U.S. patent application number 11/789812 was filed with the patent office on 2008-06-26 for system and method for accessing ferrous surfaces normally accessible only with special effort.
Invention is credited to Vince Hock, Charles Marsh, Frank Robb, Warren Whittaker.
Application Number | 20080148876 11/789812 |
Document ID | / |
Family ID | 35308140 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080148876 |
Kind Code |
A1 |
Hock; Vince ; et
al. |
June 26, 2008 |
System and method for accessing ferrous surfaces normally
accessible only with special effort
Abstract
A system incorporating a robot to inspect ferrous surfaces.
Preferably, the robot is an articulated device having a tractor
module for motive power and steering, a power module for electrical
power and communications and additional motive power, and a third
module for cleaning and inspection. The robot uses sensors and
transmits signals to a computer through a tether and receives
direction from an operator via the computer and tether. The
computer continuously monitors the location of the robot and
supports the robot during deployment. In a specific application,
the robot travels the interior of a tank on a set of magnetized
wheels. Prior to measurement, the tank surface is cleaned of
deposits by rotary cutters and rotary brushes on the third module.
The robot obtains at least thickness measurements via onboard
ultrasonic transducers that contact the cleaned surface. A method
for implementing inspection of ferrous surfaces is also
described.
Inventors: |
Hock; Vince; (Champaign,
IL) ; Marsh; Charles; (Champaign, IL) ;
Whittaker; Warren; (Pittsburgh, PA) ; Robb;
Frank; (Pittsburgh, PA) |
Correspondence
Address: |
HUMPHREYS ENGINEER CENTER SUPPORT ACTIVITY;ATTN: CEHEC-OC
7701 TELEGRAPH ROAD
ALEXANDRIA
VA
22315-3860
US
|
Family ID: |
35308140 |
Appl. No.: |
11/789812 |
Filed: |
April 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11098732 |
Apr 5, 2005 |
7296488 |
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11789812 |
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09553613 |
Apr 20, 2000 |
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11098732 |
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Current U.S.
Class: |
73/865.8 |
Current CPC
Class: |
G01N 2291/02854
20130101; G01N 29/041 20130101; G01N 2291/2632 20130101; G01N
29/265 20130101; G01N 2291/2636 20130101; G01N 29/225 20130101 |
Class at
Publication: |
73/865.8 |
International
Class: |
G01M 19/00 20060101
G01M019/00 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] Under paragraph 1(a) of Executive Order 10096, the
conditions under which this invention was made entitle the
Government of the United States, as represented by the Secretary of
the Army, to an undivided interest in any patent granted thereon by
the United States. This invention was made in part under United
States Army Construction Engineering Research Laboratory Contracts
numbered DACA88-93-C-0008 and DACA88-94-C-0024. This and related
patents are available for licensing. Please contact Bea Shahin at
217 373-7234 or Phillip Stewart at 601634-4113.
Claims
1. A wheeled conveyance employing modules coupled end-to-end along
a long axis of said conveyance, said conveyance facilitating
inspection of ferrous surfaces indisposed to ready access,
comprising: at least one central module for powering said
conveyance; at least one front module for steering said conveyance
in a current plane of operation, wherein said front module
maintains operable communication with at least said central module;
and at least one rear module for at least abrading said surfaces,
said rear module adapted to facilitate maneuvering said conveyance
onto a plane of operation different from said current plane of
operation, wherein said rear module maintains operable
communication with at least said central module, and wherein at
least one of said modules incorporates at least one sensor to
facilitate said inspection.
2. The conveyance of claim 1 in which said sensor is selected from
the group consisting 25 essentially of: acoustic sensors,
ultrasonic transducers, electrical sensors, piezoresistive sensors,
attitude sensors, contact sensors, thickness sensors,
inclinometers, mutually orthogonal inclinometers, and combinations
thereof, wherein at least one said sensor is encapsulated in a
block of dense, tough and resilient material resistant to wear due
to contacting said surfaces while said conveyance is moving.
3. The conveyance of claim 1 in which at least a part of at least
one said module is sealed and pressurized with an inert gas.
4. The conveyance of claim 1 in which said conveyance is portable
and configurable to insert into a riser of an underground tank.
5. The conveyance of claim 4 in which said conveyance weighs less
than about 18 Kg (40 lbs) and is configurable to have a diameter
perpendicular to said long axis of less than about 10 cm (4.0
inches) to permit inserting said conveyance into said riser.
6. The conveyance of claim 1 in which: said front module comprises:
at least one first wheeled axle assembly having a first at least
two polar member wheels of a first diameter, said first polar
member wheels comprising a magnetically transmissive material and
at least one permanent magnet of a second diameter smaller than
said first diameter, each said magnet coaxially mounted between
each pair of said first polar member wheels; wherein if more than
one said magnet is employed, each said magnet is mounted on said
wheeled axle assembly so as to be oriented with polarity opposing
that of a nearest mounted one of said magnets; at least a first
steering mechanism to orient said front module in said current
plane; wherein orienting said front module orients said conveyance;
at least one pivotally mounted first lever arm, wherein said first
lever arm operates on said front module to lift and lower said
front module; and first communicating assemblies in operable
communication with at least a portion of said central module to
facilitate operation of at least said first wheeled axle assembly,
said first lever arm and said steering mechanism; said central
module comprises: at least one second wheeled axle assembly having
a second at least two polar wheels of a first diameter, said second
polar member wheels comprising a magnetically transmissive
material, and at least one permanent magnet, each said magnet of a
second diameter smaller than said first diameter and coaxially
mounted between a pair of said second polar member wheels, wherein
if more than one said magnet is employed, each said magnet is
mounted on said wheeled axle assembly so as to be oriented with
polarity opposing that of a nearest mounted one of said magnets; at
least one motor; at least one first push rod; second communicating
assemblies in operable communication at least with said first
communicating assemblies to facilitate operation of said first
wheeled axle assembly, said first lever arm and said steering
mechanism; third communicating assemblies in operable communication
with at least said second wheeled axle assembly to facilitate
operation thereof; and fourth communicating assemblies in operable
communication with said rear module; and said rear module
comprises: at least one abrading device; at least one maneuvering
assembly, wherein said maneuvering assembly permits said rear
module to follow said central module onto a surface in a plane of
operation different from said current plane of operation of said
rear module, and wherein said rear module may move onto a surface
in said different plane only when said conveyance is moving in a
forward direction; at least one biasing mechanism, wherein said
biasing mechanism permits said rear module to maintain firm contact
with said surfaces of operation regardless of the orientation of
said conveyance; and fifth communicating assemblies in operable
communication with said fourth communicating assemblies, said fifth
communicating assemblies at least facilitating operation of said
abrading device and said maneuvering mechanism.
7. The conveyance of claim 6 in which at least one said motor is a
DC reversible servomotor and in which at least one said servomotor
incorporates at least one odometric encoder.
8. The conveyance of claim 6 in which at least one said polar
member wheel incorporates grooves across the width of the outer
circumference of said polar member wheel, wherein said grooves
enhance traction of said polar member wheel.
9. The conveyance of claim 6 in which said abrading device is
selected from the group consisting of rotatable brushes, rotatable
cutting wheels, scrapers, and combinations thereof.
10. The conveyance of claim 9 in which said rotatable brush is
cylindrical and axially mounted on said rear module to be
approximately parallel to, and approximately the same width as,
said second wheeled axle assembly.
11. The conveyance of claim 9 in which said scrapers are employed
in pairs, mounted adjacent the outer circumference of each of said
polar member wheels, wherein said pairs of scrapers serve to remove
debris that accumulates on said polar member wheels, and wherein a
first said scraper in each said pair is mounted to remove debris
when said conveyance is moving in a first direction and a second
said scraper in each said pair is mounted to remove debris when
said conveyance is moving in a direction opposite to said first
direction.
10. The conveyance of claim 9 in which said rotatable cutting
wheels are cylindrical and axially mounted on said rear module to
be approximately parallel to, and approximately the same width as,
said second wheeled axle assembly, wherein said cutting wheel
rotates in the direction of movement of said conveyance and is
protected by a unidirectional clutch.
11. The conveyance of claim 6 in which said abrading device
comprises at least one cylindrical rotatable brush and one
cylindrical rotatable cutting wheel, wherein each said brush and
cutting wheel is axially mounted across the width of said rear
module, perpendicular to said long axis and parallel to the plane
of operation of said conveyance, and wherein each said brush and
cutting wheel is approximately the same width as said second
wheeled axle assembly.
12. The conveyance of claim 11 in which said abrading device
comprises a first and second said rotatable brush and a first and
second said rotatable cutting wheel, wherein said first rotatable
brush and said first rotatable cutting wheel are rotated upon said
conveyance moving in a first direction, said first rotatable brush
rotated counter to the rotation direction of said first rotatable
cutting wheel, and said second rotatable brush and said second
rotatable cutting wheel are rotated upon said conveyance moving in
a second direction opposite to said first direction, said second
rotatable brush rotated counter to the rotation direction of said
second rotatable cutting wheel.
15. A method for inspecting an interior surface of a ferrous tank
of a generally cylindrical configuration with a first end plate
opposing a second end plate, said end plates at the extreme ends of
the long axis of said tank, comprising: deploying into said tank a
remotely controllable robotic vehicle comprising three modules, a
middle module connected to a front and rear module along a long
axis of said robotic vehicle, said robotic vehicle incorporating a
connection to a remote power source and controller, at least one
sensor, at least one abrading device and magnetic wheeled axle
assemblies on said front and rear modules; controlling said robotic
vehicle to navigate along a selected linear path along the long
axis of said tank to establish the orientation and position of said
robotic vehicle; generating and recording a graphical
representation of said interior surface; establishing and recording
an initial orientation and position of said robotic vehicle;
controlling said robotic vehicle to navigate a pre-established
portion of said interior surface; directing said robotic vehicle to
employ said sensor to measure the thickness of said tank at a
pre-specified sampling rate while identifying the instantaneous
location of said robotic vehicle during said measurement, wherein
said instantaneous location of said robotic vehicle is displayed on
said graphical representation; receiving signals indicative of said
thickness measurements; comparing said measurements with
pre-established criteria; wherein said locations of thickness
measurements not meeting said pre-specified criteria are displayed
on said graphical representation; and recording the position of
said locations where thickness did not meet said pre-specified
criteria.
