The DBCF-EM Gripper: Using Dual-Belt Curved-Flexure Eversion Mechanism Fingers for Confined-Space Robotic Grasping

Abstract

Conventional fingered grippers often struggle in confined spaces because limited lateral access prevents finger insertion and inward closing. This letter presents the DBCF-EM gripper, whose fingers combine a base-driven curved flexure, prescribing a tangential object-following trajectory, with a dual-belt eversion system that creates near-stationary contact surfaces and reduces sliding at the contact interfaces. This enables a low-disturbance caging grasp strategy in which the fingers propagate along the object surface rather than closing perpendicularly toward it. A prototype gripper was built for robotic tomato-removal experiments from a crate. Experiments showed contour following with a maximum deviation of 3 mm, negligible normal disturbance of at most 0.1 N, and a 91–97% reduction in tangential disturbance forces. In robotic trials, the gripper achieved 100% pick-up success and a 91% damage-free success rate, demonstrating its effectiveness for confined-space grasping.