Array type ultrasonic belt conveying coal flow intelligent measuring method

Abstract

The invention discloses an array type ultrasonic belt conveying coal flow intelligent measurement method, which comprises the following steps of: performing non-contact measurement on a coal flow speed on a belt by utilizing an ultrasonic transducer and adopting an ultrasonic pulse Doppler method to obtain the coal flow speed; the instantaneous coal flow thickness is measured by adopting an ultrasonic distance measurement principle, and the instantaneous and accumulated flow of the coal flow is given through calculation and correction; the coal shape and density are corrected in real time by utilizing artificial intelligence and machine learning technologies and a multi-modal mixed model architecture, so that the problems of poor stability, low precision, short service life, frequent calibration for ensuring the precision and the like of traditional material conveying dynamic metering equipment are effectively solved. The instantaneous coal flow of the coal conveying belt can be accurately measured in real time, and the system has the advantages of being intelligent, accurate in measured data and the like.

Description

Technical Field

[0001] The invention belongs to the field of measurement, and mainly relates to a method for intelligently measuring the flow rate of coal (or other materials) conveyed by a belt using array ultrasonic waves. Background Art

[0002] Belt conveyor is the main method of material transportation in coal mining, electric power, metallurgy, chemical industry and other industries. At present, the measurement of coal flow in belt conveyor is mostly done by piezoelectric belt scale, and there are also nuclear scale, laser scale and other methods. However, the piezoelectric belt scale has the problems of large drift, low precision, frequent calibration and complex installation in measuring coal flow. Nuclear scale has problems such as high radiation, high management responsibility and high cost. Laser scale is greatly affected by environmental factors such as humidity, dust, light, etc., high cost and large precision error, which affect its application. Array ultrasonic belt conveyor coal flow intelligent measurement equipment is a non-contact measurement, easy to install, not affected by light, humidity, dust and other environmental factors, and has broad application prospects. Summary of the invention

[0003] The purpose of the present invention is to provide an array-type ultrasonic belt conveyor coal flow intelligent measurement method. Through the array distribution of transducers, the measurement points can cover the belt cross section. Through the use of artificial intelligence and machine learning technology, the errors caused by density and shape can be effectively solved, and the coal flow measurement accuracy can be improved. It has good stability, high dynamic measurement accuracy, and is almost calibration-free.

[0004] The technical solution of the present invention is an array type ultrasonic belt conveyor coal flow intelligent measurement method, comprising the following steps:

[0005] Step (1), mounting brackets on the bridges on both sides of the belt conveyor, the upper part of the brackets is connected to the equipment box, an ultrasonic transducer and a main control circuit board are mounted in the box, and the surface of the coal flow on the belt is measured;

[0006] Step (2), using an ultrasonic transducer to perform non-contact measurement of the coal flow velocity on the belt using an ultrasonic pulse Doppler method, to obtain the coal flow velocity and perform correction;

[0007] Step (3), using the ultrasonic ranging principle to measure the instantaneous coal flow thickness, calculate and correct the instantaneous flow rate and cumulative flow rate of the coal flow, and compensate for the air sound velocity;

[0008] Step (4), installing a sound velocity calibration transmitting transducer and a sound velocity calibration receiving transducer on the bridge frames on both sides of the belt conveyor, controlling the sound velocity calibration transmitting transducer to transmit sound pulses through the main control circuit board, and detecting and timing the sound pulses received by the sound velocity calibration receiving transducer, thereby performing real-time calibration of the air sound velocity.

[0009] The main control circuit board integrates a timing control logic module, a clock generator / frequency divider, an ultra-low noise preamplifier A1, a high-Q bandpass amplifier A2, a high-Q bandpass amplifier A4, an automatic gain logarithmic amplifier A3, a delayed integration amplifier A5, a synchronous phase-sensitive amplifier A6, frequency-selective amplifiers A7 and A8, an amplifier / high-voltage drive circuit A0, a target distance detection circuit, a belt speed detection circuit or a material thickness change trend detection circuit;

[0010] The timing control logic module realizes communication with the host computer and controls the timing of the transmitting and receiving pulses of the transducer; the ultra-low noise preamplifier A1 is electrically connected to the high-Q bandpass amplifier A2, the high-Q bandpass amplifier A2 is electrically connected to the automatic gain logarithmic amplifier A3, the automatic gain logarithmic amplifier A3 and the high-Q bandpass amplifier A4 are electrically connected to the synchronous phase-sensitive amplifier A6 respectively, and the time-delay integration amplifier A5 is electrically connected to the automatic gain logarithmic amplifier A3;

