KR101055796B1 - Piezo-composite generator characterization system - Google Patents

Abstract

The present invention relates to a piezo-composite power generation device, and more particularly to a piezo-composite power generation device characteristic analysis system capable of analyzing the power generation performance of the PZT.
The present invention relates to a piezoelectric-composite generator characteristic analysis system, which stores the physical properties of each material according to the laminated form of the piezoelectric-composite generator and a moment arm (a) which is a distance from the neutral plane to the piezoelectric material as a database. Piezo-composite properties DB 110; A ratio calculation unit 120 for calculating a ratio of the moment arm and the bending stiffness according to the stacked form; A piezoelectric constant change calculation unit 130 for calculating a change in the piezoelectric constant according to the residual compressive stress of the piezoelectric-composite power generator; And a power generation performance analysis unit 140 which receives the output data of the ratio calculating unit and the piezoelectric constant change calculating unit to calculate the power plant magnetic constant of the piezoelectric composite material power generator.

Description

Piezo-composite Generating Element {System for analyzing characteristic of Piezo-Composite Generating Element}

The present invention relates to a piezo-composite power generation device, and more particularly to a piezo-composite power generation device characteristic analysis system capable of analyzing the power generation performance of the PZT.

With the development of microelectronic technology, very small devices, also known as microlectromechanical system (MEMS) devices, which were previously considered impossible, are being developed rapidly.

These tiny devices can be powered through external electrical connection, but in many cases they are disconnected from the outside while they are functioning, making it difficult to supply power.

Accordingly, researches on energy harvesting that efficiently collect energy that is present in nature but are not used and discarded, charge batteries or supply electricity to electrical devices.

Energy harvesting is a topic that has been studied in the world over the last few years. It is researched in various forms such as solar cells using solar light, piezoelectric power using wind, ocean waves, and power generation using waste heat. It is becoming. As a result, some researches are integrating MEMS with small generators that can generate power from external energy sources such as vibration, heat and solar light instead of using batteries. As an example, the overseas journal "Sensor and Actuator A (1996) 52, p. 8-p. 11" discloses a device in which a micro generator using vibration is combined with MEMS, and such a system uses solar light or heat. It is said to be more applicable than the development method.

In Korea, research on energy harvesting using piezoelectric materials is being actively conducted. Since the amount of electricity generated by the piezoelectric effect is small, research is being conducted for the purpose of applying the power of a MEMS device or a body insertion device.

According to these studies, there is a problem in that a power generation performance prediction model that can improve the power generation performance of PZT and predict the power generation performance of piezoelectric materials is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a piezo-composite generator characteristic analysis system for analyzing the performance of the piezo-composite generator.

The present invention relates to a piezoelectric-composite generator characteristic analysis system, which stores the physical properties of each material according to the laminated form of the piezoelectric-composite generator and a moment arm (a) which is a distance from the neutral plane to the piezoelectric material as a database. Piezo-composite properties DB 110; A ratio calculation unit 120 for calculating a ratio of the moment arm and the bending stiffness according to the stacked form; A piezoelectric constant change calculation unit 130 for calculating a change in the piezoelectric constant according to the residual compressive stress of the piezoelectric-composite power generator; And a power generation performance analysis unit 140 which receives the output data of the ratio calculating unit and the piezoelectric constant change calculating unit to calculate the power plant magnetic constant of the piezoelectric composite material power generator.

According to the present invention as described above, there is an effect that can predict the performance by analyzing the characteristics of the piezo-composite power generator.

1 is a block diagram of a piezo-composite generator characteristic analysis system according to an embodiment of the present invention.
2 is a view showing a laminated form of a piezoelectric-composite power generation device according to an embodiment of the present invention.
3 is a view showing characteristics of piezoelectric constants in a piezoelectric-composite power generating device stack model having a unit width (w = 1) according to an embodiment of the present invention.
4 and 5 are graphs showing changes in piezoelectric strain constant and dielectric constant from residual stress acting on PZT according to one embodiment of the present invention.
Figure 6 is a view showing the energy harvesting experiment apparatus according to the piezo-composite generator test according to an embodiment of the present invention.
FIG. 7 illustrates voltages measured by the experimental apparatus of FIG. 6 of three types of piezoelectric-composite power generating elements according to an embodiment of the present invention; FIG.

According to the present invention, in the piezoelectric-composite generator characteristic analysis system, the physical properties of each material according to the stacking form of the piezoelectric-composite generator and the moment arm (a) which is the distance from the neutral plane to the piezoelectric material are stored as a database. Piezo-composite material characteristics DB 110; A ratio calculation unit 120 for calculating a ratio of the moment arm and the bending stiffness according to the stacked form; A piezoelectric constant change calculation unit 130 for calculating a piezoelectric constant change including a piezoelectric strain constant and a dielectric constant according to the residual compressive stress of the piezoelectric-composite power generator; And a power generation performance analysis unit 140 which receives the output data of the ratio calculating unit and the piezoelectric constant change calculating unit to calculate the power plant magnetic constant of the piezoelectric composite material power generator.

