Non-sinusoidal Research Articles

Digital Signal Processor Programming using MATLAB Simulink Embedded Coder

In this work, a computer tool developed in Matlab is presented for process control in real time. The Matlab/Simulink Embedded Code toolbox allows the programming of different commercial acquisition and control cards. In addition, it is easy to supervise the practical cases implemented both from the cards commercial interfaces and from Matlab/Simulink. This work shows how to use the Texas Instruments TMS320F28335 card, the installation of the required software to program the card and the development of a practical case to prove its performance. Thus, the way of generating a sinusoidal voltage waveform using a power DC/AC converter controlled by the PWM (pulse-width modulation) modules card, is presented. This method can be used for teaching and researching purposes, and it is also used for the electric power system management.

Design and implementation of multi-level linkage mechanism bionic pectoral fin for manta ray robot

Manta rays achieve propulsion through the undulation of their pectoral fins, making them an important subject of study in bionics due to their efficient and agile swimming characteristics. However, currently, most biomimetic pectoral fins achieve a flapping pattern similar to that of biological fins by using multiple driving mechanisms. This paper designs an actively controlled bionic pectoral fin, driven by a single motor through a multi-level linkage mechanism, for a larger size and fully functional manta ray robot. Firstly, a bionic pectoral fin is designed based on a multi-level linkage mechanism driven by a single motor, and non-linear programming methods are innovatively applied to optimize the fin mechanism, making its motion profile more similar to the sinusoidal waveform of biological manta ray pectoral fins. Secondly, a dynamic model of the manta ray robot is established using dynamic mesh technology to verify the propulsion capability of the bionic pectoral fins and the robot's theoretical speed. Finally, prototypes of the manta ray robot are developed, and experimental research is conducted in a pool and lake. The experimental results show that the robot can complete straight-line swimming, buoyancy control, and turning in water, with a stable and flexible motion posture, proving the feasibility of this method.

A New Method to Synthesise the Sinusoidal Oscillator Based on Series Negative Resistance-Capacitance and its Implementation Using a Single Commercial IC, LT1228

An alternative method for synthesising the sinusoidal oscillator based on series negative resistance-capacitance is presented in this paper. The proposed topology is constructed with the series negative resistance-capacitance circuit connected in parallel with a grounded resistor and capacitor. To validate the proposed method, a new grounded series negative resistance-capacitance simulator is also proposed as a subcircuit for synthesising the sinusoidal oscillator. The series negative resistance-capacitance simulator is based on a commercially available integrated circuit (IC), LT1228. The equivalent negative resistance and equivalent negative capacitance can be adjusted electronically using an external DC bias current. The sinusoidal oscillator that is synthesised using the proposed method consists of a single LT1228, two capacitors, and three resistors. The frequency and the condition of the oscillation are orthogonally adjusted. Also, the condition of oscillation is electronically controlled. The amplitude of the sinusoidal waveform is adjustable. In addition, the output voltage node of the proposed oscillator has a low impedance, which allows it to connect to other circuits without using an additional buffer. Both PSPICE simulation and experiment are used to validate the proposed circuits.

Multi-target two-photon dual-comb LiDAR.

By substituting two-photon cross-correlation in a wide-bandgap photodiode for the coherent gating conventionally used in dual-comb ranging, two-photon dual-comb LiDAR exchanges data-intensive interferometric acquisition for a single time-stamp from which an absolute distance can be inferred. Here, we report the application of two-photon dual-comb LiDAR to obtain real-time ranging to three independent targets with only a single silicon-photodiode detector. We show precisions of 197-255 nm (2 seconds averaging time) for static targets, and real-time simultaneous ranging to three dynamic targets driven by independent sinusoidal, saw-tooth and square waveforms. Finally, we demonstrate multi-target ranging to three points on a rigid body to provide simultaneous pitch and yaw angular measurements with precisions of 27.1 arcsec (130 µrad) on a 25 mm baseline.

