CN101551229B - Piezoelectric dynamic strain sensor that can eliminate the effect of lateral strain - Google Patents

Abstract

The invention discloses a piezoelectric dynamic strain transducer which can eliminate lateral strain influence. The transducer consists of a 1-3 type piezoelectric transducer and a 3-3 type piezoelectric transducer. By theoretical derivation and calculation combining the size of the actual transducer, the proper size proportion of transducer is selected, and a group of piezoelectric dynamic straintransducers which can eliminate lateral strain influence is combined by a proper wiring mode. The piezoelectric dynamic strain transducer is stuck on the surface of a target structure when in use, can eliminate lateral strain change influence of the target structure, and is only sensitive to strain change with particular direction and plays the role of transducer. The piezoelectric dynamic straintransducer can promote wide applications of the piezoelectric dynamic strain transducer in engineering structures.

Description

Can eliminate the piezoelectricity type of dynamic strain sensor of transverse strain influence

Technical field

Invention relates to a kind of piezoelectricity type of dynamic strain sensor of eliminating the transverse strain influence, belongs to the technical field of piezoelectricity type of dynamic strain sensor.

Background technology

Piezoelectric can be as sensing element, again can be as exciting element, and it is big to have piezoelectric constant, highly sensitive; Preparation easily, the response frequency height, with low cost, be subjected to characteristics such as condition influence such as environment temperature and humidity is little, have broad application prospects, be widely used in actual engineering.

Piezoelectric sensor commonly used in the actual engineering is divided into 1-3 type piezoelectric sensor and 3-3 type piezoelectric sensor usually.Its difference is: 1-3 type piezoelectric sensor is when pasting use, and its polarised direction is perpendicular to the object construction surface, and when the object construction surface strain changed, piezoelectric sensor at the electrode stored charge, played the sensing effect by the piezoelectric effect of 1-3 direction; And 1-3 type piezoelectric sensor is when paste using, and its polarised direction is parallel to the object construction surface, and when the object construction surface strain changed, piezoelectric sensor at the electrode stored charge, played the sensing effect by the piezoelectric effect of 3-3 direction.

In practical engineering application, usually need the strain variation of the specific direction on object construction surface is monitored.And the above-mentioned characteristic of conventional piezoelectric sensor makes and has comprised the electric charge component that the strain variation that both comprised target direction in its output charge produces transverse strain again and changed the electric charge component that produces.

This just requires a kind of novel piezoelectricity type of dynamic strain sensor, can only carry out sensing to the strain variation of object construction surface specific direction, at the electrode stored charge, and insensitive to horizontal strain variation.

Summary of the invention

A kind of can effectively to eliminate object construction transverse strain variable effect only responsive and play the piezoelectricity type of dynamic strain sensor of sensing effect to the specific direction strain variation thereby the present invention seeks to provide at the defective that prior art exists.The output charge signal of this sensor has been eliminated the influence of transverse strain, only the strain variation situation of reaction structure surface specific direction.

The present invention adopts following technical scheme for achieving the above object:

The present invention can eliminate the piezoelectricity type of dynamic strain sensor of transverse strain influence, it is characterized in that this sensor is made up of 1-3 type piezoelectric strain sensor placed side by side and 3-3 type piezoelectric strain sensor, the electrode surface of 1-3 type piezoelectric strain sensor is placed up and down, the electrode surface of 3-3 type piezoelectric strain sensor is laterally placed, the positive pole of the positive pole of 1-3 type piezoelectric strain sensor electrode and 3-3 type piezoelectric strain sensor electrode connects and composes the positive output end of described piezoelectricity type of dynamic strain sensor, the negative pole of the negative pole of 1-3 type piezoelectric strain sensor electrode and 3-3 type piezoelectric strain sensor electrode connects and composes the negative output terminal of described piezoelectricity type of dynamic strain sensor, described piezoelectricity type of dynamic strain sensor is encapsulated by fexible film, and the electrode area of described 1-3 type piezoelectric strain sensor and 3-3 type piezoelectric strain sensor meets the following conditions:

Condition is a):

S _Pa/S _Pb＝-(d ₃₁+μ _pd ₃₃)/(d ₃₁+μ _pd ₃₁)，

Or condition b):

S _Pa/S _Pb＝-(d ₃₃+μ _pd ₃₁)/(d ₃₁+μ _pd ₃₁)，

Wherein, S _PaBe 1-3 type piezoelectric sensor electrode area, S _PaBe 3-3 type piezoelectric sensor electrode area, μ _pBe piezoelectric Poisson ratio, d ₃₁Be the strain piezoelectric constant of 1-3 type piezoelectric sensor, d ₃₃Strain piezoelectric constant for 3-3 type piezoelectric strain sensor.

