CN115372416A - An inductive pulse compression magnetoacoustic detection method and system - Google Patents

Abstract

The invention provides an induction type pulse compression magnetoacoustic detection method, which comprises the steps of firstly exciting an electrode material (600) to generate a thermoacoustic effect and a magnetoacoustic effect through a pulse compression magnetic field excitation module (100) and a magnet magnetostatic field module (200), then receiving thermoacoustic signals and magnetoacoustic signals through an ultrasonic transducer (300) arranged around the electrode material (600) in an array manner, and finally collecting the ultrasonic signals through a signal acquisition module (400) and a conductivity module (500) and reconstructing the conductivity of the electrode material (600); wherein the conductivity module (500) reconstructs the conductivity of the electrode material (600) by a time-reversal method and a least squares iterative algorithm. The method can realize non-contact detection of the conductivity of the electrode material of the supercapacitor without damaging the electrode material, and has the advantages of low pulse compression magnetic field intensity and low energy consumption, and the adopted system is miniaturized and is convenient to carry.

Description

An inductive pulse compression magnetoacoustic detection method and system

technical field

The invention relates to the technical field of conductivity detection, in particular to an inductive pulse compression magnetoacoustic detection method and system.

Background technique

With the continuous depletion of fossil fuels and the increasingly serious problems of environmental pollution, it has become one of the most urgent tasks for people to seek efficient, environmentally friendly and practical alternative energy sources; today, traditional lithium-ion batteries have become an indispensable part of human life. The missing part, providing a new direction of choice for the revolution of portable electronic products. However, for ever-increasing applications such as electric vehicles, grid storage, etc., the surge of electrochemical energy storage depends on the stringent performance of future batteries, such as safety, energy density, cost requirements, storage capacity, etc., while existing conventional Li-ion Battery performance does not fully meet the above requirements. Supercapacitors have attracted widespread attention due to their high safety, high energy density, long cycle life, and fast charge-discharge and energy storage characteristics.

The performance of a supercapacitor is closely related to the conductivity of its electrode material, that is, its conductivity directly determines the charge and discharge performance of the supercapacitor. important link. At present, the conductivity detection methods of supercapacitor electrode materials are mainly four-probe method and inductive thermoacoustic detection method. The four-probe method is a contact detection method. During the detection process, the contact between the probe and the electrode material will easily cause damage to the material, which will directly lead to the scrapping of the supercapacitor after detection and increase the production cost; at the same time, the shape of the target object detected by the four-probe method It is a circle or a rectangle, which is fixed for the object and narrow for the applicable object. Compared with the contact detection method, the non-contact inductive thermoacoustic detection method will not contact the electrode material and will not cause material damage. At the same time, there is no limit to the shape of the detection material and it can be applied to a wide range of objects; however, the inductive thermal acoustic detection method The acoustic detection method requires a large alternating magnetic field, high energy consumption, and high detection cost, and the inductive thermoacoustic detection method has a large system, is not easy to carry, occupies a large space, and is difficult to maintain and maintain in the later stage. Industrialization and continuous detection operations are complicated .

Contents of the invention

In view of the above existing problems in the prior art, the object of the present invention is to provide an inductive pulse compression magnetoacoustic detection method, which can realize non-contact detection of the electrical conductivity of the supercapacitor electrode material without causing damage to the electrode material, Moreover, the pulse compression magnetic field required by the method has low strength and low energy consumption, and the adopted system is miniaturized and easy to carry.

Another object of the present invention is to provide a system used in the inductive pulse compression magnetoacoustic detection method.

