Collision-tolerant Autonomous Navigation through Manhole-sized Confined Environments

This work presents the design, development and autonomous navigation of the Resilient Micro Flyer, a new type of collision-tolerant small aerial robot tailored to traversing and searching within highly confined environments including manhole-sized tubes. The robot is particularly lightweight and agile, while it implements a collision-tolerant design which renders it resilient during forcible interaction with the environment. The overall rigid design of the system is enhanced through elastic passive flaps ensuring smoother and more compliant collision which was identified to be especially useful in very confined settings. Focusing on autonomous operations in narrow environments, the presented research realizes four key functionalities, namely a) visual-inertial odometry for pose estimation, b) a policy for sufficient clearance from nearby objects relying purely on four ultra-lightweight time-of-flight sensors, c) the detection of collisions with the environment as an anomaly on the inertial measurement data, and d) the direct mechanical feedback-based self-centering and smooth traversal of very tight spaces based on its elastic flaps. The final system prototype is capable of 14min of endurance and weighs less than 500g. A comprehensive experimental study is presented in which the robot is tasked to navigate through two rooms connected via a manhole-sized (width $\times$ height equal to $0.5\times 0.4\mathbf{m}$ ) tube with a length of 2.5m.