CN111189911A - Mine safety monitoring system design method based on surface acoustic wave sensor - Google Patents

Mine safety monitoring system design method based on surface acoustic wave sensor Download PDF

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CN111189911A
CN111189911A CN202010027284.9A CN202010027284A CN111189911A CN 111189911 A CN111189911 A CN 111189911A CN 202010027284 A CN202010027284 A CN 202010027284A CN 111189911 A CN111189911 A CN 111189911A
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CN111189911B (en
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张涛
郭宁
师晓云
姜峰
朱寒
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Xian University of Science and Technology
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Abstract

The invention discloses a design method of a mine safety monitoring system based on a surface acoustic wave sensor, which comprises the following steps: firstly, manufacturing a delay line type surface acoustic wave device containing a sensitive film; selecting proper parameters forming the oscillation generating circuit; thirdly, selecting proper parameters for forming the low-frequency signal conditioning circuit; fourthly, connecting the oscillation generating circuit with the low-frequency signal conditioning circuit; fifthly, connecting the sensor group with the FPGA main controller; and sixthly, collecting and processing sensor group data. The method has simple steps and reasonable design, and the designed mine safety monitoring system has low power consumption, improves the accurate monitoring of the environmental parameters such as the temperature, the humidity, the gas concentration and the like under the mine, is convenient for the mine environmental parameters to be accurately transmitted to a monitoring center, improves the mine environment detection accuracy, and takes corresponding measures such as early warning and the like, thereby avoiding the occurrence of safety accidents.

Description

Mine safety monitoring system design method based on surface acoustic wave sensor
Technical Field
The invention belongs to the technical field of mine safety monitoring, and particularly relates to a design method of a mine safety monitoring system based on a surface acoustic wave sensor.
Background
The method is characterized in that the method analyzes the reasons of occurrence of coal mine safety accidents in China, and the most important reasons are that environmental parameters such as underground temperature, humidity and gas concentration cannot be accurately monitored, the mine environmental parameters cannot be accurately sent to a monitoring center, and measures such as early warning cannot be performed on the mine environment, so that the occurrence of safety accidents is caused.
In addition, the surface acoustic wave sensor has the advantages of high sensitivity, easiness in integration, no wireless and the like, accords with the future development trend of the sensor, and is more and more appreciated and favored by engineers in the field of sensors. The sensing system based on the surface acoustic wave technology at present puts forward more severe requirements on a matching circuit of the surface acoustic wave sensor along with the improvement of the sensitivity of the surface acoustic wave sensor, however, the problems of low system stability, high power consumption and the like commonly existing in the sensing system based on the surface acoustic wave technology at present easily cause the faults of misinformation, failure and the like of the sensing system. Therefore, a design method of a mine safety monitoring system based on a surface acoustic wave sensor is absent at present, the design is reasonable, the designed mine safety monitoring system is low in power consumption, and high-stability sensing signals are generated.
Disclosure of Invention
The invention aims to solve the technical problem that the defects in the prior art are overcome, and provides a method for designing a mine safety monitoring system based on an acoustic surface wave sensor.
In order to solve the technical problems, the invention adopts the technical scheme that: a design method of a mine safety monitoring system based on a surface acoustic wave sensor is characterized by comprising the following steps:
step one, manufacturing a delay line type surface acoustic wave device comprising a sensitive film:
step 101, selecting a piezoelectric film layer, arranging an input interdigital transducer and an output interdigital transducer on the piezoelectric film layer, arranging a sensitive film layer between the input interdigital transducer and the output interdigital transducer, and attaching the bottom surface of the sensitive film layer to the surface of the piezoelectric film layer; the structure of the input interdigital transducer is the same as that of the output interdigital transducer, the input interdigital transducer and the output interdigital transducer are symmetrically distributed around the center of the piezoelectric film layer, and sound absorption glue is coated at two ends of the piezoelectric film layer;
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device containing a sensitive film; the first pin 1 of the delay line type surface acoustic wave device containing the sensitive film is a pin of the input interdigital transducer, the second pin 2 of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the input interdigital transducer, the fourth pin 4 of the delay line type surface acoustic wave device containing the sensitive film is an output pin of the output interdigital transducer, and the third pin 3 of the delay line type surface acoustic wave device containing the sensitive film is a grounding pin of the output interdigital transducer;
step two, selecting proper parameters for forming the oscillation generating circuit:
step 201, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be integrated into an operational amplifier INA-02186;
step 202, selecting a low-pass filter LFCN-1-2 and a low-pass filter LFCN-2-2 to be low-pass filters LFCN-255;
step 203, selecting the resistance values of a resistor R1-2, a resistor R2-2, a resistor R3-2, a resistor R4-2, a resistor R5-2 and a resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-2 to be 430 omega, and selecting the resistance values of a resistor R9-2 and a resistor R10-2 to be 62 omega;
204, selecting capacitors C1-2, C2-2 and C3-2 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-2, C5-2 and C6-2 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-2, C8-2, C9-2, C10-2, C11-2 and C12-2 to have capacitance values of 300 pF-330 pF;
step 205, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
step 206, connecting the 1 st pin of the delay line type surface acoustic wave device containing the sensitive film in the step 102 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to a +9V direct current power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the resistor R4-2 and one end of the capacitor C2-2 are connected with a +9V power supply, the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with a pin 4 of a delay line type surface acoustic wave device comprising a sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with a pin 1 of an integrated amplifier INA3-2, a pin 2 of the integrated amplifier INA3-2 is both grounded with a pin 4, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit, the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
selecting proper parameters for forming the low-frequency signal conditioning circuit:
301, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
step 302, according to
Figure BDA0002362926720000041
And
Figure BDA0002362926720000042
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
303, according to the formula
Figure BDA0002362926720000043
Obtaining the resistance value of the resistor R14;
304, selecting the resistance value of the resistor R5 to be 10-20 omega, the resistance value of the resistor R6 to be 175-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402-417 omega;
step 305, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
step 306, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of the resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of the attenuator circuit, and a connection end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 307, selecting the operational amplifier OPA354aid bv as a voltage follower U1;
step 308, select op amp OPA690ID as op amp U2;
