CN108226910B - Single ultrasonic sensor detection system - Google Patents
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The invention discloses a single ultrasonic sensor detection system, which comprises two ultrasonic probes, a power supply, a signal generator, a digital oscilloscope and a computer, wherein the ultrasonic probes are formed by packaging a circuit system and an ultrasonic sensor, the circuit system is used for controlling the ultrasonic sensor to send and receive ultrasonic waves and obtain a time interval between an echo signal and a trigger signal, an ultrasonic probe I is used as a reference probe to obtain an ultrasonic standard sound velocity in the current test environment, and an ultrasonic probe II is used as a test probe to test the distance to be tested; and analyzing the data by using a computer to obtain the test distance. The invention utilizes the circuit system to realize the precise control of the ultrasonic wave transmitted and received by the single ultrasonic sensor and accurately measure the transmission time of the ultrasonic wave; the waveform data is analyzed by using a reference method, the measurement error caused by environmental factors is reduced, and the method has the advantages of high sensitivity, accurate measurement and the like.
Description
Technical Field
The invention belongs to the field of sensors, and particularly relates to a single ultrasonic sensor detection system.
Background
The ultrasonic technology has the advantages of low cost, high speed, non-contact, no damage and the like. Therefore, the ultrasonic detection technology is widely applied to many indirect detection fields, such as engineering measurement, robots, industrial automation and the like. However, the transmission and reflection of ultrasonic waves in a multilayer medium are very complicated, and quantitative detection is difficult. Meanwhile, when ultrasonic waves are transmitted in different frequencies under the same medium, the energy attenuation characteristics of the ultrasonic waves are also greatly different. Generally, as the frequency, transmission distance, absorption rate of a reflecting surface and radiation angle of an ultrasonic transducer increase, the energy attenuation of ultrasonic waves rapidly increases.
Ultrasonic transducers used for detection may be classified into a composite probe and a single probe according to the structures of an ultrasonic wave transmitting unit and an ultrasonic wave receiving unit. The composite probe consists of one transmitting transducer and one or more receiving transducers, and has the obvious features of large volume, low sensitivity, simple test circuit, etc. The single probe is only provided with a sensor with two functions of transmitting and receiving, and has small volume and high sensitivity. The test circuit is complex and the like. Because of these limitations, ultrasonic testing techniques have many difficulties in their application.
As a non-contact detection technique, ultrasonic waves can be used for distance measurement. In the field of ultrasonic detection, the measurement distance is closely related to the transmission time. At the same distance, the transit time can be achieved by parameters of medium density, ambient temperature and pressure. When the parameters are assumed to be constant, it is very important to acquire the transmission time of the ultrasound penetrating medium. Therefore, the time accuracy and response speed of the test circuitry are important for ultrasonic testing applications.
Comparing files: an ultrasonic ranging system and method (201410124601.3) of controlling its range finding, adopt two ultrasonic transducers as launcher and receiver, belong to the combined probe, therefore the conformance of two probe frequencies of this detection system is difficult to guarantee, thus has increased the measuring error; and if the echo receiving port does not receive the echo signal within a period of time, the ultrasonic wave needs to be transmitted again, so that the instantaneity of the test system is low. A set of control circuit system is designed, and the system is matched with the ultrasonic transformer of the single probe, so that the precise control of the emission and the reception of ultrasonic waves of the single probe can be realized, and the transmission time of the ultrasonic waves can be accurately measured.
Disclosure of Invention
The invention aims to accurately measure the transmission time of ultrasonic waves, provides a single ultrasonic sensor detection system, realizes the accurate control of the ultrasonic waves transmitted and received by a single probe, and solves the technical problem of large measurement error.
The invention adopts the following technical scheme that the single ultrasonic sensor detection system adopts one ultrasonic probe as a test probe, realizes the transmission and the reception of ultrasonic waves by the ultrasonic sensor through a circuit system, adopts the other ultrasonic probe as a reference probe, analyzes waveform data by using a reference method, and comprises two ultrasonic probes, a power supply, a signal generator, a digital oscilloscope and a computer, wherein:
the ultrasonic probe is formed by packaging a circuit system and an ultrasonic sensor, wherein the circuit system is used for controlling the ultrasonic sensor to send and receive ultrasonic waves and obtaining the time interval of an echo signal and a trigger signal;
the first ultrasonic probe is used as a reference probe and is used for obtaining the ultrasonic standard sound velocity in the current test environment;
the ultrasonic probe II is used as a test probe and is used for testing the distance to be tested;
the signal generator is connected with the ultrasonic probe and used for generating a trigger signal;
the digital oscilloscope is respectively connected with the first ultrasonic probe, the second ultrasonic probe and the signal generator and is used for displaying the waveforms of the echo signal and the trigger signal captured by the ultrasonic probe;
and the computer is connected with the digital oscilloscope to realize data transmission between the digital oscilloscope and the computer, and the test distance is obtained after the data is analyzed and calculated.
