WO2012049675A2 - Intrusion detection system - Google Patents
Intrusion detection system Download PDFInfo
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- WO2012049675A2 WO2012049675A2 PCT/IL2011/000789 IL2011000789W WO2012049675A2 WO 2012049675 A2 WO2012049675 A2 WO 2012049675A2 IL 2011000789 W IL2011000789 W IL 2011000789W WO 2012049675 A2 WO2012049675 A2 WO 2012049675A2
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- magnetic field
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- 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
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- 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
- G08B29/20—Calibration, including self-calibrating arrangements
- G08B29/24—Self-calibration, e.g. compensating for environmental drift or ageing of components
Definitions
- the present invention relates to the field of intrusion detection systems. More particularly, the invention relates to an intrusion detection system which comprises a plurality of magnetic sensing units, wherein each magnetic sensing unit comprises a magnetic sensor, and an accelerometer.
- Intrusion detection systems are well known and widely used for securing areas or specific sites. The larger the secured area is, the higher the complexity and cost of the system.
- Various intrusion detection systems are known, which are generally classified by their types of sensors, or by their technical structure.
- Intrusion detection systems of the prior art apply optical sensors (such as visual, IR or laser sensors), acoustic sensors, magnetic sensors, radar systems, cameras, and more.
- the magnetic sensor which detects a variation in the magnetic field in the proximity of the sensor, and this variation is used for determining whether an intrusion has occurred or not.
- the magnetic sensor of the passive type (the type to which the present invention relates) can particularly sense articles in the proximity of the sensor that are made of ferromagnetic materials, or more specifically, the magnetic sensor can sense a change in the magnetic field due to a change in the location and orientation of such articles.
- magnetic sensors are relatively cheap and reliable; (b) magnetic sensors can be used above or below the ground or underwater, or they can be installed and sense even from within concrete walls; (c) the magnetic sensors of the passive type do not radiate energy (and therefore it is hard to detect them); and (d) they have relatively small mass and volume.
- a plurality of magnetic sensors is used in intrusion detection systems, spaced apart from one another, for example at a distance of 5m- 10m from one another.
- a number of magnetic sensors are arranged along a connecting cable in a "chain-like" structure (i.e., one after the other, sometimes with other supporting units in between) and they generally each communicates with its neighboring sensors by means of said cable, or wirelessly. They may also communicate with a control center directly or via a relay unit.
- intrusion detection systems in which variation measurements as obtained from a plurality (two or more) of magnetic sensors enable accurate determination regarding the exact location and direction of the intrusion with respect to each of the involved sensors. Such determination is generally based on the use of a detection algorithm that solves the "physical problem" of determining the location of the intruding object (hereinafter also referred to as "target") and its magnetic moment.
- the detection algorithm may use numerical tools.
- determination of the exact location and direction of the intrusion based on indications from plurality of sensors highly depends on the orientation of each sensor with respect to the others in its proximity, or with respect to a predefined coordinates system. Therefore, such direction-location determination requires a very accurate leveling and calibration of the orientation of each of the sensors with respect to said predefined coordinates system at the time of installation, and it also strictly requires continuously maintaining all of the sensors at the calibrated orientation after the time of installation.
- the network of sensors is installed underground.
- the procedure of installing the network underground involves digging a trench, leveling the trench, putting the sensors and wiring within the trench, aligning each of the sensors with respect to a predefined coordinates system, fixing each of the sensors in its aligned position, and finally covering the trench.
- Said procedure of installation is very cumbersome and time consuming, and moreover, there is no easy way of knowing whether the adjustment of each specific sensor has changed after the time of the network installation.
- the invention relates to a two-mode intrusion detection system which comprises: (A) a plurality of magnetic sensing units, connected in chainlike manner and spaced apart from one another, each sensing unit comprises: (a) a magnetic sensor s for sensing a 3-D magnetic field vector of the Earth; (b) an accelerometer for sensing a 3-D acceleration vector evolving from the acceleration g of the Earth; and (c) first communication means for conveying said sensed 3-D magnetic field vector and said sensed 3-D acceleration vector to a proximate processing unit;
- each processing unit comprises (a) second communication means for communicating with one or more of said magnetic sensing units; and (b) a processor for: (B.l.) during a calibration mode, receiving from each sensing unit respectively said magnetic field vector of the Earth as measured by its respective magnetic field sensor s, and said acceleration vector as measured by said accelerometer a, and determining, based on said magnetic field vector and said acceleration vector the respective orientation of each magnetic unit with respect to a predefined coordinates system; and (B.2.) during an intrusion detection mode receiving periodically from two or more sensing units magnetic field measurements as measured respectively by corresponding magnetic field sensors s, and based on said two or more magnetic field measurements, and the known orientations of the respective magnetic units, as determined by said calibration mode, determining whether an intrusion has occurred and the location of said intrusion.
- each processing unit also comprises a sensing unit.
- a plurality of magnetic units and one processing unit form a cluster, and wherein the sensing units and processing unit of a cluster are connected by means of a multi-wired cable.
- plurality of clusters that are connected in a chain-like manner and having two segment coordinators at their ends define a segment.
- each sensing unit transfers one or more of its magnetic field measurement and its acceleration measurement to the proximate processing unit in a chain like manner via one or more of magnetic sensing units.
- each processing unit determines an intrusion based on magnetic field measurements of two or more proximate sensing units.
