Back-off: Evaluation of Robot Motion Strategies to Facilitate Human-Robot Spatial Interaction

Abstract

Standstill behavior by a robot is deemed to be ineffective and inefficient to convey a robot’s intention to yield priority to another party in spatial interaction. Instead, robots could convey their intention and, thus, their next action via motion. We developed a back-off movement to communicate the intention of yielding priority to pedestrians at bottlenecks. To evaluate human sensory perception and subjective legibility, the back-off is compared to three other motion strategies in a video study with N = 167 interviewees at the university and public spaces, where it excels regarding legibility. Implemented in a real encounter, objective motion behavior of N = 78 participants as a reaction to a stop & wait strategy, and two versions of back-off (short and long) shows an improvement of the pedestrians’ efficiency in the second encounter with the robot’s short back-off version compared to the stop strategy. Eventually, in the third encounter with all motion strategies, interaction causes only a small time consumption still required by the cognitive process of perceiving an object in the visual field. Hence, the design of kinematic parameters, back-off path and time, exhibits the potential to increase the fluency of an interaction with robots at bottlenecks.

Mobile Robot Yielding Cues for Human-Robot Spatial Interaction

“…This underlines a major motivation for this research: robots should be designed for comprehension in order to engender trust. Kauppinen et al validated the relationship between trust and comprehension with the Human Computer Trust Rating Scale, which was tested with air traffic control systems [27]. We have demonstrated this relationship in robot yielding cues.…”

Sharing the Sidewalk: Observing Delivery Robot Interactions with Pedestrians during a Pilot in Pittsburgh, PA

“…Many people would pass by the robot without helping, even if they may have understood it to be stuck (Figure 6). While improved communication design through lights and dynamic displays [30,31,39], sounds to engender empathy [28], or movement to signal intent [29,32,33] may improve communications and interaction with some people, it is also possible that some members of the public will not engage with the robots or will be actively antagonistic towards them. Such behaviors are evidenced by the incident reports provided after the pilot.…”

“…Their review of prior studies found that LED light strips may not be entirely interpretable without prior training on what the signals mean [30] and that gaze may be a more understandable signal in communicating a robot's trajectory [31]. Angelopulos et al motivate their study based on prior work with non-humanoid robots where people did not always interpret strategies such as backing off [32] or moving out of the way [33] correctly and so they proposed the use of deictic arm gestures to increase interpretability [29]. Their findings show that such arm gestures were better at conveying the path a robot would take as opposed to adjusting the robot's gaze alone.…”