Abstract:
An unmanned aerial vehicle (UAV) includes a fuselage that supports breakaway components that are attached using magnets. One component is a battery pack which powers the vehicle. Another component is a rotor set including two identical pod pairs that each support a motor and a propeller. Each motor is attached to a hub assembly that includes a plurality of spokes captured in a motor hub and sandwiched by a rigid motor printed circuit board on top and a rigid hub plate. The hub assembly construction is rigid in plane and functions to keep the motor firmly stable during operation. The hub assembly is compliant and resilient when impacted parallel to the plane. Other features of the pod pairs encage the otherwise dangerous spinning propeller. This allows the vehicle to operate with a higher level of safety than conventional UAVs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/292,164, filed Feb. 5, 2016, and entitled DURABLE MODULAR UNMANNED AERIAL VEHICLE, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
     Technical Field 
       [0002]    Embodiments disclosed herein relate generally to aerial vehicles, and more particularly to structural improvements for multi-rotor unmanned aerial vehicles (UAVs) that provide for enhanced performance and more convenient portability 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]      FIG. 1  shows a quadcopter with modular components. 
           [0004]      FIG. 2  shows a quadcopter with the modular components moved away from the fuselage. 
           [0005]      FIG. 3  is a view of the bottom side of the fuselage. 
           [0006]      FIG. 4  is an exploded view of a pod pair. 
           [0007]      FIG. 5  shows a section through a pod pair. 
           [0008]      FIG. 6  shows an exploded view of a hub assembly. 
           [0009]      FIG. 7  is an exploded view of the vibration isolation sub-assembly. 
           [0010]      FIG. 8  shows a magnet with a step feature. 
           [0011]      FIG. 9  is a magnified view of a portion of the motor hub assembly. 
           [0012]      FIG. 10  is a top view of the rotor set. 
           [0013]      FIG. 11  is an enlarged detail view of the rotor set hinge. 
           [0014]      FIG. 12  shows a view of a pod pair and a detail view of the hinge. 
           [0015]      FIG. 13  shows the a rotor set in the process of folding. 
           [0016]      FIG. 14  shows two views of a fully folded rotor set and a detail view of nested spring pins. 
           [0017]      FIG. 15  shows the gimbal attached to the video processing circuit sub-system. 
           [0018]      FIG. 16  shows the gimbal detached from the video processing circuit sub-system. 
           [0019]      FIG. 17  is an exploded view of the video processing circuit sub-system and a rear view of the gimbal mechanical and electrical connection components. 
           [0020]      FIG. 18  is an exploded view of the gimbal. 
           [0021]      FIG. 19  is an angled view of the gimbal attachment location on the fuselage. 
           [0022]      FIG. 20  is a series of frames from a high-speed video of a pod pair dropped onto a hard surface. 
       
    
    
       [0023]    Like reference numbers and designations in the various drawings indicate like elements. Note that the relative dimensions of the figures may not be drawn to scale. 
       BACKGROUND 
       [0024]    Small UAVs are increasingly used for aerial reconnaissance, typically recording video and still images for later viewing, or viewing in real-time. Depending on the size and desired lift-capacity, a typical UAV is powered by either a single gas-powered engine or several electric powered motors with the required thrust for lift being generated by at least one, but usually three or more spinning propellers. Each propeller includes one or more radially disposed blades extending from a central hub. The hub of each propeller is mechanically connected, either directly or indirectly through a transmission, to the drive shaft of the engine or each motor used. At first glance, a UAV resembles a radio controlled model helicopter, except that a helicopter&#39;s conventional tail rotor is not required with a UAV since the multi-propeller design effectively cancels out any propeller-generated rotational thrust that must otherwise be controlled using a tail-rotor in single-propeller designs. 
         [0025]    As with model helicopters, the unprotected spinning blades pose a tremendous risk with the potential of inflicting damage to the craft itself or nearby property, but more importantly to the operator of the UAV or other people or animals. 
         [0026]    Many attempts have been made to protect the blades by enclosing them in rigid frame structures or using so-called prop guards, which either partially surround or fully encircle the propellers. These frame structures or guards are generally made from EPS (expanded polystyrene), injected molded plastics, or composites and although are usually effective at preventing accidental side-contact with a spinning propeller, they usually do not survive moderate impact, should the UAV impact an object during flight. These prior art prop-protecting structures typically flex and deform during impact and cause damage to the craft and the propellers. 
