CN112394235A - Piezoelectric element detection system and method and application - Google Patents
Piezoelectric element detection system and method and application Download PDFInfo
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Abstract
The invention discloses a piezoelectric element detection system, a piezoelectric element detection method and application, which relate to the technical field of detection and comprise a driving circuit, a piezoelectric element, a signal detection circuit and a data processing module which are sequentially connected; the data processing module is used for calculating the actual output current value of the piezoelectric element, comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element is normal, and judging whether the working state of the piezoelectric element is abnormal or not. Aiming at the technical problem that the abnormal working state of the piezoelectric cantilever beam is difficult to judge, the working state of the piezoelectric cantilever beam can be detected, and the abnormal working state of the piezoelectric cantilever beam can be judged in advance.
Description
Technical Field
The invention relates to the technical field of detection, in particular to a piezoelectric element detection system and method and application.
Background
Piezoelectric ceramics is used as an intelligent material, the interconversion between electric energy and mechanical energy can be realized, wherein the piezoelectric cantilever beam structure is commonly applied and widely applied to the fields of vibration energy collectors, energy harvesters, vibration suppression, micro driving devices and the like, in the engineering application, the piezoelectric cantilever beam is used as a driver to work under a driving control circuit and act on a driven piece, and under the long-time work, the working state of the piezoelectric cantilever beam can not be fed back in time, so that under the external reasons of piezoelectric aging, adhesive layer peeling and the like, the driving effect is poor, and engineering faults can be caused under the serious condition. In addition, the working frequency of the piezoelectric cantilever beam is relatively high, and under a long-time working condition, the piezoelectric cantilever beam is worn and the like, and faults caused by self physical properties belong to a temporary change process, and the situation that when the piezoelectric cantilever beam is in a poor working state is difficult to judge.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention provides a piezoelectric element detection system, a method and application, aiming at the technical problem that the abnormal working state of a piezoelectric cantilever beam is difficult to judge.
2. Technical scheme
In order to solve the problems, the technical scheme provided by the invention is as follows:
a piezoelectric element detection system, comprising: the drive circuit, the piezoelectric element, the signal detection circuit and the data processing module are connected in sequence; the data processing module is used for calculating the actual output current value of the piezoelectric element, comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
Optionally, the data processing module stores an output current threshold when the working state of the piezoelectric element is normal.
Optionally, the piezoelectric element further comprises a storage module, configured to store an output current threshold when the working state of the piezoelectric element is normal; the storage module is connected with the data processing module.
Optionally, the system further comprises a display module, and the display module is connected with the data processing module.
Optionally, the signal detection circuit includes a noise filter circuit and a proportional amplifier circuit, which are connected in sequence, and the proportional amplifier circuit is connected with the data processing module.
Optionally, the data processing module further includes a noise filtering unit, a proportional amplification unit, a signal transformation unit and an analysis comparison unit, which are connected in sequence, and the noise filtering unit is connected with the signal detection circuit.
Optionally, the device further comprises a velocimeter for detecting the initial velocity v before and after the piezoelectric element is impacted1And terminal velocity v2(ii) a The velocimeter is connected with the data processing module.
Optionally, the velocimeter is a high-speed camera, a radar velocimeter or a laser velocimeter.
Optionally, the piezoelectric element is a piezoelectric crystal piece, a piezoelectric semiconductor or a piezoelectric ceramic piece; if the piezoelectric element is a piezoelectric crystal, the piezoelectric crystal is a piezoelectric cantilever beam, the piezoelectric cantilever beam comprises a substrate and a piezoelectric wafer, and the piezoelectric wafer is arranged on more than one side surface of the substrate.
A piezoelectric element inspection method, a piezoelectric element inspection system according to any one of the above, comprising: setting mechanical boundary conditions of the piezoelectric element, and setting electrical boundary conditions for the piezoelectric element through a driving circuit; the output signal of the piezoelectric element is transmitted to a data processing module for processing through a signal detection circuit, and the actual output current value of the piezoelectric element is obtained through calculation; and comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
Optionally, the method for calculating the output current threshold when the working state of the piezoelectric element is normal includes: velocimeter detects initial velocity v before and after piezoelectric element is impacted1And terminal velocity v2(ii) a And sending the output current to a data processing module for processing, wherein the data processing module calculates an output current threshold value when the working state of the piezoelectric element is normal.
