Wall-climbing robot

Abstract

A wall-climbing robot with an outer pad that defines a ring on its lower surface. At least two suction pads are present within the ring that are spaced from one another. At least two driving modules are present on the lower surface.

Description

WALL-CLIMBING ROBOTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and is a non-provisional of, U. S. Patent Application 63 / 728,395 (filed December 5, 2024), the entirety of which is incorporated herein by reference.STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under grant numbers IIP-1915721, IIP-2112199 awarded by the National Science Foundation and 69A3551747126 awarded by the United States Department of Transportation. The government has certain rights in the invention.BACKGROUND OF THE INVENTION

[0003] Many inspection, maintenance, and safety -related tasks must be carried out on surfaces that are vertical or even overhead. Examples include the walls of buildings, bridge piers and towers, ship hulls, storage tanks, industrial equipment, and other large structures. Working in these places is difficult and often dangerous for human operators because of the height, limited accessibility, and changing environmental conditions. Traditional methods, such as scaffolding, rope access, or crane platforms, are usually expensive to set up, slow to operate, and pose safety risks.

[0004] As infrastructure continues to age, the need for frequent checking, nondestructive testing, cleaning, and repair on these surfaces has increased. Many structures also have complicated shapes, including curves, joints, protrusions, and narrow spaces that are hard for workers to reach. For this reason, wall-climbing robots have become an important research topic, as they could improve worker safety and help reduce inspection cost and time.

[0005] However, enabling a robot to move on a vertical surface introduces several technical challenges. First, the robot must generate a stable adhesion force strong enoughto support its own weight and any tools or sensors it carries, even when moving or changing direction. Second, different surfaces, such as concrete, steel, glass, painted coatings, or corroded areas interact differently with common adhesion methods. A system that works well on a smooth surface may perform poorly on a rough or dusty one. Third, robots must often navigate obstacles, move across changes in wall orientation, or operate in tight areas. Fourth, for real-world use, wall-climbing robots need to be lightweight, energy-efficient, and able to run for long periods without large external equipment.

[0006] Many existing adhesion methods such as magnetic wheels, negative-pressure suction, electrostatic adhesion, propeller-based thrust, and bio-inspired dry or wet adhesives, they have shown progress, but each has notable limitations. Some only work on metal surfaces, while others require very' smooth and clean walls. Some systems consume too much power or depend on large pumps or fans. Others lack the stability or adaptability needed for irregular structures. Because of these limitations, there is still a need for improved technology that can adhere to and move across various wall materials with higher stability, better load capacity, and lower energy use.

[0007] The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.SUMMARY

[0008] This disclosure provides a wall-climbing robot with an outer pad that defines a ring on its lower surface. At least two suction pads are present within the ring that are spaced from one another. At least two driving modules are present on the lower surface. An advantage that may be realized in the practice of some disclosed embodiments of the robot is that the robot is able to navigate cracks in a vertical surface while maintaining adhesion to the vertical surface

[0009] In first embodiment, a wall-climbing robot is provided. The wall-climbing robot comprising: an outer pad that defines an outer perimeter of a lower planar surfaceof the wall-climbing robot; a first vacuum motor operatively connected to a first inner suction pad, the first inner suction pad being coplanar with the lower planar surface; a second vacuum motor operatively connected to a second inner suction pad, the second inner suction pad being coplanar with the lower planar surface; the first inner suction pad and the second inner suction pad being disposed within the outer perimeter of the outer pad and are separated by a distance that is at least 10% of a length of the wall-climbing robot; and a first driving module with a first driving tread and a second driving module with a second driving tread, the first driving tread and the second driving tread disposed within the outer perimeter and coplanar with the lower planar surface.