- each processing unit further comprises a third communication unit for communicating reports to one or more of segment coordinators, and wherein each segment coordinator performs high-level analysis and control based on said processing units reports.
- each processing unit determines the orientation of each magnetic sensing unit by an orientation algorithm, which is operative during said calibration mode.
- each processing unit determines whether an intrusion has occurred and the location of said intrusion by a detection algorithm, which is operative during said intrusion detection mode.
- said first communication means of the sensing unit comprises a left communication element and a right communication element, for communicating with two neighboring units respectively.
- a report from each magnetic sensing unit to a processing unit is made periodically.
- a report from each magnetic sensing unit to a processing unit during an intrusion detection mode is performed upon exceeding of a threshold.
- Fig. 1 shows in block diagram form a general structure of an intrusion detection system, according to an embodiment of the present invention
- Fig. 2 shows a detection cluster as used by the intrusion detection system of the present invention
- Fig. 3a shows in block diagram form the structure of a detection unit according to an embodiment of the present invention
- Fig. 3b shows in block diagram form the structure of a processing unit according to an embodiment of the present invention
- Fig. 4 schematically illustrates the basic structure of a magnetic sensing unit in terms of the magnetic sensor and the acceleration sensor
- Fig. 5 schematically shows two sensors si and S2 that are used for locating a ferromagnetic dipole m.
- Fig. 1 shows in block diagram form a general structure of an intrusion detection system 1, according to an embodiment of the present invention.
- a secured area 2 is surrounded by a network of magnetic sensing units 10.
- the network is divided into plurality of detection segments 3, each segment comprising a plurality of detection clusters 4, wherein each detection segment 3 is connected to a segment coordinator SC.
- Each detection cluster 4 comprises one processing unit PU and several magnetic sensing units 10.
- Each processing unit PU in turn comprises a sensing unit 10, and a processor.
- Each segment coordinator SC comprises a controller C, power supply P, and gateway g.
- each sensing unit 10 comprises a 3-axes magnetic sensor s for sensing a variation in the magnetic field in proximity of the sensor, and a 3-axes accelerometer a. Continuously, or upon sensing a magnetic field variation by sensor s, sensing unit 10 conveys sensing information to a neighboring device, which may be either another sensing unit 10 or a processing unit PU. More specifically, the sensing information is conveyed from each sensing unit to the closest processing unit through a "chain" of one or more sensing units 10. The communication between the units of the network (the sensing units, the processing units, and the SCs) is performed through connecting cable 12.
- a relatively wide bandwidth communication takes place between the sensing units 10 and the PUs, as this communication involves transfer of raw sensing data (magnetic sensing information and/or acceleration information), while the communication between the PUs and the SCs is of lower bandwidth, as this is a higher level processed information. More specifically, during a normal mode of operation of the system each sensing unit conveys in digital form to its neighboring unit (either a sensing unit or a PU) the 3-axes sensed magnetic field, which is essentially the raw magnetic field data as sensed by a sensor s within the respective sensing unit.
- each sensing unit conveys in digital form to its neighboring unit (either a sensing unit or a PU) the 3-axes sensed magnetic field as sensed by sensor s and the 3- axes measurement of the acceleration vector g of the Earth as sensed by accelerometer a.
- a detection algorithm within each PU evaluates the accumulated data, whenever received from the one or more of the sensing units of cluster 4, and determines whether a suspected intrusion has occurred, and the location and direction of the suspected intrusion.
- a detection (low-level) algorithm of the PU can determine whether a crossing of the system has occurred, its location (i.e., the two sensors between which the crossing has occurred), and the direction of the crossing, (into or out of the secured area).
- a suspected crossing is determined by a PU, it communicates this event to the proximate segment coordinator SC, or more specifically, to controller C within the respective SC.
- the SC further evaluates the data using its own high-level algorithm. More specifically, the SC receives messages from plurality of PUs and it performs evaluation in a more global manner.
- the controller C may conclude that this is a false alarm, which has been occurred due to, for example, lightning.
- the algorithm of the SC also preferably manages the system, and it may send managing messages to the various PUs, for example, it may initiate a calibration mode of all the sensing units 10, it may question the processing units about the respective cluster statuses, it may manage situation of faulty units, it may assign an address ID for specific units etc.
- the algorithm within the SC is a high level algorithm which can consider indications from more than one PU, a task which the algorithm within each specific PU cannot perform locally.
- the SC also handles simultaneous detection of several intrusions, and eliminates several simultaneous false alarms.
- Each sensing unit used in the intrusion detection systems of the prior art comprises a magnetic sensor, but it lacks an accelerometer such as the one included in each sensing unit 10 of the present invention. Therefore, in order to obtain accurate evaluation, or more specifically, to assure accurate determination regarding the direction and orientation of a movement in the proximity of the sensing units, when such occurs, the prior art requires the performance of a physical, 3-axis orientation pre- alignment at the time of installation of each magnetic sensing unit with respect to a predefined coordinates system. Without such a physical pre- alignment with respect to a predefined coordinate system, a determination of the relevant object location and the direction of crossing, is essentially impossible or is substantially inaccurate.
- the sensing unit After the physical alignment of the orientation of each sensing unit, the sensing unit has to be fixed in place order to maintain the validity of the alignment. If for any reason the orientation of one or more sensing units in the systems of the prior art changes, a re-alignment must be performed. The performance of such a re-alignment is very complicated, as in many cases the whole systems is inaccessible, as it may be underground covered by soil, may be underwater, etc.
