Non-contact Device Research Articles

Docking Method for Hovering-Type AUVs Based on Acoustic and Optical Landmarks

Autonomous underwater vehicles (AUVs) have the advantage of not requiring tether cables or human control; however, they have limited energy, and must be recovered before their batteries drain completely. To charge AUV batteries efficiently, in-situ charging systems have attracted much attention. This study proposes a method for hovering-type AUVs to dock at a seafloor station, for long-term deployment of the system with minimum human intervention. In the proposed method, an AUV docks at a seafloor station autonomously, based on both acoustic and optical landmarks attached to the station. The AUV stochastically estimates its position and orientation with regard to the station, and controls itself to land on the exact docking spot at the station. When docking is completed, the station begins electric power transmission via non-contact charging devices. The proposed method was evaluated on the AUV Tri-TON 2, and a seafloor station testbed. The vehicle succeeded in autonomous docking at the station in both the tank and sea trials. Non-contact charging during docking was also verified during the tank experiments, using the non-contact charging devices developed by our group.

Experimental and analytical study on vibration control effects of eddy-current tuned mass dampers under seismic excitations

Eddy-current tuned mass dampers (EC-TMDs) are non-contacting passive control devices and are developed on the basis of conventional tuned mass dampers. They comprise a solid mass, a stiffness element, and a damping element, wherein the damping mechanism originates from eddy currents. By relative motion between a non-magnetic conductive metal and a permanent magnet in a dynamic system, a time-varying magnetic field is induced in the conductor, thereby generating eddy currents. The eddy currents induce a magnetic field with opposite polarity, causing repulsive forces, i.e., damping forces. This technology can overcome the drawbacks of conventional tuned mass dampers, such as limited service life, deterioration of mechanical properties, and undesired additional stiffness. The experimental and analytical study of this system installed on a multi-degree-of-freedom structure is presented in this paper. A series of shaking table tests were conducted on a five-story steel-frame model with/without an EC-TMD to evaluate the effectiveness and performance of the EC-TMD in suppressing the vibration of the model under seismic excitations. The experimental results show that the EC-TMD can effectively reduce the displacement response, acceleration response, interstory drift ratio, and maximum strain of the columns under different earthquake excitations. Moreover, an analytical method was proposed on the basis of electromagnetic and structural dynamic theories. A comparison between the test and simulation results shows that the simulation method can be used to estimate the response of structures with an EC-TMD under earthquake excitations with acceptable accuracy.

Influence on the Torque Characteristics of a Non-Contact Electromagnetic Impact Device under High Rotation Speed and its Performance Improvement

We have proposed a non-contact electromagnetic impact-torque device (EMI device) using induced currents, and its characteristics have been verified using 3-D finite element method (FEM) analysis and carrying out measurements on a prototype. Our previous EMI device could not generate sufficient torques under high rotation speed due to the impedance of the coil. In order to solve this problem, the electric circuit in the EMI device has been improved by using an electrical resonant phenomenon. This paper describes the influence of the electrical resonant phenomenon on the impact torque characterstics.

Anterior segment imaging using non-invasive high-resolution optical coherence tomography

One of the most important developments in the ophthalmology and visual sciences field has been the application of new techniques for imaging the anterior and posterior segment of the eye with non-contact devices. These techniques have been developed quickly considering that are non-invasive and provide high-resolution images of the different parts of the human eye. Definitely, the most spread and used technique for non-contact imaging of the human eye is the optical coherence tomography (OCT). OCT technique was first demonstrated in 1991 by Huang et al . (1). Based on low-coherence interferometry, OCT has become a prominent biomedical imaging technique with micrometric resolution and cross-sectional imaging capabilities, being particularly suitable for ophthalmic and other tissue imaging applications requiring millimetre penetration depth. Thus, OCT is especially useful in Ophthalmology, given the ease with which light reaches the ocular structures in the anterior and posterior segments. The advantage in its application is that the light impinges directly on the tissue, without the need to use any transducer, only requiring an optical medium sufficiently transparent to obtain a detectable signal. As a curiosity, OCT has also been used for various art conservation projects, where it is used to analyse, for instance, the different layers of a painting.

Measurement of the spindle system dynamic stiffness of a machine tool using a biaxial non-contact loading device

Measurement of the spindle system dynamic stiffness of a machine tool using a biaxial non-contact loading device

Modelling and compensation of dominant thermally induced geometric errors using rotary axes’ power consumption

Thermally induced volumetric errors due to rotary axes’ activity are measured on a five-axis machine tool using a non-contact R-test device with a four-ball uncalibrated artefact and an Invar reference length. The gathered volumetric data allow to estimate intra- and inter-axis machine errors as well as the table expansion via the estimated balls position. Dominant thermal effects are modelled as functions of the measured rotary axes drive power consumption by the superposition of single-input single-output first order transfer functions. The efficiency of the model is validated with different motion sequences and by the compensated machining of a test piece.

