White Line Following For ALV Navigation

Abstract

A real time processing system and a white line following algorithm used for high speed ALV navigation on structural road are described in this paper. The real time image processing system includes a color video camera, several processors with special functions and a general purpose processing unit based on TMS 320C30 microprocessor. Each special processor performs a standard image processing operation such as image thresholding, color look-up-table, histogram statistics, morphology operation, and so on. A general purpose unit performs some algorithms at high speed. There are two buses in the system. Each processor can communicate with each other through image data bus and communicate with the host computer through extended PC-bus as well. The system is more convenient for programming and can realize vision tasks in real time. There are two steps in the white line following algorithm. The white line starting points are searched by a local threshold and hypothesis-verification method. We enhance the performance of our searching algorithm by three steps: enlarge searching area, use as many features of the white line as possible, feedback line following results to starting point searching for remove illegal starting points. In the window searching scheme, we use multi-directional local projection to find the two gray level discontinuity edges of white line in a window. According to the position orientation and intensity of the two discontinuity edges, we can determine if there is a white line segment in the window. Then we forecast the position of the next window and repeat the steps until the line following is finished according to some rules. We use continuity between two frame images and knowledge of central line of road to guide road region determination when there is one white line in an image. The testing results show that our vision system can detect solid and broken, clean and blurred white lines on the testing field successfully in any weather conditions and at any time of a day. Transactions on Information and Communications Technologies vol 16, © 1996 WIT Press, www.witpress.com, ISSN 1743-3517