Magnetic crawler with three articulated wheels for movement on pipes

Abstract

A magnetic crawler configured to move over and inspect a ferromagnetic cylindrical surface is provided. The magnetic crawler includes a chassis, a controller configured to control the crawler, a probe configured to inspect the cylindrical surface under the control of the controller, and only three articulated magnetic wheels configured to tangentially contact and magnetically adhere to the cylindrical surface. The wheels include two drive wheels each coupled to the chassis by two articulation joints and configured to drive the magnetic crawler in a desired direction over the cylindrical surface by actively rotating the two drive wheels independently about their respective drive rotation axes by respective drive motors under the control of the controller, and a rear wheel coupled to the chassis by a rear articulation joint and configured to passively rotate about a rear drive rotation axis in response to the active rotation of the two drive wheels.

Description

[Technical Field]

[0001] The present disclosure generally relates to a magnetic crawler that has only three articulated wheels and is capable of navigating and inspecting ferromagnetic pipes and other curved surfaces. [Background technology]

[0002] One of the biggest challenges in the oil and gas industry is the regular inspection of elevated assets found in refineries, gas plants, offshore platforms, and other plants and facilities. These assets contain high-elevation pipes and structures that are difficult to access during inspection operations. Often, the only practical way to inspect these is for inspectors to erect scaffolding to access the assets and perform manual inspections. Such scaffolding is expensive, creating a significant cost barrier for frequent inspections, as well as safety concerns, primarily in the form of fall and trip hazards. Summary of the Invention [Problem to be solved by the invention]

[0003] With regard to these and other problems in the art, the present disclosure aims to provide a technical solution for an effective magnetic crawler with only three articulated magnetic wheels for movement on and inspection of ferromagnetic curved surfaces. [Means for solving the problem]

[0004] According to a first aspect of the present disclosure, there is provided a magnetic crawler configured to move over and inspect a ferromagnetic cylindrical surface. 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 only three articulated magnetic wheels coupled to the chassis and configured to tangentially contact and magnetically adhere to the cylindrical surface. The three magnetic wheels include right and left drive wheels coupled to the chassis by right and left articulation joints, respectively, and configured to independently actively rotate about respective right and left drive rotation axes using respective right and left drive motors under the control of the controller to drive the magnetic crawler in a desired direction over the cylindrical surface, and rear wheels coupled to the chassis by rear articulation joints and configured to passively rotate about rear drive rotation axes in response to the active rotation of the right and left drive wheels. The right and left articulation joints provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt rotation axes to tilt the right and left drive wheels relative to the chassis and maintain tangential contact with the curvature of the cylindrical surface, while the rear articulation joint provides two degrees of freedom of rotation of the rear wheels relative to the chassis about the rear tilt rotation axis and a swivel rotation axis perpendicular to the rear tilt rotation axis, the rear tilt rotation axis tilting the rear wheels relative to the chassis and maintaining tangential contact with the curvature of the cylindrical surface, and the swivel rotation axis pivoting the rear wheels in a desired direction relative to the chassis in response to drive of the magnetic crawler.

[0005] In one embodiment consistent with the above, the right and left drive wheels are further configured to independently actively rotate in either a forward or reverse direction about their respective right and left drive rotation axes using their respective right and left drive motors under the control of the controller.

[0006] In one embodiment consistent with the above, the magnetic crawler further includes angle measurement sensors coupled to the chassis and configured, under control of the controller, to measure the angle of inclination of each of the three magnetic wheels relative to the chassis and to measure the angle of pivoting of the rear wheels relative to the chassis.

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

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

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

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

[0011] In one embodiment consistent with the above, the rear articulation joint is configured to provide 360° of rotation to the rear wheels about the rear pivot axis.

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

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

[0014] According to another aspect of the present disclosure, there is provided an automated method for using a magnetic crawler to move over and inspect a ferromagnetic cylindrical surface. The magnetic crawler includes a chassis, a controller coupled to the chassis, a probe coupled to the chassis, and only three articulated magnetic wheels coupled to the chassis. The three magnetic wheels include right and left drive wheels coupled to the chassis by right and left articulation joints, respectively, and rear wheels coupled to the chassis by rear articulation joints. The method includes the steps of inspecting the ferromagnetic cylindrical surface with the probe as controlled by the controller, tangentially contacting and magnetically attaching to the cylindrical surface with the three articulated magnetic wheels, driving the magnetic crawler in a desired direction over the cylindrical surface by actively rotating the right and left drive wheels independently about their respective right and left drive rotation axes using respective right and left drive motors as controlled by the controller, passively rotating the rear wheels about their rear drive rotation axes in response to the active rotation of the right and left drive wheels, and rotating the respective right and left articulation joints. tilting the right and left drive wheels relative to the chassis while maintaining tangential contact with the curvature of the cylindrical surface using the rear articulation joint to provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt axes of rotation, and tilting the rear wheels relative to the chassis while maintaining tangential contact with the curvature of the cylindrical surface and using the rear articulation joint to swivel the rear wheels in a desired direction relative to the chassis in response to drive of the magnetic crawler to provide two degrees of freedom of rotation of the rear wheels relative to the chassis about the rear tilt axis of rotation and a swivel axis of rotation perpendicular to the rear tilt axis of rotation.

[0015] In one embodiment consistent with the method described above, actively rotating the right and left drive wheels includes actively rotating the right and left drive wheels independently in either forward or reverse directions about their respective right and left drive rotation axes using their respective right and left drive motors as controlled by the controller.

[0016] In one embodiment consistent with the method described above, the magnetic crawler further includes an angle measurement sensor coupled to the chassis, and the method further includes using the angle measurement sensor controlled by the controller to measure the angle of each of the three magnetic wheels relative to the chassis and the angle of pivoting of the rear wheels relative to the chassis.

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

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

[0019] In one embodiment consistent with the method described above, the probe includes an ultrasonic testing (UT) sensor, and the method further includes the steps of non-destructively measuring a thickness of the cylindrical surface using the UT sensor as controlled by the controller, and performing, by the controller, two-dimensional mapping of the surface thickness across the cylindrical surface by controlling the UT sensor to measure the surface thickness while controlling drive of the right and left drive wheels along a helical path.