Preferably, the trigger signal generated by the signal generator is a negative pulse signal.
Preferably, the circuit system comprises a waveform adjusting unit, a signal generating unit, a timeout reset and self-locking unit, an echo capture and amplification unit and an input-output level conversion unit, wherein the signal generator generates a negative pulse trigger signal, the negative pulse trigger signal is input from a test trigger port of the input-output level conversion unit and output to the waveform adjusting unit, the pulse signal is input into the timeout reset and self-locking unit after being inverted by the waveform adjusting unit, a trigger signal processed by a single trigger and echo trigger control port of the timeout reset and self-locking unit is output, and an echo port located in the input-output level conversion unit receives the processed trigger signal and starts timing to serve as a timing signal; meanwhile, a trigger signal generated by the signal generator is strengthened by the waveform adjusting unit and is input into the signal generating unit, so that the ultrasonic transducer integrating sending and receiving is driven to generate ultrasonic waves, the returned ultrasonic waves are captured and amplified by the echo capturing and amplifying unit, the amplified signals are input into the overtime resetting and self-locking unit, the single-trigger and echo trigger control port outputs echo signals, the input and output level conversion unit receives the echo signals and stops timing, the input and output level conversion unit is connected with the digital oscilloscope, and the positive pulse signals are displayed on the digital oscilloscope.
Preferably, the signal generator sends a negative pulse trigger signal, and simultaneously inputs the signal of the digital oscilloscope channel one, the ultrasonic probe one and the ultrasonic probe two, the signal of the input digital oscilloscope channel one is used as a comparison signal, and the signal of the input ultrasonic probe one and the ultrasonic probe two is input into the digital oscilloscope channel two and the digital oscilloscope channel three after being processed by the circuit system and used as a timing signal.
Preferably, in the waveform adjusting unit, a negative pulse trigger signal generated by the signal generator is output from the test trigger circuit and input to the signal distribution circuit, and a positive pulse signal obtained by inverting the negative pulse trigger signal in the signal distribution circuit by using the voltage comparator is input to a single trigger signal input end of the timeout reset and self-locking unit as an initial timing signal; meanwhile, after the positive pulse signal output from the signal distribution circuit is subjected to the overturning adjustment of a Schmitt trigger in the waveform adjusting circuit, the positive pulse signal is input into the signal generating unit from the signal generating enabling end; the positive pulse signal is turned over and delayed by a Schmitt trigger in the waveform adjusting circuit to obtain a single-trigger locking signal, and the single-trigger locking signal is input into a single-trigger locking circuit of the overtime resetting and self-locking unit; the waveform adjusting unit comprises a time-out signal attenuation module, and if the trigger signal is overtime, the time-out signal attenuation module attenuates the time-out signal so as to prevent the overtime trigger signal from influencing signal transmission in the circuit.
Preferably, in the signal generating unit and the echo capturing and amplifying unit, the signal generating enable end receives the positive pulse signal, generates a driving signal through the oscillation frequency generating circuit and outputs the driving signal to the ultrasonic transducer driving circuit, the ultrasonic transducer driving circuit drives the transformer, and the transformer transmits the driving signal to the sending and receiving integrated ultrasonic transducer, so that the sending and receiving integrated ultrasonic transducer works to emit ultrasonic waves; the ultrasonic signal reflected by the medium is captured by an echo capture circuit in the echo capture and amplification unit, the captured echo signal is processed by the echo amplification circuit, and then the echo signal is detected by a detection circuit to obtain an amplified and detected echo signal.
Preferably, an oscillation frequency generating circuit in the signal generating unit adopts a 555 trigger, and a transformer, a capacitor and a resistor are subjected to impedance matching to obtain a resonant frequency fu，fuNamely the center frequency of the ultrasonic sensor and the frequency of the ultrasonic waves generated by the ultrasonic sensor.
Preferably, the frequency range of the ultrasonic sensor is 40-200 KHz, so that the test precision is ensured.
Preferably, the echo capturing circuit comprises a clamping circuit consisting of two diodes, and the clamping circuit resonates with the echo signal to capture the echo signal.
