Embedded Pressure Sensors Research Articles

Experimental Research on Thermal-Venting Characteristics of the Failure 280 Ah LiFePO4 Battery: Atmospheric Pressure Impacts and Safety Assessment

With the widespread application of lithium-ion batteries (LIBs) energy storage stations in high-altitude areas, the impact of ambient pressure on battery thermal runaway (TR) behavior and venting flow characteristics have aroused wide research attention. This paper conducts a lateral heating experiment on 280 Ah lithium iron phosphate batteries (LFPs) and proposes a method for testing battery internal pressure using an embedded pressure sensor. This paper analyzes the battery characteristic temperature, internal pressure, chamber pressure, and gas components under different chamber pressures. The experiment is carried out in a N2 atmosphere using a 1000 L insulated chamber. At 40 kPa, the battery experiences two instances of venting, with a corresponding peak in temperature on the battery’s side of 136.3 °C and 302.8 °C, and gas generation rates of 0.14 mol/s and 0.09 mol/s, respectively. The research results indicate that changes in chamber pressure significantly affect the center temperature of the battery side (Ts), the center temperature of the chamber (Tc), the opening time of the safety valve (topen), the triggering time of TR (tTR), the time difference (Δt), venting velocity, gas composition, and flammable limits. However, the internal pressure and gas content of the battery are apparently unaffected. Considering the TR characteristics mentioned above, a safety assessment method is proposed to evaluate the TR behavior and gas hazard of the battery. The results indicate that the risk at 40 kPa is much higher than the other three chamber pressures. This study provides theoretical references for the safe use and early warning of energy storage LIBs in high-altitude areas.

Advancing mental health predictions through sleep posture analysis: a stacking ensemble learning approach

Sleep posture is closely related to sleep quality, and can offer insights into an individual’s health. This correlation can potentially aid in the early detection of mental health disorders such as depression and anxiety. Current research focuses on embedding pressure sensors in bedsheets, attaching accelerometers on a subject’s chest, and installing cameras in bedrooms for sleep posture monitoring. However, such solutions sacrifice either the user's sleep comfort or privacy. This study explores the effectiveness of using contactless ultra-wideband (UWB) sensors for sleep posture monitoring. We employed a UWB dataset that is composed of the measurements from 12 volunteers during sleep. A stacking ensemble learning method is introduced for the monitoring of sleep postural transitions, which constitute two levels of learning. At the base-learner level, six transfer learning models (VGG16, ResNet50V2, MobileNet50V2, DenseNet121, VGG19, and ResNet101V2) are trained on the training dataset for initial predictions. Then, the logistic regression is employed as a meta-learner which is trained on the predictions gained from the base-learner to obtain final sleep postural transitions. In addition, a sleep posture monitoring algorithm is presented that can give accurate statistics of total sleep postural transitions. Extensive experiments are conducted, achieving the highest accuracy rate of 86.7% for the classification of sleep postural transitions. Moreover, time-series data augmentation is employed, which improves the accuracy by 13%. The privacy-preserving sleep monitoring solution presented in this paper holds promise for applications in mental health research.

Effect of fillers on the piezocapacitive behaviour of silicone rubber particulate composites

Robotics and fluid dynamics applications have created demand for development of electronic skins with embedded pressure sensors. These applications require simple and low-cost fabrication processes with large area deployment. Both structured and unstructured material approaches to sensor development have been followed. Among the various sensing mechanisms, piezo capacitive transduction is superior. This paper reports the influence of fillers on the piezo capacitive characteristics of unstructured solid silicone rubber composites. Dielectric, conductive and conductive-dielectric fillers were incorporated into solid silicone rubber and fabricated using high temperature compression moulding to form dielectric-dielectric, conductive-dielectric and conductive-dielectric dielectric composites. The results reveal that piezo capacitive sensitivity varies with filler type, filler loading, curing agent loading, mixing time and curing temperature. The experiments reveal improved normalized capacitance with pressure characteristics of linearity and sensitivity of 3.9 × 10−3 (kPa)−1 in the 0–20 kPa range of pressure. These composites are thus candidate materials for flexible pressure sensing applications.

