Sensors

2024

Jump to: 2023, 2022, 2021, 2020

30 pages, 2918 KiB

Open AccessArticle

A Theoretical Study on Static Gas Pressure Measurement via Circular Non-Touch Mode Capacitive Pressure Sensor

by Ji Wu, Xiao-Ting He and Jun-Yi Sun

Sensors 2024, 24(16), 5314; https://doi.org/10.3390/s24165314 - 16 Aug 2024

Cited by 1 | Viewed by 885

Abstract

A circular non-touch mode capacitive pressure sensor can operate in both transverse and normal uniform loading modes, but the elastic behavior of its movable electrode plate is different under the two different loading modes, making its input–output analytical relationships between pressure and capacitance [...] Read more.

A circular non-touch mode capacitive pressure sensor can operate in both transverse and normal uniform loading modes, but the elastic behavior of its movable electrode plate is different under the two different loading modes, making its input–output analytical relationships between pressure and capacitance different. This suggests that when such a sensor operates, respectively, in transverse and normal uniform loading modes, the theory of its numerical design and calibration is different, in other words, the theory for the transverse uniform loading mode (available in the literature) cannot be used as the theory for the normal uniform loading mode (not yet available in the literature). In this paper, a circular non-touch mode capacitive pressure sensor operating in normal uniform loading mode is considered. The elastic behavior of the movable electrode plate of the sensor under normal uniform loading is analytically solved with the improved governing equations, and the improved analytical solution obtained can be used to mathematically describe the movable electrode plate with larger elastic deflections, in comparison with the existing two analytical solutions in the literature. This provides a larger technical space for developing the circular non-touch mode capacitive pressure sensors used for measuring the static gas pressure (belonging to normal uniform loading). Full article

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22 pages, 28037 KiB

Open AccessReview

A Review on the Video-Based River Discharge Measurement Technique

by Meng Chen, Hua Chen, Zeheng Wu, Yu Huang, Nie Zhou and Chong-Yu Xu

Sensors 2024, 24(14), 4655; https://doi.org/10.3390/s24144655 - 18 Jul 2024

Viewed by 1603

Abstract

The hydrological monitoring of flow data is important for flood prevention and modern river management. However, traditional contact methods are increasingly struggling to meet the requirements of simplicity, accuracy, and continuity. The video-based river discharge measurement is a technique to monitor flow velocity [...] Read more.

The hydrological monitoring of flow data is important for flood prevention and modern river management. However, traditional contact methods are increasingly struggling to meet the requirements of simplicity, accuracy, and continuity. The video-based river discharge measurement is a technique to monitor flow velocity without contacting the water body by using the image-recognition algorithms, which has been verified to have the advantages of full coverage and full automation compared with the traditional contact technique. In order to provide a timely summary of the available results and to inform further research and applications, this paper reviews and synthesizes the literature on the general implementation routes of the video-based river discharge measurement technique and the principles and advances of today’s popular image-recognition algorithms for velocity detection. Then, it discusses the challenges of image-recognition algorithms in terms of image acquisition conditions, parameter uncertainties, and complex meteorological and water environments. It is concluded that the performance of this technique can be improved by enhancing the robustness and accuracy of video-based discharge measurement algorithms, minimizing weather effects, and improving computational efficiency. Finally, future development directions for further perfecting this technique are outlined. Full article

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10 pages, 5489 KiB

Open AccessArticle

Semi-Kinematic Coupling Design and Analysis for Giant Steerable Science Mirror Prototype of Thirty Meter Telescope

by Hongchao Zhao, Wenduo Chen, Qichang An, Peng Guo and Fei Yang

Sensors 2024, 24(11), 3628; https://doi.org/10.3390/s24113628 - 4 Jun 2024

Viewed by 617

Abstract

The Giant Steerable Science Mirror prototype is being developed to assess the tertiary mirror system of the Thirty Meter Telescope. In this study, a new semi-kinematic coupling design is proposed for the prototype based on three pairs of V-grooves and canoe-like components to [...] Read more.

The Giant Steerable Science Mirror prototype is being developed to assess the tertiary mirror system of the Thirty Meter Telescope. In this study, a new semi-kinematic coupling design is proposed for the prototype based on three pairs of V-grooves and canoe-like components to allow for high repeatability accuracy under heavy loads. A mathematical model was constructed to estimate the repeatability accuracy using the corresponding measurement results and machining errors. The proposed design was verified by an experiment, and the results were consistent with the mathematical model. Furthermore, the results indicate that the repeatability of the semi-kinematic coupling is sufficient for the requirement. Full article

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17 pages, 2873 KiB

Open AccessArticle

Innovative Non-Invasive and Non-Intrusive Precision Thermometry in Stainless-Steel Tanks Using Ultrasound Transducers

by Ahmed Bouzid, Saad Chidami, Tristan Quentin Lailler, Adrián Carrillo García, Tarek Ould-Bachir and Jamal Chaouki

Sensors 2024, 24(11), 3404; https://doi.org/10.3390/s24113404 - 25 May 2024

Viewed by 1497

Abstract

Measuring temperature inside chemical reactors is crucial to ensuring process control and safety. However, conventional methods face a number of limitations, such as the invasiveness and the restricted dynamic range. This paper presents a novel approach using ultrasound transducers to enable accurate temperature [...] Read more.

Measuring temperature inside chemical reactors is crucial to ensuring process control and safety. However, conventional methods face a number of limitations, such as the invasiveness and the restricted dynamic range. This paper presents a novel approach using ultrasound transducers to enable accurate temperature measurements. Our experiments, conducted within a temperature range of 28.8 to 83.8 °C, reveal a minimal temperature accuracy of 98.6% within the critical zone spanning between 70.5 and 75 °C, and an accuracy of over 99% outside this critical zone. The experiments focused on a homogeneous environment of distilled water within a stainless-steel tank. This approach will be extended in a future research in order to diversify the experimental media and non-uniform environments, while promising broader applications in chemical process monitoring and control. Full article

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16 pages, 11571 KiB

Open AccessArticle

Design and Characterization of a Powered Wheelchair Autonomous Guidance System

by Vincenzo Gallo, Irida Shallari, Marco Carratù, Valter Laino and Consolatina Liguori

Sensors 2024, 24(5), 1581; https://doi.org/10.3390/s24051581 - 29 Feb 2024

Cited by 1 | Viewed by 1159

Abstract

The current technological revolution driven by advances in machine learning has motivated a wide range of applications aiming to improve our quality of life. Representative of such applications are autonomous and semiautonomous Powered Wheelchairs (PWs), where the focus is on providing a degree [...] Read more.

The current technological revolution driven by advances in machine learning has motivated a wide range of applications aiming to improve our quality of life. Representative of such applications are autonomous and semiautonomous Powered Wheelchairs (PWs), where the focus is on providing a degree of autonomy to the wheelchair user as a matter of guidance and interaction with the environment. Based on these perspectives, the focus of the current research has been on the design of lightweight systems that provide the necessary accuracy in the navigation system while enabling an embedded implementation. This motivated us to develop a real-time measurement methodology that relies on a monocular RGB camera to detect the caregiver’s feet based on a deep learning method, followed by the distance measurement of the caregiver from the PW. An important contribution of this article is the metrological characterization of the proposed methodology in comparison with measurements made with dedicated depth cameras. Our results show that despite shifting from 3D imaging to 2D imaging, we can still obtain comparable metrological performances in distance estimation as compared with Light Detection and Ranging (LiDAR) or even improved compared with stereo cameras. In particular, we obtained comparable instrument classes with LiDAR and stereo cameras, with measurement uncertainties within a magnitude of 10 cm. This is further complemented by the significant reduction in data volume and object detection complexity, thus facilitating its deployment, primarily due to the reduced complexity of initial calibration, positioning, and deployment compared with three-dimensional segmentation algorithms. Full article

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45 pages, 4433 KiB

Open AccessArticle

An Improved Theory for Designing and Numerically Calibrating Circular Touch Mode Capacitive Pressure Sensors

by Xiao-Ting He, Xin Wang, Fei-Yan Li and Jun-Yi Sun

Sensors 2024, 24(3), 907; https://doi.org/10.3390/s24030907 - 30 Jan 2024

Cited by 2 | Viewed by 1056

Abstract

The design, especially the numerical calibration, of a circular touch mode capacitive pressure sensor is highly dependent on the accuracy of the analytical solution of the contact problem between the circular conductive membrane and the rigid plate of the sensor. In this paper, [...] Read more.

The design, especially the numerical calibration, of a circular touch mode capacitive pressure sensor is highly dependent on the accuracy of the analytical solution of the contact problem between the circular conductive membrane and the rigid plate of the sensor. In this paper, the plate/membrane contact problem is reformulated using a more accurate in-plane equilibrium equation, and a new and more accurate analytical solution is presented. On this basis, the design and numerical calibration theory for circular touch mode capacitive pressure sensors has been greatly improved and perfected. The analytical relationships of pressure and capacitance are numerically calculated using the new and previous analytical solutions, and the gradually increasing difference between the two numerical calculation results with the gradual increase in the applied pressure is graphically shown. How to use analytical solutions and analytical relationships to design and numerically calibrate a circular touch mode capacitive pressure sensor with a specified pressure detecting range is illustrated in detail. The effect of changing design parameters on capacitance–pressure analytical relationships is comprehensively investigated; thus, the direction of changing design parameters to meet the required or desired range of pressure or capacitance is clarified. Full article

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2023

Jump to: 2024, 2022, 2021, 2020

17 pages, 12527 KiB

Open AccessArticle

A New Successive Time Balancing Time-to-Digital Conversion Method

by Konrad Jurasz, Dariusz Kościelnik, Jakub Szyduczyński and Witold Machowski

Sensors 2023, 23(24), 9712; https://doi.org/10.3390/s23249712 - 8 Dec 2023

Viewed by 1207

Abstract

This paper presents a new self-clocked time-to-digital conversion method based on a binary successive approximation (SA) algorithm. Its novelty consists in combining fully clockless operation with direct conversion of the measured time interval. The lack of any reference clock makes the presented method [...] Read more.

