CN112666264B - High-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms - Google Patents
High-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms Download PDFInfo
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Abstract
The invention discloses a high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms. The adaptive ultrasonic pulse transmitting device comprises: the device comprises an excitation signal source unit, a pulse gate control unit, a single-end-to-differential circuit, a primary gate control amplifying circuit, a secondary power driving circuit, an output stage power amplifying circuit, an output filter module, a feedback control unit, a direct current power supply and an energy storage module. The invention can improve the intensity of the transmitted signal while adapting to ultrasonic transmission of various platforms, reduce harmonic components generated by the system, and reduce the overall power consumption and volume of the circuit while not reducing the output power.
Description
Technical Field
The invention relates to the technical field of nonlinear nondestructive testing, in particular to an excitation device suitable for multiple probes such as piezoelectric ultrasound and electromagnetic ultrasound, and particularly discloses a high-power self-adaptive ultrasonic transmitting device suitable for multiple platforms.
Background
The ultrasonic guided wave detection technology has the advantages of long propagation distance, high detection efficiency, low cost, no harm to human bodies and the like, and is widely applied to the field of nondestructive detection. The ultrasonic guided wave detection technology is mainly divided into two main categories of linear ultrasonic guided wave detection technology and nonlinear ultrasonic guided wave detection technology. The linear ultrasonic guided wave detection technology generally detects according to the change of time and amplitude characteristics of signals, has higher detection precision and sensitivity on damages such as cracks and holes with the size larger than the wavelength, but detects the early prediction on microcracks, fatigue damages, microdefects, interface debonding and delamination damages, even the degradation of mechanical properties such as fatigue and creep of metal materials and structures, and the change of the time and amplitude characteristics is very unobvious, thus leading to inaccurate detection results.
Nonlinear ultrasonic guided waves are very sensitive to micro-defects or state changes existing inside the material. The nonlinear ultrasonic guided wave detection technology generally analyzes the frequency domain of a received signal, and mainly observes nonlinear effects such as higher harmonics, modulation side lobes and the like of a material. The media for generating nonlinear ultrasonic guided waves are mainly piezoelectric ultrasonic transducers and electromagnetic ultrasonic transducers.
The piezoelectric ultrasonic guided wave detection technology is a more traditional ultrasonic guided wave detection method. The piezoelectric ultrasonic transducer is a capacitive load, needs an excitation signal with very high voltage amplitude, has high transduction efficiency, is simple and easy to use, and is easy to manufacture and package, so that the piezoelectric ultrasonic transducer is widely applied to various occasions. However, the characteristic that the coupling agent is needed, the surface of the detection object needs to be well coupled, and the detection object cannot work under the high-temperature condition limits the use of the detection object in some occasions.
The electromagnetic ultrasonic guided wave detection technology has the characteristics of non-contact property, no need of a coupling agent and high-temperature detection capability. These advantages make electromagnetic ultrasound detection suitable for certain specific applications. For electromagnetic ultrasonic detection, the efficiency of the electromagnetic ultrasonic transducer is low, a high-power arbitrary waveform generation signal needs to be input, the excitation device can linearly amplify the input arbitrary waveform signal, and the amplified arbitrary waveform excitation signal has enough output power so as to drive the electromagnetic ultrasonic transducer to generate ultrasonic guided waves in a structure to be detected.
However, the existing excitation devices capable of outputting excitation signals of arbitrary waveforms are designed for piezoelectric transducers. In the prior art, an excitation device for generating high-voltage arbitrary waveform consists of a general computer, a communication interface, a general signal generator, a linear power amplifier and the like, and the excitation device can be used for outputting arbitrary waveform signals, but the output signal power is low, and the excitation device cannot be compatible with an electromagnetic ultrasonic transducer at the same time. The existing electromagnetic ultrasonic transducer excitation source generally uses a resonance mode to generate an excitation signal with fixed frequency, and cannot generate high-power arbitrary waveform excitation.
Therefore, it is necessary to realize a high-power arbitrary waveform excitation signal device, which can generate high-amplitude voltage signals to drive the piezoelectric transducer and high-power and high-current signals to drive the electromagnetic ultrasonic transducer.
Disclosure of Invention
According to the defects of the prior art, the invention aims to provide a high-power self-adaptive ultrasonic arbitrary waveform pulse transmitting device which is used for improving the intensity of a transmitting signal while being suitable for ultrasonic transmission of various platforms, reducing harmonic components generated by a system, and reducing the overall power consumption and volume of a circuit while not reducing the output power. Meanwhile, the arbitrary waveform transmitting device should meet the requirement of nonlinear guided wave detection based on a digital phase locking technology, so that a subsequent signal detection module can conveniently detect weak signals.