[0011] The different clock signals emitted by the clock generator / frequency divider and the different timing signals sent by the timing control logic module are sent to the high Q bandpass amplifier A4 for processing to obtain the phase-sensitive amplified synchronization signal V G (t);

[0012] The timing control logic module processes and outputs the different clock signals received from the clock generator / frequency divider; the different clock signals emitted by the clock generator / frequency divider and the different timing signals processed by the timing control logic module are sent to the amplifier / high-voltage drive circuit A0 together, and the corresponding transducer is driven to transmit ultrasound after signal amplification processing; the transducer sends the different transmitted echoes received to the ultra-low noise preamplifier A1 for denoising processing, and then sends them together with different timing signals to the high-Q bandpass amplifier A2 for amplification processing, and the amplified signals are sent to the automatic gain logarithmic amplifier A3 for processing; the different timing signals sent by the timing control logic module are sent to the delay integration amplifier A5, and the processed signals are also sent to the automatic gain logarithmic amplifier A3 for processing;

[0013] After being processed by the automatic gain logarithmic amplifier A3, the continuous scattered echo signal V C (t);

[0014] Continuous scattered echo signal V C (t) and phase-sensitive amplifier synchronization signal V G (t) are sent to synchronous phase-sensitive amplifier A6 for processing. After phase-sensitive amplification, the output signals of frequency-selective amplifiers A7 and A8 are V D (t) and V E (t);

[0015] The timing control logic module converts different timing signals, the clock generator / divider converts different clock signals, and f(2w+ω θ ) are sent to the target distance detection circuit for signal quality detection and time phase detection. By measuring the received continuous scattered echo signal V C (t) The instantaneous distance between the transducer and the target is obtained by the delay time relative to the transmitted pulse;

[0016] The timing control logic module converts different timing signals, the clock generator / divider converts different clock signals, and the 0 ) are sent to the belt speed detection circuit, and V E The belt speed is obtained from the period of (t);

[0017] Or the timing control logic module converts different timing signals, the clock generator / divider converts different clock signals, and f(w 0 ) is simultaneously fed into the material thickness change trend detection circuit instead of the belt speed detection circuit, thereby calculating the coal flow thickness.

[0018] Furthermore, step (2) uses the belt speed detection circuit to measure V E (t) period, and the belt speed, i.e., the coal flow speed, is obtained; the specific calculation process is as follows:

[0019] The Doppler velocity measurement formula is:

[0020]

[0021] The received continuous scattered echo is expressed by formula (2):

[0022]

[0023] Then the phase-sensitive amplification synchronization signal is expressed by formula (3):

[0024] V G (t) = V m2 sin(ω 0 t+Φ) (3)

[0025] After phase-sensitive amplification, the output signals of the frequency-selective amplifiers A7 and A8 are V D (t), V E (t), respectively expressed by formula (4) and formula (5):

[0026]

[0027] In formulas (1), (2), (3), (4), and (5), υ is the belt speed; Φ is the phase difference between the synchronization signal and the echo signal; C is the sound wave speed (m / s); Δω isθ - the angular frequency shift of the scattered wave corresponding to the angle θ; ω 0 - angular frequency of the transmitted signal; θ - the angle between the transducer and the belt; V m1 -Continuous scattered echo analog signal amplitude; V m2 -Simulate signal amplitude; use belt speed detection circuit to measure V E (t) period, and the belt speed is obtained;

[0028] In order to correct the Doppler signal instability caused by the fluctuation of the coal flow measured by the belt, Δω in equation (1) is θ Average frequency shift Instead of:

[0029]

[0030] That is, the belt speed is calculated using spectrum analysis;

[0031] Then the angle θ is dynamically corrected, and the formula (1) gives:

[0032]

[0033] The linear correction formula of belt speed υ is given by this formula:

[0034]

[0035] In formula (14): θ 0 -Theoretical angle; B-beam width; ω 0 - Transmitted signal angular frequency; υ 0 - theoretical belt speed; υ j - Instantaneous belt speed; Δω θj - Instantaneous frequency shift.

[0036] Furthermore, the specific implementation method of step (3) is to use an eight-channel array scanning ultrasonic ranging circuit, wherein a seven-channel ranging circuit is used to measure the coal thickness, and an eighth-channel ranging circuit is used to compensate for the air sound velocity; the principle of each channel array scanning ultrasonic ranging circuit is the same as the principle of measuring the belt speed in step (2), except that the timing control logic module converts different timing signals, the clock generator / divider converts different clock signals, and f(w 0 ) are fed into the material thickness change trend detection circuit instead of the belt speed detection circuit, so as to calculate the coal flow thickness;

[0037] The instantaneous flow rate and cumulative flow rate of coal flow are calculated using the following formula:

[0038]

[0039]

[0040] In formula (9) and formula (10): q is instantaneous flow rate; Q is cumulative flow rate; -average density; υ j - Instantaneous belt speed; W i - measurement width of the i-th channel; L pi - the axial distance from the i-th transducer to the belt; l ij -The distance from the belt coal surface measured by the i-th transducer; L pi -l ij -i channel average coal thickness; △t j -sampling time interval; m-number of instantaneous flow sampling within a fixed time period.

