Showing papers by "Domenico Formica published in 2019"

Wearable System Based on Flexible FBG for Respiratory and Cardiac Monitoring

Abstract: There is a growing demand for strain sensors that can be embedded into wearables for several potential applications. Among others, respiratory and cardiac rates’ monitoring from chest wall displacements have driven the development of strain sensors based on fiber Bragg gratings (FBGs) coupled with polymers. In this paper, we addressed the fabrication of a flexible sensor based on an FBG encapsulated into Dragon skin 20 silicone rubber. The sensor is intended to be used for developing a wearable system for respiratory and cardiac rates’ monitoring. The sensor’s response to strain, temperature changes, and relative humidity variations has been experimentally assessed. By considering the repetitive strains induced on the chest wall by the phenomena of interest, the hysteresis response has also been analyzed. Then, an elastic band was equipped with the flexible sensor. The feasibility of this wearable system has been preliminarily assessed on healthy volunteers to evaluate its suitability for monitoring respiratory frequency ( $f_{\mathbf {R}}$ ) and heart rate (HR). The interesting results suggest that the proposed system is easy to be worn, non-invasive, stretchy, and seems to be suitable to well-match the chest wall displacements for monitoring $f_{\mathbf {R}}$ and HR. Such findings call for further investigation targeted to evaluate the accuracy of the FBG-based wearable system in monitoring respiratory and cardiac activities and the system usability in both clinical and sports sciences.

Cardio-Respiratory Monitoring in Archery Using a Smart Textile Based on Flexible Fiber Bragg Grating Sensors

Abstract: In precision sports, the control of breathing and heart rate is crucial to help the body to remain stable in the shooting position. To improve stability, archers try to adopt similar breathing patterns and to have a low heartbeat during each shot. We proposed an easy-to-use and unobtrusive smart textile (ST) which is able to detect chest wall excursions due to breathing and heart beating. The sensing part is based on two FBGs housed into a soft polymer matrix to optimize the adherence to the chest wall and the system robustness. The ST was assessed on volunteers to figure out its performance in the estimation of respiratory frequency (fR) and heart rate (HR). Then, the system was tested on two archers during four shooting sessions. This is the first study to monitor cardio-respiratory activity on archers during shooting. The good performance of the ST is supported by the low mean absolute percentage error for fR and HR estimation (≤1.97% and ≤5.74%, respectively), calculated with respect to reference signals (flow sensor for fR, photopletismography sensor for HR). Moreover, results showed the capability of the ST to estimate fR and HR during different phases of shooting action. The promising results motivate future investigations to speculate about the influence of fR and HR on archers’ performance.

Non-Contact Monitoring of Breathing Pattern and Respiratory Rate via RGB Signal Measurement

Abstract: Among all the vital signs, respiratory rate remains the least measured in several scenarios, mainly due to the intrusiveness of the sensors usually adopted. For this reason, all contactless monitoring systems are gaining increasing attention in this field. In this paper, we present a measuring system for contactless measurement of the respiratory pattern and the extraction of breath-by-breath respiratory rate. The system consists of a laptop's built-in RGB camera and an algorithm for post-processing of acquired video data. From the recording of the chest movements of a subject, the analysis of the pixel intensity changes yields a waveform indicating respiratory pattern. The proposed system has been tested on 12 volunteers, both males and females seated in front of the webcam, wearing both slim-fit and loose-fit t-shirts. The pressure-drop signal recorded at the level of nostrils with a head-mounted wearable device was used as reference respiratory pattern. The two methods have been compared in terms of mean of absolute error, standard error, and percentage error. Additionally, a Bland-Altman plot was used to investigate the bias between methods. Results show the ability of the system to record accurate values of respiratory rate, with both slim-fit and loose-fit clothing. The measuring system shows better performance on females. Bland-Altman analysis showed a bias of -0.01 breaths · min - 1 , with respiratory rate values between 10 and 43 breaths · min - 1 . Promising performance has been found in the preliminary tests simulating tachypnea.

