CN105551165A - Optical fiber perimeter security and protection system disturbance determination method based on dynamic threshold detection - Google Patents

Abstract

The invention discloses an optical fiber perimeter security and protection system disturbance determination method based on dynamic threshold detection. Through a window function method, a signal with disturbance and a noise is intercepted into short time information frames and each frame of over threshold value numbers is calculated. A maximum value, a minimum value and a difference value of the over threshold value numbers are used to determine a disturbance threshold value of a system, and a new disturbance threshold value is used to carry out disturbance determination on a next signal. The optical fiber perimeter security and protection system disturbance determination method based on the dynamic threshold detection is a technology capable of timely updating a system parameter to increase a system anti-noise capability according to an extraneous environment. Under the condition that a high detection sensitivity can be kept, system false alarm caused by environment factors of raining and the like can be eliminated.

Description

Based on the optical fiber perimeter safety-protection system disturbance determination methods that dynamic threshold detects

Technical field

The invention belongs to sensing and detection technique field, be applied in optical fiber perimeter safety-protection system especially, under the prerequisite compared with high detection sensitivity can be kept, the method that the environmental factors such as elimination is rainy cause misreport of system alert.Optical fiber perimeter safety-protection system utilizes common communications optical cable as the sensor-based system of sensor information, accurately can locate the intrusion behavior that optical cable circumference occurs.

Background technology

Along with the continuous progress of human society and the develop rapidly of scientific and technological level, safety monitoring more and more comes into one's own, no matter be electric power, the field that involves the interests of the state and the people such as water conservancy, petrochemical industry, or the field that the security requirements such as post, airport, prison are higher, perimeter security monitors the application be obtained for widely.Because sensing optic cable is laid on outdoor fence usually, inclement weather can have considerable influence to system performance, and especially heavy rain weather more can cause misreport of system.Therefore, how to eliminate the misreport of system that heavy rain weather causes and become the key issue improving system performance.

Optical fiber perimeter safety-protection system in the past often takes the method in artificial reduction system looks sensitivity on rainy day, reduces due to the misreport of system caused that rains.This method not only needs operating personnel to reset systematic parameter, and the sensitive reduction of system looks also can to the judgement of intrusion behavior, cause failing to report probability and significantly rise by influential system simultaneously.The inclement weather especially large rainy day often offender crime high-incidence season, rugged environment system more should keep higher detection sensitivity.Therefore, adopt new method keeping compared with under the prerequisite of high detection sensitivity, the wrong report that the environmental factors such as elimination is rainy cause, improves system rejection to disturbance ability.

Summary of the invention

Object keeping system of the present invention is compared with under the prerequisite of high detection sensitivity, and the wrong report that the environmental factors such as elimination is rainy cause, provides a kind of optical fiber perimeter safety-protection system disturbance determination methods detected based on dynamic threshold.The present invention improves short-time zero-crossing rate method conventional in Speech processing, effectively can get rid of rain signal interference, and gets rid of other some interference of nature to a certain extent, thus improves the antijamming capability of circumference security positioning system.

Technical scheme of the present invention is:

Based on the optical fiber perimeter safety-protection system disturbance determination methods that dynamic threshold detects, the method comprises the following steps:

1.th gets one section of disturbance light optical fiber signaling s _bn (), utilizes band-pass filter denoising, then carry out down-sampled, obtains signal s (n);

S (n) is utilized window function sub-frame processing by the 2.th, and form windowing signal x (n)=s (n)/w (n), be wherein w (n) rectangular window function, expression formula is as follows: n is window length, and m is window starting point;

3.th arranges appropriate threshold parameter L excessively, and calculate every frame forward and cross threshold number LC, LC calculation expression is as follows: wherein x (n), L are threshold parameters, are 1 when expression formula is true time Ψ, and fictitious time is 0;

The size of the 4.th more every frame LC and disturbance threshold value J, if in whole segment signal, when having continuous 3 frame LC to be greater than J, then judge that s (n) is as there being disturbing signal, if this segment signal is for thanksing for your hospitality signal, then current system disturbance threshold value is unchanged, and step leaves it at that; If this segment signal is unperturbed signal, then perform step 5;

5.th each frame of statistics crosses threshold number LC, and the value of maximum LC is Max in all frames, and the value of minimum LC is Min; The difference of maximal value Max and minimum M in is D, D=Max-Min;

6.th to arrange threshold value parameter of floating be that the expression formula of T, T is as follows: $T=\left\{\begin{array}{c}2\mathrm{Min},\mathrm{Min}\≤5\\ 10,\mathrm{Min}>5\end{array}\right.,$ Relatively the size of D and T, if D is less than T, is then judged as rain signal by this segment signal s (n); If D is greater than T, be judged as normal signal;

7.th adopts different disturbance threshold value J according to the judged result of the 6th step, and the expression formula of J is as follows: $J=\left\{\begin{array}{c}\mathrm{Min}+10,D>T\\ \mathrm{Max}+10,D\≤T\end{array}\right.,$ Wherein Max and Min is respectively LC maximal value and the minimum value of unperturbed signal s the last period (n), and T is that the threshold value of s (n) is floated parameter, D=Max-Min.

