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

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.

Toward a Regulatory Qualification of Real-World Mobility Performance Biomarkers in Parkinson’s Patients Using Digital Mobility Outcomes

“…The accuracy of state-of-the-art stereophotogrammetric systems is usually <1 mm when more than six cameras are used and the whole volume of capture is properly calibrated before beginning of the experiments [ 48 , 49 ]. The same system will also be used to establish the metrological properties and the accuracy of the DMOs estimated with a wearable multisensor system (INertial module with DIstance Sensors and Pressure insoles, INDIP [ 50 , 51 , 52 ]), which will then be used as a reference for the daily life scenarios. The INDIP system integrates inertial modules, distance sensors and pressure insoles.…”

Strategies for optimising musculoskeletal health in the 21st century

“…Diverse gait-analysis technologies have been developed and used in humans and sport horses over the past 40 years, and are constantly being refined to provide reliable measures of improvement from disease [97]. Current technologies include wearables, inertial measurement units or accelerometers which are lightweight, wireless devices to investigate activity levels, gait patterns and fitness parameters for humans and other animals [98][99][100]. Real-time or delayed-time parameters that can be analysed include ground reaction forces and foot-pressure distribution, the kinematics of joints and segments, along with dynamic electromyograms [101].…”

A wearable solution for accurate step detection based on the direct measurement of the inter-foot distance

“…The SWING 2DS includes a magneto-IMU and two DSs (mod. VL6180X, STMicroelectronics, Switzerland [12]) and represents an upgraded version of the D-MuSe system in terms of hardware performance and number of connectable DSs [3].…”