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

[0021] In one embodiment consistent with the method described above, the method further includes providing the rear wheels with 360° of rotation about the rear pivot axis by the rear articulation joint.

[0022] In one embodiment consistent with the method described above, the probe includes an ultrasonic testing (UT) sensor, and the method further includes non-destructively measuring the thickness of the cylindrical surface using the UT sensor as controlled by the controller.

[0023] In embodiments consistent with the methods described above, the cylindrical surface is a portion of a carbon steel pipe or vessel.

[0024] Any combination of the various embodiments and implementations disclosed herein can be used. These and other aspects and features can be understood from the following description of several embodiments, taken in conjunction with the accompanying drawings and claims. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 illustrates an example magnetic crawler with only three articulated magnetic wheels for inspecting a ferromagnetic cylindrical surface while moving over the cylindrical surface, according to one embodiment. [Figure 2] FIG. 1 is a cutaway view of an example magnetic crawler with only three articulated magnetic wheels for traversing a curved ferromagnetic surface (such as a carbon steel pipe), according to one embodiment. [Figure 3A] FIG. 1B is a front view illustrating rotational degrees of freedom in the tilt direction for the right and left drive wheels of an example magnetic crawler having only three articulated magnetic wheels moving in a plane, according to one embodiment. [Figure 3B] FIG. 1B is a front view illustrating rotational degrees of freedom in the tilt direction for the right and left drive wheels of an example magnetic crawler with only three articulated magnetic wheels traveling on a curved surface, according to one embodiment. [Figure 4A] FIG. 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, illustrating the rotational degrees of freedom in the turning direction for the rear wheels, with the rear wheels turning left, according to one embodiment. [Figure 4B]1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, illustrating rotational degrees of freedom in the pivot direction for the rear wheels, with the pivoting of the rear wheels toward the center, according to one embodiment. [Figure 4C] 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, illustrating the rotational degrees of freedom in the turning direction for the rear wheels, with the rear wheels turning to the right, according to one embodiment. [Figure 5] FIG. 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, showing 360° rotational freedom in the turning direction for the rear wheels, according to one embodiment. [Figure 6A] FIG. 1 is a front view of an example magnetic crawler with only three articulated magnetic wheels, illustrating the rotational degrees of freedom in the tilt direction for the rear wheels, with the rear wheels tilting to the left, according to one embodiment. [Figure 6B] FIG. 1 is a front view of an example magnetic crawler with only three articulated magnetic wheels, illustrating rotational degrees of freedom in the tilt direction for the rear wheels, with the rear wheels tilting toward the center, according to one embodiment. [Figure 6C] FIG. 1 is a front view of an example magnetic crawler with only three articulated magnetic wheels, illustrating the rotational degrees of freedom in the tilt direction for the rear wheels, with the rear wheels tilting to the right, according to one embodiment. [Figure 7] FIG. 1 illustrates an example magnetic crawler with only three articulated magnetic wheels moving on a ferromagnetic cylindrical surface (in this example, a pipe), according to one embodiment. [Figure 8A] FIG. 1 is a rear view of an example magnetic crawler with only three articulated magnetic wheels moving over a pipe, showing the rear wheels before making tangential contact with the pipe surface, according to one embodiment. [Figure 8B] FIG. 1B is a rear view of an example magnetic crawler with only three articulated magnetic wheels moving over a pipe, showing the rear wheels after making tangential contact with the pipe surface, according to one embodiment. [Figure 9A]FIG. 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, according to one embodiment, showing example angle measurements of the pivoting of the rear wheels relative to the crawler chassis compared to a center orientation, with the rear wheels pivoting to the left. [Figure 9B] FIG. 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, according to one embodiment, showing example angle measurements of the pivoting of the rear wheels relative to the crawler chassis compared to a central orientation, where the pivoting of the rear wheels is centered. [Figure 9C] FIG. 1 is a top view of an example magnetic crawler with only three articulated magnetic wheels, according to one embodiment, showing example angle measurements of the pivoting of the rear wheels relative to the crawler chassis compared to a center orientation, with the pivoting of the rear wheels to the right. [Figure 10A] FIG. 1 is a front view of an example magnetic crawler with only three articulated magnetic wheels, showing example angle measurements of the inclination of the right and left drive wheels relative to the crawler chassis on a curved surface compared to a reference direction, according to one embodiment. [Figure 10B] FIG. 1 is a front view of an example magnetic crawler with only three articulated magnetic wheels, showing example angle measurements of the inclination of the right and left drive wheels relative to the crawler chassis on a plane compared to a reference direction, according to one embodiment. [Figure 11A] FIG. 1 illustrates an example magnetic crawler with only three articulated magnetic wheels moving along a spiral path on a pipe, according to one embodiment. [Figure 11B] FIG. 11B is a close-up rear view of the magnetic crawler of FIG. 11A showing passive adjustment in tilt direction of the rear wheels to track the curved surface of the pipe on a spiral path. [Figure 12] FIG. 1 is a flow diagram of an example automated method for navigating and inspecting a ferromagnetic cylindrical surface using a magnetic crawler with only three articulated magnetic wheels, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] It is noted that the drawings are illustrative and are not necessarily to scale, and that like or similar features have the same or similar reference numbers throughout.

[0027] Example embodiments of the present disclosure are directed to a three-wheel magnetic crawler capable of traveling on curved surfaces, such as pipes, vessels, and storage tanks, as well as flat surfaces. In some such embodiments, when deployed on a pipe, the crawler can travel longitudinally (parallel to the axis of the pipe) along the length of the pipe, circumferentially around the pipe, or a combination of the two, e.g., spirally around the pipe. Also, in some such embodiments, the crawler is free-moving and rotates in place for smooth wandering motion on the pipe. In some such embodiments, the crawler passively and automatically accommodates multiple curvatures (e.g., radii of curvature) and pipe diameters without any modifications to the crawler's vehicle chassis. In some embodiments, the crawler includes or carries an inspection sensor, such as an ultrasonic testing (UT) sensor, which is an inspection technique 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, the UT sensor is used to periodically measure the steel thickness due to effects over time such as corrosion, e.g., to ensure that the steel thickness does not fall below a certain (e.g., predetermined) limit that avoids leaks, failures, and unplanned outages. In an example embodiment, the three-wheel crawler design allows for UT measurement recording over the entire surface due to the crawler's robust maneuverability on ferromagnetic pipes.