In order to solve the problems, the invention is realized according to the following technical scheme:
a high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms is used for adapting to different types of transducers, transmitting high-power ultrasonic signals and carrying out nondestructive inspection on samples, and comprises: the device comprises an excitation signal source unit, a pulse gate control unit, a single-ended to differential circuit, a primary gated amplifying circuit, a secondary power driving circuit, an output power amplifying circuit, an output filter module, a feedback control unit, a direct current power supply and an energy storage module.
The excitation signal source unit is used for respectively generating a pulse square wave signal and a sine signal with a window function, wherein a circuit for generating the pulse signal is connected with the pulse gate control unit, and a circuit for generating the sine signal is connected with the single-end to differential circuit; the pulse gate control unit is connected with the first-stage gating amplification circuit and is mainly used for isolating, driving and adjusting pulse signals generated by the excitation signal source unit; the single-end to differential circuit is also connected with the first-level gating amplification circuit and converts one path of bipolar sinusoidal signals with window functions into two differential paths of unipolar sinusoidal signals;
the first-stage gating amplifying circuit is connected with the second-stage power driving circuit, subtracts the pulse signal and the sinusoidal signal in front to obtain two differential pulse sinusoidal signals, and amplifies the two differential signals; the direct current power supply module is connected with the excitation signal source unit, the pulse gate control unit, the single-end to differential circuit, the first-stage gating amplification circuit and the like through different voltage regulators to obtain low voltage with different voltage of dozens of volts, and bias is provided for signal generation and conversion.
The secondary power driving circuit is connected with the output stage power amplifying circuit and is used for improving the signal loading capacity of the low-voltage circuit; the output stage power amplifying circuit is connected with the output filter module and used for carrying out power amplification on the two paths of differential signals and converting the two paths of differential signals into a single path of output signals with higher power through a transformer. And the output filter module filters the high-power output signal and is connected with the feedback control unit. The feedback control unit is connected with the ultrasonic transducer and used for generating a self-adaptive high-power ultrasonic pulse signal. The direct-current power supply module is connected with the secondary power driving circuit, the output stage power amplifying circuit, the output filter module, the feedback control unit and the like through the energy storage module and is used for generating stable high-voltage signals of hundreds of volts.
The excitation signal source unit generates and controls signals by a field programmable gate array and an embedded processor, and one path of the excitation signal source unit generates pulse square wave signals with variable pulse frequency and duty ratio; one path generates a window modulation sinusoidal signal with variable frequency and amplitude and selectable window function.
The pulse gate control unit comprises a digital-analog isolator, a pulse driving unit and a program-controlled potentiometer.
Furthermore, the digital-to-analog isolator is connected with the excitation signal source unit, and digital pulse signals generated by the excitation signal source unit reach the pulse driving unit after passing through the isolator.
Furthermore, the amplification effect of the pulse driving unit on the pulse square wave signal is related to the magnitude of the power supply voltage for the pulse driving unit, the program-controlled potentiometer is connected with the voltage stabilizer, the output voltage of the voltage stabilizer is adjusted through the embedded processor, and the output voltage is used as the power supply voltage of the pulse driving unit, so that the amplitude of the pulse square wave signal is controlled through a program.
The single-end to differential circuit converts one path of bipolar sinusoidal signals with window functions generated by the excitation signal source unit into two differential unipolar sinusoidal signals, the unipolar signals are generated for the purpose of subsequent signal subtraction operation, and the magnitude of direct-current component voltage of the unipolar signals is the same as the magnitude of amplitude of pulse square wave signals finally obtained by the pulse driving unit; the reason for generating two differential signals is for subsequent power amplification.
The first-level gating amplifying circuit comprises a normal-phase gating amplifying circuit and an inverse-phase gating amplifying circuit.
Furthermore, the pulse square wave signal output by the pulse driving unit and the normal phase unipolar sinusoidal signal output by the circuit are input into the normal phase program control amplifying circuit for subtraction to obtain a normal phase sinusoidal pulse signal.
Furthermore, the pulse square wave signal output by the pulse driving unit and the reversed phase unipolar sinusoidal signal output by the circuit are input into the reversed phase program control amplifying circuit for subtraction to obtain a reversed phase sinusoidal pulse signal.
The secondary power driving circuit comprises a voltage following circuit, a current feedback circuit and an MOS tube driving circuit. The first-level gating amplifying circuits of the two signals are respectively connected with the two second-level power driving circuits. The voltage follower circuit and the current feedback circuit are powered by low voltage, and the MOS tube driving circuit is powered by high voltage.
