US Patent 10025304 Time-of-flight localization

Robotic units may operate in a workspace that is shared with human workers. In order to safeguard the workers, operation of a robotic unit may be inhibited when a worker is near the robotic unit. In order to determine the position of the worker and thereby determine the proximity of the worker and the robotic unit, a time-of-flight measurement is performed to determine the distance of the worker from each of multiple reference locations within or about the workspace. A circular bounding area is defined around each reference location based on the determined distances. A bounded position area is identified as the intersection of the circular bounding areas. The worker is then indicated as being within the bounded position area.