- Fig. 2 shows a detection cluster 4 as used by the intrusion detection system of the present invention.
- each magnetic sensing unit 10 within the cluster comprises both a sensor s and an accelerometer a.
- the magnetic sensing unit 10 also comprises a microcontroller for performing A/D conversion of the sensed 3-axes magnetic field and the sensed 3-axes acceleration data, and a communication element for communicating the sensed information to the proximate sensing unit or PU.
- Connecting cable 12 includes several wires, for example, two wires for conveying low level sensing information from the sensing units 10 to the PUs, two wires for conveying high level information from the PUs to the SCs, and two additional wires for providing voltage supply from the SCs to the various units.
- Fig. 3a shows the structure of a magnetic sensing unit 10, according to one embodiment of the invention.
- the magnetic sensing unit 10 comprises a microcontroller 102 which performs the basic processing tasks of the sensing unit. More specifically, the microcontroller receives magnetic field measurement B X) B y , and B z from the 3-axes magnetic sensor 101, and a 3- axes acceleration measurement g x , g y , and g z of the Earth acceleration vector g from accelerometer 103.
- Each of said two measurements of the magnetic field and of the vector g may be received at the microcontroller in an analog form and converted to a digital form by an A/D unit within the microcontroller, or external A/Ds (not shown) may be provided such that the microcontroller receives said magnetic field and acceleration measurements already in a digital form.
- the microcontroller 102 is also responsible for the communication with the proximate PU or sensing unit to the left and/or right of the sensing unit. This is done by means of the comm-left and comm-right elements 104a and 104b and cable 12.
- Power supply element 106 receives input voltage from the external cable 12, and it produces the various DC voltages that are necessary by the various components of unit 10.
- Fig. 3b shows the structure of each PU.
- the PU comprises within it a sensing unit 10, with the addition of the low level detection algorithm 111, and a high level communication element 112, which communicates with the SC.
- the PU includes processor 122, which performs essentially all the tasks of microcontroller 102 of sensing unit 10 (as in Fig. 3a), with the addition of the intrusion evaluation using detection algorithm 112.
- the PU only receives sensing information from other sensing units, but it does not convey its own low level sensing information to other units.
- the PU evaluates the accumulated low level sensing information messages, as received from various sensing units, determines whether an intrusion has occurred, and the intrusion parameters (such as the location and direction), and conveys this information to one or more SCs via the high level communication elements 112.
- the PU is a stand alone unit, which does not comprise within it a sensor and accelerometer, while it performs only the low level evaluation algorithm, and conveys the results to one or more SCs.
- Fig. 4 schematically illustrates the basic structure of magnetic sensing unit 10. Sensor s within each sensing unit 10 has its (local) predefined 3 axes sx, s y , and s z , such that the measured magnetic fields B x , B y , and B z are measured by said sensor with respect to these coordinates. The whole system has its own, global reference coordinate system.
- each sensor in order to evaluate the magnetic field readings by each sensor, there is a need for knowing the relation between the orientation of the sensor (or sensing unit) with respect to the predefined global coordinate system.
- a 3-D physical calibration of each sensing unit has to be performed in order to aligned with said global coordinate system.
- all the sensing units have to be fixed in their aligned position during the whole life of the security system, and when for some reason they move out of their original alignment, a recalibration procedure has to be performed.
- the present invention eliminates entirely the need for physical calibration, and it enables determination of the orientation of the sensor any time when necessary.
- the sensor s and the accelerometer a are maintained in a fixed orientation within the sensing unit 10.
- the 3-axes orientation of each sensing unit (or more specifically, of the sensor s within the sensing unit) with respect to the predefined global coordinate system is determined prior to the system operation and recorded, for example, within one or more of the relevant PUs that evaluate its readings. Thereafter, each time that a reading is conveyed to the PU, the PU can evaluate the reading with respect to the recorded sensor (or sensing unit) orientation and it can thereafter correlate the reading to the global coordinate system. Moreover, as will be shown, the system can determine the orientation of each sensor s at any given time, after the system installation, and it can correct the orientation recording when necessary.
- the determination of the orientation of each sensor is based on the measurement of the orientation of the sensor with respect to two known directional vectors. More specifically, the determination is based on the finding of the sensor orientation with respect to the known g acceleration vector of the Earth, and with respect to the known direction of the Earth magnetic field vector.
- the 3-axes orientation of the sensor with respect to the Earth magnetic field vector is determined by measuring the Earth magnetic field. This is performed by sensor s itself.
- sensor s measures and conveys to the PU during the calibration period the 3 components of the Earth magnetic field vector, i.e., BEX, BE J , and BEZ.
- the Earth magnetic field vector is a vector that can be measured by sensor s of the sensing unit 10, and this measurement does not require the inclusion of any additional means within the sensing unit.
- the 3-D orientation of the sensing unit with respect to the acceleration vector g of the Earth whose direction is known is measured by the accelerometer a. More specifically, accelerometer a measures and conveys to the PU during the calibration period the 3 components of g, i.e., g x , g y , and g z .
- system 1 of the invention is performed as follows:
- the physical system i.e., wires, sensing units 10, processing units PUs, segment coordinators SCs, etc.
- the physical system is installed either underground (for example, within a trench) or above the ground (for example, within a concrete wall), or even underwater.
- the physical installation there is no need to physically align the orientation of any sensing unit 10.