Preferably, the timeout reset and self-locking unit comprises an echo signal matching circuit, the echo signal matching circuit is composed of two voltage comparators U1 and U2, and an output port of the voltage comparator U2 is a single-trigger and echo-trigger control port and is connected with the input-output level conversion unit; the trigger signal which is inverted in the waveform adjusting unit is input to the non-inverting input end of the voltage comparator U2 from the single trigger signal input end, passes through the voltage comparator U2 and is input to the input-output level conversion unit, and a timing signal is displayed on the digital oscilloscope; after the trigger signal passes through, the single trigger locking signal obtained by delaying in the waveform adjusting unit is attenuated by the single trigger locking circuit and then is input to the inverting input end of the voltage comparator U2, so that the locking of the signal transmission of the voltage comparator U2 is realized; the non-inverting input end of the voltage comparator U1 is the non-inverting input end of the voltage comparator U1, the echo signal input port of the echo signal input port is subjected to amplification and detection processing, the echo signal input port of the self-timeout reset and self-locking unit is input into the non-inverting input end of the voltage comparator U1, the single trigger locking signal output from the waveform adjusting unit is subjected to attenuation processing by the single trigger locking circuit and then is input into the inverting input end of the voltage comparator U1, the two signal intensities are matched according to the matching principle to meet the echo signal of the matching condition, namely, the amplitude of the echo signal is larger than that of the single trigger locking signal after the attenuation processing, the echo signal is output from the voltage comparator U1, meanwhile, the non-inverting input end of the input voltage comparator U2 is matched with the single trigger locking signal after the attenuation processing, and the echo signal meeting the matching condition is output to the input and output level conversion unit through the voltage comparator U2.
Preferably, the high level maintaining time of the single trigger locking signal after the attenuation processing is a blind zone time, corresponding to the length of the detection blind zone, the length S of the detection blind zonebThe calculation formula is as follows:
Sb＝λ(Ni+Nr)
excitation period TiThe following conditions are satisfied: t isi≥NiTu，
Wherein the excitation period TiFor triggering the period of the negative pulse signal, NiFor the number of excitation periods, NrNumber of ringing cycles, TuThe working period of the ultrasonic wave is shown, lambda is the wavelength of the ultrasonic wave, and the calculation formula is as follows:
λ＝v/fu
wherein f isuV is the theoretical sound velocity of the ultrasonic wave, and the calculation formula is as follows:
where T is the temperature of the test environment.
Preferably, the method for calculating the test distance comprises the following steps: and calculating the standard time interval of the two positive pulses according to the data of the reference probe, obtaining the standard sound velocity according to the standard distance, calculating the time interval of the two positive pulses according to the data of the test probe, and calculating the test distance by combining the standard sound velocity.
Preferably, the calculating the time interval is to find out the time corresponding to the rising edge of the signal by using a bisection method to obtain the time interval between two pulse signals, and specifically includes: setting the step length as P points, judging whether the ratio of the voltage amplitude of the P point to the amplitude of the first point is larger than a set value, if so, judging that the P point has a voltage value mutation point, searching the mutation point by adopting a bisection method, and if not, continuously searching the section where the amplitude value mutation point is located by adopting the bisection method; judging whether a certain point is an amplitude catastrophe point or not by judging a first derivative value of a connecting line between the certain point and a previous point, if the first derivative value is larger than zero, the point is the amplitude catastrophe point, and if the first derivative value does not meet the judgment condition, continuing to search for the catastrophe point by adopting a dichotomy method; after the first catastrophe point is found, the first catastrophe point is taken as a starting point, the falling edge of the positive pulse signal is found, namely, the amplitude catastrophe point is found, and the falling edge catastrophe point is judged if the first derivative value of a connecting line between a certain point and the previous point is judged to be less than zero; after finding the falling edge catastrophe point, continuously searching the next rising edge catastrophe point by taking the falling edge catastrophe point as a starting point; after finding the two rising edge catastrophe points, subtracting the moments of the two rising edge catastrophe points to obtain the time interval between the two positive pulse rising edges.
Preferably, P is 5-10% of the storage length of the digital oscilloscope.
The invention has the following beneficial effects: the invention relates to a single ultrasonic sensor detection system, which utilizes a circuit system to realize the precise control of the ultrasonic wave transmitted and received by the single ultrasonic sensor, can accurately measure the transmission time of the ultrasonic wave and solves the technical problem of large measurement error; the waveform data is analyzed by using the reference method, so that the measurement error caused by environmental factors can be reduced, and the method has the advantages of high sensitivity, accurate measurement and the like.
Drawings
FIG. 1 is a schematic diagram of the operation of the monolithic ultrasonic transducer of the present invention;
FIG. 2 is a schematic diagram of a referential test system of the present invention;
FIG. 3 is a functional block diagram of the circuitry of the present invention;
FIG. 4 is a test waveform displayed on a digital oscilloscope of the present invention;
FIG. 5 is a schematic diagram of the input/output level shift unit according to the present invention;
FIG. 6 is a schematic diagram of a waveform adjustment unit according to the present invention;
FIG. 7 is a schematic diagram of a signal generation unit and an echo capture and amplification unit of the present invention;
FIG. 8 is a schematic diagram of an echo capture circuit in the signal generation unit and echo capture and amplification unit of the present invention;
FIG. 9 is a schematic diagram of the transformer impedance matching of the present invention (a) an equivalent circuit of the transducer; (b) an impedance matching schematic;
FIG. 10 is a graphical illustration of echo signal strength matching of the present invention;
FIG. 11 is a schematic diagram of an echo signal matching circuit of the present invention;
FIG. 12 is a schematic circuit diagram of the timeout reset and latching unit of the present invention;
FIG. 13 is a flow chart of the data analysis computation of the present invention;
FIG. 14 is a flow chart of the time interval algorithm of the present invention.