Advantage of the present invention and beneficial outcomes are:

The present invention proposes the optical fiber perimeter security positioning system disturbance distinguished number detected based on dynamic threshold.If adopt fixed threshold to carry out disturbance differentiation; when threshold value setting is lower; often cause more false alarm because neighbourhood noise is comparatively large, higher in order to what get rid of that various Environmental Noise Influence threshold value can set usually, but high threshold value can influential system detection sensitivity.So propose a kind of algorithm that can arrange dynamic threshold according to current environment, under the prerequisite of keeping system compared with high detection sensitivity, the wrong report that the environmental factors such as elimination is rainy cause.

Accompanying drawing explanation

Fig. 1 distributed optical fiber disturbance positioning system;

The disturbance of Fig. 2 dynamic threshold differentiates process flow diagram;

Fig. 3 is without rain signal disturbance signal waveforms;

Fig. 4 is without the mistake number of threshold values figure of rain disturbing signal;

The oscillogram of Fig. 5 undisturbed on rainy day signal;

The mistake number of threshold values figure of Fig. 6 undisturbed on rainy day signal;

Fig. 7 has the oscillogram of disturbing signal rainy day;

Fig. 8 has the mistake number of threshold values figure of disturbing signal rainy day;

Embodiment

The principle of invention:

1. the ultimate principle of circumference security positioning system:

Distributed optical fiber disturbance positioning system as shown in Figure 1, this system, based on two Mach-Zehnder fibre optic interferometer principle, utilizes in optical cable two single-mode fibers to form two measuring fibers of Mach-Zehnder fibre optic interferometer to respond to the disturbing signal around optical cable.

As shown in Figure 1, after light is sent by laser instrument, the two-beam of 1:1 is divided into after coupling mechanism C1, this two-beam respectively through after circulator C2 and C3 from interfering coupling mechanism C4 and C5 at arm two ends to enter sensing loop and along the transmission of contrary both direction, interfering at the coupling mechanism place of opposite end and output on detector D1 and D2.Detector PD1 and PD2 changes into electric signal light signal, carries out next step signal transacting through being collected in computing machine by high-speed collection card after straight.The P place of sensing optic cable is disturbed, then because disturbance location is to the difference of sensing optic cable two ends distance, there is certain delay the time causing coherent light waves to arrive detector, and the time that the light wave propagated in the counterclockwise direction arrives detector PD1 is:

t ₁＝L ₁n/c

The time that the light wave propagated along clockwise direction arrives detector PD2 is:

t ₂＝(L-L ₁)n/c

In formula, L ₁for the distance of disturbance point range finder PD1, L is optical fiber total length, and n is optical fibre refractivity, and c is light speed (3 × 10 in a vacuum ⁸m/s).

Disturbance point location formula can be calculated thus:

$L_1=\frac{(t_1-t_2)c}{2n}+\frac{L}{2}$

2. the principle analysis of dynamic threshold detection method:

The signal that perimeter security system collects carries out sub-frame processing, because safety-protection system need detect climbing and signal of walking, its duration is longer than each word signal in voice, reference speech signal process frame length, and setting perimeter security system signals collecting duration is 300ms.One frame perimeter security system output signal s (n) of taking out, through windowing process, little segment signal is obtained to it and was used for asking in short-term number of threshold values, namely use certain window function w (n) to take advantage of s (n), thus form windowing signal x (n)=s (n) w (n).For rectangular window function as window function, expression formula following (wherein N is window length, and m is window starting point):

Cross number of threshold values LC in short-term may be defined as:

In formula: m represents window starting point, N represents window length, and x (n) is windowing signal, and Ψ is logical function.

