Abstract:
An unmanned aerial vehicle (UAV) that can operate both as a conventional multicopter with no wing attached, or, it can operate as a winged multicopter. The detachable wing design used in the invention provides versatility without compromising performance; the wing attachment receptacles add no weight to the wingless multicopter configuration because they also function as the leg receptacles. In one embodiment, the base multicopter configuration is a quad-copter with four propeller drives. Four tubular receptacles, two forward and two aft, provide attachment points for the vertical struts of a detachable rectangular shaped wing, these vertical struts also function as the legs of the multicopter. The wing is fabricated using lightweight struts and rip stop nylon fabric which can be easily folded into a compact shape using quick release pins. In another embodiment, the wing is fabricated using a foam core. In both embodiments, the angle of the detachable wing can be adjusted to optimize lift and drag in the forward thrust, tilted position of the multicopter.

Description:
Embodiments of the invention relate generally to Unmanned Aerial Vehicles (UAVs), personal drones, and, more particularly to multicopters with various configurations of rotary propeller drives and wing combinations thereof. 
     BACKGROUND 
     An Unmanned Aerial Vehicle (UAV), commonly referred to as a drone, is an aircraft without a human pilot. It is controlled either by remote control using a radio signal, or, autonomously using an onboard computer system. UAVs are commonly used in military operations where missions are often too hazardous to deploy manned aircraft. 
     The use of personal drones has become increasingly popular over the last few years. Manufacturers have developed a wide variety of multicopters with three or more rotary propellers that are used for lift and propulsion, with the most popular version being a four rotor quadcopter. Advances in microelectromechancial system (MEMS) gyroscopes and accelerometers have allowed onboard computers to autonomously sense and control the pitch, roll, and yaw of these rotary multicopters. Some advanced personal drones are also equipped with global positioning systems (GPS) and compass microcircuits that allow an onboard computer to fly the multicopter autonomously between preprogrammed waypoints. These systems also allow the multicopters to return safely to a home position given a low battery or lost telemetry signal situation. Multicopters are often equipped with a camera system for aerial photography. The main advantage of a multicopter its flight maneuverability including vertical takeoffs, landings, and the ability to hover in a fixed position. The main limitation of a multicopter is its limited flight time due to battery charge limitations. The typical flight time for a personal multicopter drone is 5-15 minutes. 
     Another common type of personal drone is a rotary propeller powered fixed wing plane. Fixed wing planes typically cost more than multicopters because they require servos and linkages to actuate flight control surfaces such as ailerons, a rudder, and an elevator. Fixed wing drones can be equipped with all of the sensors and onboard computers used by multicopters for autonomous flight. The main advantage of fixed wing planes is their longer flight time, typically 30-60 minutes on a battery charge. Flight time is extended because the wings provide lift. The main disadvantage of fixed wing planes is their limited flight maneuverability. Because they require a forward thrust to provide lift, they cannot perform vertical takeoffs and landings, and they cannot hover in a fixed position in space. 
     There are personal drones that integrate a multicopter platform with a fixed wing aircraft design. These personal drones typically use four propeller drives oriented in the vertical position for vertical takeoff capability. In some of these designs, once at cruising attitude, motorized mechanisms rotate the propeller drives towards the horizontal position and the aircraft functions as a fixed wing plane. In other designs, the multicopter resembles a large wing and the wing translates from a generally vertical orientation to a horizontal direction. The wings of these drones are integral to the frame of the aircraft and are therefore not detachable. These drones are often quite large because of their fixed wingspans, making them difficult to store and transport. 
     SUMMARY 
     The embodiments of the invention provide the vertical takeoff and landing (VTOL), and hovering capability of multicopters, with the extended flight times and maneuverability of fixed wing aircraft. The invention can operate both as a conventional multicopter with no wing attached, or, it can operate as a winged multicopter. The detachable wing design used in the invention provides versatility without compromising performance; the wing attachment receptacles add no weight to the wingless multicopter configuration because they also function as the leg receptacles. The vertical spars of the attached wing also function as the legs of the multicopter. 
     While operating as a multicopter without a wing, the invention weighs less and can more easily carry a camera payload for aerial photography. When operating with a wing, the invention could be used in longer, more acrobatic fights since a winged multicopter can dive and soar on wind currents. On windy days, a user may choose to fly without the wing to better control the flight of the invention. 
     The added cost and complexity of a conventional fixed wing plane design using servos and linkages to control flight control surfaces is not required because pitch, roll, yaw and forward thrust are all enabled using the multiple vertically mounted propeller drives by the same means as a conventional multicopter. The invention, along with conventional multicopters, move forward by tilting the aircraft frame and the subsequent propeller thrust vector (e.g., 1-90 degrees from horizontal), towards the direction of forward motion. The invention angles the wing control surface from horizontal so that it provides lift and minimal drag in this tilted forward thrust position. To add additional versatility in minimizing wing drag and optimizing flight performance, the invention provides adjustability to the wing attack angle (angle from horizontal). 