Optionally, the output current threshold value when the working state of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is normal is stored in the data processing module or the storage module; if the output current threshold value of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is stored in the storage module when the working state of the piezoelectric element is normal, the data processing module reads the content of the storage module; and comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
Optionally, if the piezoelectric element is a piezoelectric cantilever, the data processing module calculates an output current threshold when the working state of the piezoelectric element is normal, including:
i is the output current signal of the piezoelectric element as a sensor, ApSurface area of the piezoelectric wafer being a piezoelectric cantilever beam, d31Is a piezoelectric constant, EcIs the modulus of elasticity of the piezoelectric cantilever beam, l is the piezoelectric wafer length, v1、v2The initial speed and the final speed, zeta and w, of the piezoelectric cantilever beam under the action of external forced、wnThe vibration frequency of the piezoelectric cantilever beam with damping and the natural frequency of the piezoelectric cantilever beam without damping are respectively, and t is time.
Optionally, the calculating, by the data processing module, an output current threshold when the working state of the piezoelectric element is normal includes:
the impacted piezoelectric cantilever beam is equivalent to a single-degree-of-freedom system, and impulse u:
f is the magnitude of the external impact force applied to the piezoelectric cantilever beam, and m is the mass of the piezoelectric cantilever beam;
for an under-damped system, the differential equation of motion is:
obtaining by solution:
wherein, wnFor the natural frequency of undamped vibration,
m is the mass of the piezoelectric cantilever beam, and k is the equivalent spring constant of the piezoelectric cantilever beam;
ζ is a damping ratio of the damping member,
c is the damping coefficient of the piezoelectric cantilever beam; w is adIn order to have a frequency at which the vibration is damped,
initial conditions:
x(t＝0)＝x0＝0，
substituting the initial conditions into a motion differential equation to obtain
Bending moment M:
wherein, the thickness of the upper and lower layers of piezoelectric wafers is h1Elastic modulus of the upper piezoelectric wafer is E1The thickness of the substrate is h2The elastic modulus of the lower piezoelectric wafer is E2B is the width of the piezoelectric cantilever beam, R is the curvature radius of the neutral axis of the piezoelectric cantilever beam, and I is the inertia moment of the cross section of the piezoelectric cantilever beam in the direction of 2-2:
Ecis the equivalent elastic modulus of the piezoelectric cantilever beam,
to obtain
y1The distance between the positive stress of any point and the neutral axis of the piezoelectric cantilever beam from the point;
M(t)max＝F(t)l；
according to the formula of the flexible line, the following is calculated:
according to the first piezoelectric equation
The piezoelectric constant of the piezoelectric wafer is d31The electrode surface area is ApIntegrating the electric displacement on the surface area of the piezoelectric wafer electrode to obtain the total output charge Q of the electrode surface of the piezoelectric cantilever beam3Comprises the following steps:
using an amount of charge Q3And (3) obtaining the relation of the current changing along with the time by differentiating the time:
optionally, the method further includes: the content sent by the data processing module to the display module at least comprises the result whether the working state of the piezoelectric element is abnormal or not.
Use of a piezoelectric element detection system comprising a piezoelectric element detection system as claimed in any preceding claim.
Optionally, the piezoelectric element detection system is configured to detect an operating state of the piezoelectric element.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
the driving circuit is used for transmitting electric energy to the piezoelectric element so as to realize the electrical open circuit and the electrical short circuit of the piezoelectric element and provide different electrical boundary conditions for the piezoelectric element. Under different electrical boundary conditions and mechanical boundary conditions, when the piezoelectric element is used as a driver or a sensor, after being detected by a signal detection circuit, an output signal of the piezoelectric element is transmitted to a data processing module for processing, so that the actual output current value of the piezoelectric element can be obtained in real time, the actual output current value is compared with the output current threshold value when the working state of the piezoelectric element is normal under the corresponding electrical boundary conditions and mechanical boundary conditions, and if the actual output current value of the piezoelectric element is within the output current threshold value when the piezoelectric element normally works, the working state of the piezoelectric element is normal; if the actual output current value of the piezoelectric element is out of the output current threshold value when the piezoelectric element normally works, the working state of the piezoelectric element is abnormal. Through the process, when the piezoelectric element of the detection system works, whether the working state of the piezoelectric element is abnormal or not can be monitored in real time, so that early warning can be realized, and the conditions of potential safety hazard, economic loss, engineering accidents and the like caused by the abnormal working state of the piezoelectric element can be prevented; in other words, according to the system, the piezoelectric element can be used as a driver for driving a driven member and can also be used as a sensor for sensing and detecting signals according to different set boundary conditions, and meanwhile, the real-time self-detection function of the working state of the piezoelectric element can be realized without additional accessories.