This paper presents a new self-clocked time-to-digital conversion method based on a binary successive approximation (SA) algorithm. Its novelty consists in combining fully clockless operation with direct conversion of the measured time interval. The lack of any reference clock makes the presented method potentially predisposed to low-power solutions. Furthermore, its circuit representation is extremely simple, thereby the ability to direct conversion of time intervals is not burdened by a significant amount of components. The method is intended to measure relatively long time intervals, i.e., hundreds of microseconds. Therefore, it is suitable for e.g., biomedical applications using time-mode signal processing. Full article

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9 pages, 4842 KiB

Open AccessCommunication

A Pressure-Based Multiphase Flowmeter: Proof of Concept

by Vijay Ramakrishnan and Muhammad Arsalan

Sensors 2023, 23(16), 7267; https://doi.org/10.3390/s23167267 - 19 Aug 2023

Cited by 2 | Viewed by 2086

Abstract

Multiphase flowmeters (MPFMs) measure the flow rates of oil, gas, and brine in a pipeline. MPFMs provide remote access to real-time well production data that are essential for efficient oil field operations. Most MPFMs are complex systems requiring frequent maintenance. An MPFM that [...] Read more.

Multiphase flowmeters (MPFMs) measure the flow rates of oil, gas, and brine in a pipeline. MPFMs provide remote access to real-time well production data that are essential for efficient oil field operations. Most MPFMs are complex systems requiring frequent maintenance. An MPFM that is operationally simple and accurate is highly sought after in the energy industry. This paper describes an MPFM that uses only pressure sensors to measure gas and liquid flow rates. The design is an integration of a previously developed densitometer with an innovative Venturi-type flowmeter. New computing models with strong analytical foundations were developed, aided by empirical correlations and machine-learning-based flow-regime identification. A prototype was experimentally validated in a multiphase flow loop over a wide range of field-like conditions. The accuracy of the MPFM was compared to that of other multiphase metering techniques from similar studies. The results point to a robust, practical MPFM. Full article

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15 pages, 8304 KiB

Open AccessArticle

Transmission Line Voltage Measurement Utilizing a Calibrated Suspension Grounding Voltage Sensor

by Rujin Huang, Wenbin Zhang, Junyu Zhu, Xiangqi Zou, Hetao Wu and Chunguang Suo

Sensors 2023, 23(16), 7161; https://doi.org/10.3390/s23167161 - 14 Aug 2023

Cited by 2 | Viewed by 1659

Abstract

The accurate voltage measurement of distribution networks is of great significance in power dispatching and fault diagnosis. Voltage sensors based on the spatial electric field effect do not require grounding, which provides the possibility for the distributed measurement of transmission line voltages. However, [...] Read more.

The accurate voltage measurement of distribution networks is of great significance in power dispatching and fault diagnosis. Voltage sensors based on the spatial electric field effect do not require grounding, which provides the possibility for the distributed measurement of transmission line voltages. However, the divider ratio of suspension grounding voltage sensors is affected by the height between the sensor and the ground, as well as the distance between the sensor and the telegraph pole. In this paper, a self-calibration method based on internal capacitance transformation is proposed to realize the on-line calibration of suspension grounding voltage sensors. The calibration is accomplished by switching different parameters in the conditioning circuit, and the calibration process does not require power failure or known input excitation. In addition, the impact of electric fields in the other two phases of three-phase transmission lines on measurement through simulation research is quantified in this paper. In order to reduce the impact of interference electric fields, an equipotential shielding structure is designed. The circuit topology and probe prototype have been developed and testing has been conducted in laboratory conditions; the experimental results show that the maximum relative error of voltage amplitude is 1.65%, and the phase relative error is 0.94%. The measurement accuracy is not limited by the height to ground or the distance to the telegraph pole. In addition, in the application of an equipotential shielding probe, the maximum deviation of measured voltage is 0.7% with and without interference electric fields. Full article

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15 pages, 4298 KiB

Open AccessArticle

Fusion Filters between the No Motion No Integration Technique and Kalman Filter in Noise Optimization on a 6DoF Drone for Orientation Tracking

by Minh Long Hoang, Marco Carratù, Vincenzo Paciello and Antonio Pietrosanto

Sensors 2023, 23(12), 5603; https://doi.org/10.3390/s23125603 - 15 Jun 2023

Cited by 3 | Viewed by 1884

Abstract

The paper works on the new combination between the No Motion No Integration filter (NMNI) and the Kalman Filter (KF) to optimize the conducted vibration for orientation angles during drone operation. The drone’s roll, pitch, and yaw with just accelerometer and gyroscope were [...] Read more.

The paper works on the new combination between the No Motion No Integration filter (NMNI) and the Kalman Filter (KF) to optimize the conducted vibration for orientation angles during drone operation. The drone’s roll, pitch, and yaw with just accelerometer and gyroscope were analyzed under the noise impact. A 6 Degree of Freedom (DoF) Parrot Mambo drone with Matlab/Simulink package was used to validate the advancements before and after fusing NMNI with KF. The drone propeller motors were controlled at a suitable speed level to keep the drone on the zero-inclination ground for angle error validation. The experiments show that KF alone successfully minimizes the variation for the inclination, but it still needs the NMNI support to enhance the performance in noise deduction, with the error only about 0.02°. In addition, the NMNI algorithm successfully prevents the yaw/heading from gyroscope drifting due to the zero-value integration during no rotation with the maximum error of 0.03°. Full article

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2022

Jump to: 2024, 2023, 2021, 2020

20 pages, 2448 KiB

Open AccessArticle

Operational State Recognition of a DC Motor Using Edge Artificial Intelligence

by Konstantinos Strantzalis, Fotios Gioulekas, Panagiotis Katsaros and Andreas Symeonidis

Sensors 2022, 22(24), 9658; https://doi.org/10.3390/s22249658 - 9 Dec 2022

Cited by 2 | Viewed by 2367

Abstract

Edge artificial intelligence (EDGE-AI) refers to the execution of artificial intelligence algorithms on hardware devices while processing sensor data/signals in order to extract information and identify patterns, without utilizing the cloud. In the field of predictive maintenance for industrial applications, EDGE-AI systems can [...] Read more.

Edge artificial intelligence (EDGE-AI) refers to the execution of artificial intelligence algorithms on hardware devices while processing sensor data/signals in order to extract information and identify patterns, without utilizing the cloud. In the field of predictive maintenance for industrial applications, EDGE-AI systems can provide operational state recognition for machines and production chains, almost in real time. This work presents two methodological approaches for the detection of the operational states of a DC motor, based on sound data. Initially, features were extracted using an audio dataset. Two different Convolutional Neural Network (CNN) models were trained for the particular classification problem. These two models are subject to post-training quantization and an appropriate conversion/compression in order to be deployed to microcontroller units (MCUs) through utilizing appropriate software tools. A real-time validation experiment was conducted, including the simulation of a custom stress test environment, to check the deployed models’ performance on the recognition of the engine’s operational states and the response time for the transition between the engine’s states. Finally, the two implementations were compared in terms of classification accuracy, latency, and resource utilization, leading to promising results. Full article

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17 pages, 5332 KiB

Open AccessArticle

High-Precision ADC Spectrum Testing under Non-Coherent Sampling Conditions

by Xiaofei Peng, Jie Li, Debiao Zhang, Chenjun Hu, Ning Sun and Jie Jiang

Sensors 2022, 22(21), 8170; https://doi.org/10.3390/s22218170 - 25 Oct 2022

Cited by 2 | Viewed by 2113

Abstract

Realizing coherent sampling is one of the major bottlenecks in high-precision ADC spectrum testing. In spectrum analysis, if coherent sampling is not implemented, spectral leakage will result, which in turn leads to inaccurate test results. In this paper, a combined four-parameter sine-curve-fitting algorithm [...] Read more.

Realizing coherent sampling is one of the major bottlenecks in high-precision ADC spectrum testing. In spectrum analysis, if coherent sampling is not implemented, spectral leakage will result, which in turn leads to inaccurate test results. In this paper, a combined four-parameter sine-curve-fitting algorithm is proposed incorporating non-coherent sampling, with the amplitude, initial phase, and frequency parameters of the sine wave being obtained by fitting. The corresponding coherent sine wave is then calculated and replaced according to the obtained sine wave to reconstruct the new test data, eliminating the requirement of coherent sampling. Numerous simulations demonstrated the functionality and robustness of the algorithm, which was then used to process and analyze the measured data of two commercial high-precision ADCs. The results show that our algorithm can achieve accurate testing of ADC parameters under relaxed test conditions, which verifies the effectiveness and superiority of the scheme. Full article

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20 pages, 6964 KiB

Open AccessArticle

Static Load Characteristics of Hydrostatic Journal Bearings: Measurements and Predictions

by Howon Yi, Hyunsung Jung, Kyuman Kim and Keun Ryu

Sensors 2022, 22(19), 7466; https://doi.org/10.3390/s22197466 - 1 Oct 2022

Cited by 10 | Viewed by 3071

Abstract

Hydrostatic bearings for liquid rocket engine turbopumps provide distinctive advantages, including high load capacity even with low viscosity cryogenic fluid and extending life span by minimizing friction and wear between rotor and bearing surfaces. Application of hydrostatic bearings into turbopumps demands a reliable [...] Read more.

Hydrostatic bearings for liquid rocket engine turbopumps provide distinctive advantages, including high load capacity even with low viscosity cryogenic fluid and extending life span by minimizing friction and wear between rotor and bearing surfaces. Application of hydrostatic bearings into turbopumps demands a reliable test database with well-quantified operating parameters and experimentally validated accurate performance predictive tools. The present paper shows the comprehensive experimental data and validation of predicted static load characteristics of hydrostatic journal bearings lubricated with air, water, and liquid nitrogen. Extensive experiments for static load characteristics of hydrostatic bearings are conducted using a turbopump-rotor-bearing system simulator while increasing supply pressure (P_s) into the test bearings. The test results demonstrate notable effects of the test fluids and their temperatures, as well as P_s, on the bearing performance. In general, the measured bearing flow rate, rotor displacement, and stiffness of the test bearings steadily increase with P_s. The static load bearing characteristics predictions considering flow turbulence and compressibility matched well with the experimental results. The work with independent test data and engineering computational programs will further the implementation of hydrostatic bearings in high-performance turbopump shaft systems with improved efficiency and enhanced reusability of liquid rocket engine sub-systems. Full article

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17 pages, 5690 KiB

Open AccessArticle

Analysis of Pre-Driver and Last-Stage Power—Ground-Induced Jitter at Different PVT Corners

by Malek Souilem, Rui Melicio, Wael Dghais, Hamdi Belgacem and Eduardo Rodrigues

Sensors 2022, 22(17), 6531; https://doi.org/10.3390/s22176531 - 30 Aug 2022

Viewed by 2115

Abstract

This paper presents the study of power/ground (P/G) supply-induced jitter (PGSIJ) on a cascaded inverter output buffer. The PGSIJ analysis covers the IO buffer transient simulation under P/G supply voltage variation at three process, voltage, and temperature (PVT) corners defined at different working [...] Read more.

