Static and dynamic accuracy of an innovative miniaturized wearable platform for short range distance measurements for human movement applications

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

TRACKING OF THE HAND “PRESSURE POINT” ON THE GRIP OF A RECURVE BOW: A WEARABLE SOLUTION

The purpose of this study was to design and prototype a non-invasive wearable solution suitable for measuring speeds, accelerations and orientation of the hand-grip as well as the pressures between the hand and the grip of a recurve bow. Therefore, a device has been created that properly blends two technologies: an Inertial Measurement Unit (IMU) and a Force-Sensitive-Resistor (FSR) membrane. A preliminary evaluation of the device performance was conducted in collaboration with the Olympic athlete Mauro Nespoli. The obtained results demonstrate the potential of the proposed system, as well as highlight a number of interesting information from a biomechanical point of view, closely related to the shooting technique

Dynamic Compression of the Signal in a Charge Sensitive Amplifier: Experimental Results

This work is concerned with the experimental characterization of a Charge Sensitive Amplifier featuring dynamic signal compression, fast recovery time, low noise and reduced area occupancy. The device takes advantage of the non-linear characteristic of a feedback transistor which behaves like a voltage controlled capacitance. This property has been exploited to fit a wide input dynamic range into the available output swing. The charge amplifier can be operated in synchronous mode at high frame rates, of the order of few MHz, thanks to a wide bandwidth, an improved output stage and a fast reset network. Thanks to the small area occupancy the amplifier is suitable for integration in a 100×100 μm2 pixel area. All these features make the device a good candidate for applications where a fast frontend with a non-linear response is required, such as in imaging instrumentation for Free Electron Laser experiments. The aim of the paper is to present and discuss the experimental results coming from the characterization of the first prototype of the circuit which has been designed in a 65 nm CMOS technology. The work has been carried out in the frame of the PixFEL Project funded by the INFN, Italy

Development of a wireless low-power multi-sensor network for motion tracking applications

This work presents a novel wireless and low power Attitude and Heading Reference Systems network based on low-cost MEMS (Micro Electro-Mechanical System) sensors, developed for motion tracking systems. Biomedical and rehabilitation purposes as well as gaming and consumer electronics may be the potential applications of this network. The paper aims to describe the hardware architecture, the embedded sensor fusion algorithm and the motion tracking system

A method to improve prosthesis leg design based on pressure analysis at the socket-residual limb interface

This paper presents a methodology and tools to improve the design of lower limb prosthesis through the measurement of pressure analysis at the interface residual limb-socket. The steps of the methodology and the design tools are presented using a case study focused on a transfemoral (amputation above knee) male amputee. The experimental setup based on F-Socket Tekscan pressure system is described as well the results of some static loading tests. Pressure data are visualized with a colour pressure map over the 3D model of the residual limb acquired using an optical low cost scanner, based on MS Kinect. Previous methodology is useful to evaluate a physical prototype; in order to improve also conceptual design, the Finite Element (FE) Analysis has been carried and results reached so far have been compared with experimental tests. Pressure distributions are comparable, even if some discrepancies have been highlighted due to sensors placements and implemented FE model. Future developments have been identified in order to improve the accuracy of the numerical simulations