CN116739007B - Card reader protection device based on dynamic threshold and signal energy level judgment - Google Patents
Card reader protection device based on dynamic threshold and signal energy level judgment Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/0013—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers
- G06K7/0056—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers housing of the card connector
- G06K7/0078—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers housing of the card connector reinforced housing for protection against damage, be it due malevolent action, such as drilling and other ways of forced entry, or by accident, such as shock due to dropping
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/0013—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers
- G06K7/0086—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers the connector comprising a circuit for steering the operations of the card connector
- G06K7/0091—Methods or arrangements for sensing record carriers, e.g. for reading patterns by galvanic contacts, e.g. card connectors for ISO-7816 compliant smart cards or memory cards, e.g. SD card readers the connector comprising a circuit for steering the operations of the card connector the circuit comprising an arrangement for avoiding intrusions and unwanted access to data inside of the connector
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Abstract
The invention discloses a card reader protection device based on dynamic threshold and signal energy level judgment, which comprises a detection coil and a control board, wherein the detection coil is configured at the position of a card reader insertion port and is used for establishing an energy field at the position of the card reader insertion port according to an excitation signal and detecting energy change of the energy field at the position of the card reader insertion port; the control board is electrically connected with the detection coil, and is used for sending an excitation signal to the detection coil, acquiring an energy change signal detected by the detection coil in real time, and detecting whether the card reader card insertion slot has foreign matters or not according to the energy change signal by adopting a method based on a dynamic threshold value and a signal energy level judgment method. The invention adopts a dynamic threshold value method to solve the problem of drift of output data of the detection coil caused by various factors, adopts a signal energy level judging method to eliminate the problem of output signal change caused by interference or normal card inserting and taking operation, effectively realizes the detection of foreign matters, and reduces the false alarm rate and the false alarm rate of the protection device.
Description
Technical Field
The invention relates to the technical field of card reader protection, in particular to a card reader protection device based on dynamic threshold and signal energy level judgment.
Background
While mobile payment is increasingly used, physical bank cards are still in use over a wide range and will last for a considerable period of time. In addition, in the places where secret is involved and important protection is needed, such as the secret-involved area of the military unit, the bank vault and the like, staff needs to swipe a card to confirm the identity, and the staff can enter after authorization. The information on the card will cause larger loss once being leaked, the bank card is stolen and swiped if the information is light, and serious accidents such as national confidential leakage and the like are caused. The card swiping or reading is a high risk link of card information leakage.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a card reader protection device based on dynamic threshold and signal energy level judgment, which is used for providing real-time protection for a card reader by monitoring whether foreign matters exist near a card reader card insertion port and preventing card information leakage caused by reading a card clip ring.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
a card reader protection device based on dynamic threshold and signal energy level determination, comprising:
the detection coil is configured at the position of the card reader insertion port and is used for establishing an energy field at the position of the card reader insertion port according to the excitation signal and detecting energy change of the energy field at the position of the card reader insertion port;
the control board is electrically connected with the detection coil, is used for sending an excitation signal to the detection coil, acquires an energy change signal detected by the detection coil in real time, and detects whether foreign matters exist in the card reader card insertion slot according to the energy change signal by adopting a method based on a dynamic threshold value and a signal energy level judging method.
Further, the detection coils are configured to be at least one, and each detection coil is fixed in a protection area inside a protection cover in front of the card reader card slot by adopting a flexible circuit board.
Further, the method for determining the protection area comprises the following steps:
the projection of the protective cover is carried out from the front side of the card reader to the rear side of the card reader, the plane with the largest area is taken as a first reference plane, and all planes with the areas larger than a first threshold value of the first reference plane are taken as protective areas to be respectively provided with detection coils;
and taking the plane with the largest area as a second reference plane from the projection of the protection cover in the direction perpendicular to the card reader, and taking all planes with the areas larger than a second threshold value of the second reference plane as protection areas to respectively arrange detection coils.
