采用仿射变换的桨叶变形摄像测量Newton-Raphson算法

Affine-Transform-Based Newton-Raphson Algorithm forVideoly Measuring Blade Deformation

提出一种基于仿射变换的(Newton-Raphson,简称N-R)数字图像相关算法。首先,采用人机交互的方法在变形前后的图像中选取匹配特征点,计算仿射变换参数;然后,根据仿射变换位移模式计算目标子区中心点的位移,将其用作N-R算法的初值。为降低计算量,采用全场插值,插值运算次数降为常规插值的1%左右。仿真测试表明,基于仿射变换的N-R算法在精度保持不变的情况下显著减少计算时间,克服了常规N-R算法计算量大、效率低、只适用于无刚体转动目标等缺陷,为开发直升机桨叶变形摄像测量系统提供了算法基础。

Video measurement has great value in determining the deformation of helicopter blades and an efficient correlation algorithm of digital image is crucial.A Newton-Raphson algorithm method based on affine transform is proposed considering the characteristics of helicopter blade motion and deformation.First,affine transform parameters are determined by respectively selecting three match feature points in the reference image and deformed image using human-computer interaction method.Then,the initial displacements for Newton-Raphson algorithm is calculated based on the affine transform displacement mode.The global interpolation method is adopted to avoid superfluous and respective interpolation in the iteration process,which cuts down the amount of computation to 1% of that of the conventional method.The results show that the Newton-Raphson algorithm based on affine transform has much less computation expense with high accuracy and is suitable for objects with rigid body rotation.