Methods and systems for detecting and resolving failure events when raising and lowering a payload

A system comprising:

• a tether disposed on a spool, wherein a first end of the tether is non-fixedly wound on the spool;
• a payload coupling apparatus structured to mechanically couple a second end of the tether to a payload;
• 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;
• and
• a control system configured to control the motor to carry out tethered delivery of the payload;
• wherein the control system is further configured to, during the process of delivering the payload to a target location and while the UAV is in flight, determine that both (a) an unwound length of the tether is greater than a threshold length and (b) a motor current of the motor is greater than a threshold current for at least a predetermined timeout period, and responsively cause the UAV to initiate a flight to a different location, such that the flight of the UAV unwinds the tether and separates the first end of the tether from the spool, thereby releasing the tether from the UAV.

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 control system configured to control the motor to carry out tethered delivery of the payload;
• wherein, during a process of picking up the payload to be delivered and while the UAV is over or near to a pickup location, the control system is further configured to:
• responsive to a determination that the payload coupling apparatus is mechanically coupled to the payload, operate the motor to retract the tether and lift the payload toward the UAV;
• while retracting the tether with the payload coupled thereto, detect an error condition when both:
• (a) the unwound length of tether is greater than a threshold length and (b) a motor current of the motor is greater than a threshold current;
• make an attempt to correct the error condition by operating the motor to unwind the tether, and then resume retracting the tether;
• and
• determine that a predetermined number of attempts to correct the error condition have been made without successfully correcting the error condition, and responsively end the process of picking up the payload and initiate a payload delivery process to return the payload to the ground at or near the pickup location.

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;
• and
• a control system configured to control the motor to carry out tethered delivery of the payload;
• wherein, during a process of picking up the payload to be delivered, and while the UAV is over or near to a pickup location, the control system is further configured to:
• operate the motor to unwind the tether and lower the payload coupling apparatus to a payload attachment altitude;
• after lowering the tether and waiting for a predetermined payload attachment period, perform an attachment verification process that comprises:
• (a) operating the motor in the first mode for a predetermined attachment verification period, and (b) determining, based at least in part on a motor current during the predetermined attachment verification period, whether or not the payload coupling apparatus is mechanically coupled to the payload, wherein the control system can lower the payload coupling apparatus and repeat the attachment verification process up to a predetermined number of times when it is determined that the payload coupling apparatus is not mechanically coupled to the payload;
• and
• determine that the attachment verification process has been repeated the predetermined number of times without successful coupling of the payload coupling apparatus to the payload and responsively initiate a process to cancel pickup of the payload and initiate flight of the UAV to a different location.