step 309, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 3010, connect the output terminal of the attenuator circuit to the non-inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to the inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to one terminal of the resistor R5, connect the other terminal of the resistor R5 to one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connect the other terminal of the resistor R6 to the non-inverting input terminal of the operational amplifier U2, connect the inverting input terminal of the operational amplifier U2 to one terminal of the resistor R7 and one terminal of the resistor R8, connect the output terminal of the operational amplifier U2 to one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connect the other terminal of the resistor R9 to the base of the NPN transistor 2N3904, connect the emitter of the NPN transistor 2N3904 to ground, connect the collector of the NPN transistor 2N3904 to one terminal of the resistor R10 and the input terminal of, the other end of the resistor R10, the connection end of a positive power supply end of the voltage follower U1 and a positive power supply end of the operational amplifier U2 is connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of a negative power supply end of the voltage follower U1 and a negative power supply end of the operational amplifier U2 is connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmitt trigger is;
step four, connecting the oscillation generating circuit and the low-frequency signal conditioning circuit:
connecting the output end of the oscillation generating circuit in the step 206 with the input end of an attenuator circuit in the low-frequency signal conditioning circuit to complete the design of the methane concentration detection module;
connecting the sensor group with the FPGA main controller:
step 501, selecting a frequency divider 74HC390, connecting an output end of a low-frequency signal conditioning circuit with a 4 th pin of the frequency divider 74HC390, connecting a1 st pin of the frequency divider 74HC390 with a 10 th pin of the frequency divider 74HC390, connecting a2 nd pin of the frequency divider 74HC390 to ground, connecting a3 rd pin and a 15 th pin of the frequency divider 74HC390, connecting a6 th pin and a 12 th pin of the frequency divider 74HC390, connecting a 16 th pin of the frequency divider 74HC390 to a 5V dc power supply, connecting a 14 th pin of the frequency divider 74HC390 to ground, and connecting a 13 th pin of the frequency divider 74HC390 to an FPGA master;
step 502, connecting a surface wave temperature sensor and a surface acoustic wave humidity sensor with an FPGA main controller;
step six, acquisition and processing of sensor group data:
601, detecting the temperature in the mine according to preset sampling time by a surface wave temperature sensor, sending the detected temperature value to an FPGA main controller, detecting the humidity in the mine by a surface wave humidity sensor according to the preset sampling time, sending the detected humidity value to the FPGA main controller, detecting the methane concentration in the mine by a methane concentration detection module according to the preset sampling time, sending a detected methane concentration signal to the FPGA main controller, and carrying out ADC (analog-to-digital converter) conversion on the methane concentration signal by the FPGA main controller to obtain the methane concentration value; the FPGA main controller records a temperature value acquired at the kth sampling moment as T (k), records a humidity value acquired at the kth sampling moment as S (k), and records a methane concentration value acquired at the kth sampling moment as rho (k);
step 602, the FPGA master controller according to the formula
Figure BDA0002362926720000061
Obtaining a weighting coefficient W of a surface wave temperature sensor1(ii) a FPGA main controller according to formula
Figure BDA0002362926720000062
Obtaining weighting coefficient W of surface wave humidity sensor2(ii) a FPGA main controller according to formula
Figure BDA0002362926720000063
Obtaining the weighting coefficient W of the methane concentration detection module3(ii) a Wherein,
Figure BDA0002362926720000064
representing the variance of white noise superimposed on the temperature signal,
Figure BDA0002362926720000065
representing the variance of white noise superimposed on the humidity signal,
Figure BDA0002362926720000066
a variance representing white noise superimposed on the methane concentration signal;
step 603, the FPGA master controller performs control according to the Cr＝W1×T(k)+W2×S(k)+W3X rho (k) to obtain a fusion value C of the sensor groupr；
Step 604, the FPGA master controller combines the fusion value C of the sensor grouprComparing the first-stage early warning value with the second-stage early warning value, and obtaining a fusion value C of the sensor grouprWhen the early warning value is less than the second-level early warning value, the mine environment is safe; when the fusion value C of the sensor grouprWhen the alarm is larger than the second-stage early warning value and smaller than the first-stage early warning value, the mine environment is dangerous, and the FPGA main controller controls the alarm to give an alarm; when the fusion value C of the sensor grouprWhen the alarm is larger than the first-level early warning value, serious danger exists in the mine environment, and the FPGA main controller controls the alarm to continuously give an alarm.
The design method of the mine safety monitoring system based on the surface acoustic wave sensor is characterized by comprising the following steps: variance of white noise superimposed on the temperature signal in step 602
Figure BDA0002362926720000071
Variance of white noise superimposed on humidity signal
Figure BDA0002362926720000072
And the variance of white noise superimposed on the methane concentration signal
Figure BDA0002362926720000073
The specific acquisition process is as follows:
step A, selecting N surface wave temperature sensors to detect the temperature of the mine and sending the temperature to an FPGA main controller, wherein the FPGA main controller records the temperature value detected by the ith surface wave temperature sensor at the Kth sampling moment as Ti(K) The FPGA main controller records the temperature value detected by the jth surface wave temperature sensor at the Kth sampling moment as Tj(K) (ii) a Wherein i, j and N are positive integers, i is not equal to j, i is not more than 1 and not more than N, j is not less than 1 and not more than N, N is not less than 5, K and K ' are positive integers, K is not less than 1 and not more than K ', and K ' is the total number of samples;
step B, FPGA is based on the master controller
Figure BDA0002362926720000074
Obtaining correlation coefficients of an ith surface wave temperature sensor and a jth surface wave temperature sensor; FPGA master controller
Figure BDA0002362926720000075
Obtaining an autocorrelation coefficient of a jth surface wave temperature sensor;
step C, FPGA is based on the master controller
Figure BDA0002362926720000076
Obtained by superimposing on the temperature signalVariance of white noise of
Figure BDA0002362926720000077
D, setting N surface wave humidity sensors to detect the humidity of the mine according to the method from the step A to the step C to obtain the variance of white noise superposed on a humidity signal
Figure BDA0002362926720000078
E, setting N methane concentration detection modules to detect the methane concentration of the mine according to the method from the step A to the step C to obtain the variance of white noise superposed on a methane concentration signal
Figure BDA0002362926720000079
The design method of the mine safety monitoring system based on the surface acoustic wave sensor is characterized by comprising the following steps: the input interdigital transducer and the output interdigital transducer are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer and the output interdigital transducer are both 0.01 lambda, the widths of interdigital electrodes in the input interdigital transducer and the output interdigital transducer are 0.25 lambda, and the acoustic propagation distance between the input interdigital transducer and the output interdigital transducer is 300 lambda; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
The design method of the mine safety monitoring system based on the surface acoustic wave sensor is characterized by comprising the following steps: in the step 101, the sound absorption glue is epoxy resin glue, the thickness of the sound absorption glue is 0.1-0.8 mm, and the thickness of the piezoelectric film layer is 0.5-0.8 μm;
in the step 101, the sensitive thin film layer is a tin dioxide thin film layer, the thickness of the sensitive thin film layer is 100 nm-12 nm, gaps are formed between the distance between the two sides of the sensitive thin film layer and the distance between the input interdigital transducer and the output interdigital transducer, and the piezoelectric thin film layer is quartz.