[0028] As mentioned previously, one of the biggest challenges in the oil and gas industry is the routine inspection of elevated assets found in refineries, gas plants, offshore platforms, and other plants and facilities. These assets include high-elevation pipes and structures that are difficult to access during inspection operations. Automated, mechanical, or even robotic techniques face challenges accessing these surfaces, many of which are curved, angled, and upside-down (relative to gravity).

[0029] In response to these and other concerns, embodiments of the present disclosure are directed to effective techniques that enable robotic systems to perform inspections (e.g., sensing, measuring) on ​​these assets in a cost-effective manner. In some embodiments, a crawler is provided having a chassis and three (only) magnetic wheels attached to the crawler chassis. In some such embodiments, the configuration includes two powered (or active) magnetic wheels (e.g., right and left drive wheels) that act as front drive wheels and passive rear wheels (e.g., caster wheels). In some such embodiments, the crawler also includes a UT probe for performing UT thickness measurements on ferromagnetic curved surfaces (such as cylindrical surfaces like carbon steel pipes). In some such embodiments, the crawler can move freely over flat surfaces, containers, tanks (e.g., storage tanks), and pipes of various diameters, taking sensor measurements while doing so. There are numerous variations of a magnetic crawler with only three articulated magnetic wheels, example embodiments of which are shown in FIGS. 1-11B and described in the following text.

[0030] FIG. 1 illustrates an example magnetic crawler 100 having only three articulated magnetic wheels for inspecting a ferromagnetic cylindrical surface while moving over the surface, according to one embodiment. The magnetic crawler 100 includes a crawler chassis 110, which is coupled to (or holds, houses, or otherwise integrates with) components such as front drive wheels 120 (e.g., right and left drive wheels), rear caster wheels 130, a UT probe 150, and a controller 160. The front drive wheels 120 and rear caster wheels 130 articulate in a tilting direction so that they tilt to conform to (e.g., make tangent contact with) the curvature of a curved surface (such as a pipe) on which they are placed. Additionally, the rear caster wheels 130 articulate in a swiveling direction so that they pivot to follow the direction of movement of the crawler chassis 110. During this movement over the curved ferromagnetic surface, the UT probe 150 performs UT thickness measurements to construct a two-dimensional thickness profile (e.g., a C-scan) across the cylindrical surface from the UT thickness measurements taken while moving across the cylindrical surface.

[0031] Here, "entire" means some density, such as one thickness measurement per square inch. The pattern of measurement locations can be, for example, completely uniform (such as one measurement per inch in the longitudinal and circumferential directions), evenly distributed (e.g., by a helical path of a particular helical pitch that covers the entire cylindrical surface to a desired density), or other such dense distribution of measurement points.

[0032] Additionally, the operation of magnetic crawler 100 is controlled by controller 160, which can be a processor or logic circuit configured (e.g., by code or logic design) to perform control of the operation. For example, in some embodiments, controller 160 is a microprocessor configured by code to control the drive of front drive wheels 120 to steer crawler 100 in a desired direction or path over a curved ferromagnetic surface. In some such embodiments, controller 160 controls the operation of UT probe 150, for example, when UT probe 150 is taking thickness measurements on a cylindrical surface.

[0033] 2 is a cutaway view of an example magnetic crawler 200 having only three articulated magnetic wheels (including front drive wheels 220 and rear caster wheels 230) for traveling on curved ferromagnetic surfaces (such as carbon steel pipes), according to one embodiment. For ease of illustration and to better explain how crawler 200 runs and moves, FIG. 2 shows a simplified barebones crawler chassis 210 to better show the features of the three articulated wheels.

[0034] In further detail, the two front wheels 220 (drive wheels, or right and left drive wheels) are independently powered by respective drive motors 222. Thus, the wheels 220 can be simultaneously actuated and rotated (e.g., under the control of a controller such as controller 160) to drive the crawler 200 forward or backward. In some embodiments, the controller is further configured by code to control actuation of the front drive wheels 220 in both directions (through the drive motors 222) to perform differential steering to rotate the crawler 200 in place. These combined movements provide the controller with sufficient freedom to control the crawler 200 to move around anywhere on the surface of the pipe.

[0035] To this end, the rear caster wheels 230 provide support to the crawler 200 and are passive (non-actuated). The rear wheels 230 have multiple (e.g., two) degrees of freedom to allow the rear wheels 230 to roll behind the crawler 200 without skidding while maintaining tangential contact with curved surfaces while the crawler 200 is moving, regardless of factors such as the direction of movement, pipe diameter, or tilt. To enable such robust maneuverability, in some embodiments, the crawler 200 has four rotation axes 240: one tilt axis 242 for each front wheel 220 (right and left) and two for the rear caster wheels 230 (rear tilt axis 244 and swivel axis 246). Each front wheel 220 is rigidly attached to its motor 222 and articulating wheel holder 224. Each articulating wheel holder 224 allows the wheel to rotate about the holder's rotation axis (front tilt rotation axis 242). Thus, each of the front wheels 220 can independently conform to (eg, maintain tangential contact with) a curved surface.

[0036] Additionally, the rear caster wheels 230 are attached to inner wheel holders 234 (to provide rotation about rear tilt axis 244, similar to the front wheels), which are in turn attached to outer wheel holders 236 (to provide rotation about swivel axis 246), which are in turn attached to the crawler chassis 210. The outer holders 236 act as simple caster wheels, such as those found on office chair wheels, while the inner holders 234 also allow for roll (or tilt) angular rotation. This two-degree-of-freedom attachment of the rear caster wheels 230 to the chassis 210 improves the crawler's overall maneuverability and spiraling motion on the pipe.

[0037] 3A-3B are front views of an example magnetic crawler 300 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, according to one embodiment, showing the rotational degrees of freedom in the tilt direction for the right and left drive wheels 320. Here, the curved surface 40 represents a 6-inch pipe. In general, the curved surface can be any curved ferromagnetic surface that exhibits a radius of curvature, such as a partial or full cylinder, a sphere, or a combination, to name a few. The radius of curvature may also vary across the structure being inspected by the magnetic crawler 300.