Furthermore, the voltage follower circuit is connected with the current feedback circuit, so that the circuit impedance can be improved, the current feedback circuit is connected with the driving circuit, the current feedback circuit mainly comprises an operational amplifier, the MOS tube driving circuit mainly comprises an NMOS tube common-leakage circuit, and the NMOS tube common-leakage circuit and the MOS tube driving circuit improve the current driving capability of the circuit together, so that the generated sinusoidal pulse signal can be amplified by the power amplification circuit to obtain a high-power sinusoidal pulse signal.
The output stage power amplification circuit is composed of three groups of differential tube arrays and a transformer module and is used for amplifying the peak value of a sinusoidal pulse signal to more than one kilovolt, and the power output reaches more than 5 kW.
Furthermore, in the three groups of differential tube arrays, each group of array is formed by connecting three pairs of MOS tubes in parallel, and corresponds to a group of transformer coils with opposite windings. Each stage is composed of a pair of NMOS transistors. In the pair of MOS tubes, the source of one MOS tube is connected with the current equalizing resistor and then grounded, the grid is connected with the grid resistor, the grid resistor is connected with a secondary power driving circuit which outputs a positive phase sinusoidal pulse signal, and the drain is connected with a positive phase primary coil of the transformer circuit. The source of the other MOS tube is also connected with the current equalizing resistor and then grounded, the grid is connected with the grid resistor, the grid resistor is connected with a secondary power driving circuit which outputs an inverted sine pulse signal, and the drain is connected with an inverted primary coil of the transformer circuit.
Furthermore, the transformer module is composed of a positive phase primary coil, a negative phase primary coil and a secondary coil. And impedance transformation is carried out by adjusting the turn ratio of the primary coil and the secondary coil so as to adapt to different loads.
The output filter module consists of a power inductor and a capacitor to form an LC type filter, and filters harmonic components while not losing output power so as to obtain an excitation pulse signal with single frequency.
The feedback control unit is used for detecting the impedance of the load and feeding impedance information back to the excitation signal source unit, and the excitation signal source unit adjusts the generated transducer excitation signal according to different impedance conditions, so that the purpose of adaptive impedance matching is achieved, and the output power condition of the ultrasonic pulse transmitting device can be in the optimal state.
The direct current power supply comprises a low-voltage power supply and a high-voltage power supply. The low-voltage power supply is converted by different voltage stabilizer circuits to obtain stable voltages with different amplitudes so as to meet the requirements of various chips. A high-voltage power supply with hundreds of volts is connected with the energy storage module to provide stable large voltage and large current for instantaneous release for the output stage power amplification circuit. The energy storage module is formed by connecting a plurality of capacitors in parallel, and further, the capacity of the energy storage module can be greatly improved by adopting the electrolytic capacitor, so that the instantaneous power release requirement of the output stage power amplification circuit can be met.
The multi-platform high-power self-adaptive ultrasonic pulse transmitting device meets the requirement of subsequent nonlinear guided wave detection based on a digital phase locking technology, and the step of generating an excitation signal is as follows:
s1: analyzing the characteristics of a sample to be tested, calculating an ultrasonic guided wave frequency dispersion curve, selecting two frequencies with better frequency dispersion conditions as ultrasonic emission signal frequency information, and determining output amplitude information according to the load impedance information;
s2: the frequency information and the amplitude information are input into the feedback control unit to generate two groups of sinusoidal signals with window functions for the excitation signal, and the specific steps and requirements are as follows:
s21: generating ultrasonic transmitting signals of the two frequencies S1 by using a direct digital frequency synthesizer and a window function modulator, wherein the ultrasonic transmitting signals are respectively output digital signals of a frequency A and a frequency B, and then converting the ultrasonic transmitting signals into sine excitation analog signals through a digital-to-analog converter;
s22: synthesizing a continuous sine wave reference signal with a fixed frequency by using a direct digital frequency synthesizer; the fixed frequency sine wave should meet the following requirements:
the reference signal is two paths of same-frequency digital signals with more than 16 bits; the phase difference of the two reference signals is 90 degrees; the two reference signal frequencies are frequency A, frequency B or sum frequency or difference frequency of the frequency A and the frequency B;
s3: the sine excitation analog signal generated in the step S21 is subjected to ultrasonic pulse generation by the high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms, the signal returned by the sample to be detected and the continuous sine wave reference signal with fixed frequency generated in the step S22 are subjected to two-phase-sensitive detection calculation, and the amplitude and phase information of the signal returned by the sample to be detected are obtained through calculation;
s4: and adjusting the frequencies of the two paths of reference signals generated in the step S22, repeating the step S3 to obtain the signal amplitude and the phase of the signal returned by the sample to be detected under each frequency, and analyzing to obtain the nonlinear defect information of the sample to be detected.
