光纤马赫曾德尔干涉曲率传感器的膝关节曲率检测系统研究

在人体运动监测的过程中，膝关节运动信息在中老年慢性疾病的诊断和康复评估方面具有重要意义。研制了一种基于光纤马赫曾德尔干涉曲率传感器（Mach-Zehnder interferometer-based directional bending，MZI-BDB）的膝关节弯曲检测系统。该系统由MZI-BDB传感器、扫频激光光源、光纤耦合器、光纤隔离器、光电探测器及信号处理系统构成。MZI-BDB传感器由偏心光纤和单模光纤错位熔接而成，封装于软硅树脂片内，通过绑带固定于膝关节处。当膝关节屈曲和伸展时，诱导MZI-BDB传感器发生弯曲，传感器内透射光信号干涉场的模场状态发生变化，谐振波长发生漂移，从而对膝关节的弯曲方向和曲率进行监测。MZI-BDB传感器在正向和负向弯曲的测量角度范围为0°~90°；在正向弯曲方向上灵敏度和分辨率分别为5.29 nm/m?1和0.11 m?1；在负向弯曲方向上的灵敏度和分辨率分别为?3.11 nm/m?1和0.12 m?1。实验测试MZI-BDB传感器温度敏感度为0.043 nm/℃，该结果显示传感器对温度的不敏感特性。光电编码器与MZI-BDB传感器同时进行数据的传感采集。实验结果表明:该检测系统和光电编码器验证平台在准确度和响应度上具有一致性。

Research on knee joint curvature detection system based on fiber optic MZI-BDB curvature sensor

In the monitoring process of human motion and posture, knee movement information was of great significance in the diagnosis and rehabilitation evaluation of chronic diseases in the middle and old age. The knee directional bending measurement device using a Mach-Zehnder interferometer-based directional bending (MZI-BDB) sensor was presented in this paper. The system consisted of MZI-BDB sensor, swept laser light source, optical fiber coupler, optical fiber isolator, photodetector and signal processing system. MZI-BDB sensor was fabricated by fusion-splicing a section of eccentric core fiber (ECF) between two single-mode fibers (SMF) with core-offset. It was encapsulated in a soft silicone sheet and fixed to the knee joint by a band. When the knee joint was flexed and extended, the MZI-BDB sensor was led to bend, causing the modal interferes of the sensor changes and the resonant wavelength shifted, so as to monitor the bending direction and curvature of the knee joint. The range of measurement of MZI-BDB sensor was 0°-90° at the positive and negative bendings respectively. At the positive bending (bending direction of 0°), the proposed MZI-BDB sensor sensitivity and resolution were 5.29 nm/m?1 and 0.11 m?1 respectively. The sensitivity and resolution were ?3.11 nm/m?1 and 0.12 m?1 at the negative bending (bending direction of 180°). The temperature sensitivity of the proposed MZI-BDB was 0.043 nm/℃, which had minimal effect on the experiments. Furthermore, the photoelectric encoder and MZI-BDB sensor were used for data acquisition simultaneously. The experimental results show that the detection system and the photoelectric encoder verification platform are consistent in accuracy and responsiveness.