         [0027]    While each approach to protect the propeller from damage or contact has specific benefits, they all also include one or more weaknesses, such as being too heavy, too fragile, too large, creating excessive wind drag, or creating unwanted turbulence around the spinning propeller, which reduces performance and efficiency. Additionally, when these protections only protect the tips of the spinning propellers from the side, it remains possible to access the propellers from either the top or bottom. This accessibility creates a tremendous hazard to a person&#39;s fingers and also makes the propellers vulnerable to damage from sticks, rocks, or any other foreign objects. 
         [0028]    Another problem with conventional UAVs is that they rarely survive impact and often become “grounded” until a broken part can be repaired or replaced. The fragility of conventional UAVs is both frustrating and counter-productive to carrying out their intended task. 
       SUMMARY 
       [0029]    Certain embodiments described herein relate to a motor hub assembly, including a motor supported by a motor mount, an outer protective structure circumscribing and spaced apart from the motor mount, and a plurality of spokes extending radially outward from the mount and extending at least between the mount and the protective structure, the plurality of spokes being substantially more resistant to flexure out of a plane normal to a rotational axis of the motor than to flexure parallel to the plane normal to the rotational axis of the motor. 
         [0030]    The plurality of spokes can have a rectangular cross-section within a plane normal to a line between the motor mount and the protective structure along which the spokes extend. The assembly can include at least one propeller blade coupled to the motor and configured to rotate within a plane normal to the rotational axis of the motor. The plurality of spokes can have a cross-sectional shape which tapers to a narrower width on the side of the spokes proximate the at least one propeller blade. 
         [0031]    The motor mount can include a compliant material. The the plurality of spokes can extend along lines which do not intersect the rotational axis of the motor. 
         [0032]    The motor mount can include a central hub, the central hub including a plurality of inwardly extending slots configured to receive radially inward ends of the plurality of spokes, an upper plate overlying at least a portion of the radially inward ends of the plurality of spokes received within the plurality of inwardly extending slots, and a lower plate underlying at least a portion of the radially inward ends of the plurality of spokes received within the plurality of inwardly extending slots. The central hub can include a deformable material and can be compressed between the upper plate and the lower plate to frictionally retain the radially inward ends of the plurality of spokes. The upper plate can include a circuit board configured to carry power to the motor. 
         [0033]    The protective structure can be concentric with the motor mount. The protective structure can be concentric with an axis of rotation of the motor. The plurality of spokes can include a carbon fiber material. The plurality of spokes can include a pultruded carbon fiber material. 
         [0034]    The plurality of spokes can inhibit displacement of the motor along an axis of rotation of the motor to a greater degree than displacement of the motor within a plane normal to the axis of rotation of the motor. The the plurality of spokes can further inhibit rotation of the motor mount out of the plane normal to the axis of rotation of the motor. 
         [0035]    Some embodiments described herein relate to a motor hub assembly including a compliant motor mount, a plurality of carbon fiber spokes fastened to the motor mount and constrained compressively substantially in plane by a top rigid hub plate and a bottom rigid hub plate, and a protective outer ring, each of the plurality of fiber spokes fastened to the outer ring. The top hub plate can include a rigid circuit board configured to carry power to a motor. 
         [0036]    Some embodiments described herein relate to a thrust pod assembly including a protective structure, the protective structure including an upper portion including an inner hoop, an outer hoop, and a plurality of protective ribs connecting the inner hoop to the outer hoop, a bottom part including an outer hoop, and a cylindrical rim fastened to the outer hoop of the top part and the outer hoop of the bottom part, a compliant motor mount, and a plurality of carbon fiber spokes, each spoke fastened at one end to the outer hoop of the bottom part of the protective structure, the plurality of spokes constrained compressively substantially in plane by a top rigid hub plate and a bottom rigid hub plate. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0037]    As used herein, the term “flying mode” is used to refer to a mode in which the quadcopter is airborne, and may be under the control of a flight control subsystem. As used herein, the term “static mode” is used to refer to a mode in which the quadcopter is assembled with all modules attached and can be ready to fly. The propellers may or may not be spinning. As used herein, the term “portable mode” is used to refer to a mode in which the quadcopter modules are disassembled for transport and storage. 
