There’s a paper here on Motion Estimation for Tethered Airfoils with Tether Sag
by * Jan Hendrik Freter
Very handy for all the Yo-Yo fans
The conclusion reads as…
VI. CONCLUSION
We have considered the problem of estimating the position
of tethered airfoils from tether angle measurements and IMU
data, whereby we focused on the effect of tether sag on
the position. We proposed a novel method that adaptively
weights between the tether angles and the IMU data accord
ing to the tether force. In comparison to a state-of-the-art KF,
the developed fusion method has demonstrated to converge
signifificantly faster on simulated and experimental data and
has led to an improved accuracy. The method assures that
the tether angles are trusted whenever they are known to
be reliable. Furthermore, the method uses the IMU data to
overcome the periods when sagging occurs and the tether
angles are unreliable. However, the experimental data only
provides a proof of concept and a detailed validation study
with an accepted ground-truth measurement will be subject
of future research.
We conclude that the developed method allows the user to
increase the position estimation performance for tethered air
foils regarding the accuracy. Moreover, we provide a solution
that is independent from camera data and is not restricted by
weather or light conditions. The proposed method uses low
cost IMUs and can be applied for the systematic testing of
sport kites as well as for AWESs.