Further, the control board specifically includes:
the singlechip and the circuit channels are respectively and electrically connected with the singlechip and each detection coil; each circuit channel comprises a digital-to-analog conversion module, a voltage control oscillator, an amplifying and filtering module, a detection module and an analog-to-digital conversion module;
the digital-to-analog conversion module is used for converting a control signal sent by the singlechip into a digital signal;
the voltage control oscillator is used for adjusting the signal frequency of the excitation signal output to the corresponding detection coil according to the digital signal so as to adjust the corresponding detection coil to be in a resonance state;
the amplifying and filtering module is used for amplifying and filtering the oscillation signal output by the detection coil in the resonance state;
the detection module is used for converting the oscillation signal processed by the amplifying and filtering module into a direct current signal;
the analog-to-digital conversion module is used for converting the direct current signal into a digital signal and outputting the digital signal to the singlechip;
the singlechip is used for sending a control signal to the digital-to-analog conversion module, receiving a digital signal output by the analog-to-digital conversion module, and detecting whether foreign matters exist in the card reader card insertion port according to the digital signal by adopting a method based on a dynamic threshold value and a signal energy level judgment method.
Further, the method for detecting whether the card reader card insertion port has foreign matters by the singlechip comprises the following steps:
a1, judging whether the power-on is performed for the first time; if yes, executing the step A2; otherwise, executing the step A4;
a2, acquiring a voltage value of a digital signal output by the analog-to-digital conversion module;
a3, judging whether the voltage value is the maximum voltage value; if yes, the digital-to-analog conversion output value of the current digital-to-analog conversion module is saved, and the step A4 is executed; otherwise, adjusting the digital-to-analog conversion output value of the current digital-to-analog conversion module, and returning to the step A2;
a4, sequentially collecting voltage values of digital signals output by each detection coil through the analog-to-digital conversion module;
a5, detecting whether foreign matters exist in the card inserting port of the card reader by adopting a method based on a dynamic threshold value and a signal energy level judging method according to the acquired voltage value.
Further, the method for determining the level of the signal energy based on the dynamic threshold specifically comprises the following steps:
b1, filtering the energy change signal by adopting recursive median average filtering;
b2, calculating first-order differential data of the energy change signal after the filtering processing;
b3, extracting a data sample from the first-order differential data of the energy change signal by adopting a sliding window;
b4, judging whether the variation of the first-order differential data in the extracted data sample is larger than a data variation threshold value or not; if yes, executing the step B5; otherwise, adopting a dynamic threshold mechanism to update the dynamic reference threshold in real time;
b5, performing integral calculation on the energy change signal from the current moment to obtain a signal energy value;
b6, judging whether the difference value between the energy change signal and the dynamic reference threshold value is smaller than the detection threshold value; if yes, stopping integral calculation, and executing a step B7; otherwise, directly executing the step B7;
b7, judging whether the signal energy value calculated by integration reaches a signal energy threshold value or not; if yes, judging that foreign matters exist in the card reader card inserting port; otherwise, the dynamic reference threshold is updated in real time by adopting a dynamic threshold mechanism, and the step A1 is returned.
Further, the calculation formula for calculating the first-order differential data of the energy change signal after the filtering process is:
；
wherein ,is->Of energy variation signal of moment of timeFirst order differential data,/->Is->Energy change signal of time of day,/->Is->The energy of the moment changes the signal.
Further, an update formula for updating the dynamic reference threshold value in real time by adopting a dynamic threshold value mechanism is as follows:
；
wherein ,for dynamic reference threshold->Is->The energy of the moment changes the signal.
Further, the calculation formula for performing integral calculation on the energy change signal is:
；
wherein ,signal energy value calculated for integration, +.>Is->Time of day energy change signal，/>Is a dynamic reference threshold.
The invention has the following beneficial effects:
(1) The invention establishes a stable energy field in the protection area, realizes the detection of foreign matters by monitoring the change condition of the energy field, prevents any circuit device from being illegally installed in the protection area, and ensures that card information leakage is not caused when a card reader reads a card;
(2) The invention adopts the energy field mode to realize the protection of the card reader, has the characteristics of simple and reliable circuit and high cost performance, and simultaneously the protection mode is not influenced by the environment, temperature and humidity changes;
(3) The invention adopts MCU (single chip microcomputer) as the main control of the protection device, can conveniently realize the dynamic adjustment of the alarm threshold, and can furthest avoid false alarm while guaranteeing the detection sensitivity;
(4) The invention adopts FPC (flexible circuit board) to manufacture the detection coil, which is applicable to almost all curved surface adhesion and can realize the purpose of full coverage of the detection coil in the protection area;
(5) The invention adopts a dynamic threshold value method to solve the problem of drift of output data of the detection coil caused by various factors, adopts a signal energy level judging method to eliminate the problem of output signal change caused by interference or normal card inserting and taking operation, effectively realizes the detection of foreign matters, and reduces the false alarm rate and the false alarm rate of the protection device.
