Excitation control system based on passive and wireless ultrasonic transducer

Abstract

The invention belongs to the field of electronic circuits, and provides an excitation control system based on a passive and wireless ultrasonic transducer, which is characterized in that a first transmitting circuit receives a high-frequency excitation signal and generates a high-frequency electromagnetic wave signal after power amplification; the pulse excitation circuit based on the PNP triode rectifies the received high-frequency electromagnetic wave signal and stores energy, and generates an instantaneous pulse excitation signal; the second transmitting circuit receives the high-frequency carrier signal, provides the high-frequency carrier signal to a passive wireless ultrasonic transducer end after power amplification, and sends a demodulation reference signal to the receiving circuit; the passive wireless ultrasonic transducer end excites a low-frequency ultrasonic signal of which the frequency is the same as the resonant frequency, and after the high-frequency carrier signal is received, the low-frequency ultrasonic signal and the high-frequency carrier signal are subjected to frequency mixing modulation to obtain a high-frequency modulation signal; and the receiving circuit filters and amplifies the high-frequency modulation signal and then performs frequency mixing demodulation on the high-frequency modulation signal and a demodulation reference signal to obtain a low-frequency ultrasonic sensing signal. The power of the ultrasonic transducer can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic circuits, and in particular to an excitation control system based on a passive wireless ultrasonic transducer. Background Art

[0002] The key components of existing major equipment and facilities are prone to fatigue, damage, and failure during service or storage. Timely mastering the structural health status of key components is an effective guarantee to prevent major accidents. However, many equipment, such as rotating parts of drilling equipment, key load-bearing parts of stored weapons (projectiles), aircraft engines, wind turbine pitch bearings, special-shaped structural parts, etc., face difficulties such as limited sensor installation space and inability to assemble power supply and sensor data wires after assembly. Therefore, wireless ultrasonic transducers can be used to solve the above problems.

[0003] Therefore, if a passive wireless ultrasonic transducer is used, in the traditional ultrasonic transducer excitation method, that is, directly loading the periodic excitation signal onto the ultrasonic transducer, due to the low energy of the electromagnetic wave signal, the energy of the transducer excitation will be weak, making the excitation power of the passive wireless ultrasonic transducer too low. Summary of the invention

[0004] The purpose of the present invention is to provide an excitation control system based on a passive wireless ultrasonic transducer. The pulse excitation circuit based on a PNP transistor stores low-energy electromagnetic signals and generates instantaneous pulse excitation signals through instantaneous discharge, thereby increasing the instantaneous excitation power and achieving the purpose of increasing the ultrasonic excitation power.

[0005] The present invention solves the technical problem and adopts the following technical solution: The excitation control system of the ultrasonic transducer based on passive wireless includes: The first transmitting circuit is used to receive the high-frequency excitation signal and generate a high-frequency electromagnetic wave signal after power amplification, and input it into the pulse excitation circuit based on the PNP transistor; The pulse excitation circuit based on the PNP transistor is used to rectify and store the received high-frequency electromagnetic wave signal, generate an instantaneous pulse excitation signal, and input it into the passive wireless ultrasonic transducer; A second transmitting circuit is used to receive a high-frequency carrier signal and send it to the passive wireless ultrasonic transducer end after power amplification, and to send a demodulation reference signal to the receiving circuit; The passive wireless ultrasonic transducer end is used to excite a low-frequency ultrasonic signal having the same frequency as the resonant frequency according to the received instantaneous pulse excitation signal, and is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal after receiving the high-frequency carrier signal to obtain a high-frequency modulated signal, and send it to the receiving circuit; The receiving circuit is used to receive the high-frequency modulation signal and the demodulation reference signal, and mix and demodulate the high-frequency modulation signal with the demodulation reference signal after filtering and amplification to obtain a low-frequency ultrasonic sensor signal. The low-frequency ultrasonic sensor signal is filtered and amplified for collection by the signal collector.

[0006] Furthermore, the pulse excitation circuit based on the PNP transistor includes a first rectifier, a second rectifier, a first energy storage device, a second energy storage device and a PNP transistor; The input end of the first rectifier and the input end of the second rectifier are both connected to a high-frequency electromagnetic wave signal, the output end of the first rectifier is connected to the input end of the first energy storage device, the output end of the second rectifier is connected to the input end of the second energy storage device, the output end of the first energy storage device is connected to the emitter of the PNP transistor, the output end of the second energy storage device is connected to the base of the PNP transistor, and the collector of the PNP transistor is connected to the input end of the passive wireless ultrasonic transducer; The capacitance value of the first energy storage device is lower than the capacitance value of the second energy storage device.