The object of the present invention is achieved through the following technical solutions:

An inductive pulse compression magnetoacoustic detection method, characterized in that: comprising the following steps:

First, the electrode material of the supercapacitor is placed between the pulse compression magnetic field excitation source coil and the magnet, the electrode material is excited by the pulse compression magnetic field excitation source to generate eddy current, and a thermoacoustic effect is generated in the electrode material (that is, the material is excited by the pulse compression magnetic field excitation. , heat expansion, and emit a thermoacoustic signal), and produce a magnetoacoustic effect with the static magnetic field of the matching magnet (that is, the eddy current generates a Lorentz force under the excitation of the pulse compression magnetic field and the static magnetic field, and the electrode material is generated by the Lorentz force. vibrating, generating magnetoacoustic signals); then, the ultrasonic transducers arrayed around the electrode materials receive the thermoacoustic signals emitted by the thermal expansion of the electrode materials, and the magnetoacoustic signals (thermoacoustic signals) emitted by the electrode materials subjected to the Lorentz force The signal and the magnetoacoustic signal form an ultrasonic signal, the same below); finally, the signal acquisition module is used to process the ultrasonic signal received by the ultrasonic transducer, and the conductivity module is used to reconstruct the conductivity of the electrode material according to the ultrasonic signal;

The electrical conductivity module reconstructs the electrical conductivity of the electrode material according to the ultrasonic signal as follows: first, the thermal function and the Lorentz force divergence of the electrode material in the ultrasonic signal are reconstructed by the time-reversal method, and then the obtained thermal function and the Lorentz force divergence are reconstructed. The force divergence is used to reconstruct the electric field intensity inside the electrode material, and finally the electrical conductivity distribution of the electrode material is reconstructed by the least squares iterative algorithm.

For further optimization, the thermal function and Lorentz force divergence of the electrode material reconstructed by the time-reversal method are specifically:

The thermal function space absorption coefficient and the Lorentz force divergence in the ultrasonic signal are calculated by using the time inversion method. The specific formula is:

表示梯度、为数学计算符号，F表示待检测材料内部的洛伦兹力，

表示电极材料的洛伦兹力散度；Ω表示超声换能器所处的曲面，具体为：以电极材料所处位置为中心位置，以超声换能器与中心位置的距离为半径所获得的圆，此圆即为超声换能器所处的曲面；c_s表示声波的传播速度；r表示电极材料所处的位置；p(r_d,t)表示超声换能器在检测点r_d处接收的超声信号；t表示接收时间。In the formula, C _P represents the specific heat capacity of the electrode material (determined by the specific electrode material used); β represents the volume expansion coefficient of the electrode material (determined by the specific electrode material used); Q(r) represents the space absorption coefficient of the thermal function;

Indicates the gradient and is a symbol of mathematical calculation, F indicates the Lorentz force inside the material to be tested,

Indicates the Lorentz force divergence of the electrode material; Ω indicates the curved surface where the ultrasonic transducer is located, specifically: taking the position of the electrode material as the center position and taking the distance between the ultrasonic transducer and the center position as the radius The circle is the curved surface where the ultrasonic transducer is located; c _s represents the propagation velocity of the sound wave; r represents the position of the electrode material; p(r _d , t) represents the ultrasonic transducer at the detection point r _d Received ultrasonic signal; t represents the receiving time.

For further optimization, the propagation velocity of the sound wave is measured and calculated by an ultrasonic transducer, specifically: before the test starts, combined with the environment in which the electrode material is located, the ultrasonic transducer is used to send and receive sound waves, and through the sound wave The propagation speed of the sound wave is calculated from the propagation distance and time difference.

For further optimization, the reconstruction of the electric field intensity inside the electrode material through the obtained thermal function and the Lorentz force divergence, and the reconstruction of the conductivity distribution of the electrode material through the least squares iterative algorithm are specifically:

The electric field strength is first reconstructed by the Lorentz force divergence:

In the formula, J represents the current density inside the electrode material; B represents the magnetic flux density at the location of the electrode material; E represents the electric field strength inside the electrode material; σ represents the conductivity of the electrode material; Z represents the direction;

The electric field strength is then reconstructed by the heat function spatial absorption coefficient:

Q(r)=σ|E(r)| ² ;

Finally, the conductivity distribution of the electrode material is reconstructed by the least squares iterative algorithm:

In the formula, f(σ) represents the established least squares objective function; A represents the vector magnetic potential generated by the pulse compression current; φ represents the scalar potential.

For further optimization, the method for obtaining the vector magnetic potential generated by the pulse compression current is as follows:

First, the radius of the axisymmetric current-carrying coil is set as a, the input excitation pulse compression current is I(t), the plane where the coil is located is parallel to the plane Z=0, and the center of the coil is located at the origin of the coordinate system, then the line The vector magnetic potential A generated by the current is:

表示对载流线圈的圆周线进行积分；e表示单位矢量。In the formula, μ ₀ represents the magnetic permeability in vacuum;

Represents the integral of the circumference of the current-carrying coil; e represents the unit vector.

