Morphological intelligence in dynamic aerial docking: a Bistable Tension-Hinge Gripper

While unmanned aerial vehicles (UAVs) are increasingly expected to perform active physical interactions, dynamic aerial docking remains fundamentally challenging. Conventional active grippers struggle to achieve rapid response and reliable locking simultaneously due to sensing delays, actuation latency, and impact vulnerability. To address this challenge, this paper presents an aerial docking system that integrates mechanical design and flight control, built around a Bistable Tension-Hinge Gripper (BTHG). By incorporating morphological intelligence, the BTHG utilizes the collision impact to cross an elastic energy barrier. This triggers a rapid snap-through instability that forces the mechanism into a securely locked state. This purely passive locking process eliminates the need for continuous power or active feedback during the transient contact phase. Furthermore, the outwardly flared geometry of the gripper enlarges the capture region. Its compliant structure also absorbs collision shocks to protect the UAV during rapid physical contact. Bench tests demonstrate that the prototype completes the locking transition in 0.16 s and provides a maximum holding force of 54.8 N. When integrated with onboard perception and a PX4/ROS2 flight control framework, the BTHG enables a fully autonomous docking pipeline at approach speeds up to 1.4 m s. This pipeline seamlessly covers visual target detection, agile approach, and passive locking. By shifting the highly dynamic contact response from active software control to physical hardware design, this work enables UAVs to perform reliable dynamic docking. Such capabilities pave the way for practical applications including aerial logistics relay and UAV recovery by a mothership.