Preferably, the piezoelectric-composite generator includes a carbon / epoxy layer, a glass / epoxy layer, and a piezo-ceramic layer.

Also preferably in the first stack of piezoelectric-composite generators, a piezoelectric layer is disposed on the first glass / epoxy layer, a carbon / epoxy layer is disposed on the piezoelectric layer, and on the carbon / epoxy layer. And second and third glass / epoxy layers formed.

Also preferably in the second stack of piezoelectric-composite generators, a piezoelectric layer is disposed on the first glass / epoxy layer, a second glass / epoxy layer is disposed on the piezoelectric layer, and the second glass / A carbon / epoxy layer is disposed on the epoxy layer, and a third glass / epoxy layer is formed on the carbon / epoxy layer.

Also preferably in a third stack of piezoelectric-composite generators, a piezoelectric layer is disposed on the first glass / epoxy layer, a second glass / epoxy layer is disposed on the piezoelectric layer, and the second glass / A third glass / epoxy layer is disposed on the epoxy layer, and a carbon / epoxy layer is formed on the third glass / epoxy layer.

In addition, the ratio calculation unit 120, the moment arm (a) according to the stacking form stored in the piezoelectric-composite material properties DB (110), and the material properties of each material is imported to the bending mathematics (D) It calculates through a formula and calculates the ratio (a / D) of the said moment arm (a) and bending rigidity (D).

[Equation]

Where E _i is the modulus of elasticity of the i-th layer and I _i is the cross-sectional secondary moment of the i-th layer.

Further, preferably, the piezoelectric constant change calculation unit 130 retrieves predetermined experimental data from the piezoelectric-composite property DB, and the piezoelectric strain constant d ₃₁ is obtained from the residual stress acting on the PZT (piezoelectric ceramic). The piezoelectric constant (d ₃₁ / ε ^T ₃₃ ) according to the dielectric constant (ε ^T ₃₃ ) is calculated.

)를 산출하는 것을 특징으로 한다.
Preferably, the power generation performance analysis unit 140 receives the output data of the ratio calculation unit and the output data of the piezoelectric constant change calculation unit and receives the power factor constant of the piezoelectric composite material power generator (=

) Is calculated.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, they can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

Hereinafter, with reference to the accompanying drawings as follows.

Piezo-composite generator characteristic analysis system according to an embodiment of the present invention, as shown in Figure 1, piezo-composite material characteristics DB 110, ratio calculation unit 120, piezoelectric constant change calculation unit 130 ), The power generation performance analysis unit 140 is configured.

First, the piezo-composite properties DB 110 uses three types of piezo-composite materials, carbon / epoxy, to take advantage of design diversity in designing Piezo-Composite Generating Element (PCGE). The physical properties of each material according to the stacking form of three types of piezoelectric composite power generators that can be composed of one layer, three layers of glass / epoxy and piezoelectric ceramic (PZT), and the moment arm (a), which is the distance from the neutral plane to the piezoelectric material. A component that stores a database.

Here, the physical properties of each material according to the stacked form of the three types of piezoelectric composite power generators are shown in Table 1 below.

Although one embodiment of the present invention considers a piezoelectric-composite power generator composed of one carbon / epoxy layer, three glass / epoxy layers, and PZT, in practice, various types of composite materials may be combined.

As shown in FIG. 2, the stacked form of the piezoelectric composite power generator according to the present embodiment is a PCGE-A type, a PCGE-B type, and a PCGE-C type, and FIG. 3 shows a unit width (w = 1). Fig. 3 is a diagram defining variables necessary for analyzing the characteristics of piezoelectric constants in a general laminate model.

For reference, a simple model for predicting the characteristics of the piezo-composite power generator is introduced from the structural formula of the piezoelectric material.

The constitutive equation of the piezoelectric material, in which the energy conversion between electricity and load, occurs according to IEEE standard 176-1987.

Where T _ij is the stress, S _kl is the strain, C ^E _ijkl is the elastic modulus obtained from a constant electric field, e _kij = C ^E _ijlm d _klm is the piezoelectric stress constant (d _klm is the piezoelectric strain constant), D _i is the electrical displacement, ε ^S _ik is the dielectric constant measured at constant strain state, E _k represents the electric field, and the subscripts i, j, k, l, m = 1,2,3.

In this embodiment, a coefficient of generating element is introduced which exhibits the characteristics of the piezoelectric-composite generator.

