Magnetic Crosstalk Suppression and Probe Miniaturization of Coupled Core Fluxgate Sensors

This paper demonstrates the probe structure optimization of coupled core fluxgate magnetic sensors through finite element analysis. The obtained modelling results have been used to optimize the probe structures from horizontal- to vertical- arrangements for magnetic crosstalk suppression and probe miniaturization. The finite element analysis show that with the same distance between each adjacent fluxgate elements, the magnetic crosstalk is suppressed by 6 times and the volume is reduced by 2 times after the optimization. Furthermore, the miniaturized probes with low magnetic crosstalk have been designed and implemented. The experimental results which showed more than 5 times suppression of magnetic crosstalk verified the simulation results. Therefore, the results provide detailed reference to cope with the contradiction between volume miniaturization and magnetic crosstalk suppression in magnetic sensor-array design

Performance degradation effect countermeasures in residence times difference (RTD) fluxgate magnetic sensors

This paper aims to explore the detection defect of residence times difference (RTD) fluxgate working in low-power mode and present the countermeasures for sensor resolution improvement and linearity enhancement. The main defects are amplitude and symmetry changes induced in the output spikes of fluxgate probe due to the magnetic field. These defects lead to thresholds deviation and asymmetry, then cause severe performance degradation especially on detection resolution and linearity according to the RTD theory. To overcome such effects, the optimized RTD method based on voltage extraction and feedback technology is proposed to implement magnetic field compensation and achieve a zero-field running regime of the RTD fluxgate. In this regard, the sensor linearity is improved by a factor of 38, and the resolution degradation effect is suppressed more than 6 times, verified by the laboratory experiments. The optimized detection method proposed in this paper demonstrated a great potential to achieve lower power consumption and will make the RTD fluxgate more promising technology among bio-magnetic applications

Nondestructive testing of grating imperfections using grating-based X-ray phase-contrast imaging

We reported the usage of grating-based X-ray phase-contrast imaging in nondestructive testing of grating imperfections. It was found that electroplating flaws could be easily detected by conventional absorption signal, and in particular, we observed that the grating defects resulting from uneven ultraviolet exposure could be clearly discriminated with phase-contrast signal. The experimental results demonstrate that grating-based X-ray phase-contrast imaging, with a conventional low-brilliance X-ray source, a large field of view and a reasonable compact setup, which simultaneously yields phase- and attenuation-contrast signal of the sample, can be ready-to-use in fast nondestructive testing of various imperfections in gratings and other similar photoetching products.Comment: 6 pages, 5 figures and 2 table

Experimental Study on the Performance of a Novel Compact Electrostatic Coalescer with Helical Electrodes

As most of the light and easy oil fields have been produced or are nearing their end-life, the emulsion stability is enhanced and water cut is increasing in produced fluid which have brought challenges to oil–water separation in onshore and offshore production trains. The conventional solution to these challenges includes a combination of higher chemical dosages, larger vessels and more separation stages, which often demands increased energy consumption, higher operating costs and larger space for the production facility. It is not always feasible to address the issues by conventional means, especially for the separation process on offshore platforms. Electrostatic coalescence is an effective method to achieve demulsification and accelerate the oil–water separation process. In this paper, a novel compact electrostatic coalescer with helical electrodes was developed and its performance on treatment of water-in-oil emulsions was investigated by experiments. Focused beam reflectance measurement (FBRM) was used to make real-time online measurements of water droplet sizes in the emulsion. The average water droplet diameters and number of droplets within a certain size range are set as indicators for evaluating the effect of coalescence. We investigated the effect of electric field strength, frequency, water content and fluid velocity on the performance of coalescence. The experimental results showed that increasing the electric field strength could obviously contribute to the growth of small water droplets and coalescence. The extreme value of electric field strength achieved in the high-frequency electric field was much higher than that in the power-frequency (50 Hz) electric field, which can better promote the growth of water droplets. The initial average diameters of water droplets increase with higher water content. The rate of increment in the electric field was also increased. Its performance was compared with that of the plate electrodes to further verify the advantages of enhancing electrostatic coalescence and demulsification with helical electrodes. The research results can provide guidance for the optimization and performance improvement of a compact electrocoalescer

