Fan-Out Revisited: The Impact of the Human Element on Scalability of Human Multi-Robot Teams

This paper introduces a novel fan-out model that improves accuracy over previous models. The commonly used models rely on neglect time, the time an agent operates independently, which confounds both human and robot abilities. The proposed model separates neglect time into two functionally distinct concepts: the time a robot can operate self-sufficiently, and the time a human estimates the robot can do so. Previous research indicates fan-out is often overestimated. This work explains why robot ability provides an upper bound to fan-out, but that actual achieved fan-out is influenced by both the human and robot abilities. We conduct a study to validate this new model and show improved performance over the two most common fan-out models. The results show that both previous models overestimate as predicted. Using the new fan-out model, we show that as the difference between human estimation and robot abilities grows, the actual fan-out will fall further from the upper bound potential fan-out. By including assessments of both the robotic and human elements, the new model provides a more nuanced understanding of the dynamics at play and the factors involved in scaling Human Multi-Robot Teams.