Sensing via Collisions: a Smart Cage for Quadrotors with Applications to Self-Localization

Applications of micro unmanned aerial vehicles (UAVs) are gradually expanding into complex urban and natural environments. Despite noticeable progress, flying robots in obstacle-rich environments is still challenging. On-board processing for detecting and avoiding obstacles is possible, but at a significant computational expense, and with significant limitations (e.g., for obstacles with small cross sections, such as wires). A low-cost alternative is to mitigate physical contacts through a cage or other similar protective devices. In this paper, we propose to transform these passive protective devices into functional sensors: we introduce a suspended rim combined with a central base measuring the relative displacement of the rim; we provide a full mechanical design, and derive solutions to the inverse kinematics for recovering the collision direction in real time. As a proof of concept, we show the benefits of this novel form of sensing by embedding it in a traditional particle filter for self-localization in a known environment; our experiments show that localization is possible with a minimal sacrifice in payload capacity.