  Micro Aerial Vehicles (MAVs) are limited in their operation outdoors near
obstacles by their ability to withstand wind gusts. Currently widespread
position control methods such as Proportional Integral Derivative control do
not perform well under the influence of gusts. Incremental Nonlinear Dynamic
Inversion (INDI) is a sensor-based control technique that can control nonlinear
systems subject to disturbances. It was developed for the attitude control of
manned aircraft or MAVs. In this paper we generalize this method to the outer
loop control of MAVs under severe gust loads. Significant improvements over a
traditional Proportional Integral Derivative (PID) controller are demonstrated
in an experiment where the quadrotor flies in and out of a windtunnel exhaust
at 10 m/s. The control method does not rely on frequent position updates, as is
demonstrated in an outside experiment using a standard GPS module. Finally, we
investigate the effect of using a linearization to calculate thrust vector
increments, compared to a nonlinear calculation. The method requires little
modeling and is computationally efficient.
