RU2438186C1 - Alarm system signalling maximal concentration of methane in atmosphere - Google Patents

Abstract

FIELD: machine building. ^ SUBSTANCE: system consists of warning device and reader, of identification marks, or re-transmitters and of control room. The warning device consists of bridge measuring circuit, of an analogue switchboard, of an amplifier of direct current, of an accumulator battery, of an arithmetic and logical unit, of an analogue-digital converter, of a digital-analogue converter, of a memory device, of an indicator of a threshold level and of a key. The reader includes a master generator, a duplexer, a receiving-transmitting aerial, the first and second power amplifiers, a phase detector, a line of delay, a generator of pseudo-random sequence, a summator, a multiplier, a narrow-band filter and a phase manipulator. Each identification mark contains piezo-crystal, a micro-band aerial, electrodes, bus bars, and a set of reflectors. The control room contains a receiving aerial, an amplifier of high frequency, a search unit, a heterodyne, a mixer, an amplifier of intermediate frequency, a phase doubler, analysers and spectres, a comparison unit, a threshold unit, a delay line of key, a narrow-band filter and a divider of phase in two, a phase detector and a recording unit. ^ EFFECT: operative transmitting of information to control room for increased safety of miners. ^ 4 dwg

Description

The proposed system relates to means for controlling the mine atmosphere, and in particular to systems and devices that signal the achievement of the maximum permissible concentration of methane in the atmosphere.

Known alarm systems and devices for the degree of explosiveness of the gas-air mixture (ed. Certificate of the USSR No. 978171, 1500797, 1744625; RF patents No. 2056531, 2091781, 2094794, 2096776, 2130178, 2131601, 2161823, 2171468; US patents No. 4028057, 4134818, 4193069, 4476096, 5104513; UK patents Nos. 1378291, 2288873; Karpov E.F. et al. Automatic gas protection and control of the mine atmosphere. - M .: Nedra, 1984, pp. 101-109 and others).

Of the known systems and devices, the closest to the proposed system is the "Methane Detector" (RF patent No. 2131601, G01N 27/16, 1998), which is selected as the base object.

The known methane detector comprises a bridge measuring circuit, a DC amplifier, an analog-to-digital converter, an arithmetic logic device, a storage device and a battery.

The known device generates a warning signal about an emergency and explosive situation when reaching the maximum permissible concentration of methane in the atmosphere, but does not provide alarm information to the control center for taking appropriate measures, which reduces the safety of miners.

An object of the invention is to increase the safety of miners by quickly transmitting alarming information to a control room to take appropriate measures.

The problem is solved in that the alarm system about reaching the maximum permissible concentration of methane in the atmosphere, including, in accordance with the closest analogue, a methane detector containing a series-connected bridge circuit, two arms of which include active thermocatalytic and compensation elements of the methane sensor, an analog switch, the second input of which is connected to the output of the battery, and the third to the third output of the arithmetic-logic device, an analog-to-digital converter, and a rhyme-logic device, the second input of which is connected via a storage device to its second output, and a threshold indicator of methane, while a digital-to-analog converter and a DC amplifier are connected to the fourth output of the arithmetic-logic device, the output of which is connected to the input of the bridge measuring circuit and with the fourth input of the analog switch, differs from the nearest analogue in that it is equipped with a key, a reader, identification tags installed with a corresponding step on the ceiling of the drift, repeaters installed in the drift at a distance of direct radio visibility from each other, and a control room, and the output of the battery through a key, the second input of which is connected to the first output of the arithmetic-logic device, is connected to the reader, which is made in the form serially connected master oscillator, duplexer, the input-output of which is connected to the transceiver antenna, the first power amplifier, phase detector, the second input of which is connected to the output house of the master oscillator, delay line, adder, the second input of which is connected to the output of the pseudo-random sequence generator, phase manipulator and the second power amplifier, the output of which is connected to the second input of the duplexer, a multiplier is connected to the output of the master oscillator, the second input of which is connected to the output of the master oscillator , and a narrow-band filter, the output of which is connected to the second input of the phase manipulator, the methane detector and the reader are placed on a moving object with In order to move along the drift, each identification mark is made in the form of a piezocrystal with an aluminum thin-film interdigital transducer deposited on its surface connected to a microstrip antenna and a set of reflectors, an interdigital transducer contains two comb electrode systems, the electrodes of each of the combs are connected to each other another bus connected with a microstrip antenna, the control room is made in the form of series-connected receiving antenna, high-frequency amplifier you, a mixer, the second input of which is connected through the local oscillator to the output of the search unit, the intermediate frequency amplifier, the phase doubler, the second spectrum analyzer, the comparison unit, the second input of which is connected through the first spectrum analyzer to the output of the intermediate frequency amplifier, the threshold block, the second input of which the delay line is connected to its output, a key, the second input of which is connected to the output of the intermediate frequency amplifier, phase detector and registration unit, are connected to the output of the phase doubler in series the first narrow-band filter, the phase divider into two and the second narrow-band filter, the output of which is connected to the second input of the phase detector, the control input of the search unit is connected to the output of the threshold block, one of the relays and the control room are installed at the output and entrance to the mine, respectively.

