WO2008038289A2 - Système et procédé permettant de détecter et de classifier des dommages dans un pipeline - Google Patents

Système et procédé permettant de détecter et de classifier des dommages dans un pipeline Download PDF

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Publication number
WO2008038289A2
WO2008038289A2 PCT/IL2007/001202 IL2007001202W WO2008038289A2 WO 2008038289 A2 WO2008038289 A2 WO 2008038289A2 IL 2007001202 W IL2007001202 W IL 2007001202W WO 2008038289 A2 WO2008038289 A2 WO 2008038289A2
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WIPO (PCT)
Prior art keywords
signals
event
analysis
protected zone
further including
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PCT/IL2007/001202
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English (en)
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WO2008038289A3 (fr
Inventor
Gil Pogozelits
Boris Greenstein
Alexander Pikus
Vladimir Yagnatinsky
Eugene Ostrovsky
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Soniclynx Ltd.
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Publication of WO2008038289A2 publication Critical patent/WO2008038289A2/fr
Publication of WO2008038289A3 publication Critical patent/WO2008038289A3/fr

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
    • G08B13/1654—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems
    • G08B13/1663—Actuation by interference with mechanical vibrations in air or other fluid using passive vibration detection systems using seismic sensing means
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/18—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
    • G08B13/181—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems
    • G08B13/183—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier
    • G08B13/186—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier using light guides, e.g. optical fibres
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2491—Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/185—Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system