The present invention has following advantage: (1) provides a kind of implementation method of eliminating the piezoelectricity type of dynamic strain sensor of transverse strain influence, and the condition that the influence of the elimination of definite equation expression transverse strain is arranged is provided; (2) when needing monitoring to change unidirectional faster strain variation situation in the engineering practical structures, resistance strain gage can't be realized owing to the high frequency response scarce capacity, traditional piezoelectric strain sensor then can't realize that too the present invention has solved this actual demands of engineering well owing to be difficult to eliminate the influence of transverse strain; (3) the present invention is with low cost, only needs the 1-3 type and the 3-3 type piezoelectric sensor of a pair of specific dimensions to realize; (4) easy and simple to handle, only need both positive and negative polarity with 1-3 type piezoelectric sensor and 3-3 type piezoelectric sensor be connected respectively and promptly can be used as overall output; (5) above advantage is fit to actual engineering very much, especially the body structure surface strain variation that changes is at a high speed carried out the application of the occasion of on-line monitoring.

Description of drawings

Fig. 1 is the stickup and the principle of work synoptic diagram of piezoelectric strain sensor, wherein (a) is 1-3 type piezoelectric strain sensor, is 3-3 type piezoelectric strain sensor (b), and mark is described as follows among the figure: the x-y plane is plane, body structure surface place, the z direction is a planar process to, ε _x, ε _yBe the pairwise orthogonal component of body structure surface strain along x, y direction, the grey face is the electrode of piezoelectric strain sensor.

Fig. 2 is the profile synoptic diagram that can eliminate the piezoelectricity type of dynamic strain sensor (TSE-PZT) of transverse strain influence, and mark is described as follows among the figure: the x-y plane is plane, body structure surface place, and the z direction is a planar process to, ε _x, ε _yBe the pairwise orthogonal component of body structure surface strain along x, y direction, Pa is a 1-3 type piezoelectric strain sensor, and Pb is the 3-3 type piezoelectric strain sensor of same material, upper and lower surface encapsulates with the insulation fexible film, the grey face is the electrode of TSE-PZT ,+,-indicated the both positive and negative polarity of electrode respectively.

Fig. 3 is the inner structure synoptic diagram that can eliminate the piezoelectricity type of dynamic strain sensor (TSE-PZT) of transverse strain influence, and mark is described as follows among the figure: the x-y plane is plane, body structure surface place, and the z direction is a planar process to, ε _x, ε _yBe the pairwise orthogonal component of body structure surface strain along x, y direction, Pa is a 1-3 type piezoelectric strain sensor, Pb is the 3-3 type piezoelectric strain sensor of same material, the grey face is the electrode of piezoelectric sensor ,+,-indicated the both positive and negative polarity of electrode respectively, Pa and Pb length are l, thickness is h, and the Pa width is a, and the Pb width is b.

Fig. 4 is the situation synoptic diagram that the piezoelectricity type of dynamic strain sensor (TSE-PZT) that can eliminate transverse strain influence is applied to the pipe vibration on-line monitoring, and mark is described as follows among the figure: the monitoring objective object is the pipeline of the fixing diameter 20mm in two ends, ε _xAxial strain for pipe surface.

Fig. 5 is the size synoptic diagram that the piezoelectricity type of dynamic strain sensor (TSE-PZT) that can eliminate transverse strain influence is pasted on pipe surface, mark is described as follows among the figure: Pa and Pb length are l, thickness is h, the Pa width is a, the Pb width is b ,+,-be respectively the positive and negative output electrode of TSE-PZT, be used to connect metering circuit, ε _xBe the axial strain of pipe surface, ε _yTransverse strain for pipe surface.

