Method of actively controlling winch swing via modulated uptake and release

1. An unmanned aerial vehicle (UAV) comprising:

a winch system, wherein the winch system includes a single winch line having a first end that is secured to the payload at a single point of attachment on the payload, and wherein the winch system is controllable to vary the rate of descent of the payload;

an inertial measurement unit positioned on the payload or on the first end of the winch line, wherein the inertial measurement unit (IMU) is configured to measure oscillations of the payload a descent of the payload for delivery or ascent of the payload for retrieval; and

a control system including a processor and program instructions stored in a non-transitory computer-readable medium and executable by the processor to control the winch to perform the functions of the controller, the control system configured to:

(a) receive data from the IMU;

(b) determine oscillations of the payload based on the data received from the IMU; and

(c) operate the winch system to vary the deployment rate of the winch line so to damp oscillations of the payload during descent or ascent of the payload.

2. The UAV of claim 1 , wherein the control system is further configured to control oscillations of the payload by unwinding the winch line when the payload moves towards a bottom of a swing.

3. The UAV of claim 2 , wherein the control system is further configured to control oscillations of the payload by stopping or slowing the rate at which the winch line is unwound when the payload moves from the bottom of the swing towards a top of the swing.

4. The UAV of claim 2 , wherein the control system is further configured to control oscillations of the payload by winding the winch line in when the payload moves from the bottom of the swing towards a top of the swing.

5. The UAV of claim 1 , wherein the inertial measurement unit is configured to determine a period of oscillation of the payload during the descent of the payload.

6. The UAV of claim 5 , wherein the control system is configured to wind in the winch line at a first pair of separate points during the period of oscillation of the payload, and to unwind the winch line at a second pair of separate points during the period of oscillation of the payload.

7. The UAV of claim 1 , wherein the winch system is controllable to vary the rate of ascent of the payload; and

the control system is configured to control oscillations of the payload during ascent by operating the winch system to control the rate of ascent of the payload in response to measurements received from the inertial measurement unit.

8. The UAV of claim 7 , wherein the control system is further configured to control oscillations of the payload during ascent by winding up the winch line when the payload moves from a bottom of a swing to toward a top of the swing.

9. The UAV of claim 8 , wherein the control system is further configured to control oscillations of the payload during ascent by unwinding the winch line when the payload moves towards the bottom of the swing.

10. The UAV of claim 8 , wherein the control system is further configured to control oscillations of the payload during ascent by reducing or stopping the rate the winch line is wound in when the payload moves towards the bottom of the swing.

11. The UAV of claim 7 , wherein the inertial measurement unit is configured to determine a period of oscillation of the inertial measurement unit during ascent of the inertial measurement unit.

12. The UAV of claim 11 , wherein the control system is configured to wind in the winch line at a first rate at a first pair of separate points during the period of oscillation of the inertial measurement unit, and wind in the winch line at a second lower rate at the second pair of separate points during the period of oscillation of the inertial measurement unit.

13. The UAV of claim 12 , wherein the control system is configured to unwind the winch line at the first pair of separate points during the period of oscillation of the inertial measurement unit.

14. The UAV of claim 1 , wherein the control system is configured to wind in the winch line at a rate proportional to a velocity of the payload as the payload moves from a bottom of a swing towards a top of the swing.

15. The UAV of claim 1 , wherein the control system is further configured to control oscillations of the payload by translating the position of the UAV in response to measurements received from the inertial measurement unit.

16. The UAV of claim 1 , wherein the control system is configured to reverse the direction of winch line travel twice during a period of oscillation of the payload.