16. The method of claim 15 in which controlling said robotic
vehicle to navigate said tank comprises: first directing said
robotic vehicle to navigate along a line on a cylindrical surface
of said tank that is parallel to the long axis of said tank until
said robotic vehicle first contacts a surface not parallel to said
cylindrical surface; determining whether said first contacted
surface is one of said end plates of said tank; if said first
contacted surface is not a said end plate, directing said robotic
vehicle to circumvent said first contacted surface and further like
said contacted surfaces that are not an end plate; and if a said
subsequent contacted surface or said first contacted surface is one
of said end plates, directing said robotic vehicle to reverse
direction by implementing a small angular difference from the prior
line of travel of said robotic vehicle; next directing said robotic
vehicle to navigate in said reverse direction along said newly
acquired path on said cylindrical surface until said robotic
vehicle contacts the opposing said end plate; repeating said
navigation process by reversing direction at said opposing end
plates until the entire surface along the long axis of said tank
has been navigated; causing said robotic vehicle to transfer to a
first said end plate; directing said robotic vehicle to navigate
along a line through the center of said first end plate until said
robotic vehicle first contacts a first surface not parallel to said
first end plate; determining whether said first contacted surface
not parallel to said first end plate is said cylindrical surface;
if said first contacted surface is not said cylindrical surface,
directing said robotic vehicle to circumvent said first contacted
surface not parallel to said first end plate and further like said
contacted surfaces that are not said cylindrical surface; if a said
subsequent contacted surface or said first contacted surface not
parallel to said first end plate is said cylindrical surface,
directing said robotic vehicle to reverse direction by implementing
a small angular difference from the prior line of travel of said
robotic vehicle; repeating said navigation process as above until
the entire said first end plate surface has been navigated; causing
said robotic vehicle to transfer to said cylindrical surface;
directing said robotic vehicle to navigate said cylindrical
surface, now known as to configuration, until said robotic vehicle
contacts the second end plate; causing said robotic vehicle to
transfer to said second end plate; directing said robotic vehicle
to navigate along a line through the center of said second end
plate until said robotic vehicle first contacts a first surface not
parallel to said second end plate; determining whether said first
contacted surface not parallel to said second end plate is said
cylindrical surface; if said first contacted surface is not said
cylindrical surface, directing said robotic vehicle to circumvent
said first contacted surface not parallel to said second end plate
and further like said contacted surfaces that are not said
cylindrical surface; if a said subsequent contacted surface or said
first contacted surface not parallel to said second end plate is
said cylindrical surface, directing said robotic vehicle to reverse
direction by implementing a small angular difference from the prior
line of travel of said robotic vehicle; repeating said navigation
process as above until the entire said second end plate surface has
been navigated.
17. The method of claim 15 dispensing a liquid, said liquid serving
as a couplant between said first sensor and said tank.
18. The method of claim 15 providing at least one second sensor
fixedly mounted to the front of said robotic vehicle, wherein said
second sensor facilitates determining the location of contacted
surfaces in a plane different from that plane of the surface on
which said robotic vehicle is traveling.
19. The method of claim 18 providing a transition lever arm mounted
to said robotic vehicle and operative for lifting said magnetic
wheeled axle assembly when said robotic vehicle is transitioning
from a first said surface to another surface angular thereto.
20. The method of claim 15 providing at least one abrading device
mounted on said rear module and positioned so as to contact said
surface for cleaning said surface prior to taking measurements
thereof with said sensors.
21. A method of inspecting ferrous surfaces of a structure, said
surfaces otherwise inaccessible without employing procedures that
are expensive, time consuming, dangerous, or any combination
thereof, comprising: providing at least one inspection system
comprising: at least one articulated conveyance for accessing said
surfaces without either modifying said structure or expanding
access to said structure, each. said conveyance incorporating at
least three sections, wherein a front section turns in only a first
plane with respect to a middle section and a rear section turns to
only a second plane, different from said first plane, with respect
to said middle section; at least one tether for providing at least
power to said conveyance via a means for providing power contained
within said tether, wherein said tether may also provide at least
one source of fluids; at least one control system, at least part of
said control system being remote from said conveyance and connected
to said conveyance via connection means within said tether, wherein
said control system is in operable communication with at least one
power source external to said conveyance, and wherein said power
source may be used to power said conveyance via said means for
providing power; and at least one sensor incorporated in each said
conveyance to facilitate semi-autonomous operation thereof; and
operating said inspection system for a time period necessary to
collect at least one parameter for describing the condition of at
least part of said surfaces.
Description
RELATED INVENTIONS
[0001] Under 35 U.S.C .sctn. 121, this application claims the
benefit of prior co-pending U.S. patent application Ser. No.
11/098,732, System and Method for Accessing Ferrous Surfaces
Normally Accessible Only with Special Effort, by Hock et al., filed
Apr. 5, 2005, in turn a divisional of prior co-pending U.S. patent
application Ser. No. 09/553,613, Apparatus That Accesses a Ferrous
Surface That Is Inconvenient to Access in Order to Measure and
Assess the Condition Thereof, by Hock et al., filed Apr. 20, 2000,
now abandoned, both of which are incorporated herein by
reference.
BACKGROUND
[0003] In recent years, many tanks used for the underground storage
of liquids have been made of fiber reinforced synthetic resins, and
so will not rust or otherwise degrade over time. Traditionally,
storage tanks were made of steel, thus these tanks can corrode to
the point of perforation. Once corrosion has caused perforation,
tank contents leak into the ground and gradually leach into nearby
underground aquifers. Replacement or repair of these tanks to
correct the damage involves extensive effort and attendant expense.
In the United States, approximately 700,000 underground storage
tanks are estimated to be in service. Most store petrochemicals.
The U.S. Environmental Protection Agency (US EPA) enforces
regulations that protect against dangers inherent in defective
underground storage tanks.
[0004] 40 CFR .sctn..sctn. 280 et seq. requires that new
underground storage tanks (USTs) meet stringent standards and that
all existing USTs be certified to be within specified tolerances
for leak resistance integrity. Certification of existing tanks
requires that the tanks in current service be inspected to
determine whether they meet the applicable federal standard.
Traditional methods for inspection of USTs require access into the
tank by a worker to visually assess the surface. For a person to
enter a UST, sometimes a portion of the earth covering a tank must
be excavated and the stored liquid removed. Excavation is laborious
and even after the liquid removal potentially toxic residual fumes
remain in the tank, especially in tanks storing petrochemicals.
[0005] After an UST has been inspected and certified under 40 CFR
.sctn..sctn.280 et seq., a cathodic protection system may be
required to reduce subsequent tank corrosion, extend tank life, and
comply with updated Federal standards.
[0006] One example of a remotely controllable, self-propelled
vehicle for inspecting the interior of USTs is disclosed in U.S.
Pat. No. 5,435,405 to Schempf et al. The '405 patent describes a
mobile vehicle having endless drive tracks that are selectively
magnetically actuated during travel on the inner surfaces of a UST.
As its endless drive tracks are driven in one direction, a clutch
is intermittently engaged to cause a hollow shaft to rotate to
intermittently activate a magnetic circuit. The vehicle is capable
of climbing a vertical wall and traveling in an inverted
orientation in a ferrous structure by utilization of its magnetic
tracks. It is able to enter and operate in a tank that is filled
with liquid and carries a camera and an ultrasonic tester. The
vehicle has its basic components enclosed in hermetically sealed
and pressurized compartments to prevent explosion of the stored
liquid and to keep the liquid from seeping into the electrical and
mechanical parts. It is able to communicate signals indicative of
its findings to an external computer.
[0007] The '405 vehicle is equipped with acoustic means
facilitating navigation within an enclosed structure containing a
liquid. Calibration of the navigational system is necessary when
operating in multiple fluid types since sound travels at different
speeds in materials of different densities. While ultrasonic
transducers used by the '405 vehicle facilitate measurement of wall
thickness without determining a fixed point of reference,
deployment of ultrasonic sensors alone to measure thickness to
assess corrosive condition may be unreliable in an underground
storage tank environment. Particular frequency readings may be
affected by causes unrelated to wall thickness. For example,
readings may be compromised by equipment operator produced sounds
or vehicles traveling nearby. Another source of error may be
unknown amounts of corrosive buildup on the tank surface. The '405
vehicle incorporates no means to remove accumulated rust or
sediment before measuring wall thickness. Thus a need exists for a
mobile device to travel within a liquid filled tank to measure and
report actual tank wall thickness by performing the necessary tasks
for making reliable measurements to include removing any corrosive
buildup prior to measurement.
[0008] Further, a need exists for the remote inspection of ferrous
structures other than underground storage tanks. These other
structures include bridges, building frames, utility towers and the
like. Select embodiments of the present invention address such
applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a side elevation schematic view of an embodiment
of the present invention deployed within a storage tank, the tank
illustrated in cross section for clarity.
[0010] FIG. 2A is a side elevation view of the three modules of an
embodiment of the present invention.
[0011] FIG. 2B is a top plan view of the embodiment of FIG. 2A with
the first module of the embodiment pivoted at an angle to the
second and third modules.
[0012] FIG. 3A is a front elevation view of the leading end of the
first module of the embodiment of FIG. 2A, shown within a cross
section of a riser.
[0013] FIG. 3B is a side elevation view of the first module of the
embodiment of FIG. 2A showing a front magnetic drive wheeled axle
assembly and a lift apparatus in its idle orientation.
[0014] FIG. 3C depicts the module of FIG. 3B with the lift
apparatus in its lifting orientation.
[0015] FIG. 4 is a side elevation view of a first segment of the
second module of FIG. 2A showing the orientation and position
determination apparatus and an exploded view of the power module
pin.
[0016] FIG. 5 is a side elevation view of a second segment of the
second module of FIG. 2A.
[0017] FIG. 6 is a side elevation view of a third segment of the
second module of FIG. 2A depicting a rear magnetic drive wheeled
axle assembly.
[0018] FIG. 7 is a side elevation view of the third module of FIG.
2A.
[0019] FIG. 8A is a perspective view of a magnetic wheeled axle
assembly of an embodiment of the present invention.
[0020] FIG. 8B is a front elevation view of the front of the first
module of FIG. 2A showing the magnetized wheel in contact with a
portion of a ferrous surface with dashed lines depicting lines of
magnetic flux.
[0021] FIG. 9A is a segmented cross sectional view of a tank in
which an embodiment of the present invention is traveling
circumferentially.
[0022] FIG. 9B is a segmented cross sectional view of a tank in
which an embodiment of the present invention is traveling along a
path parallel to the tank's long axis.
[0023] FIG. 10 is an enlarged cross sectional depiction of a tether
cable assembly that may be used with an embodiment of the present
invention.
[0024] FIGS. 11A-11F show a series of sequential views of an
embodiment of the present invention executing a transition from a
horizontal surface to a vertical surface of a tank.
[0025] FIGS. 12A-12D show a series of sequential views of an
embodiment of the present invention traversing across an obstacle
in the tank.
[0026] FIG. 13 is a planar graphical map of the interior surface of
the tank being inspected with indications of the positions of an
embodiment of the present invention and a tank wall defect shown on
a grid.
[0027] FIG. 14 is a diagrammatic flow chart of a computer program
for indication of the positions of tank wall defects on the
graphical map of FIG. 13.
DETAILED DESCRIPTION
[0028] In select embodiments of the present invention, a system
facilitates access to ferrous surfaces of a structure for purposes
such as inspection thereof. In select embodiments of the present
invention, the system comprises one or more three-section
conveyances having a long axis about which the sections of the
conveyance move, the three sections connected in line along the
long axis. In select embodiments of the present invention, the
conveyance is of a size suitable for deployment upon ferrous
surfaces without either modifying the structure or expanding access
to the structure. The front section steers the conveyance by
turning in only a first plane with respect to the middle section.
