The UHVAT Gripper: Usable Holding Versatile Adjustable Tool to Grasp Different Objects

Abstract

This paper presents a novel approach to the development of finger mechanisms for fnger mechanisms for anthropomorphic grippers. The proposal approach allows to design a gripper finger that is able to break/reconnect a kinematic chain of the finger in order to change a degree of freedom, that will enable to choose between different operation modes of the grasping device. When a kinematic chain is closed the finger has got one degree of freedom (DOF), thus a trajectory of the finger is predictable that allows to execute precise pinch grasp. When the kinematic chain is opened the finger has got 2 DOF that allows to accomplish power and adaptive underactuated grasp of unknown random objects no matter of their orientation, that helps with pick-and-place tasks of heavy objects, since encompassing grasp is able to increase the gripper’s payload capacity. Closing/opening of the kinematic chain is implemented with a special link, which is able to fix its length or make it variable. In this paper, the proposed approach was used to create an usable holding versatile adjustable tool (UHVAT gripper) for industrial tasks to grasp objects with different sizes and shapes via both power types of grasps as well as precision grasps. The gripper consists of three fingers and a palm. All fingers of the gripper are actuated with one stepper motor embedded into the gripper palm. The mechanical structure of the gripper makes it adjustable to different types of grasps configurations. The structure of the finger, the mechanical design of the gripper, an analysis of the finger mechanism and simulation results are presented.