Harmonic Amplitude Ratio Research Articles

Temperature drift suppression for micro‐electro‐mechanical system gyroscope based on vibrational‐displacement control with harmonic amplitude ratio

AbstractMicro‐electro‐mechanical system gyroscope detection output is susceptible to drift due to ambient temperature variations. Furthermore, the drive‐mode vibration amplitude is affected by the signal pickup circuit and structural parameters, which significantly influence the temperature drift of the bias and scale factor (SF). This study proposes a vibration amplitude control method based on harmonic amplitude sideband‐ratio (SBR), namely SBR‐AGC, which characterizes the vibration amplitude using the harmonic amplitude ratio of the vibrational electrical signal. The constancy of vibration amplitude is maintained via closed‐loop control to suppress bias and SF temperature drift. The experimental results on cobweb‐like disk resonator gyroscope reveal that the temperature coefficient of bias in the SBR‐AGC mode lies within −20 to 60°C and decreases by 36%, and the temperature coefficient of the SF lies within −10 to 50°C and decreases by 49.7%. Therefore, the environmental adaptability of the gyroscope is effectively improved.

Effects of Molecular Size on Resolution in Charge Detection Mass Spectrometry.

Instrumental resolution of Fourier transform-charge detection mass spectrometry instruments with electrostatic ion trap detection of individual ions depends on the precision with which ion energy is determined. Energy can be selected using ion optic filters or from harmonic amplitude ratios (HARs) that provide Fellgett's advantage and eliminate the necessity of ion transmission loss to improve resolution. Unlike the ion energy-filtering method, the resolution of the HAR method increases with charge (improved S/N) and thus with mass. An analysis of the HAR method with current instrumentation indicates that higher resolution can be obtained with the HAR method than the best resolution demonstrated for instruments with energy-selective optics for ions in the low MDa range and above. However, this gain is typically unrealized because the resolution obtainable with molecular systems in this mass range is limited by sample heterogeneity. This phenomenon is illustrated with both tobacco mosaic virus (0.6-2.7 MDa) and AAV9 (3.7-4.7 MDa) samples where mass spectral resolution is limited by the sample, including salt adducts, and not by instrument resolution. Nevertheless, the ratio of full to empty AAV9 capsids and the included genome mass can be accurately obtained in a few minutes from 1× PBS buffer solution and an elution buffer containing 300+ mM nonvolatile content despite extensive adduction and lower resolution. Empty and full capsids adduct similarly indicating that salts encrust the complexes during late stages of droplet evaporation and that mass shifts can be calibrated in order to obtain accurate analyte masses even from highly salty solutions.

Vertebral Lamina State Estimation in Robotic Bone Milling Process via Vibration Signals Fusion

During the robot-assisted laminectomy, vertebral laminas are removed via automatic milling operation, while inadequate estimation of the remaining lamina thickness will result in a dangerous bone milling. In this manuscript, a dynamic milling model is established to analyze the harmonic amplitudes in the milling vibration signals. It is proved that the ratios of harmonic amplitudes in the lamina’s and cutter’s vibration signals are sensitive to the remaining lamina thickness and insensitive to other milling motion parameters. To verify this concept, a robot is applied to mill and thin the porcine spinal lamina layer by layer. The vibration signals of the cutter and lamina are collected simultaneously with an accelerometer and a laser displacement sensor. Fast Fourier transform is applied to extract the amplitude of the harmonic components whose frequency are integer multiples of the cutter spindle frequency. The results show that the classifier can estimate two critical states of the vertebral lamina before the lamina cut off with a success rate of 98.4% based on these harmonic amplitude ratios. The proposed method is beneficial to improve the safety of the automatic bone milling operation of the spinal surgical robot.

Photonic generation of flexible and adjustable microwave waveforms based on a dual-polarization Mach-Zehnder modulator.

