A method for multi-modal measurement using piezoelectret

Abstract

The application provides a method for realizing multi-mode measurement by using a piezoelectric electret, and the piezoelectric sensor is connected with a capacitance detection circuit in advance, then a gradually increasing or gradually decreasing static force is applied to the piezoelectric sensor, under the action of the gradually changing static force, the capacitance value of the piezoelectric electret changes correspondingly, so that the change relation between the capacitance value of the piezoelectric sensor and the applied static force is obtained, then the piezoelectric sensor is placed on the dynamic force to be measured, and a bias static force required for measurement is applied to the piezoelectric sensor, wherein the size of the bias static force is represented by the relative capacitance change amount according to the change relation, so that the dynamic force measurement and the determination of the size of the required bias static force are realized only by a single piezoelectric sensor, that is, the multi-mode measurement requirement of the dynamic force and the static force can be realized by using a single piezoelectric sensor.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric electret technology, and in particular to a method for achieving multimodal measurement using piezoelectric electrets. Background Technology

[0002] A piezoelectric sensor is a sensor based on the piezoelectric effect, and its sensing element is made of piezoelectric material. When a force is applied to the piezoelectric material, a charge is generated on its surface. This charge is amplified by a charge amplifier and a measuring circuit, and after impedance transformation, it becomes an electrical output proportional to the applied force.

[0003] Piezoelectric electret sensing materials are only sensitive to dynamic force signals. Therefore, in the existing technology, the piezoelectric effect alone can only measure dynamic force signals, but cannot measure the static force signals required for measuring dynamic force signals. So, in order to achieve the measurement of both dynamic and static forces, the more common solution is to combine a sensor made of a single-mode piezoelectric material with other sensors that are sensitive to static forces (such as piezoresistive and capacitive sensors) for measurement. However, such a combined measuring device cannot be measured using a single sensing material, which increases the complexity of the device, the overall size, and the production cost. Summary of the Invention

[0004] Therefore, it is necessary to provide a method that allows obtaining the relationship curve between the capacitance change of a piezoelectric sensor and the static force by first applying a gradually increasing static force to the piezoelectric sensor, and then selecting a suitable static force based on the relationship curve and using the selected static force to measure the dynamic force, thereby avoiding the need to use an additional sensor to determine the static force.

[0005] This invention provides a method for multimodal measurement using piezoelectric electrets, the method comprising the following steps:

[0006] Connect the piezoelectric sensor to the capacitance detection circuit;

[0007] A static force that is gradually increased or gradually decreased is applied to the piezoelectric sensor;

[0008] The capacitance detection circuit obtains the relative capacitance change of the piezoelectric sensor under the action of a gradually changing static force.

[0009] Determine the relative capacitance change The relationship between the applied, gradually changing static force and the change in the static force:

[0010]

[0011] Where ε0 is the vacuum permittivity, ε r The relative permittivity of the piezoelectric electret is . Indicates capacitance Differentiating the thickness d, Δd represents the change in thickness of the piezoelectric electret. The capacitance of the piezoelectric electret is represented by -Δp, which represents the static stress applied to the sample (i.e., the static force divided by the sample area). The change in value is represented by the negative sign, where the negative sign indicates compressive stress and Y represents the Young's modulus of the piezoelectric electret.

[0012] Determine the bias static force required to measure the dynamic force to be measured, wherein the bias static force is the static force applied to the piezoelectric sensor and required to measure the dynamic force by the piezoelectric sensor;

[0013] Place the piezoelectric sensor on the dynamic force to be measured;

[0014] The dynamic force is measured using the piezoelectric sensor under the applied bias static force, wherein the magnitude of the bias static force is determined according to the change relationship and the change in relative capacitance. The size is represented by [the value].

[0015] Furthermore, the method also includes:

[0016] The required bias static force is applied according to the relationship between the relative capacitance change and the static force.

[0017] Furthermore, the method also includes:

[0018] The charge response of the piezoelectric sensor during the measurement of the dynamic force is amplified by a charge amplifier.

[0019] Furthermore, the dynamic force changes with the change of the applied static force.

[0020] Furthermore, the dynamic force does not change with the change of the applied static force.

