Squeezed screw trajectories for smooth regrasping movements of robot fingers

Abstract

In dextrous robotic manipulation we are often confronted with the problem that the robot fingers need to be repositioned on the object surface, either because a finger reaches its workspace limits or because the manipulation planner decides to do so due to its manipulation strategy. In this paper we propose a trajectory type for the purpose of regrasping, named “Squeezed Screw”. It is smooth and has a relatively simple shape. It is a superposition of a movement on an ellipse with a translation in an arbitrary direction in 3D. It can be generated from only eight input parameters. An algorithm was developed to calculate the path geometry from these parameters. A comparison with a Rapidly-exploring Random Tree algorithm points out the advantages of this novel trajectory type.