Contributing Factors in Human-Robot Handshake: Compliance, Hand Grip, and Synchrony

Abstract

Physical touch, such as handshakes, plays a critical role in human-robot interaction (HRI), influencing perceived naturalness and social presence. This study investigates how arm compliance, hand grip strength, and motion synchrony jointly affect the subjective quality of a human-robot handshake. We implemented a fully actuated, tactile-sensorized humanoid hand mounted on a manipulator arm and designed a compliant, oscillatory handshake controller with adaptive synchronization. Sixteen participants experienced handshakes across a 2x2x2 factorial design, varying arm compliance, grip strength, and synchrony. Objective kinematic analysis revealed significant main and interaction effects across all factors. At the same time, subjective ratings showed clear preferences for a weaker grip and greater arm compliance, with synchrony exerting minimal influence on perceived naturalness. These results highlight a perceptual hierarchy in HRI: foundational haptic properties exert the strongest influence on user experience, while advanced kinematic adjustments have limited impact when basic comfort is lacking. This insight provides concrete guidance for designing robotic handshakes that feel more human-like and pleasant.