Drawings
FIG. 1 is a schematic diagram of a card reader protection device based on dynamic threshold and signal energy level determination in the present invention;
FIG. 2 is a schematic diagram showing the assembly of a protective cover and a detection coil in the present invention;
FIG. 3 is a schematic diagram of a detection coil configuration of a protection device according to the present invention;
FIG. 4 is a schematic diagram of an energy field established by a detection coil according to the present invention;
FIG. 5 is a schematic block diagram of the circuit of the present invention;
FIG. 6 is a schematic diagram of a main process flow of the present invention;
FIG. 7 is a diagram showing a foreign object detection determination flow according to the present invention;
FIG. 8 is a diagram of the data after detection coil filtering in the present invention;
FIG. 9 is a schematic diagram of first order differential data of filtered data according to the present invention;
fig. 10 is a diagram showing the integral expression of signal energy levels in the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.
As shown in fig. 1, an embodiment of the present invention provides a card reader protection device based on dynamic threshold and signal energy level determination, including:
the detection coil is configured at the position of the card reader insertion port and is used for establishing an energy field at the position of the card reader insertion port according to the excitation signal and detecting energy change of the energy field at the position of the card reader insertion port;
the control board is electrically connected with the detection coil, is used for sending an excitation signal to the detection coil, acquires an energy change signal detected by the detection coil in real time, and detects whether foreign matters exist in the card reader card insertion slot according to the energy change signal by adopting a method based on a dynamic threshold value and a signal energy level judging method.
The card reader related to the embodiment comprises a card reader main body 5, a card reader bayonet 4 and a protective cover 2; in this embodiment, the detection coil 3 is disposed inside the protective cover 2 in front of the card reader card insertion slot 4, a stable energy field is established in the protection area through the detection coil, when foreign matters exist in the protection area, the detection coil can detect the change of the energy field, the change of the energy field is digitized through amplifying, filtering, detecting and analog-to-digital converting the change by the control board 1, and the foreign matters in the protection area can be detected and alarm is given through data processing and foreign matters judgment, so that the card reader is protected.
In an alternative embodiment of the present invention, in order to omnidirectionally protect the area near the card reader card slot, the present embodiment configures at least one detection coil, and each detection coil is fixed in a protection area inside a protective cover in front of the card reader card slot by using a flexible circuit board, as shown in fig. 2, where a is an enlarged view of the detection coil.
The method for determining the protection area comprises the following steps:
the projection of the protection cover is carried out from the front direction of the card reader to the rear direction of the card reader, the plane with the largest area is taken as a first reference plane, and all planes with the area larger than a first threshold value of the first reference plane are taken as protection areas to respectively configure detection coils, such as a plane 3-1 and a plane 3-2 in FIG. 3;
and (3) taking the plane with the largest area as a second reference plane from the projection of the protection cover in the direction perpendicular to the card reader, and taking all planes with the areas larger than a second threshold value of the second reference plane as protection areas to respectively configure detection coils, as shown by planes 3-3 in fig. 3.
Specifically, the detection coil is manufactured by using an FPC (flexible circuit board), and is fixed on the inner side of the protective cover in front of the card reader card insertion port by using adhesive tape or glue during assembly, and the FPC (flexible circuit board) can be well attached to any curved surface of the protective cover so as to achieve the purpose of fully covering the detection coil in the protective area. The number of detection coils in the protection device can be set according to the characteristics of the area to be protected, and one detection coil can be arranged on a relatively flat or large plane.
According to the embodiment, protection can be provided for the area near the card reader card insertion port, a stable energy field can be established and the change of the energy field can be detected by adopting the detection coil designed by the FPC (flexible circuit board), and the detection coil can be perfectly attached to the structure in front of the card reader card insertion port to provide omnibearing protection due to good flexibility of the FPC.