[0007] Furthermore, the high-frequency electromagnetic wave signal is an AC signal, and after being rectified by the first rectifier and the second rectifier, the same DC charging current is input to the first energy storage device and the second energy storage device respectively; Under the action of the same DC charging current, the voltage rise rate of the second energy storage is lower than the voltage rise rate of the first energy storage, so that before the first energy storage is fully charged, the second energy storage is not fully charged, and the conduction of the PNP transistor will not be triggered at this time. After the second energy storage is fully charged, the PNP transistor is turned on. At this time, the electric energy stored in the first energy storage is applied to the passive wireless ultrasonic transducer, that is, a pulse excitation signal for applying to the passive wireless ultrasonic transducer is generated.

[0008] Furthermore, the first transmitting circuit includes a first power amplifier, a first rotating antenna and a first patch antenna; The input end of the first power amplifier is used to connect to the high-frequency excitation signal, and the output end is used to output the high-frequency excitation signal after power amplification and input it to the input end of the first rotating antenna. The output end of the first rotating antenna is used to transmit a high-frequency electromagnetic wave signal to the first patch antenna. After the first patch antenna receives the high-frequency electromagnetic wave signal, it is input into the pulse excitation circuit based on the PNP transistor.

[0009] Furthermore, the second transmitting circuit includes a second power amplifier, a second rotating antenna and a second patch antenna; The input end of the second power amplifier is used to access the high-frequency carrier signal, and the output end is used to output the high-frequency carrier signal after power amplification and input it to the input end of the second rotating antenna. The output end of the second rotating antenna is used to transmit the high-frequency carrier signal after power amplification to the second patch antenna. After receiving the high-frequency carrier signal, the second patch antenna sends it to the passive wireless ultrasonic transducer end; The second transmitting circuit uses the high frequency carrier signal which is not input to the second power amplifier as a demodulation reference signal and sends it to the receiving circuit.

[0010] Furthermore, the passive wireless ultrasonic transducer end includes a passive wireless ultrasonic transducer and a first mixer; The passive wireless ultrasonic transducer is used to receive the low-frequency ultrasonic signal and the high-frequency carrier signal, and send them to the input end of the first mixer; The first mixer is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal to obtain a high-frequency modulated signal, and send it to the receiving circuit through the output end.

[0011] Furthermore, the passive wireless ultrasonic transducer is a plasma-sprayed piezoelectric ultrasonic film, which serves as a sensing layer and is coupled to the measured element through a transition layer.

[0012] Furthermore, the receiving circuit includes a second mixer, a first filter amplifier, a second filter amplifier, a third rotating antenna and a third patch antenna; The third patch antenna is used to receive the high-frequency modulated signal and send it to the third rotating antenna. The third rotating antenna is used to send the received high-frequency modulated signal to the input end of the first filter amplifier. After being filtered and amplified by the first filter amplifier, the filtered and amplified high-frequency modulated signal is sent to the input end of the second mixer through its output end. The input end of the second mixer is used to receive the high-frequency modulation signal and the demodulation reference signal after filtering and amplification, and obtain the low-frequency ultrasonic sensor signal after mixing and demodulation, and input the low-frequency ultrasonic sensor signal to the input end of the second filter amplifier through its output end. The low-frequency ultrasonic sensor signal is filtered and amplified by the second filter amplifier and input to the input end of the signal collector through its output end.

[0013] Furthermore, the first rotating antenna, the second rotating antenna and the third rotating antenna are all connected to stepper motors, which can automatically adjust the direction and angle of the corresponding rotating antenna according to the strength of their respective received signals.

[0014] Furthermore, the automatically adjusting the direction and angle of the corresponding rotating antenna according to the strength of each received signal refers to: During the rotating antenna rotation focusing process, the rotating antenna continuously rotates while monitoring the received signal strength. When the signal strength reaches the maximum value, the rotating antenna automatically stops rotating and records the current direction and angle.

[0015] The beneficial effects of the present invention are as follows: first, a high-frequency excitation signal is received by a first transmitting circuit and a high-frequency electromagnetic wave signal is generated after power amplification, and is input into a pulse excitation circuit based on a PNP transistor; then, the received high-frequency electromagnetic wave signal is rectified and energy is stored by a pulse excitation circuit based on a PNP transistor, and an instantaneous pulse excitation signal is generated and input into a passive wireless ultrasonic transducer. Since low-energy electromagnetic signals can be stored and discharged instantaneously, the instantaneous excitation power can be increased, thereby achieving the purpose of increasing the ultrasonic excitation power; then, a high-frequency carrier signal is received by a second transmitting circuit and is input into a passive wireless ultrasonic transducer after power amplification, so that a high-frequency carrier signal can be provided for the sensing signal of the passive wireless ultrasonic transducer. At the same time, the second transmitting circuit can also send a demodulation reference signal to the receiving circuit for demodulation.