For further optimization, the specific method for obtaining the scalar potential is:

In the formula, n represents the normal unit vector of the boundary S, and the boundary S is the boundary of the area to be measured where the electrode material is located.

The system adopted in the above-mentioned inductive pulse compression magnetoacoustic detection method is characterized in that:

Including: pulse compression magnetic field excitation module, used to excite the eddy current inside the electrode material, so that the electrode material produces thermoacoustic effect; magnet static magnetic field module, used to cooperate with the pulse compression magnetic field excitation module to produce magnetoacoustic effect; ultrasonic transducer, It is used to receive the ultrasonic signal sent by the electrode material; the signal acquisition module is used to amplify and filter the ultrasonic signal in the ultrasonic transducer; the conductivity module is used to reconstruct the conductivity distribution of the electrode material;

The coil of the pulse compression magnetic field excitation module and the magnet static magnetic field module are respectively arranged on the upper and lower ends of the electrode material of the supercapacitor; the ultrasonic transducer is arranged in an array around the electrode material of the supercapacitor; the signal acquisition module They are respectively electrically connected to the pulse compression magnetic field excitation module, the ultrasonic transducer and the conductivity module.

For further optimization, the pulse compression magnetic field excitation module adopts a pulse excitation source capable of emitting alternating magnetic fields generated by continuous pulse compression currents with 2-10 high and low levels and a pulse width of 680-720 ns.

For further optimization, the magnet static magnetic field module adopts a magnet capable of generating a static magnetic field of 0.28-0.32T.

For further optimization, the signal acquisition module includes an amplifier and a filter.

The present invention has following technical effect:

Compared with the existing contact method for detecting the conductivity of the electrode material, this application can realize the non-contact detection of the conductivity of the electrode material of the supercapacitor, without contacting the electrode material, avoiding damage to the electrode material, and not needing to specifically limit the electrode The shape of the material and the effective guarantee system can target a wide range of objects; compared with the existing inductive thermoacoustic detection method, the pulse magnetic field required by this application is small: the excitation coil in the inductive thermoacoustic detection method requires an excitation voltage of about 1000V, However, the excitation voltage required by this application is not higher than 100V (that is, the required pulse compression magnetic field is small), less energy consumption, avoiding high-voltage environment detection, and effectively ensuring the safety of the test environment. The conductivity is reconstructed with the signal and the magnetoacoustic signal, the test information is complete, the accuracy of the obtained conductivity is higher, and the influence of the test error is less, especially suitable for the conductivity test of the electrode material that is greatly affected by thermal expansion

The system adopted in the detection method of this application is small, easy to carry, and can effectively reduce the space taken by the test system, thereby facilitating the test of the conductivity of the supercapacitor in the laboratory or industrial production; at the same time, the system operation adopted by the application method Simple, wide application range, convenient post-maintenance and maintenance, low testing cost.

Description of drawings

FIG. 1 is a schematic structural diagram of an inductive pulse compression magnetoacoustic detection system in an embodiment of the present invention.

100. Pulse compression magnetic field excitation module; 200. Magnet static magnetic field module; 300. Ultrasonic transducer; 400. Signal acquisition module; 401. Amplifier; 402. Filter; 500. Conductivity module; 600. Electrode material.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example:

As shown in Figure 1, an inductive pulse compression magnetoacoustic detection method is characterized in that: comprising the following steps:

