Multifunctional Parallel Gripper With Three Actuators

This article proposes a parallel gripper with a rack and pinion mechanism that is more versatile than the traditional parallel grippers with three actuators. The proposed gripper can switch between large and small fingers via lengthening and shortening actions, which improves its ability to pick up objects with various sizes and weights, as well as in narrow workspaces. This function also enables the gripper to perform three-face grasping, wherein three faces of a grasped object are securely in contact with the gripper, thereby improving the robustness of grasping. The gripper can also perform in-hand manipulations using a stand. We analyze the grasping force of the three-face grasp and show that it is more robust against external forces that generate the moment about the normal of the finger surface than the traditional two-face grasp. Finally, we demonstrate the improved abilities of the developed gripper and the robustness of the three-face grasp through the experimental results. The possible applications of this gripper include tasks in which the sizes, weights, and arrangements of the objects are not optimized for robot hands.