The design method of the mine safety monitoring system based on the surface acoustic wave sensor is characterized by comprising the following steps: in the step 604, the value range of the primary early warning value is 4.17-7.09, and the value range of the secondary early warning value is 3.62-4.16.
Compared with the prior art, the invention has the following advantages:
1. the method of the invention has simple steps and reasonable design, the designed mine safety monitoring system has low power consumption, improves the accurate monitoring of the environmental parameters such as temperature, humidity, gas concentration and the like under the mine,
2. the invention adopts the delay line type surface acoustic wave delay line type device, and the delay line type SAW device usually has longer acoustic transmission distance, so that the SAW propagation characteristic analysis is convenient during sensing detection, and the SAW propagation characteristic is fully sensed to be detected, therefore, the high sensitivity and the wide frequency modulation range are provided, and the high accuracy and the high sensitivity of information sensing are ensured.
3. The third stage amplification structure in the oscillation generating circuit ensures that the gain of the amplifier is enough to compensate the loss of the frequency selection loop of the SAW broadband surface acoustic wave delay line type device, and the third stage amplification structure is used for isolating output, thereby reducing the influence of load traction on the loop output.
4. The attenuator circuit is arranged in the low-frequency signal conditioning circuit, and the amplitude of the output signal of the low-frequency signal conditioning circuit can be dynamically adjusted through the resistor R7, the resistor R8, the resistor R9 and the resistor R10, so that the problem of supersaturation of the input of a third-stage amplifier is solved, and the stability and reliability of system signal transmission are improved.
5. The low-frequency signal conditioning circuit is added with the voltage following circuit, so that the isolation of the front stage and the rear stage of the system circuit is increased, and the load capacity of the low-frequency signal conditioning circuit is further improved.
6. The oscillation generating circuit and the low-frequency signal conditioning circuit are both powered by a positive direct-current power supply and a negative direct-current power supply, and the use of unnecessary peripheral matching components is reduced by each module, so that the overall power consumption of the system is reduced.
7. The design method of the mine safety monitoring system based on the surface acoustic wave sensor is simple and convenient to operate and good in using effect, firstly, a delay line type SAW device containing a sensitive film is manufactured, and then appropriate parameters forming an oscillation generating circuit are selected; secondly, selecting proper parameters forming a low-frequency signal conditioning circuit, connecting the reference oscillation generating circuit, the oscillation generating circuit and the low-frequency signal conditioning circuit to complete the design of a methane concentration detection module, and carrying out sensor data fusion in the detection process of the methane concentration detection module, the surface wave temperature sensor and the surface acoustic wave humidity sensor on the methane concentration, the temperature and the humidity of a mine, and avoiding white noise interference superposed on the methane concentration signal, the temperature signal or the humidity signal.
In conclusion, the method has simple steps and reasonable design, and the designed mine safety monitoring system has low power consumption, improves the accurate monitoring of the environmental parameters such as the temperature, the humidity, the gas concentration and the like under the mine, is convenient for the mine environmental parameters to be accurately transmitted to the monitoring center, is convenient for the mine environmental detection to be accurate and give early warning, thereby avoiding the occurrence of safety accidents.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic view showing a structure of a delay line type SAW device including a sensitive film according to the present invention.
Fig. 3 is a schematic circuit diagram of the oscillation generating circuit of the present invention.
Fig. 4 is a schematic circuit diagram of a low frequency signal conditioning circuit according to the present invention.
Fig. 5 is a schematic circuit diagram of the frequency divider of the present invention.
FIG. 6 is a block flow diagram of a method of the present invention.
Description of reference numerals:
1-a piezoelectric thin film layer; 2-an input interdigital transducer; 3-an output interdigital transducer;
4-a sensitive film layer; and 5, sound absorption glue. 6-an oscillation generating circuit;
8, a low-frequency signal conditioning circuit; 9-surface acoustic wave temperature sensor; 10-a master controller;
12-a delayed line surface acoustic wave device comprising a sensitive film;
13-surface acoustic wave temperature sensor; 14-alarm.
