School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore 639798, Singapore.
Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24060, USA.
Sensors (Basel). 2019 Mar 18;19(6):1350. doi: 10.3390/s19061350.
Gait analysis in unrestrained environments can be done with a single wearable ultrasonic sensor node on the lower limb and four fixed anchor nodes. The accuracy demanded by such systems is very high. Chirp signals can provide better ranging and localization performance in ultrasonic systems. However, we cannot neglect the multi-path effect in typical indoor environments for ultrasonic signals. The multi-path components closer to the line of sight component cannot be identified during correlation reception which leads to errors in the estimated range and which in turn affects the localization and tracking performance. We propose a novel method to reduce the multi-path effect in ultrasonic sensor networks in typical indoor environments. A gait analysis system with one mobile node attached to the lower limb was designed to test the performance of the proposed system during an indoor treadmill walking experiment. An optical motion capture system was used as a benchmark for the experiments. The proposed method gave better tracking accuracy compared to conventional coherent receivers. The static measurements gave 2.45 mm standard deviation compared to 10.45 mm using the classical approach. The RMSE between the ultrasonic gait analysis system and the reference system improved from 28.70 mm to 22.28 mm. The gait analysis system gave good performance for extraction of spatial and temporal parameters.
在无约束环境中，可通过在下肢佩戴单个可穿戴超声传感器节点和四个固定锚节点来进行步态分析。此类系统要求的精度非常高。啁啾信号可在超声系统中提供更好的测距和定位性能。然而，我们不能忽略典型室内环境中超声信号的多径效应。在相关接收期间，无法识别接近视线分量的多径分量，这会导致估计距离出现误差，从而影响定位和跟踪性能。我们提出了一种在典型室内环境中降低超声传感器网络中多径效应的新方法。设计了一个带有一个移动节点的下肢步态分析系统，以在室内跑步机行走实验中测试所提出系统的性能。实验采用光学运动捕捉系统作为基准。与传统相干接收器相比，所提出的方法具有更好的跟踪精度。与使用传统方法相比，静态测量的标准偏差为 2.45 毫米，而使用经典方法则为 10.45 毫米。超声步态分析系统与参考系统之间的 RMSE 从 28.70 毫米提高到 22.28 毫米。步态分析系统在提取空间和时间参数方面表现良好。