     In one embodiment of this invention, the wing is comprised of a lightweight rigid frame (e.g. carbon, aluminum, or fiberglass tubing or rods) that supports a sheet sail (e.g. ripstop nylon fabric) such as those found in many kite designs. By using a deformable sheet sail, this embodiment allows the wing to be rolled up into a small footprint for easy transport and storage. In another embodiment of this invention, the wing is constructed from a foam core, and is not foldable. 
     The above summary is not intended to describe each embodiment or every implementation of the invention. Rather, a more complete understanding of the invention will become apparent and appreciated by reference to the following Detailed Description of Exemplary Embodiments and claims in view of the accompanying figures of the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWING 
       The invention will be further described with reference to the figures of the drawing, wherein: 
         FIG. 1  is a front isometric view of the invention with no wing attached; 
         FIG. 2  is an exploded front isometric view of the electronics assembly; 
         FIG. 3  is an enlarged isometric view of the upper housing and the assembled frame spars; 
         FIG. 4  is a front isometric view of the motor mount assembly; 
         FIG. 5  is a bottom isometric view of the motor mount assembly; 
         FIG. 6  is a front isometric view of the detachable sheet sail wing assembly; 
         FIG. 7  is a front isometric view of the sheet sail; 
         FIG. 8  is an enlarged isometric view of the wing spars and connectors; 
         FIG. 9  is an enlarged isometric view of the wing spars and connectors in their detached positions; 
         FIG. 10  is a front isometric view of the invention with the sheet sail wing assembly attached; 
         FIG. 11  is a front view of the invention with the sheet sail wing assembly attached; 
         FIG. 12  is a front view of the invention with the sheet sail wing assembly attached with a lower wing angle from horizontal; 
         FIG. 13  is a front view of the invention with the sheet sail wing assembly attached in the forward thrust position; 
         FIG. 14  is a front view of the invention with the foam wing assembly attached; 
         FIG. 15  is a front isometric view of the invention with the foam wing assembly attached; 
     
    
    
     The figures are rendered primarily for clarity and are not necessarily drawn to scale. Moreover, various structure/components, including but not limited to fasteners, electrical components (wiring, cables, etc.), and the like, may be removed from some or all of the views where inclusion of such structure/components is not necessary to understand the various exemplary embodiments of the invention. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following detailed description of illustrative embodiments of the invention, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. 
     Embodiments of the invention are directed generally to Unmanned Aerial Vehicles (UAVs) also referred to herein as “personal drones”. While the embodiments of this invention use a rectangular wing configuration, other wing shapes may be used without departing from the scope of the invention. While the multicopter depicted in these embodiments uses four propeller drives, other quantities of propeller drives (e.g. 3-8 propeller drives) may be used without departing from the scope of the invention. The placement and quantity of the propeller drives can vary; typically the number of propeller drives is an even number so that the propellers can spin in opposing directions to cancel out any resultant torsional forces on the vehicle. Additional propeller drives typically provide additional lift to enable heavier payloads to be carried. 
     It is understood that individual parts may be assembled by several different means including, but not limited to, screws, bolts, adhesives, pins, retaining rings, press fits etc. without departing from the scope of the invention. 
     For simplicity, the wiring between electrical components and the motor drives has been eliminated. It is understood that all of the electrical components are connected by some form of wiring. 
       FIG. 1  is a front isometric view of the invention with no wing attached  10 . In this embodiment, the invention operates as a conventional multicopter and may use four propeller drives assemblies  14 . The four propeller drives assemblies  14  may be mounted to four motor mounts  20  using two screws to secure each motor (not shown). The motor mounts  20  may be comprised of injection molded plastic, 3D printed plastic, or made of a lightweight machined or cast material such as aluminum or titanium. 
     The electronics assembly  12  may be attached to each of the four motor mounts  20 , using four frame spars  16  that extend outward from the electronics assembly  12 . These frame spars  16  may be the same length, and be arranged at 45 degree angles in order to position the four propeller drives  14  in a symmetric pattern in order to balance the loads during flight. The electronics assembly  12  is the heaviest component in the multicopter  10  and therefore is centered between the four propeller drives  14  in order to balance weight and the loads to each drive. The frame spars  16  may consist of lightweight carbon fiber tubing (e.g. 0.375″ diameter pultruded carbon tubes distributed by Goodwinds Inc.). The frame spars  16  may also allow the motor wires (not shown) to pass through the frame spars  16  in order to protect them from damage or snagging. 
