Abstracts:This paper investigates automatic quality inspection for the components with a small diameter and deep aperture. An automatic pick-and-place system is constructed, which employs an endoscope to achieve better image quality aiming at the characteristics of the component. A coarse-to-fine contour extraction algorithm with four steps is presented to inspect the component’s quality. First, approximate locations of the targets are estimated using faster region-based convolutional neural networks (faster RCNN). Second, the corresponding edge image is obtained by using the multiscale probability boundary (mPb) detector. Third, edge enhancement is performed, which is based on the Brownian motion model. Fourth, the corresponding contours are finely extracted by edge grouping. A shape analyzing algorithm is utilized to classify the components based on the extracted contours. Comparison experiments fully demonstrate the superiority of the proposed inspection method over existing methods. Meanwhile, successful inspection results on challenging real-world image data prove that the system is of practical significance to industrial applications.

Abstracts:The concept of local parametric modeling has drawn renewed attention to frequency response function (FRF) measurements. Essentially, these approaches assume a particular parametric structure and approximate the FRF and the leakage errors in a small-frequency band around the frequency of interest. Following the successful application of the idea in the local polynomial method (LPM), the local rational method (LRM) was developed, replacing polynomial by rational approximating functions. The power of the LRM has previously been demonstrated in simulations and experiments, yet an explanation of the method’s robustness to pole-zero cancellations was lacking. At the cost of increased computation, the LRM reduces the leakage errors with several orders of magnitude with respect to its alternatives while, under commonly encountered conditions, the sensitivity to disturbing noise remains competitive to that of the standard procedures. In this paper, we provide insight into the observed virtues of the proposed method.

Abstracts:There has been tremendous interest to employ 2-D materials as sensing medium in acoustic wave sensors such as quartz crystal microbalance (QCM). We report a method to transfer polymer-free 2-D materials onto QCM through a tailor-made automated process system and resultant enhancement in the sensing characteristics of QCM. A customized polytetrafluoroethylene (PTFE) structure was designed for the automated transfer of a 2-D heterostructure material made of hexagonal boron nitride (hBN)/graphene onto the QCM. The design ensured that the 2-D material adhered to the most sensitive region of the QCM, at the center of the electrode surface. The transferred 2-D material was characterized using Raman spectroscopy and scanning electron microscopy. Also, the <inline-formula> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> characteristics of the QCM were measured before and after the transfer process using a network analyzer. We observed increment in return loss and loaded <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor (<inline-formula> <tex-math notation="LaTeX">$Q_{L}$ </tex-math></inline-formula>) in the presence of the 2-D material. In order to investigate the sensing characteristics of the 2-D material integrated QCM, relative humidity (RH) was taken as an example measurand, and experiments were carried out to study the adsorption and desorption of moisture. The 2-D material integrated QCM showed good sensitivity with excellent signal-to-noise ratio for RH variations as evidenced from the significant changes in return loss and conductance measurements. On the other hand, the bare QCM exhibited poor signal-to-noise ratio and inconsistent response to RH changes.

Abstracts:The measurement of the analyte concentration in electrochemical biosensors traditionally requires costly laboratory equipment to obtain accurate results. Innovative portable solutions have recently been proposed, but usually, they lean on personal computers (PCs) or smartphones for data elaboration and they exhibit poor resolution or portability and proprietary software. This paper presents a low-cost portable system, assembling an <italic>ad hoc</italic>-designed analog front end (AFE) and a development board equipped with a system on chip integrating a microcontroller and a Wi-Fi network processor. The wireless module enables the transmission of measurements directly to a cloud service for sharing device outcome with users (physicians, caregivers, and so on). In doing so, the system does not require neither the customized software nor other devices involved in data acquisition. Furthermore, when any Internet connection is lost, the data are stored on board for subsequent transmission when a Wi-Fi connection is available. The noise output voltage spectrum has been characterized. Since the designed device is intended to be battery-powered to enhance portability, investigations about battery lifetime were carried out. Finally, data acquired with a conventional benchtop Autolab PGSTAT-204 electrochemical workstation are compared with the outcome of our developed device to validate the effectiveness of our proposal. To this end, we selected ferri/ferrocyanide as redox probe, obtaining the calibration curves for both the platforms. The final outcomes are shown to be feasible, accurate, and repeatable.

Abstracts:The purpose of the work is to evaluate various intrinsic noise sources that limit the charge resolution of microelectromechanical systems (MEMS) vibrating-reed (VR) electrometers. We demonstrate a method of reducing total equivalent referred-to-input (RTI) noise voltage per square root hertz for an operational amplifier-based preamplifier (preamp) circuit topology. The proposed circuit&#x2019;s noise model accurately describes the various noise sources and total RTI noise voltage is experimentally verified. The noise analysis clarifies the path toward a preamp with a noise floor limited by thermal noise due to low-valued shunt resistance at its input. Furthermore, during the charge measurement, a variation of sensitivity occurs by changing the isolation (or dc blocking) capacitor of the preamp. This phenomenon also affects the noise performance of the circuit and the overall charge resolution for the electrometer. RTI noise voltage of 290 nV/<inline-formula> <tex-math notation="LaTeX">$surd $ </tex-math></inline-formula>Hz at 5.2 kHz was measured for 50 <inline-formula> <tex-math notation="LaTeX">$text{M}Omega $ </tex-math></inline-formula> of shunt resistor and 2 pF of isolation capacitor to implement a prototype of the complete preamp, along with the MEMS device fabricated in silicon-on-glass (SOG) process. Finally, we present a charge resolution model of the proposed SOG-MEMS electrometry system. The model&#x2019;s underlying design principles reveal low noise preamps accessible to the circuit designers without tangible circuitries and after-the-fact noise measurement.