Information-Based Sensor Placement for Data-Driven Estimation of Unsteady Flows

Estimation of unsteady flowfields around flight vehicles may improve flow interactions and lead to enhanced vehicle performance. Although flowfield representations can be very high-dimensional, their dynamics can sometimes have low-order representations that may be estimated using a few, appropriately placed measurements. This paper presents a sensor-selection framework for the intended application of data-driven, flowfield estimation. This framework combines data-driven modeling, steady-state Kalman filter design, and sparse, sequential sensor selection. This paper also uses the sensor selection framework to design sensor arrays that can perform well for a collection of operating conditions. Flow estimation results on numerical data show that the proposed framework produces arrays that are highly effective at flowfield estimation for the flow behind and an airfoil at a high angle of attack using embedded pressure sensors. Analysis of the flowfields reveals that paths of impinging stagnation points along the airfoil’s surface during a shedding period of the flow are highly informative locations for placement of pressure sensors.

Minimal Out-Toeing and Good Hip Scores of Severe SCFE Patients Treated With Modified Dunn Procedure and Contralateral Prophylactic Pinning at Minimal 5-year Follow up.

Slipped capital femoral epiphyses (SCFE) is associated with out-toeing of the foot and external rotation gait. But it is unknown if SCFE patients treated with the modified Dunn procedure have out-toeing at follow up.Therefore, we used instrumented gait analysis and questioned (1) do severe SCFE patients treated with a modified Dunn procedure have symmetrical foot progression angle (FPA) compared with contralateral side and compared with asymptomatic volunteers (2) what is the prevalence of out-toeing gait and what are the outcome socres at follow up. Gait analysis of 22 patients (22 hips) treated with an unilateral modified Dunn procedure for severe SCFE (slip angle >60 degrees, 2002 to 2011) was retrospectively evaluated. Of 38 patients with minimal 5-year follow up, 2 hips (4%) had avascular necrosis of the femoral head and were excluded for gait analysis. Twenty-two patients were available for gait analysis at follow up (mean follow up of 9±2 y). Mean age at follow up was 22±3 years. Mean preoperative slip angle was 64±8 degrees (33% unstable slips) and decreased postoperatively (slip angle of 8±4 degrees). Gait analysis was performed with computer-based instrumented walkway system (GAITRite) to measure FPA with embedded pressure sensors. Patients were compared with control group of 18 healthy asymptomatic volunteers (36 feet, mean age 29±6 y). (1) Mean FPA of SCFE patients (3.6±6.4 degrees) at follow up was not significantly different compared with their contralateral side (5.6±5.5 degrees) and compared with FPA of controls (4.0±4.5 degrees). (2) Of the 22 SCFE patients, most of them (19 hips, 86%) had normal FPA (-5 to 15 degrees), 2 patients had in-toeing (FPA<-5 degrees) and 1 had out-toeing (FPA >15 degrees) and was not significantly different compared with control group. (3) Mean modified Harris hip score (mHHS) was 93±11 points, mean Hip Disability and Osteoarthritis Outcome Score (HOOS) score was 91±10 points. Three patients (14%) had mHHS <80 points and walked with normal FPA. The 2 patients with in-toeing and one patient with out-toeing had mHHS >95 points. Patients with severe SCFE treated with modified Dunn procedure had mostly symmetrical FPA and good hip scores at long term follow up. This is in contrast to previous studies. Although 1 patient had out-toeing and 2 patients had in-toeing at follow up, they had good hip scores. Level III-retrospective comparative study.