[0041] Furthermore, the eighth channel ranging circuit in step (3) is used for air ultrasonic velocity compensation, which corrects the air ultrasonic velocity by measuring the delay time from the emission time to the reception time of an ultrasonic signal with a known standard constant target distance, and provides real-time dynamic sound velocity. The specific calculation is as follows. The instantaneous distance between the transducer and the measured target is expressed by formula (8):

[0042]

[0043] Where C-sound speed (m / s); T tr - the delay of detecting echo relative to the start of transmission; ΔT-the total delay of electroacoustic and acoustic-electric conversion caused by the characteristics of the transducer; n-circuit delay coefficient (n∈[0,8]); T clk13 - transducer oscillation period;

[0044] By transforming formula (8), we can get:

[0045]

[0046] In formula (12): -Instantaneous sound speed affected by environmental changes; 标 -Standard constant target spacing; n-circuit delay factor; R TRj -Instantaneous detection value of standard channel transmission and reception delay; ΔT 标 -Total delay of standard channel transducer receiving, generating sound, and sound-to-electricity conversion.

[0047] The present invention has the following beneficial effects:

[0048] 1. This method can measure the cumulative amount of coal flow conveyed by belt conveyor, which is used to calculate the production and transportation volume of coal in a certain period of time (shift).

[0049] 2. This method can measure the instantaneous amount of coal flow conveyed by the belt, and is used to monitor the flow of coal conveyed on the belt in real time and manage production.

[0050] 3. This method can adjust the belt speed by measuring the flow rate of coal conveyed by the belt, thereby achieving energy conservation and emission reduction.

[0051] 4. This method can realize automatic measurement of belt conveyor coal flow and intelligent regulation of belt operation through artificial intelligence, thereby improving the automation level of belt conveyor. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the Doppler velocity measurement principle;

[0053] Figure 2 is a schematic diagram of an array ultrasonic transducer;

[0054] Figure 3 This is a principle circuit diagram of an ultrasonic pulse Doppler velocity measurement solution of the present invention;

[0055] Figure 4 This is the schematic diagram of the eight-channel array scanning ultrasonic ranging circuit (only one channel is drawn);

[0056] Figure 5 This is the timing principle diagram of ultrasonic ranging circuit;

[0057] Figure 6 It is a schematic diagram of the change of the angle θ between the transducer and the belt. DETAILED DESCRIPTION

[0058] The following, in conjunction with the drawings in the specification, provides a detailed explanation of technical issues such as non-contact measurement of belt material speed, non-contact measurement of belt instantaneous material feed rate, environmental compensation, and material density compensation.

[0059] 1. Non-contact measurement of belt speed

[0060] Real-time and accurate measurement of belt speed is an important part of dynamic measurement. There are two main traditional measurement methods: a. Indirectly infer the belt speed by measuring the speed of the belt drive wheel or the motor reducer. b. Infer the belt speed by measuring the speed of the belt pressure wheel. Method a cannot solve the measurement error caused by the pulley sticking and slipping, and has low accuracy. With the improvement of measurement accuracy requirements, it is gradually being eliminated. Method b is widely used by existing electronic scale manufacturers. In order to prevent inaccurate measurement caused by slipping, three rollers are generally used to press the belt. The belt is often torn and scrapped at this point.

[0061] Because the belt conveyor line usually has a slope, the belt speed is not high, usually within 7 meters per second. For microwave speed measurement, the relative frequency shift is too small. For example, for a 10GHz microwave, the wavelength is 29.9mm, and the relative frequency shift is:

[0062] △f θ / f 0 =υ / C×2COSθ≈1.66×10 -9COSθ

[0063] From the above formula, we can see that for low-speed targets, microwave speed measurement has too high requirements on frequency stability, and it is very difficult to measure the speed accurately.

