Research

23 pages, 6564 KiB

Open AccessArticle

Static Characterization of the Driving, Normal and Stall Forces of a Double-Sided Moving-Permanent Magnet-Type Planar Actuator Based on Orthogonal Planar Windings

by Marilia A. da Silveira, Marcos J. Susin, Aly F. Flores Filho and David G. Dorrell

Sensors 2018, 18(10), 3526; https://doi.org/10.3390/s18103526 - 18 Oct 2018

Viewed by 2305

Abstract

This work presents a study of the traction, normal and stall forces in a two-sided planar actuator with orthogonal planar windings and a mover that comprises two cars magnetically coupled to each other through two pairs of permanent magnets (PMs). There is no [...] Read more.

This work presents a study of the traction, normal and stall forces in a two-sided planar actuator with orthogonal planar windings and a mover that comprises two cars magnetically coupled to each other through two pairs of permanent magnets (PMs). There is no ferromagnetic armature core because of the permanent magnets array in the mover and orthogonal traction forces can be generated in order to move both cars jointly in any direction on a plane. The stall force is the minimal force necessary to break up the magnetic coupling between the two cars. When one of the cars is subjected to an external force through the x- or y-axis, the cars can become out of alignment with respect to each other and the planar actuator cannot work properly. The behavior of the forces was modelled by numerical and analytical methods and experimental results were obtained from tests carried out on a prototype. The average sensitivity of the measured static propulsion planar force along either axis is 4.48 N/A. With a 20-mm displacement between the cars along the direction of the x-axis and no armature current, a magnetic stall force of 17.26 N is produced through the same axis in order to restore the alignment of the two cars. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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19 pages, 3903 KiB

Open AccessArticle

Analysis of Human Body Shadowing Effect on Wireless Sensor Networks Operating in the 2.4 GHz Band

by Łukasz Januszkiewicz

Sensors 2018, 18(10), 3412; https://doi.org/10.3390/s18103412 - 11 Oct 2018

Cited by 15 | Viewed by 6153

Abstract

Miniaturized wireless sensors are designed to run on limited power resources, requiring minimization of transmit power and lowering of the fade margin in the link budget. One factor that has an important impact on wireless sensor network design is path loss between the [...] Read more.

Miniaturized wireless sensors are designed to run on limited power resources, requiring minimization of transmit power and lowering of the fade margin in the link budget. One factor that has an important impact on wireless sensor network design is path loss between the transmitter and the receiver. This paper presents an analysis of the influence of human bodies on path loss in the 2.4 GHz band, which is commonly used for wireless sensor networks. The effect of body shadowing was first analyzed in full wave computer simulations using the finite-difference time-domain method. Due to the high numerical burden, the simulations were limited to only a small region around the human body. To analyze the performance of networks in larger indoor environments, a human body model is proposed that can be used for simulations with a ray-based computer program. The proposed model of human body is the main contribution of this paper. It was used to analyze the body shadowing effect in a typical indoor environment. The results were found to be in good agreement with measurements. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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16 pages, 6172 KiB

Open AccessArticle

Multi-Objective Optimization of a Wireless Body Area Network for Varying Body Positions

by Łukasz Januszkiewicz, Paolo Di Barba and Sławomir Hausman

Sensors 2018, 18(10), 3406; https://doi.org/10.3390/s18103406 - 11 Oct 2018

Cited by 6 | Viewed by 3398

Abstract

The purpose of this research was to improve the performance of a wireless body area sensor network, operating on a person in the seated and standing positions. Optimization-focused on both the on-body transmission channel and off-body link performance. The system consists of three [...] Read more.

The purpose of this research was to improve the performance of a wireless body area sensor network, operating on a person in the seated and standing positions. Optimization-focused on both the on-body transmission channel and off-body link performance. The system consists of three nodes. One node (on the user’s head) is fixed, while the positions of the other two (one on the user’s trunk and the other on one leg) with respect to the body (local coordinates) are design variables. The objective function used in the design process is characterized by two components: the first controls the wireless channel for on-body data transmission between the three sensor nodes, while the second controls the off-body transmission between the nodes and a remote transceiver. The optimal design procedure exploits a low-cost Estra, which is an evolutionary strategy optimization algorithm linked with Remcom XFdtd, a full-wave Finite-Difference Time-Domain (FDTD) electromagnetic field analysis package. The Pareto-like approach applied in this study searches for a non-dominated solution that gives the best compromise between on-body and off-body performance. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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17 pages, 10816 KiB

