A Programmable RCC Hand

Automated assembly by robots is plagued by two central problems—grasping and insertion. Assembly robots require an array of specialized grippers, each one designed to grasp only one or two specific objects, and they must automatically exchange grippers during an assembly task. General purpose dexterous hands, that imitate the human hand, are far more versatile but they are too complex for industrial automation. The insertion problems refers to wedging or jamming that can occur during an assembly process due to the robot’s poor positioning capability. The Remote Center of Compliance is a simple wrist-mounted compliance device that enables high speed assembly by inaccurate robots without jamming or wedging. However, the RCC must be designed for a particular peg-hole geometry and its compliance characteristics cannot be modified by the robot program. This paper proposes a single device that alleviates both grasping and insertion problems by integrating passive compliance into a three-fingered two d.o.f. hand. A kinematic model of the hand is presented that exhibits RCC properties. By modulating the angle of the fingers, the programmer can obtain different RCC characteristics. Despite the hand’s simplicity, its compliance provides considerable grasping versatility as well as a programmable RCC capability.