U.S. patent application number 13/423538 was filed with the patent office on 2012-10-18 for robotic platform.
This patent application is currently assigned to IROBOT CORPORATION. Invention is credited to Chikyung WON.
Application Number | 20120261204 13/423538 |
Document ID | / |
Family ID | 27373538 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120261204 |
Kind Code |
A1 |
WON; Chikyung |
October 18, 2012 |
ROBOTIC PLATFORM
Abstract
An articulated tracked vehicle that has a main frame includes a
pair of parallel main tracks. Each main track includes a flexible
continuous belt coupled to a corresponding side of the main frame.
A forward section includes an elongated arm pivotally coupled to
the main frame near the forward end of the main frame. The arm has
a length sufficiently long to allow the forward section to extend
below a main section in at least some degrees of rotation of the
arm, and a length shorter than the length of the main section. The
center of mass of the main section is located forward of the
rearmost point reached by the end of the arm in its pivoting about
a transverse axis. The main section is contained within the volume
defined by the main tracks and is symmetrical about a horizontal
plane, thereby allowing inverted operation of the robot.
Inventors: |
WON; Chikyung; (Tewksbury,
MA) |
Assignee: |
IROBOT CORPORATION
Bedford
MA
|
Family ID: |
27373538 |
Appl. No.: |
13/423538 |
Filed: |
March 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12140371 |
Jun 17, 2008 |
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13423538 |
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10745941 |
Dec 24, 2003 |
7597162 |
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12140371 |
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10202376 |
Jul 24, 2002 |
6668951 |
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10745941 |
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09888760 |
Jun 25, 2001 |
6431296 |
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10202376 |
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09237570 |
Jan 26, 1999 |
6263989 |
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09888760 |
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60096141 |
Aug 11, 1998 |
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60079701 |
Mar 27, 1998 |
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Current U.S.
Class: |
180/167 |
Current CPC
Class: |
B62D 55/075 20130101;
B25J 11/0025 20130101; Y10S 180/901 20130101; B62D 55/14 20130101;
B25J 5/005 20130101; B62D 55/065 20130101; B62D 55/244 20130101;
B62D 55/0655 20130101; B62D 55/12 20130101; Y10S 280/901
20130101 |
Class at
Publication: |
180/167 |
International
Class: |
G06F 17/00 20060101
G06F017/00 |
Goverment Interests
STATEMENT AS TO FEDERALLY SPONSORED RESEARCH
[0002] This invention was made in part with Government support
under contract DAAL01-97-C-0157 awarded by the Army Research
Laboratory of the Department of the Army. The Government may have
certain rights in the invention.
Claims
1. A remotely operated robot comprising: a main frame including a
front and a back, the main frame defining a length extending from
the front to the back; arms extending beyond the length of the main
frame; a plurality of compliant tracks, the plurality of compliant
tracks together extending from front to back of the main frame and
surrounding the main frame and the arms, the plurality of compliant
tracks providing a first layer of impact protection to the main
frame, each track including a compliant belt made of a flexible
material, and a plurality of elastomer cleats longitudinally spaced
along an outer surface of the compliant belt; and a plurality of
compliant pulleys arranged within the tracks adjacent the front and
the back of the main frame, intervening between the sets of
compliant tracks and the main frame to provide a second layer of
impact protection to the main frame, each compliant pulley formed
of a compliant polymer.
2. The remotely operated robot of claim 1, further comprising an
onboard control system disposed within the payload volume,
including a computer processor and memory.
3. The remotely operated robot of claim 1, wherein a span of the
vehicle is defined by the length of the main frame and the arms and
each of the arms is rotatable 360 degrees relative to the main
frame.
4. The remotely operated robot of claim 3, wherein the span of the
vehicle is variable and extends to at least 26 inches.
5. The remotely operated robot of claim 3, wherein the center of
gravity of the vehicle is within the circle of rotation of each
front track.
6. The remotely operated robot of claim 1, further comprising a
plurality of track supports, wherein each track support supports a
respective compliant track.
7. The remotely operated robot of claim 6, wherein each track
support defines a plurality of slots such that a plurality of
angled ribs extend between a top portion and a bottom portion of
the track support.
8. The remotely operated robot of claim 6, wherein at least some of
the plurality of track supports are wedge-shaped and define a
plurality of slots such that a plurality of angled ribs extend
between a top portion and a bottom portion of the track
support.
9. The remotely operated robot of claim 1, wherein each compliant
pulley of the plurality of compliant pulleys has a series of radial
or angled spokes around a central hub.
10. The remotely operated robot of claim 1, wherein each compliant
pulley of the plurality of compliant pulleys is a polyurethane
material.
11. A remotely operated robot comprising: a main frame including a
payload volume, a front, and a back, the main frame defining a
length extending from the front to the back; articulated arms, each
articulated arm having a proximal end positioned at an outer side
of the main frame and a distal end extendable beyond a length of
the main frame, each arm rotatable about the proximal end thereof
without interfering with the main frame; a plurality of compliant
tracks, the plurality of compliant tracks together extending from
front to back of the main frame and surrounding the main frame and
the arms, the plurality of compliant tracks providing a first layer
of impact protection to the payload volume of the main frame, each
track including a compliant belt made of a flexible material, and a
plurality of elastomer cleats longitudinally spaced along an outer
surface of the compliant belt; a plurality of compliant pulleys
within the plurality of compliant tracks, the compliant pulleys
being positioned at the front of the main frame, at the back of the
main frame, and at the distal end of the arms, the compliant
pulleys disposed between the sets of compliant tracks and the main
frame to provide a second layer of impact protection to the payload
volume of the main frame, each compliant pulley formed from a
compliant polymer, wherein a center of gravity of the robot is
maintained within the rotational sweep of the articulated arms.