First, the electrode material 600 of the supercapacitor is placed between the pulse compression magnetic field excitation source coil and the magnet, the electrode material 600 is excited by the pulse compression magnetic field excitation source to generate eddy currents, and a thermoacoustic effect is generated in the electrode material 600 (that is, the material is in the pulse compression magnetic field Under the action of excitation, heat expansion, and emit a thermoacoustic signal), and cooperate with the static magnetic field of the magnet to produce a magnetoacoustic effect (that is, the eddy current generates Lorentz force under the excitation of the pulse compression magnetic field and the static magnetic field, and the electrode material 600 is affected by the Lorentz force. Vibration of the magnetic force to generate a magnetoacoustic signal); then, the ultrasonic transducer 300 arranged around the electrode material 600 receives the thermoacoustic signal generated by the thermal expansion of the electrode material 600, and the electrode material 600 is subjected to the Lorentz force. The magnetoacoustic signal (the thermoacoustic signal and the magnetoacoustic signal form the ultrasonic signal, the same below); finally, the signal acquisition module 400 is used to process the ultrasonic signal received by the ultrasonic transducer 300, and the conductivity module 500 is used to reconstruct the electrode material according to the ultrasonic signal Conductivity of 600;

The electrical conductivity module 500 reconstructs the electrical conductivity of the electrode material 600 according to the ultrasonic signal specifically as follows: first, the thermal function and the Lorentz force divergence of the electrode material 600 in the ultrasonic signal are reconstructed by the time-reversal method,

Specifically:

The thermal function space absorption coefficient and the Lorentz force divergence in the ultrasonic signal are calculated by using the time inversion method. The specific formula is:

表示梯度、为数学计算符号，F表示待检测材料内部的洛伦兹力，

表示电极材料的洛伦兹力散度；Ω表示超声换能器所处的曲面，具体为：以电极材料所处位置为中心位置，以超声换能器与中心位置的距离为半径所获得的圆，此圆即为超声换能器所处的曲面；c_s表示声波的传播速度；r表示电极材料所处的位置；p(r_d,t)表示超声换能器在检测点r_d处接收的超声信号；t表示接收时间。In the formula, C _P represents the specific heat capacity of the electrode material (determined by the specific electrode material used); β represents the volume expansion coefficient of the electrode material (determined by the specific electrode material used); Q(r) represents the space absorption coefficient of the thermal function;

Indicates the gradient and is a symbol of mathematical calculation, F indicates the Lorentz force inside the material to be tested,

Indicates the Lorentz force divergence of the electrode material; Ω indicates the curved surface where the ultrasonic transducer is located, specifically: taking the position of the electrode material as the center position and taking the distance between the ultrasonic transducer and the center position as the radius The circle is the curved surface where the ultrasonic transducer is located; c _s represents the propagation velocity of the sound wave; r represents the position of the electrode material; p(r _d , t) represents the ultrasonic transducer at the detection point r _d Received ultrasonic signal; t represents the receiving time.

The propagation speed of the sound wave is measured and calculated by the ultrasonic transducer 300, specifically: before the test starts, combined with the environment where the electrode material 600 is located, the ultrasonic transducer 300 used to send and receive sound waves, and the propagation distance of the sound waves Calculate the propagation speed of the sound wave with the time difference.

Then the electric field intensity inside the electrode material 600 is reconstructed through the obtained thermal function and the Lorentz force divergence, and finally the electrical conductivity distribution of the electrode material 600 is reconstructed through the least squares iterative algorithm, specifically:

The electric field strength is first reconstructed by the Lorentz force divergence:

In the formula, J represents the current density inside the electrode material; B represents the magnetic flux density at the location of the electrode material; E represents the electric field strength inside the electrode material; σ represents the conductivity of the electrode material; Z represents the direction;

The electric field strength is then reconstructed by the heat function spatial absorption coefficient:

Q(r)=σ|E(r)| ² ;

Finally, the electrical conductivity distribution of the electrode material 600 is reconstructed by the least squares iterative algorithm:

In the formula, f(σ) represents the established least squares objective function; A represents the vector magnetic potential generated by the pulse compression current; φ represents the scalar potential.

Among them, the vector magnetic potential generated by the pulse compression current is obtained as follows:

First, the radius of the axisymmetric current-carrying coil is set as a, the input excitation pulse compression current is I(t), the plane where the coil is located is parallel to the plane Z=0, and the center of the coil is located at the origin of the coordinate system, then the line The vector magnetic potential A generated by the current is:

表示对载流线圈的圆周线进行积分；e表示单位矢量。In the formula, μ ₀ represents the magnetic permeability in vacuum;

Represents the integral of the circumference of the current-carrying coil; e represents the unit vector.