[0038] 3A-3B, the degrees of freedom shown are formed by the rotational joint attachment between the crawler chassis 310 and the articulating front (right and left) wheel holders. Due to the rigid attachment between the holders and the front wheels 320, each of the front wheels 320 tilts and adjusts its angle to maintain a perpendicular angle between itself and the surface below (also called tangential contact, since the bottom of the wheel is flush with the flat surface 20 and tangent to the curved surface 40, approximating line contact as closely as possible). These front wheel angle adjustments are automatic (passive) due to the freely rotatable wheel holders and the magnetic attraction of the wheels to the ferromagnetic, smooth curved surface as the wheels travel over the curved surface. In other words, this mechanism is designed to strengthen the magnetic wheel attachment to the surface. In contrast, without this degree of freedom in the crawler's front wheels, the front wheels could contact the pipe at a single point (such as an end point in a non-tangential contact) rather than as close to perfect linear contact as possible.

[0039] 4A-4C are top views of an example magnetic crawler 400 with only three articulated magnetic wheels, showing the rotational degrees of freedom in the pivot directions for the rear wheels 430, which are left, center, and right, respectively, according to one embodiment. This pivoting allows the passive rear wheels 430 to track and stabilize the crawler chassis 410 as driven by the front (right and left) drive wheels 420.

[0040] 4A-4C, the rear caster wheels 430 have a first rotational degree of freedom in the pivot direction that is important for supporting and balancing the crawler chassis 410. This allows the rear wheels 430 to act as a support while allowing the vehicle (crawler) to roll easily, with the wheels 430 rolling passively behind the crawler 400 without any skidding. In some embodiments, this degree of freedom is provided by a revolute joint that is directly attached to the crawler chassis 410.

[0041] 5 is a top view of an example magnetic crawler 500 with only three articulated magnetic wheels, illustrating 360° of rotational freedom in the pivot direction for the rear wheels 530, according to one embodiment, where the pivot attachments for the rear wheels 530 extend far enough away from the rest of the crawler chassis 510 that the rear wheels 530 can pivot a full 360° in both clockwise and counterclockwise directions.

[0042] In further detail with reference to Figure 5, the crawler 500 is a longer version of the previous embodiment to accommodate the longer attachment and corresponding 360° rotation of the rear wheels 530 relative to the chassis 510. This feature allows for additional capability of the crawler's drivetrain system, namely, reverse travel. This feature is added by creating sufficient space behind the crawler 500 to allow the caster wheels 530 to rotate 360°. Thus, the crawler 500 can travel forward and backward without any skidding.

[0043] 6A-6C are front views of an example magnetic crawler 600 with only three articulated magnetic wheels showing the rotational degrees of freedom in the tilt directions for the rear wheels 630, where the tilt of the rear wheels 630 is leftward, centered, and rightward, respectively, in accordance with one embodiment.

[0044] In further detail with reference to Figures 6A-6C, in some embodiments, the second degree of freedom of the rear wheels is formed by a rotational joint attachment between the outer and inner rear wheel holders. Thus, the second degree of freedom (tilt) is independent of the first degree of freedom (swivel), which is connected to the crawler chassis 610. This joint allows for helical vehicle movement with proper wheel-to-pipe contact. Additionally, because this joint allows for free, passive rotation, proper wheel-to-pipe contact is maintained with virtually all available pipe sizes (such as all pipes with a diameter of at least 6 inches).

[0045] 7 shows an example magnetic crawler 700 having only three articulated magnetic wheels (including two drive wheels 720 and a rear wheel 730) moving over a ferromagnetic cylindrical surface (in this case, a pipe 40), according to one embodiment. The crawler 700 traverses the pipe 40 in a helical path (e.g., traversing both longitudinally and circumferentially).

[0046] In further detail, referring to Figure 7, the magnetic crawler 700 shown here is a simplified (bare bones) three-wheel crawler 700 atop a 6-inch pipe 40. The crawler 700 travels on a spiral path that actuates all four revolute joints on the front wheels 720 and rear wheels 730. The spiral path tilts each wheel 720 and 730 about its aforementioned (tilt) axis of rotation to allow proper wheel contact with the pipe on this complex path, while also pivoting the rear wheels 730 about their pivot axis of rotation to allow the rear wheels 730 to properly track the rest of the crawler 700.

[0047] 8A-8B are rear views of an example magnetic crawler 800 having only three articulated magnetic wheels (including two drive wheels 820 and a rear wheel 830) moving over a pipe 40, showing the rear wheel 830 before and after making tangential contact with the pipe surface, respectively, according to one embodiment.

[0048] In further detail, referring to FIGS. 8A-8B, the magnetic crawler 800 moves along a spiral path on the 6-inch pipe 40. FIG. 8A shows the second degree of freedom of the rear wheels 830 before they are tilted (and form only contact point 831 with the pipe 40). That is, the caster wheels 830 contact the pipe 40 at a single point 831 (e.g., the bottom end of the wheels 830). This reduces magnetic adhesion and may scratch the outer surface of the pipe. In contrast, FIG. 8B shows the second degree of freedom of the rear wheels 830 after they are tilted (and form a contact line 833, or a tangential contact as close to a line as possible). Thus, there is a proper contact line 833 between the caster wheels 830 and the pipe 40. This contact line 833 also maximizes the magnetic force between the rear wheels 830 and the pipe surface. This also applies to the two front articulated (drive) wheels 820.

[0049] In some embodiments, another important feature utilized from the four degrees of freedom is through measuring the angles of these degrees of freedom. As previously mentioned, the degrees of freedom provide the magnetic crawler with the ability to move in various configurations or trajectories, such as circumferential, spiral, and longitudinal, on curved surfaces. To keep the crawler on a desired trajectory, in some embodiments, measured angular feedback from the degrees of freedom is input to a controller (such as controller 160), which is configured by code to provide the necessary corrective feedback to the drive motors to keep the crawler on the desired trajectory. The angular feedback can be sensed, for example, using a potentiometer, an encoder, or any other form of angle measurement sensor from any combination thereof.

[0050] 9A-9C are top views of an example magnetic crawler 900 with only three articulated magnetic wheels showing example angular measurements of the pivoting 939 of the rear wheels 930 relative to the crawler chassis 910 compared to a central orientation, with the pivoting 939 of the rear wheels 930 facing left, center, and right, respectively, according to one embodiment. Because the rear wheels 930 track the crawler chassis 910, the amount of pivoting 939 of the rear wheels 930 represents the degree to which the crawler 900 deviates from a straight line path (relative to the surface on which the crawler 900 is moving).