Abstracts:This paper presents an automatic scanning solution for measuring nonuniform magnetic fields captured by a tri-axial sensor connected to a time-domain acquisition system over a robotic arm. The sensor has been realized and calibrated through a canonical configuration consisting of Helmholtz coils. The acquisition system is instead executed by a Red Pitaya, which is an FPGA-based board with high performance and reliability regarding the sampling rate of the input signal. A LabVIEW software has then been developed for the acquisition of the sampled signal over time, the calculation and post-processing of the magnetic field, and the data saving. Finally, an Arduino-based robotic arm has been employed to make the acquisition system fully automated. This is particularly useful for the compliance assessment against electromagnetic field exposures at workplaces.

Abstracts:We propose a novel noniterative orientation estimation method based on the physical and geometrical properties of the acceleration, angular rate, and magnetic field vectors to estimate the orientation of motion sensor units. The proposed algorithm aims that the vertical (up) axis of the earth coordinate frame is as close as possible to the measured acceleration vector and that the north axis of the earth makes an angle with the detected magnetic field vector as close as possible to the estimated value of the magnetic dip angle. We obtain the sensor unit orientation based on the rotational quaternion transformation between the earth and the sensor unit frames. We evaluate the proposed method by incorporating it into an activity recognition scheme for daily and sports activities, which requires accurately estimated sensor unit orientations to achieve invariance to the orientations at which the units are worn on the body. Using four different classifiers on a publicly available data set, the proposed methodology achieves an average activity recognition accuracy higher than the state-of-the-art methods, as well as being computationally efficient enough to be executed in real time.

Abstracts:Strength of wideband electromagnetic radiations (EMRs) generated by telecommunication systems is a time-varying process typically characterized by a seasonal behavior due to daily and weekly variations of traffic in mobile networks summed to a stationary background generated by constant-power broadcasting systems. Besides a few papers showing the existence of peak and off-peak hours in the daily exposure, there is a significant lack of scientific literature investigating how exposure changes over time, although this is key to the three main objectives: 1) to determine the time intervals when exposure levels are expected to be the highest, 2) to assess worst case exposure and ensure that measurements are run in a conservative scenario to comply with limits enforced by national laws and European guidelines, and 3) to highlight variations in traffic to allocate network resources dynamically to optimize performance. We present a time-series analysis model that makes use of measured data to build a predictor of the exposure to wideband EMR. The main result is that exposure can be predicted by a model composed of three components capturing the average exposure, the daily and half-daily periodicity (seasonal behavior), and the correlations among residuals [modeled by an AR(2) for weekdays and Sunday, and by an AR(1) for Saturday, respectively]. We observed the strength of the periodic components differs more on weekdays compared to weekends. The forecasting model can be particularly useful to predict when exposure is expected to be the highest during the day, so that measurements carried out at that time will be conservative with respect to measurements run at other times of the day, and will therefore serve as the worst case for the assessment of compliance with exposure limits.

Abstracts:An on-site and fast synchronous measurement of coil constant and nonorthogonal angle, using an all-optical atomic magnetometer, was reported in this article. Based on the spectrum analysis of electron paramagnetic resonance of spin-polarized potassium under different magnetic fields, the measurement models of coil constant and nonorthogonal angle were established, according to which we experimentally obtained the weighted average results with related estimated uncertainties: the coil constants in the <inline-formula> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula>-, <inline-formula> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula>-, and <inline-formula> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula>-axes were (145.9 &#x00B1; 0.3) nT/mA, (149.5 &#x00B1; 0.3) nT/mA, and (129.6 &#x00B1; 0.1) nT/mA, respectively; the nonorthogonal angles existing in the <inline-formula> <tex-math notation="LaTeX">$x z$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$y z$ </tex-math></inline-formula> axes were (0.11 &#x00B1; 0.02)&#x00B0; and (0.23 &#x00B1; 0.02)&#x00B0;, respectively. The determination results of the residual magnetic field in the <inline-formula> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula>-axis, with two comparative experiments, demonstrated the validity of this on-site synchronous measurement method. The present method can be easily used in calibrating coil constant and nonorthogonal angle for all-optical atomic magnetometers, especially for miniaturized ones.

Abstracts:An <italic>in situ</italic> colored dissolved organic matter sensor based on a frequency spectrum shifted maximum-length sequence (FSSM) modulation method was proposed in this paper. The energy behavior resulting from the direct maximum-length sequence (m-sequence) modulation method was analyzed. We found a kind of twice modulation method, which optimizes m-sequence frequency spectrum structures. This novel method can effectively reduce the energy loss caused by filtering and reduce the noise introduced by demodulation. The sensitivity of the developed sensor was improved to an unprecedented level by optimizing the modulation/demodulation scheme without increasing the light-emitting diode intensity. Subsequently, we developed a cost-saving hardware sensor which can meet the requirements of the <italic>in situ</italic> measuring system with the FSSM modulation method. The equivalent input noise current of the electronic system can be as low as 12.20 fA. The limit of detection (LOD) of the sensor reached a maximum of <inline-formula> <tex-math notation="LaTeX">$0.0168 mu text {g/L}$ </tex-math></inline-formula> within a concentration range of 0&#x2013;<inline-formula> <tex-math notation="LaTeX">$3000~mu mathrm {g/L}$ </tex-math></inline-formula>, and with an R-squared value of 0.9967. The results demonstrated that the LOD of our sensors was fivefold higher than the LOD of commercially available chromophoric dissolved organic matter (CDOM) sensors and doubled its normal detection range. The sensor also exhibited excellent anti-interference ability and it can attenuate sunlight and electromagnetic interference by up to ten times while improving the stability of the system. The improvement of the CDOM sensor&#x2019;s performance is of great significance to the marine environmental information monitoring field.