Vision System Design for Mobile Robot Tracking

This chapter introduces a complete thematic of vision system for mobile robot tracking and control. It consists of a global vision system for estimation of positions and orientations of mobile robots and methods for improvement of bad operating conditions such as noise, camera lens distortion and non-uniform illumination. The basic operation of a vision system is divided into two steps. In the first, the incoming image is scanned and pixels are classified into a finite number of classes. At the same time, a segmentation algorithm is used to find the corresponding regions belonging to one of the classes. In the second step, all the regions are examined. A selection of the ones that are a part of the observed object is made by means of simple logic procedures. The novelty of the used approach is focused on optimization of the processing time needed to finish the estimation of possible object positions. Further on an approach to improve an already existing vision system performance under bad operating conditions is presented. Some fundamentals and solutions to accompanying problems in vision system design for mobile robot tracking are presented. Besides methods for filtering and improvement of identified noisy data the two main factors which deteriorate the performance are dealt with, namely, non-uniform illumination and camera lens distortion. For the former the problem area and its origins are focused on and a solution for its compensation by applying multiplicative component defined by illumination plain is given. The latter consists of two steps. In the first, radial lens distortion fundamentals are discussed. The suggested solution for its verification is realized by a geometry model of lens projection. The second step covers the perspective distortion originating from the tilt of the camera. For its correction an efficient and robust method of vanishing point detection is applied. Both correction methods contribute to a vision system performance if implemented in the appropriate manner. * E-mail address: [email protected] Gregor Klančar, Marko Lepetič, Matej Kristan et al. 120 Applicability of the presented approaches is confirmed on a robot soccer test bed. Robot soccer is a fast dynamic game and therefore needs an efficient and robust vision system. To improve the results of the robot soccer vision system the proposed camera calibration and non-uniform illumination correction algorithm are implemented. The lens correction method successfully corrects the distortion caused by the camera lens, thus achieving a more accurate and precise estimation of the object position. The illumination compensation improves robustness to irregular and non-uniform illumination which is nearly always present in real conditions.