Detailed Description
The technical solution of the present invention is further explained with reference to the embodiments according to the drawings.
FIG. 1 is a working schematic diagram of a single ultrasonic sensor of the present invention, wherein a single ultrasonic sensor detection system comprises two ultrasonic probes, a power supply, a signal generator, a digital oscilloscope and a computer, wherein:
the ultrasonic probe is formed by packaging a circuit system and an ultrasonic sensor, wherein the circuit system is used for controlling the ultrasonic sensor to send and receive ultrasonic waves and obtaining the time interval of an echo signal and a trigger signal;
the first ultrasonic probe is used as a reference probe and is used for obtaining the ultrasonic standard sound velocity in the current test environment;
the ultrasonic probe II is used as a test probe and is used for testing the distance to be tested;
the signal generator is connected with the ultrasonic probe and used for generating a trigger signal;
the digital oscilloscope is respectively connected with the first ultrasonic probe, the second ultrasonic probe and the signal generator and is used for displaying the waveforms of the echo signal and the trigger signal captured by the ultrasonic probe;
a direct current power supply in the power supply provides 10-30V direct current voltage to supply power for the ultrasonic sensor;
and the computer is connected with the digital oscilloscope, and data transmission between the digital oscilloscope and the computer is realized through software Openchoice Desktop. And programming a program through Matlab software, importing the waveform data on the digital oscilloscope into the program for analysis and calculation to obtain the time interval between two positive pulses, and calculating the test distance.
Fig. 2 is a schematic diagram of a referential test system of the present invention, and the transmission speed of ultrasonic waves in air is related to parameters such as transmission medium, ambient temperature, humidity, pressure, etc., so that if the speed of sound of ultrasonic waves is calculated by a conventional speed calculation formula, the accuracy of distance test is greatly influenced. The invention adopts a reference method, uses one sensor to construct a reference value on a standard scale, and then compares the tested data with the reference value to obtain a more accurate measured value. Firstly, a standard length l is measured by an ultrasonic sensorsTesting is carried out to obtain standard testing time tsThen, testing is carried out on the distance l to be tested to obtain the testing time t, and the distance l to be tested is obtained according to the following formula.
As a preferred embodiment, fig. 3 is a functional block diagram of a circuit system according to the present invention, in which the measuring circuit includes a waveform adjusting unit, a signal generating unit, a timeout resetting and self-locking unit, an echo capturing and amplifying unit, and an input/output level converting unit, the signal generator generates a negative pulse trigger signal, which is input from a test trigger port of the input/output level converting unit, output to the waveform adjusting unit, and input to the timeout resetting and self-locking unit after the pulse signal is inverted by the waveform adjusting unit, the trigger signal processed by the single triggering and echo triggering control port of the timeout resetting and self-locking unit is output from an echo port of the input/output level converting unit to receive the processed trigger signal and start timing as a timing signal; meanwhile, a trigger signal generated by the signal generator is strengthened by the waveform adjusting unit and is input into the signal generating unit, so that the ultrasonic transducer integrating sending and receiving is driven to generate ultrasonic waves, the returned ultrasonic waves are captured and amplified by the echo capturing and amplifying unit, the amplified signals are input into the overtime resetting and self-locking unit, the single-trigger and echo trigger control port outputs echo signals, the input and output level conversion unit receives the echo signals and stops timing, the input and output level conversion unit is connected with the digital oscilloscope, and the positive pulse signals are displayed on the digital oscilloscope.
As a preferred embodiment, fig. 4 is a test waveform displayed on a digital oscilloscope of the present invention, fig. 5 is a schematic diagram of the connection of an input/output level conversion unit of the present invention, a signal generator sends a negative pulse trigger signal, and simultaneously inputs a digital oscilloscope channel one, an ultrasonic probe one and an ultrasonic probe two, the signal of the digital oscilloscope channel one is input as a comparison signal, the trigger signal input to the ultrasonic probe is input to the digital oscilloscope as a timing signal after being processed by a circuit system, and an echo signal is input to the digital oscilloscope as a timing stop signal after being processed by the circuit system during testing.
As a preferred embodiment, fig. 6 is a schematic diagram of a waveform adjusting unit according to the present invention, in the waveform adjusting unit, a negative pulse trigger signal generated by a signal generator is output from a self-test trigger circuit and input to a signal distribution circuit, and in the signal distribution circuit, a positive pulse signal obtained by inverting the negative pulse trigger signal by using a voltage comparator is input to a single trigger signal input terminal of a timeout reset and self-locking unit as an initial timing signal; meanwhile, after the positive pulse signal output from the signal distribution circuit is subjected to the overturning adjustment of a Schmitt trigger in the waveform adjusting circuit, the positive pulse signal is input into the signal generating unit from the signal generating enabling end; the positive pulse signal is turned over and delayed by a Schmitt trigger in the waveform adjusting circuit to obtain a single-trigger locking signal, and the single-trigger locking signal is input into a single-trigger locking circuit of the overtime resetting and self-locking unit; the waveform adjusting unit comprises a time-out signal attenuation module, and if the trigger signal is overtime, the time-out signal attenuation module attenuates the time-out signal so as to prevent the overtime trigger signal from influencing signal transmission in the circuit.