By means of the technical scheme, the invention has the following advantages and beneficial technical effects:
1) Compared with the prior art, the invention improves the realization mode of the traditional high-voltage pulse transmitting circuit, adopts a multi-stage linear amplifying circuit to amplify the tiny driving signal step by step into a sine wave pulse signal with high amplitude and high power, adopts a differential array isolation driving mode, ensures the stability and the safety of the high-voltage pulse transmitting circuit, improves the defects that the traditional high-voltage pulse can only output positive pulse or negative pulse and can not meet the requirements of an electromagnetic ultrasonic probe, and realizes the high-power ultrasonic transmitting device suitable for multiple platforms.
2) The invention controls common parameters of the sinusoidal pulse signals based on the embedded processor, can generate transducer excitation signals modulated by frequency, amplitude and various window functions, can meet the requirements of piezoelectric ultrasonic probes and the excitation requirements of electromagnetic ultrasonic probes, can be applied to different application scenes in actual detection, and is particularly applied to a nonlinear guided wave detection system based on a digital phase locking technology.
Drawings
FIG. 1 is a structural diagram of a high-power adaptive ultrasonic pulse transmitting device suitable for multiple platforms according to an embodiment of the invention;
FIG. 2 is a signal chain diagram of a first-stage gated amplifier circuit and a second-stage power driver circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an output stage power amplifier circuit according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a feedback control unit in an embodiment of the present invention;
figure 5 is a flow chart of the steps of the nonlinear guided wave detection based on digital phase lock technique to generate the excitation signal.
In the figure:
1: an excitation signal source unit; 2: a pulse gate control unit; 3: a single-ended to differential circuit; 4: a first-level gate control amplifying circuit; 5: a secondary power drive circuit; 6: an output stage power amplifying circuit; 7: an output filter module; 8: a feedback control unit; 9: a direct current power supply; 10: an energy storage module; 11: a load;
50: a voltage follower circuit; 51: a current feedback circuit; 52: a MOS tube driving circuit; 60: a set of power tube arrays; 61: a primary coil of a transformer; 81: a secondary coil adjustment module; 82: and an impedance analysis module.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
The invention discloses a high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms, which structurally comprises: the device comprises an excitation signal source unit 1, a pulse gate control unit 2, a single-end-to-differential circuit 3, a primary gating amplification circuit 4, a secondary power driving circuit 5, an output power amplification circuit 6, an output filter module 7, a feedback control unit 8 and a direct-current power supply and energy storage module. The output end of the excitation signal source unit 1 is respectively connected with the pulse gate control unit 2 and the single-end to differential circuit, and is used for providing system excitation and respectively generating a pulse square wave signal and a bipolar sine signal with a window function. The pulse gate control unit 2 is connected with a first-level gate control amplifying circuit 4 and is used for isolating, driving and adjusting pulse signals generated by the driving signal source unit.
The single-end to differential circuit 3 is also connected with the first-level gating amplification circuit 4 to convert one path of bipolar sinusoidal signals with window functions into two differential paths of unipolar sinusoidal signals.
The first-level gating amplifying circuit 4 is connected with the second-level power driving circuit 5 and used for generating two differential pulse sine signals and amplifying the signals. The low-voltage direct-current power supply module is connected with the modules through different voltage stabilizers and provides power supply voltage.
The secondary power driving circuit 5 is connected with the output stage power amplifying circuit 6 and is used for improving the signal loading capacity of the low-voltage circuit. The output stage power amplifying circuit 6 is connected with the output filter module 7, and is used for performing power amplification on the two paths of differential signals, and converting the two paths of differential signals into a single path of output signal with higher power through a transformer. The input end of the feedback control unit 8 is connected with the ultrasonic transducer, and the output end is connected with the excitation signal source unit 1, and is used for generating a self-adaptive high-power ultrasonic pulse signal. The high-voltage direct-current power supply module is connected with the energy storage module and provides power supply voltage.
Example 1
Referring to fig. 1, fig. 1 is a high-power adaptive ultrasonic pulse transmitting device suitable for multiple platforms according to an embodiment of the present invention. The measuring device structurally comprises an excitation signal source unit 1, a pulse gate control unit 2, a single-ended to differential circuit 3, a primary gating amplification circuit 4, a secondary power driving circuit 5, an output power amplification circuit 6, an output filter module 7, a feedback control unit 8, a direct-current power supply 9 and an energy storage module 10.
In the embodiment shown in fig. 1, the excitation signal source unit 1 is connected to the pulse gate control unit 2 through an isolation unit, and is also connected to the single-ended to differential circuit 3. The pulse gate control unit 2 and the single-end to differential circuit 3 are connected with a first-stage gating amplification circuit 4 at the same time, and are used for generating a sinusoidal pulse signal and performing first-stage amplification on the signal. The primary gated amplifying circuit 4 is connected to a secondary power driving circuit 5 through a voltage follower. The low-voltage power supply of the direct-current power supply 9 is connected with the pulse gate control unit 2, the single-end to differential circuit 3, the first-stage gating amplification circuit 4 and part of the second-stage power driving circuit 5 through the voltage stabilizer.