[0021] Furthermore, the capacitance detection circuit is a differential pulse width modulation circuit, or a frequency modulation circuit, or an operational amplifier circuit, or a charge amplifier circuit, or a switched capacitor circuit.

[0022] Furthermore, the capacitance detection circuit is used to convert the capacitance value into a voltage signal, or a frequency signal, or a current signal and transmit it to the control chip. The control chip acquires the voltage signal, or the frequency signal, or the current signal, converts it into the corresponding capacitance value, and then calculates the change relationship between the capacitance value and the corresponding static force.

[0023] Compared to existing technologies, the advantages of this invention are as follows: By pre-connecting a piezoelectric sensor to a capacitance detection circuit, and then applying a gradually increasing or decreasing static force to the piezoelectric sensor, the capacitance value of the piezoelectric electret changes accordingly under the action of the gradually changing static force. This allows the invention to obtain the relationship between the capacitance value of the piezoelectric sensor and the applied static force. The piezoelectric sensor is then placed on the dynamic force to be measured, and the required bias static force is applied to the piezoelectric sensor. The magnitude of the bias static force is expressed as the relative capacitance change according to the relationship curve. Thus, the dynamic force measurement and the determination of the required bias static force can be achieved using only a single piezoelectric sensor. In other words, the multimodal measurement requirements of dynamic and static forces can be met using a single thin piezoelectric electret sensor. Attached Figure Description

[0024] Figure 1 This is a graph showing the relationship between the relative capacitance change rate and Young's modulus of different piezoelectric materials under a specific static force according to the present invention.

[0025] Figure 2 This is a flowchart illustrating a specific embodiment of the present invention.

[0026] Figure 3 This is a graph showing the relationship between the relative capacitance change rate of a certain piezoelectric material of the present invention and the corresponding static force.

[0027] Figure 4 This is a schematic diagram illustrating a specific embodiment of the piezoelectric sensor with an irregular hole structure according to the present invention.

[0028] Figure 5 This is an exploded view of a specific embodiment of the piezoelectric sensor of the present invention.

[0029] Figure 6 This is a schematic diagram illustrating a specific implementation of the piezoelectric material preparation process of the present invention.

[0030] Figure 7 This is a cross-sectional view of a specific embodiment of the piezoelectric material of the present invention.

[0031] Figure 8 This is a schematic diagram showing the connection between the piezoelectric sensor of the present invention and the capacitance detection circuit or charge amplifier.

[0032] Explanation of icon numbers:

[0033] Piezoelectric sensor 10, piezoelectric material 20, template layer 30, clearance groove 40, FEP layer 50, first electrode 60, second electrode 70, capacitance detection circuit 80, charge amplifier 90. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. It is understood that the accompanying drawings are provided for reference and illustration only, and are not intended to limit the present invention. The connection relationships shown in the accompanying drawings are only for clear description and do not limit the connection method.

[0035] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component, or there may be an intervening component. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be noted that, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; as a mechanical connection or an electrical connection; or as a connection within two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0036] It should also be noted that in the description of this invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] Dynamic force measurement requires the application of a static force not less than the dynamic force amplitude; otherwise, the full dynamic force cannot be effectively measured. For example, when a piezoelectric film is placed on the surface of a vibrating element, the static force exerted by the piezoelectric film on the vibrating element is small, causing the piezoelectric film to vibrate synchronously with the vibrating element. At this time, the piezoelectric film has no dynamic signal output. Therefore, only by pressing the piezoelectric film firmly onto the surface of the vibrating element and preventing the piezoelectric film from moving with the vibrating element, or at least ensuring that the vibration amplitude of the piezoelectric film is smaller than the vibration amplitude of the vibrating element, will a dynamic signal be output to measure a certain dynamic force. The dynamic force can be a weak signal or a large dynamic force.

[0038] Please see Figure 1 , Figure 1 The relationship between the relative capacitance change rate and the corresponding Young's modulus of the piezoelectric sensor 10 corresponding to piezoelectric materials 20 with different Young's moduli is shown.