         [0038]      FIG. 1  and  FIG. 2  show a quadcopter  1  with modular components including a rotor set  12 , a battery  21 , and a camera gimbal  24 . Quadcopter  1  fuselage  8  encloses an electronics sub-system that includes a power conversion circuit, motor controllers, a flight control sub-system, a gimbal control sub-system, and various sensors including an IMU, a sonar sensor, a GPS receiver, and a Wifi transceiver. The electronics sub-system is not described in detail as they are not the subject of the invention. 
       Fuselage Attachment Features 
       [0039]      FIG. 3 , a view of the bottom side of fuselage  8 , shows magnetic, power, and electrical signal interface features for rotor set  12  and battery  21  module. In the illustrated embodiment, a plurality of pod motor contacts  96 A and  96 B are gold plated pads integral to a motherboard  34  and functionally connected to the four DC motors  36 A,  36 B,  36 C, and  36 D included in rotor set  12 . Corresponding to motor contacts  96 A and  96 B are two pairs of a cylindrical pod attach magnet  100 A and  100 B, and  100 C and  110 D, fastened into and flush with the bottom surface of fuselage  8 . 
         [0040]    Two battery power contacts  104 A and  104 B are soldered onto motherboard  34  and functionally connect to battery +V and GND respectively when battery  21  is attached. Two each of a cylindrical battery attach magnet  112 A and  112 B are mounted in and flush with the bottom surface of fuselage  8 . Two each of a prismatic battery attach magnet  116 A and  116 B are mounted in and flush with the bottom surface of fuselage  8 . 
         [0041]    Magnets  100 A,  100 B,  100 C, and  100 D,  112 A and B, and  116 A and  116 B are comprised of nickel-plated neodymium and in some embodiments are fastened into fuselage  8  with cyanoacrylate adhesive. In other embodiments, such as the embodiment shown in  FIG. 8 , magnet  118  is mechanically captured in fuselage  8  by an annular step feature  120  on a magnet  118  in combination with a rib feature  124  added to fuselage  8 . 
       Lightweight and Durable Pod Construction 
       [0042]    Referring now to  FIG. 2 , rotor set  12  is comprised of pod pair  16 A and  16 B, which are identical.  FIG. 3 , an exploded assembly view, shows that pod pair  16 A includes a pod top  8  and a pod bottom  20  both manufactured of injection-molded polycarbonate plastic. Pod top  8  and pod bottom  20  both include a center enclosure portion and a circular hoop portion on either side. Pod bottom  20  includes a plurality of spoke bosses  37  which are a molded in U-shaped channel. Each of spokes  48  are inserted into a spoke boss  37 . In one embodiment spokes  48  are fastened to spoke bosses  37  with flexible epoxy adhesive. 
         [0043]    A carbon fiber rim  46 A and  46 B is fastened to both pod top  8  circular hoop portion and pod bottom  20  circular hoop portion. Referring now to  FIG. 5 , an enlarged section view of pod pair  16 A, pod top  8  circular hoop portion includes a pod top inverted U-shaped channel  22  and pod bottom  20  includes a pod bottom U-shaped channel  23  sized to accept carbon fiber rim  46 A. In one embodiment rim  46 A and  46 B are fastened to pod top  8  and pod top bottom with flexible epoxy adhesive. Rim  46 A and  46 B are fabricated by routing a flat shape out of carbon fiber sheet which is then bent into a circular shape.  FIG. 3  shows that rim  46 A includes a plurality of spoke slots  18  for accepting spokes  48  when assembled in pod pair  16 A and  16 B, providing the benefit of mechanically coupling the lightweight and stiff composite components. 
         [0044]    In another embodiment pod bottom  20  is injection-molded around rim  46 A and  46 B and spokes  48 . Then pod top  8  is fastened to the partial assembly. In another embodiment pod bottom  20  is first injection-molded, then spokes  48  and rim  46 A and  46 B are inserted into pod bottom  20  circular portions and pod bottom  20  is re-heated to form a bond around spokes  48  and rim  46 A and  46 B. 
