The platooning functionality is based on the detection of the distance, speed, and direction of the preceeding vehicle, which is localized and tracked using a single monocular image sequence.
The vehicle detection algorithm is based on the following considerations: a vehicle is generally symmetric, characterized by a rectangular bounding box which satisfies specific aspect ratio constraints, and placed in a specific region of the image. These features are used to identify vehicles in the image in the following way: first an area of interest is identified on the basis of road position and perspective constraints. This area is searched for possible vertical symmetries; not only gray level symmetries are considered, but vertical and horizontal edges symmetries as well, in order to increase the search robustness. Once the symmetry position and width has been detected, a new search begins, which is aimed at the detection of the two bottom corners of a rectangular bounding box. Finally, the top horizontal limit of the vehicle is searched for, and the preceeding vehicle localized.
The tracking phase is performed through the maximization of the correlation beetween the portion of the image cintained into the bounding box of the previous frame (partially stretched and reduced to take into account small size variations due to the increment and reduction of the relative distance) and the new frame.