Sine Signal Research Articles

Oxidation Modification of Polyacrylonitrile-Based Carbon Fiber and Its Electro-Chemical Performance as Marine Electrode for Electric Field Test

A novel sensor for ocean electric field testing has been fabricated by polyacrylonitrile-based on carbon fibers with electro-chemical oxidation. The surface profile characteristics of the carbon fibers were characterized by scanning electron microscope, Fourier transform infrared spectra and contact angle. Cyclic voltammetry and Tafel curves have been used to study its electrochemical performances. Two identical electrodes in sea water as the electric field sensor will swiftly respond to applied electric field which causes positive and negative ions to move in opposite direction, resulting in a electric potential difference (ΔE). Test result indicates that the offset potential is typically below 1 mV with a drift of 60-170 μVd−1. Typical self noise level is 1.07nV/√Hz@1Hz. The electric field response indicates that the modified electrode pair shows better response to AC sine signal of amplitude and frequency (5mV and 1 mHz) respectively than its blank. The electric field response model of the modified electrodes is creatively presented according to its electric double layer capacitance and Faraday pseudo-capacitance. Many advantages of the carbon fiber electric field electrode will make it have potential application prospect.

Experimental assessment of stiffness and energy dissipation properties of disk-shaped polymer-based composite specimens by in-plane torsion testing

Torsion testing machines are widely used either to measure the strength, stiffness and stress-strain properties of materials or to replicate real-life service conditions. In this paper, a novel experimental method is presented, based on the development of a dedicated steel structure to be used in conjunction with a universal testing machine. This equipment allows applying cyclic in-plane torsion loads on disk-shaped components. The proposed approach aims to enable the assessment of stiffness and damping properties on specimens enabling the application of higher loads in comparison with the traditional machines.Specifically, dynamic trials were performed by attaching the composite specimens and the steel structure to the testing machine, such that the uniaxial controlled displacements can be used to exert the desired cyclic loads onto the specimen. Both torsional stiffness and energy loss were measured from the steady-state load-displacement hysteresis cycles. Amplitudes of sine signals, from 0.05 to 0.2 mm, and a frequency ranging between 1 and 20 Hz, were used in the experiments. The results are presented comparing the behaviour of two polymer matrix composites, with the same number of identical laminae, but characterized by different stacking sequences, namely unidirectional and quasi-isotropic configurations.

A New Electromagnetic Emission Source Frequency and Factor Identification Approach for Nonlinear Circuits From the Output Spectrum Data

For the practical nonlinear circuits, a number of new frequencies are generated in the output spectrum, which makes electromagnetic interference location quite challenging. To mitigate this problem, an approach is proposed to identify the electromagnetic emission source frequencies and nonlinear factors from the output spectrum of nonlinear circuits. The amplitude of the output spectrum with the input of two sine signals is first calculated based on the power series. Then, the Order Image (OI) is defined to reveal the output spectrum features, and its symmetry characteristic has been comprehensively analyzed. Results show that the maximum symmetry index is observed when the reference frequencies are equal to the excitation frequencies. Based on this observation, the electromagnetic emission source frequencies can be obtained. In addition, a Backward Algorithm (BA) has been introduced to extract nonlinear factors. The proposed approach only requires the output spectrum and the amplitude of one excitation. Compared with other techniques, like the Support Vector Machines and the Recurrent Neural Network, it needs much less prior information. Finally, several examples are carried out to verify the effectiveness of the proposed approach. Results show that the emission source frequencies and nonlinear factors can be accurately extracted. Therefore, the proposed approach shows great potential in electromagnetic interference location and characteristic analysis for nonlinear circuits.

Резистивное переключение мемристоров на основе стабилизированного диоксида циркония сложными сигналами

Abstract The specific features of resistive switching, which was initiated by triangular pulses with a high-frequency sine signal imposed on them, in experimental memristor prototypes based on thin films of yttria-stabilized zirconia were examined. It was found that memristors switched by these complex signals have lower switching voltage, higher ratio of currents in low- and high-resistance states, and better long-term current stability than memristors switched by triangular pulses without the sine signal. This improvement of switching parameters is associated with resonance activation of migration of oxygen ions via vacancies in the alternating external electric field.

