CN114046916B - Self-powered pressure measurement system based on surface acoustic wave sensor and working method thereof - Google Patents
Self-powered pressure measurement system based on surface acoustic wave sensor and working method thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
- G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/04—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by acoustic means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/32—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from a charging set comprising a non-electric prime mover rotating at constant speed
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
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- H02N2/18—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing electrical output from mechanical input, e.g. generators
Abstract
The invention belongs to the technical field of surface acoustic wave sensors and discloses a self-powered pressure measurement system based on a voltage-controlled surface acoustic wave sensor. The self-powered pressure measurement system comprises a pressure measurement input module, a pressure measurement output module, a direct current conversion module and a power supply module; when the pressure measurement input module obtains pressure information, the center frequency of the pressure-controlled surface acoustic wave sensor is shifted through the deformation of the pressure sensitive film, and different pressures and corresponding frequencies can be corresponding and displayed through the processing of the pressure measurement output module; when the pressure is measured, the oscillation signal output by the surface acoustic wave sensor can be converted into a direct current signal with constant amplitude by the direct current conversion module, the two batteries are charged by the power supply module in turn, and the batteries can supply power to the pressure measurement system. The invention realizes the rapid and accurate pressure measurement, and simultaneously realizes the self-power supply of the pressure measurement system through the direct current conversion.
Description
Technical Field
The invention belongs to the technical field of surface acoustic wave sensors, and particularly relates to a self-powered pressure measurement system based on a voltage-controlled surface acoustic wave sensor and a working method thereof.
Background
The surface acoustic wave sensor is a new type of micro-acoustic sensor developed in recent years, and is a sensor which uses a surface acoustic wave device as a sensing element, reflects measured information through the change of the speed or frequency of the surface acoustic wave in the surface acoustic wave device, and converts the information into an electric signal for output.
The surface acoustic wave sensor can accurately measure physical, chemical and other information, such as temperature, pressure, gas density and the like, and has the characteristics of real-time information detection because the surface acoustic wave sensor can concentrate signals on the surface of a substrate, has high working frequency and extremely high information sensitivity precision, can quickly convert the detected information into electric signals to be output; in addition, the surface acoustic wave sensor also has the advantages of miniaturization, integration, passivity, low cost, low power consumption, direct frequency signal output and the like, so the surface acoustic wave sensor is widely applied to the technical fields of analog-digital communication and sensors.
Pressure measurement is needed in various occasions nowadays, which is an indispensable requirement of modern society, however, how to more conveniently and accurately measure pressure is a concern, and although the existing pressure measurement system can measure pressure, improvement on the power supply of the measurement system is needed. The current measurement systems mainly have the following disadvantages:
(1) The conventional pressure sensor is adopted in the current pressure measurement system to measure data, the surface of the pressure sensor deforms after pressure, so that the shape change of a built-in resistor is caused, the deformation of the resistor causes the change of the resistance value of the resistor, the change of the resistance value enables internal current to change, corresponding electric signals are generated, and the electric signals can be digitally displayed after being processed. Conventional pressure sensors have low sensitivity.
(2) Most of the existing pressure measurement systems adopt a USB (universal serial bus) for charging or an external power supply for supplying power, which is extremely inconvenient, even if a small part adopts solar power for supplying power, an additional optical sensor circuit is also needed, and the pressure measurement systems cannot work in an environment with low illumination intensity.
Disclosure of Invention
The invention aims to provide a self-powered pressure measurement system based on a pressure-controlled surface acoustic wave sensor and a working method thereof, which can measure pressure more accurately and sensitively, can supply power by self, get rid of the trouble of needing an external power supply, are convenient to use and solve the defects or problems in the background technology.