Embodiment

Be elaborated below in conjunction with the technical scheme of accompanying drawing to invention:

(1) principle of work of piezoelectric sensor and feasibility in theory

Be illustrated in figure 1 as traditional piezoelectric strain sensor synoptic diagram, figure (a) is a 1-3 matrix shape piezoelectric strain sensor, and figure (b) is a 3-3 type strip piezoelectric strain sensor, and the grey face is the electrode after polarizing.To object construction, definition x-y plane is plane, body structure surface place, the z direction be planar process to.To piezoelectric sensor, as usual, establishing polarised direction is 3 directions, and the x direction on object construction surface is 1 direction.In then following the analysis, subscript x, y, z are the object construction parameter, and subscript 1,2,3 is the piezoelectric sensor parameter.

If the object construction density of material is ρ, elastic modulus is E, and Poisson ratio is μ, and modulus of shearing is G=E/2 (1+ μ).Two class piezoelectric strain sensors use same material, and density is ρ _p, elastic modulus is E _p, Poisson ratio is μ _p, modulus of shearing is G _p=E _p/ 2 (1+ μ _p), the stress piezoelectric constant is g ₃₁, g ₃₃, the strain piezoelectric constant is d ₃₁, d ₃₃

When body structure surface produced strain variation, the strain of body structure surface any direction all can be decomposed into ε _x, ε _yTwo quadrature components.If the strain of piezoelectric sensor is ε ₁, ε ₂, ε ₃, the surface strain of object construction is ε _x, ε _y, because piezoelectric sensor is pasted on body structure surface, therefore to 1-3 type piezoelectric sensor, its plane strain is: ε ₁=ε _x, ε ₂=ε _yTo 3-3 type piezoelectric sensor, its plane strain is: ε ₁=ε _x, ε ₃=ε _y

For the piezoelectric sensor as the sensing effect, its direct piezo electric effect equation under no extra electric field is:

D ₃＝-(d ₃₁σ ₁+d ₃₁σ ₂+d ₃₃σ ₃) (1)

To 1-3 type piezoelectric strain sensor, because only lower surface and object construction stickup, so the upper surface freedom is σ ₃=0, when not considering complicated power electric coupling situation, its mechanical stress strain stress relation can be found the solution by generalized Hooke law and be drawn:

${\mathrm{\σ}}_1=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_1+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_2)=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_x+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_y)---\left(2a\right)$

${\mathrm{\σ}}_2=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_2+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_1)=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_y+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_x)---\left(2b\right)$

In like manner, to 3-3 type piezoelectric strain sensor, because only lower surface and object construction stickup, so the upper surface freedom is σ ₂=0, when not considering complicated power electric coupling situation, its mechanical stress strain stress relation can be found the solution by generalized Hooke law and be drawn:

${\mathrm{\σ}}_1=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_1+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_2)=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_x+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_y)---\left(3a\right)$

${\mathrm{\σ}}_3=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_3+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_1)=\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}({\mathrm{\ϵ}}_y+{\mathrm{\μ}}_p{\mathrm{\ϵ}}_x)---\left(3b\right)$

With (2) (3) formula difference substitution (1) formula, the electric density that obtains the accumulation of piezoelectric sensor electrode is:

1-3 type piezoelectric sensor: $D_{1-3}=-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{d}_{31}(1+{\mathrm{\μ}}_p){\mathrm{\ϵ}}_x-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{d}_{31}(1+{\mathrm{\μ}}_p){\mathrm{\ϵ}}_y---\left(4a\right)$

3-3 type piezoelectric sensor: $D_{3-3}=-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}(d_{31}+{\mathrm{\μ}}_p{d}_{33}){\mathrm{\ϵ}}_x-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}(d_{33}+{\mathrm{\μ}}_p{d}_{31}){\mathrm{\ϵ}}_y---\left(5a\right)$

Thereby the output charge of piezoelectric sensor is:

1-3 type piezoelectric sensor:

$Q_{1-3}=\underset{S1-3}{\∫\∫}{D}_{1-3}=-\underset{S1-3}{\∫\∫}[\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{d}_{31}(1+{\mathrm{\μ}}_p){\mathrm{\ϵ}}_x+\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{d}_{31}(1+{\mathrm{\μ}}_p){\mathrm{\ϵ}}_y]---\left(4b\right)$