The Effect of Nozzle Body Volume on Pressure Dynamics in a PWM Sprayer System

Highlights The variability in damping ratio between different sized nozzle tips was reduced with an increase in nozzle body volume, indicating that the previous works using pressure-sensing manifolds in PWM systems may have underestimated the nozzle pressure fluctuations. Pressure sensors installed at the nozzle body and the manifolds tested exhibited a different damping ratio, suggesting a slight change in sensor location might yield different measurements of transient pressure characteristics. A minimally invasive instrumented pressure sensor at the nozzle body is needed to accurately measure nozzle pressure dynamics. Abstract. Nozzle pressure measurements in agricultural sprayers are commonly conducted by adding a manifold between the nozzle body and nozzle tip. The additional component substantially increases the internal volume of the nozzle body, which affects nozzle pressure dynamics. This research focused on the effect of nozzle body volume on pressure dynamics when operating a spray nozzle under pulse-width-modulation control. A nozzle body and two manifolds of different volumes were instrumented with embedded pressure sensors. In a static test environment, pressure data were collected at 345 kPa nominal pressure at 50% duty cycle with a variety of nozzle orifice sizes. A second-order transfer function was used to model a portion of the dynamic pressure data. The damping ratio generally decreased as the volume of the nozzle body increased due to the addition of a manifold. The variability in damping ratio with respect to nozzle orifice size was reduced when adding a manifold. The lower damping ratios when a manifold was present generally resulted in more overshoot and slower settling time. Results also showed a slightly higher damping ratio at the nozzle body than at the manifold when either manifold was added. The differences in nozzle pressure dynamics with and without the addition of a pressure sensing manifold suggest that previous studies using instrumented nozzle bodies under PWM control may have underestimated the amplitude of pressure oscillations and the time to reach equilibrium. Keywords: Agricultural Sprayers, Measurement Accuracy, Nozzle Body Volume, Pressure Dynamics, Pulse Width Modulation (PWM).

The effect of the interaction between fall-related self-efficacy and gait function on the occurrence of falls in community-dwelling older people

BackgroundFall-related self-efficacy and gait function are known to be associated. However, whether the interaction between fall-related self-efficacy and gait function affects future falls has not been investigated.AimThe aim of this study was to investigate the effect of the interaction between fall-related self-efficacy and spatiotemporal gait parameters on the occurrence of falls in community-dwelling older people.MethodsA total of 265 elderly persons (age ≥ 65 years) living independently in the community were recruited. For gait function, spatiotemporal gait parameters at usual and maximum effort paces were measured using a 2.4-m walkway system with embedded pressure sensors. Furthermore, changes in gait parameters between usual and maximum paces were calculated (Δgait parameters). Fall-related self-efficacy was assessed using the short version of the Falls Efficacy Scale International (Short FES-I). The occurrence of falls was prospectively investigated 6 months later. The effect of the interaction between short FES-I and gait parameters on falls was analyzed using logistic regression analysis adjusted for confounding factors.ResultsSeveral gait parameters were significantly different by self-efficacy level. As for the effect of the interaction of fall-related self-efficacy and gait parameters on falls, smaller Δgait parameters in those with high efficacy were associated with higher odds ratios of falls, whereas Δgait parameters in those with low efficacy were not associated with falls.Discussion and conclusionsThe interaction between fall-related self-efficacy and gait function appeared to affect future falls. Assessments combining fall-related self-efficacy and gait function may improve the accuracy of prediction of future falls.

Experimental Investigations on the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals With Embedded Pressure Sensors

Abstract Dry gas–lubricated noncontacting mechanical seals (DGSs), most commonly found in centrifugal compressors, prevent the process of gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. Even though the noncontacting seal is proved reliable, the ultrathin gas film can still lead to a host of potential problems due to possible contact. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods, and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8100 rpm, by several high-frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programed in matlab (Luo, J., Dohmen, H. J., and Benra, F. K., 2018, “Coupled Thermal-Structural-Fluid Numerical Analysis of Gas Lubricated Mechanical Seals,” ASME Paper No. GT2018-75458), the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal, and thereby affecting the seal performance.

Experimental and numerical investigations of pressure-controlled resin transfer molding (PC-RTM)

To increase the use of fiber reinforced lightweight structural components in the automotive industry, their manufacturing processes have to obtain demanding economic requirements. One possibility is to use Compression Resin Transfer Molding (CRTM), which is fast and can be highly automated. One disadvantage can be the very high cavity pressure during injection. To avoid this disadvantage, a pressure-controlled RTM (PC-RTM) process was developed. PC-RTM uses a variable mold gap height and an embedded pressure sensor to control the cavity pressure actively during mold filling. In this work, we investigate this process by experiments and simulations with varying initial mold gap and controlled cavity pressure. We show that PC-RTM is a viable manufacturing process with short cycle times and high robustness. Furthermore, the simulations are validated by comparison to the experiments and show the same process characteristics.