[0010] In a second embodiment, a wall-climbing robot is provided. The wallclimbing robot comprising: a housing comprising: an outer pad that defines an outer perimeter of a lower planar surface of the wall-climbing robot, a first vacuum motor operatively connected to a first inner suction pad, the first inner suction pad being coplanar with the lower planar surface; a second vacuum motor operatively connected to a second inner suction pad, the second inner suction pad being coplanar with the lower planar surface; the first inner suction pad and the second inner suction pad being disposed within the outer perimeter of the outer pad and are separated by a distance that is at least 10% of a length of the wall-climbing robot; a first driving module with a first driving tread and a second driving module with a second driving tread, the first driving tread and the second driving tread disposed within the outer perimeter and coplanar with the lower planar surface; and a payload removably attached to the housing, the payload comprising at least one non-destructive testing (NDT) device.

[0011] This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended clai s. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter,nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which:

[0013] FIG. 1A and FIG. 1B are exploded views of an example of a wall-climbing robot.

[0014] FIG. 2 is a bottom plan view of the robot.

[0015] FIG. 3 is a cross section side view of the robot.

[0016] FIG. 4A is an example of a comparative robot climbing a vertical surface while FIG. 4B is an example of the robot of FIG. 1A climbing the vertical surface.

[0017] FIG. 5 is a bottom perspective view of the robot.

[0018] FIG. 6A is a cross section view an inset showing a cross section of an outer pad of the robot.

[0019] FIG. 6B is a cross section view of the outer pad of FIG. 6A shown in further details.

[0020] FIG. 7A and FIG. 7B show a drive module for use with the robot.

[0021] FIG. 8A depicts the robot without a payload attached while FIG. 8B depicts the robot with a payload attached.DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to FIG. 1A and FIG. 1B, an exploded view of a robot 100 is depicted. The robot 100 comprises a payload 800 that is removably attached. An electrical power port 102 is present that enables recharging of an onboard battery (not shown) A computer processor 104 is present that permits the robot 100 to execute computer programs. In some embodiments, an onboard camera 106 is present. The robot 100 is designed for field deployment, using negative pressure to adhere to surfaces using a suction pad 200.

[0023] FIG. 2 provides a bottom plan view of the robot 100 and the suction pad 200. The suction pad 200 comprises an outer pad 204 that defines an outer perimeter 202 of a lower planar surface of the robot 100. The suction pad 200 further comprises a first inner suction pad 206a and a second inner suction pad 206b that are disposed within the outer perimeter 202 of the outer pad 204. The inner suction pads 206a, 206b are coplanar with the lower planar surface of the robot 100. In the embodiment of FIG. 2, the inner suction pads 206a, 206b are circular with respective first and second vacuum motors 208a, 208b disposed at a center thereof. In use, the first and second vacuum motors 208a, 208b are operatively connected to respective first and second evacuated chambers 210a, 210b that are sealed by the inner suction pads 204a, 206b. In this manner the two inner suction pads 204a, 206b establish an airtight seal which permits the first and second evacuated chambers 210a, 210b to provide an adhesive force (e.g. negative pressure) to a surface upon which the robot 100 is placed. This dual chamber design allows the robot 100 to drive over gaps (e.g. cracks, transitions between two surfaces, etc.) on surfaces without losing adhesion because at least one of the first and second evacuated chambers 210a, 210b will maintain adhesion as the other passes over the gap.

[0024] In the robot 100 of FIG. 2, not only are dual chambers used, but multiple layers of suction pads are incorporated to enhance flexibility and durability. The outerpad 204 provides a seal to establish a third evacuated chamber 210c. In the event one or both of the first and second evacuated chambers 210a, 210b fails (e.g. the robot 100 passes over thick coatings, small rocks, etc.) the respective vacuum motor evacuates the third evacuated chamber 210c to establish a negative pressure within the third evacuated chamber 210c.

[0025] Referring to FIG. 3, a schematic cross section view of the robot 100 is depicted with the front 302 and back 304 of the robot 100 labeled. The first and second evacuated chambers 210a, 210b are spaced from one another by a distance 300 such that the first evacuated chamber 210a is disposed in a front half 306 of the robot 100 and the second first evacuated chamber 210b is disposed in rear half 308 of the robot 100. The distance 300 (measured from a centers of the respective evacuated chambers) is at least 10%, at least 20%, at least 30%, at least 40% or at least 50% of the length 310 of the robot 100. By spacing the two evacuated chambers 210a, 210b from one another, the robot 100 avoids both 210a, 210b simultaneously failing by passing of a gap. Such a dual chamber configuration enhances the ability of the robot 100 to adhere to a vertical surface. Like the evacuated chambers 210a, 210b, the respective vacuum motors 208a, 208b are also spaced from one another by the distance 300 (measured from their respective center of mass).

