Patent Publication Number: US-2021170826-A1

Title: Systems and methods for detecting characteristics of a multi-oriented surface

Description:
TECHNICAL FIELD 
     The invention relates generally to a device having thrust system for the purpose of adhering to a multi-oriented surface as the device traverses the environment. 
     BACKGROUND 
     Inspecting and operating on surfaces presents challenges to humans, particularly in confined spaces, large spaces, overhead areas, and when working on surfaces that are delicate or have pressure sensitivities. Inspection of these type of .locations also presents risks to the humans that are asked to perform actions in such hazardous conditions. In some applications aerial drones may service to carry out such tasks but suffer their own limitations including a substantial risk of causing damage to the object or surface being inspected should the aerial done come into contact with the object. Aerial drones may also require special operator certifications and are restricted from use in certain airspaces. 
     SUMMARY OP THE DISCLOSURE 
     According to certain embodiments, a device comprises a body, a mechanical propulsion system affixed to the body to cause the body to traverse a multi-oriented surface and to prevent contact between the body and the multi-oriented surface, a thrust system to apply a thrust force to the device that opposes a gravitational force acting on the device, and a payload with at .least one sensor to detect a characteristics of the multi-oriented surface. 
     According to certain embodiments a system for detecting the characteristics of a multi-oriented surface comprises at least one device, each of which comprises a body, a mechanical propulsion system affixed to the body to cause the body to traverse a multi-oriented surface and to prevent contact between the body and the multi-oriented surface, a thrust system to apply a thrust force to the device that opposes a gravitational force acting on the device, and a payload with at least one sensor to detect a characteristics of the multi-oriented surface. The system further comprises a controller to control each device and detect the characteristics of the multi-oriented surface using the sensors. 
     According to certain embodiments a method of detecting the characteristics of a multi-oriented surface is achieved by traversing the multi-oriented surface by at least one device, each of which comprises a body, a mechanical propulsion system affixed to the body to cause the body to traverse a multi-oriented surface and to prevent contact between the body and the multi-oriented surface, and a thrust system to apply a thrust force to the device that opposes a gravitational force acting on the device, and by then detecting characteristics of the multi-oriented surface by a number of sensors. 
     Certain embodiments may provide one or more technical advantages. As an example, certain embodiments provide advantages for allowing a drone to move about the surface of an object that may have a complicated topology and/or a delicate surface. As another example, certain embodiments provide advantages for enabling a drone to move about an inverted surface of an object that may be non-magnetic or may be intolerant of vacuum forces. Another example may be that certain embodiments provide the advantage of achieving better efficiency and/or ensuring complete adhesion of the drone to a partially-inverted surface through controlling the direction and point at which the thrust force acts upon the drone. Certain embodiments may include all, some, or none of the above-described advantages. Other advantages will be apparent to those of ordinary skill in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an example crawler drone having a thrust system for adhering to a multi-oriented surface; 
         FIGS. 2 a -2 f    illustrate a sequence of conditions under which the drone may operate as it traverses a surface having a complicated series of orientations; 
         FIG. 3  illustrates a two-dimensional view of a crawler drone ascending an inclined surface with representations of the instantaneous forces acting upon the crawler; 
         FIG. 4  illustrates a three-dimensional view of a crawler drone moving horizontally across an inclined surface with representation of the instantaneous forces acting upon the crawler; and 
         FIG. 5  illustrates the minimum thrust force necessary across the entire range of; surface orientations and headings to ensure that an example crawler drone may adhere to the multi-oriented surface without failing, sliding, or tipping. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable one of ordinary skill in the art to make and use the invention. Descriptions of specific embodiments and applications are provided only as examples and various modifications will be readily apparent to those skilled in the art. The general principles described herein may be applied to other embodiments and applications without departing from the scope of the invention. Thus, the present invention is not to fee limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail. 
     Embodiments of the present disclosure and .its advantages are best understood by referring to  FIGS. 1 through 5  of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
     During manufacturing and assembly of large objects inspection and quality control may be critical, particularly for highly-sophisticated products. A large portion of this inspection and quality control is carried out by human workers. However, there may be regions of the manufactured object that are difficult to be inspected or worked on by humans. The reasons for this may range for difficult to access areas, areas that may be completely inaccessible to humans or may other wise fey confined or at great elevation requiring special certification or other precautions. These difficulties may lead to additional expense, delays, or may also present greater risk of damage to the manufactured object (e.g., where the manufactured object may be easily damaged by dropped tools) . In addition to the challenges present, to human workers, better efficiencies may be achieved by employing inspection drones. The use of drones may supplement the manned-workforce. The use of drone 3  may also be used to deploy a fleet of drones that may be coordinated to maximize efficiency. Such a fleet of drones may be deployed for use in any manner of coordination. This control and coordination may be carried out by individual control of each drone by a separate operator or controlled in groups by an operator. It is also possible to employ either semi-autonomous or completely autonomous control. Such forms of control and coordination may use pre-arranged inspection routes or inspection courses that may enable mere efficiently completion of the task. 