[0064] Ultrasonic waves have the characteristics of low wave velocity and short wavelength, and are suitable for measuring the speed of low-speed targets. For example, 50KHz ultrasonic waves have a wavelength of about 6.8mm, and the relative frequency shift for a 2.5m / s target is:

[0065] △f θ / f 0 ≈2.94×10 -2 COSθ

[0066] The frequency shift is large, and it is easy to realize low-cost and high-precision velocity measurement. Based on the above analysis of the characteristics of ultrasound and microwaves and other factors, the present invention adopts an ultrasonic pulse Doppler velocity measurement solution.

[0067] Brackets are installed on the bridges on both sides of the conveyor belt. The top of the brackets is connected to the equipment box. Ultrasonic transducers and main control circuit boards are installed in the box to measure the distance of the coal flow surface on the belt.

[0068] A sound velocity calibration transmitting transducer and a sound velocity calibration receiving transducer are installed on the bridges on both sides of the conveyor belt. The sound velocity calibration transmitting transducer is controlled by the main control circuit board to emit sound pulses. The sound pulses received by the sound velocity calibration receiving transducer are detected and timed, thereby performing real-time calibration of the air sound velocity.

[0069] like Figure 3 As shown, the transducer with a transmission frequency of 50KHz is used to measure the belt speed. The main control circuit board integrates a timing control logic module, a clock generator / frequency divider, an ultra-low noise preamplifier A1, a high-Q bandpass amplifier A2, a high-Q bandpass amplifier A4, an automatic gain logarithmic amplifier A3, a delay integration amplifier A5, a synchronous phase-sensitive amplifier A6, frequency-selective amplifiers A7 and A8, an amplifier / high-voltage drive circuit A0, a target distance detection circuit, and a belt speed detection circuit.

[0070] The timing control logic module realizes communication with the system and controls the timing of the transducer's transmitting and receiving pulses; the ultra-low noise preamplifier A1 is electrically connected to the high-Q bandpass amplifier A2, the high-Q bandpass amplifier A2 is electrically connected to the automatic gain logarithmic amplifier A3, the automatic gain logarithmic amplifier A3 and the high-Q bandpass amplifier A4 are electrically connected to the synchronous phase-sensitive amplifier A6 respectively, and the delayed integration amplifier A5 is electrically connected to the automatic gain logarithmic amplifier A3.

[0071] The clock signal CLK3 emitted by the clock generator / frequency divider and the timing signal EN1 emitted by the timing control logic module are sent to the high Q bandpass amplifier A4 for processing to obtain the phase-sensitive synchronous amplification signal V G (t);

[0072] The timing control logic module processes the clock signal CLK1 received from the clock generator / frequency divider and outputs CTRL; the clock signal CLK3 emitted by the clock generator / frequency divider and CTRL are sent to the amplifier / high-voltage drive circuit A0 together, and after signal amplification processing, the transducer is driven to transmit ultrasound; the transducer sends the received transmission echo signal to the ultra-low noise preamplifier A1 for denoising processing, and then sends it to the high-Q bandpass amplifier A2 for amplification processing together with the timing signal EN1, and the amplified signal is sent to the automatic gain logarithmic amplifier A3 for processing;

[0073] The timing signal EN1 is sent to the delayed integrating amplifier A5, and the processed signal is also sent to the automatic gain logarithmic amplifier A3 for processing;

[0074] After the above signals are processed simultaneously by the automatic gain logarithmic amplifier A3, a continuous scattered echo signal V is obtained. C (t);

[0075] Continuous scattered echo signal V C (t) and phase-sensitive synchronous amplification signal V G (t) are sent to synchronous phase-sensitive amplifier A6 for processing. After phase-sensitive amplification, the output signals of frequency-selective amplifiers A7 and A8 are V D (t) and V E (t);

[0076] The timing control logic module converts the timing signal EN2, the clock signal CLK2 output by the clock generator / divider, and f(2w+ω θ ) are sent to the target distance detection circuit for signal quality detection and time phase detection; by measuring the received continuous scattered echo V C (t) The instantaneous distance between the transducer and the target is obtained by the delay time relative to the transmitted pulse;

[0077] The timing control logic module converts the timing signal EN3, and the clock generator / divider converts the clock signals CLK1 and CLK2 together with f(w 0 ) is sent to the belt speed detection circuit at the same time, and V E The belt speed (i.e., coal flow speed) is obtained by measuring the period (t), and the output signal DI is returned to the timing control logic module.