The secondary power driving circuit 5 is connected with the output stage power amplifying circuit 6 through a common leakage driving circuit, and is used for improving the current load capacity of the circuit before the power amplifying circuit. The output stage power amplifying circuit 6 is connected with an output filter module 7 through a transformer, the output filter module 7 is connected with a feedback control unit 8, and the output end of the feedback control unit 8 is connected with the excitation signal source unit 1 to form a self-adaptive link. The high-voltage power supply of the dc power supply 9 is connected to the output stage power amplifying circuit 6, the output filter module 7, the feedback control unit 8, and part of the second stage power driving circuit 5 through the energy storage module 10.
In this embodiment, the pulse gate control unit 2 controls the amplitude of the square wave signal by using a program-controlled potentiometer, and the principle is as follows: the embedded processor controls the resistance value of the program-controlled potentiometer through the bus, so that the output voltage of the voltage stabilizer is adjusted, and the output voltage of the voltage stabilizer is used as a power supply of the pulse gate control unit 2, so that the amplitude of the square wave signal is controlled. In some embodiments, a sliding rheostat can be used to control the amplitude of the square wave instead of a programmed potentiometer, but the advantage of using a programmed potentiometer is that the parameter adjustment of the system is more automated and intelligent.
In this embodiment, as shown in fig. 2, the single-ended to differential circuit 3 converts one path of bipolar sinusoidal signals with a window function generated by the excitation signal source unit into two differential unipolar sinusoidal signals, where the unipolar signals are generated for the subsequent signal subtraction operation, and the phase difference between the two generated unipolar signals is 180 ° for the subsequent signal amplification operation of the transformer power amplification circuit.
In this embodiment, as shown in fig. 2, the first-stage gated amplifying circuit 4 is configured to subtract the square wave signal at the output end of the pulse gate control unit 2 from the single-pole windowed sinusoidal signal output by the single-ended to differential circuit 3 to obtain a sinusoidal pulse signal. The method for realizing the sine pulse signal by subtracting is to make the amplitude of the square wave output by the pulse gate control unit 2 equal to the direct current quantity of the single-pole windowed sine signal output by the single-end to differential circuit 3, the position of the high level of the square wave is the windowed sine signal without the direct current quantity after passing through the subtracter, and after setting a certain offset of the first-level gate control amplifying circuit 4, the windowed sine signal output by the first-level gate control amplifying circuit 4 is very small and can be ignored. The low level position of the square wave passes through a first-level gate control amplifying circuit 4, the amplitude of the window-contained sinusoidal signal is reduced due to the offset of the subtracter, and the window-contained pulse sinusoidal signal required by a rear circuit is formed after the window-contained sinusoidal signal is amplified by an amplifying module of the first-level gate control amplifying circuit 4.
In this embodiment, as shown in fig. 2, the signal at the output end of the output stage power amplifying circuit 6 reaches thousands of peak-to-peak values, on one hand, in the application of ultrasonic nondestructive testing, there are fewer scenes that require the ultrasonic pulse emitting device to continuously generate the ultrasonic signal; on the other hand, the continuous opening of the MOS transistor in the output stage power amplifying circuit 6 may cause the circuit to generate a large amount of heat, and reduce the service life of the MOS transistor, so the windowed pulse sinusoidal signal is used as the excitation signal of the ultrasonic transducer. The pulse sine signal is used for controlling the duration of the sine signal by controlling the duty ratio of the square wave signal, the MOS tube is closed when no sine signal exists, and the MOS tube is opened when the sine signal exists, so that the power amplification signal is output. In addition, a window function is added to the sine signal through the embedded processor, so that the distortion of the frequency spectrum of the sine signal cut off by the square wave is reduced; and adjusts for different durations of the sinusoidal signal to meet the needs of different scenarios.
In the present embodiment, as shown in fig. 2, the secondary power driving circuit 5 includes a voltage follower circuit 50, a current feedback circuit 51, and a MOS transistor driving circuit 52 connected in the signal transfer direction.
The voltage follower circuit 50 is used for providing a more stable single power voltage for the current feedback circuit 51, and the current feedback circuit 51 and the MOS transistor drive circuit 52 are used for improving the current drive capability of the circuit. The current feedback circuit 51 adopts series current feedback, has large input impedance and small output impedance, and has better load carrying capacity. The MOS transistor driving circuit 52 adopts a common drain connection method, and has good current driving capability although the voltage amplification factor is slightly smaller than 1.