[0039] Specifically, the piezoelectric sensor 10 provides corresponding capacitance feedback based on the magnitude of the applied static force. Simultaneously, the Young's modulus of the piezoelectric material 20 in the piezoelectric sensor 10 also changes synchronously. Compared to non-porous piezoelectric materials 20 (such as PVDF, piezoelectric ceramics, etc.), porous piezoelectric materials 20 (such as tubular channel FEP piezoelectric electrets, etc.) exhibit greater deformation under the applied static force, resulting in a more significant change in their relative capacitance. This is especially true for the relatively softer piezoelectric materials 20. Therefore, the piezoelectric sensor 10 prepared using these relatively soft porous piezoelectric materials 20 can be used to calibrate the magnitude of the static force required for dynamic force testing. Thus, a single piezoelectric sensor 10 can be used to achieve multimodal measurement of static and dynamic forces.

[0040] according to Figure 1 It can be seen that when the Young's modulus of the piezoelectric material 20 of the piezoelectric sensor 10 is 1 MPa, the corresponding relative capacitance change rate under a static stress of 100 kPa is about 10%; when the Young's modulus of the piezoelectric material 20 is 10 MPa, the corresponding relative capacitance change rate is about 1%; when the Young's modulus of the piezoelectric material 20 is 100 MPa, the corresponding relative capacitance change rate is about 0.1%; and when the Young's modulus of the piezoelectric material 20 is 1 GPa, the corresponding relative capacitance change rate is about 0.01%. Therefore, piezoelectric materials 20 with different Young's moduli have significantly different relative capacitance change rates under the applied static force. Therefore, piezoelectric materials 20 with relatively small Young's modulus can be used as the piezoelectric material 20 of the piezoelectric sensor 10 for measuring static and dynamic forces.

[0041] Please see Figure 2 This invention provides a method for multimodal measurement using a piezoelectric electret, the method comprising the following steps:

[0042] Connect the piezoelectric sensor 10 to the capacitance detection circuit 80 (S100).

[0043] The piezoelectric material 20 of the piezoelectric sensor 10 can be a porous structure or a non-porous structure.

[0044] Furthermore, the piezoelectric sensor 10 is a flat plate or thin film structure and includes a piezoelectric material 20, a first electrode 60, and a second electrode 70. The piezoelectric material 20 is made of a piezoelectric polymer and is in the form of a flat plate or a thin film. The first electrode 60 and the second electrode 70 are disposed on opposite sides of the piezoelectric material 20. The first electrode 60 and the second electrode 70 are respectively connected to the capacitance detection circuit 80, the purpose of which is to detect the change in capacitance of the piezoelectric material 20 when subjected to external force.

[0045] Furthermore, the capacitance calculation formula for the piezoelectric sensor 10 is as follows:

[0046]

[0047] Where C represents the capacitance value, and ε0 is the vacuum permittivity (ε0 = 8.85 * 10⁻⁶). -12 F / m), ε r Let A be the relative permittivity of the piezoelectric material, A represent the area of ​​the overlapping region between the first electrode 60 and the second electrode 70 of the piezoelectric material 20, and d represent the thickness of the piezoelectric material 20.

[0048] According to the above formula, the capacitance value depends on the relative permittivity of the piezoelectric material 20, the overlapping area of ​​the first electrode 60 and the second electrode 70 of the piezoelectric material 20, and the thickness of the piezoelectric material 20.

[0049] A static force is applied to the piezoelectric sensor 10 (S200).

[0050] The static force applied to the piezoelectric sensor is a force that remains in the same direction but gradually increases in magnitude. As the static force gradually increases, the capacitance value of the piezoelectric sensor 10 changes accordingly.

[0051] Therefore, by applying the static force to the piezoelectric sensor 10, the thickness of the piezoelectric material 20 inside the piezoelectric sensor 10 changes under the action of the applied static force, thereby changing the capacitance value of the piezoelectric sensor 10.

[0052] The capacitance detection circuit 80 obtains the relative capacitance change of the piezoelectric sensor 10 under the applied static force.

[0053] Determine the relationship between the relative capacitance change ΔC / C and the gradually changing applied static force:

[0054]

[0055] Where ε0 is the vacuum permittivity, ε r The relative permittivity of the piezoelectric electret is . Indicates capacitance Differentiating the thickness d, Δd represents the change in thickness of the piezoelectric electret. The capacitance of the piezoelectric electret is represented by -Δp, which represents the static stress applied to the sample (i.e., the static force divided by the sample area). The change is represented by the negative sign, where the negative sign indicates compressive stress and Y represents the Young's modulus (S400) of the piezoelectric electret.