Design and Harmonic Elimination of sinusoidal pulse width modulation (SPWM) Based Five Level Cascaded H-Bridge Multilevel Inverter for Photovoltaic System for Educational Purposes

In this modern era, the electrical power system faces a shortage of fossil fuel-based energy sources. To overcome this problem, people more focus on giving towards renewable energy sources like solar energy, wind energy, and nuclear energy sources. This also can be used to overcome global warming and reduce pollution by fossil fuels. This study used a photovoltaic (PV) array to give supply to the Multilevel Inverter (MLI) with different irradiance values, which can be used for educational purposes. The sinusoidal pulse width modulation (SPWM) method is used here to control the converter. SPWM technique is the easiest technique than the other types of pulse width modulation (PWM) technique. In this technique the switching loss is very low, therefore efficiency is high. After the simulation, the output waveforms are similar to the sinusoidal waveform for the resistive load. In this topology, after simulation, the total harmonic distortion (THD) contents were found to be less by using an LC filter. The model is simulated in MATLAB/Simulink. The analysis of output voltage waveforms is discussed with the reduced THD.

Temporal light modulation: Data processing and metric calculations

There are multiple metrics used in research and industry to describe the visibility of temporal light modulation (TLM), colloquially referred to as ‘flicker’. However, the metrics are not straightforward to calculate, and the values sometimes vary according to sampling rates. This work addresses the vagaries in processing TLM waveform data and calculating the metrics. For each TLM metric, its sensitivity to sampling rate is presented, followed by recommendations for improving the reliability and consistency of calculated metrics. Appropriate sampling rates are proposed according to the nature of the waveform and metric. The analyses of this paper are based on ideal waveforms without noise or instability, but the effects of sampling rate also apply to real-world waveforms. Some metrics, such as the Stroboscopic Visibility Measure, were relatively stable (i.e. produced the same value regardless of sampling rate) – within the ranges for which they are defined – for sinusoidal and/or rectangular TLM waveforms. In contrast, short-term flicker indicator [Formula: see text] and perceived modulation [Formula: see text] values exhibited greater variability based on sampling rate. Metric values from sinusoidal waveforms were generally more stable than those from rectangular waveforms, although [Formula: see text] showed inconsistency even with sinusoidal TLM.

Stationary flow driven by non-sinusoidal time-periodic pressure gradients in wavy-walled channels

The classical problem of secondary flow driven by a sinusoidally varying pressure gradient is extended here to address periodic pressure gradients of complex waveform, which are present in many oscillatory physiological flows. A slender two-dimensional wavy-walled channel is selected as a canonical model problem. Following standard steady-streaming analyses, valid for small values of the ratio ε of the stroke length of the pulsatile motion to the channel wavelength, the spatially periodic flow is described in terms of power-law expansions of ε, with the Womersley number assumed to be of order unity. The solution found at leading order involves a time-periodic velocity with a zero time-averaged value at any given point. As in the case of a sinusoidal pressure gradient, effects of inertia enter at the following order to induce a steady flow in the form of recirculating vortices with zero net flow rate. An improved two-term asymptotic description of this secondary flow is sought by carrying the analysis to the following order. It is found that, when the pressure gradient has a waveform with multiple harmonics, the resulting velocity corrections display a nonzero flow rate, not present in the single-frequency case, which enables stationary convective transport along the channel. Direct numerical simulations for values of ε of order unity are used to investigate effects of inertia and delineate the range of validity of the asymptotic limit ε≪1. The comparisons of the time-averaged velocity obtained numerically with the two-term asymptotic description reveals that the latter remains remarkably accurate for values of ε exceeding 0.5. As an illustrative example, the results of the model problem are used to investigate the cerebrospinal-fluid flow driven along the spinal canal by the cardiac and respiratory cycles, characterized by markedly non-sinusoidal waveforms.

