Neither Fast Nor Slow: How to Fly Through Narrow Tunnels
This addresses a critical problem for autonomous drones in confined environments like inspection or rescue missions, representing an incremental improvement in domain-specific robotics.
The paper tackles the challenge of enabling autonomous multirotors to fly safely through narrow tunnels as narrow as 0.6 m by developing a system with a motion planner that generates smooth trajectories along tunnel center lines, validated through extensive flight experiments.
Nowadays, multirotors are playing important roles in abundant types of missions. During these missions, entering confined and narrow tunnels that are barely accessible to humans is desirable yet extremely challenging for multirotors. The restricted space and significant ego airflow disturbances induce control issues at both fast and slow flight speeds, meanwhile bringing about problems in state estimation and perception. Thus, a smooth trajectory at a proper speed is necessary for safe tunnel flights. To address these challenges, in this letter, a complete autonomous aerial system that can fly smoothly through tunnels with dimensions narrow to 0.6 m is presented. The system contains a motion planner that generates smooth mini-jerk trajectories along the tunnel center lines, which are extracted according to the map and Euclidean Distance Field (EDF), and its practical speed range is obtained through computational fluid dynamics (CFD) and flight data analyses. Extensive flight experiments on the quadrotor are conducted inside multiple narrow tunnels to validate the planning framework as well as the robustness of the whole system.