Inspection method using a perching UAV with a releasable crawler

1. A method of inspection or maintenance of an outwardly curved ferromagnetic surface exhibiting outward cylindrical or spherical curvature by a crawler flown to and released on the outwardly curved ferromagnetic surface by an unmanned aerial vehicle (UAV), the method comprising:

flying the UAV and attached releasable crawler to a proximity of the outwardly curved ferromagnetic surface exhibiting the outward cylindrical or spherical curvature;

perching the UAV and attached releasable crawler on the outwardly curved ferromagnetic surface, comprising:

passively articulating legs of the UAV toward the outward cylindrical or spherical curvature of the ferromagnetic surface through magnetic attraction using corresponding magnets in the legs while approaching the outwardly curved ferromagnetic surface;

magnetically attaching the articulated legs of the UAV to the outwardly curved ferromagnetic surface using the corresponding magnets; and

maintaining the magnetic attachment of the legs to the outwardly curved ferromagnetic surface throughout the perching;

detaching the attached crawler onto the outwardly curved ferromagnetic surface from the perched UAV;

maneuvering the detached crawler on the outwardly curved ferromagnetic surface while magnetically attaching the crawler to the outwardly curved ferromagnetic surface using magnetic wheels of the crawler; and

inspecting or maintaining the outwardly curved ferromagnetic surface using the magnetically attached crawler.

2. The method of claim 1 , wherein the outwardly curved ferromagnetic surface comprises a pipe, and maneuvering the detached crawler comprises performing outward circumferential scans of the pipe using the detached crawler.

3. The method of claim 1 , wherein inspecting or maintaining the outwardly curved ferromagnetic surface further comprises inspecting or maintaining the outwardly curved ferromagnetic surface during the maneuvering using a probe or tool of the magnetically attached crawler.

4. The method of claim 1 , further comprising wirelessly communicating, from the detached crawler, with the UAV or a base station.

5. The method of claim 1 , further comprising breaking the magnetic attachment of the crawler from the outwardly curved ferromagnetic surface and re-docking the detached crawler with the perched UAV after the maneuvering.

6. The method of claim 1 , further comprising:

breaking the magnetic attachment of the articulated legs from the outwardly curved ferromagnetic surface in order to magnetically detach the articulated legs from the outwardly curved ferromagnetic surface; and

flying the magnetically detached legs of the UAV away from the outwardly curved ferromagnetic surface.

7. The method of claim 6 , wherein the corresponding magnets comprise switchable permanent magnets, and breaking the magnetic attachment comprises switching the permanent magnets from a magnetized state to an unmagnetized state.

8. The method of claim 6 , wherein breaking the magnetic attachment comprises applying leverage to the magnetically attached legs using one or more detachment actuators of the UAV.

9. The method of claim 1 , further comprising scanning the proximal outwardly curved ferromagnetic surface using a laser scanner of the flying UAV.

10. The method of claim 1 , wherein the outwardly curved ferromagnetic surface comprises a pipe or a storage tank.

11. A method of inspection or maintenance of an outwardly curved ferromagnetic surface exhibiting outward cylindrical or spherical curvature by a crawler flown to and released on the outwardly curved ferromagnetic surface by an unmanned aerial vehicle (UAV), the method comprising:

flying the UAV and attached releasable crawler from an initial position to a pre-perching position in a vicinity of the outwardly curved ferromagnetic surface exhibiting the outward cylindrical or spherical curvature;

autonomously perching the UAV and attached releasable crawler on the outward cylindrical or spherical curvature of the ferromagnetic surface through magnetic attachment;

maintaining the magnetic attachment of the perched UAV and attached releasable crawler to the outward cylindrical or spherical curvature of the ferromagnetic surface;

releasing the attached crawler from the magnetically attached UAV onto, and magnetically attaching to, the outwardly curved ferromagnetic surface;

moving the released crawler over the outwardly curved ferromagnetic surface while maintaining the magnetic attachment of the released crawler to the outwardly curved ferromagnetic surface;

inspecting or maintaining the outwardly curved ferromagnetic surface using the magnetically attached crawler; and

re-docking the released crawler with the perched UAV.

12. The method of claim 11 , further comprising wirelessly communicating with the UAV from the released crawler.

13. The method of claim 11 , further comprising:

magnetically detaching the perched UAV from the outwardly curved ferromagnetic surface; and

flying the magnetically detached UAV away from the outwardly curved ferromagnetic surface to the pre-perching position.

14. The method of claim 13 , wherein flying the magnetically detached UAV comprises not carrying the re-docked crawler, and the method further comprises wirelessly communicating with the flying UAV from the released crawler.

15. The method of claim 11 , wherein inspecting or maintaining the outwardly curved ferromagnetic surface comprises marking locations of interest on the outwardly curved ferromagnetic surface.

16. The method of claim 15 , wherein inspecting or maintaining the outwardly curved ferromagnetic surface comprises measuring a thickness of the outwardly curved ferromagnetic surface, and the locations of interest comprise locations whose measured thickness is below a critical value.

17. The method of claim 15 , further comprising:

magnetically detaching the perched UAV from the outwardly curved ferromagnetic surface;

flying the magnetically detached UAV away from the outwardly curved ferromagnetic surface; and

detecting the marked locations of interest on the outwardly curved ferromagnetic surface from the flying magnetically detached UAV.

18. The method of claim 11 , further comprising:

magnetically detaching the perched UAV with the re-docked crawler from the outwardly curved ferromagnetic surface;

flying the magnetically detached UAV with the re-docked crawler away from the outwardly curved ferromagnetic surface to the pre-perching position; and

flying the magnetically detached UAV with the re-docked crawler toward another pre-perching position in a vicinity of a second outwardly curved ferromagnetic surface to be inspected or maintained by the re-docked crawler, the second outwardly curved ferromagnetic surface exhibiting outward cylindrical or spherical curvature.

19. The method of claim 11 , further comprising:

magnetically detaching the perched UAV with the re-docked crawler from the outwardly curved ferromagnetic surface; and

flying the magnetically detached UAV with the re-docked crawler away from the outwardly curved ferromagnetic surface to the initial position.

20. The method of claim 11 , wherein autonomously perching the UAV comprises sensing the outwardly curved ferromagnetic surface using a depth camera or laser scanner of the UAV in order to produce sensed depth camera or laser scanner data, and touching down on the outwardly curved ferromagnetic surface using the sensed depth camera or laser scanner data.

21. The method of claim 20 , wherein

sensing the outwardly curved ferromagnetic surface comprises producing sensed ferromagnetic surface data, and

autonomously perching the UAV further comprises aligning the UAV at a pre-touchdown position using the sensed ferromagnetic surface data.

22. The method of claim 11 , wherein the outwardly curved ferromagnetic surface comprises a pipe or a storage tank.