真空热环境下结构热变形试验方法研究

RESEARCH ON THE TEST METHOD OF STRUCTURE THERMAL DEFORMATION IN THE VACUUM THERMAL ENVIRONMENT

航天器空间结构的尺寸稳定性直接关系到航天器有效载荷和平台的在轨运行性能。为改进空间结构在轨环境下的尺寸变形测量与验证方法,开展了地面模拟在轨真空热环境下的结构热变形试验方法研究。在对国内外相关试验方法与测量系统典型案例分析的基础上,基于工业摄影测量原理提出了单相机+多摄站测量方式的试验方案,并研制了相机保护系统和相机二维运动机构,相机在真空热环境下通过运动机构的弧形导轨可以在一个弧面内二维运动进行不同角度图像拍摄,用来满足多摄站的测量需求;随后针对真空热环境下测量,分析了相机保护系统的光学窗口对测量相机标定结果的影响,通过仿真与试验验证了相机拍摄景深、圆形标志点对比度和比例因子对测量精度的影响,并提出了采集多曝光图像处理方法,从不同曝光下拍摄的圆形标志点图像中优选最佳的圆心提取和识别结果进行融合计算,来保证获取较好的对比度和亮度图像。最后结合典型试验件对提出的真空热环境下结构热变形测量方法进行了试验验证,试验结果达到0.043 mm的测量精度,表明该方法可以有效满足未来航天器空间结构热变形的测量需要。

The performances of spacecraft payloads and platforms on orbit are influenced by dimensional stability of spacecraft structure.This article had researched the test method of structure thermal deformation in the vacuum thermal environment simulated on the ground to improve measurement and verification method of the space structure deformation on orbit.It presented a single-camera and multistation photogrammetric measurement scheme,based on the analysis of related test methods and typical measurement systems.Then a camera protection system and a two-dimensional motion mechanism was developed.The camera can complete the image acquisition at different stations in a arc surface through the arc shaped guide of the motion mechanism in the vacuum thermal environment,and satisfy the measurement requirement of multistation.The influence on the camera calibration due to the optical window of the camera protection system had been discussed.Besides,the effect of the scene depth,the contrast of circular feature points and scale factor on the measurement accuracy was verified by the simulation and experiment,then a multi-exposure image processing method was proposed,which selecting the best circle center extraction and recognition results from circular feature point images taken from different exposures to fusion computation,ensuring better contrast and brightness images were obtained.Finally,the structure thermal deformation measurement method in the vacuum thermal environment proposed in this article was test and verified through a typical test piece,the test results all reached a measuring accuracy of 0.043 mm,and it proved that this method can effectively meet the needs of thermal deformation measurement for the spacecraft structure in the future.