Precision grasp planning with Gifu Hand III based on fast marching square

Abstract

This paper presents a novel methodology for planning the movements of a robotic hand when a precision grasp is going to be performed. The approach used is based on the standard Fast Marching Square (FM2) path planning method and its application to robot formations motion planning. In this case, the hand is considered to be a kinematic chain in which a mobile robot is located at every joint position. The robot formation is therefore deformable among the positions allowed by the mechanical limits of the joints. To perform a given precision grasp, the task is divided into two phases. First the hand approaches the object. FM2 is used to calculate a fast and smooth path towards the object to be grasped. While the hand is covering it, the formation updates its shape according to the map of velocities calculated in FM2. The second phase consists on performing the precision grasp. Every finger is modelled as a robot formation and a path is calculated for each fingertip so that they reach the grasping points on the object. The position of the joints of the fingers is computed using an inverse kinematics algorithm. Simulations show the usefulness of this approach thanks to a good performance of the approaching and the grasping tasks.