As shown in fig. 3, 3 detection coils are arranged for the protection device in order to provide a detection coil arrangement diagram for the protection device. The number and shape of the detection coils can be flexibly configured according to the characteristics of the protective cover, and the configuration is based on the fact that the energy field established by the detection coils covers the periphery of the card slot as much as possible so as to provide omnibearing protection. The energy field established by the inspection coil is shown in fig. 4, and the effective detection range is slightly larger than the size of the inspection coil, so that the design of the inspection coil and the selection of the installation position are mainly based on a large flat surface of the protective cover:
1. based on the actual mounting position relation between the protective cover and the card reader, the projection of the protective cover is made from the front of the card reader to the rear of the card reader, and the detection coils are arranged on all surfaces with the area larger than 20% of the area of S1 by taking the largest flat surface as a reference (the area is marked as S1).
2. The projection of the protective cover is made from the direction perpendicular to the card reader, and the detection coils are arranged on all surfaces with the area larger than 20% of the area of S2 by taking the largest flat surface as a reference (the area is recorded as S2).
In an alternative embodiment of the present invention, the control board of this embodiment specifically includes:
the singlechip and the circuit channels are respectively and electrically connected with the singlechip and each detection coil; each circuit channel comprises a digital-to-analog conversion module, a voltage control oscillator, an amplifying and filtering module, a detection module and an analog-to-digital conversion module;
the digital-to-analog conversion module is used for converting a control signal sent by the singlechip into a digital signal;
the voltage control oscillator is used for adjusting the signal frequency of the excitation signal output to the corresponding detection coil according to the digital signal so as to adjust the corresponding detection coil to be in a resonance state;
the amplifying and filtering module is used for amplifying and filtering the oscillation signal output by the detection coil in the resonance state;
the detection module is used for converting the oscillation signal processed by the amplifying and filtering module into a direct current signal;
the analog-to-digital conversion module is used for converting the direct current signal into a digital signal and outputting the digital signal to the singlechip;
the singlechip is used for sending a control signal to the digital-to-analog conversion module, receiving a digital signal output by the analog-to-digital conversion module, and detecting whether foreign matters exist in the card reader card insertion port according to the digital signal by adopting a method based on a dynamic threshold value and a signal energy level judgment method.
In the embodiment, the MCU (single chip microcomputer) controls the DAC (digital-to-analog conversion) to output a direct current signal to act on the VCO (voltage control oscillator) so that the detection coil is in a resonance state, and the maximum energy field can be established at the moment, thereby ensuring the detection sensitivity of the device; through amplifying, filtering, detecting and digital-to-analog conversion on the signal output by the detection coil, the MCU can acquire the change condition of the energy field in real time, when foreign matters enter the energy field, the energy field is disturbed, the MCU can detect the change in real time through data processing so as to realize alarming, real-time protection is provided for the card reader, and card information leakage caused by reading a snap ring joint is prevented.
As shown in fig. 5, in order to provide a schematic circuit diagram of the protection device, the number of detection coils can be arbitrarily configured according to the structural characteristics of the protection cover, and only the number of circuit channels needs to be correspondingly increased or decreased. The detection coil can establish a stable energy field under the excitation of a VCO (voltage controlled oscillator) and can monitor the change condition of the energy field. MCU (single chip microcomputer) controls VCO (voltage controlled oscillator) through DAC (digital to analog conversion), and output frequency of VCO (voltage controlled oscillator) can be adjusted by changing input digital size of DAC (digital to analog conversion). The detection coil monitors the change of the energy field and converts the change into the change of the voltage amplitude, because the voltage amplitude output by the detection coil is very small, the detection module is required to convert an alternating current signal into a direct current signal through amplification, filtering and the like, the ADC (analog to digital conversion) module is used for converting an analog signal into a digital signal and outputting the digital signal to the MCU (single chip microcomputer), and whether foreign matters exist in a protection area or not is identified through software. MCU (singlechip) forms closed-loop control through DAC (digital-to-analog conversion) and ADC (analog-to-digital conversion), can realize the function of parameter matching to any detection coil, and makes each detection coil be in resonance state when working. The state indicating circuit is used for indicating the working state of the device, and when foreign matters are detected, the MCU (single chip microcomputer) switches the state indication and outputs an alarm signal through the alarm circuit.
