Fly Out The Window: Exploiting Discrete-Time Flatness for Fast Vision-Based Multirotor Flight

TL;DR

This paper introduces a novel control approach for multirotor drones that leverages discrete-time flatness to enable fast, robust vision-based flight without relying on precise state estimation, demonstrated through simulations and outdoor experiments.

Contribution

It is the first to show discrete-time flatness in multirotor dynamics and uses this property to design controllers that are robust to noisy measurements.

Findings

Robust control achieved without full state estimation.

Successful outdoor flights at speeds up to 10 m/s.

Outperforms traditional controllers relying on accurate state estimates.

Abstract

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.