Wearable sensory motor interfaces for supernumerary robotic fingers

Abstract

This chapter presents the design and development a new generation of extremely wearable haptic interfaces, acting as sensorimotor interfaces between the human wearer and the supernumerary robotic fingers. The small size and the specific shape of the developed devices guarantees an easy and intuitive wearability and leave the user’s fingertips bare in order to not constraint the user’s interaction with the surrounding environment in any way. Based on psychophysics evaluations, our novel interfaces deliver information about the cooperative task being performed (e.g., quality of the grasp) and the state of the extra-finger(s) where they are expected, providing the subject with a direct and co-located perception of the haptic feedback. Although the richness of the delivered information is very important, we strongly believe that sensorimotor consistency is crucial to design natural and embodied interfaces. In particular, two kinds of interfaces namely “vibrotactile ring” and hRing are proposed. The human user is able to control the motion of the robotic finger through switchs placed on rings, while being provided with vibrotactile and cutaneous feedback about the forces exerted by the robotic finger on the environment. To understand how to control the vibrotactile and cutaneous interface to evoke the most effective sensations, we executed perceptual experiments to evaluate its absolute and differential thresholds. We also carried out experiments with the subjects and haptic feedback significantly improved the performance in task execution in terms of completion time, exerted force, perceived effectiveness and wearability.