In digital image correlation (DIC) measurements of non-uniform deformation fields, the undermatched problem is often a key factor limiting measurement accuracy. Existing optimization strategies for undermatched problem mostly rely on a priori assumptions about the order of the deformation field to be measured. This prerequisite imposes significant limitations on their application in unpredictable complex real-world scenarios. To address this issue, a decentralized difference-based improved method for undermatched systematic error is proposed. This method can effectively compensate for undermatched errors in non-uniform deformation fields without requiring any prior information. Numerical simulations results show that the method is suitable for high-order non-uniform deformation fields, can reduce the undermatched error of the first-order shape function by 97.0%. It can achieve higher computational accuracy and stability than mainstream second-order shape function. Its optimization performance has been effectively validated in practical engineering applications.

This study proposes a novel digital image processing system that combines a diffraction-limited resolution (DLRF)-based measurement technique with a windowed form-center tracking algorithm. To evaluate the accuracy of this system, this paper compares and analyzes the effectiveness of conventional digital image techniques and DLRF-based methods for deformation displacement measurements. In addition, the study includes thermal stability tests under ambient noise and uniform high temperature conditions to evaluate the stability performance of the system in a complex environment. The experimental results show that the DLRF-based digital image correlation method proposed in this study performs well in reducing the mean deviation (from a maximum of 5.17 × 10-3 to 1.73 × 10-3) and root-mean-square error (from a maximum of 5.14 × 10-3 to 0.75 × 10-3). It is worth noting that the DLRF method is faster in processing when using the single-precision format than the double-precision format, with a speedup of up to 1.05 times. In addition, the multiple displacement averaging processing method can effectively filter the noise in the test, and the noise effect is only in the range of 0 to 2 μm in most areas. In the analysis of test points 10-34 and 57-80, the displacement error is controlled within 5 μm, indicating that the modified structural analysis model can be used for on-orbit micrometer-scale thermal deformation analysis. The study proves the high accuracy and stability of the digital image system proposed in this paper in the measurement of deformation displacement, which provides adequate technical support for accurate measurement in related fields.

Aiming at the three-dimensional deformation measurement requirement of the high-stability structure of spacecraft in space multi-physical fields, a comprehensive instrument protection device in a vacuum high-low temperature environment is developed using ultra-low temperature anti-condensation and vacuum heat insulation technology. This ensures that the digital image correlation (DIC) measurement camera always remains in a constant temperature and pressure environment and can stably exert its original efficiency in space multi-physical field environments. Subsequently, a path-dependent DIC method based on a graphics processing unit computing parallel acceleration is proposed by combining a pre-interpolation strategy and integrated image technology, which realizes high-precision matching of digital images before and after deformation in a spatial multi-physical field environment and improves the computing efficiency. To address the problem that a common reference point may deform significantly in a space environment with a large temperature change, which leads to inaccurate system accuracy, combined with a random sampling consistency algorithm and singular value decomposition method, the optimal registration of the coordinate system and the solution of deformation were realized by setting the threshold of the reference point margin screening. Finally, a three-dimensional deformation measurement system in high- and low-temperature vacuum environments was built, and the three-dimensional deformation measurement of the satellite antenna in high- and low-temperature vacuum environments was verified, which proves the effectiveness and accuracy of the above method.

The error estimation formula is one of the key points in DIC research. However, most of the correlation criterion used in the research of DIC error is SSD instead of the most commonly used ZNSSD. And the existing error estimation formulas are very complicated, which is not conducive to analyse the relationship between interpolation algorithm, gradient calculation method, image spectrum and error. Therefore, there is a need to derive the error formulae applicable to all SSD class correlation criteria and to find the intermediate variables between the interpolation algorithm, gradient algorithm, image spectrum and error based on the general formulae to facilitate the analysis. This work derives the interpolation error generalization and random error generalization for DIC using SSD class correlation criterion, by using the frequency domain based approach. The Error Coefficient Matrix (ECM) is proposed in order to carry out the analysis of the impact on the computational error of the DIC. The DIC methods using SSD class correlation criterion yield almost identical results and are not limited to the expectation or variance of the error. The low-frequency portion of the EMC has a greater influence on the error than high-frequency portion. Conversely, the high-frequency portion of the image spectrum has a greater influence on the error. Among the commonly used interpolation and gradient algorithms discussed in this work, the smallest RMSE are found in the B-spline and Centre difference algorithms, which are 11% and 83% of the maximum, respectively. The findings of this work help to generalise the existing SSD-based findings to ZNSSD, such as optimal subset size, optimal speckle radius, etc. In addition, the best combination of algorithms used in DIC operations is the combination of B-splines and Centre difference operators.