BodyCompass

Monitoring sleep posture is important for avoiding bedsores after surgery, reducing apnea events, tracking the progression of Parkinson's disease, and even alerting epilepsy patients to potentially fatal sleep postures. Today, there is no easy way to track sleep postures. Past work has proposed installing cameras in the bedroom, mounting accelerometers on the subject's chest, or embedding pressure sensors in their bedsheets. Unfortunately, such solutions jeopardize either the privacy of the user or their sleep comfort. In this paper, we introduce BodyCompass, the first RF-based system that provides accurate sleep posture monitoring overnight in the user's own home. BodyCompass works by studying the RF reflections in the environment. It disentangles RF signals that bounced off the subject's body from other multipath signals. It then analyzes those signals via a custom machine learning algorithm to infer the subject's sleep posture. BodyCompass is easily transferable and can apply to new homes and users with minimal effort. We empirically evaluate BodyCompass using over 200 nights of sleep data from 26 subjects in their own homes. Our results show that, given one week, one night, or 16 minutes of labeled data from the subject, BodyCompass's corresponding accuracy is 94%, 87%, and 84%, respectively.

Agreement between the GAITRite® System and the Wearable Sensor BTS G-Walk®for measurement of gait parameters in healthy adults and Parkinson's disease patients.

BackgroundNowadays, the most widely used types of wearable sensors in gait analysis are inertial sensors. The aim of the study was to assess the agreement between two different systems for measuring gait parameters (inertial sensor vs. electronic walkway) on healthy control subjects (HC) and patients with Parkinson’s disease (PD).MethodsForty healthy volunteers (26 men, 14 women, mean age 58.7 ± 7.7 years) participated in the study and 24 PD patients (19 men, five women, mean age 62.7 ± 9.8 years). Each participant walked across an electronic walkway, GAITRite, with embedded pressure sensors at their preferred walking speed. Concurrently a G-Walk sensor was attached with a semi-elastic belt to the L5 spinal segment of the subject. Walking speed, cadence, stride duration, stride length, stance, swing, single support and double support phase values were compared between both systems.ResultsThe Passing-Bablock regression slope line manifested the values closest to 1.00 for cadence and stride duration (0.99 ≤ 1.00) in both groups. The slope of other parameters varied between 0.26 (double support duration in PD) and 1.74 (duration of single support for HC). The mean square error confirmed the best fit of the regression line for speed, stride duration and stride length. The y-intercepts showed higher systematic error in PD than HC for speed, stance, swing, and single support phases.ConclusionsThe final results of this study indicate that the G-Walk system can be used for evaluating the gait characteristics of the healthy subjects as well as the PD patients. However, the duration of the gait cycle phases should be used with caution due to the presence of a systematic error.

DEVELOPMENT OF GAIT DIAGNOSTIC TECHNOLOGY FOR LONG-DISTANCE RUNNERS VIA SMART INSOLES

Aim. The article deals with the development of methods and software for the analysis of the running pattern in long-distance runners using smart insoles to prevent the development of athlete’s injuries. Materials and Methods. Insoles with embedded pressure sensors, an accelerometer, a gyroscope, and a specially designed software for analyzing the pattern of running and pressure distribution in the foot. Results. The technique of diagnostics and analysis of the running pattern, which allows preventing the development of tendon inflammation, Morton neuroma, and plantar fasciitis, is presented. Conclusion. The technique and the software deve­loped allow to analyze the patterns of running in stayers, diagnose, and prevent the development of injuries

Toward a Smart Compliant Robotic Gripper Equipped with 3D‐Designed Cellular Fingers

