14 results about "Bessel function" patented technology

The invention discloses a sine frequency modulation harmonic error compensation method based on Bessel function modulation characteristics, and relates to the technical field of sine frequency modulation nonlinear parameter compensation and high-precision measurement of target absolute distance based on multi-wavelength interference. The problem that the constant phase demodulation precision is insufficient due to the fact that carrier harmonic waves, accompanying amplitude modulation and modulation depth errors cannot be effectively suppressed due to laser modulation nonlinearity in existing sine frequency modulation distance measurement is solved. According to the method, after sine frequency modulation interference signals are collected, high-pass filtering is carried out to remove low-frequency components, Hilbert transform is carried out to remove envelope suppression associated amplitude modulation, window function frequency mixing is carried out to extract modulation depth, a matched carrier containing second harmonics is constructed, and frequency modulation harmonic parameter optimization is achieved through baseband amplitude maximization. And finally, carrying out orthogonal demodulation on the compensated interference signal to obtain a high-precision constant phase. The method is suitable for high-precision multi-wavelength interference ranging, precision displacement measurement and optical metering systems.

This invention discloses a method and system for measuring the frequency response of an electro-optic modulator based on a spectral analyzer. The system includes a laser, a 95:5 single-mode fiber splitter, an optical power meter, an electro-optic modulator, a control power supply, an RF signal generator, and a spectral analyzer. The measurement method includes the following steps: calculating a calibration factor to correct optical power drift through optical path splitting, driving the modulator by applying several discrete single-frequency RF points, and measuring the carrier power P0(f) using the spectral analyzer. i ) and the first-order sideband power P1(f i ), and determined by the power ratio R(f) i )=10 (P1‑P0) / 10 Combining the Jacobi–Anger expansion / Bessel function relation, the phase modulation index β(f) is solved by inverse solution. i Then, the phase transfer function H(f) at each frequency point is calculated and fitted. i The continuous frequency response S of the modulator is obtained. 21 This invention simplifies the testing process, reduces reliance on high-speed photodetectors and vector network analyzers, and enables high-precision electro-optic response testing of electro-optic modulators at high frequencies.

The application discloses a non-circular sparse array DOA estimation performance evaluation method based on information theory, which comprises the following steps: firstly, a multi-dimensional probability density function (PDF) of a received signal is constructed, a joint PDF of the received signal and DOA and a DOA posteriori PDF are derived through information theory, and a system DOA information quantity is obtained by simplifying the DOA posteriori PDF with a Bessel function; then, a DOA posteriori PDF of given noise is derived, and a DOA information approximate upper limit is obtained by simplifying the DOA posteriori PDF with a Taylor expansion; finally, a DOA estimation performance index entropy error is obtained by using the posteriori differential entropy; the application builds a non-circular sparse array system DOA information theory framework based on information theory, in actual signal processing, the entropy error of a parameter can be calculated only by estimating the posteriori PDF of the parameter, and a performance limit independent of an algorithm is provided; in addition, it is found through simulation that the DOA information quantity approaches the DOA information upper limit under a high signal-to-noise ratio, and the entropy error approaches the Cramer-Rao limit, thereby verifying the rationality of the index.

The invention discloses a novel modal shape function construction method suitable for a variable cross-section flexible structure, and the method comprises the following steps: firstly, building a linear kinetic equation of a flexible wing based on an Euler-Bernoulli beam theory and a Lagrange principle; secondly, geometric and physical parameters in the equation are normalized through dimensionless variable substitution, and the coupling relation between different variables is simplified; secondly, formalizing the solution into a linear combination of a first type of Bessel function and a second type of Bessel function by adopting a special function expansion method so as to ensure that boundary conditions are met and effectively reflect the influence of section change on modal characteristics; and finally, solving the inherent frequency and a modal shape function by constructing a novel modal shape function. According to the method, iteration and approximate truncation are not needed, the inherent frequency and the modal shape can be rapidly and accurately calculated, the calculation efficiency is remarkably improved, high calculation precision is guaranteed, and the method is suitable for efficient dynamic analysis of a complex structure.

The invention discloses a micro-motion exploration frequency dispersion curve extraction method, device and medium, and relates to the technical field of micro-motion exploration, and the method comprises the following steps: S1, calculating the average cross-correlation spectrum of each station pair according to the recorded data of a plurality of stations in an observation array; s2, aiming at the average cross-correlation spectrum of each station pair, identifying a first intersection point frequency of the average cross-correlation spectrum and a frequency axis; s3, based on the first intersection point frequency, performing piecewise fitting on the average cross-correlation spectrum to extract a phase velocity: for a frequency band not greater than the first intersection point frequency, performing fitting by adopting a zero-order Bessel function J0; and for a frequency band of which the frequency is greater than the frequency of the first intersection point, performing fitting by adopting a first-class zero-order Hankel function H0 (1). In a single method, the contradiction of artifact interference in a high frequency band and insufficient detection depth in a low frequency band in the prior art is overcome at the same time, the accuracy and reliability of frequency dispersion curve extraction under the sparse array condition are improved, and the detection depth of micro-motion exploration is effectively expanded.

