Real-time Humanoid Visual System based on Region Segmentation for obstacle determination
Date Issued
2011
Date
2011
Author(s)
Liu, Geng-Hua
Abstract
This thesis proposes one real-time visual system completely, and the suitable control methods are developed for the especial humanoid eye mechanism by our self. This eye mechanism has five degree of freedoms to control the horizontal and vertical rotations of two eyeballs and opening of two eyelids. PMMA is chosen as the material for convenience of CNC machining and its lightness. Those used motors and control boards are also mini and light.
The analyzed images are inputted from mini webcams, and then the visual program use region-based corresponding result between images with different viewpoints and disparities of those corresponded regions to calculate the spatial distances between the eye mechanism and those objects represented by corresponded region pairs. For the balance between efficacy of region separation and computing efficiency to satisfy real-time operation, this research uses the algorithm of k-mean classification as the basis to classify image pixels by color statistics and also improves the color space to let it more uniform in description of chromatism for better efficacy. The accelerative program mechanism for regions extraction is also designed to let the passing times of each region boundary decrease to only one in actual searching stage.
Those centroid pairs from corresponded regions are considered that the basis of distance determination. The errors of calculated distance are affected by parameters calibration of image sensors and precision of eyeballs’ rotational angles control. Therefore, the eye mechanism is also installed with angle gauges and analog-to-digital board to achieve real-time feedback of horizontal rotations. The revision of vertical rotation control by software is designed because the difficulty of installation and applying of the extra equation from coordinate transformation.
To meet the requirement of real-time operation finally, this research also involves the help by Nvidia graphic cards and CUDA toolkits. After suitable parallelization of original serial program and operation on GPU of graphic cards, the efficiency of visual system obtains 5 to 10 times improvement by the higher ability in general computation of current GPU based system. Finally, the operation frequency of this visual system achieves more than 30 Hz which meets the general definition of real-time operation.
Subjects
humanoid robot
visual system
real-time operation
angle control
parallelized design
Type
thesis
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