Usual lightweight soft robotic bodies built with elastomer materials show lack of structural stiffness that limits their use in many practical applications. Herein, an architectured robotic body design with deformable cellular structures, which is easy to fabricate, lightweight, mechanically durable, and compliant while maintaining its resilience, is proposed. The cellular body design overcomes not only the stiffness limitation but also other drawbacks of most common soft bodies that may damage from high pressure or impact. An artificial cellular finger is printed together with embedded pressure sensors on the fingertip to form a functional system in a single‐building process with the advantage of multi‐material 3D printing. The integrated architectured grippers, composed of cellular fingers with a repeatable, reliable bending profile, demonstrate maximum gripping force as 16 N on actuation, with gripping capability of various objects. 3D cellular designs open up new possibilities for architectured robotic bodies that can immensely widen their space of applications.

‘Optical-acoustic-stress’ responses in failure progress of cemented gangue-fly ash backfill material under uniaxial compression

ABSTRACTCemented gangue-fly ash backfill material (CGFBM) is made of coal gangue, fly ash, cementation materials and additives. It has been widely used in the field of backfill mining to control surface subsidence and to protect the environment. Partial backfill mining technology attracts much attention for its lower cost, and a large number of unconfined backfill structures (UBS) are formed based on it. Aimed at the stability monitoring of UBS in partial backfill, the failure progress of the CGFBM were obtained by uniaxial compression tests. The ‘optical-acoustic-stress’ responses of the specimens were monitored by Digital Image Correlation (DIC) technique, Acoustic Emission (AE) technique, Ultrasonic Testing (UT) technique and embedded pressure sensors. The advantages of each method in the stability monitoring of UBS was discussed. It is found that different monitoring methods have different sensitivity to different failure characteristics. The AE ringing count signal response is more sensitive to the pore compression and micro-crack generation in initial compaction stage and elastic compression stage. The central stress can be used to acquire the bearing capacity of the core bearing area after the top stress. The DIC response and UT response can be used to quantitatively evaluate the damage degree of the specimen. The stability of the UBS can be monitored by the jointly methods of ‘optical-acoustic-stress’ in partial backfill mining.

Failure analyses of unconfined CCWBM body in uniaxial compression based on central pressure variation.

Cemented coal waste backfill material (CCWBM) is made of coal gangue, fly ash and cementitious materials. It has been widely used in the field of backfill mining to control surface subsidence and protect the environment. A large number of unconfined backfill bodies without lateral support are formed in partial backfill mining. To study the failure characteristics of unconfined CCWBM body in partial backfill, the stress-strain curves of the CCWBM were obtained by uniaxial compression tests at different ages (1-28 d). The central pressure was measured by the embedded pressure sensors. The failure characteristics of the specimen were monitored by acoustic emission (AE) positioning technique. Three observations can be made. 1. The central pressure variation curves lag behind the mean stress change curves. The central pressure curve can be divided into three stages: slow increase stage, rapid growth stage and decline stage. It has two pressure manifestations: early appearance and peak appearance. They can be as the failure precursor and instability critical, respectively. 2. The specimen forms a central elastic bearing area in the process of compression. The plastic area develops to the inner side with the increase of pressure, and an upper and lower compound cone-shaped residual area is finally formed. 3. The embedded pressure sensor can be used to monitor the instability of the unconfined backfill body. The research results can provide guidance for the in-situ stability monitoring and reinforcement of unconfined CCWBM body in partial backfill.

Assessment of Embedded Conjugated Polymer Sensor Arrays for Potential Load Transmission Measurement in Orthopaedic Implants.

Load transfer through orthopaedic joint implants is poorly understood. The longer-term outcomes of these implants are just starting to be studied, making it imperative to monitor contact loads across the entire joint implant interface to elucidate the force transmission and distribution mechanisms exhibited by these implants in service. This study proposes and demonstrates the design, implementation, and characterization of a 3D-printed smart polymer sensor array using conductive polyaniline (PANI) structures embedded within a polymeric parent phase. The piezoresistive characteristics of PANI were investigated to characterize the sensing behaviour inherent to these embedded pressure sensor arrays, including the experimental determination of the stable response of PANI to continuous loading, stability throughout the course of loading and unloading cycles, and finally sensor repeatability and linearity in response to incremental loading cycles. This specially developed multi-material additive manufacturing process for PANI is shown be an attractive approach for the fabrication of implant components having embedded smart-polymer sensors, which could ultimately be employed for the measurement and analysis of joint loads in orthopaedic implants for in vitro testing.

