Uniform vs. Lognormal Kinematics in Robots: Perceptual Preferences for Robotic Movements

TL;DR

This study investigates human perceptual preferences for robotic movements by comparing traditional trapezoidal speed profiles with human-like bell-shaped profiles, implemented on industrial robots and tested through visual and tactile interactions.

Contribution

It introduces a method to generate human-like bell-shaped movements in industrial robots based on the lognormality principle, and evaluates human preferences for these movements.

Findings

Humans prefer bell-shaped, human-like movements over trapezoidal robotic movements.

Preference varies between visual observation and tactile interaction.

The developed method successfully produces human-like movements on industrial robots.

Abstract

Collaborative robots or cobots interact with humans in a common work environment. In cobots, one under investigated but important issue is related to their movement and how it is perceived by humans. This paper tries to analyze whether humans prefer a robot moving in a human or in a robotic fashion. To this end, the present work lays out what differentiates the movement performed by an industrial robotic arm from that performed by a human one. The main difference lies in the fact that the robotic movement has a trapezoidal speed profile, while for the human arm, the speed profile is bell-shaped and during complex movements, it can be considered as a sum of superimposed bell-shaped movements. Based on the lognormality principle, a procedure was developed for a robotic arm to perform human-like movements. Both speed profiles were implemented in two industrial robots, namely, an ABB IRB 120 and a Universal Robot UR3. Three tests were used to study the subjects' preference when seeing both movements and another analyzed the same when interacting with the robot by touching its ends with their fingers.