细径形状传感器在医学上有多种潜在的应用, 如乳腺肿瘤胸部穿刺针的定位、肠道内窥镜的形状显示、心脏血管导管的定位等, 其形状重建和末端定位精度一直是研究者关心的主要问题之一。为了提高光纤光栅形状传感器的形状重建精度, 本文研究了沿基材母线等间隔分布的FBG形状传感器的应变传递规律并对其进行实验验证。此形状传感器利用环氧树脂胶将FBG封装至镍钛合金丝表面, 形成FBG形状传感器的基材-黏结层-光纤-黏结层的四层复合材料结构。根据光纤光栅传感器应变传递力学简化模型, 推导出相应的平均应变传递率公式; 分别研究光纤至基材中心距、黏结层长度、厚度和弹性模量对光纤光栅传感器平均应变传递率的影响。实验结果表明, 封装后的光纤光栅传感器平均应变传递率在有效范围内随着基材长度的增加而增加, 黏结层外径的增加对其影响不大, 验证了理论模型的可用性。将应变传递率引入形状重建中, 改进了FBG形状传感器的形状重建算法, 末端相对定位精度由原来的3.5%提高到2.7%。

Small-diameter shape sensors have a variety of potential applications in medicine such as the positioning of breast tumor chest needles, shape display of intestinal endoscopes, and positioning of cardiac vascular catheters. The shape-reconstruction and end-positioning accuracies of shape sensors have always been major concerns of researchers. To improve the shape-reconstruction accuracy of a fiber Bragg grating (FBG) shape sensor, the strain transfer law of an FBG shape sensor with 90° distribution of fiber around the center of the substrate was studied and verified experimentally. Epoxy resin glues the FBG to the surface of the nickel-titanium alloy wire to form a four-layer structure of the substrate-bonding layer-fiber-bonding layer of the FBG shape sensor. Based on a simplified model of strain transmission mechanics of the FBG sensor, the corresponding average strain transfer rate formula was derived. The effects of the fiber-to-substrate center distance, bond layer length, thickness, and elastic modulus on the average strain transfer rate of FBG sensors were also analyzed and experimentally verified. Experimental results show that the average strain transmission rate of the packaged FBG sensor increases with increasing substrate length in the effective range, whereas an increase in the outer diameter of the bond layer has little effect on the average strain transmission rate, thus verifying the applicability of the theoretical model. The strain transfer rate is introduced into the shape reconstruction, and the shape-reconstruction accuracy of the FBG shape sensor is reduced from 3.5% to 2.7%.