Fuzzy-PID controller with variable universe for tillage depth control on tractor-implement

A control algorithm of fuzzy-PID controller with variable universe (VUFPID) was proposed to realize fast and accurate adjustment of tillage depth control on tractor-implement and adapt to the complex and changeable agricultural environments. The electro-hydraulic hitch system was modeled through transfer functions of the electrically operated hydraulic valve and the hydraulic cylinder. And the VUFPID controller was designed in accordance with the error of tillage depth and the error rate of tillage depth. Then, the designed controller was simulated by comparing with PID controller and fuzzy PID controller. Also, field experiments were conducted to assess stability of the proposed controller. According to the simulation results, the proposed controller can adjust the hitch system to the set depth more quickly and steadily than the other controllers, with the minimum tracking error of 1.13 mm for the simulation with sine signal, and the shortest response time of 0.261 s and lowest overshoot of 12.4% for the simulation with step signal. As for the field experiments, the results are in good agreement with the simulation results, and the proposed controller shows good stability with the maximum error of tillage depth of 7.8% at the set depth of 10–20 cm. The proposed controller has good adaptability and anti-interference in tillage depth control.

A portable laser-based sensor for detecting H2S in domestic natural gas

Hydrogen sulfide (H2S) is a highly toxic gaseous component of natural gas that poses a significant hazard during the use of natural gas for domestic purposes; therefore, a high-sensitivity, on-line detection method is extremely important to ensure its safety for domestic use. In this work, a portable sensor was developed based on near-infrared tunable diode laser absorption spectroscopy (TDLAS). A special Herriott multipass cell (MPC) combined with a home-made embedded electronics system allowed for the fabrication of a compact sensor with a size of 50 × 20 × 10 cm3. A rugged movable cell was used for detecting contaminated gas samples. An embedded electronic system with a diameter of 8 cm was implemented to control the laser, acquire and process electronic signal. To reduce external interference, the calibration-free TDLAS (wavelength modulation frequency-2f/direct sine signal) was employed to suppress common field measurement noise. Based on the results of Allan deviation analysis, the limit of system detection could reach 0.14 ppm using the H2S absorption line at 6336.61 cm−1. It is suitable for on-line measurement because of its rapid response time. Its feasibility is validated for monitoring H2S in a domestic natural gas of pipeline. This work demonstrates a system for real-time and field measurement of H2S, which can be used to address the security risks associated with using natural gas.

Measurement of soil electrical conductivity based on direct digital synthesizer (DDS) and digital oscilloscope

A soil electrical conductivity (EC) measurement system based on direct digital synthesizer (DDS) and digital oscilloscope was developed. The system took the “current-voltage four-electrode method” as the design principal and adopted a six-pin structure of the probe, two center pins to measure the soil EC in shallow layer, two outside pins to measure the soil EC in deep layer, and two middle pins for inputting the driving current. A signal generating circuit using DDS technology was adopted to generate sine signals, which was connected with the two middle pins. A digital oscilloscope was used to record and store the two soil output signals with noises in microseconds, which were from the two center pins and two outside pins, respectively. Then a digital bandpass filter was used to filter the soil output signals recorded by the digital oscilloscope. Compared with the traditional analog filter circuit, the digital filter could filter out the noises of all frequency except for the frequency of the excitation source. It could improve the effect of filtering and the accuracy of the soil EC measurement system. The DDS circuit could provide more stable sine signals with larger amplitudes. The use of digital oscilloscope enables us to analyze the soil output signals in microseconds and measure the soil EC more accurately. The new soil EC measurement system based on DDS and digital oscilloscope can provide a new effective tool for soil sensing in precision agriculture. Keywords: soil electrical conductivity, direct digital synthesizer, digital oscilloscope, precision agriculture, current-voltage four-electrode method DOI: 10.25165/j.ijabe.20191206.4840 Citation: Pei X S, Meng C, Li M Z, Yang W, Zhou P. Measurement of soil electrical conductivity based on direct digital synthesizer (DDS) and digital oscilloscope. Int J Agric & Biol Eng, 2019; 12(6): 162–168.

