阅读说明：本技术 一种飞机电源供电特性频率瞬变参数校准方法 (Aircraft power supply characteristic frequency transient parameter calibration method ) 是由 王建强 王文健 肖彬 王鹏飞 侯毅 于 2020-12-09 设计创作，主要内容包括：本发明公开的一种飞机电源供电特性频率瞬变参数校准方法,属于电学测量技术领域。本发明对频率瞬变参数校准过程中由离散希尔伯特变换算法引入的不确定度评定进行评定,实现方法为：数据采集系统对输出的频率瞬变信号进行采集后基于离散希尔伯特变换算法得到瞬时频率。分析离散希尔伯特变换在频率发生瞬时变化时由于采样率不足导致的端点效应造成的误差所引入的不确定度。根据离散希尔伯特变换得到瞬时频率的原理,将瞬时频率与原信号和原信号的希尔伯特变换建立关系,基于数值仿真技术,在不同采样率下计算端点效应引入的误差,进而评价不确定度,完善飞机电源供电特性测试系统频率瞬变参数校准结果的不确定度分析,使得校准结果更加准确可靠。(The invention discloses a method for calibrating frequency transient parameters of power supply characteristics of an aircraft power supply, and belongs to the technical field of electrical measurement. The invention evaluates the uncertainty evaluation introduced by a discrete Hilbert transform algorithm in the process of calibrating the frequency transient parameters, and the realization method comprises the following steps: the data acquisition system acquires the output frequency transient signal and then obtains the instantaneous frequency based on a discrete Hilbert transform algorithm. The uncertainty introduced by the error of the discrete hilbert transform due to the end-point effect caused by insufficient sampling rate when the frequency changes instantaneously is analyzed. The method comprises the steps of establishing a relation between instantaneous frequency and Hilbert transform of an original signal according to the principle that the instantaneous frequency is obtained through discrete Hilbert transform, calculating errors introduced by an end point effect under different sampling rates based on a numerical simulation technology, evaluating uncertainty, and perfecting uncertainty analysis of a frequency transient parameter calibration result of an aircraft power supply characteristic test system, so that the calibration result is more accurate and reliable.)

1. A method for calibrating frequency transient parameters of power supply characteristics of an aircraft power supply is characterized by comprising the following steps: the method for evaluating the uncertainty introduced by a discrete Hilbert transform algorithm in the frequency transient parameter calibration process of the aircraft power supply characteristic test system comprises the following steps: acquiring the output frequency transient signal by a data acquisition system and then obtaining instantaneous frequency based on a discrete Hilbert transform algorithm; analyzing the uncertainty introduced by errors caused by an end point effect due to insufficient sampling rate when the frequency of the discrete Hilbert transform is instantaneously changed; the method comprises the steps of obtaining an instantaneous frequency according to discrete Hilbert transform, establishing a relation between the instantaneous frequency and Hilbert transform of an original signal and the original signal, calculating errors introduced by an end point effect under different sampling rates based on a numerical simulation technology, evaluating uncertainty, and perfecting uncertainty analysis of a frequency transient parameter calibration result of an aircraft power supply characteristic test system so that the calibration result is more accurate and reliable.

2. An aircraft power supply characteristic frequency transient parameter calibration method as defined in claim 1, wherein: the numerical simulation technology selects Matlab simulation technology.

3. An aircraft power supply characteristic frequency transient parameter calibration method as defined in claim 1 or 2, characterized in that: the realization method is that,

determining the relation between transient frequency and original signal and Hilbert transform thereof;

firstly, obtaining transient frequency f (n), original signal s (n) obtained by collection and discrete Hilbert transform of the original signalThe relationship between:

in an analog system, the instantaneous frequency of the signal is given by equations (1), (2) and (3);

wherein the content of the first and second substances,for the hilbert transform of the original signal s (t),to analyze the phase of the signal, f (t) is the time-frequency characteristic curve of the original signal;

carrying the formula (2) into the formula (3), and converting to obtain a formula (4);

because the actual data is a sequence obtained by a data acquisition system, discrete Hilbert transform is also adopted in the processing process, and therefore, the formula (4) is discretized, and differential is replaced by difference to obtain a formula (5), namely, the relation between the transient frequency and the original signal and the Hilbert transform is determined;

wherein s (n) is the acquisition sequence of the original signal,discrete Hilbert transform of the original signal, f (n) time-frequency characteristic sequence of the original signal;

step two, calculating uncertainty u caused by errors caused by insufficient sampling rate, namely realizing evaluation of uncertainty introduced by a discrete Hilbert transform algorithm, and perfecting uncertainty analysis of a frequency transient parameter calibration result of an aircraft power supply characteristic test system, so that the calibration result is more accurate and reliable;

as shown in the formula (5), the instantaneous frequency can be calculated from the original signal and the hilbert transform sequence of the original signal, and the uncertainty u can be obtained by the following steps;

the sampling rate of the signal is fs, the instantaneous frequency f (n) of the signal s (n) is calculated, and the instantaneous frequency value f of the transient moment is recorded₀；