The rear section is able to turn in only a second plane, the second
plane being as much as fully perpendicular to the first plane in
which the conveyance was being steered by the first section.
[0029] In select embodiments of the present invention, the front
section incorporates a first part of a first connection assembly
for connection to the middle section, one or more magnetic wheeled
axle assemblies comprising polar member wheels and annular
permanent magnets and one or more pivotable lever arms. The front
section steers and transfers part of the power to propel the
conveyance.
[0030] In select embodiments of the present invention, the middle
section incorporates one or more magnetic wheeled axle assemblies
comprising polar member wheels and annular permanent magnets. In
select embodiments of the present invention, the middle section
incorporates a second part of the first connection assembly for
connection to the front section, a first part of a second
connection assembly for connection to the rear section, and one or
more motors incorporating interoperable connections to one or more
devices in each of the front, middle and rear sections and one or
more push rods.
[0031] In select embodiments of the present invention, the rear
section incorporates a second part of the second connection
assembly for connection to the middle section, and one or more
abrading devices. In select embodiments of the present invention,
the rear section may articulate to permit changing the plane of
operation of the conveyance only if each of the front, middle and
rear sections are approximately aligned along the centerline of the
long axis of the conveyance.
[0032] In select embodiments of the present invention, the
conveyance may move to a surface of operation in a plane different
from the plane of the surface of current operation only in a
forward direction such that the front section is moved to a new
surface of operation prior to the middle and rear sections.
[0033] In select embodiments of the present invention, one or more
tethers provide communication with the conveyance from external
sources. In select embodiments of the present invention, a tether
incorporates means for distributing power, means for distributing
control signals and means for distributing fluids to the
conveyance.
[0034] In select embodiments of the present invention, one or more
control systems communicate with the means for distributing control
signals, part of which control system is remote from the conveyance
and communicating with the conveyance via the means for
distributing control signals. The control system communicates with
one or more power sources external to the conveyance, the power
sources energizing the motors used in the conveyance and one or
more sensors incorporated in the conveyance to facilitate at least
navigation and inspection functions.
[0035] In select embodiments of the present invention, the
conveyance may move onto a surface in a different plane only when
the front section is moving in a forward direction.
[0036] In select embodiments of the present invention, the
conveyance responds to input from one or more first contact
switches communicating with a first pair of sensors located on the
front of the front section, the sensors mounted on a first
telescoping mount that is parallel to the front side of the front
section, the mount compressing equally along its length upon
contact with a surface that is approximately perpendicular to the
direction of operation of the conveyance, the compression
activating one or more first contact switches.
[0037] In select embodiments of the present invention, a second
pair of sensors is mounted on a second telescoping mount that is
parallel to the back of the rear section, the mount compressing
upon contact in a manner similar to the front mount, the
compression activating one or more second contact switches, such
that activating a second contact switch alerts the conveyance to
the need to alter course.
[0038] In select embodiments of the present invention, one or more
of the motors is a reversible servomotor, and one or more of the
reversible servomotors incorporates one or more odometric
encoders.
[0039] In select embodiments of the present invention, the abrading
device is selected from the group consisting of rotatable brushes,
rotatable cutting wheels, scrapers, and combinations thereof, such
that the rotatable brushes and rotatable cutting wheels are powered
by one or more motors. In select embodiments of the present
invention, scrapers are employed in pairs, mounted adjacent the
outer circumference of each of the polar member wheels such that
the pairs of scrapers serve to remove debris that accumulates on
the polar member wheels. In select embodiments of the present
invention, a first scraper in the pair is mounted to remove debris
when the conveyance is moving in a first direction and a second
scraper in the pair is mounted to remove debris when the conveyance
is moving in a direction opposite to the first direction.
[0040] In select embodiments of the present invention, the abrading
device comprises one or more first rotatable cylindrical brushes
coaxially mounted on the rear section to be approximately parallel
to, and approximately the same width as, the wheeled axle
assemblies. In select embodiments of the present invention, the
abrading device comprise one or more first rotatable cylindrical
cutting wheels coaxially mounted on the rear section to be
approximately parallel to, and approximately the same width as, the
wheeled axle assemblies such that the first cutting wheel rotates
in the direction of movement of the conveyance and is protected by
a unidirectional clutch. In select embodiments of the present
invention, the abrading device comprises one or more cooperating
pairs of abrading devices, each pair comprising a cylindrical
rotatable brush and a cylindrical rotatable cutting wheel, the pair
coaxially mounted across the width of the rear section so as to be
parallel to the plane of operation of the conveyance and
approximately the same width as the wheeled axle assemblies.
[0041] In select embodiments of the present invention, the abrading
device comprises a first and second cooperating pair, the first
brush and first cutting wheel of the first pair rotating upon the
conveyance moving in a first direction such that the first rotating
brush rotates counter to the rotation of the first cutting wheel.
The second rotating brush and second cutting wheel of the second
pair are rotated upon the conveyance moving in a second direction
opposite to the first direction, the second rotating brush rotating
counter to the second cutting wheel.
[0042] In select embodiments of the present invention, each
magnetic wheeled axle assembly comprises three or more polar member
wheels of a first diameter coaxially mounted parallel one to the
other on each of the wheeled axle assemblies and two or more
annular permanent magnets of a second diameter smaller than the
first diameter, such that each magnet is mounted coaxially so as to
separate each of the polar member wheels from another of the polar
member wheels and the magnets closest to each other are oriented
with opposing polarities. In select embodiments of the present
invention, one or more polar member wheels incorporate grooves
across the width of the outer circumference of the polar member
wheel, the grooves enhancing traction of the polar member
wheels.
[0043] In select embodiments of the present invention, the
conveyance is portable and configurable to insert into a riser of
an underground tank. In select embodiments of the present
invention, the conveyance weighs less than about 18 Kg (40 lbs) and
is configurable to have a diameter perpendicular to the long axis
thereof of less than about 10 cm (4.0 inches) to permit insertion
into the riser.
[0044] In select embodiments of the present invention, the front
section comprises one or more magnetic wheeled axle assemblies
incorporating three or more polar member wheels and two or more
magnets; a first steering mechanism for orienting the front section
in a single plane such that orienting the front section in a single
plane also orients the conveyance; one or more pivotally mounted
first lever arms, the first lever arm operating to lift the front
section from a first surface upon which the first wheeled axle
assembly is resting and to lower the first wheeled axle assembly to
rest upon a surface that may be different from the first surface;
and first communicating assemblies that facilitate operation of the
first wheeled axle assembly, the first lever arm and the steering
mechanism.
[0045] In select embodiments of the present invention, the middle
section comprises one or more second wheeled axle assemblies each
having three or more polar member wheels and two or more magnets;
one or more motors; one or more first push rods; a first part of a
maneuvering assembly; second communicating assemblies communicating
with some of the first communicating assemblies; third
communicating assemblies communicating with the second wheeled axle
assembly; and fourth communicating assemblies communicating with
some parts of the middle and rear sections.
[0046] In select embodiments of the present invention, the rear
section comprises one or more abrading devices; a second part of
the maneuvering assembly, the maneuvering assembly permitting the
rear section to follow the middle section onto a surface in a plane
of operation different from a plane of operation in which the rear
section is operating; one or more biasing mechanisms such that the
biasing mechanisms permit the rear section to maintain firm contact
with the surfaces regardless of orientation of the conveyance; and
fifth communicating assemblies communicating with some of the
fourth communicating assemblies to facilitate operation of the
abrading device.
[0047] In select embodiments of the present invention, the tether
comprises a flexible hollow conduit environmentally sealed at the
juncture with the conveyance and suitable for holding material
selected from the group consisting of: cables, tubes, tubular nylon
core, tubular nylon filler, coaxial cable, extruded jackets,
braided jackets, insulated copper wire, wire, hose, pressurized
hose, and combinations thereof.
[0048] In select embodiments of the present invention, the sensors
are selected from the group consisting essentially of: acoustic
sensors, ultrasonic transducers, electrical sensors, piezoresistive
sensors, attitude sensors, contact sensors, thickness sensors,
inclinometers, mutually orthogonal inclinometers, and combinations
thereof. In select embodiments of the present invention, one or
more of the sensors is encapsulated in a block of dense, tough and
resilient material suitable for continuously contacting the
surfaces while the conveyance is moving.
[0049] In select embodiments of the present invention, the control
system comprises one or more personal computers, the computers
interfaced to the conveyance via a tether, such that the computers
facilitate control of the conveyance, positioning of the
conveyance, mapping of the surfaces, assessment of the surfaces,
and defect identification and location.
[0050] In select embodiments of the present invention, a supply of
pressurized inert gas is interfaced to the conveyance via the
tether.
[0051] In select embodiments of the present invention, one or more
power sources supplies electrical power, preferably DC power, to
the conveyance via the interface to the means for supplying power
within the tether.
[0052] In select embodiments of the present invention, one or more
transceivers are incorporated in one or more of the sections to
enable communication between the conveyance and the computer.
[0053] In select embodiments of the present invention, one or more
retrieval bars are affixed to the rear section of the conveyance to
facilitate recovery of the conveyance from a confined location.
[0054] In select embodiments of the present invention, one or more
sections are sealed at least partly and pressurized with an inert
gas.
[0055] In select embodiments of the present invention, a wheeled
conveyance employs modules coupled end-to-end, the wheeled
conveyance facilitating inspection of ferrous surfaces indisposed
to ready access. In select embodiments of the present invention,
the wheeled conveyance comprises one or more central modules for
powering it; one or more front modules for steering it in its
current plane of operation, the front module communicating with the
central module; and one or more rear modules that abrade the
surface to permit onboard sensors to take measurements of the
surface, the rear module also adapted to facilitate maneuvering the
wheeled conveyance onto a plane of operation different from a
current plane of operation, the rear module communicating with the
central module.
[0056] In select embodiments of the present invention, the front
module comprises one or more first wheeled axle assemblies having a
first two or more polar member wheels of a first diameter, the
first polar member wheels comprising a magnetically transmissive
material and one or more permanent magnets of a second diameter
smaller than the first diameter, each magnet coaxially mounted
between a pair of the first polar member wheels such that if more
than one magnet is employed, each magnet is mounted on the first
wheeled axle assembly so as to be oriented with polarity opposing
that of a nearest mounted one of the magnets; a first steering
mechanism to orient the front module in the current plane of
operation only, such that orienting the front module orients the
wheeled conveyance; one or more pivotally mounted first lever arms
such that the first lever arm operates on the front module to lift
and lower the front module and first communicating assemblies
communicating with a portion of the central module to facilitate
operation of the first wheeled axle assembly, the first lever arm
and the steering mechanism.