Power quality monitoring and analysis of aerodrome supply system: A study in Gautam Buddha International Airport, Nepal

The power supply system may contain disturbances leading to variations in voltage and frequency from their nominal value, non-sinusoidal waveform injection, presence of negative and zero sequence components, etc. Power quality is a measure of characteristic disturbances present in the power supply which ensures the importance of quality of service and consumer requirements. Electrical equipment installed in an aerodrome is more sensitive and prone to disturbance present at the power supply end. This study provides results of a theoretical power flow study, power quality monitoring, quality analysis, and probable remedies for power quality issues in an aerodrome electrical supply system in Nepal. Power quality measurement for supply from the utility here, Nepal Electricity Authority, and internal power generations in Gautam Buddha International Airport (GBIA) Siddharthanagar, Rupandehi, Nepal is performed by using theoretical load flow approach and continuous monitoring using a power data analyzer. The scope and origin of various disturbances which may induce power quality issues are analyzed. It is observed that the power supply at GBIA has voltage fluctuations of about ±12% and total voltage harmonic distortion of 6.5% with the presence of negative and zero sequence components. A remedial solution for the power quality problem is proposed for future enhancement of the electrical supply system at GBIA.

Development of Extractor-Classifier-Regulator integrated anomaly detection model for turning process

Anomaly detection is important for safety and productivity in manufacturing systems. Together with the development in IoT, data-driven approach turns out as the most promising alternative for up-to-date anomaly detection. While applying modern A.I solutions into manufacturing for anomaly detection, however, it is often encountered that insufficient anomalous data is available for training deep-learning models. The most manufacturing systems are optimized to run at the best conditions so that anomalies rarely occur in the actual production lines. In this study, we proposed and developed an Extractor-Classifier-Regulator integrated anomaly detection model (ECR model) which combines the feature extractor, classifier and regulator in a block stacked way. This model requires the “normal” data only for training, and is capable of identifying the anomality based on the density of distribution in the extracted feature space. The framework described in the Section 2 yields that the ECR model is an end-to-end learning architecture, requires no pre-process for feature extraction and selection. The performance of the proposed model was first verified in the Section 3, by use of the phase-shifted sinusoidal waveforms generated artificially. The results suggested that our ECR model well yielded the degree of abnormality corresponding to the deviation of each variable from the “normal” datasets. The proposed model was then implemented into a turning process of Inconel 718 to detect cutting failure caused by tool wear. The experimental setup including machine tool, workpiece, tool holder, data acquisition system, time sequential signals related to the cutting process were detailed in the Section 4. After being trained by AE (Acoustic Emission) or sound signals captured in the “normal” cutting stage, the proposed model was able to derive anomaly scores which well matched with the cutting stages of “normal”, “transitional” and “anomalous” corresponding to the tool wear.

Electrowetting-assisted pool boiling heat transfer characteristics under low gravity conditions

In pool boiling under low gravity conditions, the vapor bubbles remain attached to the heating surface, which deteriorates the heat transfer rate. The present work demonstrates the integration of the electrowetting (EW) technique to resolve the bubble departure problem in pool boiling at low gravity conditions. A phase-field-based numerical method with a dynamic contact angle model has been implemented in COMSOL Multiphysics (V5.3) to investigate the problem. The bubble dynamics in the electrowetting integrated pool boiling for low gravity conditions are analyzed at various frequencies for different voltage waveforms, i.e., square, sinusoidal, and triangle. The EW technique increases the departure frequency of the bubble and the heat transfer rate compared to the conventional pool boiling. The sinusoidal voltage waveform shows the best performance among different voltage waveforms, producing 119.3% higher bubble departure frequency and 74.3% heat transfer enhancement than the conventional pool boiling.