The inverse compositional Gauss-Newton (IC-GN) DIC algorithm is now the most popular DIC algorithm. The error analysis of the algorithm is necessary. However, the effect of the gradient operator on the error cannot be systematically analysed due to the different dimensions of the gradient operator. In this paper, the 1-D and 2-D gradient operators are incorporated into the same framework by decomposing the gradient operator into two parts: gradient acquisition and gradient filtering. Based on the above analysis, a DIC method based on gradient filtering is constructed and the simulation analysis results show that the systematic error is reduced to less than 10% of the original ICGN-DIC algorithm, enhancing the robustness to noise variations. Finally, validation is performed using an open-source dataset. It is demonstrated that the proposed method can reduce the system error to less than 15%.

In light of the need for spacecraft manufacturing to enhance real-time control capabilities and production efficiency in the manufacturing process, this paper designed a synchronous modeling scheme for the satellite manufacturing system driven by real-time perception information, based on the optimal layout of the workshop's Internet of Things (IoT) system. This paper focuses on the research of manufacturing process-oriented multimodal recognition technology of perception information and manufacturing system synchronous modeling technology based on real-time perception. The real-time, data-driven, synchronous modeling of the manufacturing system realized the complete mapping and control of the product manufacturing process in a virtual environment. It constructed a manufacturing system synchronous modeling system based on real-time perception. The system had been applied in the development of several models of honeycomb sandwich panels, including the Mars rover, and has achieved the expected results.

基于数字散斑干涉技术同时测量微小偏摆和俯仰角的方法具有非接触测量、无合作靶镜、高测量分辨力、高测量精度等优点,但在确定相位图的条纹方向环节耗时较长,导致测量速度较慢.为了加快测量速度,对相位处理流程和角度测量算法进行了研究,提出了一种改进方法.该方法直接利用相位图上3个点的相位值来同时确定偏摆和俯仰角,不需要计算条纹方向和进行相应的全局图像处理,减少了算法运行时间,提升了测量速度.该方法不仅保留了原方法的所有优点,而且具有测量模型简单、误差源少、测量速度快的特点.

A machine vision-based automatic inspection system for satellite honeycomb sandwich panel assembly compliance is designed through image segmentation technology based on 3D reconstruction and registration and contour extraction technology based on the grayscale image for the rapid measurement of the assembly compliance of inserts of the satellite honeycomb sandwich structural panels before the cover is closed. Matching and calculating the inspection data with the read CAD model to determine the wrong and missed installed embedded parts and styrofoam and calculate their position accuracy. The effectiveness of the method has been proven through validation tests on actual satellite honeycomb sandwich structural panel products, with over 300% improvement in efficiency compared with the traditional manual visual method.

舵机连杆拉压刚度的准确测量对于飞行器舵机的安全服役至关重要,而拉压刚度的准确测量则高度依赖于舵机连杆变形的高精度测量.传统的夹持式引伸计虽然可用于材料或结构拉压变形的精确测量,但其测量标距通常较为有限,不能满足复杂工程结构(如飞行器舵机连杆等)变形测量的实际需求.基于远心成像镜头的非接触光学视频引伸计也能满足结构变形的高精度测量,但其视场同样受限于远心镜头的物理尺寸(镜头直径).为了克服现有高精度视频引伸计的不足,本文首先建立了基于远心成像和组合式平面镜的超灵敏视频引伸计系统.通过平面反射镜和反射棱镜的辅助作用,本文建立的超灵敏视频引伸计在保留远心成像优点(对离面位移不敏感)的同时,扩大了系统的测量标距,克服了原有高精度视频引伸计的不足.然后,通过圆棒试样的单轴拉伸实验,比较了本文建立的测量系统与应变片及夹持式引伸计的测量精度,测量结果显示本文建立的超灵敏视频引伸计与应变片和夹持式引伸计之间的测量误差均在1士3με以内.最后,利用该系统测量了舵机连杆在拉压载荷作用下的变形响应,并结合载荷数据进一步计算得到了舵机连杆的拉压刚度.

Abstract. Although various camera calibration methods have been proposed, most of these methods cannot deliver accurate determination of the intrinsic camera parameters, because of the coupling errors existing between intrinsic and extrinsic camera parameters and the use of explicit distortion models. Here, we propose a model-free method for accurate camera calibration, which utilizes phase-shifted fringe patterns shown on a liquid crystal display (LCD) screen for estimating the intrinsic parameters of a camera and correcting lens distortion. Horizontal and vertical fringe patterns are consecutively displayed on the LCD screen, which is placed at two positions parallel to the camera sensor plane. These fringe patterns are captured by the camera from the front viewpoint for calculating the absolute phase maps. Then, the images with lens distortion can be transformed to the distortion-free images using an inverse mapping operation. Subsequently, the principal point coordinates are calculated according to the geometric imaging relationship between the positions of the two LCD screens. Finally, the focal length can be estimated using the similarity of triangles formed by the obtained principal point coordinates and the obtained phase maps at the two positions. Both simulated and real experiments are performed to verify the validity of the proposed method. The results demonstrate that this method not only successfully eliminates coupling errors but also perfectly corrects lens distortion.