     Two motor spars  18  may be used to stiffen, especially in torsion, the motor mounts  20  by joining each of the two pairs together. The multicopter  10  may rest on the ground using four legs  22 . The four legs may form a square with equidistance between the legs in order to maximize symmetry and weight balance. The distance between legs may be in the range of 12 to 24 inches. The ends of the legs may be protected using a boot  24 . This boot may be an elastomer (e.g. urethane, silicone) and may be attached using a friction fit for easy removal. Both the legs  22  and the motor spars  18  may be comprised of a smaller diameter, lightweight carbon fiber tubing (e.g. 0.240″ diameter pultruded carbon tubes distributed by Goodwinds Inc.). 
       FIG. 2  is a exploded front isometric view of the electronics assembly  12 . The lower housing  30 , upper housing  32  and the door  34  may be comprised of injection molded parts, but could also be 3D printed parts or machined or cast in a lightweight material such as aluminum or titanium. The electrical components may be mounted to a lower plate  54  and an upper plate  56  which may be die cut or laser cut out of a lightweight metallic sheet such as aluminum or titanium. The upper plate  56  may secure a power distribution board  64  used to control and distribute the high currents sent to the propeller drives  14  (e.g., Power Distribution Board distributed by 3D Robotics). This board may be mounted using standoffs and small screws and nuts (not shown). Additional cables and wiring (not shown) connect all of the electrical components within the electronics assembly  12 . 
     The lower housing  30  may house the battery  66  (e.g., Lipro Power Pack 3s/11.1V 3500 mAh). Since the battery is frequently inserted and removed between charges, an door  34  may be opened and closed using one of four threaded posts  36  as a hinge. These threaded posts  36  and threaded post screws  38  may be used to assemble the door  34 , the upper housing  32 , and the lower housing  30 . The door  34  may remain closed using a threaded thumb screw  40  that screws into a threaded door boss  42  that is part of the upper housing  32 . The threads of this boss  42  (also shown in  FIG. 3 ) may be either cut directly, or by using a heat staked or adhesively bonded threaded insert (not show). The lower housing  30  may also house a radio controlled receiver  60  that contains an antenna. The radio controlled receiver  60  may be used to send control commands and flight status information back to a base station receiver (e.g., 915 MHz 3DR RC Receiver distributed by 3D Robotics). 
     The lower plate  54  may be used to fixate an autopilot processing unit  58  (e.g., Pixhawk PX4 Autopilot distributed by 3D Robotics). The autopilot unit  58  may be attached to the lower plate  54  using double backed very high bond (VHB) acrylic foam tape, or using screws (not shown). The lower plate  54  may also house the global positioning module  62  (e.g., 3DR uBlox GPS module distributed by 3D Robotics) and may be mounted using standoffs and small screws and nuts (not shown). The lower plate  54  may be attached to the lower housing  30  using screws (not shown) that thread into lower plate threaded bosses  50 . 
     In order to help cool the electrical components, air vents  48  may be formed into the door  34 , upper housing  32  and the lower housing  30 . In order to evenly distribute the weight of the heavier electrical components (e.g. battery, power board, GPS, autopilot), they may be stacked on top of each other such that the center of mass of each component passes through the plane of symmetry of the electronics assembly  12 . Maintaining symmetry for all of the components in the invention ensures a balanced weight distribution during flight. 
       FIG. 3  is an enlarged isometric view of the upper housing  32  and the assembled frame spars  16 . The four frame spars  16  may be fixated to the upper housing  32  by inserting them into four tubular frame spar receptacles  46 . The four frame spars  16  may be further fixated by the use of set screws (not shown) threaded into set screw bosses  70 . Propeller drive  14  wires (not shown) may be routed through the frame spars  16  from the electronics assembly  12  through holes  72  in the upper housing  32 . The upper plate  56  may be attached to the upper housing  32  using screws (not shown) that thread into upper plate threaded bosses  52 . 
       FIG. 4  is a front isometric view of the motor mount  20  assembly, and  FIG. 5  is a bottom isometric view of the motor mount  20  assembly. The propeller drives  14  may consist of the motor  80  (e.g. 850Kv AC2830-358 sold by 3D Robotics Inc.), a propeller  82  (e.g. APC 11x47 Push Pull Set sold by 3D Robotics Inc.), and propeller mounting hardware  84  (e.g. Propeller fastener kit sold by 3D Robotics Inc.). Propeller drive  14  may be rigidly attached to the motor mount  20  using screws (not shown) through access holes  90 . Two of the four propeller drives  14  spin in opposite directions in order to cancel out any net torsional forces, and the propellers are mounted as a means to provide thrust in the same direction with their axes aligned in the same upward vertical direction. 