[0026] Additionally, the use of two vacuum motors 208a, 208b further promotes stability when adhered to a vertical surface. Referring to FIG. 4A, if a single vacuum motor 400 were used in a robot 402 climbing a vertical surface 404, the rotation moment (given by mgxL) is unstable. The single vacuum motor provides only one adhesion point with the robot 402 balancing on this single support. When the robot 402 tilts even slightly, the center of mass moves away from that support point, and the resulting torque increases the tilt instead of correcting it. In contrast, and with reference to FIG. 4B, the robot 100 uses two vacuum motors 208a, 208b spaced by the distance 300 with corresponding inner suction pads 206a, 206b. The two inner suction pads 206a, 206 provide two independent support points. When the robot 100 tilts, one side generates astronger reaction force, creating a restoring moment that brings the robot 100 back toward its original position. This causes the rotation moment to be stable.

[0027] FIG. 5 is a perspective bottom view of the robot 100. Each of the vacuum motors 208a, 208b is equipped with respective first and second air filters 500a, 500b that prevent debris (e.g. dust, small rocks, etc.) from being pulled into the vacuum motors 208a, 208b In one embodiment, the first and second air filters 500a, 500b are high efficiency particulate air (HEPA) filters.

[0028] FIG. 6A is a cross section end view of the robot 100 with an inset showing a cross section of a section of the outer pad 204 This insert is shown in further detail in FIG. 6B. The outer pad 204 comprises a bottom contact ring 600 that contacts the surface the robot 100 is disposed on. The bottom contact ring 600 defines a ring that circumscribes an inner portion of the outer pad 204. The bottom contact ring 600 is coplanar with the lower planar surface of the robot 100. In some embodiments, the bottom contact ring consists of a silicon rubber. An inner ring 602 is present that is disposed directly above the bottom contact ring 600, In some embodiments, the inner ring 602 is contiguous with the bottom contact ring 600. In other embodiments, a protective ring 604 is present between, and contiguous with, both the inner ring 602 and the bottom contact ring 600.

[0029] In some embodiments, the inner ring 602 consists of a foam such as a polyurethane foam or a poly(phenylene methylene) foam. In some embodiments, the inner ring 602 has a Shore-A hardness of about 50 and is compressible. In the embodiment of FIG. 6B, the protective ring 604 has a horizontal section that directly contacts the bottom contact ring 600 and is parallel to the lower planar surface of the robot 100. The protective ring 604 also has a vertical section that is orientated at about a 90° angle relative to the lower planar surface The protective ring 604 is monolithic such that the horizontal section and the vertical section are unitary. As used herein, the term ‘'about” as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain embodiments, the term “approximately” or “about” refers to a range of values that fall within 25%, 20%, 19%, 18%, 17%, 16%,15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context. In some embodiments, the protective ring 604 consists of a polyethylene terephthalate (PETF) or a polyfluoroalkyl substance (PFAS). In one embodiment, the protective ring 604 consists of a polytetrafluoroethylene (PTFE) such as the PTFE sold under the tradename TEFLON® A gap 606 is present between the inner ring 602 and the protective ring 604 that provides clearance for deformation of the outer pad 204 In some embodiments, the gap 606 is present on two opposite sides of the inner ring 602, at least one of which is the side facing the protective ring 604.

[0030] The disclosed design of the outer pad 204 causes the suction pad 200 to have similarly to a two-dimensional (2D) material, meaning it exhibits high deformation in vertical direction 608 (due to the compressibility of the inner ring 602) while limiting deformation in shear direction 610 (due to the presence of the gap 606). This is desirable for the robot 100, as it uses high vertical deformation for adhesion without excessive lateral movement.