Smart Textile Based on Piezoresistive Sensing Elements for Respiratory Monitoring

Abstract: Wearable systems are gaining large interest in applications related to the monitoring of physiological parameters. Piezoresistive strain sensors are a valid option to develop wearables for several medical applications. Among them, respiratory monitoring can be performed by recording chest movements. The aim of this paper is threefold: 1) the experimental assessment of elastic piezoresistive textile; 2) the influence of length and width on piezoresistive response; and 3) the use of these elements to develop a smart textile (ST) for respiratory monitoring. The ST consists of six piezoresistive elements. The static calibration and the hysteresis analysis were carried out to assess the characteristics of the piezoresistive elements. The feasibility assessment of the ST for respiratory monitoring was performed on four healthy volunteers under two conditions (i.e., quiet breathing and tachypnea). Respiratory frequency values were estimated by the ST and compared with the ones gathered by means of a reference system (i.e., a motion capture system). Length and width influence both the sensitivity and hysteresis of the piezoresistive element. Regarding the ST performance, good agreement with data provided by the reference system was found. Indeed, results obtained by considering the output of single sensing elements and their sum were promising: the difference between the average respiratory frequency was always lower than 1% and 4% during quiet breathing and tachypnea, respectively. The proposed ST seems to be suitable for respiratory frequency monitoring in a wide range of values, where unobtrusiveness is of great value.

Different level of virtualization of sight and touch produces the uncanny valley of avatar's hand embodiment.

Abstract: Humans increasingly often act through virtual and robotic avatars, which can feed back to their user only virtual sensory information. Since avatar is user’s embodiment and body image is mostly based on senses, how virtualization of sensory inputs affects avatar self-attribution is a key question for understanding nowadays human behavior. By manipulating visual and tactile inputs in a series of experiments fashioned after the rubber hand illusion, we assessed the relative weight of the virtualization of sight (Real, Robotic, Virtual) and of touch (Real, Virtual) on artificial hand embodiment. Virtualization decreased embodiment, but unexpectedly lowest embodiment was found when only one sense was virtual. Discordant levels of virtualization of sight and touch elicited revulsion, extending the concept of the uncanny valley to avatar embodiment. Besides timing, spatial constraints and realism of feedback, a matched degree of virtualization of seen and felt stimuli is a further constraint in building the representation of the body.

Throughput Analysis of BLE Sensor Network for Motion Tracking of Human Movements

Abstract: In the world of smart cities, domotics, wearable sensors, and smart devices, an important role is played by the communication technology involved in the data transmission between nodes of the sensor network. Among a wide set of standard wireless technologies already available on the market, Bluetooth low energy (BLE) is becoming one of the most widespread and exploited. The aim of this paper is to propose a methodology for analyzing and characterizing throughput performance in general sensor network applications. In particular, we want to assess the effective BLE performance in order to investigate its possible usage in applications that require high throughput, such as body area network (BAN) for motion tracking of human movements, using magneto-inertial sensor units (M-IMUs). In addition to this, we have also studied how different nodes, with different hardware, software, and firmware, can affect the network performance. The results of this paper show how different typologies of nodes can be better exploited dependently on the specific application they are involved in. In fact, we define how to set up BLE parameters in order to push this technology to its limit. Finally, we address the specific case of using BLE as the wireless infrastructure of a BAN for human motion tracking: in this scenario, we show that BLE can be employed to successfully transmit M-IMU data from 5 peripheral nodes with a sampling frequency higher than 200 Hz.

Cardiac monitoring with a smart textile based on polymer-encapsulated FBG: influence of sensor positioning

Abstract: In recent years, wearables are exploding in popularity as unobtrusive devices able to extend traditional healthcare delivery systems. Smart textiles are one of the main innovative types of wearables used for non-invasive and continuous monitoring of cardiac activity. A prominent solution is based on the detection of vibrations induced on the chest surface by the heart beating (i.e., precordial motions). In the literature, different sensor positions have been investigated, but it appears to be a lack of accepted standard points for the detection of heart-induced motions. In this work, a smart textile based on fiber Bragg grating (FBG) sensor has been proposed to detect the precordial motions on the chest. The feasibility of the smart textile for cardiac monitoring has been evaluated on three volunteers at three measurement points. Then, the influence of the measurement site on the response of the smart textile has been preliminarily assessed in terms of peak-to-peak amplitude of the signal. The signal amplitude is greater than the noise, so it allows detecting precordial motions. These promising results foster future investigations on the capability and performance of the system in estimating heart rate. Further tests will also be devoted to finding out the optimal measurement points to standardize the sensors positioning in this specific application.

