METHOD FOR DETECTING MOVING ELECTROCONDUCTIVE OBJECTS

Abstract

 The application describes a method for the detection of electrically conductive moving elements, which comprises the arrangement of measuring devices (3) located in a monitored space along a protected boundary or perimeter at equal or different distances from each other and connected to each other by a connecting cable (1), the measuring devices having the form of converters converting a magnetic field into an electric voltage, and emitters (4) connected to each other by another connecting cable (2) and having the form of converters converting electric voltage into a magnetic field, wherein changes of the parameters of the resulting field created by the emitters are detected by the measuring devices (3), and information on the detection of an electrically conductive object or a group of electrically conductive objects is worked out for given combinations of measured parameters. To enhance the reliability of the detection of one or several electrically conductive moving objects and to increase the accuracy of the localisation of the place or places where the protected boundary (perimeter) is crossed by the one or several electrically conductive objects, according to the invention the measuring devices (3) are equipped with apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields, "measuring device/emitter pairs" are formed from neighbouring and adjacent measuring devices (3) and emitters (4), the "measuring device/emitter" pairs also identify information on the detection of an electrically conductive object worked out by each "measuring device/emitter" pair, said information is transmitted to the central information analysis and processing apparatus (14), which generates a warning of the detection of an electrically conductive object or a group of electrically conductive objects, indicating the place of the detection of the object or the places of the detection of the objects.

Description

[0001] The invention relates to the field of security and provides for the detection of electrically conductive objects moving along an arbitrary route. The invention particularly relates to a method for the detection of electrically conductive moving elements, which comprises the arrangement of measuring devices located in a monitored space along a protected boundary or perimeter at equal or different distances from each other and connected to each other by a connecting cable, the measuring devices having the form of converters converting a magnetic field into an electric voltage, and emitters connected to each other by another connecting cable and having the form of converters converting electric voltage into a magnetic field, wherein changes of the parameters of the resulting field created by the emitters (which is the sum of the primary field and the secondary fields) are detected by the measuring devices, and information on the detection of an electrically conductive object or a group of electrically conductive objects is worked out for given combinations of measured parameters.

[0002] The invention can be used to detect an intruder or a number of intruders (a person, a group of persons, other biological objects) which penetrate(s) some monitored space, for example a country border, a protected boundary or protected perimeter of a potentially dangerous facility or any other protected facility (for instance a nuclear power station, a facility for the production of chemicals or military goods, an arsenal for nuclear or conventional weapons, a storage for community funds, an object of socio-cultural importance or of importance for the national economy, private property etc.). It is irrelevant in which way the detected object penetrates or tries to penetrate the monitored space: standing up, bent, creeping through thick grass, between shrubbery and trees, under water or under snow, in constructions, on transport vehicles or carts, on horseback or on another animal. The invention is useful for the detection of a wide range of electrically conductive moving objects (metal and others) and for utilisation in their safety systems, for example to warn of and prevent collisions of transport vehicles.

[0003] At the present time, several methods for the detection of moving objects are known, which can be divided into the following groups, based on the particular properties of the detected object, its elements and/or items thereon:

1. The group comprising methods for the detection of moving objects having magnetic properties. The limitations of the application of the methods of this group are caused by the necessity to observe a number of conditions. Thus, for instance, the method implemented in the apparatus described in SU 492413 allows the detection of an object if the trajectory of its movement is known and if permanent magnets are fixed on the detected object. The method implemented in the apparatus described in RU 2106692 C1 allows the detection of an object (an intruder) if it carries magnetic items and causes a vibration of the ground.

2. The group comprising methods for the detection of moving objects having ferromagnetic properties, high electric conductivity, the ability to interact with the magnetic field of the earth and/or creating their own electromagnetic field by their movement. The listed properties of such objects also determine the range of practical applications of these methods. Moreover the application of methods of this group requires the fulfilment of a number of other (additional) conditions. Thus, for instance, the method described in SU 591905 can be utilized for the detection of transport vehicles which must necessarily enter a monitored area and cross its border(s) by a previously known route. Another method for the detection of moving objects is described in SU 1490681 A1. However, in this case the transport vehicles must necessarily follow a previously known route via an iron detector. The method described by RU 204003 C1 can be utilized for the detection of objects such as bathyscaphes, deep water appliances and other such objects which create their own electromagnetic field by their movement. The method implemented in the apparatus described in RU 2174244 C1 is intended for the detection and tracking of a large metal-containing object from an underwater search facility.

3. The group comprising methods for the detection of moving objects having poor electric conductivity, for instance biological objects. The electric conductivity of objects detected by the methods of this group is many times smaller than the electric conductivity of objects detected by the methods belonging to the other groups. Thus, for instance, the electric conductivity of the human body is several million times smaller than the electric conductivity of aluminium.

