Maintaining a stable phase difference between multiple tethered vehicles lifting a payload
A system to maintain a phase difference is disclosed. Two or more aircraft fly in a continuous periodic trajectory. The system maintains a phase difference between the two or more aircraft. Telemetry information for a reference aircraft moving in a first periodic trajectory is received. A phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory is determined. A variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference is determined. A new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the new periodic trajectory is determined, and the primary aircraft is maneuvered to follow the new trajectory.
1. A system to maintain a target phase difference comprising:
an interface configured to receive telemetry information for a reference aircraft moving in a first periodic trajectory; and
a processor configured to:
determine a phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory, wherein the primary aircraft and the reference aircraft are configured to lift a common payload;
determine a variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference;
determine a new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the first periodic trajectory; and
cause the primary aircraft to move in the new trajectory, wherein the new trajectory is a tighter circle and a higher altitude relative to a trajectory of the reference aircraft.
2. The system of claim 1 , wherein the processor is configured to determine the primary aircraft to be ahead or behind of a target position based on the variance in phase difference.
3. The system of claim 1 , wherein in the event that the primary aircraft is determined to be behind of a target position based on the variance in phase difference, the processor is configured to compute the new trajectory such that the primary aircraft moves towards a center of the first periodic trajectory.
4. The system of claim 1 , wherein in the event that the primary aircraft is determined to be ahead of a target position based on the variance in phase difference, the processor is configured to compute the new trajectory such that the primary aircraft moves away from a center of the first periodic trajectory.
5. The system of claim 1 , wherein the phase difference is determined based at least in part on one or more of the following: a sensor data, a visual data, and a location data.
6. The system of claim 1 , wherein the primary aircraft comprises one or more of the following: a global positioning system, a ground reference sensor, a line angle sensor, and a camera.
7. The system of claim 1 , wherein the primary aircraft communicates with the reference aircraft.
8. The system of claim 1 , wherein the new trajectory is a translation of the first periodic trajectory.
9. The system of claim 1 , wherein the reference aircraft further moves in the new trajectory.
10. The system of claim 1 , wherein the primary aircraft is upwind of the reference aircraft, and the processor is further configured to instruct the primary aircraft to fly closer to a vertical of the payload to bear a greater load compared with the reference aircraft to cause a battery of the primary aircraft to be preserved.
11. The system of claim 1 , wherein the new trajectory compensates for wind effects.
12. The system of claim 1 , wherein the primary aircraft comprises the interface and the processor.
13. The system of claim 1 , wherein the interface and the processor are provided in the primary aircraft, and the interface and the processor are in communication with the reference aircraft.
14. The system of claim 1 , wherein the primary aircraft and the reference aircraft are configured to lift the payload via at least one tether.
15. The system of claim 1 , wherein the primary aircraft and the reference aircraft are configured to lift the payload via at least one tether and the payload comprises a camera or sensor.
16. The system of claim 1 , wherein a throttle level of the primary aircraft is determined that decreases the variance in the phase difference.
17. The system of claim 1 , wherein a throttle level of the primary aircraft is determined that decreases the variance in the phase difference in the event that the new trajectory does not optimally decrease the variance in the phase difference.
18. A method to maintain a target phase difference, comprising:
receiving telemetry information for a reference aircraft moving in a first periodic trajectory;
determining, using a processor, a phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory, wherein the primary aircraft and the reference aircraft are configured to lift a common payload;
determining a variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference;
determining a new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the first periodic trajectory; and
causing the primary aircraft to move in the new trajectory, wherein the new trajectory is a tighter circle and a higher altitude relative to a trajectory of the reference aircraft.
19. A computer program product for maintaining a target phase difference, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:
receiving telemetry information for a reference aircraft moving in a first periodic trajectory;
determining a phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory, wherein the primary aircraft and the reference aircraft are configured to lift a common payload;
determining a variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference;
determining a new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the first periodic trajectory; and
causing the primary aircraft to move in the new trajectory, wherein the new trajectory is a tighter circle and a higher altitude relative to a trajectory of the reference aircraft.