12. The remotely operated robot of claim 11, further comprising an
onboard control system disposed within the payload volume,
including a computer processor and memory.
13. The remotely operated robot of claim 11, wherein a span of the
vehicle is defined by the length of the main frame and the arms and
each of the arms is rotatable 360 degrees relative to the main
frame.
14. The remotely operated robot of claim 13, wherein the span of
the vehicle is variable and extends to at least 26 inches.
15. The remotely operated robot of claim 11, wherein each arm is
shorter than the length of the main frame.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. patent application is a continuation of and claims
priority under 35 U.S.C. .sctn.120 from U.S. patent application
Ser. No. 12/140,371, filed on Jun. 17, 2008; which is a
continuation of U.S. patent application Ser. No. 10/745,941, filed
on Dec. 24, 2003, now U.S. Pat. No. 7,597,162; which is a
divisional of U.S. patent application Ser. No. 10/202,376, filed on
Jul. 24, 2002, now U.S. Pat. No. 6,668,951; which is a divisional
of U.S. patent application Ser. No. 09/888,760, filed on Jun. 25,
2001, now U.S. Pat. No. 6,431,296; which is a divisional of U.S.
patent application Ser. No. 09/237,570, filed on Jan. 26, 1999, now
U.S. Pat. No. 6,263,989; which claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application 60/096,141, filed Aug.
11, 1998, and U.S. Provisional Application 60/079,701, filed Mar.
27, 1998. The disclosures of these prior applications are
considered part of the disclosure of this application and are
hereby incorporated herein by reference in their entireties.
BACKGROUND OF THE INVENTION
[0003] The invention relates to a robotically controlled mobility
platform.
[0004] Robots are useful in a variety of civilian, military, and
law enforcement applications. For instance, a robotically
controlled mobility platform inspect or search buildings with
structural damage caused by earthquakes, floods, or hurricanes, or
inspect buildings or outdoor sites contaminated with radiation,
biological agents such as viruses or bacteria, or chemical spills.
The platform can carry appropriate sensor systems for its
inspection or search tasks. Military applications include
operations that are deemed too dangerous for soldiers. For
instance, the robot can be used to leverage the effectiveness of a
human "pointman." Law enforcement applications include
reconnaissance, surveillance, bomb disposal and security
patrols.
[0005] The mobility approaches that have been used in prior robotic
platforms exhibit various shortcomings, many of which are addressed
by the present invention.
SUMMARY OF THE INVENTION
[0006] In one aspect, in general, the invention is an articulated
tracked vehicle. The vehicle has a main section which includes a
main frame and a forward section. The main frame has two sides and
a front end, and includes a pair of parallel main tracks. Each main
track includes a flexible continuous belt coupled to a
corresponding side of the main frame. The forward section includes
an elongated arm having a proximal end and a distal end. The
proximal end of the arm is pivotally coupled to the main frame near
the forward end of the main frame about a transverse axis that is
generally perpendicular to the sides of the main frame.
[0007] Alternative embodiments include one or more of the following
features:
[0008] The arm is sufficiently long to allow the forward section to
extend below the main section in at least some degrees of rotation
of the arm, and the arm is shorter than the length of the main
section.
[0009] The center of mass of the main section is located forward of
the rearmost point reached by the distal end of the arm in its
pivoting about the transverse axis.
[0010] The main section is contained within the volume defined by
the main tracks and is symmetrical about a horizontal plane,
thereby allowing inverted operation of the robot.
[0011] The vehicle is dimensioned for climbing a set of stairs. At
a first adjusted angle between the main section and the forward
section, the forward section rises more than the rise of the
bottom-most of the set of stairs. At a second adjusted angle
between the main section and the forward section, the length
spanned by the combination of the main section and the forward
section being greater than the diagonal span of two successive
stairs. The center of gravity of the vehicle is located in a
position so that the vehicle remains statically stable as it climbs
the stairs at the second adjusted angle.
[0012] The forward section includes a second arm, also pivotally
coupled to the main frame near its forward end. For instance, the
arms are coupled to the main frame such that they rotate outside
the main tracks. The two arms can be rigidly coupled and rotated
together by the articulator motor. The articulator motor provides
sufficient torque between the main frame and the arms to raise the
rear end of the main section thereby supporting the vehicle on the
front section. Continuous rotation of the arms can provide forward
locomotion of the vehicle. A harmonic drive can be coupled between
the articulator motor and the two arm. The harmonic drive provides
a torque to the two arms greater than the torque provided to it by
the articulator motor. A clutch can be coupled between the
articulator motor and the two arms. The clutch allows rotation of
the arms without rotation of the motor if the torque between the
arms and the main section exceeds a limit. A pair of flexible
forward tracks can be coupled to the two arms.
[0013] A pair of drive pulleys for supporting and driving each of
the main and forward tracks are included, one on each side of the
vehicle. The drive pulleys are coaxial with the transverse axis of
rotation of the arms, and are joined so that they rotate together.
The vehicle can include a pair of drive motors, one coupled to both
the main and forward drive pulleys on a corresponding side of the
vehicle.
