Magnetic crawler with three articulated wheels for travelling on pipes

Abstract

A magnetic crawler configured to travel on and inspect a ferromagnetic cylindrical surface is provided. The crawler includes a chassis, a controller configured to control the crawler, a probe configured to inspect the cylindrical surface under control of the controller, and three articulated magnetic wheels configured to be in tangential contact with and magnetically adhere to the cylindrical surface. The wheels include two drive wheels coupled to the chassis by two articulated joints, respectively, and configured to drive the crawler in a desired direction on the cylindrical surface by independently actively rotating the two drive wheels about respective drive rotation axes by respective drive motors under control of the controller, and a rear wheel coupled to the chassis by a rear articulated joint and configured to be passively rotated about a rear drive rotation axis in response to active rotation of the two drive wheels.

Description

Technical Field

[0001] This disclosure generally relates to a magnetic crawler having only three articulated wheels and capable of traveling and inspecting ferromagnetic pipes and other curved surfaces. Background Technology

[0002] One of the biggest challenges facing the oil and gas industry is the regular inspection of elevated assets in refineries, gas plants, offshore platforms, and other facilities. These assets include elevated pipelines and structures that are difficult to access during inspections. Often, the only feasible way to inspect them is to erect scaffolding to allow inspectors to access the asset and conduct manual inspections. Such scaffolding is not only expensive and a significant cost barrier for frequent inspections, but it also creates safety problems, primarily in the form of falls and tripping hazards.

[0003] In view of these and other problems in the art, this disclosure aims to provide a technical solution for an effective magnetic crawler having only three articulated magnetic wheels for traveling and inspecting ferromagnetic curved surfaces. Summary of the Invention

[0004] According to a first aspect of this disclosure, a magnetic crawler configured to travel on and inspect a ferromagnetic cylindrical surface is provided. The magnetic crawler includes: a chassis; a controller coupled to the chassis and configured to control the magnetic crawler; a probe coupled to the chassis and configured to inspect the ferromagnetic cylindrical surface under the control of the controller; and three articulated magnetic wheels coupled to the chassis and configured to tangentially contact and magnetically attach to the cylindrical surface. These three magnetic wheels include: a right drive wheel and a left drive wheel, respectively coupled to the chassis via a right articulated joint and a left articulated joint, and configured to drive the magnetic crawler along a desired direction on the cylindrical surface by independently and actively rotating on their respective right and left drive rotation axes under the control of the controller; and a rear wheel, coupled to the chassis via a rear articulated joint, and configured to passively rotate about a rear drive rotation axis in response to the active rotation of the right and left drive wheels. The right and left articulated joints provide the right and left drive wheels with a single rotational degree of freedom relative to the chassis about their respective right and left tilt rotation axes, allowing the right and left drive wheels to tilt relative to the chassis while remaining tangent to the curvature of the cylindrical surface. The rear articulated joint provides the rear wheels with two rotational degrees of freedom relative to the chassis: a rear tilt rotation axis for tilting the rear wheels relative to the chassis while maintaining tangency to the curvature of the cylindrical surface, and a rotation axis for rotating the rear wheels relative to the chassis in a desired direction in response to the magnetic crawler's actuation.

[0005] In one embodiment consistent with the above embodiments, the right drive wheel and the left drive wheel are further configured to independently and actively rotate in a forward or backward direction around their respective right drive axis and left drive axis under the control of the controller using their respective right drive motor and left drive motor.

[0006] In one embodiment consistent with the above embodiments, the magnetic crawler further includes an angle measurement sensor connected to the chassis and configured to measure the respective tilt angles of the three magnetic wheels relative to the chassis under the control of the controller, and to measure the rotation angle of the rear wheel relative to the chassis.

[0007] In one embodiment consistent with the above embodiments, the controller is further configured to maintain the magnetic crawler on a desired trajectory on a cylindrical surface by controlling the drive of the right and left drive wheels using measured angles.

[0008] In one embodiment consistent with the above embodiments, the desired trajectory is a helical path with a desired pitch and a cylindrical surface.

[0009] In one embodiment consistent with the above embodiments, the probe includes an ultrasonic testing (UT) sensor configured to nondestructively measure the thickness of a cylindrical surface under the control of a controller, and the controller is further configured to perform a two-dimensional mapping of the surface thickness across the entire cylindrical surface by controlling the UT sensor to measure the surface thickness and simultaneously controlling the driving of the right and left drive wheels along a helical path.

[0010] In one embodiment consistent with the above embodiments, the controller is further configured to use the measured angles and the geometry of the magnetic crawler to estimate the attitude of the magnetic crawler relative to the cylindrical surface.

[0011] In one embodiment consistent with the above embodiments, the rear articulated joint is configured to allow the rear wheel to rotate 360° about the rear swing axis.

[0012] In one embodiment consistent with the above embodiments, the probe includes an ultrasonic testing (UT) sensor configured to non-destructively measure the thickness of a cylindrical surface under the control of a controller.

[0013] In one embodiment consistent with the above embodiments, the cylindrical surface is part of a carbon steel pipe or container.

[0014] According to another aspect of this disclosure, an automated method is provided for traversing and inspecting a ferromagnetic cylindrical surface using a magnetic crawler. The magnetic crawler includes a chassis, a controller connected to the chassis, a probe connected to the chassis, and three articulated magnetic wheels connected to the chassis. The three magnetic wheels include a right drive wheel and a left drive wheel connected to the chassis via right and left articulated joints, respectively, and a rear wheel connected to the chassis via a rear articulated joint. The method includes: inspecting the ferromagnetic cylindrical surface through the probe under the control of the controller; tangentially contacting and magnetically attaching the three articulated magnetic wheels to the cylindrical surface; driving the magnetic crawler along a desired direction on the cylindrical surface by independently and actively rotating the right and left drive wheels about their respective right and left drive rotation axes under the control of the controller; passively rotating the rear wheel about the rear drive rotation axis in response to the active rotation of the right and left drive wheels; and tilting the right and left drive wheels relative to the chassis. The driving wheels, using corresponding right and left articulated joints to keep them tangent to the curvature of the cylindrical surface, provide a single rotational degree of freedom for the right and left drive wheels relative to the chassis about their respective right and left tilt rotation axes; and the rear wheels are tilted relative to the chassis while remaining tangent to the curvature of the cylindrical surface, and, in response to the drive of the magnetic crawler, the rear articulated joint is used to rotate the rear wheels relative to the chassis in a desired direction, providing two rotational degrees of freedom for the rear wheels relative to the chassis about a rear tilt rotation axis and a rotational axis perpendicular to the rear tilt rotation axis.