       Pod Fastening For Durability and Weight Reduction 
       [0045]    Referring again to  FIG. 3  the center enclosure portions of pod top  8  and pod bottom  20  are fastened together by adhering battery side label  25  to battery side label VHB  26 , which is in turn adhered to the battery side surfaces of pod top  8  and pod bottom  20 . Likewise fuselage side label  29  is adhered to fuselage side label VHB  30 , which is in turn adhered to the fuselage side surfaces of pod top  8  and pod bottom  20 . Fuselage side label  29  and battery side label  25  are comprised of 0.010 inch thick polycarbonate sheet die cut to shape. Fuselage side label VHB  30  and battery side label VHB  26  are comprised of 5906 0.15 mm thick VHB tape due cut to shape. A top label  4  is a die cut polycarbonate 0.010 inch thick sheet die cut to shape and is adhered to the top surface of pod top  8  by a die cut VHB top label VHB  6  part also comprised of 5906 VHB tape. 5906 tape is manufactured by 3M Company of St. Paul, Minn. 
         [0046]      FIG. 3  shows that the top, front, and rear surfaces of center enclosure portion of pod top  8  and pod bottom  20  include large openings. Top label  4 , fuselage side label  29 , and battery side label  25  all function as thin, lightweight enclosure walls providing for a substantially sealed enclosure. Additionally the fastening means provided by fuselage side label VHB  30 , battery side label VHB  26 , and top label VHB  6  dynamically strains but does not release thereby absorbing impact if quadcopter  1  crashes. 
       Motor Vibration Isolation Sub-System 
       [0047]    In some embodiments, quadcopter  1  can be used to record high definition images and video while flying. All aerial vehicles are susceptible to various internal and external dynamic loads that cause the vehicle to change its position and/or orientation. The purpose of 2-axis gimbal  24  is to dynamically respond to the motions of quadcopter  1  to maintain a substantially steady view of the imaged subject. One source of internal loads are vibrations produced by DC motors  36  and the propellers  78 A and B, and propellers  82 A and B.  FIG. 4  shows a motor vibration isolation sub-assembly  28  that functions to isolate motor  36 A, B, C, and D, and propeller  78 A and B, and  82 A and B vibrations from gimbal  24  mounted on fuselage  8 . 
         [0048]      FIG. 7  shows that vibration isolation sub-assembly  28  is comprised of a connector plate  60 , a magnet  56 A and  56 B, a vibration isolation flexure sub-assembly  40 , the stainless steel dowel pins  64  and  64 B, an 8-pin spring-loaded connector  68 , a connector PCB  72 , and a pin header  76 . 
         [0049]    Each of pod magnet  56 A and  56 B are fastened into cavities in connector plate  60  with cyanoacrylate glue. Connector plate  60  cavities are sized so that the top surface of magnet  56 A and  56 B are flush with the adjacent top surface of connector plate  60 . In another embodiment magnet fastening is accomplished as shown in  FIG. 8  incorporating magnet  118  with annular step feature  120  in combination with a step feature  124  added to connector plate  60 . 
         [0050]    Connector plate  60  is positioned in vibration isolation sub-assembly  28 A and  28 B such that connector plate  60  partially protrudes from the top surface of pod top  8 , but never comes in contact with pod top  8  when quadcopter  1  is in flying mode. There is a substantially rigid mechanical connection between each of motors  36 A and  36 B and pod bottom  20 . Pod top  8  and pod bottom  20  are also fixedly attached. Therefore when quadcopter  1  is in flying mode, motor  36 A and  36 B are coupled to pod bottom  20  and pod top  8  which vibrates substantially at the same frequency and energy as motors  36 A and  36 B. 
         [0051]    Connector plate  60  is mechanically attached to pod bottom  20  by a vibration isolation wire sub-assembly  40 A and  40 B, each of which is comprised of a wire  84  with a crimp  88 A and  88 B fixedly attached at each end. Crimp  88 A is fixedly captured in connector plate  60  and crimp  88 B is fixedly captured in an isolation wire mount  80 . Isolation wire mount  80  is fixedly attached to pod bottom  20 . 