The invention relates to the technical field of satellite system engineering and micro-vibration suppression, in particular to a method for quickly constructing and optimizing an optical remote sensing satellite micro-vibration suppression index system, which comprises the following steps of: acquiring an imaging quality index threshold, a system static modulation transfer function value, a structure transfer function data set and a flywheel disturbance source characteristic data set; constructing a system-level frequency domain response model based on a frequency domain transfer function chain, calculating a modulation transfer function attenuation factor caused by high-frequency micro-vibration by utilizing a zero-order Bessel function and a time delay integral smoothing function, and establishing a reverse design inequality to solve an allowable maximum disturbance force upper limit curve of the flywheel under different rotating speed frequencies; and vibration isolation device design parameters or flywheel model selection strategies are output through comparison with a flywheel actual measurement disturbance spectrum. According to the method, the problems that existing time domain simulation calculation is low in efficiency and lacks parameter inverse solution capacity are solved, millisecond-level rapid evaluation and direct design guidance are achieved, and the overall satellite scheme argumentation period is remarkably shortened.

The invention relates to the technical field of transformer station grounding grid evaluation, and provides a dynamic evaluation method and system for power station grounding short circuit transfer potential, and the method comprises the steps: employing a Wenner quadrupole method to measure the apparent resistivity of soil, and constructing an apparent resistivity-depth change curve; reversely deducing the resistivity and the thickness of each layer of soil by adopting an inversion algorithm and combining an analysis kernel function and Bessel function expansion, so as to obtain soil layering parameters of a multi-layer and non-uniform structure; and obtaining a short-circuit current, a grounding grid structure and the obtained soil layering parameters, and obtaining a grounding short-circuit transfer potential of the grounding grid of the to-be-evaluated power station by adopting coupling simulation analysis mixed with a finite element method and a moment method. According to the method, the real soil model is constructed by combining the Wenner quadrupole method measurement and the inversion algorithm, and the finite element and moment method coupling simulation is introduced, so that the grounding short circuit transfer potential is accurately evaluated, and the prediction precision and the system safety under the complex geological condition are remarkably improved.

The invention discloses a rapid calculation method and system for a grid-connected current THD of a high-voltage direct-hanging energy storage system, and belongs to the technical field of high-voltage direct-hanging energy storage systems. The method aims at solving the problems that existing THD calculation depends on multi-power-frequency period sampling, is slow in updating and cannot adapt to a scene with inconsistent modulation signals of in-phase sub-modules. The method comprises the following steps: sampling to obtain system parameters and modulation signals; calculating modulation signal adjustment quantity amplitude and additional fundamental frequency voltage; a final modulation signal is obtained through alpha-beta axis vector superposition; calculating a harmonic voltage amplitude based on a carrier phase-shifting modulation model and a Bessel function; deriving a harmonic current amplitude and a fundamental current amplitude, and solving THD; and the harmonic calculation frequency is dynamically adjusted through error verification. Only control variables are used for calculation, the calculation speed is high, the precision is high, the relative error is smaller than or equal to 5%, the DSP burden is reduced, control strategy adjustment can be rapidly supported, and stable operation of a power grid is guaranteed.

The invention discloses an electromagnetic sensor signal analysis method and system based on real abrasive particle dynamic trajectory and time-harmonic field intensity coupling, and belongs to the field of mechanical equipment state monitoring and sensor simulation. The method comprises the following steps: firstly, based on a CFD-DEM coupling theory, combining abrasive particle multi-physical field stress, and accurately reconstructing a real three-dimensional dynamic track in a complex flow field of a lubricating oil pipeline; and establishing a three-dimensional time-harmonic magnetic field analysis model based on magnetic vector potential and a modified Bessel function, constructing a dynamic mapping relation between the transient position of the abrasive particles and a non-uniform magnetic field, quantifying the disturbance characteristic of the abrasive particle eddy current to the magnetic field, and solving the transient response of the sensor induced electromotive force. Abrasive particle size, material conductivity and magnetic conductivity parameter correction are fused, simulation distortion caused by a simplified motion model and neglect of radial magnetic field difference in a traditional theory is overcome, and high-precision prediction of dynamic signals of the whole process that the abrasive particles pass through the sensor is achieved. The method is suitable for health monitoring of aero-engines and industrial gearboxes.