[0057] In select embodiments of the present invention, the central
module comprises one or more second wheeled axle assemblies having
a second two or more polar member wheels of a first diameter, the
second polar member wheels comprising a magnetically transmissive
material, and one or more permanent magnets, each magnet coaxially
mounted between a pair of the second polar member wheels, such that
if more than one magnet is employed, each magnet is mounted on the
wheeled axle assembly so as to be oriented with polarity opposing
that of a nearest mounted one of the magnets; one or more motors,
preferably reversing servomotors; one or more first push rods;
second communicating assemblies communicating with the first
communicating assemblies to facilitate operation of the first
wheeled axle assembly, the first lever arm and the steering
mechanism; third communicating assemblies communicating with the
second wheeled axle assembly to facilitate operation thereof and
fourth communicating assemblies communicating with the rear
module.
[0058] In select embodiments of the present invention, the rear
module comprises one or more abrading devices; one or more
maneuvering assemblies, such that the maneuvering assembly permits
the rear module to follow the central module onto a surface in a
plane of operation different from the current plane of operation of
the rear module, such that the rear module may move onto a surface
in a different plane only when the wheeled conveyance is moving in
a forward direction; one or more biasing mechanisms such that the
biasing mechanisms permit the rear module to maintain firm contact
with the surface regardless of orientation of the wheeled
conveyance and fifth communicating assemblies communicating with
the fourth communicating assemblies to facilitate operation of the
abrading devices and the maneuvering mechanisms.
[0059] In select embodiments of the wheeled conveyance of the
present invention, one or more of the motors is a reversible
servomotor, preferably DC powered, and one or more servomotors
incorporate one or more odometric encoders.
[0060] In select embodiments of the wheeled conveyance of the
present invention, the abrading device is selected from the group
consisting of rotatable brushes, rotatable cutting wheels,
scrapers, and combinations thereof. In select embodiments of the
wheeled conveyance of the present invention, the scrapers are
employed in pairs, mounted adjacent the outer circumference of each
of the polar member wheels such that the pairs of scrapers serve to
remove debris that accumulates on the polar member wheels and such
that a first scraper in each pair is mounted to remove debris when
the wheeled conveyance is moving in a first direction and a second
scraper in each pair is mounted to remove debris when the wheeled
conveyance is moving in a direction opposite to the first
direction.
[0061] In select embodiments of the present invention, the wheeled
conveyance is provided with first and second magnetic wheeled axle
assemblies, each assembly comprising three polar member wheels of a
first diameter coaxially mounted parallel one to the other on each
of the first and second wheeled axle assemblies, respectively, and
two annular magnets, each of the two magnets coaxially mounted
between a pair of polar member wheels on each of the first and
second wheeled axle assemblies, the magnets having a smaller
diameter than the polar member wheels as mounted on the respective
wheeled axle assemblies.
[0062] In select embodiments of the present invention, the wheeled
conveyance incorporates one or more polar member wheels that have
grooves cut across the width of the outer circumference of the
polar member wheel such that the grooves enhance traction of the
polar member wheel.
[0063] In select embodiments of the present invention, the wheeled
conveyance is portable and configurable to insert into a riser of
an underground tank. In select embodiments of the present
invention, the wheeled conveyance weighs less than about 18 Kg (40
lbs) and is configurable to have a diameter perpendicular to its
long axis of less than about 10 cm (4.0 inches) to permit insertion
into the riser.
[0064] In select embodiments of the wheeled conveyance of the
present invention, the abrading device comprises one or more
rotatable cylindrical brushes coaxially mounted on the rear module
to be approximately parallel to, and approximately the same width
as, the wheeled axle assembly of the rear module. In select
embodiments of the wheeled conveyance of the present invention, the
abrading device comprises one or more rotatable cylindrical cutting
wheels coaxially mounted on the rear module to be approximately
parallel to, and approximately the same width as, the wheeled axle
assembly of the rear module, such that the cutting wheel rotates in
the direction of movement of the wheeled conveyance and is
protected by a unidirectional clutch. In select embodiments of the
wheeled conveyance of the present invention, the abrading device
comprises one or more cylindrical rotatable brushes and one or more
cylindrical rotatable cutting wheels, such that the brushes and
cutting wheels are coaxially mounted across the width of the rear
module, perpendicular to the long axis and parallel to the plane of
operation of the wheeled conveyance such that each brush and
cutting wheel is approximately the same width as the wheeled axle
assembly of the rear module.
[0065] In select embodiments of the wheeled conveyance of the
present invention, the abrading device comprises a first and second
rotating brush and a first and second cutting wheel, such that the
first rotating brush and the first cutting wheel are rotated upon
the wheeled conveyance moving in a first direction, the first
rotating brush rotated counter to the rotation direction of the
first cutting wheel, and the second rotating brush and the second
cutting wheel are rotated upon the wheeled conveyance moving in a
second direction opposite to the first direction, the second
rotating brush rotated counter to the rotation direction of the
second cutting wheel.
[0066] In select embodiments of the wheeled conveyance of the
present invention, the sensors are selected from the group
consisting essentially of: acoustic sensors, ultrasonic
transducers, electrical sensors, piezoresistive sensors, attitude
sensors, contact sensors, thickness sensors, inclinometers,
mutually orthogonal inclinometers, and combinations thereof, such
that one or more of the sensors is encapsulated in a block of
dense, tough and resilient material suitable for continuously
contacting the surface upon which the wheeled conveyance is
moving.
[0067] In select embodiments of the wheeled conveyance of the
present invention, parts of one or more of the modules are sealed
and pressurized with an inert gas.
[0068] In select embodiments of the present invention, a method is
provided for inspecting an interior surface of a ferrous tank. The
method comprises: deploying into the tank a remotely controllable
robotic vehicle employing magnetic wheeled assemblies; controlling
the robotic vehicle to navigate along a selected linear path to
establish the orientation and position of the robotic vehicle;
providing a graphical representation of the interior surface;
determining the orientation and position of the robotic vehicle;
controlling the robotic vehicle to navigate a pattern that covers a
major portion of the interior surface, preferably all of the
surface; directing the robotic vehicle to employ one or more first
sensors to measure the thickness of the tank at select intervals in
the pattern; receiving signals indicative of the thickness
measurements from the robotic vehicle; identifying one or more
instantaneous locations of the robotic vehicle, such that the
locations may be displayed on the graphical representation;
comparing the signals with a predetermined thickness standard; and
recording the position of the signals that indicate regions of the
surface to be out of standard thickness, such that the regions may
be displayed on the graphical representation.
[0069] In select embodiments of the present invention, the method
of controlling the robotic vehicle to navigate the pattern
comprises first directing the robotic vehicle to navigate along a
line on a cylindrical surface of the tank, the cylindrical surface
being parallel to the long axis of the tank, until the robotic
vehicle first contacts a surface not parallel to the cylindrical
surface; determining whether the first contacted surface is a first
end plate of the tank; if the first contacted surface is not a
first end plate, directing the robotic vehicle to circumvent the
first contacted surface and further like contacted surfaces that
are not a first end plate; and if a subsequent contacted surface or
the first contacted surface is the first end plate, directing the
robotic vehicle to reverse direction by implementing a small
angular difference from the prior line of travel of the robotic
vehicle; repeating the above navigation process until the entire
cylindrical surface has been navigated; causing the robotic vehicle
to transfer to a first end plate; directing the robotic vehicle to
navigate along a line through the center of the first end plate
until the robotic vehicle first contacts a first surface not
parallel to the first end plate; determining whether the first
contacted surface not parallel to the first end plate is the
cylindrical surface; if the first contacted surface is not the
cylindrical surface, directing the robotic vehicle to circumvent
the first contacted surface not parallel to the first end plate and
further like contacted surfaces that are not the cylindrical
surface; if a subsequent contacted surface or a first contacted
surface not parallel to the first end plate is the cylindrical
surface, directing the robotic vehicle to reverse direction by
implementing a small angular difference from the prior line of
travel of the robotic vehicle; repeating the navigation process
until the entire first end plate surface has been navigated;
causing the robotic vehicle to transfer to the cylindrical surface;
directing the robotic vehicle to navigate the cylindrical surface,
now known as to configuration, until the robotic vehicle contacts
the second end plate; causing the robotic vehicle to transfer to
the second end plate; directing the robotic vehicle to navigate
along a line through the center of the second end plate until the
robotic vehicle first contacts a first surface not parallel to the
second end plate; determining whether the first contacted surface
not parallel to the second end plate is the cylindrical surface; if
the first contacted surface is not the cylindrical surface,
directing the robotic vehicle to circumvent the first contacted
surface not parallel to the second end plate and further like
contacted surfaces that are not the cylindrical surface; if a
subsequent contacted surface or the first contacted surface not
parallel to the second end plate is the cylindrical surface,
directing the robotic vehicle to reverse direction by implementing
a small angular difference from the prior line of travel of the
robotic vehicle and repeating the navigation process employed for
the first end plate until the entire second end plate surface has
been navigated.
[0070] In select embodiments of the present invention, the method
also permits dispensing a liquid, the liquid serving as a couplant
between sensors and the tank.
[0071] In select embodiments of the present invention, the method
provides one or more second sensors fixedly mounted to the front of
the robotic vehicle, the second sensor facilitating determination
of the location of contacted surfaces in a plane different from
that plane of the surface on which the robotic vehicle is
traveling.
[0072] In select embodiments of the present invention, the method
provides for a transition lever arm mounted to the robotic vehicle,
the lever arm operative for lifting the first magnetic wheeled axle
assembly when the robotic vehicle is transitioning from a first
surface to another surface angular thereto.
[0073] In select embodiments of the present invention, the method
provides for one or more scrapers mounted on the rear module and
positioned so as to contact the surface to clean it.
[0074] In select embodiments of the present invention, a method is
provided for inspecting ferrous surfaces of a structure, the
surfaces otherwise inaccessible without employing procedures that
are expensive, time consuming, dangerous, or any combination
thereof. The method comprises providing one or more inspection
systems, each comprising one or more articulated conveyances of a
size suitable for accessing the surfaces without either modifying
the structure or expanding access to the structure, each conveyance
incorporating three or more sections, such that a front section
turns in only a first plane with respect to a middle section and a
rear section turns to only a second plane, different from the first
plane, with respect to the middle section; one or more tethers for
providing power and other capacity to the conveyance, such that the
tether may also provide one or more sources of fluid; one or more
control systems, part of the control system being remote from the
conveyance and connected to the conveyance via connection means
within the tether, such that the control system communicates with
one or more power sources external to the conveyance, such that the
power source may be used to power the conveyance and one or more
sensors incorporated in each conveyance to facilitate
semi-autonomous operation. In select embodiments of the present
invention, the method provides for operating the above inspection
system for a time period necessary to collect one or more
parameters suitable to describe the condition of the surface being
inspected.
[0075] FIG. I schematically illustrates a remotely controllable
robotic vehicle 20 for inspecting and assessing the corrosive
damage to an underground storage tank (UST) 10. The UST 10
comprises cylindrical wall 12, walls or end plates 14A and 14B, and
a riser 16. The riser 16 is located at the top of the UST 10 and is
adapted to receive liquid into the UST 10. As depicted in FIG. 1,
the UST 10 and the robotic vehicle 20 are not drawn to scale for
convenience of illustration. The robotic vehicle 20 is configured
to enter the UST 10 through a riser 16 with a typical inside
diameter of 10.2 cm. (4 inches), as further illustrated in FIG. 3A.