[0014] On each side of the main frame, two compliant pulleys are
coupled between one of the main tracks and the main frame, and
multiple compliant track supports are coupled between the tracks
and the side plates. Each pulley includes a compliant outer rim, a
hub, and multiple compliant spoke segments coupled between the rim
and the hub.
[0015] Multiple compliant longitudinal track supports coupled
between the main frame and the continuous belts. Each longitudinal
track support has a series of open slots forming a series of rib
sections between the upper and lower edges of the support.
[0016] The pulleys and main frame are recessed within the volumes
defined by the tracks.
[0017] Each track includes a flexible continuous belt and a series
of compliant cleats attached transversely on the outside of the
belt.
[0018] The main tracks each include a longitudinal rib coupled to
the inside surface of the belt, and each of the pulleys includes a
channel around its circumference which accepts the longitudinal
rib. The channels are dimensioned larger than the rib thereby
allowing debris to be caught between a pulley and a tracks without
dislodging the track from the pulley.
[0019] In another aspect, in general, the invention is a method for
operating an articulated tracked vehicle having a main tracked
chassis and a pivoting forward arm for the vehicle to climb a set
of stairs. The method includes pivoting the arm to raise the arm
higher than the rise of the bottom-most stair of the set of stairs,
then approaching the first stair until the arm contacts the first
stair. The method further includes driving the main tracks until
the main tracks contacts the first stair, and then pivoting the arm
to extend the tracked base of the vehicle. The method then includes
driving the main tracks to ascend the set of stairs.
[0020] In another aspect, in general, the invention is a method for
inverting an articulated tracked vehicle which has a main tracked
chassis and a pivoting arm. The method includes supporting the
vehicle on the main tracks in a first vertical orientation,
supporting the vehicle on the pivoting arm, and then pivoting the
arm to raise the main chassis above the supporting surface. Further
pivoting of the arm passes the main chassis past a stable point.
This results in the vehicle being supported on the main tracks in a
second vertical orientation, the second vertical orientation being
inverted with respect to the first orientation.
[0021] Aspects of the invention include one or more of the
following advantages. One advantage is immediate recovery from
tumbles in which the vehicle lands on its "back." The vehicle can
operate with either side up and therefore does not necessarily
require righting. Also, if one vertical orientation is preferable
over another, for example, due to placement of sensors, the robot
can invert itself to attain a preferred orientation.
[0022] Another advantage is impact resistance. Impact resistance
allows the robot to operate even after collisions, falls, or
tumbles. Furthermore, impact resistance allows deploying the robot
in a variety of ways including tossing it from a height, such as
from a window or from a helicopter.
[0023] The housing of components within the track volume has the
advantage that the robot's components are less likely to be damaged
in a fall or tumble. Recessing the side plates of the robot frame
within the track volume also reduces the likelihood of impacting
the frame in such a tumble or fall.
[0024] The robot's forward center of gravity has the advantage that
it aids stair climbing and climbing of steep inclines. Also, a
center of gravity within the extent of the forward articulated
section allows the robot to perform a self righting operation and
to operate in an upright posture by supporting the platform solely
on the forward section. The robot's articulated body, including
continuously rotatable arms, has the advantage that the robot can
be driven using a "paddling" action of the arms. This mode of
driving the vehicle is useful, for instance, when the tracks have
inadequate fraction, for example due to an obstruction supporting
the center of the frame.
[0025] Compliant idler and drive pulleys provide robustness to
debris that may be caught between the tracks and the pulleys. Also,
raised segments on the tracks mating with corresponding channels in
the outside rims of the idler and drive pulleys reduces the
possibility of "throwing" a track. Loose mating of the raised
segments and the channels also permits debris being caught between
the pulleys and the track without throwing a track or stalling a
drive motor.
[0026] Other features and advantages of the invention will be
apparent from the following detailed description, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 illustrates teleoperator control of a robot;
[0028] FIG. 2 is a functional block diagram of system components of
a robot;
[0029] FIGS. 3a-c are a perspective, side, and top view,
respectively, of a robot;
[0030] FIGS. 4a-g show idler and drive pulleys;
[0031] FIG. 5 is a perspective view of a robot frame;
[0032] FIG. 6 is a schematic side view of the stowed position;
[0033] FIG. 7a is a schematic side view of the inclined
position;
[0034] FIGS. 7b-c are schematic side views of a maneuver to raise
an object using the inclined position;
[0035] FIGS. 8a-c are schematic side views of a maneuver to achieve
an upright position;
[0036] FIG. 9 is a schematic front view of the "wheelie"
position;
[0037] FIGS. 10a-b are schematic side views of a self-righting
maneuver;
[0038] FIG. 11 is a schematic view of a stair climbing
maneuver;
[0039] FIGS. 12a-c are schematic side views of a maneuver to
recover from a high centering;
[0040] FIG. 13 is a schematic side view illustrating "paddling"
using the arms;
[0041] FIGS. 14a-b are schematic views showing camera
placement;
[0042] FIGS. 15a-b are schematic views showing placement of sonar
sensors;
[0043] FIGS. 16a-b are schematic views showing placement of
infra-red sensors;
[0044] FIG. 17 is a diagram showing a door opening mechanism.
DETAILED DESCRIPTION
[0045] Referring to FIG. 1, a version of the system includes a
robot 100, and a remote control system 150. Remote control system
150 allows an operator 160 to control robot 100 from a distance.