As a preferred embodiment, fig. 7 is a schematic diagram of a signal generating unit and an echo amplifying and capturing unit according to the present invention, in the signal generating unit and the echo capturing and amplifying unit, a signal generating enable terminal receives a positive pulse signal and then generates a driving signal through an oscillation frequency generating circuit to be output to an ultrasonic transducer driving circuit, the ultrasonic transducer driving circuit drives a transformer, and the transformer transmits the driving signal to an ultrasonic transducer integrated with transmitting and receiving, so that the ultrasonic transducer integrated with transmitting and receiving operates to emit ultrasonic waves; the ultrasonic signal reflected by the medium is captured by an echo capture circuit in the echo capture and amplification unit, the captured echo signal is processed by the echo amplification circuit, and then the echo signal is detected by a detection circuit to obtain an amplified and detected echo signal. And comparing the amplitude of the amplified and detected echo signal with the amplitude of the attenuated single trigger locking signal through an voltage comparator, and outputting the echo signal to an input and output circuit when the amplitude of the echo signal is larger than the amplitude of the attenuated single trigger locking signal, so that a positive pulse signal of the echo is displayed on the digital oscilloscope.
As a preferred embodiment, fig. 8 is a schematic circuit diagram of a signal generating unit and an echo capturing and amplifying unit according to the present invention, wherein an oscillation frequency generating circuit in the signal generating unit employs a 555 flip-flop, and a transformer is impedance-matched with a capacitor C1 and a resistor R1. The transmitting cone angle of the transducer for transmitting ultrasonic waves is less than 10 ℃, and the ultrasonic transducer with the frequency range of 40-200 KHz can be adopted to ensure the testing accuracy.
As a preferred embodiment, the echo capturing circuit mainly comprises a clamping circuit composed of two diodes, and can resonate with the echo signal, thereby capturing the echo signal. The captured echo signals are processed by an echo amplification circuit. The amplifying circuit can adopt a low-power consumption current amplifier SA614A to amplify the echo signal, and then the echo signal is detected by the detection circuit.
FIG. 9 is a schematic diagram of the transformer impedance matching of the present invention (a) an equivalent circuit of the transducer; (b) impedance matching scheme, CpIs a static parallel capacitor, Ld、Cd、RdRespectively representing dynamic equivalent inductance, dynamic equivalent capacitance and dynamic loss resistance. When inductance LdAnd a capacitor CdAt resonance, Ld、Cd、RdThe series circuit formed can be equivalent to a resistor RpAt this time, the inductance LdAnd a capacitor CdResonant frequency fuThe calculation formula is as follows:
at the same time fuAlso the center frequency of the ultrasonic transducer and the frequency of the ultrasonic waves generated by the transducer.
When the secondary coil L of the transformermWhen the resonant frequency is in resonance with the static parallel capacitance Cp, the calculation formula of the resonant frequency is as follows:
when the system impedances match, f and fuAnd therefore, the secondary coil of the transformer is calculated as follows:
as a preferred embodiment, FIG. 10 is a diagram illustrating the intensity matching of echo signals according to the present invention, where VEThe signal intensity of the ultrasonic wave is exponentially attenuated as the transmission distance increases, which is the intensity of the echo signal. VRThe single-trigger locking signal is obtained by attenuating the single-trigger locking signal through a single-trigger locking circuit as a reference level signal intensity, and the signal intensity of the single-trigger locking signal is 5-10% smaller than that of the echo signal so as to ensure that the echo signal can be detected. FIG. 11 is of the present inventionAn echo signal matching circuit schematic diagram, fig. 12 is a circuit schematic diagram of a timeout reset and self-locking unit of the present invention, the timeout reset and self-locking unit includes an echo signal matching circuit, the echo signal matching circuit is composed of two voltage comparators U1 and U2, an output port of the voltage comparator U2 is a single trigger and echo trigger control port, and is connected with an input-output level conversion unit; the port CR inputs a one-time trigger locking signal, the locking signal is subjected to signal attenuation processing through a one-time trigger locking circuit, and the one-time trigger locking circuit consists of resistors R4 and an RC charging and discharging circuit consisting of a resistor R5 and a capacitor C1, so that the amplitudes of signals input to the inverting input ends of the voltage comparators U1 and U2 are the same as the attenuation amplitudes shown by VR in FIG. 10; the port C is a single trigger signal input end, the trigger signal which is inverted in the waveform adjusting unit is input to a non-inverting input end of a voltage comparator U2, the trigger signal passes through the voltage comparator U2 and then is input to an input and output level conversion unit, and a timing signal is displayed on a digital oscilloscope; after the trigger signal passes through, the single trigger locking signal obtained by delaying in the waveform adjusting unit is input to the inverting input end of the voltage comparator U2 after being attenuated by the single trigger locking circuit, so that the signal transmission of the voltage comparator U2 is locked, and secondary trigger is prevented; the echo signal self-timeout reset and self-locking echo signal input port which is subjected to amplification detection processing is input into the non-inverting input end of a voltage comparator U1, a single trigger locking signal output from a waveform adjusting unit is input into the inverting input end of a voltage comparator U1 after being subjected to signal attenuation processing of a single trigger locking circuit, the two signal intensities are matched according to the matching principle of the graph 10, an echo signal meeting the matching condition, namely when the amplitude of the echo signal is larger than that of the single trigger locking signal after the attenuation processing, the echo signal is output from the voltage comparator U1, meanwhile, the non-inverting input end of the voltage comparator U2 is matched with the single trigger locking signal after the attenuation processing again, and the echo signal meeting the condition is output to an input and output unit through the voltage comparator U2.
