Tactile Zoning for Quadruped Companion Robots: User Expectations and Body-Region Material Mappings

Abstract

While quadruped robots are increasingly deployed as social companions, their tactile design remains underdeveloped, typically featuring uniform shells that prioritize durability over affective engagement. To address this gap, this paper introduces “tactile zoning,” defined as the differentiation of surface materials across a robot's body regions, as an exploratory approach to understanding users' tactile expectations for quadruped companion robots. A formative questionnaire $(\mathbf{N}=\mathbf{1 2 0})$ suggested moderate interest in differentiated rather than uniform robot surfaces. Subsequently, a physical mapping experiment $(\mathbf{N}=\mathbf{2 1})$ asked participants to evaluate seven materials and assign them to body regions of a quadruped robot under two ownership contexts (a personal home companion and a shared therapy assistant). Across conditions, soft and biomimetic textiles (Fur, PET Fibre) were more frequently assigned to primary interaction regions including the top of head and back, whereas more industrial or durable materials (Leather, Silicone Rubber) were more often placed on peripheral regions (legs). Generalized Linear Mixed Models showed that higher companion-role congruence ratings were associated with selection for the Back $(\boldsymbol{\beta}=\mathbf{0. 6 2 1}, \mathbf{p}<\boldsymbol{. 0 0 1})$ and Top of Head $(\boldsymbol{\beta}=\mathbf{0. 4 7 3}, \mathbf{p}<\boldsymbol{. 0 0 1})$, but not for the Tail $\boldsymbol{(} \boldsymbol{\beta}$= 0.046, p =. 663). Ownership context produced modest shifts in material assignment patterns, with a significant Preference × Context interaction for the Abdomen $(\boldsymbol{\beta}=\mathbf{0. 3 9 5}, \boldsymbol{p}=\boldsymbol{. 0 1 1})$. These findings provide exploratory evidence that users hold differentiated tactile expectations across robot body regions, offering a basis for future work on multi-material design in quadruped companion robots.