A micro-vibration target detector

Abstract

The present invention provides a micro-vibration target detector, comprising: a detector, an adaptive envelope detection circuit and an adaptive threshold adjustment circuit, wherein the detector is connected to the adaptive envelope detection circuit, and the adaptive envelope detection circuit is connected to the adaptive threshold adjustment circuit; the detector is used to collect micro-vibration signals and transmit the collected micro-vibration signals to the adaptive envelope detection circuit, and the adaptive envelope detection circuit converts the higher-frequency micro-vibration signals into low-frequency envelope signals, and the adaptive threshold adjustment circuit is used to adjust the reference thresholds under different environments according to the detection results to improve the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a micro-vibration target detector. Background Art

[0002] The inventors of the present invention discovered during research that, in wireless sensor network (WSN) nodes, vibration sensors are mainly used to detect ground microseismic signals around WSN nodes. In the prior art, the sampling frequency of the microprocessor system of the wireless sensor network is greater than 400 Hz and the sampling time lasts for at least 3 seconds. This method has the problems of large memory occupation by sampling data, large signal processing calculation amount, and high energy consumption of the microprocessor system. This requires WSN nodes to have strong computing power and battery life. Summary of the invention

[0003] In view of this, the present invention provides a micro-vibration target detector to at least solve the problem that the sampling data occupies a large amount of memory.

[0004] Specifically, the present invention is achieved through the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides a microvibration target detector, comprising: a detector, an adaptive envelope detection circuit and an adaptive threshold adjustment circuit, wherein the detector is connected to the adaptive envelope detection circuit, and the adaptive envelope detection circuit is connected to the adaptive threshold adjustment circuit;

[0006] The detector is used to collect micro-vibration signals and transmit the collected micro-vibration signals to the adaptive envelope detection circuit, which converts the higher-frequency micro-vibration signals into low-frequency envelope signals. The adaptive threshold adjustment circuit is used to adjust the reference thresholds under different environments according to the detection results to improve the accuracy of detection.

[0007] Optionally, the geophone comprises: a geophone probe, a high-pass filter, a band-stop filter and a low-pass filter;

[0008] The geophone probe is installed at the bottom of the WSN node shell to detect ground microvibration signals; the high-pass filter is used to filter the output signals at both ends of the geophone probe to isolate DC and suppress low-frequency interference signals; the band-stop filter is used to suppress AC interference, and the low-pass filter is used to suppress high-frequency signal interference.

[0009] Optionally, the adaptive envelope detection circuit comprises: a DC blocking filter circuit, a first operational amplifier, a series resistor, two parallel resistors and a Schottky diode;

[0010] The DC blocking filter circuit is connected to an operational amplifier, the operational amplifier is connected in series with a series resistor, two parallel resistors are connected in parallel with a capacitor, and the Schottky diode is connected between the two parallel circuits.

[0011] Optionally, the detector comprises: a second operational amplifier, a common-direction amplifier circuit, a first-order low-pass filter and a comparison circuit; the comparison circuit comprises: a comparator, a digitally controlled potentiometer and a resistor;

[0012] The input end of the same-direction amplifier circuit is connected to the input end of the second operational amplifier, the output end of the same-direction amplifier circuit is connected to the output end of the second operational amplifier, the output end of the second operational amplifier is connected to a first-order low-pass filter, and the first-order low-pass filter is connected to the comparison circuit.

[0013] A microvibration target detector provided in an embodiment of the present invention includes: a detector, an adaptive envelope detection circuit and an adaptive threshold adjustment circuit, the detector is connected to the adaptive envelope detection circuit, and the adaptive envelope detection circuit is connected to the adaptive threshold adjustment circuit; the detector is used to collect microvibration signals and transmit the collected microvibration signals to the adaptive envelope detection circuit, the adaptive envelope detection circuit converts the higher frequency microvibration signals into low frequency envelope signals, and the adaptive threshold adjustment circuit is used to adjust the comparison threshold according to the detection environment to improve the accuracy of the comparison. The present application has the following positive effects: the use of an adaptive envelope detector to convert a higher frequency microvibration signal into a low frequency envelope signal can not only reduce the sampling rate of the microprocessor system, reduce the microprocessor memory, and simplify the microvibration target recognition algorithm, but also greatly improve the target recognition processing speed and reduce the power consumption of the microprocessor system, without affecting the accuracy of target recognition. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic structural diagram of a microvibration target detector shown in an exemplary embodiment of the present invention;

