Towards understanding human decisions in human-robot interactions

In this paper, we conducted an experiment with four human participants whom were asked to follow a robot gripper with unknown motion as close as possible. The results show that human beings resort to a fairly complicated and continuously changing control strategy. We hypothesize that this strategy can be explained by (1) a feedforward (preview) model of the machine's motion, and further by (2) human being's uncertainty in this preview. To test (1), we demonstrate that feedforward control can indeed improve the fitting of the model to the experimental data, and that the feedback gain and the preview length vary across subjects. This model, however, does not explain temporally changing human behavior observed during the experiment. To this end, we propose an extension of the human control model where human behavior is influenced by the preview uncertainty. The extended model incorporates a higher-level planner that determines a target state for a short time interval, and a lower-level controller that meets the target through real-time control. The developed model helps predict detailed human behavior during their interactions with robots.