Gradient-based point tracking method and its application in the modal test of a solar array model

Abstract

Structural dynamic testing is of great importance for a built-up aerospace structure. The response acquisition is commonly time and labor-consuming when the size of the test structure is large. The recently developed image-based measurement techniques, such as point tracking (PT) method, are well-suited to obtain the responses of lightweight and flexible membrane structures in structural dynamic testing. This paper develops two new PT methods: the improved PT method and the gradient-based PT method. In order to access the accuracy of the two methods and the original PT method, a comparison experiment of a cantilever beam is conducted, where the laser Doppler vibrometer signal is set as the reference. For the testing of a solar array model, the gradient-based PT method is applied to extract the responses of the 254 points on the surface. The first five modes of the solar array are estimated based on the extracted responses from the gradient-based PT method, which show agreement with the results from the traditional measurement technique. The gradient-based PT method shows advantages in reducing testing time, saving labor, and providing high spatial resolution in mode shapes.