[0015] Figure 2 is a schematic structural diagram of a seismic detector probe shown in an exemplary embodiment of the present invention;

[0016] Figure 3 It is a connection diagram of a band-stop notch filter and a low-pass filter of a seismic detector probe shown in an exemplary embodiment of the present invention;

[0017] Figure 4 is a structural schematic diagram of an adaptive envelope detection circuit shown in an exemplary embodiment of the present invention;

[0018] Figure 5 is a schematic diagram of an adaptive threshold adjustment circuit according to an exemplary embodiment of the present invention;

[0019] Figure 6 It is a schematic diagram of a micro-vibration excitation source shown in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0020] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0021] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0022] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0023] In wireless sensor network (WSN) nodes, vibration sensors are mainly used to detect ground microseismic signals around WSN nodes. The vibration frequency caused by the movement of people, animals, wheeled vehicles and tracked vehicles is usually within the range of 200Hz. In order to use the ARM microprocessor system to analyze, process and identify target signals, the sampling frequency of the microprocessor system is greater than 400Hz, and the sampling time lasts at least 3 seconds. This method has the problems of large memory usage of sampling data, large signal processing calculation, and high energy consumption of the microprocessor system, which is very disadvantageous for WSN nodes powered by lithium batteries and with limited computing power. In addition, WSN nodes based on magnetoelectric seismic detectors are equipped with tail cone accessories. The tail cone is inserted into the soil ground and pressed tightly to achieve close coupling between the seismic detector and the ground, or the bottom of the seismic detector is closely coupled to the hard ground by gluing, so that it can detect ground microseismic signals. Such WSN nodes are inconvenient to carry and deploy.

[0024] To solve the above problems, the sensitivity of the magnetoelectric seismic detector must be improved first, so that the seismic detector node (WSN node) can be directly placed on the ground (except for swamps) to detect the ground micro-vibration signal caused by the movement of people, animals and vehicles. At the same time, in the seismic detector node, an envelope detection circuit is introduced so that the microprocessor directly samples the amplitude envelope of the micro-vibration signal and processes it to extract and identify the target characteristics, rather than sampling and processing the original micro-vibration signal. In this way, the sampling frequency of the microprocessor system can be reduced and the signal processing algorithm program can be simplified, thereby achieving rapid target identification and reducing the power consumption of the microprocessor. In addition, in order to reduce the false alarm probability or missed detection probability of the micro-vibration target detector, an auxiliary device for adaptively adjusting the envelope detector gain and the comparator warning threshold should be added to compensate for the adverse effects caused by changes in environmental parameters. To this end, the applicant of the present invention proposes a design scheme for a tail-free micro-vibration target detector based on adaptive envelope detection technology.

[0025] Reference Figure 1 As shown, a micro-vibration target detector provided in this embodiment includes: a detector 100, an adaptive envelope detection circuit 200 and an adaptive threshold adjustment circuit 300, the detector 100 is connected to the adaptive envelope detection circuit 200, and the adaptive envelope detection circuit 200 is connected to the adaptive threshold adjustment circuit 300.

[0026] The detector 100 is used to collect micro-vibration signals and transmit the collected micro-vibration signals to the adaptive envelope detection circuit 200, which converts the higher frequency micro-vibration signals into low frequency envelope signals. The adaptive threshold adjustment circuit 300 is used to adjust the reference thresholds under different environments according to the detection results to improve the accuracy of detection.

[0027] In one embodiment of the present application, the above-mentioned detector includes: a seismic detector probe, a high-pass filter, a band-stop filter and a low-pass filter.

[0028] The geophone probe is installed at the bottom of the WSN node shell to detect ground microvibration signals; the high-pass filter is used to filter the output signals at both ends of the geophone probe to isolate DC and suppress low-frequency interference signals; the band-stop filter is used to suppress AC interference, and the low-pass filter is used to suppress high-frequency signal interference.

[0029] For example, Figure 2 is a schematic structural diagram of a seismic detector probe shown in an exemplary embodiment of the present invention; Figure 3 is a connection diagram of a band-stop notch filter and a low-pass filter of a seismic detector probe shown in an exemplary embodiment of the present invention; first, refer to Figure 2The geophone probe uses a PS-10R ultra-high sensitivity magnetoelectric geophone probe, which is installed at the bottom of the WSN node shell to detect ground microvibration signals. In order to avoid the damage of the signal conditioning circuit caused by the lightning surge voltage that may be induced by the magnetoelectric geophone, a bidirectional transient voltage suppression diode (SHK_U1) is connected in parallel between the two output terminals of the geophone and the ground wire to protect the subsequent circuit. Capacitors C11 and C12 and resistors R11 and R12 form two identical high-pass filters (with a cut-off frequency of 10Hz) to filter the output signals at both ends of the geophone to isolate DC and suppress low-frequency interference signals. Resistor R13 and precision instrument amplifier (SHK_U2) form the pre-amplifier circuit of the geophone, and its gain is determined by the resistance value of resistor R13.

