CN102435913A - Method for detecting aircraft cable fault by use of Wigner data distribution matrix - Google Patents

Abstract

The invention relates to a method for detecting aircraft cable fault by use of Wigner data distribution matrix. The method comprises the following steps: an incoming reference signal setting step, including a center frequency selection stage, a frequency bandwidth selection stage and a stage for selecting time width of the incoming reference signal according to the selected center frequency and the frequency bandwidth; a signal transmission step, including transmitting the set incoming reference signal to a to-be-tested cable with a receiving interface; a noise reducing step, including receiving a reflection signal of the to-be-tested cable with the receiving interface, and reducing noise of the received reflection signal of the to-be-tested cable by using a wavelet coefficient shrinkage noise reduction method, to reduce the influence of noise signals on the reflection signal; and a fault information processing step, including calculating the correlation between the incoming reference signal and the reflection signal, and calculating local peak time in the correlation function waveform to accurately determine the fault position of the aircraft cable. According to the invention, this kind of fault information is more obvious by using Wigner data distribution matrix, thereby improving fault detection efficiency of aircraft cables.

Description

Utilize Wigner DATA DISTRIBUTION matrix to detect the method for plane cable fault

Technical field

The present invention relates to a kind of plane cable fault detection method.Particularly relate to a kind of method of utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault.

Background technology

Along with the fast development of Chinese national economy, aviation transport has got into a fast-developing period, and the flight safety problem has obtained increasing concern.Happen occasionally by the aircraft fire of Aircraft Cables short circuit initiation and the signal transmission errors that causes by plane cable fault, caused a lot of aircraft accidents, make plane cable fault diagnosis and orientation problem, become one of International Civil Aviation circle problem demanding prompt solution.Each aeronautical maintenance department is necessary to detect rule according to certain maintenance, adopts advanced diagnosis and localization method and instrument that Aircraft Cables is regularly detected, and in time finds cable fault to be positioned cable fault.

The plane cable fault type is a lot, except open circuit fault, low-resistance fault and the high resistive fault three quasi-representative faults of general cable, also comprises the first-class failure and special of intermittent defect, local fault and cross-over connection that Aircraft Cables itself is had.

The method that detects to plane cable fault at present mainly contains otdr measurement method and frequency domain reflection mensuration.Detection method as shown in Figure 1 comprises, uses the step signal generator to cable one end emission rising edge pulse signal, and this signal reflects at the cable fault place, and receiver module is gathered the time domain waveform of reflected signal simultaneously.If the fault place of cable is an open fault, this demonstrates one and the equidirectional pulse of transponder pulse on oscillograph; If the fault place of cable is a short trouble, then on oscillograph, show one and the reciprocal pulse of transponder pulse.Mistiming according between transponder pulse and the reflected impulse is measured the trouble spot.But; Open circuit when the part takes place Aircraft Cables, connect when disconnected during the wire harness inner cable; When connecting when breaking when perhaps Aircraft Cables shielded metal twine penetrates insulation course and Aircraft Cables; Influence to its characteristic impedance is less, and the signal that above-mentioned two kinds of reflection measurement methods reflect changes very faint, and these intermittent defects are difficult to be diagnosed.When Aircraft Cables generation continuous fault, above-mentioned two kinds of reflection measurement methods can produce the multiple reflection phenomenon, and except that first trouble spot was easy to judge, other trouble spots were difficult to judge.Under general measurement environment, above-mentioned two kinds of reflection measurement methods need be carried out processing and amplifying to faint reflected signal, cause noise signal also by corresponding amplification, and influence has increased the rate of false alarm of plane cable fault to the judgement of fault reflected signal.

Summary of the invention

Technical matters to be solved by this invention is; A kind of time linear FM signal of utilizing is provided; Aircraft Cables reflected signal to be measured is carried out noise reduction process; The time-frequency distributions correlativity of utilization incident reference signal and reflected signal, the Wigner DATA DISTRIBUTION matrix that utilizes that detects plane cable fault and definite abort situation detects the method for plane cable fault.