Definitions

  • the present invention relates to systems and methods for detecting intrusions, more particularly it relates to systems and methods for territory protection from unauthorized intruders and from malicious sabotaging of objects in security-sensitive aieas.
  • Different methods and systems for the protection of territories, buildings and other constructions are known.
  • Known in the art are methods that make use of geophones which are sensitive to the vibrations in the environment and in the ground in particular for gathering acoustic signals created by actions of intruders or caused by processes occurring in an environment. Geophones are used in passive intrusion detection systems.
  • Geophones depending on the character of the protected zone, are placed under a superficial layer of the ground or on constructed elements of buildings such as the walls, the floor, or the ceiling. Alternatively, geophones may be attached to wire barriers and used to detect a variety of inputs such as a walking person, a running person, a walking bird, destruction of constructed elements, industrial noise or different kinds of vehicles.
  • the main challenge in such systems is in the signal analysis process.
  • the detected signals must be reliably classified according to their location and origin. Misidentification of signals may cause one of two problems: false positive and false negative errors. False positive errors are false alarms caused by a misidentification of signals produced by a benign source and erroneously setting off the alarm. False negative errors prevent the system from identifying intruders.
  • Using frequency-based methods do not enable separating in all cases events adequately enough, because in real conditions there are no precisely separated frequency ranges for each event, and chosen ranges do not always meet the real requirements of intruder identification. For example, the frequency based methods may not enable distinguishing between different gaits of an intruder.
  • Kerr "Intrusion detection apparatus having multiple channel signal processing", Patent number US 5,194,848, which is incorporated herein as if fully set forth herein, describes multi-channel signal processing with changing filter on each channel to allocate intruders. An alarm is triggered if the input amplitude for a given frequency range exceeds the threshold level during a predetermined period of time. The resulting signal (alarm signal) is then formed by a logical circuit that collects confirming signals from all channels based on a predetermined combination.
  • Pakhomov System for detecting intruders
  • US 6,529,130 which is incorporated herein as if fully set forth herein, describes a system that performs analysis of the bending of initial signals to allocate signals of intruders.
  • the approach proposed by Pakhomov includes using the amplitude threshold, definition of the average distance between maximal values and moments of time appropriate to them, in order to move accurately definition root- mean-square values and values of root-mean-square deviations for these intervals.
  • Pakhomov uses accumulation of data during a time interval of 4-6 seconds for recognition. For many systems this time interval does not correspond to system requirements. During this time interval an intruder may easily cross a protected zone (10-20 meters) and essential information for analysis may be lost.
  • GEOQUIP company developed and manufactures the perimeter security and intrusion classification (PSICON) system, comprised of a chain of geophones and an analyzer.
  • the geophones are used for vibration detection in the perimeter area of the protected object.
  • the vibrations received by the geophones which may be caused by the activity of intruders, are transformed to electric signals and sent to an analyzer which uses coded representation of the alarm images appropriate to known events, like the occurrence of an intruder, for recognition. These images are stored in system memory and compared with measured data by a method of 'neuron nets'.
  • PSICON allows the finding out and identifying the vibrations caused by the attempts of intruders to overcome a protective barrier with or without the help of a ladder.
  • the patent does not relate to protecting territories that have no surrounding walls.
  • Optical fibers may be used as a means for detecting intrusion in a protected zone. An optical fiber enables detecting an intrusion along the length of the fiber, whereby the fiber is the sensing element and is suitable for protecting zones that have a large perimeter of, e.g., several hundred meters or kilometers.
  • the detection relies on sensor output analysis.
  • the method comprises the steps of collecting signals from the geophone sensors, performing analysis on different mathematical dimensions of the signals, and identifying at least one event type according to signal patterns appearing in the analysis.
  • the event may be a vehicle riding and the identification is performed by analyzing the density of distribution of the transformed signals.
  • the event may be a person walking and the identification is performed by using a correlation function on inputs signals from two geophones which are in close proximity, and which have received signals with maximal energy.
  • the event may be caused by the presence of birds and the identification is performed by using a correlation function on inputs signals from two geophones which are in close proximity, and which have received signals with maximal energy.
  • the event may be caused by an external event wherein the identification is performed by using a correlation function on inputs signals from two geophones which are in close proximity, and which have received signals with maximal energy.
  • the method may also include the steps of sampling the signals and dividing the sampled signals into frames.
  • the analysis may be performed on each frame.
  • the sufficient duration for the recognition of the considered events should be greater than the frame duration.
  • the analysis may include calculating the first norm of the absolute value of the signals and a second norm of the energy of the signals.
  • the method may also include the step of selecting the output signal of a single sensor.
  • the selected sensor is the sensor with the highest norms.
