Generating Multi-level Linguistic Spatial Descriptions from Range Sensor Readings Using the Histogram of Forces

In this paper, we show how linguistic expressions can be generated to describe the spatial relations between a mobile robot and its environment, using readings from a ring of sonar sensors. Our work is motivated by the study of human-robot communication for novice robot users. The ultimate goal is to exploit these linguistic expressions for navigation of the mobile robot in an unknown environment, where the expressions represent the qualitative state of the robot in terms that are easily understood by humans. The notion of the histogram of forces was presented in previous work and used to generate linguistic descriptions of relative positions in digital images. Here, we demonstrate that it also permits fast processing of vector data and can be applied to a robot with range sensors moving in a dynamic environment. We introduce a new method for detecting partially and completely surrounded conditions, and we show that detailed descriptions can be obtained as well as coarse ones. Numerous examples are included, illustrating a variety of situations.