The technical scheme that the present invention adopted is: a kind of method of utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault comprises the steps:

(1) incident reference signal is set, and comprises that centre frequency select stage, selected stage of frequency bandwidth and according to time width stage of selected centre frequency and frequency bandwidth selection incident reference signal;

(2) the incident reference signal of setting is sent to the cable under test with receiving interface;

(3) noise reduction process comprises the reflected signal that receives the cable under test with receiving interface, and utilizes wavelet coefficient to shrink noise-reduction method the reflected signal of the cable under test that received is carried out noise reduction process, reduces the influence of noise signal to reflected signal;

(4) failure message is handled, and comprises the correlativity of calculating incident reference signal and reflected signal, accurately confirms the plane cable fault position through local peaking's time in the calculating related function waveform again.

The described centre frequency of step 1 is selected to be the centre frequency of confirming incoming signal through the damped system of RF energy, specifically is to obtain centre frequency ω through following formula ₀:

ω _s＝∫ω|s(ω)| ²dω＝ω ₀

S (ω) is the Fourier transform of signal.

The described frequency bandwidth of step 1 is selected to be to obtain frequency bandwidth B through following formula _s:

$B_s^2={\∫(\mathrm{\ω}-{\mathrm{\ω}}_s)}^2{\left|s\left(\mathrm{\ω}\right)\right|}^2\mathrm{d\ω}=\frac{{\mathrm{\α}}^2+{\mathrm{\β}}^2}{2\mathrm{\α}}$

α, β are respectively time width, band width, and the band width size adopts 2 times centre frequency, and s (ω) is the Fourier transform of signal.

The time width of the described incident reference signal of step 1 is set at 45～55ns.

The correlativity of step 4 described calculating incident reference signal and reflected signal obtains through following formula

$C_{\mathrm{sr}}\left(t\right)=\∫\∫\frac{2\mathrm{\π}}{E_s{E}_r}{W}_r(t^{\′},\mathrm{\ω})W_s(t^{\′}-t,\mathrm{\ω})\mathrm{d\ω}{\mathrm{dt}}^{\′}$

W wherein _r(t ω) is the Wigner distribution of reflected signal, W _s(t, ω) for the Wigner of incident reference signal distributes, with cable under test fault distance x given after, the time-frequency related function C of reflected signal _Sr(t) confirm as:

α, β are respectively time width, band width.

The described wavelet coefficient that utilizes of step 3 shrinks noise-reduction method, is to carry out noise reduction process according to reflected signal noise intensity method of estimation design threshold wave filter.

The time-frequency related function C of the described reflected signal of step 4 _Sr(t) be limited between 0 and 1, when t=x/v, the time-frequency related function C of reflected signal _Sr(t) peak value occurs, when fault was cross-over connection fault, a plurality of peak values appearred in reflected signal, then time-frequency related function C _Sr(t) a plurality of local peakings of corresponding appearance confirm fault distance according to the time that local peaking occurs.

The described plane cable fault of step 4 position obtains through following formula

$d=\frac{v\·(t_2-t_1)}{2}$

Wherein, d is the plane cable fault position, and v is the waveform transmission speed, t ₁Be reference waveform signal launch time, t ₂It is fault point reflection signal time.

The method of utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault of the present invention is at first constructed an incident reference signal, and this signal is a time linear FM signal, makes can in additional band, use RF energy when cable fault detects with the location.Then reflected signal is carried out noise reduction process, reduce the influence of noise signal, use the time-frequency distributions correlativity of incident reference signal and reflected signal at last, detect plane cable fault and definite abort situation reflected signal.To local fault, continuous fault in the peculiar fault of Aircraft Cables and stride that adapter fault reflected signal is faint, signal attenuation is serious and cause the problem that is difficult to detect; Adopt Wigner DATA DISTRIBUTION matrix to make such failure message more obvious; Improve plane cable fault diagnosis recall rate, thereby can improve the fault detect efficient of Aircraft Cables.

