This paper modifies an adaptive multicopter autopilot to mitigate
instabilities caused by adaptive parameter drift and presents simulation and
experimental results to validate the modified autopilot. The modified adaptive
controller is obtained by including a static nonlinearity in the adaptive loop,
updated by the retrospective cost adaptive control algorithm. It is shown in
simulation and physical test experiments that the adaptive autopilot with
proposed modifications can continually improve the fixed-gain autopilot as well
as prevent the drift of the adaptive parameters, thus improving the robustness
of the adaptive autopilot.Comment: 6 pages, 16 figures, submitted to IROS 202