In order to achieve the above object, an embodiment of the present invention provides a self-powered pressure measurement system based on a voltage-controlled surface acoustic wave sensor, which is characterized by comprising a pressure measurement input module, a pressure measurement output module, a dc conversion module, and a power supply module;
the pressure measurement input module comprises a pressure-controlled surface acoustic wave sensor; the surface acoustic wave sensor is used for generating a sinusoidal oscillation signal when the sensitive film deforms under the condition of pressure; the surface acoustic wave sensor generates sinusoidal oscillation signals with different center frequencies along with different applied pressures;
the pressure measurement output module comprises a PWM (pulse-width modulation) circuit, a frequency detector, a pressure conversion circuit and an LCD (liquid crystal display); the PWM modulation circuit is used for converting an analog signal into a digital signal; the frequency detector is used for detecting the frequency of the digital signal modulated by the PWM modulation circuit; the pressure conversion circuit performs pressure conversion according to a linear relation between pressure and frequency; the LCD display is used for displaying the output pressure value;
the direct current conversion module is composed of a rectification circuit, a filter circuit and a voltage stabilizing circuit, and is used for converting sinusoidal oscillation signals output by the surface acoustic wave sensor into stable direct current voltage; the direct current voltage provided by the direct current conversion module is used for charging the power supply module;
the power supply module comprises a battery state query submodule, a first switch, a second switch, a first battery and a second battery; the battery state query submodule is used for querying whether the first battery and the second battery are in a full-charge state or not, and the direct current conversion module charges the first battery or the second battery according to the condition queried by the battery state query submodule; when the first battery is fully charged, the direct current conversion module charges the second battery, and direct current voltage in the first battery is used for supplying power to the whole system; the first battery is not fully charged, the direct current conversion module charges the first battery, and direct current voltage in the second battery is used for supplying power to the whole pressure measurement system.
Furthermore, the piezoelectric substrate of the pressure-controlled surface acoustic wave sensor is made of piezoelectric material quartz, and the electrode material is aluminum.
Furthermore, the pressure-controlled surface acoustic wave sensor consists of a pressure-controlled phase shifter, an amplifier, a reflection grid array A, an input transducer A, an output transducer B, a reflection grid array C, an input transducer C, a pressure sensitive film, an output transducer D and a reflection grid array D; the reflection grating array A, the input transducer A, the output transducer B and the reflection grating array B form a first acoustic surface wave double-end resonator; the reflecting grating array C, the input transducer C, the pressure sensitive film, the output transducer D and the reflecting grating array D form a second acoustic surface wave double-end resonator; the double-end resonator I and the amplifier form one path of surface acoustic wave oscillator I, the double-end resonator II, the amplifier and the voltage-controlled phase shifter form the other path of surface acoustic wave oscillator II, and signals in the two paths of oscillators are superposed at the input end of the amplifier to obtain an in-phase component and a quadrature component; when the orthogonal component is zero, namely the phase offset of the current at the input end of the amplifier is integral multiple of 2 pi, and the in-phase component enables the open-loop gain to be larger than 1, namely the product of the amplitude of the current at the input end of the amplifier and the amplifier gain is larger than 1, the voltage-controlled surface acoustic wave sensor oscillates to generate sine wave output.
Further, the rectifier circuit comprises a bridge rectifier circuit consisting of a diode D1, a diode D2, a diode D3 and a diode D4, and the rectifier circuit is used for adjusting the voltage of the sinusoidal oscillation signal Vi, which is a negative value and output by the voltage-controlled surface acoustic wave sensor, to a corresponding rated positive voltage; the filter circuit comprises a polar capacitor C0 and is used for converting the rectified voltage V1 into direct-current voltage; the voltage stabilizing circuit comprises a three-terminal voltage regulator LM7812, and is used for stabilizing fluctuating voltage into constant voltage to supply power to the battery.
Furthermore, the battery state query submodule can be completed through a voltage measurement chip, and whether the battery is fully charged or not is judged by measuring whether the voltage in the battery reaches a rated voltage or not.
Further, the first switch is connected with the first battery, and the second switch is connected with the second battery.