  • the method may also include the step of filtering the samples of the sensor using a high-pass filter, wherein the filtering enables emphasizing features of the signals.
  • the different mathematical dimensions may include the signal dimension and the spectrum dimension.
  • the analysis may be performed on the envelope of the signal dimension.
  • the analysis of the envelope may be performed according to the construction of the density of the transformed samples distribution.
  • the analysis may include an estimation of the cross-spectral density of the sequences of the filtered samples of two sufficient informative seismograms of a given frame. The estimation may be performed by preliminary calculations of a cross-correlation function of the frames.
  • the sensors may be extended in the protected zone in different directions.
  • the cross- correlation function may be performed based on power spectral density estimations.
  • the method may also include the step of activating an alarm if the identified event is identified as an intrusion of the protected zone.
  • the method may also include the step of calculating the differential output beams transmitted through at least two fibre optic strands of fibre optic strands which are installed in the protected zone.
  • the method may also include the step of identifying an intrusion in the protected zone in accordance with the calculated deferential output of the beams.
  • the system includes a data collecting device for collecting signals from the geophone sensors, a calculating device for performing analysis on different mathematical dimensions of the collected signals, and a module for identifying at least one event type according to signal patterns appearing in the analysis.
  • the event may be a vehicle riding or a person walking. The event may be caused by the presence of birds or by an external event.
  • the system may also include alarming means for alerting if the event is identified as an intrusion.
  • the system may also include at least two fibre optic strands which installed in the protected zone and a transmitter device for transmitting a laser beam through the fibre optic strands.
  • the system may also include a receiver device for measuring the differential output in the beams transmitted through the fibre optic strands, and a calculating device for identifying intrusions whenever the measured differential in the output beams exceeds a predetermined threshold.
  • Figure 1 is a block diagram of the data collection and data processing system in accordance with some embodiments of the present invention.
  • Figures 2a, 2b, 2c and 2d are examples for signals collected by the sensors of the system, whereas Figure 2a is an example for the signal produced by a person walking; Figure
  • FIG. 2b is an example for the signal produced by a vehicle in motion
  • Figure 2c is an example for the signal produced by an easy impact such as by the presence of birds
  • Figure 2d is an example for the signal produced by a sound which was not produced by an event in the monitored zone
  • Figure 3 is a flowchart illustrating an intruder detection method in accordance with an embodiment of the present invention.
  • Figure 4 is a flowchart illustrating the first and the second algorithms of the intruder detection method in accordance with an embodiment of the present invention
  • Figure 5 is an illustration of the density of distribution functions of the transformed signals for four events: a person walking, a vehicle riding, the presence of a bird and external noise;
  • Figure 6 includes illustrations of separate representation of density of distribution functions for four events: a person walking, a vehicle riding, the presence of a bird and external noise;
  • Figure 7 includes illustrations of comparative diagrams of the power spectral density estimation for three events: a person walking, the presence of a bird and external noise;
  • Figure 8 includes illustrations of comparative diagrams of the power spectral density estimation for three events: a person walking, the presence of a bird and external noise;
  • Figure 9 includes illustrations of comparative diagrams of the power spectral density estimation for three events: a person walking, the presence of a bird and external noise;
  • Figure 10 includes illustrations of comparative diagrams of the power spectral density estimation for three frames of event of a vehicle riding
  • Figure 11 is an illustration of a schematic diagram of conventional common view of the components of an embodiment of the present invention.
  • Figure 12 is an illustration of a schematic diagram of conventional view in plane of the components of an embodiment of the present invention.
  • the present invention discloses a system and a method for intrusion detection in a protected zone.
  • the system is comprised of a multiplicity of sensors strategically located in the region of interest (ROI) and a main processing unit which analyzes the input signals of these sensors for the purpose of distinguishing between actual intrusions and harmless events. It is the purpose of the present invention to provide a system and a method which allow the optimization of the scanned parameters. According to embodiments of the present invention the input from the sensors is analyzed using a method which minimizes the time it takes to scan the ROI and maximizes the coverage of the ROI by the sensors. [050] It is to be understood that an embodiment is an example or implementation of the inventions. The various appearances of "one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments.
  • Methods of the present invention may be implemented by performing or completing manually, automatically, or a combination thereof, selected steps or tasks.
  • method refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the art to which the invention belongs.
  • Embodiments of the present invention are comprised of several aspects.
  • the first aspect consists of using signal analysis of the signals received from seismic gauges-sensors which are positioned in the ROI using several mathematical methods.
  • this processing includes analysis of several mathematical dimensions such as the signal dimension and the spectral dimension.
  • the method enables the making of distinctions between signals which are closely related in form.
  • the second aspect of the invention includes processing which is made by arrays- frames allocated by sliding windowing.
