Telecommunications Laboratory LABTEL, Electrical Engineering Department, Federal University of Espírito Santo, Espírito Santo 29075-910, Brazil.
Mechanical Engineering Department, Federal University of Espírito Santo, Espírito Santo 29075-910, Brazil.
Sensors (Basel). 2019 Jul 5;19(13):2962. doi: 10.3390/s19132962.
In this paper, we report the development of a portable energy-efficient interrogator (Perrogator) for wavelength-based optical sensors. The interrogator is based on a compact solution encompassing a white light source and the spectral convolution between the sensor and a tunable filter, which is acquired by a photodetector, where a microcontroller has two functions: (i) To control the filter tuning and to (ii) acquire the photodetector signal. Then, the data is sent to a single-board computer for further signal processing. Furthermore, the employed single-board computer has a Wi-Fi module, which can be used to send the sensors data to the cloud. The proposed approach resulted in an interrogator with a resolution as high as 3.82 pm (for 15.64 nm sweeping range) and maximum acquisition frequency of about 210 Hz (with lower resolution ~15.30 pm). Perrogator was compared with a commercial fiber Bragg grating (FBG) interrogator for strain measurements and good agreement between both devices was found (1.226 pm/µε for the commercial interrogator and 1.201 pm/µε for the proposed approach with root mean square error of 0.0144 and 0.0153, respectively), where the Perrogator has the additional advantages of lower cost, higher portability and lower energy consumption. In order to demonstrate such advantages in conjunction with the high acquisition frequency allowed us to demonstrate two wearable applications using the proposed interrogation device over FBG and Fabry-Perot interferometer (FPI) sensors. In the first application, an FBG-embedded smart textile for knee angle assessment was used to analyze the gait of a healthy person. Due to the capability of reconstructing the FBG spectra, it was possible to employ a technique based on the FBG wavelength shift and reflectivity to decouple the effects of the bending angle and axial strain on the FBG response. The measurement of the knee angle as well as the estimation of the angular and axial displacements on the grating that can be correlated to the variations of the knee center of rotation were performed. In the second application, a FPI was embedded in a chest band for simultaneous measurement of breath and heart rates, where good agreement (error below 5%) was found with the reference sensors in all analyzed cases.
本文报道了一种用于基于波长的光学传感器的便携式节能询问器（Perrogator）的开发。该询问器基于一个紧凑的解决方案，包括一个白光光源和传感器与可调谐滤波器之间的光谱卷积，由光电探测器获取，其中微控制器具有两个功能：（i）控制滤波器调谐，（ii）获取光电探测器信号。然后，数据被发送到单板计算机进行进一步的信号处理。此外，所采用的单板计算机具有 Wi-Fi 模块，可用于将传感器数据发送到云端。所提出的方法导致询问器的分辨率高达 3.82 pm（对于 15.64nm 的扫描范围），最大采集频率约为 210 Hz（较低分辨率约为 15.30 pm）。Perrogator 与商用光纤布拉格光栅（FBG）询问器进行了应变测量比较，发现两种设备之间具有良好的一致性（商用询问器为 1.226 pm/με，所提出的方法为 1.201 pm/με，均方根误差分别为 0.0144 和 0.0153），其中 Perrogator 具有成本更低、便携性更高和能耗更低的额外优势。为了展示这种优势，以及允许的高采集频率，我们展示了两个使用所提出的询问设备的可穿戴应用，分别是 FBG 和 Fabry-Perot 干涉仪（FPI）传感器。在第一个应用中，使用嵌入 FBG 的智能纺织品进行膝关节角度评估，以分析健康人的步态。由于能够重建 FBG 光谱，因此可以采用基于 FBG 波长移动和反射率的技术来分离弯曲角度和轴向应变对 FBG 响应的影响。对膝关节角度进行了测量，并对光栅上的角位移和轴向位移进行了估计，这些位移与膝关节旋转中心的变化相关。在第二个应用中，在胸带中嵌入了一个 FPI，用于同时测量呼吸和心率，在所有分析的情况下，与参考传感器的吻合度都很好（误差低于 5%）。
