Maximum Amplitude Error Research Articles

Preparation of a superior damping coating and study on vibration damping properties

In this paper, a superior damping coating was prepared, which can be easily sprayed onto the samples, showing a promising application in the vibration reduction for aircraft. This paper aims to investigate the effect of filler content, size and coating thickness on the damping properties of aluminum flake samples. It is found that the vibration of the sample is significantly suppressed with the vibration reduction rate of the coating reaching 63.23%. Moreover, the damping ratio of the coating was calculated using the half-power bandwidth method, based on which the finite element simulation model was established. The simulation results are in perfect agreement with the test ones, and the maximum vibration amplitude error stayed within 9.06%. These results fully demonstrated the effectiveness and practicality of the damping coating.

Research and Modeling on the Characteristic Changes of EMI Filter Passive Components under the Influence of Aging

At present, the power density of power electronic devices in data centers and electric vehicles is constantly increasing, and numerous electronic components are concentrated in a tight, high-temperature environment, which aggravates the performance degradation of electronic components. Consequently, X and Y capacitors, common-mode inductors, and differential-mode inductors used for electromagnetic interference (EMI) suppression suffer from aging effects, and their performance continues to decline. However, the electromagnetic compatibility test is often conducted immediately after the power electronic equipment leaves the factory. The electromagnetic compatibility of power electronic equipment is affected by aging, which is not assessed in current industrial testing. This study conducts aging experiments on passive electronic components in EMI filters and measures the impedance in the frequency range from 150 kHz to 30 MHz. Subsequently, a multi-element aging model based on electromagnetic field analysis is established. The proposed model is suitable for electromagnetic compatibility analysis considering aging. Finally, the aging performance of a commercial two-stage EMI filter is predicted to verify the model proposed in the study. The proposed model explains the degeneration of the EMI filter with aging in the frequency range of 150 kHz to 1 MHz, with a maximum amplitude error of 0.58 dB and phase error of 1.0°.

Design and analysis of variable attenuator with simultaneous minimized flat amplitude error and insertion phase variations

This paper presents a design of an analog variable attenuator with simultaneous minimized flat amplitude error and insertion phase variation over a wide bandwidth and high attenuation range. The parasitic of PIN is compensated with series transmission lines loaded and shunt capacitors to achieve minimum flat amplitude error and insertion phase variation. Mechanism for simultaneous reduction in flat amplitude error and phase variations is obtained by developing an analytical design equation using the PIN diode equivalent circuit model. For the experimental validation, two kinds of proposed attenuators are designed and measured over 1 GHz bandwidth at a center frequency (f0) of 3.5 GHz. The measurement results are consistent with the simulation results. From the experiments, design-I provides an attenuation variation of 0.9 dB to 20 dB with a maximum flat amplitude error of 0.65 dB and insertion phase variation of 5.70° over 1 GHz bandwidth. Similarly, the design-II provides an attenuation variation of 1.06 dB to 20 dB with a maximum amplitude error of 0.49 dB and insertion phase variation of 3.19° over the same 1 GHz bandwidth.

Dynamic Characteristics Analysis and Finite Element Simulation of Steel–BFPC Machine Tool Joint Surface

Abstract The dynamic performance of the steel–Basalt fiber polymer concrete (BFPC) machine tool joint surface (referred to as the joint surface) has a significant impact on the overall BFPC machine tool performance; however, its dynamic characteristics remain unclear. In order to solve this problem, the influence of roughness and surface pressure on the dynamic performance of joint surface was studied experimentally, and a neural network prediction model for the dynamic performance of the joint surface was established. A BFPC bed was designed and manufactured, and BFPC bed’s dynamic performance was tested experimentally. The finite element simulation model of BFPC bed was established with equivalent spring-damper element. The BFPC bed’s dynamic performance without considering the influence of the joint surface and considering the influence of the joint surface was studied separately. The results show that the maximum error of the natural frequency of the BFPC bed was 6.937% considering the influence of the joint surface, which was much lower than the error without considering the influence of the joint surface. The maximum amplitude error of the X-axis and Z-axis acceleration of the BFPC bed was 6.917% and 5.15%, which were much smaller than the error without considering the influence of the joint surface. It proves the accuracy of the neural network prediction model for dynamic performance of the joint surface and the validity of the finite element simulation method for the joint surface. It provides theoretical support for the design analysis of BFPC machine tool.

Accurate Measurement of the True Plane-Wave Shielding Effectiveness of Thick Polymer Composite Materials via Rectangular Waveguides.