The robotic vehicle 20 is specifically configured to enter through
the riser 16 by having an elongate shape, by having its wheels
tucked within the contours of its body, and by being formed in a
substantially round cross section to optimize space utilization of
the robotic vehicle 20. Alternatively, if the riser 16 is not of
sufficient diameter, or not serviceable, for the robotic vehicle 20
to be deployed therethrough, entry would be through a manway (not
shown separately) that may require excavation. Generally, it is not
necessary to drain the liquid stored in the UST 10 since the
components of the robotic vehicle 20 are sealed within one or more
housings and the electrical power supplied through a tether 28 by a
power source (not shown separately) is considered to be safe if
provided at not more than 24 volts DC. In select embodiments of the
present invention, the robotic vehicle 20 receives power from and
communicates with a computer 100 through the tether 28. In select
embodiments of the present invention, the tether 28 (shown and
described in detail in connection with FIG. 10) includes power and
communication wires and fluid transmitting tubes. In select
embodiments of the present invention, connections are made to
individual components for such purposes as power transmission and
communication. In select embodiments of the present invention, such
connections are made to a computer 100 that may be programmed for
automatic operation or manual control of the robotic vehicle
20.
[0076] Refer to FIG. 1. In select embodiments of the present
invention, to accommodate the need to traverse and inspect the
interior surface of the UST 10, the robotic vehicle 20 is
constructed in three pivotally connected and articulated modules
22, 24, 26, each adapted for a specialized function. The lead or
forward module, hereafter identified as tractor 22, is attached to
and followed by a power module 24. The power module 24 is connected
to and followed by a cleaning and inspection module 26. In FIG. 1,
the robotic vehicle 20 is shown in transition from the interior
surface of a cylindrical wall 12 upwards onto the interior surface
of an end plate 14A. Travel of the robotic vehicle 20 within the
UST 10 is enabled by use of motor driven magnetic wheeled axle
assemblies as shown in FIG. 8A.
[0077] Refer to FIGS. 2A and 2B, showing the robotic vehicle 20 in
side elevation and top plan views, respectively. As illustrated in
FIGS. 2A and 2B, the robotic vehicle 20 may be deployed both
vertically and horizontally. For example, the cleaning and
inspection module 26 is designed to pivot in either an upward or
downward direction only. The tractor module 22 is designed to pivot
only laterally to the left or right. Since the robotic vehicle 20
is operative in various orientations, e.g., horizontal mode with
wheels facing down, inverted horizontal mode with wheels facing up,
and vertical mode as occurs on the end plates 14A, 14B; relative
movement of the robotic vehicle 20 will be described from the
perspective of the horizontal mode with wheels facing down unless
otherwise noted. In the horizontal mode, the horizontal plane is
referred to as the X-Z plane, and its two mutually orthogonal
vertical planes are the X-Y and Z-Y planes. Sealing of the housing
of the robotic vehicle 20 against leakage is accomplished by use of
an RTV silicone compound between stationary parts and with O-rings
for sealing shafts that move through housing walls. Once the
housing of the robotic vehicle 20 is sealed, a pressurized gas,
such as air or nitrogen, is introduced to the interior of the
housing to prevent seepage of liquid into the housing. The tractor
module 22 is flexibly assembled and connected to the power module
24 by a vertical front pivot joint 34 including a pin 84. This
arrangement facilitates angular flexure between the tractor module
22 and the power module 24 only in the X-Z plane. The cleaning and
inspection module 26 is assembled and connected to the power module
24 by a horizontal rear pivot joint 44. The rear pivot joint 44
enables angular flexure between the power module 24 and the
cleaning and inspection module 26 only in the vertical planes X-Y
and Z-Y.
[0078] Refer to FIG. 2B illustrating the power module 24 as
constructed with a forward segment 80, a middle segment 90, and a
rear segment 96. In select embodiments of the present invention,
electrically energized, reversible motors 92 and 110 drive various
functions in the robotic vehicle 20. FIG. 2B shows the connections
of these motors 92, 110 to tractor 22 and cleaning and inspecting
module 26. The middle segment 90 contains the motor 110 that
generates and transmits drive power to the front magnetized wheeled
axle assembly 32. Power is transmitted from the motor 110 to the
magnetized wheeled axle assembly 32 by means of a drive shaft 112.
In select embodiments of the present invention, the drive shaft 112
includes a telescoping universal joint (not shown separately) at
its transition to a drive mechanism housed in the tractor module
22. The forward end of the shaft 112 connects to a gear reducer 30
(see FIG. 3B) located in the tractor module 22. In select
embodiments of the present invention, the gear reducer 30 drives
the front magnetized wheeled axle assembly 32 through the chain 31
and the sprocket 70 depicted in FIG. 3B. In select embodiments of
the present invention, the motor 92 (see FIG. 2B) and other
electric apparatus in the body of the robotic vehicle 20 are
powered at 24 volts DC. Use of DC power permits reversing the
direction of drive without the added circuitry typically required
with use of AC motors. In select embodiments of the present
invention, small, reversible, high-speed electric motors are used
in conjunction with worm and wheel type gear reducers (not shown
separately) to conserve space. Typically, in select embodiments of
the present invention, the worm and wheel type gear reducers are
each immersed in an oil bath. In select embodiments of the present
invention, the electric motors 92, 110 that drive the robotic
vehicle 20 meet the design specification requirement of 30 lbf of
power per wheel 32, based on a system force balance analysis.
[0079] Refer to FIG. 2B. In select embodiments of the present
invention, a shaft 40 is actuated to pivot the tractor module 22
laterally about pin 84 relative to the power module 24 to
accomplish steering. In select embodiments of the present
invention, the shaft 40 is moved linearly by a linear actuator (not
shown separately) formed by the lead screw motor 106. In select
embodiments of the present invention, the shaft 40 is configured to
pass to the front end of the power module 24 and connect to the
coupling 38 on the tractor module 22, thereby causing the tractor
module 22 to change its direction of travel.
[0080] The middle segment 90 of the power module 24 houses a
reversible, electric motor 98 that supplies power through a worm
and wheel gear reducer 102 (in the rear segment 96) to the rear
magnetized wheeled axle assembly 42. Via the reducer 102, the rear
magnetized wheeled axle assembly 42 is caused to rotate at the same
speed and in the same direction as the forward magnetized wheel
axle assembly 32. An incremental encoder (not shown separately)
having a digital output communicates with the rear wheel drive
motor 98 to obtain odometric data. In some applications of select
embodiments of the present invention, a degree of slippage between
the magnetized wheel asemblies 32, 42 and the surface of operation
may occur, thus affecting the odometer reading. Thus, position
verification may be accomplished by an operator (not shown
separately) or by a computer 100 when the robotic vehicle 20
contacts a known fixed object, e.g., within the UST 10 this may be
an end wall 14A, B. Thus, the occurrence of slippage does not
preclude maintaining reasonably accurate real-time information
regarding the position of the robotic vehicle 20. Another encoder
(not shown separately), operable in a manner similar to that of the
first encoder, may communicate with the drive for the front
magnetized wheeled axle assembly 32, thereby improving reported
positional accuracy.
[0081] Refer to FIGS. 2B and 6. The motor 98 drives a shaft 108
that communicates with a gear reducer 133 that drives a sprocket
132 through a worm wheel (not shown separately) mounted on the
pivot shaft 44. A chain 134 connects the drive sprocket 132 to
drive the sprocket 136.
[0082] Refer to FIGS. 2B, 3B, 3C, and 7. The sprocket 136 is
mounted to provide power to the rotary cutters 124A, B and brushes
126A, B of the cleaning and inspection module 26. The motor 92 is
housed in the forward segment 80 for supplying linear power to the
lead screw 93. The lead screw 93 operates linearly to contact and
move the push rod 48, in turn, causing the transition lever arm 46
to pivot so as to lift the front end of the tractor module 22 as
depicted in FIG. 3C. The lead screw 93 is aligned with the push rod
48 when the tractor module 22 is aligned with the power module
24.
[0083] In summary, the drive motors are: the motor 92 to drive the
front magnetized wheeled axle assembly 32; the motor 98 to drive
the rear magnetized wheeled axle assembly 42 and the cutters 124A,
B and brushes 126A, B of cleaning and inspection module 26; the
motor 106 to drive the steering function of the tractor module 22;
and the motor 110 to activate the lifting function of the
transition lever arm 46 and the rear push rod 137 (FIG. 6).
[0084] Refer to FIGS. 3A, 3B, 3C and 8A. The tractor module 22
includes the front magnetized drive wheeled axle assembly 32 that
is driven by a two-stage reduction drive. The front drive wheeled
axle assembly 32 is mounted to the tractor module 22 far forward so
as to protrude from the body of the tractor module 22 in a forward
direction of travel. The front drive wheeled axle assembly 32 is
also tucked within the substantially round body of the robotic
vehicle 20 to limit the cross sectional size thereof to enable
entry through a riser 16 as shown in FIG. 1. Typical risers have a
diameter of four inches (about 10 cm). As the front magnetized
wheeled axle assembly 32 moves along the surface of the UST 10,
loose particles of oxidized iron (rust) adhere to the contacting
surfaces of the front magnetized wheeled axle assembly 32. Thus, in
select embodiments of the present invention, a pair of scrapers
36A, B, preferably of a corrosion resistant material such as
stainless steel, are mounted on the body of the tractor module 22
so that an edge of each presses against the cylindrical surface of
the drive wheels 74A, B, 76 (FIG. 8A) of the front magnetic wheeled
axle assembly 32, dislodging particles that accumulate thereon. The
scrapers 36A, B (FIG. 3C) are mounted to permit dislodging when the
robotic vehicle 20 is operating in either direction. As shown in
FIG. 2B, the directional rod 40 that connects to the coupling 38
through the clevis 41 operates to turn the tractor module 22 in the
plane of travel only. A shaft 40 communicates linearly with the
power module 24 in a direction parallel to the long axis of the
power module 24 to cause the tractor module 22 to pivot about the
pivot joint 34. A coupling 38, preferably formed with a slot that
is substantially perpendicular to the long axis of the tractor
module 22, permits the shaft 40 to move without restriction.
[0085] Refer to FIGS. 3A, B, and C, depicting a pair of contact
sensors, 50A, B mounted on the front left and front right corners,
respectively, of the tractor module 22. Each contact sensor 50A, B
communicates with a contact switch (not shown separately),
preferably digital, that generates a signal in response to the
leading outer surface of either contact sensor 50A, B contacting
something. The contact sensors 50A, B are mounted on the
telescoping supports 52 configured to collapse into the tractor
module 22 upon a corresponding sensor 50A, B contacting something.