We have proposed a photonic waveform generation scheme based on a dual-polarization Mach-Zehnder modulator (DPol-MZM). In this scheme, a dual-frequency optical signal generated by RF optical carrier suppression modulation via a Mach-Zehnder modulator (MZM) is divided into two beams; one is further modulated by the RF signal via a DPol-MZM to generate ±1st and ±3rd-order sidebands, and the other is further modulated by the RF signal via a second MZM to generate ±2nd-order sidebands. After two modulated optical signals are detected by a balanced photodiode, the second, fourth, and sixth-order harmonics without cross-beating terms are generated in the differential photocurrent. Since the harmonic amplitudes can be controlled independently by the optical power of the two optical beams and the DC biases of the DPol-MZM, the waveforms can be tuned conveniently. Based on the simulation, frequency-doubled triangular, rectangular, and sawtooth waveforms with a full-duty cycle at a repetition rate of 20 GHz are successfully generated with their harmonic amplitude ratio in the electric spectrum close to the ideal amplitude ratio, and the symmetry of the triangular waveform from 20% to 80% is tuned.

The Effects of Damage to the Outer Race Bearing on the Efficiency of the Induction Motor Using Fast Fourier Transform (FFT) Method

Bearing is an induction motor component that helps the rotor to move freely, in industrial applications it is important to maintain bearing performance in induction motors. In its use, bearing damage is one of the biggest types of damage that is often found in induction motors. Bearing damage can lead to increased vibration, increased noise, increased working temperature, and decreased efficiency. Efficiency reduction can be used as information on the condition of the motor so that this information can be used to detect damage before more serious damage occurs. This research discusses the stator current analysis method and the efficiency of damage to the motor through two harmonic amplitude ratios equipped with the fast Fourier transform (FFT) algorithm in detecting damage to the outer race bearing. It is hoped that this efficiency can be used as an evaluation of the extent to which motor energy waste occurs before more severe damage. The efficiency results on the damage to the outer race bearing using the FFT method get the highest efficiency value of 1.47 and the lowest value of 0.66.

Influence of temperature-dependent acoustic and thermal parameters and nonlinear harmonics on the prediction of thermal lesion under HIFU ablation.

According to the traditional method of high intensity focused ultrasound (HIFU) treatment, the acoustic and thermal characteristic parameters of constant temperature (room temperature or body temperature) are used to predict thermal lesion. Based on the nonlinear spherical beam equation (SBE) and Pennes bio-heat transfer equation, and a new acoustic-thermal coupled model is proposed. The constant and temperature-dependent acoustic and thermal characteristic parameters are used to predict thermal lesion, and the predicted lesion area are compared with each other. Moreover, the relationship between harmonic amplitude ratio (P2/P1) and thermal lesion is studied. Combined with the known experimental data of acoustic and thermal characteristic parameters of biological tissue and data fitting method, the relationship between acoustic and thermal characteristic parameters and temperature is obtained; and the thermal lesion simulation calculation is carried out by using the acoustic and thermal characteristic parameters under constant temperature and temperature- dependent acoustic and thermal characteristic parameters, respectively. The simulation results show that under the same irradiation condition, the thermal lesion predicted by temperature-dependent acoustic and thermal characteristic parameters is larger than that predicted by traditional method, and the thermal lesion increases with the decrease of harmonic amplitude ratio.

Sinusoidal model-based hypernasality detection in cleft palate speech using CVCV sequence

Hypernasality in the speech of children with cleft palate is a consequence of velopharyngeal insufficiency. The spectral analysis of hypernasal speech shows the presence of nasal formants and anti-formants in the spectrum which affects the harmonic-intensity. The nasal formants increase whereas the anti-formants decrease the magnitude of harmonics around its location of addition. Hence, the spectrum of hypernasal and normal speech is different from each other. To capture the spectral difference, three features namely, normalized harmonic amplitude (NHA), harmonic amplitude ratio (HAR), and prominent harmonics frequency (PHF) are proposed in this work. NHA feature is the magnitude of harmonics after their normalization with respect to the maximum magnitude, HAR feature is the relative magnitude of harmonics with respect to their previous harmonics, and the PHF feature is the frequencies of prominent harmonics in the spectrum. The combination of three features gives an accuracy of 82.46%, 87.89%, 84.25% for /a/, /i/ and /u/ vowels respectively for the detection of hypernasality using support vector machine classifier.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics.

