An Integrated Approach to Aerial Grasping: Combining a Bistable Gripper With Adaptive Control

Aerial robots equipped with grasping capabilities can have many applications ranging from infrastructure inspection and maintenance to precision agriculture. However, robust aerial grasping is challenging since the robot has to maintain an accurate position and orientation relative to the grasping object, while negotiating various forms of uncertainties (e.g., contact force from the object). To address such challenges, this paper presents an integral approach by combining a novel passive gripper design and advanced adaptive control methods to enable robust aerial grasping. The gripper is enabled by a prestressed band with two stable states (flat and curled). In this case, it can automatically initiate the grasping process upon contact with an object. The gripper also features a cable-driven system by a single DC motor to open the gripper without using cumbersome pneumatics. Since the gripper is passively triggered and initially has a straight shape, it can function without precisely aligning the gripper with the object (within an 80-mm tolerance). The proposed adaptive control scheme eliminates the need for any a priori knowledge (nominal or upper bounds) of uncertainties. The closed-loop stability of the system is analyzed via Lyapunov-based method. Combining the gripper and the adaptive control, we conduct comparative real-time experiments to demonstrate the effectiveness of the proposed integrated system for grasping. The proposed integrated approach can pave the way to enhance aerial grasping for different applications.