This paper presents a methodology for accurately gauging the true plane wave shielding effectiveness of composite polymer materials via rectangular waveguides. Since the wave propagation of the waveguides is not in the form of plane wave patterns, it is necessary to post-process the S-parameters for the measured data of the waveguide lines to obtain such patterns and ascertain the effectiveness of true plane wave shielding. The authors propose two different methods to achieve this. The first applies simple renormalization of S-parameters, where reference impedance is changed from the value for the waveguide to that for free space, which ensures good accuracy of shielding effectiveness with a small degree of discontinuity across the range of frequencies. The other relies on rigorous extraction of the composite materials’ effective permittivity and permeability ascertained from rectangular waveguides; afterward, plane wave shielding effectiveness is calculated analytically and gives very high accuracy. Both procedures assume the given samples are isotropic in character. We validated the accuracy of the methodologies by conducting tests on a set of synthetic samples of 2 mm thickness with unit permittivity and variable conductivity and on a dielectric material of known permittivity (FR4 laminate). The applicability of both methods was further proven by analyzing the isotropic composite materials, a process involving the use of iron particles embedded in a dielectric matrix. The synthetic samples and an FR4 material were tested to check the accuracy of the methods. Based on numerical studies and measurements, we concluded that materials with a shielding effectiveness of up to 25 dB could be measured at a maximum amplitude error of 1 dB to 3dB to a frequency of 18 GHz, depending on the relative permittivity of the material; hence, the first method was suitable for approximation purposes. For maximal accuracy, the second method typically demonstrated an amplitude error of below 0.5 dB to the same frequency across the entire range.

A low-speed linear stage based on vibration trajectory control of a bending hybrid piezoelectric ultrasonic motor

The speed control tends to receive the restriction of dead-zone phenomenon when an ultrasonic motor (USM) works at the low speed range. A linear motion stage is designed and fabricated, in which a bending hybrid type USM using two separated bending modes is chosen for the low speed characteristic study. The shape and size of the vibration trajectory of the driving foot can be changed flexibly to realize the control of the output speed by controlling the vibration amplitudes of the driving foot in vertical and horizontal directions independently. The low speed characteristic experiment of the motion stage is accomplished based on a conventional PID controller, the speeds of 5 mm/s, 10 mm/s, 20 mm/s, 50 mm/s are achieved in the step control, respectively. In the sinusoidal speed control experiment, the reference speed varies sinusoidally with an amplitude of 20 mm/s, the maximum phase lag and amplitude error are lower than 3° and 3%, respectively. It is demonstrated that the low speed movement of the proposed linear motion stage can be realized by changing the vibration trajectory of the driving foot.

Improved Three-Dimension Mathematical Model for Voltage Inversion of AC Overhead Transmission Lines

The voltages on the AC overhead transmission lines (OTLs) can be calculated inversely based on the measured electric field around the lines, which will much contribute to the non-contact condition monitoring of OTLs. To more realistically simulate the actual operating state of OTLs in the wild, a refined catenary equation of OTL with consideration of the vertical suspension and horizontal deflection is established, and the according improved three-dimensional electric field mathematical model are proposed. Furthermore, the OTLs' voltages are calculated based on an improved optimization algorithm that combines particle swarm algorithm and genetic algorithm. Some simulation and experiment cases by setting different measurement errors and wind speeds are employed to verify the improving effect of the proposed model. The analysis results shown that the three-phase maximum amplitude error is 6.48% and maximum phase error is 6.26° when the electric field measuring error is as high as 20% (beyond the normal level); on the other hand, the maximum amplitude error and phase error are 2.54% and 0.96° respectively when the wind speed is set to the strong wind of 15m/s. The results demonstrate the accuracy and robustness of the proposed model.

A 28 GHz four-channel phased-array transceiver in 65-nm CMOS technology for 5G applications

A 28 GHz fully integrated 4-channel TX/RX 5G beam-forming transceiver is implemented in 65-nm CMOS technology. Each TX/RX channel can be digitally controlled with 5.625° phase step and 2 dB gain step. The transceiver employs a heterodyne architecture with 6 GHz intermediate frequency (IF). The transceiver works in a band of frequencies between 26 GHz and 30 GHz. The up/down-conversion mixers are integrated on the same chip with a shared LO chain. The phased-array power combining/splitting is done using a Wilkinson power combiner/divider. Each channel features 3.4–3.9 dB NF and −5 to −3.5 dBm IIP3 in RX mode, high OP1dB of 14.7 dBm and 18 dB gain in TX mode. The maximum rms amplitude and phase error for each channel is 0.25 dB and 1.5° across gain and phase states, respectively. The RFIC area is 5.29 × 3.4 mm2 including pads and it consumes 240 mW per channel in TX mode, 120 mW per channel in RX mode and 174 mW for the LO chain with a total power of 1.58 W from a 1.2 V supply.

