A Passive Morphing Soft Quadrotor for Physical Interaction in Constrained Environments

This paper presents a soft-body quadrotor with passive morphing capabilities, designed for physical interaction in constrained environments. The soft body is composed of a dual-layer silicone grid integrated with an outer skeleton with parallel linkages. The designed airframe can maintain its original shape in free flight without requiring active control. When subjected to external forces during interaction with the environment, the quadrotor passively deforms and automatically returns to its original shape once free flight is resumed. To enable self-shape awareness, a vision-based perception approach is adopted, utilizing a downward-facing camera to monitor the frame. Given the unknown traversability of the environment, we propose a variable impedance controller that adaptively regulates the quadrotor's interaction behavior. Additionally, an adaptive attitude controller is employed to address model uncertainties. The effectiveness of the proposed design is validated through real-world experiments, including collisions with unknown environmental obstacles and traversal through narrow passageways.