  • Each frame comprises a defined quantity of seismograms and every seismogram corresponds to its own geophone.
  • Each seismogram contains a defined quantity of digitalized samples, which is equal to window duration multiplied by digitization frequency. Window duration is minimal, but is no less than the duration of the intervals containing a part of the energy of each analyzed signal which is sufficient for recognition.
  • An additional aspect consists of analyzing the density of distribution of the transformed signals, which enables separating the signal produced by a vehicle from other groups of signals including signals produced by a person walking and by external noises. This enables the exclusion of frames containing vehicle signals, and the reduction of the number of possible events to be analyzed at the following steps.
  • Another aspect of embodiments of the present invention consists of using a correlation function as an additional stage in the recognition procedure.
  • This stage allows distinguishing between different signals which are similar in their form and duration. Distinguishing between these signals is difficult due to the disorder of parameters of real signals.
  • the arguments of this correlation function are inputs signals from two geophones which are in close proximity, and which have received signals with maximal energy. Cross- correlation of these signals, received from such geophones, especially if these geophones are located in environments with rather low wave distribution velocity, enable distinguishing between signals which have similar forms, like the steps of a person walking and the presence of a bird.
  • the proposed system and method for intruder identification allows decreasing the analysis time to approximately one second and decreasing the probability of false alarms even when only two geophones are used.
  • the method is programmed to provide optimal results for typical events which have the greatest probability of occurring, both within the limits of a protected zone and in its nearest vicinity.
  • the method is programmed to identify four types of events: a person walking, the movement of a vehicle, the presence of a bird and external noises.
  • the method also enables identifying other types of events such as the impacts of a hammer or a driii.
  • the proposed system combines a laser light source, optical fibre strands which are pressure sensitive transducers, a photo- optic receiver, a signal processing unit and an external response system operatively connected to produce a relatively simple, trouble free physical security system.
  • the divided laser beam is directed into two optical fibres, built in the ground along the protected pipeline.
  • the radiation received from each of the two photodiode receivers is directed to a differential amplifier.
  • the two fibre waveguides are optically and electrically arranged so that only changes in one fibre strand with respect to the other are detected.
  • the differentia measurement capability results in an extremely high sensitivity concurrent with a high common mode rejection against effects or changes in both fibres.
  • System noise is reduced by the provision of band pass filter that is connected to the output of the differential amplifier. If the differential optical signal exceeds a predetermined threshold, it triggers a response such as setting off the alarm.
  • FIG. 1 is a block diagram illustrating the components of the disclosed system in accordance with an embodiment of the present invention.
  • Geophones sensors 100 are placed within a protected zone according to their sensitivity and in view of the environmental parameters. Cables 110 are connected to each geophone 100 and their other outputs are connected to data collecting device 120. The output of collecting device 120 is connected to a calculating device such as a computer 130, containing the processing program. Alarm system 140 is connected to an output of computer 130.
  • the scheme of the connection of geophone 100 to a device of data collection 120 can be consecutive or parallel, depending on the organization of the interface.
  • each living being or technical mechanical means causes the occurrence of seismic fluctuations extending in the ground and perceived with the geophones 100.
  • the numbers of the needed geophone sensors 100 is defined by the size of a protected zone, their sensitivity and resolution. For example, using standard geophones in an environment of sandy ground, the distance between geophones should not exceed 10-20 meters.
  • Collecting device 120 receives electrical signals forming by geophones sensors 100.
  • Computer 130 performs the transformation of signals into digital form (sampling) with frequency ranging between several hundreds and several thousand Hertz.
  • the digital data stream forming from received signals, inputted into computer 130, consists of separate seismograms each of which corresponds to its own geophone sensor 100.
  • the dataflow is divided by a sliding window into separate arrays (frames) according to the accepted scheme of processing, as well as the duration of an energetically significant part of a signal or ⁇ he frequency characteristic of the intruder and extraneous preventing events.
  • Each frame represents a matrix each line of which, consisting of a sequence of samples, corresponds to one sensor control and represents a seismogram.
  • the quantity of lines is equal to the number of sensors.
  • the quantity of columns (quantity of elements in a seismogram) is equal to the duration of the record of said frame increased by the frequency of digitization.
  • the division into frames is possibly carried out with or without overlapping depending on the sampling requirements. Creating overlaps between consecutive frames ensure that signals are not divided between frames, and enables avoiding erroneous recognition of the truncated parts.
  • the duration of a sliding time window is determined so as to be as small as possible, but sufficient to allow analysis of all considered events. This requirement corresponds to that of the duration of the significant part of energy.
  • the sufficient duration for the recognition of the considered events should not be greater than the frame duration. Accordingly, all seismograms within the limits of said frame have the same duration.