3-3 type piezoelectric sensor:

$Q_{3-3}=\underset{S3-3}{\∫\∫}{D}_{3-3}=-\underset{S3-3}{\∫\∫}[\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{(d}_{31}+{\mathrm{\μ}}_p{d}_{33}){\mathrm{\ϵ}}_x+\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}{(d}_{33}+{\mathrm{\μ}}_p{d}_{31}){\mathrm{\ϵ}}_y]---\left(5b\right)$

Wherein

Represent respectively 1-3 type piezoelectric strain sensor and 3-3 type piezoelectric strain sensor electrode surface are got integration.By the result as seen, no matter be 1-3 type piezoelectric strain sensor or 3-3 type piezoelectric strain sensor, its output has all comprised and ε _x, ε _yThe part that two components of strain are relevant.Because E _p, d ₃₁, d ₃₃All can not be 0, μ _pCan not get-1, so two parts all can not get 0.Be the conventional piezoelectric sensor regardless of geometric shape, bonding method is how, all can't reach the purpose of eliminating the transverse strain variable effect.

But strain piezoelectric constant that it should be noted that piezoelectric commonly used is d ₃₁With d ₃₃Usually opposite in sign, and d ₃₃Absolute value is relatively large.Therefore,, choose suitable physical dimension and array mode, may eliminate wherein and ε by 1-3 type piezoelectric strain sensor and 3-3 type piezoelectric strain sensor combinations are used _x, ε _yRelevant a certain and only keep another, thus realize eliminating the design of the piezoelectricity type of dynamic strain sensor of transverse strain influence.

(2) eliminate the sensing effect implementation method that transverse strain influences

As the above analysis, when 1-3 type piezoelectric strain sensor and 3-3 type piezoelectric strain sensor combinations are pasted on the object construction surface, select suitable size sensor and connected mode may eliminate in total output charge and ε _x, ε _yRelevant a certain and only keep another.

Design proposal of the present invention such as Fig. 2 are the basic synoptic diagram of the piezoelectricity type of dynamic strain sensor (transverse strain eliminated piezoelectric transducer, below brief note is TSE-PZT) that can eliminate transverse strain influence.TSE-PZT is combined by 1-3 type piezoelectric strain sensor Pa and 3-3 type piezoelectric strain sensor Pb, and two surfaces are encapsulated by fexible film up and down, can effectively transmit the object construction surface strain variations.

The actual internal structure of TSE-PZT and the mode of connection such as Fig. 3 export anodal being connected with the Pb positive pole of Pa as total positive electrode of whole TSE-PZT, the Pa negative pole is connected with the Pb negative pole, as total negative electrode output of TSE-PZT.So the electric charge of TSE-PZT the two poles of the earth accumulation is the algebraic sum of Pa and Pb the two poles of the earth stored charge.

Because the piezoelectric strain sensor is compared with object construction, general size is less, can think that therefore the strain when object construction stickup TSE-PZT place is ε _x, ε _yThe time, the strain of Pa and Pb is ε ₁=ε _x, ε ₃=ε _yThen this moment Pa and Pb two electrode stored charges respectively such as (4b) (5b) description, so the output charge of whole TSE-PZT is both algebraic sum:

$Q_{\mathrm{AI}}=Q_{\mathrm{Pa}}+Q_{\mathrm{Pb}}=\underset{\mathrm{Pa}}{\∫\∫}{D}_{\mathrm{Pa}}+\underset{\mathrm{Pb}}{\∫\∫}{D}_{\mathrm{Pb}}$

$=-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}[\underset{\mathrm{Pa}}{\∫\∫}(d_{31}+{\mathrm{\μ}}_p{d}_{31})+\underset{\mathrm{Pb}}{\∫\∫}(d_{31}+{\mathrm{\μ}}_p{d}_{33})]{\mathrm{\ϵ}}_x---\left(6\right)$

$-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}[\underset{\mathrm{Pa}}{\∫\∫}(d_{31}+{\mathrm{\μ}}_p{d}_{31})+\underset{\mathrm{Pb}}{\∫\∫}(d_{33}+{\mathrm{\μ}}_p{d}_{31})]{\mathrm{\ϵ}}_y$

