Frequency Sweep Method Research Articles

Method for Measuring the Phase Spectrum of the Output of a Frequency Source Used in the Calibration of an Electroshock Weapon Characterization System.

Electroshock weapons (ESWs) output a transient burst of impulse-like high-voltage electrical signals that can incapacitate a human target. To ensure safe and effective operation of ESW, their outputs must be accurately measured. Accordingly, the systems used to measure the output of an ESW must be accurately characterized, and their response functions must be known for subsequent processing of the ESW output waveforms (current and high voltage). The long epochs (> 5 s) and high-bandwidth frequency content (> 200 MHz) of the ESW output require unique measurement instrumentation and calibration tools. A frequency-domain swept-frequency method is proposed here for the calibration of the phase response of an ESW measurement system. This method, although motivated by the ESW measurement application, is also applicable to other systems.

Improvement of the damping capacity of the linear damper with an oil groove in the linear guideway system

This article presents an experimental investigation into the damping characteristics of a linear damper with a newly designed oil groove. The damping performance of the damper is tested in four different viscosity grades by the sweep frequency method. And a test bench is used to move the damper for a several kilometers to examine the damping maintenance. The experimental results show that a higher oil viscosity leads to a higher damping capacity of the linear damper, and the increase in the oil viscosity will improve the damping maintenance of the damper. The newly designed oil groove efficiently improved the damping capacity of the linear damper; a proper oil selection will further optimize the effect of the oil groove via minimizing the oil leakage.

On-wafer probing-kit for RF characterization of silicon photonic integrated transceivers.

A wafer-level and high-efficiency radio frequency (RF) testing of a photonic device is highly desired in the fabrication and characterization of large-scale photonic integration circuits. In this work, we propose on-wafer probing kit designs, and demonstrate a damage-free, self-calibrated RF characterization of an integrated silicon photonic transceiver with a heterodyne mixing approach. Reduced or even free of fiber coupling off chip operation can be achieved with the on-wafer probing-kit to extract the frequency responses of broadband modulators and photodetectors in the photonic integration transceiver, with no requirement of electro-optical or opto-electrical calibration. A proof-of-concept probing kit is designed and fabricated with an on-chip electroabsorption modulator (EAM) and photodetectors by heterogeneously integrated III-V material on silicon substrate. On-wafer RF measurements with the self-calibration method are experimentally demonstrated with an accuracy analysis compared with the conventional swept-frequency method. The on-wafer and full-electrical test nature of the probing kit significantly advances performance monitoring of photonic integration circuits during chip fabrication, and promisingly offers predictable outcome and yield analysis before packaging.

Research on cutting vibration characteristics of face-milling involute gear

Abstract Traditional machining methods, such as gear hobbing, gear shaping and gear milling, etc, are commonly used for cutting machining of gear tooth profile, which cannot meet huge machining demand of gears to a certain extent. This article proposes to utilize a face-milling machining method in involute gear machining, which can be used to reduce production cost effectively. Cutting vibration generated during cutting machining has a direct effect on the machining accuracy and machined surface quality of workpiece. Therefore, it is desiderated to perform in-depth research regarding this issue. ADAMS software was used to establish a rigid-flexible coupling virtual prototyping model of face-milling gear milling system and a cutting vibration system model. Cutting vibration analysis was performed for face-milling gear by adopting quick sine frequency sweep method, so that the frequency response characteristics of workpiece in three directions X , Y and Z and space were acquired. The research results will provide reference and theoretical foundation for actual application of face-milling gear machining technology.