[0056] According to the above formula, we can see that: Therefore, the change in relative capacitance of the piezoelectric sensor 10 is related not only to the magnitude of the applied static force, but also to the Young's modulus of the piezoelectric material 20. Obtaining the change relationship diagram provides a more intuitive understanding of the change in relative capacitance. The relationship between the static force and the change.

[0057] Furthermore, taking the porous piezoelectric material 20 as an example, the Young's modulus and relative permittivity of the porous piezoelectric material 20 will change with the thickness of the piezoelectric material 20. Therefore, the capacitance value of the piezoelectric sensor 10 will also be affected by the change in Young's modulus and relative permittivity caused by the change in the thickness of the piezoelectric material 20 due to the static force.

[0058] To make it easier to understand, let's take pulse testing as an example. Although pulse is a dynamic force, the dynamic force of pulse is actually relatively weak. Therefore, when measuring pulse, a static force needs to be applied to make the measured pulse signal larger and more accurate.

[0059] Specifically, when measuring dynamic force using piezoelectric material 20, since the dynamic force has a certain vibration amplitude, and when piezoelectric material 20 is placed on the dynamic force, it often moves with the dynamic force at a basically synchronized vibration amplitude. Therefore, the piezoelectric material 20 is unlikely to have a significant piezoelectric response. Therefore, in order to make the piezoelectric material 20 have a significant piezoelectric response, a static force needs to be applied to the piezoelectric material so that the piezoelectric material 20 does not move with the dynamic force at a basically synchronized vibration amplitude. In order to make the piezoelectric material 20 have the optimal piezoelectric response during measurement and to make the measured dynamic force signal the best, the bias static force needs to be applied to the piezoelectric material.

[0060] Typically, the area of ​​the piezoelectric material 20 in the sensor used to measure pulse is approximately 2 cm². 2When the applied static force is between 0N and 20N, according to the pressure calculation formula P=F / S, the actual pressure (i.e., static force divided by area) experienced by the piezoelectric material 20 sensor is between 0kPa and 100kPa.

[0061] It should be noted that when measuring the vibration signal of the pulse, since the cross-section of the blood vessel is roughly circular, the blood pressure value can be considered constant. However, because the blood vessel is prone to deformation under the action of applied static force, when the static bias force is small, the contact area between the piezoelectric film and the blood vessel is small. At this time, the pressure on the piezoelectric film from the blood vessel is small. When an appropriate pressure is applied, the blood vessel is flattened, and the contact area between the blood vessel and the piezoelectric film increases. Therefore, the effective pressure increases accordingly (pressure equals pressure multiplied by area, i.e., F = PS). At this time, the piezoelectric response signal rises. However, if the static force is too large, the blood vessel will be closed, and the pulse signal cannot be detected. Therefore, there is an optimal static force when measuring the pulse signal. In this embodiment, the pulse signal measured under a static force of approximately 5N is optimal.

[0062] Furthermore, according to the formula It can be seen that for a certain piezoelectric material 20, when the applied static force changes, the change in relative capacitance will change accordingly with the change in static force. Taking pulse measurement as an example, for instance... Figure 3 As shown, in order to achieve more accurate pulse measurement, a pre-calibrated optimal static force of 5N needs to be applied to the piezoelectric sensor 10. Therefore, when placing the piezoelectric sensor 10 on the pulse, it is necessary to determine that the applied static force is 5N. At this time, the relative capacitance change rate can be confirmed by the capacitance value output by the piezoelectric sensor 10. When the static force corresponding to the relative capacitance change rate reaches 5N, the optimal static force to be applied is calibrated, thereby achieving the calibration of the static force required for dynamic force measurement through a single piezoelectric sensor 10.

[0063] Specifically, in such Figure 3 The relative capacitance change rate corresponding to a static force of 5N is 111.8%. Therefore, when it is necessary to calibrate the applied static force of 5N, it is sufficient to have the relative capacitance change rate fed back by the piezoelectric sensor 10 be 111.8%.