In a preferred embodiment, the high level holding time of the single trigger lock signal after the attenuation processing is a dead zone time corresponding to the length of the detection dead zone, and the dead zone time is activatedThe length of the excitation period, the material of the transducer and the frequency of the working ultrasonic wave. Length S of detection blind zonebThe calculation formula is as follows:
Sb＝λ(Ni+Nr)
excitation period TiThe following conditions are satisfied: t isi≥NiTu，
Wherein the excitation period TiFor triggering the period of the negative pulse signal, NiFor the number of excitation periods, NrNumber of ringing cycles, TuThe working period of the ultrasonic wave is shown, lambda is the wavelength of the ultrasonic wave, and the calculation formula is as follows:
λ＝v/fu
wherein f isuV is the theoretical sound velocity of the ultrasonic wave, and the calculation formula is as follows:
where T is the temperature of the test environment.
As a preferred embodiment, the OpenChoice Desktop software of tack is used to realize data transmission between the digital oscilloscope and the computer, and then the acquired data is imported into Matlab software, and the data is analyzed and calculated through related programs, so as to obtain the testing distance. Fig. 13 shows a flow chart of data analysis and calculation, and the method for calculating the test distance includes: and calculating the standard time interval of the two positive pulses according to the data of the reference probe, obtaining the standard sound velocity according to the standard distance, calculating the time interval of the two positive pulses according to the data of the test probe, and calculating the test distance by combining the standard sound velocity.
The waveform data displayed by the digital oscilloscope channel 2 is obtained by the ultrasonic probe 1, the data is led into Matlab software, and the sound velocity of the ultrasonic wave in the current test environment is obtained through program operation. The digital oscilloscope channel 3 is obtained by the ultrasonic probe 2, data is led into Matlab software, then the time interval between two positive pulses is calculated, and the testing distance can be obtained by combining the sound velocity.
As a preferred embodiment, fig. 14 is a flowchart of the time interval algorithm of the present invention, and the calculating the time interval is to find the time corresponding to the rising edge of the signal by using bisection to obtain the time interval between two pulse signals, which specifically includes: setting the step length as P points, judging whether the ratio of the voltage amplitude of the P point to the amplitude of the first point is larger than a set value, if so, judging that the P point has a voltage value mutation point, searching the mutation point by adopting a bisection method, and if not, continuously searching the section where the amplitude value mutation point is located by adopting the bisection method; judging whether a certain point is an amplitude catastrophe point or not by judging a first derivative value of a connecting line between the certain point and a previous point, if the first derivative value is larger than zero, the point is the amplitude catastrophe point, and if the first derivative value does not meet the judgment condition, continuing to search for the catastrophe point by adopting a dichotomy method; after the first catastrophe point is found, the first catastrophe point is taken as a starting point, the falling edge of the positive pulse signal is found, namely, the amplitude catastrophe point is found, and the falling edge catastrophe point is judged if the first derivative value of a connecting line between a certain point and the previous point is judged to be less than zero; after finding the falling edge catastrophe point, continuously searching the next rising edge catastrophe point by taking the falling edge catastrophe point as a starting point; after finding the two rising edge catastrophe points, subtracting the moments of the two rising edge catastrophe points to obtain the time interval between the two positive pulse rising edges. Wherein the P is 5-10% of the storage length of the digital oscilloscope.
