Abstract:
A system of transporting micro-cargo incorporates an unmanned aerial vehicle (UAV) having a tether capture device. A tether is connected to and suspends a micro cargo container with a suspension system to vertically extend the tether. The system having a first pickup state and a second flight state with a transition between the first and second states. The first state provides the micro-container unsuspended via the tether from the suspension system. The transition state provides engagement of the tether by the UAV, the tether positioning the micro-cargo container with respect to the capture device which secures the tether. The second state is then entered with the micro-cargo towed by the UAV in cruising flight to its destination.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a division of application Ser. No. 13/482,859 filed on May 29, 2012 having a title of UAV CAPTURE OF MICRO CARGO ALOFT and having a common assignee with the present application, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND INFORMATION 
     Field 
     Embodiments of the disclosure relate generally to the field of extraction of micro cargo by air pickup and more particularly providing a system for capture of a of a suspended micro cargo tethered by an Unmanned Aerial Vehicle (UAV) with a tether capture device. 
     Background 
     Extraction of cargo from remote sites typically requires either ground or air transport from a first location to a desired transport point. For extraction by air the aircraft must land, take the cargo onboard, take off and fly to the destination. For small parcels or “micro cargo”, the time, fuel and potential hazards of landing an aircraft to retrieve the micro cargo or the lack of suitable landing sites may require transport of the cargo by land. In certain instances such as biological or natural disasters, landing an aircraft for retrieval of a micro cargo such as biological samples in medical emergencies or epidemics or radiological samples in a nuclear disaster may not be advisable. Similarly, clandestine removal of micro cargo such as computer storage media or physical materials may not allow the use of normal aircraft. 
     It is therefore desirable to provide a method and system for aerial retrieval and transport of micro cargo in which landing is not required. 
     SUMMARY 
     Embodiments disclosed herein provide a system of transporting micro-cargo incorporating an unmanned aerial vehicle (UAV) having a tether capture device. A tether is connected to and suspends a micro cargo container with a suspension system to vertically extend the tether. The system having a first pickup state and a second flight state with a transition between the first and second states. The first state provides the micro-container suspended via the tether from the suspension system. The transition state provides engagement of the tether by the UAV, the tether positioning the micro-cargo container with respect to the capture device which secures the tether. The second state is then entered with the micro-cargo towed or retracted into the body for transport by the UAV in cruising flight to its destination. 
     The embodiments allow method for transport of micro cargo wherein a micro cargo is loaded into a micro cargo container and suspended. The micro cargo container is constrained with a securing line to position the micro cargo container with respect to a surface placing the system in a first state. A UAV having a tether capture device is directed to the suspended tether for engagement. In a transition state, the tether is engaged with a leading edge of one wing of the UAV and the tether slides to the capture device. The tether capture device engages the tether. The micro cargo container is then towed with the UAV in a second system state. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is pictorial view of an example UAV for use with the present system; 
         FIG. 2  is a pictorial schematic of an embodiment of a example micro cargo lofting system; 
         FIG. 3A  is a pictorial schematic of an embodiment of a micro cargo pickup suspension system; 
         FIG. 3B  is a pictorial schematic of a second embodiment of a micro cargo pickup suspension system; 
         FIG. 3C  is a pictorial schematic of an alternative embodiment of the tether for capture by flying the nose of the UAV into an open loop in the tether for a symmetric flight configuration; 
         FIG. 4A  is a detailed isometric of a wingtip mounted tether capture device prior to engagement of a tether; 
         FIG. 4B  is a detailed isometric of the wingtip mounted tether capture device after engagement of the tether; 
         FIG. 5A  is a top view of an alternative embodiment for placement of tether capture devices on the wing leading edge; 
         FIG. 5B  is a top view of an alternative UAV embodiment with leading edge mounted tether capture devices; 
         FIG. 6A  is a pictorial view of the UAV with the micro cargo in tow; 
         FIG. 6B  is a pictorial view of the UAV with aerodynamic balloon and micro cargo container in tow; 
         FIG. 6C  is a schematic view of a tether guillotine for deflating the balloon; 
         FIG. 6D  is a pictorial view of the UAV with a reeled in micro cargo container; and, 
         FIG. 7  is a flow chart depicting the operation of the embodiments of the system as disclosed. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein provide a system for retrieving a micro cargo suspended with a tether using a UAV. The UAV engages the tether without landing and tows the micro cargo container to a desired location. 
