In this paper, we present a novel controller for safe, efficient, and intuitive robot-to-human object handovers and a set of experiments to evaluate user responses to the robot's handover behavior. The controller enables a robot to mimic human behavior by actively regulating the applied grip force according to the measured load force during a handover. We provide an implementation of the controller on a Willow Garage PR2 robot, demonstrating the feasibility of realizing our design on robots with basic sensor/actuator capabilities. A user study comparing four variations of our controller shows that our design yields both human-like and human-preferred object handovers.

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Robotic site preparation has been identified as an integral precursor to human landings on Mars. Many species of social insect carry out the site preparation task when they construct their nests. A site preparation algorithm was developed based on the nest construction behavior of a particular species of ant, Leptothorax albipennis. In this paper, we present a new approach to modeling the temporal behavior of a multiple-robot system and apply it to our construction algorithm. In order to validate our model, experiments with multiple physical robots were conducted. Not only did the results of our experiments closely follow the predictions of our model, but the sites prepared by our robots appeared very similar to the nests built by the ants that were our inspiration.

In collaborative tasks, people often communicate using nonverbal gestures to coordinate actions. When two people reach for the same object at the same time, they often respond to an imminent potential collision with jerky halting hand motions that we term hesitation gestures. Successful implementation of such communicative conflict response behaviour onto robots can be useful. In a myriad of human-robot interaction contexts involving shared spaces and objects, this behaviour can provide a fast and effective means for robots to express awareness of conflict and cede right-of-way during collaborative work with users. Our previous work suggests that when a six-degree-of-freedom (6-DOF) robot traces a simplified trajectory of recorded human hesitation gestures, these robot motions are also perceived by humans as hesitation gestures. In this work, we present a characteristic motion profile derived from the recorded human hesitation motions, called the Acceleration-based Hesitation Profile (AHP). We test its efficacy to generate communicative hesitation responses by a robot in a fast-paced human-robot interaction experiment. Compared to traditional abrupt stopping behaviours, we did not find sufficient evidence that the AHP-based robot responses improve human perception of the robot or human-robot task completion time. However, results from our in situ experiment suggest that subjects can recognize AHP-based robot responses as hesitations and distinguish them to be different from abrupt stopping behaviours.