基于超灵敏视频引伸计的飞行器舵机连杆拉压刚度准确测量

Accurate tensile/compressive stiffness measurement of the connecting rod of flight vehicle steering engine based on an ultrasensitive video extensometer

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±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。

The accurate measurement of tensile and compressive stiffness of the connecting rod is critical to the safety of flight vehicle steering engine,while the high-accuracy tensile/compressive stiffness is highly dependent on the accurate measurement of connecting rod deformation.Conventional clip-on extensometer can be used for accurate tensile/compressive deformation measurements of materials or structures.However,the measurement range of these mechanical extensometers is generally very limited,and cannot meet the actual needs of complex engineering structures such as the connecting rod of flight vehicle steering engine.Non-contact optical video extensometer based on telecentric lenses can also realize high-accuracy deformation measurements,but their field of view is also limited to physical dimensions(lens diameter)of telecentric lenses.In order to overcome the disadvantages of the existing high-accuracy video extensometer,we established an ultrasensitive video extensometer based on telecentric imaging and a four-mirror adapter.With the aids of planar mirror and reflection prism,the established ultrasensitive video extensometer increases its measuring range while retaining the advantage of telecentric imaging,thus overcoming the disadvantages of the existing high-accuracy video-extensometer.Then,we compared the accuracy from the established system and the strain gauge to the clip-on extensometer through the tensile test of a cylinder sample.Experimental results showed that the errors from the ultrasensitive video and the strain gauge to the clip-on extensometer were both within 1±3με.Finally,the tensile/compressive deformation of the connecting rod of flight vehicle steering engine was measured by the established system,and then used to determine the tensile/compressive stiffness by combining with load data.