The operator can select different levels of human control over the
robot, ranging from a teleoperation mode, in which the operator
directly controls the motors and actuators on the robot, to
autonomous operation, in which the operator passes higher-level
command to the robot. In partially autonomous operation, robot 100
can perform tasks such as following a wall, recovering from being
stuck in an opening or due to high centering on an obstruction,
evading a moving object, or seeking light.
[0046] Robot 100 moves around its environment on a pair of parallel
main tracks 110 and a pair of tapered forward tracks 120. Main
tracks 110 are mounted on a main body 140 of the robot. Robot 100
is articulated. In particular, forward tracks 120 are mounted on a
pair of forward arms 130, which are pivotally attached to the main
body 140 and can be positioned at any angle to main body 140. Robot
100 is designed to move about in a variety of environments,
including an urban environment of buildings (including staircases),
streets, underground tunnels, and building ruble, as well as in
vegetation, such as through grass and around trees. Robot 100 has a
variety of features which provide robust operation in these
environments, including impact resistance, tolerance of debris
entrainment, and invertible operability. The robot's design is
symmetrical about a horizontal plane so that it looks the same
upside down and can operate identically in either orientation.
Therefore, the robot can recover quickly from a tumble or fall in
which it is inverted.
[0047] Referring to FIG. 2, robot 100 includes an onboard control
system 210, which includes one or more computer processors and
associated memory systems. Onboard control system 210 is coupled to
a drive system 220, which includes motors that drive main and
forward tracks 110 and 120 and drive arms 130. Onboard control
system 210 is coupled to a communication system 230, which
includes, for example, a radio for exchanging control and feedback
information with remote control system 150. Robot 100 can
optionally carry a sensor system 240, including, for example, a
camera, to provide feedback to operator 160. Sensor system 240 also
provides input to onboard control system 210, such as the angle
between arms 130 and the main body. These inputs are used during
fully or partially autonomous operation. Robot 100 can also
optionally carry a manipulator system 250, including, for example,
a door opening device, for use under remote or autonomous
control.
[0048] FIGS. 3a-c show robot 100 in a fully extended configuration
in which forward arms 130 extend beyond the front of main body 140.
The combination of forward tracks 120 and main tracks 110 and
provide an extended length base. Main body 140 includes a
vertically symmetrical rigid frame 310 which includes parallel
vertical side plates 312. Side plates 312 are rigidly coupled by
tubes 320 and 322 and an articulator shaft 330. The rigid
components are designed for strength and low weight and are made
from a material such as 7075-T6 aluminum. Alternative versions of
the robot can use other materials, such as other lightweight
metals, polymers, or composite materials.
[0049] Referring to FIGS. 4a-f, main tracks 110 and front tracks
120 include compliant belts made of a solid polyurethane or a
similar flexible material. The belts are highly abrasion resistant
and have high strength and minimal stretch due to internal steel or
fiber cording. Referring to FIGS. 4a-d, each main track 100 is
driven by a toothed main drive pulley 342. Teeth 410 in each main
drive pulley 342 mate with grooves 412 on the inside surface of the
corresponding main track 110. Referring to FIGS. 4e-f, a smooth
surfaced main idler pulley 340 supports each main track 110 at the
rear of the robot. Both main drive pulleys 342 and main idler
pulleys 340 have V-shaped channels 343 around their circumference.
These grooves loosely mate with an integral offset V-shaped rib 341
on the inside of each main track 110. The main and front tracks
have soft elastomer cleats 350 spaced along their length. In
alternative embodiments, main and front tracks are smooth
high-friction tracks.
[0050] Alternative versions of the robot can use other types of
tracks, such as tracks made up of discrete elements. However,
debris may be caught between elements and such tracks are generally
heavier than flexible belts. Other flexible materials can also be
used for continuous belt tracks. Referring back to FIGS. 3a-c, each
front track 120 is narrower but otherwise similar to main tracks
110, having grooves and a V-shaped segment on the inside surface,
and soft cleats 350 attached to the outside surface. A front drive
pulley 344 drives each front track 120. Each front drive pulley 344
is toothed and has a central V-shaped channel that loosely mates
with the V-shaped rib on the inside of the corresponding front
track 120. On each side, front drive pulley 344 is coaxial with
main drive pulley 342, and both drive pulleys on a particular side
turn in unison on a common axle. A smaller smooth surfaced front
idler pulley 346, which also has a V-shaped channel, supports each
front track 120 at the extreme end of the corresponding arm
130.
[0051] Referring again to FIGS. 4a-f, each of the drive and idler
pulleys 340, 342, 344, 346 are compliant (75 D durometer) and are
made of a polyurethane or a similar material. Although flexible,
the design and material stiffness provides resistance to lateral
loading. Each pulley has a series of radial spokes 352 around a
central hub 354. Spokes 352 support a thin outer rim section 356.
The combination of spokes 352 and thin outer ring section 356
provide a compliant support for the track that can deform if debris
is caught between outer ring section 356 and the track. This allows
debris to be caught without necessarily stalling a drive motor or
throwing a track.
[0052] Referring to FIG. 4g, an alternative version of the idler
and drive pulleys also has a spoke pattern, but the spokes are
"angled" rather than being radial. Angled spokes 357 have less
tendency to buckle on direct impact. Alternative materials can also
be used, providing more or less compliance, depending on the impact
resistance and payload capacity requirements for the robot.