Detailed Description
As shown in fig. 1 to 5, a method for designing a mine safety monitoring system based on a surface acoustic wave sensor includes the following steps:
step one, manufacturing a delay line type surface acoustic wave device comprising a sensitive film:
step 101, selecting a piezoelectric film layer 1, arranging an input interdigital transducer 2 and an output interdigital transducer 3 on the piezoelectric film layer 1, arranging a sensitive film layer 4 between the input interdigital transducer 2 and the output interdigital transducer 3, and attaching the bottom surface of the sensitive film layer 4 to the surface of the piezoelectric film layer 1; the structure of the input interdigital transducer 2 is the same as that of the output interdigital transducer 3, the input interdigital transducer 2 and the output interdigital transducer 3 are symmetrically distributed about the center of the piezoelectric film layer 1, and sound absorption glue 5 is coated on two ends of the piezoelectric film layer 1;
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device 12 containing a sensitive film; the 1 st pin of the delay line type surface acoustic wave device 12 containing the sensitive film is a pin of the input interdigital transducer 2, the 2 nd pin of the delay line type surface acoustic wave device 12 containing the sensitive film is a grounding pin of the input interdigital transducer 2, the 4 th pin of the delay line type surface acoustic wave device 12 containing the sensitive film is an output pin of the output interdigital transducer 3, and the 3 rd pin of the delay line type surface acoustic wave device 12 containing the sensitive film is a grounding pin of the output interdigital transducer 3;
step two, selecting proper parameters for forming the oscillation generating circuit:
step 201, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be integrated into an operational amplifier INA-02186;
step 202, selecting a low-pass filter LFCN-1-2 and a low-pass filter LFCN-2-2 to be low-pass filters LFCN-255;
step 203, selecting the resistance values of a resistor R1-2, a resistor R2-2, a resistor R3-2, a resistor R4-2, a resistor R5-2 and a resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-2 to be 430 omega, and selecting the resistance values of a resistor R9-2 and a resistor R10-2 to be 62 omega;
in this embodiment, it is further preferable that the resistance values of the resistor R1-2, the resistor R2-2, the resistor R3-2, the resistor R4-2, the resistor R5-2 and the resistor R6-2 are 100 Ω, and the resistance value of the resistor R7-2 is 270 Ω.
204, selecting capacitors C1-2, C2-2 and C3-2 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-2, C5-2 and C6-2 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-2, C8-2, C9-2, C10-2, C11-2 and C12-2 to have capacitance values of 300 pF-330 pF;
in the embodiment, it is further preferable that the capacitance values of the capacitor C1-2, the capacitor C2-2 and the capacitor C3-2 are 1 μ F, the capacitance values of the capacitor C4-2, the capacitor C5-2 and the capacitor C6-2 are 300pF, and the capacitance values of the capacitor C7-2, the capacitor C8-2, the capacitor C9-2, the capacitor C10-2, the capacitor C11-2 and the capacitor C12-2 are all 300 pF.
Step 205, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
in this embodiment, it is further preferable that the inductance values of the inductor L1-2, the inductor L2-2, and the inductor L3-2 be 120 nH.
Step 206, connecting the 1 st pin of the delay line type surface acoustic wave device 12 containing the sensitive film in the step 102 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to +9V DC power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the resistor R4-2 and one end of the capacitor C2-2 are connected with a +9V power supply, the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with the 4 th pin of the delay line type surface acoustic wave device 12 comprising the sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with the 1 st pin of an integrated amplifier INA3-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA3-2 are both grounded, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit 6, the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
selecting proper parameters for forming the low-frequency signal conditioning circuit:
301, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
in this embodiment, the resistance values of R4 and R10 are 1k Ω, R9 is 200 Ω, and R12 is 50 Ω.
Step 302, according to
Figure BDA0002362926720000131
And
Figure BDA0002362926720000132
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
in this embodiment, the attenuation amplitude of the attenuator circuit is designed to be 9.5dB, the input-output voltage ratio of the attenuator circuit is 2.9853, and the resistance values of the resistor R13 and the resistor R15 are 100.4 Ω, so that in order to purchase the resistor, the resistance values of the resistor R13 and the resistor R15 are selected to be 100 Ω in specific implementation.
303, according to the formula
Figure BDA0002362926720000133
Obtaining the resistance value of the resistor R14;
in this embodiment, when the resistance values of the resistor R13 and the resistor R15 are 100.4 Ω, the resistance value of the resistor R14 is 66.3 Ω, and therefore, in order to purchase the resistor, the resistance value of the resistor R14 is 68 Ω.
304, selecting the resistance value of the resistor R5 to be 10-20 omega, the resistance value of the resistor R6 to be 175-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402-417 omega;
in this embodiment, it is further preferable that the resistance value of the resistor R5 is 10 Ω, the resistance value of the resistor R6 is 175 Ω, and the resistance values of the resistors R7 and R8 are 402 Ω.
Step 305, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
in this embodiment, it is further preferable that the capacitance values of the capacitor C2, the capacitor C3, and the capacitor C6 be 0.1 μ F, and the capacitance values of the capacitor C4 and the capacitor C5 be 6.8 μ F.
