Flexible, Semi-Autonomous Grasping for Assistive Robotics

Abstract

This paper proposes a scheme to provide flexible semi-autonomous grasping capabilities to an assistive robotic manipulator. The testbed consists of a five-finger robotic hand mounted on a robotic arm. During teleoperation, the position of the hand is continuously controlled in the three translational degrees of freedom, and the user has no direct influence over the rotational behavior. The proposed semi-autonomy scheme assists the user for moving and orienting the hand towards the object, and automates the grasping process when it is triggered. The velocity commands issued by the user are enhanced using virtual fixtures, which are not preprogrammed to support one approach direction to the (known) object, but are adapted online according to the intended movement. The approach is validated with a psycho-physical user study where the participants grasp objects in a simulation environment using a SpaceMouse interface. This setting serves as a testbed for the target application in which disabled subjects will control the real robotic system with an interface based on bio-signals. The user study compares the semi-autonomous and the pure teleoperation modes in terms of objective and subjective measures, showing an increase in performance and a decrease in workload for the proposed semi-autonomous mode.