In the present embodiment, as shown in fig. 3, the output stage power amplifying circuit 6 is formed by three groups of circuits in parallel, each group including a power tube array 61 and a transformer primary coil 62.
This power tube array 61 should adopt high pressure resistant MOS pipe, and in the parallelly connected array structure of MOS pipe, the grid of every MOS pipe is in the same place through the resistance joint respectively, and the small difference of self parameters such as the on-resistance of MOS pipe leads to the electric current of each pipe parallelly connected big or small difference easily, and signal mutual interference appears the oscillation, can not output normal signal, generates heat in a large number simultaneously. The MOS tube has positive temperature coefficient, when one path of current is overlarge, the temperature of the MOS tube rises, the resistance is increased, and therefore the current is reduced, and the current equalizing effect is achieved.
In the actual work of the circuit, the current equalizing effect of the MOS tube can not meet the requirement, so that a current equalizing resistor needs to be connected to the source level of the tube, the current equalizing effect of the MOS tube array is improved, and signals can be stably amplified.
Two primary coils in the transformer primary coil 62 have opposite winding directions, and two paths of output signals with a phase difference of 180 degrees correspond to the power tube array 61, and output signals with wider swing amplitude are obtained through transformer coupling. The signals are amplified through the three groups of power tube arrays 61, and finally high-power signals with thousands of peak values are realized so as to meet the excitation requirement of the ultrasonic transducer. The transformer module has the following functions: and adjusting the turn ratio of the primary coil and the secondary coil to perform impedance transformation so as to adapt to different loads.
In the embodiment shown in fig. 1, the output filter module 7 is composed of a power inductor and a capacitor, and forms an LC type filter to filter out harmonic components without losing output power, so as to obtain an excitation pulse signal of a single frequency.
In the present embodiment, as shown in fig. 4, the feedback control unit 8 includes a secondary coil adjustment module 81 and an impedance analysis module 82.
The impedance analysis module 82 is connected to the load 11 and the excitation signal source unit 1, and is configured to detect the impedance of the load 11 and feed back impedance information to the excitation signal source unit 1, where the excitation signal source unit generates control signals according to different impedance conditions to control the secondary coil adjustment module 81 to switch to different gears, so as to implement adaptive impedance matching and maintain the optimal output efficiency of the ultrasonic pulse transmitting apparatus, so as to meet the requirements of different transducer loads.
In the embodiment shown in fig. 1, the dc power supply 9 includes a low voltage power supply and a high voltage power supply. The low-voltage power supply is converted by different voltage stabilizer circuits to obtain stable voltages with different amplitudes so as to meet the requirements of various chips. A high-voltage power supply of several hundred volts is connected with the energy storage module 10 to provide stable large voltage and large current released instantaneously for the output stage power amplification circuit 6. The energy storage module 10 is formed by connecting a plurality of capacitors in parallel, and the capacity of the energy storage module can be greatly improved by adopting the electrolytic capacitor so as to meet the requirement of instantaneous power release of the output stage power amplification circuit.
In this embodiment, as shown in fig. 5, the high-power adaptive ultrasonic pulse transmitting apparatus of the present invention should meet the requirement of the subsequent nonlinear guided wave detection based on the digital phase-locked technique, and the step of generating the excitation signal is as follows:
110: analyzing the characteristics of a sample to be tested, calculating an ultrasonic guided wave frequency dispersion curve, selecting two frequencies with better frequency dispersion conditions as ultrasonic emission signal frequency information, and determining output amplitude information according to the load impedance information.
111: the frequency information and the amplitude information are input into the feedback control unit to generate two groups of sinusoidal signals with window functions for the excitation signals, ultrasonic emission signals with two frequencies are generated 110 by using a direct digital frequency synthesizer and a window function modulator, the ultrasonic emission signals are respectively output digital signals with frequency A and frequency B, and the ultrasonic emission signals are converted into sinusoidal excitation analog signals through a digital-to-analog converter.
112: a continuous fixed frequency sine wave reference signal is synthesized using a direct digital frequency synthesizer. The fixed frequency sine wave should meet the following requirements:
the reference signal is two paths of same-frequency digital signals with more than 16 bits; the phase difference of the two reference signals is 90 degrees; the two reference signal frequencies are frequency A, frequency B or sum frequency or difference frequency of the frequency A and the frequency B;
113, generating ultrasonic pulses by the high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms according to the embodiment of the invention by the sine excitation analog signal generated by the 111, performing two-phase-sensitive detection calculation on a signal returned by the sample to be detected and a continuous sine wave reference signal with fixed frequency generated by the 112, and calculating to obtain amplitude and phase information of the signal returned by the sample to be detected.