Description of drawings

Fig. 1 is the Time Domain Reflectometry method plane cable fault diagnostic method process flow diagram of prior art;

Fig. 2 detects the plane cable fault method flow diagram for the Wigner DATA DISTRIBUTION matrix that utilizes provided by the invention.

Embodiment

Utilize the method for Wigner DATA DISTRIBUTION matrix detection plane cable fault to make detailed description below in conjunction with embodiment and accompanying drawing to kind of the present invention.

As shown in Figure 2, kind of the present invention utilizes Wigner DATA DISTRIBUTION matrix to detect the method for plane cable fault, comprises the steps:

(1) incident reference signal is set, and comprises that centre frequency select stage, selected stage of frequency bandwidth and according to time width stage of selected centre frequency and frequency bandwidth selection incident reference signal; Wherein,

The dough softening of incident reference signal when the centre frequency of incident reference signal has determined through cable.Upper frequency has higher spatial resolution small echo, but also has more decay simultaneously, and described centre frequency is selected to be the centre frequency of confirming incoming signal through the damped system of RF energy, specifically is to obtain centre frequency ω through following formula ₀:

ω _s＝∫ω|s(ω)| ²dω＝ω ₀

S (ω) is the Fourier transform of signal;

Described frequency bandwidth is selected to be to obtain frequency bandwidth B through following formula _s:

$B_s^2={\∫(\mathrm{\ω}-{\mathrm{\ω}}_s)}^2{\left|s\left(\mathrm{\ω}\right)\right|}^2\mathrm{d\ω}=\frac{{\mathrm{\α}}^2+{\mathrm{\β}}^2}{2\mathrm{\α}}$

α, β are respectively time width, band width, and the band width size adopts 2 times centre frequency, and time width is to set according to the centre frequency of incoming signal and frequency bandwidth, and s (ω) is the Fourier transform of signal;

The time width of described incident reference signal is a centre frequency of taking all factors into consideration incident reference signal damping capacity and incident reference signal, and the frequency bandwidth of incident reference signal, and reduces to test the blind area as far as possible, is set at 45～55ns.

(2) the incident reference signal of setting is sent to the cable under test with receiving interface;

(3) noise reduction process comprises the reflected signal that receives the cable under test with receiving interface, and utilizes wavelet coefficient to shrink noise-reduction method the reflected signal of the cable under test that received is carried out noise reduction process, reduces the influence of noise signal to reflected signal;

The described wavelet coefficient that utilizes shrinks noise-reduction method, is to carry out noise reduction process according to reflected signal noise intensity method of estimation design threshold wave filter.

(4) failure message is handled, and comprises the correlativity of calculating incident reference signal and reflected signal, accurately confirms the plane cable fault position through local peaking's time in the calculating related function waveform again.

The correlativity of described calculating incident reference signal and reflected signal obtains through following formula

$C_{\mathrm{sr}}\left(t\right)=\∫\∫\frac{2\mathrm{\π}}{E_s{E}_r}{W}_r(t^{\′},\mathrm{\ω})W_s(t^{\′}-t,\mathrm{\ω})\mathrm{d\ω}{\mathrm{dt}}^{\′}$

W wherein _r(t ω) is the Wigner distribution of reflected signal, W _s(t, ω) for the Wigner of incident reference signal distributes, with cable under test length x given after, reflected signal C _Sr(t) time-frequency related function is confirmed as:

α, β are respectively time width, band width.

Can find out the time-frequency related function C of reflected signal _sR (t) is limited between 0 and 1, when t=x/v, and the time-frequency related function C of reflected signal _Sr(t) peak value appears.When fault was cross-over connection fault, a plurality of peak values appearred in reflected signal, its time-frequency related function C _Sr(t) a plurality of local peakings of corresponding appearance confirm fault distance according to the time that local peaking occurs.