         [0052]      FIG. 7  also shows that a motor rigid flex  92 A and  92  B includes a flexible portion that is located inside the enclosure created by pod top  8  and pod bottom  20 , and is soldered to a pin header  76  which in turn is soldered to a connector PCB  72 , providing an electrical circuit for powering motors  36 A and  36 B. The flexible portion of rigid flex circuit  92 A and  92 B is substantially thin and is designed with extra length to form a service loop. Therefore the flexible portion of rigid flex circuit  92 A and  92 B exerts minimal load on connector plate  60 . 
         [0053]    Connector plate  60  is substantially rigidly attached to fuselage  8  by the magnetic force of magnet couples comprising pod attach magnets  100 A, B, C, and D and, and pod magnets  56 A and  56 B. Therefore when quadcopter  1  is in flying mode fuselage  8  vibrates substantially less than pod top  8  due to the free length and flexibility of wire  84 . 
       Magnetic Module Attachment System 
       [0054]    Referring now to  FIG. 2  and  FIG. 3 , pod magnet  56 A and  56 B are mounted in connector plate with reversed polarities. Pod attach magnets  100 A, B, C, and D are mounted with corresponding opposite polarities so that rotor set  12  is firmly magnetically attached to fuselage  8 . Likewise battery attach magnets  112 A and  112 B are configured with reverse polarity, as are battery attach magnets  116 A and  116 B. Battery magnets  140 A,  140 B,  144 A, and  144 B are mounted with corresponding opposite polarities so that battery  21  is firmly magnetically attached to fuselage  8 . Configuring magnet pairs in close vicinity as described constitutes a closed magnetic field that reduces the interference of the stray magnetic fields on a magnetometer  150  included in the rear section of fuselage  8  while increasing the magnetic field strength. 
       Pod Motor Hub Construction 
       [0055]      FIG. 6  shows that hub assembly  32  is comprised of a flexible motor hub  44 A co-molded around a portion of a plurality of pultruded carbon fiber spokes  48 . In one embodiment there are twelve spokes  48  per motor. In another embodiment, spokes  48  are fastened to motor hub  44  with a toughened instant adhesive. Motor hub  44 A is sandwiched between the rigid portion of motor rigid-flex circuit  92 A and a carbon fiber hub plate  52 . When assembled a flexible portion of motor rigid-flex  92 A is fastened to one of spoke  48  by a motor flex VHB tape  94 . DC motor  36  is fastened to hub assembly  32  by four screws (not shown) inserted from the bottom through hub plate  52 . In one embodiment motor hub  44 A is molded out of a thermos-plastic elastomer with a durometer of SHORE 80A. In another embodiment, motor hub  44 A is molded out of polycarbonate plastic. 
         [0056]    Referring again to  FIG. 6 , spokes  48  are arranged tangentially, providing for a longer spoke  48  length and increased motor hub  44 A to spoke  48  bond surface area and increased portion of spoke  48  that is clamped by the rigid portion of motor rigid-flex circuit  92 A and hub plate  52 , thereby increasing the stiffness of hub assembly  321   n  one embodiment carbon fiber pultruded spokes  48  have a rectangular cross section. In another embodiment carbon fiber pultruded spokes  136  have a teardrop cross section shape oriented with the wider cross section dimension near the propellers. This streamlined cross sectional shape has a substantially lower drag coefficient, thereby increasing the efficiency of the propellers. In another embodiment, spokes X have an oval cross-section which substantially reduces the drag induced by a cross-wind. 
         [0057]    The pod pair plane may be defined as the plane where the motor rotational axis is normal, for example in  FIG. 10  the pod pair plane is parallel to the drawing sheet. The embodiment of hub assembly  32  that includes elastomeric motor hub  44 A results in pod pair  16 A that is substantially rigid in torsion and bending in the pod pair plane, but is compliant when impacted from directions parallel or close to parallel to the pod pair plane.  FIG. 20  shows a series of frames from a high-video of a pod pair dropped from 10 feet onto a hard surface. The video images show that spokes  48 , pod top  8  hoop feature, pod bottom hoop feature  20 , and rim  46 B deflect to absorb and return the impact energy, causing pod pair  16 A to bounce with no damage. 
