Detection of dominant planar surfaces in disparity images based on random sampling

U ovom članku ispituje se praktična primjenjivost RANSAC-pristupa za detekciju ravnih površina na slikama dispariteta dobivenim pomoću stereo vizije. Težište istraživanja je primjena u interijerima, gdje je velik dio dominantnih površina jednolično obojen, što predstavlja poseban problem za stereo viziju. Ispitano je nekoliko jednostavnih modifikacija osnovnog RANSAC-algoritma s ciljem utvrđivanja koliko oni mogu poboljšati njegovu učinkovitost. Predložene su dvije jednostavne mjere točnosti rekonstrukcija ravnih površina. Provedeno je eksperimentalno istraživanje na slikama snimljenim sustavom stereo vizije montiranom na mobilnog robota koji se kretao hodnicima fakulteta.In this paper, the applicability of RANSAC-approach to planar surface detection in disparity images obtained by stereo vision is investigated. This study is specially focused on application in indoor environments, where many of the dominant surfaces are uniformly colored, which poses additional difficulties to stereo vision. Several simple modifications to the basic RANSAC-algorithm are examined and improvements achieved by these modifications are evaluated. Two simple performance measures for evaluating the accuracy of planar surface detection are proposed. An experimental study is performed using images acquired by a stereo vision system mounted on a mobile robot moving in an indoor environment

Stereo-Based Obstacle Avoidance in Indoor Environments with Active Sensor Re-Calibration

We present a stereo-based obstacle avoidance system for mobile vehicles. The system operates in three steps. First, it models the surface geometry of supporting surface and removes the supporting surface from the scene. Next, it segments the remaining stereo disparities into connected components in image and disparity space. Finally, it projects the resulting connected components onto the supporting surface and plans a path around them. One interesting aspect of this system is that it can detect both positive and "negative" obstacles (e.g. stairways) in its path. The algorithm

Feature recognition and obstacle detection for drive assistance in indoor environments

The goal of this research project was to develop a robust feature recognition and obstacle detection method for smart wheelchair navigation in indoor environments. As two types of depth sensors were employed, two different methods were proposed and implemented in this thesis. The two methods combined information of colour, edge, depth and motion to detect obstacles, compute movements and recognize indoor room features. The first method was based on a stereo vision sensor and started with optimizing the noisy disparity images, then, RANSAC was used to estimate the ground plane, followed by a watershed based image segmentation algorithm for ground pixel classification. Meanwhile, a novel algorithm named a standard deviation ridge straight line detector was performed to extract straight lines from the RGB images. The algorithm is able to provide more useful information than using the Canny edge detector and the Hough Transform. Then, the novel drop-off detection and stairs-up detection algorithms based on the proposed straight line detector were carried out. Moreover, the camera movements were calculated by optical flow. The second method was based on a structured light sensor. After RANSAC ground plane estimation, morphology operations were applied to smooth the ground surface area. Then, an obstacle detection algorithm was carried out to create a top-down map of the ground plane using inverse perspective mapping and segment obstacles using a region growing-based algorithm. Both the drop-off and open door detection algorithms employ the straight lines extracted from depth discontinuities maps. The performance and accuracy of the two proposed methods were evaluated. Results show that the ground plane classification using the first method achieved 98.58% true positives, and the figure improved with the second method to 99%. The drop-off detection algorithms using the first method also achieved good results, with no false negatives found in the test video sequences. The system provided the top-down maps of the surroundings to detect and segment obstacles correctly. Overall, the results showing accurate distances to various detected indoor features and obstacles, suggests that this proposed colour/edge/motion/depth approach would be useful as a navigation aid through doorways and hallways