The data processing module stores an output current threshold value when the working state of the piezoelectric element is normal. According to the practical application requirement of the piezoelectric element, the piezoelectric element sets a corresponding electrical boundary condition and a corresponding mechanical boundary condition, and the data processing module stores an output current threshold value when the working state of the piezoelectric element is normal under the electrical boundary condition and the mechanical boundary condition, so that the data processing module compares the output current threshold value with the actual output current value of the piezoelectric element to judge whether the working state of the piezoelectric element is abnormal or not.
Drawings
Fig. 1 is a schematic structural diagram of a piezoelectric element detection system according to an embodiment of the present invention;
FIG. 2 is one of the equivalent circuit diagrams of the piezoelectric cantilever;
FIG. 3 is a schematic diagram of the piezoelectric cantilever beam under impact force.
Detailed Description
For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings. The terms first, second, and the like in the present invention are provided for convenience of describing the technical solution of the present invention, and have no specific limiting effect, but are all generic terms, and do not limit the technical solution of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; 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.
Example 1
A piezoelectric element detection system, as shown in fig. 1, comprising: the driving circuit 9, the piezoelectric element 4, the signal detection circuit 10 and the data processing module 11 are connected in sequence; the data processing module 11 is configured to calculate an actual output current value of the piezoelectric element 4, compare the actual output current value of the piezoelectric element 4 with an output current threshold value when the working state of the piezoelectric element 4 is normal, and determine whether the working state of the piezoelectric element 4 is abnormal.
The driving circuit 9 is used for transmitting electric energy to the piezoelectric element 4 to realize the electrical open circuit and the electrical short circuit of the piezoelectric element 4, and provide different electrical boundary conditions for the piezoelectric element 4, and according to different application occasions of the piezoelectric element 4, the mechanical boundary conditions of the piezoelectric element 4 are different, and the mechanical boundary conditions and the electrical boundary conditions are combined to form four types of boundary conditions of the piezoelectric element 4 so as to adapt to different practical application requirements. Under different electrical boundary conditions and mechanical boundary conditions, when the piezoelectric element 4 is used as a driver or a sensor, after a signal output by the piezoelectric element 4 is detected by a signal detection circuit, the signal is transmitted to the data processing module 11 for processing, so that an actual output current value of the piezoelectric element 4 can be obtained in real time, the actual output current value is compared with an output current threshold value when the working state of the piezoelectric element 4 is normal under the corresponding electrical boundary conditions and mechanical boundary conditions, and if the actual output current value of the piezoelectric element 4 is within the output current threshold value when the piezoelectric element 4 normally works, the working state of the piezoelectric element 4 is normal; if the actual output current value of the piezoelectric element 4 is out of the output current threshold value at the time of normal operation of the piezoelectric element 4, the operation state of the piezoelectric element 4 is abnormal. Through the process, when the piezoelectric element 4 of the detection system works, whether the working state of the piezoelectric element 4 is abnormal or not can be monitored in real time, so that early warning can be realized, and the conditions of potential safety hazards, economic loss, engineering accidents and the like caused by the abnormal working state of the piezoelectric element 4 can be prevented; in other words, according to the system, the piezoelectric element 4 can be used as a driver for driving a driven member or as a sensor for sensing and detecting signals according to different set boundary conditions, and meanwhile, the real-time self-detection function of the working state of the piezoelectric element 4 can be realized without additional accessories.
