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为了实现对水下机械手运动范围的检测,研发了一套多目立体视觉测量系统。通过测量机械手末端空间运动轨迹,利用空间圆拟合算法可计算出被测关节的实际运动范围。对其中的核心算法空间圆拟合进行了研究。首先空间圆可看作是由一个平面与球体相交而成,其圆心必定在球体上任意两点连线的中垂面上,可基于空间向量的拟合方法推导出中垂面的方程,与拟合的空间平面联立即可求出空间圆方程,进而利用拟合出来的空间圆的圆心坐标求出圆半径。然后对实际测量过程中的错误跟踪点进行了分析,如果在空间圆拟合的过程中对错误跟踪点不加以去除,则会带来错误的拟合结果,从而会大大影响测量结果的正确性。最后提出了基于RANSAC(Random Sample Consensus)的空间圆拟合算法,它可以从一组包含错误点的测量数据集中通过迭代方式有效剔除粗大误差点,从而估计出数学模型的参数和正确的拟合结果。仿真测试及实际测量实验的结果表明,当粗大误差点所占总测量点数的比例小于20%时,所提出的算法可有效地剔除所有粗大误差点,很好地解决了机械手运动范围检测系统在实际工程应用中所遇到的问题。
In order to detect the range of motion of the underwater manipulator, a multi-eye stereoscopic vision measurement system was developed. By measuring the trajectory of the robot’s end space, the space circle fitting algorithm can be used to calculate the actual range of motion of the measured joint. The circle fitting of the core algorithm among them has been studied. First of all, the circle can be regarded as the intersection of a plane and the sphere. The center of the circle must be on the middle vertical plane of any two points on the sphere. Based on the fitting method of space vector, Simultaneously, the circular equations of the space can be obtained by simultaneous fitting of the space planes, and then the circle radius can be obtained by using the center coordinates of the fitted circular space. Then the error tracking points in the actual measurement process are analyzed. If the error tracking points are not removed during the fitting of the space circle, the result of the error fitting will be incorrect, which will greatly affect the accuracy of the measurement results . Finally, a space circle fitting algorithm based on RANSAC (Random Sample Consensus) is proposed, which can effectively remove coarse error points from a set of measurement data sets containing error points by iteration, so as to estimate the parameters of the mathematical model and the correct fitting result. The results of simulation test and actual measurement experiment show that the proposed algorithm can effectively eliminate all the coarse error points when the ratio of coarse error points to the total number of measurement points is less than 20%, which can well solve the problem that the robot motion range detection system Problems encountered in practical engineering applications.