     As shown in  FIG. 1 , a UAV  10  for use with the system embodiments may be an air vehicle similar to the Boeing ScanEagle. The UAV  10  incorporates a fuselage  12 , wings  14  and a propulsion system such as a reciprocating engine and propeller  16 . At least one tether capture device  18 , which will be described in greater detail subsequently, is provided for engagement of a tether supporting the micro cargo. 
     As shown in  FIG. 2 , one embodiment for suspending the micro cargo is to employ a balloon  20  from which a tether  22  attached to the balloon at a first end extends to carry a micro cargo container  24  attached at a second end. In certain instances, the balloon  20 , tether  22  and micro cargo container could be free floating, however, advanced guidance and intercept systems would be required. In an example embodiment, a securing line  26  extends downward from the micro cargo container  24  to a release element such as lower separation link  28  which is attached to a stake  30  or similar securing device on the ground or launch surface  32 . In the embodiment shown, the first end of the tether  22  is attached to the balloon  20  with a suspension separation link  34  as a release element. The tether  22  may include capture nodes  36  spaced along the length of the tether to assist in securing the tether to the tether capture device  18  as will be described in greater detail subsequently. Suspension if the micro cargo container in this pre-capture position provides a first state for the system. 
     As shown in  FIG. 2 , the UAV  10  approaches the suspended tether  22  for engagement by the tether capture device  18  as will be described in greater detail subsequently. Upon engagement, for the embodiment shown, drag forces created by the balloon  20  and the ground stake  30  cause the suspension separation link  34  and the lower separation link  28  to rupture or separate allowing the tether  22 , micro cargo container  24  and securing line  26  to trail behind the UAV in tow. The engagement of the tether with associated secondary events such as separation of the balloon and ground stake constitutes a transition state for the system. Once capture has been accomplished, the UAV with the micro cargo container in tow constitutes a second state for the system. 
       FIG. 3A  demonstrates an alternative embodiment for suspending the micro cargo using a suspension arm  40  for the first state of the system. The suspension arm  40  may be supported from a building, a crane, a ship or other land or sea vehicle or as a portion of a UAV launching system as disclosed in U.S. Pat. No. 7,090,166 entitled METHODS AND APPARATUSES FOR LAUNCHING UNMANNED AIRCRAFT, INCLUDING METHODS AND APPARATUSES FOR TRANSMITTING FORCES TO THE AIRCRAFT DURING LAUNCH issued on Aug. 15, 2006 and having a common assignee with the present invention, the disclosure of which is incorporated herein by reference. The suspension arm  40  may have extendable elements  40   a  to increase height and/or horizontal distance from the mounting point. Additionally, the suspension arm may include pulleys  41   a  and  4   b  for positioning of the tether  22 . As shown for the balloon suspension system of  FIG. 2 , the micro cargo container  24  is suspended with the tether  22 . A suspension separation link  34  attaches the tether  22  to the suspension arm  40  and a securing line  26  extends downward from the micro cargo container  24  to a lower separation link  28  which is attached to a stake  30  or similar securing device on the ground or launch surface  32 . 
     A second embodiment for fixed suspension of the micro cargo container is shown in  FIG. 3B . In stead of a structural suspension arm, a natural or environmental element such as a tree branch  42  is employed to suspend the tether  22  in the first state of the system. The micro cargo container  24  is suspended with the tether  22 , a suspension separation link  34  attaches the tether  22  to the tree branch  42  and a securing line  26  extends downward from the micro cargo container  24  to a lower separation link  28 . An alternative for production of drag to assist in securing the tether  22  in the tether capture device  18 , a drag producing device such as a drag chute  44 , is shown in  FIG. 3B . The drag chute  44  is attached to the lower separation link  28 . When initially contacted by the UAV  10  and tether capture device  18  during the transition state, the combination of the tree branch and aerodynamic force on the drag chute  44  provides the necessary force to secure the tether  22  in the tether capture device  18 . As previously described with respect to the prior embodiments, the continued drag force then results in separation of the suspension separation link  34  and lower separation link  28  to disencumber the towed tether  22  and micro cargo container  24  for better performance of the UAV  10 . Use of a drag chute may also be employed if the terminal end of the securing line is place in the water with the tether suspended from a balloon or suspension arm on a ship. 
     As shown in  FIG. 3C , an alternative arrangement of the tether  22  may be provided such that capture is achieved by flying the nose  11  of the UAV  10  into an open loop  35  in the tether for a symmetric flight configuration upon capture. 