We present a method to calculate the ion saturation current, Isat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of Isat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating Te. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

A Phoneme Harmonic Generator

In the paper we present a new speech harmonic generator that retains the mutual harmonic amplitude ratio. This ratio is important for retaining the speaker timbre in the synthesized signal. The fourth order quasipolynomial model is chosen as the harmonic model in time domain. A new amplitude and phase determining algorithm is derived and its stepwise form presented. A harmonic generator is excited by dynamic pseudo-periodic input sequences. An example of the synthesized harmonic of the vowel “a” and its comparison with the true sound signal harmonic is given. DOI: http://dx.doi.org/10.5755/j01.itc.45.1.7657

Effect of Localized Microstructure Evolution on Higher Harmonic Generation of Guided Waves

The use of nonlinear ultrasonics to characterize microstructural evolution is investigated with the aim of enabling earlier remaining useful life prediction and thereby greatly improving condition based maintenance. Higher harmonic generation is sensitive to microstructural features, whose evolution is indicative of ongoing damage processes. Localized plastic deformation is controlled in an aluminum sample by varying the notch length, which dictates the extent of the plastic zone. The essentials of higher harmonic generation analysis for ultrasonic guided waves are highlighted to provide a means to select a primary mode that generates a strong higher harmonic. Experimental methods to use magnetostrictive transducers for third harmonic generation measurements are described. Experimental results on aluminum plates indicate that plastic deformation increases the third harmonic by up to a factor of five and that the harmonic amplitude ratio $$A_{3}$$ / $$A_{1}^{3}$$ is sensitive to the plastic strain magnitude. These initial results show that when the plastic strain is localized, the $$A_{3}$$ / $$A_{1}^{3 }$$ ratio appears to be proportional to the plastic zone-to-propagation distance ratio.

Analysis of Detection Methods of RF Vibrometer for Complex Motion Measurement

In this paper, the detection technique of the previously reported wavelength-division-sensing RF vibrometer is thoroughly analyzed by investigating the Bessel function coefficient of harmonics in the baseband spectrum. The analysis provides guidelines on the selection of harmonic pairs to help improve detection accuracy and reliability. A new detection method that utilizes multiple harmonic pairs under a fixed carrier frequency proves to be a more reliable approach for RF vibrometers. The sensitivity of harmonic amplitude ratio to the excess phase angle is explored as well. The results show that by using insensitive harmonic pairs, information about the characteristics of the vibration system and the external driving force are still attainable even when the phase angles are unknown. Real-time monitoring of various harmonic vibrations has been realized through a LabVIEW program with a user interface that provides visualization of the vibration patterns. The function of through-wall detection of the RF vibrometer has also been verified by conducting all measurements behind a wall with a detection distance of 1.5 m.

Nonlinear Ultrasonic Techniques for Testing Micro-Defects in Metal Matrix Composite Structure

Micro-defects inside metal matrix composite structure seriously influence the mechanic properties of materials and can undermine machine operations. In order to detect the micro-defects, we can make use of one of the nonlinear acoustic features, i.e., harmonics, which usually appear together with ultrasound when propagating through a damaged material. Based on the relationship between the harmonics, a method of using nonlinear acoustic harmonic amplitude ratio to distinguish micro-defects in metal matrix composite structure is discussed. The test results show that acoustic features, such as second harmonic excitation efficiency were very obvious for the damaged group samples. The method presented is effective in detecting the micro-defects, which means that nonlinear acoustic waves may provide us a good solution for quantitative evaluation of the early damages in metal matrix composite structure.