This paper presents the study of power/ground (P/G) supply-induced jitter (PGSIJ) on a cascaded inverter output buffer. The PGSIJ analysis covers the IO buffer transient simulation under P/G supply voltage variation at three process, voltage, and temperature (PVT) corners defined at different working temperatures and distinct

P / G

DC supply voltages at the pre-driver (i.e.,

V_{D D}

/

V_{S S}

) and last stage (i.e.,

V_{D D Q} / V_{S S Q}

). Firstly, the induced jitter contributions by the pre-driver, as well as the last, stage are compared and studied. Secondly, the shared and decoupled P/G supply topologies are investigated. The outcomes of these simulation analyses with respect to worst case jitter corners are determined, while highlighting the importance of modeling the pre-driver circuit behavior to include the induced jitter in the input–output buffer information specification (IBIS)-like model. Accordingly, the measured PGSIJ depends on the corners to be analyzed and, therefore, the designer needs to explore the worst-case corner for the driver’s technology node and the most supply voltage noise affecting the jitter output for signal and power integrity (SiPI) simulations. Finally, the jitter transfer function sensitivity to the amplitude and frequency/phase variations of the separate and combined impacts of the pre-driver and last stage are explored, while discussing the superposition of the power supply induced jitter (PSIJ) induced by both the driver’s IO stages under small signal and large signal supply voltage variations. The linear superposition of the separate PSIJ effects by the pre-driver and last stage depends on the amplitude of the variation of the supply voltage that can drive the transistor to their nonlinear working regions. Full article

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10 pages, 2414 KiB

Open AccessCommunication

Measurement of Linear Springs’ Stiffness Factor Using Ultrasonic Sensing

by Zhongwei Zhang, Xiyan Zhang, Bohui Ma, Mengyao Ding, Bowen Zhu and Dezheng Tong

Sensors 2022, 22(15), 5878; https://doi.org/10.3390/s22155878 - 5 Aug 2022

Cited by 4 | Viewed by 1985

Abstract

We designed an ultrasonic testing instrument that consisted of a single-chip microcomputer module, a digital display module, and an ultrasonic sensor module, which conveniently eliminated the troubles faced by the traditional Jolly’s scale. For comparison purpose, three linear springs’ stiffness factors were measured [...] Read more.

We designed an ultrasonic testing instrument that consisted of a single-chip microcomputer module, a digital display module, and an ultrasonic sensor module, which conveniently eliminated the troubles faced by the traditional Jolly’s scale. For comparison purpose, three linear springs’ stiffness factors were measured by Jolly’s scale and by our ultrasonic testing instrument. We found that our instrument could more conveniently and in real time display the distance values between the ultrasonic ranging module and the horizontal bottom plate when loading different weights. By processing these distance data, we found that our instrument was more convenient for obtaining the linear springs’ stiffness factors and that the results were more accurate than those of Jolly’s scale. This study verified that our instrument can accurately realize the performance of Jolly’s scale under diverse temperatures and humidity levels with high data reliability and perfect stability. Full article

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33 pages, 5439 KiB

Open AccessArticle

A Further Theoretical Study of Capacitive Pressure Sensors Based on Thin Film Elastic Deflection and Parallel Plate Capacitor: Refined Closed-Form Solution and Numerical Calibration

by Ying Guo, Bo Li, Qi Zhang, Xiao-Ting He and Jun-Yi Sun

Sensors 2022, 22(8), 2848; https://doi.org/10.3390/s22082848 - 7 Apr 2022

Cited by 2 | Viewed by 2565

Abstract

The capacitive pressure sensor based on thin film elastic deflection and a parallel plate capacitor uses a non-conductive elastic annular thin film centrally connected to a conductive, rigid, flat, concentric-circular thin plate as a pressure sensing unit. On application of pressure, the non-conductive [...] Read more.

The capacitive pressure sensor based on thin film elastic deflection and a parallel plate capacitor uses a non-conductive elastic annular thin film centrally connected to a conductive, rigid, flat, concentric-circular thin plate as a pressure sensing unit. On application of pressure, the non-conductive thin film deflects elastically, which in turn moves the conductive thin plate (as a movable upper electrode plate of the parallel plate capacitor) towards the lower electrode plate, resulting in a change in the capacitance of the capacitor. Therefore, the applied pressure can be determined by measuring the capacitance change, based on the closed-form solution for the elastic behavior of the annular thin film under pressure. Such capacitive pressure sensors are more suitable for large-sized sensors such as those used for building-facade wind pressure measurements, etc. In this paper, a further theoretical study of such capacitive pressure sensors is presented. The newly presented, more refined closed-form solution can greatly reduce the output pressure error under the same input capacitance, in comparison with the previously presented closed-form solution. A numerical example of how to use the resulting closed-form solution to numerically calibrate input–output characteristics is given for the first time. The variation trend of pressure operation ranges and input–output characteristics with important parametric variations, which can be used for guiding the design of such capacitive pressure sensors, is investigated. Full article

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17 pages, 6046 KiB

Open AccessArticle

Development of an Accurate and Robust Air-Coupled Ultrasonic Time-of-Flight Measurement Technique

by Benjamin Bühling, Stefan Küttenbaum, Stefan Maack and Christoph Strangfeld

Sensors 2022, 22(6), 2135; https://doi.org/10.3390/s22062135 - 9 Mar 2022

Cited by 7 | Viewed by 4053

Abstract

Ultrasonic time-of-flight (ToF) measurements enable the non-destructive characterization of material parameters as well as the reconstruction of scatterers inside a specimen. The time-consuming and potentially damaging procedure of applying a liquid couplant between specimen and transducer can be avoided by using air-coupled ultrasound. [...] Read more.

Ultrasonic time-of-flight (ToF) measurements enable the non-destructive characterization of material parameters as well as the reconstruction of scatterers inside a specimen. The time-consuming and potentially damaging procedure of applying a liquid couplant between specimen and transducer can be avoided by using air-coupled ultrasound. However, to obtain accurate ToF results, the waveform and travel time of the acoustic signal through the air, which are influenced by the ambient conditions, need to be considered. The placement of microphones as signal receivers is restricted to locations where they do not affect the sound field. This study presents a novel method for in-air ranging and ToF determination that is non-invasive and robust to changing ambient conditions or waveform variations. The in-air travel time was determined by utilizing the azimuthal directivity of a laser Doppler vibrometer operated in refracto-vibrometry (RV) mode. The time of entry of the acoustic signal was determined using the autocorrelation of the RV signal. The same signal was further used as a reference for determining the ToF through the specimen in transmission mode via cross-correlation. The derived signal processing procedure was verified in experiments on a polyamide specimen. Here, a ranging accuracy of

< 0.1

mm and a transmission ToF accuracy of

0.3

μ

s were achieved. Thus, the proposed method enables fast and accurate non-invasive ToF measurements that do not require knowledge about transducer characteristics or ambient conditions. Full article

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30 pages, 9843 KiB

Open AccessArticle

Design of an Estimator Using the Artificial Neural Network Technique to Characterise the Braking of a Motor Vehicle

by María Garrosa, Ester Olmeda, Vicente Díaz and Mᵃ Fernanda Mendoza-Petit

Sensors 2022, 22(4), 1644; https://doi.org/10.3390/s22041644 - 19 Feb 2022

Cited by 2 | Viewed by 2568

Abstract

Automatic systems are increasingly being applied in the automotive industry to improve driving safety and passenger comfort, reduce traffic and increase energy efficiency. The objective of this work is focused on improving the automatic brake assistance systems of motor vehicles trying to imitate [...] Read more.

Automatic systems are increasingly being applied in the automotive industry to improve driving safety and passenger comfort, reduce traffic and increase energy efficiency. The objective of this work is focused on improving the automatic brake assistance systems of motor vehicles trying to imitate human behaviour but correcting possible human errors such as distractions, lack of visibility or time reaction. The proposed system can optimise the intensity of the braking according to the available distance to carry out the manoeuvre and the vehicle speed to be as less aggressive as possible, thus giving priority to the comfort of the driver. A series of tests are carried out in this work with a vehicle instrumented with sensors that provide real-time information about the braking system. The data obtained experimentally during the dynamic tests are used to design an estimator using the Artificial Neural Network (ANN) technique. This information makes it possible to characterise all braking situations based on the pressure of the brake circuit, the type of manoeuvre and the test speed. Thanks to this ANN, it is possible to estimate the requirements of the braking system in real driving situations and carry out the manoeuvres automatically. Experiments and simulations verified the proposed method for the estimation of braking pressure in real deceleration scenarios. Full article

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2021

Jump to: 2024, 2023, 2022, 2020

15 pages, 730 KiB

Open AccessArticle

Enabling Fine Sample Rate Settings in DSOs with Time-Interleaved ADCs

by Mauro D’Arco, Ettore Napoli, Efstratios Zacharelos, Leopoldo Angrisani and Antonio Giuseppe Maria Strollo

Sensors 2022, 22(1), 234; https://doi.org/10.3390/s22010234 - 29 Dec 2021

Viewed by 1754

Abstract

The time-base used by digital storage oscilloscopes allows limited selections of the sample rate, namely constrained to a few integer submultiples of the maximum sample rate. This limitation offers the advantage of simplifying the data transfer from the analog-to-digital converter to the acquisition [...] Read more.

