The accuracy in orientation tracking attainable by using inertial measurement units (IMU) when measuring human motion is still an open issue. This study presents a systematic quantification of the ...accuracy under static conditions and typical human dynamics, simulated by means of a robotic arm. Two sensor fusion algorithms, selected from the classes of the stochastic and complementary methods, are considered. The proposed protocol implements controlled and repeatable experimental conditions and validates accuracy for an extensive set of dynamic movements, that differ in frequency and amplitude of the movement. We found that dynamic performance of the tracking is only slightly dependent on the sensor fusion algorithm. Instead, it is dependent on the amplitude and frequency of the movement and a major contribution to the error derives from the orientation of the rotation axis w.r.t. the gravity vector. Absolute and relative errors upper bounds are found respectively in the range 0.7° ÷ 8.2° and 1.0° ÷ 10.3°. Alongside dynamic, static accuracy is thoroughly investigated, also with an emphasis on convergence behavior of the different algorithms. Reported results emphasize critical issues associated with the use of this technology and provide a baseline level of performance for the human motion related application.
Small, compact and embedded sensors are a pervasive technology in everyday life for a wide number of applications (e.g., wearable devices, domotics, e-health systems, etc.). In this context, wireless ...transmission plays a key role, and among available solutions, Bluetooth Low Energy (BLE) is gaining more and more popularity. BLE merges together good performance, low-energy consumption and widespread diffusion. The aim of this work is to review the main methodologies adopted to investigate BLE performance. The first part of this review is an in-depth description of the protocol, highlighting the main characteristics and implementation details. The second part reviews the state of the art on BLE characteristics and performance. In particular, we analyze throughput, maximum number of connectable sensors, power consumption, latency and maximum reachable range, with the aim to identify what are the current limits of BLE technology. The main results can be resumed as follows: throughput may theoretically reach the limit of ~230 kbps, but actual applications analyzed in this review show throughputs limited to ~100 kbps; the maximum reachable range is strictly dependent on the radio power, and it goes up to a few tens of meters; the maximum number of nodes in the network depends on connection parameters, on the network architecture and specific device characteristics, but it is usually lower than 10; power consumption and latency are largely modeled and analyzed and are strictly dependent on a huge number of parameters. Most of these characteristics are based on analytical models, but there is a need for rigorous experimental evaluations to understand the actual limits.
During last decades, Magnetic Resonance (MR)--compatible sensors based on different techniques have been developed due to growing demand for application in medicine. There are several technological ...solutions to design MR-compatible sensors, among them, the one based on optical fibers presents several attractive features. The high elasticity and small size allow designing miniaturized fiber optic sensors (FOS) with metrological characteristics (e.g., accuracy, sensitivity, zero drift, and frequency response) adequate for most common medical applications; the immunity from electromagnetic interference and the absence of electrical connection to the patient make FOS suitable to be used in high electromagnetic field and intrinsically safer than conventional technologies. These two features further heightened the potential role of FOS in medicine making them especially attractive for application in MRI. This paper provides an overview of MR-compatible FOS, focusing on the sensors employed for measuring physical parameters in medicine (i.e., temperature, force, torque, strain, and position). The working principles of the most promising FOS are reviewed in terms of their relevant advantages and disadvantages, together with their applications in medicine.
Violin is one of the most complex musical instruments to learn. The learning process requires constant training and many hours of exercise and is primarily based on a student–teacher interaction ...where the latter guides the beginner through verbal instructions, visual demonstrations, and physical guidance. The teacher’s instruction and practice allow the student to learn gradually how to perform the correct gesture autonomously. Unfortunately, these traditional teaching methods require the constant supervision of a teacher and the interpretation of non-real-time feedback provided after the performance. To address these limitations, this work presents a novel interface (Visual Interface for Bowing Evaluation—VIBE) to facilitate student’s progression throughout the learning process, even in the absence of direct teacher intervention. The proposed interface allows two key parameters of bowing movements to be monitored, namely, the angle between the bow and the string (i.e., α angle) and the bow tilt (i.e., β angle), providing real-time visual feedback on how to correctly move the bow. Results collected on 24 beginners (12 exposed to visual feedback, 12 in a control group) showed a positive effect of the real-time visual feedback on the improvement of bow control. Moreover, the subjects exposed to visual feedback judged the latter as useful to correct their movement and clear in terms of the presentation of data. Although the task was rated as harder when performed with the additional feedback, the subjects did not perceive the presence of a violin teacher as essential to interpret the feedback.