[0004] The purpose of the method according to the invention lies in the detection of any electrically conductive objects moving through a monitored space along an arbitrary route, including objects having poor electric conductivity and moving along an arbitrary route.

[0005] Single effects of the method according to the invention are comprised in the method for detecting the location of moving metal objects described in SU 1246905 A3, namely: With the aid of a current-carrying loop (which can also be a magnetic dipole), eddy currents are caused in the object, their level is assessed, and on this basis the location of the object is determined. However, an increase of the accuracy of the localisation of the object by this method is achieved by measuring the inductivity, which, because of the difficulties with the technical implementation and the necessity of the object to be in the area of the induction loop at the instance of its detection, practically excludes the possibility of the detection of objects with poor electric conductivity. This is the very reason why this known method is utilized only for the detection of the location of automobiles and other objects having high electric conductivity.

[0006] The most pertinent one of the known methods with respect to the method according to the invention is the method implemented in the apparatus which is schematically shown in Fig. 1 and which is described in RU 2071121 C1. In this known method the detection of an intruder crossing a protected boundary is rendered possible by application of a number of emitters 4 in the form of converters converting electric voltage into a magnetic field, which are connected by a connecting cable 2, and a number of receivers 3 in the form of converters converting a magnetic field into electric voltage, which are connected by a connecting cable 1, the emitters 4 and the receivers 3 being connected in series one after the other. A generator 5, a reference voltage generator 12, a phase switcher 11, an amplifier 6, a synchronous detector 7, a band filter 8, a threshold block 9 and an alarm signal generator 10 of said apparatus emit (or do not emit) an alarm signal, based on the input signal from the receivers 3 processed by them, which alarm signal shows the detection (or the absence of such detection) of an "intruder". The usage of the magnetic field emitters 4 (which are essentially magnetic dipoles) in this method causes, when it is implemented, a rated passage of the detected object along directions lying in planes (or in planes near these) which run through vectors of the magnetic momentums of the emitters 4 and their verticals, and in planes (or in planes near these) running through vectors of the magnetic momentums of the receivers 3 and their verticals. The reason for this is that the signals generated by the object detected along said directions are far weaker than the signals generated by the same object along other directions. Enhancing them to a level required for the detection of the object without making the apparatus implementing the method more prone to interferences is, in practice, hard to achieve. Besides, the known method makes the apparatus more prone to interferences and lessens the reliability of the detection of an object crossing the protected boundary (perimeter) in other directions. The reason for the latter is that the input signal to be processed is the sum of signals from all even or all uneven receivers rather than a signal from the receiver which, together with the emitter adjacent to it, localises the place (the section) where the object crosses the protected boundary (perimeter). This also means that when electrically conductive moving objects are detected, this method cannot distinguish the number of sections where the crossing of the protected boundary (perimeter) took place - whether it was in one or several sections, and in which particular section. In the implementation of this method the level of the useful signal depends on the distance between the emitter 4 and the receiver 3. In practice, it is generally not possible to keep up the rated distance between the emitters 4 and the receivers 3. Deviances from rated distances are caused by natural or artificial obstacles (trees, boulders, engineers' communication lines etc.), which in its turn makes it harder to install the apparatuses which implement the method when installed at the facility. The detection zone will turn out to be uneven. In some sections strong enhancement will be necessary, which makes the entire system more prone to interferences. Moreover this method excludes the possibility of changing the construction of the emitters 4 and receivers 3 by means of the apparatus. The levels of the primary magnetic fields of the emitters 4 and the sensitivity of the receivers 3 can be set only when the apparatus is manufactured under factory conditions or during its installation on the facility and cannot be changed during usage without carrying out the assembly and installation all over again.

[0007] On the basis of the above, the object of the invention was to establish a method for the detection of one or several electrically conductive moving objects with greater reliability and a more accurate localisation of the place or places where the protected boundary (perimeter) is crossed by one or several electrically conductive objects.

[0008] With regard to the method, the features of which are mentioned at the beginning of the description, the object of the invention is achieved due to the fact that the measuring devices are equipped with apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields, "measuring device/emitter pairs" are formed from neighbouring and adjacent measuring devices and emitters, the "measuring device/emitter" pairs also identify information on the detection of an electrically conductive object established by each "measuring device/emitter" pair, said information is transmitted to the central information analysis and processing apparatus, which generates a warning of the detection of an electrically conductive object or a group of electrically conductive objects, indicating the place of the detection of the object or the places of the detection of the objects.