Track the maximum power of a photovoltaic to control a cascade five-level inverter a single-phase grid-connected with a fuzzy logic control

<p>This research presents tracking the maximum power of a<em> </em>photovoltaic to control a five-level inverter, a cascade type connecting a single-phase grid-connected system with a fuzzy logic control model. Maximum power tracking control In this research, the principle of controlling the maximum current amplitude of the photovoltaic multiplied by the sine signal per unit that used as a reference current compared to the grid current. Signal comparison with the PID controller allows the creation of five levels of PWM of cascade control of five-level inverter connects single-phase grids. The results of the simulation test using the program MATLAB/Simulink to compare with the generated prototype found that the fuzzy logic principle was used to control the maximum power tracking conditions of the P&O method, when the amount of radiation light intensity decreases suddenly, making it possible to track the maximum power of the photovoltaic. Also, when<em> </em>the inverter connected to the grid by controlling the power<em> </em>angle to compare results between the simulation and the prototype — found that the current flowing into the grid increases according to the power angle control. Resulting in a nearby waveform, sine wave and an out of phase angle to the grid voltage because the system is in the inverter mode, and the harmonic spectrum of the grid currently has total harmonic distortion (THD) is reduced as an indication of the proposed system can be developed and applications.</p>

Band Structure of Phononic Crystal Consist of Hollow Aluminum Cylinders in Different Media; Finite Element Analysis

In this study, we investigated band structure of a 2D Phononic Crystal (PnC) which was consist of hollow aluminum cylinders in different media. To validate the finite element predictions, we made a square lattice PnC which has lattice constant a = 14mm, outer radius r1 = 5mm and inner radius r2 = 4mm of cylinders. In our experimental measurement, by using a signal generator software, we sent 100 Hz-20kHz sine signal for 5 seconds duration from speaker to the PnC where placed 1m away from. With the help of a microphone, we recorded the sound in front of the PnC (Pin ) and backside the PnC (Pout ). Then we were converted our recording into frequency domain by standard FFT algorithm, we calculated the Transmission Loss value according to the formula TL = 20*log10 (Pout / Pin ) and obtained the experimental Transmission Loss. After experimental validation, we conducted band structure analysis of different combination of the 2D PnC by finite element method.

Hardware co-simulation of 1024-point FFT and it's Implementation, in Simulink, Xilinx Vivado IDE on Zynq-7000 FPGA

In this paper a 1024-point FFT Algorithm is implemented on Zynq-7000 FPGA device. The design implementation uses Hardware co-simulation in Simulink and Xilinx Vivado environments with Zynq-7000 FPGA target evaluation board using JTAG setup. The power parameter for the configured FFT IP core for 1024 point and the signal source DDS block are estimated. The DDS with both sine and cosine signal outputs enabled, consume a power of 0.277 W, whereas, the 1024 point FFT core consume a power of 0.044 W. Further when 2 DDSs were instanced to generate orthogonal sine and cosine sources for OFDM signals of same frequency 1MHz each, a total of 0.277W power is consumed. When a single DDS core is configured for both sine or cosine signal only configuration by instancing a 1024-point FFT core the total power consumed is 0.268W and 0.267W, respectively, a 1mW higher to cosine case. Further, when 1024 point FFT core power alone is calculated it is found to be 0.044W (or 44mW). When a single DDS is instanced for OFDM signal generation by opting both the sine cosine signals, it consumed a total power of 0.233 W saving a power of 0.044W or 44mW by sine or cosine data re-use from the LUT ROM of DDS. Thus saving a power of 44mW by using data re-use through LUT’s of DDS. This is a significant power saving. In this, hardware co-simulation process, Xilinx system generator tool (Sysgen) is used. This implementation is coded using Verilog HDL, verified on Xilinx Vivado platform on the Zynq-7000 FPGA device. Note that Zynq-7000 is supporting hardware co-simulation, hence the 1024-point FFT has been implemented on this device. The simulation results are captured on Xilinx signal viewer for a proper conclusion.