Claims (12)
1. Monomer ultrasonic sensor detecting system, its characterized in that includes two ultrasonic probe, power, signal generator, digital oscilloscope and computer, wherein:
the ultrasonic probe comprises a circuit system and an ultrasonic sensor, wherein the circuit system is used for controlling the ultrasonic sensor to send and receive ultrasonic waves and obtaining a time interval between an echo signal and a trigger signal; the first ultrasonic probe is used as a reference probe and is used for obtaining the ultrasonic standard sound velocity in the current test environment;
the ultrasonic probe II is used as a test probe and is used for testing the distance to be tested;
the signal generator is connected with the ultrasonic probe and used for generating a trigger signal;
the digital oscilloscope is respectively connected with the first ultrasonic probe, the second ultrasonic probe and the signal generator and is used for displaying the waveforms of the echo signal and the trigger signal captured by the ultrasonic probe;
the computer is connected with the digital oscilloscope to realize data transmission between the digital oscilloscope and the computer, and the test distance is obtained after the data is analyzed and calculated;
the trigger signal generated by the signal generator is a negative pulse signal;
the circuit system comprises a waveform adjusting unit, a signal generating unit, an overtime reset and self-locking unit, an echo capture and amplification unit and an input-output level conversion unit, wherein a signal generator generates a negative pulse trigger signal, the negative pulse trigger signal is input from the input-output level conversion unit and output to the waveform adjusting unit, the pulse signal is input into the overtime reset and self-locking unit after being inverted by the waveform adjusting unit, a single trigger and echo trigger control port of the overtime reset and self-locking unit outputs a processed trigger signal, and the input-output level conversion unit receives the processed trigger signal and starts timing to serve as a timing signal; meanwhile, a trigger signal generated by the signal generator is strengthened by the waveform adjusting unit and is input into the signal generating unit, so that the ultrasonic transducer integrating sending and receiving is driven to generate ultrasonic waves, the returned ultrasonic waves are captured and amplified by the echo capturing and amplifying unit, the amplified signals are input into the overtime resetting and self-locking unit, the single-trigger and echo trigger control port outputs echo signals, the input and output level conversion unit receives the echo signals and stops timing, the input and output level conversion unit is connected with the digital oscilloscope, and the positive pulse signals are displayed on the digital oscilloscope.
2. The monolithic ultrasonic sensor detection system of claim 1, wherein the signal generator generates a negative pulse trigger signal and inputs the negative pulse trigger signal to the first digital oscilloscope channel, the first ultrasonic probe and the second ultrasonic probe simultaneously, the signal input to the first digital oscilloscope channel serves as a reference signal, and the signal input to the first ultrasonic probe and the second ultrasonic probe is processed by the control circuit system and then input to the second digital oscilloscope channel and the third digital oscilloscope channel to serve as a timing signal.
3. The ultrasonic sensor detection system of claim 1, wherein in the waveform adjustment unit, a negative pulse trigger signal generated by the signal generator is output from the test trigger circuit and input to the signal distribution circuit, and in the signal distribution circuit, a positive pulse signal obtained by inverting the negative pulse trigger signal by using the voltage comparator is input to a single trigger signal input end of the timeout reset and self-locking unit as an initial timing signal; meanwhile, after the positive pulse signal output from the signal distribution circuit is subjected to the overturning adjustment of a Schmitt trigger in the waveform adjusting circuit, the positive pulse signal is input into the signal generating unit from the signal generating enabling end; the positive pulse signal is turned over and delayed by a Schmitt trigger in the waveform adjusting circuit to obtain a single-trigger locking signal, and the single-trigger locking signal is input into a single-trigger locking circuit of the overtime resetting and self-locking unit; the waveform adjusting unit comprises a timeout signal attenuation module, and if the trigger signal is overtime, the timeout signal attenuation module attenuates the timeout signal.
4. The monolithic ultrasonic sensor probe system of claim 1, wherein in the signal generating unit and the echo capturing and amplifying unit, the signal generating enable terminal receives the positive pulse signal and then generates a driving signal through the oscillation frequency generating circuit to be transmitted to the ultrasonic transducer driving circuit, the ultrasonic transducer driving circuit drives the transformer, and the transformer transmits the driving signal to the transmitting and receiving integrated ultrasonic transducer to enable the transmitting and receiving integrated ultrasonic transducer to work to emit ultrasonic waves; the ultrasonic signal reflected by the medium is captured by an echo capture circuit in the echo capture and amplification unit, the captured echo signal is processed by the echo amplification circuit, and then the echo signal is detected by a detection circuit to obtain an amplified and detected echo signal.
5. The monolithic ultrasonic sensor probe system of claim 4, wherein the ultrasonic sensor probe system is a single-body ultrasonic sensor probe systemThe oscillation frequency generating circuit in the signal generating unit adopts a 555 trigger, and the transformer is matched with the capacitor and the resistor in impedance to obtain the resonant frequency fu，fuNamely the center frequency of the ultrasonic sensor and the frequency of the ultrasonic waves generated by the ultrasonic sensor.
6. The monolithic ultrasonic sensor probe system as claimed in claim 5, wherein the frequency range of the ultrasonic sensor is 40-200 KHz.
7. The monolithic ultrasonic sensor probe system of claim 4, wherein the echo capture circuit comprises a clamp circuit consisting of two diodes, and resonates with the echo signal to capture the echo signal.
