter 34. In other embodiments, a single active
emitter operatively connected to appropriate optics can be used to
create multiple emission points, including the two emitter system
disclosed herein.
[0045] Because of potential interference from sunlight and other IR
sources, most IR devices, such as remote controls, personal digital
assistances and other IR communication devices, modulate the
emitted signal. Herein, the emitters 32 & 34 modulate the beam
at 38 kHz. In addition, IR devices modulate the beam to provide a
serial bit stream to the unit being controlled to tell it what to
do. In an embodiment of the present invention, additional
modulation of the beam at a frequency, for example 500 Hz,
different from the frequency of common IR bit streams prevents
interference with other IR equipment.
[0046] While the preferred embodiment uses an infrared signal, the
system and method of the present invention can use other signals
such as electromagnetic energy to accomplish the goals, including
radio waves, X-rays, microwaves, etc. Many of these types of waves
have significant drawbacks. For example, radio waves are more
difficult and expensive to make directional, and visible light
suffers from interference from many sources and may be distracting
to users. Sound waves could also be used, but it is similarly
difficult to make purely directional and tend to scatter and
reflect more.
[0047] Robot
[0048] As shown in FIGS. 3A & 3B, in the preferred embodiment,
the robot 20 comprises a substantially circular shell 21 mounted to
a chassis containing two wheels 22 & 23 mounted on opposite
sides of a center line, wherein each of the wheels 22 & 23 can
be independently driven to allow the robot to turn. In the
preferred embodiment, the wheels are mounted in such a manner as to
allow the robot to turn substantially in place. The preferred
embodiment of the robot 20 also comprises motors 24, cleaning
mechanism 25, rechargeable battery 26, microprocessor 27, and
various tactile and optical sensors 28.
[0049] In FIG. 5 is illustrated a hardware block diagram of a robot
similar to the one shown in FIGS. 3A & 3B. The hardware is
built around a Winbond W78 XXX Series 8-bit processor. The
processor is controlled by software stored in ROM. The system shown
in FIG. 5 includes various control functions and motor drivers,
along with various sensors (e.g. physical bump sensors, cliff
sensors, the RCON detector/sensor).
[0050] For the instant invention, the robot also has an RCON
detector 50, which in the preferred embodiment is a standard IR
receiver module, which comprises a photodiode and related
amplification and detection circuitry, mounted below an
omni-directional lens, where omni-directional refers to a single
plane. In a preferred embodiment, the IR receiver module is East
Dynamic Corporation p/n IRM-86013. However, any IR receiver module,
regardless of modulation or peak detection wavelength, can be used
as long as the RCON emitter is also changed to match the receiver.
As shown in FIGS. 3A & 3B, the RCON detector is mounted at the
highest point on the robot 20 and toward the front of the robot, as
defined by the primary traveling direction of the robot, as
indicated by an arrow in FIG. 3B.
[0051] While the RCON detector should be mounted at the highest
point of the robot in order to avoid shadows, it is desirable in
certain applications to minimize the height of the robot 20 and/or
the RCON detector 50 to prevent operational difficulties and to
allow the robot 20 to pass under furniture or other obstacles. In
certain embodiments, the RCON detector 50 can be spring mounted to
allow the detector to collapse into the body of the robot when the
robot runs under a solid overhanging object.
[0052] FIG. 4 shows in detail the preferred embodiment of the RCON
detector 50. The RCON detector includes a lens 52 that allows in
the barrier signal (or rays) 42 from all directions through the
outer lens wall 54 and focuses the signal at focal point 55. At the
same time, the method and systems of the present invention are
likely to be used in the presence of sunlight. Because direct
sunlight can easily saturate the IR detector 55, efforts may be
made to exclude sunlight from the RCON detector 50. Therefore, in
the preferred embodiment, opaque plastic horizontal plate 57 is
used, which is supported by post 58.
[0053] The lens 52 used in the preferred embodiment is a primarily
cylindrical device designed to accept rays perpendicular to the
axis of the lens and to reject rays substantially above or
substantially below the plane perpendicular to the axis of the
lens. The lens focuses horizontal rays primarily on IR detector 55
mounted below the lens.
[0054] In the preferred embodiment, the geometry of the lens is
determined by rotating a parabola about its focus, where the focus
is collocated with the active element of the receiver 55. The inner
lens wall 53 is thereby defined by the swept parabola. The rays are
reflected by the phenomena called total internal reflection,
defined here by the discontinuation between the lens material and
the material internal to the inner lens wall 53. The preferred
embodiment is constructed of clear polycarbonate chosen for its low
cost and index of refraction.
