tailieunhanh - Robot Vision 2011 Part 3

Tham khảo tài liệu 'robot vision 2011 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 72 Robot Vision The next movement direction is given as a vector pointing to the center of the widest polar obstacle-free zone. Positive angles result for turns to the right and negative angles for turns to the left. 6. Implementation and Experimental Results Overall Performance of the Classifier To test the proposed strategy a Pioneer 3DX robot with a calibrated wide angle camera was programmed to navigate in different scenarios such as environments with obstacles of regular and irregular shape with textured and untextured floor and environments with specularities or under low illumination conditions. The operative parameter settings were robot speed 40mm s the radius of the ROI 1 5m for the hysteresis thresholding low level 40 and high level 50 camera height 430mm p -9 initial Ỡ 0 and finally f . For each scene the complete navigation algorithm was run over successive pairs of consecutive frames so that the effect of IPT was noticeable. Increasing the frame rate decreases the IPT effect over the obstacle points and decreasing the frame rate delays the execution of the algorithm. Frames were originally recorded with a resolution of 1024 X 768 pixels but then they were down-sampled to a resolution of 256 X192 pixels in order to reduce the computation time. All frames were also undistorted to correct the error in the image feature position due to the distortion introduced by the lens and thus to increase the accuracy in the calculation of the point world coordinates. The implementation of the SIFT features detection and matching process was performed following the methods and approaches described in Lowe 2004 . The camera world coordinates were calculated for each frame by dead reckoning taking into account the relative camera position with respect to the robot center. First of all the classifier performance was formally determined using ROC curves Bowyer et al. 2001 . These curves were computed for every pair of consecutive images