[0030] Reference Figure 3 As shown, in Figure 3 In the figure, resistors R21, R22, R23 and capacitors C21, C22, C23 form a double T-type 50Hz band-stop filter to suppress interference from the mains (50Hz AC); a voltage follower composed of a low-power operational amplifier (SHK_U3-1 / 2) serves as an impedance isolation buffer between the band-stop filter and the subsequent low-pass filter; a second-order Butterworth low-pass filter (cut-off frequency 200Hz) composed of an operational amplifier (SHK_U3-2 / 2), resistors R24, R25 and capacitors C24, C25 is used to suppress high-frequency signal interference.

[0031] In an embodiment of the present application, the above-mentioned adaptive envelope detection circuit includes: a DC blocking filter circuit, a first operational amplifier, a series resistor, two parallel resistors and a Schottky diode; the DC blocking filter circuit is connected to the operational amplifier, the operational amplifier is connected in series with the series resistor, the two parallel resistors are connected in parallel with a capacitor, and the Schottky diode is connected between the two parallel circuits.

[0032] Figure 4 is a schematic diagram of the structure of an adaptive envelope detection circuit shown in an exemplary embodiment of the present invention; exemplarily, refer to Figure 4 As shown, capacitor C1 and resistor R1 form a DC blocking filter; a single-power low-power operational amplifier (SHK_U4-1 / 2, called the first operational amplifier for easy distinction), a diode D, resistors R2, R3, R4, capacitor C2, and a Schottky diode SD form an envelope detector. The charging time constant of the detector is τ1 = R2 × C2, and the discharging time constant is τ2 ≥ (R3 / / R4) × C2, and τ2>>τ1. Here, the main function of introducing the Schottky diode SD is to reduce the DC component of the amplitude envelope signal.

[0033] In one embodiment of the present application, the above-mentioned detector includes: a second operational amplifier, a same-direction amplifier circuit, a first-order low-pass filter and a comparison circuit; the comparison circuit includes: a comparator, a digitally controlled potentiometer and a resistor; the input end of the same-direction amplifier circuit is connected to the input end of the second operational amplifier, the output end of the same-direction amplifier circuit is connected to the output end of the second operational amplifier, the output end of the second operational amplifier is connected to the first-order low-pass filter, and the first-order low-pass filter is connected to the comparison circuit.

[0034] Figure 5 is a schematic diagram of an adaptive threshold adjustment circuit shown in an exemplary embodiment of the present invention; Figure 5 As shown, a single-power low-power operational amplifier (SHK_U4-2 / 2, which can be the second operational amplifier for easy distinction), resistors R1, R2, R3 and IIC digitally controlled potentiometer (SHK_U5-1 / 2) constitute a gain-controllable unidirectional amplifier, and resistor R4 and capacitor C4 constitute a first-order low-pass filter (cut-off frequency is less than 10Hz); a single-power low-power comparator (SHK_U6, OTC output), an IIC digitally controlled potentiometer (SHK_U5-2 / 2) and resistor R5 constitute a threshold-controllable comparator circuit, capacitor C2 is used to filter out threshold level noise, and resistor R6 and an LED light are used to display the output state of the comparator.

[0035] In one embodiment of the present application, a micro-vibration excitation source is also provided to ensure the power supply of the detector.

[0036] Figure 6 is a schematic diagram of a micro-vibration excitation source shown in an exemplary embodiment of the present invention, referring to Figure 6 As shown, the micro-vibration excitation source is specifically described as follows: the resistor R1 and the inverter (SHK_U7) constitute the switch circuit (normally closed, the inverter outputs a low level) of the LDO (low dropout) linear voltage regulator (SHK_U8), which is controlled by the microprocessor IO interface (MPU_IO); the capacitors C1 and C2 are used for power supply filtering; the typical output voltage of the LDO linear voltage regulator (SHK_U8) is 2.84V (output current 120mA), which is used to drive the flat button vibration motor (rated voltage / current: 3V / 80mA). The resistor R2 and the light-emitting diode LED are used to display the working status of the micro-vibration excitation source.

