TY  - JOUR
T1  - Review of L1 Adaptive Control for Solving the Wing Rock Problem
AU - Carlos Suárez, F. AU - Cesar Castellanos, J. AU - Jorge Sofrony, E. 
JO  - Journal of Engineering and Applied Sciences
VL  - 16
IS  - 9
SP  - 296
EP  - 303
PY  - 2021
DA  - 2001/08/19
SN  - 1816-949x
DO  - jeasci.2021.296.303
UR  - https://makhillpublications.co/view-article.php?doi=jeasci.2021.296.303
KW  - L1 norm
KW  -adaptive control
KW  -automatic control
KW  -nonlinear system
KW  -analog filter
AB  - This article presents an L1 Adaptive Control
technique to solve the wing rock stabilization problem
which is described as a second order nonlinear system.
The wing rock phenomenon is characterized by the
appearance of a limit cycle in flight dynamics, caused by
flow asymmetries that build nonlinear aerodynamic roll
damping. The problem has been treated in the literature
using L1 Adaptive technique, but several questions arise,
especially in the way the prefilter is chosen such that the
resulting augmented system is in fact L1 and guarantees
closed loop stability under actuator and model
dynamicsuncertainties. It is found in this article that L1
first order filters used in the simulations reproduce results
of referenced authors but higher order L1 filters used,
generate unstable response, even though the calculation of
named L1 Norm Condition, considered in L1 adaptive
control theory as necessary and sufficient condition is met
which is an exception to the theory. It is shown also that
the choice of a proper third order filter instead of an
strictly proper render steady state response with stationary
error. Two schemes for the same wing rock system
dynamics are treated, reproducing results of referenced
authors in this article but higher strictly proper L1 filters
used, generate unstable response not reproducing others
results.
ER  -