Development of a non-contact handing device with a swirling flow

Development of a non-contact handing device with a swirling flow

THE BIOPHYSICAL PARAMETER MEASUREMENTS FROM PPG SIGNAL

Early investigation on blood circulation by Hertzman (1937) leads to the observation of vital body signs such as respiration rate, heart rate (HR), blood oxygenation and vascular assessment using photoplethysmographic (PPG) device. PPG is a noninvasive, painless optical technique used to monitor the pulsations linked to alteration in the blood volume. The PPG waveform is a summation of pulsatile and nonpulsatile components and contains useful information about the physiological systems. With the breakthrough in technology and development of powerful analytical tools, PPG devices are constantly being used in advanced medical equipments such as smart-watches and smart-wristbands for HR monitoring, pulse oximeters for measuring respiratory rate and noncontact PPG device for blood oxygen saturation measurement. This paper presents description on PPG and its characteristic waveform and working principle. It also includes brief explanation on nonlinear analysis of PPG signals and salient applications of PPG followed by its advantages and limitations.

Optimization of the GPU-based data evaluation for the low coherence interferometry

Abstract Optical interferometers as non-contact measurement devices are very desirable for the measurement of surface roughness and topography. Compared to phase shifting interferometers (PSIs) with a limited measurement range and a scan step of maximum λ/4, the optical interferometers like low coherence interferometers (LCIs) evaluating the degree of fringe coherence allow a larger vertical measurement range. Their vertical measurement range is only limited by the scan length allowed by the linear piezo stage and the coherence length of the light source. To evaluate the obtained data for a large range, the common LCIs require much computation time. To overcome this drawback, we present an evaluation algorithm based on the Hilbert-Transform and curve fitting (Levenberg–Marquardt algorithm) using Compute Unified Device Architecture (CUDA) technology, which allows parallel and independent data evaluation on General Purpose Graphics Processing Unit (GPGPU). Firstly, the evaluation algorithm is implemented and tested on an in-house developed LCI, which is based on Michelson configurations. Furthermore, we focus on the performance optimization of the GPU-based program using the different approaches to further achieve efficient and accurate massive parallel computing. Finally, the performance comparison for evaluating measurement data using different approaches is discussed in this paper.

Mapping Soil Texture by Electromagnetic Induction: A Case for Regional Data Coordination

Core Ideas High-resolution soil texture maps can improve efficiencies in precision irrigation. Noncontact EMI methods can generate high-resolution maps quickly and at low cost. Mapping with EMI requires robust correlations between soil ECa and soil texture. Accuracy of high-resolution maps may be reduced by nontarget soil characteristics. Neural networks can predict soil properties accurately by combining measurements. High-resolution soil maps are needed to guide precision irrigation, fertilization, and crop management decisions. A mobile, noncontact device can be used to map apparent electromagnetic conductivity (ECa) with detailed spatial resolution (<10 m). Maps of other characteristics can be generated by determining the correlation between the measured ECa and physical samples. Soil mapping services are now offered by commercial vendors and are used to estimate properties that are relevant to soil management, including nitrate and micronutrients, soil pH, texture, and water holding capacity. In this study, ECa maps were compared with 390 colocated physical samples, distributed over three cultivated fields comprising a total area of 140 ha. Principal component analysis and linear regression were used to identify factors that confounded ECa measurement and reduced map fidelity. When correlation was conducted in each field independently, low variability in soil texture reduced the accuracy of predicting texture from ECa. To compensate, a combination of four properties was used to train a neural network model, which yielded an improved prediction. Using such methods to establish regionally specific models for ECa readings could enable robust mapping of soil characteristics via rapid and low-cost electromagnetic measurements. The results confirm that ECa can be a used to map texture at field scales and that additional quality controls can augment the predictive power of ECa.

Noncontact Imaging Plethysmography for Accurate Estimation of Physiological Parameters

In this paper, a novel non-contact device that accurately measures physiological parameters is proposed. This system consists of a CCD camera and a set of band pass filters. To eliminate the noise from the original signal, threshold segment and image registration algorithm are used. In addition, motion artifact is a vital issue that cannot be ignored. Here, an adaptive filter based on wavelet transform is introduced to reduce the motion artifact. Besides, the influence of ambient light intensity is discussed, which the result demonstrates that the change of ambient light intensity has no obvious impact on measurement results. Compared with the traditional contact method, this method is more convenient when mechanical isolation is required. Contrast experiment was performed with a multi-parameter monitor and a CO-oximeter. The comparison showed that our method is comparable with the contact method.