[0015] In one embodiment consistent with the above method, actively rotating the right drive wheel and the left drive wheel includes, under the control of the controller, using their respective right drive motors and left drive motors to independently rotate the right drive wheel and the left drive wheel forward or backward around their respective right drive axis and left drive axis.

[0016] In one embodiment consistent with the above method, the magnetic crawler further includes an angle measuring sensor coupled to the chassis, and the method further includes using the angle measuring sensor controlled by the controller to measure the respective tilt angles of the three magnetic wheels relative to the chassis, and to measure the rotation angle of the rear wheel relative to the chassis.

[0017] In one embodiment consistent with the above method, the method further includes maintaining the magnetic crawler on a desired trajectory on a cylindrical surface by a controller using measured angles to control the drive of the right and left drive wheels.

[0018] In one embodiment consistent with the above method, the desired trajectory is a helical path with a desired pitch and a cylindrical surface.

[0019] In one embodiment consistent with the above method, the probe includes an ultrasonic testing (UT) sensor, and the method further includes using the UT sensor to nondestructively measure the thickness of a cylindrical surface under the control of a controller, and the controller performs a two-dimensional mapping of the surface thickness on the entire cylindrical surface by controlling the UT sensor to measure the surface thickness while simultaneously controlling the drive of the right and left drive wheels along a helical path.

[0020] In one embodiment consistent with the above method, the method further includes using a controller to estimate the attitude of the magnetic crawler relative to the cylindrical surface using measured angles and the geometry of the magnetic crawler.

[0021] In one embodiment consistent with the above method, the method further includes enabling the rear wheel to rotate 360° around the rear swing axis via a rear articulated joint.

[0022] In one embodiment consistent with the above method, the probe includes an ultrasonic testing (UT) sensor, and the method further includes using the UT sensor under the control of a controller to nondestructively measure the thickness of a cylindrical surface.

[0023] In one embodiment consistent with the above method, the cylindrical surface is part of a carbon steel pipe or container.

[0024] Any combination of the various embodiments and implementations disclosed herein can be used. These and other aspects and features can be understood by reading the description of some embodiments below, along with the accompanying drawings and claims. Attached Figure Description

[0025] Figure 1 An exemplary magnetic crawler with only three articulated magnetic wheels is shown in one embodiment, which travels on a ferromagnetic cylindrical surface while inspecting it.

[0026] Figure 2 This is a cross-sectional view of an exemplary magnetic crawler of one embodiment, which has only three articulated magnetic wheels for traveling on a curved ferromagnetic surface (such as a carbon steel pipe).

[0027] Figures 3A-3B This is a front view of an exemplary magnetic crawler of one embodiment, having only three articulated magnetic wheels that travel on flat and curved surfaces respectively, and showing the rotational degrees of freedom of the left and right drive wheels along the tilt direction.

[0028] Figures 4A-4C This is a top view of an exemplary magnetic crawler with only three articulated magnetic wheels according to one embodiment, showing the rotational degrees of freedom of the rear wheel along the direction of rotation, wherein the rear wheel rotates to the left, center, and right, respectively.

[0029] Figure 5 This is a top view of an exemplary magnetic crawler with only three articulated magnetic wheels in one embodiment, showing the rear wheel's 360° rotational freedom along the direction of rotation.

[0030] Figures 6A-6C This is a front view of an exemplary magnetic crawler with only three articulated magnetic wheels according to one embodiment, showing the rotational degrees of freedom of the rear wheels along the tilt direction, wherein the rear wheels tilt to the left, center, and right, respectively.

[0031] Figure 7 An exemplary magnetic crawler with only three articulated magnetic wheels is shown in one embodiment as it travels on a ferromagnetic cylindrical surface (in this case, a pipe).

[0032] Figures 8A-8B This is a rear view of an exemplary magnetic crawler with only three articulated magnetic wheels traveling on a pipe, showing the rear wheels before and after tangential contact with the pipe surface.

[0033] Figures 9A-9C This is a top view of an exemplary magnetic crawler with only three articulated magnetic wheels according to one embodiment, showing exemplary angular measurements of the rotation of the rear wheels relative to the crawler chassis relative to a centering orientation, wherein the rear wheels rotate to the left, center, and right, respectively.

[0034] Figures 10A-10B This is a front view of an exemplary magnetic crawler with only three articulated magnetic wheels according to one embodiment, showing exemplary angular measurements of the tilt of the right and left drive wheels relative to the crawler chassis relative to a reference direction on curved and flat surfaces, respectively.

[0035] Figure 11A An exemplary magnetic crawler with only three articulated magnetic wheels is shown in one embodiment as it travels along a spiral path on a pipe.

[0036] Figure 11B yes Figure 11A An enlarged rear view of the magnetic crawler shows the rear wheels passively adjusted in the tilt direction to follow the curved surface of the pipe on a helical path.

[0037] Figure 12 This is a flowchart of an exemplary automated method for traversing and inspecting a ferromagnetic cylindrical surface using a magnetic crawler with only three articulated magnetic wheels, as described in one embodiment.

[0038] It should be noted that the accompanying drawings are exemplary and not necessarily drawn to scale, and that the same or similar features have the same or similar reference numerals in all the drawings. Detailed Implementation

[0039] Exemplary embodiments of this disclosure relate to a three-wheeled magnetic crawler capable of traversing curved surfaces such as pipes, containers, and tanks, as well as flat surfaces. In some such embodiments, when deployed on a pipe, the crawler is capable of longitudinally driving (parallel to the pipe's axis), circumferentially driving around the pipe, or a combination of both, such as helically driving around the pipe. Furthermore, in some such embodiments, the crawler is freely maneuverable and can turn in place to smoothly roam over the pipe. In some such embodiments, the crawler passively and automatically adapts and adjusts to various curvatures (e.g., radii of curvature) and pipe diameters without requiring any modifications to the crawler's vehicle chassis. In some embodiments, the crawler includes or carries inspection sensors, such as ultrasonic testing (UT) sensors, an inspection technique used in the oil and gas industry. In some embodiments, UT sensors are used as a non-destructive testing technique for inspecting steel surfaces. In some such embodiments, taking into account the effects that occur over time (e.g., corrosion), UT sensors are used to periodically measure the thickness of the steel to ensure that the steel thickness does not fall below a certain (e.g., predetermined) critical limit to avoid leaks, malfunctions, and unexpected downtime. In an exemplary embodiment, the three-wheeled crawler design enables UT measurement recording across the entire surface because the crawler has robust maneuverability on ferromagnetic pipes.

