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

TL;DR

This paper presents a novel integrated system combining a passive bistable gripper with adaptive control for robust aerial grasping, capable of handling uncertainties and misalignments without prior knowledge, demonstrated through real-time experiments.

Contribution

It introduces a passive bistable gripper with a cable-driven opening mechanism and an adaptive control scheme that does not require prior uncertainty bounds, enhancing aerial grasping robustness.

Findings

Successful real-time grasping experiments demonstrate system effectiveness.

The gripper can initiate grasping without precise alignment within 80 mm tolerance.

Adaptive control ensures stability without prior uncertainty bounds.

Abstract

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.