Vision-based stress estimation model for steel frame structures with rigid links

This paper presents a stress estimation model for the safety evaluation of steel frame structures with rigid links using a vision-based monitoring system. In this model, the deformed shape of a structure under external loads is estimated via displacements measured by a motion capture system (MCS), which is a non-contact displacement measurement device. During the estimation of the deformed shape, the effective lengths of the rigid link ranges in the frame structure are identified. The radius of the curvature of the structural member to be monitored is calculated using the estimated deformed shape and is employed to estimate stress. Using MCS in the presented model, the safety of a structure can be assessed gauge-freely. In addition, because the stress is directly extracted from the radius of the curvature obtained from the measured deformed shape, information on the loadings and boundary conditions of the structure are not required. Furthermore, the model, which includes the identification of the effective lengths of the rigid links, can consider the influences of the stiffness of the connection and support on the deformation in the stress estimation. To verify the applicability of the presented model, static loading tests for a steel frame specimen were conducted. By comparing the stress estimated by the model with the measured stress, the validity of the model was confirmed.

Review on Advanced Short-Range Multimode Continuous-Wave Radar Architectures for Healthcare Applications

Short-range radar systems are noncontact devices that are attracting much attention from the RF/microwave community. In particular, they are being applied in healthcare contexts, ranging from hospital to indoor and outdoor environments, e.g., for monitoring of vital signs and/or tracking of human activities. This article reviews the standard architectures for short-range biomedical radars and presents recently proposed hybrid schemes, which combine different operation modes, leading to performance improvement. Specifically, hybridizations associated with Doppler, frequency-modulated continuous-wave, and tone-ranging-based schemes are provided from theoretical and simulation viewpoints. Some experiments on vital-sign monitoring and human-aware localization are also reported.

Analyses of truck powertrain torque and vibration

The article deals with an analysis of the mean value of the torque of the truck with 8×8 drive. Torque was measured using a noncontact device on the powertrain shaft. This shaft is used to drive the first front axle. For a better understanding of the experiment results, computational model of the truck was developed in Simulink software. To build the computational model, custom library was used and users could create different modifications of vehicles. Subsequently, analysis of torsional vibration was carried out. In the first study, the truck showed problems with directional vibrations and noise after reaching a certain speed, therefore, this article also continues with an analysis of the torsional vibration.

Development and validation of a noncontact spectroscopic device for hemoglobin estimation at point-of-care.

Anemia severely and adversely affects human health and socioeconomic development. Measuring hemoglobin with the minimal involvement of human and financial resources has always been challenging. We describe a translational spectroscopic technique for noncontact hemoglobin measurement at low-resource point-of-care settings in human subjects, independent of their skin color, age, and sex, by measuring the optical spectrum of the blood flowing in the vascular bed of the bulbar conjunctiva. We developed software on the LabVIEW platform for automatic data acquisition and interpretation by nonexperts. The device is calibrated by comparing the differential absorbance of light of wavelength 576 and 600 nm with the clinical hemoglobin level of the subject. Our proposed method is consistent with the results obtained using the current gold standard, the automated hematology analyzer. The proposed noncontact optical device for hemoglobin estimation is highly efficient, inexpensive, feasible, and extremely useful in low-resource point-of-care settings. The device output correlates with the different degrees of anemia with absolute and trending accuracy similar to those of widely used invasive methods. Moreover, the device can instantaneously transmit the generated report to a medical expert through e-mail, text messaging, or mobile apps.

Distribution of IOP measured with an air puff tonometer in a young population

PurposeTo determine the normal range of intraocular pressure (IOP) in the young and its association with certain corneal parameters using a non-contact device. MethodsSubjects were selected from students of Mashhad University of Medical Sciences through stratified sampling. All participants had visual acuity testing, corneal imaging, a comprehensive slit-lamp examination by an ophthalmologist, and IOP measurement using a non-contact air-puff tonometer. ResultsOf the 1280 invitees, 1073 (83.8%) participated, and 1027 were eligible. Mean IOP was 16.38 mmHg [95% confidence interval (CI): 16.22–16.53] in the total sample, 16.14 mmHg (95% CI: 15.84–16.45) in men, and 16.48 mmHg (95% CI: 16.31–16.66) in women. There was a significant IOP difference between myopes and emmetropes (P = 0.031). Based on the multiple linear regression model, IOP associated directly with age and central corneal thickness (CCT), and inversely with corneal diameter, spherical equivalent (SE), and keratoconus. Based on standardized coefficients of the regression model, CCT and SE had the strongest association with IOP. ConclusionsIn the present study, we demonstrated the IOP distribution in a young population using a non-contact method. CCT and SE were strongly associated with IOP.