[0064] Please refer to the following: Figure 1When the Young's modulus of the piezoelectric material 20 is less than 1 MPa, the relative capacitance change rate of the measured piezoelectric sensor 10 is more obvious, and the measurement accuracy requirement of the capacitance measuring instrument will be relatively low. At this time, it will be more accurate to calibrate the optimal static force by the relative capacitance change rate. If a more precise capacitance measuring instrument is used for measurement, a piezoelectric material 20 with a Young's modulus of less than 10 MPa can be used.

[0065] Preferably, when measuring weak dynamic forces such as pulse, the piezoelectric material 20 can be selected from tubular channel fluorinated ethylene propylene (FEP) piezoelectric electrets, polypropylene (PP) porous membrane piezoelectric electrets, etc.

[0066] Please see Figures 4-7 The piezoelectric material 20 may be, but is not limited to, an irregular porous structure or a regular porous structure.

[0067] Please refer to the following: Figures 5-7 Taking a regular porous structure as an example, the piezoelectric material 20 made of FEP material can be prepared, but is not limited to, in the following ways:

[0068] First, a template layer 30 is placed between two FEP layers 50, wherein the width of the template layer 30 is smaller than the width of the FEP layer 50, the length of the template layer 30 is greater than the length of the FEP layer 50, and the two ends of the template layer 30 extend out of the two FEP layers 50 respectively along the length direction of the template layer 30, and the template layer 30 is provided with a plurality of clearance grooves 40 at a certain distance at least in the part between the two FEP layers 50.

[0069] Secondly, the two FEP layers 50 are hot-pressed together to bond them into one piece.

[0070] Then, the template layer 30 is extracted from between the two FEP layers 50, so that the portion of the template layer 30 located between the two relief grooves 40 has a regular hole structure between the two FEP layers 50.

[0071] In some implementations, one end of the template layer 30 needs to be cut off first so that the cut template layer 30 can be pulled out from between the two FEP layers 50 that are bonded together through the other end.

[0072] Preferably, the template layer 30 is PTFE (polytetrafluoroethylene). PTFE has the characteristics of high temperature resistance and low coefficient of friction. Therefore, when the two FEPs are hot-pressed, the PTFE will not bond with the FEP layer 50. At the same time, after the hot pressing is completed, due to its low coefficient of friction, the PTFE can be easily extracted from between the two FEP layers 50 after hot pressing, so that the formed holes maintain a regular structure.

[0073] Finally, the two FEP layers 50 are polarized.

[0074] Determine the bias static force required to measure the dynamic force to be measured, wherein the bias static force is the static force applied to the piezoelectric sensor and required to accurately measure the magnitude of the dynamic force by the piezoelectric sensor (S500).

[0075] Specifically, under the action of the biased static force, the piezoelectric material 20 electret exhibits a significant piezoelectric response.

[0076] The piezoelectric sensor is placed on the dynamic force to be measured (S600).

[0077] Furthermore, the method also includes:

[0078] The required bias static force is applied according to the relationship between the relative capacitance change and the static force (S700).

[0079] The dynamic force is measured using the piezoelectric electret sensor under the applied bias static force (S800), wherein the magnitude of the bias static force is determined according to the change relationship and the change in relative capacitance. The size is represented by [the value].

[0080] Under a suitable static force, because the capacitance of the piezoelectric sensor 10 has a significant capacitive response, when measuring a weak dynamic force, the piezoelectric sensor 10 will have a significant piezoelectric response under the action of the bias static force, thereby achieving a more efficient and accurate measurement of a weak dynamic force.

[0081] Furthermore, the method also includes:

[0082] The charge response of the piezoelectric sensor 10 during the measurement of the dynamic force is amplified by the charge amplifier 90 (S900).

[0083] The charge amplifier 90 further amplifies the charge response, thereby improving the accuracy and effectiveness of the measurement.

[0084] Furthermore, the capacitance detection circuit 80 is a differential pulse width modulation circuit, or a frequency modulation circuit, or an operational amplifier circuit, or a charge amplifier circuit, or a switched capacitor circuit.

[0085] Furthermore, the capacitance detection circuit 80 is used to convert the capacitance value into a voltage signal, or a frequency signal, or a current signal and transmit it to the control chip. The control chip acquires the voltage signal, or the frequency signal, or the current signal, converts it into the corresponding capacitance value, and then calculates the change relationship between the capacitance value and the corresponding static force.