The degree of telescoping allows the front magnetized drive wheeled
axle assembly 32 to touch and magnetically grip a surface
perpendicular to the surface on which the robotic vehicle 20 is
traveling prior to contact. Contact by both sensors 50A, B
simultaneously is interpreted by the computer 100 as a contact with
a perpendicular surface. Contact by only one of the sensors 50A, B
indicates a less than perpendicular relationship between robotic
vehicle 20 and the contacted surface. In select embodiments of the
present invention, maximum adhesive force for the front magnetized
drive wheeled axle assembly 32 is achieved by contact with the
surface along a tangent across the face and parallel to the axis of
the drive wheeled axle assembly 32. Thus, it is preferred that the
tractor module 22 contacts the surface for transition, e.g.,
transition from a cylindrical wall 12 to an end plate 14A,
perpendicularly. With the initial data from the contact sensors
50A, B as to the relative angle of contact of the tractor module
22, correction is made through program control by the computer 100
to achieve perpendicular approach. Attaining perpendicularity is
accomplished by moving the robotic vehicle 20 backwards from the
contacted surface and making additional approaches to achieve
approximately simultaneous contact by sensors 50A, B:
[0086] Refer to FIGS. 3B, 3C, 4 and 6. For the robotic vehicle 20
to perform a transition from one surface to another approximately
perpendicularly disposed, it is necessary to first separate the
drive wheeled axle assembly 32 from the current surface of travel.
Separation is accomplished by actuation of the transition lever arm
46 pivotally mounted at the pivot 46p. Alternate mechanisms, such
as a linearly actuated push rod also accomplish this function. The
transition lever arm 46 is L- shaped, with its upper end 46'
positioned adjacent the forward end of the push rod 48. As the lead
screw 93 (FIG. 4) pushes against the push rod 48, the push rod 48
moves forward (to the viewer's left in FIG. 3C). The actuation of
the push rod 48 from its retracted position (FIG. 3B) to its
extended position (FIG. 3C) forces the transition lever arm 46 to
pivot about the pin 46p counterclockwise as shown by the arrow K.
The downward force of the transition lever arm 46 lifts the front
of the tractor module 22 so as to separate the front magnetized
drive wheeled axle assembly 32 from the surface of the UST 10. When
the push rod 48 retracts, the cam 46 pivots back to its initial
position with the aid of a biasing means, such as a spring 49 or
the like. The push rod 48 is slidingly mounted in bearings (not
shown separately) in the wall of the tractor module 22 and not
physically connected to the lead screw 93 (FIG. 4). When the
tractor module 22 is at an angle to the power module 24, as in FIG.
2B, the push rod 48 is at a similar angle and not aligned with the
lead screw 93. Thus, it is necessary to put the tractor module 22
and the power module 24 in substantial alignment prior to actuating
the transition lever arm 46. As seen in FIG. 6, a solenoid-actuated
push rod 137 is positioned to lift the rear magnetized drive
wheeled axle assembly 42 in a manner similar to the way that the
front magnetized drive wheeled axle assembly 32 is lifted.
[0087] Refer to FIGS. 8A and 8B. FIG. 8A illustrates the axial
configuration of the front magnetized drive wheeled axle assembly
32. The front magnetized drive wheeled axle assembly 32 is an
assembly of five disk-like members 72, 74a, 74b, and 76
interspersed axially along a shaft 78. The outer polar members 74a,
b are located toward the ends of the shaft 78, respectively, and
the inner polar member 76 is centrally located along the shaft 78.
The polar members 74a, 74b and 76 are made of magnetically
transmissive material not adapted to permanently retain significant
magnetic properties, such as a low carbon steel. Between each of
the outer polar members 74a, 74b and the inner polar member 76 is
an axially polar magnetic member 72, each formed of a permanently
magnetic material. In select embodiments of the present invention,
the axial magnetic members 72 are formed of rare earth materials,
e.g., neodymium iron, and oriented such that their poles are
opposite to one another, as illustrated in FIG. 8B. In this
arrangement, magnetic flux M is radiated between magnetic members
72 through polar members 74a, 74b and 76 to establish a strong
magnetic bond between the robotic vehicle 20 and the ferrous
surface upon which it operates. The shaft 78 passes through the
members 72, 74a, 74b and 76 and mounts the sprocket 70 to receive
drive power from the chain 31 (FIG. 3C). The rear drive wheeled
axle assembly 42 is constructed similarly.
[0088] Refer to FIG. 8A. Due to the irregular interior surface of a
typical UST 10 and the frequent occurrence of lumps on that
surface, select embodiments of the present invention employ a tread
pattern to improve traction of the magnetized drive wheeled axle
assemblies 32, 42. Multiple grooves 79 are formed on the outer
periphery of each polar member 74a, 74b and 76 in a direction
approximately parallel to the shaft 78. In one embodiment of the
present invention there are six grooves 79 uniformly dispersed
around each polar member 74a, 74b and 76. In select embodiments of
the present invention, the grooves 79 may be aligned one to another
across the face of the three polar members 74a, 74b and 76,
although a non-aligned pattern is also suitable.
[0089] Refer to FIGS. 8A and 8B. Each polar member 74a, 74b and 76
is formed with a relatively large diameter D.sub.p and each
magnetic member 72 with a relatively small diameter D.sub.m. The
pattern of magnetic flux M is shown schematically as dashed lines
from each magnetic member 72 through respective polar members 74a,
74b and 76 to a ferrous surface such as the tank wall 12. This
configuration enhances the flux pattern by causing it to intensify
through the polar members 74a, 74b and 76. In addition, the large
diameter polar members 74Aa, 74b and 76 protect the smaller
diameter magnetic members 72 from damage due to wear or impact.
[0090] Refer to FIGS. 8A, 9A and 9B. With diameter D.sub.p of outer
polar members 74a, 74b and the inner polar member 76 being
substantially equal, all polar members 74a, 74b and 76 are in
contact with the interior surfaces 12, 14A, B of the cylindrical
UST 10 in only two relative orientations of the robotic vehicle 20.
One orientation occurs when operating on planar tank end plates
14a, 14b (FIG. 1) and the other when operating circumferentially on
the cylindrical wall 12 (FIG. 9A). When the robotic vehicle 20
operates along a path parallel to the long axis of the UST 10 or on
a path at an angle between a "parallel axial" path and a
circumferential path, the inner polar member 76 does not contact
the surface 12. The maximum air gap G (FIG. 9B) is typically small
between the inner polar member 76 and the surface 12. Magnetic flux
M travels across the gap G to attract to the ferrous surface 12.
For example, in the case of the UST 10 having a diameter of 2.4
meters (8 feet), and the front drive polar members (wheels) 74a,
74b and 76 having a diameter of 5 cm (about 2 inches) and the
length of the shaft 78 of 5.6 cm (about 2.2 inches), the maximum
air gap G between the periphery of the inner polar member 76 and
the tank wall 12 is approximately 0.33 mm (0.013 inches). Larger
diameter tanks 10 have a proportionally smaller gap G. In select
embodiments of the present invention, the magnetized drive wheeled
axle assemblies 32, 42 produce a combined attractive force of 207
lbf. This is sufficient to support a robotic vehicle 20 of about 18
Kg (40 lbs).
[0091] Refer to FIGS. 2A and 2B illustrating a robotic vehicle 20
in assembled condition including three main modules 22, 24, and 26.
The power module 24 comprises a forward segment 80 (FIG. 4), a
middle segment 90 (FIG. 5), and a rear segment 96 (FIG. 6). In
select embodiments of the present invention, each segment 80, 90,
96 is built separately and assembled to the other segments so as to
form the integrated power module 24.
[0092] Refer to FIG. 4 illustrating the forward segment 80. In
select embodiments of the present invention, the forward segment
contains an orientation sensor 86 that comprises three mutually
orthogonal piezoresistive inclinometers (not shown separately).
This type of inclinometer has a flexible beam, typically silicon
material, supporting a mass at one end of each inclinometer. Each
inclinometer is sensitive along one axis only. As the orientation
of the robotic vehicle 20 changes, the mass shifts in relation to
the fixed end of the beam, causing the beam to bend. The silicon
material changes in electrical resistance in proportion to strain,
providing a property that can be readily measured and converted to
an orientation reading. By feedback and analysis of signals
received from each of the X, Y, and Z inclinometers, the computer
100 determines the yaw, pitch, and roll orientation of the robotic
vehicle 20. Similarly, in select embodiments of the present
invention, the computer 100 is able to detect a change in direction
of the robotic vehicle 20 as it travels the interior of the UST
10.
[0093] The transformation mathematics used to relate the
inclinometer readings to angular orientation of the robotic vehicle
simplify to the following: Robotic vehicle roll angle=arctan (Y
accelerometer reading/Z accelerometer reading). Robotic vehicle
pitch angle=arctan (X accelerometer reading/Z accelerometer
reading). Robotic vehicle yaw angle=arctan (Y accelerometer
reading/X accelerometer reading). In select embodiments of the
present invention, the computer 100 uses the calculated information
together with data from the odometric encoder in the motor 98 to
continuously track the position of the robotic vehicle 20.
[0094] The forward segment 80 pivotally connects to the tractor
module 22 at a pivot frame 82 with a pin 84 (FIG. 4). The pin 84 is
positioned by any conventional means, such as snap rings (not shown
separately) fitted in grooves 84a, 84b (FIG. 4) at each end
thereof.
[0095] Refer to FIG. 5, illustrating the middle segment 90 of the
power module 24 (FIG. 2B). The middle segment 90 communicates with
the computer 100 via the tether 28 and contains the motor 110 for
generating drive power to the front magnetized drive wheeled axle
assembly 32. In addition, the middle segment 90 houses the motor 98
for steering the robotic vehicle 20 and the motor 106 for actuating
the transition lever arm 46. On assembly, the middle segment 90 is
fastened to the forward segment 80 (FIG. 2B) and the rear segment
96 (FIG. 2B) by appropriate fastening means (not shown separately)
to become the power module 24.
[0096] Refer to FIG. 6, depicting the rear segment 96 of the power
module 24 (FIG. 2B). The rear segment 96 comprises the shaft 108
that is connected at its driven end to the motor 98 (FIG. 5). The
shaft 108 mounts the worm gear reducer 102 that, in turn, drives
the rear magnetized drive wheeled axle assembly 42 through a set of
sprockets 105, 142, and 144 and chain 146. This permits the power
module 24 to operate in the same direction and at the same speed as
the tractor module 22. Although the front magnetized drive wheeled
axle assembly 32 is driven by a first motor 110 and the rear
magnetized drive wheeled axle assembly 42 by a second motor 98 the
motors 98, 110 are controlled by the computer 100 to operate at the
same speed. In select embodiments of the present invention, the
motors 98, 110 are servomotors that enable maximum control of speed
and direction. The scrapers 104a, 104b are each mounted with an
edge pressed in contact with the rear magnetized drive wheels (not
shown separately but of similar configuration to the polar members
(wheels) 74a, 74b and 76 of the front wheeled axle assembly 32) to
continuously remove rust particles from the peripheral surfaces
thereof. The scrapers 104a, 104b are oriented in opposite
directions so as to accommodate forward and reverse rotation of the
rear magnetized drive wheeled axle assembly 42. A pivot shaft 44
extends outwardly from each side of the segment 96 for pivotally
connecting the cleaning and inspection module 26 (FIG. 2B).
