Active tether control for a tethered multirotor

A method for controlling an active tether comprising:

• transmitting a desired motor current setpoint to a current controller;
• rotating a motor and driving a cable reel;
• applying a spring tension to a tensioning pulley responsive to the position of the tensioning pulley;
• generating a feedback signal proportional to the tensioning pulley position;
• receiving a tensioning pulley position feedback signal;
• reading the desired current at an output of a tension controller;
• and
• returning an estimated tension feedback signal required to drive the cable reel to a position to apply a desired tension on the active tether.

A control system for tensioning an active tether for a multirotor unmanned aerial system, the control system comprising:

• a tensioning pulley and a tensioning spring;
• the tensioning spring arranged to generate a variable tension force on the active tether;
• a transducer connected adjacent to the tensioning spring to sense a linear displacement position of the tensioning pulley and to transmit a position signal to a controller, the position signal proportional to the linear displacement position;
• a servomotor in communication with the controller for receiving a control signal from the controller;
• the controller configured to:
• transmit a desired motor current setpoint to a current controller;
• receive a motor position feedback signal indicative of motor position;
• read the desired current at the output of a tension controller;
• and
• return an estimated tension feedback signal to generate an output current required to drive the cable reel to a position to apply the desired tension on the active tether;
• the servomotor configured to drive a cable reel in response to the estimated tension feedback signal, the cable reel being rotatably mounted in the frame for spooling the tether in response to rotation of the servomotor;
• wherein the cable reel is rotated by the servomotor to maintain a predetermined tension on the tensioning spring.