CN115598216A - Ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation - Google Patents

Ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation Download PDF

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CN115598216A
CN115598216A CN202211300116.8A CN202211300116A CN115598216A CN 115598216 A CN115598216 A CN 115598216A CN 202211300116 A CN202211300116 A CN 202211300116A CN 115598216 A CN115598216 A CN 115598216A
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longitudinal
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茹聪
董兴蒙
路艳齐
王永豪
夏济根
翟宇文
武振鹏
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China Institute of Radio Wave Propagation CETC 22 Research Institute
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China Institute of Radio Wave Propagation CETC 22 Research Institute
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/011—Velocity or travel time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
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Abstract

The invention discloses an ultrasonic rock longitudinal and transverse wave speed measuring device and method based on coded excitation. The measuring device disclosed by the invention applies the coding excitation technology to the measurement of the longitudinal and transverse wave sound velocity of the rock, and can improve the signal-to-noise ratio of an observed waveform under the condition of not losing resolution; different excitation voltages can be selected for rocks with different lithology, the amplitude of the transmitted signal is improved in a high-voltage excitation mode, and the signal-to-noise ratio of the observed waveform is further enhanced; adopt the longitudinal and transverse wave integral type ultrasonic probe, can measure the longitudinal wave of rock, transverse wave speed under same environment, need not to relapse dismouting probe, avoid traditional equipment to disturb because of the environmental factor that the change probe brought, improved measurement of efficiency simultaneously.

Description

Ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation
Technical Field
The invention belongs to the field of ultrasonic rock measurement, and particularly relates to an ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation in the field, which are used for ultrasonic detection of the longitudinal and transverse wave velocity of a rock test piece.
Background
The acoustic properties (elastic modulus, sound velocity, attenuation coefficient, etc.) of rock are important parameters of rock materials, and have great correlation with the internal structure of rock and rock strength. In a laboratory, the relation between the rock structure and the elastic parameters is generally researched by an ultrasonic transmission method, namely, ultrasonic pulses are transmitted at one end of a rock test piece, a transmission signal is received at the other end by using a receiving transducer, and then the recorded waveform data is analyzed to research the change of the acoustic parameters. However, in practical tests, due to the bandwidth limitation of the transducer, background noise interference, poor coupling, rock frequency attenuation and the like, the signal to noise ratio of a received signal is low, and the ultrasonic penetration capability is insufficient, so that the difficulty in information identification is caused.
The solution to the above problem is generally to increase the amplitude of the transmitted signal and the signal-to-noise ratio of the desired signal. Most ultrasonic rock sound velocity measurement devices achieve the improvement of the amplitude of the transmitted signal by improving the excitation voltage. Considering that the limit voltage value borne by the ultrasonic transducer and the increase of the excitation voltage can increase the design difficulty of the hardware driving circuit, the excitation voltage of the current measuring device is mostly concentrated between 200V and 400V.
The coding excitation technology is a method capable of improving the signal-to-noise ratio of an effective signal, and is widely applied to the fields of medical ultrasonic imaging, radar systems, nondestructive testing and the like. The method can obtain the same signal-to-noise ratio and resolution ratio as high-power single-pulse signals by using a low-power signal generator to transmit coded signals. In consideration of the complexity of the rock ultrasonic detection problem, the introduction of the coded excitation technology into the rock ultrasonic detection field has many specific problems, such as the rock frequency-dependent attenuation problem, the nonlinear propagation problem of waves caused by the complex structure inside the rock, and the like, which affect the compression performance of the coded excitation technology. Although some researchers have carried out related work to research and study the propagation of the coded signal in the rock and the pulse-pressing mechanism thereof, at present, no ultrasonic rock sound velocity measuring device applies the coded excitation technology to the actual rock acoustic characteristic measuring process.
Disclosure of Invention
The invention aims to solve the technical problem of providing an ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation for ultrasonic measurement of a rock mass test piece in a laboratory by starting from improving the amplitude of a transmitted signal and the effective signal-to-noise ratio in order to obtain higher signal-to-noise ratio in rock ultrasonic measurement under different conditions and improve the rock measurement precision.
