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In order to solve vibration signals inaccurate character in gearbox during nonstationary course with traditional computed order analysis, the computed order analysis is improved and the nonlinearity fitting order analysis method is explored. Firstly, the nonstationary vibration signals in the gearbox are sampled at constant time increments in time-domain and then the data are resampled with nonlinearity...
With the power system development, the application of non-linear power components is becoming more and more extensive, and the power quality situation of power system has become increasingly severe. This paper proposes a novel method based on mathematical morphology (MM) and Hilbert-Huang transform (HHT), which is used to detect and analyze power quality disturbances. To effectively suppress noises,...
Aiming on the problem of low precision and cross term in the conventional method of multi-component LFM signal detection and parameter estimation. A time-frequency associated analyzed method based on wavelet transform and time-frequency reassignment and Hough transform is propased. Overcome the interferences of cross term by wavelet transform, guarantee the accuracy by time-frequency reassignment,...
Frequency synthesizer is an important component in the modem electronic systems. This paper studied a kind of frequency synthesizer in the UAV system and put forward an improvement method for DDS (Direct Digital Synthesis) & PLL (Phase Locked Loop) hybrid frequency synthesizer. Be further to raise PLL performance in fast locking and noise immunity ability in the improvement method, a PLL with...
To analyze harmonic accurately is significant to the stability of power system. HHT (Hilbert-Huang Transform) is adopted to analyze harmonic in order to overcome the shortcoming of FFT method and wavelet analysis method. The power quality signals are decomposed by empirical mode decomposition (EMD) method, and then a series of intrinsic mode function (IMF) are obtained. Owing to different IMFs correspond...
A synchronization scheme of DS/FH hybrid spread spectrum signals based on fast frequency identification is proposed, for high dynamic characteristic of signals in TT&C system. On basis of providing the mathematical model of synchronization process of the signal, three-dimensional mean acquisition time expression as well as probabilities of detection and false alarm of acquisition system with PN...
The Global Positioning System (GPS) can provide a precise frequency reference to control local oven controlled crystal oscillator (OCXO). Based on the analysis of the GPS receiver's timing signal-one hundred pulses per second (100PPS), this signal is adopted to act as the reference signal. Instead of a normal phase detector or a professional frequency counter, a high resolution time to digit converter...
Aiming at the increasingly serious pipeline damages because of the artificial factors, we investigate the characteristic of seismic signals and develop a monitoring and pre-warning system for security of pipelines based on multi-seismic sensors. There were many sensors and processing modules to acquire the seismic signals generated by the ground targets. The non-stationary signal analysis method based...
To measure the frequency deviations of two frequency sources, we can examine the time difference. Cause the low precision of direct measurement can't meet the high accuracy requirement. Dual-mixer time difference measurement can improve the measurement accuracy. This paper introduced the principle of dual-mixer time difference measuring and contribution to frequency measurement of high accuracy and...
Coriolis mass flowmeter (CMF) provides direct measurement of mass flow and is generally regarded as the most accurate and precise flow technology in industry. The precondition of its precision measurement is to maintain the flowtube vibration at its natural frequency, which is realized by closed-loop control. Based on the CMF open-loop characteristic test experiment, this paper analysis the experiment...
The paper proposes improved S-transform (IST) to detect and classify power quality (PQ) disturbances with time-domain analysis. First, the theory of S-transform (ST) is introduced. To enhance the analytic power of ST in different non-stationary signal processing, IST is achieved by adding an adjustable factor to the Gaussian window function of the normal ST. The adjusted factor changes the velocity...
The range profile is redundant and disordered because the sample interval time is less than transmitted pulse width. The accurate estimation and optimization of the target range profile are essential for realizing the airborne microwave sensor detection system. In this paper, an algorithm for the real-time estimation and optimization of the target range profile due to over-sampling is presented for...
This paper mainly researches atomic time algorithm, and its influence on atomic time scale level. With the improving of atomic clock level internationally, atomic time scale system is continuously promoted. Different atomic time scale system needs different algorithm. An atomic time algorithm should be applied in fit time scale system. ALGOS is adopted by BIPM to calculate TAI. AT1 algorithm and an...
Making use of sound card of high cost performance to substitute data acquisition card, and combining with virtual instrument technique and beat method frequency measurement realizes high-precision frequency measurement. But the existence of the sampling rate deviation resulting from sound card crystal oscillator inaccuracy greatly reduces frequency measurement precision, so error mathematics model...
For nonstationary signal in rock bolts detecting, an effective denoise method based on Hilbert-Huang transform is presented, and a few key questions using HHT method are discussed. At first, by empirical mode decomposition (EMD) algorithm, a sum of intrinsic mode functions (IMF) are got, and then, the IMF coefficients in useful signal dominative layer are proceeded using soft threshold method, at...
The auscultatory method has been widely used in clinical practice and is considered to be the gold standard for blood pressure (BP) measurement. However, some subjective factors, such as the observer bias and the terminal digital preference, may inevitably influence the observer measurements. To decrease the observer error in the auscultatory BP measurement, the visual auscultatory blood pressure...
Ultrasonic is a good means to measure the thickness of bottom sediment in drilling hole. The echo signal of the sediment is weak and with high noise usually. This paper adopts Gabor filter to process the ultrasonic echos. The constrainted relationships between Gabor filter's parameters and frequency characteristics have been analyzed and presented. The time-domain standard deviation sigmat and oscillation...
According to the fault of rotor bar breakage, the paper put forward a diagnosis method to extract the fault characteristic signal in stator current, by signal processing with Fourier Transform and wavelet transform theory. To validate its feasibility, simulation and experiment on frequency converter sets are made, and the results show that the given method perform well in the fault diagnosis application.
The fault signal of rotor rub is a typical nonlinear and non-stationary data. HHT is considered an effective method on that kind signal and the crucial step is EMD. However, one of the major drawbacks of the EMD method is mode mixing. Ensemble Empirical Mode Decomposition (EEMD) has been proposed recently. This method overcomes the mode mixing and represents a major improvement of the EMD method....
This paper describes a new clock servo algorithm to adjust slave clock of IEEE1588. This algorithm can correct clock time error and clock frequency error in one sync cycle. For this purpose, there are two input variables being used in clock servo, clock time error and clock frequency error. The frequency compensated clock which supports this algorithm is introduced in this paper. And the method that...
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