  • the quantity of samples in a seismogram is defined by its duration and frequency of digitization; it usually ranges from 1000 Hz up to 4000 Hz for the ground, and is within a considerably wider range for dense environments, such as concrete.
  • the frame duration is 1 second.
  • the frequency of digitization is 1000 Hz.
  • Examples for signals caused by four types of actions which are essential to the protection of a protected zone are shown in Figures 2a, 2b, 2c and 2d. These signals are shown as the frames consisting of two seismograms after their digitization.
  • the horizontal axes, abscissae represent values of time (in terms of digitization samples), and the vertical axes, ordinatae, the amplitudes of the samples.
  • Examples for signals caused by a person walking are recorded by the sensors as shown in Figure 2a.
  • Examples for signals caused by the presence of large birds are shown in Figure 2b. These examples show that the signals caused by walking and birds are very similar in duration and form, a fact which makes their recognition more difficult.
  • Examples for signals caused by a moving vehicle are shown in Figure 2c.
  • An example for a signal caused by external noise is shown in Figure 2d. These diagrams show the affinity between expected signals.
  • FIG. 3 is a flowchart illustrating the method of signal analysis and the detection of the presence of an intruder in accordance with some embodiments of the present invention.
  • the signals, received by the sensors, are gathered by collecting device 120 (step 210) and transmitted to computer 130 where they are transformed to the digital form. Then they are sampled (step 220) and divided into frames (step 230). These frames are sequentially analyzed.
  • the analysis of the obtained data begins with the reception of the next frame.
  • the norm is calculated (algorithm step 240) for each seismogram of a given frame.
  • the sum of the absolute value of samples of each seismogram of said frame is used to calculate this norm.
  • the other norm which may be calculated is energy (equal the sum of quadrate samples).
  • the disclosed method may use any one of the two.
  • a seismogram is selected (step 250), such as the seismogram with the greatest sum.
  • This seismogram is selected as a sufficiently informative seismogram; it consists of an array of samples.
  • first algorithm (step 270) and the second algorithm (step 290) are activated and their consequent conditions - first condition (step 280) and second condition (step 300) - are checked as described below. Provided that both conditions are found to indicate that an intrusion has occurred, the alarm is activated (step 310).
  • the first algorithm is designed to distinguish between the event of a vehicle moving in the protected zone and all other events; the second algorithm is designed to distinguish between the remaining events and the event of a person walking.
  • FIG. 4 is a detailed block diagram illustrating the first and the second algorithm in accordance with the present invention.
  • the first algorithm 270 begins with calculating the absolute values (step 272) of the sequences of filtered samples, and defining the maximal value of sequence elements (step 273). For improving the division of various events the distribution function of the elements of the sequence are defined (step 274).
  • the first algorithm performs processing in the signal dimension and carries out the analysis envelope of the sequence using features of signals envelope caused by vehicle movement.
  • the analysis of these envelopes is carried out according to the construction of density of the transformed samples distribution (step 275).
  • ns(k) values are equal to the number of the transformed samples values which belong to the k-th interval of values: from g (k+l)-mg to g (k)-mg, where g(k+l) ⁇ g(k) and g(kmax) ⁇ l.
  • This distribution function is constructed for the transformed sequence of samples and allows the estimation of the form of the sequence envelope in an indirect way.
  • the envelopes corresponding to events of a person walking and the presence of a bird have the peak form of the limited duration ( ⁇ 0.15-0.2 sec).
  • the signal created by the movement of a vehicle has a smooth envelope with limited range of values.
  • the distribution function for similar events is, therefore, a flattened curve.
  • the transformations of initial signals enable obtaining the substantially significant differences of said distribution functions for these two groups of events.
  • ns(l) ⁇ tk(l) or ns(2) >tk(2) where tk(l) and tk(2) are predetermined parameters of the first and second intervals accordingly.
  • the first condition is ns(l) ⁇ tk(l).
  • the satisfaction of the first condition defines the event as the movement of a vehicle. In this case the following steps are carried out: identifying intruder absence, ending given frame check, accepting next frame and repeating this procedure according to the preceding. Provided that the first condition is not satisfied then event of a moving vehicle is excluded from the group of possible events. The subsequent analysis defines a person-intruder among the remaining three events using the second algorithm 290.
  • the second algorithm 290 affords performance of an estimation of the cross-spectral density of the sequences of the filtered samples of two sufficient informative seismograms of a given frame.
  • the second sufficient informative seismogram outputs, for example, the seismogram which has the second largest sum of absolute values of initial samples following the first.
  • this estimation is afforded by preliminary calculation of a cross-correlation function (step 292) of two sequences of the filtered samples.
  • the cross- correlation function allows allocating the common features of signals which are captured by two sensors extended in the environment in different directions.
  • a spectral transformation of the cross-correlation function enables comparing the results for different events.
  • PSD power spectral density
  • FIGs 7, 8, 9 and 10 illustrate comparative diagrams of the power spectral density estimation for different events.
  • the values of PSD estimation are given in relative units and are plotted as ordinates - amplitude.
  • the frequency parameter "f" is plotted on the horizontal axis.
  • MaxPSD(j) is the maximal value of PSD on the j-th interval
  • a(j) is the predetermined weight factors on j-th interval