[0078] The timing control logic circuit realizes the communication with the system and the timing control of the ultrasonic transmission and reception pulse train. A1 (preamplifier) ​​and A2 (bandpass amplifier) ​​ensure low noise of the detection circuit and preliminary anti-environmental noise capability. When ultrasonic waves propagate in the air, the sound intensity decays exponentially, and because the velocity measurement echo is a scattered wave, the dynamic range of the echo intensity is extremely wide (about 60dB), so A3 (automatic gain logarithmic amplifier) ​​and A5 (delayed integration amplifier) ​​provide nonlinear wide dynamic range (-30dB ~ +60dB) and distance compensation signal amplification function. A4 (high Q bandpass amplifier) ​​and A6 (synchronous phase-sensitive amplifier) ​​provide excellent signal selection capabilities, further improving the signal-to-noise ratio.

[0079] 2. Non-contact measurement of coal flow velocity on the belt using ultrasonic transducer and ultrasonic pulse Doppler method

[0080] (2.1) According to the Doppler velocity measurement formula:

[0081]

[0082] See also Figure 1 .

[0083] Then the received continuous scattered echo ( Figure 3 Point C in the middle) can be expressed by formula (2):

[0084]

[0085] The phase-sensitive amplification synchronization signal ( Figure 3 The G point in the middle can be expressed by formula (3):

[0086] V G (t) = V m2 sin(ω 0 t+Φ) (3)

[0087] After phase-sensitive amplification, the output signals of the frequency-selective amplifiers A7 and A8 are:

[0088]

[0089] In formulas (1), (2), (3), (4), and (5), υ is the belt speed; Φ is the phase difference between the synchronization signal and the echo signal; C is the wave speed (m / s); Δω is θ - the angular frequency shift of the scattered wave corresponding to the angle θ; ω 0 - angular frequency of the transmitted signal; θ - the angle between the transducer and the belt; V m1 -Continuous scattered echo analog signal amplitude; V m2 -Analog signal amplitude.

[0090] It can be seen that V in formula (4)D The angular frequency of (t) is about 2 times the angular frequency of the transmitted signal, the wavelength is shorter, and the ranging is more advantageous. In formula (5), V E The angular frequency of (t) is a low-frequency signal that is proportional to the measured belt coal flow velocity and has a much longer period, which is beneficial to the measurement of belt speed.

[0091] (2.2) Compensation of velocity measurement error caused by transducer beam width

[0092] Through on-site observation of the properties of the velocity Doppler signal, it was found that the Doppler signal is not a steady-state signal, and sometimes even a quasi-steady-state signal cannot be achieved, so the velocity measurement error according to formula (1) is large. Another phenomenon is that the Doppler frequency shift fluctuates with the material thickness. The thicker the material, the higher the frequency shift, and vice versa. Through analysis, it is believed that the frequency fluctuation is caused by the transducer beam width and the material fluctuation, which is equivalent to the change of the angle θ with the material fluctuation. Figure 6 It can be seen that in the AC section, the dynamic θ′ angle is smaller than the standard angle θ; while in the BA section, the dynamic θ′ angle is larger than the standard angle θ, which causes the calculated belt speed to be unstable. At the same time, the stable state of the Doppler signal is destroyed, and the measurement accuracy cannot be improved without correction.

[0093] (2.2.1) Replace frequency shift with average frequency shift

[0094] Since the non-contact Doppler signal is sometimes a narrow-band random signal, we can replace Δω in equation (1) with θ Average frequency shift Instead of:

[0095]

[0096] That is, the belt speed is calculated using spectrum analysis.

[0097] (2.2.2) Dynamic correction of angle θ

[0098] From (1), we can get:

[0099]

[0100] The linear correction formula of belt speed υ is given by this formula:

[0101]

[0102] In formula (14): θ 0 -Theoretical angle between the transducer and the belt; c-wave speed (m / s); B-beam width; ω 0 - Transmitted signal angular frequency; υ 0 - theoretical belt speed; υ j - Instantaneous belt speed; Δω θj-Instantaneous frequency shift. 3. Non-contact measurement of instantaneous coal flow on belt

[0103] (3.1) Circuit principle

[0104] The invention adopts the ultrasonic distance measurement principle to measure the instantaneous coal thickness and gives the instantaneous and cumulative flow through calculation and correction. Figure 2 is a schematic diagram of an ultrasonic transducer array. Figure 4 This is the schematic diagram of the eight-channel array scanning ultrasonic ranging circuit (only one channel is drawn). The measurement principle is the same as Figure 3 The principle is similar, but the difference is that the measured signal is a reflected wave, not a scattered echo, and the signal is much stronger, so the circuit gain is reduced by about 20dB. The transducer transmission frequency is different, which is 75KHz. The clock generator / divider output frequency is also different. The material thickness change trend detection circuit is used instead of the belt speed detection circuit, so the instantaneous coal flow thickness can be measured. The circuit will not be described in detail here.

