System and method for optical tether departure angle measurement from winch

A method for measuring tether departure angle, α, from a winch mounted to a surface vehicle (SV) used to reel and payout an umbilical tether attached to an unmanned aerial vehicle (UAV) under slack tether control, the method comprising:

• providing a support structure connected to the winch;
• providing an optical measurement device attached to the support structure and configured for generating a series of returns from within an area slice within a field-of-view (FoV) including the tether, each return provided in polar coordinates including a range from the optical measurement device to the tether and an angle relative to an origin angle;
• converting each return to Cartesian coordinates;
• box filtering each of the Cartesian returns to eliminate Cartesian returns outside of minimum and maximum x and y positions of the tether within the FoV to obtain box filtered returns;
• morphologically filtering each of the box filtered returns by grouping adjacent box filtered returns into groupings, each grouping having a size based on total number of adjacent returns to obtain sized groupings;
• selecting a largest of the sized groupings as most likely to represent the tether;
• determining a centroid position within the largest grouping and a distance, a, from the optical measurement device to the centroid position;
• and
• determining the tether departure angle, α, using:
• the distance, a, representing side a of a triangle;
• a predetermined distance, c, measured from the optical measurement device to a tether guide departure point on the winch, the distance, c, representing side c of the triangle;
• a predetermined angle, B, measured between the sides a and c of the triangle;
• and
• a predetermined angle, θ, measured between a vertical line and the side c of the triangle.

A kit for upgrading a winch to optically measure a tether departure angle, the winch including a base frame configured for mounting to a surface vehicle (SV), a passive tether guide mounted to the base frame from which the tether departure angle is measured relative to horizontal, the winch further including a reel supported between two base frame support arms of the base frame, the reel configured to reel and payout an umbilical tether in coordination with the passive tether guide and rotationally driven by a motor, the tether connected at one end to the winch mounted to the SV, the tether passing through the passive tether guide, and the tether connected at an opposite end to an uncrewed aerial vehicle (UAV), the kit comprising:

• a support structure including:
• two angled support brackets, each angled support bracket having a proximal end and a distal end, each of the proximal ends configured for mounting to a respective one of the two base frame support arms;
• and
• a bridge configured to connect between the distal ends of the two angled support brackets;
• and
• an optical measurement device configured for mounting to the bridge and aimed toward the tether during operation of the winch and configured to output dynamic distance measurements from the optical measurement device to the tether during operation of the winch, the dynamic distance measurements used to calculate the tether departure angle.