The time-base used by digital storage oscilloscopes allows limited selections of the sample rate, namely constrained to a few integer submultiples of the maximum sample rate. This limitation offers the advantage of simplifying the data transfer from the analog-to-digital converter to the acquisition memory, and of assuring stability performances, expressed in terms of absolute jitter, that are independent of the chosen sample rate. On the counterpart, it prevents an optimal usage of the memory resources of the oscilloscope and compels to post processing operations in several applications. A time-base that allows selecting the sample rate with very fine frequency resolution, in particular as a rational submultiple of the maximum rate, is proposed. The proposal addresses the oscilloscopes with time-interleaved converters, that require a dedicated and multifaceted approach with respect to architectures where a single monolithic converter is in charge of signal digitization. The proposed time-base allows selecting with fine frequency resolution sample rate values up to 200 GHz and beyond, still assuring jitter performances independent of the sample rate selection. Full article

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16 pages, 3116 KiB

Open AccessArticle

The Use of Smartphone Photogrammetry to Digitise Transtibial Sockets: Optimisation of Method and Quantitative Evaluation of Suitability

by Sean Cullen, Ruth Mackay, Amir Mohagheghi and Xinli Du

Sensors 2021, 21(24), 8405; https://doi.org/10.3390/s21248405 - 16 Dec 2021

Cited by 12 | Viewed by 3517

Abstract

The fit of a lower limb prosthetic socket is critical for user comfort and the quality of life of lower limb amputees. Sockets are conventionally produced using hand-crafted patient-based casting techniques. Modern digital techniques offer a host of advantages to the process and [...] Read more.

The fit of a lower limb prosthetic socket is critical for user comfort and the quality of life of lower limb amputees. Sockets are conventionally produced using hand-crafted patient-based casting techniques. Modern digital techniques offer a host of advantages to the process and ultimately lead to improving the lives of amputees. However, commercially available scanning equipment required is often expensive and proprietary. Smartphone photogrammetry could offer a low cost alternative, but there is no widely accepted imaging technique for prosthetic socket digitisation. Therefore, this paper aims to determine an optimal imaging technique for whole socket photogrammetry and evaluate the resultant scan measurement accuracy. A 3D printed transtibial socket was produced to create digital and physical twins, as reference models. The printed socket was photographed from 360 positions and simplified genetic algorithms were used to design a series of experiments, whereby a collection of photos were processed using Autodesk ReCap. The most fit technique was used to assess accuracy. The accuracy of the socket wall volume, surface area and height were 61.63%, 99.61% and 99.90%, respectively, when compared to the digital reference model. The scanned model had a wall thickness ranging from 2.075 mm at the top to 7.758 mm towards the base of the socket, compared to a consistent thickness of 2.025 mm in the control model. The technique selected did not show sufficient accuracy for clinical application due to the degradation of accuracy nearer to the base of the socket interior. However, using an internal wall thickness estimation, scans may be of sufficient accuracy for clinical use; assuming a uniform wall thickness. Full article

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13 pages, 3087 KiB

Open AccessArticle

Systematization and Comparison of the Binary Successive Approximation Variants

by Konrad Jurasz, Dariusz Kościelnik, Jakub Szyduczyński and Marek Miśkowicz

Sensors 2021, 21(24), 8267; https://doi.org/10.3390/s21248267 - 10 Dec 2021

Cited by 1 | Viewed by 2555

Abstract

This paper presents a systematization and a comparison of the binary successive approximation (SA) variants. Three different variants are distinguished and all of them are applied in the analog-to-digital conversion. Regardless of an analog-to-digital converter circuit solution, the adoption of the specific SA [...] Read more.

This paper presents a systematization and a comparison of the binary successive approximation (SA) variants. Three different variants are distinguished and all of them are applied in the analog-to-digital conversion. Regardless of an analog-to-digital converter circuit solution, the adoption of the specific SA variant imposes a particular character of the conversion process and related parameters. One of them is the ability to direct conversion of non-removeable physical quantities such as time intervals. Referencing to this aspect a general systematization of the variants and a name for each of them is proposed. In addition, the article raises the issues related to the complexity of implementation and energy consumption for each of the discussed binary SA variants. Full article

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11 pages, 1733 KiB

Open AccessArticle

A Quality Control Check to Ensure Comparability of Stereophotogrammetric Data between Sessions and Systems

by Kirsty Scott, Tecla Bonci, Lisa Alcock, Ellen Buckley, Clint Hansen, Eran Gazit, Lars Schwickert, Andrea Cereatti, Claudia Mazzà and on behalf of the Mobilise-D Consortium

Sensors 2021, 21(24), 8223; https://doi.org/10.3390/s21248223 - 9 Dec 2021

Cited by 3 | Viewed by 3528

Abstract

Optoelectronic stereophotogrammetric (SP) systems are widely used in human movement research for clinical diagnostics, interventional applications, and as a reference system for validating alternative technologies. Regardless of the application, SP systems exhibit different random and systematic errors depending on camera specifications, system setup [...] Read more.

Optoelectronic stereophotogrammetric (SP) systems are widely used in human movement research for clinical diagnostics, interventional applications, and as a reference system for validating alternative technologies. Regardless of the application, SP systems exhibit different random and systematic errors depending on camera specifications, system setup and laboratory environment, which hinders comparing SP data between sessions and across different systems. While many methods have been proposed to quantify and report the errors of SP systems, they are rarely utilized due to their complexity and need for additional equipment. In response, an easy-to-use quality control (QC) check has been designed that can be completed immediately prior to a data collection. This QC check requires minimal training for the operator and no additional equipment. In addition, a custom graphical user interface ensures automatic processing of the errors in an easy-to-read format for immediate interpretation. On initial deployment in a multicentric study, the check (i) proved to be feasible to perform in a short timeframe with minimal burden to the operator, and (ii) quantified the level of random and systematic errors between sessions and systems, ensuring comparability of data in a variety of protocol setups, including repeated measures, longitudinal studies and multicentric studies. Full article

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9 pages, 1919 KiB

Open AccessCommunication

Soft and Hard Iron Compensation for the Compasses of an Operational Towed Hydrophone Array without Sensor Motion by a Helmholtz Coil

by Tommaso Lapucci, Luigi Troiano, Carlo Carobbi and Lorenzo Capineri

Sensors 2021, 21(23), 8104; https://doi.org/10.3390/s21238104 - 3 Dec 2021

Cited by 1 | Viewed by 2719

Abstract

Usually, towed hydrophone arrays are instrumented with a set of compasses. Data from these sensors are utilized while beamforming the acoustic signal for target bearing estimation. However, elements of the hydrophone array mounted in the neighborhood of a compass can affect the Earth’s [...] Read more.

Usually, towed hydrophone arrays are instrumented with a set of compasses. Data from these sensors are utilized while beamforming the acoustic signal for target bearing estimation. However, elements of the hydrophone array mounted in the neighborhood of a compass can affect the Earth’s magnetic field detection. The effects depend upon the materials and magnetic environment present in the vicinity of the platform hosting the compass. If the disturbances are constant in time, they can be compensated for by means of a magnetic calibration procedure. This process is commonly known as soft and hard iron compensation. In this paper, a solution is presented for carrying out the magnetic calibration of a COTS (Commercial Off the Shelf) digital compass without sensor motion. This approach is particularly suited in applications where a physical rotation of the platform that hosts the sensor is unfeasible. In our case, the platform consists in an assembled and operational towed hydrophone array. A standard calibration process relies on physical rotation of the platform and thus on the use of the geomagnetic field as a reference during the compensation. As a variation on this approach, we generate an artificial reference magnetic field to simulate the impractical physical rotation. We obtain this by using a tri-axial Helmholtz coil, which enables programmability of the reference magnetic field and assures the required field uniformity. In our work, the simulated geomagnetic field is characterized in terms of its uncertainty. The analysis indicates that our method and experimental set-up represent a suitably accurate approach for the soft and hard iron compensation of the compasses equipped in the hydrophone array under test. Full article

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14 pages, 3882 KiB

Open AccessArticle

Environmental Monitoring of the Littoral Zone of Lake Baikal Using a Network of Automatic Hydro-Meteorological Stations: Development and Trial Run

by Mikhail Makarov, Ilya Aslamov and Ruslan Gnatovsky

Sensors 2021, 21(22), 7659; https://doi.org/10.3390/s21227659 - 18 Nov 2021

Cited by 3 | Viewed by 3076

Abstract

An automatic hydro-meteorological station (AHMS) was designed to monitor the littoral zone of Lake Baikal in areas with high anthropogenic pressure. The developed AHMS was installed near the Bolshiye Koty settlement (southern basin). This AHMS is the first experience focused on obtaining the [...] Read more.

An automatic hydro-meteorological station (AHMS) was designed to monitor the littoral zone of Lake Baikal in areas with high anthropogenic pressure. The developed AHMS was installed near the Bolshiye Koty settlement (southern basin). This AHMS is the first experience focused on obtaining the necessary competencies for the development of a monitoring network of the Baikal natural territory. To increase the flexibility of adjustment and repeatability, we developed AHMS as a low-cost modular system. AHMS is equipped with a weather station and sensors measuring water temperature, pH, dissolved oxygen, redox potential, conductivity, chlorophyll-a, and turbidity. This article describes the main AHMS functions (hardware and software) and measures taken to ensure data quality control. We present the results of the first two periods of its operation. The data acquired during this periods have demonstrated that, to obtain accurate measurements and to detect and correct errors that were mainly due to biofouling of the sensors and calibration bias, a correlation between AHMS and laboratory studies is necessary for parameters such as pH and chlorophyll-a. The gained experience should become the basis for the further development of the monitoring network of the Baikal natural territory. Full article

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15 pages, 2885 KiB

Open AccessArticle

Effect of Corneal Tilt on the Determination of Asphericity

by Alejandra Consejo, Arwa Fathy, Bernardo T. Lopes, Renato Ambrósio, Jr. and Ahmed Abass

Sensors 2021, 21(22), 7636; https://doi.org/10.3390/s21227636 - 17 Nov 2021

Cited by 8 | Viewed by 2622

Abstract

Purpose: To quantify the effect of levelling the corneal surface around the optical axis on the calculated values of corneal asphericity when conic and biconic models are used to fit the anterior corneal surface. Methods: This cross-sectional study starts with a mathematical simulation [...] Read more.