[0016] Then, through the passive wireless ultrasonic transducer end, according to the received instantaneous pulse excitation signal, a low-frequency ultrasonic signal with the same frequency as the resonant frequency is excited. After receiving the high-frequency carrier signal, the low-frequency ultrasonic signal is mixed and modulated with the high-frequency carrier signal to obtain a high-frequency modulated signal, and it is sent to the receiving circuit; finally, through the receiving circuit, the high-frequency modulated signal and the demodulation reference signal are received, and the high-frequency modulated signal is filtered and amplified and mixed and demodulated with the demodulation reference signal to obtain a low-frequency ultrasonic sensor signal. The low-frequency ultrasonic sensor signal is filtered and amplified for collection by the signal collector.

[0017] Therefore, through the excitation control method of the passive wireless ultrasonic transducer of the present invention, low-energy electromagnetic signals can be stored, and instantaneous pulse excitation signals can be generated through instantaneous discharge, thereby increasing the instantaneous excitation power and achieving the purpose of increasing the ultrasonic excitation power, thereby avoiding the problem of weak energy excitation of the transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the circuit composition of the excitation control system based on passive wireless ultrasonic transducer in the first embodiment of the present invention; Figure 2 It is a schematic diagram of the overall structure of the excitation control system based on the passive wireless ultrasonic transducer in the second embodiment of the present invention; Figure 3 This is a schematic diagram of the voltage rise rate of two energy storage devices with different capacities in the second embodiment of the present invention; Figure 4 Schematic diagram of the discharge rate of two transducers in the second embodiment of the present invention; Figure 5 Schematic diagram of an equivalent resonant circuit of a passive wireless ultrasonic transducer in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of plasma spraying a workpiece in the second embodiment of the present invention; Figure 7 It is a schematic diagram of the case where a transition layer is produced when bonding the piezoelectric ceramic and the metal part in the second embodiment of the present invention; Figure 8 It is a schematic diagram of the structure of an adaptive rotatable antenna in Embodiment 2 of the present invention.

[0019] Wherein, 101 represents a first transmitting circuit, 102 represents a pulse excitation circuit based on a PNP transistor, 103 represents a second transmitting circuit, 104 represents a passive wireless ultrasonic transducer end, 105 represents a receiving circuit, Q represents a PNP transistor, f 1 Indicates the frequency f 1 The high frequency excitation signal, f 2 Indicates the frequency f 2 The carrier excitation signal, f u Indicates the frequency f u of ultrasonic signals. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. Example 1

[0021] This embodiment provides an excitation control system based on a passive wireless ultrasonic transducer. The circuit diagram thereof is shown in Figure 1 , where the system consists of the following parts: The first transmitting circuit is used to receive the high-frequency excitation signal and generate a high-frequency electromagnetic wave signal after power amplification, and input it into the pulse excitation circuit based on the PNP transistor; The pulse excitation circuit based on the PNP transistor is used to rectify and store the received high-frequency electromagnetic wave signal, generate an instantaneous pulse excitation signal, and input it into the passive wireless ultrasonic transducer; A second transmitting circuit is used to receive a high-frequency carrier signal and send it to the passive wireless ultrasonic transducer end after power amplification, and to send a demodulation reference signal to the receiving circuit; The passive wireless ultrasonic transducer end is used to excite a low-frequency ultrasonic signal having the same frequency as the resonant frequency according to the received instantaneous pulse excitation signal, and is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal after receiving the high-frequency carrier signal to obtain a high-frequency modulated signal, and send it to the receiving circuit; The receiving circuit is used to receive the high-frequency modulation signal and the demodulation reference signal, and mix and demodulate the high-frequency modulation signal with the demodulation reference signal after filtering and amplification to obtain a low-frequency ultrasonic sensor signal. The low-frequency ultrasonic sensor signal is filtered and amplified for collection by the signal collector.