Hardware co-simulation of 1024-point FFT and it's Implementation, in Simulink, Xilinx Vivado IDE on Zynq-7000 FPGA

In this paper a 1024-point FFT Algorithm is implemented on Zynq-7000 FPGA device. The design implementation uses Hardware co-simulation in Simulink and Xilinx Vivado environments with Zynq-7000 FPGA target evaluation board using JTAG setup. The power parameter for the configured FFT IP core for 1024 point and the signal source DDS block are estimated. The DDS with both sine and cosine signal outputs enabled, consume a power of 0.277 W, whereas, the 1024 point FFT core consume a power of 0.044 W. Further when 2 DDSs were instanced to generate orthogonal sine and cosine sources for OFDM signals of same frequency 1MHz each, a total of 0.277W power is consumed. When a single DDS core is configured for both sine or cosine signal only configuration by instancing a 1024-point FFT core the total power consumed is 0.268W and 0.267W, respectively, a 1mW higher to cosine case. Further, when 1024 point FFT core power alone is calculated it is found to be 0.044W (or 44mW). When a single DDS is instanced for OFDM signal generation by opting both the sine cosine signals, it consumed a total power of 0.233 W saving a power of 0.044W or 44mW by sine or cosine data re-use from the LUT ROM of DDS. Thus saving a power of 44mW by using data re-use through LUT’s of DDS. This is a significant power saving. In this, hardware co-simulation process, Xilinx system generator tool (Sysgen) is used. This implementation is coded using Verilog HDL, verified on Xilinx Vivado platform on the Zynq-7000 FPGA device. Note that Zynq-7000 is supporting hardware co-simulation, hence the 1024-point FFT has been implemented on this device. The simulation results are captured on Xilinx signal viewer for a proper conclusion.

A Novel Adjustable Parameters PID Control of Dual-motor Driving Servo System

ABSTRACTIn order to reduce the adverse effect of backlash nonlinearity on dual-motor driving servo system, the system model is firstly described. Then a novel adjustable parameters PID control algorithm combining fuzzy RBF neural network control with PID control is proposed for the first time, and analyzed its stability. In the simulation analysis, the system track step signal, ramp signal and sine signal respectively. Simultaneously, different interference signal were applied to system output when system tracking different signal. Simulation results show that the proposed control algorithm has smaller tracking error and better anti-interference ability than that of mere PID control, because PID parameters can automatically be adjusted as the system tracking error changes. In the end, white noise interference signal are applied to system output in the experiment analysis. The experiment results also validate the higher tracking accuracy and stronger robustness of the proposed control algorithm than that of PID control.

Effect of the excitation waveform on the average power and peak power delivered by a piezoelectric generator

Abstract The theoretical power delivered by piezoelectric generators (PG) is a key parameter for their design optimization and for the determination of the power management circuit which should be designed especially for the targeted device to be supplied. Most often, when the PG is connected to a resistive load, a maximum of average power occurs at a given load value which should be determined by sweeping the resistive load. Although the determination of this optimal load is obvious in the case of a sine signal, as it is matching the internal impedance of the PG, the cases of non-sine signals are more complex. In this paper, we show that the waveform of the mechanical force applied to the PG significantly influences the generated power and the optimal load. We propose a method to predict the average power produced by a PG as a function of the load, even if the waveform is not a sine. The study is focused on a square waveform with variable exponential rising time, corresponding to realistic mechanical excitations, and shows that the force rising time drastically influences the mean power delivered by PGs having a capacitive internal impedance, for example some ZnO nanowires-based PGs. We also show that the peak instantaneous power, often reported as PG performance metric in literature, largely overestimates the truly available power.

Design and Development of a Self-Calibration- Based Inductive Absolute Angular Position Sensor

This paper presents an inductive-based sensor for absolute angular position measurement. Its structure is basically similar to a resolver, but it has two groups of pickup coils that use the same magnetic field to produce two different signals for absolute measurement and online self-calibration. The proposed sensor mainly consists of a ferromagnetic stator, two ferromagnetic rotors, and four groups of coils. Two groups of coils in the stator working as excitation coils are supplied with quadrature alternating current (AC) signals to generate quadrature magnetic fields both in temporal and spatial domains. The other two groups of coils in the rotors working as pickup coils receive magnetic fields to produce two sine signals whose phases are proportional to the displacement of the rotors. However, the phases of the sine signals have different periods of variation in the full measurement range. The sensor uses this different phase variation to determine the absolute angular position and perform the online self-calibration. A sensor model has been built and simulated first to verify the feasibility of the sensor. Then, a sensor prototype was developed based on the sensor model. The experimental results of the sensor prototype show that the sensor has big but regular measurement error using any group of pickup coils before conducting calibration, and finally, the measurement error reduced up to 85% by use of the online self-calibration method presented in this paper.