[0053] Referring to FIG. 5, on each side, between drive pulley 342
and idler pulley 340. Compliant main track supports 314 provide
support for main track 110. Track supports 314 are made of the same
material as the drive and idler pulleys. Main track supports 314
are attached by screws to the top and bottom surfaces of side
plates 312. Each main track support 314 has a series of angled
slots. The slots in the track supports are formed such that a
series of angled ribs 315 join the top and bottom edges of the
tract support. These ribs bend when the top and bottom edges of a
track support are forced together, thereby providing compliant
support for each track.
[0054] Referring back to FIGS. 3a-b, front tracks 120 are supported
by arm side plates 332 using front track supports 334. Front track
supports 334 are wedge-shaped and each has a series of angled slots
similar to those in main track supports 314. The arm side plates
332 on each side of the robot are rigidly coupled to one another
through articulator shaft 330, and therefore move together.
[0055] Referring to FIG. 3b, front arms 130 can be continuously
rotated around articulator axle 330 as indicated by circle 360. On
each side, an arm support 362 is attached to the side plate 312.
When arms 130 are rotated to a "stowed" position next to the side
plates 312, the front idler pulleys 346 have a clearance fit next
to the corresponding arm supports 362. Both arm supports 362 and
arms 130 have polymer pieces, such as Derlin, on the mating
surfaces.
[0056] The robot's mobility system is powered by three separate
electrical motors. Referring to FIG. 3c, on each side of the robot
a respective identical drive motor 370 is coupled to main and front
drive pulleys 342 and 344 by a chain and sprocket mechanism (not
shown).
[0057] Referring still to FIG. 3c, an articulator drive motor 372
is used to control the angle between arms 130 and the main body.
Articulator drive motor 372 is coupled to the input of a harmonic
drive 374 which provides a gear reduction to articulator axle 330.
Harmonic drive 374 has a central opening through which articulator
axle 330 passes. The output of harmonic drive 374 is coupled to a
slip clutch 376 which provides output torque to articulator axle
330. Slip clutch screws 378 are tightened to provide adequate
transfer of torque to rotate arms 130 while allowing the
articulator axle to slip in the event that a large torque is
applied to the arms. Articulator axle 330 passes through a central
opening in drive pulleys 342 and 344 and is attached to arm side
plates 332.
[0058] In this version of the robot, drive motors 370 and
articulator motor 372 are 90 watt DC brushed motors. In other
versions of the robot, brushless motors can be used. Drive motors
370 are geared down 32.7:1 to the drive pulleys. Harmonic drive 374
provides a 427:1 gear reduction between articulator drive motor 372
and articulator axle 330, thereby providing a maximum torque of
approximately 127 N m to arms 130. Slip clutch 376 prevents
overloading of harmonic drive 374 if the torque exceeds the maximum
torque that can be provided by articulator drive motor 372, for
instance due to an impact on the arms.
[0059] Due to the placement of the motor and drive components, the
center of mass of robot 100 is well forward. In particular,
referring to FIG. 3b, center of mass 364 falls within the circle
360 of rotation of arms 130. This location enables or aids certain
maneuvers such as stair climbing and self righting, as are
described below.
[0060] Referring to FIG. 3c, robot 100 includes a payload volume
370 between side plates 312, and between structural tubes 320 and
322. The main body, including the payload volume, and the drive
motors and drives, is housed in a thin, impact resistance,
polycarbonate shell (not shown). The main body is totally within
the volume defined by the main tracks, and furthermore is
sufficiently thin to provide ground clearance in both upright and
inverted orientations of the robot.
[0061] As an alternative to payload being contained within payload
volume 370, payloads can be placed on the top of the robot,
preferably near the center of mass to aid operations such as stair
climbing. Although invertible operation may not be possible in this
case, larger payloads can be carried in this way.
[0062] Referring again to FIG. 5, each of the idler pulleys are
attached to side plates 312 by a pulley holder 510 which attaches
to the side plate using a series of radially positioned screws 515.
Screws 515 pass through slots 520 in the side plates. This allows
each pulley holder to slide in a back and forth direction. A
tensioning screw 530 passes through a hole in side plate 312 and
mates with threads in pulley holder 510. Tensioning screw 530 is
used to adjust the position of the pulley holder prior to
tightening the screws. Pulley holders 510 include ball bearings 530
which support the idler pulleys. A similar slot and tensioning
screw arrangement is used on the front tracks (not shown in FIG.
5). The front and main drive pulleys are attached to side plates
314 using similar pulley holders which mate with holes 522 (rather
than slots) in the side plates 312. The tensioning mechanism allows
easy replacement of the tracks, for example, to change a cleat
design or material to better match the environment the robot must
traverse.
[0063] Rather than using ball bearings 530 to support the drive and
idler pulleys, alternative versions of the robot can use small
diameter polymer bearings. Although polymer bearings have somewhat
greater friction, they cost less than ball bearings and reduce
maintenance due to dirt contamination. Polymer bearings are also
more shock resistant than ball bearings.
[0064] This version of robot 100 is sized to be portable, and is
approximately 62.5 cm (24.6'') long (with arms stowed) by 50.8 cm
(20'') wide by 16.8 cm (6.3'') high, and weighs 10.5 kg (23 lbs.)
The robot can be carried by a person on his or her back, for
example, attached to a special frame or stowed in a backpack.
Structural tube 320 can also serve as a carrying handle.
