An Underactuated PASA Finger Capable of Perfectly Linear Motion With Compensatory Displacement

Abstract

This paper presents a novel design for a robotic end effector. In particular, the design features a multifingered underactuated gripper capable of performing parallel and self-adaptive (PASA) grasping. The unique use of an eccentric cam fixed to a modified four-bar linkage mechanism allows the finger to compensate for the typical gap distance found during parallel pinching, improving the ability to grasp objects against surfaces and in tight spaces. A static analysis is performed on the design to determine the equilibrium conditions necessary for a successful grasp using this design in both the PASA modes. The mechanics of a four-bar mechanism are used to determine the grasp velocity and positioning of the hand in both grasp modes. Experimental results with a finger prototype confirm the desired closing trajectory.