The invention adopts the following technical scheme:
in an ultrasonic rock longitudinal and transverse wave velocity measuring device based on coded excitation, the improvement is that: the device comprises a main control module, a code modulation module, a transmitting module, a longitudinal and transverse wave integrated transmitting probe, a longitudinal and transverse wave integrated receiving probe, a data acquisition module and a data processing module; the main control module is electrically connected with the code modulation module, the transmitting module, the data acquisition module and the data processing module, and sends a set code to the code modulation module according to a user instruction sent by the data processing module, and sets an excitation voltage, a longitudinal wave channel and a transverse wave channel of the transmitting module; the code modulation module performs phase modulation on the set code sent by the main control module, generates a phase code signal and sends the phase code signal to the transmitting module; the transmitting module generates positive and negative high-voltage excitation signals according to the phase coding signals, and excites the longitudinal and transverse wave integrated transmitting probe from a set longitudinal wave channel or transverse wave channel by using the positive and negative high-voltage excitation signals, so that the longitudinal and transverse wave integrated transmitting probe emits ultrasonic mechanical waves to the rock, the longitudinal and transverse wave integrated receiving probe receives the ultrasonic mechanical waves transmitted through the rock, converts the ultrasonic mechanical waves into transmission wave electric signals and transmits the transmission wave electric signals to the data acquisition module, and the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signals to obtain transmission wave original waveforms which are uploaded to the data processing module through the main control module.
Furthermore, the master control module adopts ZYNQ-7020 as a master control chip.
Further, the coded modulation module adopts spartan6 as a main chip.
Further, the excitation voltage of the transmitting module reaches 800V at most.
Furthermore, the transmitting module comprises a high-voltage MOS combined tube, a relay and a DC adjustable high-voltage module; the high-voltage MOS combined tube comprises an N-MOS tube, a P-MOS tube and a driving chip EL7222, the transmitting module converts a phase coding signal into a control signal of the N-MOS tube and a control signal of the P-MOS tube, the N-MOS tube transmits a positive high-voltage excitation signal when being conducted, and the P-MOS tube transmits a negative high-voltage excitation signal when being conducted; the main control module controls the transmitting module to switch a longitudinal wave channel and a transverse wave channel through a relay; the main control module sets the excitation voltage of the transmitting module through the DC adjustable high-voltage module.
Furthermore, the data acquisition module adopts a 14-bit high-speed ADC, and the sampling rate reaches 65MPS.
The improvement of a measuring method using the measuring device is that the measuring method comprises the following steps:
step 1, respectively attaching a longitudinal wave and transverse wave integrated transmitting probe and a longitudinal wave and transverse wave integrated receiving probe to two opposite sides of a rock, setting coding and exciting voltage in a data processing module by a user, selecting a longitudinal wave channel and a transverse wave channel, and issuing the setting and selection to a main control module in a user instruction form;
step 2, the main control module sends a set code to the code modulation module according to a user instruction, and sets an excitation voltage, a longitudinal wave channel and a transverse wave channel of the transmitting module;
and 3, performing phase modulation on the set code sent by the main control module by using a code modulation module to generate a phase code signal s (t), and sending the phase code signal s (t) to a transmitting module, wherein a phase modulation function is expressed as follows:
Figure BDA0003904246260000021
in the above formula, the first and second carbon atoms are,
Figure BDA0003904246260000022
represents linear convolution, delta () represents square wave, T represents time, T represents termination time, T is more than or equal to 0 and less than or equal to T, p (T) is a sub-pulse function, c is coding, and N is coding length;
step 4, the transmitting module drives the high-voltage MOS combined tube according to the phase coding signal after phase modulation to generate positive and negative high-voltage excitation signals, and the positive and negative high-voltage excitation signals are used for exciting the longitudinal and transverse wave integrated transmitting probe from a set longitudinal wave channel or transverse wave channel to send ultrasonic mechanical waves to the rock;
step 5, the longitudinal and transverse wave integrated receiving probe receives the ultrasonic mechanical wave transmitted through the rock, converts the ultrasonic mechanical wave into a transmission wave electric signal and transmits the transmission wave electric signal to the data acquisition module;
step 6, the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signal to obtain a transmission wave original waveform r (t) and sends the transmission wave original waveform r (t) to the main control module;
and 7, uploading the original transmitted wave waveform r (t) to a data processing module by a main control module, performing pulse compression by the data processing module to obtain a pulse compression waveform h (t), maximizing the signal-to-noise ratio by the pulse compression through a matched filter, and expressing the pulse response function of the matched filter as follows:
h(t)＝w·s(τ d -t) (2)
in the above formula: w is a gain factor, τ d The duration of the excitation signal, s (τ) d -t) represents τ d -a phase encoded signal at time t;
and 8, after the data processing module acquires the pulse compression waveform h (t), automatically picking up the first arrival of the pulse compression waveform by using a Bayes information criterion, and calculating the wave velocity of the measured rock according to the first arrival, wherein the calculation formula of the Bayes information criterion is as follows:
BIC(q 0 )＝q 0 ln(var{X(1,q 0 )})+(M-q 0 -1)ln(var{X(q 0 +1,M)})-q 0 ln(M) (3)
in the above formula: BIC represents Bayesian information value of observed waveform data, the minimum point is the accurate position of first arrival, X represents observed waveform data, M is the number of sampling points of observed waveform, q 0 Represents the first arrival position and var represents the variance.