     Recently, aerial drones have become more prevalent. These aerial drones, such as quadcopter or multi-rotor drones, present certain benefits as described above by have their own set of limitations. Current aerial drones are generally not well suited for performing inspections in particular orientations and may also have difficultly transitioning between orientations. Furthermore, an aerial drone may present a greater risk of causing damage to the objected to be inspected. For example, quadcopters with exposed blades may cause significant damage to an object if the rotating blades come into contact with the surface of the object. Another drawback of aerial drones is that in particular locations they may have certain restrictions, for example. Federal Aviation Administration approval or line of sign restrictions. Of course, the rapid consumption of power reserves required to continuously suspend the aerial drone makes such aerial drones less effective for carrying out inspections where an object may have a large surface to inspect that could otherwise be accomplished beneath a drone resting on the surface. Other types of drones, such as those that use magnets or suction forces to adhere to a surface, may not be suitable for many applications. Tor instance, this mechanism of adhering to a surface would not be suitable for non-magnetic objects or objects that have a surface that is intolerant of vacuum forces (e.g., thin-film surfaces or surfaces that may be destroyed by small scrapes). A number of ether drawbacks to existing designs are al 3 c well known in the art.  FIG. 1  illustrates an example crawler drone  100  that that may be used to traverse a multi-oriented surface  120 . Multi-oriented surface  120  may include a particularly challenging surface to completely traverse. For example, in the aerospace manufacturing industry a multi-oriented surface  120  may be either the internal or external surface of an aircraft fuselage, a confined fuel tank incorporated into the wing of an aircraft, or a tail vertical stabilizer that would otherwise require a human technician to use scaffolding and a harness to reach. Multi-oriented surface  120  may also be located in an environment inhospitable to humans such as an environment with extreme temperature or where contaminants and other environmental pollutants are present. 
     There may be a number of characteristics associated with the multi-oriented surface  120 . For instance, the characteristics of the multi-oriented surface  120  may include the tensile strength, pressure rating, and magnetic properties of the multi-oriented surface  120 . The characteristics of the multi-oriented surface  120  may also include, for example, one or more defects  121  in the manufacturing of the multi-oriented surface  120 . As an example, defect  121  may include any form of flaw such as a surface scratch, blemish, cracks, delamination, spalling, cavities, improper welds, or other assembly flaws. 
     Crawler drone  100  may have a body  101  providing structure to the drone and supporting other systems of crawler drone  100 . Crawler drone  100  may also have a mechanical propulsion system  102  affixed to the crawler drone  100 . As illustrated, the mechanical propulsion system  102  of crawler drone  100  includes four wheels. The mechanical propulsion system  102  may include any number of wheels, continuous tracks, omni-directional ball wheels, and casters depending on the application and the characteristics of the particular multi-oriented surface  120 . For instance, wheels of a greater width or tracks may be selected for a particularly delicate multi-oriented surface  120  to ensure greater distribution of the weight of crawler drone  100  or greater of the thrust force through the mechanical propulsion system  102  onto the multi-oriented surface  120 . The mechanical propulsion system  102  may also include a motor  102   a  to turn the wheels or tracks of the crawler drone  100  to enable the crawler drone to drive or traverse the multi-oriented surface  120 . The mechanical propulsion system  102  may include any number of electric motors, in the illustrated embodiment the mechanical propulsion system  102  include one electric motor  102   a  at each of the wheels. 