[0051] 9A-9C, in further detail, swivel 939 represents the angle of caster wheel 930 that needs to be corrected through feedback to keep crawler 900 moving straight. If caster wheel 930 deviates from the centerline (e.g., FIGS. 9A and 9C with non-zero swivel), correction angle 939 (i.e., the angle between the dashed and solid reference lines) is input to a controller, which is programmed to command the drive motors to adapt accordingly to maintain caster wheel 930 in a straight configuration (e.g., FIG. 9B).

[0052] 10A-10B are front views of an example magnetic crawler 1000 having only three articulated magnetic wheels (including two drive wheels 1020 and a rear wheel 1030) showing example angular measurements of the tilt 1027 of the right and left drive wheels 1020 relative to the crawler chassis 1010 on curved surface 40 and flat surface 20, respectively, compared to a reference direction, according to one embodiment. Here, the tilt 1027 is measured by a component (in this case, the wheel holder 1024, as shown by the solid line) whose orientation changes directly with tilt relative to the crawler chassis 1010 (as shown by the vertical or dashed line).

[0053] 10A-10B, FIG. 10A shows a crawler 1000 traversing a curved surface (or pipe) 40 longitudinally along the length of the pipe 40 (in this example, on top of the pipe 40). As the crawler 1000 moves longitudinally along the top of the pipe, it maintains the same tilt (but in opposite directions) for the two drive wheels 1020 without tilting or pivoting the rear wheels 1030 together (or more specifically, the controller is programmed to use the measured angles to drive the wheel motors to maintain this). 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 steer and correct the crawler's path (via the drive wheels 1020) to keep the crawler 1000 straight over the pipe 40. FIG. 10B shows how the controller can be programmed to determine when the crawler 1000 is on a flat surface 20 since no tilt or rotation is measured at the wheels when the crawler 1000 moves around in a straight line.

[0054] Figure 11A shows an example magnetic crawler 1100 with only three articulated magnetic wheels moving along a spiral path on a pipe 40, according to one embodiment. Figure 11B is a close-up rear view of the magnetic crawler 1100 of Figure 11A, showing the passive adjustment of the rear wheels 1130 in the tilt direction to track the curved surface of the pipe 40 on the spiral path.

[0055] 11A-11B, the crawler 1100 is shown helically traversing the surface of the pipe 40, where the measured angles of the articulation joints are input to a controller. The controller is programmed or otherwise configured (e.g., by code or logic) to detect any deviations in the measured angles and what would be expected at the desired helical pitch. The controller is further programmed or otherwise configured to use any such measured deviations to adjust the drive of the drive wheels to return the crawler 1100 to the desired helical pitch of the traverse and ensure proper and accurate tracking along the desired helix.

[0056] The crawler 1100 traversing the spiral path demonstrates the importance of four degrees of freedom for the three articulated magnetic wheels. As the crawler 1100 begins its spiral path on the pipe 40, the second degree of freedom (tilt) in the caster wheel 1130 rotates due to its passive self-tuning design. The adjusted rotation angle 1135 is shown in FIG. 11B. This angle 1135 varies for different spiral trajectories depending on factors such as the spiral pitch. The controller is further configured to use feedback from this joint (such as angle measurement feedback) to control the actuation of the drive wheels to ensure the crawler 1100 follows the desired spiral path without significant deviations and to correct or compensate for any significant deviations detected.

[0057] A controller (such as controller 160) is programmed or otherwise configured to control some aspects of the magnetic crawler. In an example embodiment, the controller is programmed to control drive motors to independently power two magnetic drive wheels to steer the magnetic crawler over a ferromagnetic curved surface. In some such embodiments, the controller is programmed to control a probe on the crawler to inspect the surface while moving over it. In some embodiments, the controller is programmed to use angle measurement feedback from each of the four revolute joints as feedback to adjust the drive of the crawler to reach or maintain a desired trajectory over the surface.

[0058] In some embodiments, the controller is programmed to combine the mathematical model into an accurate estimate of the crawler's attitude and its orientation relative to the pipe, based on the crawler's geometry (e.g., location of the axis of rotation) and angle data from the revolute joints. In some such embodiments, the controller is further configured to use this attitude estimate to keep the crawler on a desired trajectory. In some such embodiments, the controller is further programmed to improve the accuracy of this attitude estimate and course-keeping by fusing the attitude estimate with additional data, for example, from an inertial measurement unit (IMU), a satellite navigation system (e.g., GPS), or known geometry of the surroundings (such as the pipe diameter the crawler is traversing).

[0059] In some embodiments, the controller is programmed to use feedback from the joint angle measurements to better control and track the trajectory of the magnetic crawler. In some such embodiments, the controller is programmed to control the execution of an inspection scan of the curved ferromagnetic surface over this trajectory by controlling a probe (such as a UT thickness sensor) to periodically or continuously inspect the surface while correlating this inspection data with determined locations on the surface of the pipe where the data was acquired. In some such embodiments, the controller is further programmed to improve the quality of the inspection scan through strengthening the correlation between the inspection data and the locations on the surface of the pipe being inspected (e.g., through better pose estimation, crawler movement, or use of revolute joint angle measurements, to name a few).

[0060] In some embodiments, the controller is programmed to control the crawler-mounted UT thickness probe to take pipe thickness measurements in a B-scan (or continuous linear) approach, e.g., longitudinally along the length of the pipe (parallel to the pipe axis) or circumferentially around the circumference of the pipe (equidistant from a point on the pipe axis). In some embodiments, the controller is programmed to control the UT thickness probe to take pipe thickness measurements in a C-scan (or full two-dimensional surface mapping) approach. In some such embodiments, the controller is programmed to perform C-scans by traversing the pipe in a helical path with a helical pitch small enough to cover the surface of the pipe (e.g., to a desired density of UT thickness measurement locations that effectively creates a surface thickness map of the entire two-dimensional surface area of ​​the pipe).