Viscoelastic behaviour of silica filled natural rubber composites – Correlation of shear with elongational testing

Dynamic mechanical behaviour of natural rubber-silica composites was studied by a frequency sweep method at different temperatures (40 °C,70 °C and 100 °C) using a dynamic mechanical analyzer and a rotorless rheometer, RPA, in an attempt to establish a correlation between the two. The composites with silica content up to 40 phr were studied. It was found that the dependence of dynamic modulus on the frequency as obtained from both the instruments followed a similar trend. This suggests that the dynamic mechanical properties of rubber compounds can be determined even during curing. A correlation could be arrived at between the two sets of data, making it possible to predict one set knowing the other. The impact of silane coupling agent, bis (3-triethoxysilylpropyl tetrasulphide), TESPT, on viscoelasticity was also investigated. The mechanical properties were improved in the presence of TESPT. Additionally, an increase in thermal stability was also observed in the presence of TESPT. Scanning electron micrographs showed the better filler dispersion in the case of silane-coupled silica composites.

Linearization and Control of Series-Series Compensated Inductive Power Transfer System Based on Extended Describing Function Concept

The extended describing function (EDF) is a well-known method for modelling resonant converters due to its high accuracy. However, it requires complex mathematical formulation effort. This paper presents a simplified non-linear mathematical model of series-series (SS) compensated inductive power transfer (IPT) system, considering zero-voltage switching in the inverter. This simplified mathematical model permits the user to derive the small-signal model using the EDF method, with less computational effort, while maintaining the accuracy of an actual physical model. The derived model has been verified using a frequency sweep method in PLECS. The small-signal model has been used to design the voltage loop controller for a SS compensated IPT system. The designed controller was implemented on a 3.6 kW experimental setup, to test its robustness.

Dynamic Optical Fiber Sensing With Brillouin Optical Time Domain Reflectometry: Application to Pipeline Vibration Monitoring

Brillouin distributed optical fiber strain sensors are often limited to static events because of necessary long acquisition time due to the frequency sweep technique. Dynamic distributed strain monitoring is necessary to ensure the integrity of linear structures submitted to fatigue loading or vibrations, such as subsea risers or flowlines, overhead pipelines, long bridges, railways, or high-rise towers. In this paper, a novel dynamic Brillouin optical time domain reflectometer for single ended truly distributed strain measurement based on the slope-assisted method is presented. The optical local oscillator frequency is adjusted to measure Brillouin backscattered power at the maximum slope of the Brillouin gain spectrum along the fiber length. Any strain variation inducing Brillouin frequency shift will be detected by amplitude variation. To demonstrate the performance of our acquisition system, three optical fibers have been implemented along a 10 m steel pipe submitted to vibration. Through this mockup testing, we were able to measure the oscillation damping time and the geometrical displacement of the pipe in real time. A 7.6 Hz acquisition rate was achieved with a strain error of ± 40 μ strain and with a spatial resolution of 1 m. From integration of longitudinal strains, pipe displacement is calculated with an error of ± 12 mm. A performance comparison between frequency sweep and slope assisted method is made with a 2 km fiber sensor.

Fast frequency sweep method for indirect boundary element models arising in acoustics

This paper presents an efficient approach for computing frequency sweeps with fine increments of acoustic systems described by the variational indirect boundary element method. The matrices arising from such boundary element discretizations are fully populated and their assembly is computationally demanding as it involves the calculation of double surface integrals for each system matrix entry. Therefore, the two operations performed when computing the response at one frequency, namely assembling the system matrix and solving the associated linear system, may be of the same order of magnitude in terms of the required computational time. The proposed fast frequency sweep approach accelerates both operations. First, it avoids forming the system matrices for each individual frequency. Matrices are only assembled at a few master frequencies, while for the rest, interpolation is used on scaled quantities determined at the master frequencies. Second, it avoids solving a dense linear system at each frequency. Padé approximants constructed via the well-conditioned asymptotic waveform evaluation algorithm are used to extrapolate the response around expansion frequencies using derivative information. The proposed method was tested on an exterior acoustics application representing an academic test case, as well as on an interior/exterior application representing an industrial test case.