Eliminating upper harmonic noise in vibroseis data via numerical simulation

SUMMARY In conventional vibroseis signal processing, algorithms including cross-correlation and deconvolution are applied to convert the raw trace data into a seismic section. However, their performance deteriorates when the trace data are corrupted by the harmonic noise. An important issue of vibroseis data enhancement is the treatment or suppression upper harmonics. In this contribution, I present algorithm to eliminate the harmonic distortion, all at once, in both down- and up-sweep conventional vibroseis data using a simulation process for harmonic distortion in the correlated data. This technique consists of four steps: (1) cross-correlating the raw data with fundamental sweep then dividing the trace to several windows and detecting the windows contain fundamental energy for each response reflector; (2) calculating the harmonic amplitude ratio when applying the Fourier transform on the upper harmonic components and the fundamental, and dividing the upper harmonic components by the fundamental to remove the unknown convolutional effects; (3) using the harmonic amplitude ratio to simulate the upper harmonics associated with the fundamental energy in down- and up-sweep data. When the harmonic amplitude ratio is convolved with a portion of data containing the fundamental energy in the correlated data in time domain, I can get simulation for the upper harmonics existed in the original data and (4) subtracting the simulated harmonics from correlated traces using direct optimization procedure. Accordingly, I developed a procedure for attenuating upper harmonics in the positive and negative times of the correlated traces depending on accurate simulation for the correlated harmonics. The procedure was tested on both synthetic and field data sets. The correlated trace thus obtained will be freed substantially of correlation noise; that is the correlation-ghost sweeps (produced by severe harmonic distortion at positive and negative correlation times) are eliminated without degrading the seismic information content of the trace.

Influence of an ambipolar field and target boundary blurring on transition radiation from fast electrons of laser plasma

It is shown that the blurring of the rear side of a thin laser target leads to a decrease in the intensity of higher harmonics in the spectrum of coherent transition radiation and that the scale of the boundary inhomogeneity can be estimated from the amplitude ratio of harmonics. Deceleration of the electron flow in an ambipolar electric field at the rear boundary of a target leads to a decrease in the intensity of lower harmonics in the spectrum of coherent transition radiation, and the strength of the ambipolar field can be estimated from the amplitude ratio of harmonics. A change in the permittivity of a dielectric laser target with frequency can lead to an increase in the intensity of some harmonics in the spectrum due to the Vavilov-Cherenkov mechanism.

Measuring immeasurable sound pressure levels

The AWSUM(K) processors developed by R. A. Wagstaff make possible the detection of narrowband signals deeply buried in wind noise. However, the signal‐to‐noise ratio one obtains with the AWSUM(K) processors is not the ratio of signal power to noise power, but a nonphysical ratio that depends on the coherence of the signal and the noise distribution. A recently developed theory, used in conjunction with the AWSUM(K) processors, allows the recovery of a physically meaningful signal‐to‐noise ratio, even when wind noise prevents a direct measurement of the signal. Thus, it is possible not only to detect a signal buried in wind noise, but also to estimate the physical sound pressure level. Such a capability can be important for identifying a source using, for example, the ratio of harmonic amplitudes produced by a particular engine in a ground vehicle. The theory for recovering the physical sound pressure level will be discussed and applications to field data will be presented.

Tracking the harmonic response of magnetically-soft sensors for wireless temperature, stress, and corrosive monitoring.

This paper describes the application of magnetically-soft ribbon-like sensors for measurement of temperature and stress, as well as corrosive monitoring, based upon changes in the amplitudes of the higher-order harmonics generated by the sensors in response to a magnetic interrogation signal. The sensors operate independently of mass loading, and so can be placed or rigidly embedded inside nonmetallic, opaque structures such as concrete or plastic. The passive harmonic-based sensor is remotely monitored through a single coplanar interrogation and detection coil. Effects due to the relative location of the sensor are eliminated by tracking harmonic amplitude ratios, thereby, enabling wide area monitoring. The wireless, passive, mass loading independent nature of the described sensor platform makes it ideally suited for long-term structural monitoring applications, such as measurement of temperature and stress inside concrete structures. A theoretical model is presented to explain the origin and behavior of the higher-order harmonics in response to temperature and stress.