The data processing module 11 stores an output current threshold value when the working state of the piezoelectric element 4 is normal. According to the actual application requirement of the piezoelectric element 4, the piezoelectric element 4 sets corresponding electrical boundary conditions and mechanical boundary conditions, and the data processing module 11 stores the output current threshold value when the working state of the piezoelectric element 4 is normal under the electrical boundary conditions and the mechanical boundary conditions, so that the data processing module 11 compares the output current threshold value with the actual output current value of the piezoelectric element 4 to judge whether the working state of the piezoelectric element 4 is abnormal or not.
The piezoelectric element 4 is used for outputting the output current threshold value when the working state is normal; the storage module is connected with the data processing module 11. The data processing module 11 reads the output current threshold value of the piezoelectric element 4 in the normal working state under the corresponding electrical boundary condition and the mechanical boundary condition from the storage module; and comparing the actual output current value of the piezoelectric element 4 obtained by real-time processing to judge whether the working state of the piezoelectric element 4 is abnormal or not.
The device also comprises a display module, and the display module is connected with the data processing module 11. The data processing module 11 processes the received analog signal of the signal detection circuit 10 to obtain the current value actually output when the piezoelectric element 4 works in real time, and the information such as the result of judging whether the working state of the piezoelectric element 4 is abnormal or not by comparing the current value with the current threshold value in the normal working state of the piezoelectric element 4, and transmits the information to the display module for displaying, so as to directly observe and obtain the system detection result and the result of judging whether the piezoelectric element 4 works abnormally or not.
The signal detection circuit 10 comprises a noise filter circuit and a proportional amplification circuit which are connected in sequence, and the proportional amplification circuit is connected with the data processing module 11. The signal detection circuit 10 in the system comprises a noise filter circuit and a proportional amplification circuit which are connected in sequence. That is, the signal detection circuit 3 has the characteristics of high amplification factor, high sensitivity and high input impedance, and is used for filtering noise of the real-time output signal of the piezoelectric element 4 and performing numerical amplification on the output signal, so that the data processing module 11 can further process the output signal.
The data processing module 11 further comprises a noise filtering unit, a proportional amplification unit, a signal conversion unit and an analysis comparison unit which are connected in sequence, wherein the noise filtering unit is connected with the signal detection circuit 10. The data processing module 11 has the functional characteristics of high amplification factor, high sensitivity and high input impedance, and is used for filtering noise of the output signal of the signal detection circuit 10 and amplifying the output signal value, so that the signal conversion unit processes and extracts a required signal index, and then sends the signal index to the analysis comparison unit, and the result of whether the working state of the piezoelectric element 4 is abnormal is obtained through comparison and analysis.
Also comprises a velocimeter for detecting the initial velocity v before and after the piezoelectric element 4 is impacted1And terminal velocity v2(ii) a The velocimeter is connected with the data processing module 11. The data processing module 11 receives the initial velocity v before and after the piezoelectric element 4 is impacted from the velocimeter1And terminal velocity v2Then, according to a corresponding piezoelectric equation, calculating an output current threshold value when the working state of the piezoelectric element 4 is normal under the mechanical boundary condition, and storing the output current threshold value in the data processing module 11 or the storage module, so that when the detection system works, the data processing module 11 compares the actual current value of the piezoelectric element 4 with the actual current value to judge whether the working state of the piezoelectric element 4 is abnormal in real time, the piezoelectric element 4 can be used as a sensor or a driver, and when sensing or driving is realized, whether the working state of the piezoelectric element 4 is abnormal can be monitored in real time to give early warning, so that the detection system is ensured to have an effective and safe working state, corresponding practical application requirements are realized, and engineering safety is ensured.
The velocimeter is a high-speed camera 8, a radar velocimeter or a laser velocimeter. The velocimeter is used for acquiring the initial velocity v before and after the piezoelectric element 4 is impacted1And terminal velocity v2(ii) a The high-speed camera 8, the radar velocimeter or the laser velocimeter can be selected so as to calculate the output current threshold value when the working state of the piezoelectric element 4 is normal under the corresponding mechanical boundary condition and the corresponding electrical boundary condition.
