Evaluating the Impact of Time-to-Collision Constraint and Head Gaze on Usability for Robot Navigation in a Corridor

Navigation of robots among humans is still an open problem, especially in confined locations (e.g. narrow corridors, doors). This article aims at finding how an anthropomorphic robot, like a PR2 robot with a height of 1.33 m, should behave when crossing a human in a narrow corridor in order to increase its usability. Two experiments studied how a combination of robot head behavior and navigation strategy can enhance robot legibility. Experiment 1 aimed to measure where a pedestrian looks when crossing another pedestrian, comparing the nature of the pedestrian: human or a robot. Based on the results of this experiment and the literature, we then designed a robot behavior exhibiting mutual manifestness by both modifying its trajectory to be more legible, and using its head to glance at the human. Experiment 2 evaluated this behavior in real situations of pedestrians crossing a robot. The visual behavior and user experience of pedestrians were assessed. The first experiment revealed that humans primarily look at the robot's head just before crossing. The second experiment showed that when crossing a human in a narrow corridor, both modifying the robot trajectory and glancing at the human is necessary to significantly increase the usability of the robot. We suggest using mutual manifestness is crucial for an anthropomorphic robot when crossing a human in a corridor. It should be conveyed both by altering the trajectory and by showing the robot awareness of the human presence through the robot head motion. Small changes in robot trajectory and manifesting robot perception of the human via a user identified robot head can avoid users' hesitation and feeling of threat.