Purpose: To quantify the effect of levelling the corneal surface around the optical axis on the calculated values of corneal asphericity when conic and biconic models are used to fit the anterior corneal surface. Methods: This cross-sectional study starts with a mathematical simulation proving the concept of the effect that the eye’s tilt has on the corneal asphericity calculation. Spherical, conic and biconic models are considered and compared. Further, corneal asphericity is analysed in the eyes of 177 healthy participants aged 35.4 ± 15.2. The optical axis was determined using an optimization procedure via the Levenberg–Marquardt nonlinear least-squares algorithm, before fitting the corneal surface to spherical, conic and biconic models. The influence of pupil size (aperture radii of 1.5, 3.0, 4.0 and 5.0 mm) on corneal radius and asphericity was also analysed. Results: In computer simulations, eye tilt caused an increase in the apical radii of the surface with the increase of the tilt angle in both positive and negative directions and aperture radii in all models. Fitting the cornea to spherical models did not show a significant difference between the raw-measured corneal surfaces and the levelled surfaces for right and left eyes. When the conic models were fitted to the cornea, changes in the radii of the cornea among the raw-measured corneal surfaces’ data and levelled data were not significant; however, significant differences were recorded in the asphericity of the anterior surfaces at radii of aperture 1.5 mm (p < 0.01). With the biconic model, the posterior surfaces recorded significant asphericity differences at aperture radii of 1.5 mm, 3 mm, 4 mm and 5 mm (p = 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively) in the nasal temporal direction of right eyes and left eyes (p < 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively). In the superior–inferior direction, significant changes were only noticed at aperture radii of 1.5 mm for both right and left eyes (p = 0.05, p < 0.01). Conclusions: Estimation of human corneal asphericity from topography or tomography data using conic and biconic models of corneas are affected by eyes’ natural tilt. In contrast, the apical radii of the cornea are less affected. Using corneal asphericity in certain applications such as fitting contact lenses, corneal implant design, planning for refractive surgery and mathematical modelling when a geometrical centre of the eye is needed should be implemented with caution. Full article

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18 pages, 7316 KiB

Open AccessArticle

Interchannel Interference and Mitigation in Distributed MIMO RF Sensing

by Sahil Waqar and Matthias Pätzold

Sensors 2021, 21(22), 7496; https://doi.org/10.3390/s21227496 - 11 Nov 2021

Cited by 6 | Viewed by 3028

Abstract

In this paper, we analyze and mitigate the cross-channel interference, which is found in multiple-input multiple-output (MIMO) radio frequency (RF) sensing systems. For a millimeter wave (mm-Wave) MIMO system, we present a geometrical three-dimensional (3D) channel model to simulate the time-variant (TV) trajectories [...] Read more.

In this paper, we analyze and mitigate the cross-channel interference, which is found in multiple-input multiple-output (MIMO) radio frequency (RF) sensing systems. For a millimeter wave (mm-Wave) MIMO system, we present a geometrical three-dimensional (3D) channel model to simulate the time-variant (TV) trajectories of a moving scatterer. We collected RF data using a state-of-the-art radar known as Ancortek SDR-KIT 2400T2R4, which is a frequency-modulated continuous wave (FMCW) MIMO radar system operating in the K-band. The Ancortek radar is currently the only K-band MIMO commercial radar system that offers customized antenna configurations. It is shown that this radar system encounters the problem of interference between the various subchannels. We propose an optimal approach to mitigate the problem of cross-channel interference by inducing a propagation delay in one of the channels and apply range gating. The measurement results prove the effectiveness of the proposed approach by demonstrating a complete elimination of the interference problem. The application of the proposed solution on Ancortek’s SDR-KIT 2400T2R4 allows resolving all subchannel links in a distributed MIMO configuration. This allows using MIMO RF sensing techniques to track a moving scatterer (target) regardless of its direction of motion. Full article

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21 pages, 2210 KiB

Open AccessReview

Virtual Reality-Based Therapy Improves Fatigue, Impact, and Quality of Life in Patients with Multiple Sclerosis. A Systematic Review with a Meta-Analysis

by Irene Cortés-Pérez, Marcelina Sánchez-Alcalá, Francisco Antonio Nieto-Escámez, Yolanda Castellote-Caballero, Esteban Obrero-Gaitán and María Catalina Osuna-Pérez

Sensors 2021, 21(21), 7389; https://doi.org/10.3390/s21217389 - 6 Nov 2021

Cited by 37 | Viewed by 7235

Abstract

Patients with multiple sclerosis (PwMS) have a high level of fatigue and a reduced quality of life (QoL) due to the impact of multiple sclerosis (MS). Virtual reality-based therapy (VRBT) is being used to reduce disability in PwMS. The aim of this study [...] Read more.

Patients with multiple sclerosis (PwMS) have a high level of fatigue and a reduced quality of life (QoL) due to the impact of multiple sclerosis (MS). Virtual reality-based therapy (VRBT) is being used to reduce disability in PwMS. The aim of this study was to assess the effect of VRBT on fatigue, the impact of MS, and QoL in PwMS. Methods: A systematic review with meta-analysis was conducted through a bibliographic search on PubMed, Scopus, Web of Science, and PEDro up to April 2021. We included randomized controlled trials (RCTs) with PwMS that received VRBT in comparison to conventional therapy (CT) including physiotherapy, balance and strength exercises, and stretching or physical activity, among others; or in comparison to simple observation; in order to assess fatigue, MS-impact, and QoL. The effect size was calculated using Cohen’s standardized mean difference with a 95% confidence interval (95% CI). Results: Twelve RCTs that provided data from 606 PwMS (42.83 ± 6.86 years old and 70% women) were included. The methodological quality mean, according to the PEDro Scale, was 5.83 ± 0.83 points. Our global findings showed that VRBT is effective at reducing fatigue (SMD −0.33; 95% CI −0.61, −0.06), lowering the impact of MS (SMD −0.3; 95% CI −0.55, −0.04), and increasing overall QoL (0.5; 95% CI 0.23, 0.76). Subgroup analysis showed the following: (1) VRBT is better than CT at reducing fatigue (SMD −0.4; 95% CI −0.7, −0.11), as well as in improving the mental dimension of QoL (SMD 0.51; 95% CI 0.02, 1); (2) VRBT is better than simple observation at reducing the impact of MS (SMD −0.61; 95% CI −0.97, −0.23) and increasing overall QoL (SMD 0.79; 95% CI 0.3, 1.28); and (3) when combined with CT, VRBT is more effective than CT in improving the global (SMD 0.6, 95% CI 0.13, 1.07), physical (SMD 0.87; 95% CI 0.3, 1.43), and mental dimensions (SMD 0.6; 95% CI 0.08, 1.11) of QoL. Conclusion: VRBT is effective at reducing fatigue and MS impact and improving QoL in PwMS. Full article

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18 pages, 2056 KiB

Open AccessArticle

Digital Impedance Emulator for Battery Measurement System Calibration

by Francesco Santoni, Alessio De Angelis, Antonio Moschitta and Paolo Carbone

Sensors 2021, 21(21), 7377; https://doi.org/10.3390/s21217377 - 6 Nov 2021

Cited by 9 | Viewed by 3132

Abstract

Meaningful information on the internal state of a battery can be derived by measuring its impedance. Accordingly, battery management systems based on electrochemical impedance spectroscopy are now recognized as a feasible solutions for online battery control and diagnostic. Since the impedance of a [...] Read more.

Meaningful information on the internal state of a battery can be derived by measuring its impedance. Accordingly, battery management systems based on electrochemical impedance spectroscopy are now recognized as a feasible solutions for online battery control and diagnostic. Since the impedance of a battery is always changing along with its state of charge and aging effects, it is important to have a stable impedance reference in order to calibrate and test a battery management system. In this work we propose a programmable impedance emulator that in principle could be used for the calibration of any battery management system based on electrochemical impedance spectroscopy. A digital finite-impulse-response filter is implemented, whose frequency response is programmed so as to reproduce exactly the impedance of a real battery in the frequency domain. The whole design process of the filter is presented in detail. An analytical expression for the impedance of real battery in the frequency domain is derived from an equivalent circuit model. The model is validated both through numerical simulations and experimental tests. In particular, the filter is implemented on a low-cost microcontroller unit, and the emulated impedance is measured by means of a custom-made electrochemical impedance spectroscopy measuring system, and verified by using standard commercial bench instruments. Results on this prototype show the feasibility of using the proposed emulator as a fully controllable and low-cost reference for calibrating battery impedance measurement systems. Full article

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17 pages, 489 KiB

Open AccessArticle

Comparison of Mathematical Methods for Compensating a Current Signal under Current Transformers Saturation Conditions

by Ismoil Odinaev, Aminjon Gulakhmadov, Pavel Murzin, Alexander Tavlintsev, Sergey Semenenko, Evgenii Kokorin, Murodbek Safaraliev and Xi Chen

Sensors 2021, 21(21), 7273; https://doi.org/10.3390/s21217273 - 1 Nov 2021

Cited by 4 | Viewed by 2180

Abstract

Current measurements from electromagnetic current transformers are essential for the construction of secondary circuit systems, including for protection systems. Magnetic core of these transformers are at risk of saturation, as a result of which maloperation of protection algorithms can possibly occur. The paper [...] Read more.

Current measurements from electromagnetic current transformers are essential for the construction of secondary circuit systems, including for protection systems. Magnetic core of these transformers are at risk of saturation, as a result of which maloperation of protection algorithms can possibly occur. The paper considers methods for recovering a current signal in the saturation mode of current transformers. The advantages and disadvantages of methods for detecting the occurrence of current transformers core saturation are described. A comparative analysis of mathematical methods for recovering a current signal is given, their approbation was carried out, and the most promising of them was revealed. The stability and sensitivity of recovery methods were tested by adding white noise to the measured signal and taking into account the initial flux density (remanent magnetization) in the current transformers core. Their comparison is given on the basis of angular, magnitude, and total errors at a given simulation interval. Full article

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18 pages, 13226 KiB

Open AccessArticle

Neural-Network Based Modeling of I/O Buffer Predriver under Power/Ground Supply Voltage Variations

by Malek Souilem, Jai Narayan Tripathi, Rui Melicio, Wael Dghais, Hamdi Belgacem and Eduardo M. G. Rodrigues

Sensors 2021, 21(18), 6074; https://doi.org/10.3390/s21186074 - 10 Sep 2021

Cited by 2 | Viewed by 2306

Abstract

This paper presents a neural-network based nonlinear behavioral modelling of I/O buffer that accounts for timing distortion introduced by nonlinear switching behavior of the predriver electrical circuit under power and ground supply voltage (PGSV) variations. Model structure and I/O device characterization along with [...] Read more.