114: and adjusting the frequencies of the two paths of reference signals generated in the step S22, and repeating the step S3.
115: and obtaining the signal amplitude and the phase of the signal returned by the sample to be detected under each frequency.
116: and analyzing to obtain the nonlinear defect information of the sample to be detected.
To further illustrate, the above nonlinear guided wave detection based on digital phase-lock technique is implemented for a specific frequencyUltrasonic guided wave signal, two ultrasonic guided wave signals with input, wherein, f is 2 (t)＝A 2 sin(2πf 2 t+φ 2 ) Two paths of ultrasonic signals with different frequencies are input into a sample, and if the sample has a nonlinear effect, the following nonlinear signals are generated:
f r (t)＝A r sin(2π(f 1 ±f 2 )t+φ)；
generating two paths of reference signals with the same frequency and 90-degree phase difference;
f R (t)＝sin(2πf R t)；
f R (t)＝cos(2πf R t)；
respectively carrying out frequency mixing operation with the signals to be measured:
setting a reference frequency f R ＝f 1 ±f 2 Is simplified to obtain
The result of the above formula has three parts, wherein the first part comprises the amplitude f of the signal to be measured R The amplitude of the reference signal and the cosine value of the phase difference of the input signal relative to the reference signal, and under the condition that the input useful signal and the reference signal are stable in analysis, the part can be considered as a certain value, namely a direct current signal; similarly, the second part is the double frequency alternating current signal of the original reference signal; the third part is the multiplication of the noise signal and the reference signal, and the random signal has no correlation with the reference signal according to the completeness of the sine signal, and the integral result is zero.
The signals obtained after the frequency mixing pass through a filtering unit to output signals of the orthogonal component output end as
Outputting signals of the in-phase component output terminalIs composed of
The two signals are subjected to square root operation and arc tangent operation to obtain amplitude information A of the measured intermediate frequency modulation signal r (t) and phase information phi r . The structural performance of the material can be effectively analyzed by analyzing the amplitude and phase information of the ultrasonic guided wave signals in different frequency components.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (6)
1. A high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms is characterized by comprising: an excitation signal source unit, a pulse gate control unit, a single-end to differential circuit, a primary gate control amplifying circuit, a secondary power driving circuit, an output stage power amplifying circuit, an output filter module, a feedback control unit, a direct current power supply and an energy storage module,
the excitation signal source unit is connected with the pulse gate control unit through the isolation unit and is simultaneously connected with the single-end-to-differential circuit; the pulse gate control unit and the single-end to differential circuit are simultaneously connected with a first-stage gating amplification circuit and are used for generating a sinusoidal pulse signal and carrying out first-stage amplification on the signal; the first-level gate control amplifying circuit is connected with the second-level power driving circuit through a voltage follower;
the excitation signal source unit is used for respectively using a universal input/output port to generate pulse square wave signals, using a digital-to-analog converter to generate bipolar sine wave signals modulated by window functions, connecting a circuit for generating the pulse square wave signals with the pulse gate control unit, and connecting a circuit for generating the bipolar sine wave signals modulated by the window functions with the single-ended to differential circuit; the single-end-to-differential circuit converts one path of bipolar sinusoidal signals with window functions into two differential paths of unipolar sinusoidal signals;
the second-stage power driving circuit is connected with the output-stage power amplifying circuit through the common-drain driving circuit; the output stage power amplifying circuit is connected with an output filter module through a transformer, the output filter module is connected with a feedback control unit, and the output end of the feedback control unit is connected with an excitation signal source unit to form a self-adaptive link; the high-voltage power supply of the direct-current power supply is connected with the output stage power amplifying circuit, the output filter module, the feedback control unit and part of the secondary power driving circuit through the energy storage module;
the first-stage gating amplifying circuit is connected with the second-stage power driving circuit, and carries out analog subtraction operation on the front pulse square wave signal and the two single-stage sinusoidal signals to obtain two sinusoidal pulse signals in the form of differential signals and amplify the two differential signals;
the direct-current power supply is connected with the excitation signal source unit, the pulse gate control unit, the single-end to differential circuit and the primary gate control amplifying circuit through different voltage stabilizers to obtain corresponding level signals and provide bias for signal generation and conversion;
the feedback control unit is connected with the ultrasonic transducer and is used for generating a self-adaptive high-power ultrasonic pulse signal;
the low-voltage power supply of the direct-current power supply is connected with the pulse gate control unit, the single-ended to differential circuit, the primary gating amplification circuit and part of the secondary power driving circuit through the voltage stabilizer.