[0009] The arrangement of the apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields immediately in the measuring devices and the paired identification of the measuring devices and emitters allows to achieve the following advantages:

• the detection zone is formed more evenly due to the elimination of dependency of the useful signal on the phase connections;
• there is the possibility of obtaining a narrow transmission frequency band of the working circuit determined only by tactical requirements, which in its turn significantly enhances the stability of the system against the influence of outer electromagnetic interferences;
• the dependency of the useful signal on the ambient conditions and the instability of the emitters, in particular due to instability of the enhancement coefficients of the high frequency enhancers, is significantly reduced (because there is the possibility to compute the relative amount of increase of the signal).

[0010] According to one of the preferred embodiments of the method according to the invention, the measuring devices and emitters are arranged in pairs. The advantage of this embodiment is that zones of decreased sensitivity are eliminated (by the special arrangement of "measuring device/emitter" pairs, each measuring device and each emitter (except the outermost ones) are situated between a measuring device and an emitter of one pair).

[0011] Preferably microcontrollers are used as apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields.

[0012] Preferably a processor is used as the central information analysis and processing apparatus.

[0013] The advantage of the usage of microcontrollers and a processor is determined by the possibility to carry out difficult algorithms when processing the obtained information, by the stability of the technical characteristics of the system and its competitive economic indicators.

[0014] According to another preferred embodiment of the method according to the invention, antennas with a radiation resistance not exceeding 300 ohm are used in the measuring devices and emitters, which antennas allow to achieve an even sensitivity of the "measuring device/emitter" pairs along the protected boundary (perimeter).

[0015] According to the following preferred embodiment of the method according to the invention, the values of the high frequency working voltages are chosen to be higher than 1 MHz, which allows the detection of biological objects and other objects having poor electric conductivity.

[0016] At a response of the system, the central information analysis and processing apparatus automatically switches on or allows a switch-on of the technical means for maintaining security, if required, and issues information to the personnel or the crew so that they can decide for themselves.

[0017] Information from peripheral apparatuses and from the central information analysis and processing apparatus can be transmitted either by connecting cables (electrical or optical) or by a radio channel.

[0018] Below, the invention will be described in more detail based on the example - which does not limit the scope of the invention - of one of its possible embodiments, with reference to the drawings accompanying this Description, in which:

Fig. 1

is a schematic view of the known apparatus implementing the known method for the detection of electrically conductive moving objects,

Fig. 2

is a schematic view of the apparatus implementing the method for the detection of electrically conductive moving objects according to the invention, and

Fig. 3

is a schematic view illustrating the paired arrangement of the emitters and measuring devices.

[0019] The apparatus shown in Fig. 2 is one of the preferred apparatuses implementing the method according to the invention and allowing an increase of the reliability of the detection and the accuracy of the localisation of the place or places where the electrically conductive object(s), in particular biological object(s), cross(es) the protected boundary (perimeter). To this end, measuring devices 3 of a magnetic and an electric field are placed in the monitored space (along the protected boundary) at equal or unequal distances to one another, while next to them and/or between them emitters 4 with a quasi-stationary electromagnetic field are arranged in a regular or irregular manner. A processing block 14, i.e. the central information analysis and processing apparatus, is placed e.g. in a section cabinet or at the place to be protected. The processing block 14 and the peripheral apparatuses, i.e. the measuring devices 3 and emitters 4 are connected to one another by cables 1 and 2 respectively. The processing block 14 consists of a unit for conditioning the voltage of the power supply, generators for high frequency sinusoidal signals, a frequency changer, capacity boosters, an intermediate frequency generator, filters and buffers, an exchanger, a processor, an apparatus for coordination with the connecting line, an apparatus for protection against polarity reversals and an apparatus for protection against static electricity and lightning discharges. The emitters 4 comprise a capacity booster for high frequency signals charged on the emitter antenna having a low radiation resistance not exceeding 300 ohm. The measuring devices 3 comprise the same low-ohm antenna as the emitters, a synchronous high frequency detector, a filter, a video signal detector and a periphery microcontroller which has the function of an apparatus for primary analysis and processing of the parameters of the operational readiness of the measuring devices and the emitters and changes in the parameters of the magnetic and electric fields.

