Grounding Language to Landmarks in Arbitrary Outdoor Environments

Robots operating in outdoor, urban environments need the ability to follow complex natural language commands which refer to never-before-seen landmarks. Existing approaches to this problem are limited because they require training a language model for the landmarks of a particular environment before a robot can understand commands referring to those landmarks. To generalize to new environments outside of the training set, we present a framework that parses references to landmarks, then assesses semantic similarities between the referring expression and landmarks in a predefined semantic map of the world, and ultimately translates natural language commands to motion plans for a drone. This framework allows the robot to ground natural language phrases to landmarks in a map when both the referring expressions to landmarks and the landmarks themselves have not been seen during training. We test our framework with a 14-person user evaluation demonstrating an end-to-end accuracy of 76.19% in an unseen environment. Subjective measures show that users find our system to have high performance and low workload. These results demonstrate our approach enables untrained users to control a robot in large unseen outdoor environments with unconstrained natural language.