[0040] As mentioned earlier, one of the biggest challenges facing the oil and gas industry is the regular inspection of elevated assets in refineries, gas plants, offshore platforms, and other facilities. These assets include elevated pipelines and structures that are difficult to access during inspections. Even automated, mechanical, or robotic technologies face challenges in accessing these surfaces, many of which are curved, lateral, and inverted (relative to gravity).

[0041] Considering these and other issues, embodiments of this disclosure relate to efficient techniques that allow robotic systems to inspect (e.g., sense, measure) these assets in a cost-effective manner. In some embodiments, a crawler with a chassis and (only) three magnetic wheels attached to the chassis is provided. In some such embodiments, the configuration includes two motorized (or active) magnetic wheels (e.g., a right drive wheel and a left drive wheel) as front drive wheels, and a passive rear wheel (e.g., a caster). In some such embodiments, the crawler also includes a UT probe for measuring the thickness of ferromagnetic curved surfaces (e.g., cylindrical surfaces in carbon steel pipes). In some such embodiments, the crawler is free to maneuver on flat surfaces, containers, tanks (e.g., storage tanks), and pipes of various diameters, and is able to perform sensor measurements while doing so. Magnetic crawlers with only three articulated magnetic wheels have various variations. Figure 1-11B Some exemplary embodiments of them are shown in the figure and described below.

[0042] Figure 1 An exemplary magnetic crawler 100, having only three articulated magnetic wheels and traveling on a ferromagnetic cylindrical surface while inspecting it, is shown as one embodiment. The magnetic crawler 100 includes a crawler chassis 110 coupled to (or retaining, containing, or otherwise integrated into) components such as front drive wheels 120 (e.g., right and left drive wheels), rear casters 130, a UT probe 150, and a controller 160. The front drive wheels 120 and rear casters 130 are hinged in an inclined direction such that they are tilted to match (e.g., tangentially contact) the curvature of the curved surface (e.g., a pipe) on which they are deployed. Furthermore, the rear casters 130 are hinged in a rotational direction such that they pivot to follow the travel direction of the crawler chassis 110. During this travel over the curved ferromagnetic surface, the UT probe 150 performs UT thickness measurements to construct a two-dimensional thickness profile (e.g., C-scan) of the entire cylindrical surface based on the UT thickness measurements obtained while traveling over the entire cylindrical surface.

[0043] Here, "entire" means a certain degree of density, such as one thickness measurement per square inch. The pattern of measurement locations can be, for example, completely uniform (e.g., one measurement per inch in the longitudinal and circumferential directions), uniformly distributed (e.g., covering the entire cylindrical surface through a helical path of a specific pitch to achieve the desired density), or other such dense distribution of measurement points.

[0044] Furthermore, the operation of the magnetic crawler 100 is controlled by a controller 160, which may be a processor or logic circuit configured (e.g., by code or logic design) to perform operational control. For example, in some embodiments, the controller 160 is a microprocessor configured by code to control the drive of the front drive wheel 120 to maneuver the crawler 100 along a curved ferromagnetic surface in a desired direction or path. In some such embodiments, the controller 160 controls the operation of the UT probe 150, for example, when the UT probe 150 performs thickness measurements on a cylindrical surface.

[0045] Figure 2 This is a cross-sectional view of an exemplary magnetic crawler 200, one embodiment, having only three articulated magnetic wheels (including a front drive wheel 220 and a rear caster wheel 230) for traveling on a curved ferromagnetic surface (e.g., a carbon steel pipe). For ease of illustration and to better explain how the crawler 200 is driven and moved, Figure 2 A simplified bare crawler chassis 210 is shown to better illustrate the features of the three articulated wheels.

[0046] More specifically, the two front wheels 220 (drive wheels, or right drive wheel and left drive wheel) are independently actuated by their respective drive motors 222. Thus, the wheels 220 can be uniformly actuated and rotated (e.g., under the control of a controller (e.g., controller 160)) to drive the crawler 200 forward or backward. In some embodiments, the controller is also coded to control the actuation of the front drive wheels 220 in opposite directions (via drive motors 222) to perform differential steering and turn the crawler 200 in place. These combined movements provide the controller with sufficient degrees of freedom to control the crawler 200 to roam at any position on the pipe surface.

[0047] For this purpose, the rear caster 230 provides support for the crawler 200 and is passive (unacted). The rear caster 230 has multiple (e.g., two) degrees of freedom to allow the rear caster 230 to roll behind the crawler 200 without sideslipping, while maintaining tangential contact with the curved surface as the crawler 200 moves, regardless of factors such as direction of movement, pipe diameter, or inclination. To achieve this robust maneuverability, in some embodiments, the crawler 200 has four axes of rotation 240: one tilt axis 242 for each front wheel 220 (right and left), and two axes for the rear caster 230 (rear tilt axis 244 and rotation axis 246). Each front wheel 220 is rigidly attached to its motor 222 and articulated wheel carrier 224. Each articulated wheel carrier 224 allows the wheel to rotate about the axis of rotation of the wheel carrier (front tilt axis of rotation 242). In this way, each front wheel 220 can independently follow the curved surface (e.g., maintain tangential contact).

[0048] Furthermore, the rear caster 230 is attached to the inner wheel frame 234 (similar to the front wheel, to provide rotation about the rear tilt axis of rotation 244), which in turn is connected to the outer wheel frame 236 (providing rotation about the slewing axis of rotation 246), which in turn is connected to the crawler chassis 210. The outer wheel frame 236 functions as a simple caster (e.g., a caster in an office chair), while the inner wheel frame 234 also allows for rotation at a rolling (or tilting) angle. This two-degree-of-freedom attachment of the rear caster 230 to the chassis 210 enhances the crawler's overall maneuverability and helical maneuverability on pipes.

[0049] Figures 3A-3B This is a front view of an exemplary magnetic crawler 300 of one embodiment, having only three articulated magnetic wheels (drive wheels 320 and rear wheels 330) traveling on a flat surface 20 and a curved surface 40 respectively, and showing the rotational degrees of freedom of the left and right drive wheels 320 along the inclined direction. Here, the curved surface 40 represents a six-inch pipe. Generally, a curved surface can be any curved ferromagnetic surface exhibiting a radius of curvature, such as a partially or fully cylindrical, spherical, or combination thereof. The radius of curvature can also vary on the structure being inspected by the magnetic crawler 300.