Quantitative Analysis of GPR Signals: Transmitted Wavelet, Amplitude Decay, and Sampling-Related Amplitude Distortions

We study the importance of accurately recording signal amplitudes for the quantitative analysis of GPR data sets. Specifically, we measure the peak amplitudes of signals emitted by GPR antennas with different central frequencies and study their amplitude decay with distance, in order to extrapolate the peak amplitude of the wavelet initially transmitted by each antenna. The purpose is to compare the reference and reflected amplitudes in order to accurately estimate the subsurface EM impedance contrasts. Moreover, we study how sampling-related amplitude distortions can affect the quantitative analysis, and subsequently the resulting subsurface models, even in the absence of aliasing effects. The well-known Nyquist–Shannon theorem gives practical lower limits for the sampling rate in order to preserve the spectral content of a digitized signal; however, we show that it does not prevent possible amplitude distortions. In particular, we demonstrate that significant and unrecoverable loss of amplitude information occurs even at sampling rates well above the Nyquist–Shannon threshold. Interpolation may theoretically reduce such amplitude distortions; however, its accuracy would depend on the implemented algorithm and it is not verifiable in real data sets, since the actual amplitude information is limited to the sampled values. Moreover, re-sampling the interpolated signal simply reintroduces the initial problem, when a new sampling rate is selected. Our analysis suggests that, in order to limit the maximum peak amplitude error within 5%, the sampling rate selected during data acquisition must be at least 12 times the signal central frequency, which is higher than the commonly adopted standards.

Enhancement of lung sounds based on empirical mode decomposition and Fourier transform algorithm

Background and objectiveThere is always heart sound (HS) signal interfering during the recording of lung sound (LS) signals. This obscures the features of LS signals and creates confusion on pathological states, if any, of the lungs. In this work, a new method is proposed for reduction of heart sound interference which is based on empirical mode decomposition (EMD) technique and prediction algorithm. MethodIn this approach, first the mixed signal is split into several components in terms of intrinsic mode functions (IMFs). Thereafter, HS-included segments are localized and removed from them. The missing values of the gap thus produced, is predicted by a new Fast Fourier Transform (FFT) based prediction algorithm and the time domain LS signal is reconstructed by taking an inverse FFT of the estimated missing values. ResultsThe experiments have been conducted on simulated and recorded HS corrupted LS signals at three different flow rates and various SNR levels. The performance of the proposed method is evaluated by qualitative and quantitative analysis of the results. ConclusionsIt is found that the proposed method is superior to the baseline method in terms of quantitative and qualitative measurement. The developed method gives better results compared to baseline method for different SNR levels. Our method gives cross correlation index (CCI) of 0.9488, signal to deviation ratio (SDR) of 9.8262, and normalized maximum amplitude error (NMAE) of 26.94 for 0 dB SNR value.

Hybrid force control of astronaut rehabilitative training robot under active loading mode

In order to mitigate the effects of space adaptation syndrome (SAS) and improve the training efficiency of the astronauts, a novel astronaut rehabilitative training robot (ART) was proposed. ART can help the astronauts to carry out the bench press training in the microgravity environment. Firstly, a dynamic model of cable driven unit (CDU) was established whose accuracy was verified through the model identification. Secondly, to improve the accuracy and the speed of the active loading, an active loading hybrid force controller was proposed on the basis of the dynamic model of the CDU. Finally, the actual effect of the hybrid force controller was tested by simulations and experiments. The results suggest that the hybrid force controller can significantly improve the precision and the dynamic performance of the active loading with the maximum phase lag of the active loading being 9° and the maximum amplitude error being 2% at the frequency range of 10 Hz. The controller can meet the design requirements.

Laser characteristic effect on the trace gas detection

In this paper, we study the effects of laser scanning step length and width characteristic on tunable diode laser absorption spectrum detection system, theoretically derive the principle of interaction between laser and gas absorption line, and analyse the principle of effects of step duration and height about scanning signal (ramp) on the laser central wavelength. After setting the simulation parameters, the curve between the number of ramp steps and the maximum scanning error is obtained. If the scanning signal has 4000 steps in one cycle, the error is less than 1‰ with full width at half maximum (FWHM) value being greater than 0.01 cm-1. The curves between laser linewidth and maximum amplitude or linewidth error are simulated, and also the relationship between laser linewidth and minimum FWHM is given with linewidth error maximum values being 1% and 0.5%. On condition that temperature coefficient n is 0.9 and air-broadened coefficient is 0.005, this paper gives the relationship among pressure, temperature and FWHM, from which the suitable pressure P and temperature T range are deduced. It can provide the relevant theoretical basis for selecting the laser and gas absorption lines and also for improving the system detection limit.

