Underactuated gripper that is able to convert from precision to power grasp by a variable transmission ratio

Abstract

This paper investigates the possibility of converting grasped objects from precision grasps to power grasps using a variable transmission ratio for an underactuated finger. Reconfiguration happens when the precision grasp converts to a power grasp, because the number of contact points changes which changes the topology of the grasp. To this effect, a variable radius pulley was designed. A simulation study is presented to analyse grasping behaviour and a potential energy method is used to predict the equilibrium positions of finger and object. With this method stable and unstable equilibrium positions are determined. This is followed by an experiment to verify the theory. This paper is a first step in dextrous manipulation with large movements of objects using underactuated fingers. © Springer-Verlag London 2012.