[0050] For more detailed information, please refer to [link / reference]. Figures 3A-3B The degrees of freedom shown are formed by a rotary joint attachment between the crawler chassis 310 and the articulated front (right and left) wheel frames. Due to the rigid attachment between the frame and the front wheels 320, each front wheel 320 tilts and adjusts its angle to maintain a perpendicular angle (also known as tangential contact, as the bottom of the wheel is flush with the flat surface 20 and tangential to the curved surface 40, approaching linear contact as closely as possible) between itself and the surface below. These front wheel angle adjustments are automatic (passive) due to the freely rotating wheel frame and the magnetic attraction of the wheelset to the ferromagnetic smooth surface when the wheel travels on the curved surface. In other words, the mechanism is designed to enhance the magnetic adhesion of the wheelset to the surface. In contrast, if the crawler's front wheels did not have this degree of freedom, the front wheels might contact the pipe at some point (e.g., the end point of non-tangential contact) instead of approaching perfectly linear contact.

[0051] Figures 4A-4C This is a top view of an exemplary magnetic crawler 400 with only three articulated magnetic wheels according to one embodiment, showing the rotational degrees of freedom of the rear wheel 430 along the direction of rotation, wherein the rear wheel 430 rotates to the left, center, and right, respectively. This rotation allows the passive rear wheel 430 to follow and stabilize the crawler chassis 410 when driven by the front (right and left) drive wheels 420.

[0052] For more detailed information, please refer to [link / reference]. Figures 4A-4CThe rear caster wheel 430 has a first rotational degree of freedom in the direction of rotation, which is important for supporting and balancing the crawler chassis 410. Therefore, the rear wheel 430 serves as a support wheel, while also making the vehicle (crawler) easy to steer, and the wheel 430 passively rolls behind the crawler 400 without any sideslip. In some embodiments, this degree of freedom is formed by a rotary joint directly attached to the crawler chassis 410.

[0053] Figure 5 This is a top view of an exemplary magnetic crawler 500 with only three articulated magnetic wheels according to one embodiment, showing the rear wheel 530 having 360° rotational freedom along the rotational direction. Here, the rotational attachments of the rear wheel 530 extend sufficiently from the rest of the crawler chassis 510 that the rear wheel 530 is capable of rotating a full 360° in both clockwise and counterclockwise directions.

[0054] For more detailed information, please refer to [link / reference]. Figure 5 The crawler 500 is a longer version than the previous embodiment to accommodate a longer attachment of the rear wheel 530 relative to the chassis 510 and a corresponding 360° rotation. This feature allows for the additional capability of the crawler's drivetrain, namely, reverse propulsion. This feature is added by creating sufficient space at the rear of the crawler 500 to allow the caster 530 to rotate 360 ​​degrees. Thus, the crawler 500 is able to drive forward and backward without any sideslip.

[0055] Figures 6A-6C This is a front view of an exemplary magnetic crawler 600 with only three articulated magnetic wheels according to one embodiment, showing the rotational degrees of freedom of the rear wheel 630 along the tilt direction, wherein the rear wheel 630 tilts to the left, center, and right, respectively.

[0056] For more detailed information, please refer to [link / reference]. Figures 6A-6C In some embodiments, the second degree of freedom of the rear wheels is formed by a swivel joint attachment between the outer and inner rear wheel carriers. Thus, the second degree of freedom (tilt) is independent of the first degree of freedom (rotation) connected to the chassis 610 of the crawler. This joint allows the vehicle to helically move while maintaining good contact between the wheels and the pipe. Furthermore, because this joint allows for both free and passive rotation, the wheels maintain proper contact with the pipe effectively for virtually all available pipe sizes (e.g., all pipes with a diameter of at least 6 inches).

[0057] Figure 7 An exemplary magnetic crawler 700, having only three articulated magnetic wheels (including two drive wheels 720 and a rear wheel 730) according to one embodiment, is shown in its configuration as it travels on a ferromagnetic cylindrical surface (in this case, pipe 40). The crawler 700 travels along a helical path through pipe 40 (e.g., both transverse to the longitudinal and circumferential directions).

[0058] For more detailed information, please refer to [link / reference]. Figure 7 The magnetic crawler 700 shown here is a simplified (bare) three-wheeled crawler 700 mounted on top of a six-inch pipe 40. The crawler 700 is driven along a helical path. This helical path activates all four rotary joints on the front wheel 720 and the rear wheel 730. This helical path tilts each wheel 720 and 730 about its aforementioned (tilted) axis of rotation to allow the wheel to make proper contact with the pipe on this complex path, while also causing the rear wheel 730 to rotate about its axis of rotation to allow the rear wheel 730 to properly follow the rest of the crawler 700.

[0059] Figures 8A-8B The following is a rear view of an exemplary magnetic crawler 800 having only three articulated magnetic wheels (including two drive wheels 820 and a rear wheel 830) traveling on a pipe 40, showing the rear wheel 830 before and after tangential contact with the pipe surface.

[0060] For more detailed information, please refer to [link / reference]. Figures 8A-8B The magnetic crawler 800 moves along a spiral path on a six-inch pipe 40. Figure 8A The second degree of freedom of the rear wheel is shown before the rear wheel 830 is tilted (and only forms a contact point 831 with the pipe 40). That is, the caster 830 contacts the pipe 40 at a single point 831 (e.g., the end point of the bottom of the wheel 830). This reduces magnetic adhesion and may scratch the outer surface of the pipe. In contrast, Figure 8B The second degree of freedom of the rear wheel is shown after tilting the rear wheel 830 (and making the contact line 833, or tangential contact, as close to a straight line as possible). This establishes a suitable contact line 833 between the caster 830 and the pipe 40. Furthermore, this contact line 833 maximizes the magnetic force between the rear wheel 830 and the pipe surface. The same applies to the two front articulated (drive) wheels 820.

[0061] In some embodiments, another important feature utilized from the four degrees of freedom is obtained by measuring the angles of these degrees of freedom. As mentioned above, degrees of freedom provide the magnetic crawler with the ability to maneuver in various shapes or trajectories, such as circumferential, helical, and longitudinal motions on curved surfaces. To keep the crawler on a desired trajectory, in some embodiments, angular feedback from the measured degrees of freedom is input to a controller (e.g., controller 160), which is coded to provide the necessary corrective feedback to the drive motor to keep the crawler on the desired trajectory. For example, potentiometers, encoders, or any other form of angle measurement sensor for these joints can be used to sense the angular feedback.