A schematic illustration of one of the mine drifts is shown in Fig. 1, where the following notation is introduced: 26 - mine drift, 27 - shaft passage (pit), 23 - movable object, 24.i - identification marks placed on the drift ceiling, 25. j - repeaters installed in the drift 26 at a distance of direct radio visibility from each other. At the entrance and exit of the mine, control room 32 and 25.m are installed on the repeater (i = 1, 2, ..., n, j = 1, 2, ..., m).

The structural diagram of a methane detector 23.1 and a reader 23.2 mounted on a movable object 23, is presented in figure 2. The functional diagram of the identification tag is shown in Fig.3. The structural diagram of the control room is presented in figure 4.

The methane detector 23.1 contains a series-connected bridge measuring circuit 1, two arms of which include active thermocatalytic and compensation elements of a methane sensor, an analog switch 2, the second input of which is connected to the output of the battery 4, and the third to the third output of the arithmetic-logic device 5, analog-to-digital Converter 6, arithmetic-logic device 5, the second input of which is connected via its storage device 8 to its second output, indicator 9 of the methane threshold level, etc. this is connected to the fourth output of the arithmetic-logic device 5 digital-to-analog Converter 7 and a DC amplifier 3, the output of which is connected to the input of the bridge measurement circuit 1 and to the fourth input of the analog switch 2. The output of the battery 4 through the key 10, the second input of which is connected to the first output of the arithmetic-logic device 5 is connected to a reader 23.2, which is made in the form of series-connected master oscillator 11, duplexer 12, the input-output of which is connected to a transmitting antenna 13, a first power amplifier 14, a phase detector 15, the second input of which is connected to the output of the master oscillator 11, the delay line 16, the adder 18, the second input of which is connected to the output of the pseudo-random sequence generator 17, the phase manipulator 21 and the second power amplifier 22, the output of which is connected to the second input of the duplexer 12. A multiplier 19 is connected to the output of the master oscillator 11, the second input of which is connected to the output of the master oscillator 11, and the narrow-band filter 20, you the course of which is connected to the second input of the phase manipulator 21.

The methane detector 23.1 and the reader 23.2 are located on the movable object 23.

The identification mark 24.i (i = 1, 2, ..., n) is made in the form of a piezocrystal 25.i with an aluminum thin-film interdigital transducer (IDT) deposited on its surface connected to a microstrip antenna 26.i and a set of reflectors 30. i. The IDT of surface acoustic waves (SAW) contains two comb systems of electrodes 27.i, buses 28.i and 29.i, which connect the electrodes of each of the combs to each other. Tires 28.i and 29.i, in turn, are connected to the microstrip antenna 26.i.

The control room 32 is made in the form of a series-connected receiving antenna 31, a high-frequency amplifier 33, a mixer 36, the second input of which is connected through the local oscillator 35 to the output of the search unit 34, an intermediate frequency amplifier 37, a phase doubler 40, a second spectrum analyzer 41, and a comparison unit 42 the second input of which is connected through the first spectrum analyzer 39 to the output of the intermediate frequency amplifier 37, of the threshold unit 43, the second input of which is connected through its delay line 44 to its output, a key 45, the second input of which is connected to the output house 37 an intermediate frequency amplifier, a phase detector 49 and register unit 50. The output of the phase doubler 40 is connected in series with the first narrow-band filter 46, the phase divider 47 into two and the second narrow-band filter 48, the output of which is connected to the second input of the phase detector 49. Spectrum analyzers 39 and 41, phase doubler 39, comparison unit 42, threshold block 43 and a delay line 44 form a detector (selector) 38 PSK signals. The control room 32 is installed at the entrance to the mine. And one of the repeaters, for example 25.m, is at the exit of the mine (drift).

The proposed system works as follows.

A plan of mine drifts is drawn up, distances according to this plan between identification marks 24.i (i = 1, 2, ..., n), which should serve as coordinate marks, are measured and placed with the appropriate step on the ceiling of the drift (Fig. 1). The methane detector 23.1 and the reader 23.1 are placed on a movable object 23, which has the ability to move along the mine drift. As a moving object, a trolley, trolley, robot, etc. can be used. In the drift 26 of the mine are also located repeaters 25.j (j = 1, 2, ..., m) at a distance of direct radio visibility from each other.