Bender elements in stiff cemented clay: shear wave velocity (Vs) correction by applying wavelength considerations

For the quality control of cement mixing in clays, small-strain shear stiffness Gmax is now increasingly being used due to enhanced repeatability in shear wave velocity (Vs) measurements. These stiff cemented clays have higher resonant frequencies that require the use of higher input frequencies in bender element testing for reliable Vs measurements. However, the practical requirements for suitable signals (with minimal near-field effects and wave reflections) can often be difficult to implement. To facilitate such Vs measurements, the current study proposes a methodology that can correct Vs values corresponding to lower wave propagation distance to wavelength ratios (Ltt/λ) to more reliable values of Vs at reference Ltt/λ criterion suggested in previous studies (e.g., 2, 3.33, and 4). Two clay types are mixed with ordinary Portland cement and various mix ratios are utilized to cover a wider range of soil stiffnesses. Based on the collected database, it is found that the resulting fitting functions enable the reasonable estimation of the stabilized Vs values corresponding to the suggested Ltt/λ criterion regardless of the nature of the input sine signal.

Boosting the information transfer rate of an SSVEP-BCI system using maximal-phase-locking value and minimal-distance spatial filter banks

For Brain-Computer Interface (BCI) systems, improving the Information Transfer Rate (ITR) is a very critical issue. This study focuses on a Steady-State Visually Evoked Potential (SSVEP)-based BCI because of its advantage of high ITR. Unsupervised Canonical Correlation Analysis (CCA)-based method has been widely employed because of its high efficiency and easy implementation. In a recent study, an ensemble-CCA method based on individual training data was proposed and achieved an excellent performance with ITR of 267 bit/min. A 40-target SSVEP-BCI speller was investigated in this study, using an integration of Minimal-Distance (MD) and Maximal-Phase-locking value (MP) approaches. In the MD approach, a spatial filter is developed to minimize the distance between the training data and the reference sine signal, and in this study, two different types of distance were compared. In the MP approach, a spatial filter is developed to maximize the Phase-Locking Value (PLV) between the training calibration data and the reference sine signal. In addition to the fundamental frequency of stimulation, the harmonics were used to train MD and MP spatial filters, which formed spatial filter banks. The test data epoch was multiplied by the MP and MD spatial filter banks, and the distances and PLVs were extracted as features for recognition. Across 12 subjects with a 0.4 s-data length, the proposed method realized an average classification accuracy and ITR of 93% and 307 bit/min, respectively, which is significantly higher than the current state-of-the-art method. To the best of our knowledge, these results suggest that the proposed method has achieved the highest ITR in SSVEP-BCI studies.

Electrochemical and Electric Field Response Properties of Highly Sensitive Electrodes Based on Carbon Fiber With Oxygen and Nitrogen Surface Groups

In this paper, a high-sensitive carbon fiber electrode enriched oxygen and nitrogen groups were prepared using a method combining oxidation and graft modification. The surface compositions were analyzed by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical results show that the modified carbon fibers have a better electric double layer performance and a lower capacitive impedance at the lower frequency. The offset potential of the electrode pairs is typically below 1 mV with a drift of less than $40~\mu \text{V}$ /day. Typical measured noise level is below 2 nV/rt (Hz) at 1 Hz. The modified carbon fiber electrode pairs exhibit a good response to the ac sine signal of amplitude 1 mV and frequency 1 mHz. The sensitivity is increased by 82% and 59%, respectively, in comparison with Ag/AgCl electrode pair. The possible mechanism of the electric field response is discussed by the model of the electric double layer. This carbon fiber electrodes could provide the potential candidate and the theoretical basis for the design of high-sensitivity marine electric field sensor.

