Verification of flexible cable model using visual material point tracking

The flexible cable is widely applied in the field of astronautics and aeronautics, and has the characteristics of large structure, low rigidity and large deformation. In large range motion, the displacement, rotation and elastic deformation of the flexible cable are coupled with each other, increasing the difficulties in dynamic modeling of the flexible cable. To verify the accuracy of the dynamic model for the flexible cable, the non-contact visual measurement method is used. The movement area of the cable is extracted by a series of image preprocessing methods, such as background modeling, and image difference, smoothing and binarization. The cable centerline is obtained by the hierarchical-connected skeletonization algorithm based on distance transform, and the planer position of the centerline is calculated by solving the camera external matrix. With even gray level, the cable does not have obvious image characteristics, making it difficult to track a specific point of the cable. In the previous methods, the feature point on the cable is pasted or sprayed, affecting the dynamic characteristics of the flexible cable. A material point tracking algorithm which can adapt to the bending and longitudinal elastic deformation of the flexible cable is proposed. The algorithm can be used to track any point of the cable without additional features. The dynamic model for the flexible cable is built based on the absolute nodal coordinate formulation, and the simulation results are consistent with the experimental results. Compared with other measurement methods, the material point tracking algorithm can reduce the factors of external interference in the measurement process, providing accurate experimental reference results for dynamic model verification.