Compared the joint angle measuring method with add to favorites the stereo vision method, the stereo vision method has the advantages of Inhibitors,Modulators,Libraries involving non-contact sensing and providing direct measurements. Besides, it��s very difficult to fit angular sensors at the joints of parallel mechanism of the robot due to the restrictions of the mechanism used in this study.To reconstruct a 3D space by stereo images using binocular cues, the disparities of the corresponding points in stereo pairs have to be known. Therefore, solving the stereo correspondence problem has been the most important stage on the 3D reconstruction. Some published studies [6�C9] have attempted to solve the stereo correspondence problem. The most popular and well-known method is to use epipolar constraints [10] to reduce the stereo matching region from an area to a straight line.

For an uncalibrated stereo rig (i.e., both intrinsic and extrinsic parameters are unknown) [11�C13], the fundamental matrix F often needs to be computed to express epipolar constraints on uncalibrated stereo pairs. In contrast, a calibrated stereo rig with known intrinsic and extrinsic parameters can use so-called epipolar rectification [14,15] to transform Inhibitors,Modulators,Libraries each corresponding stereo pair for making the epipolar lines parallel and at the same horizontal rows, which greatly reduces the stereo matching region to a horizontal row. In this paper, the epipolar rectification algorithm [15] is adapted, which is a compact and clear stereo rectification algorithm and can provide MATLAB code for research reference.

Inhibitors,Modulators,Libraries Since the algorithm assumes that the stereo rig is calibrated, camera calibration needs to be performed first.The camera calibration procedure in this paper was accomplished using the Camera Calibration Toolbox of MATLAB [16] developed by Bouquet. Bouquet��s main initialization phase of camera calibration inspires by Zhang [17] that uses a chessboard as calibration Inhibitors,Modulators,Libraries pattern to obtain both intrinsic and extrinsic camera parameters, and Bouquet��s intrinsic camera model inspired by Heikkil? and Silv��n [18] which includes two extra distortion coefficients of Zhang��s intrinsic camera model to get more precise stereo rectification. After stereo rectification is done, the correspondence problem of desired target is solved.The Circle Hough Transform (CHT) [19] is one of the best known methods which aims to detect lines or circles in an image.

The algorithm transforms each edge point in edge map to parameter space and plots histogram of parameter space in an accumulator space as output image in which the highest-frequency Dacomitinib accumulator Ivacaftor molecular weight cell (i.e., pixel with the highest gray value) is the outcome. If circle radii are unknown, the parameter space is a three-dimensional space, and that requires a large amount of computing power for the algorithm, which is the major drawback for real-time application. Kimme et al.