This paper presents a neural-network based nonlinear behavioral modelling of I/O buffer that accounts for timing distortion introduced by nonlinear switching behavior of the predriver electrical circuit under power and ground supply voltage (PGSV) variations. Model structure and I/O device characterization along with extraction procedure were described. The last stage of the I/O buffer is modelled as nonlinear current-voltage (I-V) and capacitance voltage (C-V) functions capturing the nonlinear dynamic impedances of the pull-up and pull-down transistors. The mathematical model structure of the predriver was derived from the analysis of the large-signal electrical circuit switching behavior. Accordingly, a generic and surrogate multilayer neural network (NN) structure was considered in this work. Timing series data which reflects the nonlinear switching behavior of the multistage predriver’s circuit PGSV variations, were used to train the NN model. The proposed model was implemented in the time-domain solver and validated against the reference transistor level (TL) model and the state-of-the-art input-output buffer information specification (IBIS) behavioral model under different scenarios. The analysis of jitter was performed using the eye diagrams plotted at different metrics values. Full article

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17 pages, 4099 KiB

Open AccessArticle

A Temperature-Compensation Technique for Improving Resolver Accuracy

by Wandee Petchmaneelumka, Vanchai Riewruja, Kanoknuch Songsuwankit and Apinai Rerkratn

Sensors 2021, 21(18), 6069; https://doi.org/10.3390/s21186069 - 10 Sep 2021

Cited by 2 | Viewed by 2477

Abstract

Variation in the ambient temperature deteriorates the accuracy of a resolver. In this paper, a temperature-compensation technique is introduced to improve resolver accuracy. The ambient temperature causes deviations in the resolver signal; therefore, the disturbed signal is investigated through the change in current [...] Read more.

Variation in the ambient temperature deteriorates the accuracy of a resolver. In this paper, a temperature-compensation technique is introduced to improve resolver accuracy. The ambient temperature causes deviations in the resolver signal; therefore, the disturbed signal is investigated through the change in current in the primary winding of the resolver. For the proposed technique, the primary winding of the resolver is driven by a class-AB output stage of an operational amplifier (opamp), where the primary winding current forms part of the supply current of the opamp. The opamp supply-current sensing technique is used to extract the primary winding current. The error of the resolver signal due to temperature variations is directly evaluated from the supply current of the opamp. Therefore, the proposed technique does not require a temperature-sensitive device. Using the proposed technique, the error of the resolver signal when the ambient temperature increases to 70 °C can be minimized from 1.463% without temperature compensation to 0.017% with temperature compensation. The performance of the proposed technique is discussed in detail and is confirmed by experimental implementation using commercial devices. The results show that the proposed circuit can compensate for wide variations in ambient temperature. Full article

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14 pages, 5007 KiB

Open AccessArticle

The Fundamental Approach of the Digital Twin Application in Railway Turnouts with Innovative Monitoring of Weather Conditions

by Arkadiusz Kampczyk and Katarzyna Dybeł

Sensors 2021, 21(17), 5757; https://doi.org/10.3390/s21175757 - 26 Aug 2021

Cited by 52 | Viewed by 5691

Abstract

Improving railway safety depends heavily on the reliability of railway turnouts. The realization of effective, reliable and continuous observations for the spatial analysis and evaluation of the technical condition of railway turnouts is one of the factors affecting safety in railway traffic. The [...] Read more.

Improving railway safety depends heavily on the reliability of railway turnouts. The realization of effective, reliable and continuous observations for the spatial analysis and evaluation of the technical condition of railway turnouts is one of the factors affecting safety in railway traffic. The mode and scope of monitoring changes in geometric parameters of railway turnouts with associated indicators needs improvement. The application of digital twins to railway turnouts requires the inclusion of fundamental data indicating their condition along with innovative monitoring of weather conditions. This paper presents an innovative solution for monitoring the status of temperature and other atmospheric conditions. A UbiBot WS1 WIFI wireless temperature logger was used, with an external DS18B20 temperature sensor integrated into an S49 (49E1)-type rail as T_szyn WS1 WIFI. Measurements were made between January and May (winter/spring) at fixed time intervals and at the same measurement point. The aim of the research is to present elements of a fundamental approach of applying digital twins to railway turnouts requiring the consideration and demonstration of rail temperature conditions as a component in the data acquisition of railway turnout condition data and other constituent atmospheric conditions through an innovative solution. The research showed that the presented innovative solution is an effective support for the application of digital twins to railway turnouts and ongoing surveying and diagnostic work of other elements of rail transport infrastructure. The applicability of the T_gCWRII second temperature difference indicator in the monitoring of railway turnouts was also confirmed. Full article

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17 pages, 8657 KiB

Open AccessArticle

Star Sensor Denoising Algorithm Based on Edge Protection

by Kaili Lu, Enhai Liu, Rujin Zhao, Hui Zhang and Hong Tian

Sensors 2021, 21(16), 5255; https://doi.org/10.3390/s21165255 - 4 Aug 2021

Cited by 6 | Viewed by 2601

Abstract

Single-pixel noise commonly appearing in a star sensor can cause an unexpected error in centroid extraction. To overcome this problem, this paper proposes a star image denoising algorithm, named Improved Gaussian Side Window Filtering (IGSWF). Firstly, the IGSWF algorithm uses four special triangular [...] Read more.

Single-pixel noise commonly appearing in a star sensor can cause an unexpected error in centroid extraction. To overcome this problem, this paper proposes a star image denoising algorithm, named Improved Gaussian Side Window Filtering (IGSWF). Firstly, the IGSWF algorithm uses four special triangular Gaussian subtemplates for edge protection. Secondly, it exploits a reconstruction function based on the characteristic of stars and noise. The proposed IGSWF algorithm was successfully verified through simulations and evaluated in a star sensor. The experimental results indicated that the IGSWF algorithm performed better in preserving the shape of stars and eliminating the single-pixel noise and the centroid estimation error (CEE) value after using the IGSWF algorithm was eight times smaller than the original value, six times smaller than that after traditional window filtering, and three times smaller than that after the side window filtering. Full article

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23 pages, 4316 KiB

Open AccessArticle

Geometric Measurements on a CNC Machining Device as an Element of Closed Door Technology

by Grzegorz Bomba, Artur Ornat and Piotr Gierlak

Sensors 2021, 21(14), 4852; https://doi.org/10.3390/s21144852 - 16 Jul 2021

Cited by 5 | Viewed by 4840

Abstract

The article discusses the quality testing of a measuring system consisting of a CNC machine with measuring probes. The research was conducted in a broader context regarding the implementation of the closed door technology, i.e., production without human intervention, in an aviation plant [...] Read more.

The article discusses the quality testing of a measuring system consisting of a CNC machine with measuring probes. The research was conducted in a broader context regarding the implementation of the closed door technology, i.e., production without human intervention, in an aviation plant manufacturing aircraft gearbox systems. This technology may involve automated measuring operations performed in machining centers, and not in measuring laboratories, provided that the quality of the measurements is appropriate. The aim of the study was to investigate whether the CNC machining device can be used to measure the geometric features of aircraft gearbox housing. For this purpose, measurement experiments were carried out with the use of three different probes. Measurements were carried out using four sequences of increasing complexity, so that, after error analysis, it was possible to find the causes of possible irregularities. A reference ring with known dimensions and position in the working space of the machine was used for the measurements performed as part of the assessment of the measurement system. The quality of the measurements was evaluated with the use of repeatability and reproducibility testing and statistical process control. The analysis results showed that the tested measurement system ensures adequate accuracy and repeatability, and the measurement process is characterized with adequate efficiency in relation to the manufacturing tolerance of the components produced using the machine. Thus, it was proven that the measurement process can be carried out on a machining device, which enables its integration into the closed door technology. Full article

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13 pages, 1760 KiB

Open AccessArticle

A Two-Channel DFT Spectrum Analyzer for Fluctuation Enhanced Sensing Based on a PC Audio Board

by Emanuele Cardillo, Graziella Scandurra, Gino Giusi and Carmine Ciofi

Sensors 2021, 21(13), 4307; https://doi.org/10.3390/s21134307 - 24 Jun 2021

Cited by 2 | Viewed by 2489

Abstract

The main requirement for using the Fluctuation Enhanced Sensing technique is the ability to perform low-frequency noise measurements. The portability of the measurement system is also a quite desirable feature not limited to this specific application. In this paper, an approach for the [...] Read more.

The main requirement for using the Fluctuation Enhanced Sensing technique is the ability to perform low-frequency noise measurements. The portability of the measurement system is also a quite desirable feature not limited to this specific application. In this paper, an approach for the realization of a dual channel spectrum analyzer that is capable of exploring frequencies down to DC, although based on a USB sound card, is proposed. The lower frequency range of the input signals, which is outside the frequency range of the sound board, is upconverted to higher frequencies by means of a very simple modulation board. Then, the entire spectrum is reconstructed numerically by proper elaboration. With the exception of the modulation board, the approach we propose does not rely on any specific hardware. Thanks to the efficiency of the spectra estimation and reconstruction software, which is based on a public domain library, the system can be built on a low-cost computer single board computer, such as the Raspberry PI3. Moreover, when equipped with an optical TCP/IP link, it behaves as a compact spectrum analyzer that along with the device under test can be placed into a shielded environment, thus being isolated from external electromagnetic interferences. Full article

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13 pages, 1632 KiB

Open AccessArticle

Multi-Location External Workload Profile in Women’s Basketball Players. A Case Study at the Semiprofessional-Level

by Carlos D. Gómez-Carmona, David Mancha-Triguero, José Pino-Ortega and Sergio J. Ibáñez

Sensors 2021, 21(13), 4277; https://doi.org/10.3390/s21134277 - 22 Jun 2021

Cited by 5 | Viewed by 2976

Abstract

The external workload measured in one anatomical location does not determine the total load supported by the human body. Therefore, the purpose of the present study was to characterize the multi-location external workload through PlayerLoad_RT of 13 semi-professional women’s basketball players, as [...] Read more.

