Inner-Loop Control of Fixed-Wing Unmanned Aerial Vehicles in Icing Conditions

This paper compares a model reference adaptive control (MRAC) scheme with PID con- trollers. Both are developed for the Skywalker X8 fixed-wing unmanned aerial vehicle operating in icing conditions, encompassing asymmetric icing on the wings and reduced control effective- ness. The MRAC scheme is given by a linear model with a bias term to capture unmodeled effects, and modified with the projection operator to increase robustness. The findings in this paper show that the MRAC control scheme and the PID controller demonstrate similar qualities in tracking performance with the MRAC performing better under certain conditions. Overall, both controllers exhibit the most difficulty when the icing level is severely asymmetric. Examining the bias and integral terms of the adaptive controller and PID controller, respectively, shows that the bias terms when the adaptive rate is lowered, and to some degree the roll integral term, are able to detect icing.