[0055] The omni-directional nature of the RCON detector 50 allows a
system with only a single RCON detector 50 to function equally well
regardless of the angle of incident radiation from the RCON
transmitter. If the RCON detector 50 is insensitive to the beams 43
& 44 from certain angles, then the robot 20 can break through
the confining beams 42 & 44 when the robot 20 approaches the
beam(s) such that the beam(s) occupies the RCON detector 50 blind
spot.
[0056] In addition, in the preferred embodiment, the RCON
transmitter 30 is battery powered. This imposes a high sensitivity
requirement on the robot-mounted detector 50 in order to promote
long battery life in the emitter 30. As such, the RCON detection
system should be designed to gather as much IR as possible from the
emitter(s).
[0057] The RCON detector of the preferred embodiment is designed to
be triggered by modulated IR above a certain intensity threshold.
If the IR levels are below the given threshold, the RCON detector
computes no detection whatsoever and therefore triggers no specific
control commands.
[0058] One of skill in the art will recognize that in alternative
embodiments multiple RCON detectors 50 can be used. FIG. 6
illustrates such an embodiments using six side-mounted sensors 50.
Each of the sensors should be oriented in a manner to have its
field of view correspond to that of the single, top mounted sensor.
Because a single, omni-directional RCON detector should be mounted
at the highest point of the robot for optimal performance, it is
possible to lower the profile of the robot by incorporating
multiple detectors.
[0059] As disclosed above, the system and method of the present
invention can be used with any number of robots existing in the
prior art, including those designed for indoor cleaning
applications.
[0060] Operation of System & Method
[0061] As shown in FIGS. 8A-C, an IR beam is used to divide the
space (living room 10 and dining room 12) into two distinct areas.
The robot has a sensor for detecting this beam 42 mounted at the
robot's top front. As seen in FIG. 8B, whenever a measurable level
of IR radiation strikes the detector the robot's IR avoidance
behavior is triggered. In a preferred embodiment, this behavior
causes the robot to spin in place to the left until the IR signal
falls below detectable levels (FIG. 8C). The robot then resumes its
previous motion. Spinning left is desired in certain systems
because, by convention, the robot may attempt to keep all objects
to its right during following operations. The robot's confinement
behavior is consistent with its other behaviors if it spins left on
detecting the confining beam 42. In this embodiment, the IR sensor
acts as a gradient detector. When the robot encounters a region of
higher IR intensity the robot spins in place. Because the IR sensor
is mounted at the front of the robot and because the robot does not
move backward, the sensor always sees the increasing IR intensity
before other parts of the robot. Thus spinning in place causes the
sensor to translate to a region of decreased intensity--away from
the beam.
[0062] In another preferred embodiment, the room confinement
behavior works as a single behavior in a strictly priority based
behavior system which controls the robot's motion. Each of the
behaviors is assigned a priority, and the behavior with the highest
priority requests control of the robot at any given time and has
full control of the robot. These behaviors may include driving
forward, turning when bumped, spiraling, etc. The confinement
behavior is one of the highest priority behaviors. It requests
control of the robot when the room confinement IR sensor has
detected a signal from a room confinement transmitter.
[0063] A flow-chart of a preferred embodiment of the control logic
of the confinement behavior is shown in FIG. 7A. The robot
determines whether the RCON detector detects a signal (step 110).
If a signal is detected, the robot chooses a turning direction
(step 120). The robot then begins to turn in the chosen direction
until the signal is no longer detected (step 120). The robot then
begins to turn in the chosen direction until the signal is no
longer detected (step 130). Once the signal is no longer detected,
the robot continues turning for an additional distance (step
140).
[0064] In the preferred embodiment of step 120, the direction is
chosen through the algorithm illustrated in the flow chart shown in
FIG. 7B. The robot's control logic keeps track of the robot's
discrete interactions with the beam. The robot first increments the
counter by one (step 122). On odd numbered interactions, the robot
chooses a new turning direction randomly (steps 124 & 126); on
even numbered interactions, the robot again uses its most recent
turning direction.
[0065] In other embodiments, the robot can always turn a single
direction or choose a direction randomly. When the robot always
turns one direction, the robot may get stuck in a loop by turning
away from the beam, bumping into another obstacle in a room,
turning back toward the beam, seeing the beam again, turning away,
bumping again, ad infinitum. Moreover, when the robot only turns in
a single direction, it preferentially ends up at one end of the
beam. Where the robot's task is to complete work evenly throughout
a room, such as cleaning, a single turning direction is not
optimal. If the direction is chosen purely randomly, the robot may
turn back and forth quite a bit as it encounters the beam more than
once.
[0066] In the preferred embodiment of step 140, the robot turns an
additional 20 degrees from the point at which the signal is lost.
The amount of the turn, which was selected arbitrarily in the
preferred embodiment, is left to the particular robot and
application. The additional turn prevents the robot from
re-encountering the confinement beam immediately after exiting the
beam. For various applications, the amount of additional movement
(linear or turning) can be a predetermined distance or time, or in
the alternative may include a random component.
