Stable, open-loop precision manipulation with underactuated hands

Abstract

This paper discusses dexterous, within-hand manipulation with differential-type underactuated hands. We discuss the fact that not only can this class of hands, which to date have been considered almost exclusively for adaptive grasping, be utilized for precision manipulation, but also that the reduction of the number of actuators and constraints can make within-hand manipulation easier to implement and control. Next, we introduce an analytical framework for evaluating the dexterous workspace of objects held within the fingertips in a precision grasp. A set of design principles for underactuated fingers are developed that enable fingertip grasping and manipulation. Finally, we apply this framework to analyze the workspace of stable object configurations for an object held within a pinch grasp of a two-fingered underactuated planar hand, demonstrating a large and useful workspace despite only one actuator per finger. The in-hand manipulation workspace for the iRobot-Harvard-Yale Hand is experimentally measured and presented.