[0022] In this embodiment, since a passive wireless ultrasonic transducer is required, a traditional transducer is not used, and a traditional transducer excitation method is not used, a high-frequency excitation signal is not directly applied to the passive wireless ultrasonic transducer. If a periodic excitation signal is directly loaded onto the ultrasonic transducer, the energy of the transducer excitation will be weak due to the low energy of the electromagnetic wave signal. In the present invention, after the first transmitting circuit emits a high-frequency electromagnetic wave signal, the high-frequency electromagnetic wave signal is rectified and stored by a pulse excitation circuit based on a PNP transistor, and an instantaneous pulse excitation signal is generated through an instantaneous discharge method to increase the instantaneous excitation power, which is then input into the passive wireless ultrasonic transducer. Therefore, the ultrasonic excitation power can be increased and the problem of weak transducer excitation energy can be avoided. Example 2

[0023] On the basis of Example 1, the passive wireless ultrasonic transducer excitation control system provided in this embodiment has an overall structural diagram as shown in Figure 2. The system also includes a first transmitting circuit 101, a PNP transistor-based pulse excitation circuit 102, a second transmitting circuit 103, a passive wireless ultrasonic transducer end 104 and a receiving circuit 105.

[0024] In this embodiment, after using the passive wireless ultrasonic transducer end, since the antenna transmits low-frequency signals of ultrasonic frequencies, its size will be very large. Therefore, when the antenna is used for signal transmission in the two-way transmitting circuit, high-frequency signal transmission is used, which can greatly reduce the size of the antenna. If the electromagnetic wave signal is directly transmitted at the ultrasonic working frequency, the size of the antenna will be very large, which is not conducive to use and thus loses its practical value.

[0025] Therefore, in the above system of this embodiment, the first transmitting circuit 101 may include a first power amplifier, a first rotating antenna and a first patch antenna; the input end of the first power amplifier is used to access a high-frequency excitation signal, and its frequency is f1 The output end is used to output the high-frequency excitation signal after power amplification and input it to the input end of the first rotating antenna. The output end of the first rotating antenna is used to transmit a high-frequency electromagnetic wave signal to the first patch antenna. After the first patch antenna receives the high-frequency electromagnetic wave signal, it is input to the pulse excitation circuit 102 based on the PNP transistor.

[0026] In this embodiment, the PNP transistor-based pulse excitation circuit 102 may include a first rectifier, a second rectifier, a first energy storage device, a second energy storage device and a PNP transistor Q; the input end of the first rectifier and the input end of the second rectifier are both connected to a high-frequency electromagnetic wave signal, the output end of the first rectifier is connected to the input end of the first energy storage device, the output end of the second rectifier is connected to the input end of the second energy storage device, the output end of the first energy storage device is connected to the emitter of the PNP transistor Q, the output end of the second energy storage device is connected to the base of the PNP transistor Q, and the collector of the PNP transistor Q is connected to the input end of the passive wireless ultrasonic transducer; here, due to the use of an energy storage capacitor, low-energy electromagnetic signals can be stored, and the instantaneous excitation power can be increased by controlling the instantaneous discharge of the PNP tube, thereby achieving the purpose of increasing the ultrasonic excitation power.

[0027] like Figure 3 As shown, the capacitance value of the first energy storage device is lower than the capacitance value of the second energy storage device. Figure 3 The energy storage device charging process in the diagram is essentially a capacitor. The ordinate represents the voltage across the capacitor, and the abscissa represents the capacitor charging time. Since the charging voltage is a DC current, and the capacitance value of the first energy storage device is lower than that of the second energy storage device, according to the formula: △U=I△t÷C, it can be concluded that the relationship between the voltage and time of the two energy storage devices changes linearly and the first energy storage device is fully charged first. V1 and t1 represent the total charging voltage and charging time of the first energy storage device, respectively, and V2 and t2 represent the total charging voltage and charging time of the second energy storage device, respectively.

[0028] Here, since the efficiency of wireless electromagnetic wave energy transmission is low and the frequency of general ultrasound is several MHz, if the ultrasound is directly excited by an excitation signal of ultrasonic frequency through an antenna, the power of the required excitation signal will be very high, and the size of the transmitting and receiving antennas will be very large, and the miniaturization of the instrument system and the sensor cannot be achieved. Therefore, the system excitation end of this embodiment generates a high-frequency excitation signal with a frequency of f 1 , after being amplified by the first power amplifier, is input to the first rotating antenna. The transmission frequency of the first rotating antenna is f 1The high-frequency electromagnetic waves are received by the first patch antenna and rectified by two rectifiers, so that the high-frequency AC signals received by the antenna can be rectified into DC signals. The back ends of the two DC signals are each connected to an energy storage device, namely, an energy storage capacitor, which is used to store weak DC current.