0060 A Classification Based Generative Approach to Selective Targeting of Global Slow Oscillations during Sleep

Abstract Introduction Interacting with sleep slow oscillations (0.5,15 Hz) is essential to understanding the mechanisms underlying their role in sleep functions, including homeostasis, synaptic reorganization, and memory consolidation. Current approaches to SO-based non-invasive closed loop alternate current stimulation (cl-tACs) focus on timing, and do not differentiate among oscillations based on their space-time profiles. In this study, we leverage machine learning and global optimization to introduce a generative model of brain stimulation protocols targeting Global SOs. Methods We identify a stimulation protocol that matches a Global SO in two stages: first focusing on the electrode montage, and then on the stimulation waveform. Using the sleep night of 22 volunteers acquired in the lab with high density EEG (175 electrodes), we labeled the SOs as Global/non-Global SOs based on their co-detection on the scalp at a small delay (0.4s). We used the current density (CSD) profile of each SO in cortical and subcortical regions to develop a well-trained classifier (based on weighted k-nearest neighbors). We identify as optimal the electrode montage that resulted in CSDs labeled as Global with highest likelihood by the classifier. We then parameterized a sinusoidal waveform and identified optimum parameters with a genetic algorithm that used feature ranking to establish a weighted distance metric to target Global SO profile built from sleep data. We repeat this approach focusing on Global SO dynamics at a slow time scale and a faster time scale (200ms vs 20ms resolution). Results We identified optimal stimulation profiles matching Global SOs at both time scales. At slow time scale, montage selection relied only on CSD near the SO trough and in the reward network and the brainstem. Linear waveforms over-performed sinusoidal waveforms for fit at low time scales. At fast time scale, CSD at both trough and 500ms before the trough were strongly selective for Global vs. non-Global SO. Conclusion Global SOs are a gating mechanism for large-scale neural communication, a necessary substrate for systems consolidation and long-term memory formation. This data-driven method builds on natural sleep data to shape a stimulation protocol that imitates Global SO dynamics and is generalizable to other SO types. Support (if any)

The theoretical model and sinusoidal optimization strategy for oscillating shear valve type continuous waves generator

Continuous-wave mud generator is widely adopted for real-time downhole data transmission of deep wells in the oil industry. There have been many studies on rotor structure optimization of continuous rotary valve tools but few studies on the different optimization mechanisms of oscillating shear valve tools. In this paper, a theoretical model of pressure wave generation for oscillating shear valve tools was presented, and the reason for the non-sinusoidal waveform was analyzed theoretically for the first time. A series of rotor rotation strategies were proposed to improve the sinusoidal properties of pressure waves without changing the mechanical structure of the rotor. Finally, CFD with different parameters was conducted to verify the feasibility of the optimization scheme. The numerical results give the recommended range of parameters under different control schemes. In addition, the relationship between throttle pressure drop and pressure wave waveform is found through comparison with previous research of the team, which provides a new research idea for the optimization of the pressure wave in the future.

An Improved Multi-Pulse Rectifier Circuit for Input Current Harmonic Suppression Using Passive Devices

Renewable energy resources, such as solar and wind, are increasingly being integrated into power systems to promote sustainable and clean energy generation. However, the intermittent nature of these resources poses challenges in terms of harmonics, power factor and power quality. This paper focuses on the use of multi-pulse rectifiers (MPR) as a solution for enhancing the performance and grid integration of renewable energy resources. A novel approach is introduced, combining a phase-shifting transformer that provides a five-phase input to a series of 20-pulse rectifiers with a pulse-tripling circuit (PPTC). By modulating the resultant currents of bridge rectifiers with PPTC, the rectifier’s pulse number is raised from 20 to 60, resulting in enhanced reduction of input current harmonics. The proposed rectifier configuration achieves an input current with an approximate sinusoidal waveform, exhibiting a Total Harmonic Distortion (THD) of less than 4%. The proposed scheme offers several advantages. It is simple, utilizing only passive components without the need for active devices, making it easy to implement, improving the performance of rectifier, ensuring compliance with power quality standards, and enabling reliable operation in medium- and high-voltage electronic systems.

Impulsive motion causes time-dependent nonlinear convective Williamson nanofluid flow across a rough conical surface: Semi-similar analysis

