Smart leash had a lot of problems & finally got a lot of upgrades in 2024.  The mane evolution was a frictionless ball bearing system with hall effect angle sensor.

This requires making a lookup table to convert the imprecise analog readings to angles.

The frictionless angle sensor introduced a new problem of the structure flapping at a certain resonant frequency.  Defeating the flapping required detuning the frequency response of the steering controller around the resonant frequency. 

The result was a steering controller which responded less to .4Hz than 1Hz & a better tool for plotting the frequency response.  That made it track very accurately.

Other attempts to reduce the amount of mass being swung around were failures.

It needed another control law where sharper turns would be performed at minimum speed, with a ramping to full speed as the turn angle decreased.  That keeps it from running away.

It got a braking algorithm where retraction would cause it to apply reverse proportionally to the amount the wheels turned beyond where the leash was retracted.

Instead of responding to angle & length, it needed to convert to X & Y.  Then steering would respond to X while speed would respond to Y.  This allowed it to follow with a sideways offset & get better video.  The trick with a sideways offset is distance & angle feedback cross into each other.  Converting to XY made it easier to defeat the crosstalk but it also created the problem of a minimum following distance required to detect X.  Below the minimum distance, it can't steer.  There's a complicated algorithm for transitioning in & out of minimum following distance.  It involves certain resets of the steering controller to allow it to do minimum speed turns while not running away.  It's still a bit problematic.

Another evolution was being able to change the sideways offset with the paw controller. 

That allows better camera angles.

The leash evolved to a more complicated & robust user interface than younger lion imagined. 

Problems remane with dirt building up inside the spool & the cable not always winding evenly.  Dirt buildup & cross windings are the mane causes of failures to retract.  When this happens, the mane symptom is loss of steering control.  The cable has to stay tensioned in order to detect angle.  Fortunately, the problem has only been when its moving slowly & it quickly unsticks.  The sound of the servo behaving erratically is the 1st sign of the retraction starting to get stuck because of dirt.