On spectra of ionospheric conductivity variations during a heating experiment

Appearance of the harmonics in the spectrum of artificial emissions generated during heating experiments has been reported earlier. Usually, it relates with square modulation of HF powerful wave and distortion of this time dependence due to characteristic time of electron heating/cooling. In the EISCAT‐Heating experiment in November 1993, a quasi‐sinusoidal modulation regime was used. Observations show the clear harmonic structure in artificial emissions in this case too. In the present paper we discuss a generation of harmonics of a modulation frequency due to nonlinear dependence of value of the ionosphere conductivity disturbance from effective radiated power (ERP). A numerical model is used for calculations of the spectrum of the integral conductivity disturbance variation as a function of electron density profile and ERP. For the modulation frequency in the range of 1–100 Hz, the characteristic time of electron heating/cooling was neglected, and intensity ratios of the second and third harmonics to the fundamental frequency reach 0.4 and 0.15, respectively. For the modulation frequency 1375 Hz, time integration of the electron energy balance equation was used. The different characteristic time constants of the electron heating/cooling at different altitudes make the behavior of the intensity ratio and phase shift of the harmonics of the integral conductivity disturbance variations more complicated. The values of the harmonic amplitude ratio in this case decrease to 0.25 and 0.1.

Macular flicker electroretinograms in Best vitelliform dystrophy.

The aim of this study was to evaluate the function of the neurosensory retina in Best vitelliform macular dystrophy (BMD) by recording the focal electroretinogram (ERG) fundamental and 2nd harmonic components, which are known to be dominated by receptoral and postreceptoral activity, respectively. FERGs were recorded in response to a uniform field (9 x 9 deg) flickered sinusoidally at either 8 Hz or 32 Hz (peak frequencies for the 2nd and fundamental harmonic, respectively). The fundamental component of the response to the 32-Hz stimulus and the 2nd harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. The fundamental-2nd harmonic amplitude ratio was taken as an index of the relative changes in the FERG components. Eleven patients with BMD and vitelliform stage macular lesions were evaluated. Results were compared with those obtained from 13 patients with Type 2 Stargardt macular dystrophy (STD) according to the Noble and Carr Classification, and 29 normal control subjects. Four BMD and four STD patients were also followed electrophysiologically over a 48 month period. Compared to controls, BMD patients showed losses of both FERG fundamental and 2nd harmonic amplitudes, and an increase in the fundamental and increase in the fundamental-2nd harmonic ratio. STD patients also showed losses of both fundamental and 2nd harmonic, but the fundamental-2nd harmonic ratio was normal. In BMD patients, but not in those with STD, the fundamental amplitude tended to decrease over the follow-up period. The results indicate that BMD involves neurosensory abnormalities early in the disease process. The increased fundamental-2nd harmonic ratio suggests that a postreceptoral dysfunction may be present in addition to that of photoreceptors. This differs from STD, where losses appear to affect primarily the receptoral retina. Receptoral losses in BMD may progress throughout the medium-term follow up.

ELF harmonic radiation from the Tromsø Heating Facility

Using a new experimental technique the response of the auroral ionosphere to a very powerful HF wave amplitude modulated by an ELF square wave has been determined independent of the obfuscating effects of earth‐ionosphere‐waveguide resonances. It has been found that when resonance effects are compensated for, the odd harmonic amplitude ratios are predominantly those one would expect for a square wave, slightly modified by the non‐linear relationship between generated ELF signal and HF radiated power. The even harmonic amplitude ratios are found to be much lower than those observed in earlier experiments and have been modelled by assuming unequal electron heating and cooling time constants and hence different rise and fall times for the ionospheric currents.