Study of resin flow in carbon fiber reinforced polymer composites by means of pressure sensors

This paper presents an evaluation of resin flow in carbon fiber reinforced polymer by means of small embedded pressure sensors. High-quality carbon fiber reinforced polymer parts require entire impregnation of fibers with resin before resin curing starts. Small piezo-resistive pressure sensors are used to measure the vacuum hold and to track resin flow and pressure elevation inside the composite part. The sensors are placed at different locations in the fiber stacks. Real-time pressure changes are obtained inside the laminate during infusion. To reduce the size of the embedded sensing element, the sensor dies are flip-chipped on a thin printed circuit board. The two component thermoset resin (RIM 035 c) and uni-directional carbon fiber with the alignment of 30° are used in a complex-shaped mold. The result shows that the flip-chipped piezo-resistive pressure sensors can be used in conductive fibers to monitor resin arrival and pressure development in vacuum assisted resin transfer molding infusion processes. The sensors are supplied by a constant current source to compensate the sensitivity reduction if the temperature changes in the curing process.

Development of an anthropomorphic musical performance robot capable of playing the flute and saxophone: Embedding pressure sensors into the artificial lips as well as the re-designing of the artificial lips and lung mechanisms

The authors are developing anthropomorphic musical performance robots as an approach to understand the human motor control and to enhance the human–robot interaction from an engineering point of view. For this purpose; since 1990, we have developed an anthropomorphic flutist robot. As one of our long-term approaches, we aim to develop an anthropomorphic musical performance robot capable of playing different kinds of woodwind instruments, e.g. flute and saxophone. In this paper, the improvements of the mechanical design and sensing system of the Waseda Flutist Robot No. 4 Refined V (WF-4RV) are detailed. As for the sensing system, an array of sensors has been designed to detect the lip’s pressure distribution. On the other hand, the lips and lung have been re-designed to enable the flutist robot to play the saxophone.

Sensorized toys for measuring manipulation capabilities of infants at home.

Preterm infants, i.e. babies born after a gestation period shorter than 37 weeks, spend less time exploring objects. The quantitative measurement of grasping actions and forces in infants can give insights on their typical or atypical motor development. The aim of this work was to test a new tool, a kit of sensorized toys, to longitudinally measure, monitor and promote preterm infants manipulation capabilities with a purposive training in an ecological environment. This study presents preliminary analysis of grasping activity. Three preterm infants performed 4 weeks of daily training at home. Sensorized toys with embedded pressure sensors were used as part of the training to allow quantitative analysis of grasping (pressure and acceleration applied to toys while playing). Each toy was placed on the midline, while the infant was in supine position. Preliminary data show differences in the grasping parameters in relation to infants age and the performed daily training. Ongoing clinical trial will allow a full validation of this new tool for promoting object exploration in preterm infants.

Sensorized graspable devices for the study of motor imitation in infants.

Researches regarding neonatal imitation are of great clinical interest since they can provide evidences of an innate mechanism underlying action understanding; the study can be led through the analysis of infants' spontaneous movements, like grasping, that are recognized as markers of neural activity. To this aim, a portable and non-intrusive device has been designed and developed to measure infants' grasping during the presentation of specific visual stimuli. The device is composed of two soft handles with embedded pressure sensors. During trials action observation should produce an increase of the measured pressure exerted by the infant's hand, according to the imitation-based paradigm of the defined clinical protocol. The final prototype has been tested within a pilot study and it has been proved to be suitable for monitoring infants' imitation abilities, meeting all the clinical specifications in terms of size, weight, safety and sensitivity. Preliminary acquired results are a starting point to clarify mechanisms related to imitation and sensorimotor system growth. The present methodology could be employed to boosts investigation on the development of mirror neurons in infants.