     The motor mount  20  may be attached to frame spar  16  by inserting it into a frame spar receptacle  98  and further securing it using set screws (not shown) threaded into set screw bosses  94 . This frame spar receptacle  98  may be a thru hole formed into the motor mount  20  allowing wires to pass between the electronics assembly  12  and the propeller drives  14 . The motor mount  20  may be further stiffened (especially in torsion) by attaching a motor spar  18  that attaches a pair of motor mounts  20 . The motor spar may be fixated by inserting into a motor spar receptacle  96  and further securing it using a set screw (not shown) threaded into a set screw hole  88 . The leg  22  may be attached to the motor mount  20  using a vertical spar receptacle  86 , which may be a thru hole formed into the motor mount  20 . The leg  22  may be further secured using one or more set screws (not shown) threaded into a set screw holes  92 . 
       FIG. 6  is a front isometric view of the detachable sheet sail wing assembly  100 . The sheet sail wing assembly may be comprised of a sheet sail  102 , two lateral spars  104   a  and  104   b , two spine spars  106   a  and  106   b , two front vertical spars  108   a  and  108   b , and two rear vertical spars  110   a  and  110   b . The spars may be comprised of lightweight carbon fiber tubing (e.g. 0.240″ diameter pultruded carbon tubes distributed by Goodwinds Inc.). The sheet sail  102  may be comprised of a common kite material (e.g. ripstop nylon fabric).  FIG. 7  is a front isometric view of the sheet sail. The lateral spars  104   a  and  104   b , may be secured using seams  120  sewn into the sheet sail  102 . Cutouts  122  may be cut into the sheet sail  102  to provide clearance for spar connectors. 
       FIG. 8  is an enlarged isometric view of the wing spars and connectors. Two spars may be joined together using a spar connector  130  and a pivot connector  136 . The spar connector  130  may be fixated to the spars using a thru hole  134  and threaded holes  132  for set screws (not shown). The pivot connectors  136  may be attached to the end of a spar by inserting it into a blind hole  138  and using adhesive to secure the connector. The two connectors may then be joined together using a quick release pin  140 . The quick release pin  140  allows the spars to be quickly disassembled (as shown n  FIG. 9 ) to enable the wing to be folded into a compact shape (e.g. rolled into a tight cylindrical shape) for easy transport and storage. The quick release pin  140  may use a spring loaded ball  146  to secure the pin in holes  142  and  144  in the connectors. 
       FIG. 10  is a front isometric view of the multicopter  10  with the sheet sail wing assembly  200  attached. The vertical spar receptacles  86   a ,  86   b ,  86   c , and  86   d  in the motor mounts  20  serve a dual purpose whereby the legs  22  may be removed so that the vertical spars of a wing assembly  108   a ,  108   b ,  110   a , and  110   b  may then be inserted into the vertical spar receptacles so that the vertical spars may act to secure the wing and act as the legs of the multicopter. This dual purpose ensures the multicopter contains no added features with added weight to secure a detachable wing. 
       FIG. 11  and  FIG. 12  are front views of the multicopter with the sheet sail wing assembly attached  200 , each view shows the wing angle from horizontal  210  in two different positions.  FIG. 13  is a front view of the multicopter with the sheet sail wing assembly attached  200  in the forward thrust position with the propeller thrust vector  212   a  and  212   b  tilted forward towards the direction of motion. When a winged multicopter  200  moves forward, it tilts its frame forward which decreases the wing angle from horizontal  210  as shown in  FIG. 13 . There exists an optimal wing angle from horizontal  210  that provides lift with minimal drag for a given forward speed (and resulting tilt angle). The winged multicopter  200  allows this angle to be adjusted (see  FIG. 11  and  FIG. 12 ) by changing the length of the front vertical spars  108   a  and  108   b . Changing the lengths of these spars changes the wing angle with horizontal  210 . The spar connectors  130  (see  FIG. 8 ) positions must also be adjusted slightly along the axial spars  106  by loosening and retightening the set screws  132  at the new angle  210  position. The simplest way to adjust the lengths of the front vertical spars  108   a  and  108   b  is to carry sets of these spars at various lengths for quick changouts using the quick release pins  140 . Providing adjustability in the wing angle from horizontal  210  allows added versatility in optimizing wing angles for various cruising speeds. 
       FIG. 14  is a front view of the multicopter with the foam wing assembly attached  300 .  FIG. 15  is a front isomeric view of the multicopter with a detachable foam wing assembly attached  300 . The foam wing construction may take many forms, typically it may involve a hard resin shell over a foam wing shape for added durability and strength. Strut reinforcements (as shown in  FIG. 6 ) may also form the inner structure of the foam wing. The foam wing is an alternate embodiment that would function the same as the foldable sheet sail wing  100  with adjustability in the wing angle from horizontal  210  in the same manner described previously. The multicopter with a detachable foam wing  300  may also include cutouts  304  for easy access to detach vertical struts. The detachable foam wing assembly would not fold for easy transport and storage.