[0065] Main tracks 110 are 7.6 cm wide (3'') and front tracks 120
are 5.1 cm wide (2''). Cleats 350 extend 0.95 cm (0.4'') from the
outside surface of the tracks. Approximately half of the frontal
area of the robot is tracked. Main tracks 110 are wide for maximum
"grab" of the surface during normal high speed locomotion and are
separated sufficiently for efficient skid steering. Front tracks
120 are as small as possible to be effective while minimizing the
mass of arms 130. In alternative versions of the robot, the front
tracks can be made even narrower since the articulation is designed
for limited use in certain situations, such as stair climbing.
[0066] All the main and front drive and idler pulleys are 2.54 cm
(1'') wide, thereby minimizing the area that debris can be caught
between the pulleys and the tracks, while still being able to
deliver maximum power to the tracks.
[0067] Rigid frame 310 and payload volume provide a ground
clearance of 4.1 cm (1.6'') on either side. The robot can carry a
payload of up to 10 kg (22 lbs.). If the payload is positioned over
the center of mass, the robot can still perform operations such as
stair climbing.
[0068] In operation, robot 100 is designed to maneuver at high
speed in rough terrain. It may collide with objects and suffer
tumbles and falls. For instance, the robot may tumble when
descending stairs. Furthermore, the robot may be deployed by
tossing it out of a helicopter. Therefore, the robot is designed to
be as impact resistant as possible. Also, as the robot is
completely invertible, it can immediately continue operation after
it is inverted in a fall or collision.
[0069] Impact resistance is accomplished, in part, by surrounding
much of the vehicle with compliant main and front tracks 110 and
120 with soft cleats 350. The tracks and cleats provide a first
layer of impact protection. The tracks are supported by compliant
idler and drive pulleys 340, 342, 344, and 346 and by compliant
main and front track supports 314 and 334, which, working together,
provide a second layer of impact protection.
[0070] Referring back to FIG. 3a, side plates 312 are recessed
within the track volume, thereby reducing the likelihood that the
frame will be directly impacted from the side in a tumble or a
fall. Similarly, the main body and payload volume are recessed
relative to the top and bottom of the main tracks, thereby reducing
the likelihood that the main body will be impacted.
[0071] In the event of a tumble or a fall, arms 130 can be
vulnerable to damage if they are extended away from the main body.
For instance, a fall laterally onto the tip of an arm could damage
it. However, arms 130 are, in general, used in situations where the
possibility of a fall is small. In most operations, the robot will
have the arms "stowed" at its sides. Arm supports 362 provide
significant lateral support to the arms during impacts in the
stowed position. To further prevent possible damage, when robot 100
detects that it is in free fall using its sensor system, it
automatically assumes the stowed position without requiring
operator intervention.
[0072] Robot 100 is designed to maneuver in dirt and debris. There
is a possibility that such dirt and debris can be caught between
the tracks and the drive and idler pulleys. The idler and drive
pulleys are compliant and can tolerate material being caught
between them and the tracks. The V-shaped ribs 341 (FIG. 4) on the
inside surfaces of the tracks which mate with the V-shaped channels
343 on the pulleys are deep enough to prevent "throwing" a track.
Also, the fit between the V-shaped channel and the V-shaped grooves
is loose thereby allowing debris to be caught without necessarily
dislodging the V-shaped segment. Furthermore, the idler pulleys do
not have teeth, thereby further reducing the effect of debris
entrainment by allowing debris to pass under the idler pulleys in
the grooves of the tracks. Finally, the pulleys are narrow, thereby
minimizing the places that debris can be caught.
[0073] Further debris resistance can be obtained in alternative
versions of the robot using active debris removal approaches. For
instance, a stiff brush positioned before each pulley can prevent
debris from entering the pulleys. Compressed air jets can also be
used in place of the brushes to remove debris on the tracks.
Flexible or rigid skirts, placed at an angle in front of each of
the pulleys, can also divert debris before it enters the
pulley.
[0074] Referring to FIG. 3c, robot 100 is controlled using left and
right drive motors 370 and articulator motor 372. Steering is
accomplished using differential speed of the tracks on either side
of the robot. The robot will, in principle, skid around its center
of gravity 364 (shown in FIG. 3c) allowing complete turning with
the extremes of the robot staying within a 100 cm (39.4'') diameter
circle.
[0075] In operation, robot 100 has several mobility modes including
fully extended, stowed arms, inclined, upright, and "wheelie"
modes. In addition, robot 100 can perform several maneuvers
including self righting, stair climbing, and recovery from high
centering.
[0076] A fully extended mode is shown in FIGS. 3a-c. In this mode,
the longest possible "wheelbase" is achieved. This mode is useful,
for instance, in a stair-climbing maneuver describe below.
[0077] Referring to the schematic view of FIG. 6, the stowed arms
mode is the most compact configuration of robot 100. Arms 130 are
stowed next to the main track such that both main tracks 110 and
forward tracks 120 provide traction. This configuration is used for
high speed mobility and for traversing rough terrain. It is also
the configuration that is used when robot 100 is launched by
tossing or dropping it through a window or door or when the robot
tumbles.
[0078] Referring to FIG. 7a, robot 100 can deploy arms 130 to raise
the forward end of the main body in an inclined mobility mode. This
posture is useful for increasing ground clearance to traverse
rubble-strewn terrain and to increase the height of sensors on the
platform, such as a CCD camera. Note that in the inclined mobility
mode, the robot travels on four points of contact at the extreme
ends of each track, somewhat as it were on wheels instead of
tracks.
