Vision-guided autonomous stair climbing

The Tactical Mobile Robot (TMR) program calls for autonomous mobility in an urban environment. Among all man-made structures which pose as barriers for a mobile robot stairs are the most obvious and ubiquitous structure an autonomous urban robot needs to be able to handle. The Urban II chassis by IS Robotics provides a mechanically simple and elegant way to enable the stair-climbing capability. This paper addresses the issue of using computer vision techniques to control the vehicle automatically when climbing stairs. The algorithm is based in detecting stair edges from a monocular sequence. It is shown that the position and orientation of the stair edges can be used to compute the 3D orientation and position of the vehicle relative to the stairs. Robust examination of those parameters is the key to reliable performance. A combination of techniques such as medium filtering, histogram peak finding, outlier rejection and weighted average are shown to be effective in practice. At the end, we briefly explain our work-in-progress in automatic corner-turning in climbing multiple flights of stairs.