Let the new sampling rate be 2^kFs (k ═ 1,2,3, …), and new instantaneous frequency values are calculated until f is found_kIf the difference between the current frequency value and the instantaneous frequency value obtained by the previous updating is smaller than a preset threshold value, the error introduced by the end point effect cannot be obviously reduced by increasing the sampling rate;

let Δ f be f₀-f_kCalculating the uncertainty contribution of the part according to uniform distribution

And the uncertainty u is obtained, namely, the uncertainty introduced by the discrete Hilbert transform algorithm is evaluated, and the uncertainty analysis of the frequency transient parameter calibration result of the aircraft power supply characteristic test system is perfected, so that the calibration result is more accurate and reliable.

4. An aircraft power supply characteristic frequency transient parameter calibration method as defined in claim 3, wherein: the difference of instantaneous frequency values is less than the preset threshold value

Technical Field

The invention relates to a method for calibrating frequency transient parameters of power supply characteristics of an aircraft power supply, and belongs to the technical field of electrical measurement.

Background

At present, power supply systems of large-scale military and civil aircraft at home and abroad generally adopt a constant-frequency alternating-current or variable-frequency alternating-current power supply system, and meanwhile, the research focus of electrical parameter testing of an aircraft power grid is gradually transferred to the research of transient parameters by steady-state parameters such as voltage, current, distortion and modulation, wherein the steady-state parameters comprise frequency transient parameters. According to the regulation of relevant standards, the calibration of frequency transient parameters requires the acquisition of the whole variation process by a data acquisition system, and the transient time and the transient frequency value are obtained by data analysis.

The mainstream instantaneous frequency extraction method comprises the modes of short-time Fourier transform, wavelet transform, Hilbert transform and the like, and the time resolution and the frequency resolution of the wavelet transform and the short-time Fourier transform algorithm cannot be considered at the same time, so that the Hilbert transform is a better choice for the situation of the text. Based on a discrete Hilbert transform algorithm in Matlab, a time domain signal is transformed into a frequency domain by means of an FFT algorithm, a Hilbert transform frequency spectrum is obtained through recombination of the frequency domain, and finally, the signal is transformed into a time domain by means of an IFFT algorithm, so that Hilbert transform is completed. According to the method, an end point effect is generated at a position where an original signal waveform is suddenly changed due to insufficient sampling rate, so that a discrete Hilbert transform result is deviated, and uncertainty is introduced.

Disclosure of Invention

In order to solve the problems of incomplete uncertainty evaluation process and unreliable calibration result in the conventional aircraft power supply characteristic frequency transient parameter calibration method, the invention aims to provide the aircraft power supply characteristic frequency transient parameter calibration method.

The purpose of the invention is realized by the following technical scheme:

the invention discloses a method for calibrating frequency transient parameters of power supply characteristics of an aircraft power supply, which is used for evaluating uncertainty introduced by a discrete Hilbert transform algorithm in the process of calibrating the frequency transient parameters of a power supply characteristic test system of the aircraft power supply and comprises the following steps: and acquiring the output frequency transient signal by a data acquisition system, and then obtaining the instantaneous frequency based on a discrete Hilbert transform algorithm. The uncertainty introduced by the error of the discrete hilbert transform due to the end-point effect caused by insufficient sampling rate when the frequency changes instantaneously is analyzed. The method comprises the steps of obtaining an instantaneous frequency according to discrete Hilbert transform, establishing a relation between the instantaneous frequency and Hilbert transform of an original signal and the original signal, calculating errors introduced by an end point effect under different sampling rates based on a numerical simulation technology, evaluating uncertainty, and perfecting uncertainty analysis of a frequency transient parameter calibration result of an aircraft power supply characteristic test system so that the calibration result is more accurate and reliable.

Preferably, the numerical simulation technology is preferably Matlab simulation technology.

The invention discloses a method for calibrating frequency transient parameters of power supply characteristics of an aircraft power supply.

Step one, determining the relation between the transient frequency and the original signal and the Hilbert transform thereof.

Firstly, obtaining transient frequency f (n), original signal s (n) obtained by collection and discrete Hilbert transform of the original signalThe relationship between:

in an analog system, the instantaneous frequency of the signal is obtained by equations (1), (2) and (3).

Wherein the content of the first and second substances,for the hilbert transform of the original signal s (t),to analyze the phase of the signal, f (t) is the time-frequency characteristic curve of the original signal.

The formula (2) is brought into the formula (3) and converted to obtain the formula (4).