The invention has the beneficial effects that:
the measuring device disclosed by the invention applies the coding excitation technology to the measurement of the longitudinal and transverse wave sound velocity of the rock, and can improve the signal-to-noise ratio of an observed waveform under the condition of not losing resolution; different excitation voltages can be selected for rocks with different lithology, the amplitude of the transmitted signal is improved in a high-voltage excitation mode, and the signal-to-noise ratio of the observed waveform is further enhanced; adopt the longitudinal and transverse wave integral type ultrasonic probe, can measure the longitudinal wave of rock, transverse wave speed under same environment, need not to relapse dismouting probe, avoid traditional equipment to disturb because of the environmental factor that the change probe brought, improved measurement of efficiency simultaneously.
The measuring method disclosed by the invention improves the signal-to-noise ratio of the observed waveform and the measuring precision of the longitudinal and transverse wave speeds of the rock by adopting the phase modulation and pulse compression signal receiving technology.
Drawings
FIG. 1 is a block diagram of the components of the disclosed measurement device;
FIG. 2 is a schematic circuit diagram of a transmitter module of the disclosed measurement apparatus;
FIG. 3 is a schematic flow chart of a disclosed measurement method;
FIG. 4 is a graph comparing observed waveforms for coded excitation and single pulse excitation.
Reference numerals: the device comprises a main control module, a 2-code modulation module, a 3-transmitting module, a 4-longitudinal and transverse wave integrated transmitting probe, a 5-longitudinal and transverse wave integrated receiving probe, a 6-data acquisition module and a 7-data processing module.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Embodiment 1, this embodiment discloses an ultrasonic rock longitudinal and transverse wave speed measuring device based on coding excitation for the longitudinal and transverse wave ultrasonic measurement of laboratory rock (rock mass test piece), can solve the current rock ultrasonic measurement in-process and observe that the wave form SNR is low, the big problem of rock sound velocity measurement error, can effectively improve the measurement accuracy and the measurement efficiency of laboratory rock (rock mass test piece) longitudinal and transverse wave speed.
As shown in fig. 1, the measuring device includes a main control module 1, a code modulation module 2, a transmitting module 3, a longitudinal and transverse wave integrated transmitting probe 4, a longitudinal and transverse wave integrated receiving probe 5, a data acquisition module 6 and a data processing module 7; by adopting the longitudinal and transverse wave integrated probe, the longitudinal wave sound velocity and the transverse wave sound velocity can be measured successively after the rock test piece is successfully installed, the longitudinal wave sound velocity and the transverse wave sound velocity can be measured in the same experimental environment, the interference of an external environment caused by repeated replacement of the measuring probe is avoided, and the measuring efficiency is improved while the accuracy of measurement of the longitudinal and transverse wave velocities of the rock is enhanced.
The main control module is electrically connected with the code modulation module, the transmitting module, the data acquisition module and the data processing module, and sends a set code to the code modulation module according to a user instruction sent by the data processing module, and sets an excitation voltage, a longitudinal wave channel and a transverse wave channel of the transmitting module; the code modulation module performs phase modulation on the set code sent by the main control module, generates a phase code signal and sends the phase code signal to the transmitting module; the transmitting module generates positive and negative high-voltage excitation signals according to the phase coding signals, and excites the longitudinal and transverse wave integrated transmitting probe from a set longitudinal wave channel or transverse wave channel by using the positive and negative high-voltage excitation signals, so that the longitudinal and transverse wave integrated transmitting probe emits ultrasonic mechanical waves to the rock, the longitudinal and transverse wave integrated receiving probe receives the ultrasonic mechanical waves transmitted through the rock, converts the ultrasonic mechanical waves into transmission wave electric signals and transmits the transmission wave electric signals to the data acquisition module, and the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signals to obtain transmission wave original waveforms which are uploaded to the data processing module through the main control module.