Bolt early looseness monitoring using modified vibro-acoustic modulation by time-reversal

Abstract Structural health monitoring (SHM) of bolted joints has played a vital role in estimation of bolt looseness and prediction of residual service life of bolted connections, thus saving money and significantly improving the efficiency of maintenance routines across industries. In the past decades, several SHM methods, particularly acoustic/ultrasonic methods, have been used to identify the health status of bolted connections. Compared to the linear ultrasound techniques such as active sensing, the vibro-acoustic modulation (VAM) method that is based on nonlinear ultrasonic features has proven its efficiency in bolt early looseness monitoring; however, some drawbacks impede its practical use. The main contribution of this paper is to develop a modified VAM (MVAM) that can circumvent existing problems with practical implementation and provide higher sensitivity. First, the shaker used in the traditional VAM was replaced by a piezoceramic transducer to improve its practicality. Moreover, instead of sine waves, linear swept sine signals were used for both low-frequency (LF) pump vibration and high-frequency (HF) probe wave. In other words, no a priori knowledge of the structural condition is needed, which further broadens the scope of application. Subsequently, the time reversal (TR) method was applied to overcome problems including signal energy dissipation and low signal-to-noise ratio (SNR) in traditional VAM. Moreover, the noise-assisted multivariate empirical mode decomposition (NA-MEMD) and multiscale multivariate sample entropy (MMSE) were used to develop a new damage index (DI) for bolt early looseness monitoring. Finally, multiple repeated experiments were conducted to verify the accuracy of the proposed method and its ability to simplify bolt early looseness monitoring in terms of practical operation, by comparing the proposed MMSE-based DI with nonlinear DI of traditional VAM method.

Modulation Induced Current Imbalance and Its Sensorless Control of a GaN-Based Four-Phase DC–DC Power Amplifier

The development of wide band-gap semiconductor devices is rapidly promoting the development of power electronics technology, especially in high frequency (HF) power converter region. A category of HF power converter is switch-mode power amplifier (PA). This paper focuses on the implementation of a multiphase dc–dc PA with high bandwidth and high power rate. When naturally sampled phase-shifted carrier modulation is implemented in the practical digital control system to control this HF power converter, the pulsewidth error problem caused by limited domain frequency of control chip becomes much severer. As a result, dc voltage component of each phase becomes different under several conditions, leading to current imbalance among phase inductors. This paper analyzes this problem and proposes a sensorless control method to solve it, based on the injection of random sequence in reference wave. A four-phase prototype employing GaN devices is fabricated, switching at 1 MHz. Current imbalance and effectiveness of the proposed control method are verified by experimental results. The prototype is capable of uniformly amplifying sine signal within 200 kHz and a 350 kHz bandwidth random signal, with peak output power up to 810 W.

High-Precision Light Spot Position Detection in Low SNR Condition Based on Quadrant Detector

In free space optical communications, long-distance transmission leads to the attenuation of beacon light, where we adopt a quadrant detector (QD) to receive the weak signal. However, the background light interferes so strongly that the output signal-to-noise ratio (SNR) of QD is at a low level, which causes a decrease in accuracy of the direct detection method. This requires finding a new light spot detection method, so an improved detection method is proposed. Because the dark current noise and the background light noise are both white noise, we adopt a Kalman filter to estimate the real output of four electric signals of QD. Unfortunately, running these through an amplifier introduces some direct current (DC) offsets into the signals. In order to balance the effect of the DC offsets, we consider using the modulation method, where we employ a sine signal to modulate the intensity of the beacon light at the transmitting end, after which we can give an inverse gain to move the center of signals to near zero to eliminate the DC offsets when we calculate the data. In Kalman filtering, we use the peak values of the signals in every period after the analog to digital converter (ADC) as the elements of the measurement matrix. Experimental results show that even when QD output SNR is about −10 dB, the detection root-mean-square errors decrease by 51.5% using the improved detection method compared with the direct detection method. Moreover, Kalman filtering does not require a large amount of data, which means it works efficiently, can reduce the cost of hardware resources, and is available for the real-time calculation of spot position.