Reduced Order Models for Blade-To-Blade Damping Variability in Mistuned Blisks

A novel reduced order modeling methodology to capture blade-to-blade variability in damping in blisks is presented. This new approach generalizes the concept of component mode mistuning (CMM), which was developed to capture stiffness and mass mistuning (and did not include variability in damping among the blades). This work focuses on modeling large variability in damping. Such variability is significant in many applications and particularly important for modeling damping coatings. Similar to the CMM based studies, structural damping is used to capture the damping effects due to the mechanical energy dissipation caused by internal friction within the blade material. The steady state harmonic responses of the blades are obtained using the novel reduced order modeling methodology and are validated by comparison with simulation results obtained using a full order model in ANSYS with a maximum amplitude error of 0.3%. It is observed that there is no strong correlation between the engine order of excitation and both the variation in the response from blade to blade and the blade amplification factors. The effects of damping mistuning are studied statistically through Monte Carlo simulations. For this purpose, the blisk model is subjected to multiple traveling wave excitations. The uncertainty in the various mechanisms responsible for dissipation of energy and the uncontrollability of these dissipation mechanisms makes it difficult to assign a reliable value for the loss factor of each blade. Hence, large variations (up to ±80%) in the structural damping coefficients of the blades are simulated.

High efficient ECG compression based on reversible round-off non-recursive 1-D discrete periodized wavelet transform

Error propagation and word-length-growth are two intrinsic effects influencing the performance of wavelet-based ECG data compression methods. To overcome these influences, a non-recursive 1-D discrete periodized wavelet transform (1-D NRDPWT) and a reversible round-off linear transformation (RROLT) theorem are developed. The 1-D NRDPWT can resist truncation error propagation in decomposition processes. By suppressing the word- length-growth effect, RROLT theorem enables the 1-D NRDPWT process to obtain reversible octave coefficients with minimum dynamic range (MDR). A non-linear quantization algorithm with high compression ratio (CR) is also developed. This algorithm supplies high and low octave coefficients with small and large decimal quantization scales, respectively. Evaluation is based on the percentage root-mean-square difference (PRD) performance measure, the maximum amplitude error (MAE), and visual inspection of the reconstructed signals. By using the MIT-BIH arrhythmia database, the experimental results show that this new approach can obtain a superior compression performance, particularly in high CR situations.

Wavelet-Based Enhancement of Lung and Bowel Sounds Using Fractal Dimension Thresholding —Part II: Application Results

The application of the wavelet transform-fractal dimension-based (WT-FD) filter of Part I of this paper to real bioacoustic data, which include explosive lung sounds (ELS) and explosive bowel sounds (EBS) recorded from patients with pulmonary or gastrointestinal dysfunction, respectively, is presented in this paper. The objective of the latter is the evaluation of the performance of the WT-FD filter on different types of bioacoustic signals, varying not only in their structural morphology but also in the degree of their noise contamination. As it is thoroughly described in Part I of this paper, the WT-FD filter uses the fractal dimension to form an efficient way of thresholding the WT coefficients at different resolution scales, keeping, thus, only those that can contribute to the accurate reconstruction of the ELS and EBS signals. Quantitative and qualitative analysis of the experimental results show an efficient performance of the WT-FD filter to circumvent the noise presence (100% detectability rate, 100% sensitivity, 100% specificity) by faithfully extracting the authentic structure of ELS and EBS from the background noise. The WT-FD filter does not require any noise reference signal or noise reference templates. The results from a noise stress test (mean cross-correlation index of the original and the estimated signal converging to 100%; mean normalized maximum amplitude error converging to 0.7%) prove its robustness to various noise levels (0-20 dB), enabling its potential use in similar noise cases met in everyday clinical medicine. Furthermore, the efficient performance of the WT-FD filter facilitates the physician to better interpret the auscultation findings. Due to its simplicity and low computational cost, the WT-FD filter can possibly be implemented in a real-time context to serve as a tool for the continuous ELS and EBS screening.