[0031] Referring again to FIG. 2, the robot 100 comprises at least two drive modules, including a first drive module 700a and a second drive module 700b. In one embodiment, two drive modules are present. FIG. 7A and FIG. 7B depict the first drive module 700a in further detail In some embodiments, the first drive module 700a and the second drive module 700b are identical or are mirror images of one another. The drive module 700a comprises a driving tread 702 and a plurality of drive sprockets that rotate the driving tread 702. The driving tread 702 is coplanar with respect to the lower planar surface of the robot 100, thereby allowing the drive tread 702 to engage the surface the robot 100 is disposed on. By selectively actuating each of the drive modules 700a, 700b in a forward or reverse direction, the robot 100 that can move forward, backward or turn.

[0032] In one embodiment, the driving module 700a is powered by a 24V brushless direct current motor 706 (BLDC), controlled through pulse width modulation (PWM) and equipped with a Hall effect encoder. Between the motor shaft (not shown) and thedriving shaft 710, a 90-degree worm-gear box 708 is connected. The worm-gear box 708 provides a self-locking feature, which can stop the movement of the robot 100 when there is no power or control signal input. This feature ensures the stability of the robot 100, particularly when it is climbing on a vertical surface, as the force of gravity would otherwise cause the robot 100 to move downward without the self-locking mechanism.

[0033] The drive modules 700a, 700b are removeable from the robot 100 such that different drive modules with different driving treads 702 (see Table 1) can be used, each specifically designed to optimize interaction with different surface types. The drive modules 700a, 700b may be secured to the robot 100 using any number of conventional means (e.g. snap connectors, screws, etc ).

[0034] The removable configuration increases the versatility of the robot 100 in different operational environments. The maximum speed of the driving module 700a can be adjusted, offering flexibility to match the inspection speed with the specific requirements of the task. This adjustable speed feature allows for precise control of the movement of the robot 100, ensuring it performs effectively across a wide range of inspection activities.Table 1. driving tread 702 materials and capabilitiesMaterial of the Driving treads ApplicationPolyvinylchloride (PVC) conveyor belt Concrete, brick wallsRubber conveyor belt Aluminum, painted walls, coating surfacesSilicon rubber belt Glass, AcrylicNitrile butadiene rubber (NBR) Wood, PVC plasticMagnetic belt Steel surfaces, Ship, oil tank

[0035] Referring to FIG. 8 A and FIG. 8B, in some embodiments the robot 100 comprises a payload 800 mounted to a housing 802 of the robot 100 such that the payload 800 can interact with the surface the robot 100 is disposed on. FIG. 8A depicts the robot 100 without a payload while FIG. 8B depicts the robot 100 with the payload 800.

[0036] The payload 800 carries at least one non-destructive testing (NDT) device for horizontal scanning of the surface the robot 100 is disposed on. The payload 800 can carry several sensors for inspections, such as a ground-penetrating radar (GPR), a camera (e.g. an infrared camera, a thermal camera or conventional camera), an impact echo / sounding (IE / IS) sensor, an ultrasonic sensor and an environmental sensor (e.g. a particular matter (PM) sensor, an ultra violet (UV) sensor, a temperature sensor, a humidity sensor, a carbon monoxide sensor, a carbon dioxide sensor), and the like. The payload 800 may also have accessories other than NTD devices such as lights (e.g. light emitting diodes, LEDs), liner actuators (extending up to 300 mm, up to 350 mm, up to 400 mm, up to 250 mm or up to 500 mm), etc. In some embodiments, the robot 100 is configured to store data from the NTD devices in an onboard data storage unit (e.g. a flash drive). In other embodiments, the robot 100 is configured to stream data from the NTD devices to a remote-control unit for remote storage.