The time-dependent nonlinear convective Williamson nanofluid flow over a rough conical surface in the presence of numerous diffusions and Arrhenius activation energy effects are the main focus of the investigation in this paper. The unsteady flow is essentially due to the impulsive mainstream flow. Two diffusive species, namely, liquid Hydrogen and liquid Nitrogen, occur in the flow under investigation. A sinusoidal waveform mathematically models the rough conical surface with small amplitude and high frequency. Thus, the surface gradients, namely skin friction, exhibit wavy effects in the boundary layer regime. In the current flow problem, the governing equations for the fluid flow are highly coupled nonlinear PDEs that depend on the proper initial and boundary conditions. Mangler's transformations are used to convert them into non-dimensional forms, and implicit finite difference approximation and quasilinearization are employed to produce numerical semi-similar solutions. The numerical results representing the boundary layer effects are displayed graphically and analyzed for parametric values. The friction experienced by the rough surface is strongly fluctuating for higher values of Williamson parameter W. The heat transfer rate Rex-1/2Nu increases approximately by 61% and 63% at ξ=0.8 when Nt decreases from Nt=0.5 to Nt=0.1, for the cases of W = 0 (Newtonian fluid) and W = 1(Williamson fluid), respectively. Additionally, there is a strong correlation between the current findings and the related results previously published in the literature.

Power quality enhancement of distribution grid using a photovoltaic based hybrid active power filter with three level converter

This paper employs a second-order sequence filter (SOSF) and proportional–integral (PI) controller to control a hybrid active power filter with photovoltaic (HAPF-PV) through three-level neutral point clamped (NPC) converters. The PV system uses perturbation and observation (P&O) method to track the maximum power point and drive a boost DC/DC converter. A reference signal of a shunt active power filter (SAPF) is generated by estimating the real (not imaginary) term of the polluted load current. The estimation of this term relies on adopting a SOSF and sampling that its input at points the load voltage crosses the zero. SAPF is responsible for compensating grid current harmonics. The suggested approach helps obtain fundamental real term of the polluted unbalanced load current with good accuracy and minimal mathematical computations. In addition to improve power quality, this system can produce green output using the PV arrays connected to the HAPF via a DC-link. HAPF-PV has advantages of power quality enhancement and distributed generation simultaneously. Also, in this system, three-level NPC converters are used in order to reduce harmonic currents injected into the grid by HAPF-PV. Escalating the converter output voltage had led to obtaining output sinusoidal waveform of the converter, and so in this paper, a three-level NPC converter with a neutral point is used to reduce harmonics due to PWM switching. Besides, a series active power filter (SeAPF) is presented for series compensation such as voltage sag/swell. The scheme was implemented in MATLAB considering various types of disturbances including the PCC voltage sag/swell, unbalanced load and changes in irradiance.

Coherence‐based integrated detection and assessment algorithm for voltages and currents unbalance/disturbance in three‐phase synchronous generators: A validation of simulation results

AbstractThe phenomenon of imbalance is a variation of voltage and current waveforms from a perfect sinusoidal waveform, which is considered a crucial challenge in power systems. Uneven loads and disturbances result in three‐phase voltage/current unbalance that leads to a temperature rise and low output curves at synchronous machines. Thus, the unbalance/fault must be recognized and avoided. This article suggests a methodology to detect and evaluate three‐phase voltage and current unbalance/fault using a coherence algorithm. The suggested scheme develops integrated protection functions that can be divided into three modules: voltage unbalance, current unbalance, and power factor unbalance. Therefore, it can be useful in mitigation techniques applied to compensate the voltage unbalance effects. The present protection introduces a new proposal of closed‐tripping curves based on the values range of nine coherence factors. To investigate the protection performance, a segment of power grid with real parameters’ information is simulated utilizing ATP platform. Several fault types, such as shunt and series faults, are conducted on the simulated system to analyze the results and monitor the system status using the coherence statistic processed in MATLAB software. The results show that the approach is smart, swift, precise, reliable and stable. Moreover, the algorithm can be practically implemented, and represents a base for digital unbalance/fault detectors and relays because its performance is superior in detecting Power Quality Disturbances (PQDs).

Automatic Reduction of THD for Non-Linear Load by Using Microcontroller

Abstract: In a perfect world, the term harmonics used to describe power quality would refer to how pure the voltage and current waveforms are when they take the shape of sinusoidal. Power quality is veritably important to commercial and industrial power system designs. ideally, the electrical supply should be a perfect sinusoidal waveform without any kind of distortion or disruption. If the current or voltage waveforms are distorted from its ideal form it'll be nominated as harmonic distortion. This harmonic distortion could affect because of numerous reasons.