     The wheels or tracks of mechanical propulsion system  102  may supported by a suspension system  103 . As illustrated, the suspension system  103  is integrated as part of crawler drone  100  and may be affixed to body  101 . The suspension system  103  may serve to ensure that all of the wheels or a sufficient portion of the tracks of mechanical propulsion system  102  remains in contact with the multi-oriented surface  120 . In certain embodiments the suspension system may have actuators  103   a  for the purpose of raising, lowering, or: adjusting the tilt, or orientation of the body  101  and the entire crawler drone  100  with respect to the multi-oriented surface  120 . This may be done to lift the body  101  of crawler drone  100  over a protrusion of the multi-oriented surface  120  so as to ensure that the crawler drone  100  may be completely contact free as it traverses the multi-oriented surface  102 , other than the contact between the mechanical propulsion system  102  and the multi-oriented surface  120 . Additionally, actuators  103   a  may be selectively engaged to tilt the crawler drone  100 . This may have particular benefits as will be described in further detail with respect to the descriptions of  FIGS. 3-5 . 
     The crawler drone  100  also includes a thrust system  104  to provide a normal force on the crawler drone  100 . The normal force applied to the crawler drone  100  by the thrust system  104  may assist the crawler drone  100  in adhering to multi-oriented surface  120 . When the thrust system  104  is sized correctly it may provide a sufficient normal force to ensure that the mechanical propulsion system  102  of the crawler drone  100  maintains contact with the multi-oriented surface  120  through the full range of orientations, including a completely inverted orientation. In such an instance the thrust system  104  must provide a thrust force that is greater than the gravitation force acting upon the crawler drone  100 . The appropriate thrust force is further detailed with respect to the disclosure of  FIG. 5  herein. It is also recognized that the thrust system  104  may also be configured so a to reduce the negative suction pressure at the bottom of the crawler drone  100  that may otherwise be problematic to the face of particularly delicate multi-oriented surfaces  120 . This may be accomplished by, for example, locating the intakes for the thrust system  104  at the sides of the body  101  so as to draw in air at the sides and avoid the possibility of a vacuum occurring on the face of the multi-oriented surface  120 . 
     As illustrated in  FIG. 1  the thrust system is incorporated into body  101  but other configurations for thrust system  104  are also envisioned, for example, external rotor blades. Furthermore, in certain embodiments thrust system  104  may include more than one ducted fan, for instance four ducted fans may ail be located about the periphery of body  101  such that the power of each ducted fan may be controlled to cause a moment to act about the center of gravity of the crawler drone  100 . This moment may be beneficial to cause the suspension system  103  to slump thereby resulting in the angle of the thrust force applied to the crawler drone  100  by the thrust system  104  to be slightly off from normal. In certain other embodiments, the thrust system  104  nay include control vanes to adjust the angle of the thrust force. As may be appreciated, this angling of the thrust force may help to control the force applied by the mechanical propulsion system  102  to the multi-oriented surface  120  in situations where the characteristics of the multi-oriented surface  120  cannot support a large force. This angling of the thrust force may also be beneficial in assisting the mechanical propulsion system  102  in mounting an inclined portion of the multi-oriented surface. This angled thrust force will be described in further detail with respect to the descriptions associated with  FIGS. 2 a   - 3 . 
     Crawler drone  100  also includes a payload  105  for accomplishing a host of tasks. As illustrated, crawler drone  100  has a sensor for detecting defects  121  associated with the multi-oriented surface  120 . The sensor of payload  105  may be any combination of a visual-spectrum camera, an infrared camera, a thermal camera, a laser scanner, an X-ray module, an ultrasonic non-destructive testing module, or any other type of sen 3 or for determine characteristics associated with the multi-oriented surface  120 . As the crawler drone  100  traverses the multi-oriented surface  120  the sensor of payload  105  may detect a detect  121 . These detected defects  121  may be captured in the recorded data or otherwise identified. For example, the crawler drone  100  may indicate the presence of the defect  121  by placing a marker on the multi-oriented surface  120  that is near the defect  121 . Such markers may include an ink mark, a paint mark, a sticker, or other conceivable marker. In certain other embodiments payload  105  may al 3 c include a tool for making repairs to the defect  121  of the multi-oriented surface  120 . Tools equipped to the payload  105  may include a paint applicator, a sealant applicator, a glue applicator, a sanding apparatus, a debarring apparatus, a cutting apparatus, a welding apparatus, a rivet applicator, a marker, a sticker applicator, or any other tool as may readily be apparent to one of skill in the art of manufacturing. In other embodiments, the payload  105  may also include a tool delivery system for transporting a tool to a human work, or other system to carry out the repair. 