In an optional embodiment of the present invention, the method for detecting whether the foreign matter exists in the card reader card insertion port by using the single chip microcomputer is as follows:
a1, judging whether the power-on is performed for the first time; if yes, executing the step A2; otherwise, executing the step A4;
a2, acquiring a voltage value of a digital signal output by the analog-to-digital conversion module;
a3, judging whether the voltage value is the maximum voltage value; if yes, the digital-to-analog conversion output value of the current digital-to-analog conversion module is saved, and the step A4 is executed; otherwise, adjusting the digital-to-analog conversion output value of the current digital-to-analog conversion module, and returning to the step A2;
a4, sequentially collecting voltage values of digital signals output by each detection coil through the analog-to-digital conversion module;
a5, detecting whether foreign matters exist in the card inserting port of the card reader by adopting a method based on a dynamic threshold value and a signal energy level judging method according to the acquired voltage value.
As shown in fig. 6, in order to provide a main program flow chart of the protection device, the MCU (single chip microcomputer) can perform independent parameter matching on each detection coil and save the parameters, and during operation, the MCU (single chip microcomputer) scans each detection coil in turn, processes data and performs foreign matter detection and judgment, and updates the alarm output state and log according to the judgment structure.
According to the embodiment, through closed-loop control, the MCU (single chip microcomputer) can carry out independent parameter matching on each detection coil and save the parameters, on one hand, a stable energy field can be established, on the other hand, the parameters of each detection coil can be automatically matched, and the detection sensitivity is improved.
In an optional embodiment of the invention, the method for determining a level of signal energy and based on the dynamic threshold specifically includes:
b1, filtering the energy change signal by adopting recursive median average filtering;
b2, calculating first-order differential data of the energy change signal after the filtering processing; the calculation formula is as follows:
；
wherein ,is->First order differential data of the energy variation signal of the moment,/->Is thatEnergy change signal of time of day,/->Is->An energy change signal at a time;
b3, extracting a data sample from the first-order differential data of the energy change signal by adopting a sliding window;
b4, judging whether the variation of the first-order differential data in the extracted data sample is larger than a data variation threshold value or not; if yes, executing the step B5; otherwise, adopting a dynamic threshold mechanism to update the dynamic reference threshold in real time; the update formula is:
；
wherein ,for dynamic reference threshold->Is->An energy change signal at a time;
b5, performing integral calculation on the energy change signal from the current moment to obtain a signal energy value; the calculation formula is as follows:
；
wherein ,signal energy value calculated for integration, +.>Is->Energy change signal of time of day,/->Is a dynamic reference threshold;
b6, judging whether the difference value between the energy change signal and the dynamic reference threshold value is smaller than the detection threshold value; if yes, stopping integral calculation, and executing a step B7; otherwise, directly executing the step B7;
b7, judging whether the signal energy value calculated by integration reaches a signal energy threshold value or not; if yes, judging that foreign matters exist in the card reader card inserting port; otherwise, the dynamic reference threshold is updated in real time by adopting a dynamic threshold mechanism, and the step A1 is returned.
Specifically, as shown in fig. 7, a flowchart of the detection and determination of foreign matter in the protection device is shown.
In this embodiment, first, recursive median average filtering is used to filter the data output by the detection coil, and the filtered data is shown in fig. 8, where it is known that, except for the occurrence of abrupt data changes at the positions a and b, the overall change trend of the data is slowly increased, and the change is caused by the change of the operating environment parameters of the protection device.
Then, a first derivative of the output data of the detection coil is calculated, a group of results with the length of M are stored through a sliding window, and each time the data is updated and stored into the head of the queue, the tail data of the queue is discarded. Since the ADC samples at a fixed frequency, the first derivative of the detection coil output signal can be expressed as
。
Fig. 9 shows the first differential of the filtered data output by the detection coil, and the data mutation occurs at the positions a and b, and the data mutation is consistent with the position of the data chart in fig. 8.