- the trench can be covered;
- a calibration software within each PU can obtain from each sensing unit 10 of the system the measured direction of the sensing unit with respect to the Earth magnetic field vector (as sensed by sensor s), and the measured direction of the sensing unit with respect to the acceleration vector g of the earth (3 components in 3 axes - as measured by accelerometer a). Having obtained these measurements (6 components, 3 directional components relating to the magnetic field measured with respect to the Earth magnetic field, and 3 directional components relating to the measured acceleration vector with respect to acceleration vector g of the Earth), the calibration process can fully determine and record the 3-D orientation of each specific sensor s (located within a specific sensing unit) respectively. Such a procedure is performed by all the PUs, each performing its determination with respect to the sensing units within its own cluster.
- the system as described can determine or verify at any given time (i.e., even after the coverage of the trench) the respective orientations of all the sensors s, and can update its recorded orientations Oi - On within storage 128 accordingly. This is done without any need for physical calibration. As shown, the installation of the system is much simpler in compare to the prior art, particularly, as there is no need to physically align and fix separately the orientation of each of the various sensors s during or after the network installation.
- the system of the present invention uses a tracking and detection algorithm, to determine the location of the intrusion, and its direction.
- the use of such algorithm can eliminate false alarms, due to, for example, movements of objects near the sensors that do not perform intrusion.
- the finding of the orientation of each sensor is essential. In order to perform tracking of a ferromagnetic object (magnetic dipole m), there is a need to determine its location at any given time. As also shown in Fig.
- ⁇ represents the free space permeability.
- B(r) is the magnetic field vector at point r caused by magnetic moment m of a specific magnetic dipole.
- R represents the distance between the magnetic moment location of the dipole and the relevant sensor.
- Fig. 6 shows the geometric model of the problem, which defines the distances between the two sensors si and S2 respectively and the magnetic dipole represented by its magnetic moment m.
- the vectors r and r ' represent the direction vectors between the two sensors respectively and the dipole.
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Abstract
The invention relates to a two-mode intrusion detection system which comprises: (A) a plurality of magnetic sensing units, connected in chain-like manner and spaced apart from one another, each sensing unit comprises: (a) a magnetic sensor s for sensing a 3-D magnetic field vector of the Earth; (b) an accelerometer for sensing a 3-D acceleration vector evolving from the acceleration g of the Earth; and (c) first communication means for conveying said sensed 3-D magnetic field vector and said sensed 3-D acceleration vector to a proximate processing unit; B. one or more processing units, each processing unit comprises (a) second communication means for communicating with one or more of said magnetic sensing units; and (b) a processor for: (B.1.) during a calibration mode, receiving from each sensing unit respectively said magnetic field vector of the Earth as measured by its respective magnetic field sensor s, and said acceleration vector as measured by said accelerometer a, and determining, based on said magnetic field vector and said acceleration vector the respective orientation of each magnetic unit with respect to a predefined coordinates system; and (B.2.) during an intrusion detection mode receiving periodically from two or more sensing units magnetic field measurements as measured respectively by corresponding magnetic field sensors s, and based on said two or more magnetic field measurements, and the known orientations of the respective magnetic units, as determined by said calibration mode, determining whether an intrusion has occurred and the location of said intrusion.
Description
Intrusion Detection System
Field of the Invention
The present invention relates to the field of intrusion detection systems. More particularly, the invention relates to an intrusion detection system which comprises a plurality of magnetic sensing units, wherein each magnetic sensing unit comprises a magnetic sensor, and an accelerometer.
Background of the Invention
Intrusion detection systems are well known and widely used for securing areas or specific sites. The larger the secured area is, the higher the complexity and cost of the system. Various intrusion detection systems are known, which are generally classified by their types of sensors, or by their technical structure. Intrusion detection systems of the prior art apply optical sensors (such as visual, IR or laser sensors), acoustic sensors, magnetic sensors, radar systems, cameras, and more.
One type of sensors, which is commonly used in intrusion detection systems is the magnetic sensor, which detects a variation in the magnetic field in the proximity of the sensor, and this variation is used for determining whether an intrusion has occurred or not. The magnetic sensor of the passive type (the type to which the present invention relates) can particularly sense articles in the proximity of the sensor that are made of ferromagnetic materials, or more specifically, the magnetic sensor can sense a change in the magnetic field due to a change in the location and orientation of such articles. There are various advantages to the use of magnetic sensors, as follows: (a) magnetic sensors are relatively cheap and reliable; (b) magnetic sensors can be used above or below the ground or underwater, or they can be installed and sense even from within concrete walls; (c) the magnetic sensors of the passive type do not radiate energy
(and therefore it is hard to detect them); and (d) they have relatively small mass and volume. Generally, a plurality of magnetic sensors is used in intrusion detection systems, spaced apart from one another, for example at a distance of 5m- 10m from one another. Typically, a number of magnetic sensors are arranged along a connecting cable in a "chain-like" structure (i.e., one after the other, sometimes with other supporting units in between) and they generally each communicates with its neighboring sensors by means of said cable, or wirelessly. They may also communicate with a control center directly or via a relay unit.