[0029] Generally, the high-frequency electromagnetic wave signal is an AC signal. After being rectified by the first rectifier and the second rectifier, the same DC charging current is input to the first energy storage device and the second energy storage device respectively. Under the action of the same DC charging current, the voltage rise rate of the second energy storage device is lower than the voltage rise rate of the first energy storage device, so that before the first energy storage device is fully charged, the second energy storage device is not fully charged, and the conduction of the PNP transistor will not be triggered at this time. After the second energy storage device is fully charged, the PNP transistor is turned on. At this time, the electric energy stored in the first energy storage device is applied to the passive wireless ultrasonic transducer, that is, a pulse excitation signal for applying to the passive wireless ultrasonic transducer is generated. Compared with the actual periodic electromagnetic wave excitation directly to the ultrasonic transducer, this method can significantly improve the excitation power.

[0030] like Figure 4 As shown, the two energy storage devices can match different discharge impedances, so that the first energy storage device discharges quickly and the second energy storage device discharges slowly, which can ensure that the excitation signal applied to the passive wireless ultrasonic transducer is a pulse excitation, and at the moment of discharge of the first energy storage device, the rapid discharge of the second energy storage device will not cause the PNP transistor Q to be cut off, thereby affecting the full release of the energy of the first energy storage device. Figure 4 The discharge process of the energy storage device in the diagram, the ordinate represents the voltage across the capacitor, and the abscissa represents the capacitor discharge time. Here, since the current is no longer direct current during the discharge process, the discharge process is no longer a linear change. Similarly, based on the relationship between the capacitor voltage and current, it can be concluded that the relationship between the voltage and time of the two energy storage devices presents a nonlinear change and the first energy storage device discharges faster.

[0031] like Figure 5 As shown in the figure, the piezoelectric film or piezoelectric sheet of the ultrasonic transducer is equivalent to a capacitor. After reasonable impedance matching, a resonant circuit can be formed. When a pulse excitation is applied to the ultrasonic transducer, an ultrasonic wave with the same frequency as the resonant frequency can be excited. fu .for Figure 5 The equivalent resonant circuit in, where V represents the excitation voltage, L represents the inductance, C represents the capacitance, which is essentially the equivalent of the ultrasonic transducer, R and R1 represent two resistors, V is mainly used to provide a voltage signal of a specific frequency for the subsequent operation, and this frequency needs to match the resonant frequency of the subsequent circuit, the role of L and C is to produce resonance to make the signal as good as possible, the role of the parallel resistor R1 is to increase the damping to stabilize the circuit, adjust the quality factor, and provide partial load matching, and the role of the series resistor R is to limit the current, divide the voltage, and adjust the overall circuit characteristics.

[0032] In actual applications, because traditional piezoelectric ultrasonic sensors are based on the piezoelectric effect, when a high-frequency AC voltage is applied to piezoelectric ceramics, the piezoelectric ceramics vibrate at high frequency due to the piezoelectric effect, generating ultrasonic waves that are applied to the object being tested. When the high-frequency echo is applied to the piezoelectric ceramics, a voltage signal is generated on the piezoelectric ceramics. In engineering applications, the information of the metal parts being tested is fed back based on the echo voltage signal. Piezoelectric ultrasonic sensors usually require a coupling medium to allow the sound energy to penetrate the object being tested, and different coupling agents produce different effects. Liquid coupling agents also face a series of problems such as coupling agent flow, volatilization, and corrosion. In addition, piezoelectric ultrasonic sensors need to be in contact with the object being tested for measurement, and cannot complete measurements at extremely high temperatures.

[0033] Therefore, the passive wireless ultrasonic transducer in this embodiment is a plasma-sprayed piezoelectric ultrasonic film, which serves as a sensing layer and is coupled to the measured element through a transition layer. This process can ensure that there is no coupling between the ultrasonic transducer and the measured component, thereby ensuring long-term reliability. Among them, plasma spraying technology is used to spray a piezoelectric ceramic coating on the surface of the metal to be measured, and the piezoelectric ceramic coating can form a piezoelectric ultrasonic transducer after polarization. There is a significant difference between piezoelectric ceramic materials and ordinary thermal barrier coating (TBCS) ceramic materials in terms of bonding with metal parts, that is, piezoelectric ceramics are not easy to bond with metal parts, which makes the plasma-sprayed piezoelectric ceramic coating very easy to fall off.