Switching Assistance for Exoskeletons During Cyclic Motions

Abstract: This paper proposes a novel control algorithm for torque-controlled exoskeletons assisting cyclic movements. The control strategy is based on the injection of energy parcels into the human-robot system with a timing that minimizes perturbations, i.e., when the angular momentum is maximum. Electromyographic activity of main flexor-extensor knee muscles showed that the proposed controller mostly favors extensor muscles during extension, with a statistically significant reduction in muscular activity in the range of 10-20% in 60 out of 72 trials (i.e., 83%), while no effect related to swinging speed was recorded (speed variation was lower than 10% in 92% of the trials). In the remaining cases muscular activity increment, when statistically significant, was less than 10%. These results showed that the proposed algorithm reduced muscular effort during the most energetically demanding part of the movement (the extension of the knee against gravity) without perturbing the spatio-temporal characteristics of the task and making it particularly suitable for application in exoskeleton-assisted cyclic motions.

Influence of motion artifacts on a smart garment for monitoring respiratory rate

Abstract: Wearable devices are gaining large acceptance in the continuous monitoring of vital signs. Among others, respiratory rate (f R ) can be used to detect physiological abnormalities and health status changes.The purpose of this work was to investigate how the output of a smart garment used for respiratory monitoring is influenced by walking and running. This garment consists of three bands, each one embeds two piezoresistive elements sensitive to strain.Experimental trials were carried out on a volunteer who worn the three bands at the level of upper thorax, inferior thorax and abdomen during three different activities (i.e., static pose, walking and running). A treadmill was used to set specific speeds (i.e., from 1.6 km•h−1 to 8.8 km•h−1). The f R values estimated by the proposed garment were compared to the ones monitored by a reference system (i.e., a flowmeter).The analysis in the frequency-domain demonstrated differences up to 3 bpm between the average f R estimated by the two systems. The mean absolute error (MAE) was used to investigate the performances of the garment against the reference device in estimating the instantaneous f R . MAE increased with speed (it reached 1.8 bpm during running). Bland-Altman analysis showed a bias of -0.02±2.02 bpm when all the data of walking and running were considered.The garment based on 6 sensing elements provides good performances for estimating both average and instantaneous f R values during activities of walking and running.

A wearable system based on fiber Bragg grating for monitoring respiratory and heart activity of archers

Abstract: This study focuses on the monitoring of respiratory and heart activities on archers. These activities are linked with performance in precision sports since they can compromise the postural stability. In particular, soft sensors based a fiber Bragg grating (FBG) embedded into a Dragon Skin 10 polymer brick (90 mm length, 24 mm width, 1 mm thick) have been proposed to instrument a wearable system. The movements of the chest wall due to respiratory and the cardiac activities are transmitted through two bands housing an FBG. The consequent change of the FBG output provides an indirect method to monitor respiratory and heart activities.The positions of the instrumented bands on the athlete have been optimized by processing biomechanical data recorded on four archers during the shooting phase and quiet breathing. Then, we investigated the capability of the system to monitor respiratory- and cardiac-induced movements of the chest wall. Tests were performed on two volunteers during different respiratory phases and the simulation of the shooting phase.The output of the two instrumented bands reflects the chest wall movement due to respiration and cardiac pumping (during apnea). These results can be considered the first step toward the analysis of the relationship between archer’s performance and cardiorespiratory activity. Besides, the use of the proposed system may be beneficial for analyzing the influence of the mentioned physiological activities on the performance in precision sports athletes.

Wearable system based on piezoresistive sensors for monitoring bowing technique in musicians

Abstract: We present an easy to wear and use wearable system to monitor wrist and elbow movements in musicians. The system is based on two piezoresistive sensors embedded into a garment. Pilot tests on an adult double-bass player were carried out to assess the feasibility of the device for monitoring bowing technique. Results show promising performances in identifying string changes and bow strokes. The proposed system allows for studying regularity and timing of bowing movements, thus being potentially useful in learning contexts, especially with beginner musicians.

