Real-time vehicle following through a novel symmetry-based approach

This paper describes a novel approach to real-time vehicle following. A scheme, called `symmetry axis detection and filtering based on symmetry constraints,' is proposed and has been implemented. This scheme incorporates many elements of our research efforts in sensor-based control of mobile robots and manipulators. The proposed algorithm detects and tracks the rear portion of the exterior of a leading vehicle via a camera mounted on a vehicle that belongs to a platoon. Our scheme uses the symmetry property of the shape of most vehicles. In particular, our technique takes advantage of the stable contour symmetry instead of the intensity symmetry which is noisy and prone to errors when the environmental lighting conditions change. An algorithm that employs a voting technique is proposed in order to detect the vertical symmetry axis of the leading vehicle. A filtering method based on symmetry constraints is performed to eliminate the pixels which do not contribute to the leading vehicle's contour. As a result of the filtering, a distinct symmetric contour is obtained. This distinct symmetric contour facilitates computation of the bounding-box which corresponds to the leading vehicle's contour. Robustness and real-time performance of the symmetry-based scheme are greatly enhanced by using an adaptive processing window, the local symmetry properties, and a filtering procedure.