Anomaly Detection in Gait Cycles Using a PDMS Embedded FBG Sensor

Walking is one of the most natural yet risky motor functions performed by the body. The manner of walking, or gait, depends on the proper functioning of the lower limbs, alignment of ankle and knee joints, and the balance of the body, without which our body is prone to falls. Aging leads to improper functioning of the lower limbs leading to abnormalities in gait and increased risk of falling in the elderly. Hence, gait analysis is necessary in providing better healthcare and fall prevention for elderly. In this work, a polydimethylsiloxane (PDMS)-embedded fiber Bragg grating (FBG)-based sensor in a wearable band is proposed for the detection of improper gait with focus on knee angle measurement. The PDMS-embedded sensor, in the dimensions of ASTM D412 standard, is placed on the thigh for experimental measurements. The sensor is found to exhibit a nonlinear response to bending and extension of the knee which fits a second degree polynomial implying the requirements for advanced methods for linearization to enable absolute measurement of angles. From the gait perspective, the change in Bragg wavelength during activities as measured in relation to a reference reading holds importance in the identification of anomalies. Hence, tests were conducted to monitor the shift in wavelength during activities like walking (normal and time controlled) to monitor the gait, balancing on one leg and sit and stand trials. The proposed sensor is capable of distinguishing the different activities and variations in gait on path with and without obstacles.