[0037] The detector provided by the present application adopts an ultra-high sensitivity magnetoelectric seismic detector probe, a dual power supply instrument amplifier, a dual T-type 50Hz band-stop filter, a second-order low-pass filter and an adaptive envelope detector to form a high-sensitivity seismic detector, so that the ground micro-vibration signal caused by the movement of people, animals or vehicles can be detected without the need for a tail vertebrae attachment. The amplitude envelope characteristics of the ground micro-vibration signal (10-200Hz) caused by the movement of people, animals or vehicles are detected by the envelope detection method, which is used to determine whether there is human, animal or vehicle movement around the micro-vibration target detector.

[0038] It constitutes an adaptive gain adjustment device for a high-sensitivity seismic detector and an adaptive threshold adjustment device for a comparator. The microvibration excitation source is turned on regularly, and the gain / threshold adjustment program based on the fuzzy logic algorithm is started. The algorithm is adaptive and automatically adjusts the circuit gain of the microvibration target detector and the warning threshold of the comparator in different detection environments (such as cement, sand detection environment, etc.) to improve its environmental adaptability and reduce the probability of false alarm or missed alarm. Here, the output state of the comparator is flipped erroneously to indicate a false alarm; the output state of the comparator is insensitive to the microvibration signal to indicate a missed alarm.

[0039] The microvibration target detector provided in the above embodiment of the present application is composed of functional components such as a detector, an adaptive envelope detection circuit, and an adaptive threshold adjustment circuit. Among them, the detector is composed of an ultra-high sensitivity magnetoelectric seismic detector probe and its signal conditioning circuit; the adaptive envelope detection circuit and the adaptive threshold adjustment circuit also include an ARM microprocessor system, a digitally controlled potentiometer, a flat button vibration motor and other electronic components. The specific description is as follows:

[0040] The high-sensitivity seismic detector includes ultra-high-sensitivity magnetoelectric seismic detector probe, instrument amplifier, double-T type 50Hz band-stop notch filter and second-order Butterworth low-pass filter and other functional components. The seismic detector output signal S1 passes through a high-pass filter, a peak detector and a low-pass filter and a DC voltage translation circuit to obtain the micro-vibration amplitude envelope signal S2. In order to improve the processing gain of the signal conditioning circuit, a multi-stage filter is used here to filter the signal.

[0041] The micro-vibration amplitude envelope signal S2 is connected to the input of the gain-controllable unidirectional operational amplifier, and the output of the unidirectional operational amplifier is connected in series with a first-order low-pass filter. The output signal of the low-pass filter is divided into two paths: one is connected to the analog-to-digital converter (ADC) of the ARM microprocessor, and the other is connected to the reverse input of the comparator with a controllable threshold, and the output state of the comparator is used as the interrupt signal (INT) of the ARM microprocessor. Here, an IIC digital potentiometer is used as the feedback resistor of the unidirectional operational amplifier, and the ARM microprocessor is used to adjust the resistance of the digital potentiometer to achieve gain control; similarly, the ARM microprocessor is used to adjust the resistance of another IIC digital potentiometer to achieve the threshold control of the comparator (the potential of the unidirectional input terminal of the comparator). When the amplified and filtered micro-vibration amplitude envelope signal (SHK_AOUT) exceeds the warning threshold, the ARM microprocessor immediately starts the interrupt service program - sampling and processing the amplitude envelope signal to determine whether there is human, animal or vehicle movement around the detector.

[0042] A DC drive power supply and a flat button vibration motor (installed at the bottom of the geophone node housing) are used to generate micro-vibration signals as micro-vibration excitation sources for adjusting the envelope detector gain and comparator threshold. The micro-vibration excitation source is turned on, and the micro-vibration envelope signal is sampled using the ADC port of the ARM microprocessor. If the sampling peak value does not reach the full scale of the ADC, the digital control potentiometer is adjusted through the IIC interface of the ARM microprocessor to gradually increase the gain of the same-direction operational amplifier until the sampling peak value reaches the full scale of the ADC, and the corresponding IIC digital control potentiometer resistance value is used as the initial feedback resistance value of the same-direction operational amplifier; the micro-vibration excitation source is turned off, and the output signal of the micro-vibration target detector is sampled using the ADC port of the ARM microprocessor, and its average value / peak value is calculated, and 1.2 or 1.5 times of the average value / peak value is used as the initial threshold.