Step 306, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of the resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of the attenuator circuit, and a connection end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 307, selecting the operational amplifier OPA354aid bv as a voltage follower U1;
step 308, select op amp OPA690ID as op amp U2;
step 309, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 3010, connect the output terminal of the attenuator circuit to the non-inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to the inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to one terminal of the resistor R5, connect the other terminal of the resistor R5 to one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connect the other terminal of the resistor R6 to the non-inverting input terminal of the operational amplifier U2, connect the inverting input terminal of the operational amplifier U2 to one terminal of the resistor R7 and one terminal of the resistor R8, connect the output terminal of the operational amplifier U2 to one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connect the other terminal of the resistor R9 to the base of the NPN transistor 2N3904, connect the emitter of the NPN transistor 2N3904 to ground, connect the collector of the NPN transistor 2N3904 to one terminal of the resistor R10 and the input terminal of, the other end of the resistor R10, the connection end of a positive power supply end of the voltage follower U1 and a positive power supply end of the operational amplifier U2 is connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of a negative power supply end of the voltage follower U1 and a negative power supply end of the operational amplifier U2 is connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmitt trigger is;
step four, connecting the oscillation generating circuit and the low-frequency signal conditioning circuit:
connecting the output end of the oscillation generating circuit 6 in the step 206 with the input end of the attenuator circuit in the low-frequency signal conditioning circuit 8 to complete the design of the methane concentration detection module;
connecting the sensor group with the FPGA main controller:
step 501, selecting a frequency divider as the frequency divider 74HC390, connecting the output end of the low-frequency signal conditioning circuit 8 with the 4 th pin of the frequency divider 74HC390, connecting the 1 st pin of the frequency divider 74HC390 with the 10 th pin of the frequency divider 74HC390, grounding the 2 nd pin of the frequency divider 74HC390, connecting the 3 rd pin and the 15 th pin of the frequency divider 74HC390, connecting the 6 th pin and the 12 th pin of the frequency divider 74HC390, connecting the 16 th pin of the frequency divider 74HC390 with a 5V dc power supply, grounding the 14 th pin of the frequency divider 74HC390, and connecting the 13 th pin of the frequency divider 74HC390 with the FPGA master 10;
step 502, connecting the surface wave temperature sensor 9 and the surface acoustic wave humidity sensor 13 with the FPGA master controller 10;
step six, acquisition and processing of sensor group data:
601, detecting the temperature in the mine by a surface wave temperature sensor 9 according to preset sampling time, sending the detected temperature value to an FPGA main controller 10, detecting the humidity in the mine by a surface wave humidity sensor 13 according to the preset sampling time, sending the detected humidity value to the FPGA main controller 10, detecting the methane concentration in the mine by a methane concentration detection module according to the preset sampling time, sending a detected methane concentration signal to the FPGA main controller 10, and carrying out ADC (analog to digital converter) conversion on the methane concentration signal by the FPGA main controller 10 to obtain a methane concentration value; the FPGA main controller 10 records a temperature value acquired at the kth sampling moment as T (k), the FPGA main controller 10 records a humidity value acquired at the kth sampling moment as S (k), and the FPGA main controller 10 records a methane concentration value acquired at the kth sampling moment as rho (k);
step 602, the FPGA master controller 10 according to the formula
Figure BDA0002362926720000151
Obtaining a weighting coefficient W of a surface wave temperature sensor1(ii) a The FPGA master controller 10 is according to the formula
Figure BDA0002362926720000152
Obtaining weighting coefficient W of surface wave humidity sensor2(ii) a The FPGA master controller 10 is according to the formula
Figure BDA0002362926720000153
Obtaining the weighting coefficient W of the methane concentration detection module3(ii) a Wherein,
Figure BDA0002362926720000154
representing the variance of white noise superimposed on the temperature signal,
Figure BDA0002362926720000155
representing the variance of white noise superimposed on the humidity signal,
Figure BDA0002362926720000156
a variance representing white noise superimposed on the methane concentration signal;
step 603, the FPGA master controller 10 performs control according to Cr＝W1×T(k)+W2×S(k)+W3X rho (k) to obtain a fusion value C of the sensor groupr；
Step 604, the FPGA master controller 10 combines the fusion value C of the sensor grouprComparing the first-stage early warning value with the second-stage early warning value, and obtaining a fusion value C of the sensor grouprWhen the early warning value is less than the second-level early warning value, the mine environment is safe; when the fusion value C of the sensor grouprWhen the alarm is larger than the second-stage early warning value and smaller than the first-stage early warning value, the mine environment is dangerous, and the FPGA main controller 10 controls the alarm 14 to give an alarm; when the fusion value C of the sensor grouprWhen the early warning value is greater than the first-level early warning value, serious danger exists in the mine environment, and the FPGA main controller 10 controls the alarm 14 to continuously give an alarm.
In this embodiment, the variance of white noise superimposed on the temperature signal in step 602
Figure BDA0002362926720000161
Variance of white noise superimposed on humidity signal
Figure BDA0002362926720000162
And the variance of white noise superimposed on the methane concentration signal
Figure BDA0002362926720000163
The specific acquisition process is as follows:
step A, selecting N surface wave temperature sensors to detect the temperature of the mine and sending the temperature to the FPGA main controller 10, wherein the FPGA main controller 10 records the temperature value detected by the ith surface wave temperature sensor at the Kth sampling moment as Ti(K) The FPGA master controller 10 records the temperature value detected by the jth surface wave temperature sensor at the kth sampling moment as Tj(K) (ii) a Wherein i, j and N are positive integers, i is not equal to j, i is not more than 1 and not more than N, j is not less than 1 and not more than N, N is not less than 5, K and K ' are positive integers, K is not less than 1 and not more than K ', and K ' is the total number of samples;
step B, FPGA master controller 10 according to
Figure BDA0002362926720000164
Obtaining correlation coefficients of an ith surface wave temperature sensor and a jth surface wave temperature sensor; FPGA master controller 10 according to
Figure BDA0002362926720000165
Obtaining an autocorrelation coefficient of a jth surface wave temperature sensor;
step C,FPGA master controller 10 according to
Figure BDA0002362926720000166
Obtaining the variance of white noise superimposed on the temperature signal
Figure BDA0002362926720000167
D, setting N surface wave humidity sensors to detect the humidity of the mine according to the method from the step A to the step C to obtain the variance of white noise superposed on a humidity signal
Figure BDA0002362926720000168
E, setting N methane concentration detection modules to detect the methane concentration of the mine according to the method from the step A to the step C to obtain the variance of white noise superposed on a methane concentration signal
Figure BDA0002362926720000169
In this embodiment, the input interdigital transducer 2 and the output interdigital transducer 3 are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer 2 and the output interdigital transducer 3 are both 0.01 λ, the widths of interdigital electrodes in the input interdigital transducer 2 and the output interdigital transducer 3 are 0.25 λ, and the acoustic propagation distance between the input interdigital transducer 2 and the output interdigital transducer 3 is 300 λ; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
In the embodiment, in the step 101, the sound absorption glue 5 is an epoxy resin glue, the thickness of the sound absorption glue 5 is 0.1mm to 0.8mm, and the thickness of the piezoelectric film layer 1 is 0.5 μm to 0.8 μm;
in the step 101, the sensitive thin film layer 4 is a tin dioxide thin film layer, the thickness of the sensitive thin film layer 4 is 100 nm-12 nm, gaps are formed between the distance between the two sides of the sensitive thin film layer 4 and the distance between the input interdigital transducer 2 and the output interdigital transducer 3, and the piezoelectric thin film layer 1 is quartz.