[0062] Figures 9A-9CThis is a top view of an exemplary magnetic crawler 900 with only three articulated magnetic wheels according to one embodiment, showing exemplary angular measurements of the rotation 939 of the rear wheel 930 relative to the crawler chassis 910 relative to a centering orientation, wherein the rear wheel 930 rotates 939 to the left, center, and right, respectively. Since the rear wheel 930 follows the crawler chassis 910, the amount of rotation 939 of the rear wheel 930 represents the degree to which the crawler 900 deviates from a straight path (relative to the surface on which the crawler 900 moves).

[0063] For more detailed information, please refer to [link / reference]. Figures 9A-9C The rotation 939 indicates that the angle of the caster 930 needs to be corrected via feedback to keep the crawler 900 traveling in a straight line. If the caster 930 deviates from the centerline (e.g.) Figure 9A and 9C If the caster 930 has a non-zero rotation, then the correction angle 939 (i.e., the angle between the dashed line and the solid reference line) will be input into the controller, which is programmed to command the drive motor to make corresponding adjustments to keep the caster 930 in a straight position (e.g., with a non-zero rotation). Figure 9B ).

[0064] Figures 10A-10B This is a front view of an exemplary magnetic crawler 1000 having only three articulated magnetic wheels (including two drive wheels 1020 and a rear wheel 1030) according to one embodiment. It shows exemplary angular measurements of the tilt 1027 of the left and right drive wheels 1020 relative to the crawler chassis 1010 on the curved surface 40 and the flat surface 20, respectively, relative to a reference direction. Here, the tilt 1027 is measured by a component whose orientation relative to the crawler chassis 1010 (as shown by vertical lines or dashed lines) changes directly with the tilt (in this case, the wheel frame 1024, as shown by solid lines).

[0065] For more detailed information, please refer to [link / reference]. Figures 10A-10B , Figure 10A The image shows a crawler 1000 traveling longitudinally along the length of a pipe 40 across a curved surface (or pipe) 40 (in this example, at the top of the pipe 40). As the crawler 1000 travels longitudinally along the top of the pipe, it maintains (or more specifically, the controller is programmed to use measured angles to drive the wheel motors to maintain) the same tilt angle (but in opposite directions) on both drive wheels 1020, and the rear wheel 1030 does not tilt or turn. If the crawler 1000 begins to drift to the right or left, the tilt angle will be different, and the controller is further programmed to use this feedback to control the drive motors to manipulate and correct the crawler's path (via the drive wheels 1020) to keep the crawler 1000 in a straight line at the top of the pipe 40. Figure 10BThe controller is shown to determine when the crawler 1000 is on the flat surface 20, because when the crawler 1000 moves in a straight line, the tilt or rotation of the wheels is not measured.

[0066] Figure 11A An exemplary magnetic crawler 1100 with only three articulated magnetic wheels is shown in one embodiment as it travels along a spiral path on a pipe 40. Figure 11B yes Figure 11A An enlarged rear view of the magnetic crawler 1100 shows the rear wheel 1130 passively adjusted in the tilt direction to follow the curved surface of the pipe 40 on a helical path.

[0067] For more detailed information, please refer to [link / reference]. Figure 11A-11B The crawler 1100 travels helically across the surface of the pipe 40. Here, the measured angle of the articulated joint is input to the controller. The controller is programmed or otherwise configured (e.g., via code or logic) to detect any deviations in the measured angle and the expected deviations when using the desired pitch. The controller is also programmed or otherwise configured to use any such measured deviations to adjust the drive of the drive wheel so that the crawler 1100 returns to the desired pitch of travel and ensures a proper and accurate trajectory along the desired helix.

[0068] The crawler 1100 traveling on the spiral path demonstrates the importance of four degrees of freedom for the three articulated magnetic wheels. As the crawler 1100 begins to travel along the spiral path on the pipe 40, the second degree of freedom (tilt) of the caster 1130 rotates due to its passive, self-adjusting design. Figure 11B The adjusted rotation angle 1135 is shown. This angle 1135 varies for different helical trajectories, depending on factors such as pitch. The controller is also configured to use feedback from the joint (e.g., angle measurement feedback) to ensure that the crawler 1100 travels on the desired helical path without significant deviation, and to control the drive of the drive wheels to correct or compensate for any significant deviations detected.

[0069] A controller (e.g., controller 160) is programmed or otherwise configured to control various aspects of the magnetic crawler. In an exemplary embodiment, the controller is programmed to control drive motors to independently power two magnetic drive wheels to maneuver the magnetic crawler on a ferromagnetic curved surface. In some such embodiments, the controller is programmed to control probes on the crawler to inspect the surface while maneuvering on it. In some embodiments, the controller is programmed to use angular measurement feedback from each of the four rotary joints as feedback to adjust the crawler's drive such that the crawler achieves or maintains a desired trajectory on the curved surface.

[0070] In some embodiments, the controller is programmed to combine a crawler mathematical model based on the crawler's geometry (e.g., the position of its axis of rotation) and angular data from the rotary joint into an accurate estimate of the crawler's attitude and its orientation relative to the pipe. In some such embodiments, the controller is also configured to use the attitude estimate to keep the crawler on a desired trajectory. In some such embodiments, the controller is also programmed to improve the accuracy of the attitude estimate and trajectory keeping by fusing the attitude estimate with further data obtained from inertial measurement units (IMUs), satellite navigation devices (e.g., GPS), or known geometry of the surrounding environment (e.g., the diameter of the pipe the crawler traverses).

[0071] In some embodiments, the controller is programmed to use feedback from joint angle measurements to better control and follow the trajectory of the magnetic crawler. In some such embodiments, the controller is programmed to control a probe (e.g., a UT thickness sensor) to periodically or continuously inspect a surface while correlating the inspection data with a defined position on the pipe surface from which the data is obtained, thereby controlling the inspection scan of a curved ferromagnetic surface along that trajectory. In some such embodiments, the controller is also programmed to enhance the quality of the inspection scan by improving the correlation between the inspection data and the position on the surface of the inspected pipe (e.g., by using better attitude estimation, crawler navigation, or rotary joint angle measurements, etc.).

[0072] In some embodiments, the controller is programmed to control the UT thickness probe attached to the crawler to perform pipe thickness measurements in a B-scan (or continuous linear) manner, for example, longitudinally along the length of the pipe (parallel to the pipe axis) or circumferentially around the circumference of the pipe (equidistant from points on the pipe axis). In some embodiments, the controller is programmed to control the UT thickness probe to perform pipe thickness measurements in a C-scan (or complete two-dimensional surface mapping) manner. In some such embodiments, the controller is programmed to perform a C-scan by traversing the pipe along a helical path with a sufficiently small helical pitch to cover the surface of the pipe (e.g., to achieve the desired density at the UT thickness measurement location to effectively generate a surface thickness map of the entire two-dimensional surface area of ​​the pipe).