There are some intrusion detection systems in which variation measurements as obtained from a plurality (two or more) of magnetic sensors enable accurate determination regarding the exact location and direction of the intrusion with respect to each of the involved sensors. Such determination is generally based on the use of a detection algorithm that solves the "physical problem" of determining the location of the intruding object (hereinafter also referred to as "target") and its magnetic moment. The detection algorithm may use numerical tools. However, such determination of the exact location and direction of the intrusion, based on indications from plurality of sensors highly depends on the orientation of each sensor with respect to the others in its proximity, or with respect to a predefined coordinates system. Therefore, such direction-location determination requires a very accurate leveling and calibration of the orientation of each of the sensors with respect to said predefined coordinates system at the time of installation, and it also strictly requires continuously maintaining all of the sensors at the calibrated orientation after the time of installation.
For example, it is common to install a network of magnetic sensors along a secured border or around a secured area. In some cases, the network of
sensors is installed underground. The procedure of installing the network underground involves digging a trench, leveling the trench, putting the sensors and wiring within the trench, aligning each of the sensors with respect to a predefined coordinates system, fixing each of the sensors in its aligned position, and finally covering the trench. Said procedure of installation is very cumbersome and time consuming, and moreover, there is no easy way of knowing whether the adjustment of each specific sensor has changed after the time of the network installation.
It is therefore an object of the present invention to simplify the installation of a security network which is based on magnetic sensors.
It is another object of the present invention to eliminate the requirement for aligning each of the network magnetic sensors during the installation.
It is still another object of the present invention to eliminate the strict necessity of maintaining each of the magnetic sensors at a fixed orientation during the whole life of the security system, after the initial sensor alignment.
Other objects and advantages of the invention will become apparent as the description proceeds.
Summary of the Invention
The invention relates to a two-mode intrusion detection system which comprises: (A) a plurality of magnetic sensing units, connected in chainlike manner and spaced apart from one another, each sensing unit comprises: (a) a magnetic sensor s for sensing a 3-D magnetic field vector of the Earth; (b) an accelerometer for sensing a 3-D acceleration vector evolving from the acceleration g of the Earth; and (c) first communication
means for conveying said sensed 3-D magnetic field vector and said sensed 3-D acceleration vector to a proximate processing unit;
B. one or more processing units, each processing unit comprises (a) second communication means for communicating with one or more of said magnetic sensing units; and (b) a processor for: (B.l.) during a calibration mode, receiving from each sensing unit respectively said magnetic field vector of the Earth as measured by its respective magnetic field sensor s, and said acceleration vector as measured by said accelerometer a, and determining, based on said magnetic field vector and said acceleration vector the respective orientation of each magnetic unit with respect to a predefined coordinates system; and (B.2.) during an intrusion detection mode receiving periodically from two or more sensing units magnetic field measurements as measured respectively by corresponding magnetic field sensors s, and based on said two or more magnetic field measurements, and the known orientations of the respective magnetic units, as determined by said calibration mode, determining whether an intrusion has occurred and the location of said intrusion.
Preferably, each processing unit also comprises a sensing unit.
Preferably, a plurality of magnetic units and one processing unit form a cluster, and wherein the sensing units and processing unit of a cluster are connected by means of a multi-wired cable.
Preferably, plurality of clusters that are connected in a chain-like manner and having two segment coordinators at their ends define a segment.
Preferably, each sensing unit transfers one or more of its magnetic field measurement and its acceleration measurement to the proximate
processing unit in a chain like manner via one or more of magnetic sensing units.
Preferably, each processing unit determines an intrusion based on magnetic field measurements of two or more proximate sensing units.
Preferably, each processing unit further comprises a third communication unit for communicating reports to one or more of segment coordinators, and wherein each segment coordinator performs high-level analysis and control based on said processing units reports.
Preferably, each processing unit determines the orientation of each magnetic sensing unit by an orientation algorithm, which is operative during said calibration mode.
Preferably, each processing unit determines whether an intrusion has occurred and the location of said intrusion by a detection algorithm, which is operative during said intrusion detection mode.
Preferably, said first communication means of the sensing unit comprises a left communication element and a right communication element, for communicating with two neighboring units respectively.
Preferably, a report from each magnetic sensing unit to a processing unit is made periodically.
Preferably, a report from each magnetic sensing unit to a processing unit during an intrusion detection mode is performed upon exceeding of a threshold.
Brief Description of the Drawings
Fig. 1 shows in block diagram form a general structure of an intrusion detection system, according to an embodiment of the present invention;
Fig. 2 shows a detection cluster as used by the intrusion detection system of the present invention;
Fig. 3a shows in block diagram form the structure of a detection unit according to an embodiment of the present invention;
Fig. 3b shows in block diagram form the structure of a processing unit according to an embodiment of the present invention;
Fig. 4 schematically illustrates the basic structure of a magnetic sensing unit in terms of the magnetic sensor and the acceleration sensor; and
Fig. 5 schematically shows two sensors si and S2 that are used for locating a ferromagnetic dipole m.
Detailed Description of Preferred Embodiments
Fig. 1 shows in block diagram form a general structure of an intrusion detection system 1, according to an embodiment of the present invention. A secured area 2 is surrounded by a network of magnetic sensing units 10. The network is divided into plurality of detection segments 3, each segment comprising a plurality of detection clusters 4, wherein each detection segment 3 is connected to a segment coordinator SC. Each detection cluster 4 comprises one processing unit PU and several magnetic sensing units 10. Each processing unit PU in turn comprises a sensing unit 10, and a processor. Each segment coordinator SC comprises a controller C, power supply P, and gateway g.