In this embodiment, the value range of the primary warning value in step 604 is 4.17 to 7.09, and the value range of the secondary warning value is 3.62 to 4.16.
In conclusion, the method has simple steps and reasonable design, the designed mine safety monitoring system has low power consumption, the methane concentration detection module, the surface wave temperature sensor and the surface acoustic wave humidity sensor perform sensor data fusion in the process of detecting the concentration, temperature and humidity of methane under a mine, white noise interference superposed on a methane concentration signal, a temperature signal or a humidity signal is avoided, accurate monitoring of environmental parameters such as temperature, humidity and methane gas concentration under the mine is improved, mine environmental parameters can be accurately transmitted to a monitoring center conveniently, the mine environment detection is accurate, early warning is made conveniently, and safety accidents are avoided.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (5)

1. A design method of a mine safety monitoring system based on a surface acoustic wave sensor is characterized by comprising the following steps:
step one, manufacturing a delay line type surface acoustic wave device comprising a sensitive film:
101, selecting a piezoelectric film layer (1), arranging an input interdigital transducer (2) and an output interdigital transducer (3) on the piezoelectric film layer (1), arranging a sensitive film layer (4) between the input interdigital transducer (2) and the output interdigital transducer (3), and attaching the bottom surface of the sensitive film layer (4) to the surface of the piezoelectric film layer (1); the structure of the input interdigital transducer (2) is the same as that of the output interdigital transducer (3), the input interdigital transducer (2) and the output interdigital transducer (3) are symmetrically distributed around the center of the piezoelectric film layer (1), and sound absorption glue (5) is coated on two ends of the piezoelectric film layer (1);
102, packaging the delay line type surface acoustic wave device obtained in the step 101 by adopting lead bonding equipment to obtain a delay line type surface acoustic wave device (12) containing a sensitive film; the 1 st pin of the delay line type surface acoustic wave device (12) containing the sensitive film is a pin of the input interdigital transducer (2), the 2 nd pin of the delay line type surface acoustic wave device (12) containing the sensitive film is a grounding pin of the input interdigital transducer (2), the 4 th pin of the delay line type surface acoustic wave device (12) containing the sensitive film is an output pin of the output interdigital transducer (3), and the 3 rd pin of the delay line type surface acoustic wave device (12) containing the sensitive film is a grounding pin of the output interdigital transducer (3);
step two, selecting proper parameters for forming the oscillation generating circuit:
step 201, selecting the integrated operational amplifier INA1-2, the integrated operational amplifier INA2-2 and the integrated operational amplifier INA3-2 to be integrated into an operational amplifier INA-02186;
step 202, selecting a low-pass filter LFCN-1-2 and a low-pass filter LFCN-2-2 to be low-pass filters LFCN-255;
step 203, selecting the resistance values of a resistor R1-2, a resistor R2-2, a resistor R3-2, a resistor R4-2, a resistor R5-2 and a resistor R6-2 to be 100 omega-110 omega, selecting the resistance value of a resistor R7-2 to be 270 omega-300 omega, selecting the resistance value of a resistor R8-2 to be 430 omega, and selecting the resistance values of a resistor R9-2 and a resistor R10-2 to be 62 omega;
204, selecting capacitors C1-2, C2-2 and C3-2 to have capacitance values of 1 muF-3 muF, selecting capacitors C4-2, C5-2 and C6-2 to have capacitance values of 300 pF-330 pF, selecting capacitors C7-2, C8-2, C9-2, C10-2, C11-2 and C12-2 to have capacitance values of 300 pF-330 pF;
step 205, selecting the inductance values of the inductor L1-2, the inductor L2-2 and the inductor L3-2 to be 120 nH-124 nH, and selecting the inductance values of the inductor L4-2, the inductor L5-2 and the inductor L6-2 to be 8.2 nH;
step 206, connecting the 1 st pin of the delay line type surface acoustic wave device (12) containing the sensitive film in the step 102 with one end of an inductor L4-2, connecting the other end of the inductor L4-2 with one end of a capacitor C7-2, connecting the other end of the capacitor C7-2 to an input pin of an integrated amplifier INA1-2, connecting the 2 nd pin and the 4 th pin of the integrated amplifier INA1-2 to ground, connecting the 3 rd pin of the integrated amplifier INA1-2 with one end of the inductor L1-2 and one end of the capacitor C8-2, connecting the other end of the inductor L1-2 with one end of the capacitor C4-2, one end of a resistor R1-2 and one end of a resistor R2-2, connecting the other end of the resistor R1-2, the other end of the resistor R2-2 and one end of the capacitor C1-2 to a +9V direct current power supply, the other end of the capacitor C4-2 and the other end of the capacitor C1-2 are both grounded; the other end of the capacitor C8-2 is connected with the 1 st pin of the low-pass filter LFCN-1-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-1-2 are grounded, the 3 rd pin of the low-pass filter LFCN-1-2 is connected with one end of the capacitor C9-2, one end of the capacitor C9-2 is connected with the 1 st pin of the integrated amplifier INA2-2, the 2 nd pin and the 4 th pin of the integrated amplifier INA2-2 are grounded, the 3 rd pin of the integrated amplifier INA2-2 is connected with one end of an inductor L2-2 and one end of a capacitor C10-2, the other end of the inductor L2-2 is connected with one end of a capacitor C5-2, one end of a resistor R3-2 and one end of a resistor R4-2, the other end of the resistor R3-2, the other end of the resistor R4-2 and one end of the capacitor C2-2 are connected with a +9V power supply, the other end of the capacitor C5-2 and the other end of the capacitor C2-2 are both grounded; the other end of the capacitor C10-2 is connected with one end of a resistor R7-2 and one end of an inductor L6-2, one end of the inductor L6-2 is connected with one end of an inductor L5-2, the other end of the inductor L5-2 is connected with a pin 4 of a delay line type surface acoustic wave device (12) comprising a sensitive film, the other end of the resistor R7-2 is connected with one end of a resistor R8-2 and one end of a resistor R9-2, the other end of the resistor R8-2 is connected with one end of a resistor R10-2 and one end of a capacitor C11-2, the other