The piezoelectric element 4 is a piezoelectric crystal piece, a piezoelectric semiconductor or a piezoelectric ceramic piece; if the piezoelectric element is a piezoelectric crystal, the piezoelectric crystal is a piezoelectric cantilever beam, the piezoelectric cantilever beam comprises a substrate and a piezoelectric wafer, and the piezoelectric wafer is arranged on more than one side surface of the substrate. The piezoelectric element 4 is a piezoelectric cantilever beam or a piezoelectric ceramic piece, if the piezoelectric element is a piezoelectric cantilever beam, the piezoelectric cantilever beam comprises a substrate 6 and piezoelectric wafers, the piezoelectric wafers comprise an upper piezoelectric wafer 5 and a lower piezoelectric wafer 7, and the piezoelectric wafers are arranged on more than one side surface of the substrate 6. When a piezoelectric wafer is arranged on one side surface of the substrate 6, the piezoelectric cantilever beam is a single-wafer piezoelectric cantilever beam; when the two side surfaces of the substrate 6 are both provided with the piezoelectric wafers, the piezoelectric cantilever is a bimorph piezoelectric cantilever, as shown in fig. 1.
Example 2
A piezoelectric element detection method, a piezoelectric element detection system according to any one of embodiments 1, comprising: setting mechanical boundary conditions of the piezoelectric element 4, and setting electrical boundary conditions for the piezoelectric element 4 through the driving circuit 9; the output signal of the piezoelectric element 4 is transmitted to the data processing module 11 for processing through the signal detection circuit 10, and the actual output current value of the piezoelectric element 4 is obtained through calculation; the actual output current value of the piezoelectric element 4 is compared with an output current threshold value at which the operating state of the piezoelectric element 4 is normal under the set mechanical boundary condition and electrical boundary condition, and it is determined whether the operating state of the piezoelectric element 4 is abnormal.
Under different electrical boundary conditions and mechanical boundary conditions, when the piezoelectric element 4 is used as a driver or a sensor, after an output signal of the piezoelectric element 4 is detected by the signal detection circuit 10, the output signal is transmitted to the data processing module 11 for processing, so that an actual output current value of the piezoelectric element 4 can be obtained in real time, the actual output current value is compared with an output current threshold value when the working state of the piezoelectric element 4 is normal under the corresponding electrical boundary conditions and mechanical boundary conditions, and if the actual output current value of the piezoelectric element 4 is within the output current threshold value when the piezoelectric element normally works, the working state of the piezoelectric element 4 is normal; if the actual output current value of the piezoelectric element 4 is out of the output current threshold value at the time of normal operation of the piezoelectric element 4, the operation state of the piezoelectric element 4 is abnormal.
By the method, when the piezoelectric element 4 works, whether the working state of the piezoelectric element 4 is abnormal or not can be monitored in real time, so that early warning can be given in advance, and the conditions of potential safety hazards, economic loss, engineering accidents and the like caused by the abnormal working state of the piezoelectric element 4 can be prevented; in other words, according to the method, the piezoelectric element 4 can be used as a driver for driving a driven member and also can be used as a sensor for sensing and detecting signals according to different set boundary conditions, and meanwhile, the function of real-time self-detection of the working state of the piezoelectric element 4 can be realized without additional accessories.
The method for calculating the output current threshold value when the working state of the piezoelectric element 4 is normal comprises the following steps: the velocimeter detects the initial velocity v before and after the piezoelectric element 4 is impacted1And terminal velocity v2(ii) a The output current is sent to the data processing module 11 for processing, and the data processing module 11 calculates the output current threshold value when the working state of the piezoelectric element 4 is normal.
The velocimeter can select any one of the high-speed camera 8, the radar velocimeter or the laser velocimeter; under the first class of boundary conditions, namely mechanical freedom and electrical short circuit, the detected initial and final speeds are substituted into a theoretical formula, the current change rule of the piezoelectric cantilever beam after collision is calculated, frequency domain analysis is carried out on the current change rule to obtain the characteristic frequency of the piezoelectric cantilever beam, and the threshold values of the output current of the piezoelectric element 4 in the time domain and the frequency domain during normal work are obtained through multiple tests.
The output current threshold value when the working state of the piezoelectric element 4 under the set mechanical boundary condition and the set electrical boundary condition is normal is stored in the data processing module 11 or the storage module; if the output current threshold value of the piezoelectric element 4 under the set mechanical boundary condition and the set electrical boundary condition is stored in the storage module when the working state is normal, the data processing module 11 reads the content of the storage module; the actual output current value of the piezoelectric element 4 is compared with an output current threshold value at which the operating state of the piezoelectric element 4 is normal under the set mechanical boundary condition and electrical boundary condition, and it is determined whether the operating state of the piezoelectric element 4 is abnormal.