After turning on the supply voltage, the operating voltage is set on the bridge measuring circuit 1. For this, using the arithmetic logic device 5, a code corresponding to its minimum output voltage is set on the digital-analog converter 7. Then, through the analog switch 2, the voltage from the output of the DC amplifier 3 is supplied to the input of the analog-to-digital converter 6. If the voltage at the input of the bridge measuring circuit 1 is lower than the nominal value, then the voltage is increased using the digital-to-analog converter 7. This is continued until the voltage at the input of the bridge measuring circuit 1 reaches the nominal (operating) value. This method of setting the operating voltage of the bridge measuring circuit 1 made it possible to exclude sources of reference voltage and control elements.

When methane appears in the analyzed gas mixture, its catalytic oxidation occurs on the surface of the working sensitive element, which leads to an increase in temperature and an increase in the resistance of the sensitive element. In this case, an unbalance signal appears in the bridge measuring circuit 1, the value of which is proportional to the methane content in the analyzed air. The signal from the output of the bridge measurement circuit 1 through the analog switch 2 is fed to the input of the analog-to-digital converter 6. The signal value measured from the output of the bridge measurement circuit 1 is compared with the signal value corresponding to the alarm threshold that is in memory 8 (obtained at calibration of the detector). If the signal from the bridge measuring circuit 1 exceeds the signal value corresponding to the threshold level of methane, then the arithmetic logic device 5 gives a warning signal to the indicator 9 of the threshold level.

The same signal is fed to the control input of key 10, opening it. In the initial state, the key 10 is always closed. In this case, the supply voltage of the battery 4 through the public key 10 is supplied to the reader 23.2.

At the same time, the high-frequency oscillation is formed by the master oscillator 11 of the reader 23.2

u ₁ (t) = U ₁ · Cos (w ₁ t + φ ₁ ), 0≤t≤T ₁ ,

which through the duplexer 12 enters the antenna 13, it is radiated by it and irradiates the nearest identification mark 24.i (i = 1, 2, ..., n). A high-frequency harmonic oscillation u ₁ (t) at a frequency w _{1 is} captured by a microstrip antenna 26.i tuned to a frequency w ₁ is converted by an interdigital transducer into an acoustic wave that propagates along the surface of a piezocrystal 25.i and is reflected from a set of reflectors 30.i and again converted into a complex signal with phase shift keying (PSK)

u ₂ (t) = U ₂ · Cos [w ₁ t + (φ _к1 (t) + φ ₁ ], 0≤t≤T ₁ ,

where φ _к1 (t) = {0, π} is the manipulated component of the phase, which displays the law of phase manipulation in accordance with the modulating code M ₁ (t), which displays the coordinates of the identification label, and φ _к1 (t) = const for Kτ _Э <t <(k + 1) τ _e and can change abruptly at t = Кτ _e , i.e. at the borders between elementary premises (K = 1, 2, ..., N-1);

τ _e , N - the duration and number of chips that make up the signal of duration T ₁ (T ₁ = N · τ _e ).

In this case, the internal structure of the formed complex QPSK signal is determined by the topology of the interdigital transducer, has an individual character and contains information about the location of the identification mark on the ceiling of the drift. As an example, figure 3 shows a code fragment M ₁ (t).

The generated complex QPSK signal is emitted by the microstrip antenna 26. i is transmitted to the antenna by the transceiver antenna 13 and fed through the duplexer 12 and the power amplifier 14 to the first (information) input of the phase detector 15, the high-frequency oscillation u ₁ ( t) from the output of the master oscillator 11 as a reference voltage. The output of the phase detector 15 produces a low-frequency voltage

u _н1 (t) = U _н1 · _{Cosφ к1} (t), 0≤t≤T ₁ ,

where U _н1 = ½U ₁ · U ₂ ;

proportional to the modulating code M ₁ (t).

This voltage is supplied to the input of the delay line 16, where it is delayed by a time τ ₃ equal to the duration τ _{1 of the} modulating code M ₁ (t), and supplied to the first input of the adder 18. The code M ₂ (t) of the moving object 23 is supplied to the second input of the last (trolley, trolley, robot, etc.) from the output of the generator 17 of a pseudo-random sequence (PSP) of duration τ ₂ . The output of the adder 18 is formed by the total modulating code M _∑ (t) = M ₁ (t) + M ₂ (t), duration τ = τ ₁ + τ ₂ . The modulating sum code M ₁ (t) is supplied to the first input of the phase manipulator 21.

