Information Engineering Unit, Department of Information Engineering, Political Sciences and Communication Sciences, University of Sassari, Sassari 07100 (SS), Italy.
Department of Electronics and Telecommunications, Politecnico di Torino, Torino 10129 (TO), Italy.
Sensors (Basel). 2017 Jun 24;17(7):1492. doi: 10.3390/s17071492.
Magneto-inertial measurement units (MIMU) are a suitable solution to assess human motor performance both indoors and outdoors. However, relevant quantities such as step width and base of support, which play an important role in gait stability, cannot be directly measured using MIMU alone. To overcome this limitation, we developed a wearable platform specifically designed for human movement analysis applications, which integrates a MIMU and an Infrared Time-of-Flight proximity sensor (IR-ToF), allowing for the estimate of inter-object distance. We proposed a thorough testing protocol for evaluating the IR-ToF sensor performances under experimental conditions resembling those encountered during gait. In particular, we tested the sensor performance for different (i) target colors; (ii) sensor-target distances (up to 200 mm) and (iii) sensor-target angles of incidence (AoI) (up to 60 ∘ ). Both static and dynamic conditions were analyzed. A pendulum, simulating the oscillation of a human leg, was used to generate highly repeatable oscillations with a maximum angular velocity of 6 rad/s. Results showed that the IR-ToF proximity sensor was not sensitive to variations of both distance and target color (except for black). Conversely, a relationship between error magnitude and AoI values was found. For AoI equal to 0 ∘ , the IR-ToF sensor performed equally well both in static and dynamic acquisitions with a distance mean absolute error <1.5 mm. Errors increased up to 3.6 mm (static) and 11.9 mm (dynamic) for AoI equal to ± 30 ∘ , and up to 7.8 mm (static) and 25.6 mm (dynamic) for AoI equal to ± 60 ∘ . In addition, the wearable platform was used during a preliminary experiment for the estimation of the inter-foot distance on a single healthy subject while walking. In conclusion, the combination of magneto-inertial unit and IR-ToF technology represents a valuable alternative solution in terms of accuracy, sampling frequency, dimension and power consumption, compared to existing technologies.
磁惯性测量单元 (MIMU) 是一种在室内和室外评估人体运动性能的合适解决方案。然而，步宽和支撑基础等相关量在步态稳定性中起着重要作用，不能仅使用 MIMU 直接测量。为了克服这一限制，我们开发了一种专门为人体运动分析应用设计的可穿戴平台，该平台集成了 MIMU 和红外飞行时间 (IR-ToF) 接近传感器，可用于估计物体间的距离。我们提出了一个全面的测试协议，用于评估在类似于步态过程中遇到的实验条件下的 IR-ToF 传感器性能。特别是，我们测试了传感器在不同 (i) 目标颜色；(ii) 传感器-目标距离（最高 200mm）和 (iii) 传感器-目标入射角 (AoI)（最高 60 ∘ ）下的性能。分析了静态和动态条件。一个模拟人腿摆动的摆锤用于产生具有最大角速度 6rad/s 的高度可重复的摆动。结果表明，IR-ToF 接近传感器对距离和目标颜色的变化都不敏感（黑色除外）。相反，发现了误差幅度与 AoI 值之间的关系。对于 AoI 等于 0 ∘ ，IR-ToF 传感器在静态和动态采集时表现同样良好，距离平均绝对误差 <1.5mm。当 AoI 等于 ± 30 ∘ 时，误差增加到 3.6mm（静态）和 11.9mm（动态），当 AoI 等于 ± 60 ∘ 时，误差增加到 7.8mm（静态）和 25.6mm（动态）。此外，在一项初步实验中，使用可穿戴平台在单个健康受试者行走时估计足间距离。总之，与现有技术相比，磁惯性单元和 IR-ToF 技术的组合在准确性、采样频率、尺寸和功耗方面代表了一种有价值的替代解决方案。