[0105] Likewise, the circuit has low noise, high selectivity, high signal-to-noise ratio, strong noise suppression, wide dynamic range, etc., and has automatic gain, time gain compensation, and signal quality assurance circuits.

[0106] Adapting to the transducer, in the eight-channel array scanning ultrasonic ranging circuit (or more than eight channels according to the belt width, eight channels are used as an example here), seven channels of ranging circuits are used to measure the thickness of coal (or other materials), and the eighth channel of ranging circuits is used for air sound velocity compensation. Figure 4 Only the single-channel array scanning ultrasonic ranging circuit is drawn.

[0107] For quasi-stationary ranging, Figure 4 After phase-sensitive amplification, the output signals of points D and E of frequency-selective amplifiers A7 and A8 are V D (t) and V E (t) can be expressed as:

[0108] V D (t)= - V DM COS(2w 0 t+Φ) (6)

[0109] V E (t)= V EM COSΦ (7)

[0110] Where V DM 、V EM are the peak values ​​of the high-frequency part and the low-frequency part after echo processing; Φ is the phase difference between the synchronization signal and the echo signal; w 0 is the angular frequency of the transmitted signal.

[0111] The ultrasonic ranging circuit has further improved the ability to suppress the same frequency pulse noise to prevent false detection. Transmitting and receiving synchronous clock, transmission excitation enhancement mechanism, mobile receiving window anti-interference mechanism, signal quality detection anti-interference and other functional circuits have been considered.

[0112] The timing principle of ultrasonic ranging circuit is as follows Figure 5 As shown. Figure 5 It can be seen that the instantaneous distance between the transducer and the target is expressed by formula (8):

[0113]

[0114] Where C is the speed of sound (m / s); T tr - the delay of detecting echo relative to the time of starting transmission;

[0115] ΔT—total delay of electroacoustic and acoustic-electric conversion caused by transducer characteristics; n—circuit delay coefficient of this method (n∈[0,8]); T clk13 —Transducer oscillation period.

[0116] (3.2) Calculation principle of instantaneous and cumulative flow

[0117] The instantaneous flow rate and cumulative flow rate of coal flow are calculated using the following formula:

[0118]

[0119]

[0120] Where: q—instantaneous flow; Q—accumulated flow; —average density; j —Instantaneous belt speed; W i —Measurement width of the i-th channel; L pi is the distance from the axial direction of the i-th transducer to the belt; l ij L is the distance from the belt coal surface measured by the i-th transducer; pi -l ij —average coal thickness in channel i; △t j —Sampling time interval; m is the number of instantaneous flow sampling times within a fixed time period (e.g. 1 minute or 1 hour).

[0121] IV. Compensation measures to improve measurement accuracy (4.1) Ultrasonic velocity compensation

[0122] The working environment of dynamic measurement equipment in industrial production is poor, and the temperature, humidity, and atmospheric pressure change greatly. These factors will inevitably cause changes in parameters such as sound velocity and circuit, affecting the measurement accuracy and stability of the equipment. For example, the speed of sound:

[0123] C=331.45+0.61t (t—℃, degrees Celsius) (11)

[0124] This shows that temperature has a significant impact on the speed of sound. In order to comprehensively compensate for the changes in the speed of sound caused by changes in environmental parameters such as ambient temperature, pressure, and humidity, we added an eighth distance measurement circuit for ultrasonic speed compensation. By measuring the delay time from the emission time to the signal reception time of an ultrasonic signal with a known standard constant target distance, the air speed of sound is corrected to provide real-time dynamic speed of sound. By transforming formula (8), we get:

[0125]

[0126] In formula (12): —Instantaneous sound speed affected by environmental changes; l 标 —Standard constant target spacing; n—circuit delay coefficient; T TRj —Instantaneous detection value of standard channel receiving and sending delay; ΔT 标 —Total delay of standard channel transducer receiving, generating sound, and sound-to-electricity conversion.

[0127] (4.2) Coal flow density and shape compensation

[0128] Since the coal on the belt is in the form of powder, block, or a mixture of powder and block, the coal flow is unevenly distributed, causing the density of the coal flow to change continuously, thus affecting the measurement accuracy.

[0129] The present invention uses artificial intelligence and machine learning technologies, adopts a multimodal hybrid model architecture, such as shape-density joint modeling, and uses visual data to directly quantify the porosity of coal, solving the problem of underestimated density of block coal due to loose stacking. The model can automatically learn changes in coal types (such as switching from pulverized coal to gangue) without manual adjustment of parameters; the model can also learn online and transfer learning to cope with changes in coal types and environment, and has strong adaptability.