[0037] In one embodiment, the payload 800 is removable such that different NDT devices, or combinations of devices can be selectively attached to the housing 802. This adaptability enhances the utility of the robot 100 in a wide variety of fields such as construction, maintenance, and inspection, making it a versatile tool for a wide range of applications. In some embodiments, the robot 100 comprises a universal serial bus (USB) port that is operatively connected to the microprocessor of the robot 100. The payload 800 may comprise a USB cable that connects to the USB port and thereby conveys data and / or instructions between the NDT devices and the microprocessor.

[0038] In some embodiments, the robot 100 comprises an inertial measurement unit (IMU) with a Kalman filter, a Proportional-Integral-Derivative (PID) control, encoders for path planning and three-dimensional (3D) mapping and / or a wireless communication unit configured to wireless transmit and receive data from a remote-control unit. In one embodiment, the robot 100 has a logic circuit that detects if the robot 100 has been placed in a predetermined climbing mode. If the robot 100 is in the climbing mode, the IMU can determine if the robot 100 is at a vertical orientation and, if so, inspection of the underlying vertical surface. If the robot 100 is not in the climbing mode, then the robotcan be deemed to be in a free motion state where no inspection is needed. Such a configuration helps prevent inspection errors.

[0039] In one embodiment, a remote-control unit is present that permits wireless control of the robot 100 using the wireless communication unit. The remote control unit is not particularly limited and can, for example, allow for manual control of movement (both direction and velocity) of the robot 100, convey images from a camera on the robot 100, record conveyed images as a video or a snapshot, selectively turn lights on the robot 100 on or off, display the negative pressure reading in one or more of the evacuated chambers 210a, 210b, 210c, display the current velocity of the robot 100 or turn an automated movement protocol on or off. In one embodiment, remote control unit calibrates by measuring the surrounding pressure when the robot 100 is initiated. Once the vacuum motors vacuum motors 208a, 208b are activated, the remote-control unit calculates and shows the pressure difference, offering a visual indication of vacuum stability. The remote-control unit can also monitor CPU load, RAM usage, internal storage usage, flash drive storage capacity. In one embodiment, an onboard camera (e.g. onboard camera 106 in FIG. 1A) is present on an external surface of the robot 100 itself, thus providing the ability to wirelessly transmit video to the remote-control unit irrespective of the presence of a payload 800.

[0040] In one embodiment, the robot 100 is compact, measuring 380mm (width) x 380mm (depth) x 250mm (height), and lightweight at 6kg. Despite the compact configure, the robot 100 has been shown to cany a payload of around 2.5kg. The robot 100 works on low voltage, needing only 24V and has low power consumption.

[0041] The robot 100 automates tasks that would otherwise require human workers to operate in dangerous or difficult environments, such as tall buildings, bridges, or industrial facilities. The robot 100 minimizes human involvement in risky operations, cuts down on expensive equipment, and saves time by inspecting large areas more quickly. In addition, the NDT devices provide accurate real-time data which improving the quality of inspections and enabling long-term monitoring for early problem detection. The robot 100 provides a safer, more efficient, and more accurate solution for inspectingand maintaining concrete structures, especially in hard-to-reach or hazardous areas, compared to conventional robots. The robot 100 reduces the risks and costs associated with manual inspections, speeds the inspection process, and ensures more reliable, precise and consistent data collection.

[0042] Non-limiting examples of specific applications include inspection of bridge piers (including the submerged or elevated sections of bridge piers that are difficult for traditional inspection methods, especially in areas with harsh weather conditions or water), wind turbines (especially at great height which require regular inspections, including the vertical surfaces of the towers and blades, detecting cracks, corrosion, and structural weakness), oil storage tanks ( the cylindrical tanks can be challenging for conventional inspection due to their size and height), high-rise buildings (building facades and external surfaces, particularly in cities with high-rise structures, the robot cab perform regular maintenance inspections, detecting cracks, material degradation, or issues with external systems like windows), and dams (especially in hard-to-reach places, can be checked using the robot 100 to ensure they are structurally sound and free from erosion).