Bowing is the fundamental motor action responsible for sound production in violin playing. A lot of effort is required to control such a complex technique, especially at the beginning of violin ...training, also due to a lack of quantitative assessments of bowing movements. Here, we present magneto-inertial measurement units (MIMUs) and an optical sensor interface for the real-time monitoring of the fundamental parameters of bowing. Two MIMUs and a sound recorder were used to estimate the bow orientation and acquire sounds. An optical motion capture system was used as the gold standard for comparison. Four optical sensors positioned on the bow stick measured the stick–hair distance. During a pilot test, a musician was asked to perform strokes using different sections of the bow at different paces. Distance data were used to train two classifiers, a linear discriminant (LD) classifier and a decision tree (DT) classifier, to estimate the bow section used. The DT classifier reached the best classification accuracy (94.2%). Larger data analysis on nine violin beginners showed that the orientation error was less than 2°; the bow tilt correlated with the audio information (r134=−0.973, 95% CI −0.981,−0.962, p<0.001). The results confirmed that the interface provides reliable information on the bowing technique that might improve the learning performance of violin beginners.
During development, motor skills are fundamental in supporting interactions with the external world. The ability to plan actions is a particularly important aspect of motor skill since it is involved ...in many daily activities. In this work, we studied the development of motor planning longitudinally in children with an older sibling with Autism Spectrum Disorder (ASD) who are at heightened risk (HR) for the disorder and children with no such risk (low risk; LR) using a shape sorter task. Children were observed at 14, 18, 24 and 36 months. Three HR children with a later diagnosis of ASD (HR-ASD) were analyzed separately from the rest of the sample. Behavioral and kinematic data indicated that precision demands significantly influenced children's actions, and that children's performance improved with age. No differences were found between the HR and LR groups, but a descriptive analysis of data from the three HR-ASD suggested differences in the variables describing children's action (as reaching time and acceleration) as well as variables describing children's performance (as the adjustment of the shapes).
Finger-tapping tasks have been widely adopted to investigate auditory-motor synchronization, i.e., the coupling of movement with an external auditory rhythm. However, the discrete nature of these ...movements usually limits their application to the study of beat perception in the context of isochronous rhythms. The purpose of the present pilot study was to test an innovative task that allows investigating bodily responses to complex, non-isochronous rhythms. A conductor’s baton was provided to 16 healthy subjects, divided into 2 different groups depending on the years of musical training they had received (musicians or non-musicians). Ad hoc-created melodies, including notes of different durations, were played to the subjects. Each subject was asked to move the baton up and down according to the changes in pitch contour. Software for video analysis and modelling (Tracker
®
) was used to track the movement of the baton tip. The main parameters used for the analysis were the velocity peaks in the vertical axis. In the musician group, the number of velocity peaks exactly matched the number of notes, while in the non-musician group, the number of velocity peaks exceeded the number of notes. An exploratory data analysis using Poincaré plots suggested a greater degree of coupling between hand–arm movements and melody in musicians both with isochronous and non-isochronous rhythms. The calculated root mean square error (RMSE) between the note onset times and the velocity peaks, and the analysis of the distribution of velocity peaks in relationship to note onset times confirmed the effect of musical training. Notwithstanding the small number of participants, these results suggest that this novel behavioural task could be used to investigate auditory-motor coupling in the context of music in an ecologically valid setting. Furthermore, the task may be used for rhythm training and rehabilitation in neurological patients with movement disorders.
In the last decades, several studies showed that wearable sensors, used for assessing Parkinson's disease (PD) motor symptoms and recording their fluctuations, could provide a quantitative and ...reliable tool for patient's motor performance monitoring.
The aim of this study is to make a step forward the capability of quantitatively describing PD motor symptoms. The specific aims are: identify the most sensible place where to locate sensors to monitor PD bradykinesia and rigidity, and identify objective indexes able to discriminate PD OFF/ON motor status, and PD patients from healthy subjects (HSs).
Fourteen PD patients (H&Y stage 1-2.5), and 13 age-matched HSs, were enrolled. Five magneto-inertial wearable sensors, placed on index finger, thumb, metacarpus, wrist, and arm, were used as motion tracking systems. Sensors were placed on the most affected arm of PD patients, and on dominant hand of HS. Three UPDRS part III tasks were evaluated: rigidity (task 22), finger tapping (task 23), and prono-supination movements of the hands (task 25). A movement disorders expert rated the three tasks according to the UPDRS part III scoring system. In order to describe each task, different kinematic indexes from sensors were extracted and analyzed.