The specific method to obtain the scalar potential is:

In the formula, n represents the normal unit vector of the boundary S, and the boundary S is the boundary of the area to be measured where the electrode material is located.

The system adopted in the above-mentioned inductive pulse compression magnetoacoustic detection method,

It includes: a pulse compression magnetic field excitation module 100, which is used to excite the inside of the electrode material 600 to generate eddy current, so that the electrode material 600 produces a thermoacoustic effect; a magnet static magnetic field module 200, which is used to cooperate with the pulse compression magnetic field excitation module 100 to generate a magnetoacoustic effect The ultrasonic transducer 300 is used to receive the ultrasonic signal sent by the electrode material 600; the signal acquisition module 400 is used to amplify and filter the ultrasonic signal in the ultrasonic transducer 300; the conductivity module 500 is used to reconstruct the electrode material Conductivity distribution of 600;

The coil of the pulse compression magnetic field excitation module 100 and the magnet static magnetic field module 200 are respectively arranged on the upper and lower ends of the electrode material 600 of the supercapacitor; the ultrasonic transducer 300 is arranged in an array around the electrode material 600 of the supercapacitor; the signal acquisition module 400 They are respectively electrically connected to the pulse compression magnetic field excitation module 100 , the ultrasonic transducer 300 and the conductivity module 500 .

The pulse compression magnetic field excitation module 100 adopts the pulse excitation source that can send out the alternating magnetic field generated by the continuous pulse compression current of 2-10 high and low levels and the pulse width of 680-720 ns (preferably 700 ns); the magnet static magnetic field module 200 adopts A magnet capable of generating a static magnetic field of 0.28-0.32T (preferably 0.3T); the signal acquisition module 400 includes an amplifier 401 and a filter 402 .

During the test, at first the electrode material 600 is placed between the coil of the pulse compression magnetic field excitation module 100 and the magnet static magnetic field module 200 (as shown in Figure 1), then the pulse compression magnetic field excitation module 100 is started to excite the electrode material 600; the electrode material 600 The eddy current is generated inside, and under the joint action of the static magnetic field of the magnet static magnetic field module 200, two effects are produced, one is the thermoacoustic effect, that is, the material expands when heated and emits a thermoacoustic signal; the other is the magnetoacoustic effect, that is, the The eddy current is affected by the static magnetic field to generate Lorentz force, and the vibration sends out a magnetoacoustic signal; the ultrasonic signal composed of the thermoacoustic signal and the magnetoacoustic signal is received by the ultrasonic transducer 300 arranged in an array around the electrode material 600, and the signal is collected The amplification and filtering inside the module 400 are transmitted to the conductivity module 500 , and finally the conductivity module 500 combines the time inversion method and the least squares iterative algorithm to reconstruct the conductivity distribution of the electrode material 600 .

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. An inductive pulse compression magnetoacoustic detection method, characterized in that: comprises the following steps: First, the electrode material (600) of the supercapacitor is placed between the pulse compression magnetic field excitation source coil and the magnet, the electrode material (600) is excited by the pulse compression magnetic field excitation source to generate eddy current, and a thermoacoustic effect is generated in the electrode material (600), and cooperate with the static magnetic field of the magnet to produce a magnetoacoustic effect; then, the ultrasonic transducer (300) arranged around the electrode material (600) receives the thermoacoustic signal from the thermal expansion of the electrode material (600), and the electrode material (600 ) is a magnetoacoustic signal sent by Lorentz force; finally, the signal acquisition module (400) is used to process the ultrasonic signal received by the ultrasonic transducer (300), and the conductivity module (500) is used to reconstruct the electrode material according to the ultrasonic signal ( 600) conductivity; The electrical conductivity module (500) reconstructs the electrical conductivity of the electrode material (600) according to the ultrasonic signal specifically as follows: first, the thermal function and the Lorentz force divergence of the electrode material (600) in the ultrasonic signal are reconstructed by the time-reversal method, and then The electric field intensity inside the electrode material (600) is reconstructed through the obtained thermal function and the Lorentz force divergence, and finally the electrical conductivity distribution of the electrode material (600) is reconstructed through a least squares iterative algorithm. 2. A kind of inductive pulse compression magnetoacoustic detection method according to claim 1, is characterized in that: described heat function and Lorentz force divergence of described rebuilding electrode material (600) by time inversion method are specifically: The thermal function space absorption coefficient and the Lorentz force divergence in the ultrasonic signal are calculated by using the time inversion method. The specific formula is:

In the formula, C _P represents the specific heat capacity of the electrode material; β represents the volume expansion coefficient of the electrode material; Q(r) represents the space absorption coefficient of the thermal function;

Indicates the gradient and is a symbol of mathematical calculation, F indicates the Lorentz force inside the material to be tested,

Indicates the Lorentz force divergence of the electrode material; Ω indicates the curved surface where the ultrasonic transducer is located, specifically: taking the position of the electrode material as the center position and taking the distance between the ultrasonic transducer and the center position as the radius The circle is the curved surface where the ultrasonic transducer is located; c _s represents the propagation velocity of the sound wave; r represents the position of the electrode material; p(r _d , t) represents the ultrasonic transducer at the detection point r _d Received ultrasonic signal; t represents the receiving time. 3. A kind of inductive pulse compression magnetoacoustic detection method according to claim 1 or 2, characterized in that: the electric field intensity inside the electrode material (600) is reconstructed by the obtained heat function and Lorentz force divergence , and the electrical conductivity distribution of the electrode material (600) reconstructed by the least squares iterative algorithm is specifically: The electric field strength is first reconstructed by the Lorentz force divergence:

In the formula, J represents the current density inside the electrode material; B represents the magnetic flux density at the location of the electrode material; E represents the electric field strength inside the electrode material; σ represents the conductivity of the electrode material; Z represents the direction; The electric field strength is then reconstructed by the heat function spatial absorption coefficient: Q(r)=σ|E(r)| ² ;

Finally, the electrical conductivity distribution of the electrode material (600) is reconstructed by the least squares iterative algorithm:

In the formula, f(σ) represents the established least squares objective function; A represents the vector magnetic potential generated by the pulse compression current; φ represents the scalar potential. 4. An inductive pulse compression magnetoacoustic detection method according to any one of claims 1 to 3, characterized in that: the vector magnetic potential generated by the pulse compression current is obtained as follows: First, the radius of the axisymmetric current-carrying coil is set as a, the input excitation pulse compression current is I(t), the plane where the coil is located is parallel to the plane Z=0, and the center of the coil is located at the origin of the coordinate system, then the line The vector magnetic potential A generated by the current is:

In the formula, μ ₀ represents the magnetic permeability in vacuum;

Represents the integral of the circumference of the current-carrying coil; e represents the unit vector. 5. A kind of inductive pulse compression magnetoacoustic detection method according to claim 1, characterized in that: The system adopted in the method includes: a pulse compression magnetic field excitation module (100), used to excite the eddy current generated inside the electrode material (600), so that the electrode material (600) produces a thermoacoustic effect; a magnet static magnetic field module (200), used Cooperating with the pulse compression magnetic field excitation module (100) to generate magneto-acoustic effects; the ultrasonic transducer (300) is used to receive the ultrasonic signal sent by the electrode material (600); the signal acquisition module (400) is used to transduce ultrasonic energy The ultrasonic signal in the device (300) is amplified and filtered; the conductivity module (500) is used to reconstruct the conductivity distribution of the electrode material (600); The coil and the magnet static magnetic field module (200) of the pulse compression magnetic field excitation module (100) are respectively arranged on the upper and lower ends of the electrode material (600) of the supercapacitor; the ultrasonic transducers (300) are arranged in an array on the supercapacitor Around the electrode material (600) of the capacitor; the signal acquisition module (400) is electrically connected to the pulse compression magnetic field excitation module (100), the ultrasonic transducer (300), and the conductivity module (500). 6. An inductive pulse compression magnetoacoustic detection method according to claim 5, characterized in that: the pulse compression magnetic field excitation module (100) adopts a method capable of emitting 2 to 10 high and low levels, and both are 680 to 720 ns The pulse excitation source of the alternating magnetic field generated by the continuous pulse compression current of pulse width.

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