Improving the Accuracy of Digital Unbalanced Impedance Bridges

This article presents an automatic digital unbalanced impedance bridge for comparing two-port impedances: R-R, R-C and C-C. The bridge consists of a two-channel digital source of voltage sinusoidal waveforms supplying the bridge arms and a three-channel precise digitizer, by means of which the complex ratio of the source output voltages and the relative bridge unbalanced voltage are determined. The hardware implementation of the bridge is based on a relatively inexpensive universal data acquisition (DAQ) card by National Instruments, USB-6281, which contains, among others, a multi-channel 18-bit analog-to-digital converter (ADC) and two 16-bit digital-to-analog converters (DAC). Thanks to the new approach to the bridge operation algorithm, consisting in the use of the interpolation method in the comparison process, the influence of the accuracy of the measurement of the bridge unbalanced voltage and some bridge parasitic admittances on the uncertainty of the impedance comparison were minimized. This simplifies the measurement procedure and shortens its execution time. The obtained results confirmed that a relatively simple digital unbalanced bridge can compare impedance standards with an uncertainty of less than 10−5. By reducing the requirements regarding the uncertainty of the measurement, and thus its execution time, the presented bridge supplemented with impedance sensors can be used in many areas of industry.

Numerical Study of Flow Control on Simplified High-Lift Configurations

Enhancement in the aerodynamic performance of wings and airfoils is very notable when Active Flow Control (AFC) is applied to Short Take-off and Landing aircraft (STOL). The present numerical study shows the application of steady, pulsed and synthetic tangential jets applied to the plain flap shoulder of a modified NASA Trapezoidal Wing. Pulsed jets are modeled by sinusoidal and square waveforms while synthetic jets are modeled only by pure sine waveform. The freestream airflow conditions are Mach number equal to 0.2 and Reynolds number equal to 4.3 million based on the mean aerodynamic chord. The presented simulations are two-dimensional and based on RANS for steady jet cases and URANS for pulsed and synthetic cases, compiled with the open-source suite SU2 and adapted for time varying boundary conditions. Numerical results for modified configurations based on the same baseline wing profile considering different leading edges, jet slot height, flap position, blowing mass flow, type and frequency of the jets are presented. Curves of pressure coefficient distribution revealed a substantial influence upstream of the AFC, around the slat and main element. The jet slot height analysis showed that the lift gain is also influenced by the slot size due to the change of the local flow velocity considering the same blowing momentum coefficient. Regarding the jet frequency, no significant differences on the lift coefficients were found between the reduced frequencies F+ equal to 1 and 2. Results of aerodynamic loads showed an improved lift coefficient in relation to the baseline airfoil when pulsed and steady jets are employed. Pulsed jets under square waveform were effective even at high deflected flap condition at 50°, with a significant gain in the lift coefficient of 36%, in relation to the uncontrolled case, combined with a drag reduction of 20%, and a decrease in mass flow up to 49% in relation to the steady jet for the same lift gain. Although sine and square waveform results presented similar improvements for lift, the drag is around 15% higher for the former. When compared with the steady jet case, the mass flow reduction is 36% for the sinewave. Synthetic jets with zero-net-mass-flux proved superior to the baseline conventional multi-element airfoil only with deployed flap at 50°, where a modest lift improvement of 5% was observed.

Mathematical modelling and simulation of leak detection system in crude oil pipeline

A first-order differential leak detection model that accurately detects leaks in a crude oil pipeline is presented. This model incorporates a leak factor KL in the axial direction, which is simulated by applying the finite element method of numerical solution using COMSOL multi-physics software. Additionally, the model includes the transport equation for turbulent kinetic energy and the rate of kinetic energy model. Eigenvalues for velocities and pressures were determined and plotted against time for various pipe segments. The system is stable when the Eigenvalue is zero, but a leak is declared when the Eigenvalue for pressure or velocity is less than one. The study shows that pressure measurements are more sensitive parameters for detecting leaks than velocity measurements, and the sinusoidal waveform characterizes leak behaviours for velocity.