Massive Multi-Frequency Eddy Current Method for Clad Material Inspection

The aim of this paper is to present a massive multi-frequency method for detection of cracks in clad materials. A system excited by a voltage waveform obtained as a sum of many sinusoidal components is proposed for this purpose. Studies show that, the multi-frequency method can be successfully used for detection and assessment of the defects depth in such kind of materials. The experimental verification is done and selected results of measurements are presented. with a depth of changes in the tested structure. That can be useful in applications such as measuring the thickness of conductive coatings on conductive base metal, detection and identification flaws in the material surface, differentiating between flaws in various layers of built-up structure. The additional advantages is that utilization of numerous frequency components in the excitation signal allow to fully test the structure as every single frequency consists independent information. Therefore, impact of noise can be reduced. Moreover presented method is much faster than Swept Frequency Methods and can be used complementary or as a substitute for the standard ECT.

The finite element analysis of the in plane and out of plane harmonic responses of piezoresponse force microscopy cantilever

The harmonic response under the in plane and out of plane driving force separately and model analysis of the widely used SCM-PIT probe were carried out in the consideration of the typical piezoresponse force microscopy working condition by finite element method. It is shown that there are symmetric modes of the resonance at 68, 408, 1139, 2244 kHz, and antisymmetric modes at 646, 1020, and 3077 kHz in the first seven eigenmodes. The symmetric modes of the harmonic response are verified by the frequency sweep method from the piezoresponse phase signals experimentally. It is also revealed that different driving frequencies should be used in the resonance-enhanced PFM imaging in the consideration of the domain structures. The driving frequency of 68, 408, 1139, 2244 kHz should be preferred in the resonance-enhanced PFM imaging of the out of plane domains, while the driving frequency of 646, 1020 and 3077 kHz should be used for the imaging of in plane domains in order of achieved the best resonance-enhanced effect.

A new efficient approach for fast and accurate design of frequency selective surfaces based on geometry estimation networks

Artificial neural networks are a favorite modern tool for high accuracy designing frequency selective surfaces (FSSs) in RF and microwave engineering field. In this paper, a new fast and precise ANN-based algorithm for designing FSSs is presented. This algorithm, unless the previous works, can develop the structures with due attention to features of incident waves and improve the applicability of developed FSSs. For achieving this algorithm, at first, a new method is presented for the better preparation of training datasets, called frequency sweep method (FSM). The advantage of FSM is to reduce the size of training datasets and prevent from superfluous simulations. So the time needed for the preparation of training datasets and to train the networks is less than before. Following that, FSM is used to train geometry estimation ANN (GEANN) with primary goal of FSSs design in little time and without any optimization algorithm. The proposed design procedure is complete design and analysis unit that consisted of a sequence of GEANN and traditional response calculation ANNs (RCANNs). GEANN is used to estimate geometric dimensions of FSSs with desired incident wave, and RCANNs are used to calculate the frequency response of FSSs under other various incident waves. The results show that required time for designing FSS is less than 30 ms, and errors are <1 %. Both analytical and experimental results confirm the correctness of predicted values.

MIMO Repetitive Control of an Active Magnetic Bearing Spindle

Abstract: We present the identification and control of an open loop unstable MIMO Active Magnetic Bearing Spindle (AMBS) for machining applications. A 20th order model is obtained from reducing a higher order model identified by the ARX method. For verification purposes, the model is compared to the system’s frequency responses obtained by the frequency sweep method. The model is used to design a linear quadratic optimal controller, where the weighting gains are tuned by simulation and experiment. A plug-in repetitive controller for asymptotic regulation and tracking of signals synchronous to the spindle rotation is designed by formulating the control design as a model matching filter design problem. The model matching’s optimal solutions for the non-minimum phase MIMO stabilized system are obtained respectively for H ∞ and H 2 norm minimizations. Simulation and experimental results are presented to compare the proposed MIMO repetitive control design methods and demonstrate the control performance.

