Aggressive Quadrotor Flight through Narrow Gaps with Onboard Sensing and Computing

In this paper, we address one of the main challenges towards autonomous quadrotor flight in complex environments, which is flight through narrow gaps. We present a method that allows a quadrotor to autonomously and safely pass through a narrow, inclined gap using only its onboard visualinertial sensors and computer. Previous works have addressed quadrotor flight through gaps using external motion-capture systems for state estimation. Instead, we estimate the state by fusing gap detection from a single onboard camera with an IMU. Our method generates a trajectory that considers geometric, dynamic, and perception constraints: during the approach maneuver, the quadrotor always faces the gap to allow state estimation, while respecting the vehicle dynamics; during the traverse through the gap, the distance of the quadrotor to the edges of the gap is maximized. Furthermore, we replan the trajectory during its execution to cope with the varying uncertainty of the state estimate. We successfully evaluate and demonstrate the proposed approach in many real experiments, achieving a success rate of 80% and gap orientations up to 45◦. To the best of our knowledge, this is the first work that addresses and successfully reports aggressive flight through narrow gaps using only onboard sensing and computing. SUPPLEMENTARY MATERIAL Video of the experiments: https://www.youtube.com/watch?v=meSItatXQ7M