         [0058]      FIG. 9  is a magnified view of a portion of hub assembly  32  with only spoke  48  that is laminated to motor flex circuit  92 A shown. Three each of a spring contact  132 A, B, and C are soldered to pod motor contacts  96 A, B, and C. Motor  36  includes corresponding electrical contacts that align with spring contacts  132 A, B, and C when motor  36  is assembled to hub assembly  32 . In one embodiment spring contacts  132 A, B, and C are part number 1447360-8 manufactured by TE Connectivity, Inc. of Berwyn, Pa. 
       Pod Hinge Design 
       [0059]    Referring now to  FIG. 11  and  FIG. 12 , rotor set  12  includes a hinge flexure  12 A and  12 B that connect pod pair  16 A and  16 B. In one embodiment hinge flexure  12 A and  12 B is die cut 0.0325 inch thick graphene reinforced nitrile rubber sheet.  FIG. 12  includes a drawing (not to scale) of the flattened die cut shape of hinge flexure  12 A that shows an oval hole at each end. Detail A in  FIG. 12  shows hinge flexure  12 B mounted to pod pair  16 A in the flexed state when rotor set  12  is in the open and mounted configuration (rotor set  16 B is not shown). 
         [0060]      FIG. 11  shows two views of a hinge flange  38 A and  38 B to which hinge flexure  12 A is mounted. Hinge flange  38 A is a feature integral to pod top  8  and includes a stem and an enlarged flange feature. Hinge flexure  12 A die cut oval holes are smaller in size than hinge flange  38 A flange feature. One end of hinge flexure  12 A is stretched over hinge flange  38 A and is retained by hinge flange  38 A enlarged flange feature. Likewise the other end of hinge flexure  12 A is stretched over hinge flange  38 B on pod top  8  in pod pair  16 B. When rotor set  12  is in the open configuration, as shown in  FIG. 10 , hinge flexures  12 A and  12 B are in a stretched tension state thereby constraining pod pair  16 A and  16 B together. 
         [0061]    Referring now to  FIG. 4 , pod bottom  20  includes the hinge magnet bosses  41 A and  41 B, into which are placed the hinge magnets  32 A and  32 B with opposite polarity. In one embodiment hinge magnets  32 A and  32 B are fastened with cyanoacrylate adhesive. When rotor set  12  is in the open position and constrained by stretched hinge flexures  12 A and  12 B, hinge magnet  32 A and  32 B opposite polarity magnetic fields accurately and firmly align and reversibly fasten rotor set  12 . Applying a firm rotational force along rotor set  12  virtual hinge axis (denoted by the dashed line in  FIG. 10 ) will break the magnetic bond and allow pod pair  16 A and  16 B to rotate to the closed position, shown in  FIG. 14 . 
         [0062]      FIG. 14  shows two views of rotor set  12  in the closed position. Referring now to  FIG. 10 , spring-loaded connector  68  is located off-center in connector plate  60  by one-quarter of the spring pin pitch. In one embodiment the pitch of the spring pins in spring-loaded connector  68  is 2.54 mm, therefore the offset is 0.635 mm. Because rotor set  12  is comprised of two identical pod pairs  16 A and  16 B, where  16 B is rotated so that hinge magnets  32 A and  32 B are apositioned when rotor set  12  is open, the combined offsets of each of spring-loaded loaded connector  68  results in a relative offset of one-half of the spring pin pitch.  FIG. 14  DETAIL B therefore shows that spring-loaded pins nest beside each other when rotor set  12  is in the closed position. 
         [0063]    In the rotor set  12  closed position shown in  FIG. 14 , pod connector magnet  56 A and  56 B in each of pod pair  16 A and  16 B are apositioned and close together so that there is a magnetic attraction force acting to keep rotor set  12  in the closed position. 
       Modular Gimbal Attachment 
       [0064]      FIG. 16  shows the components associated with a modular replaceable camera gimbal  24 . Gimbal  24  includes two axes of rotation for the purpose of camera aiming and stabilization. A gimbal mount  180  is fixedly attached to a roll stage  53  (shown in  FIG. 18 ). In one embodiment gimbal mount  180  is a comprised of injection-molded polycarbonate plastic. A camera rigid-flexible circuit assembly  49  is configured with service loop lengths to allow for rotational motion of roll stage  53  and pitch stage  56 .  FIG. 16  and  FIG. 18  show that camera flex circuit  49  extends into and is fastened to a cavity in gimbal mount  180 . A circuit board rigid portion  196  of camera flex circuit  49  provides support for a gimbal connector  188  shown also in  FIG. 18 . In one embodiment gimbal connector  188  is a surface mount board-to-board connector, part number DF40C-30DP, manufactured by Hirose Electric, U.S.A., Inc., of Lombard, Ill. 