Described plane cable fault position obtains through following formula

$d=\frac{v\·(t_2-t_1)}{2}$

Wherein, d is the plane cable fault position, and v is the waveform transmission speed, t ₁Be reference waveform signal launch time, t ₂It is fault point reflection signal time.

Claims (8)

1. a method of utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault is characterized in that, comprises the steps:

(1) incident reference signal is set, and comprises that centre frequency select stage, selected stage of frequency bandwidth and according to time width stage of selected centre frequency and frequency bandwidth selection incident reference signal;

(2) the incident reference signal of setting is sent to the cable under test with receiving interface;

(3) noise reduction process comprises the reflected signal that receives the cable under test with receiving interface, and utilizes wavelet coefficient to shrink noise-reduction method the reflected signal of the cable under test that received is carried out noise reduction process, reduces the influence of noise signal to reflected signal;

(4) failure message is handled, and comprises the correlativity of calculating incident reference signal and reflected signal, accurately confirms the plane cable fault position through local peaking's time in the calculating related function waveform again.

2. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1; It is characterized in that; The described centre frequency of step 1 is selected to be the centre frequency of confirming incoming signal through the damped system of RF energy, specifically is to obtain centre frequency ω through following formula ₀:

ω _s＝∫ω|s(ω)| ²dω＝ω ₀

S (ω) is the Fourier transform of signal.

3. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1 is characterized in that the described frequency bandwidth of step 1 is selected to be to obtain frequency bandwidth B through following formula _s:

$B_s^2={\∫(\mathrm{\ω}-{\mathrm{\ω}}_s)}^2{\left|s\left(\mathrm{\ω}\right)\right|}^2\mathrm{d\ω}=\frac{{\mathrm{\α}}^2+{\mathrm{\β}}^2}{2\mathrm{\α}}$

α, β are respectively time width, band width, and the band width size adopts 2 times centre frequency, and s (ω) is the Fourier transform of signal.

4. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1 is characterized in that the time width of the described incident reference signal of step 1 is set at 45～55ns.

5. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1 is characterized in that the correlativity of step 4 described calculating incident reference signal and reflected signal obtains through following formula

$C_{\mathrm{sr}}\left(t\right)=\∫\∫\frac{2\mathrm{\π}}{E_s{E}_r}{W}_r(t^{\′},\mathrm{\ω})W_s(t^{\′}-t,\mathrm{\ω})\mathrm{d\ω}{\mathrm{dt}}^{\′}$

W wherein _r(t ω) is the Wigner distribution of reflected signal, W _s(t, ω) for the Wigner of incident reference signal distributes, with cable under test fault distance x given after, the time-frequency related function C of reflected signal _Sr(t) confirm as:

α, β are respectively time width, band width.

6. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1; It is characterized in that; The described wavelet coefficient that utilizes of step 3 shrinks noise-reduction method, is to carry out noise reduction process according to reflected signal noise intensity method of estimation design threshold wave filter.

7. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1 is characterized in that the time-frequency related function C of the described reflected signal of step 4 _Sr(t) be limited between 0 and 1, when t=x/v, the time-frequency related function C of reflected signal _Sr(t) peak value occurs, when fault was cross-over connection fault, a plurality of peak values appearred in reflected signal, then time-frequency related function C _Sr(t) a plurality of local peakings of corresponding appearance confirm fault distance according to the time that local peaking occurs.

8. the method for utilizing Wigner DATA DISTRIBUTION matrix to detect plane cable fault according to claim 1 is characterized in that the described plane cable fault of step 4 position obtains through following formula

$d=\frac{v\·(t_2-t_1)}{2}$

Wherein, d is the plane cable fault position, and v is the waveform transmission speed, t ₁Be reference waveform signal launch time, t ₂It is fault point reflection signal time.

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