As will be elaborated hereinafter, each sensing unit 10 comprises a 3-axes magnetic sensor s for sensing a variation in the magnetic field in
proximity of the sensor, and a 3-axes accelerometer a. Continuously, or upon sensing a magnetic field variation by sensor s, sensing unit 10 conveys sensing information to a neighboring device, which may be either another sensing unit 10 or a processing unit PU. More specifically, the sensing information is conveyed from each sensing unit to the closest processing unit through a "chain" of one or more sensing units 10. The communication between the units of the network (the sensing units, the processing units, and the SCs) is performed through connecting cable 12. A relatively wide bandwidth communication takes place between the sensing units 10 and the PUs, as this communication involves transfer of raw sensing data (magnetic sensing information and/or acceleration information), while the communication between the PUs and the SCs is of lower bandwidth, as this is a higher level processed information. More specifically, during a normal mode of operation of the system each sensing unit conveys in digital form to its neighboring unit (either a sensing unit or a PU) the 3-axes sensed magnetic field, which is essentially the raw magnetic field data as sensed by a sensor s within the respective sensing unit. During a calibration mode of operation of the system each sensing unit conveys in digital form to its neighboring unit (either a sensing unit or a PU) the 3-axes sensed magnetic field as sensed by sensor s and the 3- axes measurement of the acceleration vector g of the Earth as sensed by accelerometer a. In normal operation, a detection algorithm within each PU evaluates the accumulated data, whenever received from the one or more of the sensing units of cluster 4, and determines whether a suspected intrusion has occurred, and the location and direction of the suspected intrusion. More specifically, upon receipt of 3-axes sensed magnetic field information from one or more sensors s, a detection (low-level) algorithm of the PU can determine whether a crossing of the system has occurred, its location (i.e., the two sensors between which the crossing has occurred), and the direction of the crossing, (into or out of the secured area).
Whenever a suspected crossing is determined by a PU, it communicates this event to the proximate segment coordinator SC, or more specifically, to controller C within the respective SC. Upon receipt of such one or more event messages by controller C from one or more processing units PU, the SC further evaluates the data using its own high-level algorithm. More specifically, the SC receives messages from plurality of PUs and it performs evaluation in a more global manner. For example, if 30 (or more) simultaneous event information messages are received at the SC from various PUs indicating a magnetic field variation in 30 different locations, the controller C may conclude that this is a false alarm, which has been occurred due to, for example, lightning. The algorithm of the SC also preferably manages the system, and it may send managing messages to the various PUs, for example, it may initiate a calibration mode of all the sensing units 10, it may question the processing units about the respective cluster statuses, it may manage situation of faulty units, it may assign an address ID for specific units etc. More specifically, the algorithm within the SC is a high level algorithm which can consider indications from more than one PU, a task which the algorithm within each specific PU cannot perform locally. Preferably, the SC also handles simultaneous detection of several intrusions, and eliminates several simultaneous false alarms.
Each sensing unit used in the intrusion detection systems of the prior art comprises a magnetic sensor, but it lacks an accelerometer such as the one included in each sensing unit 10 of the present invention. Therefore, in order to obtain accurate evaluation, or more specifically, to assure accurate determination regarding the direction and orientation of a movement in the proximity of the sensing units, when such occurs, the prior art requires the performance of a physical, 3-axis orientation pre- alignment at the time of installation of each magnetic sensing unit with respect to a predefined coordinates system. Without such a physical pre-
alignment with respect to a predefined coordinate system, a determination of the relevant object location and the direction of crossing, is essentially impossible or is substantially inaccurate. Moreover, after the physical alignment of the orientation of each sensing unit, the sensing unit has to be fixed in place order to maintain the validity of the alignment. If for any reason the orientation of one or more sensing units in the systems of the prior art changes, a re-alignment must be performed. The performance of such a re-alignment is very complicated, as in many cases the whole systems is inaccessible, as it may be underground covered by soil, may be underwater, etc.
Fig. 2 shows a detection cluster 4 as used by the intrusion detection system of the present invention. As schematically shown, each magnetic sensing unit 10 within the cluster comprises both a sensor s and an accelerometer a. The magnetic sensing unit 10 also comprises a microcontroller for performing A/D conversion of the sensed 3-axes magnetic field and the sensed 3-axes acceleration data, and a communication element for communicating the sensed information to the proximate sensing unit or PU. Connecting cable 12 includes several wires, for example, two wires for conveying low level sensing information from the sensing units 10 to the PUs, two wires for conveying high level information from the PUs to the SCs, and two additional wires for providing voltage supply from the SCs to the various units.
Fig. 3a shows the structure of a magnetic sensing unit 10, according to one embodiment of the invention. The magnetic sensing unit 10 comprises a microcontroller 102 which performs the basic processing tasks of the sensing unit. More specifically, the microcontroller receives magnetic field measurement BX) By, and Bz from the 3-axes magnetic sensor 101, and a 3- axes acceleration measurement gx, gy, and gz of the Earth acceleration
vector g from accelerometer 103. Each of said two measurements of the magnetic field and of the vector g may be received at the microcontroller in an analog form and converted to a digital form by an A/D unit within the microcontroller, or external A/Ds (not shown) may be provided such that the microcontroller receives said magnetic field and acceleration measurements already in a digital form. The microcontroller 102 is also responsible for the communication with the proximate PU or sensing unit to the left and/or right of the sensing unit. This is done by means of the comm-left and comm-right elements 104a and 104b and cable 12. Power supply element 106 receives input voltage from the external cable 12, and it produces the various DC voltages that are necessary by the various components of unit 10. Fig. 3b shows the structure of each PU. Preferably the PU comprises within it a sensing unit 10, with the addition of the low level detection algorithm 111, and a high level communication element 112, which communicates with the SC. The PU includes processor 122, which performs essentially all the tasks of microcontroller 102 of sensing unit 10 (as in Fig. 3a), with the addition of the intrusion evaluation using detection algorithm 112. The PU only receives sensing information from other sensing units, but it does not convey its own low level sensing information to other units. The PU evaluates the accumulated low level sensing information messages, as received from various sensing units, determines whether an intrusion has occurred, and the intrusion parameters (such as the location and direction), and conveys this information to one or more SCs via the high level communication elements 112. In an alternative case, the PU is a stand alone unit, which does not comprise within it a sensor and accelerometer, while it performs only the low level evaluation algorithm, and conveys the results to one or more SCs.
