Unmanned aerial vehicle with optimized rotor geometry, asymmetri arm configuration, and integrated structural members

An unmanned aerial vehicle airframe, comprising:

• a. a central body defining a plurality of receptacles, each of said receptacles having a non-circular internal geometry;
• b. a plurality of arms, each arm constructed from a hollow tube having a non-circular external cross-section comprising two parallel flat opposing surfaces and two opposing convexly filleted surfaces, shaped to be received by one of said receptacles, thereby forming an integrated connection between each said arm and said central body, wherein the integrated connection prevents rotational torque relative to the central body;
• and
• c. a plurality of propulsion units, each propulsion unit comprising a motor having a flat mounting base, wherein each said motor is mounted directly to said at least one flat external surface of one of said arms.

A method of designing a bi-planar multi-rotor UAV having a first set of rotors of radius r and diameter D=2r disposed in a first plane and a second set of rotors disposed in a second plane vertically separated from the first plane by a distance h, the method comprising the steps of:

• a. defining a target aerodynamic performance limit characterized by a maximum allowable hover-power penalty (P/P0);
• b. determining a value for an empirical interaction parameter β using the predetermined data correlation curve of FIG. 10 based on the normalized vertical separation ratio (h/D) by referencing a provided data correlation;
• c. utilizing a quantitative model to calculate a fractional rotor overlap area, f, that corresponds to said predetermined hover-power penalty, wherein said quantitative model relates a hover-power multiplier, P/P0, to said fractional rotor overlap area by the formula:
• P
• P
• 0
• =
• 1
• +
• β
• ⁢
• f
• ;
• calculating a required plan-view center spacing (d) between an upper rotor and a lower rotor using an intersection area formula:
• a
• =
• 2
• ⁢
• r
• 2
• ⁢
• cos
• -
• 1
• ⁢
• (
• d
• 2
• ⁢
• r
• )
• -
• d
• 2
• ⁢
• 4
• ⁢
• r
• 2
• -
• d
• 2
• ,
• f
• =
• a
• π
• ⁢
• r
• 2
• ;
• d. determining a first arm length (L1) and a second arm length (L2) that satisfy said spacing for a given stagger angle;
• and
• e. fabricating said unmanned aerial vehicle with said first and second arm lengths.

An unmanned aerial vehicle (UAV) airframe, comprising:

• a. a central body defining a plurality of receptacles having non-circular internal geometry;
• b. a plurality of hollow arms having a non-circular external cross-section comprising two parallel flat external surfaces and two opposing convexly filleted sides, each arm received in a corresponding receptacle to form an integrated connection substantially free of external load-bearing clamping hardware;
• and
• c. a mechanical impedance transformer disposed at or adjacent to a junction of at least one arm and the central body, the mechanical impedance transformer comprising at least one localized segment that changes mechanical impedance by at least one of (i) a geometric change in cross-section and (ii) a material change relative to an adjacent portion of the arm, the transformer being configured to create a mechanical impedance mismatch sufficient to reflect and attenuate vibration energy propagating along the arm toward the central body.