The main control module adopts ZYNQ-7020 as a main control chip and is responsible for the work of controlling the work flow, receiving and executing the instruction, controlling the excitation voltage, collecting and uploading the transmitted wave data and the like.
The code modulation module adopts spartan6 as a main chip and is responsible for carrying out phase modulation on binary codes to generate phase coding signals, so that the problem of low efficiency caused by directly sending codes is avoided, and the frequency spectrum control can be better carried out.
The user can select different codes and excitation voltages according to the requirement, the maximum excitation voltage of the transmitting module reaches 800V, the problems that the common ultrasonic equipment is low in excitation voltage and cannot continuously excite and transmit the codes are effectively solved, and the transmitting signal with high amplitude can be generated.
The longitudinal wave and transverse wave integrated probe is responsible for generating and receiving ultrasonic signals and can respectively generate and receive longitudinal wave signals and transverse wave signals in the same measuring environment.
As shown in fig. 2, the transmitting module includes a high voltage MOS combination tube, a relay, and a DC adjustable high voltage module; the high-voltage MOS combined tube comprises an N-MOS tube Q1, a P-MOS tube Q2 and a driving chip EL7222, and can continuously send positive and negative high-voltage excitation signals, a transmitting module converts phase coding signals into control signals SIGL + and SIGL-of the N-MOS tube and the P-MOS tube, the N-MOS tube is connected with positive voltage, the P-MOS tube is connected with negative voltage, when the code is 1, a positive pulse signal SIGL + triggers the N-MOS tube to be conducted and transmits the positive high-voltage excitation signals, and when the code is 0, a negative pulse signal SIGL-triggers the P-MOS tube to be conducted and transmits the negative high-voltage excitation signals. The main control module controls the transmitting module to switch a longitudinal wave channel and a transverse wave channel through a relay K1;
the excitation voltage is provided by a DC adjustable high-voltage module, the high-voltage module is controlled by voltage, and the main control module sets the excitation voltage of the transmitting module through the DC adjustable high-voltage module.
The data acquisition module is responsible for processing and acquiring the electric signal of the transmission wave, adopts a 14-bit high-speed ADC, has a sampling rate of 65MPS and can realize accurate acquisition of the electric signal of the transmission wave.
The data processing module is an upper computer module and is responsible for receiving the original waveform of the transmitted wave sent by the main control module and performing pulse compression processing to obtain a pulse compression waveform, and performing initial pickup of the sound wave and calculation of the sound velocity.
The embodiment also discloses a measuring method, which uses the measuring device and comprises the following steps:
step 1, correctly connecting a measuring device, respectively attaching a longitudinal wave and transverse wave integrated transmitting probe and a longitudinal wave and transverse wave integrated receiving probe to two opposite sides of a rock, setting codes and excitation voltage in a data processing module by a user, selecting a longitudinal wave channel and a transverse wave channel, and issuing the setting and selection to a main control module in a user instruction form; the user can realize the measurement of longitudinal and transverse waves under the same external environment by switching the longitudinal and transverse wave channels, and the influence of the change of the external environment brought by the dismounting device on the longitudinal and transverse wave sound velocity is avoided.
Step 2, the main control module sends a set code to the code modulation module according to a user instruction, and sets an excitation voltage and longitudinal and transverse wave channels of the transmitting module;
and 3, performing phase modulation on the set code transmitted by the main control module by using the code modulation module to generate a phase code signal s (t), and transmitting the phase code signal s (t) to the transmitting module, wherein a phase modulation function is expressed as follows:
Figure BDA0003904246260000051
in the above formula, the first and second carbon atoms are,
Figure BDA0003904246260000052
represents linear convolution, delta () represents square wave, T represents time, T represents termination time, T is more than or equal to 0 and less than or equal to T, p (T) is a sub-pulse function, c is coding, and N is coding length;
step 4, the transmitting module drives the high-voltage MOS combined tube according to the phase coding signal after phase modulation to generate a positive high-voltage excitation signal and a negative high-voltage excitation signal, and the positive high-voltage excitation signal and the negative high-voltage excitation signal are used for exciting a longitudinal transverse wave integrated transmitting probe from a set longitudinal wave channel or a set transverse wave channel to send a group of ultrasonic mechanical waves to the rock;
step 5, after receiving the ultrasonic mechanical wave transmitted through the rock, the longitudinal and transverse wave integrated receiving probe converts the ultrasonic mechanical wave into a weak transmitted wave electric signal and transmits the weak transmitted wave electric signal to the data acquisition module;
step 6, the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signal to obtain a transmission wave original waveform r (t) and sends the transmission wave original waveform r (t) to the main control module;
step 7, the main control module uploads the original waveform r (t) of the transmitted wave to the data processing module, the data processing module performs pulse compression to obtain a pulse compression waveform h (t), the pulse compression can maximize the signal-to-noise ratio through the matched filter, and the pulse response function of the matched filter is expressed as follows:
h(t)＝w·s(τ d -t) (2)
in the above formula: w is a gain factor, τ d The duration of the excitation signal, s (τ) d -t) represents τ d -a phase encoded signal at time t;
the electric signal of the transmitted wave is pre-amplified and gain-adjusted, and then the data processing module performs pulse compression on the original waveform of the transmitted wave, so that the signal-to-noise ratio of the signal can be greatly improved, and a more accurate first arrival of the transmitted wave is extracted.