Because the actual data is a sequence obtained by a data acquisition system, discrete Hilbert transform is also adopted in the processing process, and therefore, the formula (4) is discretized, and difference is used for replacing differentiation to obtain a formula (5), namely, the relation between the transient frequency and the original signal and the Hilbert transform is determined.

Wherein s (n) is the acquisition sequence of the original signal,is discrete Hilbert transform of the original signal, and f (n) is a time-frequency characteristic sequence of the original signal.

And step two, calculating uncertainty u caused by errors caused by insufficient sampling rate, namely realizing evaluation of uncertainty introduced by a discrete Hilbert transform algorithm, and perfecting uncertainty analysis of a frequency transient parameter calibration result of the aircraft power supply characteristic test system, so that the calibration result is more accurate and reliable.

As is clear from equation (5), the instantaneous frequency can be calculated from the original signal and the hilbert transform sequence of the original signal, and the uncertainty u can be obtained by the following procedure.

The sampling rate of the signal is fs, the instantaneous frequency f (n) of the signal s (n) is calculated, and the instantaneous frequency value f of the transient moment is recorded₀；

Let the new sampling rate be 2^kFs (k ═ 1,2,3, …), and new instantaneous frequency values are calculated until f is found_kIf the difference between the current frequency value and the instantaneous frequency value obtained by the previous updating is smaller than a preset threshold value, the error introduced by the end point effect cannot be obviously reduced by increasing the sampling rate;

let Δ f be f₀-f_kCalculating the uncertainty contribution of the part according to uniform distribution

And the uncertainty u is obtained, namely, the uncertainty introduced by the discrete Hilbert transform algorithm is evaluated, and the uncertainty analysis of the frequency transient parameter calibration result of the aircraft power supply characteristic test system is perfected, so that the calibration result is more accurate and reliable.

Preferably, the difference in instantaneous frequency values being less than a predetermined threshold value means

Has the advantages that:

the invention discloses a method for calibrating the frequency transient parameters of the power supply characteristics of an aircraft power supply, which is characterized in that errors introduced by an end point effect are calculated under different sampling rates by a numerical simulation technology, instantaneous frequency can be calculated by a Hilbert transform sequence of an original signal and an original signal, uncertainty introduced by a discrete Hilbert transform algorithm is evaluated, uncertainty analysis of the frequency transient parameter calibration result of a power supply characteristic test system of the aircraft power supply is perfected, uncertainty introduced by each link of the calibration method can be more comprehensively evaluated in the calibration process of the frequency transient parameters of the power supply characteristics of the aircraft power supply, and the calibration result is more accurate and reliable.

Drawings

FIG. 1 is a flow chart of a frequency transient parameter calibration process of an aircraft power supply characteristic test system.

Detailed Description

The following examples illustrate the invention in detail.

As shown in fig. 1, in the method for calibrating the frequency transient parameter of the power supply characteristic of the aircraft disclosed in the present embodiment, the primary source of uncertainty u of the frequency transient parameter calibration result is an error introduced by an "end effect" due to insufficient sampling rate at a sudden change of the waveform.

Step one, determining the relation between the transient frequency and the original signal and the Hilbert transform thereof.

And simulating an original signal s (n) according to the frequency transient signal characteristic of the power supply characteristic of the airplane power supply, wherein the process is as follows. Setting the sampling rate fs of the signal to be 10MS/s and the total sampling point number to be 10M according to the highest acquisition rate of the used high-precision data acquisition system, creating two sine wave sequences s1 and s2, wherein the frequencies are respectively the lower limit and the upper limit f of the frequency conversion alternating current power supply system in the aircraft power supply system₁360Hz and f₂＝800Hz。

Signal s is defined as equation (8).

And step two, calculating uncertainty u caused by errors caused by insufficient sampling rate, namely realizing evaluation of uncertainty introduced by a discrete Hilbert transform algorithm, and perfecting uncertainty analysis of a frequency transient parameter calibration result of the aircraft power supply characteristic test system, so that the calibration result is more accurate and reliable.

Calculating the instantaneous frequency f (n) of the signal s (n) according to the formula (5), and recordingInstantaneous frequency value f of time₀＝800.835Hz；

Let the new sampling rate be 2^kFs (k ═ 1,2,3, …), and new instantaneous frequency values are calculated until f is found_kThe difference of the instantaneous frequency value obtained in the previous step is less than 0.0001 time;

let Δ f be f₀-f_k0.825Hz, the partial uncertainty contribution is calculated in a uniform distribution, then

And the uncertainty u is obtained, namely, the uncertainty introduced by the discrete Hilbert transform algorithm is evaluated, and the uncertainty analysis of the frequency transient parameter calibration result of the aircraft power supply characteristic test system is perfected, so that the calibration result is more accurate and reliable.

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.