     The crawler drone  100  may also include a controller  106 . As illustrated, the controller  106  is mounted to the body  101  of the crawler drone  100 . This configuration may be used for an autonomous crawler drone  100  but may also be used for manual or semi-autonomous control where the directions are provided to the controller  106  through wireless communication (e.g., Bluetooth, Wi-Fi, or other radio telecommunications). However, in certain other embodiments, the controller may be located remote to the crawler drone  100 . For example, a tether may be communicatively coupled with the crawler drone  100  to provide direction and control to the crawler drone. Controller  106  may also have various inputs and outputs to facilitate the retrieval of data from the sensor of payload  105  (e.g., USB, MicroSD, remote media streaming, as well as other storage devices). 
       FIGS. 2 a -2 f    illustrate a sequence of transitions performed by a simplified representation of a crawler drone  200 , such as that illustrated in  FIG. 1 , as it traverses a complex multi-oriented surface  220 . A number of simplified forces acting upon the crawler drone  200  are represented in each of the  FIGS. 2 a -2 f   . These forces correspond as follows: F T  is the thrust force applied by the thrust system  104 ; F N  is the effective normal force from the multi-oriented surface  220  acting upon the crawler drone  200 ; mg is the force of gravity acting upon the crawler drone  200 ; and F f  is the friction force acting on the wheels of the mechanical propulsion system  102 . For the four-wheeled embodiment illustrated in  FIG. 1  it is understood that there would be four friction forces, and four normal forces acting along the points of contact of each of the four wheels of the mechanical propulsion system  102 , however these forces have been simplified in their representations throughout  FIGS. 2 a -2 f    for clarify. Furthermore, the various forces as illustrated are not all to scale but; in combination with the following descriptions serve to inform some of the functionality of the crawler drone  200 . 
     As illustrated in  FIG. 2 a   , when the crawler drone  200  is scaling a vertically-oriented multi-oriented surface  220  the thrust force is directed towards the bottom of the multi-oriented surface that, in combination with the friction force of the mechanical propulsion system  102 , causes the crawler drone  200  to adhere to the multi-oriented surface. With a sufficient thrust force from the thrust system  104 , the mechanical propulsion system  102  may locomote around the multi-oriented surface  220 . As illustrated in  FIG. 2 a    the crawler  220  my traverse the vertical-portion of the multi-oriented surface in an upward direction until it reaches the position as illustrated in  FIG. 2 b   . By slightly angling the thrust force applied to the crawler drone  200  by to the thrust system  104 , the normal component of the thrust force may lessen the force applied to the multi-oriented surface  220  and the vertical component may also assist the mechanical propulsion system  102  in overcoming the gravitational force in the direction of travel. 
     As illustrated in  FIG. 2 b   , the suspension system  103  may be capable of lifting the body  101  of the crawler drone  200 , such as by actuators  103 , above any point of the multi-oriented surface  220  to avoid any damage that might result from contact or even with placing the thrust system  104  within close proximity of the multi-oriented surface  220 . 
     As the crawler drone  200  transitions from the vertical orientation of  FIG. 2 a   , to an inclined orientation of  FIG. 2 b   , then to a horizontal orientation as illustrated in  FIG. 2 c   , the thrust force produced by the thrust system  104  may be progressively decreased until, in some embodiments, it may ultimately be completely reduced to a zero-magnitude condition once the crawler drone is on a level plane, such as illustrated in  FIG. 2 c   . In  FIG. 2 c    the crawler drone  200  may traverse the multi-oriented surface  200  powered entirely by the mechanical propulsion system  102 . In other embodiments the crawler drone  200  may traverse the multi-oriented surface  200  by applying a thrust force by the thrust system  104  angled in the direction of travel, in such a case the friction force would act in the opposite direction as that illustrated in  FIG. 2   c.    
     In  FIG. 2 d    the crawler drone  200  is shown transitioning the multi-oriented surface  220  from a horizontal orientation to a vertical orientation. Here, the thrust system  104  may again need to be engaged to ensure a sufficient friction force may result at each of the points of contact of the mechanical propulsion system  102 . Additionally, depending on the length of overhang between the body  101  of the crawler drone  200  and the radius of transition or curvature of the multi-oriented surface  220 , the suspension system  103  may raise the body  101  or extend the mechanical propulsion system  102  to avoid contact with the multi-oriented surface  220 . 
     For purposes of brevity, the next orientation shown in  FIG. 2 d    occurs after the crawler drone has transitioned through the vertical portion. Reference may be made to the description with respect to  FIG. 2 a    for the intermediate operation of the crawler drone  200  between  FIGS. 2 c  and 2 d   . In many respects, the operation of the crawler drone  200  in traversing the concave transition of  FIG. 2 e    will be similar to that of  FIG. 2 d    with the notable distinction that the thrust force will be greater in the partially-inverted orientation of  FIG. 2 e   . This effect occurs because the thrust force of the thrust system  104  as oriented In  FIG. 2 e    is opposed to the gravitational force acting on the crawler drone  200  compared with the orientation show in in  FIG. 2   d.    
