  Humans engaged in collaborative activities are naturally able to convey their
intentions to teammates through multi-modal communication, which is made up of
explicit and implicit cues. Similarly, a more natural form of human-robot
collaboration may be achieved by enabling robots to convey their intentions to
human teammates via multiple communication channels. In this paper, we
postulate that a better communication may take place should collaborative
robots be able to anticipate their movements to human teammates in an intuitive
way. In order to support such a claim, we propose a robot system's architecture
through which robots can communicate planned motions to human teammates
leveraging a Mixed Reality interface powered by modern head-mounted displays.
Specifically, the robot's hologram, which is superimposed to the real robot in
the human teammate's point of view, shows the robot's future movements,
allowing the human to understand them in advance, and possibly react to them in
an appropriate way. We conduct a preliminary user study to evaluate the
effectiveness of the proposed anticipatory visualization during a complex
collaborative task. The experimental results suggest that an improved and more
natural collaboration can be achieved by employing this anticipatory
communication mode.