Lower Limb Motion Recognition Method Based on Improved Wavelet Packet Transform and Unscented Kalman Neural Network

Exoskeleton robot is a typical application to assist the motion of lower limbs. To make the lower extremity exoskeleton more flexible, it is necessary to identify various motion intentions of the lower limbs of the human body. Although more sEMG sensors can be used to identify more lower limb motion intention, with the increase in the number of sensors, more and more data need to be processed. In the process of human motion, the collected sEMG signal is easy to be interfered with noise. To improve the practicality of the lower extremity exoskeleton robot, this paper proposed a wavelet packet transform- (WPT-) based sliding window difference average filtering feature extract algorithm and the unscented Kalman neural network (UKFNN) recognition algorithm. We established an sEMG energy feature model, using a sliding window difference average filtering method to suppress noise interference and extracted stable feature values and using UKF filtering to optimize the neural network weights to improve the adaptability and accuracy of the recognition model. In this paper, we collected the sEMG signals of three muscles to identify six lower limb motion intentions. The average accuracy of 94.83% is proposed in this paper. Experiments show that the algorithm improves the accuracy and anti-interference of motion intention recognition of lower limb sEMG signals. The algorithm is superior to the backpropagation neural network (BPNN) recognition algorithm in the lower limb motion intention recognition and proves the effectiveness, novelty, and reliability of the method in this paper

Design and Implementation of Close-Loop Detection for Coupled Core Fluxgate Magnetic Sensors

This paper presents a closed-loop detection strategy with significant potential to solve the detection defects existed in the residence-times difference (RTD) method of the coupled core fluxgate magnetic sensors. The external magnetic field (e.g. Earth's magnetic field), as the main source of these detection defects, has been analyzed by the theoretical investigation. To overcome such deficiencies, the close-loop detection method based on the analog-type RTD readout method and magnetic flux-balance detection is utilized to implement external magnetic field real-time compensation and achieve a near-zero-field working state of the magnetic material. The fluxgate with the optimized detection strategy and vertical arrangement structure has been designed, fabricated and examined, and the preliminary results showed steady operation and a detection resolution of ±0.10 nT. The optimized detection method based on the balance detection concept proposed in this manuscript demonstrated a great potential to obtain the optimal detection performances which are embedded in the coupling-induced oscillation of nonlinear dynamics

Virtual Laboratory Application Development for Mobile Terminal

It is highly important to finish the experiments while learning the course of digital circuit design is to confirm the theoretical knowledge in the experiment, which makes the learning process an extremely good expansion. However, in the actual situation, digital design laboratories are often in short supply, which is mainly reflected in its spatial limitations, the limitations on the number of instruments and instrument stability limitations, especially in some poor and developing countries. This paper designed a mobile virtual laboratory application (VL-APP) for learning digital design to help students perform virtual experiments to conduct new thoughts anywhere and anytime, which also support anyone familiar with the instruments used in the digital area. It mainly aims at the simulation experiment of a specific experiment in the digital design experiment, and provides the model and script basis for the users to design the experiment independently. Selecting Unity3D and 3ds-max for the software platform, Android for the test installation environment, the APP testing results showed that it is good enough to be applied right now

Study on machining performance of fixed-abrasive lap-grinding plate with random grid structure

To meet the increasing requirements on material removal efficiency, surface quality, and subsurface damage in the ultra-precision grinding process, a textured-fixed abrasive plate (T-FAP) with random grid structure based on the Voronoi Diagram is proposed. The abrasive tool is fabricated by using UV-curable resin and micro-level alumina abrasive grains. The influence of time-varying texture characteristics of surface wear on the machining performance is studied via MATLAB image analysis and numerical simulation of the grinding trajectory. The lap-grinding experiment of the aluminum workpieces is carried out to analyze the material removal efficiency and workpiece surface roughness obtained from the T-FAP grinding process. The results show that the surface roughness of the workpiece processed with the T-FAP grinding is 0.84 μm, and that the material removal rate is 3.21 μm/min. Compared with the traditional fixed abrasive grinding tool, the T-FAP grinding ensures the material removal efficiency and obtains high surface accuracy as well