end of the resistor R9-2 and the other end of the resistor R10-2 are both grounded, the other end of the capacitor C11-2 is connected with a pin 1 of an integrated amplifier INA3-2, a pin 2 and a pin 4 of the integrated amplifier INA3-2 are both grounded, the 3 rd pin of the integrated amplifier INA3-2 is connected to one end of a capacitor C12-2 and one end of an inductor L3-2, the other end of the capacitor C12-2 is connected to pin 1 of the low pass filter LFCN-2-2, the 2 nd pin and the 4 th pin of the low-pass filter LFCN-2-2 are grounded, the 3 rd pin of the low-pass filter LFCN-2-2 is the output end of the oscillation generating circuit (6), the other end of one end of the inductor L3-2 is connected with one end of the capacitor C6-2, one end of the resistor R5-2 and one end of the resistor R6-2, the other end of the resistor R5-2, the other end of the resistor R6-2 and one end of the capacitor C3-2 are all connected with a +9V direct-current power supply, the other end of the capacitor C3-2 and the other end of the capacitor C6-2 are both grounded;
selecting proper parameters for forming the low-frequency signal conditioning circuit:
301, selecting the resistance values of the resistor R4 and the resistor R10 to be 1k omega-1.2 k omega, the resistance value of the resistor R9 to be 200 omega-220 omega, and the resistance value of the resistor R12 to be 50 omega-51 omega;
step 302, according to
Figure FDA0002362926710000031
And
Figure FDA0002362926710000032
obtaining resistance values of a resistor R13 and a resistor R15; wherein, VrRepresenting the input voltage, V, of the attenuator circuitoutRepresents the output voltage of the attenuator circuit, and N represents the input-to-output voltage ratio of the attenuator circuit;
303, according to the formula
Figure FDA0002362926710000033
Obtaining the resistance value of the resistor R14;
304, selecting the resistance value of the resistor R5 to be 10-20 omega, the resistance value of the resistor R6 to be 175-200 omega, and the resistance values of the resistor R7 and the resistor R8 to be 402-417 omega;
step 305, selecting the capacitance value of the capacitor C1 as 100pF, the capacitance values of the capacitor C2, the capacitor C3 and the capacitor C6 as 0.1 muF-1 muF, and the capacitance values of the capacitor C4 and the capacitor C5 as 6.8 muF-7.3 muF;
step 306, connecting one end of a resistor R12 with one end of a resistor R14 and one end of a resistor R13, connecting the other end of the resistor R14 with one end of a resistor R15, connecting the other end of the resistor R13 with the other end of a resistor R15, wherein the other end of the resistor R12 is an input end of the attenuator circuit, and a connection end of the other end of the resistor R14 with one end of a resistor R15 is an output end of the attenuator circuit;
step 307, selecting the operational amplifier OPA354aid bv as a voltage follower U1;
step 308, select op amp OPA690ID as op amp U2;
step 309, selecting the NPN type transistor as an NPN type transistor 2N3904, and selecting the Schmitt trigger as a 74LS14D Schmitt trigger;
step 3010, connect the output terminal of the attenuator circuit to the non-inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to the inverting input terminal of the voltage follower U1, connect the output terminal of the voltage follower U1 to one terminal of the resistor R5, connect the other terminal of the resistor R5 to one terminal of the capacitor C1, one terminal of the resistor R4 and one terminal of the resistor R6, connect the other terminal of the resistor R6 to the non-inverting input terminal of the operational amplifier U2, connect the inverting input terminal of the operational amplifier U2 to one terminal of the resistor R7 and one terminal of the resistor R8, connect the output terminal of the operational amplifier U2 to one terminal of the capacitor C3, the other terminal of the resistor R8 and one terminal of the resistor R9, connect the other terminal of the resistor R9 to the base of the NPN transistor 2N3904, connect the emitter of the NPN transistor 2N3904 to ground, connect the collector of the NPN transistor 2N3904 to one terminal of the resistor R10 and the input terminal of, the other end of the resistor R10, the connection end of a positive power supply end of the voltage follower U1 and a positive power supply end of the operational amplifier U2 is connected with a +5V direct-current power supply, one end of the capacitor C2 and one end of the capacitor C4, the other end of the capacitor C3, the connection end of a negative power supply end of the voltage follower U1 and a negative power supply end of the operational amplifier U2 is connected with a-5V direct-current power supply, one end of the capacitor C5 and one end of the capacitor C6, the other end of the capacitor C2, the other end of the capacitor C4, the other end of the capacitor C5 and the other end of the capacitor C6 are grounded, and the output end of the 74LS14D Schmitt trigger is;
step four, connecting the oscillation generating circuit and the low-frequency signal conditioning circuit:
connecting the output end of the oscillation generating circuit (6) in the step 206 with the input end of an attenuator circuit in the low-frequency signal conditioning circuit (8) to complete the design of the methane concentration detection module;
connecting the sensor group with the FPGA main controller:
step 501, selecting a frequency divider as the frequency divider 74HC390, connecting an output end of a low-frequency signal conditioning circuit (8) with a 4 th pin of the frequency divider 74HC390, connecting a1 st pin of the frequency divider 74HC390 with a 10 th pin of the frequency divider 74HC390, grounding a2 nd pin of the frequency divider 74HC390, connecting a3 rd pin and a 15 th pin of the frequency divider 74HC390, connecting a6 th pin and a 12 th pin of the frequency divider 74HC390, connecting a 16 th pin of the frequency divider 74HC390 with a 5V direct-current power supply, grounding a 14 th pin of the frequency divider 74HC390, and connecting a 13 th pin of the frequency divider 74HC390 with an FPGA master (10);
step 502, connecting a surface wave temperature sensor (9) and a surface acoustic wave humidity sensor (13) with an FPGA master controller (10);
step six, acquisition and processing of sensor group data:
