Evaluating Fluency in Human–Robot Collaboration

Collaborative fluency is the coordinated meshing of joint activities between members of a well-synchronized team. In recent years, researchers in human-robot collaboration have been developing robots to work alongside humans aiming not only at task efficiency, but also at human-robot fluency. As part of this effort, we have developed a number of metrics to evaluate the level of fluency in human-robot shared-location teamwork. While these metrics are being used in existing research, there has been no systematic discussion on how to measure fluency and how the commonly used metrics perform and compare. In this paper, we codify subjective and objective human-robot fluency metrics, provide an analytical model for four objective metrics, and assess their dynamics in a turn-taking framework. We also report on a user study linking objective and subjective fluency metrics and survey recent use of these metrics in the literature.