[0073] In some embodiments, the mobility system (e.g., three articulated magnetic wheels, having two independently driven drive wheels and one passive rear wheel, with tilting rotary joints on all three wheels and a rotary joint on the rear wheel) allows the magnetic crawler (controlled by a controller programmed to control the crawler) to travel on convex surfaces (e.g., the outer surface of pipes, straight pipes, tanks, etc.) and also on concave surfaces (e.g., the inner surface of pipes and the outer surface of bends (e.g., bends or bend joints that have both convex and concave portions)).

[0074] refer to Figure 1-11B In some exemplary embodiments, a magnetic crawler (e.g., magnetic crawler 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1100) is provided to travel over and inspect a ferromagnetic cylindrical surface (e.g., pipe 40 or storage tank). The magnetic crawler includes a chassis (e.g., crawler chassis 110, 210, 310, 410, 510, 610, 910, or 1010), a controller (e.g., controller 160) coupled to the chassis, a probe (e.g., UT probe 150) coupled to the chassis, and three articulated magnetic wheels coupled to the chassis. The controller (e.g., a microprocessor) is coded to control the magnetic crawler. The probe inspects the ferromagnetic cylindrical surface under the control of the controller. The three articulated magnetic wheels include two (right and left) drive wheels (e.g., drive wheels 120, 220, 320, 420, 720, 820, or 1020) and a passive rear wheel (e.g., rear wheel 130, 230, 330, 430, 530, 630, 730, 830, 930, 1030, or 1130). The magnetic wheels are in tangential contact with the cylindrical surface (e.g., linearly or as close to a line as possible) and are magnetically attached to the cylindrical surface.

[0075] The right and left drive wheels are connected to the chassis via right and left articulated joints (e.g., wheel carriers 224 or 1024), respectively. Furthermore, under the control of the controller, the right and left drive wheels drive the magnetic crawler along a desired direction (e.g., longitudinal, circumferential, or helical) on a cylindrical surface by independently and actively rotating around their respective right and left drive rotation axes using corresponding right and left drive motors (e.g., drive motor 222). The rear wheels are connected to the chassis via rear articulated joints (e.g., inner wheel carrier 234 and outer wheel carrier 236). Furthermore, the rear wheels passively rotate around the rear drive rotation axis in response to the active rotation of the right and left drive wheels.

[0076] The right and left articulated joints provide the right and left drive wheels with a single rotational degree of freedom relative to the chassis about their respective right and left tilting rotation axes (e.g., front tilting rotation axis 242), allowing the right and left drive wheels to tilt relative to the chassis while remaining tangent to the curvature of the cylindrical surface. The rear articulated joint provides the rear wheels with two rotational degrees of freedom relative to the chassis about a rear tilting rotation axis (e.g., rear tilting rotation axis 244) and a rotational axis perpendicular to the rear tilting rotation axis (e.g., rotational rotation axis 246). The rear tilting rotation axis tilts the rear wheels relative to the chassis while remaining tangent to the curvature of the cylindrical surface. The rotational rotation axis rotates the rear wheels relative to the chassis in a desired direction in response to the drive of the magnetic crawler.

[0077] In one embodiment, the right and left drive wheels, under the control of a controller, independently and actively rotate in a forward or backward direction about their respective right and left drive rotation axes (to achieve differential steering and in-situ steering). In one embodiment, the magnetic crawler also includes angle measurement sensors coupled to the chassis. These angle measurement sensors, under the control of the controller, measure the corresponding angles of tilt (e.g., tilt 1027°) of the three magnetic wheels relative to the chassis, and measure the angle of rotation (e.g., rotation 939°) of the rear wheel relative to the chassis. In one embodiment, the controller is also coded to maintain the magnetic crawler on a desired trajectory on a cylindrical surface by controlling the drive of the right and left drive wheels using the measured angles. In one embodiment, the desired trajectory is a helical path with a desired pitch on the cylindrical surface.

[0078] In one embodiment, the probe includes an ultrasonic testing (UT) sensor that non-destructively measures the thickness of the cylindrical surface under the control of a controller. Furthermore, the controller is coded to perform a two-dimensional mapping (e.g., C-scan) of the surface thickness across the entire cylindrical surface by controlling the UT sensor to measure the surface thickness and simultaneously controlling the drive of the left and right drive wheels along a helical path. In one embodiment, the controller is also coded to estimate the attitude of the magnetic crawler relative to the cylindrical surface using the measured angles and the geometry of the magnetic crawler. In one embodiment, the rear articulated joint enables 360° rotation of the rear wheels about the rear slewing axis. In one embodiment, the cylindrical surface is part of a carbon steel pipe or container (e.g., a storage tank).

[0079] The techniques described herein can be implemented using a combination of sensors, cameras, and other devices, including computing or other logic circuitry configured (e.g., programmed) to perform tasks assigned to them. These devices are located on or within (or otherwise close to) the chassis of the magnetic crawler to implement these techniques. In some example embodiments, the control logic is implemented as computer code configured to execute on computing circuitry (e.g., a microprocessor) to perform control steps as part of the techniques.

[0080] Figure 12This is a flowchart of an example automated method 1200 using a magnetic crawler (e.g., magnetic crawler 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1100) with only three articulated magnetic wheels to travel and inspect a ferromagnetic cylindrical surface (e.g., pipe 40). The magnetic crawler includes a chassis (e.g., crawler chassis 110, 210, 310, 410, 510, 610, 910, or 1010), a controller (e.g., controller 160) coupled to the chassis, a probe (e.g., UT probe 150) coupled to the chassis, and three articulated magnetic wheels coupled to the chassis. Method 1200 is partially or fully automated under the control of an electronic controller configured (e.g., coded, such as programmed) to perform the steps of method 1200. The three magnetic wheels include a right drive wheel and a left drive wheel (e.g., drive wheels 120, 220, 320, 420, 420, 720, 820, or 1020) connected to the chassis via a right hinge joint and a left hinge joint (e.g., hinge wheel carriers 224 and 1024), respectively, and a rear wheel (e.g., rear wheels 130, 230, 330, 430, 530, 630, 730, 830, 930, 1030, or 1130) connected to the chassis via a rear hinge joint (e.g., inner caster carrier 234 and outer caster carrier 236).