High-frequency oscillation u ₁ (t) from the output of the master oscillator 11 simultaneously arrives at two inputs of the multiplier 19, the output of which is generated

u ₃ (t) = U ₃ · Cos (w ₂ t + φ ₂ ), 0≤t≤T ₁ ,

where U ₃ = ½U ₁ ² ;

w ₂ = 2w ₁ ; φ ₂ = 2φ ₁ .

This voltage is supplied to the second input of the phase manipulator 21, at the output of which a complex PSK signal is formed

u ₄ (t) = U ₄ · Cos [w ₂ t + φ _к2 (t) + φ ₂ ], 0≤t≤T ₁ ,

which through the power amplifier 22 and the duplexer 12 enters the transceiver antenna 13, is transmitted by it to the air, sequentially re-transmitted by the relays 25.j (j = 1, 2, ..., m), is caught by the receiving antenna 31 of the control room 32, installed on the Earth’s surface, in the immediate vicinity of the mine entrance, and through the high-frequency amplifier 33, it enters the first input of the mixer 36, the second input of which supplies the voltage of the local oscillator 35 of the ramp frequency

u _g (t) = U _g Cos (w _g t + πγt ² + φ _g ), 0≤t≤T _p ,

- скорость изменения частоты гетеродина;Where

- rate of change of the local oscillator frequency;

T _p - the period of perestroika.

It should be noted that viewing a given range with a frequency of D _{f is} carried out using the search unit 34, which periodically with a period T _p, according to the sawtooth law, tunes the frequency of the local oscillator 35.

At the output of the mixer 36, voltages of combination frequencies are generated. The amplifier 37 allocates an intermediate frequency voltage

u _up (t) = U _up · Cos [w _up t + φ _к2 (t) -πγt ² + φ _up ], 0≤t≤T ₁ ,

where U _up = ½U ₄ · U _g ;

w _up = w _c -w _g is the intermediate frequency;

φ _uр = φ _с -φ _g ,

which is a complex signal with combined phase shift keying and linear frequency modulation (QPSK-LFM).

The voltage u _up (t) from the output of the intermediate frequency amplifier 37 is supplied to the input of the detector 38, consisting of a phase doubler 40, spectrum analyzers 39 and 41, a comparison unit 42, a threshold block 43, and a delay line 44.

A voltage is generated at the output of the phase doubler 39

u ₅ (t) = U ₅ Cos (2w _up t-2πγt ² + 2φ _up ), 0≤t≤T ₁ ,

where U ₅ = ½U _for ² ,

in which phase manipulation is already absent.

The spectrum width Δf _{2 of the} second harmonic of the signal is determined by the duration T _{1 of the} signal

,

,

whereas the width of the spectrum of the input QPSK signal is determined by the duration of its elementary premises

,

,

those. the spectrum width of the second harmonic of the signal is N times smaller than the spectrum width of the input signal

.

.

Therefore, when the phase of the QPSK signal is doubled by two, its spectral width “folds” N times. This circumstance makes it possible to detect and select the QPSK signal even when its power at the receiver input is less than the power of noise and interference.

The width of the spectrum Δf _{c of the} input QPSK signal is measured using the spectrum analyzer 39, and the spectrum width Δf _{2 of the} second harmonic of the signal is measured using the spectrum analyzer 41. Voltages U _I and U _II proportional to Δf _c and Δf _2, respectively, from the outputs of the analyzers 39 and 41 of the spectrum are supplied to the two inputs of the comparison unit 42. Since U _I >> U _II , a positive voltage is generated at the output of the comparison unit 42, which exceeds the threshold level U of the _pores in the threshold block 43. The threshold voltage U _pop is selected so that it is exceeded by random noise. When the threshold level U _p is exceeded, a constant voltage is generated in the threshold block 43, which is supplied to the control input of the key 45, opening it. In the initial state, the key 45 is always closed. A constant voltage from the output of the threshold block 43 is simultaneously supplied to the control input of the search block 34, stopping it, and to the input of the delay line 44. Upon termination of the tuning of the local oscillator 35 by the amplifier 37, the following voltage is released

U _up1 (t) = U _up · Cos [w _up t + φ _к2 (t) + φ _up ], 0≤t≤T ₁ ,

which through the public key 45 enters the first input of the phase detector 49. At the output of the phase doubler 40 in this case, the following voltage is generated

u ₆ (t) = U ₅ Cos (2w _up t + 2φ _up ), 0≤t≤T ₁ ,

which is allocated by a narrow-band filter 46 and fed to the input of the phase divider 47 into two, at the output of which a voltage is generated

u ₇ (t) = U ₅ · Cos (w _up t + φ _up ), 0≤t≤T ₁ ,

which is allocated by a narrow-band filter 48 and fed to the second (reference) input of the phase detector 49. A low-frequency voltage is generated at the output of the phase detector 49

u _n2 (t) = U _n2 ; Cosφ _k2 (t),

where U _Н2 = ½U _up · U ₅ ,

proportional to the total modulating code M _∑ (t). This voltage is detected by the registration unit 50. The delay time τ _{3 of} the delay line 44 is selected so that it is possible to select and fix the detected PSK signal.

