Real-time Step-Edge Estimation Using Stereo Images for Biped Robot

Abstract

A state-of-the-art biped robot takes footsteps that its heel or tiptoe overhangs step corner edges while ascending and descending stairs, as humans naturally do. Taking the overhang step strategy requires a real-time sensing method for estimating step edge positions in high precision. In this paper we propose a step edge estimation method using stereo images for the biped robot taking the overhang step strategy. After extracting planar areas from a 3D occupancy grid map generated from range sensor measurements, we estimate the plane parameters of each area by a fast direct method using stereo images. Then we obtain the line edge of each step so that the line segments the view area into two image regions both of which have small absolute difference values between stereo images. Our real-time estimation method enables the biped robot to smoothly walk on stairs and bumps. The validity of our method is demonstrated through on-line experiments using stereo cameras mounted on the body of a biped robot traversing real stairs.