[0061] In some embodiments, the described locomotion system (e.g., three articulated magnetic wheels with two independently driven active wheels and one passive rear wheel, with tilt rotation joints on all three wheels and also a swivel rotation joint on the rear wheel) enables the magnetic crawler (as controlled by a controller programmed to control the crawler) to travel not only on convex surfaces, such as the exterior surfaces of pipes, straight pipes, storage tanks, etc., but also on concave surfaces, such as the interior surfaces of pipes and the exterior surfaces of elbows (e.g., elbows or elbow-pipe joints having both convex and concave portions).

[0062] 1-11B, in some exemplary embodiments, a magnetic crawler (such as magnetic crawler 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1100) is provided that moves over and inspects a ferromagnetic cylindrical surface (such as a pipe 40 or a storage tank). The magnetic crawler includes a chassis (such as crawler chassis 110, 210, 310, 410, 510, 610, 910, or 1010), a controller (such as controller 160) coupled to the chassis, a probe (such as UT probe 150) coupled to the chassis, and only three articulated magnetic wheels coupled to the chassis. The controller (e.g., a microprocessor) is configured by code 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 (such as drive wheels 120, 220, 320, 420, 720, 820, or 1020) and one passive rear wheel (such as rear wheel 130, 230, 330, 430, 530, 630, 730, 830, 930, 1030, or 1130). The magnetic wheels contact and magnetically attach to the cylindrical surface tangentially (e.g., linearly, or as close to a line as possible).

[0063] The right and left drive wheels are coupled to the chassis by right and left articulation joints (such as wheel holders 224 or 1024), respectively. Additionally, the right and left drive wheels independently and actively rotate about their respective right and left drive rotation axes using respective right and left drive motors (such as drive motor 222) under the control of a controller to drive the magnetic crawler in a desired direction (e.g., longitudinally, circumferentially, or helically) on the cylindrical surface. The rear wheels are coupled to the chassis by rear articulation joints (such as inner caster wheel holder 234 and outer caster wheel holder 236). Additionally, the rear wheels passively rotate about their rear drive rotation axes in response to the active rotation of the right and left drive wheels.

[0064] The right and left articulation joints provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt rotation axes (such as front tilt rotation axis 242) for tilting the right and left drive wheels relative to the chassis to maintain tangential contact with the curvature of the cylindrical surface. The rear articulation joint provides two degrees of freedom of rotation of the rear wheels relative to the chassis about a rear tilt rotation axis (such as rear tilt rotation axis 244) and a swivel rotation axis perpendicular to the rear tilt rotation axis (such as swivel rotation axis 246). The rear tilt rotation axis tilts the rear wheels relative to the chassis to maintain tangential contact with the curvature of the cylindrical surface. The swivel rotation axis responsive to drive of the magnetic crawler allows the rear wheels to pivot in a desired direction relative to the chassis.

[0065] In one embodiment, the right and left drive wheels independently actively rotate in either forward or reverse directions about their respective right and left drive rotation axes (to provide differential steering and in-place rotation) using their respective right and left drive motors under the control of a controller. In one embodiment, the magnetic crawler further includes angle measurement sensors coupled to the chassis. The angle measurement sensors measure, under the control of the controller, the respective angles of tilt (such as tilt 1027) of the three magnetic wheels relative to the chassis and the angle of turn (such as turn 939) of the rear wheels relative to the chassis. In one embodiment, the controller is further configured by the code to maintain the magnetic crawler on a desired trajectory on the 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 having a desired helical pitch on the cylindrical surface.

[0066] In one embodiment, the probe includes an ultrasonic testing (UT) sensor that, under control of the controller, non-destructively measures the thickness of the cylindrical surface. Additionally, the controller is further configured by code to perform two-dimensional mapping (such as a C-scan) of the surface thickness across the cylindrical surface by controlling the UT sensor to measure the surface thickness while controlling the drive of the right and left drive wheels along a helical path. In one embodiment, the controller is further configured by code to estimate the orientation of the magnetic crawler relative to the cylindrical surface using the measured angle and the geometry of the magnetic crawler. In one embodiment, the rear articulation joint provides the rear wheels with 360° of rotation about the rear pivot axis. In one embodiment, the cylindrical surface is a portion of a carbon steel pipe or a vessel (such as a storage tank).

[0067] 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 their assigned tasks. These devices are located on or within (or otherwise near) the chassis of the magnetic crawler to perform these techniques. In some example embodiments, control logic is implemented as computer code configured to run on computing circuitry (such as a microprocessor) that performs the control steps that are part of the techniques.

[0068] 12 is a flow diagram of an example automated method 1200 for moving over and inspecting a ferromagnetic cylindrical surface (such as pipe 40) using a magnetic crawler (such as magnetic crawler 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1100) having only three articulated magnetic wheels, according to one embodiment. The magnetic crawler includes a chassis (such as crawler chassis 110, 210, 310, 410, 510, 610, 910, or 1010), a controller (such as controller 160) coupled to the chassis, a probe (such as UT probe 150) coupled to the chassis, and only three articulated magnetic wheels coupled to the chassis. Method 1200 is partially or fully automated under the control of an electronic controller, which is configured (e.g., programmed, e.g., by code) to perform the steps of method 1200. The three magnetic wheels include right and left drive wheels (such as drive wheels 120, 220, 320, 420, 720, 820, or 1020) coupled to the chassis by right and left articulation joints (such as articulation wheel holders 224 and 1024), respectively, and rear wheels (such as rear wheels 130, 230, 330, 430, 530, 630, 730, 830, 930, 1030, or 1130) coupled to the chassis by rear articulation joints (such as inner caster wheel holder 234 and outer caster wheel holder 236).

[0069] Some or all of method 1200 can be implemented using the components and techniques illustrated in FIGS. 1-11B. Additionally, some of this and other methods disclosed herein can be implemented on or using an on-board controller, such as a custom or pre-programmed logic device, circuit, or processor, such as a programmable logic circuit (PLC), computer, software, or other circuit (e.g., ASIC, FPGA) configured with code or logic to perform its assigned tasks. The device, circuit, or processor can also be, for example, a dedicated or shared hardware device (such as a laptop, single-board computer (SBC), workstation, tablet, smartphone, part of a server, or dedicated hardware circuit, such as in an FPGA or ASIC), or computer server, or part of a server or computer system. The device, circuit, or processor can include a non-transitory computer-readable medium (e.g., a read-only memory (ROM), flash drive, or disk drive) storing instructions that, when executed on one or more processors, cause portions of method 1200 (or other disclosed methods) to be performed. It should be noted that in other embodiments, the order of operations can be changed and some of the operations can be omitted. Some of the method 1200 may also be performed using logic, circuitry, or a processor located on or in electronic communication with a processing circuit configured with code that performs those portions of the method 1200.

