Autonomous continuum grasping

Abstract

A continuum manipulator, such as a multi-section trunk/tentacle robot, is promising for deft manipulation of a wide range of objects of different shapes and sizes. Given an object, a continuum manipulator tries to grasp it by wrapping tightly around it. Autonomous grasping requires realtime determination of whether an object can be grasped after it is identified, and if so, the feasible whole-arm wrapping around configurations of the robot to grasp it, which we call grasping configurations, as well as the path leading to a grasping configuration. In this paper, we describe the process for autonomous grasping from object detection to executing the grasping motion and achieving force-closure grasps, with a focus on a general analysis of all possible types of planar grasping configurations of a three-section continuum manipulator. We further provide conditions for existence of solutions and describe how to find a valid grasping configuration and the associated path automatically if one exists. Experimental results with the OctArm manipulator validate our approach, and shows that the entire process to determine an autonomous grasping operation, which includes automatic detection of the target object and determination of a grasping configuration and a path to the grasping configuration that avoids obstacles, can take just a small fraction of a second. Once a grasping configuration is reached, the manipulator can lift the object stably, i.e., a force-closure grasp can be achieved.