초록 ▼

A platform including two winged aircraft are tethered during flight by a single tether near their respective centers of gravity. The tether is windable about a reel, so that a distance between the aircraft can be changed during flight. The aircraft contain avionics configured to enable autonomous fl

A platform including two winged aircraft are tethered during flight by a single tether near their respective centers of gravity. The tether is windable about a reel, so that a distance between the aircraft can be changed during flight. The aircraft contain avionics configured to enable autonomous flight using natural wind gradients. One aircraft imposes aerodynamic forces on the other, through the tether, while flying at an altitude where wind speed is significantly different than wind speed at an altitude of the other aircraft. The two aircraft cruise back and forth within a maximum distance from a station on the ground. Cruise conditions are established using an iterative computer algorithm which utilizes flight measurements. The aircraft communicate information between each other, and the ground, and contain a payload which performs a useful function at high altitudes.

대표청구항 ▼

1. A method of station-keeping, comprising: connecting first and second winged aircraft together by a tether and a tether length adjustment mechanism, the first and second aircraft containing fixed and moveable control surfaces and avionics configured to enable said respective first and second aircr

1. A method of station-keeping, comprising: connecting first and second winged aircraft together by a tether and a tether length adjustment mechanism, the first and second aircraft containing fixed and moveable control surfaces and avionics configured to enable said respective first and second aircraft to perform autonomous flight using a natural wind differential, the avionics including software stored on non-transitory media, the software configured to determine a flight path for each of the aircraft, including to calculate a current relative wind velocity vector for the connected aircraft by using data obtained by subtracting the wind velocity vectors of each aircraft in accordance with the formula {right arrow over (V)}RW={right arrow over (V)}W1−{right arrow over (V)}W2; andchanging a length of said tether, during flight of the first and second aircraft, using said tether length adjustment mechanism, to thereby change a distance between said first and second aircraft when said first and second aircraft are in flight. 2. The method of claim 1, further including flying the first and second aircraft, connected by the tether, at different altitudes with respect to each other, where the wind speed is substantially different at the different altitudes. 3. The method of claim 1, wherein the software is further configured to calculate a flight path for forward and reverse segments of travel according to the formula H⇀fwd,rev=V->RW×(±1⁢k^)V->RW. 4. The method of claim 1, wherein the avionics are configured to attempt to maintain a yaw angle of substantially zero. 5. The method of claim 1, the software further configured to estimate the required ground speed of connected aircraft, and roll, angle of attack, and relative horizontal separation of each of the connected aircraft during flight, by solving the following system of equations D⇀S+L⇀S+W⇀S+T⇀1+F⇀C,S=0⇀D⇀B+L⇀B+W⇀B+T⇀N+F⇀C,B=0⇀D⇀1+L⇀1+W⇀1-T⇀1-T⇀2+F⇀C,1⁢0⇀⁢…D⇀N+L⇀N+W⇀N-T⇀N-1-T⇀N+F⇀C,N=0⇀wherein the subscripts S and B represent the first and second aircraft, respectively, and numerical subscripts represent segments of the tether connecting the two aircraft, and wherein the vectors D, L, W, T, and FC, represent the estimated drag, lift, weight, tether tension, and correction forces, respectively. 6. The method of claim 5, wherein the software is further configured to calculate the solution to the system of equations including a set of inequality constraints. 7. The method of claim 5, wherein the software is further configured to use an optimization procedure to solve the constrained system of equations. 8. The method of claim 5, further comprising performing additional iterations of the system of equations, in which the correction force vector is adjusted until vehicle acceleration magnitudes are within a predetermined tolerance, ε, of the null vector. 9. The method of claim 1, further having the first and second aircraft attain the target heading, ground speed, aircraft orientation, and respective horizontal separation, using the avionics, the tether and tether length adjustment mechanism, and propulsion. 10. The method of claim 1, wherein the software is further configured to calculate the difference between the actual acceleration and computing a correction force in accordance with the following formulas, in sequence a⇀S=a⇀raw,S+FT,SmSF⇀C,S=F⇀C,S-a⇀S*mSa⇀B=a⇀raw,B+FT,BmBF⇀C,B=F⇀C,B-a⇀B*mBwherein a is acceleration, FT is the current thrust force, m is vehicle mass, and the subscript raw is a measured value. 11. The method of claim 1, wherein said tether is a single tether connectable near the center of gravity of said first and second aircraft at a single point. 12. A station-keeping apparatus, comprising: first and second winged aircraft each containing fixed and moveable control surfaces and avionics configured to enable said respective first and second aircraft to perform autonomous flight;a tether connectable near the center of gravity of said first and second aircraft;at least one reel connected to at least one of said first and second winged aircraft and operative to increase or decrease a length of said tether extending between said first and second aircraft when said tether is connected, to thereby change a distance between said first and second aircraft when said first and second aircraft are in flight;a computer connected to at least one of said first and second aircraft and operative to execute software stored on non-transitory media configured to calculate a flight path for forward and reverse segments of travel of said first and second aircraft according to the formula H⇀fwd,rev=V->RW×(±1⁢k^)V->RW. 13. The apparatus of claim 12, wherein said tether is at least 500 meters in length. 14. The apparatus of claim 12, wherein said tether length is between 500 meters and 8 kilometers in length. 15. The apparatus of claim 12, wherein said first and second vehicles are configured to fly at different altitudes. 16. The apparatus of claim 12, wherein at least one of said aircraft further includes a docking mechanism configured to attach and release said aircraft from a deployment vehicle. 17. The apparatus of claim 12, further including onboard propulsion within at least one of said first and second aircraft. 18. The apparatus of claim 12, further including a wind turbine and generator configured to provide electricity during a flight of at least one of said first or second aircraft. 19. The apparatus of claim 12, wherein the tether length adjuster includes a mechanism selected from the group consisting of: reel, spool, pulley, pinch rollers, moveable gripper, and gripping arm. 20. The apparatus of claim 12, wherein said software is further configured to estimate the required ground speed of said first and second connected aircraft, and roll, angle of attack, and relative horizontal separation of each of the connected aircraft during flight, by solving the following system of equations D⇀S+L⇀S+W⇀S+T⇀1+F⇀C,S=0⇀D⇀B+L⇀B+W⇀B+T⇀N+F⇀C,B=0⇀D⇀1+L⇀1+W⇀1-T⇀1-T⇀2+F⇀C,1⁢0⇀⁢…D⇀N+L⇀N+W⇀N-T⇀N-1-T⇀N+F⇀C,N=0⇀wherein the subscripts S and B represent the first and second aircraft, respectively, and numerical subscripts represent segments of the tether connecting the two aircraft, and wherein the vectors D, L, W, T, and FC, represent the estimated drag, lift, weight, tether tension, and correction forces, respectively.