[0020] The apparatus shown in Fig. 2 works as follows. When the power supply apparatus is supplied with high frequency voltage from the generator arranged in processing block 14, said voltage is supplied via the connecting cable 2 to the input of one of the emitters 4, while the reference voltage from the other generator, which is also arranged in processing block 14, is supplied to the input of the corresponding measuring device 3. The capacity of the voltage reaching the input of the emitter 4 is increased and is further transmitted to its antenna. In the surrounding space a quasi-stationary electromagnetic field is created. A voltage occurs at the antenna of the measuring device 3, determined by the component composition of the field influencing the measuring device, which is detected by the synchronous detector. After corresponding filtering, the voltage is supplied via an analogue-to-digital converter to the input of the microcontroller, which is part of the measuring device 3 and which identifies this voltage as a direct signal, i.e. as the level of voltage on a section of the working "measuring device/emitter" pair in the absence of an object to be detected. The microcontroller of the measuring device 3 also analyses the amount of effective voltages, compares them with given ones, works out the information on the operational readiness of the measuring device 3 and the emitter 4 and, in the event that they do not match, issues information thereon to the processor. Moreover the microcontroller of the measuring device 3 carries out the processing of the detected signal so as to form a working frequency band of the required width, compares the effective voltage with an activation threshold, adjusts the activation threshold, carries out a selection of signals according to individual parameters, in particular according to the rate of change of the leading and trailing edges of the voltage, and effects an exchange of information with the processor with the aid of the periphery apparatuses. When an intruder appears in the section of the "measuring device/emitter" pair, the component composition of the electromagnetic field changes in the place where the measuring device 3 is arranged, which causes a corresponding change of the voltage at the input of its microcontroller. Based on the results of the analysis, the microcontroller of the changing voltage works out the information on the detection of an intruder (of an electrically conductive object). The obtained information together with the identifier of the exact measuring device 3 is passed to the processor of the processing block 14 via a connecting interface. The central information analysis and processing apparatus, i.e. processing block 14, issues a warning about the detection of an electrically conductive object or a group of electrically conductive objects, indicating the place of the detection, automatically switches on the technical means for maintaining security or enables their switch-on, and issues information to the monitoring personnel or the crew of the transport vehicle so that they can make their own decision. Further, the processor of processing block 14 switches off the working "measuring device/emitter" pair and switches on a new "measuring device/emitter" pair, continuously repeating this process for all "measuring device/emitter" pairs.

[0021] The apparatus shown in Fig. 2 may also consist of only one "measuring device/emitter" pair, and the use of this configuration is recommended for instance in the monitoring of entrances, passages for pedestrians and vehicles, mountain ways and paths, in collision warning systems and systems for the prevention of vehicle collisions.

[0022] Fig. 3 shows a version with a paired arrangement of the measuring devices 3 connected to one another by a connecting cable 1 and the emitters 4 connected to one another by a connecting cable 2. In this version, along the protected boundary (perimeter) an emitter 4 is arranged, then another emitter 4, then a measuring device 3, then another measuring device 3, then an emitter 4, then an emitter 4, then a measuring device 3, then a measuring device 3 and so on. An equivalent arrangement from the point of view of detecting an object is the arrangement according to the following plan: A measuring device 3, then a measuring device 3, then an emitter 4, then another emitter 4, then a measuring device 3, then a measuring device 3, then an emitter 4, then another emitter 4 and so on.

[0023] The apparatus shown in Fig. 3 works in analogy to the apparatus schematically shown in Fig. 2. The distance between the emitters 4 and the measuring devices 3 are chosen so that a useful signal can be generated, which is sufficient to detect one or several electrically conductive moving objects and prevent an influence of the measuring devices 3 on each other (the increase or decrease of the emitted signal must not exceed 30 %).

Claims

1. Method for the detection of electrically conductive moving objects, which comprises the arrangement of measuring devices located in a monitored space along a protected boundary or perimeter at equal or different distances from each other and connected to each other by a connecting cable, the measuring devices having the form of converters converting a magnetic field into an electric voltage, and emitters connected to each other by another connecting cable and having the form of converters converting electric voltage into a magnetic field, wherein changes of the parameters of the resulting field created by the emitters are detected by the measuring devices, and information on the detection of an electrically conductive object or a group of electrically conductive objects is worked out for given combinations of measured parameters, characterised in that the measuring devices are equipped with apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields, "measuring device/emitter pairs" are formed from neighbouring and adjacent measuring devices and emitters, the "measuring device/emitter" pairs also identify information on the detection of an electrically conductive object worked out by each "measuring device/emitter" pair, said information is transmitted to the central information analysis and processing apparatus, which generates a warning of the detection of an electrically conductive object or a group of electrically conductive objects, indicating the place of the detection of the object or the places of the detection of the objects.

2. Method according to claim 1, characterised in that the measuring devices are arranged along the protected boundary or perimeter in pairs and the emitters are arranged along the protected boundary or perimeter in pairs.

3. Method according to claim 1, characterised in that microcontrollers are used as apparatuses for primary analysis and processing of the measured changes in the parameters of the magnetic and electric fields.

4. Method according to claim 1, characterised in that a processor is used as the central information analysis and processing apparatus.

5. Method according to claim 1, characterised in that antennas with a radiation resistance not exceeding 300 ohm are applied in the measuring devices and emitters.

6. Method according to claim 1, characterised in that the frequency of the high frequency working voltages is selected to exceed 1 MHz.

7. Method according to claim 1, characterised in that the central information analysis and processing apparatus automatically switches on or enables the switch-on of the technical means of maintaining security, if required, and issues information to the personnel or the crew so that they can make their own decision.

Drawing