[0034] The plasma spraying piezoelectric ultrasonic film in this embodiment sprays piezoelectric ceramics on the surface of the measured object, integrates the signal sensitive unit with the measured object, completes the acquisition of the measured object signal, and the plasma spraying process is set as follows: (1) Use acetone to clean the metal surface. Acetone, as an organic solvent, is both fat-soluble and water-soluble, and can effectively clean the dirt on the surface of the metal part being tested; (2) Grinding and drying treatment; (3) Sandblasting: The function of sandblasting is to increase the surface roughness of the substrate, and after spraying, it can enhance the bonding strength between the coating and the substrate; (4) Introducing a bonding transition layer between the metal structure and the piezoelectric ceramic coating, that is, spraying the mixture of homogeneous metal powder of the metal part being tested and piezoelectric ceramic powder; (5) During the bonding transition layer spraying process, the proportion of metal powder and ceramic powder is gradually reduced, such as Figure 6As shown, the powder feeding pipe 1 and the powder feeding pipe 2 are used to control the proportion of metal powder and ceramic powder, so that the piezoelectric ceramic and the metal part are closely combined; in the process of spraying the bonding transition layer, in order to solve the problem that the piezoelectric ceramic and the metal are not easy to bond, in this embodiment, the processed device is first heated to a certain temperature to reduce the difference in thermal expansion coefficient between the coating and the device, and improve the bonding strength of the layer. Secondly, the initial ratio of metal powder and piezoelectric ceramic powder is set to 3:1 to start spraying, and spray layer by layer according to the ratio of 2.6:1, 2.2:1, 1.8:1, 1.4:1, and 1:1, and finally form a combination of 6 layers of coating, collect signals gradually transition from the tested part to the metal and finally to the piezoelectric ceramic, collect the return value of the signal, and the excitation signal gradually transitions from the piezoelectric ceramic to the metal and finally to the tested part to form an ultrasonic wave; (6) Apply silver paste on the sprayed surface, polarize under high voltage, prepare electrodes and test the piezoelectric ceramic performance; see Figure 7 Plasma spraying of piezoelectric ultrasonic film realizes the coupling-free connection between the passive wireless ultrasonic transducer and the device under test, solving the long-standing problem of piezoelectric ultrasound relying on coupling agents and being unable to measure in extremely high temperature environments. It also ensures the stability of the long-term sensing structure. Among them, the biggest difference between ultrasonic spraying and different ceramic spraying is that piezoelectric ceramic powder is not easy to combine with metal bodies (ordinary ceramics are easy to combine), so a transition layer is made during spraying, mixing metal powder with ceramic powder, and gradually adjusting the ratio of the two powders to form a transition layer.

[0035] In this embodiment, the second transmitting circuit 103 may include a second power amplifier, a second rotating antenna and a second patch antenna; the input end of the second power amplifier is used to access a high-frequency carrier signal, whose frequency is f 2 , whose output end is used to output the high-frequency carrier signal after power amplification and input it to the input end of the second rotating antenna. The output end of the second rotating antenna is used to transmit the high-frequency carrier signal after power amplification to the second patch antenna. After receiving the high-frequency carrier signal, the second patch antenna sends it to the passive wireless ultrasonic transducer end, which can provide a high-frequency carrier signal for the sensor signal of the transducer. At the same time, the second transmitting circuit 103 uses the high-frequency carrier signal that is not input to the second power amplifier as a demodulation reference signal, and its frequency is also f 2 .

[0036] In actual application, after ultrasonic waves propagate in the test piece, they encounter target signals such as defects, and then reflect the sensing signal to the ultrasonic transducer, thereby generating a frequency f uHowever, the sensor signal is very weak. If it is directly connected to the transmitting antenna, the electromagnetic wave signal excited by the antenna will be extremely weak, and the receiving antenna cannot receive the effective sensor signal. In addition, since the frequency of the ultrasonic signal is very low, if the low-frequency signal is to be directly transmitted, the size of the transmitting antenna at the passive wireless ultrasonic transducer end will be very large, resulting in the sensor being unable to be installed on the device under test. Therefore, in this embodiment, the sensor signal received by the passive wireless ultrasonic transducer is input to the first mixer, and the system excitation end is synchronously excited to generate a frequency of f 2 The carrier excitation signal is transmitted to the second patch antenna through the second power amplifier and the second rotating antenna, and then the frequency is f 2 The carrier excitation signal is also input to the first mixer, and the frequency is f 2 ± f u The modulation signal, f 2 The frequency is much greater than f u The modulated signal is transmitted through the third patch antenna as an electromagnetic signal and received by the third rotating antenna. After filtering and amplification, the frequency is f 2 ± f u The demodulated signal is input to the second mixer and mixed with the frequency f 2 After mixing the demodulation reference signal, the frequency can be obtained. f u The ultrasonic sensor signal can be collected by the signal collector after filtering and amplification.

