Abstract:
An unmanned aerial vehicle includes a tubular base structure, a motor having a stator, the stator being connected to the tubular base structure, an energy storage module configured to supply power to the motor, and at least one propeller driven by the motor, wherein the tubular base structure houses at least one cable for routing power or signals, or a fuel conduit or wire conduit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 62/327,014, filed on Apr. 25, 2016, which is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to aerial vehicles and, more particularly, to an unmanned aerial vehicle having a tubular base structure. 
       BACKGROUND OF THE INVENTION 
       [0003]    An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot aboard. Its flight is controlled either autonomously by onboard computers or by the remote control of a pilot on the ground or in another vehicle. UAVs are commonly used in military and special operations applications, and are increasingly finding uses in civil, commercial and recreational applications, such as policing and surveillance, aerial filming, and delivering of packages to end consumers. 
         [0004]    Existing UAVs may be of the single rotor or dual coaxial rotor type, which provide a number of distinctive advantages over other UAV designs. For example these types of UAVs typically have a compact footprint, a small rotor disc surface area, and a small circumference, which makes them particularly suitable for a number of application where close interaction with people and reliable operation even with environment disturbances is essential. 
         [0005]    One notable problem when designing single rotor or dual coaxial rotor UAVs is the inherent difficulty of the proper weight distribution throughout the UAV. Three important high-mass objects, the propulsion system (including the electric motor and propellers), the energy source module (typically a battery), and the cargo module (e.g., a cargo compartment, camera or other useful cargo/instrument the UAV transports), must often be taken into account, which affect the weight distribution of the UAV. 
         [0006]    In view of the above, there is therefore a need for a UAV design in which the weight of the UAV is distributed in such a way as to minimize the inertial moment of the UAV. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide an unmanned aerial vehicle. 
         [0008]    It is another object of the present invention to provide an unmanned aerial vehicle in which the weight of the UAV is distributed in such a way as to minimize the inertial moment of the UAV. 
         [0009]    It is another object of the present invention to provide an unmanned aerial vehicle that provides a shorter path for signal and/or power-carrying cables as compared to existing vehicles. 
         [0010]    These and other objects are achieved by the present invention. 
         [0011]    According to an embodiment of the present invention an unmanned aerial vehicle includes a tubular base structure, a motor having a stator, the stator being connected to the tubular base structure, an energy storage module configured to supply power to the motor, and at least one propeller driven by the motor, wherein the tubular base structure houses at least one cable for routing power or signals, or a fuel conduit or wire conduit. 
         [0012]    According to another embodiment of the present invention, a method for minimizing the inertial moment of an unmanned aerial vehicle includes providing a tubular base structure having a generally hollow interior, an upper end and a lower end, equipping the tubular base structure with a motor and at least one propeller configured to be driven by the motor, connecting a hollow compartment to one of the upper end of the tubular base structure and the lower end of the tubular base structure, and connecting an energy storage module to the tubular base structure, the energy storage module being configured to supply power or fuel to the motor. The tubular base structure houses at least one cable for routing power or signals, or a fuel conduit or wire conduit. 
         [0013]    According to yet another embodiment of the present invention, an unmanned aerial vehicle includes a tubular base structure having a generally hollow interior, an upper end and a lower end, an upper mounting fixture associated with the upper end, a lower mounting fixture associated with the lower end, a motor operatively connected to the tubular base structure, at least one propeller configured to be driven by the motor, a generally hollow compartment mounted to one of the upper mounting fixture and the lower mounting fixture, and an energy storage module mounted to the other of the upper mounting fixture and the lower mounting fixture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: 
           [0015]      FIG. 1  is a perspective view of a portion of an unmanned aerial vehicle according to an embodiment of the present invention. 
           [0016]      FIG. 2  is a cross-sectional view of the unmanned aerial vehicle of  FIG. 1 . 
           [0017]      FIG. 3  is a side elevational view of an unmanned aerial vehicle, according to another embodiment of the present invention. 
           [0018]      FIG. 4  is a top plan view of the unmanned aerial vehicle of  FIG. 3 . 
           [0019]      FIG. 5  is a cross-sectional view of area A of  FIG. 3 . 
