Passive Demonstrations of Light-Based Robot Signals for Improved Human Interpretability

When mobile robots navigate crowded, human-populated environments, the potential for conflict arises in the form of intersecting trajectories. This study investigates the use of light-emitting diodes (LEDs) arranged along the chassis of a robot in an arrangement similar to a turn signal on a car as a non-anthropomorphic, yet familiar signal to convey the intended path of a mobile service robot. We study the scenario of a human and a robot heading directly toward each other in a hallway, which may give rise to the familiar human experience in which both parties step to the right, then the left, then the right, continuing to block each other's paths until they are able to coordinate their movements and pass each other. We conducted a pilot study which revealed that people do not always interpret this signal as one may expect, which would be similar to how a car uses its turn signal. This motivated a 2 × 2 experiment in which the robot either does or does not use LEDs to indicate its intended direction of travel, and in which study participants either are able to or unable to witness the robot's "lane-changing" behavior further down the hallway prior to coming into direct proximal contact with the robot. The results demonstrate that exposing participants to the robot's use of the LED signal only once prior to passing each other in the hallway is sufficient to disambiguate its meaning to the user, and thus greatly enhances its utility in-situ, with no direct instruction or training to the user. These findings suggest a paradigm of passive demonstration of such signals in future applications.