The Harmonic Suppression Characteristic Analysis of a Phase-Shifting Reactor in Rectifier System

Multiple rectifier technology is an effective method to reduce the harmonic current injected from converter to the grid [1], and phase-shifting reactor (PSR) is a kind of magnetic equipment which can be used to realize the function of phase-shifting[2]-[4]. In the multiphase rectifying system, the phase-shifting property of PSR plays an important role in harmonic suppression, meanwhile, as an inductive device, its filtering property cannot be neglected. Therefore, with the purpose of evaluating the phase-shifting and filtering properties of PSR in the harmonic current suppression, three kinds of reactors with approximate harmonic suppression effect in the 6-phase rectifying system are designed, one is without phase-shifting, and the other two are with phase-shifting in different phase-shifting angle. And then, based on the Fast Fourier Transform (FFT) algorithm and the frequency sweep method, the phase-shifting and filtering properties are respectively revealed by the harmonic current spectrum diagram and the amplitude-frequency characteristic curve. Lastly, the idea to introduce the low-pass filter's design method to the design of PSR to strengthen the harmonic suppression effect is proposed.

Radiated spurious emission measurements using fast Fourier transform‐based time domain scan

In this study, the use of time domain (TD) scan based on fast Fourier transform technique for radiated spurious emission (RSE) measurements is investigated. Measurement time and results of TD scan are compared with those of conventional frequency sweep method. The RSE measurements carried out are based on two different wireless technologies, that is, GSM 900 and GSM 1800. The findings show that the TD scan can reduce overall RSE test time up to 86% with comparable measurement results.

Frequency characteristic measurement of a fiber optic gyroscope using a correlation spectrum analysis method based on a pseudo-random sequence

The frequency characteristic is an important indicator of a system’s dynamic performance. The identification of a fiber optic gyroscope (FOG)’s frequency characteristic using a correlation spectrum analysis method based on a pseudo-random sequence is proposed. Taking the angle vibrator as the source of the test rotation stimulation and a pseudo-random sequence as the test signal, the frequency characteristic of a FOG is calculated according to the power spectral density of the rotation rate signal and the cross-power spectral density of the FOG’s output signal and rotation rate signal. A theoretical simulation is done to confirm the validity of this method. An experiment system is built and the test results indicate that the measurement error of the normalized amplitude–frequency response is less than 0.01, that the error of the phase–frequency response is less than 0.3 rad, and the overall measurement accuracy is superior to the traditional frequency-sweep method. By using this method, the FOG’s amplitude–frequency response and phase–frequency response can be measured simultaneously, quickly, accurately, and with a high frequency resolution. The described method meets the requirements of engineering applications.

On τ ‐decomposition frequency‐sweeping strategy to rational‐order fractional systems with commensurate delays

This study presents an effective analysis procedure to give the bounded input bounded output stability intervals of time delay for a class of commensurate delayed fractional-order systems with rational order. First, it is proposed that the analysis on multi-valued characteristic function of delayed fractional-order systems can be conducted equivalent on the consideration of the principal branch. The statement makes the generalisation of the τ-decomposition method in integer order case possible. With the convenience in studying delayed systems, the frequency-sweeping method is applied logically, and the PIRs and the cross-direction around them can be determined through the frequency-sweeping curves simultaneously. Moreover, the verification of the neutral stability condition of fractional-order delayed systems is considered in a systematic manner. At last, some examples show that the proposed strategy is practically useful in the analysis and design of feedback control for both integer and fractional-order systems with time delays.

Magnetorheology of core–shell typed dual-coated carbonyl iron particle fabricated by a sol–gel and self-assembly process

Micron-sized soft-magnetic carbonyl iron (CI) particles, which are the most widely applied magnetic particles in magnetorheological (MR) fluids, were evaluated as a candidate for modification by coating to reduce their density and provide rich surface properties. Both silica and multi-walled carbon nanotubes (MWNTs) dual-coated soft-magnetic CI particles were fabricated and applied as magneto-responsive solid particles in an MR fluid. The silane-grafted CI microspheres were coated with the first layer of silica using a sol–gel method, and the second layer of MWNTs was then wrapped using a layer-by-layer process in both positive and negative polyelectrolytes. The rheological properties from the dynamic and steady shear tests of the MR fluid when dispersed in silicone oil were examined using a rotational rheometer under an applied magnetic field. The Schwarzl equation was also used to determine relaxation modulus of the MR fluid, based on the dynamic moduli measured from a frequency sweep method.