[0070] In method 1200, processing begins at step 1210, inspecting a ferromagnetic cylindrical surface with a probe as controlled by a controller (e.g., performing a UT thickness measurement with UT probe 150). Additionally, method 1200 includes step 1220, magnetically attaching (e.g., linear contact or as close to linear contact as possible) to the cylindrical surface with three articulating magnetic wheels in tangential contact. Method 1200 further includes step 1230, driving the magnetic crawler in a desired direction on the cylindrical surface by actively rotating the right and left drive wheels independently about their respective right and left drive rotation axes using respective right and left drive motors (such as drive motor 222) as controlled by the controller. Method 1200 also includes step 1240, passively rotating the rear wheels about their rear drive rotation axes in response to the active rotation of the right and left drive wheels.

[0071] Additionally, method 1200 includes step 1250 of tilting the right and left drive wheels relative to the chassis while maintaining their tangential contact with the curvature of the cylindrical surface using the respective right and left articulation joints to provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt rotation axes (such as tilt rotation axis 242). Method 1200 further includes step 1260 of tilting the rear wheels relative to the chassis while maintaining tangential contact with the curvature of the cylindrical surface and using the rear articulation joints to pivot the rear wheels in a desired direction relative to the chassis in response to drive of the magnetic crawler to provide two degrees of freedom of rotation of the rear wheels relative to the chassis about the rear tilt rotation axis (such as rear tilt rotation axis 244) and a swivel rotation axis perpendicular to the rear tilt rotation axis (such as swivel rotation axis 246).

[0072] In some embodiments, actively rotating the right and left drive wheels includes actively rotating the right and left drive wheels independently in either forward or reverse directions (e.g., with differential steering or in-place rotation) about their respective right and left drive rotation axes using their respective right and left drive motors as controlled by the controller. In some embodiments, the magnetic crawler further includes angle measurement sensors coupled to the chassis, and method 1200 further includes using the angle measurement sensors as controlled by the controller to measure each angle of tilt (such as tilt 1027) of the three magnetic wheels relative to the chassis and to measure an angle of turn (such as turn 939) of the rear wheels relative to the chassis. In some embodiments, method 1200 further includes maintaining, by the controller, the magnetic crawler on a desired trajectory on the cylindrical surface by controlling the drive of the right and left drive wheels using the measured angles. In some embodiments, the desired trajectory is a helical path having a desired helical pitch on the cylindrical surface.

[0073] In some embodiments, the probe includes an ultrasonic testing (UT) sensor (such as UT probe 150), and method 1200 further includes non-destructively measuring the thickness of the cylindrical surface using the UT sensor as controlled by the controller, and performing, by the controller, two-dimensional mapping of the surface thickness across the cylindrical surface by controlling the UT sensor to measure the surface thickness while controlling drive of the right and left drive wheels along the helical track. In some embodiments, method 1200 further includes, by the controller, estimating the attitude of the magnetic crawler relative to the cylindrical surface using the measured angle and the shape of the magnetic crawler. In some embodiments, method 1200 further includes providing the rear wheels with 360° rotation about a rear pivot axis by a rear articulation joint. In some embodiments, the cylindrical surface is a portion of a carbon steel pipe or a vessel (such as a storage tank).

[0074] The methods described herein may be implemented in part by software or firmware in machine-readable form on a tangible (e.g., non-transitory) storage medium. For example, the software or firmware may be in the form of a computer program comprising computer program code adapted to perform some of the steps of any of the methods described herein when the program is executed on a computer or suitable hardware device (e.g., FPGA), and where the computer program may be embodied 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., but do not include propagated signals. While a propagated signal may reside on a tangible storage medium, the propagated signal itself is not an example of a tangible storage medium. The software may be suitable for execution on a parallel or serial processor such that the method steps can be performed in any suitable order, or simultaneously.

[0075] It should be further understood that like or similar numerals in the drawings represent like or similar elements throughout the several views, and that not all components or steps described and illustrated with reference to the figures are required for all embodiments or configurations.

[0076] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will be further understood that as used herein, the terms "comprises" and / or "comprising" specify the presence of stated 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.

[0077] Orientational terms are used herein merely for convenience and reference purposes and should not be construed as limiting. However, it is recognized that these terms may be used with respect to the viewer. Therefore, no limitation is implied or should be inferred. Additionally, the use of ordinal numbers (e.g., first, second, third) is for purposes of distinction, not counting. For example, the use of "third" does not imply a corresponding "first" or "second." Also, the phraseology and terminology used herein are for purposes of description and should not be considered limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein means the inclusion of the subsequently listed items and equivalents thereof, as well as additional items.

[0078] The above-described subject matter is provided by way of example and should not be construed as limiting. Various modifications and variations can be made to the subject matter described herein without following the example embodiments and applications shown and described, and without departing from the true spirit and scope of the invention encompassed by this disclosure, as defined by the set of provisions in the following claims and by structures and functions or steps equivalent to those provisions. [Explanation of symbols]

[0079] 100 Magnetic Crawlers 110 crawler chassis 120 front drive wheels 130 Rear caster wheel 150 UT probe 160 Controller 200 Magnetic Crawler 210 crawler chassis 220 front drive wheels 222 Drive motor 224 Articulated Wheel Holder 230 Rear caster wheel 234 Inner wheel holder 236 Outer wheel holder 240 Rotational Axis 242 Front tilting axis 244 Rear tilting rotation axis 246 Swivel Axis 20 planes 40 curved surface 300 Magnetic Crawler 310 crawler chassis 320 Drive Wheel 330 rear wheel 400 Magnetic Crawler 410 crawler chassis 420 front drive wheels 430 Rear caster wheel 500 Magnetic Crawler 510 crawler chassis 530 rear wheel 600 Magnetic Crawler 610 chassis 630 rear wheel 700 Magnetic Crawler 720 Drive Wheel 730 rear wheel 800 Magnetic Crawler 820 Drive Wheel 830 rear wheel 831 Contact points 833 Contact Line 900 Magnetic Crawler 910 crawler chassis 930 rear wheel 939 Turn 1000 Magnetic Crawlers 1010 Crawler Chassis 1020 Drive Wheel 1024 Wheel holder 1027 Incline 1030 rear wheel 1100 Magnetic Crawler 1130 rear wheel 1135 rotation angle