The external workload measured in one anatomical location does not determine the total load supported by the human body. Therefore, the purpose of the present study was to characterize the multi-location external workload through PlayerLoad_RT of 13 semi-professional women’s basketball players, as well as to analyze differences among anatomical locations (inter-scapulae line, lumbar region, 2× knee, 2× ankle) and laterality (left vs. right) during five tests that represent the most common movements in basketball—(a) linear locomotion, 30-15 IFT; (b) acceleration and deceleration, 16.25-m RSA (c) curvilinear locomotion, 6.75-m arc (d) jump, Abalakov test (e) small-sided game, 10’ 3 vs. 3 10 × 15-m. Statistical analysis was composed of a repeated-measures t-test and eta partial squared effect size. Regarding laterality, differences were found only in curvilinear locomotion, with a higher workload in the outer leg (p < 0.01; η_p² = 0.33–0.63). In the vertical profile, differences among anatomical locations were found in all tests (p < 0.01; η_p² = 0.56–0.98). The nearer location to ground contact showed higher values except between the scapulae and lumbar region during jumps (p = 0.83; η_p² = 0.00). In conclusion, the multi-location assessment of external workload through a previously validated test battery will make it possible to understand the individual effect of external workload in each anatomical location that depends on the type of locomotion. These results should be considered when designing specific strategies for training and injury prevention. Full article

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16 pages, 1758 KiB

Open AccessArticle

Evaluating Pedometer Algorithms on Semi-Regular and Unstructured Gaits

by Ryan Mattfeld, Elliot Jesch and Adam Hoover

Sensors 2021, 21(13), 4260; https://doi.org/10.3390/s21134260 - 22 Jun 2021

Cited by 7 | Viewed by 4189

Abstract

Pedometers are popular for counting steps as a daily measure of physical activity, however, errors as high as 96% have been reported in previous work. Many reasons for pedometer error have been studied, including walking speed, sensor position on the body and pedometer [...] Read more.

Pedometers are popular for counting steps as a daily measure of physical activity, however, errors as high as 96% have been reported in previous work. Many reasons for pedometer error have been studied, including walking speed, sensor position on the body and pedometer algorithm, demonstrating some differences in error. However, we hypothesize that the largest source of error may be due to differences in the regularity of gait during different activities. During some activities, gait tends to be regular and the repetitiveness of individual steps makes them easy to identify in an accelerometer signal. During other activities of everyday life, gait is frequently semi-regular or unstructured, which we hypothesize makes it difficult to identify and count individual steps. In this work, we test this hypothesis by evaluating the three most common types of pedometer algorithm on a new data set that varies the regularity of gait. A total of 30 participants were video recorded performing three different activities: walking a path (regular gait), conducting a within-building activity (semi-regular gait), and conducting a within-room activity (unstructured gait). Participants were instrumented with accelerometers on the wrist, hip and ankle. Collectively, 60,805 steps were manually annotated for ground truth using synchronized video. The main contribution of this paper is to evaluate pedometer algorithms when the consistency of gait changes to simulate everyday life activities other than exercise. In our study, we found that semi-regular and unstructured gaits resulted in 5–466% error. This demonstrates the need to evaluate pedometer algorithms on activities that vary the regularity of gait. Our dataset is publicly available with links provided in the introduction and Data Availability Statement. Full article

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21 pages, 5699 KiB

Open AccessArticle

Sensor Integrated Load-Bearing Structures: Measuring Axis Extension with DIC-Based Transducers

by Nassr Al-Baradoni and Peter Groche

Sensors 2021, 21(12), 4104; https://doi.org/10.3390/s21124104 - 15 Jun 2021

Cited by 8 | Viewed by 3448

Abstract

In this paper we present a novel, cost-effective camera-based multi-axis force/torque sensor concept for integration into metallic load-bearing structures. A two-part pattern consisting of a directly incident and mirrored light beam is projected onto the imaging sensor surface. This allows the capturing of [...] Read more.

In this paper we present a novel, cost-effective camera-based multi-axis force/torque sensor concept for integration into metallic load-bearing structures. A two-part pattern consisting of a directly incident and mirrored light beam is projected onto the imaging sensor surface. This allows the capturing of 3D displacements, occurring due to structure deformation under load in a single image. The displacement of defined features in size and position can be accurately analyzed and determined through digital image correlation (DIC). Validation on a prototype shows good accuracy of the measurement and a unique identification of all in- and out-of-plane displacement components under multiaxial load. Measurements show a maximum deviation related to the maximum measured values between 2.5% and 4.8% for uniaxial loads (

F_{x}, F_{y}, F_{z}, M_{z})

and between 2.5% and 10.43% for combined bending, torsion and axial load. In the course of the investigations, the measurement inaccuracy was partly attributed to the joint used between the sensor parts and the structure as well as to eccentric load. Full article

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13 pages, 2792 KiB

Open AccessArticle

Design and Validation of a Portable Machine Learning-Based Electronic Nose

by Yixu Huang, Iyll-Joon Doh and Euiwon Bae

Sensors 2021, 21(11), 3923; https://doi.org/10.3390/s21113923 - 7 Jun 2021

Cited by 27 | Viewed by 5142

Abstract

Volatile organic compounds (VOCs) are chemicals emitted by various groups, such as foods, bacteria, and plants. While there are specific pathways and biological features significantly related to such VOCs, detection of these is achieved mostly by human odor testing or high-end methods such [...] Read more.

Volatile organic compounds (VOCs) are chemicals emitted by various groups, such as foods, bacteria, and plants. While there are specific pathways and biological features significantly related to such VOCs, detection of these is achieved mostly by human odor testing or high-end methods such as gas chromatography–mass spectrometry that can analyze the gaseous component. However, odor characterization can be quite helpful in the rapid classification of some samples in sufficient concentrations. Lower-cost metal-oxide gas sensors have the potential to allow the same type of detection with less training required. Here, we report a portable, battery-powered electronic nose system that utilizes multiple metal-oxide gas sensors and machine learning algorithms to detect and classify VOCs. An in-house circuit was designed with ten metal-oxide sensors and voltage dividers; an STM32 microcontroller was used for data acquisition with 12-bit analog-to-digital conversion. For classification of target samples, a supervised machine learning algorithm such as support vector machine (SVM) was applied to classify the VOCs based on the measurement results. The coefficient of variation (standard deviation divided by mean) of 8 of the 10 sensors stayed below 10%, indicating the excellent repeatability of these sensors. As a proof of concept, four different types of wine samples and three different oil samples were classified, and the training model reported 100% and 98% accuracy based on the confusion matrix analysis, respectively. When the trained model was challenged against new sets of data, sensitivity and specificity of 98.5% and 98.6% were achieved for the wine test and 96.3% and 93.3% for the oil test, respectively, when the SVM classifier was used. These results suggest that the metal-oxide sensors are suitable for usage in food authentication applications. Full article

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20 pages, 1959 KiB

Open AccessReview

Real-Time Measurement of Drilling Fluid Rheological Properties: A Review

by Naipeng Liu, Di Zhang, Hui Gao, Yule Hu and Longchen Duan

Sensors 2021, 21(11), 3592; https://doi.org/10.3390/s21113592 - 21 May 2021

Cited by 40 | Viewed by 7225

Abstract

The accurate and frequent measurement of the drilling fluid’s rheological properties is essential for proper hydraulic management. It is also important for intelligent drilling, providing drilling fluid data to establish the optimization model of the rate of penetration. Appropriate drilling fluid properties can [...] Read more.

The accurate and frequent measurement of the drilling fluid’s rheological properties is essential for proper hydraulic management. It is also important for intelligent drilling, providing drilling fluid data to establish the optimization model of the rate of penetration. Appropriate drilling fluid properties can improve drilling efficiency and prevent accidents. However, the drilling fluid properties are mainly measured in the laboratory. This hinders the real-time optimization of drilling fluid performance and the decision-making process. If the drilling fluid’s properties cannot be detected and the decision-making process does not respond in time, the rate of penetration will slow, potentially causing accidents and serious economic losses. Therefore, it is important to measure the drilling fluid’s properties for drilling engineering in real time. This paper summarizes the real-time measurement methods for rheological properties. The main methods include the following four types: an online rotational Couette viscometer, pipe viscometer, mathematical and physical model or artificial intelligence model based on a Marsh funnel, and acoustic technology. This paper elaborates on the principle, advantages, limitations, and usage of each method. It prospects the real-time measurement of drilling fluid rheological properties and promotes the development of the real-time measurement of drilling rheological properties. Full article

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10 pages, 2075 KiB

Open AccessCommunication

Utilization of Inertial Measurement Units for Determining the Sequential Chain of Baseball Strike Posture

by Yun-Ju Lee, Po-Chieh Lin, Ling-Ying Chen, Yu-Jung Chen and Jing Nong Liang

Sensors 2021, 21(9), 3280; https://doi.org/10.3390/s21093280 - 10 May 2021

Cited by 1 | Viewed by 2520

Abstract

The purpose of this study was to employ inertial measurement units (IMU) with an eye-tracking device to investigate different swing strategies between two levels of batters. The participants were 20 healthy males aged 20 to 30 years old, with ten professional and ten [...] Read more.

The purpose of this study was to employ inertial measurement units (IMU) with an eye-tracking device to investigate different swing strategies between two levels of batters. The participants were 20 healthy males aged 20 to 30 years old, with ten professional and ten amateur batters. Eye gaze position, head, shoulder, trunk, and pelvis angular velocity, and ground reaction forces were recorded. The results showed that professional batters rotated segments more rhythmically and efficiently than the amateur group. Firstly, the professional group spent less time in the preparation stages. Secondly, the maximum angular velocity timing of each segment of the professional group was centralized in the swing cycle. Thirdly, the amateur group had significantly earlier gaze timing of the maximum angular velocity than the professional group. Moreover, the maximum angular velocity timing of the gaze was the earliest parameter among the five segments, and significantly earlier (at least 16.32% of cycle time) than the maximum angular velocity of the head, shoulder, trunk, and pelvis within the amateur group. The visual-motor coordination strategies were different between the two groups, which could successfully be determined by wearable instruments of IMU. Full article

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16 pages, 3667 KiB

Open AccessArticle

Star Identification Based on Multilayer Voting Algorithm for Star Sensors

by Meiying Liu, Xin Wei, Desheng Wen and Hu Wang

Sensors 2021, 21(9), 3084; https://doi.org/10.3390/s21093084 - 28 Apr 2021

Cited by 12 | Viewed by 2837

Abstract

This paper describes the multilayer voting algorithm, a novel autonomous star identification method for spacecraft attitude determination. The proposed algorithm includes two processes: an initial match process and a verification process. In the initial match process, a triangle voting scheme is used to [...] Read more.