[0043] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.1

Claims

What is claimed is:

1. A wall-climbing robot comprising:an outer pad that defines an outer perimeter of a lower planar surface of the wallclimbing robot;a first vacuum motor operatively connected to a first inner suction pad, the first inner suction pad being coplanar with the lower planar surface;a second vacuum motor operatively connected to a second inner suction pad, the second inner suction pad being coplanar with the lower planar surface; the first inner suction pad and the second inner suction pad being disposed within the outer perimeter of the outer pad and are separated by a distance that is at least 10% of a length of the wall-climbing robot; anda first driving module with a first driving tread and a second driving module with a second driving tread, the first driving tread and the second driving tread disposed within the outer perimeter and coplanar with the lower planar surface.

2. The wall-climbing robot as recite in claim 1, wherein the distance is at least 20% of the length of the wall-climbing robot.

3. The w'all -climbing robot as recite in claim 1, wherein the distance is at least 30% of the length of the wall-climbing robot.

4. The wall-climbing robot as recite in claim 1, wherein the distance is at least 40% of the length of the wall-climbing robot.

5. The wall-climbing robot as recite in claim 1, wherein the distance is at least 50% of the length of the wall-climbing robot.

6. The wall-climbing robot as recite in claim 1, wherein the outer pad comprises a bottom contact ring and an inner ring, the bottom contact ring configured to contact a surface of a structure, the inner ring being a compressible material that is disposed above the bottom contact ring.

7. The wall-climbing robot as recite in claim 6, wherein the compressible material is a polyurethane foam or a poly(phenylene methylene) foam.

8. The wall-climbing robot as recite in claim 7, wherein the bottom contact ring is a polytetrafluoroethylene ring.

9. The wall-climbing robot as recite in claim 6, wherein the outer pad further comprises a protective ring having a horizontal section and a vertical section, the horizontal section being between, and contiguous with, both the inner ring and the bottom contact ring and the vertical section being disposed at an angle of about 90° to the lower planar surface and spaced from the inner ring by a gap.

10. The wall-climbing robot as recite in claim 1, wherein the first inner suction pad provides a first evacuated chamber, the second inner suction pad provides a second evacuated chamber and the outer pad provides a third evacuated chamber, the first evacuated chamber and the second evacuated chamber being within the third evacuated chamber.

11. A wall-climbing robot comprising:a housing comprising:an outer pad that defines an outer perimeter of a lower planar surface of the wall -climbing robot,a first vacuum motor operatively connected to a first inner suction pad, the first inner suction pad being coplanar with the lower planar surface;a second vacuum motor operatively connected to a second inner suction pad, the second inner suction pad being coplanar with the lower planar surface; the first inner suction pad and the second inner suction pad being disposed within the outer perimeter of the outer pad and are separated by a distance that is at least 10% of a length of the wall-climbing robot, a first driving module with a first driving tread and a second driving module with a second driving tread, the first driving tread and the second driving tread disposed within the outer perimeter and coplanar with the lower planar surface; anda payload removably attached to the housing, the payload comprising at least one non-destructive testing (NDT) device.

12. The wall-climbing robot as recite in claim 11, wherein the first inner suction pad provides a first evacuated chamber, the second inner suction pad provides a second evacuated chamber and the outer pad provides a third evacuated chamber, the first evacuated chamber and the second evacuated chamber being within the third evacuated chamber.

13. The wall-climbing robot as recite in claim 12, wherein the outer pad comprises a bottom contact ring and an inner ring, the bottom contact ring configured to contact a surface of a structure, the inner ring being a compressible material that is disposed above the bottom contact ring.

14. The wall-climbing robot as recite in claim 13, wherein the outer pad further comprises a protective ring having a horizontal section and a vertical section, the horizontal section being between, and contiguous with, both the inner ring and the bottom contact ring and the vertical section being disposed at an angle of about 90° to the lower planar surface and spaced from the inner ring by a gap.

15. The wall-climbing robot as recite in claim 11, wherein the wall-climbing robot has a front half and a rear half, the pay load being removably attached to the housing at the front half.

16. The wall-climbing robot as recite in claim 15, wherein the first inner suction pad is disposed in the front half and the second inner suction pad is disposed in the rear half.

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