Claims

1. A magnetic crawler configured to move over and inspect a ferromagnetic cylindrical surface having a thickness, 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 the control of the controller; only three articulated magnetic wheels coupled to the chassis and configured to contact and magnetically adhere to the cylindrical surface; right and left drive wheels respectively coupled to the chassis by right and left articulated joints and configured to drive the magnetic crawler in a desired direction on the cylindrical surface by independent active rotation about respective right and left drive rotation axes using respective right and left drive motors under the control of the controller; rear wheels coupled to the chassis by rear articulated joints and configured to passively rotate about rear drive rotation axes in response to the active rotation of the right and left drive wheels; only three articulated magnetic wheels, including: Including, the right and left articulation joints respectively provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt rotation axes to tilt the right and left drive wheels relative to the chassis to maintain said contact with the curvature of the cylindrical surface; the rear articulation joint provides two degrees of freedom of rotation of the rear wheels relative to the chassis about a rear tilt axis of rotation and a pivot axis of rotation perpendicular to the rear tilt axis of rotation, the rear tilt axis of rotation tilting the rear wheels relative to the chassis to maintain the contact with the curvature of the cylindrical surface, and the pivot axis of rotation pivoting the rear wheels relative to the chassis in the desired direction in response to the driving of the magnetic crawler. Magnetic crawler.

2. 2. The magnetic crawler of claim 1, wherein the right and left drive wheels are further configured to independently actively rotate in either a forward or reverse direction about their respective right and left drive rotation axes using their respective right and left drive motors under control of the controller.

3. 2. The magnetic crawler of claim 1, further comprising an angle measurement sensor coupled to the chassis and configured under control of the controller to measure the angle of each of the tilt of the three magnetic wheels relative to the chassis and to measure the angle of the pivot of the rear wheels relative to the chassis.

4. 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 drive of the right and left drive wheels using the measured angle.

5. The magnetic crawler of claim 4 , wherein the desired trajectory is a helical path having a desired helical pitch on the cylindrical surface.

6. 6. The magnetic crawler of claim 5, wherein the probe includes an ultrasonic testing (UT) sensor configured to non-destructively measure a thickness of the cylindrical surface under control of the controller, the controller being further configured to perform two-dimensional mapping of the thickness across the cylindrical surface by controlling the UT sensor to measure the thickness while controlling drive of the right and left drive wheels along the helical path.

7. The magnetic crawler of claim 3 , wherein the controller is further configured to estimate an attitude of the magnetic crawler relative to the cylindrical surface using the measured angle and location of the axis of rotation.

8. The magnetic crawler of claim 1 , wherein the rear articulation joint is configured to provide 360° of rotation to the rear wheels about the pivot axis of rotation.

9. The magnetic crawler of claim 1 , wherein the probe includes an ultrasonic testing (UT) sensor configured to non-destructively measure a thickness of the cylindrical surface under 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. 1. An automated method for moving over and inspecting a ferromagnetic cylindrical surface using a magnetic crawler including: a chassis; a controller coupled to the chassis; a probe coupled to the chassis; and only three articulated magnetic wheels coupled to the chassis, the magnetic crawler including right and left drive wheels coupled to the chassis by right and left articulation joints, respectively, and rear wheels coupled to the chassis by rear articulation joints, the method comprising: inspecting the ferromagnetic cylindrical surface with the probe as controlled by the controller; contacting and magnetically adhering to the cylindrical surface with the three articulated magnetic wheels; driving the magnetic crawler in a desired direction on the cylindrical surface by active rotation of the right and left drive wheels independently about respective right and left drive rotation axes using respective right and left drive motors as controlled by the controller; passively rotating the rear wheels 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 their contact with the curvature of the cylindrical surface using the respective right and left articulation joints to provide a single degree of freedom of rotation of the right and left drive wheels relative to the chassis about respective right and left tilt rotation axes; tilting the rear wheels relative to the chassis while maintaining the contact with the curvature of the cylindrical surface and using the rear articulation joint to pivot the rear wheels relative to the chassis in the desired direction in response to the driving of the magnetic crawler to provide two degrees of freedom of rotation of the rear wheels relative to the chassis about a rear tilt axis of rotation and a pivot axis of rotation perpendicular to the rear tilt axis of rotation; An automated method, including:

12. 12. The method of claim 11, wherein actively rotating the right and left drive wheels comprises actively rotating the right and left drive wheels independently in either forward or reverse directions about their respective right and left drive rotation axes using their respective right and left drive motors as controlled by the controller.

13. 12. The method of claim 11, wherein the magnetic crawler further includes an angle measurement sensor coupled to the chassis, the method further including using the angle measurement sensor as controlled by the controller to measure the angle of each of the tilt of the three magnetic wheels relative to the chassis and to measure the angle of the turn of the rear wheels relative to the chassis.

14. 14. The method of claim 13, further comprising the step of: maintaining, by the controller, the magnetic crawler on a desired trajectory on the cylindrical surface by controlling the drive of the right and left drive wheels using the measured angle.

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

16. 16. The method of claim 15, wherein the probe includes an ultrasonic testing (UT) sensor, the method further comprising: non-destructively measuring a thickness of the cylindrical surface using the UT sensor as controlled by the controller; and performing, by the controller, two-dimensional mapping of the thickness across the cylindrical surface by controlling the UT sensor to measure the thickness while controlling drive of the right and left drive wheels along the helical path.

17. The method of claim 13 further comprising estimating, by the controller, an attitude of the magnetic crawler relative to the cylindrical surface using the measured angle and axis of rotation location.

18. 12. The method of claim 11, further comprising providing 360 degrees of rotation to the rear wheels about the pivot axis of rotation with the rear articulation joint.

19. 12. The method of claim 11, wherein the probe includes an ultrasonic testing (UT) sensor, the method further comprising non-destructively measuring a thickness of the cylindrical surface using the UT sensor as controlled by 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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