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To improve the detection capability of satellite-based synthetic aperture radar, a large antenna array with a length scale of 100 meters is urgently needed. However, the structural deformation of the large antenna leads to phase errors, which will significantly reduce the antenna gain; hence, real-time and high-precision profile measurements of the antenna are essential for active compensation of the phase and thus improving the antenna gain. Nevertheless, the conditions of antenna in-orbit measurements are rather severe because of limited installation locations of measurement instruments, large areas, and long distance to be measured, and unstable measurement environments. To deal with the issues, we propose a three-dimensional displacement measurement method for the antenna plate based on laser distance measuring and digital image correlation (DIC). The proposed method uses the DIC method to retrieve the in-plane displacement information in combination with a laser range finder to provide depth information. A Scheimpflug camera is used to overcome the limitation of the depth of field of traditional cameras and enable clear imaging of the full field. Moreover, a vibration compensation scheme is proposed to eliminate the measurement error of the target displacement caused by the random vibration (within 0.01°) of the camera support rod. The results of the experiment in a laboratory setting show that the proposed method can effectively eliminate the measurement error caused by camera vibration (50 mm) and reduce the displacement measurement error to within 1 mm with a measurement range of 60 m, which can meet the measurement requirements of next-generation large satellite antennas.

This work studied a flexible and stretchable magnetoactive elastomer (MAE) film consisting of carbonyl iron (CI) particles and polydimethylsiloxane (PDMS) elastomer matrix. The deformation of the MAE film was investigated using digital image correlation (DIC) and laser Doppler velocimetry (LDV) methods. The MAE film with free boundary is highly wrinkled under a magnetic field generated by an electromagnet with the current of 0.65 A. While in fixed boundary condition, the maximum deformation appears at the center point, and the maximum displacement reaches 0.63 mm when the current is 3 A. The finite element method (FEM) results demonstrate that the maximum internal stress and strain are 33 kPa and 2.3%, respectively. The FEM results are in good agreement with the DIC and LDV tests. With the exceptional magnetic controllability, the MAE film can find extensive applications in intelligent control systems, acoustic absorption devices, and haptics.

In the measurement of plate specimens, traditional two-dimensional (2D) digital image correlation (DIC) is challenged by two aspects: (1) the slant optical axis (misalignment of the optical camera axis and the object surface) and (2) out-of-plane motions (including translations and rotations) of the specimens. There are measurement errors in the results measured by 2D DIC, especially when the out-of-plane motions are big enough. To solve this problem, a novel compensation method has been proposed to correct the unsatisfactory results. The proposed compensation method consists of three main parts: 1) a pre-calibration step is used to determine the intrinsic parameters and lens distortions; 2) a compensation panel (a rigid panel with several markers located at known positions) is mounted to the specimen to track the specimen’s motion so that the relative coordinate transformation between the compensation panel and the 2D DIC setup can be calculated using the coordinate transform algorithm; 3) three-dimensional world coordinates of measuring points on the specimen can be reconstructed via the coordinate transform algorithm and used to calculate deformations. Simulations have been carried out to validate the proposed compensation method. Results come out that when the extensometer length is 400 pixels, the strain accuracy reaches 10 μ e no matter out-of-plane translations (less than 1/200 of the object distance) nor out-of-plane rotations (rotation angle less than 5°) occur. The proposed compensation method leads to good results even when the out-of-plane translation reaches several percents of the object distance or the out-of-plane rotation angle reaches tens of degrees. The proposed compensation method has been applied in tensile experiments to obtain high-accuracy results as well.

The traditional two-dimensional (2D) digital image correlation (DIC) method often leads to results without enough accuracy due to the out-of-plane motions of the specimens in the deformation measurements of plate specimens. To remove the effects of the out-of-plane motions, a compensation method for the 2D DIC method has been developed. The compensation method sharply improves the measuring accuracy of the 2D DIC method. However, the existing compensation method often deduces compensation parameters with strong fluctuations. To solve these problems, an improved compensation method is proposed. The proposed method employs an extra single camera calibration to determine the distortion parameters so that the corresponding coefficient matrix is not affected by the experimental noise. For simplicity, the extensometer line measurement is taken as an example to compare the measuring accuracy of the two compensation methods. Static experiments have been carried out to analyze effects of different measuring parameters. Tensile experiments indicate that the measuring results of the improved compensation method are not only comparative with the results measured by the 3D DIC method but also accord with the results of the strain gage. Besides, a real-time extensometer measuring system with a measurement accuracy of 5 μe at a rate of 28 fps, has been developed.