[0037] In application, the passive wireless ultrasonic transducer end may include a passive wireless ultrasonic transducer and a first mixer, wherein the passive wireless ultrasonic transducer is used to receive a low-frequency ultrasonic signal and a high-frequency carrier signal and send them to the input end of the first mixer; the first mixer is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal to obtain a frequency of f 2 ± f u The high-frequency modulated signal is sent to the receiving circuit through the output end.

[0038] It should be pointed out that the receiving circuit 105 in this embodiment may include a second mixer, a first filter amplifier, a second filter amplifier, a third rotating antenna and a third patch antenna; the third patch antenna is used to receive a high-frequency modulated signal and send it to the third rotating antenna, and the third rotating antenna is used to send the received high-frequency modulated signal to the input end of the first filter amplifier, and after filtering and amplification by the first filter amplifier, the filtered and amplified high-frequency modulated signal is sent to the input end of the second mixer through its output end; the input end of the second mixer is used to receive the filtered and amplified high-frequency modulated signal and a demodulation reference signal, and obtain a low-frequency ultrasonic sensor signal after mixing and demodulation, and input the low-frequency ultrasonic sensor signal to the input end of the second filter amplifier through its output end, and the low-frequency ultrasonic sensor signal is filtered and amplified by the second filter amplifier and input to the input end of the signal collector through its output end.

[0039] Here, since the sensing signal in the above-mentioned system of this embodiment is weak, and the directivity of the antenna will significantly affect the propagation intensity and receiving sensitivity of the electromagnetic wave in space, three rotating antennas are set in this embodiment, and the rotating antenna is connected to a stepping motor. The acquisition system can automatically adjust the spatial directivity of the antenna according to parameters such as the amplitude of the received signal to achieve the optimal signal transmission and reception effect. When the antenna rotates, it will receive signals in different directions, and the strength of the signal will change with the direction and angle of the antenna. During the rotation process and the autofocus process, the antenna will continue to rotate while monitoring the received signal strength. When the signal strength reaches the maximum value, the antenna will automatically stop rotating and record the current direction and angle. This process will be repeated until the position with the strongest signal is found.

[0040] Therefore, see Figure 8 In this embodiment, the first rotating antenna, the second rotating antenna and the third rotating antenna are all connected to a stepping motor, which can automatically adjust the direction and angle of the corresponding rotating antenna according to the strength of the respective received signals. The automatic adjustment of the direction and angle of the corresponding rotating antenna according to the strength of the respective received signals means that during the rotating focusing process of the rotating antenna, the rotating antenna continuously rotates while monitoring the received signal strength. When the signal strength reaches the maximum value, the rotating antenna automatically stops rotating and records the current direction and angle.

[0041] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An excitation control system based on a passive wireless ultrasonic transducer, characterized in that: include: The first transmitting circuit is used to receive the high-frequency excitation signal and generate a high-frequency electromagnetic wave signal after power amplification, and input it into the pulse excitation circuit based on the PNP transistor; The pulse excitation circuit based on the PNP transistor is used to rectify and store the received high-frequency electromagnetic wave signal, generate an instantaneous pulse excitation signal, and input it into the passive wireless ultrasonic transducer; A second transmitting circuit is used to receive a high-frequency carrier signal and send it to the passive wireless ultrasonic transducer end after power amplification, and to send a demodulation reference signal to the receiving circuit; The passive wireless ultrasonic transducer end is used to excite a low-frequency ultrasonic signal having the same frequency as the resonant frequency according to the received instantaneous pulse excitation signal, and is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal after receiving the high-frequency carrier signal to obtain a high-frequency modulated signal, and send it to the receiving circuit; The receiving circuit is used to receive the high-frequency modulation signal and the demodulation reference signal, and mix and demodulate the high-frequency modulation signal with the demodulation reference signal after filtering and amplification to obtain a low-frequency ultrasonic sensor signal. The low-frequency ultrasonic sensor signal is filtered and amplified for collection by the signal collector.

2. The passive wireless ultrasonic transducer-based excitation control system according to claim 1, characterized in that: The pulse excitation circuit based on the PNP transistor comprises a first rectifier, a second rectifier, a first energy storage device, a second energy storage device and a PNP transistor; The input end of the first rectifier and the input end of the second rectifier are both connected to a high-frequency electromagnetic wave signal, the output end of the first rectifier is connected to the input end of the first energy storage device, the output end of the second rectifier is connected to the input end of the second energy storage device, the output end of the first energy storage device is connected to the emitter of the PNP transistor, the output end of the second energy storage device is connected to the base of the PNP transistor, and the collector of the PNP transistor is connected to the input end of the passive wireless ultrasonic transducer; The capacitance value of the first energy storage device is lower than the capacitance value of the second energy storage device.