에 대하여 압전 재료 상하에 발생하는 전압

는 다음과 같이 나타낼 수 있다.Stress generated by the force P in the model having the unit width (w = 1) as shown in FIG. 3

Voltage generated above and below the piezoelectric material

Can be expressed as:

를 발전소자상수라 명명하였다.
Here, ε ^T ₃₃ is the polling direction (three direction) dielectric constant measured in the state of constant strain, a is the moment arm, the distance between the piezoelectric material from the neutral plane, and D is the bending stiffness with respect to the neutral plane. Considering Equation 2, the moment acting on PZT (M = aP) generates electricity, the voltage is proportional to the force, and if the applied force is the same, the voltage is related to d ₃₁ , ε ^T _ij , a, D It can be seen that there is. Therefore, in this embodiment, the proportionality constant of Equation 2

Is called the plant constant.

Next, the ratio calculation unit 120 is a component that calculates a / D, which is the ratio of the moment arm and the bending stiffness, to the three stacking forms described above.

Here, the ratio calculation unit loads the moment arm (a) according to the three stacking forms stored in the piezoelectric-composite properties DB 110 and the material property information of each material, and calculates the bending stiffness (D) by using Equation 3 below. Calculate.

Where E _i is the modulus of elasticity of the i-th layer and I _i is the cross-sectional secondary moment of the i-th layer.

Through the ratio calculation unit 120, the a / D values of the respective piezoelectric-composite power generating elements are shown as shown in Table 2 below.

PCGE-C, which has the most rigid carbon / epoxy layer at the outermost side, has the highest bending stiffness, but the a / D value appears to be the smallest because the moment arm is also the largest.

Next, the piezoelectric constant change calculation unit 130 is a component that calculates the piezoelectric constant change according to the residual stress.

When the piezo-composite generator is manufactured according to the composite molding process, the residual compressive stress acts on the PZT due to the difference in the coefficient of thermal expansion between the constituent materials. In general, the piezoelectric constant d ₃₁ and the dielectric constant ε ^T ₃₃ have a compressive stress. Equation (2) shows that the voltage generated in the piezoelectric-composite generator is proportional to d ₃₁ and inversely proportional to ε ^T ₃₃ .

ANSYS ^TM , a commercial finite element analysis program, was used to calculate the residual compressive stress of the piezo-composite generator. When thermal analysis is performed using the properties of carbon / epoxy, glass / epoxy and PZT stored in the piezoelectric-composite material DB 110 and the molding temperature (177 ° C.), the displacement and internal residual stress generated after molding can be calculated. .

The change in piezoelectric strain constant and dielectric constant from residual stress acting on PZT (piezoelectric ceramic) can be calculated from the experimental results in FIGS. 4 and 5, and these experimental data should be stored in a database. Here, reference is made to the results of the experiment (Krueger HHA 1968. "Stress sensitivity of piezoelectric ceramics: part 3. sensitivity to compressive stress perpendicular to the polar axis," Journal of the Acoustical Society of America, 45: 583-91.) Are stored in the database.

Table 3 shows the results of calculating the residual compressive stress, piezoelectric strain constant and dielectric constant of the piezo-composite generators calculated using the finite element analysis program. The% values in parentheses represent the magnitude relative to the value of PZT 3203HD. For example, in the case of PCGE-A, d ₃₁ is 36.4% larger than the original value and ε ^T ₃₃ is 1.5% larger due to the influence of residual compressive stress in the PZT. On the other hand, in the case of PCGE-C type, d ₃₁ and ε ^T ₃₃ become smaller at the same time.

Next, the power generation performance analysis unit 140 receives the output of the ratio calculation unit 120 and the piezoelectric constant change calculation unit 130, and performs the function of analyzing the power generation performance of the piezoelectric-composite power generator (PCGE). do.

Here, the plant magnetic constant of the PCGE can be calculated from the results of Table 2 of the ratio calculation unit 120 and Table 3 of the piezoelectric constant change calculation unit 130, and are shown in Table 4 below.

For types PCGE-A and B, the values of d ₃₁ and ε ^T ₃₃ increase and the ratio between the two increases, while for types PCGE-C, d ₃₁ and ε ^T ₃₃ decreases but the ratio between them is large. You lose.

In summary, power generation performance was found to be excellent in the order of A, B, C type, and A type 51% and B type 31% were better than C type.

Three stacked forms of the piezoelectric-composite power generators according to the present embodiment were tested using an excitation device as shown in FIG.

It is mounted on three types of piezo-composite generators and generates sinusoidal functions using B & K's 3560D FFT analyzer. At this time, the same magnitude of vibration was applied to the PCGE, and the voltage generated from the PCGE was measured using an Agilent multimeter. In order to confirm that the same magnitude of vibration was applied, the accelerometer was mounted on the excitation part and the excitation acceleration was measured by using the B & K 3560D FFT analyzer.