The embodiment of the invention discloses a working method of a self-powered pressure measurement system based on a pressure-controlled surface acoustic wave sensor, which is characterized by comprising the following steps of:
s1, under the condition of compression, a sensitive film of the surface acoustic wave sensor deforms and generates a sinusoidal oscillation signal Vi; the sinusoidal oscillation signal Vi is used as a pressure measurement input signal and is transmitted to a direct current conversion module;
s2, the direct current conversion module rectifies the sinusoidal oscillation signal Vi through a rectification circuit, and the rectification circuit can adjust the voltage of the sinusoidal oscillation signal Vi which is a negative value into a corresponding rated positive voltage by utilizing the unidirectional conductivity of a diode; a polarity capacitor C0 is connected behind the rectifying circuit, so that the rectified voltage V1 can be converted into direct-current voltage; the direct-current voltage can stabilize the fluctuating voltage into constant voltage Vo through the voltage stabilizing circuit to supply power to the power supply module;
s3, when the measuring system starts to work, the first switch is closed, the second switch is opened, the direct-current voltage output by the voltage stabilizing chip LM7812 charges the first battery, meanwhile, the voltage of the first battery is detected through the battery state query submodule, if the rated voltage is 3.6V, the first battery is fully charged, the first switch is opened, the second switch is closed, the direct-current voltage charges the second battery, and the direct-current voltage in the first battery is used for supplying power for the whole pressure measuring system; at the moment, whether the second battery reaches the rated voltage is detected, if the second battery reaches the rated voltage, the first battery is charged by the direct current conversion module which is not full of electricity, and the direct current voltage in the second battery is used for supplying power to the whole pressure measurement system; the charging and discharging of the two batteries are realized, a power supply is provided for a measuring system, and the non-regeneration of the system is realized;
s4, a voltage Vi output by the pressure measurement input module is input to the pressure measurement output module, a sinusoidal oscillation signal output by the pressure-controlled surface acoustic wave sensor is changed into a square wave through PWM modulation, conversion from an analog signal to a digital signal is achieved, the frequency of the square wave and the frequency of the sinusoidal oscillation signal have a corresponding relation, and in a frequency detector, the frequency measured by the frequency detector can be 10 times of the output frequency of the pressure-controlled surface acoustic wave sensor by taking the middle point when the adjacent voltage value is 0; the pressure conversion circuit converts the pressure according to the linear corresponding relation between the pressure and the frequency, and displays the pressure value through the LCD.
Preferably, in step S4, the linear correspondence between the pressure and the frequency is obtained by: before pressure conversion, the output frequency and pressure relation of the pressure-controlled surface acoustic wave sensor can be tested, different known pressures act on the pressure-controlled surface acoustic wave sensor, the pressure-controlled surface acoustic wave sensor outputs different frequencies, a linear corresponding relation between the pressure and the frequency is obtained, the pressure and frequency corresponding relation of the pressure-controlled surface acoustic wave sensor can be fitted by the measured frequency and pressure, a program is written in through a hardware description language, and the conversion between the frequency and the pressure can be realized by using Cyclone IV.
The technical scheme of the invention has the following beneficial effects:
(1) The self-powered pressure measurement system based on the pressure-controlled surface acoustic wave sensor and the working method thereof realize that when pressure is measured, specific numerical values can be displayed quickly and accurately through the LCD, signal energy output by the pressure-controlled surface acoustic wave sensor is collected through the self-powered module, the whole device is powered, and the passivity of the measurement system is realized.
(2) The signals in the two oscillators are superposed at the input end of the amplifier to obtain an in-phase component and a quadrature component. When the orthogonal component is zero, namely the phase offset of the current at the input end of the amplifier is integral multiple of 2 pi, and the in-phase component enables the open-loop gain to be larger than 1, namely the product of the amplitude of the current at the input end of the amplifier and the gain of the amplifier is larger than 1, the voltage-controlled surface acoustic wave sensor oscillates to generate sine wave output. Because the insertion loss of the surface acoustic wave resonator is smaller than that of the surface acoustic wave delay line, the Q value of the surface acoustic wave resonator is larger than that of the surface acoustic wave delay line, and the pressure-controlled surface acoustic wave sensor formed by two surface acoustic wave resonators is easier to realize single-mode oscillation, so that the frequency stability of the pressure-controlled surface acoustic wave sensor is higher.
(3) The pressure-controlled surface acoustic wave sensor has the advantages of high precision, small volume, low power consumption, strong sensitivity and the like, and can work under the passive and wireless conditions, so that the pressure-controlled surface acoustic wave sensor can be used for replacing the traditional pressure sensor.
Drawings
Fig. 1 is a block diagram of a self-powered pressure measurement system based on a voltage-controlled surface acoustic wave sensor according to the present invention.
Fig. 2 is a schematic structural diagram of an acoustic surface pressure sensor according to an embodiment of the present invention.
Fig. 3 is a flowchart illustrating the operation of the battery status query submodule according to the embodiment of the present invention.
Fig. 4 is a schematic diagram of PWM modulation according to an embodiment of the present invention.
Fig. 5 is a circuit diagram of dc conversion according to an embodiment of the invention.