[0079] Referring to FIGS. 7b-c, by combining the inclined mode with
the fully extended mode, the robot can lift and carry objects,
rather like a forklift. Referring to FIG. 7b, robot 100 first
adopts the fully extended position with its arms 130 outstretched
and then maneuvers its arms under an object 630 to be carried or
lifted. Referring to FIG. 7c, robot 100 then raises itself into the
inclined mobility position, thus raising object 630. The object
needs to be small enough to fit between the tracks, of course, in
order to be carried away by the robot.
[0080] Referring to FIGS. 8a-c, to assume an upright "prairie dog"
mode, robot 100 balances the main body on arms 130. Referring to
FIG. 8a, robot 100 begins in a stowed position, and then using
articulator drive motor 372 (FIG. 3c) applies a torque to the arms.
Since the center of gravity is within arc of the arms (as shown in
FIG. 3b), the main body is raised (FIG. 8b) until it reaches a high
position (FIG. 8c) which is short of the point at which the robot
would topple. As is described further below, this upright position
allows sensors to be placed at the highest possible elevation, and
also provides the smallest possible wheel base. In this upright
mobility mode, the robot is able to drive on the front tracks and
to pivot in place with the tracks staying within a small circle, in
principle, as small as 60 cm (23.6'') diameter. Therefore, the
upright mobility position is useful for navigating in narrow
corridors and passageways.
[0081] Referring to FIG. 9, a side "wheelie" mobility mode is used
to navigate a passageway that is even smaller than the width of the
robot in the upright position. In the side wheelie mode, the robot
rests one track on the side wall and the other track on the floor.
It then moves forward in a tilted orientation as shown.
[0082] Referring to FIG. 10a-b, a self righting maneuver is related
to the upright mobility mode. In this maneuver, in order to invert
itself, the robot begins in a stowed mode and raises itself as it
does when attaining the upright mobility mode (FIGS. 8a-c).
However, rather than stopping in the upright position shown in FIG.
10a rotation is continued past the vertical point and the robot
falls over (FIG. 10b), thereby completing the inversion.
[0083] Referring to FIG. 11, robot 100 can raise arms 130 in order
to mount an obstacle, such as a stair 1010, in its path. To mount
the first step of staircase 1110, robot 100 raises its arms 130 and
drives forward to raise its main tracks 110 onto the first stair.
The robot then assumes a fully extended mode thereby extending its
wheelbase to increase it stability and to provide as smooth a ride
a possible up the stairs. Soft cleats 350 (not shown in FIG. 11)
provide mechanical locking with the stair edge needed to drive the
robot up the stairs.
[0084] Robot 100 is specifically dimensioned to climb common stairs
in this version, with step dimensions of up to a 17.8 cm (7'') rise
and 27.9 cm (11'') tread. As the robot tilts or inclines, the
vertical projection of the center of gravity (CG) with respect to
the ground moves backwards. For stable travel on stairs, the
extended wheel base of the main and forward tracks in the fully
extended mode span a minimum of two steps (i.e. at least 66.2 cm
(26.1'') for 17.8 cm (7'') by 27.9 cm (11'') stairs) such that the
vehicle is supported by at least two stair treads at all times.
Note that robot 100 can climb larger stairs for which it cannot
span two steps, but the traverse will not be as smooth as the robot
will bob with each step.
[0085] To avoid nosing up or down (pitch instability) while
climbing stairs, the vertical projections of the center of gravity
is located in a stable range which is at least one step span (i.e.,
33.1 cm (13'') for 17.8 cm (7'') by 27.9 cm (11'') stairs) in front
of the furthest rear main track ground contact and at least one
step span behind the front most front track ground contact.
[0086] Alternative versions of the robot can use shorter track
dimensions that do not satisfy the requirement of spanning two
steps, and the center of gravity can be outside the stable range.
Although such robots may not be as stable on stairs, inertial
effects add to dynamic stability at increased velocities, smoothing
the traverse on stairs. Also, the front extremities of arms 130 can
be weighted to move the center of gravity forward in the fully
extended position. However, adding weight at the end of the arms
also has the negative effect of reducing robustness.
[0087] Referring to FIGS. 12a-c, robot 100 has relatively small
vertical clearance below its main body. In this version of the
robot, in order to accommodate the drive motors and gearing within
the front section of the mobility platform resulted in only 4.11 cm
(1.6'') ground clearance on both top and bottom of the robot.
Referring to FIG. 12a, robot 100 can lose traction in a high
centering situation in which it rests on an obstacle 1110.
Referring to FIGS. 12b-c, arms 130 are lowered (illustrated here as
swinging clockwise to the front of the robot) to gain traction with
the ground and then the robot can drive away in the inclined
mobility mode.
[0088] Referring to FIG. 13, another mode of recovery from high
centering makes use of continuous rotation of arms 130. Continuous
rotation in one direction essentially "paddles" the robot off
obstacle 1210 using only the articulator drive motor 370, for
example.
[0089] Note that the likelihood of a high centering situation is
reduced for robot 100 since approximately half of the frontal area
that is tracked. Therefore, obstacles are as likely to encounter
the tracks as to pass under the main body.
[0090] The robot's low and forward positioned center of gravity
also allows the robot to climb steep inclines, given enough
traction, without the robot toppling. Based on the location of the
center of mass, this version of the robot can, in principal, climb
a 77 incline.