2. High power adaptive ultrasonic pulse emitting device adapted for multiple platforms according to claim 1, characterized in that: the pulse gate control unit consists of a digital isolator, a pulse driving unit and an adjustable potentiometer;
the adjustable potentiometer is a slide rheostat or a program control potentiometer; for the program-controlled potentiometer, the embedded processor is connected with the program-controlled potentiometer, the resistance value of the program-controlled potentiometer is controlled through the bus, the output voltage of the voltage stabilizer is further adjusted, and the voltage stabilizer is connected with the pulse gate control unit and used as a power supply of the pulse gate control unit, so that the high-level amplitude of the pulse square wave signal is controlled.
3. High power adaptive ultrasonic pulse emitting device adapted for multiple platforms according to claim 1, characterized in that: the first-level gating amplification circuit comprises a subtractor module and a signal amplification module;
the subtracter module subtracts the pulse square wave signal from the windowed unipolar sinusoidal signal to obtain a sinusoidal pulse signal; the subtracter has a certain offset, so that the signals obtained by subtraction have the signal with a high level part weakened and the noise signals with a low level part inhibited, thereby obtaining sine pulse signals, and the signal amplification module amplifies the sine pulse signals.
4. High power adaptive ultrasound pulse emitting device for multiple platforms, according to claim 1, characterized by: the output stage power amplification circuit comprises three groups of differential tube arrays and a transformer module;
in the three groups of differential tube arrays, each group of array is formed by connecting three pairs of MOS tubes in parallel, corresponding to a group of transformer coils with opposite windings, and each pair of the three groups of differential tube arrays is formed by a pair of NMOS tubes;
one MOS tube of the pair of MOS tubes has its source connected to the current equalizing resistor and then grounded, its gate connected to the grid resistor, the grid resistor connected to the secondary power driving circuit for outputting positive phase sine pulse signal, and its drain connected to the positive phase primary coil of the transformer circuit,
the source electrode of the other MOS tube is also connected with the current equalizing resistor and then grounded, the grid electrode is connected with the grid electrode resistor, the grid electrode resistor is connected with a secondary power driving circuit which outputs an inverted sine pulse signal, and the drain electrode is connected with an inverted primary coil of the transformer circuit.
5. High power adaptive ultrasonic pulse emitting device adapted for multiple platforms according to claim 1, characterized in that:
the feedback control unit comprises a secondary coil adjusting module and an impedance analyzing module; the impedance analysis module is connected with the load and the excitation signal source unit and used for detecting the impedance of the load and feeding impedance information back to the excitation signal source unit, the excitation signal source unit adjusts the generated excitation signal according to the impedance characteristic conditions of different ultrasonic transducers, and the impedance matching loop is output for chip selection.
6. A signal excitation method and a subsequent detection method suitable for nonlinear guided wave detection of a digital phase-locked technology are characterized by comprising the following steps:
s1: analyzing the characteristics of a sample to be tested, calculating an ultrasonic guided wave frequency dispersion curve, selecting two frequencies with better frequency dispersion conditions as ultrasonic emission signal frequency information, and determining output amplitude information according to load impedance information;
s2: the frequency information and the amplitude information are input into a feedback control unit to generate two groups of sinusoidal signals with window functions for the excitation signals, and the specific steps and requirements are as follows:
s21: generating ultrasonic transmitting signals of the two frequencies S1 by using a direct digital frequency synthesizer and a window function modulator, wherein the ultrasonic transmitting signals are respectively output digital signals of a frequency A and a frequency B, and then converting the output digital signals into sine excitation analog signals through a digital-to-analog converter;
s22: synthesizing a continuous sine wave reference signal with a fixed frequency by using a direct digital frequency synthesizer; the fixed frequency sine wave should meet the following requirements:
the reference signal is two paths of same-frequency digital signals with more than 16 bits; the phase difference of the two reference signals is 90 degrees; the two reference signal frequencies are frequency A, frequency B or sum frequency or difference frequency of the frequency A and the frequency B;
s3: the sine excitation analog signal generated in the step S21 is subjected to ultrasonic pulse generation by the high-power self-adaptive ultrasonic pulse transmitting device suitable for multiple platforms in claim 1, a signal returned by a sample to be detected and a continuous sine wave reference signal with fixed frequency generated in the step S22 are subjected to two-phase-sensitive detection calculation, and amplitude and phase information of the signal returned by the sample to be detected are obtained through calculation;
s4: adjusting the frequencies of the two paths of reference signals generated in the step S22, repeating the step S3 to obtain the signal amplitude and the phase of the signal returned by the sample to be tested under each frequency, and analyzing to obtain the nonlinear defect information of the sample to be tested;
the direct digital frequency synthesizer that generates the output digital signal and the sine wave reference signal should be driven by the same clock source, and the frequency control words are derived from the frequency a, the frequency B, and the result of both through mathematical calculations.
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