Wherein

Represent respectively Pa and Pb electrode surface are got integration.Because it is irrelevant to be integrated the Xiang Junyu physical dimension, therefore can directly replace integral sign with electrode area, so formula (6) turns to:

$Q_{\mathrm{AI}}=Q_{\mathrm{Pa}}+Q_{\mathrm{Pb}}=\underset{\mathrm{Pa}}{\∫\∫}{D}_{\mathrm{Pa}}+\underset{\mathrm{Pb}}{\∫\∫}{D}_{\mathrm{Pb}}$

$=-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}[S_{\mathrm{Pa}}(d_{31}+{\mathrm{\μ}}_p{d}_{31})+S_{\mathrm{Pb}}(d_{31}+{\mathrm{\μ}}_p{d}_{33})]{\mathrm{\ϵ}}_x---\left(7\right)$

$-\frac{E_p}{1-{{\mathrm{\μ}}_p}^2}[S_{\mathrm{Pa}}(d_{31}+{\mathrm{\μ}}_p{d}_{31})+S_{\mathrm{Pb}}(d_{33}+{\mathrm{\μ}}_p{d}_{31})]{\mathrm{\ϵ}}_y$

Wherein, S _Pa, S _PbBe respectively the electrode area of Pa and Pb.

By the result of formula (7) as seen, can eliminate the influence that transverse strain changes by following dual mode:

A) work as S _Pa(d ₃₁+ μ _pd ₃₁)+S _Pb(d ₃₁+ μ _pd ₃₃)=0, i.e. S _Pa/ S _Pb=-(d ₃₁+ μ _pd ₃₃)/(d ₃₁+ μ _pd ₃₁) time, the first of formula (7) is about ε _xBe 0, this moment the TSE-PZT output charge only with ε _yBe correlated with, promptly eliminated the transverse strain variable effect of x direction.

B) work as S _Pa(d ₃₁+ μ _pd ₃₁)+S _Pb(d ₃₃+ μ _pd ₃₁)=0, i.e. S _Pa/ S _Pb=-(d ₃₃+ μ _pd ₃₁)/(d ₃₁+ μ _pd ₃₁) time, the first of formula (7) is about ε _yBe 0, this moment the TSE-PZT output charge only with ε _xBe correlated with, promptly eliminated the transverse strain variable effect of y direction.

For the piezoelectric of making sensor commonly used in the engineering, generally Poisson ratio μ p is less than 1, and d ₃₁With d ₃₃Opposite in sign and d33 absolute value are bigger.In conjunction with above-mentioned a) b) two conditions as seen, for a) situation of condition, need Pb electrode area S usually _PbMuch larger than Pa electrode area S _Pa, even may ratio be negative, this is difficult to realize in practical engineering application relatively.And for condition b) situation, Pa electrode area S _PaWith Pb electrode area S _PbCan realize at the same order of magnitude.Therefore, condition b) practical engineering application has higher utility undoubtedly.

As shown in Figure 4, present embodiment will design a kind of piezoelectricity type of dynamic strain sensor of eliminating the transverse strain influence and be applied to the pipe vibration on-line monitoring, comprise the following steps:

(1) choose suitable piezoelectricity type of dynamic strain sensor size according to monitoring target:

As shown in Figure 4, present embodiment is with a kind of piezoelectricity type of dynamic strain sensor application of transverse strain influence and vibration online monitoring of the two ends fixed-piping of diameter 20mm eliminated.When pipeline produced vibration, its surface certainly existed along it axial, i.e. the strain variation ε of x direction _x, at this moment, because the uncertainty of its vibrational state, pipe surface also may produce transverse strain to be changed, and we only need monitor axial strain, therefore paste the piezoelectricity type of dynamic strain sensor that this can eliminate the transverse strain influence at the target pipe surface.

As shown in Figure 5, because the monitoring objective pipe diameter is less, reach desirable sticking effect, the piezoelectricity type of dynamic strain sensor lateral dimension of choosing should be much smaller than diameter, and be to guarantee that its output charge amount can reach easy examination criteria, should choose long sensor length l.Tentatively choose sensor width (being slightly larger than a+b) for about 8mm, length l=20mm.

