A New Human-Likeness and Comfort Index for Robot Movements Along Prescribed Paths

2026-07-09

AI Summary

This study addresses the relationship between human-likeness and perceived comfort in physical human–robot interaction when robots follow predefined trajectories. Building upon the temporal regularities of human motion and its log-normal characteristics, the work proposes the first prior human-likeness index capable of quantitatively assessing the anthropomorphism of a trajectory prior to execution. Through three rounds of physical interaction experiments involving 68 participants, combined with analyses of trajectory time laws and subjective comfort ratings, the study demonstrates that the proposed index exhibits significant and globally consistent correlation with human comfort preferences. These findings provide a predictable and quantifiable basis for generating human-like robot trajectories that align with user comfort expectations.

Abstract

As human-robot interaction rapidly spreads in numerous fields, the subject of robot acceptance gains increasing importance. Visual similarity to the human body, as occurs for humanoids, is generally not enough to ensure acceptance in physical interaction, as acceptance directly links to comfort and ergonomics, which are measured in terms of the quality of the robot movement perceived by the human. This paper discusses the connection between comfort and similarity of the robot movement to the human one. By considering the kinematic characterization of human movement, this paper focuses on the time laws of such movements, wherein the end-effector path is prescribed. Based on the lognormality principle for modeling human movements, a human-likeness index is defined and used to provide an a priori characterization of trajectories. Such an index can be used to evaluate the performance of trajectory generation algorithms in producing human-like movements before they are actually executed. For validation purposes, 68 subjects are required to judge their comfort. The results of three experimental campaigns involving a physical interaction with a robot demonstrate a globally consistent trend between the preference in terms of perceived comfort and the distribution of the suggested human-likeness index.

Problem

• human-likeness
• comfort
• robot movement
• human-robot interaction
• trajectory

Innovation

• human-likeness index
• lognormality principle
• trajectory generation
• human-robot interaction
• movement comfort