[0130] Through the above measures, the influence of coal density and shape on the measurement accuracy of ultrasonic belt flow can be corrected, the measurement accuracy of the system can be improved, real-time monitoring and adaptive calibration of coal flow can be realized, and at the same time, it can adapt to the complex and changeable industrial environment and improve the automation level of coal mines.

[0131] All measuring channels of the present invention use a phase-locked amplification method, which has good anti-interference, large sensitivity and dynamic range, and high signal-to-noise ratio. The detection accuracy is improved through various software and hardware compensations.

[0132] With the development of electronic technology, ultrasonic testing technology is a feasible way to use dynamic metering equipment. The equipment manufacturing cost and maintenance cost are low, suitable for mass production. It can be applied in coal mines, power plants, and metallurgical fields.

Claims

1. An array type ultrasonic belt conveyor coal flow intelligent measurement method, characterized in that: The following steps are involved: Step (1), mounting brackets on the bridges on both sides of the belt conveyor, the upper part of the brackets is connected to the equipment box, an ultrasonic transducer and a main control circuit board are mounted in the box, and the surface of the coal flow on the belt is measured; Step (2), using an ultrasonic transducer to perform non-contact measurement of the coal flow velocity on the belt using an ultrasonic pulse Doppler method, to obtain the coal flow velocity and perform correction; Step (3), using the ultrasonic ranging principle to measure the instantaneous coal flow thickness, calculate and correct the instantaneous flow rate and cumulative flow rate of the coal flow, and compensate for the air sound velocity; Step (4), installing a sound velocity calibration transmitting transducer and a sound velocity calibration receiving transducer on the bridge frames on both sides of the belt conveyor, controlling the sound velocity calibration transmitting transducer to transmit sound pulses through the main control circuit board, and detecting and timing the sound pulses received by the sound velocity calibration receiving transducer, thereby performing real-time calibration of the air sound velocity.

2. The array-type ultrasonic belt conveyor coal flow intelligent measurement method according to claim 1 is characterized in that: The main control circuit board integrates a timing control logic module, a clock generator / frequency divider, an ultra-low noise preamplifier A1, a high-Q bandpass amplifier A2, a high-Q bandpass amplifier A4, an automatic gain logarithmic amplifier A3, a delayed integration amplifier A5, a synchronous phase-sensitive amplifier A6, frequency-selective amplifiers A7 and A8, an amplifier / high-voltage drive circuit A0, a target distance detection circuit, a belt speed detection circuit or a material thickness change trend detection circuit; The timing control logic module realizes communication with the host computer and controls the timing of the transmitting and receiving pulses of the transducer; the ultra-low noise preamplifier A1 is electrically connected to the high-Q bandpass amplifier A2, the high-Q bandpass amplifier A2 is electrically connected to the automatic gain logarithmic amplifier A3, the automatic gain logarithmic amplifier A3 and the high-Q bandpass amplifier A4 are electrically connected to the synchronous phase-sensitive amplifier A6 respectively, and the time-delay integration amplifier A5 is electrically connected to the automatic gain logarithmic amplifier A3; The different clock signals emitted by the clock generator / frequency divider and the different timing signals sent by the timing control logic module are sent to the high Q bandpass amplifier A4 for processing to obtain the phase-sensitive amplified synchronization signal V G (t); The timing control logic module processes and outputs the different clock signals received from the clock generator / frequency divider; The different clock signals emitted by the clock generator / frequency divider and the different timing signals processed by the timing control logic module are sent to the amplifier / high-voltage drive circuit A0 together, and after the signal amplification processing, the corresponding transducer is driven to transmit ultrasonic waves; the transducer sends the received different transmission echoes to the ultra-low noise preamplifier A1 for denoising processing, and then sends them together with the different timing signals to the high-Q bandpass amplifier A2 for amplification processing, and the amplified signals are sent to the automatic gain logarithmic amplifier A3 for processing; the different timing signals sent by the timing control logic module are sent to the delay integration amplifier A5, and the processed signals are also sent to the automatic gain logarithmic amplifier A3 for processing; After being processed by the automatic gain logarithmic amplifier A3, the continuous scattered echo signal V C (t); Continuous scattered echo signal V C (t) and phase-sensitive amplifier synchronization signal V G (t) are sent to synchronous phase-sensitive amplifier A6 for processing. After phase-sensitive amplification, the output signals of frequency-selective amplifiers A7 and A8 are V D (t) and V E (t); The timing control logic module converts different timing signals, the clock generator / divider converts different clock signals, and f(2w+ω θ ) are sent to the target distance detection circuit for signal quality detection and time phase detection. By measuring the received continuous scattered echo signal V C (t) The instantaneous distance between the transducer and the target is obtained by the delay time relative to the transmitted pulse; The timing control logic module sends different timing signals, the clock generator / divider sends different clock signals, and f(w0) to the belt speed detection circuit. By measuring V E The belt speed is obtained from the period of (t); Or the timing control logic module sends different timing signals, the clock generator / divider sends different clock signals, and f(w0) to the material thickness change trend detection circuit instead of the belt speed detection circuit, so as to calculate the coal flow thickness.