  • j 1,3,4,5...jmax. Q ⁇ 2).
  • step 294 The necessity of these weight factors (step 294) is dictated by the complicated and unsteady forms of real signals. Then the analysis of said distribution function is carried out and the second condition is checked (step 295).
  • the given frame corresponds to either the event of external noise or to the presence of a bird, and this frame does not carry information about intrusion. Since no intrusion was detected the method ends the analysis of the given frame, retrieves the next frame and starts the analysis procedure from the beginning. Provided that intrusion was detected, the method activates the alarm (step 310), and the method ends the analysis of the given frame, retrieves the next frame and starts the analysis procedure from the beginning.
  • the PSD calculations make use of a window size of 256 samples and the sampling frequency of 1000 Hz.
  • Figure 11 is a schematic diagram of conventional common view of the components of an embodiment of the present invention
  • Figure 12 is an illustration of a schematic diagram of conventional view in plane of the components of an embodiment of the present invention. Illustrated is a fibre optic security system for detecting unauthorized activity in the vicinity of pipelines.
  • the pipelines optionally include oil, gas or water pipelines.
  • the system consists of transmitter subsystem 6, pairs of fibre optic waveguides l ⁇ and 7 2 receiver 8 and alarm device 9.
  • Transmitter subsystem 6 consists of laser source 10 and beam divider 11 operatively connected to fibre optic strands forming two waveguides 1 ⁇ and 1%.
  • Receiver 8 consists of photodiodes 12 and 13, preamplifiers 14 and 15, differential amplifier 16, band pass filter 17, threshold detector 18 and output signal timer 19 which are operatively connected.
  • Fibre optic waveguides I x and I 2 may be, for instance, low-loss silicone polymer clad glass core fibre; however, any other type of fibre is also within the scope of the present invention. Fibres 7i and 7 2 are installed underground.
  • Photodiodes 12 and 13 may be any type of PIN diodes, such as Honeywell fibre optic detectors. Photodiodes 12 and 13 operate in the photovoltaic mode and are connected to the input lads of two operational amplifiers preamplifiers 14 and 15. Amplifiers 14 and 15 are contained in a simple package to minimize temperature drift. Amplifiers 14 and 15 are identical with regard to the arrangement and value of the components.
  • Preamplifiers 14 and 15 are connected to a differential amplifier 16.
  • the purpose of this amplifier 16 is to amplify any voltage difference between the output from preamplifiers 14 and 15.
  • the output of differential amplifier 16 is connected to bandpass filter 17. Any extraneous noise introduced by the photodiodes 12, 13 preamplifier 14, 15 and differential amplifier 16 is eliminated.
  • the output from bandpass filter 17 is connected to threshold detector 18. If the input exceeds a predetermined level (for example 10V), a signal appears at the output of the threshold detector 18. Either a positive or negative signal exceeding the 50 milli-volt level will cause a 10V signal output.
  • a predetermined level for example 10V
  • the output of threshold detector 18 is connected to output signal timer 19.
  • Output signal timer 19 provides an output of fixed duration every time the threshold detector 18 generates an output signal. The duration of the output signal of timer 19 is determined by predefined parameters.
  • the laser beams in waveguides 7i and 7 2 are identical and no difference is detected by differential amplifier 16. In such Cases the output of differential amplifier 16 is zero and the subsequent circuits 17, 18, 19 and 9 are inoperative. Whenever a small pressure is exerted anywhere along the length of either fibre 7i or 7 2 an optical loss occurs at that point and less light is received at photodiodes 12 or 13. Such pressure may result from an intruder stepping on optical fibre 7i or 7 2 buried in the ground near the pipeline.
  • the radiation received at detectors 12 and 13 is no longer equal as a result of an optical loss occurring in one of the fibres 7i or 1 % .
  • This signal difference is amplified by the differential amplifier 16. After passing through the band filter 17 the differential voltage is incident on a threshold detector 18. If the signal exceeds a preset threshold, threshold device 18 issues a large voltage signal which triggers timer circuit 19. Timer circuit 19 activates alarm device 9 for a preset amount of time.
  • FIG. 1 It is to be understood that some embodiments of the invention may be implemented, for example, using a machine-readable medium or article which may store an instruction or a set of instructions that, if executed by a machine, cause the machine to perform a method or operations or both in accordance with embodiments of the invention.
  • a machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware or software or both.
  • the machine-readable medium or article may includes but is not limited to any suitable type of memory unit, memory device, memory article, memory medium, storage article, storage device, storage medium or storage unit such as, for example, memory, removable or non-removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, optical disk, hard disk, floppy disk, Compact Disk Recordable (CD- R), Compact Disk Read Only Memory (CD-ROM), Compact Disk Rewriteable (CD-RW), magnetic media, various types of Digital Versatile Disks (DVDs), a tape, a cassette, or the like.
  • memory removable or non-removable media
  • erasable or non-erasable media writeable or re-writeable media
  • digital or analog media optical disk, hard disk, floppy disk, Compact Disk Recordable (CD- R), Compact Disk Read Only Memory (CD-ROM), Compact Disk Rewriteable (CD-RW), magnetic media, various types of Digital Versatile Disk
  • the instructions may include any suitable type of code, for example, an executable code, a compiled code, a dynamic code, a static code, interpreted code, a source code or the like, and may be implemented using any suitable high-level, low-level, object-oriented, visual, compiled or interpreted programming language.
  • a compiled or interpreted programming language may be, for example, C, C++, Java, Pascal, MATLAB, BASIC, Cobol, Fortran, assembly language, machine code and the like.