[0081] Method 1200 can be used in part or in whole. Figure 1-11B The methods and techniques described herein are executed using the components and techniques shown. Furthermore, portions of the methods and other methods disclosed herein may be executed on or using an onboard controller, such as a custom or pre-programmed logic device, circuit, or processor, such as a programmable logic circuit (PLC), computer, software, or other circuitry configured by code or logic (e.g., ASIC, FPGA), to perform tasks assigned to them. The device, circuit, or processor may also be, for example, a dedicated or shared hardware device (e.g., a laptop, single-board computer (SBC), workstation, tablet, smartphone, part of a server, or dedicated hardware circuitry (e.g., in an FPGA or ASIC), etc.), or a computer server, or part of a server or computer system. The device, circuit, or processor may include a non-transitory computer-readable medium (CRM) storing instructions (e.g., read-only memory (ROM), flash drive, or disk drive) that, when executed on one or more processors, cause portions of method 700 (or other disclosed methods) to be executed. It should be noted that in other embodiments, the order of operations may be changed, and some operations may be omitted. A portion of method 1200 may also be executed using logic, circuitry, or a processor located on or in electrical communication with a processing circuitry configured by code to execute these portions of method 1200.

[0082] In method 1200, the process begins with step 1210, where a probe controlled by a controller examines a ferromagnetic cylindrical surface (e.g., performing UT thickness measurement using UT probe 150). Furthermore, method 1200 includes the step of magnetically attaching to the cylindrical surface via three articulated magnetic wheels making tangential contact 1220 (e.g., linear contact or as close to linear contact as possible). Method 1200 also includes step 1230, whereby the right and left drive wheels are actively rotated independently about their respective right and left drive rotation axes by a corresponding right drive motor and left drive motor (e.g., drive motor 222) controlled by the controller, thereby driving the magnetic crawler along a desired direction on the cylindrical surface. Method 1200 further includes step 1240, whereby the rear wheel is passively rotated about a rear drive rotation axis in response to the active rotation of the right and left drive wheels.

[0083] Furthermore, method 1200 includes the step of tilting the right and left drive wheels relative to the chassis by 1250 while using corresponding right and left articulated joints to keep them tangent to the curvature of the cylindrical surface, to provide the right and left drive wheels with a single rotational degree of freedom relative to the chassis about their respective right and left tilt rotation axes (e.g., tilt rotation axis 242). Method 1200 also includes the step of tilting the rear wheels relative to the chassis by 1260 while keeping them tangent to the curvature of the cylindrical surface, and using a rear articulated joint to rotate the rear wheels relative to the chassis in a desired direction in response to the drive of the magnetic crawler, to provide the rear wheels with two rotational degrees of freedom relative to the chassis about a rear tilt rotation axis (e.g., rear tilt rotation axis 244) and a rotational axis perpendicular to the rear tilt rotation axis (e.g., rotational rotation axis 246).

[0084] In some embodiments, actively rotating the right and left drive wheels includes, under the control of a controller, independently rotating the right and left drive wheels forward or backward around their respective right and left drive axes (e.g., performing differential steering and stationary steering). In some embodiments, the magnetic crawler further includes an angle measuring sensor coupled to the chassis, and the method 1200 further includes the step of using the angle measuring sensor controlled by the controller to measure the angle of the respective tilt of the three magnetic wheels relative to the chassis (e.g., tilt 1027), and to measure the angle of rotation of the rear wheel relative to the chassis (e.g., rotation 939). In some embodiments, the method further includes the step of maintaining the magnetic crawler on a desired trajectory on a cylindrical surface by the controller controlling the drive of the right and left drive wheels using the measured angles. In some embodiments, the desired trajectory is a helical path with a desired pitch on the cylindrical surface.

[0085] In some embodiments, the probe includes an ultrasonic testing (UT) sensor (e.g., UT probe 150), and the method 1200 further includes the step of non-destructively measuring the thickness of the cylindrical surface using the UT sensor under the control of a controller, and performing a two-dimensional mapping of the surface thickness across the entire cylindrical surface by the controller controlling the UT sensor to measure the surface thickness while simultaneously controlling the drive of the right and left drive wheels along a helical path. In some embodiments, the method 1200 further includes the step of estimating the attitude of the magnetic crawler relative to the cylindrical surface by the controller using measured angles and the geometry of the magnetic crawler. In some embodiments, the method 1200 further includes the step of achieving 360° rotation of the rear wheel about the rear swing axis via a rear hinge joint. In some embodiments, the cylindrical surface is part of a carbon steel pipe or container (e.g., a storage tank).

[0086] The methods described herein can be implemented in part by software or firmware in a machine-readable form on a tangible (e.g., non-transitory) storage medium. For example, the software or firmware can be in the form of a computer program containing computer program code adapted to perform some steps of any of the methods described herein when run on a computer or suitable hardware device (e.g., an FPGA), and the computer program can be contained on a computer-readable medium. Examples of tangible storage media include computer storage devices having computer-readable media, such as disks, thumb drives, flash memory, etc., and do not include propagated signals. Propagated signals can exist in tangible storage media, but the propagated signals themselves are not instances of tangible storage media. The software can be adapted to execute on a parallel or serial processor, such that the method steps can be executed in any suitable order or simultaneously.

[0087] It should also be understood that the same or similar reference numerals in the accompanying drawings indicate the same or similar elements in multiple drawings, and not all embodiments or arrangements require reference to all parts or steps described and shown in the accompanying drawings.

[0088] The terminology used in this disclosure is for illustrative purposes only and does not constitute any limitation. Unless expressly stated in the context, the singular forms “a,” “an,” and “described” as used herein are intended to cover the plural forms. It should also be understood that, when used in this specification, the term “comprising” or its grammatical variations refer to the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0089] The directional terms used herein are for convention and reference purposes only and should not be construed as restrictive. However, it should be recognized that these terms may be used by the observer as a reference. Therefore, no limitation is implied or inferred from them. Furthermore, ordinal numbers (e.g., first, second, third) are used for distinction rather than counting. For example, the use of “third” does not imply a corresponding “first” or “second”. In addition, the wording and terminology used herein are for illustrative purposes and should not be considered restrictive. The use of the terms “comprising,” “including,” or “having,” and their variations thereof, in this document means to encompass the items listed thereafter, as well as their equivalents and additional items.

[0090] The foregoing subject matter is exemplary only and should not be considered limiting. Various modifications and changes can be made to the subject matter described herein without departing from the true spirit and scope of the invention as covered by this disclosure, which is limited only by a set of the following claims and the structures, functions or steps equivalent to those claims.