[0043] In the actual detection process, the micro-vibration excitation source can be turned on at regular intervals, and the fuzzy logic algorithm can be used to adjust the gain of the envelope detector and the threshold of the comparator to reduce the false alarm probability or missed detection probability of the micro-vibration target detector.

[0044] Furthermore, this application has at least the following positive effects:

[0045] (1) An ultra-high-sensitivity magnetoelectric seismic detector probe and a dual-power signal conditioning circuit with high signal processing gain are used to form a high-sensitivity seismic detector, which can detect ground micro-vibration signals caused by the movement of people, animals or vehicles without the need for a tail vertebrae attachment.

[0046] (2) An envelope detector is used to convert the higher frequency micro-vibration signal (fmax = 200 Hz) into a low frequency envelope signal (less than 10 Hz). This can not only reduce the sampling rate of the microprocessor system, reduce the microprocessor memory, and simplify the micro-vibration target recognition algorithm, but also greatly improve the target recognition speed and reduce the power consumption of the microprocessor system without affecting the accuracy of target recognition.

[0047] (3) By using an additional micro-vibration excitation source, dual digitally controlled potentiometers, an ARM microprocessor system, and other electronic components, the envelope detector gain and comparator threshold are adjusted regularly to suppress the adverse effects caused by changes in environmental parameters, thereby reducing the false alarm probability or missed detection probability of the micro-vibration target detector.

[0048] (4) In order to reduce the power consumption of the vibration target detector, not only all electronic components use micro-power devices, but also the power supply of each functional module is controllable to facilitate energy scheduling and realize time-sharing work.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A microvibration target detector, characterized in that: include: A detector, an adaptive envelope detection circuit and an adaptive threshold adjustment circuit, wherein the detector is connected to the adaptive envelope detection circuit, and the adaptive envelope detection circuit is connected to the adaptive threshold adjustment circuit; The detector is used to collect micro-vibration signals and transmit the collected micro-vibration signals to the adaptive envelope detection circuit, which converts the higher-frequency micro-vibration signals into low-frequency envelope signals. The adaptive threshold adjustment circuit is used to adjust the reference thresholds under different environments according to the detection results to improve the accuracy of detection; The detector comprises: a seismic detector probe, a high-pass filter, a band-stop filter and a low-pass filter; The geophone probe is installed at the bottom of the WSN node housing to detect ground microvibration signals; the high-pass filter is used to filter the output signals at both ends of the geophone probe to isolate DC and suppress low-frequency interference signals; the band-stop filter is used to suppress AC interference, and the low-pass filter is used to suppress high-frequency signal interference; A bidirectional transient voltage suppression diode is connected in parallel between the two output terminals of the seismic detector and the ground line to protect the subsequent circuit; the first capacitors C11 and C12 and the first resistors R11 and R12 form two identical high-pass filters to filter the output signals at both ends of the seismic detector to isolate the direct current and suppress low-frequency interference signals; the resistor R13 and the precision instrument amplifier form the pre-amplifier circuit of the seismic detector, and its gain is determined by the resistance value of the resistor R13; The second resistors R21, R22, R23 and the second capacitors C21, C22, C23 form a double T-type 50Hz band-stop filter for suppressing AC interference; the voltage follower composed of a low-power operational amplifier serves as an impedance isolation buffer between the band-stop filter and the subsequent low-pass filter; the second-order Butterworth low-pass filter composed of an operational amplifier, resistors R24, R25 and capacitors C24, C25 is used to suppress high-frequency signal interference.

2. The microvibration target detector according to claim 1, characterized in that: The adaptive envelope detection circuit comprises: a DC blocking filter circuit, a first operational amplifier, a series resistor, two parallel resistors and a Schottky diode; The DC blocking filter circuit is connected to an operational amplifier, the operational amplifier is connected in series with a series resistor, two parallel resistors are connected in parallel with a capacitor, and the Schottky diode is connected between the two parallel circuits.

3. The microvibration target detector according to claim 1, characterized in that: The adaptive threshold adjustment circuit includes: a second operational amplifier, a same-direction amplifier circuit, a first-order low-pass filter and a comparison circuit; the comparison circuit includes: a comparator, a digitally controlled potentiometer and a resistor; The input end of the same-direction amplifier circuit is connected to the input end of the second operational amplifier, the output end of the same-direction amplifier circuit is connected to the output end of the second operational amplifier, the output end of the second operational amplifier is connected to a first-order low-pass filter, and the first-order low-pass filter is connected to the comparison circuit.

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