Flexible Morphing Aerial Robot with Inflatable Structure for Perching-Based Human-Robot Interaction

In nature, birds perch to rest and to survey their predators and prey. In human-managed contexts, perching also facilitates interaction with humans such as falconry. Recently, researchers have developed perching-capable aerial robots as a way to save energy, and deformable structures demonstrate significant advantages in efficiency of perching and compactness of configuration. However, ensuring flight stability remains challenging for deformable aerial robots due to the difficulty of controlling flexible arms. Furthermore, perching for human interaction requires high compliance along with safety. Thus, this study aims to develop a deformable aerial robot capable of perching on humans with high flexibility and grasping ability. To overcome the challenges of stability of both flight and perching, we propose a hybrid morphing structure that combines a unilateral flexible arm and pneumatic inflatable actuators. This design allows the robot's arms to remain rigid during flight and soft while perching for more effective grasping. We also develop a pneumatic control system that improves pressure regulation while integrating safe and compliant contact and adjustable grasping forces, enhancing interaction capabilities and reducing energy consumption. Besides, we focus on the structural characteristics of the unilateral flexible arm and identify sufficient conditions under which standard quadrotor modeling and control remain effective in terms of flight stability. Finally, the developed prototype demonstrates the feasibility of compliant perching maneuvers on humans, as well as the robust recovery even after arm deformation caused by thrust reductions during flight. To the best of our knowledge, this work is the first to achieve an aerial robot capable of perching on humans for interaction.