Linear markers for robot navigation with panoramic vision

A vision based navigation system is presented for determining a mobile robot´s position and orientation using panoramic imagery. An omni-directional image sensor mounted on the robot is useful in obtaining a 360 field of view, permitting navigational markers from all sides to be viewed simultaneously. A robust marker-based system is presented using vertically positioned linear markers as landmarks. The markers consist of linearly encoded digital patterns, similar to a barcode but distinguishable with less pixels. A set of patterns are orthogonal from one another and are readily recognized with any continous section visible. With a vertically posed panoramic image sensor, these vertically mounted linear markers appear along radial lines. The panoramic image is pre-processed according to edge directions to find candidate regions which are spatially sampled into digital symbols. This extracted binary sequence is examined to determine if it belongs in the marker pattern set. This system is shown to be robust even with the low resolution of a panoramic sensor with 800x800 active pixels. Experiments are shown with synthetic imagery and with three real prototype systems.i