This paper describes the multilayer voting algorithm, a novel autonomous star identification method for spacecraft attitude determination. The proposed algorithm includes two processes: an initial match process and a verification process. In the initial match process, a triangle voting scheme is used to acquire candidates of the detected stars, in which the triangle unit is adopted as the basic voting unit. During the identification process, feature extraction is implemented, and each triangle unit is described by its singular values. Then the singular values are used to search for candidates of the imaged triangle units, which further improve the efficiency and robustness of the algorithm. After the initial match step, a verification method is applied to eliminate incorrect candidates from the initial results and then outputting the final match results of the imaged stars. Experiments show that our algorithm has more robustness to position noise, magnitude noise, and false stars than the other three algorithms, the identification speed of our algorithm is largely faster than the geometric voting algorithm and optimized grid algorithm. However, it takes more memory, and SVD also seems faster. Full article

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12 pages, 15483 KiB

Open AccessCommunication

In and Al Schottky Contacts Comparison on P-Type Chlorine-Doped CdTe

by Igor Vasylchenko, Roman Grill, Marián Betušiak, Eduard Belas, Petr Praus, Pavel Moravec and Pavel Höschl

Sensors 2021, 21(8), 2783; https://doi.org/10.3390/s21082783 - 15 Apr 2021

Cited by 5 | Viewed by 2437

Abstract

The performance of the CdTe radiation detectors heavily relies on the method of contact preparation. A convenient research method addressing this problem is the laser-induced transient current technique. In this paper, we compare the performance of two CdTe crystals which underwent different metallization [...] Read more.

The performance of the CdTe radiation detectors heavily relies on the method of contact preparation. A convenient research method addressing this problem is the laser-induced transient current technique. In this paper, we compare the performance of two CdTe crystals which underwent different metallization processes. We showed that appropriately designed Au/Al contacts induce much less bulk polarization than commercial Pt/In electrodes under the same working conditions and can thus provide a convenient alternative to the industry standard. The comparison was based on the monitoring of the time-dependent sensor polarization measuring transient currents excited by above-bandgap laser illumination complemented by the Am 241 gamma spectroscopy. The theoretical analysis of current waveforms and radiation spectra enabled us to determine the charge carrier mobility, mobility-lifetime products of electrons and holes, and temporal and bias dependence of the space charge formation. Full article

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13 pages, 4850 KiB

Open AccessCommunication

Design and Experiments of a Portable Seabed Integrated Detection Sonar

by Jingxin Ma, Haisen Li, Jianjun Zhu, Weidong Du, Chao Xu and Xinyang Wang

Sensors 2021, 21(8), 2633; https://doi.org/10.3390/s21082633 - 9 Apr 2021

Cited by 6 | Viewed by 3273

Abstract

The integrated observation of seabed topography, sediment geomorphology and sub-bottom profile information is very important for seabed remote sensing and mapping. To improve the efficiency of seabed detection and meet the needs of portable development of detection equipment, we developed a portable seabed [...] Read more.

The integrated observation of seabed topography, sediment geomorphology and sub-bottom profile information is very important for seabed remote sensing and mapping. To improve the efficiency of seabed detection and meet the needs of portable development of detection equipment, we developed a portable seabed feature integrated detection sonar (PSIDS) with whcih a single sonar device can simultaneously detect the above three types of seabed information. The underwater transducer is mainly composed of the following three components: a parametric emission array as the sound source, a high frequency receiving linear array for multibeam echo signal collection, and a two-dimensional vector hydrophone for receiving the low-frequency sediment echo signal. Field experiments were conducted to validate the performance of the PSIDS on 11–17 January 2018 in Jiaozhou Bay, China. (1) PSIDS could perform the functions of both multibeam sonar and sub-bottom profiler; (2) The synchronously and integrated measurement of various seabed information was achieved by alternately emitting multibeam echo-sounding and sub-bottom profiling signal using parametric source. The detection results proved the feasibility and practicability of PSIDS to achieve multiple seafloor characteristics. PSIDS provides a new idea for developing integrated seabed detection sonar. In terms of convenience and data fusion, it is a good option to use this equipment for integrated seabed detection. Full article

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19 pages, 7238 KiB

Open AccessArticle

Body Temperature—Indoor Condition Monitor and Activity Recognition by MEMS Accelerometer Based on IoT-Alert System for People in Quarantine Due to COVID-19

by Minh Long Hoang, Marco Carratù, Vincenzo Paciello and Antonio Pietrosanto

Sensors 2021, 21(7), 2313; https://doi.org/10.3390/s21072313 - 26 Mar 2021

Cited by 51 | Viewed by 8658

Abstract

Coronavirus disease 19 (COVID-19) is a virus that spreads through contact with the respiratory droplets of infected persons, so quarantine is mandatory to break the infection chain. This paper proposes a wearable device with the Internet of Things (IoT) integration for real-time monitoring [...] Read more.

Coronavirus disease 19 (COVID-19) is a virus that spreads through contact with the respiratory droplets of infected persons, so quarantine is mandatory to break the infection chain. This paper proposes a wearable device with the Internet of Things (IoT) integration for real-time monitoring of body temperature the indoor condition via an alert system to the person in quarantine. The alert is transferred when the body thermal exceeds the allowed threshold temperature. Moreover, an algorithm Repetition Spikes Counter (RSC) based on an accelerometer is employed in the role of human activity recognition to realize whether the quarantined person is doing physical exercise or not, for auto-adjustment of threshold temperature. The real-time warning and stored data analysis support the family members/doctors in following and updating the quarantined people’s body temperature behavior in the tele-distance. The experiment includes an M5stickC wearable device, a Microelectromechanical system (MEMS) accelerometer, an infrared thermometer, and a digital temperature sensor equipped with the user’s wrist. The indoor temperature and humidity are measured to restrict the virus spread and supervise the room condition of the person in quarantine. The information is transferred to the cloud via Wi-Fi with Message Queue Telemetry Transport (MQTT) broker. The Bluetooth is integrated as an option for the data transfer from the self-isolated person to the electronic device of a family member in the case of Wi-Fi failed connection. The tested result was obtained from a student in quarantine for 14 days. The designed system successfully monitored the body temperature, exercise activity, and indoor condition of the quarantined person that handy during the Covid-19 pandemic. Full article

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23 pages, 6971 KiB

Open AccessArticle

Design and Implementation of a Real-Time Multi-Beam Sonar System Based on FPGA and DSP

by Haowen Tian, Shixu Guo, Peng Zhao, Minyu Gong and Chao Shen

Sensors 2021, 21(4), 1425; https://doi.org/10.3390/s21041425 - 18 Feb 2021

Cited by 23 | Viewed by 6331

Abstract

Aiming at addressing the contradiction between the high-speed real-time positioning and multi-channel signal processing in multi-beam sonar systems, in this work we present a real-time multi-beam sonar system based on a Field Programmable Gate Array (FPGA) and Digital Signal Processing (DSP) from two [...] Read more.

Aiming at addressing the contradiction between the high-speed real-time positioning and multi-channel signal processing in multi-beam sonar systems, in this work we present a real-time multi-beam sonar system based on a Field Programmable Gate Array (FPGA) and Digital Signal Processing (DSP) from two perspectives, i.e., hardware implementation and software optimization. In terms of hardware, an efficient high-voltage pulse transmitting module and a multi-channel data acquisition module with time versus gain (TVG) compensation with characteristics such as low noise and high phase amplitude consistency, are proposed. In terms of algorithms, we study three beamforming methods, namely delay-and-sum (D&S), direct-method (DM) and Chirp Zeta Transform (CZT). We compare the computational efficiency of DM and CZT in the digital domain. In terms of software, according to the transmission bandwidth of the Gigabit Ethernet and a serial rapid IO (SRIO) interface, the data transmission paths of the acquired data and the beam pattern between the FPGA, the DSP, and a personal computer (PC) are planned. A master-slave multi-core pipelined signal processing architecture is designed based on DSP, which enhances the data throughput of the signal processor by seven times as compared with that of the single-core operation. The experimental results reveal that the sound source level of the transmitting module is around 190.25 dB, the transmitting beam width is 64° × 64°, the background noise of the acquisition module is less than 4 μVrms, the amplitude consistency error of each channel is less than −6.55 dB, and the phase consistency error is less than 0.2°. It is noteworthy that the beam number of the sonar system is 90 × 90, the scanning angle interval is 0.33°, the working distance ranges from 5 m to 40 m, and the maximum distance resolution is 0.384 m. In the positioning experiment performed in this work; the 3-D real-time position of the baffle placed in the detection sector is realized. Please note that the maximum deviation of azimuth is 2°, the maximum deviation of elevation is 2.3°, and the maximum distance deviation is 0.379 m. Full article

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2020

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13 pages, 19003 KiB

Open AccessLetter

Device for Contact Measurement of Turbine Blade Geometry in Robotic Grinding Process

by Dariusz Szybicki, Andrzej Burghardt, Krzysztof Kurc and Piotr Gierlak

Sensors 2020, 20(24), 7053; https://doi.org/10.3390/s20247053 - 9 Dec 2020

Cited by 7 | Viewed by 3791

Abstract

The article discusses the design, implementation, and testing of the accuracy of a measuring device used to measure the thickness of aircraft engine blades subjected to a robotic grinding process. The assumptions that the measuring device should meet were presented. The manufactured device [...] Read more.

The article discusses the design, implementation, and testing of the accuracy of a measuring device used to measure the thickness of aircraft engine blades subjected to a robotic grinding process. The assumptions that the measuring device should meet were presented. The manufactured device was subjected to accuracy and repeatability tests using a standard workpiece. The analysis of research results proved that the measuring device exhibits an accuracy of one order of magnitude better than the accuracy required for blades. For control of the grinding process, the results should be perceived as appropriate. Then, the device was subjected to verification consisting in using it to measure the thickness of aircraft engine blades. The constructed device can be used, not only for inspection of final products, but also for control of the robotic grinding process because thanks to the output interface it can be used in the robotic station’s feedback loop. Full article

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