[0086] The usage is as follows: Specifically, such as Figure 8 As shown, the piezoelectric sensor 10 is first connected to the capacitance detection circuit 80 (i.e., the connection switch is connected to 1). After the capacitance change relationship of the piezoelectric sensor 10 under the static force is measured by the capacitance detection circuit 80, the bias static force required to measure the dynamic force to be measured is determined. The piezoelectric sensor 10 is then placed on the dynamic force to be measured, and the bias static force is applied to the piezoelectric sensor 10. The capacitance value fed back by the piezoelectric sensor 10 is used to determine whether the applied static force reaches the bias static force. Then, the piezoelectric sensor 10 is connected to the charge amplifier 90 (i.e., the connection switch is connected to 2), so that the piezoelectric sensor 10 outputs the change relationship of the measured charge value of the dynamic force with the measurement time through the charge amplifier 90.

[0087] Compared to existing technologies that cannot measure and represent static and dynamic forces using a single piezoelectric material 20, and that require multiple different types of sensors to achieve multimodal measurement of static and dynamic forces, this invention achieves multimodal measurement of static and dynamic forces by obtaining the relationship between static force and relative capacitance change rate, and using this relationship to represent the bias static force required to measure the dynamic force as the relative capacitance change rate.

[0088] In the specification and claims of this application, the terms "comprising / including" and "having / including" and variations thereof are used to specify the presence of the stated features, values, steps or components, but do not exclude the presence or addition of one or more other features, values, steps, components or combinations thereof.

[0089] Some features of the present invention are described in different embodiments for clarity; however, these features may also be described in combination in a single embodiment. Conversely, some features of the present invention are described only in a single embodiment for brevity; however, these features may also be described individually or in any suitable combination in different embodiments.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for multimodal measurement using piezoelectric electrets, characterized in that, The method includes the following steps: Connect the piezoelectric sensor to the capacitance detection circuit; A static force that is gradually increased or gradually decreased is applied to the piezoelectric sensor; The capacitance detection circuit obtains the relative capacitance change of the piezoelectric sensor under the action of a gradually changing static force. Determine the relative capacitance change. The relationship between the applied, gradually changing static force and the change in the static force: ； in, The vacuum permittivity, The relative permittivity of the piezoelectric electret is . This indicates that the capacitance is differentiated with respect to the thickness d. This indicates the change in thickness of the piezoelectric electret. The capacitance of a piezoelectric electret is - This represents the change in static stress applied to the sample, where the negative sign indicates compressive stress. This indicates the Young's modulus of the piezoelectric electret. Determine the bias static force required to measure the dynamic force to be measured, wherein the bias static force is the static force applied to the piezoelectric sensor and required to measure the dynamic force by the piezoelectric sensor; Place the piezoelectric sensor on the dynamic force to be measured; The dynamic force is measured using the piezoelectric electret sensor under the applied bias static force, wherein the magnitude of the bias static force is determined according to the change relationship and the change in relative capacitance. The size is represented by [the value].

2. The method for multimodal measurement using a piezoelectric electret according to claim 1, characterized in that, The method further includes: The required bias static force is applied according to the relationship between the relative capacitance change and the static force.

3. The method for multimodal measurement using a piezoelectric electret according to claim 1, characterized in that, The method further includes: The charge response of the piezoelectric sensor during the measurement of the dynamic force is amplified by a charge amplifier.

4. The method for multimodal measurement using a piezoelectric electret according to claim 1, characterized in that, The dynamic force changes as the applied static force changes.

5. The method for multimodal measurement using a piezoelectric electret according to claim 1, characterized in that, The dynamic force does not change with the change of the applied static force.

6. The method for multimodal measurement using a piezoelectric electret according to claim 1, characterized in that, The capacitance detection circuit is a differential pulse width modulation circuit, or a frequency modulation circuit, or an operational amplifier circuit, or a charge amplifier circuit, or a switched capacitor circuit.

7. The method for multimodal measurement using a piezoelectric electret according to claim 6, characterized in that, The capacitance detection circuit is used to convert the capacitance value into a voltage signal, frequency signal, or current signal and transmit it to the control chip. The control chip acquires the voltage signal, frequency signal, or current signal, converts it into the corresponding capacitance value, and then calculates the change relationship between the capacitance value and the corresponding static force.

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