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Sensors (Basel). 2017 Jun 24;17(7). pii: E1492. doi: 10.3390/s17071492.

Static and Dynamic Accuracy of an Innovative Miniaturized Wearable Platform for Short Range Distance Measurements for Human Movement Applications.

Author information

1
Information Engineering Unit, Department of Information Engineering, Political Sciences and Communication Sciences, University of Sassari, Sassari 07100 (SS), Italy. sbertuletti@uniss.it.
2
Information Engineering Unit, Department of Information Engineering, Political Sciences and Communication Sciences, University of Sassari, Sassari 07100 (SS), Italy. acereatti@uniss.it.
3
Department of Electronics and Telecommunications, Politecnico di Torino, Torino 10129 (TO), Italy. acereatti@uniss.it.
4
Department of Engineering and Applied Sciences, University of Bergamo, Dalmine 24044 (BG), Italy. daniele.comotti@unibg.it.
5
Department of Engineering and Applied Sciences, University of Bergamo, Dalmine 24044 (BG), Italy. michele.caldara@unibg.it.
6
Information Engineering Unit, Department of Information Engineering, Political Sciences and Communication Sciences, University of Sassari, Sassari 07100 (SS), Italy. dellacro@uniss.it.

Abstract

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.

KEYWORDS:

distance estimation; human movement analysis; inertial sensors; proximity sensors; step width; time-of-flight; wearable devices

PMID:
28672803
PMCID:
PMC5539655
DOI:
10.3390/s17071492
[Indexed for MEDLINE]
Free PMC Article

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