This paper investigates a hybrid robot that integrates physical and AR body parts, focusing on how the presentation modalities of the head and arms impact human perception of social presence. We implemented a hybrid robot system that allows switching the presentation modalities of the head and arms between physical and AR, and compared four conditions: both physical, physical head and AR arms, AR head and physical arms, and both AR. Two experiments were conducted with different tasks: material explanation and multi-party discussion. These experiments demonstrate that the hybrid robot with a physical head and AR arms effectively overcomes AR device limitations, achieving a social presence comparable to or greater than that of a fully physical robot. The findings also show that the specific AR-presented body parts significantly influence evaluations, underscoring the importance of careful design in hybrid robots.

This paper introduces HoloBots, a mixed reality remote collaboration system that augments holographic telepresence with synchronized mobile robots. Beyond existing mixed reality telepresence, HoloBots lets remote users not only be visually and spatially present, but also physically engage with local users and their environment. HoloBots allows the users to touch, grasp, manipulate, and interact with the remote physical environment as if they were co-located in the same shared space. We achieve this by synchronizing holographic user motion (Hololens 2 and Azure Kinect) with tabletop mobile robots (Sony Toio). Beyond the existing physical telepresence, HoloBots contributes to an exploration of broader design space, such as object actuation, virtual hand physicalization, world-in-miniature exploration, shared tangible interfaces, embodied guidance, and haptic communication. We evaluate our system with twelve participants by comparing it with hologram-only and robot-only conditions. Both quantitative and qualitative results confirm that our system significantly enhances the level of co-presence and shared experience, compared to the other conditions.