A geometric framework for the estimation of joint stiffness of the human wrist

Abstract: Estimating joint stiffness is of paramount importance for studying human motor control and for clinical assessment of neurological diseases. Usually stiffness estimation is performed using cumbersome instrumentations (e.g. robots), and by approximating robot joint angles and torques to the human ones. This paper proposes a methodology and an experimental setup to measure wrist joint stiffness in unstructured environments, with the twofold aim of: 1) providing a geometric framework in order to derive angular displacements and torques at the wrist Flexion/Extension (FE) and Radial/Ulnar Deviation (RUD) axes of rotation, using a subject specific kinematic model; 2) suggesting an experimental setup made of two portable sensors for motion tracking and one load cell, to allow for measurements in out-of-the-lab scenarios. We tested our method on a hardware mockup of wrist kinematics, providing a ground truth for estimated angles and torques at FE and RUD joints. The experimental validation showed average absolute errors in FE and RUD angles of 0.005 rad and 0.0167 rad respectively, and an average error of FE and RUD torques of 0.006 Nm and 0.003 Nm.

Force monitoring during Peripheral Nerve Blocks: design and feasibility assessment of a new noninvasive system

Abstract: This study focuses on the development of a noninvasive system for monitoring the force exerted by the anesthesiologist on the syringe during peripheral nerve blocks (PNBs). During this procedure, local anesthetic solutions are injected around a specific peripheral nerve. The injection pressure, and in turn the force exerted by the anesthesiologist may be related to the efficacy and safety of PNBs. The proposed system is based on i) a mechanical part fixed to the syringe used for the injection; ii) three piezoresistive force sensors which measure the force exerted by the anesthesiologist to inject the anesthetic solution. Indeed, the clinician performs the PNB by pushing with three fingers on three different parts of the syringe; iii) a custom printed circuit board, which pre-processes, collects and transmits the relevant signals.During the calibration of the three sensors, the clinical scenario has been mimicked by interposing the finger of a volunteer between the indenter of the testing machine and the active area of each sensor. These experiments provide the calibration curve of the system (for each sensor), which allows estimating the force exerted by the anesthesiologist during the injection of the anesthetic solution during PNB. Finally, the system has been tested on a patient undergoing PNB on adductor canal. During the whole experiment, the system was able to correctly follow the force exerted by the three fingertips of the clinician. These results are promising, but they can be considered just a first step toward the development of a system for supporting the clinician during PNB.

Methodology for the Evaluation of Magneto-Inertial Orientation Filters in SO(3)

Abstract: In the last years, inertial measurement units are playing a primary role in bioengineering for motion tracking research. These devices are cost-effective and can be successfully used for accurate, non-invasive and portable motion tracking.In the literature there is a lack of rigorously assessment in the accuracy estimation of the orientation. Technical specification of commercial systems reported by vendors are presented with caveats and are poorly documented.The objective of this work is to find a standard and reliable methodology, defined in SO(3) orthogonal group, to tune and compare sensor fusion filters used to get orientation from M-IMU sensors. As a matter of fact, each filter exploits some gain parameters to tune the output of the filter. Knowing that, it is important to understand how to tune these parameters, but also find a way to compare all the filters, in order to understand which of them is the best solution to apply.To evaluate this method we have chosen a set of filter already present in the state of the art and we generated, starting from a known trajectory, synthetic M-IMU data to be used as ground truth, in order to compare the orientation angle defined by this trajectory with output of the sensor fusion algorithms.The output error is very low, around 0.005 rad by mean. This results evidences the reliability and efficacy of our method and confirms how the tuning of gain parameters can drive through better performance.

The influence of posture, applied force and perturbation direction on hip joint viscoelasticity.

Abstract: Limb viscoelasticity is a critical factor used to regulate the interaction with the environment. It plays a key role in modelling human sensorimotor control, and can be used to assess the condition of healthy and neurologically affected individuals. This paper reports the estimation of hip joint viscoelasticity during voluntary force control using a novel device that applies a leg displacement without constraining the hip joint. The influence of hip angle, applied limb force and perturbation direction on the stiffness values was studied in ten subjects. No difference was detected in the hip joint stiffness between the dominant and non-dominant legs, but a small dependency was observed on the perturbation direction. Both hip stiffness and viscosity increased monotonically with the applied force magnitude, with posture to being observed to have a slight influence. These results are in line with previous measurements carried out on upper limbs, and can be used as a baseline for lower limb movement simulation and further neuromechanical investigations.