3. The array-type ultrasonic belt conveyor coal flow intelligent measurement method according to claim 2 is characterized in that: Step (2) Use the belt speed detection circuit to measure V E (t) period, and the belt speed, i.e., the coal flow speed, is obtained; the specific calculation process is as follows: The Doppler velocity measurement formula is: The received continuous scattered echo is expressed by formula (2): Then the phase-sensitive amplification synchronization signal is expressed by formula (3): V G (t)=V m2 sin(ω0t+Φ) (3) After phase-sensitive amplification, the output signals of the frequency-selective amplifiers A7 and A8 are V D (t), V E (t), respectively expressed by formula (4) and formula (5): In formulas (1), (2), (3), (4), and (5), υ is the belt speed; Φ is the phase difference between the synchronization signal and the echo signal; C is the sound wave speed (m / s); Δω is θ - angular frequency shift of the scattered wave corresponding to angle θ; ω0- angular frequency of the transmitted signal; θ- angle between the transducer and the belt; V m1 -Continuous scattered echo analog signal amplitude; V m2 -Analog signal amplitude; In order to correct the Doppler signal instability caused by the fluctuation of the coal flow measured by the belt, Δω in equation (1) is θ Average frequency shift Instead of: (In the formula )(13) That is, the belt speed is calculated by spectrum analysis method, where: ω0-transmitted signal angular frequency; θ-angle between transducer and belt; C-sound wave speed (m / s); - average frequency shift; Then dynamically correct the angle θ: From formula (1), we get: The linear correction formula of belt speed υ is given as follows: In formula (14): θ0-theoretical angle between transducer and belt; B-beam width; υ0-theoretical belt speed; C-sound wave speed (m / s); υ j -Instantaneous belt speed; ω0-transmitted signal angular frequency; Δω θj - Instantaneous frequency shift.

4. The array-type ultrasonic belt conveyor coal flow intelligent measurement method according to claim 3 is characterized in that: The specific implementation method of step (3) is to use an eight-channel array scanning ultrasonic ranging circuit, wherein seven-channel ranging circuits are used to measure coal thickness, and the eighth-channel ranging circuit is used to compensate for air ultrasonic velocity; the principle of each channel array scanning ultrasonic ranging circuit is the same as the principle of measuring belt speed in step (2), except that the timing control logic module sends different timing signals, and the clock generator / divider sends different clock signals together with f(w0) to the material thickness change trend detection circuit instead of the belt speed detection circuit, so as to calculate the coal flow thickness; The instantaneous flow rate and cumulative flow rate of coal flow are obtained using the following formula: In formula (9) and (10): q is instantaneous flow rate; Q is cumulative flow rate; - average density; υ j - Instantaneous belt speed; W i - measurement width of the i-th channel; L pi - the axial distance from the i-th transducer to the belt; l ij -The distance from the belt coal surface measured by the i-th transducer; L pi -l ij -i channel average coal thickness; △t j -sampling time interval; m-number of instantaneous flow sampling within a fixed time period.

5. The array ultrasonic belt conveyor coal flow intelligent measurement method according to claim 4 is characterized in that: Step (3) The eighth channel distance measurement circuit is used for air ultrasonic velocity compensation. The air ultrasonic velocity is corrected by measuring the delay time from the emission time to the reception time of an ultrasonic signal with a known standard constant target distance, and a real-time dynamic sound velocity is provided. The specific calculation is as follows. The instantaneous distance between the transducer and the measured target is expressed as: In formula (8): C-sound speed (m / s); T tr - the delay of detecting echo relative to the start of transmission; ΔT-the total delay of electroacoustic and acoustic-electric conversion caused by the characteristics of the transducer; n-circuit delay coefficient (n∈[0,8]); T clk13 - transducer oscillation period; By transforming formula (8), we can get: Where: -Instantaneous sound speed affected by environmental changes; 标 - Standard constant target spacing; n-circuit delay coefficient; R TRj -Instantaneous detection value of standard channel receiving and sending delay; ΔT 标 -Total delay of standard channel transducer receiving, generating sound, and sound-to-electricity conversion.

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