It is lower that number of threshold values crossed in short-term by optical fiber in normal weather undisturbed situation, thanks for your hospitality crossing number of threshold values in short-term and having suddenly a larger rising of signal segment, whether therefore can distinguish and thanks for your hospitality by arranging disturbance judgment threshold J, Fig. 3 and Fig. 4 is respectively the oscillogram of normal disturbances signal and crosses number of threshold values figure.But cross number of threshold values in large rainy day undisturbed situation in short-term and also can remain on a higher number, as shown in Figure 6.In order to get rid of the interference on rainy day, utilize dynamic threshold detection algorithm of crossing can upgrade system disturbance threshold value J, as Fig. 8 according to current unperturbed signal.So just can eliminate the impact that heavy rain weather judges disturbance.

Calculate perimeter security system and judge whether that the process flow diagram of thanksing for your hospitality is as Fig. 2.

Embodiment 1:

Build positioning distributed fibre-optical disturbance positioning system as shown in Figure 1, knock optical cable simulated disturbance at normal weather and heavy rain weather respectively, compare rainy day and normal weather thankss for your hospitality unperturbed situation.Disturbance light signal in optical fiber is become electric signal by the photodetector in this system, obtains the 0.3s signal comprising disturbing signal and processes.Experimental result is as follows:

1. under obtaining one section of normal weather, 300ms thankss for your hospitality signal waveforms as shown in Figure 3, and the mistake number of threshold values figure after process as shown in Figure 4.During normal weather unperturbed, data waveform frequency is lower as can see from Figure 3, and in Fig. 4, mistake threshold number LC maintains lower level always, and the value according to its disturbance of dynamic threshold algorithm threshold value J is 10.Can be easier to judge whether thanks for your hospitality.

2. under obtaining heavy rain weather, 300ms undisturbed signal waveforms as shown in Figure 5, and its signal frequency increases significantly compared with Fig. 3 unperturbed segment signal.Fig. 6 is the mistake number of threshold values figure after process, although under being in unperturbed state, it is crossed number of threshold values LC and keeps between 10 and 20 always, is greater than the disturbance threshold value in Fig. 4.

3. under obtaining heavy rain weather, knock optical cable simulated disturbance signal waveforms as shown in Figure 7, when the disturbance of 1500 places occurs, the signal frequency of unperturbed before its signal frequency is greater than.Fig. 8 is the mistake number of threshold values figure of this signal, although cross number of threshold values during unperturbed to be in higher level always, after being through the process of dynamic disturbances thresholding algorithm, its disturbance threshold value is in a higher scope, can not cause the false alarm of system.When there being disturbance to occur, the mistake number of threshold values LC caused by disturbance exceedes disturbance threshold value J, causes system alarm.

Claims (1)

1., based on the optical fiber perimeter safety-protection system disturbance determination methods that dynamic threshold detects, it is characterized in that comprising the following steps:

(1) one section of disturbance light optical fiber signaling s is got _bn (), utilizes band-pass filter denoising, then carry out down-sampled, obtains signal s (n);

(2) s (n) is utilized window function sub-frame processing, form windowing signal x (n)=s (n) w (n), be wherein w (n) rectangular window function, expression formula is as follows: n is window length, and m is window starting point;

(3) arrange appropriate threshold parameter L excessively, calculate every frame forward and cross threshold number LC, LC calculation expression is as follows: wherein x (n), L are threshold parameters, are 1 when expression formula is true time Ψ, and fictitious time is 0;

(4) size of more every frame LC and disturbance threshold value J, if in whole segment signal, when having continuous 3 frame LC to be greater than J, then judges that s (n) is as there being disturbing signal; If this segment signal is for thanksing for your hospitality signal, then current system disturbance threshold value is unchanged, and step leaves it at that; If this segment signal is unperturbed signal, then perform step 5;

(5) add up each frame and cross threshold number LC, the value of maximum LC is Max in all frames, and the value of minimum LC is Min; The difference of maximal value Max and minimum M in is D, D=Max-Min;

(6) arranging threshold value parameter of floating is that the expression formula of T, T is as follows: $T=\left\{\begin{array}{c}2Min,Min\≤5\\ 10,Min>5\end{array}\right.,$ Relatively the size of D and T, if D is less than T, is then judged as rain signal by this segment signal s (n); If D is greater than T, be judged as normal signal;

(7) adopt different disturbance threshold value J according to the judged result of the 6th step, the expression formula of J is as follows: $J=\left\{\begin{array}{c}Max+10,D>T\\ Max+10,D\≤T\end{array}\right.,$ Wherein Max and Min is respectively LC maximal value and the minimum value of unperturbed signal s the last period (n), and T is that the threshold value of s (n) is floated parameter, D=Max-Min.