Fig. 6 is a schematic waveform diagram of the dc conversion process according to the embodiment of the present invention.
Description of reference numerals: 1. a pressure measurement input module; 11. pressure; 12. a surface acoustic wave pressure sensor; 2. a pressure measurement output module; 21. a PWM modulation circuit; 22. a frequency detector; 23. a pressure conversion circuit; 24. an LCD display; 3. a DC conversion module; 31. a rectifying circuit; 32. a filter circuit; 33. a voltage stabilizing circuit; 4. a power supply module; 41. a battery state query submodule; 42. a first switch; 43. a second switch; 44. a first battery; 45. a second battery.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The invention provides a self-powered pressure measurement system based on a pressure-controlled surface acoustic wave sensor, which comprises a pressure measurement input module 1, a pressure 1 measurement output module, a direct current conversion module 3 and a power supply module 4, wherein the system is shown in figure 1; the pressure measurement input module 1 comprises a pressure-controlled surface acoustic wave sensor; the surface acoustic wave sensor is used for generating a sinusoidal oscillation signal when the sensitive film deforms under the condition of pressure 11; the surface acoustic wave sensor generates sinusoidal oscillation signals with different center frequencies along with different applied pressures 11; the pressure measurement output module comprises a PWM modulation circuit 21, a frequency detector 22, a pressure conversion circuit and an LCD display 24; the PWM modulation circuit 21 is configured to convert an analog signal into a digital signal; the frequency detector 22 is used for detecting the frequency of the digital signal modulated by the PWM modulation circuit 21; the pressure conversion circuit performs pressure conversion according to a linear relation between the pressure 11 and the frequency; the LCD display 24 is used for displaying the output pressure value; the direct current conversion module 3 is composed of a rectification circuit 31, a filter circuit 32 and a voltage stabilizing circuit 33, and the direct current conversion module 3 is used for converting sinusoidal oscillation signals output by the surface acoustic wave sensor into stable direct current voltage; the direct current voltage provided by the direct current conversion module 3 charges the power supply module 4; the power supply module 4 comprises a battery state query submodule 41, a first switch 42, a second switch 43, a first battery 44 and a second battery 45; the battery state query submodule 41 is configured to query whether the first battery 44 and the second battery 45 are in a full state, and the dc conversion module 3 charges the first battery 44 or the second battery 45 according to the condition queried by the battery state query submodule 41; when the first battery 44 is fully charged, the dc conversion module 3 charges the second battery 45, and the dc voltage in the first battery 44 is used for supplying power to the whole system; the first battery 44 is not fully charged, the dc conversion module 3 charges the first battery 44, and the dc voltage in the second battery 45 is used for supplying power to the entire pressure measurement system. When the pressure 11 is measured, the specific numerical value can be displayed rapidly and accurately through the LCD screen, the signal energy output by the pressure-controlled surface acoustic wave sensor is collected through the self-powered module 4, the power is supplied to the whole device, and the passivity of the measuring system is realized.
As shown in fig. 2, the voltage-controlled surface acoustic wave sensor is composed of a voltage-controlled phase shifter, an amplifier, a reflection grating array a, an input transducer a, an output transducer B, a reflection grating array C, an input transducer C, a pressure-sensitive film, an output transducer D, and a reflection grating array D; the reflection grating array A, the input transducer A, the output transducer B and the reflection grating array B form a first acoustic surface wave double-end resonator; and the reflecting grating array C, the input transducer C, the pressure sensitive film, the output transducer D and the reflecting grating array D form a second acoustic surface wave double-end resonator. In fig. 2, a first double-ended resonator and an amplifier form a first surface acoustic wave oscillator, a second double-ended resonator, an amplifier and a voltage-controlled phase shifter form a second surface acoustic wave oscillator, and signals in the two oscillators are superposed at the input end of the amplifier to obtain an in-phase component and a quadrature component. When the orthogonal component is zero, namely the phase offset of the current at the input end of the amplifier is integral multiple of 2 pi, and the in-phase component enables the open-loop gain to be larger than 1, namely the product of the amplitude of the current at the input end of the amplifier and the gain of the amplifier is larger than 1, the voltage-controlled surface acoustic wave sensor oscillates to generate sine wave output. Because the insertion loss of the surface acoustic wave resonator is smaller than that of the surface acoustic wave delay line, the Q value of the surface acoustic wave resonator is larger than that of the surface acoustic wave delay line, and the pressure-controlled surface acoustic wave sensor formed by two surface acoustic wave resonators is easier to realize single-mode oscillation, so that the frequency stability of the pressure-controlled surface acoustic wave sensor is higher.