Fig. 4 schematically illustrates the basic structure of magnetic sensing unit 10. Sensor s within each sensing unit 10 has its (local) predefined 3 axes sx, sy, and sz, such that the measured magnetic fields Bx, By, and Bz are measured by said sensor with respect to these coordinates. The whole system has its own, global reference coordinate system. Therefore, in order to evaluate the magnetic field readings by each sensor, there is a need for knowing the relation between the orientation of the sensor (or sensing unit) with respect to the predefined global coordinate system. In the prior art, a 3-D physical calibration of each sensing unit has to be performed in order to aligned with said global coordinate system. Moreover, all the sensing units have to be fixed in their aligned position during the whole life of the security system, and when for some reason they move out of their original alignment, a recalibration procedure has to be performed. The present invention eliminates entirely the need for physical calibration, and it enables determination of the orientation of the sensor any time when necessary. The sensor s and the accelerometer a are maintained in a fixed orientation within the sensing unit 10. In view of their close proximity, they may sometimes be considered as being aligned and sharing a same local coordinate system (i.e., that the coordinate system x y', z', of the accelerator a overlaps the coordinate system x, y, z, of sensor s.
According to the present invention, the 3-axes orientation of each sensing unit (or more specifically, of the sensor s within the sensing unit) with respect to the predefined global coordinate system is determined prior to the system operation and recorded, for example, within one or more of the relevant PUs that evaluate its readings. Thereafter, each time that a reading is conveyed to the PU, the PU can evaluate the reading with respect to the recorded sensor (or sensing unit) orientation and it can thereafter correlate the reading to the global coordinate system. Moreover, as will be shown, the system can determine the orientation of each sensor
s at any given time, after the system installation, and it can correct the orientation recording when necessary.
The determination of the orientation of each sensor is based on the measurement of the orientation of the sensor with respect to two known directional vectors. More specifically, the determination is based on the finding of the sensor orientation with respect to the known g acceleration vector of the Earth, and with respect to the known direction of the Earth magnetic field vector. During the "calibration mode" of the system (the term "calibration" refers to the determination of each sensor orientation, and not to any physical alignment of the sensor orientation as is performed in the prior art), the 3-axes orientation of the sensor with respect to the Earth magnetic field vector is determined by measuring the Earth magnetic field. This is performed by sensor s itself. More specifically, sensor s measures and conveys to the PU during the calibration period the 3 components of the Earth magnetic field vector, i.e., BEX, BEJ, and BEZ. It should be noted that the Earth magnetic field vector is a vector that can be measured by sensor s of the sensing unit 10, and this measurement does not require the inclusion of any additional means within the sensing unit. The 3-D orientation of the sensing unit with respect to the acceleration vector g of the Earth whose direction is known is measured by the accelerometer a. More specifically, accelerometer a measures and conveys to the PU during the calibration period the 3 components of g, i.e., gx, gy, and gz. Said two measurements ΟΪ ΒΕΧ, BEy, and BEZ, and of gx, gy, and gz fully enable the exact determination of the orientation of the respective sensor with respect to the global coordinates system (it should be noted that in order to determine orientation with respect to known three axes, the finding of the orientation with respect to two of them suffice, and the orientation with respect to the third one evolves geometrically in view of the orthogonality). As said, the calibration
of the system in which the orientation of each specific sensor s is determined, can be performed any time, when necessary, and the orientation of each of the sensors with respect to the global coordinates can be updated and recorded following the performance of such a procedure. Such a calibration procedure according to the invention eliminates any need for a physical calibration.
The installation of system 1 of the invention is performed as follows:
A. First, the physical system (i.e., wires, sensing units 10, processing units PUs, segment coordinators SCs, etc.) is installed either underground (for example, within a trench) or above the ground (for example, within a concrete wall), or even underwater. During the physical installation, there is no need to physically align the orientation of any sensing unit 10. Upon completion of the physical installation, and if the system is installed underground, the trench can be covered;
B. The system is transferred to a calibration mode, and a calibration process is performed. A calibration software within each PU can obtain from each sensing unit 10 of the system the measured direction of the sensing unit with respect to the Earth magnetic field vector (as sensed by sensor s), and the measured direction of the sensing unit with respect to the acceleration vector g of the earth (3 components in 3 axes - as measured by accelerometer a). Having obtained these measurements (6 components, 3 directional components relating to the magnetic field measured with respect to the Earth magnetic field, and 3 directional components relating to the measured acceleration vector with respect to acceleration vector g of the Earth), the calibration process can fully determine and record the 3-D orientation of each specific sensor s (located within a specific sensing unit) respectively. Such a procedure is performed by
all the PUs, each performing its determination with respect to the sensing units within its own cluster.
