A method for fast encoder-free mapping in unstructured environments

The primary purpose of rescue robots is to locate victims within a disaster environment, either to report their position or to deliver aid. Although there exist several solutions for mapping and localizing a robot in an unknown environment, they often require an estimate of the robot's motion. In a disaster site, a robot might not have effective motion encoders, either because of the discontinuous nature of the terrain or because the robot's locomotion devices do not remain in constant contact with the ground. We have developed an algorithm for tracking the position of a robot in a disaster environment and generating a map that functions in real time. Our solution is based on a range finder device and is robust to temporary errors in the range scan. By aligning each scan to an occupancy grid of prior scan data, we can find the robot's position more accurately than current techniques that align only to the previous scan. The accurate position tracking allows us to more efficiently implement a solution to the mapping problem. In addition, our solution can track the position of the robot and generate a map based on three‐dimensional scan data, instead of requiring that the range sensor be fixed in a level plane. © 2011 Wiley Periodicals, Inc.