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Methods and systems for raising and lowering a payload

  • US 10,232,940 B2
  • Filed: 12/22/2016
  • Issued: 03/19/2019
  • Est. Priority Date: 09/09/2016
  • Status: Active Grant
First Claim
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1. A system comprising:

  • a tether disposed on a spool;

    a motor arranged in an unmanned aerial vehicle (UAV), wherein operating the motor in a first mode and a second mode respectively counters and assists unwinding of the tether due to gravity;

    a payload coupling apparatus structured to mechanically couple the tether to a payload;

    a payload latch switchable between a closed position that prevents the payload from being lowered from the UAV and an open position that allows the payload to be lowered from the UAV; and

    a control system configured to determine that the UAV is located at a pickup location and responsively operate in a payload pickup mode, wherein during operation in the payload pickup mode the control system is configured to;

    open the payload latch;

    operate the motor to unwind a predetermined length of the tether corresponding to an expected payload attachment altitude for the payload coupling apparatus;

    after unwinding the predetermined length of the tether and waiting for a predetermined payload attachment period, operate the motor in the first mode for a predetermined attachment verification period;

    determine, based at least in part on motor current during the predetermined attachment verification period, that the payload coupling apparatus is mechanically coupled to the payload;

    responsive to the determination that the payload coupling apparatus is mechanically coupled to the payload, operate the motor to retract the tether;

    while retracting the tether, determine that both;

    (a) an unwound length of the tether is less than a threshold length and (b) motor current during the retraction of the tether is greater than a threshold current, and responsively operate the motor to pull the payload into a receptacle on a lower surface of the UAV; and

    after operation of the motor to pull the payload into the receptacle, close the payload latch to secure the payload in the receptacle.

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