C. Having recorded all the respective orientations Oi-On of the various sensors s with respect to predefined global coordinate system, when a magnetic field reading data is received from two or more sensing units regarding possible intrusion (i.e., said information includes an indication regarding a variation in the measured magnetic field by each of the relevant sensors) the detection algorithm within the respective PU can determine the location and direction of the possible intrusion, particularly as the orientation of each of the reporting sensors s is known.
The system as described can determine or verify at any given time (i.e., even after the coverage of the trench) the respective orientations of all the sensors s, and can update its recorded orientations Oi - On within storage 128 accordingly. This is done without any need for physical calibration. As shown, the installation of the system is much simpler in compare to the prior art, particularly, as there is no need to physically align and fix separately the orientation of each of the various sensors s during or after the network installation.
Preferably, the system of the present invention uses a tracking and detection algorithm, to determine the location of the intrusion, and its direction. Moreover, the use of such algorithm can eliminate false alarms, due to, for example, movements of objects near the sensors that do not perform intrusion. For this algorithm, the finding of the orientation of each sensor is essential. In order to perform tracking of a ferromagnetic object (magnetic dipole m), there is a need to determine its location at any given time. As also shown in Fig. 5 (which schematically shows two
sensors si and s_> for locating a ferromagnetic magnetic dipole m), this can be done by referring to the object as a magnetic dipole, and solving a physical equation which defines the magnetic field B of the dipole as a function of its location R and its magnetic moment M, as follows:
(1)
μο represents the free space permeability. B(r) is the magnetic field vector at point r caused by magnetic moment m of a specific magnetic dipole. R represents the distance between the magnetic moment location of the dipole and the relevant sensor.
The equation is a non-linear equation with 6 degrees of freedom. Therefore, in order to solve this equation, the solving of 6 separate equations, with 6 unknowns is necessary. For this purpose, two sensors, each measuring the magnetic field caused by the object in 3 axes suffice. Fig. 6 shows the geometric model of the problem, which defines the distances between the two sensors si and S2 respectively and the magnetic dipole represented by its magnetic moment m. The vectors r and r ' represent the direction vectors between the two sensors respectively and the dipole.
While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.
Claims
1. A two-mode intrusion detection system which comprises:
A. a plurality of magnetic sensing units, connected in chain-like manner and spaced apart from one another, each sensing unit comprises: (a) a magnetic sensor s for sensing a 3-D magnetic field vector of the Earth; (b) an accelerometer for sensing a 3-D acceleration vector evolving from the acceleration g of the Earth; and (c) first communication means for conveying said sensed 3-D magnetic field vector and said sensed 3-D acceleration vector to a proximate processing unit;
B. One or more processing units, each processing unit comprises (a) second communication means for communicating with one or more of said magnetic sensing units; and (b) a processor for:
B. l. during a calibration mode, receiving from each sensing unit respectively said magnetic field vector of the Earth as measured by its respective magnetic field sensor s, and said acceleration vector as measured by said accelerometer a, and determining, based on said magnetic field vector and said acceleration vector the respective orientation of each magnetic unit with respect to a predefined coordinates system; and
B.2. during an intrusion detection mode receiving periodically from two or more sensing units magnetic field measurements as measured respectively by corresponding magnetic field sensors s, and based on said two or more magnetic field measurements, and the known orientations of the respective magnetic units, as determined by said calibration mode, determining whether an intrusion has occurred and the location of said intrusion.
2. System according to claim 1, wherein each processing unit also comprises a sensing unit.
3. System according to claim 1, wherein a plurality of magnetic units and one processing unit form a cluster, and wherein the sensing units and processing unit of a cluster are connected by means of a multi-wired cable.
4. System according to claim 3, wherein plurality of clusters that are connected in a chain-like manner and having two segment coordinators at their ends define a segment.
5. System according to claim 4, wherein each sensing unit transfers one or more of its magnetic field measurement and its acceleration measurement to the proximate processing unit in a chain like manner via one or more of magnetic sensing units.
6. System according to claim 1, wherein each processing unit determines an intrusion based on magnetic field measurements of two or more proximate sensing units.
7. System according to claim 4, wherein each processing unit further comprises a third communication unit for communicating reports to one or more of segment coordinators, and wherein each segment coordinator performs high-level analysis and control based on said processing units reports.
8. System according to claim 1, wherein each processing unit determines the orientation of each magnetic sensing unit by an orientation algorithm, which is operative during said calibration mode.
9. System according to claim 1, wherein each processing unit determines whether an intrusion has occurred and the location of said intrusion by a detection algorithm, which is operative during said intrusion detection mode.
10. System according to claim 1, wherein said first communication means of the sensing unit comprises a left communication element and a right communication element, for communicating with two neighboring units respectively.
11. System according to claim 1, wherein a report from each magnetic sensing unit to a processing unit is made periodically.
12. System according to claim 1 wherein a report from each magnetic sensing unit to a processing unit during an intrusion detection mode is performed upon exceeding of a threshold.
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RU186543U1 (en) * | 2018-09-12 | 2019-01-23 | Акционерное общество "Федеральный научно-производственный центр "Производственное объединение "Старт" им. М.В. Проценко" (АО "ФНПЦ ПО "Старт" им. М.В. Проценко") | Low Energy Consolidated Seismic Magnetometric Detector |
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