Perching and Grasping Using a Passive Dynamic Bioinspired Gripper

The ability to grasp objects broadens the application range of unmanned aerial vehicles (UAVs) by allowing interactions with the environment. The difficulty in performing a mid-air grasp is the high probability of impact between the UAV's foot and the target. For a successful grasp, the foot must smoothly absorb the energy of impact and simultaneously engage with the target in a short period of time. We present a bioinspired passive dynamic foot in which the claws are actuated solely by the impact energy. Our gripper simultaneously resolves the issue of smooth absorption of the impact energy and fast closure of the claws by linking the motion of an ankle linkage and the claws through soft tendons. We study the dynamics of impact and use the stiffness of the tendon as our design/control parameter to adjust the mechanics of the gripper for smooth recycling of the impact energy. Our gripper closes within 45 milliseconds after initial contact with the impacting object without requiring any controller or actuation energy. An electro-adhesive locking mechanism attached to the tendon locks the claws within 20 milliseconds after reaching closed configuration. We demonstrated the effectiveness of our gripper by integrating it in a UAV and performing a variety of passive dynamic perching and grasping tasks.