8. The monolithic ultrasonic sensor detection system of claim 2, wherein the timeout reset and self-locking unit comprises an echo signal matching circuit, the echo signal matching circuit is composed of two voltage comparators U1 and U2, an output port of the voltage comparator U2 is a single-shot and echo-shot control port, and is connected with the input-output level conversion unit; the trigger signal which is inverted in the waveform adjusting unit is input to the non-inverting input end of the voltage comparator U2 from the single trigger signal input end, passes through the voltage comparator U2 and is input to the input-output level conversion unit, and a timing signal is displayed on the digital oscilloscope; after the trigger signal passes through, the single trigger locking signal obtained by delaying in the waveform adjusting unit is attenuated by the single trigger locking circuit and then is input to the inverting input end of the voltage comparator U2, so that the locking of the signal transmission of the voltage comparator U2 is realized; the non-inverting input end of the voltage comparator U1 is an echo signal input port, the echo signal input port of the echo signal self-timeout reset and self-locking unit which is processed by amplification and detection is input into the non-inverting input end of the voltage comparator U1, the single trigger locking signal output from the waveform adjusting unit is input into the inverting input end of the voltage comparator U1 after being attenuated by the single trigger locking circuit, the two signal intensities are matched according to the matching principle, the echo signal meeting the matching condition, namely, the amplitude of the echo signal is larger than that of the single trigger locking signal after the attenuation processing, the echo signal is output from the voltage comparator U1, meanwhile, the non-inverting input end of the input voltage comparator U2 is matched with the single trigger locking signal after the attenuation processing, and the echo signal meeting the matching condition is output to the input and output level conversion unit through the voltage comparator U2.
9. The ultrasonic sensor-on-a-chip detection system of claim 8, wherein the high-level holding time of the attenuated one-shot lock signal is a dead zone time corresponding to the length of the detection dead zone, the length of the detection dead zone SbThe calculation formula is as follows:
Sb＝λ(Ni+Nr)
excitation period TiThe following conditions are satisfied: t isi≥NiTu，
Wherein the excitation period TiFor triggering the period of the negative pulse signal, NiFor the number of excitation periods, NrNumber of ringing cycles, TuThe working period of the ultrasonic wave is shown, lambda is the wavelength of the ultrasonic wave, and the calculation formula is as follows:
λ＝v/fu
wherein f isuV is the theoretical sound velocity of the ultrasonic wave, and the calculation formula is as follows:
where T is the temperature of the test environment.
10. The monolithic ultrasonic sensor probe system of claim 1, wherein the test distance is calculated by: and calculating the standard time interval of the two positive pulses according to the data of the reference probe, obtaining the standard sound velocity according to the standard distance, calculating the time interval of the two positive pulses according to the data of the test probe, and multiplying the time interval of the two positive pulses by the standard sound velocity to calculate the test distance.
11. The monolithic ultrasonic sensor probe system of claim 10, wherein the calculating the time interval is to find out the time corresponding to the rising edge of the signal by using a bisection method to obtain the time interval between two pulse signals, and specifically comprises: setting the step length as P points, judging whether the ratio of the voltage amplitude of the P point to the amplitude of the first point is larger than a set value, if so, judging that the P point has a voltage value mutation point, searching the mutation point by adopting a bisection method, and if not, continuously searching the section where the amplitude value mutation point is located by adopting the bisection method; judging whether a certain point is an amplitude catastrophe point or not by judging a first derivative value of a connecting line between the certain point and a previous point, if the first derivative value is larger than zero, the point is the amplitude catastrophe point, and if the first derivative value does not meet the judgment condition, continuing to search for the catastrophe point by adopting a dichotomy method; after the first catastrophe point is found, the first catastrophe point is taken as a starting point, the falling edge of the positive pulse signal is found, namely, the amplitude catastrophe point is found, and the falling edge catastrophe point is judged if the first derivative value of a connecting line between a certain point and the previous point is less than zero; after finding the falling edge catastrophe point, continuously searching the next rising edge catastrophe point by taking the falling edge catastrophe point as a starting point; after finding the two rising edge catastrophe points, subtracting the moments of the two rising edge catastrophe points to obtain the time interval between the two positive pulse rising edges.
12. The monolithic ultrasonic sensor probe system of claim 11, wherein P is 5-10% of the storage length of the digital oscilloscope.
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| DE102018124024A1 (en) * | 2018-09-28 | 2020-04-02 | Valeo Schalter Und Sensoren Gmbh | Method for operating an ultrasonic sensor of a vehicle with reduced diagnosis in a measuring operation of the ultrasonic sensor, and ultrasonic sensor device |
| CN110907059A (en) * | 2019-11-27 | 2020-03-24 | 广东美的厨房电器制造有限公司 | Temperature control method and device for electric appliance, electric appliance and computer readable storage medium |
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