3. The passive wireless ultrasonic transducer-based excitation control system according to claim 2, characterized in that: The high-frequency electromagnetic wave signal is an AC signal, and after being rectified by the first rectifier and the second rectifier, the same DC charging current is input to the first energy storage device and the second energy storage device respectively; Under the action of the same DC charging current, the voltage rise rate of the second energy storage is lower than the voltage rise rate of the first energy storage, so that before the first energy storage is fully charged, the second energy storage is not fully charged, and the conduction of the PNP transistor will not be triggered at this time. After the second energy storage is fully charged, the PNP transistor is turned on. At this time, the electric energy stored in the first energy storage is applied to the passive wireless ultrasonic transducer, that is, a pulse excitation signal for applying to the passive wireless ultrasonic transducer is generated.

4. The passive wireless ultrasonic transducer-based excitation control system according to claim 1, characterized in that: The first transmitting circuit includes a first power amplifier, a first rotating antenna and a first patch antenna; The input end of the first power amplifier is used to connect to the high-frequency excitation signal, and the output end is used to output the high-frequency excitation signal after power amplification and input it to the input end of the first rotating antenna. The output end of the first rotating antenna is used to transmit a high-frequency electromagnetic wave signal to the first patch antenna. After the first patch antenna receives the high-frequency electromagnetic wave signal, it is input into the pulse excitation circuit based on the PNP transistor.

5. The passive wireless ultrasonic transducer-based excitation control system according to claim 4, characterized in that: The second transmitting circuit includes a second power amplifier, a second rotating antenna and a second patch antenna; The input end of the second power amplifier is used to access the high-frequency carrier signal, and the output end is used to output the high-frequency carrier signal after power amplification and input it to the input end of the second rotating antenna. The output end of the second rotating antenna is used to transmit the high-frequency carrier signal after power amplification to the second patch antenna. After receiving the high-frequency carrier signal, the second patch antenna sends it to the passive wireless ultrasonic transducer end; The second transmitting circuit uses the high-frequency carrier signal of the carrier excitation signal which is not input into the second power amplifier as a demodulation reference signal and sends it to the receiving circuit.

6. The passive wireless ultrasonic transducer-based excitation control system according to claim 5, characterized in that: The passive wireless ultrasonic transducer end includes a passive wireless ultrasonic transducer and a first mixer; The passive wireless ultrasonic transducer is used to receive the low-frequency ultrasonic signal and the high-frequency carrier signal, and send them to the input end of the first mixer; The first mixer is used to mix and modulate the low-frequency ultrasonic signal with the high-frequency carrier signal to obtain a high-frequency modulated signal, and send it to the receiving circuit through the output end.

7. The passive wireless ultrasonic transducer-based excitation control system according to claim 6, characterized in that: The passive wireless ultrasonic transducer is a plasma-sprayed piezoelectric ultrasonic film, which serves as a sensing layer and is coupled to the measured element through a transition layer.

8. The passive wireless ultrasonic transducer-based excitation control system according to claim 6, characterized in that: The receiving circuit includes a second mixer, a first filter amplifier, a second filter amplifier, a third rotating antenna and a third patch antenna; The third patch antenna is used to receive the high-frequency modulated signal and send it to the third rotating antenna. The third rotating antenna is used to send the received high-frequency modulated signal to the input end of the first filter amplifier. After being filtered and amplified by the first filter amplifier, the filtered and amplified high-frequency modulated signal is sent to the input end of the second mixer through its output end. The input end of the second mixer is used to receive the high-frequency modulation signal and the demodulation reference signal after filtering and amplification, and obtain the low-frequency ultrasonic sensor signal after mixing and demodulation, and input the low-frequency ultrasonic sensor signal to the input end of the second filter amplifier through its output end. The low-frequency ultrasonic sensor signal is filtered and amplified by the second filter amplifier and input to the input end of the signal collector through its output end.

9. The passive wireless ultrasonic transducer-based excitation control system according to claim 8, characterized in that: The first rotating antenna, the second rotating antenna and the third rotating antenna are all connected to a stepping motor, which can automatically adjust the direction and angle of the corresponding rotating antenna according to the strength of the respective received signals.

10. The passive wireless ultrasonic transducer-based excitation control system according to claim 9, characterized in that: The automatic adjustment of the direction and angle of the corresponding rotating antenna according to the strength of the respective received signals refers to: During the rotating antenna rotation focusing process, the rotating antenna continuously rotates while monitoring the received signal strength. When the signal strength reaches the maximum value, the rotating antenna automatically stops rotating and records the current direction and angle.

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