If the piezoelectric element 4 is a piezoelectric cantilever, the data processing module 11 calculates an output current threshold when the working state of the piezoelectric element 4 is normal, including:
i is the output current signal of the piezoelectric element as a sensor, ApSurface area of the piezoelectric wafer being a piezoelectric cantilever beam, d31Is a piezoelectric constant, EcIs the modulus of elasticity of the piezoelectric cantilever beam, l is the piezoelectric wafer length, v1、v2The initial speed and the final speed, zeta and w, of the piezoelectric cantilever beam under the action of external forced、wnThe vibration frequency of the piezoelectric cantilever beam with damping and the natural frequency of the piezoelectric cantilever beam without damping are respectively, and t is time.
The data processing module 11 calculates the output current threshold when the working state of the piezoelectric element 4 is normal, and includes: a simplified model of the impact of a piezoelectric cantilever during oscillation is shown in figure 3, where the force is typically applied for a period of time and then ceases to be applied. When the excitation force F is relatively large, but the action time Δ t is short, the magnitude of this impulse can be measured by the change in system momentum it causes. The impacted piezoelectric cantilever beam is equivalent to a single-degree-of-freedom system, and impulse u:
f is the magnitude of the external impact force applied to the piezoelectric cantilever beam, and m is the mass of the piezoelectric cantilever beam; since dt approaches 0, if Fdt is finite, the value of F needs to approach infinity, where the impulse can be used as a very meaningful analysis tool to quantify the magnitude of F;
for an under-damped system, the differential equation of motion is:
obtaining by solution:
wherein, wnFor the natural frequency of undamped vibration,
m is the mass of the piezoelectric cantilever beam, and k is the equivalent spring constant of the piezoelectric cantilever beam;
ζ is a damping ratio of the damping member,
c is the damping coefficient of the piezoelectric cantilever beam; w is adIn order to have a frequency at which the vibration is damped,
initial conditions:
x(t＝0)＝x0＝0，
substituting the initial conditions into a motion differential equation to obtain
And 2.3, because the upper layer and the lower layer of the piezoelectric cantilever beam are piezoelectric wafers and the middle layer is high carbon fiber, calculating the equivalent elastic modulus of the piezoelectric cantilever beam, and taking the bending piezoelectric cantilever beam as a model, wherein the bending moment M is as follows:
wherein, the thickness of the upper and lower layers of piezoelectric wafers is h1The elastic modulus of the upper piezoelectric wafer 5 is E1The thickness of the substrate is h2Push-down transistorThe sheet 7 has an elastic modulus E2B is the width of the piezoelectric cantilever beam, R is the curvature radius of the neutral axis of the piezoelectric cantilever beam, and I is the inertia moment of the cross section of the piezoelectric cantilever beam in the direction of 2-2:
Ecis the equivalent elastic modulus of the piezoelectric cantilever beam,
to obtain
y1The distance between the positive stress of any point and the neutral axis of the piezoelectric cantilever beam from the point;
M(t)max＝F(t)l；
according to the formula of the flexible line, the following is calculated:
calculating according to a first piezoelectric equation:
the piezoelectric wafer is made of PZT-5H with a piezoelectric constant d31The electrode surface area is ApIntegrating the electric displacement on the surface area of the electrode to obtain the total output charge Q of the electrode surface of the piezoelectric ceramic sensor3Comprises the following steps:
using an amount of charge Q3And (3) obtaining the relation of the current changing along with the time by differentiating the time:
and thirdly, detecting characteristic frequency in the signal through the decoupling piezoelectric cantilever beam, comparing with a theoretical threshold value, judging whether the action of the piezoelectric cantilever beam driver is abnormal or not, and if the signal is abnormal or has a trend of deviating from the threshold value, early warning is carried out in time.
The method further comprises the following steps: the content sent by the data processing module 11 to the display module at least includes the result of whether the working state of the piezoelectric element 4 is abnormal. The display module displays the result of whether the working state of the piezoelectric element 4 is abnormal or not, and can also display current signals output by the piezoelectric element 4 in real time, including time domain signals or frequency domain signals.