In this example, the piezoelectric substrate of the pressure-controlled surface acoustic wave sensor is made of quartz, which is a piezoelectric material with an electromechanical coupling coefficient of 0.16%, and the electrodes are made of aluminum. The center frequency of the voltage-controlled surface acoustic wave sensor is 50MHz, when the pressure is applied, the pressure sensitive film of the voltage-controlled surface acoustic wave sensor is weakly deformed, the frequency of the output sine oscillation signal is near 50MHz, the output sine oscillation signal is divided into 10 equal parts according to equal intervals through a PWM (pulse-width modulation) circuit 21 shown in FIG. 4, each part of waveform corresponds to a square wave pulse with equal area, the middle point of the sine wave is superposed with the corresponding middle point of the square wave, the square wave and the sine oscillation signal in FIG. 4 are equivalent according to an impulse equivalent principle, the sine oscillation signal output by the voltage-controlled surface acoustic wave sensor is changed into the square wave through the PWM circuit 21, the conversion from an analog signal to a digital signal is realized, the frequency of the square wave and the frequency of the sine oscillation signal have a corresponding relation, in a frequency detector 22, the middle point when the adjacent voltage value is 0 is taken, as shown by a dotted line in FIG. 4, and the frequency measured by the frequency detector 22 is 10 times of the output frequency of the voltage-controlled surface acoustic wave sensor.
Before pressure conversion, the relationship between the output frequency and the pressure 11 of the pressure-controlled surface acoustic wave sensor can be tested, different known pressures act on the pressure-controlled surface acoustic wave sensor, the pressure-controlled surface acoustic wave sensor outputs different frequencies, due to the linear corresponding relationship between the pressure 11 and the frequency, the corresponding relationship between the pressure 11 and the frequency of the pressure-controlled surface acoustic wave sensor can be fitted by the measured frequency and the measured pressure 11, programs are written in through a hardware description language, namely, the conversion between the frequency and the pressure 11 can be realized by using Cyclone IV, and the pressure value is displayed through an LCD 24.
In the self-powered process, the dc conversion module 3 is mainly implemented by rectification, filtering and voltage stabilization, the sinusoidal oscillation signal output by the saw oscillator is rectified, i.e. the negative half-cycle waveform of the sinusoidal oscillation signal is converted into the corresponding positive half-cycle, then the ac component is reduced by the filtering of the filter capacitor, the dc component is increased, and finally the dc voltage is stabilized by the voltage stabilizing circuit 33 to be constant. By adopting the circuit shown in fig. 5, the sinusoidal oscillation signal Vi output by the voltage-controlled surface acoustic wave sensor passes through the bridge rectifier circuit 31 composed of D1, D2, D3 and D4, by utilizing the unidirectional conductivity of the diode, the voltage of the sinusoidal oscillation signal Vi which is a negative value can be adjusted to a corresponding rated positive voltage, a polar capacitor C0 is connected behind the rectifier bridge, namely, the rectified voltage V1 can be converted into a direct current voltage, because the rectified voltage value fluctuates and the battery needs a stable direct current voltage for charging, a three-terminal voltage stabilizer LM7812 is connected after rectification, and the three-terminal voltage stabilizer LM7812 can stabilize the fluctuated voltage to a constant voltage for supplying power to the battery. As shown in fig. 6, the sinusoidal oscillation signal Vi output by the voltage-controlled surface acoustic wave sensor firstly passes through the rectifier bridge D1, D2, D3, D4 and the polar capacitor C0, the input end of the three-terminal regulator LM7812 is connected with the rectified voltage V1, the GND terminal is grounded, in order to change the rectified voltage V1 into more stable dc voltage, the bypass capacitor C2, C3 and the polar capacitor C1 are also connected, so that the output end generates more stable 12V dc voltage, the voltage is respectively connected with the first switch 42 and the second switch 43, and the two switches are respectively charged by the first battery 44 and the second battery 45 under the control of the state query module.