A low computational complexity algorithm for ECG signal compression

In this work, a filter bank-based algorithm for electrocardiogram (ECG) signals compression is proposed. The new coder consists of three different stages. In the first one—the subband decomposition stage—we compare the performance of a nearly perfect reconstruction (N-PR) cosine-modulated filter bank with the wavelet packet (WP) technique. Both schemes use the same coding algorithm, thus permitting an effective comparison. The target of the comparison is the quality of the reconstructed signal, which must remain within predetermined accuracy limits. We employ the most widely used quality criterion for the compressed ECG: the percentage root-mean-square difference (PRD). It is complemented by means of the maximum amplitude error (MAX). The tests have been done for the 12 principal cardiac leads, and the amount of compression is evaluated by means of the mean number of bits per sample (MBPS) and the compression ratio (CR). The implementation cost for both the filter bank and the WP technique has also been studied. The results show that the N-PR cosine-modulated filter bank method outperforms the WP technique in both quality and efficiency.

The Adriatic Sea M2 and K1 tides by 3D model and data assimilation

In the present work we explore the impact of assimilating local tide-gauge and altimetric data on the quality of predicting the major Adriatic tides ( M 2 and K 1). To that end we compute optimal tidal open boundary conditions for a 3D high-resolution finite-element model by using an incremental assimilation formalism. The essence of the method is the use of two dynamical models where the solution in the complex 3D high-resolution model is sought via assimilation of prediction errors into the simpler 2D model with explicit inverse. In the central numerical experiment, harmonic constants from 12 tide gauges are assimilated and the results are analysed at 31 locations, hence 19 independent ones. The data assimilation contributes to the reduction of maximum amplitude error from 5.6 to 0.5 cm for M 2 and from 3.9 to 0.1 cm for K 1. The assimilation procedure is repeated by assimilating suitably processed Topex/Poseidon altimeter data, again validating the outcome at 31 tide gauge locations. The result was very similar to the gauge-data assimilation outcome. The model output is also validated with the current data, not used in the assimilation. At two locations and at three depths the model was able to reproduce the major and the minor semi-axes of tidal ellipses, as well as their orientations very well.

Implementation and performance evaluation of a broad-band digital harmonic vector voltmeter

A broad-band digital harmonic vector voltmeter previously proposed and theoretically studied by the authors was implemented by using a special-purpose random sampling strategy to avoid the bandwidth limitations due to the finite conversion time of the S/H-ADC devices. The experimental results showed that the bandwidth of the instrument is limited only by that of the S/H devices of the acquisition channels, according to the theoretical findings. The maximum amplitude error was not greater than 2%.

ECG coding by wavelet-based linear prediction.

This paper presents a novel coding scheme for electrocardiogram (ECG). Following beat delineation, the periods of the beats are normalized by multirate processing. After amplitude normalization, discrete wavelet transform is applied to each beat. Due to the period and amplitude normalization, the wavelet transform coefficients bear a high correlation across beats at identical locations. To increase the compression ratio, the residual sequence obtained after linear prediction of the significant wavelet coefficients is transmitted to the decoder. The difference between the actual period and the mean beat period, and that between the actual scale factor and the average amplitude scale factor are also transmitted for each beat. At the decoder, the inverse wavelet transform is computed from the reconstructed wavelet transform coefficients. The original amplitude and period of each beat are then recovered. The approximation achieved, at an average rate of 180 b/s, is of high quality. We have evaluated the normalized maximum amplitude error and its position in each cycle, in addition to the normalized root mean square error. The significant feature of the proposed technique is that, while the error is nearly uniform throughout the cycle, the diagnostically crucial QRS region is kept free of maximal reconstruction error.

2.5-D wave equations and high‐frequency asymptotics

The need for modeling 3-D seismic data in a 2-D setting has motivated investigators to create so‐called 2.5-D modeling methods. One such method proposed by Liner involves the use of an approximate 2.5-D wave operator for constant‐density media. The traveltimes and amplitudes predicted by high‐frequency asymptotic ray series (WKBJ) analysis of the Liner 2.5-D wave equation match those predicted by Bleistein’s 2.5-D ray‐theoretic development in constant wavespeed media. However, high‐frequency analysis indicates that the Liner 2.5-D variable wavespeed equation will have a maximum amplitude error of ±35% in a linear c(z) model where the wavespeed doubles or halves from the beginning to the end of a raypath. These amplitudes are comparable to those produced by converting 2-D data to 2.5-D using correction factors of the type proposed by Emersoy and Oristaglio and Deregowski and Brown, with the exception being that the Liner equation lacks the half derivative waveform correction present in these operators. An alternate method of constructing 2.5-D wave operators based on the WKBJ analysis is proposed. This method permits variable density (acoustic) 2.5-D wave operators to be derived.