High Power Electromechanical Characterization of Piezoceramics and Low Frequency Ultrasound Transducers by Using Algorithm for Tracking Changes in Resonant Frequency and Electrical Impedance

Electromechanical and acoustical characterization of PZT piezoceramic elements and high-power ultrasound transducers has been done around resonance frequencies in order to determine the features of the models that describe the considered devices, both as equivalent circuits and as nonlinear oscillators. Several measurement methods have been compared, including the frequency-sweeping method with constant excitation voltage, the magnitude-sweeping method at a constant excitation frequency and the method that uses impulse excitation. The parameters that describe the losses in a coupled nonlinear electro-mechanical-acoustical system greatly depend on the type of excitation and its level. A novel algorithm is tested, designed for tracking the changes of the series resonance frequency and impedance magnitude and phase with the excitation level. It enables a more precise determination of the resonance frequency and impedance changes over different levels of excitation, which is especially important in high-power resonant applications. The characterization based on frequency sweeping at different excitation levels is influenced by changing electrical parameters (current, voltage, power) due to different complex loading of the excitation amplifier and the changes of thermodynamic conditions. The characterization of transducers in loaded condition through frequency sweeping at higher signal levels gives no results when cavitation in front of the horn appears, because the impedance magnitude changes at higher excitation voltages. Using the tracking algorithm, the impedance magnitude at resonance frequency has been determined in a range of different excitation levels up to 35 VRMS. Before the onset of nonlinear effects such as cavitation or acoustic streaming, the impedance magnitude increases due to viscosity effects.

A Novel Adaptive Frequency Injection Method for Power Electronic System Impedance Measurement

Power electronic systems are prone to negative impedance instability due to the constant-power nature of the individual components. The impedance measurement, therefore, is very important during the system designing because of the close relationship between impedance and stability. However, traditional frequency sweep methods, by injecting a series of sinusoidal perturbation signals equidistantly, always select the frequency interval on experience accumulating without guiding theory, which result in low accuracy, low reliability, and low efficiency. In this paper, the relationship between measured results and the frequency interval is built first, then the frequency interval selection criteria of injection signals are derived accordingly. Afterward, based on the above analysis, a novel adaptive frequency injection method of impedance measurement is proposed to figure out the practical issues in power electronic system impedance measurement process. With this method, variable frequency interval can be selected according to characteristics of the measured network automatically. Compared to the traditional frequency sweep method, the proposed one can measure impedance more accurately and efficiently. The simulation and experimental results validate the effectiveness of the proposed method.

Faster frequency sweep methods for structural vibration and acoustics analyses

The design of large, complex structures typically requires knowledge of the mode shape and forced response near major resonances to ensure deflection, vibration, and the resulting stress are kept below acceptable levels, and to guide design changes where necessary. Finite element analysis (FEA) is commonly used to predict Frequency Response Functions (FRF) of the structure. However, as the complexity and detail of the structure grows, the system matrices, and the computational resources needed to solve them, get large. Furthermore, the need to use small frequency steps to accurately capture the resonant response peaks can drive up the number of FRF calculations required. Thus, the FRF calculation can be computationally expensive for large structural systems. Several approaches have been proposed that can significantly accelerate the overall process by approximating the frequency dependent response. Approximation approaches based on Krylov Galerkin Projection (KGP) and Pade calculate the forced response at only a few frequencies, then use the response and its derivatives to reconstruct the FRF in-between the selected direct calculation points. This paper first validates the two approaches with analytic solutions for a simply supported plate, and then benchmarks several numerical examples to demonstrate the accuracy and efficiency of the new approximate methods.