Expressing and Inferring Action Carefulness in Human-to-Robot Handovers

TL;DR

This paper explores how implicit communication through subtle kinematic modulations can improve human-robot handovers by inferring object properties and expressing action carefulness, leading to more efficient interactions.

Contribution

It introduces an ecological approach to infer object characteristics from natural human movements and a robot controller that modulates motion to communicate object properties.

Findings

Humans adjust their kinematics based on object content during handovers.

The system reliably infers carefulness before action completion.

Expressive robot movements improve task efficiency.

Abstract

Implicit communication plays such a crucial role during social exchanges that it must be considered for a good experience in human-robot interaction. This work addresses implicit communication associated with the detection of physical properties, transport, and manipulation of objects. We propose an ecological approach to infer object characteristics from subtle modulations of the natural kinematics occurring during human object manipulation. Similarly, we take inspiration from human strategies to shape robot movements to be communicative of the object properties while pursuing the action goals. In a realistic HRI scenario, participants handed over cups - filled with water or empty - to a robotic manipulator that sorted them. We implemented an online classifier to differentiate careful/not careful human movements, associated with the cups' content. We compared our proposed "expressive" controller, which modulates the movements according to the cup filling, against a neutral motion controller. Results show that human kinematics is adjusted during the task, as a function of the cup content, even in reach-to-grasp motion. Moreover, the carefulness during the handover of full cups can be reliably inferred online, well before action completion. Finally, although questionnaires did not reveal explicit preferences from participants, the expressive robot condition improved task efficiency.