     Lastly, as illustrated in  FIG. 2 f   , the crawler drone  200  is in a completely-inverted orientation. In order to remain adhered to the multi-oriented surface  220 , the thrust system  104  must produce a thrust force at least as great as the gravitational force acting on the crawler drone  200 . In certain embodiments, when in the fully inverted orientation, the thrust system may be at its greatest thrust output, however, as described further with respect to  FIG. 5 , in certain instances this may not be the case. 
       FIG. 3  illustrates a simplified free body diagram of a crawler drone  300  moving in an ascending direction along a sloped multi-oriented surface  320 . As illustrated, the crawler drone  300  has mechanical propulsion system  302  illustrated as a pair of wheels in contact with the multi-oriented surface  320 . A thrust force FT is also illustrated as effectively acting upon a point  315  within body  301  of the crawler drone  300 . Additionally, the center of gravity  310  of the crawler drone  300  is represented as a point. Other nomenclature illustrated include: θ—The angle of slope of the multi-oriented surface  320 ; mg—The gravitation force acting upon the crawler drone  300 ; F T —The thrust force produced by the thrust system  104 ; β—The angle of the thrust force off from normal to the multi-oriented surface  320 ; L—The length of the wheelbase of the mechanical propulsion system  302 ; L C —The distance between the front of the mechanical propulsion system  302  and the center of gravity  310 ; L T —The distance between the front of the mechanical propulsion system  302  and the point  315  upon which the thrust force acts; h C —The distance from the center of gravity  310  of the crawler drone  300  to the multi-oriented surface  320 ; h T —The distance from the point  315  upon which the thrust force acts to the multi-oriented surface  320 ; F Nf, Nr —The normal force applied to the front and rear wheels of the mechanical propulsion system  302 , respectively; and F ff, fr —The frictional force applied to the front and rear wheels of the mechanical propulsion system  302 , respectively. 
     Consideration of the distances between the point  315  and the center of gravity  310  may be used to control the rotational moment applied to the crawler drone  300 . This distance from the point  315  to the center, of gravity  310  may be controlled, for example, where a thrust system  104  includes more than one ducted fan by controlling the different fan speeds to locate the point of the effective thrust; force to be closer to those fans with a greater magnitude. This moment may induce a rotational force causing the suspension system  103  to slump in response to the rotational force. The slumping of the suspension system  103  therefore causes the body  301  of the crawler drone  300  to change its angle slightly. By doing so, even for embodiments of crawler drones  300  that have a fixed angle thrust system  104  the angle β of the thrust force may be controlled. Additionally, as previously described, the angle β may be adjusted either by the thrust system  104 , by an active suspension system  103  with actuators  103   a , by the thrust system  302  in combination with the suspension system  103 , or any combination thereof. 
     As a simple example, when the thrust force is held at a constant, as the angle β increases the normal forces F Nf, Nr  acting on the mechanical propulsion system  302  will decrease and the force parallel to the multi-oriented surface  320  will increase, hereinafter this parallel force that is a component of the thrust, force will be referred as a pushing force. For a range of thrust forces, there will be a corresponding angle β such that the pushing force will equal the sliding component of the gravitational force acting on the crawler drone  300  such that the crawler drone  300  may be stable in place without rolling down the multi-oriented surface  320  having a slope of θ. Either increasing the thrust force, increasing the angle β of the thrust force for the same slope of θ, or a combination thereof may cause the crawler drone  300  to move up the slope of the multi-oriented surface  320  or used in combination to assist the mechanical propulsion system  302  to traverse up the multi-oriented surface  320 . Likewise, as the thrust force and the angle β of the thrust force are decreased the sliding component, of the gravitational force may tend to cause the crawler drone  300  to roll down the multi-oriented surface  320 . This may be advantageous when it is desired to descend a multi-oriented surface by allowing the gravitational force to inherently cause the crawler drone  300  to traverse down the multi-oriented surface thereby achieving a reduction in the energy expenditure by either or both of the thrust system  104  and the mechanical propulsion system  302 . 