The first-order differential variation of the output data of the detection coil is compared with the data variation threshold. When the first-order differential variation of the output data of the detection coil is not greater than the data variation threshold delta' u When the foreign matter is not present in the protection area. In order to solve the problem of false alarm caused by the change of the working environment of the protection device, the embodiment adopts a dynamic threshold mechanism to calculate the signal energy level, and the dynamic reference threshold is recorded asUcom. When no foreign matter is detected in the protection area, the dynamic reference threshold value is updated in real timeUcomIs the value of (1):
；
when the first-order differential change of the output data of the detection coil is larger than the data change threshold delta' u When the card is inserted and pulled normally or the interference signal is strong, the foreign matter exists in the protection area, so that the influence of short disturbance of the energy field in the protection area caused by the normal insertion and pulling of the card by the staff is filtered, and the false alarm of the event is avoided by adopting a judgment mode based on the signal energy level. The specific mechanism of the signal energy level judging mode is as follows:
because the interference signal has the characteristics of randomness, short signal duration and the like, and the operation time of normal card insertion and extraction of a worker is also within a few seconds, the total amount of energy change in a protection area caused by the two conditions is smaller, otherwise, if foreign matters exist in the protection area for a longer time, the total amount of energy change in the protection area is larger, and when the signal energy change level exceeds a certain level, an alarm is triggered, and by adopting the method, the false alarm can be effectively reduced, and the reliability of the protection device is improved.
The signal energy can be calculated by integrating the amount of change in the output of the detection coil due to the signal:
；
when a signal abrupt change is detected, i.e. the first order derivative is greater than the data change threshold delta' u When the integral value exceeds the alarm threshold value, the integral operation is started to calculate the signal energy levelP max The integration is stopped and the user can modify this value to adjust the sensitivity of the protection device. When detecting the coil output signal and the dynamic reference thresholdUcomAnd ending the signal energy integration flow and judging whether to alarm or not when the difference is smaller than the detection threshold value delta u.
The integral representation of the signal energy level of fig. 10 shows that the signal duration is shorter at a, although the detection coil data change is larger, the signal energy level is lower, and the signal can be easily filtered. And the signal at the position corresponding to the position b has longer duration, and the signal energy integral value of the signal at the position corresponding to the position b is rapidly increased, so that the alarm output can be rapidly triggered.
Because the environment parameters such as temperature and humidity of the operation of the protection device and normal card inserting and taking operations can cause the output data of the detection coil of the protection device to drift and jump in a short time, in order to improve the stability of the protection device and reduce the false alarm rate, the embodiment adopts a dynamic threshold method to solve the problem of the drift of the output data of the detection coil caused by various factors, adopts a signal energy level judging method to eliminate the problem of the change of the output signal caused by interference or normal card inserting and taking operations, effectively realizes the detection of foreign matters and reduces the false alarm rate and false alarm rate of the protection device.
According to the embodiment, the detection coil dynamic reference threshold is adopted, so that data drift caused by the change of the working environment of the protection device is effectively counteracted, the sensitivity and the reliability are improved, the interference such as manual operation is reliably filtered out by adopting the judgment algorithm based on the signal energy level, the system stability is improved, and the false alarm rate is reduced.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The principles and embodiments of the present invention have been described in detail with reference to specific examples, which are provided to facilitate understanding of the method and core ideas of the present invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (7)
1. A card reader protection device based on dynamic threshold and signal energy level determination, comprising:
the detection coil is configured at the position of the card reader insertion port and is used for establishing an energy field at the position of the card reader insertion port according to the excitation signal and detecting energy change of the energy field at the position of the card reader insertion port;
the control board is electrically connected with the detection coil, is used for sending an excitation signal to the detection coil, acquiring an energy change signal detected by the detection coil in real time, and detecting whether a foreign object exists in the card reader card slot according to the energy change signal by adopting a method for judging based on a dynamic threshold value and a signal energy level;
the method for detecting whether foreign matters exist in the card reader card insertion port according to the energy change signal by adopting the method for judging the energy level of the signal based on the dynamic threshold value comprises the following steps:
a1, judging whether the power-on is performed for the first time; if yes, executing the step A2; otherwise, executing the step A4;
a2, acquiring a voltage value of a digital signal output by the analog-to-digital conversion module;