Open AccessArticle

Many-Objective Automated Optimization of a Four-Band Antenna for Multiband Wireless Sensor Networks

by Łukasz Januszkiewicz, Paolo Di Barba, Łukasz Jopek and Sławomir Hausman

Sensors 2018, 18(10), 3309; https://doi.org/10.3390/s18103309 - 02 Oct 2018

Cited by 16 | Viewed by 3034

Abstract

This paper describes a new design and an optimization framework for a four-band antenna to be used in wireless sensor networks. The antenna is designed to operate effectively in two open frequency bands (ISM—Industrial, Scientific, Medical), 2.4 GHz and 5.8 GHz, as well [...] Read more.

This paper describes a new design and an optimization framework for a four-band antenna to be used in wireless sensor networks. The antenna is designed to operate effectively in two open frequency bands (ISM—Industrial, Scientific, Medical), 2.4 GHz and 5.8 GHz, as well as in two bands allocated for the fifth-generation (5G) cellular networks, 0.7 GHz and 3.5 GHz. Our initial design was developed using the trial and error approach, modifying a circular disc monopole antenna widely used in ultra wideband (UWB) systems. This initial design covered the three upper bands, but impedance matching within the 700 MHz band was unsatisfactory. The antenna performance was then improved significantly using an optimization algorithm that applies a bi-objective fully-Paretian approach to its nine-parameter geometry. The optimization criteria were impedance matching and radiation efficiency. The final design exhibits good impedance matching in all four desired bands with the Voltage Standing Wave Ratio (VSWR) value below 2 and radiation efficiency of 88%. The simulated antenna performance was verified experimentally. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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14 pages, 3479 KiB

Open AccessArticle

Optimal Design of Electromagnetically Actuated MEMS Cantilevers

by Paolo Di Barba, Teodor Gotszalk, Wojciech Majstrzyk, Maria Evelina Mognaschi, Karolina Orłowska, Sławomir Wiak and Andrzej Sierakowski

Sensors 2018, 18(8), 2533; https://doi.org/10.3390/s18082533 - 02 Aug 2018

Cited by 14 | Viewed by 3410

Abstract

In this paper we present the numerical and experimental results of a design optimization of electromagnetic cantilevers. In particular, a cost-effective technique of evolutionary computing enabling the simultaneous minimization of multiple criteria is applied. A set of optimal solutions are subsequently fabricated and [...] Read more.

In this paper we present the numerical and experimental results of a design optimization of electromagnetic cantilevers. In particular, a cost-effective technique of evolutionary computing enabling the simultaneous minimization of multiple criteria is applied. A set of optimal solutions are subsequently fabricated and measured. The designed cantilevers are fabricated in arrays, which makes the comparison and measurements of the sensor properties reliable. The microfabrication process, based on the silicon on insulator (SOI) technology, is proposed in order to minimize parasitic phenomena and enable efficient electromagnetic actuation. Measurements on the fabricated prototypes assessed the proposed methodological approach. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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11 pages, 3288 KiB

Open AccessArticle

Modelling of a Hall Effect-Based Current Sensor with an Open Core Magnetic Concentrator

by Ivan Yatchev, Mehmet Sen, Iosko Balabozov and Ivan Kostov

Sensors 2018, 18(4), 1260; https://doi.org/10.3390/s18041260 - 19 Apr 2018

Cited by 14 | Viewed by 4954

Abstract

The present paper deals with the modelling of a Hall effect current sensor with open core magnetic concentrator. 3D magnetic field modelling is carried out using the finite element method (FEM) and Comsol Multiphysics software. Two rectangular core constructions are considered. Different geometric [...] Read more.

The present paper deals with the modelling of a Hall effect current sensor with open core magnetic concentrator. 3D magnetic field modelling is carried out using the finite element method (FEM) and Comsol Multiphysics software. Two rectangular core constructions are considered. Different geometric parameters of the magnetic concentrator are varied and their influence on the sensor characteristic is studied, with the aim of reducing the dependence on the output signal on the distance to the conductor. Of the studied parameters, core window length leads to the most significant change in the sensor characteristic. Future work can include the optimization of the sensor construction. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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11 pages, 1922 KiB

Open AccessArticle

Control of the Singular Points Location for Miniature Switches with Magnetically Driven Contacts

by Xin Wang, Marcin Habrych, Bogdan Miedzinski and Julian Wosik

Sensors 2018, 18(2), 350; https://doi.org/10.3390/s18020350 - 26 Jan 2018

Cited by 2 | Viewed by 3273

Abstract

This paper presents and discusses usefulness and possibility of control of the singular points location of a driving magnetic field under as structure considerations as well as selection of energizing magnet systems for miniature electromagnetic switches. The sample results of theoretical analysis and [...] Read more.