     Furthermore, as the angle θ of the slope of the multi-oriented surface  320  increases the angle β of the thrust force or the magnitude of the thrust force must correspondingly increase. These effects may be better described with respect to the three-dimensional depiction of a simplified crawler drone  400  as illustrated in  FIG. 4  along with the associated thrust force diagram of  FIG. 5 . 
       FIG. 4  introduces some* additional concepts to the simplified two-dimensional free body diagram of  FIG. 3 . Here, as illustrated, the crawler drone  400  has a body  401  along with a mechanical propulsion system  402 , In certain embodiments the mechanical propulsion system  402  may include four wheels for traversing the multi-oriented surface  420 . For the sake of clarity, those concepts introduced with respect to  FIG. 3  will not be repeated here and the focus will instead be directed to concepts unique to the three-dimensional representation of the crawler drone  400  on a multi-oriented surface  420 . 
     Vector notation has been implemented for the illustration of the crawler drone  400  in  FIG. 4 . In contrast to the two-dimensional representation, here the friction forces on each wheel of the mechanical propulsion system  402  there two components of the friction force illustrated as applied to each wheel. First is a friction force F f  in the direction of travel ê t  and second is a friction force F f  perpendicular to the direction of travel ê b  which accounts for the slipping force resultant from the gravitational force F g  acting on the crawler drone  400 . The third force acting on each of the wheels is the normal force F N . Each of these three forces for the four wheels are followed by a series of letters to indicate which wheel the force corresponds to. The notation scheme is as follows: Force friction or normal, front or rear, left or right, direction . For instance, the friction force F fflê     b    could otherwise be expressed as the friction force F f  for the wheel in the front f left l in the direction of ê b . Likewise, the normal force F Nrr  corresponds to the normal force F N  applied to the rear r right r wheel of the mechanical propulsion system  402 . These friction and normal forces acting on the mechanical propulsion system  402  all occur at the points of contact between the wheels and the multi-oriented surface  420  which may extend further away from the center of gravity than the edge of the body  401 , here the distance from the point of contact and the axis of rotation about the center of gravity  410  would be half the distance of L and half the distance of W. These distances are important to consider possible tipping of the crawler drone  400  across the entire range of slope angles θ of the multi-oriented surface  420 . 
     As illustrated, the crawler drone  400  is traveling in the direction ê t  along the multi-oriented surface  420  having a slope of angle θ. This represents a heading angle ϕ of ninety degrees whereas a heading angle ϕ of zero degrees would correspond to directly up the slope θ of the multi-oriented surface  420 . Likewise, a heading angle ϕ of one hundred and eighty degrees would correspond to directly down the slope θ of the multi-oriented surface  420 . In addition, internal forces resisting the change in movement of the crawler drone  400  have been accounted for and represented by F l . 
       FIG. 5  is a chart where the surface represents the minimum thrust force necessary for an example crawler drone such as the one illustrated in  FIG. 1  that undergoes the set of forces applied to it as described with respect to  FIG. 4 . This chart plots the thrust force required to be produced by the thrust system  104  along the vertical axis. Along the other two axes are the angle of slope θ or surface incline of the multi-oriented surface  120  and the heading angle ϕ of the crawler across the entire range of surface orientations and headings. Any thrust force of a magnitude greater than that indicated by the surface of the plot should be sufficient to ensure that the crawler drone  100  remains adhered to the multi-oriented surface  100  without falling, sliding, or tipping at the particular heading ϕ and slope θ. It is recognized, however, that a greater thrust force may consume energy reserves at a greater rate and may further impart an undesirably-large force on the multi-oriented surface  120  in certain instances. 
     This insight may be used to control the instantaneous thrust force to allow for some safety margin but not overconsume energy reserves, thus prolonging the duration that a crawler drone  100  may perform its operations. Furthermore, the thrust force may be controlled in relation to the normal force that would be applied to the multi-oriented surface  100  to prevent damage during the course of performing the operations of the crawler drone  100 . This insight may further be used to pre-compute an ideal path or course for a crawler drone  100 . For example, the crawler drone  100  may have a path that operates in a predominately inverted orientation to begin with while the power reserves or battery of crawler drone is at its maximum and then move to less-steep orientations as the power reserves are depleted where the energy expenditure would be less strenuous. Where multiple crawler drones  100  are employed as platoons or in a fleet the amount of operations to be performed in areas that require greater thrust forces may be more efficiently spread among the number of crawler drones  100 . These considerations and others may be programed or computed by the controller  106  either at the outset or may be dynamically calculated and communicated with other crawler drones  100  or human operators. Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     Although the present disclosure includes several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.