       FIG. 4A  is a partially schematic, isometric illustration of an outboard portion of the wing  14  and the winglet  50  of the UAV  10  shown in  FIG. 1 . In this embodiment, the wing  14  includes a leading edge  52  (which can be swept), an outboard edge  54 , and the tether capture device  18  positioned at the outboard edge  54 . In other embodiments, each wing  14  can include a plurality of tether capture devices  18  located along the span of the wing  14  as will be discussed with respect to  FIGS. 5A and 5B . In any of these embodiments, the tether capture device  18  can include a cleat  56  fixedly attached to the wing  14  that engages the tether  22  to securely attach tether  22  to the aircraft  10 . The cleat  56  can include a cleat body  58 , a cleat slot  60  positioned in the cleat body  58 , and a gate or retainer  62  attached to the cleat body  58 . As the UAV  10  flies toward the tether  22  (as indicated by arrow A), the tether  22  strikes the wing leading edge  52 . Drag created by the suspended condition of the tether  22  from either the balloon  20 , suspension arm  40  or tree branch  42  causes the UAV to yaw toward the tether  22 , which then slides outboard along the leading edge  52  toward the tether capture device  18  (as indicated by arrow B). The tether  22  then passes into the cleat slot  60 , which is sized to pinch the diameter of the tether  22 , and is retained in the cleat slot  60  by the retainer  62 , as described in greater detail below with reference to  FIG. 4B . In other embodiments, the retainer  62  can be eliminated and the tether  22  can still be securely pinched in the cleat slot  60 . As previously described, tension on the two ends of the tether from the suspension point link and the ground retention link urge the tether into the pinching cleat. If uneven tension is present in the two ends of the tether causing the tether to slide along its axis in the cleat slot, engagement of a capture node  36  as previously described will position the tether for engagement in the cleat slot. 
     If the UAV  10  is not properly aligned with the tether  22  during its approach, the tether  22  may strike the tether capture device  18  instead of the leading edge  52 . In one embodiment, the cleat body  54  includes a cleat leading edge  64  which is swept aft so as to deflect the tether  22  away from the UAV  10 . This can prevent fouling of the line  22  and can reduce the yawing moment imparted to the UAV  10 , allowing the UAV  10  to recover from the missed capture and to return for another capture attempt. 
       FIG. 4B  is an enlarged, isometric illustration of a portion of the wing  14  and the tether capture device  18  described above with reference to  FIG. 4A . As described above with reference to  FIG. 4A , the tether  22  travels outboard along the wing leading edge  52  to position the tether  22  at the cleat slot  60  of the tether capture device  18 . In one aspect of this embodiment, the retainer  62  of the cleat  60  includes two or more closure arms (two are shown in  FIG. 9B  as a first closure arm  66   a  and a second closure arm  66   b ) that extend over the cleat slot  60 . The retainer  62  is pivotally mounted to the cleat body  58  at a pivot joint  68 , and is forced toward a closed position (shown in  FIG. 4B ) by a spring  70 . As the tether  22  strikes the first closure arm  66   a  from outside the cleat slot  60 , the force on the first closure arm  66   a  forces the retainer  62  to rotate about the pivot joint  68  (as indicated by arrow C) to an open position, allowing the tether  22  to move into the cleat slot  60 . The tether  22  continues through the cleat slot  60 , allowing the retainer  62  to begin closing as it passes the first closure arm  66   a . The tether  22  then strikes the second closure arm  66   b  to force the retainer  62  back open again, and then travels further in the slot  60 . In one aspect of this embodiment, the slot  60  (which can be tapered) has a width that is less than a diameter of the tether  22 . Accordingly, the tether  22  can be pinched in the slot  60  as the tether  22  travels outboard and aft, securing the UAV  10  to the tether  22 . The momentum of the UAV  10  relative to the tether  22  provides the impetus to securely engage the tether  22  with the tether capture device  18 . 
     As described above, the retainer  62  can include a first closure arm  66   a  and a second closure arm  66   b . One advantage of a retainer  62  having a first closure arm  66   a  and a second closure arm  66   b  is that, if the relative velocity between the tether  22  and the UAV  10  is insufficient to cause the tether  22  to travel to the end of the cleat slot  60 , the retainer  62  can close around the tether  22 , with the tether  22  positioned between the first closure arm  66   a , and the second closure arm  66   b . Accordingly, this arrangement can arrest and secure the line  22  even though the tether  22  has a relatively low outboard and aft velocity component relative to the UAV  10 . Additionally, if the tether  22  is not pinched within the cleat slot  60 , the capture nodes  36  above or below the closure arms  66   a  or  66   b  will secure the tether  22  within the retainer  62 . 