[0091] Robot 100 includes the capability of carrying a variety of
sensors, including cameras, sonar sensors, infra-red detectors,
inertial sensors, motor position, velocity and torque sensors,
inclinometers, a magnetic compass, and microphones. Sensors can be
placed on all surfaces of the robot.
[0092] Sensors can be shielded within the track volume or within
the protective shell of the main body. The front and rear of the
vehicle has room for sensors within the 24.4 cm (10'') width not
covered by tracks, although the rear is partially occluded by the
rear handle. The top and bottom of payload volume 370 (FIG. 3c) is
free for sensor placement, as are side plates 312. Sensors mounted
to the front of arm supports 362 are occluded when arms 130 are
stowed. Sensors can also be mounted on arm side plates 332.
Articulator axle 330 is hollow allowing power and signal cables
from the arms to pass to a slip ring allowing continuous rotation
of the arms. The robot's self-righting capability permits the use
of fewer specialty sensors since not all sensors have to be
duplicated on both the top and the bottom of the main body. When
there is redundancy of sensors on both the top and bottom of the
robot, this feature allows the robot to continue functioning if one
or more of its sensors fails--it simply inverts and uses the
undamaged sensors on the other side.
[0093] Referring to FIGS. 14a-b, a two- or three-camera array 1310,
which is used for stereoscopic vision, is placed at the top of the
robot for operation predominantly in the upright mobility position
only (FIG. 14b). Another camera 1320 is placed at the front of the
robot for navigation and video transmission back to remote control
system 150. Camera array 1310 and camera 1320 have fields of view
1315 and 1325 respectively. A microphone (not shown) is placed at
the front for surveillance and for providing directional
information. A rate gyroscope is placed near the center of gravity
364 of the robot. Optional accelerometers can be located near the
rate gyroscope.
[0094] Referring to FIGS. 15a-b, two sonar sensors 1420 are placed
at the top and bottom of the robot respectively, for operation in
the upright position (FIG. 15b). Two more sonar sensors 1410 are
placed on the sides of the robot to be as high as possible when the
robot is in the upright position. The sonar sensors are positioned
high off the ground because they have a fairly large cone of
sensitivity, and may be confused by the ground or very small
objects if placed low to the ground.
[0095] Referring to FIGS. 16a-b, four infrared sensors 1530 are
placed at the front of the robot, and two on each side 1510 and
1520, one in the back and one in the front. The side-back IR's are
in the same position as the side sonar sensors and can be used in
either upright or stowed position, while the side-front infra-red
sensors 1520 are occluded by the arms in stowed position and are
only used in upright position.
[0096] In this version of the robot, there are no rear-facing
sensors, although they can be added if needed. Robot 100 can move
to its upright mobility position to use the sonar sensor on the
bottom of the robot. Or, it can rotate quickly in either the stowed
position or the upright position, which has a very small turn
radius, to use its entire sensor suite to acquire information about
the environment in any direction.
[0097] In addition to placing sensors directly on the outside
surface of the robot, a retractable sensor mast can be extended
away from the top or the bottom of the robot. Sensors, such as
cameras, can be mounted on the sensor mast. Robot 100 can include a
variety of manipulators. Referring to FIG. 17, one such manipulator
is a door opening mechanism that allows robot 100 to open a closed
door with a standard height door knob 1620. An extendable mast 1630
is attached to the robot. Mast 1630 has a high friction, flexible
hoop 1640 at the top of the mast. Hoop 1640 is rotated by an
actuator located within the attachment section of the hoop and
mast. The procedure for engaging door knob 1620 is reminiscent of a
ring toss game. The object is to place the hoop, which remains
attached to the mast, over the door knob. Once the hoop is over the
door knob, the mast retracts to snug the hoop against the door
knob. The hoop is then rotated and the door knob is rotated due to
the frictional forces holding the hoop against the door knob. Once
the door has been jarred opened, the mast extends to disengage the
hoop from the doorknob.
[0098] Alternative versions of the robot can be completely
waterproofed, thereby allowing underwater operation. Also, larger
or smaller versions of the robot can be used for different
applications. The drive system in other versions of the robot can
allow independent rotation of the arm on each side of the robot,
and separate drive motors for the main and front tracks can be
used.
[0099] Remote control system 150 (FIG. 1) provides a user interface
to operator 160 that allows teleoperation of robot 100.
[0100] Alternative versions of the remote control system 150
support teleoperation as well as a means of switching between
teleoperation and autonomous control. The user interface permits
transitions between autonomous and teleoperated control that are
almost imperceptible to the user. That is, the user can interrupt
autonomous operation of the robot at any time to give commands and
direction, and the robot would operate autonomously when not
receiving particular directions from the user. The system provides
a predetermined warning signals to the operator, for instance if it
is unable to operate autonomously, possibly by means of a vibrating
unit that could be worn by the operator and which would be
effective in a noisy environment. In addition, the user can add
additional tasks to the robot's mission and request notification
from the robot when milestone tasks have been achieved.
[0101] Versions of the robot can perform various autonomous tasks
which can be initiated by the operator from remote control system
150. These include obstacle avoidance, wall following, climbing
stairs, recovery from high centering, returning "home," opening
doors, searching for a designated object, and mapping. The robot
can use the various mobility modes described above in these
autonomous operations, and if necessary, can call for operator
assistance during its execution of a task. Alternative
configurations of articulated bodies can be used. For example, a
single central "arm" can be used and the arm or arms do not
necessarily have to be tracked.
[0102] Other embodiments of the invention are within the scope of
the following claims.
* * * * *