The research on vibration-driven system with several internal masses is of great significance for creeping robots in some narrow space, while seldom scholars study the planar motion with continuously changing curvature. The planar locomotion of this system with two internal masses, driven by three-phase motion, under viscous and anisotropic friction is studied in this paper. When the period ratio of the two moving internal masses is equal to 1, the trajectory of the system is a circle. The analytical solutions of steady-state linear velocity and angular velocity of circular motion are obtained by using the averaging method. When the period ratio is not equal to 1, the trajectory of the system is a linear. The influence of relative acceleration and the period ratio of the two moving internal masses on the planar motion of the system is analyzed by using the Velocity-Verlet integration method, which is verified by the Runge-Kutta method. The planar locomotion of the system can be obtained. It follows from the above analysis results that the six types of the switching trajectory can arise by controlling the driven parameters. Finally, integrating the different switching trajectories, one can obtain any continuous-curvature paths, which has important application value for the trajectory planning of the mobile robot.

In recent years, university-industry collaboration (UIC) is known as a new mode of the research and development (R&D) of the composite technology, which is widely focused by the composite industry. In present research, the overall development, regional distribution and cooperation relationship of the UIC in the advanced composites material industry is analyzed according to the advanced composites material patents (ACMPs) applied by universities and enterprises from 2009 to 2014 in China. Results obtained in the study show that the overall development of UIC in the advanced composites material industry is at the stage of tracking and catching-up. At present, the UIC system is far from perfect and the mechanism of scientific achievement transformation has not been still established in the advanced composites material industry. Geographical distance has not significant impact on the ACMPs applied by universities and enterprises. There are considerably differences about ACMPs among the eastern, central and western regions, which has positive correlation with the level of economic development. The cooperation relationship of UIC in the advanced composites material industry is comparatively loose and the characteristic of network is not obvious. The UIC model is not widely recognized.

A finite difference method is used to do direct numerical simulation (DNS) of hypersonic unsteady flowfield under the action of freestream pulse wave. The response of the hypersonic flowfield to freestream pulse wave is studied, and the generation and evolution characteristics of the boundary layer disturbance waves are discussed. The effects of the pulse wave types on the disturbance mode in the boundary layer are investigated. Results show that the freestream disturbance waves significantly change the shock standoff distance, the distribution of flowfield parameters and the thermodynamic state of boundary layer. In the nose area, the main disturbance modes in the boundary layer are distributed near the fundamental mode. With the evolution of disturbance along with streamwise, the main disturbance modes are transformed from the dominant state of the fundamental mode to the collective leadership state of the second order and the third order harmonic frequency. The intensity of bow shock has significant effects on both the fundamental mode and the harmonic modes in each order. The strong shear structure of boundary layer under different types of freestream pulse waves reveals different stability characteristics. The effects of different types of freestream pulse waves are significant on the distribution and evolution of disturbance modes. The narrowing of frequency band and the decreasing of main disturbance mode clusters exist in the boundary layer both for fast acoustic wave, slow acoustic wave and entropy wave.

The Hashin failure model and the 3D progressive damage method-based user material subroutine are employed to characterize the impact damage characteristics of composite layer, and surface based cohesive behaviour are introduced to characterize the interlaminar mechanical property in this paper.The dynamic response process of the carbon/epoxy composite laminates subjected to low-velocity impact load under different interlayer surface strength conditions are simulated, and the effects of interlayer interface strength on the ballistic property of composite materials are emphatically analysed.Results show that the impact dynamic response of composite laminated plates is a process of stress waves propagation, reflection, and interference between layer and layer.The kinetic energy dissipation of bullet varies depending on the interlayer surface strength of carbon/epoxy composite laminates.The kinetic energy absorbing performance of carbon/epoxy composite laminates is directly altered by the interlayer surface strength.The interlayer surface strength of laminates also directly impacts of the elastic strain energy carbon/epoxy composite and the kinetic energy dissipation of bullet in laminates failure.Namely, the transformed form of the bullet kinetic energy is affected by the interlayer surface strength significantly.In general, the interlayer surface strength presents a significant role on whether the failure form, the contact force, the kinetic energy dissipation process, the elastic strain energy composite laminates or the kinetic energy dissipation of bullet in laminates failure during the impact process.