601, a surface wave temperature sensor (9) detects the temperature in a mine according to preset sampling time, and sends the detected temperature value to an FPGA master controller (10), a surface wave humidity sensor (13) detects the humidity in the mine according to the preset sampling time and sends the detected humidity value to the FPGA master controller (10), a methane concentration detection module detects the methane concentration in the mine according to the preset sampling time and sends a detected methane concentration signal to the FPGA master controller (10), and the FPGA master controller (10) performs ADC (analog-to-digital converter) on the methane concentration signal to obtain a methane concentration value; the temperature value acquired at the kth sampling moment is recorded as T (k) by the FPGA main controller (10), the humidity value acquired at the kth sampling moment is recorded as S (k) by the FPGA main controller (10), and the methane concentration value acquired at the kth sampling moment is recorded as rho (k) by the FPGA main controller (10);
step 602, the FPGA master controller (10) according to a formula
Figure FDA0002362926710000051
Obtaining a weighting coefficient W of a surface wave temperature sensor1(ii) a FPGA main controller (10) according to the formula
Figure FDA0002362926710000052
Obtaining surface wave humidity sensorWeighting factor W of sensor2(ii) a FPGA main controller (10) according to the formula
Figure FDA0002362926710000053
Obtaining the weighting coefficient W of the methane concentration detection module3(ii) a Wherein,
Figure FDA0002362926710000054
representing the variance of white noise superimposed on the temperature signal,
Figure FDA0002362926710000055
representing the variance of white noise superimposed on the humidity signal,
Figure FDA0002362926710000061
a variance representing white noise superimposed on the methane concentration signal;
step 603, the FPGA master controller (10) performs control according to Cr＝W1×T(k)+W2×S(k)+W3X rho (k) to obtain a fusion value C of the sensor groupr；
Step 604, the FPGA master controller (10) enables the fusion value C of the sensor grouprComparing the first-stage early warning value with the second-stage early warning value, and obtaining a fusion value C of the sensor grouprWhen the early warning value is less than the second-level early warning value, the mine environment is safe; when the fusion value C of the sensor grouprWhen the alarm is larger than the second-stage early warning value and smaller than the first-stage early warning value, the mine environment is dangerous, and the FPGA main controller (10) controls the alarm (14) to give an alarm; when the fusion value C of the sensor grouprWhen the early warning value is larger than the first-level early warning value, serious danger exists in the mine environment, and the FPGA main controller (10) controls the alarm (14) to continuously alarm.
2. The design method of the mine safety monitoring system based on the surface acoustic wave sensor, as claimed in claim 1, is characterized in that: variance of white noise superimposed on the temperature signal in step 602
Figure FDA0002362926710000062
Superposed on wetVariance of white noise on the noise signal
Figure FDA0002362926710000063
And the variance of white noise superimposed on the methane concentration signal
Figure FDA0002362926710000064
The specific acquisition process is as follows:
a, selecting N surface wave temperature sensors to detect the temperature of the mine and sending the temperature to an FPGA main controller (10), wherein the FPGA main controller (10) records the temperature value detected by the ith surface wave temperature sensor at the Kth sampling moment as Ti(K) The FPGA main controller (10) records the temperature value detected by the jth surface wave temperature sensor at the Kth sampling moment as Tj(K) (ii) a Wherein i, j and N are positive integers, i is not equal to j, i is not more than 1 and not more than N, j is not less than 1 and not more than N, N is not less than 5, K and K ' are positive integers, K is not less than 1 and not more than K ', and K ' is the total number of samples;
step B, FPGA the master controller (10) according to
Figure FDA0002362926710000065
Obtaining correlation coefficients of an ith surface wave temperature sensor and a jth surface wave temperature sensor; FPGA master controller (10) according to
Figure FDA0002362926710000066
Obtaining an autocorrelation coefficient of a jth surface wave temperature sensor;
step C, FPGA the master controller (10) according to
Figure FDA0002362926710000067
Obtaining the variance of white noise superimposed on the temperature signal
Figure FDA0002362926710000068
D, setting N surface wave humidity sensors to detect the humidity of the mine according to the method from the step A to the step C to obtain a method of white noise superposed on a humidity signalDifference (D)
Figure FDA0002362926710000071
E, setting N methane concentration detection modules to detect the methane concentration of the mine according to the method from the step A to the step C to obtain the variance of white noise superposed on a methane concentration signal
Figure FDA0002362926710000072
3. The design method of the mine safety monitoring system based on the surface acoustic wave sensor, as claimed in claim 1, is characterized in that: the input interdigital transducer (2) and the output interdigital transducer (3) are made of Al, Pt, Au or Mo, the thicknesses of the input interdigital transducer (2) and the output interdigital transducer (3) are both 0.01 lambda, the widths of interdigital electrodes in the input interdigital transducer (2) and the output interdigital transducer (3) are 0.25 lambda, and the acoustic propagation distance between the input interdigital transducer (2) and the output interdigital transducer (3) is 300 lambda; wherein, lambda represents the wavelength of the surface acoustic wave, and the value range of the wavelength lambda of the surface acoustic wave is 4nm to 4000 nm.
4. The design method of the mine safety monitoring system based on the surface acoustic wave sensor, as claimed in claim 1, is characterized in that: in the step 101, the sound absorption glue (5) is epoxy resin glue, the thickness of the sound absorption glue (5) is 0.1-0.8 mm, and the thickness of the piezoelectric film layer (1) is 0.5-0.8 μm;
in the step 101, the sensitive thin film layer (4) is a tin dioxide thin film layer, the thickness of the sensitive thin film layer (4) is 100 nm-12 nm, gaps are formed between the two sides of the sensitive thin film layer (4) and the distance between the input interdigital transducer (2) and the output interdigital transducer (3), and the piezoelectric thin film layer (1) is quartz.
5. The design method of the mine safety monitoring system based on the surface acoustic wave sensor, as claimed in claim 1, is characterized in that: in the step 604, the value range of the primary early warning value is 4.17-7.09, and the value range of the secondary early warning value is 3.62-4.16.
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