  Current control design for fast vision-based flight tends to rely on
high-rate, high-dimensional and perfect state estimation. This is challenging
in real-world environments due to imperfect sensing and state estimation drift
and noise. In this letter, we present an alternative control design that
bypasses the need for a state estimate by exploiting discrete-time flatness. To
the best of our knowledge, this is the first work to demonstrate that
discrete-time flatness holds for the Euler discretization of multirotor
dynamics. This allows us to design a controller using only a window of input
and output information. We highlight in simulation how exploiting this property
in control design can provide robustness to noisy output measurements (where
estimating higher-order derivatives and the full state can be challenging).
Fast vision-based navigation requires high performance flight despite possibly
noisy high-rate real-time position estimation. In outdoor experiments, we show
the application of discrete-time flatness to vision-based flight at speeds up
to 10 m/s and how it can outperform controllers that hinge on accurate state
estimation.