Smartphone viewing distance and sleep: an experimental study utilizing motion capture technology.

There are studies reporting the negative impact of smartphone utilization on sleep. It is considered that reduction of melatonin secretion under the blue light exposure from smart-phone displays is one of the causes. The viewing distance may cause sleep disturbance, because the viewing distance determines the screen illuminance and/or asthenopia. However, to date, there has been no study closely investigating the impact of viewing distance on sleep; therefore, we sought to determine the relationship between smartphone viewing distance and subjective sleep status. Twenty-three nursing students (mean age ± standard deviation of 19.7±3.1 years) participated in the study. Subjective sleep status was assessed using the Pittsburgh Sleep Quality Index, morningness–eveningness questionnaire, and the Epworth sleepiness scale. We used the distance between the head and the hand while holding a smartphone to measure the viewing distance while using smartphones in sitting and lying positions. The distance was calculated using the three-dimensional coordinates obtained by a noncontact motion-sensing device. The viewing distance of smartphones in the sitting position ranged from 13.3 to 32.9 cm among participants. In the lying position, it ranged from 9.9 to 21.3cm. The viewing distance was longer in the sitting position than in the lying position (mean ± standard deviation: 20.3±4.7 vs 16.4±2.7, respectively, P<0.01). We found that the short viewing distance in the lying position had a positive correlation to a poorer sleep state (R2=0.27, P<0.05), lower sleep efficiency (R2=0.35, P<0.05), and longer sleep latency (R2=0.38, P<0.05). Moreover, smartphone viewing distances in lying position correlated negatively with subjective sleep status. Therefore, when recommending ideal smartphone use in lying position, one should take into account the viewing distances.

Validation of the Sonomat Against PSG and Quantitative Measurement of Partial Upper Airway Obstruction in Children With Sleep-Disordered Breathing

To validate the Sonomat against polysomnography (PSG) metrics in children and to objectively measure snoring and stertor to produce a quantitative indicator of partial upper airway obstruction that accurately reflects the pathology of pediatric sleep-disordered breathing (SDB). Simultaneous PSG and Sonomat recordings were performed in 76 children (46 male, age 5.8 ± 2.8, BMI = 18.5 ± 3.8 kg/m2). Sleep time, individual respiratory events and the apnea/hypopnea index (AHI) were compared. Obstructed breathing sounds were measured from the unobtrusive non-contact experimental device. There was no significant difference in total sleep time (TST), respiratory events or AHI values, the latter over-estimated by 0.3 events hr-1 by the Sonomat. Poor signal quality was minimal and gender, BMI, and body position did not adversely influence event detection. Obstructive and central events were classified correctly. The number of runs and duration of snoring (13 399 events, 20% TST) and stertor (5748 events, 24% TST) were an order of magnitude greater than respiratory events (1367 events, 1% TST). Many children defined as normal by PSG had just as many or more runs of snoring and stertor as those with mild, moderate and severe obstructive sleep apnea (OSA). The Sonomat accurately diagnoses SDB in children using current metrics. In addition, it permits quantification of partial airway obstruction that can be used to better describe pediatric SDB. Its non-contact design makes it ideal for use in children.

Torque characteristic analysis and measurement of axial flux-type non-contact permanent magnet device with Halbach array based on 3D analytical method

This paper addresses the torque characteristic analysis of an axial flux-type non-contact permanent magnet device with a Halbach magnet array using a 3D analytical method based on transfer relations. We obtain the magnetic field distribution due to the permanent magnet. The magnetic torque is derived from the magnetic field using a Maxwell stress tensor. The analytical results are validated extensively by comparison with 3D finite element analysis. Therefore, we derive an accurate analytical solution to reduce the analysis time, and we present an experimental verification using a manufactured model.

Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste

The effects of graphene oxide (GO) on the early-age hydration process and mechanical properties of Portland cement paste were experimentally investigated in this study. Based on an isothermal calorimeter measurement, the hydration rate of cement was observed to increase with the increase of GO content by nucleation effect. On the other hand, the electrical resistivity development of GO-cement paste was monitored using a non-contact electrical resistivity device. The result showed that electrical the resistivity of GO-cement paste was evidently higher than that of plain cement paste. However, cement paste with excessive amounts of GO exhibited a decreased electrical resistivity due to the massive ion diffusion caused by GO. Compared to plain cement paste, the GO-cement paste exhibited obviously higher compressive and flexural strengths, but the enhancements in compressive strength began to decline when the GO amount was greater than 0.04%. The microstructure characterization indicated that GO can apparently densify the cement pastes with less porosity and hydrates networking, which is consistent with the results of hydration acceleration and strength enhancement.