And 8, after the data processing module acquires the pulse compression waveform h (t), automatically picking up the first arrival of the pulse compression waveform by using a Bayesian information criterion, and calculating the wave velocity of the detected rock according to the first arrival, wherein the calculation formula of the Bayesian information criterion is as follows:
BIC(q 0 )＝q 0 ln(var{X(1,q 0 )})+(M-q 0 -1)ln(var{X(q 0 +1,M)})-q 0 ln(M) (3)
in the above formula: BIC represents Bayesian information value of observed waveform data, the minimum point is the accurate position of first arrival, X represents observed waveform data, M is the number of sampling points of observed waveform, q 0 The first arrival position is represented and var represents the variance.
Specifically, taking the example of detecting red sandstone with a length of 50mm, the whole measurement flow is shown in fig. 3. First, a rock specimen is placed on a measuring device and an appropriate excitation voltage is selected according to the lithology of the rock. And secondly, the transmitting module transmits positive and negative high-voltage excitation signals to the transmitting probe according to preset excitation voltage and coding information, and the excitation signals penetrate through the rock test piece and are received by the receiving probe at the other end to obtain an original waveform of rock measurement. And then, the data processing module performs pulse compression on the acquired original waveform to acquire a pulse compressed waveform. And finally, automatically picking up the first arrival of the pulse compression waveform by using a Bayesian information criterion, and calculating the wave velocity of the tested rock test piece according to the first arrival.
Fig. 4 shows a comparison graph of observed waveforms of a single pulse excitation and a coding excitation in the red sandstone sound velocity measurement. As can be seen from the figure, the signal-to-noise ratio of the observed waveform based on the coded excitation technology is higher, and the first arrival of the ultrasonic wave is easier to be accurately picked up.

Claims (7)

1. An ultrasonic rock longitudinal and transverse wave velocity measuring device based on coded excitation is characterized in that: the device comprises a main control module, a code modulation module, a transmitting module, a longitudinal and transverse wave integrated transmitting probe, a longitudinal and transverse wave integrated receiving probe, a data acquisition module and a data processing module; the main control module is electrically connected with the code modulation module, the transmitting module, the data acquisition module and the data processing module, and sends a set code to the code modulation module according to a user instruction sent by the data processing module, and sets an excitation voltage, a longitudinal wave channel and a transverse wave channel of the transmitting module; the code modulation module performs phase modulation on the set code sent by the main control module, generates a phase code signal and sends the phase code signal to the transmitting module; the transmitting module generates positive and negative high-voltage excitation signals according to the phase coding signals, and excites the longitudinal and transverse wave integrated transmitting probe from a set longitudinal wave channel or transverse wave channel by using the positive and negative high-voltage excitation signals, so that the longitudinal and transverse wave integrated transmitting probe emits ultrasonic mechanical waves to the rock, the longitudinal and transverse wave integrated receiving probe receives the ultrasonic mechanical waves transmitted through the rock, converts the ultrasonic mechanical waves into transmission wave electric signals and transmits the transmission wave electric signals to the data acquisition module, and the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signals to obtain transmission wave original waveforms which are uploaded to the data processing module through the main control module.
2. The ultrasonic rock longitudinal and transverse wave velocity measurement device based on coded excitation according to claim 1, characterized in that: the main control module adopts ZYNQ-7020 as a main control chip.
3. The ultrasonic rock longitudinal and transverse wave velocity measurement device based on coded excitation according to claim 1, characterized in that: the encoding modulation module adopts spartan6 as a main chip.
