The Six Hug Commandments: Design and Evaluation of a Human-Sized Hugging Robot with Visual and Haptic Perception

authors: Alexis Block, Sammy Christen, Roger Gassert, Otmar Hilliges and Katherine J. Kuchenbecker
publication: ACM/IEEE International Conference on Human-Robot Interaction (HRI), March 2021



Receiving a hug is one of the best ways to feel socially supported, and the lack of social touch can have severe negative effects on an individual's well-being. Based on previous research both within and outside of HRI, we propose six tenets ("commandments") of natural and enjoyable robotic hugging: a hugging robot should be soft, be warm, be human sized, visually perceive its user, adjust its embrace to the user's size and position, and reliably release when the user wants to end the hug. Prior work validated the first two tenets, and the final four are new. We followed all six tenets to create a new robotic platform, HuggieBot 2.0, that has a soft, warm, inflated body (HuggieChest) and uses visual and haptic sensing to deliver closed-loop hugging. We first verified the outward appeal of this platform in comparison to the previous PR2-based HuggieBot 1.0 via an online video-watching study involving 117 users. We then conducted an in-person experiment in which 32 users each exchanged eight hugs with HuggieBot 2.0, experiencing all combinations of visual hug initiation, haptic sizing, and haptic releasing. The results show that adding haptic reactivity definitively improves user perception a hugging robot, largely verifying our four new tenets and illuminating several interesting opportunities for further improvement.

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This work is partially supported by the Max Planck ETH Center for Learning Systems and the IEEE Technical Committee on Haptics. The authors thank Bernard Javot, Michaela Wieland, Hasti Seifi, Felix Grüninger, Joey Burns, Ilona Jacobi, Ravali Gourishetti, Ben Richardson, Meike Pech, Nati Egana, Mayumi Mohan, and Kinova Robotics for supporting various aspects of this research project.