a3, judging whether the voltage value is the maximum voltage value; if yes, the digital-to-analog conversion output value of the current digital-to-analog conversion module is saved, and the step A4 is executed; otherwise, adjusting the digital-to-analog conversion output value of the current digital-to-analog conversion module, and returning to the step A2;
a4, sequentially collecting voltage values of digital signals output by each detection coil through the analog-to-digital conversion module;
a5, detecting whether foreign matters exist in the card reader card insertion port or not by adopting a method based on a dynamic threshold value and a signal energy level judging method according to the acquired voltage value;
b1, filtering the energy change signal by adopting recursive median average filtering;
b2, calculating first-order differential data of the energy change signal after the filtering processing;
b3, extracting a data sample from the first-order differential data of the energy change signal by adopting a sliding window;
b4, judging whether the variation of the first-order differential data in the extracted data sample is larger than a data variation threshold value or not; if yes, executing the step B5; otherwise, adopting a dynamic threshold mechanism to update the dynamic reference threshold in real time;
b5, performing integral calculation on the energy change signal from the current moment to obtain a signal energy value;
b6, judging whether the difference value between the energy change signal and the dynamic reference threshold value is smaller than the detection threshold value; if yes, stopping integral calculation, and executing a step B7; otherwise, directly executing the step B7;
b7, judging whether the signal energy value calculated by integration reaches a signal energy threshold value or not; if yes, judging that foreign matters exist in the card reader card inserting port; otherwise, the dynamic reference threshold is updated in real time by adopting a dynamic threshold mechanism, and the step A1 is returned.
2. The card reader protection device based on dynamic threshold and signal energy level determination as in claim 1 wherein the detection coils are configured as at least one, each detection coil being secured to a protective area inside a protective cover in front of a card reader card slot using a flexible circuit board.
3. The card reader protection device based on dynamic threshold and signal energy level determination as claimed in claim 2, wherein the protection area determination method is as follows:
the projection of the protective cover is carried out from the front side of the card reader to the rear side of the card reader, the plane with the largest area is taken as a first reference plane, and all planes with the areas larger than a first threshold value of the first reference plane are taken as protective areas to be respectively provided with detection coils;
and taking the plane with the largest area as a second reference plane from the projection of the protection cover in the direction perpendicular to the card reader, and taking all planes with the areas larger than a second threshold value of the second reference plane as protection areas to respectively arrange detection coils.
4. The card reader protection device based on dynamic threshold and signal energy level determination of claim 1, wherein the control board specifically comprises:
the singlechip and the circuit channels are respectively and electrically connected with the singlechip and each detection coil; each circuit channel comprises a digital-to-analog conversion module, a voltage control oscillator, an amplifying and filtering module, a detection module and an analog-to-digital conversion module;
the digital-to-analog conversion module is used for converting a control signal sent by the singlechip into a digital signal;
the voltage control oscillator is used for adjusting the signal frequency of the excitation signal output to the corresponding detection coil according to the digital signal so as to adjust the corresponding detection coil to be in a resonance state;
the amplifying and filtering module is used for amplifying and filtering the oscillation signal output by the detection coil in the resonance state;
the detection module is used for converting the oscillation signal processed by the amplifying and filtering module into a direct current signal;
the analog-to-digital conversion module is used for converting the direct current signal into a digital signal and outputting the digital signal to the singlechip;
the singlechip is used for sending a control signal to the digital-to-analog conversion module, receiving a digital signal output by the analog-to-digital conversion module, and detecting whether foreign matters exist in the card reader card insertion port according to the digital signal by adopting a method based on a dynamic threshold value and a signal energy level judgment method.
5. The card reader protection device based on dynamic threshold and signal energy level determination according to claim 1, wherein the calculation formula for calculating the first-order differential data of the filtered energy variation signal is:
；
wherein ,is->First order differential data of the energy variation signal of the moment,/->Is thatEnergy change signal of time of day,/->Is->The energy of the moment changes the signal.
6. The card reader protection device based on dynamic threshold and signal energy level determination as claimed in claim 1, wherein the update formula for updating the dynamic reference threshold in real time using the dynamic threshold mechanism is:
；
wherein ,for dynamic reference threshold->Is->The energy of the moment changes the signal.
7. The card reader protection device based on dynamic threshold and signal energy level determination as claimed in claim 1, wherein the calculation formula for performing integral calculation on the energy variation signal is:
；
wherein ,signal energy value calculated for integration, +.>Is->Energy change signal of time of day,/->Is a dynamic reference threshold.
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