Claims

1. A magnetic crawler configured to travel on and inspect a ferromagnetic cylindrical surface, the magnetic crawler comprising: a chassis; a controller coupled to the chassis and configured to control the magnetic crawler; a probe coupled to the chassis and configured to inspect the ferromagnetic cylindrical surface under control of the controller; and three articulated magnetic wheels coupled to the chassis and configured to tangentially contact and magnetically adhere to the cylindrical surface, the three articulated magnetic wheels comprising: right and left drive wheels coupled to the chassis through right and left articulation joints, respectively, and configured to drive the magnetic crawler in a desired direction on the cylindrical surface by independently actively rotating around respective right and left drive rotation axes using respective right and left drive motors under control of the controller; and a rear wheel coupled to the chassis through a rear articulation joint and configured to passively rotate around a rear drive rotation axis in response to active rotation of the right and left drive wheels, wherein the right and left articulation joints provide a single rotational degree of freedom of the right and left drive wheels around respective right and left tilt rotation axes relative to the chassis to tilt the right and left drive wheels relative to the chassis and maintain tangency to a curvature of the cylindrical surface; and wherein the rear articulation joint provides two rotational degrees of freedom of the rear wheel around a rear tilt rotation axis and a slew rotation axis perpendicular to the rear tilt rotation axis relative to the chassis, the rear tilt rotation axis to tilt the rear wheel relative to the chassis and maintain tangency to the curvature of the cylindrical surface, the slew rotation axis to slew the rear wheel relative to the chassis in the desired direction in response to driving of the magnetic crawler.

2. The magnetic crawler of claim 1, wherein the right and left drive wheels are further configured to actively rotate around the right and left drive rotation axes in forward or rearward directions using the right and left drive motors of the right and left drive wheels, respectively, under control of the controller.

3. The magnetic crawler of claim 1, further comprising an angle measurement sensor coupled to the chassis and configured to measure respective tilt angles of the three articulated magnetic wheels relative to the chassis and a slew angle of the rear wheel relative to the chassis under control of the controller.

4. The magnetic crawler of claim 3, wherein the controller is further configured to maintain the magnetic crawler on a desired trajectory on the cylindrical surface by controlling driving of the right and left drive wheels using the measured angles.

5. The magnetic crawler of claim 4, wherein the desired trajectory is a helical path having a desired pitch of the cylindrical surface. ​ 6. The magnetic crawler of claim 5, wherein the probe comprises an ultrasonic testing sensor configured to measure the thickness of the cylindrical surface non-destructively under the control of the controller, and the controller is further configured to perform a two-dimensional mapping of the surface thickness across the cylindrical surface by controlling the ultrasonic testing sensor to measure the surface thickness while simultaneously controlling the right and left drive wheels to be driven along the helical path.

7. The magnetic crawler of claim 3, wherein the controller is further configured to estimate the pose of the magnetic crawler relative to the cylindrical surface using the measured angle and the geometry of the magnetic crawler.

8. The magnetic crawler of claim 1, wherein the rear articulation joint is configured to enable 360° rotation of the rear wheel about the rear slew rotation axis.

9. The magnetic crawler of claim 1, wherein the probe comprises an ultrasonic testing sensor configured to measure the thickness of the cylindrical surface non-destructively under the control of the controller.

10. The magnetic crawler of claim 1, wherein the cylindrical surface is a portion of a carbon steel pipe or vessel.

11. An automated method of traveling and inspecting a ferromagnetic cylindrical surface using a magnetic crawler, the magnetic crawler comprising a chassis, a controller coupled to the chassis, a probe coupled to the chassis, and three articulating magnetic wheels coupled to the chassis, the three articulating magnetic wheels comprising right and left drive wheels coupled to the chassis by right and left articulation joints, respectively, and a rear wheel coupled to the chassis by a rear articulation joint, the method comprising: inspecting the ferromagnetic cylindrical surface by the probe under the control of the controller; contacting and magnetically adhering to the cylindrical surface with the three articulating magnetic wheels in a tangential direction; driving the magnetic crawler in a desired direction on the cylindrical surface by independently actively rotating the right and left drive wheels about respective right and left drive rotation axes using respective right and left drive motors under the control of the controller; passively rotating the rear wheel about a rear drive rotation axis in response to the active rotation of the right and left drive wheels; tilting the right and left drive wheels relative to the chassis while maintaining the right and left drive wheels tangent to the curvature of the cylindrical surface using respective right and left articulation joints to provide a single rotational degree of freedom of the right and left drive wheels about respective right and left tilt rotation axes relative to the chassis, respectively; and tilting the rear wheel relative to the chassis while maintaining tangency to the curvature of the cylindrical surface, and slewing the rear wheel relative to the chassis in a desired direction using the rear articulation joint in response to the driving of the magnetic crawler to provide two rotational degrees of freedom of the rear wheel about a rear tilt rotation axis and a slew rotation axis perpendicular to the rear tilt rotation axis relative to the chassis.

12. The method of claim 11, wherein actively rotating the right and left drive wheels comprises independently actively rotating the right and left drive wheels forward or backward about their respective right and left drive rotational axes using their respective right and left drive motors under control of the controller.

13. The method of claim 11, wherein the magnetic crawler further comprises an angle measurement sensor coupled to the chassis, and the method further comprises measuring respective tilt angles of the three articulated magnetic wheels relative to the chassis using the angle measurement sensor controlled by the controller, and measuring a slew angle of the rear wheel relative to the chassis.

14. The method of claim 13, further comprising using the measured angles by the controller to control the driving of the right and left drive wheels to maintain the magnetic crawler on a desired trajectory on the cylindrical surface.

15. The method of claim 14, wherein the desired trajectory is a helical path having a desired pitch of the cylindrical surface.

16. The method of claim 15, wherein the probe comprises an ultrasonic test sensor, and the method further comprises non-destructively measuring a thickness of the cylindrical surface using the ultrasonic test sensor under control of the controller, and performing a two-dimensional mapping of the surface thickness across the cylindrical surface by the controller by controlling the ultrasonic test sensor to measure the surface thickness while controlling the driving of the right and left drive wheels along the helical path.

17. The method of claim 13, further comprising estimating, by the controller, a pose of the magnetic crawler relative to the cylindrical surface using the measured angles and a geometry of the magnetic crawler.

18. The method of claim 11, further comprising enabling 360° rotation of the rear wheel about the rear slew rotational axis through the rear articulation joint.

19. The method of claim 11, wherein the probe comprises an ultrasonic test sensor, and the method further comprises non-destructively measuring a thickness of the cylindrical surface using the ultrasonic test sensor under control of the controller.

20. The method of claim 11, wherein the cylindrical surface is a portion of a carbon steel pipe or vessel.

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