[0097] The shaft 108 mounts a first sprocket 140 that drives a
second sprocket 138 via a first chain (not numbered). The second
sprocket 138 is mounted coaxially with the worm gear 133 that
delivers power to a third sprocket 132 via an intermediate co-axial
worm gear (not shown separately) behind the third sprocket 132. A
second chain 134 engages the third sprocket 132 and drives a fourth
sprocket 136 (FIG. 7) to provide power to the power and cleaning
module 26.
[0098] In select embodiments of the present invention, the robotic
vehicle 20 includes a solenoid-actuated push rod 137, oriented
horizontally and positioned above the rear magnetized drive wheeled
axle assembly 42 in rear section 96. The push rod 137 is operative
to break the magnetic grip of the rear magnetized drive wheeled
axle assembly 42 on the surface of the ferrous structure it is
contacting.
[0099] Refer to FIGS. 2A, 5 and 10, illustrating the tether 28
connected to the robotic vehicle 20 at the middle segment 90. The
tether 28 is formed as an assembly of cables and tubes adapted to
perform several functions in communication with the robotic vehicle
20. A cross sectional view of the tether 28, is shown in FIG. 10
and a description and function for each of the components of the
tether 28 is listed in the following chart. The tubular core 281 is
used to provide a foundation about which to assemble the other
components of the tether 28 in a generally cylindrical shape.
[0100] In select embodiments of the present invention, the cables
and structural components of the tether 28 are as listed in the
table below:
TABLE-US-00001 PART DESCRIPTION QUANTITY FUNCTION 281 Tubular nylon
core 1 Couplant fluid/UT block 282 24 AWG wire with double 4
Steering and transition motor outer-wrap served shielding and
sensor power 283 3 pairs - 28 AWG wire with 3 Position signals
transmitted 0.5 mil polyester tape wrap 284 Tubular nylon filler 1
Pressurized gas conduit 285 20 AWG wire with 0.5 mil 3 Ground wires
polyester tape wrap 286 16 AWG wire with single 2 Drive motor power
served shielding 287 50 (coaxial cable with braided 1 Ultrasonic
transducer signals shielding and two layers of 0.5 mil polyester
tape wrap at 50% lap) 288 1.0 mil polyester wrap at 50% lap 1
Encasement 289 HYTREL .RTM. extruded jacket at 20 mils 1 Encasement
290 KEVLAR .RTM. braided jacket 1 Encasement 291 HYTREL .RTM.
extruded jacket at 50 mils 1 Protection
(HYTREL.RTM. and KEVLAR.RTM. are registered trademarks of E.I.
duPont de Nemours and Company.) As noted above, the specific
function and connection of the cables and tubes comprising the
tether 28 are such as to be apparent to those skilled in the trade,
and as such are not detailed further.
[0101] In select embodiments of the present invention, the tether
28 is involved in the physical deployment into and retrieval of the
robotic vehicle 20 from the UST 10; in supplying electric power to
perform the motor drive operations, the ultrasonic inspection
operation, and transmitting the orientation, travel, and
communication signals; and in transmitting signals from the robotic
vehicle 20 to the computer 100. In select embodiments of the
present invention, the robotic vehicle 20 must drag a length of the
tether 28 through the UST 10, at times involving support of its
catenary weight as the robotic vehicle 20 traverses the "roof" or
end walls of the UST 10. The tether 28 is typically 45 m. (150 ft.)
in length. Thus, it is important to keep the weight of the tether
28 at a minimum.
[0102] In select embodiments of the present invention, the
combination of the tractor module 22 and the power module 24
described above is operative for moving and controlling the
movement of the robotic vehicle 20 within the UST 10 by
implementation of signals from the computer 100.
[0103] Refer to FIG. 7. In select embodiments of the present
invention, the identification of defects in the walls of a UST 10
is facilitated by the cleaning and inspection module 26. As
described above, the cleaning and inspection module 26 is pivotally
connected to the power module 24 at the horizontal pivot pin 44
with a first bar 114 pivotally mounted on either side thereof. The
rear portion of each bar 114 is pivotally connected to module 26 at
a rear pivot shaft 116, positioned toward the rear portion of
cleaning and inspection module 26. The rear pivot shaft 116 mounts
the fourth sprocket 136 and the third sprocket 132 (FIG. 6)
involved in the transmission of power for the cleaning and
inspection module 26. A pair of telescoping pressurized struts 118,
mounted to the shaft 115 at the back ends of the struts 118 and to
the power module 24 (FIG. 6) at the front ends of the struts 118,
prevents the cleaning and inspection module from moving
horizontally while limiting the degree to which the cleaning and
inspection module 26 can pivot vertically in relation to the power
module 24. In select embodiments of the present invention, the
struts 118 are of the telescoping cylinder type and are filled with
nitrogen or other substantially inert gas. In select embodiments of
the present invention, a supply of pressurized gas (not shown
separately) may be connected to the struts 118.
[0104] In select embodiments of the present invention as designed
above, the cleaning and inspection module 26 is held in contact
with the surface on which the robotic vehicle 20 is traveling,
regardless of the orientation of the robotic vehicle 20. The stop
120 mounted rigidly to the side of the cleaning and inspection
module 26 allows the forward end of the cleaning and inspection
module 26 to pivot down to a limited degree with respect to the
first bars 114. The tension springs 121 are assembled between the
shaft 115 and a selected anchor point 117 on the housing of the
cleaning and inspection module 26 to bias the module 26 in the
counterclockwise direction in relation to an anchor point 117. This
bias pressure, in combination with the operation of the struts 118,
assures that the cleaning and inspection module 26 stays in
intimate contact with the surface regardless of the orientation of
the robotic vehicle 20.
[0105] In select embodiments of the present invention, the cleaning
and inspection module 26 includes devices for scraping residue off
the surface to be inspected. Power is transmitted to the cleaning
and inspection module 26 from the third sprocket 132 on the power
module 24 via the second chain 134 that is connected at its rear
end to the fourth sprocket 136. For the second chain 134 to connect
between the pivotally connected power 24 and inspection and
cleaning 26 modules, the chain engaging sprockets must be coaxial
with the front 44 and rear 116 pivot points for the first bars 114.
As illustrated in FIG. 7, the left (or front) end of the first bars
114 are assembled to the front pivot shaft 44 that is positioned in
the rear segment 96 of the power module 26 (FIG. 6). In select
embodiments of the present invention, the fourth sprocket 136 is
commonly mounted with the fifth driving sprocket 122 that is
connected to the duplicate cutting wheels 124a, 124b. The forward
cutting wheel 124a and the rear cutting wheel 124b and duplicate
rotary brushes 126a, 126b are connected to the fifth sprocket 122
through a third drive chain 128. The cutting wheels 124a, 124b are
formed with a series of substantially sharp edges E spaced around
the diameter thereof and extending across their widths. The cutting
wheels 124a, 124b, especially the sharp edges thereof, are formed
preferably of hardened steel or the like. The rotary brushes 126a,
126b are formed with a series of flexible bristles spaced around
the diameter thereof and extending across their widths. In select
embodiments of the present invention, the bristles of the brushes
126a, 126b are of polymeric material. In select embodiments of the
present invention, the cutting wheels 124a, 124b are mounted at the
forward and rearmost ends of the cleaning and inspection module 26
and the two rotary brushes 126a, 126b are mounted therebetween. As
illustrated in FIG. 7, the cutting edges E of the forward cutting
wheel 124a are angled to cut when the forward cutting wheel 124a
rotates in the counterclockwise direction and the cutting edges E
of the rear cutting wheel 124b are angled to cut in the clockwise
direction. The fifth sprocket 122 drives the cutting wheels 124a,
124b and the rotary brushes 126a, 126b via the third drive chain
128.
[0106] An idler sprocket 130 is positioned substantially in the
center of the third drive chain 128 and is adapted for adjustment
to provide chain tension as needed. The third drive chain 128 is
entrained in serpentine fashion around a series of sprockets (not
shown separately) to cause the forward cutting wheel 124a to rotate
in a first direction and the rotary brush 126a to rotate in an
opposite direction. The same counter rotation occurs with the rear
cutting wheel 124b and the rear rotary brush 126b. In select
embodiments of the present invention, the cutting wheels 124a, 124b
are rotated at a speed about three times faster than the speed of
the drive wheeled axle assemblies 32, 42 to effectively remove
deposits. In select embodiments of the present invention, to assist
the movement of the robotic vehicle 20, the cutting wheels 124a,
124b operate in the same rotational direction as the drive wheeled
axle assemblies 32, 42, albeit faster.
[0107] If a cutting wheel rotating in a direction opposite to the
direction of travel were to encounter an obstacle such as a weld
seam, a jam could occur. To avoid this type of jamming, in select
embodiments of the present invention each cutting wheel 124a, 124b
is driven by use of a unidirectional clutch (not shown separately)
to enable rotation in the selected drive direction only. In select
embodiments of the present invention, a first unidirectional clutch
mounted to the front magnetized drive wheeled axle assembly 32
permits rotation thereof only in the counterclockwise direction
(FIG. 3B) and a second unidirectional clutch mounted to the rear
magnetized drive wheeled axle assembly 42 permits rotation thereof
only in the clockwise direction. When the robotic vehicle 20 drives
forward, with the tractor module 22 going first, the forward
cutting wheel 124a and both rotary brushes 126a, 126b operate. When
the robotic vehicle 20 reverses, i.e., with the tractor module 22
trailing, the motor 110 for driving the front magnetized drive
wheeled axle assembly 32 and the motor 98 for driving the rear
magnetized drive wheeled axle assembly 42 and the cutting wheels
124a, 124b are reversed, and the rear cutting wheel 124b and both
rotary brushes 126a, 126b operate. By rotating the rotary brushes
126a, 126b in the direction opposite to their adjacent respective
cutting wheels 124a, 124b, the particles loosened by the cutting
wheels 124a, 124b are removed from the path of travel of the
ultrasonic sensor unit.