An application of a piezoelectric element detection system, comprising the piezoelectric element detection system according to any one of the embodiments 1; it is conceivable that a piezoelectric element detection system is applied to detection of relevant parameters in an environment with high performance requirements, such as products or technical fields of automobiles, printers and the like, on one hand, the piezoelectric element is required to work normally as a driver or a sensor, on the other hand, the working state of the piezoelectric element applied to the above occasions is ensured to be normal, and the relevant products or technologies are ensured to work normally, so that safety is ensured. When the piezoelectric element detection system is applied, the technical effects of driving or sensing detection can be realized; on the other hand, the real-time detection and monitoring of whether the working state of the device is abnormal can be realized, and once the abnormality is found, early warning can be carried out in advance, and preventive measures can be taken in advance; the conditions that the related products or technical functions of the piezoelectric element detection system are invalid, further faults or safety accidents are caused, and the like are prevented from occurring due to the fact that the piezoelectric element works abnormally or fails, and related losses can be reduced.
In addition, the piezoelectric element detection system is used for detecting the working state of the piezoelectric element, and can realize the detection and judgment of the normal or abnormal state of the piezoelectric element by executing the piezoelectric element detection method according to any technical scheme, and can be matched with a control system, a control center or a display screen and the like of related products or technologies to directly or indirectly display the working state of the piezoelectric element in the embodiment or the working state of the related products or technologies of the piezoelectric element detection system applying the embodiment, so as to early warn the conditions of faults or safety accidents of the related products or technologies caused by the abnormal working state of the piezoelectric element in advance and realize the technical effect of early warning; in the application, the type and the type of the piezoelectric element can be selected and determined according to the specific application scene, the cost performance, the performance index requirement and other factors; without being limited by the enumeration of the present embodiments; in addition, the application or scenario of a piezoelectric element detection system is not limited by the present embodiment, and it can be adapted and modified to fit related products or technical fields, and is within the scope of the present embodiment.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (17)
1. A piezoelectric element detection system, comprising:
the drive circuit, the piezoelectric element, the signal detection circuit and the data processing module are connected in sequence;
the data processing module is used for calculating the actual output current value of the piezoelectric element, comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
2. The piezoelectric element detection system according to claim 1, wherein the data processing module stores an output current threshold value when the operating state of the piezoelectric element is normal.
3. The piezoelectric element detection system according to claim 1, further comprising a storage module, configured to store an output current threshold value when the operating state of the piezoelectric element is normal; the storage module is connected with the data processing module.
4. The piezoelectric element detection system according to claim 1, further comprising a display module, wherein the display module is connected with the data processing module.
5. The piezoelectric element detection system according to claim 1, wherein the signal detection circuit comprises a noise filter circuit and a proportional amplifier circuit which are connected in sequence, and the proportional amplifier circuit is connected with the data processing module.
6. The piezoelectric element detection system according to claim 1, wherein the data processing module further comprises a noise filtering unit, a proportional amplifying unit, a signal transforming unit and an analyzing and comparing unit which are connected in sequence, and the noise filtering unit is connected with the signal detection circuit.
7. A piezoelectric element detection system according to any one of claims 1 to 6, further comprising a velocimeter for detecting an initial velocity v of the piezoelectric element before and after impact1And terminal velocity v2(ii) a The velocimeter is connected with the data processing module.
8. The piezoelectric element inspection system according to claim 7, wherein the velocimeter is a high-speed camera, a radar velocimeter or a laser velocimeter.
9. The piezoelectric element detection system according to claim 7, wherein the piezoelectric element is a piezoelectric crystal, a piezoelectric semiconductor or a piezoelectric ceramic;
if the piezoelectric element is a piezoelectric crystal, the piezoelectric crystal is a piezoelectric cantilever beam, the piezoelectric cantilever beam comprises a substrate and a piezoelectric wafer, and the piezoelectric wafer is arranged on more than one side surface of the substrate.
