  Grasping using an aerial robot can have many applications ranging from
infrastructure inspection and maintenance to precise agriculture. However,
aerial grasping is a challenging problem 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, in this paper, we integrate a novel
passive gripper design and advanced adaptive control methods to enable robust
aerial grasping. The gripper is enabled by a pre-stressed band with two stable
states (a flat shape and a curled shape). 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). Our 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 experimental results to demonstrate the
effectiveness of the proposed integrated system for grasping. Our integrated
approach can pave the way to enhance aerial grasping for different
applications.