[0108] In select embodiments of the present invention, one or more
ultrasonic transducers (not shown separately) are encapsulated in a
block 60 (FIG. 7) preferably formed of a dense, tough, and
resilient material, such as an ultra high molecular weight
polyethylene resin. This block 60 is positioned between forward
rotary brush 126a and rear rotary brush 126b. The block 60 is
biased downwardly to maintain firm contact with the operating
surface for transmitting its sonic signal directly to the surface
without having to broach an intervening gap. When the UST 10 is at
least partially liquid filled, a lubricant layer exists between the
block 60 and at least some of the tank's surface. In select
embodiments of the present invention, when the tank is empty,
ultrasonic transducer performance is enhanced and the wear on block
60 is minimized via use of a lubricating couplant liquid
transmitted through the tube 281 in the tether 28 (FIG. 10). In
select embodiments of the present invention, the ultrasonic
transducers are 2-10 MHz pulse echo transducers, adapted for
determining wall thickness when coupled with appropriate analytic
computer programming therefor. In select embodiments of the present
invention, several 10-Mhz ultrasonic transducers are arrayed in a
scan path width of about 2.5 cm. (1 inch). In select embodiments of
the present invention, ultrasonic data from the transducers are
processed with a commercially available program such as that
available from INFORMATRICS TESTPRO or the like. In select
embodiments of the present invention, the cutting wheels 124a, 124b
and rotary brushes 126a, 126b operate either in forward or reverse
travel of the robotic vehicle 20 and engage the surface ahead of
the transducers in the block 60. This ensures a reasonably clean
surface for reliable measurements. In select embodiments of the
present invention, the ultrasonic transducers may make between
approximately 30 and 100 measurements per second. At a speed of
approximately 77 mm (3 inches) per second, measurements may be
collected about every 0.77-2.6 mm (0.03-0.10 inches).
[0109] Refer to FIGS. 11A-11F depicting a robotic vehicle 20 as it
progresses in sequential steps from a first surface of the
cylindrical wall 12 of an UST 20 to a second surface of a wall or
end plate 14a orthogonal thereto.
[0110] Assume the robotic vehicle 20 is oriented substantially
perpendicular to the surface to which it is transferring. Refer to
FIG. 11A. Contact sensor 50b (FIGS. 3C, 11E, 11F) and 50a (not
shown in FIGS. 11A-F) contacts the end plate 14a of the UST 10.
FIG. 11B illustrates a second step in the transition of the robotic
vehicle 20 from the cylindrical wall 12 to the end plate 14a in
which the robotic vehicle 20 continues to travel and presses a
leading outer surface of the contact sensors 50a, 50b against end
plate. 14a whereby contact sensors 50a, 50b are telescoped to
contact the body of the tractor module 22. A signal, generated by a
contact switch (not shown separately) communicating with the
contact sensors 50a, 50b, is transmitted to cause the transition
lever arm 46 to pivot downwardly as shown in FIG. 11C. The
transition lever arm 46 is pivoted downwardly by movement of the
linear actuator 48 as described above. The transition lever arm 46
lifts the forward end of the tractor module 22 off the surface 12.
The transition lever arm 46 being connected at the location of the
pin 46P (FIGS. 3B and 3C) moves the robotic vehicle 20 closer to
the end plate 14a during its pivoting action so that the front
magnetized drive wheeled axle assembly 32 efficiently makes
magnetic contact with the end plate 14a. During this transition
period, the tractor module 22 is precluded from moving laterally
with respect to the other two modules 24, 26. The connection
between the cleaning and inspection module 26 and the power module
24 allows relative movement of these two modules 24, 26 in the
vertical direction only as depicted in FIGS. 11C-E.
[0111] Refer to FIGS. 11C-E. The front magnetized drive wheeled
axle assembly 32 powers the front end of the robotic vehicle 20
along the end plate 14a as the rear magnetized drive wheeled axle
assembly 42 continues to drive on the cylindrical wall 12, further
assisting the robotic vehicle 20 to climb up the end plate 14a. In
changing its orientation from horizontal to upwardly angled (FIG.
11D), the contact sensors 50a, 50b disengage from the end plate 14a
and the transition lever arm 46 retracts within the housing of
tractor module 22. The mid-point in the transition of the robotic
vehicle 20 from the horizontal surface 12 to the vertical surface
14a is illustrated in FIG. 11E, with the robotic vehicle 20 forming
a right angle between the power module 24 and the cleaning and
inspection module 26. To accommodate the transition between the
horizontal surface 12 and the vertical surface 14A, the drive
wheeled axle assemblies 32 and 42 are mounted on the robotic
vehicle 20 so that a respective forward and rearward portion of the
peripheral surface of each wheeled axle assembly 32, 42 extends
radially outward from the end of the respective modules 22, 24. The
rear push rod 137 (FIG. 6) is positioned perpendicular to the
horizontal surface 12. When the solenoid (not shown separately) of
the push rod 137 is energized, the rear push rod 137 extends to
move the rear magnetized drive wheeled axle assembly 42 away from
the horizontal surface 12 facilitating the rear magnetized drive
wheeled axle assembly 42 to climb the end plate 14a.
[0112] Refer to FIG. 11F, depicting the robotic vehicle 20 after
the transition is completed from the horizontal surface 12 to the
end plate 14a. In select embodiments of the present invention, the
path for inspection of the end plates 14a, 14b is preferred to
follow a series of diametral lines, each being angularly displaced
from the previous one. Employing this pattern, the entire surface
of each of the end plates 14a, 14b is inspected.
[0113] Refer to FIGS. 12A-D. Obstacles encountered within a storage
tank include raised seams, wave suppression plates, and internal
ribs. FIGS. 12 A-D depict the robotic vehicle 20 navigating an
obstacle. In select embodiments of the present invention,
identification of an obstacle is based on a computer comparison of
the known dimensions of an UST 10 with the distance the robotic
vehicle 20 has traveled in a straight line since last contacting a
perpendicular surface, such as a wall. In FIG. 12A, the contact
sensor 50b contacts the rib 54. As described above for
transitioning to another plane of operation, the transition lever
46 is pivoted downwardly and lifts the front of the tractor module
22 up, as shown in FIG. 11C. As the tractor 22 proceeds forward,
the front magnetized wheeled axle assembly 32 rolls up onto the rib
54 and the transition lever arm 46 retracts, as shown in FIG. 12B.
As depicted in FIG. 12C, when the rear magnetized wheeled axle
assembly 42 pushes the robotic vehicle 20, the front magnetized
wheeled axel assembly 32 is rolled completely over the rib 54 and
is able to roll on the horizontal surface 12 again. The rear
magnetized drive wheeled axle assembly 42 continues to drive and to
push the robotic vehicle 20 until it hits the rib 54 at which time
the front drive wheeled axle assembly is able to assist in pulling
the rear drive wheeled axle assembly over the rib 54. Normal
driving resumes when both magnetized wheeled axle assemblies 32, 42
are again in contact with the horizontal surface 12 as shown in
FIG. 12D, even though the inspection and cleaning module 26 is
still being pulled over the rib 54.
[0114] Upon initial insertion of the robotic vehicle 20 through the
riser 16 into an UST 10, neither the position nor orientation of
the robotic vehicle 20 is known to the computer 100. Thus, in
select embodiments of the present invention, the robotic vehicle 20
is directed to maneuver through a series of preliminary runs for
the purpose of initial orientation and position determination. The
robotic vehicle 20 travels first in an arbitrary straight line.
Signals generated by its three mutually orthogonal on-board
inclinometers are monitored by the computer 100 to determine the
shape and slope of the path being traversed. The robotic vehicle 20
is next directed to operate along a horizontal line. At one point,
a contact sensor 50a, 50b on the tractor module 22 contacts a
surface approximately perpendicular to the surface on which the
robotic vehicle 20 is operating. The computer 100 combines the
contact data with stored data on the direction of travel of the
robotic vehicle 20 to establish position. Basic position and
orientation information is now available for the robotic vehicle 20
to begin inspecting the interior of the UST 10 to evaluate its
surface condition and transmit data for the computer 100 to create
a record of defects. In select embodiments of the present
invention, a preferred path is for the robotic vehicle 20 to travel
forward along a first straight line on the cylindrical surface of
the wall 12 until it contacts an end plate 14a, 14b, then reverse
direction to travel backward to the opposite end plate 14a, 14b
along a line that is substantially parallel to and slightly offset
from the previous path. When the entire process of tank inspection
has been completed, the robotic vehicle 20 is lifted from the UST
10 by the tether 28 to a position near the riser 16 through which
it entered. In select embodiments of the present invention, the
tether 28 is connected to the robotic vehicle 20 causing the back
of the robotic vehicle 20 to tip up. The back of the robotic
vehicle 20 is fitted with a retrieval bar (not shown separately)
adapted for engaging by a retrieval hook (not shown separately) for
removing the robotic vehicle 20 from the UST 10.
[0115] Refer to FIG. 13 depicting a flat projected map of the
interior surface of the UST 10. The map includes the unfurled
surface of the cylindrical wall 12 and the end plates 14a, 14b,
each divided by reference grid lines. In select embodiments of the
present invention, the surface of the cylindrical wall 12 is marked
by square grid lines and the surface of the end plates 14a, 14b by
radial grid lines. The generation of these grids and plotting of
the position of the robotic vehicle 20 thereon are accomplished
through a mapping program loaded on the computer 100. For
illustration, points locating defects of an UST 10 are marked with
an "X" on the map of FIG. 13, whereas the present location of the
robotic vehicle 20 is marked by a small circle.
[0116] Refer to FIG. 14, a flow chart on the operation of the
mapping function of select embodiments of the present invention.
The location of the robotic vehicle 20 within a UST 10 is
determined by combining a start position 160 with data obtained
from the on-board inclinometers 162 and the encoder-odometer 164.
These data provide a new position 166 that is marked 168 with a
temporary designation, such as the "X" shown on the map of FIG. 13.
Measurements of the wall thickness are generated constantly by the
ultrasonic transducers in the block 60. The ultrasonic transducer
wall measurement 172 is taken to derive a measured thickness 174 as
an input to a determination 178 that compares the measurement 174
with a minimum thickness 176. If the measured thickness is below
the minimum, the temporary position "X" is made permanent as a
defect 170 for establishing in a record 180 of defect locations.
Whether the measured thickness is below or within tolerance, it is
added to the accumulating total (record) 180 of measurements taken.
This enable a determination of percentage defects 182. A final test
is a comparison 186 of the calculated percent defects with an
established maximum percentage allowed 184, the results of which if
positive invokes a request for repair 188, and if negative, a pass
190 with no required remediation.
[0117] In select embodiments of the present invention, the robotic
vehicle 20 may be manipulated autonomously by a computer 100 or by
an operator controlling the robotic vehicle 20, or both. Operator
control is preferable if the environment being traversed is unknown
and potential risk indicates need for an informed immediate
decision. In known environments, an automated program involving
initial orientation of the robotic vehicle followed by a prescribed
pattern of navigating is warranted. Programmed control of the
robotic vehicle is most practical in cases of repeat inspections of
known devices.
[0118] Accordingly, all such modifications are intended to be
included within the scope of this invention as defined in the
following claims. In the claims, means-plus-function clauses are
intended to cover the structures described herein as performing the
recited function and not only structural equivalents, but also
equivalent structures. Thus, although a nail and a screw may not be
structural equivalents in that a nail employs a cylindrical surface
to secure wooden parts together, whereas a screw employs a helical
surface, in the environment of fastening wooden parts, a nail and a
screw may be equivalent structures.
[0119] The abstract of the disclosure is provided to comply with
the rules requiring an abstract that will allow a searcher to
quickly ascertain the subject matter of the technical disclosure of
any patent issued from this disclosure. 37 CFR .sctn. 1.72(b). Any
advantages and benefits described may not apply to all embodiments
of the invention.
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