4. The ultrasonic rock longitudinal and transverse wave velocity measurement device based on coded excitation according to claim 1, characterized in that: the excitation voltage of the transmitting module reaches 800V at most.
5. The ultrasonic rock longitudinal and transverse wave velocity measurement device based on coded excitation according to claim 1, characterized in that: the transmitting module comprises a high-voltage MOS combined tube, a relay and a DC adjustable high-voltage module; the high-voltage MOS combined tube comprises an N-MOS tube, a P-MOS tube and a driving chip EL7222, the transmitting module converts a phase coding signal into a control signal of the N-MOS tube and a control signal of the P-MOS tube, the N-MOS tube transmits a positive high-voltage excitation signal when being conducted, and the P-MOS tube transmits a negative high-voltage excitation signal when being conducted; the main control module controls the transmitting module to switch a longitudinal wave channel and a transverse wave channel through a relay; the main control module sets the excitation voltage of the transmitting module through the DC adjustable high-voltage module.
6. The ultrasonic rock longitudinal and transverse wave velocity measurement device based on coded excitation according to claim 1, characterized in that: the data acquisition module adopts a 14-bit high-speed ADC, and the sampling rate reaches 65MPS.
7. A measuring method using the measuring apparatus according to claim 5, characterized by comprising the steps of:
step 1, respectively attaching a longitudinal wave and transverse wave integrated transmitting probe and a longitudinal wave and transverse wave integrated receiving probe to two opposite sides of a rock, setting coding and exciting voltage in a data processing module by a user, selecting a longitudinal wave channel and a transverse wave channel, and issuing the setting and selection to a main control module in a user instruction form;
step 2, the main control module sends a set code to the code modulation module according to a user instruction, and sets an excitation voltage and longitudinal and transverse wave channels of the transmitting module;
and 3, performing phase modulation on the set code sent by the main control module by using a code modulation module to generate a phase code signal s (t), and sending the phase code signal s (t) to a transmitting module, wherein a phase modulation function is expressed as follows:
Figure FDA0003904246250000021
in the above-mentioned formula, the compound has the following structure,
Figure FDA0003904246250000022
represents linear convolution, delta () represents square wave, T represents time, T represents termination time, T is more than or equal to 0 and less than or equal to T, p (T) is a sub-pulse function, c is coding, and N is coding length;
step 4, the transmitting module drives the high-voltage MOS combined tube according to the phase coding signal after phase modulation to generate a positive high-voltage excitation signal and a negative high-voltage excitation signal, and the positive high-voltage excitation signal and the negative high-voltage excitation signal are used for exciting a longitudinal transverse wave integrated transmitting probe from a set longitudinal wave channel or a transverse wave channel to send ultrasonic mechanical waves to the rock;
step 5, the longitudinal and transverse wave integrated receiving probe receives the ultrasonic mechanical wave transmitted through the rock, converts the ultrasonic mechanical wave into a transmission wave electric signal and transmits the transmission wave electric signal to the data acquisition module;
step 6, the data acquisition module performs pre-amplification, gain adjustment, filtering and A/D conversion on the received transmission wave electric signal to obtain a transmission wave original waveform r (t) and sends the transmission wave original waveform r (t) to the main control module;
and 7, uploading the original transmitted wave waveform r (t) to a data processing module by a main control module, performing pulse compression by the data processing module to obtain a pulse compression waveform h (t), maximizing the signal-to-noise ratio by the pulse compression through a matched filter, and expressing the pulse response function of the matched filter as follows:
h(t)＝w·s(τ d -t) (2)
in the above formula: w is a gain factor, τ d For the duration of the excitation signal, s (τ) d -t) represents τ d -a phase encoded signal at time t;
and 8, after the data processing module acquires the pulse compression waveform h (t), automatically picking up the first arrival of the pulse compression waveform by using a Bayes information criterion, and calculating the wave velocity of the measured rock according to the first arrival, wherein the calculation formula of the Bayes information criterion is as follows:
BIC(q 0 )＝q 0 ln(var{X(1,q 0 )})+(M-q 0 -1)ln(var{X(q 0 +1,M)})-q 0 ln(M) (3)
in the above formula: BIC represents Bayesian information value of observed waveform data, the minimum point is the accurate position of first arrival, X represents observed waveform data, M is the number of sampling points of observed waveform, q 0 Represents the first arrival position and var represents the variance.
CN202211300116.8A 2022-10-24 2022-10-24 Ultrasonic rock longitudinal and transverse wave velocity measuring device and method based on coded excitation Pending CN115598216A (en)

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