The hypersonic flow over a blunt wedge under freestream impulse wave is analyzed by direct numerical simulation and the nonlinear evolution of disturbance wave modes in the boundary layers is discussed. Results show that, under impulse wave, the thermodynamic mechanism and shear flow structure in the boundary layer is sharply changed, and the effect of the reflection wave between bow shock and wall on shear flow structure is larger than that of freestream impulse wave. Both the disturbance waves with frequency less than fundamental mode and the harmonic modes in hypersonic boundary layer are induced under impulse wave. Flow recompression plays a significant role in the evolution of disturbance waves in the boundary layer. Low frequency disturbances are the dominant mode in the nose boundary layer. With the evolution of disturbance waves along streamwise, the boundary layer will be dominated by the second harmonic mode (x>2.3), and all disturbance modes decrease along streamwise except the second order harmonic mode (x>4.5).

An unsteady hypersonic blunt wedge flowfield under freestream slow acoustic wave is solved by direct numerical simulation (DNS), and the receptivity characteristics of the boundary layer under slow acoustic disturbance with different amplitudes are analyzed. Results show that slow acoustic wave in the freestream not only has a significant effect on the aerothermodynamics characteristics of hypersonic flowfield and boundary layer, but also on the bow shock characteristics. It shows that the maximum amplitudes of the disturbance modes in the boundary layer are positively correlated with the disturbance amplitude of the freestream. The bigger the amplitude of the freestream disturbance gets, the earlier the high-frequency disturbance mode exists, and the stronger the high frequency interference is. The larger amplitude of freestream disturbance wave can accelerate the generation of the higher order harmonic modes in boundary layer. Furthermore, the transformation position and the times of the dominant mode in the boundary layer differ under various amplitude of freestream disturbance, and compared with the smaller amplitude's slow acoustic disturbance in the freestream, the larger amplitude disturbance can accelerate the first transformation of the dominant mode in boundary layer, and also delay its second transformation.

A high dimensional stable composite truss used for a certain satellite is discussed in this paper. Through the material selection, the ply design, and the CTE test & analysis, a high precision composite truss is manufactured, and the thermal deformation of the truss is measured. It is shown that the high dimensional stable structure made of high modulus CFRP with micrometer level accuracy can be obtained through an appropriate ply design. Some suggestions are made for reducing the thermal deformation and improving the dimensional stability & measurement accuracy. It is the first successful practice of the high dimensional stable composite structure being used for the ultra-stable satellite platform.

为了研究碳纤维不锈钢层板的冲击动态响应以及热载荷条件下的冲击性能,采用ABAQUS/Explicit,编写基于复合材料渐进损伤用户子程序VUMAT;引入Johnson-Cook模型,仿真计算了碳纤维增强环氧树脂基复合材料-SS304不锈钢层板热载条件下冲击动态响应过程;分析了其冲击动态响应及渐进损伤,着重讨论了热载荷条件对碳纤维金属层板的冲击能量吸收、接触力等抗冲击性能及失效模式的影响.结果显示,高速冲击载荷作用下,纤维层的脆性断裂、金属层的塑性变形以及纤维层与金属层之间的脱层是碳纤维不锈钢层板的主要失效形式.热载荷的存在直接影响了冲头的接触力,随环境温度升高,接触力总体上降低,子弹的速度衰减越慢,剩余速度增大.结果表明,热载荷降低了纤维金属板的冲击动能吸收特性,弱化了碳纤维金属板的抗冲击性能.无论是纤维金属层板的整体破坏,还是纤维失效、基体失效和脱层失效,热载荷都产生了重要影响.

Materials of satellite integration truss frame are required to withstand temperature that range from about – 250 °C ~ + 150 °C. In order to reduce structural components deformation caused by such temperature change, material of truss frame mostly adopts laminated composite material tubes, whose linear thermal expansion coefficient (LTEC) is very small. Therefore, accurate measurement of LTEC of truss frame materials over a broad temperature range is essential for successful mission. To address this issue, this paper proposes a general experiment platform for measuring LTEC of laminated composite material specimen reaching length up to one meter in the temperature range from – 100 °C to +100 °C. The platform uses light-density optical fiber probe to measure length variation and thermocouple to record temperature variation. Thereafter, the thermal expansion coefficient and its measurement uncertainty can be obtained by establishing and solving mathematical model. Finally, LTEC measurement of a tubular composite materials specimen is conducted. The experiment result demonstrates the validity and practicality of the experiment platform and the measurement accuracy of LTEC which can reach up to 10-7/°C.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9708