[0067] In still other embodiments, the robot's avoidance behavior
may include reversing the robot's direction until the beam 42 is no
longer detected.
[0068] In other embodiments, the RCON detector is able to determine
the gradient levels of the beam. This information can be used to
send the robot in the direction of the lowest level of detection
and prevent the situation where the robot is situated entirely
within the beam and therefore turns in 360 degrees without the
detector exiting the beam. In these embodiments, if the robot turns
360 degrees without exiting the beam, the control logic may give a
higher priority to a "gradient behavior". The gradient behavior
divides the possible robot headings into a fixed number of angular
bins, each bin covering an equal sweep of the angular area around
the robot. The robot then turns at a constant rate while sampling
the number of detections in each angular bin. (For a system using
infrared signals, detection counts are monotonically related to the
signal strength). After the robot has rotated more than 360
degrees, the gradient behavior commands the robot to turn toward
the angular bin with the lowest detection count. When the robot
achieves the correct heading, the gradient behavior commands the
robot to move forward a predetermined distance, for example
one-half of the width of the robot, then control is released from
the gradient behavior. If necessary, this process repeats until the
robot has moved into a region where IR intensity is below the
detection threshold.
[0069] One of skill in the art will recognize that the
emitter/detector system can also be used to guide the robot in any
number of ways. For example, the beam 42 could be used to allow the
robot to perform work parallel to the edge of the beam, allowing,
for example, the floor right up to the edge of the room confinement
beam to be cleaned.
[0070] In an alternative embodiment of the present invention, the
RCON transmitter may comprise both a signal emitter and a signal
detector. As shown in FIG. 9A, the RCON transmitter 210 includes
both a primary emitter 212 and a detector 214. The RCON transmitter
210 is placed at one end of the desired barrier and a
retroreflector 230 is placed at the opposite end of the desired
barrier. The retroreflector, which reflects the beam back toward
the emitter regardless of the orientation of the retroreflector
relative to the beam, can be constructed from, for example,
standard bicycle reflectors. As shown in FIG. 9A, primary emitter
212 produces beam 242. A portion of beam 242 reflects from
retroreflector 230 and is detected by detector 214.
[0071] In the embodiment shown in FIGS. 9A & 9B, the IR
radiation emitted by the primary emitter 212 can be modulated in
either of two ways constituting signal A or signal B. During normal
operation, the beam 242 emitted from the primary emitter 212 is
reflected by the retroreflective material 230 back into the
detector 214. When this is true the RCON transmitter broadcasts
signal A, which is received by robot 220. As shown in FIG. 9B, if
the robot or other object comes between the emitter 212 and the
retroreflective material 230 then no signal is returned to the
receiver 214 and the RCON transmitter 210 broadcasts signal B,
which is received by robot 220. The robot 220 then uses this
information to improve its performance. The robot turns away from
the beam as described previously only when the robot detects signal
B. When the robot detects signal A no action is taken.
[0072] For certain applications, the embodiment shown in FIGS. 9A
and 9B provides improved performance. For example, in cleaning
application, the completeness of cleaning is improved because the
robot tends to clean up to the line connecting the confinement
device and the retro-reflective material. Also, this embodiment is
more resistant to beam blockage. If furniture or other obstacles
partially occlude the beam, the robot tends to turn away when it is
further from crossing the beam. Finally, an indicator, such as an
LED, can be added to the RCON transmitter to indicate when the
device is functioning and correctly aimed.
[0073] In other embodiments, the RCON transmitter can be used to
define an annular confinement region. For example, an RCON
transmitter with two omni-directional emitters may be employed,
wherein the first emitter would broadcast the standard modulated
beam and the second emitter would a emit radiation 180 degrees out
of phase with the output of the first emitter, but with less power.
The robot would be programmed to turn when the IR was not detected.
As the robot gets further from the emitter, it would eventually,
lose the beam and turn back into it. As it gets closer, the
radiation from the second emitter would jam the radiation from the
first emitter, creating essentially unmodulated IR. The detector
would fail to detect this, and the robot would again turn back into
the annulus.
[0074] In yet another embodiment, the RCON transmitter can be used
as "home base". For example, once the voltage of the robot's
battery drops below a predetermined level, the robot can use the
gradient detection behavior to home in on the RCON transmitter.
This allows the user to easily find the robot when it has finished
cleaning instead of it randomly ending up in corners, under
furniture, etc.
[0075] Although the description above contain many specificities,
there should not be construed as limiting the scope of the
invention but as merely providing illustrations of some of the
presently preferred embodiments of this invention.
[0076] Other embodiments of the invention are within the scope of
the following claims.
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