Four kinematic indexes were extracted: fatigability; total time; total power; smoothness. The last three well-described PD OFF/ON motor status, during finger-tapping task, with an index finger sensor. During prono-supination task, wrist sensor was able to differentiate PD OFF/ON motor condition. Smoothness index, used as a rigidity descriptor, provided a good discrimination of the PD OFF/ON motor status. Total power index, showed the best accuracy for PD vs healthy discrimination, with any sensor location among index finger, thumb, metacarpus, and wrist.
The present study shows that, in order to better describe the kinematic features of Parkinsonian movements, wearable sensors should be placed on a distal location on upper limb, on index finger or wrist. The proposed indexes demonstrated a good correlation with clinical scores, thus providing a quantitative tool for research purposes in future studies in this field.
The anatomy of the human hand is characterized by intrinsic coupling mechanisms at the level of the tendons and bone structure. The intra-finger constraints, in particular, represent coupled ...movements of the joints of the same finger. Previous studies verified the existence of intra-finger couplings for circular and prismatic grasps, and hypothesized the existence of such couplings for free flexion-extension movements of the fingers without, however, quantifying them. The aim of this work was: i) to calculate subject-specific intra-finger couplings during flexion movements in the free space by exploiting a marker-based motion capture system and a validated kinematic protocol to guarantee high accuracy of the reconstructed hand kinematics, ii) to understand the effect of the hand size and of the finger on the coupling relations, and iii) to establish generalized coupling coefficients that could be used to simplify the kinematic hand model. To this purpose, ten healthy subjects performed flexion-extension movements of the fingers. Subject-specific couplings were extracted through linear regression analysis on pairs of adjacent joint angle trajectories: proximal couplings represented the relation between the Proximal-Inter-Phalangeal and MetaCarpo-Phalangeal joints for the long fingers and between the MetaCarpo-Phalangeal and Carpo-MetaCarpal joints for the thumb, whereas distal couplings represented the relation between the Distal-Inter-Phalangeal and Proximal-Inter-Phalangeal joints for the long fingers and between Inter-Phalangeal and MetaCarpo-Phalangeal joints for the thumb. The subject-specific coupling coefficients were independent from the hand size, and a difference between the distal couplings of the thumb and of the index, middle and ring fingers was highlighted. Regression analysis on the average flexion trajectories calculated on the ten participants showed a linear trend for both proximal and distal couplings (<inline-formula> <tex-math notation="LaTeX">R^{2}>0.97 </tex-math></inline-formula>) and small Root Mean Square Errors (1.63 deg on average). Coupling coefficients ranged 1.4 - 1.9 and 0.7 - 0.9 for the proximal and distal couplings respectively. Given its distinctive kinematic structure, the thumb exhibited a particular behaviour, as its proximal and distal couplings were the same. The extracted couplings represent normative coupling values on a population of ten individuals. The obtained results suggest the possibility of simplifying the kinematic hand model by imposing linear relations between the joints of each finger, thus reducing the number of independent degrees of freedom to one for each finger. This could be used to define input design parameters for the development of biomimetic hand prostheses and exoskeletons.
The acquisition of a fluid and legible handwriting in elementary school has a positive impact on multiple skills (e.g., reading, memory, and learning of novel information). In recent years, the ...growing percentages of children that encounter mild to severe difficulties in the acquisition of grapho-motor parameters (GMPs) has highlighted the importance of timely and reliable assessments. Unfortunately, currently available tests relying on pen and paper and human-based coding (HBC) require extensive coding time, and provide little or no information on motor processes enacted during handwriting. To overcome these limitations, this work presents a novel screen-based platform for Grapho-motor Handwriting Evaluation & Exercise (GHEE). It was designed to support both fully automatic machine-based coding (MBC) of quantitative GMPs and human-machine interaction coding (MBC+HBC) of GMPs accounting for qualitative aspects of a child's personal handwriting style (i.e., qualitative GMPs). Our main goal was to test: the GHEE coding approach in a relevant environment to assess its reliability compared to HBC; the efficacy of human-machine interaction in supporting coding of qualitative GMPs; and the possibility to provide data on kinematic aspects of handwriting. The preliminary results on 10 elementary school children showed reliability of fully automatic MBC of quantitative GMPs with respect to traditional HBC, a higher resolution of mixed human-machine interaction systems in assessing qualitative GMPs, and suitability of this technology in providing new information on handwriting kinematics.
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