           [0020]      FIG. 6  is side, cross-sectional view of the unmanned aerial vehicle of  FIG. 3 , shown with a battery compartment and cargo compartment attached to the vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    With reference to  FIGS. 1 and 2 , an unmanned aerial vehicle (“UAV”)  10  according to an embodiment of the present invention is illustrated. The UAV  10  may generally take the form of any UAV known in the art. As illustrated therein, the UAV is depicted as a dual coaxial rotor UAV. The UAV  10  includes a tubular base structure  12  operatively connected to a motor having a rotor  14  and a stator  16 . As best illustrated in  FIG. 2 , the tubular base structure  12  is rigidly attached to the stator of the motor (or to the stators of both motors in the case of a dual coaxial rotor). In an embodiment, the stator(s)  16  and the tubular base structure  12  are integrated into a single structure. 
         [0022]    The tubular base structure  12  preferably includes, or is otherwise connected to, an upper flange  18  and a lower flange  20  (or similar mounting fixtures), the purposes of which will be described hereinafter. The tubular base  12  also includes a rotor flange  22  connected to the rotor  14 , which is utilized to attach propellers  24 ,  26  to the rotor  14  using bolts  28  or other suitable fasteners. The tubular base structure  12  is spatially mounted along the center of rotation of the propellers  24 ,  26  of the UAV. 
         [0023]    As also shown in  FIG. 2 , the unmanned aerial vehicle  10  includes a plurality of internal ball bearings  30  that facilitate rotation of the propellers  24 ,  26 , and power cables  32  for connecting the motor coils to an electronic speed controller (not shown) for the motor. 
         [0024]    Referring now to  FIGS. 3-6 , an unmanned aerial vehicle  100  according to another embodiment of the present invention is illustrated. The unmanned aerial vehicle  100  is substantially similar to the unmanned aerial vehicle  10  described above in connection with  FIGS. 1 and 2 , where like reference numerals designate like part. 
         [0025]      FIG. 6  shows the UAV  100  with a hollow cargo compartment  110  having a lid  112  and a energy source module  114  attached to the tubular base structure  12  via the upper and lower flanges  18 ,  20 , respectively. The lower flange  20  may also be utilized to connect auxiliary electronics to the UAV. The cargo compartment  110  may be utilized to contain packages or other cargo for delivery to end customers. 
         [0026]    In either of the embodiments described above, the tubular base structure  12  is manufactured from a lightweight material with high rigidity. Suitable materials may include impregnated carbon fiber, aluminum, magnesium or injection molded polymers (with or without reinforcement fillers). In certain embodiments, the tubular base structure  12  may be manufactured with numerous openings for weight reduction and/or cable routing purposes. Importantly, the tubular base structure  12  is generally hollow and defines a vertical pathway therethrough, and is therefore particularly suitable for use for running power cables to the rotor motors of the UAV, for running power cables from the battery to the motor electronic speed controller module and/or other electronics, for routing signaling cables, and for various multi-purpose conduits. Moreover, the tubular base structure  12  serves as a base structure for the attachment of the energy source module  114 , the cargo compartment  110  and control mechanisms. 
         [0027]    Importantly, the configuration of the tubular base structure provides an as short as possible path to route the power cables from electronic speed control module(s) to the energy source module, and from the motor(s) to the electronic speed control module(s). It also provides an as short as possible path to route signal and/or power carrying cables from the upper subsection of the UAV to the lower subsection of the UAV, in the cases where different electronic components, and/or sensors and/or actuators are distributed in both the lower and the upper subsections. For all power cables this improves the efficiency and reduces the voltage drop; for all signal cables, this improves signal to noise ratio by reducing the noise. 
         [0028]    In yet other embodiments, it is contemplated that the interior of the tubular base structure  12  can be utilized for at least partially integrating or housing the energy source module of the UAV (e.g., a battery or fuel tank). Importantly, positioning the energy source module within the tubular base structure  12  mitigates the offsetting effect that a top-mounted or bottom-mounted energy source module typically has on the center of mass of the UAV. 
         [0029]    Importantly, the ability to pass cables through the tubular base structure, and the ability to house the energy storage module (e.g., battery, fuel tank, fuel cell, etc.) within the hollow base structure provides a more optimal weight distribution than existing vehicles. In particular, by locating the center of mass more closely to the geometric center of the UAV, inertial moments of the UAV can be minimized to an extent heretofore not seen in the art. 
         [0030]    Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of this disclosure.