         [0065]      FIG. 16  shows that an image processing rigid-flexible circuit board assembly  44  includes a flexible portion  160  with a rigid circuit board portion  192 . Image processing circuit board assembly  44  is located inside fuselage  8 , which is illustrated in  FIG. 20 , and includes the video encoding processor  152  and an SDRAM integrated circuit  156 . Other electrical components required for the function of image processing assembly  44  are not shown as they would be well known to one skilled in the art of image processing electronics design. 
         [0066]    Rigid circuit board  192  supports a soldered surface mount connector  184  that electrically and mechanically mates with gimbal connector  188  when gimbal  24  is installed in fuselage  8 . In one embodiment connector  184  is a surface mount board-to-board connector, part number DF40C(2.0)-30DS-0.4V, also manufactured by Hirose Electric, U.S.A., Inc., of Lombard, Ill. 
         [0067]    Rigid circuit board portion  192  is fixedly attached to a gimbal screw plate  176 .  FIG. 19  is a front angled view of fuselage  8  with several parts removed. Gimbal screw plate  176  is fastened to the inside surface of a vertical gimbal attach wall  200  such that the two screw boss portions of gimbal screw plate  176  extend through two holes in gimbal attach wall  200 . In one embodiment gimbal screw plate is manufactured out of stainless steel and the screw boss portions are threaded for M2 screws. 
         [0068]    Gimbal  24  mechanically attaches to fuselage  8  with the screws  172 A and B as shown in  FIG. 16  and  FIG. 17 .  FIG. 18  shows in a rear view of gimbal  24  that gimbal mount  180  includes two concave bosses that fit closely over gimbal screw plate  176  protruding screw bosses. When screws  172 A and B are tightened in gimbal screw plate  176 , gimbal  24  is pulled tight against gimbal attach wall  200 . 
         [0069]      FIG. 18 , an exploded view of gimbal  24 , shows that camera flex circuit  49  includes an image sensor  164  that is functionally electrically connected to image processing circuit assembly  44  when gimbal  24  is attached to fuselage  8 . In one embodiment image sensor  164  is part number IMX377, manufactured by Sony Corporation of Tokyo, Japan. The IMX377 image sensor is capable of capturing 4K (4000×3000 pixels). 
         [0070]    Connector  184  is held rigidly to gimbal screw plate  176 , which is in turn rigidly attached to gimbal attach wall  200 . Connector  188  in gimbal  24  is soldered to rigid circuit board  196  which is compliantly constrained against the rear walls of gimbal mount  180  by a gimbal rubber  168  part. In one embodiment gimbal rubber  168  is comprised of a thermos-plastic elastomer with a durometer of SHORE A 60. This provides a compliant fit between connector  184  and connector  188  when gimbal  24  is screwed tightly to fuselage  8 . 
         [0071]    It should be noted that the terms “couple,” “coupling,” “coupled” or other variations of the word couple as used herein may indicate either an indirect connection or a direct connection. For example, if a first component is “coupled” to a second component, the first component may be either indirectly connected to the second component or directly connected to the second component. As used herein, the term “plurality” denotes two or more. For example, a plurality of components indicates two or more components. 
         [0072]    In the foregoing description, specific details are given to provide a thorough understanding of the examples. However, it will be understood by one of ordinary skill in the art that the examples may be practiced without these specific details. For example, electrical components/devices may be shown in block diagrams in order not to obscure the examples in unnecessary detail. In other instances, such components, other structures and techniques may be shown in detail to further explain the examples. 
         [0073]    Headings are included herein for reference and to aid in locating various sections. These headings are not intended to limit the scope of the concepts described with respect thereto. Such concepts may have applicability throughout the entire specification. 
         [0074]    The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.