In the process of inquiring the battery status, as shown in fig. 1 and 3, the first switch 42 is connected to the first battery 44, the second switch 43 is connected to the second battery 45, and the status inquiring sub-module can be implemented by the voltage measuring chip, and determine whether the battery is fully charged by measuring whether the voltage in the battery reaches the rated voltage. The battery adopts a lithium ion polymer battery with the rated voltage of 3.6V. When the measuring system starts to work, the first switch 42 is closed, the second switch 43 is opened, the first battery 44 is charged by the direct-current voltage output by the voltage stabilizing chip LM7812, meanwhile, by detecting the voltage of the first battery 44, if the rated voltage reaches 3.6V, the first battery 44 is fully charged, the first switch 42 is opened, the second switch 43 is closed, the direct-current voltage charges the second battery 45, the first battery 44 supplies power, and at this time, the rated voltage of the second battery 45 is detected again. Through the process of fig. 3, the charging and discharging of the two batteries can be realized, a power supply is provided for the measuring device, and the non-utilization of the system is realized.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (6)
1. A working method of a self-powered pressure measurement system based on a pressure-controlled surface acoustic wave sensor is characterized in that the self-powered pressure measurement system comprises a pressure measurement input module, a pressure measurement output module, a direct current conversion module and a power supply module;
the pressure measurement input module comprises a pressure-controlled surface acoustic wave sensor; the surface acoustic wave sensor is used for generating a sinusoidal oscillation signal when the sensitive film deforms under the condition of pressure; the surface acoustic wave sensor generates sinusoidal oscillation signals with different center frequencies along with different applied pressures;
the pressure measurement output module comprises a PWM (pulse-width modulation) circuit, a frequency detector, a pressure conversion circuit and an LCD (liquid crystal display); the PWM modulation circuit is used for converting an analog signal into a digital signal; the frequency detector is used for detecting the frequency of the digital signal modulated by the PWM modulation circuit; the pressure conversion circuit performs pressure conversion according to a linear relation between pressure and frequency; the LCD display is used for displaying the output pressure value;
the direct current conversion module is composed of a rectification circuit, a filter circuit and a voltage stabilizing circuit, and is used for converting sinusoidal oscillation signals output by the surface acoustic wave sensor into stable direct current voltage; the direct current voltage provided by the direct current conversion module is used for charging the power supply module;
the power supply module comprises a battery state query submodule, a first switch, a second switch, a first battery and a second battery; the battery state query submodule is used for querying whether the first battery and the second battery are in a full-power state or not, and the direct current conversion module charges the first battery or the second battery according to the condition queried by the battery state query submodule; when the first battery is fully charged, the direct current conversion module charges the second battery, and direct current voltage in the first battery is used for supplying power to the whole system; the direct current conversion module charges the first battery when the first battery is not fully charged, and direct current voltage in the second battery is used for supplying power to the whole pressure measurement system;
the pressure-controlled surface acoustic wave sensor consists of a pressure-controlled phase shifter, an amplifier, a reflection grid array A, an input transducer A, an output transducer B, a reflection grid array C, an input transducer C, a pressure sensitive film, an output transducer D and a reflection grid array D; the reflecting grating array A, the input transducer A, the output transducer B and the reflecting grating array B form a first acoustic surface wave double-end resonator; the reflecting grating array C, the input transducer C, the pressure sensitive film, the output transducer D and the reflecting grating array D form a second acoustic surface wave double-end resonator; the double-end resonator I and the amplifier form one path of surface acoustic wave oscillator I, the double-end resonator II, the amplifier and the voltage-controlled phase shifter form the other path of surface acoustic wave oscillator II, and signals in the two paths of oscillators are superposed at the input end of the amplifier to obtain an in-phase component and a quadrature component; when the orthogonal component is zero, namely the phase offset of the current at the input end of the amplifier is an integral multiple of 2 pi, and the in-phase component enables the open-loop gain to be larger than 1, namely the product of the amplitude of the current at the input end of the amplifier and the gain of the amplifier is larger than 1, the voltage-controlled surface acoustic wave sensor oscillates to generate sine wave output;
the working method of the self-powered pressure measurement system specifically comprises the following processes:
s1, under the condition of compression, a sensitive film of the surface acoustic wave sensor deforms and generates a sinusoidal oscillation signal Vi; the sinusoidal oscillation signal Vi is used as a pressure measurement input signal and is transmitted to the direct current conversion module;
s2, the direct current conversion module rectifies the sinusoidal oscillation signal Vi into a corresponding rated positive voltage V1 through a rectification circuit, and the rectification circuit can adjust the voltage of the sinusoidal oscillation signal Vi which is a negative value into the corresponding rated positive voltage by utilizing the unidirectional conductivity of a diode; a polarity capacitor C0 is connected behind the rectifying circuit, so that the rectified voltage V1 can be converted into direct-current voltage; the direct-current voltage can stabilize the fluctuating voltage into constant voltage Vo through the voltage stabilizing circuit to supply power to the power supply module;
s3, when the measuring system starts to work, the first switch is closed, the second switch is opened, the direct-current voltage output by the voltage stabilizing chip LM7812 charges the first battery, meanwhile, the voltage of the first battery is detected by the battery state query submodule, if the rated voltage reaches 3.6V, the first battery is full, the first switch is opened, the second switch is closed, the direct-current voltage charges the second battery, and the direct-current voltage in the first battery is used for supplying power for the whole pressure measuring system; at the moment, whether the second battery reaches the rated voltage is detected, if the second battery reaches the rated voltage, the first battery is charged by the direct current conversion module which is not full of electricity, and the direct current voltage in the second battery is used for supplying power to the whole pressure measurement system; the charging and discharging of the two batteries are realized, a power supply is provided for a measuring system, and the non-regeneration of the system is realized;
s4, a voltage Vi output by the pressure measurement input module is input to the pressure measurement output module, a sinusoidal oscillation signal output by the pressure-controlled surface acoustic wave sensor is changed into a square wave through PWM modulation, conversion from an analog signal to a digital signal is achieved, the frequency of the square wave and the frequency of the sinusoidal oscillation signal have a corresponding relation, and in a frequency detector, the frequency measured by the frequency detector can be 10 times of the output frequency of the pressure-controlled surface acoustic wave sensor by taking the middle point when the adjacent voltage value is 0; the pressure conversion circuit converts the pressure according to the linear corresponding relation between the pressure and the frequency, and displays the pressure value through the LCD.
2. The operating method of a self-powered pressure measurement system based on a voltage-controlled surface acoustic wave sensor according to claim 1, wherein a piezoelectric substrate of the voltage-controlled surface acoustic wave sensor is made of a piezoelectric material quartz, and an electrode is made of aluminum.
3. The method according to claim 1, wherein the rectifier circuit comprises a bridge rectifier circuit consisting of a diode D1, a diode D2, a diode D3 and a diode D4, and the rectifier circuit is configured to adjust a voltage of the sinusoidal oscillation signal Vi output by the voltage-controlled surface acoustic wave sensor, which is a negative value, to a corresponding rated positive voltage; the filter circuit comprises a polar capacitor C0 and is used for converting the rectified voltage V1 into direct-current voltage; the voltage stabilizing circuit comprises a three-terminal voltage regulator LM7812 and is used for stabilizing fluctuating voltage into constant voltage and supplying power to the battery.
4. The method as claimed in claim 1, wherein the sub-module for querying battery status is implemented by a voltage measurement chip, and the battery is fully charged by measuring whether the voltage in the battery reaches a rated voltage.
5. The method of claim 1, wherein the first switch is coupled to a first battery and the second switch is coupled to a second battery.
6. The method according to claim 1, wherein in step S4, the linear correspondence between pressure and frequency is obtained by: before pressure conversion, the output frequency and pressure relation of the pressure-controlled surface acoustic wave sensor can be tested, different known pressures act on the pressure-controlled surface acoustic wave sensor, the pressure-controlled surface acoustic wave sensor outputs different frequencies, a linear corresponding relation between the pressure and the frequency is obtained, the pressure and frequency corresponding relation of the pressure-controlled surface acoustic wave sensor can be fitted by the measured frequency and pressure, a program is written in through a hardware description language, and the conversion between the frequency and the pressure can be realized by using Cyclone IV.
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| CN202210029789.8A CN114046916B (en) | 2022-01-12 | 2022-01-12 | Self-powered pressure measurement system based on surface acoustic wave sensor and working method thereof |
| PCT/CN2023/070085 WO2023134499A1 (en) | 2022-01-12 | 2023-01-03 | Self-powered pressure measurement system based on surface acoustic wave sensor, and operating method therefor |
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