This paper presents and discusses usefulness and possibility of control of the singular points location of a driving magnetic field under as structure considerations as well as selection of energizing magnet systems for miniature electromagnetic switches. The sample results of theoretical analysis and experimental testing concern selected reed switches with normally open contacts as well as a developed miniature switch with a metallic ball contact. It must be noted that the switch with the contact performed by means of the metallic tiny ball can be effectively used both as a change-over switch as well as a detector of the energizing magnetic field distribution under designing and assembling of any electromagnetic contact device preferably with an increased degree of integration and miniaturization. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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11 pages, 4258 KiB

Open AccessArticle

A Circular Microstrip Antenna Sensor for Direction Sensitive Strain Evaluation

by Przemyslaw Lopato and Michal Herbko

Sensors 2018, 18(1), 310; https://doi.org/10.3390/s18010310 - 20 Jan 2018

Cited by 52 | Viewed by 7480

Abstract

In this paper, a circular microstrip antenna for stress evaluation is studied. This kind of microstrip sensor can be utilized in structural health monitoring systems. Reflection coefficient S₁₁ is measured to determine deformation/strain value. The proposed sensor is adhesively connected to the [...] Read more.

In this paper, a circular microstrip antenna for stress evaluation is studied. This kind of microstrip sensor can be utilized in structural health monitoring systems. Reflection coefficient S₁₁ is measured to determine deformation/strain value. The proposed sensor is adhesively connected to the studied sample. Applied strain causes a change in patch geometry and influences current distribution both in patch and ground plane. Changing the current flow in patch influences the value of resonant frequency. In this paper, two different resonant frequencies were analysed because in each case, different current distributions in patch were obtained. The sensor was designed for operating frequency of 2.5 GHz (at fundamental mode), which results in a diameter less than 55 mm. Obtained sensitivity was up to 1 MHz/100 MPa, resolution depends on utilized vector network analyser. Moreover, the directional characteristics for both resonant frequencies were defined, studied using numerical model and verified by measurements. Thus far, microstrip antennas have been used in deformation measurement only if the direction of external force was well known. Obtained directional characteristics of the sensor allow the determination of direction and value of stress by one sensor. This method of measurement can be an alternative to the rosette strain gauge. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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15 pages, 5634 KiB

Open AccessArticle

Multi-Sensor Data Integration Using Deep Learning for Characterization of Defects in Steel Elements

by Grzegorz Psuj

Sensors 2018, 18(1), 292; https://doi.org/10.3390/s18010292 - 19 Jan 2018

Cited by 92 | Viewed by 8931

Abstract

Nowadays, there is a strong demand for inspection systems integrating both high sensitivity under various testing conditions and advanced processing allowing automatic identification of the examined object state and detection of threats. This paper presents the possibility of utilization of a magnetic multi-sensor [...] Read more.

Nowadays, there is a strong demand for inspection systems integrating both high sensitivity under various testing conditions and advanced processing allowing automatic identification of the examined object state and detection of threats. This paper presents the possibility of utilization of a magnetic multi-sensor matrix transducer for characterization of defected areas in steel elements and a deep learning based algorithm for integration of data and final identification of the object state. The transducer allows sensing of a magnetic vector in a single location in different directions. Thus, it enables detecting and characterizing any material changes that affect magnetic properties regardless of their orientation in reference to the scanning direction. To assess the general application capability of the system, steel elements with rectangular-shaped artificial defects were used. First, a database was constructed considering numerical and measurements results. A finite element method was used to run a simulation process and provide transducer signal patterns for different defect arrangements. Next, the algorithm integrating responses of the transducer collected in a single position was applied, and a convolutional neural network was used for implementation of the material state evaluation model. Then, validation of the obtained model was carried out. In this paper, the procedure for updating the evaluated local state, referring to the neighboring area results, is presented. Finally, the results and future perspective are discussed. Full article

(This article belongs to the Special Issue Small Devices and the High-Tech Society)

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