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  • Electromagnetism (AREA)
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  • Burglar Alarm Systems (AREA)

Abstract

La présente invention concerne un système et un procédé permettant de détecter une intrusion dans une zone protégée. Le système selon l'invention est constitué d'une pluralité de capteurs placés de manière stratégique dans la zone d'intérêt, et d'une unité de traitement principale qui analyse les signaux d'entrée desdits capteurs afin de distinguer une véritable intrusion d'un événement anodin. Le but de l'invention est d'obtenir un système et un procédé qui permettent d'optimiser les paramètres balayés. Des modes de réalisation de la présente invention consistent à analyser l'entrée issue des capteurs à l'aide d'un procédé qui réduit au minimum le temps nécessaire au balayage de la zone d'intérêt et augmente au maximum la couverture de la zone d'intérêt par les capteurs.
PCT/IL2007/001202 2006-09-28 2007-10-07 Système et procédé permettant de détecter et de classifier des dommages dans un pipeline WO2008038289A2 (fr)

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US84764606P 2006-09-28 2006-09-28
US60/847,646 2006-09-28

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WO2008038289A3 WO2008038289A3 (fr) 2009-04-23

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WO2010125374A1 (fr) * 2009-04-27 2010-11-04 Becatech Limited Appareil et procédé de protection de structures sécurisées
CN112363400A (zh) * 2020-11-28 2021-02-12 长春工程学院 基于光纤传感器信号和异常编码的电缆隧道入侵监测方法

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US6529130B2 (en) * 2001-02-16 2003-03-04 General Phosphorix Llc System for detecting intruders

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US4857912A (en) * 1988-07-27 1989-08-15 The United States Of America As Represented By The Secretary Of The Navy Intelligent security assessment system
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US6529130B2 (en) * 2001-02-16 2003-03-04 General Phosphorix Llc System for detecting intruders

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010125374A1 (fr) * 2009-04-27 2010-11-04 Becatech Limited Appareil et procédé de protection de structures sécurisées
CN112363400A (zh) * 2020-11-28 2021-02-12 长春工程学院 基于光纤传感器信号和异常编码的电缆隧道入侵监测方法
CN112363400B (zh) * 2020-11-28 2022-06-24 长春工程学院 基于光纤传感器信号和异常编码的电缆隧道入侵监测方法

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