10. A piezoelectric element inspection method, a piezoelectric element inspection system according to any one of claims 1 to 9, comprising:
setting mechanical boundary conditions of the piezoelectric element, and setting electrical boundary conditions for the piezoelectric element through a driving circuit;
the output signal of the piezoelectric element is transmitted to a data processing module for processing through a signal detection circuit, and the actual output current value of the piezoelectric element is obtained through calculation;
and comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
11. The method for detecting a piezoelectric element according to claim 10, wherein the method for calculating the output current threshold value when the operating state of the piezoelectric element is normal includes:
velocimeter detects initial velocity v before and after piezoelectric element is impacted1And terminal velocity v2；
Is sent to the data processing module for processing,
and the data processing module calculates the output current threshold value when the working state of the piezoelectric element is normal.
12. The method according to claim 10, wherein the threshold value of the output current when the operating state of the piezoelectric element under the set mechanical boundary condition and the electrical boundary condition is normal is stored in a data processing module or a storage module;
if the output current threshold value of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition when the working state is normal is stored in the storage module,
the data processing module reads the content of the storage module;
and comparing the actual output current value of the piezoelectric element with the output current threshold value when the working state of the piezoelectric element under the set mechanical boundary condition and the set electrical boundary condition is normal, and judging whether the working state of the piezoelectric element is abnormal or not.
13. The method as claimed in claim 11, wherein if the piezoelectric element is a piezoelectric cantilever, the calculating, by the data processing module, an output current threshold when the operating state of the piezoelectric element is normal includes:
i is the output current signal of the piezoelectric element as a sensor, ApSurface area of the piezoelectric wafer being a piezoelectric cantilever beam, d31Is a piezoelectric constant, EcIs the modulus of elasticity of the piezoelectric cantilever beam, l is the piezoelectric wafer length, v1、v2The initial speed and the final speed, zeta and w, of the piezoelectric cantilever beam under the action of external forced、wnThe vibration frequency of the piezoelectric cantilever beam with damping and the natural frequency of the piezoelectric cantilever beam without damping are respectively, and t is time.
14. The method as claimed in claim 13, wherein the step of calculating the output current threshold when the working state of the piezoelectric element is normal by the data processing module comprises:
the impacted piezoelectric cantilever beam is equivalent to a single-degree-of-freedom system, and impulse u:
f is the magnitude of the external impact force applied to the piezoelectric cantilever beam, and m is the mass of the piezoelectric cantilever beam;
for an under-damped system, the differential equation of motion is:
obtaining by solution:
wherein, wnFor the natural frequency of undamped vibration,
m is the mass of the piezoelectric cantilever beam, and k is the equivalent spring constant of the piezoelectric cantilever beam;
ζ is a damping ratio of the damping member,
c is the damping coefficient of the piezoelectric cantilever beam; w is adIn order to have a frequency at which the vibration is damped,
initial conditions:
x(t＝0)＝x0＝0，
substituting the initial conditions into a motion differential equation to obtain
Bending moment M:
wherein, the thickness of the upper and lower layers of piezoelectric wafers is h1Elastic modulus of the upper piezoelectric wafer is E1The thickness of the substrate is h2The elastic modulus of the lower piezoelectric wafer is E2B is the width of the piezoelectric cantilever beam, R is the curvature radius of the neutral axis of the piezoelectric cantilever beam, and I is the inertia moment of the cross section of the piezoelectric cantilever beam in the direction of 2-2:
Ecis the equivalent elastic modulus of the piezoelectric cantilever beam,
to obtain
y1The distance between the positive stress of any point and the neutral axis of the piezoelectric cantilever beam from the point;
M(t)max＝F(t)l；
according to the formula of the flexible line, the following is calculated:
according to the first piezoelectric equation
The piezoelectric constant of the piezoelectric wafer is d31The electrode surface area is ApIntegrating the electric displacement on the surface area of the piezoelectric wafer electrode to obtain the total output charge Q of the electrode surface of the piezoelectric cantilever beam3Comprises the following steps:
using an amount of charge Q3And (3) obtaining the relation of the current changing along with the time by differentiating the time:
15. a piezoelectric element inspection method according to any one of claims 10 to 14, further comprising:
the content sent by the data processing module to the display module at least comprises the result whether the working state of the piezoelectric element is abnormal or not.
16. Use of a piezoelectric element detection system comprising a piezoelectric element detection system according to any one of claims 1 to 9.
17. Use of a piezoelectric element detection system according to claim 16 for detecting the operating state of a piezoelectric element.
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