This invention discloses a method for spatial domain filtering and spectrum correction of broadband signals in the mode domain of a circular array. The method involves performing a Discrete Fourier Transform (DFT) on the received time-domain data to obtain the array element frequency domain data. The broadband signal frequency band data is then extracted and subjected to a Circular Fourier Transform (CFT) to obtain the sub-band data in the mode domain. The distance between frequency points and the zeros of the Bessel function within the broadband signal frequency band is calculated, and a zero-point correction method is used to replace the frequency points. Sub-band frequency points in the mode domain are selected according to the correction results. The sub-band weighting vectors for mode domain beamforming are obtained according to the minimum variance and distortion-free criterion for data independence, and the beamformer is calculated. The sub-band data in the mode domain are weighted and summed based on the weighting vectors of each sub-band to obtain the beam output frequency domain data. Zeros are padded at all frequency points except for the broadband signal frequency domain data. An Inverse Fourier Transform is then performed on the beam output frequency domain data to obtain the beamforming output data sequence. This invention effectively preserves the original spectral components of the broadband signal while improving the signal-to-noise ratio.

The application provides a kind of GIL loss fast calculation method considering electromagnetic space distribution, relate to high voltage gas insulated transmission technology field, solve the problem that existing GIL loss calculation method is difficult to consider physical rigor and calculation efficiency.The method, the coaxial hollow cylindrical structure electromagnetic field model of GIL is established, and then the diffusion equation of time-harmonic electromagnetic field is constructed and the boundary condition is set;Solving time adopts the linear combination of first kind Bessel function and second kind Bessel function as the general solution form, determines the undetermined coefficient, obtains the magnetic field intensity and electric field intensity distribution expression in the conductor region and shell region;Finally, based on the Poynting theorem, the analytical expression of unit length conductor ohmic loss and shell eddy current loss is calculated and derived, and the conductivity parameter is embedded in the form of explicit function of temperature, that is, the GIL loss calculation is completed.The calculation realized by the application can provide a clear, differentiable and traceable heat source coupling interface for the heat network model.

The present application belongs to the technical field of underwater acoustic channel and physical field, and relates to a numerical hybrid calculation method of forward scattering acoustic field of a regular shape object underwater. The method comprises: obtaining an initial projection profile of a three-dimensional geometric model of the regular shape object under a specified projection plane and an incident direction; dividing discrete points of the initial projection profile into upper boundary points and lower boundary points; interpolating and completing the upper boundary points and the lower boundary points, so that the upper boundary points and the lower boundary points have the same number and share the same horizontal coordinates; discretizing the completed projection profile by using trapezoidal plane elements; calculating a forward scattering far field pattern function based on the discretization result; and calculating a forward scattering target strength of the object. The method provided by the present application can cover the shape range of the scattering object applicable to the analytical method, and does not need to calculate complex series expressions composed of special functions such as Bessel functions and spherical harmonic waves, thereby obviously improving the calculation efficiency.

The invention belongs to the technical field of radar imaging, and particularly relates to a three-dimensional imaging method based on a uniform circular ring array radar, and the method comprises the steps: carrying out the initial negative Bessel function compensation according to the priori pitch angle information of a target mass center, obtaining a rough two-dimensional image, and carrying out the simple interference according to the rough two-dimensional image, and obtaining the rough pitch angle information of each scattering point of a target; performing fine negative Bessel function compensation according to the rough pitch angle of each scattering point of the target to obtain an accurate two-dimensional image; performing two-step interference according to the precise two-dimensional image to obtain precise pitch angle information of each scattering point; and selecting a receiving array element for echo phase interference according to error analysis. According to the invention, the distance-azimuth angle two-dimensional imaging performance can be improved and the echo phase discontinuity can be reduced; the pitch angle of each scattering point of the target is accurately reconstructed under the condition that image registration and phase unwrapping are not carried out; meanwhile, the receiving array elements used for echo phase interference are optimized so as to minimize the influence of each error factor on the pitch angle reconstruction error.

The application provides a metal pipeline conductivity measurement method based on high-frequency eddy current, which comprises the following steps: designing an absolute eddy current sensor, arranging a sensor coil coaxially on the inner side of a metal pipeline, and generating eddy current by inputting high-frequency alternating current into the coil; establishing a simplified high-frequency eddy current detection analytical theory model, and setting the geometric size of the sensor and the pipeline; analyzing the relationship between the real part of the change of eddy current impedance under high-frequency excitation and the conductivity of the pipeline by using a Bessel function and a spatial resolution expression; setting the conductivity of the metal pipeline according to the analysis result, fitting the relationship between the change of impedance and the conductivity by using a power function; and inversely deriving the actual conductivity of the metal pipeline according to the measurement result of the coil impedance and the fitted power function curve. The application can effectively measure the conductivity of the metal pipeline.