1-DOF band-based gripper using iris mechanism

Abstract

Soft grippers, which are robotic end-effectors made from deformable materials such as silicone or elastomers, offer inherent compliance and flexibility. These characteristics are crucial for grasping delicate or irregularly shaped objects without causing damage, making them suitable for applications where conventional rigid grippers may fail. Although various soft grippers have been developed recently, several challenges remain, including control accuracy, low capacity, and gripping force. In this paper, we propose a novel band-based lightweight (260 g), high-payload (maximum: 30.6 kg) gripper inspired by the human iris. Like the human iris adjusts the size of the pupil, the gripper modulates its grasping area by rotating the outer ring concentrically while keeping the inner ring stationary. In particular, the proposed grippers ensure both the robustness of position inaccuracy and grasp stability without relying on the manipulator. During this sequence, the bands intersect and topologically intertwine to form a grasp area. By wrapping the bands around the object, the gripper can achieve a high gripping force (146.1 N) and a stable grip. Regardless of whether the object has a position error, the gripper's self-centering property allows it to hold the object stably. Experiments were conducted to evaluate the grasping capability for various object shapes and weights and compared its performance with other grippers in Table 2. The gripper's gripping performance was demonstrated with several experiments and by successfully gripping complex geometries like a chestnut burr and very small object like 0.1 mm wire. The proposed gripper can be utilized for tasks where a soft and stable grip is essential, such as harvesting delicate or geometrically complex crops.