(2) piezoelectricity dynamic sensitive implement body size is determined:

Present embodiment is chosen piezoelectric P-51 commonly used in the engineering reality as piezoelectricity type of dynamic strain sensor material, and material parameter is: Poisson ratio is μ _p=0.32, the strain piezoelectric constant is d ₃₁=180 * 10 ^-12C/N, d ₃₃=-420 * 10 ^-12C/N.

Choose electrode area condition b), i.e. S _Pa/ S _Pb=-(d ₃₃+ μ _pd ₃₁) (d ₃₁+ μ _pd ₃₁).Then can be only to the x direction strain monitor.With the substitution of P-51 material parameter, obtain:

S _Pa/S _Pb＝-(d ₃₃+μ _pd ₃₁)/(d ₃₁+μ _pd ₃₁)＝2.96 (8)

Formula (8) is the area ratio condition of the transverse strain the eliminated influence that present embodiment need satisfy.

In the present embodiment, Pa and Pb use with a collection of P-51 piezoelectric, get the width b=h of Pb, for satisfying the described electrode area ratio of formula (8) condition, then can calculate a/h=2.96, a/h=2.96.

The piezoelectricity type of dynamic strain sensor of the transverse strain the eliminated influence of using in the present embodiment is chosen l=20mm, b=h=2mm, then a=2.96h=5.92mm.

The Pa and the Pb of above-mentioned size are encapsulated by two fexible films, and inner lead links to each other Pa as total output cathode with the positive pole of Pb, Pa is linked to each other with the negative pole of Pb as total output negative pole.

(3) realization of pipe vibration on-line monitoring:

As shown in Figure 5, when pipe vibration, the strain variation of pipe surface can be decomposed into axial strain ε _xWith transverse strain ε _yTwo quadrature components.After pasting the piezoelectricity type of dynamic strain sensor can eliminate the transverse strain influence at pipe surface, the output charge of this piezoelectricity type of dynamic strain sensor only with the axial strain ε of axial pipe surface _xChange about and and transverse strain ε _yVariation is irrelevant, thereby can realize the on-line monitoring of pipe vibration situation.

Claims (1)

1. A piezoelectric dynamic strain sensor that can eliminate the influence of transverse strain is characterized in that the sensor is made up of 1-3 type piezoelectric strain sensors and 3-3 type piezoelectric strain sensors placed side by side, and 1-3 type piezoelectric strain sensors The electrode surface of the strain sensor is placed up and down, the electrode surface of the 3-3 type piezoelectric strain sensor is placed horizontally, and the positive electrode of the 1-3 type piezoelectric strain sensor electrode is connected with the positive electrode of the 3-3 type piezoelectric strain sensor electrode to form the piezoelectric strain sensor. The positive output terminal of the electric dynamic strain sensor, the negative pole of the 1-3 type piezoelectric strain sensor electrode is connected with the negative pole of the 3-3 type piezoelectric strain sensor electrode to form the negative output terminal of the piezoelectric dynamic strain sensor, and the piezoelectric The dynamic strain sensor is encapsulated by a flexible film, and the electrode areas of the 1-3 type piezoelectric strain sensor and the 3-3 type piezoelectric strain sensor meet the following conditions: Condition a): S _Pa /S _Pb = -(d ₃₁ +μ _p d ₃₃ )/(d ₃₁ +μ _p d ₃₁ ), or condition b): S _Pa /S _Pb = -(d ₃₃ +μ _p d ₃₁ )/(d ₃₁ +μ _p d ₃₁ ), Among them, S _Pa is the electrode area of the 1-3 type piezoelectric strain sensor, S _Pb is the area of the 3-3 type piezoelectric strain sensor electrode, μ _p is the Poisson’s ratio of the piezoelectric material, and d ₃₁ is the 1-3 type piezoelectric The strain piezoelectric constant of the strain sensor, d ₃₃ is the strain piezoelectric constant of the 3-3 type piezoelectric strain sensor, and the 1-3 type piezoelectric strain sensor and the 3-3 type piezoelectric strain sensor use the same piezoelectric material production.

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