Since the experiment according to the present embodiment introduces the concept of a piezoelectric-composite generator, the characteristics of the excitation frequency in a relatively low region up to 50 Hz are considered.

FIG. 7 shows voltages measured after the three types of piezo-composite power generating elements were mounted in the experimental apparatus shown in FIG. 6. The excitation frequency increased from 1 Hz to 50 Hz. The voltage generated at each piezo-composite generator showed a constant value regardless of frequency, because the range of excitation frequencies was low.

The magnitudes of the voltage values were 3.2V for type A, 2.8V for type B, and 2.2V for type C. This result can be confirmed that the magnitude of generator constants shown in Table 4 are the same. Table 5 shows the result of comparison with the voltage value generated in the type C generator.

This shows that the model is expected to show a 3% and 9% improvement in performance compared to the experiment, which is in good agreement with the experimental results.

From the above results, it was confirmed that the piezoelectric-composite power generator proposed in this study can improve the power generation performance of PZT according to the design method.

The piezoelectric-composite generator characteristic analysis system according to the present embodiment created a model that can predict the characteristics of the piezoelectric-composite generator, and introduced the power factor magnetic constant to verify the validity through experiments.

As a result of experimentally examining the power generation performance of three types of piezo-composite generators with the same material, it was confirmed that the analytical model showed the improvement of the generation performance of the piezo-composite generator.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

110: piezo-composite properties DB
120: ratio calculation unit
130: piezoelectric constant change calculation unit
140: power generation performance analysis unit

Claims (8)

In the piezo-composite generator characteristic analysis system,
A piezoelectric-composite material DB 110 for storing physical properties of each material according to the stacking form of the piezoelectric-composite power generator and a moment arm a that is a distance from the neutral plane to the piezoelectric material in a database;
A ratio calculation unit 120 for calculating a ratio of the moment arm and the bending stiffness according to the stacked form;
A piezoelectric constant change calculation unit 130 for calculating a piezoelectric constant change including a piezoelectric strain constant and a dielectric constant according to the residual compressive stress of the piezoelectric-composite power generator; And
Piezo-composite power generator characteristics comprising a; power generation performance analysis unit 140 for receiving the output data of the ratio calculation unit and the piezoelectric constant change calculation unit to calculate the power generator magnetic constant of the piezoelectric composite material power generator; Analysis system. The method of claim 1,
The piezoelectric-composite power generator,
A piezo-composite generator characterization system comprising a carbon / epoxy layer, a glass / epoxy layer, and a piezo-ceramic layer. The method of claim 1,
The first laminated form of the piezoelectric-composite power generator,
A piezoelectric layer disposed on a first glass / epoxy layer, a carbon / epoxy layer disposed on the piezoelectric layer, and a second and third glass / epoxy layer formed on the carbon / epoxy layer. -Composite material generator characterization system. The method of claim 1,
The second stacked form of the piezo-composite power generator,
A piezoelectric layer is disposed on the first glass / epoxy layer, a second glass / epoxy layer is disposed on the piezoelectric layer, a carbon / epoxy layer is disposed on the second glass / epoxy layer, and the carbon / epoxy A piezo-composite generator characterization system, wherein a third glass / epoxy layer is formed on the layer. The method of claim 1,
The third stacked form of the piezo-composite power generator,
A piezoelectric layer is disposed on the first glass / epoxy layer, a second glass / epoxy layer is disposed on the piezoelectric layer, a third glass / epoxy layer is disposed on the second glass / epoxy layer, and the second 3 Piezo-composite generator characterization system, characterized in that the carbon / epoxy layer formed on the glass / epoxy layer. The method of claim 1,
The ratio calculation unit 120,
The moment arm (a) according to the lamination form stored in the piezoelectric-composite material DB 110 and the material property information of each material are loaded to calculate the bending stiffness (D) through Equation 1 below, and the moment arm (a). A piezoelectric-composite generator characteristic analysis system, characterized in that it calculates the ratio (a / D) of bending strength (D)).
[Equation 1]

Where E _i is the modulus of elasticity of the i-th layer and I _i is the cross-sectional secondary moment of the i-th layer. The method of claim 1,
The piezoelectric constant change calculation unit 130,
The piezo-from the composite attribute DB, group imported experimental data set, PZT (piezoelectric ceramic), the piezoelectric constant of the piezoelectric strain constant (d ₃₁₎ and the dielectric constant (ε ^T ₃₃₎ from the residual stress acting on the (d ₃₁ / ε ^T ₃₃ ) piezo-composite generator characteristic analysis system characterized in that it calculates. The method of claim 1,
The power generation performance analysis unit 140,
The power factor coefficient of the piezoelectric-composite power generator receives the output data of the ratio calculating unit and the output data of the piezoelectric constant change calculating unit (

Piezo-composite generator characteristic analysis system, characterized in that to calculate).

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