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中文摘要：
针对现有的Freeman八方向链码码间距过大、采样必须为方格采样、编码过程需要人工干预的不足，提出一种新的链码方法，并利用该方法将封闭曲线链码化。根据封闭曲线的周期性，将其参数方程展成傅里叶级数，导出傅里叶系数与曲线链码之间的关系式。利用傅里叶系数计算封闭曲线的形状特征，建立以形状特征为参数的欧氏距离。通过改变抽油系统仿真程序中的粘滞阻尼系数和库仑摩擦因数，获得不同形状的仿真地面功图曲线。建立实测与仿真地面功图曲线形状特征间的欧氏距离，以该距离为优化目标函数，寻优得到使目标函数值满足给定误差的仿真功图曲线，该功图对应的一组阻尼系数和摩擦因数即为相应抽油系统的粘滞阻尼系数和库仑摩擦因数。以4口实测油井为例进行系统阻尼系数的辨识研究，结果表明了所提方法的正确性和有效性。
英文摘要：
Aimed at the shortcomings of the eight-directional Freeman chain code method, a new 24-directional chain code is put forward to encode the closed boundary curve of an image. The parametric equation of the closed boundary curve is transformed into Fourier series whose coefficients can be computed according to curve＇s chain codes. By means of these coefficients, shape characteristics of the boundary curve are extracted. The Euclidean distance based on shape characteristics is introduced as the measurement of similar degree between two different closed boundary curves. Changing the value of viscous damping coefficient and Coulomb friction coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is less than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the sucker-rod pumping system of directional well. In the end, an example is given to show the correctness and effectiveness of the presented method.
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