At the end of this time, the voltage from the output of the threshold block 43 is supplied to the reset input and resets its contents to zero. In this case, the key 45 is closed, and the search unit 34 is turned on, i.e. they return to their original state.

When the next QPSK signal is detected at a different frequency, for example, from a different drift, the operation of the control room 32 occurs in a similar way.

Thus, the proposed system in comparison with the prototype and other technical solutions provides increased safety for miners. This is achieved by promptly transmitting alarming information to the control room for appropriate action. For this, complex phase-shift signals, moving objects, identification tags and repeaters are used.

The main feature of identification SAW tags are small dimensions, long service life and lack of power sources.

Complex QPSK signals have energetic and structural secrecy.

The energy secrecy of the FMN signals is due to their high compressibility in time and spectrum with optimal processing, which reduces the instantaneous radiated power. As a result of this, a complex QPSK signal at the receiving point may be masked by noise and interference. Moreover, the energy of the QPSK signal is by no means small, it is simply distributed over the time-frequency domain so that at each point in this region the signal power is less than the power of noise and interference.

The structural secrecy of complex QPSK signals is caused by a wide variety of their forms and significant ranges of parameter values, which makes it difficult to optimize or at least quasi-optimal processing of complex QPSK signals of an a priori unknown structure in order to increase the sensitivity of the receiving device.

Complex QPSK signals offer great opportunities in the technique of transmitting messages from mine drifts to a control room. They allow the use of structural selection. This means that it becomes possible to separate signals operating in the same frequency band and at the same time intervals.

Claims (1)

An alarm system about the achievement of the maximum permissible concentration of methane in the atmosphere, including a methane detector containing a series-connected bridge circuit, two arms of which include active thermocatalytic and compensation elements of a methane sensor, an analog switch, the second input of which is connected to the output of the battery, and the third - with the third output of the arithmetic-logic device, an analog-to-digital converter, the arithmetic-logical device, the second input of which through the memory the device is connected to its second output, and a methane threshold level indicator, while a digital-to-analog converter and a DC amplifier are connected to the fourth output of the arithmetic-logic device, the output of which is connected to the input of the bridge measuring circuit and to the fourth input of the analog switch, characterized in that it is equipped with a key, a reader, identification tags installed with the appropriate pitch on the ceiling of the drift, repeaters installed in the drift at a distance and direct radio visibility from each other, and the control room, and the output of the battery through the key, the second input of which is connected to the first output of the arithmetic-logic device, is connected to a reader, which is made in the form of series-connected master oscillator, duplexer, the input-output of which is connected with a transceiver antenna, a first power amplifier, a phase detector, the second input of which is connected to the output of the master oscillator, a delay line, an adder, the second input of which is connected to the output of a pseudo-random sequence generator, a phase manipulator and a second power amplifier, the output of which is connected to the second input of the duplexer, a multiplier is connected to the output of the master oscillator, the second input of which is connected to the output of the master oscillator, and a narrow-band filter, the output of which is connected to the second input of the phase manipulator, the signaling device methane and a reader are placed on a moving object with the ability to move along the drift, each identification mark is made in the form of a piezocrystal and with an aluminum thin-film interdigital transducer deposited on its surface connected to a microstrip antenna and a set of reflectors, the interdigital transducer contains two comb electrode systems, the electrodes of each of the combs are connected to each other by buses connected to the microstrip antenna, the control room is made in the form of series-connected receiving antenna, high-frequency amplifier, mixer, the second input of which is connected through the local oscillator to the output of the search unit, amplifier intermediate frequency, phase doubler, second spectrum analyzer, comparison unit, the second input of which through the first spectrum analyzer is connected to the output of the intermediate frequency amplifier, a threshold unit, the second input of which is connected via its delay line to its output, a key, the second input of which is connected to the amplifier output the intermediate frequency, phase detector and recording unit, the first narrow-band filter, the phase divider into two and the second narrow-band filter, the output of which with one with a second input of the phase detector, the control input of the search block is connected to the output of the threshold unit, one of the repeaters and control station installed at the shaft output and input respectively.

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