     As previously described, multiple tether capture devices may be attached to the wings  14  of the UAV  10 . As shown in  FIG. 5A , inboard tether capture devices  18   a  are attached closer to the fuselage  12  with wing tip tether capture devices  18   b  located as previously described. Multiple capture devices allows compensation for minor course deviation by the UAV when intercepting the tether but allowing capture on either the inboard or wing tip capture device. While only two devices are shown in each wing, multiple devices may be attached with closer spacing. Placement of capture devices inboard closer to the fuselage  12  reduces the yaw moment created by the towed micro cargo container  24  and improves efficiency of the UAV  10  during the second state of the system for towing flight. 
       FIG. 5B  demonstrates an alternative configuration of the UAV  10  with forward swept wings  14 . In this configuration, yaw created by interception of the tether  22  is reduced and placement of the tether capture devices  18  at a more inboard location on the wing is practical even with minor course deviations during intercept since the entire wing half span may be employed to “funnel” the tether  22  into the tether capture device  18  during the transition state. 
     The second state of the system with the micro cargo container  24  in tow by the UAV  10  is shown in  FIG. 6A . The suspension separation link  34  and lower separation link  28  have separated leaving the tether  22  and lower securing line  26  trailing in the air stream. While shown in  FIGS. 2, 3A and 3B  as located at the extremes of the tether and securing line the separation links may be placed to reduce the trailing length of the tether and securing line in tow. Also as shown in  FIG. 6A , the tether  22  may employ differing weight or configuration such as flag portion  23  to achieve differential drag on the towed elements to properly position the tether within the tether capture device  18 . In example embodiments, the separation links may be reduced diameter portions of the tether and securing line forming frangible links which rupture under the drag forces induced by the UAV capture or they may be separable elements such as hook and loop fasteners or spring loaded devices. In alternative systems, active separation devices such as hot wire cutters or laser cutting systems may be employed to sever the tether and securing line. 
     Alternatively as shown in  FIG. 6B , the balloon  20   a  may be a streamlined shape such that excessive drag is not created and separation of the tether from the balloon is not required for adequate towing performance by the UAV. The micro cargo container  22   a  may also be aerodynamically streamlined for better towing performance. 
     Rather than separating from the balloon  20 , the balloon may be punctured to deflate thereby reducing the drag during tow in the second state of the system. As shown in  FIG. 6C , the tether may employ a guillotine section  22   b  having a sharp or barbed profile extending over the balloon  20  and pulling through a slip ring or similar arrangement such that drag created by the capture tether tightens the guillotine section to puncture the balloon. Alternatively as with the severing of the tether, active systems such as laser or heated wires may be employed to puncture the balloon. 
     Improvement in aerodynamic performance may also be achieved by reeling the tether into the UAV or into the micro cargo container after capture and separation. As shown in  FIG. 6D , the capture device  18  may be attached to the UAV with a spring loaded reel  40  which, when activated, reels in the captured tether  22  onto a spool  42  drawing the micro cargo container  24  into close proximity to the UAV  10 . For embodiments as disclosed with respect to  FIG. 3C , the cargo container may be reeled into an enclosed bay within the UAV fuselage  12   
       FIG. 7  shows the operation of the system as described for the embodiments herein. A micro cargo is loaded into a micro cargo container, step  702 , and suspended by a tether, from a balloon, suspension arm or natural object, with a securing line to position the micro cargo container with respect to a surface placing the system in a first state, step  704 . A UAV having a tether capture device is directed to the suspended tether for engagement, step  706 . In a transition state, the tether contacts the leading edge of one wing of the UAV and slides to the tether capture device, step  708 . The tether capture device engages the tether by pinching the tether in a slot, engaging the tether with closure arms and/or engaging a suspension node as the tether is drawn through the capture device, step  710 . In releasing embodiments, a suspension link and a lower link are ruptured freeing the tether and securing line allowing the UAV to be placed in a second state for the system with the micro cargo container in tow, step  712 . In alternative embodiments for a balloon suspension, the tether may remain attached to the balloon which is aerodynamically streamlined for tow or the balloon may be punctured or otherwise deflated for flagging during tow, step  714 . The tether may alternatively be reeled in for trailing in close proximity to the UAV or for encapsulation within a bay in the UAV fuselage, step  716 . 
     Having now described various embodiments of the disclosure in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present disclosure as defined in the following claims.