For both humans and robots, one of the key elements of collaboration is the collaborating agents’ ability to communicate and mesh their individual plans with each other. Even after the collaborators have decided on a joint task, the details of the task such as the how, when, and where are often determined as the collaborative activity unfolds. The primary objective of this thesis is to enable fluent communication between human and robotic agents such that they can interactively figure out unspoken details and resolve unforeseen conflicts that arise during a human-robot collaboration.

The author first explores whether robot nonverbal cues inspired by human behaviours can elicit desirable responses from a human user to interweave unspoken – yet essential – spatial-temporal details of an interaction. Results from a series of experiments demonstrate that a robot cue, like gaze, can have a significant influence on when a human recipient reaches out to receive an object from a robot.

Subsequently, the author focuses on hesitation gestures – a type of gesture humans naturally use to express uncertainty – to explore whether members of a human-robot dyad can negotiate a desired outcome of an interaction through a nonverbal dialog. The author presents a reactive, real-time trajectory generator, the Negotiative Hesitation Generator (NHG), which has been devised to enable such nonverbal negotiation to take place between a human and a robot. The NHG was implemented on a robot for human-robot interaction experiments where, by design, spontaneous resource conflicts often arose between the two agents. Results from these studies suggest that use of the NHG can enable a type of nonverbal negotiation of resource conflicts to take place. They also demonstrate how such real-time negotiations between a human-robot dyad can lead to a faster resolution of conflicts and a significantly improved outcome of the collaborative task, without jeopardizing the safety of the user.

This thesis advances our understanding of the influence that nonverbal robot behaviours can have on human users. It also demonstrates the feasibility and efficacy of nonverbal negotiations as a mode of interaction for human-robot collaboration.